CA1133221A - Means for orienting and transferring web of thermoplastic material - Google Patents
Means for orienting and transferring web of thermoplastic materialInfo
- Publication number
- CA1133221A CA1133221A CA386,351A CA386351A CA1133221A CA 1133221 A CA1133221 A CA 1133221A CA 386351 A CA386351 A CA 386351A CA 1133221 A CA1133221 A CA 1133221A
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- web
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- receiving
- discs
- stretching
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Abstract
ABSTRACT OF THE DISCLOSURE
Means are provided herein for continuously orienting and trans-ferring a continuous web of thermoplastic material conformally onto the periphery of a polygonal rotating mold from an extruder. The means includes web receiving and advancing means ingesting the web. Web stretch-ing means are provided downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing the web toward a polygonal rotary mold. Finally, web transfer means are mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rotating mold for receiving the laterally stretched web from the web stretching means and conformally juxtaposing the stretched web with the peripheral surface of the rotating mold. In this invention, at least one of the web receiving and advancing means and the web transfer means imparts a longitudinal stretch to the web to impart biaxial orientation thereto prior to its con-formal juxtaposition with the peripheral surface of the rotating mold.
Such system which is provided is very facile and variable with regard to unique and unusual shapes.
Means are provided herein for continuously orienting and trans-ferring a continuous web of thermoplastic material conformally onto the periphery of a polygonal rotating mold from an extruder. The means includes web receiving and advancing means ingesting the web. Web stretch-ing means are provided downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing the web toward a polygonal rotary mold. Finally, web transfer means are mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rotating mold for receiving the laterally stretched web from the web stretching means and conformally juxtaposing the stretched web with the peripheral surface of the rotating mold. In this invention, at least one of the web receiving and advancing means and the web transfer means imparts a longitudinal stretch to the web to impart biaxial orientation thereto prior to its con-formal juxtaposition with the peripheral surface of the rotating mold.
Such system which is provided is very facile and variable with regard to unique and unusual shapes.
Description
`` 11;~;~21 This invention relates to apparatus for biaxially orienting thermoplastic materials, e.g.,polystyrene. More particularly, it relates to a means for continuously orienting and transferring a continuous web of material conformingly onto the periphery of a polygonal rotating mold from an extruder.
This application is a division of application Serial No. 323,052 filed March 9, 1979.
The specifics of the following discussion and specification refers to oriented polystyrene material, hereinafter referred to as OPS but it - 10 should be expressly understood that the apparatus constituing the present invention is applicable to a wide variety of thermoplastic materials, polymers or mixtures of polymers including other such materials, e.g., polymers of ethylene, polypropylene, styrene, vinyl chloride, etc.
While individual materials have problems which are often peculiar to those materials and hamper commercial exploitation of them, the poly-styrene materials exhibit low-cost, high stiffness and excellent trans-parency when properly oriented and the proper molecular orientation further enhances the polystyrene material by removing its inherent brittleness in the absence of molecular orientation.
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, 1133~21 There are various prior art approaches to mitigating the brittleness factor in polystyrene materials, by the use of impact modifiers and the like. However, this decreases the stiffness,eliminates transparency and increases the cost significantly.
Therefore, prior art approaches to remedy the brittle- ¦
ness problem and increase the impact resistance of poly-styrene result in certain undesirable properties which did not exist prior to the addition of such modifiers.
Accordingly, if such materials could be used in a relatively unmodified state in manufacturing sheets or , strips of this material in a continuous extruding ~ethod in which continuous biaxial orientation is imparted to , this m,ate,rial and then, without destroying the continuity or 15 the ~ethod , mold articles or otherwise form articles from it, all of the desirable physical properties of the material .
could be realized. At the same time all of the desirabili-ties, speed and efficiencies of a fully continuous process could be realized in the ultimate product cost.
This integrated approach which combines continuous , extrusion, orientation and forming in rapid succession is the crux of the present invention. n Heretofore, the conventional approaches " e,g. with foam sheet materials and non-foamed or non-cellular sheet 25 materials has been to first produce sheeting, store it in .
rolled form and terminate the initial process at that point.
Then, subseguently~ the sheeting is unrolled, reheated and subsequently for~ed into products or articles in its reheated state. As ~.ith all thermoplastic techniques, there are three basic interrelated variables involved in procéssing thermoplastic materials which affect both the nature of the operation and the characteristics of the final product. These variables are temperature, time and ph)~sical state, with the latter variable dealing with pressure, I _ stress, etc.
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This application is a division of application Serial No. 323,052 filed March 9, 1979.
The specifics of the following discussion and specification refers to oriented polystyrene material, hereinafter referred to as OPS but it - 10 should be expressly understood that the apparatus constituing the present invention is applicable to a wide variety of thermoplastic materials, polymers or mixtures of polymers including other such materials, e.g., polymers of ethylene, polypropylene, styrene, vinyl chloride, etc.
While individual materials have problems which are often peculiar to those materials and hamper commercial exploitation of them, the poly-styrene materials exhibit low-cost, high stiffness and excellent trans-parency when properly oriented and the proper molecular orientation further enhances the polystyrene material by removing its inherent brittleness in the absence of molecular orientation.
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, 1133~21 There are various prior art approaches to mitigating the brittleness factor in polystyrene materials, by the use of impact modifiers and the like. However, this decreases the stiffness,eliminates transparency and increases the cost significantly.
Therefore, prior art approaches to remedy the brittle- ¦
ness problem and increase the impact resistance of poly-styrene result in certain undesirable properties which did not exist prior to the addition of such modifiers.
Accordingly, if such materials could be used in a relatively unmodified state in manufacturing sheets or , strips of this material in a continuous extruding ~ethod in which continuous biaxial orientation is imparted to , this m,ate,rial and then, without destroying the continuity or 15 the ~ethod , mold articles or otherwise form articles from it, all of the desirable physical properties of the material .
could be realized. At the same time all of the desirabili-ties, speed and efficiencies of a fully continuous process could be realized in the ultimate product cost.
This integrated approach which combines continuous , extrusion, orientation and forming in rapid succession is the crux of the present invention. n Heretofore, the conventional approaches " e,g. with foam sheet materials and non-foamed or non-cellular sheet 25 materials has been to first produce sheeting, store it in .
rolled form and terminate the initial process at that point.
Then, subseguently~ the sheeting is unrolled, reheated and subsequently for~ed into products or articles in its reheated state. As ~.ith all thermoplastic techniques, there are three basic interrelated variables involved in procéssing thermoplastic materials which affect both the nature of the operation and the characteristics of the final product. These variables are temperature, time and ph)~sical state, with the latter variable dealing with pressure, I _ stress, etc.
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- 2 - _ 1133~21 As a general rule, temperature and time should be L
minimized variables because extended heat history can materially affect the properties of an end product. In the case of OPS, for example, the temperature at which the r 5 material must be oriented represents a compromise between levels which are best from a flow point of view and levels which are best from a stress (orientation) point of view. L
Once a stress is imposed at a given temperature, for example, a molecular orientation is achieved. However, the 10 longer the increment of time involved between the achieve- _ ment of that orientation and a subsequent operation, the more stress (orientation) will again be relaxed. According-ly, the degree of orientation of a particular material is not necessarily a sole function of the amount of heat 15 stretching applied to that material to create the orienta-tion since relaxation of that orientation may simultaneously be taking place.
Therefore, a high speed, integrated approach is unique and important not only from a standpoint of cost but also l ~
20 from the standpoint of results heretofore not otherwise .
attainable.
These inherent advantages of a high speed integrated ~
approach are important in relatively thin products , e.g. l ;-those with wall thicknesses of ~005 too.010 inches and 25 become increasingly significant with products having wall thicknesses greater thano.010 inches. This is due to the fact that conventional systems as heretofore defined, necessarily involve not only greater time/temperature exposure during the production of heating from which the 30 ultimate products are formed, but also involve the reheating and subsequent recooling of the sheet during the subsequent forming operation. Accordingly, the relief of stress occurs .
during reheating and subsequent recooling as well as during a possible relaxation during the production of the sheeting _ 35 per se.
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Theoretically, the ideal method would be to bia~ially orient the thermoplastic material, form and cook it simultaneously. In conventional systems, the time factor is significant and therefore detrimental. Accordingly, the shorter the time factor the less detrimental the effect thereof on the maintenance of a stressed or oriented condi-tion of the material.
Of the conventional methods employed for the production of articles made from material which is biaxially oriented, perhaps the most popular and widely used prior art system involves the extrusion of a sheet from a slot die onto a roll, the temperature of the said roll being controlled, and then through a series of additional rolls ~hich first bring the sheet to an appropriate temperature level for orientation and then longitudinally stretch the sheet between tlYO rulls running at different speeds. This longi-tudinal stretching or drafting orients the material in the machine direction. ~he material with the longitudinal orientation is then passed onto a tenter frame to orient it transversely in a manner well-known in the art. Since con-ventional tentering involves large, heavy equipment, it is also necessary that temperatures be ma`intained in the sheeting through the use of large, expcnsive ovens. After the sheeting has been oriented both longitudinally and transversely, it is then rolled and stored for subsequent use.
The forming of OPS sheeting is usu~lly carried out on non-rotating thermoforming equipment with special provisions for the OPS material. It is necessary that the reheating of the sheetin~ as it is fed into the forming e~uipment be maintained uniformly througllout its width and length.
As the material reaches a satisfactory forming temperature, the stretches which have been imposed during the biaxial orientation must be resisted by ade~uate clamping devices in order to preclude the sheet from shrinking back to its original dimensions and losin~ the orientation therein.
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~ 33Z21 Since most non-rotary forming equipment is necessarily intermittent in its operation, the intermittent feeding of oriented sheet in such conventional forming equipment im-- poses inllerent difficulties in the creation and maintenance 5 of uniform temperature conditions throughout the forming area of the sheet~
There are several other approaches which ]-ave been used to some extent in the production of biaxially oriented sheeting. One of these, the bubble process 9 is typically 10 the way much thermoplastic film is produced. By proper control of temperature and stretching, it is possible to produce a biaxially oriented film or sheet using this bubble technique. However, in practice it is proven to be very critical because of temperature unifoTmity requirements.
