CA1193817A - Injection molding core ring gate system - Google Patents
Injection molding core ring gate systemInfo
- Publication number
- CA1193817A CA1193817A CA000422305A CA422305A CA1193817A CA 1193817 A CA1193817 A CA 1193817A CA 000422305 A CA000422305 A CA 000422305A CA 422305 A CA422305 A CA 422305A CA 1193817 A CA1193817 A CA 1193817A
- Authority
- CA
- Canada
- Prior art keywords
- valve pin
- cavity
- gate
- head portion
- melt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001746 injection moulding Methods 0.000 title claims abstract description 13
- 239000000155 melt Substances 0.000 claims abstract description 32
- 238000001816 cooling Methods 0.000 claims abstract description 21
- 238000000465 moulding Methods 0.000 claims abstract description 11
- 230000007246 mechanism Effects 0.000 claims abstract description 9
- DMFGNRRURHSENX-UHFFFAOYSA-N beryllium copper Chemical compound [Be].[Cu] DMFGNRRURHSENX-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052751 metal Inorganic materials 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 7
- 230000006872 improvement Effects 0.000 claims description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 3
- 239000010959 steel Substances 0.000 claims description 3
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 2
- 239000012530 fluid Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012943 hotmelt Substances 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- NLZUEZXRPGMBCV-UHFFFAOYSA-N Butylhydroxytoluene Chemical compound CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 NLZUEZXRPGMBCV-UHFFFAOYSA-N 0.000 description 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 235000011089 carbon dioxide Nutrition 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 235000002020 sage Nutrition 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/27—Sprue channels ; Runner channels or runner nozzles
- B29C45/28—Closure devices therefor
- B29C45/2896—Closure devices therefor extending in or through the mould cavity, e.g. valves mounted opposite the sprue channel
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to an injection molding system with core ring gating which is used for making products with an opening through them formed by the valve pin. The system has a melt passage which conveys pres-surize melt from a molding machine through a manifold to a bore in a gate insert, through which it flows along around the valve pin to the gate. The valve pin has a head portion extending from a reduced neck portion. The gate and the opening through the cavity are in alignment and substantially equal in diameter and the head portion of the valve pin fits closely through them into a bore in the ejector side of the mold. Actuating mechanism drives the valve pin forwardly to the open position in which the reduced neck portion extends past the gate into the cavity to allow the pressurized melt to flow into the cavity.
The valve pin is then retracted to the closed position on which the head portion closes off the gate. One portion of the head portion is hollow to form an insulative air space and another portion adjacent the tip end is filled with a beryllium copper plug. This structure provides the advantage for large diameter valve pins of improving the cooling rate in the closed position. The air space reduces the mass of the head portion of the valve pin and reduces the flow of heat into the head portion. The highly conductive plug increases the transfer of heat away from the head portion to the cooled mold platen.
This invention relates to an injection molding system with core ring gating which is used for making products with an opening through them formed by the valve pin. The system has a melt passage which conveys pres-surize melt from a molding machine through a manifold to a bore in a gate insert, through which it flows along around the valve pin to the gate. The valve pin has a head portion extending from a reduced neck portion. The gate and the opening through the cavity are in alignment and substantially equal in diameter and the head portion of the valve pin fits closely through them into a bore in the ejector side of the mold. Actuating mechanism drives the valve pin forwardly to the open position in which the reduced neck portion extends past the gate into the cavity to allow the pressurized melt to flow into the cavity.
The valve pin is then retracted to the closed position on which the head portion closes off the gate. One portion of the head portion is hollow to form an insulative air space and another portion adjacent the tip end is filled with a beryllium copper plug. This structure provides the advantage for large diameter valve pins of improving the cooling rate in the closed position. The air space reduces the mass of the head portion of the valve pin and reduces the flow of heat into the head portion. The highly conductive plug increases the transfer of heat away from the head portion to the cooled mold platen.
Description
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BACKGROUND OF THE INVENTION
1 This invention relates to injection molding and more particularly to an improved injection molding valve gated system for making a product with an opening extend-ing through it.
This type of gating in which the valve pin extends completely through the cavity is known as core ring gating. The opening through the product is the hole formed by the valve pin. A system for core ring gating is described in the applicantts Canadian patent application Serial No. 412,175 filed September 24, 1982, and the present invention is an improvement to that system.
In a core ring gate injection molding system, the head portion adjacent the tip or forward end of the valve pin which extends through the cavity is received in the movable mold pla-ten on the other side. However, when the cavity has filled and the valve pin is actuated to the closed position, if the valve pin has a large diameter, an excessive amount of heat flows along it to the melt in the cavity and to the movable mold platen on the other , ~
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1 side. In other words, it is difficult to cool the head portion of the valve pin with the result that the system will not operate quickly and satisfac-torily. While the extent of this problem depends to some degree upon the type of material being molded and the shape of the product, generally speaking, the larger the diameter of the valve pin, the greater the problem.
SI~MMARY OF THE INVENTION
Accordingly, it is an object of the invention to at least partially overcome this problem by providing a system with a valve pin arrangement which restricts the amount of heat loss through and improves the cooling of the valve pin ~n the area of the cavity.
To this end, in one of its aspects, the invention provides an injection molding system for filling a cavity with an opening therethrough having a gate insert with a bore therethrough, an elongated valve pin with a tip end which extends through the bore in the gate insert, for~ardly through a gate leading to the cavity and then through the opening through the cavity, the,gate and the opening through the cavity being in alignment and substantially e~ual in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed posltion and a forward open position in which the valve pin ex~ends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve 3~
l pin in the ga-te insert to convey pressurized melt from a molding machine to the gate, the valve pin having a head por-tion adjacent the tip end which is substantially equal in diameter -to -the gate and the opening through -the cavity and a reduced neck portion which extends past the gate in the open position to provide for the flow o-f pressuri~ed melt into the cavity, with the improvement wherein a portion of the head portion of the valve pin is hollow and another portion adjacent the tip end of the valve pin is Eilled with a highly conductive metal.
