CA1197960A

CA1197960A - Injection blow molding

Info

Publication number: CA1197960A
Application number: CA000423487A
Authority: CA
Inventors: Siegfried S. Roy
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-04-12
Filing date: 1983-03-14
Publication date: 1985-12-17
Also published as: NZ203601A; DE3363881D1; KR840004379A; KR890000875B1; IE53973B1; AU558240B2; AR231815A1; ATE20209T1; IL68158A0; AU1251983A; MX162478A; ES521381A0; BR8301840A; ES8404906A1; ZA831965B; IE830547L; US4615667A; IL68158A; JPS591227A; EP0092904B1

Abstract

ABSTRACT OF THE DISCLOSURE IMPROVEMENTS RELATING TO INJECTION BLOW MOLDING The present invention provides an injection blow molding process and apparatus for use in the blow molding of containers in which a preform (1) is molded onto a core (20) and is subsequently moved relative to the core to space a body portion (8) of the preform from the core to facilitate the temperature conditioning of the preform to achieve a desired biorientation of the thermoplastic material from which the preform is made when the preform is blow molded to form a container. The temperature conditioning may be achieved by allowing stabilization of the temperature gradient through the material of the preform with or without the assistance of a supply of gas to the preform at a desired temperature.

Description

7~

IMPROVEMENTS REI~ATING TO INJECTION ~LOW MOLDING

The present invention relates to a process and apparatus for manufacturing hollow articles of thermoplastic material, for example, polyester, polypropylene, polyethylene, nylon, from injected molded or compression molded preforms which are inflated until they take the shape of the desired articles.
It is known in the prior art to effect such a process by pressing the edge of a substantially molten or pasty 10 preform onto the neck of a hollow blow mold which has the shape of the desired article. The preform is then blown or inflated within this mold, starting from the edge thereof, until it completely touches the entire interior of the blow mold and, on contact with this wall, the lS distended preform cools instantaneously, thereby permanently assuming the shape of the mold, i.e. the desired article.
For obvious reasons of production speed and in,order to prevent the soft preform from being left supporting its 20 own weight between the injection and blowing phases of the process, the blowing head is generally incorporated in the core upon which the preform or parison is injected. The core containing this blowing head is then conveyed to the entrance of the blow mold.
In the injection blow molding apparatus which are presently being used in the market, such as the Piotrowski system, in which the preform remains with the core and is transferred to the blow station to ma~e a container, precise temperature conditioning, which is essential for 30 obtaining optimum biorientat;on levels required to attain high mechanical strength properties, such as impact and stress resistance, in the finally blown container, are difficult to control, predict, or achieve especially in -the following situations:

., .

a. When the preform has a thlckness around 2.5 mm and the final blown container has a wall thickness of possibly 0.~5 mm or less. This is especially true when the blow ratio between the preform wall and the blown container is fairly high, such as lO to 1, a basic requirement for high orientation levels.
b. Use of certain resins such as PET, polyester, polypropylene, polyethylene, nylon, etc. are practically impossible to control on a predictable basis in present 10 injection blow mold equipmen-t, in which the core travels with the preform to the blow station. These resins in their hot semi-molten soft state or at their optimum blowing temperatures tend to adhere or stick unpredictably to parts of the metal core when blow air is introduced for 15 blowiny the container. This condition causes poor material distribution in the walls of the container and in extreme cases folds, blowouts, pleats and other distortions.
c. In the manufacture of consistently controlled 20 bioriented containers for use as pressure vessels i.e.
beverage, beer and other carbonated clrinks, made from PEI' bioriented containers, orientation levels in the wal]s of the containers have to be predictable and consistent and this can only be accomplished by fairly precise control of 25 the preform temperature at the time it is blown to form the container. This predictability in control is presently not available on equipment being used in the marketplace.
In present injection blow molding apparatus 30 temperature control of the cross section of the preform wall is not possible. The core which is carrying cooling fluid tends to overcool the inner layer of the preform which is in direct contact with the core. The outer layer of plastic in the preform does not cool at the same rate 35 and only by convection to ambient air. The only primary ...