15 Also this technique is not usable when it comes to thicker material such as that used in thermoformed articles or products on the ordeT of meat trays, containers and table-ware.
r Further, there is some equipment in use which simul-20 taneously stretches transversely and longitudinall)r. This equipment obviates the use of longitudinal stretching rolls e-g- those previously described, but it has certain disadvantages, namely, the amount of selvage which must be discarded due to the increased scalloped effect resulting 25 from clamps which are necessarily moved further apart in the longitudinal direction in order to achieve such a simultaneous biaxial stretching action.
The molecular orientation of thermoplastic materials, as previously indicated, results in significant improve-30 ments in many of the characteristics of certain of these materials. Biaxial orientation is essential in most packaging and disposable products. If orientation is only in one direction, even though properties may be substan-tially improved in tl-at direction, they are reduced in tl-e 35 other dimensions. Typical of products which are oriented in one direction only are monofilaments and fibers.
1133~21 During orientation~ the molecules in the materlal are shifted from random coil entanglement to a relative alignment parallel to principal axes of stretch. This results in significant improvements in physical properties, optical properties and in improved barrier properties and stress crack resistance.
For example, among the physical property improvements, the impact strength in materials, e.g., OPS, are improved on the order of ten times with two to three times the tensile strength of non-oriented polystyrene and as much as three times the improvement in yield elongation.
By a broad aspect of this invention, means are provided for continuously orienting and transferring a continuous web of thermoplastic material conformally onto the peri-pllery of a polygonal rotating mold from an extruder, the means comprising: web receiving and advancing means ingesting the web; web stretching means downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing same toward a polygonal rotary mold; and web transfer means mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rota-ting mold for receiving the laterally stretched web from the web stretch-ing means and conformally juxtaposing the stretched web with the peripheral , ~33~
surface of the rotating mold; at least one of the web receiving and advan-cing means and the web transfer means imparting a longltudinal stretch to the web to impart biaxial orientation thereto prior to its conformal juxta-position with the peripheral surface of the rotating mold.
By one variant, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differ-ent peripheral velocities to impart longitudinal stretch to the web.
By another variant, the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and the discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
By still another variant, the web transfer means comprises:
first, second and third roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation therein on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the oriented web therebetween.
By a further variant, the web receiving and advancing means com-prise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; the web transfer means comprising: first, second and third roller means mounted transversely of the web with the second roller commonly adja-cent the other rollers; and a common frame mounting the roller mcans for rotation therein on parallel axes of rotation with the first roller immedi--ately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the 113~
oriented web therebetween.
By still another variant, the web stretching means comprises a pair of rotating discs, each disc hav~ng peripherally disposed teeth engaging a respective edge of the web when first received therein and .he discs being divergently oriented in a downstream sense such that the ~eeth constrain the web to be stretched to a width commensurate with the diver-gence of the discs; the web transfer means comprising: first, second and third roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation therein on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition wiih the peripheral surface of the rotating mold ; with the oriented web therebetween.
By yet a further variant, the web receiving and advancing means comprise first and second loller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and the discs being divergently oriented - 20 in a down stream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs; and the web transfer means co~prises: first, second and `hird roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation there-in on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the oriented web therebetween.
By a variation thereof, the web transfer means is mounted !
1133~21 substantially independently of the web stretching means.
By another varlation, the web transfer means is mounted substan tlally independently of the web stretching means and the means further includes further means mounting the common frame for rotation on the axis of rotation of the first roller.
By still another aspect of this invention, means are provided for continuously manufacturing oriented thermoplastic molded articles from granulated and comminuted polystyrene material comprising: extruder means for assimilating raw thermoplastic material and extruding it into a strip;
charging means for providing granulated and comminuted thermoplastic material to the extruder means; regulating means controlling the By another aspect of this invention, means are provided for con-tinuously orienting and transferring a continuous web of thermoplastic material conformally onto the periphery of a polygonal rotating mold from an extruder, the means comprising: web receiving and advancing means ingesting the web; web stretching means downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing same toward a polygonal rotary mold; and web ; transfer means mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rotating mold for receiving the laterally stretched web from the web stretching means and conformally juxtaposing the stretched web with the peripheral surface of the rotating mold; at least one of the web receiving and advancing means and the web transfer means imparting a longitudinal stretch to the web to impart biaxial orientation thereto prior to its conformal juxtaposition with the peripheral surface of the rotating mold; the web transfer means comprising an odd number of three or more roller means _ g _ 32;~1 mounted transversely of the web with the roller means parallel and adjacent for receiving the web on the peripheral surfaces thereof in a serpentine path; a common frame mounting the roller means for rotation therein with an upstream roller means immediately adjacent the web stretching means and a downstream roller means in rolling juxtaposition with the peripheral surface of the rotating mold; and the remaining odd number of roller means being intermediate the upstream and downstream roller means for transpor-ting the oriented web therebetween in the serpentine path.
By one variant thereof, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web.
By another variant, the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received thérein and the discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
By still another variant, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; and the web stretching means comprises a pair of rotating discs~
each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and t11e discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
The above-identified parent application pr~vided a method which commenced with the continuous extrusion of a relatively narrow strip of thermoplastic material from a die at a relatively high linear speed and which is extruded ".:
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at the preferred orientation temperature. If the extruslon temperature is above the desired orientation temperature then it may be passed over cooling rolls in order to bring it do~n to the desired orientation tem-perature. The strip is then passed through differential speed rolls, if desired, to impart a predetermined maximum or partial amount of longitu-dinal or machine direction stretch orientation thereto and immediately subsequent to this orientation is passed into a transverse stretching station which consists basically of a pair of divergently disposed rotating saw blade-like devices which engage the strip along each edge and divide it into a series of increments which are then continuously separated trans-versely to a distance of approximately three times the original dimension of the extruded strip.
, 1133'~Zl Since the longitudinal direction is also desirably oriented by stretching on an order of ma~nitude of three times the original dimension, if this has not been achieved by the stretching rolls upstream from the trans-verse stretching mechanism, the balance of the longitudinal ` stretching may be taken care of downstream from the transverse stretching apparatus. All of the foregoing steps, however, are performed on a continuous and uninter-rupted basis. `
After the proper degree of orientation has been biaxially imparted to the extruded and now lengthened and widened strip of material, the material is continuously transferred onto the perimeter of a rotating polygon mold, each segment of ~hich contains a forming cavity and reten-tion devices to hold the stretched sheet to its new dimensions at the point of transfer.
The sheet is then thermoformed onto the mold cavities on the rotating polygon sequentially and is chilled against the mold surface below the distortion point of the oriented sheeting to thereby set the material and retain the orien--; tation therein.
Downstream from the rotating polygon mold device is a continuous and sequential severing apparatus which contin-uously and sequentially severs the formed articles from the selvage and then accumulates the articles for stac~ing and packaging while gathering the selvage for reuse. The selvage is reused by recycling it to the ra~ material processor which includes a device Ior admixing thermoplastic i pellets and chopped up selvage.
In order to enhance the operation and the quality control, the biaxial orientation equipment must be physically engaged, in some part, at its output point with the rotating polygon mold means and therefore, problems of inertial interaction bet~een these two devices have been noted. Novel means are provided herein forprecluding the full inertial effect ~ taking place and includes a structure which in fact minimizes, _ _ _ _ . .
, 11~3~21 to an optimum degree, the equipment inertia present at the mold-orientation equipment interface thereby to preclude uneven longitudinal stresses from being imparted to the material because of this inertialproblem at the interface.
In the accompanying drawings, Figure 1 is a schematic of a continuous extrusion, biaxial orien-tation and forming system wherein the extrudate is ext~uded at orientation temperature;
Figure 2 is another embodiment of another continuous system in which the extrudate is at a higher temperature than is considered optimum for orientation and in which a series of cooling rolls are provided for establishing the desirable orientation temperature downstream from the extruder;
Figure 3A is an enlarged schematic of the biaxial orientation apparatus of the system of .Figure 2 illustrating the several positions at which orientation can occur;
Figures 3B, 3C and 3D are schematic stretch diagrams showing the several modes of biaxial orientation of the extrude which is possible in correlation with the relative position of the extrudate in the orientation 20 apparatus of Figure 3A;
Figure 4 is a schematic of a low inertia e~odiment;
Figure 5A is a top pL~n schematic illustrating the transverse stretching blades used in a means set at maximum divergence;
Figure 5B is a top plan schematic illustrating the trc~nsverse stretching blades used in a means set at minimum divergence (mutually parallel); and Figure 6 is a top plan partial schematic of the embodl~ent of Figure 4.
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` 11~3Z21 Referring in detail to the drawings and with particular reference to Figure 1, an extruder 10 is illustrated as having an output to a die 12 which forms a narrow web 14 of polystyrene or other thermoplastic extrudate at a tempera-ture approximating the optimum temperature for subsequent biaxial orientation of the extrudate 14.
From tlle die 12, the web-like extrudate 14 is shown as .
passing over an input roller means 16, beneath a transverse stretcher blade assembly 18, and subsequently, over an out-put roller assembly Z0, the latter being juxtaposed with the periphery of a mold wheel assembly 22 which is of poly-gonal cross-sectional shape and which is rotated about a r central axis 22A. The web of extrudate 14 passes beneath 15 the mold wheel 22 which rotates clockwise as shown in the drawing. Each flat on the periphery of the mold wheel 22 r includes a mold cavity MC, a plurality of which are shown in dotted lines in Figure 1.
Suitable vacuum means or a combination of positive 20 pressure, vacuum and/or male die members are provided to cooperate with the mold cavities MC to form predetermined shapes corresponding to those initially imparted to the ~ .
.mold cavity in the web 14 and these products 24 are schematically shown in cross-section leaving the uppeTmost .
` 25 portion of the mold wheel 22 and passing in a reverse ; direction back over the extruder 10 as illustrated by the directional arrow 26.
The rotational velocity of the input roller assembly 16 relative to the transverse stretching blade assembly 18 may be set differentially to impart a longitudinal stretch or a machine direction stretch to the web 1~ and a similar differential rotational velocity between the peripheries Of r . the output roller assembly ~0 and the transverse stretcher blade assembly 18 may also be provided to impart additional machine direction stretch or orientation to the .leb 14.