Further objects and advantages of the inven-tion will appear from the following description, taken together with the accompanying drawings.
Figure l is a sectional view of a portion of a valve gated injection molding system according to a preferred embodiment of the inventioni Figure 2 is an enlarged sectional view of a smaller portion of the system showing the valve pin in the closed position; and Fiyure 3 is a view similar to Figure 2 showing the valve pin in the open position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is first made to Figure 1 which shows one cavity 10 of a multi-cavity in~ection molding system.
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1 The system has a gate insert 12 which is seated in a ma~i~old plate 14. The gate insert 12 has a central bore 16 therethrough which extends an elongated valve pin 18. The val~e pin 18 is located by a bushing seal 20 seated in a spacer plate 22 in alignment wi-th a gate 24 and an opening 26 through the cavity 10. A
screw 27 with a driven end 28 is connected by coupling 29 to the valve pin 18. The valve pin 18 has a tip end 30 which extends forwardly through the gate 24 and through the opening 26 through the cavity and is received in the movable mold platen 32.
The driven end 28 of the screw 27 connected to the valve pin 18 is engaged by hydraulic actuating mech.anism 34 located in the back plate 36. The actuat-ing mechansim includes a piston 38 which reciprocates in a cylinder 40 seated in the back plate 36. The screw 27 extends through the piston 38 and is secured to it by a plug 44 which is screwed into the piston 38 using a hexagonal wrench which fits into a socket 46.
The piston 38 has an O-ring ~8 seated to provide a seal between it and the inner surface 50 of the cylinder 40. A high temperature seal is provided by a.V-shaped fle~ible ring 52 which is seated aro~nd the screw 27 and held in position by an expansion washer 54 seated in a groove. The piston 38 and the valve pin 18 are 1 actuated by applying controlled sources (not shown) of oil (or other hydraulic fluid) to opposite sides of the piston 38 through hydraulic fluid ducts 56,58.
The inner cylinder 40 has a removable cap 64 against which an abutment sleeve 66 is seated. As may be seen and explained more fully below, the travel of the valve pin 18 in the rearward closed position is limited by this sleeve 66 and this may be adjusted by using a sleeve 66 of a different height. The cylinder 40 has a flanged portion 68 which is secured to the back plate 3S by a number of bolts 70. Cooling water lines 72 also extend through the back plate 36 to maintain it at a predetermined temperature.
The valve pin 18 is formed of H13 steel, but has a cartridge heater 74 and a thermocouple 76 cast into it with a copper fiiling 78 generally as described in the applicant's Canadian patent application 417,9g5 filed December 17, 1982. Another elongated heater 80 is located in the melt passage 82 which extends thro~gh the manifold plate 14 and the ga-te insert 12 to collnect to the bore 16 of the gate insert adjacent the valve pin 18. The bushing seal 20 has a circumferential opening 84 extending around the valve pin 18 which initially fills with melt to form a seal. Cooling water 1 at predetermined controlled temperatures flows through conduits 86 in the gate insert 12 and the mold platen 32 and ~-ring seals 88 are providea to prevent leakage.
As may clearly be seen in Figures 2 and 3, -the gate 24 and the opening 26 through the cavity 10 are substantially the same diameter as and in alignment with a bore 90 extending into the movable mold platen 32. The valve pin 18 has a head portion 92 which is substantially the same diameter and extends from a neck portion 94 with a reduced diameter to the tip end 30. The head portion 92 of the valve pin 18 has a hollow well 96 extending from the tip end 30 and a beryllium copper plug 98 is secured in the well 96 adjacent the tip end 30. This leaves an insulative air space 100 from the plug 98 to the end 102 of the well near the beginning of the reduced neck portion 94. In this em~odiment, the beryllium copper plug 98 is secured in the well by heat seating it in place~
This is done by first forming the well and the plug to close tolerances and then cooling the plug with dry ice before inserting it into the well.
In use, following assembly of the system as described, electrical power is applied to the cold terminal 104 of the cartridge heater 74 in the valve ~ 38~7 1 pin 18 ~s well as to the heater 80 in the manifold plate 14 to heat them up to predetermined temperatures.
Pressurizea melt is introduced Erom a molding machine (not shown) into the melt passage 82 in the manifold plate 14 where it 10ws around the hea-ter 80 and into the bore 16 of the gate insert 12. The melt then flows along the valve pin 18 to the ~ate 24. As will be appreciated, the melt flowing next to the heater 80 and the heated valve pin 18 will be maintained in a molten state, but some of the melt around the outside o the melt passage 82 and bore 16 will solidify to provide an additional insulative effect. Pressurized hydraulic ~luid applied to the hydraulic fluid ducts 56,58 controls the operation of the valve pin 18 according to a predetermined cycle. When the valve pin is driven forwardly to the open position shown in Figure 3, the melt flows through the gate 24 around the neck portion 94 of the valve pin 18 to fill the cavity 10. The junction between the neck portion 94 and the head portion 92 is bevelled to make the flow through this area as smooth as possible. After the cavity 10 is Eilled, the high injection pressure is held for a short period of time to pack and the valve pin 18 is then actuated to the rearward closed position shown in Figure 2. The melt pressure is then reduced and, after the melt in the cavity has cooled sufficiently to ~ ~3~7 1 solidify, the mold is opened and the product ejected.
Ccnventional ejector pins necessary to e~ec-t the produc-t from the cavity 10 are not shown for ease of illustration.
Similarly, in some cases, it may be necessary to provide the movable mold platen 32 with a slightly undercut collar (not shown) to slightly engage the product suf-ficiently to withdraw it from the valve pin extending through it.