1~7~

cooling that -the outer layer gets is when it is stationary in the injection cavity. Heat transmission from the outer layer of the preform to the core is slow due to the poor heat transfer characteristics of plastics in general. This condition causes the temperature gradient through the cross section of the preEorm wall to be very steep, especially in thicker preforms which are required for high blow ratios.
High blow ratios are required to obtain biorientation levels in the blown container walls.
To get maximum utilization of plastic in a con-tainer it is necessary to maximize the mechanical properties through biorientation at the specific optimum temperature for a particular resin being used.
The part of the cross section of the preform which is 15 nearest to the optimum orienting temperature develops the best mechanical properties when blown into a container.
Consequently the portion of the plastic in the preform in higher and lower temperature bands tend to have poorer mechanical properties.
It then becomes obvious that to obtain the best results the entire cross section of that portion of the preform that needs to have optimum mechanical properties should be as close to the precise biorienting temperature at the time it is blown. There should be a minimum and, if possible, no temperature gradient. The process temperature window for optimum orientation levels in most resins is fairly small.
It is an object o~ the present invention to overcome problems of temperature conditioning of preforms and to achieve this with an economically effective production rate~

According to the invention, there is provided an injection blow molding press for use in making blow molded hollow articles having a neck with a neck opening, comprising at least one preform core having a free end and having a portion of constant cross section adjacent i-ts base end and an adjoining tapered portion, a preform injection molding station and a blow molding s-tation, means for mounting the core for step-wise movement to bring the core at different times into registry with the preform injection 10 molding station and the blow molding station, means for shifting the preform on the core prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and the.reby provide spacing between the preform and the tapered portion of the core, and 15 neck ring split means for the core including neck engaging elements relatively movable in a direction radially toward and away from the outside of the neck of the article being formed and further including means at the blow molding station for moving the elements towarcl the neck to establish 20 sealing contact of the preform against the portion of the core of constant cross section.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in 25 which:

v Figure 1, is an elevation of a preform shown sectioned on one side of its longitudinal axis;
Figure 2, is a fragmentary elevation of a core with the preform of Eligure 1 silown in fragmentary section, with its body portion spaced from the core and its neck portion in sealing contact with core, Figure 3, is a fragmentary sectional elevation of the core of Fi~ure 2;
Figure 4, is a diagrammatic part sectional elevation 10 of an injection blow molding machine with the injection molding of a first preform completed on the core at station A and the cooling of a second preform taking place on the core at station B;
Figure 5, is the fragmentary sectional elevation of 15 the machine of Figure 4, with the second preform spaced from core at station B for temperature conditioning thereof to a temperature at which desired biorientation of the material thereof will occur upon stretching of this material by blow molding;
Figure 6, is a fragmentary sectional elevation of the machine of Figure 4 with the second preform blown to full form at the orienting temperature;
Figure 7, is a fragmentary sectional elevation of the machine of Figure 4 preparatory to opening the blow mold;
Figure 8, is a fragmentary sectional elevation of the machine of Figure 4 with the blow mold open and the container blow molded from the second preform in the process of ejection;
Figure 9, is a fragmentary sectional elevation of the 30 machine of Figure 4 with blow and injection molds fully open and immediately before the first preform has been transferred to the blow molding station B pxeparatory to t~le closing of the blow and injection molds for the injection moldin~ of another preform thereby to reach the 35 operational condition of the machine shown in Figure 4.

. . . ~

~ ~7~Q

Figure lO, is an elevation of multi-cavity injection blow molding apparatus incorporating the features illustrated diagrammatically in the machine of Figures 4 to 9, shown in the fully open position of the blow and injection mold assemblies;
Figure 11, is a diagrammatic illustration of the temperature control system of the machine of Figure lO; and Figure 12, is diagrammatic representation of a four station alternative embodiment to the two stage embodiment 1~ illustrated with reference to Figures 4 through 11.
With reference to Figure 1 a one piece pre~Eorm 1 injection molded from a thermoplastic material, for example, polyester, consists of a neck or open end portion