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The transverse stretcher blade assembly 18 is best illustrated by joint reference to Figures 1, 5A and 5B in which the transverse stretcher blade assembly 18 is illus-trated as including first and second circular saw blades 18A and 18B, respectively, which are mounted on downstream pivots PA and PB, respectively, which in turn, are suitably - mounted by any well-known means on a machine frame such that the saw blades 18A and 18B are adjustable about the pivot means PA and PB between a maximum divergence of 45 to the machine direction or product center line illustrated - in Figures 5A and 5B as produce center line 14CL and which are driven about central blade axes by means of drive pulleys DA and DB which are also positioned for movement with the blades l8A and 18B about the said respective pivot means PA and PB.
The teeth 18T about the periphery of each blade engage the outermost edges of the web 14 and cause it to change from its initial extruded dimension at the input side of the blades to a much wider dimension commensurate with the 20 divergence at which the blades are set at the outyut side - I
thereof. In this manner, a transverse orientation is imparted to the web 14 in a continuous manner as it traverses the transverse orientation blade assembly 18 from the input roll assembly 16 to the output roll assembly 20.
In the schematic of Figure 1, the entire assembly of the input rollers 16, transverse orientation rollers 18 and ` output rollers 20 is a unitary structure mounted on a common vertical post which is schematically illustrated at 28 and whiçh post 28 is biased by suitable means 30 such that the output roller assembly 20 closely follo~s the peripheral contours of the polygon shaped mold IYheel 22.
As a result~ the oscillation of the vertical support ~8 about its center point 28C occurs as sho~Yn by the arcuate arrow 28D in Figure 1.
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Therefore, if the speed of the mold whcel 22 isincreased to a point where production speeds of a highly - .desirable level are obtainedJ the inertial forces in the ' combined integrated input-transverse orientation-output roll ¦' assembly 16-18-20 are such that the roller assembly 20 at the output will not properly follow the contour of the mold wheel 22 and will place uneven longitudinal stresses in the biaxially oriented material, resulting in inferior products I .
and in some cases, an improper alignment on the mold wheel.
; 10 22. This results, of course, in products which are inferior I
and which defy efforts to provide satisfactory quality control. At slower speeds, however, the continuity of the method and apparatus of Figure 1 provides a highly desirable I r process with high quality end products 24.
In the event that the'extruder 10 emits material from the die 12 which is at a higher temperature than the optimum one for imparting biaxial orientation to the material in the web 14, then the system schematically illustrated in Figure 2 is utilized to bring the extrudate web 14 down to the proper orientation'temperature. The-embodiment of Figure 2 also illustrates the use of another preferred . .
embodiment of input and output roller assemblies to impart~ I .
machine direction or longitudinal orientation to the extrudate web 14.
As illustrated in Figure 2, the e~truder 10 and the :
-j die 12 feed an extrudate web 14 first into a bank of cooling rolls CR whicll are provided, as is well-kno~n in the art, : with a suitable heat exchange medium and control therefor, '. or which simply provide the proper reach of web material 14 for ~ given temperature of extrusion to permit it to cool sufficiently in the ambient conditions of the process equipment, such that when it reaches the input roll assembly. .
16 it is at the proper t-mperature for ori~ntation.
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" 1133~1 The inl~ut roller assembly 16 is illustrated as including a first roller 16A and a second roller 16B which receives the web 14 in a serpentine path therebetween and which rolls lGA
` and 16B are driven at differential rotational velocities to impart a longitudinal or machine direction orientation or stretch to the web 14 prior to the engagement of the said web 14 with the teeth 18T of the transverse stretcher blade ' assembly 18.
Similarly to the input roller assembly 16, the output roll assembly 20 is shown as comprising first and second output rolls 20A and 20B extending downstream, in that order, from the transverse blade assembly 18 and which further includes the concept of driving these rollers at selectively differential rotational velocities to impart further longi-tudinal stretch, if desired, to the web 14 downstream of andsubsequent to the impartation of transverse orientation thereto. The downstream output roller 20B is engaged with the periphery of the polygon mold wheel ~2 such that in its rotation about the center 22A, the oriented web material 14 will be immediately placed upon the periphery of the mold wheel 22, the latter being provided with suitable gripping means e-~- . serrations, vacuum ori-fices or the like, schematically shown as upstanding teeth 22T on one of the ; flats of the mold wheel 22 for piercing OT otherwise securely engaging theweb to hold it against a relaxation of-the imparted orientation therein during the molding process - on the periphery of the mold wheel 22.
As in Figure 1, the web 14 is shown leaving the mold wheel 22 with formed products 24 therein heading back towa,rds the direction of the extruder 10.
In this context, re~erence is now made to Figure 4 in which the molded products 24 travelling in the return direction 26 are delivered tn ~ cutter means 32 which scvers the molded products 24 from the selvage of the web 14 and causes the - severed products 24 to be stacked in a suitable product stack 24S which is schematically sho-~n in Figure 4.
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While the severed products travel to a stack 24S, the selvage 14S travels to a selvage recycling means 34 which cooperates with a source of new plastic granules or pellets ;i - 36 to place both reground selvage and the pellets 36 into a mixer assembly 38 of a type well-known in the art to redirect both fresh raw material and recycled selvage into the extruder 10.
Figure 4 also includes a low inertia embodiment apparatus ; which will be m,ore fully described ata later ~*~r point herein. For the present, the foregoing des-`~ cription of Figure 4 is to illustrate that the recycling of the selvage after separation of the selvage 14S from the products 14 is a com,mon feature ofall of preferred embodiments and is to be considered as included in the description of the embodi-ments of Figures 1 and 2.
In order to fully explain at this point in time the orientation process in the biaxial mode, reference is now -made to Figures 3A, 35B, 3C and 3D, with Figure 3A being an enlarged partial schematic.of the biaxial orientation portion of Figure 2.
. In practice, the longitudinal stretching or machine direction stretching or orientation can be carried out immediately before or immediately after the transverse stretching or half before or half after the said trans-verse stretching. Furthermore, an~ other ratio of initial machine direction stretch and final machine direction stretch is also feasible. The degree of transverse or longitudinal orientation can be varied to suit a particular pro~uct which may have depth or shape re~uiring less initial orientation of the sheetin~ in one or another direction. Therefore, a system is provided which is very facile and variable with regard to uniqueand unusual molded shapes.
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The amDunt of selvage which falls outside of the transverse stretcher blades 18A and 18B is the same as that amount of selvage which falls outside of the holding devices 22T about the periphery of the mold wheel 22. These holding de~ices 22T, as ; illustrated, for example, in Figure 6, are along both peripheral edges of the mold wheel 22 which is shown in partial top-plan ~iew in Figure 6.
In practice, the holding devices or gripping devices 22T about the periphery of the mold wlleel can be made effective on the mold wheel station where the web 14 is initially engaged and where molding initially takes place and can be deactivated or rendered ineffective on the stripping or molded product removal side or stations of the mold wlleel polygon 22 such that the strip~ing of the finished products 24 and selvage 14S from the mold wheel 22 is facilitated.
In Figures 3A - 3D, the zone subtended in the web 14 by the transverse stretcher assembly 18 is identified as a transverse stretching zone TS which is preceeded on the upstream side by a machine stretch zone MSl and on the do~n-stream side by a machine stretch zone MS2.
Referring now to Figure 3B, it can be seen that all of the machine orientation or longitudinal st~etch has been effectuated in the zone MS2 as indicated by the wider spacing between the edge adjacent dots 14I whic~l are uti-lized to designate equal increments of unbiased web 14 in the initial spacing shown in the zone MSl of Figure 3B
which is a totally unoriented configuration and spacing.
This spacing is incremental in both the longitudinal and transverse directions of the web, i.e., the dots 14I
define biaxial increments of the web 14.
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li33Z21 Referring next to Figure 3C, it can be seen that the rota~ional velocity of the transverse stretcher blades 18A
is such that the web travels faster in the transverse stretching zone TS and therefoTe has imparted to it both transverse and longitudinal stretch and has no additional longitudinal stretch imparted to it in the downstream or second machine stretch zone MS2. The zone MSl upstream of the transverse stretching zone TS illustrates no biaxial orientation upstream of the transverse zone TS.
Referring next to Figure 3D, it can be seen that in the - initial upstream zone MSl that no biaxial orientation is imparted to the web 14, that in the zone TS both transverse and partial machine direction stretch are imparted to the web 14 and in downstream zone MS2 additional longitudinal or machine direction stretch is imparted to the web 14.
The foregoing clearly illustrates the wide variety of lon~itudinal and t~ansverse stretch modes which can be effectuated. In all cases, of ~ course, the tTansverse stretcnlng lS achleved withln tne zone TS and not within the upstream and downstream zones MSl and MS2, respectively.
If in the zone MSl in either of the foregoing diagrams of Figures 3B, 3C or 3D, the dots 14I in the upstream zone MSl were to vary in spacing longitudinally of the web 14, then that would be indicative of a differential peripheral velocity of the rollers 16A and 16B which would impar~
machine direction stretch to the web 14 in the upstream zone MSl.
Referring further to Figure 3A, the diameter of the rolls 16A, 16B, 20A and 20B are kept as small as is consis-tent with minimizing the deflection of these rolls under load. Also, the distance between the rolls in the respec-tive Toll pairs 16 and 20 is preferably no greater than to allow for slight clearance of the web or extrudate 14 which minimizes the shrinkback which otherwise occurs as the material is transferred from one roll to another.
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The surface speed of the second roll 16B is usually L
faster than the surface speed of the first roll 16Aso as to achieve longitudinal stretch in the upstream area MSl and preferably, the. surface speed of the roller 16Bas compared to that of the roller 16Ais such that 50% of the longitudinal or machine direction orientation occurs in the transfer of material from the Toller 16A onto the roller 16B.
Also, as shown in Figure 3A, the teeth 18T on the trans-verse stretcher blade 18A are very close to the surface of the second roller 16B and the perimeter speed of the blades is preferably slightly faster than the surface speed of the roller 16B thereby making the transfer of material from one to the other more effective. The teeth 18T actually pene-15 trate the edge of the web or strip 14 so as to hold the material securely as transverse stretching takes place due to the angular orientation of the blades 18A and 18B, the latter being best shown with reference to Figures 5A and 5B.