It is, of course, necessary that the s~stem be capable of running quickly and reliably without plugging or s-ticking over a long period of time. Depend-ing somewhat upon the type of material being molded and the shape of the product this has not been possible with previous systems in situations where an opening 26 through the product greater ihan say one third inches in diameter it required. As mentioned above, the problem is that the mass of the head portion 92 becomes so great that after it is closed it is not possible to sufficiently cool it to permit the melt in the surround-ing cavity 10 to solidify in the time available. Theheat from the head portion of the valve pin must be transferred to the adjacent water cooled mold platen 32, but in previous systems this hea-t is replaced to some exten-t by heat conduc-ted forwardly along the valve pin from the neck portion 94. With -the present structure, the applicant has found that this problem may be over~ome, l or at least relieved to a great extent. The provision of the insulative air space lO0 greatly reduces the amoun-t of heat flowing into the head portion 92 oE the valve pin 18 in -the closed position and also reduces the mass of metal which has ~o be cooled. The provision of the highly conductive beryllium copper plug 98 accelerates the transfer of heat away from the area of the cavitiy to the cooled mold platen 32. The relative sizes of the plug 98 and the air space lO0 may be varied for different cooling rates required for different applications and different materials. ~he cooling rate may also be varied somewhat by adjusting the travel or position of the valve pin in the rearward closed position.
The further rearward the head portion 92 is in the closed position, the more of the air space lO0 located in -the gate 24 and the more of the beryllium copper plug located adjacent the cavity and therefore, the faster the melt in the cavity is cooled. Of course, there is a limit in that too much cooling can seal off the nozzle bore 16 adjacent the gate 24 resulting in unacceptable plugging. Ho~ever, the limit of ~earward travel may be quickly and easily adjusted by replacing the abutment sleeve 66 by one of a different height.
Although the description of this core ring gated injection molding system has only been given with respect to a particular embodiment, it is not to be a7 1 construed in a limiting sense. Variations and modifications will occur to those skilled in the art. For instance, the system components may be made of other available components and other types of manifolds, nozzles and actuating mechanism may be used. Therefore, for a definition of the invention, reference is made to the attached claims.
SUPPEEMENTARY DISCLOSURE
In addition to the subject matter described in the principal disclosure, khis invention includes core ring gated injection molding systems according to further embodiments of the in~ention.
These further embodiments relate to the difficulty of rapidly cooling the melt in the cavity and show the head portion of the valve pin extending a consiaerable distance into the bore in the movable mold platen to overcome this problem. To this end, one embodiment of the invention provides an injection molding system for filling a cavity defined between a cavity plate and a cool movable mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate in the cavity plate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and subs-tantially equal in diameter, ....
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1 valve pin ac-tuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which ex-tends through a manifold and around the valve pin to convey pressuriæed melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the -tip end which is substantially equal in diameter to the gate, the opening through -the cavity, and the bore in the movable mold platen, and a reduced neck portion which extends past the gate in the open position to provide for the flow of - pressurized melt into the cavity, wherein the head portion of the valve pin extends a considerable distance into the bore in the movable mold platen in the retracted closed position to provide sufficient cooling from the cool mold platen to rapidl~ cool the melt in the cavity adjacent the valve pin.
Figure 4 is a sectional view of a portion of a valve gated molding system according to a first embodiment of the invention, showing the valve pin in the retracted closed position;
. Figure 5 is an enlarged sectional view of a smaller portion of the system seen in Figure 4, showing the valve pin in the open position;
Figure 6 is a similar view according to a second embodiment of the invention, showing the valve pin in the retracted closèd position;
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~7(~ L f 1 Figure 7 is a further enlarged view of the system seen in Figure 6, showing the valve pin in the open position; and Figure 8 is a view similar to Figure 7, showing another embodiment of the invention.
Reference is now made to the e~bodiment in Figures 4 and 5 which shows one heated nozzle 110 of a multi cavi~y hydraulically actuated valve gated injection molding system seated in a cavity plate 112. The heated nozzle 110 has a central bore 14 through which extends an elongated valve pin 116 ~hich has a tip end 118 and a driven end 120. A manifold 122 extends between the heated nozzle 110 and a back plate 124 and is positioned relative to the cavity plate 112 by a locating ring 126.
A melt pa~sage 128 branches out from a recessed inlet 30 which receives the molding machine (not shown) and extends through the heated nozzle 110 to a gate 132 through a land in the cavity plate 112 which leads to the cavity 134 in the cavity plate 112. As may be seen, the melt passage 128 extends around the valve pin 16 in an enlarged portion 136 of the bore 114 through the heated noæzle 110. Tn this embodiment, the melt passage 128 joins the bore 114 in a stainless steel bushing seal 138 which is seated in the heated nozzle 110, as described in the applicantls U.S.
Patent No. 4,026,518 entitled "Bushing Seal for Valve Gated ~njection Mold" which issued May 31, 1977. The hea~ed nozzle 10 is formed primarily of a beryllium copper alloy, but has a corrosion resistant inner portion 140 formed of stainless steel.
1 The valve pin 116 which is formed of H13 steel is driven by a hydraulic actuating mechanism 142 which is seated in the back plate 124. It includes a hydraulically driven piston 144 which reciprocates in a cylinder 146. The cylinder 146 is seated in an opening in the back plate 1~4 in alignment with the valve pin 116 and has a threaded mouth 148 with a circular cap 150 for removal of the piston 144. The cylinder 146 is secured in position by bolts 152 which extend through a collar portion 154 and into the back plate 124. The valve pin 116 extends through a central hol~ 156 in the piston 144 and a plug 158 is then screwed in against the enlarged head or driven end 120 of the valve p~n to seal against an oil leak and securely attach it to the piston.
The piston 144 is driven by applying a controlled source of pressurized hydraulic fluid (not shown) to opposite sides of the piston through fluid ducts 160.