2 and a body portion 3. The neck portion has a 15 cylindrical interior surface 4 and an exterior surface upon which .is formed a thread 5 and a flange 6. The hollow body portion 3 is provided with a smooth interior transition from the neck portion 2 to a frusto-conical interior section 8 closed at its narrow end, remote from 20 neck portion 2, by a hemispherical end portion 9.
The interior of the preform 1 conforms with a core about which the preform was injection molded in a mold cavity with the cylindrical interior surface 4 rendering it possible to n~ove the preform longitudinally, along axis 25 lO relative to the core, once the core and preform have been removed from the mold cavity, thereby to space the body portion of the preform from the correspon~ing portion of the core to permit the temperature of the body portion of the preform to be regulated as desired throughout the : 30 wall thickness of the preform, while at the same time maintaining a seal between the cylindrical interior surface 4 of the preform with the corresponding cylindrical su~:Eace of the core, to facilitate subsequent blow molding of the preform to form a bioriented ~5 thermoplastic container.
. . . ~

iQ

The core upon which the preform l is molded is core 20 illustrated in Figures 2 and 3. Core 20 has a cylindrical exterior sealing surface 21 which seals the neck portion of a preforln injection molded thereon by virtue of the cooperation of the core 20 with a split thread former 22 (shown in Figure 2 only). The exterior surface of the remainder o~ the core which is in communication with the preform conforms to the interior surface shape of the body portion of the preform and includes a smooth transition lO portion 23, a frusto-conical section 24 and an end portion 25.
The taper of the frusto-conical section is such that when the preform and core are moved relative to one another longitudinally of axis 10, the preform becomes 15 thermally isolated from the core to a desired extent for timely temperature regulation of the pre~orm in preparation for blow moldin~ while, at the same time, the cylin~rical interior surface of the neck portion of the preform maintains a sealing engagement with -the 20 cylindrical sealing surface 21 of the core.
With reference to Figure 3 the core 20 is a bi-metallic structure designed so that heat transfer is greater where required thereby to obtain the desired stretching effect for orienting the container material 25 during the blow molding operation while the cooler portions of the preform, which receive the least amount of stretch, act as a piston to stretch the areas that are at the orienting temperature. 1~he core consists of a steel outer body 26 and a copper nose and central cylindrical 30 portion 27 defininy, on the central cylindrical portion a spiral cooling tube 28. The beryllium copper nose and central portion 27 define an a~ial hiyh pressure air supply tube 29 controlled by a steel pressure valve 30 which is opened. when desired, to permit high pressure air to blow from the preform into a container within a blow mold.

With reference to Figures 4 through 9 an injection blow molding apparatus 40 includes a preform injection molding station A supported by a fixed platen 41 for cooperation with an injection molding material extruder 42, a blow ~olding station B supported by a movable platen 43 which is mcvable along supports 44 in the direction of arrow 45 (Figure 4) to the position shown in Figure 9 and back again, and a core supporting turret 46 mounted on intermediate platen 47 disposed intermediate platens 41 10 and 43 and movable in the direction of arrow 45 from the position shown in Figure 4 to the position shown in Figure 9, in which latter position the t~rret 46 is rotatable about axis 48 to reverse the positions of the cores 49 and SO, and back again.
lS The cores 49 and 50 are as described with reference to Fiyures 2 and 3 with the cylindrical portion of each core being circumscribed by a split thread forming membe,r 51.
The thread forming member 51 of core 49 together with injection mold 52 defines a cavity into which 20 thermoplastic material is injected by the extruder 42 to form a preform, such as that described wit]l reference to Figure 1. The split thread forming member 51 of core 50 which carries a preform, following transfer thereof from station A to station B, serves to maintain a sealing 25Contact be-tween the preform and the core 50 while the preform is blow molded in blow mold 53.
Each split thread forming member 51 is supported by a thread split holder 54. The thread split holder 54 and its associated split thread forming member is mounted for 30movement by actuating pins 55 from the position shown in Figure 4 to the position shown in Figures 5, 6, 7, ~ and 9 thereby to slide the preform at station B along the core to pro~ide the above mentioned thermally isolating space between the preform and the core while retaining a sealing 35engagement between the cylindrical sealing portion of the core and the neck portion of-the preform.