The third or initial output rolleT 20A is also posi-tioned very close to thé teeth 18T of the blades 18A and 18B
so as to minimize shrinkback at this particular transfer point comprised by the interface between the said roll 20A
and the blades 18A and 18B. The surface speed of the roller 20A is usually and preferably slightly faster than the perimeter speed of the transverse stretching blades 18A and 18B and the fourth roller 20B is maintained close to the t]lird roller 20A in order to minimi~e shrinXback during the transfer from one roller to another. Usually, the`
fourth roll 20B is run faster than the third roller 20A ~ith the preferred speed being such as to accomplish the remain-ing 50% of the longitudinal or machine direction oricntation in the web 14. The web 14, as it leaves the fourth or interfacing roller 20B onto the mold wheel 22,isthus fully biax~ally oriented.
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~33221 As disclosed with reference to Figures 1 and 2, the entire orientation device 16-18-20 in the particular embodiments of Figures 1, 2 and 3A is pivoted about the pivot points 28C and a suitable means 30. e-g- a spring schematically shown in Fgiure 1 or a pneumatic cylinder schematically shown in Figure 2 is provided to bias the final output or interfacing roller 20B against ~he peri-pheral shoulders of the mold wheel 22 such that the teeth 22T on the mold l~heel will avoid contact with the roller surface~ but will penetrate and retain the web 14 in its biaxially oriented condition over each face of the mold wheel 22 such that a uniform web is presented to each mold cavity ~5C therein.
All of the longitudinal stretching rollers 16A, 16B,, , 20A a,nd 20B,are,preferably coated with fluorocarbon e-g- that known by the Trade Mark TEFLON to avoid sticking of the web 14 thereto- Also such rollers are usually made with thin-walled steel tubes in order to minimize the heat retention capacity and heat transfer to the ends of the rollers. Therefore, in the area of contact with the web 14, the rolls reach about the same temperature as that of the web itself.
A low inertia orientation apparatus will now be described with further reference to Fig~s 4, 5A,5B and 6.
In this embodiment, the output rollers 20 of the previous embodiments are replaced by an output roller set 120 which is comprised of three rollers 120A, 120B and 120C mounted on a common frame 120D which is biased by suitable means 120E to~ard the mold wheel 22 SUC]I that the fi~al output or interfacing roller 120C is engagcd ~ith the mold wheel 22 in a manner similar to that of the final roller 20B in the previous embodimcnts.
The biasing means 120E can be any suitable dcvice such as a compression spring or a pneumatic spring or cylinder such as already described in reference to the embodiments of Figure 1 and Figure 2, res~ectively.
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The common support 120D for the downstream output roller set 120 is pivoted on the center line of the upstream roller 120A of that set and the transverse stretching saw blades 18 and the inpùt stretch rolls 16 are fixedly mounted in the embodiments of Figures 4 and 6 as opposed to being mounted for movement about a central point 28C such as previously described in Figures 1 and 2.
Thus, only the inertia of the three output stretching and interface rollers 120A - 120C and the frame 120D on which these are mounted is involved in the interfacing of the biaxially oriented web 14 and the undulating peripheral surface of the rotating mold polygon 22. Through the use of three rollers, disproportionate elongation due to oscilla-tion is avoided and a more uniformly elongated web 14 will result than would result with the use of two rollers. The gap between the three rollers 120A - 120C is kept very small to avoid shrinkbac~ of the now biaxially oriented ~eb traversing these rolls. Because the inertia of this particular output stretch and interface roll means has been minimi~ed, the mass and inertia of the remaining portions of the biaxial orientation equipment is not critical.
The drive means DA and DB on the transverse stretch saw blades 18A adn 18B, respectively, and the nearest rollers thereto, namely, the upstream interface roller 16B and the downstream initial roller 120A are all driven preferably from a common drive motor through various drive belts or chains and the rollers 16B and 120A are illustrated in Figure 6 as being driven by a common drive belt DC ~.hich engages drive pulleys or sl~rockets Sl and S2 mounted on the shafts of the rollers 120A and 16B, respectively.
Further, the roller 16B includes a passive output gearing Gl ~hick is engaged l~lith compatible gearing ~of a predetermined ratio) G2 mounted on the shaft of the initial input roller 16A such that the differential speed bet~.~een the rollers 16A and 16B can be effectuated from the same common drive means DC that drives both the rollers 16B
and 120A.
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~ hus,the ratio of the gears Gl and G2 can be cllanged to vary the amount of longitudinal stretch achieved between the initial input rollers 16A and-16B.
The last two rolls 120B an~l 120C on the downstream side of the transverse stretcher blades 18 are not driven from the stretcher apparatus. The last output or interface roll 120C is driven by the surface speed of the mold wheel or polygon 22 with which it is in contact and this speed is established and selected to provide the proper longitudinal orientation when measured against the fixed speed of the initial output Toll 120A. The middle roll 120B of the output roller group 120 merely idles and reaches a speed in between that of the toher two rolls 120A and 120C of the set 120.
-In order to maintain a constant dimensional relation-ship between the transverse stretch saw blades 18A and 18B
and the initial output roller 120A, the blades 18A and 18B
are pivoted at their downstream edge on the pivots PA and PB, respectively, rather than at the centeT of the said blades 18A and 18B. Therefore, the relationship between these blades 18A and 18B and the output roller 120A remains constant during adjustment of the blades between a direction parallel to the machine direction oriented at 45 with respect to the machine direction.
The second roller 16B and its companion input roll 16A
in the input stretch roll set 16 move in and out to adjust to the position of the transverse stretch saw blades 18A
and 18B depending upon the adjusted position Gf the latteT.
Suitable stop means or bosses are provided on the saw blade adj~stment brackets to interact wi~h the mounting of the various input rollers 16A and 16B to preclude ~engagement of the rolls with the saw blade but maintaining the desired immediate proximity thereof.
- 1133;Z2i The material tension of the web 14 proceeding beneath the roller 16A back over the roller 16B and thence beneath the sa~ blades 18A and 18B is sufficient, since the web 14 initially approaches thé roll 16A from above, to cause the roll 16A to track the movements of the roll 16B and thereby maintain the desired minimum spacing by way of the material tension in the web 14.
Suitable means are also provided within the mounting bracket 120D of the output roll set 120 to provide for moving the three rollers 120A, 120B and 120C apart and bac~
together again to provide for the threading of material - therethrough at the beginning of an extrusion and orientation and molding cycle and then placing the rollers under a suffi-cient bias to provide a predetermined minimum spacing and pressure thereon such as by small air cylinders or the like, all of which is within the purview of one-o ordinary skill in the art.
If the molded products 24 are desired to be nine inch plates having a material thickness on the order of~.010 inches, a stretch ratio of 3 to 1 is established for both the transverse and longitudinal oTientation of the web 14, by way of an exemplary process parameter. In this case, the die opening would be on the order f 0 090 inches of web thickness and 3 inches inwidth plus perhaps a one-quarter inch allowance for selvage. The polystyrene resin which is to be converted to OPS resin would be extruded at preferably, 425F. The extrudate would be cooled to 280F by the cooling rools CR before entering the initial rollers 16A and 16B of the stretcher apparatus of an aspect of the present invention.
At an output rate of approximately 600 pounds of ~eb material per hour, the speed of the extrudate~would be 90 feet per minute before entering the initial rolls 16 of the stretcher assembly and ~ 270 feet per minute 3s leaving the last or interfacing roller 120C of the stretchcr assembly. This 270 foot per minute speed would match the speed of the mold surface or mold polygon 22.
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~133221 Fifty percent of the longitudinal orientation in the web 14 would yrobably be accomplished between the rollers 16A and 16B, all of the transverse orientation between the transverse stretcher blades 18A and 18B and the remaining 50% of the longitudinal orientation established between the roll 120A at the input of the group 120 and the roll 120C
interfacing the biaxially oriented web material with the mold polygon 22.
The mold polygon or mold wheel 22, for example, might have 15 mold cavities MC and would be in that event, four feet in diameter. The ratio of selvage to finished product would be - 50-50. The plate 24 would weight ~ 10 grams and 324 plates per minute would be produced at a mold wheel speed of 21rpm.
In achieving the transverse orientation with the blades 18A and 18B, these blades would be gapped at three and one-eighth inches on their upstream side and nine and three-eighth inches on their downstream side to effectuate the three for one transverse stretch desired.
Accordingly it can be seen that a continuous ~eth~d with a relatively high speed of production and high qualit~
control with a low~inertia apparatus is readily effectuated by the embodiments of Figures 4, 5A, 5B and 6.
minimized variables because extended heat history can materially affect the properties of an end product. In the case of OPS, for example, the temperature at which the r 5 material must be oriented represents a compromise between levels which are best from a flow point of view and levels which are best from a stress (orientation) point of view. L
Once a stress is imposed at a given temperature, for example, a molecular orientation is achieved. However, the 10 longer the increment of time involved between the achieve- _ ment of that orientation and a subsequent operation, the more stress (orientation) will again be relaxed. According-ly, the degree of orientation of a particular material is not necessarily a sole function of the amount of heat 15 stretching applied to that material to create the orienta-tion since relaxation of that orientation may simultaneously be taking place.
Therefore, a high speed, integrated approach is unique and important not only from a standpoint of cost but also l ~
20 from the standpoint of results heretofore not otherwise .
attainable.
These inherent advantages of a high speed integrated ~
approach are important in relatively thin products , e.g. l ;-those with wall thicknesses of ~005 too.010 inches and 25 become increasingly significant with products having wall thicknesses greater thano.010 inches. This is due to the fact that conventional systems as heretofore defined, necessarily involve not only greater time/temperature exposure during the production of heating from which the 30 ultimate products are formed, but also involve the reheating and subsequent recooling of the sheet during the subsequent forming operation. Accordingly, the relief of stress occurs .
during reheating and subsequent recooling as well as during a possible relaxation during the production of the sheeting _ 35 per se.