A V-shaped flexible ring 162 seated in the cylinder 146 provides a high temperature seal around the piston 144 to prevent leakage of the hydraulic fluid. Several O-.rings 164 are also provided to prevent leakage of the hydraulic fluid.
The nozzle 110 is heated by an electric heating element 166 which is cas-t into it and which receives power from a source (not shown) through terminals 168 ,~,,.
)3~3~7 1 This is, of course, controlled to substantially maintain the melt flowing through the melt passage 128 at a desired temperature~ On the other hand, the back plate 124 and the cavity plate 112 are cooled by cooling elements 170. In order to avoid unacceptable heat transfer, the hot manifold 22 and nozzle 110 are separated from the cooled cavity plate 112 and back plate 124 by insulative air gaps 172 which are provided by the locating ring 126 and the insulation bushing 174 which supports the heated nozzle 110 in the cavity plate 112. A hollow nozzle seal 176 bridges the air gap 172 around the gate 32 which prevents the escape of pressurized melt into the air gap 172. The nozzle seal 176 is seated in the heated nozzle 110 and the cavity plate 112 which accurately locates the forward portion of the nozzle 110 with respect to the gate 132.
The nozzle seal 176 is normally ~ormed of a aorrosion resistant and relatively poor conductive metal such as a titanium alloy and its shape will be described in more detail below.
As may be seen, each cavity 134 is formed by the cavity plate 112 and a movable mold platen 178 which is opened along a parting line 180. In the particular example being illustrated, the product is a year wheel 181 which is ~ormed with a central gate hole 182 equal in diameter to the gate 132. The mold 3~7 1 platen 178 also has a bore 184 which is of the same diameter and in alignrnent with the gate 32 and -the central bore 114 of the heated nozzle 110. The nozzle seal 176 similarly has a cylindrical inner surface 186 which forms a bore 188 which is the same size and in alignment with the others to receive the valve pin 116. Referring -to Figure 5, it may be seen that the valve pin 116 has a cylindrical head portion 190 adjacent the tip end 118. The head portion 190 extends forwardly from a neck portion 192 with a reduced diameter which joins the head portion 190 at a shoulder 194. The head portion 190 extends through the nozzle seal 176, ~ate 132, cavity 134 and a considerable distance into the bore 184 of the cooled mold platen and is of a size to fit closely in them to prevent unacceptable leakage of the pressurized melt. As will be further described below, the cavity 134 is provided with a portion which forms a slightly undercut collar 196 on the product 181.
In use, following assembly of the system shown in Figures 4 and 5, electrical power is applied to the terminals 168 of the heating element 166 and the heated nozzle 110 is heated up to the desired operating temperature. Pressurized melt from the molding machine is introduced into the melt passage 128 and controlled hydraulic pressure is applied to the actuating mechanism according to a predetermined cycle in a conventional manner. When the valve pin 116 is driven forward to 33~7 1 the open position shown in Figure 5, with the neck portion 192 extending into the cavity 134, the melt flows through the nozzle seal 176 and the gate 132 around the reduced neck portion. It is, of course, preferable that the components of the system be shaped to eliminate any "dead spots" in the melt flow and to ~ake the flow as smooth as possible. After sufficient melt has been in]ected into the cavity 134 to fill it, the high injection pressure is held for a short period of time to pack. The actuating mechanism then retracts the valve pin to the closed position shown in Figure 4 in which the shoulder 194 of the valve pin llG is approximately in line with the shoulder 198 formed at the rear of the inner surface 186 of the nozzle seal 176. As may be seen, in this position the hot melt which is held at the forward end of the melt passage 128 around the neck portion 192 of the valve pin 116 is thermally separated from the cooled cavity plate 112 by the noz21e seal 76 made of poorly conductive titanium. The thickness and shape of the nozzle seal 176 may be designed in conjuction with the selection of its material to optimize the amount of heat which flows through it from the heated nozzle 110 to the cavity plate 112.
After the melt in the cavity has cooled sufficiently, the mold is opened at the parting line 180, and the product 181 ejected. By way of example, 1 for a typical application, the fill time could be approximately 1 second, the packing time app~oximately 3-4 seconds, and the cooling time approximately 12-15 seconds. It will be appreciated that it is very important that cycle time be kept to a minimum, and that the cooling time represents a considerable portion of the cycle. Furthermore, it is importan-t to provide cooling to the inner portion of the part adjacent the valve pin as, in addition to reducing cooling time, this results in more uniform cooling of the part which assures ~;men~ional integrity of -the bore and also facilitates ejection. In fact, it is important to pro-vide sufficient cooling in the inner portion of the cavity both during and after filling and packing as this avoids undue "shrinkage" of the product. If there is too much "shrinkage"
during cooling or "after shrinkage" following e~ection, the molded product will be of unacceptable quality. ~hus, the present invention provides that the head portion 190 of the valve pin 116 extends into the bore 184 in the movable mold platen 178 a considerable distance even in the retracted closed position to provide for rapid cooling of the melt in the cavity 134 adjacent the valve pin 116 through the head portion 190 to the cool mold platen 178~ It is apparent that there must be sufficient ~5 clearance of the head portion 190 of the valve pin 116 in the bore 184 in the mold platen and this reduces cooling. Therefore, the area of contact between the 1 head portion 190 and the bore 184 mus-t be increased by lengthening the head portion 190 to increase the distance it extends into -the bore However, lengthening the head portion 190 has the accompanying disadvantage that ejection of the molded product is more difficult.
In order to withdraw the molded product 181 from the valve pin 116 extending through it, it is of course necessary to overcome the forces between them. Thus, the cavity 134 is designed to form a slightly undercut collar 196 which holds the product 181 on the mold platen 178 as it separates from the cavity plate 112.