~9'7~

I'he actuating pins 55 are moved by means o hydraulic ac~uators 56 mounted on the fixed platen 41 when the turret supporting intermediate platen 47 is in the position shown in Figure 4. Spring biased detents 57 mounted in the intermediate platen are arranged to resiliently engage grooves 58 in at least one of the actuating pins 55 thereby to resiliently locate the actuating pins in one or other of the positions shown in Figure 4 and Pigures 5, 6, 7, 8 and 9 respectively.
It will be appreciated that in alternative arrangements falling within the scope of the present invention:
(a) the split thread forming member and its holder at station A may be arranged to remain at station A while the 15 core 49 with the preform formed on it is moved with the intermediate platen 47 to a position in which it is rotated to station B with the split thread forming member shown at station B being replaced by a more economical clampin~ member able to engage the preform at station B to 20 clamp that preform into sealing engagement with the core which carries the pre~orm at station B;
(b) the thread split holder 54 at station B is actuated b~ pneumatic, electrical or mechanical means which may be mounted on the fi~ed platen, the intermediate 25 platen, the turret or the movable platen and which include, though are not restric-ted to, an eccentric or cam arrangement which moves the preform relative to the core by the desired amount during rotation of the turret to move a preform and core from 5 tation A to station B.
Closure struts 59 mounted on the movable platen 43 transmit closure forces from the movable platen 43 by way of the turret ~6 -to close the injection mold arrangement 49, 51, 52 agains-t the injection pressures encountered while injection molding a preform at station A.

The -turret 46 is provided with air inlet passages 60 for transmitting high pressure air for the blow molding operation through the center of the core positioned at station ~ and with coolant passages 61 for supply of S coolant to the spiral cooling tubes of the cores at stations A and B. A hydraulically oparat0d ejector pin 62 is mounted on the movable pl.aten 43 for ejectin~ a container following the blow molding operation from the blow mold 53.
The blow mold 53 is provided with air passages 63 for supplying air at a desired temperature into the cavity of the blow mold to achieve a desired temperature conditioning of a preform at station B, when it is spaced from its core as described above, to place the preform in 15 appropriate temperature condition for blow molding to produce the desired bioriented thermoplastic container.
The injection mold 52 and the blow mold 53 are provided with passages 64 for coolant in a manner known in the prior art.
~0 ~lile the present invention is being described with reference to~an injection blow molding apparatus utilizing a rotating turret (a Piotrowski turret) in which the turret is rotated 180 from an injection molding station at which a preform is injection molded to a blow molding 25 station with the blow molding and the injection molding being independently carried out possibly simultaneously, it will be appreciated that the present invention is not : restricted to the use of such apparatus and that many forms of injection blow molding apparatus will be 30 appropriate including, but not limited to, apparatus in which the preform and its core are maintained at the injection molding station with the blow mold arrangement being substituted -for the injection mold or to oscillating or rotary systems in which injection ~lolds and blow ~lolds 35 are alternated either circumferentially or radially (or in ., . ~

7~

any other manner) with the cores being moved sequentially from an injection molding station to a blow molding station and onto or back to an injection molding station, etc.
The sequence of operation of the injection blow molding apparatus described with reference to Figures 5 through 9 will now be described with reference to these figures which in numerical sequence show the apparatus at various sequential stages of its cyclic operation.
Figure 4 shows the apparatus immediately following completion of the injection molding of a preform on core 49 at station A. In this operational condition the injection molding a~sembly 49, 51 and 52 iq held closed by the closure force supplied by the movable platen 43 by way 15 of struts 59 and turret 55. A previously molded preform is shown in blow mold 53 on -the core 50 at station B. The split thread forming members are in their closed positions in which they clamp the neck of the preforms against their respective cylindrical sealing suxfaces of cores 49 and 20 50- In this condition the preform on core 50 is being cooled by the cooling action of the coolant passing through passage 28 in core 50 and by air being blown into the blow mold 53 by way of air pae;sages 63.
Figure 5 shows the apparatus in the next sta~e of 25 operation in which the pre~or~n Oll core ~9 is cooling a~d the hydraulic actuators 56 have been operated to move actuating pins 55 to move the thread split holder 54 and split thread forming member 51 a-t station B laterally of the turret 46 to space the body portion of the preform at 3U station B from the core 50 while maintaining the neck of the preform at station B in sealing contact with the cylindrical sealing surface of the core 50, thereby to provide for the desired temperature conditioning of that preform.