_ il33Z2~
Theoretically, the ideal method would be to bia~ially orient the thermoplastic material, form and cook it simultaneously. In conventional systems, the time factor is significant and therefore detrimental. Accordingly, the shorter the time factor the less detrimental the effect thereof on the maintenance of a stressed or oriented condi-tion of the material.
Of the conventional methods employed for the production of articles made from material which is biaxially oriented, perhaps the most popular and widely used prior art system involves the extrusion of a sheet from a slot die onto a roll, the temperature of the said roll being controlled, and then through a series of additional rolls ~hich first bring the sheet to an appropriate temperature level for orientation and then longitudinally stretch the sheet between tlYO rulls running at different speeds. This longi-tudinal stretching or drafting orients the material in the machine direction. ~he material with the longitudinal orientation is then passed onto a tenter frame to orient it transversely in a manner well-known in the art. Since con-ventional tentering involves large, heavy equipment, it is also necessary that temperatures be ma`intained in the sheeting through the use of large, expcnsive ovens. After the sheeting has been oriented both longitudinally and transversely, it is then rolled and stored for subsequent use.
The forming of OPS sheeting is usu~lly carried out on non-rotating thermoforming equipment with special provisions for the OPS material. It is necessary that the reheating of the sheetin~ as it is fed into the forming e~uipment be maintained uniformly througllout its width and length.
As the material reaches a satisfactory forming temperature, the stretches which have been imposed during the biaxial orientation must be resisted by ade~uate clamping devices in order to preclude the sheet from shrinking back to its original dimensions and losin~ the orientation therein.
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~ 33Z21 Since most non-rotary forming equipment is necessarily intermittent in its operation, the intermittent feeding of oriented sheet in such conventional forming equipment im-- poses inllerent difficulties in the creation and maintenance 5 of uniform temperature conditions throughout the forming area of the sheet~
There are several other approaches which ]-ave been used to some extent in the production of biaxially oriented sheeting. One of these, the bubble process 9 is typically 10 the way much thermoplastic film is produced. By proper control of temperature and stretching, it is possible to produce a biaxially oriented film or sheet using this bubble technique. However, in practice it is proven to be very critical because of temperature unifoTmity requirements.
15 Also this technique is not usable when it comes to thicker material such as that used in thermoformed articles or products on the ordeT of meat trays, containers and table-ware.
r Further, there is some equipment in use which simul-20 taneously stretches transversely and longitudinall)r. This equipment obviates the use of longitudinal stretching rolls e-g- those previously described, but it has certain disadvantages, namely, the amount of selvage which must be discarded due to the increased scalloped effect resulting 25 from clamps which are necessarily moved further apart in the longitudinal direction in order to achieve such a simultaneous biaxial stretching action.
The molecular orientation of thermoplastic materials, as previously indicated, results in significant improve-30 ments in many of the characteristics of certain of these materials. Biaxial orientation is essential in most packaging and disposable products. If orientation is only in one direction, even though properties may be substan-tially improved in tl-at direction, they are reduced in tl-e 35 other dimensions. Typical of products which are oriented in one direction only are monofilaments and fibers.
1133~21 During orientation~ the molecules in the materlal are shifted from random coil entanglement to a relative alignment parallel to principal axes of stretch. This results in significant improvements in physical properties, optical properties and in improved barrier properties and stress crack resistance.
For example, among the physical property improvements, the impact strength in materials, e.g., OPS, are improved on the order of ten times with two to three times the tensile strength of non-oriented polystyrene and as much as three times the improvement in yield elongation.
By a broad aspect of this invention, means are provided for continuously orienting and transferring a continuous web of thermoplastic material conformally onto the peri-pllery of a polygonal rotating mold from an extruder, the means comprising: web receiving and advancing means ingesting the web; web stretching means downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing same toward a polygonal rotary mold; and web transfer means mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rota-ting mold for receiving the laterally stretched web from the web stretch-ing means and conformally juxtaposing the stretched web with the peripheral , ~33~
surface of the rotating mold; at least one of the web receiving and advan-cing means and the web transfer means imparting a longltudinal stretch to the web to impart biaxial orientation thereto prior to its conformal juxta-position with the peripheral surface of the rotating mold.
By one variant, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differ-ent peripheral velocities to impart longitudinal stretch to the web.
By another variant, the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and the discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
By still another variant, the web transfer means comprises:
first, second and third roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation therein on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the oriented web therebetween.
By a further variant, the web receiving and advancing means com-prise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; the web transfer means comprising: first, second and third roller means mounted transversely of the web with the second roller commonly adja-cent the other rollers; and a common frame mounting the roller mcans for rotation therein on parallel axes of rotation with the first roller immedi--ately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the 113~
oriented web therebetween.
By still another variant, the web stretching means comprises a pair of rotating discs, each disc hav~ng peripherally disposed teeth engaging a respective edge of the web when first received therein and .he discs being divergently oriented in a downstream sense such that the ~eeth constrain the web to be stretched to a width commensurate with the diver-gence of the discs; the web transfer means comprising: first, second and third roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation therein on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition wiih the peripheral surface of the rotating mold ; with the oriented web therebetween.
By yet a further variant, the web receiving and advancing means comprise first and second loller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and the discs being divergently oriented - 20 in a down stream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs; and the web transfer means co~prises: first, second and `hird roller means mounted transversely of the web with the second roller commonly adjacent the other rollers; and a common frame mounting the roller means for rotation there-in on parallel axes of rotation with the first roller immediately adjacent the web stretching means and the third roller in rolling juxtaposition with the peripheral surface of the rotating mold with the oriented web therebetween.
By a variation thereof, the web transfer means is mounted !
1133~21 substantially independently of the web stretching means.
By another varlation, the web transfer means is mounted substan tlally independently of the web stretching means and the means further includes further means mounting the common frame for rotation on the axis of rotation of the first roller.
By still another aspect of this invention, means are provided for continuously manufacturing oriented thermoplastic molded articles from granulated and comminuted polystyrene material comprising: extruder means for assimilating raw thermoplastic material and extruding it into a strip;
charging means for providing granulated and comminuted thermoplastic material to the extruder means; regulating means controlling the By another aspect of this invention, means are provided for con-tinuously orienting and transferring a continuous web of thermoplastic material conformally onto the periphery of a polygonal rotating mold from an extruder, the means comprising: web receiving and advancing means ingesting the web; web stretching means downstream of the web receiving means for next receiving the web and imparting at least a lateral stretch to the web and advancing same toward a polygonal rotary mold; and web ; transfer means mounted immediately downstream from the web stretching means in peripheral surface following relationship with the polygonal rotating mold for receiving the laterally stretched web from the web stretching means and conformally juxtaposing the stretched web with the peripheral surface of the rotating mold; at least one of the web receiving and advancing means and the web transfer means imparting a longitudinal stretch to the web to impart biaxial orientation thereto prior to its conformal juxtaposition with the peripheral surface of the rotating mold; the web transfer means comprising an odd number of three or more roller means _ g _ 32;~1 mounted transversely of the web with the roller means parallel and adjacent for receiving the web on the peripheral surfaces thereof in a serpentine path; a common frame mounting the roller means for rotation therein with an upstream roller means immediately adjacent the web stretching means and a downstream roller means in rolling juxtaposition with the peripheral surface of the rotating mold; and the remaining odd number of roller means being intermediate the upstream and downstream roller means for transpor-ting the oriented web therebetween in the serpentine path.
By one variant thereof, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web.
By another variant, the web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of the web when first received thérein and the discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
By still another variant, the web receiving and advancing means comprise first and second roller means and means driving the roller means at differential peripheral velocities to impart longitudinal stretch to the web; and the web stretching means comprises a pair of rotating discs~
each disc having peripherally disposed teeth engaging a respective edge of the web when first received therein and t11e discs being divergently oriented in a downstream sense such that the teeth constrain the web to be stretched to a width commensurate with the divergence of the discs.
The above-identified parent application pr~vided a method which commenced with the continuous extrusion of a relatively narrow strip of thermoplastic material from a die at a relatively high linear speed and which is extruded ".:
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at the preferred orientation temperature. If the extruslon temperature is above the desired orientation temperature then it may be passed over cooling rolls in order to bring it do~n to the desired orientation tem-perature. The strip is then passed through differential speed rolls, if desired, to impart a predetermined maximum or partial amount of longitu-dinal or machine direction stretch orientation thereto and immediately subsequent to this orientation is passed into a transverse stretching station which consists basically of a pair of divergently disposed rotating saw blade-like devices which engage the strip along each edge and divide it into a series of increments which are then continuously separated trans-versely to a distance of approximately three times the original dimension of the extruded strip.
, 1133'~Zl Since the longitudinal direction is also desirably oriented by stretching on an order of ma~nitude of three times the original dimension, if this has not been achieved by the stretching rolls upstream from the trans-verse stretching mechanism, the balance of the longitudinal ` stretching may be taken care of downstream from the transverse stretching apparatus. All of the foregoing steps, however, are performed on a continuous and uninter-rupted basis. `
After the proper degree of orientation has been biaxially imparted to the extruded and now lengthened and widened strip of material, the material is continuously transferred onto the perimeter of a rotating polygon mold, each segment of ~hich contains a forming cavity and reten-tion devices to hold the stretched sheet to its new dimensions at the point of transfer.
The sheet is then thermoformed onto the mold cavities on the rotating polygon sequentially and is chilled against the mold surface below the distortion point of the oriented sheeting to thereby set the material and retain the orien--; tation therein.
Downstream from the rotating polygon mold device is a continuous and sequential severing apparatus which contin-uously and sequentially severs the formed articles from the selvage and then accumulates the articles for stac~ing and packaging while gathering the selvage for reuse. The selvage is reused by recycling it to the ra~ material processor which includes a device Ior admixing thermoplastic i pellets and chopped up selvage.
In order to enhance the operation and the quality control, the biaxial orientation equipment must be physically engaged, in some part, at its output point with the rotating polygon mold means and therefore, problems of inertial interaction bet~een these two devices have been noted. Novel means are provided herein forprecluding the full inertial effect ~ taking place and includes a structure which in fact minimizes, _ _ _ _ . .