Although the mold platen 178 is normally formed of a number of sections depending upon the configuration of the cavity, it is shown here as a single section for ease of illustration. Similarly, the ejector pins which eject the produ~t 181 from the cavity 134 after it opens are not shown. The ejector pins apply enough force to the molded product 181 to sufficiently compress the undercut collar 196 and release the product from the mold platen 178. After the product has been ejected, the mold is closed again and the sequence is repeated. It is, of course, necessary that the system be sufficiently reliable to run continuously for a long period of time without a malfunction due to plugging or sticking, nor deterioration of the polymer of the product. This system, in which 1 the stationary melt during the period when the v~lve pin is in the cl.osed posi-tion is completely separated further from the cooled cavity plate, has been found to be very satisfactory in this regard.
Figures 6 and 7 illustrate another embodiment of the invention in which many items are the same as those of the embodiment shown in Figures 4 and 5 and are described and illustrated using the same reference numerals. In fact, most of the structure and the operation of this embodiment is identical to that described above, and need not be repeated. The differences are that in this embodiment the head portion 190 of the valve pin 116 is formed with a hollow well 200 extending from the tip end 118 and 15 ` a copper plug 202 is seated in it adiacent the tip end 118. This provides an insulative air space 204 adjacent the neck portion 192 of the valve pin 116 While, in this embodiment, the plug 202 is heat seated in the well 200 and is shown as having a head 206 which locates it in the well and determines the length oE
air space 204, it is apparent other structures and other highly conductive metals could be used. Xn fact, the plu~ 202 could be formed of the same metal as the valve pin 116.
In use, the air space 204 provides the valve pin with greater thermal separation between the hot nozzle 110 and the cool cavity plate 112 and mold ,~
33B~3L7 1 platen 178. Thus, in the open position shown in Figure 7, the hot neck portion 192 of the valve pin 116 extends down into a p~rtion of the cavity 134 to facilitate filling, but the air space 204 insulates this from the cooling effect of the copper plug 202. On the other hand, the higher conductivity of the plug 202 results in more rapid cooliny of the melt in the cavity adjacent the valve pin, ~ut the air space 204 prevents excessive h.eat loss from the neck portion 192. In the 10 closed position shown in Figure 6, the thermal separate provided by the air space occurs in the area where the hot melt is separated from the cooled cavity plate 112.
While the relative si~es of the plug 202 and the air space 204 may be adjusted for different applications and materials, this arrangement is particularly advantageous for large diameter valve pins, for example where the diameter o~ the head portion 190 is greater than one half inches.
Figure 8 is a view similar to Figure 7 showing another embodiment of the invention. In this embodiment, the head portion 190 of the valve pin is formed with a highly conductive heat pipe 210 received in the well 200 rather than the copper plug. As may be seen, the heat pipe 210 is formed of a hollow titanium tube 212 which is partially filled with deionized, degassed, distilled water under a partial vacuum. The tube 212 is hrazed in place in the well 200 to leave the air space 204 1 between the heat pipe 210 and the neck portion 192 of the valve pin. It is apparent that the tube 212 may be ~ormed of other suitable mat~rials and that other fluids may be sealed in it depending upon the application according to well known heat pipe technology.
In use~ the system operates generally the same as ~escribed above in regard to Figures 7 and 8.
However, in this case, the heat from the mel~t vaporizes th.e water in the tube 212 and the vapour pressure cases it to circulate towards the tip end 118 where it is cooled from the cool mold platen 178. As is well known, circulation is very rapid and results in heat being transferred quickly alons the heat pipe 210 with a m; n; mllm temperature drop along its length. Thus, m~imllm cooling is provided to the part adjacent the valve pin, and the air space 204 provides thermal separation from the neck portion of the valve pin.
.Still further variations and modifications of the invention will occur to those skilled in the art.
For example, this core ring gating system can be used with other types of valve gated in~ection molding systems.
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BACKGROUND OF THE INVENTION
1 This invention relates to injection molding and more particularly to an improved injection molding valve gated system for making a product with an opening extend-ing through it.
This type of gating in which the valve pin extends completely through the cavity is known as core ring gating. The opening through the product is the hole formed by the valve pin. A system for core ring gating is described in the applicantts Canadian patent application Serial No. 412,175 filed September 24, 1982, and the present invention is an improvement to that system.
In a core ring gate injection molding system, the head portion adjacent the tip or forward end of the valve pin which extends through the cavity is received in the movable mold pla-ten on the other side. However, when the cavity has filled and the valve pin is actuated to the closed position, if the valve pin has a large diameter, an excessive amount of heat flows along it to the melt in the cavity and to the movable mold platen on the other , ~
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1 side. In other words, it is difficult to cool the head portion of the valve pin with the result that the system will not operate quickly and satisfac-torily. While the extent of this problem depends to some degree upon the type of material being molded and the shape of the product, generally speaking, the larger the diameter of the valve pin, the greater the problem.
SI~MMARY OF THE INVENTION
Accordingly, it is an object of the invention to at least partially overcome this problem by providing a system with a valve pin arrangement which restricts the amount of heat loss through and improves the cooling of the valve pin ~n the area of the cavity.
To this end, in one of its aspects, the invention provides an injection molding system for filling a cavity with an opening therethrough having a gate insert with a bore therethrough, an elongated valve pin with a tip end which extends through the bore in the gate insert, for~ardly through a gate leading to the cavity and then through the opening through the cavity, the,gate and the opening through the cavity being in alignment and substantially e~ual in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed posltion and a forward open position in which the valve pin ex~ends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve 3~
l pin in the ga-te insert to convey pressurized melt from a molding machine to the gate, the valve pin having a head por-tion adjacent the tip end which is substantially equal in diameter -to -the gate and the opening through -the cavity and a reduced neck portion which extends past the gate in the open position to provide for the flow o-f pressuri~ed melt into the cavity, with the improvement wherein a portion of the head portion of the valve pin is hollow and another portion adjacent the tip end of the valve pin is Eilled with a highly conductive metal.