. . . ~

~97~6~

At station A the cooling of the preform by the mold 52 occurs for only 2 to 3 seconds as the outside surface of the preform shrinks away from the internal surface of the mold after this time. At station B the space between the core and the body portion of the preform is typically of the order of .005 inche~. The spacin~ of the pre~orm from the core conditions the temperature of the preform which, during cooling on core 50 has become too cool on its internal surface while being insufficiently cooled on its 10 exterior surface whereby the interior surface of the preform is too cold for effective blow molding while the exterior surface is too fluid. By virtue of -the movement of the preform to provide a gap between the preform and the core, the temperature gradient throuyh the material of 15 the preform can be allowed to equalize under the influence of air being blown into the blow mold 53 through the passages 63 to provide a desired temperature condition in the preform for efec-tive blow molding. Achieving this temperature conditioning the outer and inner surface 20 temperatures of the preform are allowed or caused to come close to equilibrium at the orie~ting temperature desired. The ability to release the preform from the core at any time within the processing cycle, after indexing, provides considerable freedom of control in varying the 25 conditioning temperatures and temperature gradients.
During this sequence of oper~tions it will be noted that the preform is never removed from the core upon which it was injection molded until af-ter the blow mol~ing operation to produce a bioriented container has taken 30 place.
Figure 6 illustrates the ~age in the sequence of operations of the injection blow molding apparatus in which air at a pressure of 300 to 350 lbs./square inch is supplied along the central tube past the valve of core 50 35to inflate the now temperature conditioned preform until :~, o it engages the walls of the blow mold cavity of blow mold 53. The proper temperature conditioning of the preform together with the correct design of the core and cavity of tl~e blow mold 53 ensures proper stretch and blow ratios.
The core, as described with reference to Figure 3, has a higher heat conductive metal forming the end portion than that of the side walls of the main body part oE the core~
The preform tip is also thinner than the wall sections and because Orc its lower temperature resulting from the 10 conductive end portion of the core, is stiffer than the wall portions of the preform. This causes the end portion of the preform to act as a piston when air under pressure is supplied through the core which causes a relatively high stre-tch in the wall of the preform in both the axial 15 and circumferential direction. This provides the desired biorientation of the material of the container.
Following the blow molding operation in the blow mold 53, the split thread forming member 51 and its thread split holder 54, which are in two halves split ZO diametrically across the center line of the threads of the container to be produced, are moved apart by a head split mechanism 65 to the position shown in Figure 7 in which the neck of the container which has been blown in blow mold 53 is released.
Subsecluentl~, the movable platen ~3 is moved in the direction of arrow 45 to the position shown in Figure 8 and the ejector pin 62 is actuated to eject the container ~rom the blow mold.
After ejection of the container, as illustrated in 30 Figure 8, the intermediate platen is moved in the direction of arrow 47 to the position shown in Figure g in which the turret 46 can rotate about axis 48 to move the preform which has been injection molded at station A to station B in preparation for closing of -the injection and 35 blow moldin~ apparatus in order that it adopt the position 79~