, 11~3~21 to an optimum degree, the equipment inertia present at the mold-orientation equipment interface thereby to preclude uneven longitudinal stresses from being imparted to the material because of this inertialproblem at the interface.
In the accompanying drawings, Figure 1 is a schematic of a continuous extrusion, biaxial orien-tation and forming system wherein the extrudate is ext~uded at orientation temperature;
Figure 2 is another embodiment of another continuous system in which the extrudate is at a higher temperature than is considered optimum for orientation and in which a series of cooling rolls are provided for establishing the desirable orientation temperature downstream from the extruder;
Figure 3A is an enlarged schematic of the biaxial orientation apparatus of the system of .Figure 2 illustrating the several positions at which orientation can occur;
Figures 3B, 3C and 3D are schematic stretch diagrams showing the several modes of biaxial orientation of the extrude which is possible in correlation with the relative position of the extrudate in the orientation 20 apparatus of Figure 3A;
Figure 4 is a schematic of a low inertia e~odiment;
Figure 5A is a top pL~n schematic illustrating the transverse stretching blades used in a means set at maximum divergence;
Figure 5B is a top plan schematic illustrating the trc~nsverse stretching blades used in a means set at minimum divergence (mutually parallel); and Figure 6 is a top plan partial schematic of the embodl~ent of Figure 4.
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` 11~3Z21 Referring in detail to the drawings and with particular reference to Figure 1, an extruder 10 is illustrated as having an output to a die 12 which forms a narrow web 14 of polystyrene or other thermoplastic extrudate at a tempera-ture approximating the optimum temperature for subsequent biaxial orientation of the extrudate 14.
From tlle die 12, the web-like extrudate 14 is shown as .
passing over an input roller means 16, beneath a transverse stretcher blade assembly 18, and subsequently, over an out-put roller assembly Z0, the latter being juxtaposed with the periphery of a mold wheel assembly 22 which is of poly-gonal cross-sectional shape and which is rotated about a r central axis 22A. The web of extrudate 14 passes beneath 15 the mold wheel 22 which rotates clockwise as shown in the drawing. Each flat on the periphery of the mold wheel 22 r includes a mold cavity MC, a plurality of which are shown in dotted lines in Figure 1.
Suitable vacuum means or a combination of positive 20 pressure, vacuum and/or male die members are provided to cooperate with the mold cavities MC to form predetermined shapes corresponding to those initially imparted to the ~ .
.mold cavity in the web 14 and these products 24 are schematically shown in cross-section leaving the uppeTmost .
` 25 portion of the mold wheel 22 and passing in a reverse ; direction back over the extruder 10 as illustrated by the directional arrow 26.
The rotational velocity of the input roller assembly 16 relative to the transverse stretching blade assembly 18 may be set differentially to impart a longitudinal stretch or a machine direction stretch to the web 1~ and a similar differential rotational velocity between the peripheries Of r . the output roller assembly ~0 and the transverse stretcher blade assembly 18 may also be provided to impart additional machine direction stretch or orientation to the .leb 14.
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The transverse stretcher blade assembly 18 is best illustrated by joint reference to Figures 1, 5A and 5B in which the transverse stretcher blade assembly 18 is illus-trated as including first and second circular saw blades 18A and 18B, respectively, which are mounted on downstream pivots PA and PB, respectively, which in turn, are suitably - mounted by any well-known means on a machine frame such that the saw blades 18A and 18B are adjustable about the pivot means PA and PB between a maximum divergence of 45 to the machine direction or product center line illustrated - in Figures 5A and 5B as produce center line 14CL and which are driven about central blade axes by means of drive pulleys DA and DB which are also positioned for movement with the blades l8A and 18B about the said respective pivot means PA and PB.
The teeth 18T about the periphery of each blade engage the outermost edges of the web 14 and cause it to change from its initial extruded dimension at the input side of the blades to a much wider dimension commensurate with the 20 divergence at which the blades are set at the outyut side - I
thereof. In this manner, a transverse orientation is imparted to the web 14 in a continuous manner as it traverses the transverse orientation blade assembly 18 from the input roll assembly 16 to the output roll assembly 20.
In the schematic of Figure 1, the entire assembly of the input rollers 16, transverse orientation rollers 18 and ` output rollers 20 is a unitary structure mounted on a common vertical post which is schematically illustrated at 28 and whiçh post 28 is biased by suitable means 30 such that the output roller assembly 20 closely follo~s the peripheral contours of the polygon shaped mold IYheel 22.
As a result~ the oscillation of the vertical support ~8 about its center point 28C occurs as sho~Yn by the arcuate arrow 28D in Figure 1.
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Therefore, if the speed of the mold whcel 22 isincreased to a point where production speeds of a highly - .desirable level are obtainedJ the inertial forces in the ' combined integrated input-transverse orientation-output roll ¦' assembly 16-18-20 are such that the roller assembly 20 at the output will not properly follow the contour of the mold wheel 22 and will place uneven longitudinal stresses in the biaxially oriented material, resulting in inferior products I .
and in some cases, an improper alignment on the mold wheel.
; 10 22. This results, of course, in products which are inferior I
and which defy efforts to provide satisfactory quality control. At slower speeds, however, the continuity of the method and apparatus of Figure 1 provides a highly desirable I r process with high quality end products 24.
In the event that the'extruder 10 emits material from the die 12 which is at a higher temperature than the optimum one for imparting biaxial orientation to the material in the web 14, then the system schematically illustrated in Figure 2 is utilized to bring the extrudate web 14 down to the proper orientation'temperature. The-embodiment of Figure 2 also illustrates the use of another preferred . .
embodiment of input and output roller assemblies to impart~ I .
machine direction or longitudinal orientation to the extrudate web 14.
As illustrated in Figure 2, the e~truder 10 and the :
-j die 12 feed an extrudate web 14 first into a bank of cooling rolls CR whicll are provided, as is well-kno~n in the art, : with a suitable heat exchange medium and control therefor, '. or which simply provide the proper reach of web material 14 for ~ given temperature of extrusion to permit it to cool sufficiently in the ambient conditions of the process equipment, such that when it reaches the input roll assembly. .
16 it is at the proper t-mperature for ori~ntation.
' - 16 -_ . . . . . .......... . ..... . . . . . . . . . . . .
, - : ;
" 1133~1 The inl~ut roller assembly 16 is illustrated as including a first roller 16A and a second roller 16B which receives the web 14 in a serpentine path therebetween and which rolls lGA
` and 16B are driven at differential rotational velocities to impart a longitudinal or machine direction orientation or stretch to the web 14 prior to the engagement of the said web 14 with the teeth 18T of the transverse stretcher blade ' assembly 18.
Similarly to the input roller assembly 16, the output roll assembly 20 is shown as comprising first and second output rolls 20A and 20B extending downstream, in that order, from the transverse blade assembly 18 and which further includes the concept of driving these rollers at selectively differential rotational velocities to impart further longi-tudinal stretch, if desired, to the web 14 downstream of andsubsequent to the impartation of transverse orientation thereto. The downstream output roller 20B is engaged with the periphery of the polygon mold wheel ~2 such that in its rotation about the center 22A, the oriented web material 14 will be immediately placed upon the periphery of the mold wheel 22, the latter being provided with suitable gripping means e-~- . serrations, vacuum ori-fices or the like, schematically shown as upstanding teeth 22T on one of the ; flats of the mold wheel 22 for piercing OT otherwise securely engaging theweb to hold it against a relaxation of-the imparted orientation therein during the molding process - on the periphery of the mold wheel 22.
As in Figure 1, the web 14 is shown leaving the mold wheel 22 with formed products 24 therein heading back towa,rds the direction of the extruder 10.
In this context, re~erence is now made to Figure 4 in which the molded products 24 travelling in the return direction 26 are delivered tn ~ cutter means 32 which scvers the molded products 24 from the selvage of the web 14 and causes the - severed products 24 to be stacked in a suitable product stack 24S which is schematically sho-~n in Figure 4.
:
~ .
~133ZZ~
While the severed products travel to a stack 24S, the selvage 14S travels to a selvage recycling means 34 which cooperates with a source of new plastic granules or pellets ;i - 36 to place both reground selvage and the pellets 36 into a mixer assembly 38 of a type well-known in the art to redirect both fresh raw material and recycled selvage into the extruder 10.
Figure 4 also includes a low inertia embodiment apparatus ; which will be m,ore fully described ata later ~*~r point herein. For the present, the foregoing des-`~ cription of Figure 4 is to illustrate that the recycling of the selvage after separation of the selvage 14S from the products 14 is a com,mon feature ofall of preferred embodiments and is to be considered as included in the description of the embodi-ments of Figures 1 and 2.
In order to fully explain at this point in time the orientation process in the biaxial mode, reference is now -made to Figures 3A, 35B, 3C and 3D, with Figure 3A being an enlarged partial schematic.of the biaxial orientation portion of Figure 2.
. In practice, the longitudinal stretching or machine direction stretching or orientation can be carried out immediately before or immediately after the transverse stretching or half before or half after the said trans-verse stretching. Furthermore, an~ other ratio of initial machine direction stretch and final machine direction stretch is also feasible. The degree of transverse or longitudinal orientation can be varied to suit a particular pro~uct which may have depth or shape re~uiring less initial orientation of the sheetin~ in one or another direction. Therefore, a system is provided which is very facile and variable with regard to uniqueand unusual molded shapes.
-:: . J
` -' 1~33Z ~
The amDunt of selvage which falls outside of the transverse stretcher blades 18A and 18B is the same as that amount of selvage which falls outside of the holding devices 22T about the periphery of the mold wheel 22. These holding de~ices 22T, as ; illustrated, for example, in Figure 6, are along both peripheral edges of the mold wheel 22 which is shown in partial top-plan ~iew in Figure 6.
In practice, the holding devices or gripping devices 22T about the periphery of the mold wlleel can be made effective on the mold wheel station where the web 14 is initially engaged and where molding initially takes place and can be deactivated or rendered ineffective on the stripping or molded product removal side or stations of the mold wlleel polygon 22 such that the strip~ing of the finished products 24 and selvage 14S from the mold wheel 22 is facilitated.