Further objects and advantages of the inven-tion will appear from the following description, taken together with the accompanying drawings.
Figure l is a sectional view of a portion of a valve gated injection molding system according to a preferred embodiment of the inventioni Figure 2 is an enlarged sectional view of a smaller portion of the system showing the valve pin in the closed position; and Fiyure 3 is a view similar to Figure 2 showing the valve pin in the open position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is first made to Figure 1 which shows one cavity 10 of a multi-cavity in~ection molding system.
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1 The system has a gate insert 12 which is seated in a ma~i~old plate 14. The gate insert 12 has a central bore 16 therethrough which extends an elongated valve pin 18. The val~e pin 18 is located by a bushing seal 20 seated in a spacer plate 22 in alignment wi-th a gate 24 and an opening 26 through the cavity 10. A
screw 27 with a driven end 28 is connected by coupling 29 to the valve pin 18. The valve pin 18 has a tip end 30 which extends forwardly through the gate 24 and through the opening 26 through the cavity and is received in the movable mold platen 32.
The driven end 28 of the screw 27 connected to the valve pin 18 is engaged by hydraulic actuating mech.anism 34 located in the back plate 36. The actuat-ing mechansim includes a piston 38 which reciprocates in a cylinder 40 seated in the back plate 36. The screw 27 extends through the piston 38 and is secured to it by a plug 44 which is screwed into the piston 38 using a hexagonal wrench which fits into a socket 46.
The piston 38 has an O-ring ~8 seated to provide a seal between it and the inner surface 50 of the cylinder 40. A high temperature seal is provided by a.V-shaped fle~ible ring 52 which is seated aro~nd the screw 27 and held in position by an expansion washer 54 seated in a groove. The piston 38 and the valve pin 18 are 1 actuated by applying controlled sources (not shown) of oil (or other hydraulic fluid) to opposite sides of the piston 38 through hydraulic fluid ducts 56,58.
The inner cylinder 40 has a removable cap 64 against which an abutment sleeve 66 is seated. As may be seen and explained more fully below, the travel of the valve pin 18 in the rearward closed position is limited by this sleeve 66 and this may be adjusted by using a sleeve 66 of a different height. The cylinder 40 has a flanged portion 68 which is secured to the back plate 3S by a number of bolts 70. Cooling water lines 72 also extend through the back plate 36 to maintain it at a predetermined temperature.
The valve pin 18 is formed of H13 steel, but has a cartridge heater 74 and a thermocouple 76 cast into it with a copper fiiling 78 generally as described in the applicant's Canadian patent application 417,9g5 filed December 17, 1982. Another elongated heater 80 is located in the melt passage 82 which extends thro~gh the manifold plate 14 and the ga-te insert 12 to collnect to the bore 16 of the gate insert adjacent the valve pin 18. The bushing seal 20 has a circumferential opening 84 extending around the valve pin 18 which initially fills with melt to form a seal. Cooling water 1 at predetermined controlled temperatures flows through conduits 86 in the gate insert 12 and the mold platen 32 and ~-ring seals 88 are providea to prevent leakage.
As may clearly be seen in Figures 2 and 3, -the gate 24 and the opening 26 through the cavity 10 are substantially the same diameter as and in alignment with a bore 90 extending into the movable mold platen 32. The valve pin 18 has a head portion 92 which is substantially the same diameter and extends from a neck portion 94 with a reduced diameter to the tip end 30. The head portion 92 of the valve pin 18 has a hollow well 96 extending from the tip end 30 and a beryllium copper plug 98 is secured in the well 96 adjacent the tip end 30. This leaves an insulative air space 100 from the plug 98 to the end 102 of the well near the beginning of the reduced neck portion 94. In this em~odiment, the beryllium copper plug 98 is secured in the well by heat seating it in place~
This is done by first forming the well and the plug to close tolerances and then cooling the plug with dry ice before inserting it into the well.
In use, following assembly of the system as described, electrical power is applied to the cold terminal 104 of the cartridge heater 74 in the valve ~ 38~7 1 pin 18 ~s well as to the heater 80 in the manifold plate 14 to heat them up to predetermined temperatures.
Pressurizea melt is introduced Erom a molding machine (not shown) into the melt passage 82 in the manifold plate 14 where it 10ws around the hea-ter 80 and into the bore 16 of the gate insert 12. The melt then flows along the valve pin 18 to the ~ate 24. As will be appreciated, the melt flowing next to the heater 80 and the heated valve pin 18 will be maintained in a molten state, but some of the melt around the outside o the melt passage 82 and bore 16 will solidify to provide an additional insulative effect. Pressurized hydraulic ~luid applied to the hydraulic fluid ducts 56,58 controls the operation of the valve pin 18 according to a predetermined cycle. When the valve pin is driven forwardly to the open position shown in Figure 3, the melt flows through the gate 24 around the neck portion 94 of the valve pin 18 to fill the cavity 10. The junction between the neck portion 94 and the head portion 92 is bevelled to make the flow through this area as smooth as possible. After the cavity 10 is Eilled, the high injection pressure is held for a short period of time to pack and the valve pin 18 is then actuated to the rearward closed position shown in Figure 2. The melt pressure is then reduced and, after the melt in the cavity has cooled sufficiently to ~ ~3~7 1 solidify, the mold is opened and the product ejected.
Ccnventional ejector pins necessary to e~ec-t the produc-t from the cavity 10 are not shown for ease of illustration.
Similarly, in some cases, it may be necessary to provide the movable mold platen 32 with a slightly undercut collar (not shown) to slightly engage the product suf-ficiently to withdraw it from the valve pin extending through it.