shown in Figure 4 in preparation for injection molding a further preform at station A and temperature conditioning the preform which is being moved to station ~ and subsequently blow molding that preform. During this mold closing the closing pressure move the split thread forming member 51 and its holder 54 back into the position in which they abut the turret 46 and the head split mechanism 65 is operated to close the split members together about the cylindrical sealing surface of the core at station A
10 thereby to define the neck portion of the preform to be molded.
Figure 10 illustrates a production injection blow molding apparatus utilizing the present invention in an arranyement in which there are twelve identical injection 15 molds and associated cores disposed in two vertical parallel rows of six with a similar arran~ement of blow molds and associated cores. The apparatus of Figure 10 includes an extruder assembly 66, a twelve cavity injection mold unit 67, a rotatable core mounting turret 20 68 adapted to rotate through 180 , and back, about axis 48 and a twelve cavity blow mold 69. The opening and closing of the mold units of the apparatus is carried out by a mold clamping unit 70. The apparatus is supported on a bed 71 which carries the controls utilized for operating.
25 the apparatus.
Figure 11 illustrates the temperature control arrangements utilized in the injection molds, the cores, and the blow molds. Again, parts corresponding to those discussed with respect to Figures 4 through 9 are given 30 similar reference numerals.
Figure 12 illustrates an alternative cons-truction of injection blow molding apparatus u-tilizing the present invention in a four stage rotary motion of a turret ~1 in which a core ~2 is sequentially rotated from station P to 35 stations Q, R and S prior to return to station P. At , station P a preform is injection molded on a core in a manner similar to that discussed with reference to Figures 4 through 9. The core and preform shape are the same as described with reference to Fiyures 1, 2 and 3 and the neck of the preform is held in sealing engagement with -the core by a split thread forming member 83, again in similar manner to that described in reference to Figures 4 through g. Following formation of the preform at station P, the turret is rotated through 90 and the core and preform 10 are placed in a preblow heating chamber 84 which has a plurality of heating zones W, X, Y and Z by virture of which the temperature of various portions of the preform can be very accurately controlled prior to movement of the preform to the blow molding station R. At station Q the 15 split thread forming member 8~ is moved away from the turret in the direction of arrow 85 to move the preform along the core to provide a desired spacing of the preform body portion from the core as discussed above with reference to Figures 1 through 9 to provide desired 20 temperature conditioning of the preform prior to pre-blowing. At station Q the preform, once this temperature conditioning is achieved, is blown to form an intermediate size preform contacting the walls of cavity 86 of the preblow heating chamber with the partially blown ~5 preorm then being temperature controlled as desired preparatory to moving to the blow station R, by programmed control of the temperatures of zones W, X, Y and Z. When the desired temperature of the partially blown preform is achieved, the preblow heating chamber 84 is withdrawn and 30 the turret rotated a further 90 to bring the core and partially blown preform to the blow molding station R.
The split thread forming member 83 maintains the neck of the preform in sealing engagement with the cylindrical sealing surface of the core throughout the processing 35 steps carried out at stations P, Q and R.
.,, ~

~ ~ ~79~

At the blow molding station R a blow mold 87 is moved into place over the pre-blown and temperature conditioned preform and the blow molding is completed as previously described. Subsequently to this blow molding, the turret is rotated a further 90 to bring the now blown bioriented container to station S where the split thread forming member is open and the container ejected.
It will be appreciated that the four stages of ~his arrangement can be operated together whereby four 10 containers in various stages of manuacture are made together.
By use of the four stage process described with reference to Figure 12, containers of more complex structure and variable wall thickness can be produced and 15 no temperature control is required in the blow mold at station R with a high production rate consequently being possible.
Although the invention has so far been described with reference to containers having a thread ~ormed on the neck 20 of the preform, it will be appreciatecl the invention is not restricted to the production of such containers and that necks with Elange or other configurations can readily be produced by the invention of the present application.
The present application is, urt11er, able efectively to 25 produce wide mouth small containers which presently cannot be made economically by injection blow molding.
Apart from the design of preform, core and injection blow molding apparatus, the present invention also provides an innovative process for blow molding as follows.
A preform is injection molded in an injection mold cavity on a core to which a neck portion of the preform is sealed and by virtue of the shape of which the preform can be moved longitudinally of the core to space the main body of ~he preform from the core a sufficient distance to 35 provide desired thermal isolation of the preform from the . . . ~

9~

core while at the same time t~le seal of the neck of the preform against the core is maintained. The preform spaced from the core is then conditioned as to temperature to produce a desired temperature distribution throughout the material of the preform for a desired blow molding performance. Following this temperature conditioning which may include the blowing of air at a controlled temperature over the exterior and/or the interior surfaces of the preform, the preform is blown in a blow mold to 10 produce a bioriented thermoplastic material container.
Between the temperature conditioning of the preform and the blow molding step, the preform may be part blown to a preblow shape which is subsequently temperature controlled -to a desired temperature condition prior to a final blow 15 molding step. The fully blown container is then released and ejected. In a preferred form of the process, a preform and core upon which it is mounted, are indexed from the injection station to the blow molding station with injection and blow molding thereby being possible at the 20 same time.
The present invention has been described with a symmetrical circular preorm. However, it will be appreciated that other cross-sectional shapes fall within the scope of the present invention. In addition, it is 25 the inte~ior surEace(s) of the preform which are designed to achieve a qeal with the core while permitting relative movement to introduce a thermally isolating gap. of course, the exterior surface(s) of the preform may be whatever is desired to produce the materia~ distribution 30 for the container to be blown from the preform.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are as defined as follows:

1. An injection blow molding press for use in making blow molded hollow articles comprising at least two preform cores having free ends extended in different directions from each other and each having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station positioned to cooperate with cores extended in said different directions, a turret for mounting said cores, the turret being mounted for step-wise angular movement to sequentially bring said cores into registry with the preform injection molding station and the blow molding station, a neck ring split for each core positioned to cooperate with the portion thereof of constant cross section, each neck ring split being mounted on the turret with freedom for movement axially of its associated core, means for relatively shifting said turret and said injection molding and blowing stations and providing for entry of each core sequentially into an injection molding station and a blow molding station, a mounting holder for each neck ring split, each holder being shiftably mounted on the turret and providing for shifting movement of the neck ring split axially of the portion of the core of constant cross section, means providing for shifting movement of the holder for each neck ring in a direction toward the base end of its associated core when the core is in the injection molding station, and means mounted on the turret for shifting the holder for each neck ring split with respect to the turret to a position displaced toward the free end of its associated core when the turret is positioned to bring the core into registry with the blow molding station.

2. Apparatus as defined in Claim 1 and further including means for circulating a heat transfer gas in contact with a surface of the tapered portion of the preform when the neck ring split is shifted to a position displaced toward the free end of the core.

3. Apparatus as defined in Claim 2 in which the means for circulating heat transfer gas comprises means for introducing the heat transfer gas into contact with the exterior surface of the preform when the preform is in registry with the blow molding station.

4. Apparatus as defined in Claim 3 and further including providing for introduction of blowing gas into the preform in the blow molding station subsequent to intro-duction of the heat transfer gas.

5. Apparatus as defined in Claim 1 in which the injection blow molding press develops a clamp pressure by means including a fixed platen on which the preform injection station is mounted, a movable platen on which the blow molding station is mounted, and an intermediate platen on which the turret and the mounting holders for the neck ring splits are movably mounted.

6. Apparatus as defined in Claim 5 in which said means providing for shifting movement of each neck ring holder provides for said shifting movement to said displaced position independently of the press clamp pressure.

7. An injection blow molding press for use in making blow molded hollow articles comprising a fixed platen, a preform injection molding station connected with said fixed platen, a movable platen, a blow molding station mounted on said movable platen, an intermediate platen, a turret mounted on said intermediate platen with freedom for angular movement, at least two preform cores mounted on said turret and having free ends extended in opposite directions, each preform core having a portion of constant cross section adjacent its base end and an adjoining tapered portion, the turret being mounted for angular movement to sequentially bring said cores into registry with the preform injection molding station and the blow molding station, a neck ring split for each core positioned to cooperate with the portion thereof of constant cross section, each neck ring split being mounted on the turret with freedom for movement axially of its associated core, means for relatively shifting said turret with respect to said injection molding and blowing stations and providing for entry of each core sequentially into an injection molding station and a blow molding station, a mounting holder for each neck ring split, each holder being shiftably mounted on the turret and providing for shifting movement of the neck ring split axially of the portion of the core of constant cross section, means providing for shifting movement of the holder for each neck ring in a direction toward the base end of its associated core when the core is in the injection molding station, and means mounted on the turret for shifting the holder for each neck ring split with respect to the turret to a position displaced toward the free end of its associated core when the turret is positioned to bring the core into registry with the blow molding station.

8. An injection blow molding press as defined in Claim 7 in which said means providing for shifting move-ment of each neck ring holder provides for said shifting movement to said displaced position independently of the press clamp pressure against the fixed platen.