In Figures 3A - 3D, the zone subtended in the web 14 by the transverse stretcher assembly 18 is identified as a transverse stretching zone TS which is preceeded on the upstream side by a machine stretch zone MSl and on the do~n-stream side by a machine stretch zone MS2.
Referring now to Figure 3B, it can be seen that all of the machine orientation or longitudinal st~etch has been effectuated in the zone MS2 as indicated by the wider spacing between the edge adjacent dots 14I whic~l are uti-lized to designate equal increments of unbiased web 14 in the initial spacing shown in the zone MSl of Figure 3B
which is a totally unoriented configuration and spacing.
This spacing is incremental in both the longitudinal and transverse directions of the web, i.e., the dots 14I
define biaxial increments of the web 14.
. .~, _ , ~
. . .
li33Z21 Referring next to Figure 3C, it can be seen that the rota~ional velocity of the transverse stretcher blades 18A
is such that the web travels faster in the transverse stretching zone TS and therefoTe has imparted to it both transverse and longitudinal stretch and has no additional longitudinal stretch imparted to it in the downstream or second machine stretch zone MS2. The zone MSl upstream of the transverse stretching zone TS illustrates no biaxial orientation upstream of the transverse zone TS.
Referring next to Figure 3D, it can be seen that in the - initial upstream zone MSl that no biaxial orientation is imparted to the web 14, that in the zone TS both transverse and partial machine direction stretch are imparted to the web 14 and in downstream zone MS2 additional longitudinal or machine direction stretch is imparted to the web 14.
The foregoing clearly illustrates the wide variety of lon~itudinal and t~ansverse stretch modes which can be effectuated. In all cases, of ~ course, the tTansverse stretcnlng lS achleved withln tne zone TS and not within the upstream and downstream zones MSl and MS2, respectively.
If in the zone MSl in either of the foregoing diagrams of Figures 3B, 3C or 3D, the dots 14I in the upstream zone MSl were to vary in spacing longitudinally of the web 14, then that would be indicative of a differential peripheral velocity of the rollers 16A and 16B which would impar~
machine direction stretch to the web 14 in the upstream zone MSl.
Referring further to Figure 3A, the diameter of the rolls 16A, 16B, 20A and 20B are kept as small as is consis-tent with minimizing the deflection of these rolls under load. Also, the distance between the rolls in the respec-tive Toll pairs 16 and 20 is preferably no greater than to allow for slight clearance of the web or extrudate 14 which minimizes the shrinkback which otherwise occurs as the material is transferred from one roll to another.
.--- i ., , . -.
.
The surface speed of the second roll 16B is usually L
faster than the surface speed of the first roll 16Aso as to achieve longitudinal stretch in the upstream area MSl and preferably, the. surface speed of the roller 16Bas compared to that of the roller 16Ais such that 50% of the longitudinal or machine direction orientation occurs in the transfer of material from the Toller 16A onto the roller 16B.
Also, as shown in Figure 3A, the teeth 18T on the trans-verse stretcher blade 18A are very close to the surface of the second roller 16B and the perimeter speed of the blades is preferably slightly faster than the surface speed of the roller 16B thereby making the transfer of material from one to the other more effective. The teeth 18T actually pene-15 trate the edge of the web or strip 14 so as to hold the material securely as transverse stretching takes place due to the angular orientation of the blades 18A and 18B, the latter being best shown with reference to Figures 5A and 5B.
The third or initial output rolleT 20A is also posi-tioned very close to thé teeth 18T of the blades 18A and 18B
so as to minimize shrinkback at this particular transfer point comprised by the interface between the said roll 20A
and the blades 18A and 18B. The surface speed of the roller 20A is usually and preferably slightly faster than the perimeter speed of the transverse stretching blades 18A and 18B and the fourth roller 20B is maintained close to the t]lird roller 20A in order to minimi~e shrinXback during the transfer from one roller to another. Usually, the`
fourth roll 20B is run faster than the third roller 20A ~ith the preferred speed being such as to accomplish the remain-ing 50% of the longitudinal or machine direction oricntation in the web 14. The web 14, as it leaves the fourth or interfacing roller 20B onto the mold wheel 22,isthus fully biax~ally oriented.
.
J
~33221 As disclosed with reference to Figures 1 and 2, the entire orientation device 16-18-20 in the particular embodiments of Figures 1, 2 and 3A is pivoted about the pivot points 28C and a suitable means 30. e-g- a spring schematically shown in Fgiure 1 or a pneumatic cylinder schematically shown in Figure 2 is provided to bias the final output or interfacing roller 20B against ~he peri-pheral shoulders of the mold wheel 22 such that the teeth 22T on the mold l~heel will avoid contact with the roller surface~ but will penetrate and retain the web 14 in its biaxially oriented condition over each face of the mold wheel 22 such that a uniform web is presented to each mold cavity ~5C therein.
All of the longitudinal stretching rollers 16A, 16B,, , 20A a,nd 20B,are,preferably coated with fluorocarbon e-g- that known by the Trade Mark TEFLON to avoid sticking of the web 14 thereto- Also such rollers are usually made with thin-walled steel tubes in order to minimize the heat retention capacity and heat transfer to the ends of the rollers. Therefore, in the area of contact with the web 14, the rolls reach about the same temperature as that of the web itself.
A low inertia orientation apparatus will now be described with further reference to Fig~s 4, 5A,5B and 6.
In this embodiment, the output rollers 20 of the previous embodiments are replaced by an output roller set 120 which is comprised of three rollers 120A, 120B and 120C mounted on a common frame 120D which is biased by suitable means 120E to~ard the mold wheel 22 SUC]I that the fi~al output or interfacing roller 120C is engagcd ~ith the mold wheel 22 in a manner similar to that of the final roller 20B in the previous embodimcnts.
The biasing means 120E can be any suitable dcvice such as a compression spring or a pneumatic spring or cylinder such as already described in reference to the embodiments of Figure 1 and Figure 2, res~ectively.
. .
..
..
. .
- - ;
, ~133'~2~
The common support 120D for the downstream output roller set 120 is pivoted on the center line of the upstream roller 120A of that set and the transverse stretching saw blades 18 and the inpùt stretch rolls 16 are fixedly mounted in the embodiments of Figures 4 and 6 as opposed to being mounted for movement about a central point 28C such as previously described in Figures 1 and 2.
Thus, only the inertia of the three output stretching and interface rollers 120A - 120C and the frame 120D on which these are mounted is involved in the interfacing of the biaxially oriented web 14 and the undulating peripheral surface of the rotating mold polygon 22. Through the use of three rollers, disproportionate elongation due to oscilla-tion is avoided and a more uniformly elongated web 14 will result than would result with the use of two rollers. The gap between the three rollers 120A - 120C is kept very small to avoid shrinkbac~ of the now biaxially oriented ~eb traversing these rolls. Because the inertia of this particular output stretch and interface roll means has been minimi~ed, the mass and inertia of the remaining portions of the biaxial orientation equipment is not critical.
The drive means DA and DB on the transverse stretch saw blades 18A adn 18B, respectively, and the nearest rollers thereto, namely, the upstream interface roller 16B and the downstream initial roller 120A are all driven preferably from a common drive motor through various drive belts or chains and the rollers 16B and 120A are illustrated in Figure 6 as being driven by a common drive belt DC ~.hich engages drive pulleys or sl~rockets Sl and S2 mounted on the shafts of the rollers 120A and 16B, respectively.
Further, the roller 16B includes a passive output gearing Gl ~hick is engaged l~lith compatible gearing ~of a predetermined ratio) G2 mounted on the shaft of the initial input roller 16A such that the differential speed bet~.~een the rollers 16A and 16B can be effectuated from the same common drive means DC that drives both the rollers 16B
and 120A.
__ ~_ _ 1~33ZZ~
~ hus,the ratio of the gears Gl and G2 can be cllanged to vary the amount of longitudinal stretch achieved between the initial input rollers 16A and-16B.
The last two rolls 120B an~l 120C on the downstream side of the transverse stretcher blades 18 are not driven from the stretcher apparatus. The last output or interface roll 120C is driven by the surface speed of the mold wheel or polygon 22 with which it is in contact and this speed is established and selected to provide the proper longitudinal orientation when measured against the fixed speed of the initial output Toll 120A. The middle roll 120B of the output roller group 120 merely idles and reaches a speed in between that of the toher two rolls 120A and 120C of the set 120.
-In order to maintain a constant dimensional relation-ship between the transverse stretch saw blades 18A and 18B
and the initial output roller 120A, the blades 18A and 18B
are pivoted at their downstream edge on the pivots PA and PB, respectively, rather than at the centeT of the said blades 18A and 18B. Therefore, the relationship between these blades 18A and 18B and the output roller 120A remains constant during adjustment of the blades between a direction parallel to the machine direction oriented at 45 with respect to the machine direction.
The second roller 16B and its companion input roll 16A
in the input stretch roll set 16 move in and out to adjust to the position of the transverse stretch saw blades 18A
and 18B depending upon the adjusted position Gf the latteT.
Suitable stop means or bosses are provided on the saw blade adj~stment brackets to interact wi~h the mounting of the various input rollers 16A and 16B to preclude ~engagement of the rolls with the saw blade but maintaining the desired immediate proximity thereof.
- 1133;Z2i The material tension of the web 14 proceeding beneath the roller 16A back over the roller 16B and thence beneath the sa~ blades 18A and 18B is sufficient, since the web 14 initially approaches thé roll 16A from above, to cause the roll 16A to track the movements of the roll 16B and thereby maintain the desired minimum spacing by way of the material tension in the web 14.
Suitable means are also provided within the mounting bracket 120D of the output roll set 120 to provide for moving the three rollers 120A, 120B and 120C apart and bac~
together again to provide for the threading of material - therethrough at the beginning of an extrusion and orientation and molding cycle and then placing the rollers under a suffi-cient bias to provide a predetermined minimum spacing and pressure thereon such as by small air cylinders or the like, all of which is within the purview of one-o ordinary skill in the art.