It is, of course, necessary that the s~stem be capable of running quickly and reliably without plugging or s-ticking over a long period of time. Depend-ing somewhat upon the type of material being molded and the shape of the product this has not been possible with previous systems in situations where an opening 26 through the product greater ihan say one third inches in diameter it required. As mentioned above, the problem is that the mass of the head portion 92 becomes so great that after it is closed it is not possible to sufficiently cool it to permit the melt in the surround-ing cavity 10 to solidify in the time available. Theheat from the head portion of the valve pin must be transferred to the adjacent water cooled mold platen 32, but in previous systems this hea-t is replaced to some exten-t by heat conduc-ted forwardly along the valve pin from the neck portion 94. With -the present structure, the applicant has found that this problem may be over~ome, l or at least relieved to a great extent. The provision of the insulative air space lO0 greatly reduces the amoun-t of heat flowing into the head portion 92 oE the valve pin 18 in -the closed position and also reduces the mass of metal which has ~o be cooled. The provision of the highly conductive beryllium copper plug 98 accelerates the transfer of heat away from the area of the cavitiy to the cooled mold platen 32. The relative sizes of the plug 98 and the air space lO0 may be varied for different cooling rates required for different applications and different materials. ~he cooling rate may also be varied somewhat by adjusting the travel or position of the valve pin in the rearward closed position.
The further rearward the head portion 92 is in the closed position, the more of the air space lO0 located in -the gate 24 and the more of the beryllium copper plug located adjacent the cavity and therefore, the faster the melt in the cavity is cooled. Of course, there is a limit in that too much cooling can seal off the nozzle bore 16 adjacent the gate 24 resulting in unacceptable plugging. Ho~ever, the limit of ~earward travel may be quickly and easily adjusted by replacing the abutment sleeve 66 by one of a different height.
Although the description of this core ring gated injection molding system has only been given with respect to a particular embodiment, it is not to be a7 1 construed in a limiting sense. Variations and modifications will occur to those skilled in the art. For instance, the system components may be made of other available components and other types of manifolds, nozzles and actuating mechanism may be used. Therefore, for a definition of the invention, reference is made to the attached claims.
SUPPEEMENTARY DISCLOSURE
In addition to the subject matter described in the principal disclosure, khis invention includes core ring gated injection molding systems according to further embodiments of the in~ention.
These further embodiments relate to the difficulty of rapidly cooling the melt in the cavity and show the head portion of the valve pin extending a consiaerable distance into the bore in the movable mold platen to overcome this problem. To this end, one embodiment of the invention provides an injection molding system for filling a cavity defined between a cavity plate and a cool movable mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate in the cavity plate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and subs-tantially equal in diameter, ....
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1 valve pin ac-tuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which ex-tends through a manifold and around the valve pin to convey pressuriæed melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the -tip end which is substantially equal in diameter to the gate, the opening through -the cavity, and the bore in the movable mold platen, and a reduced neck portion which extends past the gate in the open position to provide for the flow of - pressurized melt into the cavity, wherein the head portion of the valve pin extends a considerable distance into the bore in the movable mold platen in the retracted closed position to provide sufficient cooling from the cool mold platen to rapidl~ cool the melt in the cavity adjacent the valve pin.
Figure 4 is a sectional view of a portion of a valve gated molding system according to a first embodiment of the invention, showing the valve pin in the retracted closed position;
. Figure 5 is an enlarged sectional view of a smaller portion of the system seen in Figure 4, showing the valve pin in the open position;
Figure 6 is a similar view according to a second embodiment of the invention, showing the valve pin in the retracted closèd position;
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~7(~ L f 1 Figure 7 is a further enlarged view of the system seen in Figure 6, showing the valve pin in the open position; and Figure 8 is a view similar to Figure 7, showing another embodiment of the invention.
Reference is now made to the e~bodiment in Figures 4 and 5 which shows one heated nozzle 110 of a multi cavi~y hydraulically actuated valve gated injection molding system seated in a cavity plate 112. The heated nozzle 110 has a central bore 14 through which extends an elongated valve pin 116 ~hich has a tip end 118 and a driven end 120. A manifold 122 extends between the heated nozzle 110 and a back plate 124 and is positioned relative to the cavity plate 112 by a locating ring 126.
A melt pa~sage 128 branches out from a recessed inlet 30 which receives the molding machine (not shown) and extends through the heated nozzle 110 to a gate 132 through a land in the cavity plate 112 which leads to the cavity 134 in the cavity plate 112. As may be seen, the melt passage 128 extends around the valve pin 16 in an enlarged portion 136 of the bore 114 through the heated noæzle 110. Tn this embodiment, the melt passage 128 joins the bore 114 in a stainless steel bushing seal 138 which is seated in the heated nozzle 110, as described in the applicantls U.S.
Patent No. 4,026,518 entitled "Bushing Seal for Valve Gated ~njection Mold" which issued May 31, 1977. The hea~ed nozzle 10 is formed primarily of a beryllium copper alloy, but has a corrosion resistant inner portion 140 formed of stainless steel.
1 The valve pin 116 which is formed of H13 steel is driven by a hydraulic actuating mechanism 142 which is seated in the back plate 124. It includes a hydraulically driven piston 144 which reciprocates in a cylinder 146. The cylinder 146 is seated in an opening in the back plate 1~4 in alignment with the valve pin 116 and has a threaded mouth 148 with a circular cap 150 for removal of the piston 144. The cylinder 146 is secured in position by bolts 152 which extend through a collar portion 154 and into the back plate 124. The valve pin 116 extends through a central hol~ 156 in the piston 144 and a plug 158 is then screwed in against the enlarged head or driven end 120 of the valve p~n to seal against an oil leak and securely attach it to the piston.
The piston 144 is driven by applying a controlled source of pressurized hydraulic fluid (not shown) to opposite sides of the piston through fluid ducts 160.