9. An injection blow molding press for use in making blow molded hollow articles comprising at least two preform cores having free ends extended in different directions from each other and each having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station positioned to cooperate with cores extended in said different directions, a turret for mounting said cores, the turret being mounted for step-wise angular movement to bring said cores at different times into registry with the preform injection molding station and the blow molding station, neck ring split means for the cores including means for clamping the preform in sealing contact with the portion of the core of constant cross section prior to the blow molding, and further including shiftable means adapted to engage the base portion of the preform formed on a core in the region of the portion of the core of constant cross section, means for shifting said shiftable means prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and thereby provide spacing between the preform and said tapered portion of the core, and means for relatively shifting said turret and said injection molding and blowing stations and providing for entry of each core into an injection molding station and blow molding station at different times.

10. An injection blow molding press for use in making blow molded hollow articles comprising at least two preform cores having free ends extended in different directions from each other and each having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station positioned to cooperate with cores extended in said different directions, the preform injection molding station including means for forming a preform having an open end with a portion of reduced outside diameter axially spaced from the end opening in the preform in the region of constant diameter of the core, mounting means for said cores, said mounting means providing for step-wise angular movement to bring each one of said cores at different times into registry with the preform injection molding station and the blow molding station, neck ring split means for the cores including shiftable means adapted to engage said portion of the preform of reduced outside diameter in the region of the portion of the core of constant cross section, means for shifting said shiftable means prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and thereby shift the preform toward the free end of the core to provide spacing between the preform and said tapered portion of the core while maintaining sealing contact between the preform and the portion of the core of constant cross section, and means for relatively shifting said mounting means and said injection molding and blowing stations and providing for entry of each core into an injection molding station and a blow molding station at different times.

11. An injection blow molding press for use in making blow molded hollow articles having a neck with a neck opening, comprising at least two preform cores having free ends extended in different directions from each other and each having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station positioned to cooperate with cores extended in said different directions, a turret for mounting said cores, the turret being mounted for step-wise angular movement to bring each of said cores at different times into registry with the preform injection molding station and the blow molding station, means for shifting the preform on the core prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and thereby provide spacing between the preform and said tapered portion of the core, neck ring split means for the cores including neck engaging elements relatively movable in a direction radially toward and away from the outside of the neck of the article being formed and further including means at the blow molding station for maintaining sealing contact of the preform with the portion of the core of constant cross section, and means for relatively shifting said turret and said injection molding and blowing stations and providing for entry of each core into an injection molding station and a blow molding station at different times.

12. An injection blow molding press for use in making blow molded hollow articles having a neck with a neck opening, comprising at least one preform core having a free end and having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station, means for mounting the core for step-wise movement to bring said core at different times into registry with the preform injection molding station and the blow molding station, means for shifting the preform on the core prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and thereby provide spacing between the preform and said tapered portion of the core, and neck ring split means for the core including neck engaging elements relatively mov-able in a direction radially toward and away from the out-side of the neck of the article being formed and further including means at the blow molding station for maintaining said elements in position to maintain sealing contact of the preform against the portion of the core of constant cross section during the blow molding.

13. An injection blow molding press for use in making blow molded hollow articles, comprising at least two preform cores having free ends extended in different directions from each other and each having a portion of constant cross section adjacent its base end and an adjoining tapered portion, a preform injection molding station and a blow molding station positioned to cooperate with cores extended in said different directions, the preform injection molding station including means for forming a preform having a neck with an open end with a portion of reduced outside diameter axially spaced from the end opening in the preform in the region of constant diameter of the core, mounting means for said cores, said mounting means providing for step-wise angular movement to bring each of said cores at different times into registry with the preform injection molding station and the blow molding station, means for shifting the preform on the core prior to the blow molding of the article in the blow molding station in a direction toward the free end of the core and thereby provide spacing between the preform and said tapered portion of the core, neck ring split means for the cores including neck engaging elements relatively movable in a direction radially toward and away from the outside of the said portion of the neck of the preform of reduced diameter and further including means at the blow molding station for maintaining said elements in position to maintain sealing contact of the preform against the portion of the core of constant cross section during the blow molding, and means for relatively shifting said mounting means and said injection molding and blowing stations and providing for entry of each core into an injection molding station and a blow molding station at different times.