If the molded products 24 are desired to be nine inch plates having a material thickness on the order of~.010 inches, a stretch ratio of 3 to 1 is established for both the transverse and longitudinal oTientation of the web 14, by way of an exemplary process parameter. In this case, the die opening would be on the order f 0 090 inches of web thickness and 3 inches inwidth plus perhaps a one-quarter inch allowance for selvage. The polystyrene resin which is to be converted to OPS resin would be extruded at preferably, 425F. The extrudate would be cooled to 280F by the cooling rools CR before entering the initial rollers 16A and 16B of the stretcher apparatus of an aspect of the present invention.
At an output rate of approximately 600 pounds of ~eb material per hour, the speed of the extrudate~would be 90 feet per minute before entering the initial rolls 16 of the stretcher assembly and ~ 270 feet per minute 3s leaving the last or interfacing roller 120C of the stretchcr assembly. This 270 foot per minute speed would match the speed of the mold surface or mold polygon 22.
. . _ .
~133221 Fifty percent of the longitudinal orientation in the web 14 would yrobably be accomplished between the rollers 16A and 16B, all of the transverse orientation between the transverse stretcher blades 18A and 18B and the remaining 50% of the longitudinal orientation established between the roll 120A at the input of the group 120 and the roll 120C
interfacing the biaxially oriented web material with the mold polygon 22.
The mold polygon or mold wheel 22, for example, might have 15 mold cavities MC and would be in that event, four feet in diameter. The ratio of selvage to finished product would be - 50-50. The plate 24 would weight ~ 10 grams and 324 plates per minute would be produced at a mold wheel speed of 21rpm.
In achieving the transverse orientation with the blades 18A and 18B, these blades would be gapped at three and one-eighth inches on their upstream side and nine and three-eighth inches on their downstream side to effectuate the three for one transverse stretch desired.
Accordingly it can be seen that a continuous ~eth~d with a relatively high speed of production and high qualit~
control with a low~inertia apparatus is readily effectuated by the embodiments of Figures 4, 5A, 5B and 6.
Claims (14)
1. Means for continuously orienting and transferring a continu-ous web of thermoplastic material conformally onto the periphery of a poly-gonal rotating mold from an extruder, the means comprising:
web receiving and advancing means ingesting said web;
web stretching means downstream of said web receiving means for next receiving said web and imparting at least a lateral stretch to said web and advancing same toward said polygonal rotary mold; and web transfer means mounted immediately downstream from said web stretching means in peripheral surface following relationship with said polygonal rotating mold for receiving the laterally stretched web from said web stretching means and conformally juxtaposing said stretched web with said peripheral surface of said rotating mold;
at least one of said web receiving and advancing means and said web transfer means imparting a longitudinal stretch to said web to impart biaxial orientation thereto prior to its conformal juxtaposition with said peripheral surface of said rotating mold.
web receiving and advancing means ingesting said web;
web stretching means downstream of said web receiving means for next receiving said web and imparting at least a lateral stretch to said web and advancing same toward said polygonal rotary mold; and web transfer means mounted immediately downstream from said web stretching means in peripheral surface following relationship with said polygonal rotating mold for receiving the laterally stretched web from said web stretching means and conformally juxtaposing said stretched web with said peripheral surface of said rotating mold;
at least one of said web receiving and advancing means and said web transfer means imparting a longitudinal stretch to said web to impart biaxial orientation thereto prior to its conformal juxtaposition with said peripheral surface of said rotating mold.
2. The means of claim 1 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web.
3. The means of claim 1 wherein said web stretching means com-prises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth constrain said web to be stretched to a width commensurate with the divergence of said discs.
4. The means of claim 1 wherein said web transfer means comprises:
first, second and third roller means mounted transversely of said web with said second roller commonly adjacent the other said rollers;
and a common frame mounting said roller means for rotation there-in on parallel axes of rotation with said first roller immediately adja-cent said web stretching means and said third roller in rolling juxtaposi-tion with said peripheral surface of said rotating mold with said oriented web therebetween.
first, second and third roller means mounted transversely of said web with said second roller commonly adjacent the other said rollers;
and a common frame mounting said roller means for rotation there-in on parallel axes of rotation with said first roller immediately adja-cent said web stretching means and said third roller in rolling juxtaposi-tion with said peripheral surface of said rotating mold with said oriented web therebetween.
5. The means of claim 1 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web; and wherein said web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first receiving therein-and said discs being divergently oriented in a downstream sense such that said teeth con-strain said web to be stretched to a width commensurate with the divergence of said discs.
6. The means of claim 1 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web; and wherein said web transfer means comprises:
first, second and third roller means mounted trans-versely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxtaposition with said peripheral surface of said rotating mold with said oriented web therebetween.
first, second and third roller means mounted trans-versely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxtaposition with said peripheral surface of said rotating mold with said oriented web therebetween.
7. The means of claim 1 wherein said web stretching means com-prises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth constrain said web to be stretched to a width commensurate with the divergence of said discs; and wherein said web transfer means comprises:
first, second and third roller means mounted trans-versely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxta-position with said peripheral surface of said rotating mold with said oriented web therebetween.
first, second and third roller means mounted trans-versely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxta-position with said peripheral surface of said rotating mold with said oriented web therebetween.
8. The means of claim 1 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web;
wherein said web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth constrain said web to be stretched to a width commensurate with the diver-gence of said discs; and wherein said web transfer means comprises:
first, second and third roller means mounted transversely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxta-position with said peripheral surface of said rotating mold with said oriented web therebetween.
wherein said web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth constrain said web to be stretched to a width commensurate with the diver-gence of said discs; and wherein said web transfer means comprises:
first, second and third roller means mounted transversely of said web with said second roller commonly adjacent the other said rollers; and a common frame mounting said roller means for rotation therein on parallel axes of rotation with said first roller immediately adjacent said web stretching means and said third roller in rolling juxta-position with said peripheral surface of said rotating mold with said oriented web therebetween.
9. The means of claims 1,2 or 3 wherein said web transfer means is mounted substantially independently of said web stretching means.
10. The means of claims 4, 5 or 6 wherein said web transfer means is mounted substantially independently of said web stretching means and further includes means mounting said common frame for rotation on the axis of rotation of said first roller.
11. Means for continuously orienting and transferring a continu-ous web of thermoplastic material conformally onto the periphery of a polygonal rotating mold from an extruder, said means comprising:
web receiving and advancing means ingesting said web;
web stretching means downstream of said web receiving means for next receiving said web and imparting at least a lateral stretch to said seb and advancing same toward a said polygonal rotary mold; and web transfer means mounted immediately downstream from said web stretching means in peripheral surface following relationship with said polygonal rotating mold for receiving the laterally stretched web from said web stretching means and conformally juxtaposing said stretched web with said peripheral surface of said rotating mold;
at least one of said web receiving and advancing means and said web transfer means imparting a longitudinal stretch to said web to impart biaxial orientation thereto prior to its conformal juxtaposition with said peripheral surface of said rotating mold;
wherein said web transfer means comprises an odd number of three or more roller means mounted transversely of said web with said roller means parallel and adjacent for receiving said web on the peripheral surfaces thereof in a serpentine path;
a common frame mounting said roller means for rotation therein with an upstream roller means immediately adjacent said web stretching means and a downstream roller means in rolling juxtaposition with said peripheral surface of said rotating mold; and the remaining odd number of roller means being intermediate said upstream and downstream roller means for transporting said oriented web therebetween in said serpentine path.
web receiving and advancing means ingesting said web;
web stretching means downstream of said web receiving means for next receiving said web and imparting at least a lateral stretch to said seb and advancing same toward a said polygonal rotary mold; and web transfer means mounted immediately downstream from said web stretching means in peripheral surface following relationship with said polygonal rotating mold for receiving the laterally stretched web from said web stretching means and conformally juxtaposing said stretched web with said peripheral surface of said rotating mold;
at least one of said web receiving and advancing means and said web transfer means imparting a longitudinal stretch to said web to impart biaxial orientation thereto prior to its conformal juxtaposition with said peripheral surface of said rotating mold;
wherein said web transfer means comprises an odd number of three or more roller means mounted transversely of said web with said roller means parallel and adjacent for receiving said web on the peripheral surfaces thereof in a serpentine path;
a common frame mounting said roller means for rotation therein with an upstream roller means immediately adjacent said web stretching means and a downstream roller means in rolling juxtaposition with said peripheral surface of said rotating mold; and the remaining odd number of roller means being intermediate said upstream and downstream roller means for transporting said oriented web therebetween in said serpentine path.
12.The means of claim 11 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web.
13. The means of claim 11 wherein said web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth constrain said web to be stretched to a width commensurate with the divergence of said discs.
14. The means of claim 11 wherein said web receiving and advan-cing means comprise first and second roller means and means driving said roller means at differential peripheral velocities to impart longitudinal stretch to said web; and wherein said web stretching means comprises a pair of rotating discs, each disc having peripherally disposed teeth engaging a respective edge of said web when first received therein and said discs being divergently oriented in a downstream sense such that said teeth con-strain said web to be stretched to a width commensurate with the diver-gence of said discs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA386,351A CA1133221A (en) | 1978-03-13 | 1981-09-21 | Means for orienting and transferring web of thermoplastic material |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/886,160 US4250129A (en) | 1978-03-13 | 1978-03-13 | Method for the continuous formation of biaxially oriented thermoplastic materials and forming articles therefrom in a continuous process |
| US886,160 | 1978-03-13 | ||
| CA323,052A CA1127364A (en) | 1978-03-13 | 1979-03-09 | Method and apparatus for the continuous formation of biaxially oriented thermoplastic materials and forming articles therefrom in a continuous process |
| CA386,351A CA1133221A (en) | 1978-03-13 | 1981-09-21 | Means for orienting and transferring web of thermoplastic material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1133221A true CA1133221A (en) | 1982-10-12 |
Family
ID=27166127
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA386,351A Expired CA1133221A (en) | 1978-03-13 | 1981-09-21 | Means for orienting and transferring web of thermoplastic material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1133221A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6136396A (en) * | 1996-08-12 | 2000-10-24 | Tenneco Packaging Inc. | Polymeric articles having antistatic properties and methods for their manufacture |
-
1981
- 1981-09-21 CA CA386,351A patent/CA1133221A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6136396A (en) * | 1996-08-12 | 2000-10-24 | Tenneco Packaging Inc. | Polymeric articles having antistatic properties and methods for their manufacture |
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