A V-shaped flexible ring 162 seated in the cylinder 146 provides a high temperature seal around the piston 144 to prevent leakage of the hydraulic fluid. Several O-.rings 164 are also provided to prevent leakage of the hydraulic fluid.
The nozzle 110 is heated by an electric heating element 166 which is cas-t into it and which receives power from a source (not shown) through terminals 168 ,~,,.
)3~3~7 1 This is, of course, controlled to substantially maintain the melt flowing through the melt passage 128 at a desired temperature~ On the other hand, the back plate 124 and the cavity plate 112 are cooled by cooling elements 170. In order to avoid unacceptable heat transfer, the hot manifold 22 and nozzle 110 are separated from the cooled cavity plate 112 and back plate 124 by insulative air gaps 172 which are provided by the locating ring 126 and the insulation bushing 174 which supports the heated nozzle 110 in the cavity plate 112. A hollow nozzle seal 176 bridges the air gap 172 around the gate 32 which prevents the escape of pressurized melt into the air gap 172. The nozzle seal 176 is seated in the heated nozzle 110 and the cavity plate 112 which accurately locates the forward portion of the nozzle 110 with respect to the gate 132.
The nozzle seal 176 is normally ~ormed of a aorrosion resistant and relatively poor conductive metal such as a titanium alloy and its shape will be described in more detail below.
As may be seen, each cavity 134 is formed by the cavity plate 112 and a movable mold platen 178 which is opened along a parting line 180. In the particular example being illustrated, the product is a year wheel 181 which is ~ormed with a central gate hole 182 equal in diameter to the gate 132. The mold 3~7 1 platen 178 also has a bore 184 which is of the same diameter and in alignrnent with the gate 32 and -the central bore 114 of the heated nozzle 110. The nozzle seal 176 similarly has a cylindrical inner surface 186 which forms a bore 188 which is the same size and in alignment with the others to receive the valve pin 116. Referring -to Figure 5, it may be seen that the valve pin 116 has a cylindrical head portion 190 adjacent the tip end 118. The head portion 190 extends forwardly from a neck portion 192 with a reduced diameter which joins the head portion 190 at a shoulder 194. The head portion 190 extends through the nozzle seal 176, ~ate 132, cavity 134 and a considerable distance into the bore 184 of the cooled mold platen and is of a size to fit closely in them to prevent unacceptable leakage of the pressurized melt. As will be further described below, the cavity 134 is provided with a portion which forms a slightly undercut collar 196 on the product 181.
In use, following assembly of the system shown in Figures 4 and 5, electrical power is applied to the terminals 168 of the heating element 166 and the heated nozzle 110 is heated up to the desired operating temperature. Pressurized melt from the molding machine is introduced into the melt passage 128 and controlled hydraulic pressure is applied to the actuating mechanism according to a predetermined cycle in a conventional manner. When the valve pin 116 is driven forward to 33~7 1 the open position shown in Figure 5, with the neck portion 192 extending into the cavity 134, the melt flows through the nozzle seal 176 and the gate 132 around the reduced neck portion. It is, of course, preferable that the components of the system be shaped to eliminate any "dead spots" in the melt flow and to ~ake the flow as smooth as possible. After sufficient melt has been in]ected into the cavity 134 to fill it, the high injection pressure is held for a short period of time to pack. The actuating mechanism then retracts the valve pin to the closed position shown in Figure 4 in which the shoulder 194 of the valve pin llG is approximately in line with the shoulder 198 formed at the rear of the inner surface 186 of the nozzle seal 176. As may be seen, in this position the hot melt which is held at the forward end of the melt passage 128 around the neck portion 192 of the valve pin 116 is thermally separated from the cooled cavity plate 112 by the noz21e seal 76 made of poorly conductive titanium. The thickness and shape of the nozzle seal 176 may be designed in conjuction with the selection of its material to optimize the amount of heat which flows through it from the heated nozzle 110 to the cavity plate 112.
After the melt in the cavity has cooled sufficiently, the mold is opened at the parting line 180, and the product 181 ejected. By way of example, 1 for a typical application, the fill time could be approximately 1 second, the packing time app~oximately 3-4 seconds, and the cooling time approximately 12-15 seconds. It will be appreciated that it is very important that cycle time be kept to a minimum, and that the cooling time represents a considerable portion of the cycle. Furthermore, it is importan-t to provide cooling to the inner portion of the part adjacent the valve pin as, in addition to reducing cooling time, this results in more uniform cooling of the part which assures ~;men~ional integrity of -the bore and also facilitates ejection. In fact, it is important to pro-vide sufficient cooling in the inner portion of the cavity both during and after filling and packing as this avoids undue "shrinkage" of the product. If there is too much "shrinkage"
during cooling or "after shrinkage" following e~ection, the molded product will be of unacceptable quality. ~hus, the present invention provides that the head portion 190 of the valve pin 116 extends into the bore 184 in the movable mold platen 178 a considerable distance even in the retracted closed position to provide for rapid cooling of the melt in the cavity 134 adjacent the valve pin 116 through the head portion 190 to the cool mold platen 178~ It is apparent that there must be sufficient ~5 clearance of the head portion 190 of the valve pin 116 in the bore 184 in the mold platen and this reduces cooling. Therefore, the area of contact between the 1 head portion 190 and the bore 184 mus-t be increased by lengthening the head portion 190 to increase the distance it extends into -the bore However, lengthening the head portion 190 has the accompanying disadvantage that ejection of the molded product is more difficult.
In order to withdraw the molded product 181 from the valve pin 116 extending through it, it is of course necessary to overcome the forces between them. Thus, the cavity 134 is designed to form a slightly undercut collar 196 which holds the product 181 on the mold platen 178 as it separates from the cavity plate 112.
Although the mold platen 178 is normally formed of a number of sections depending upon the configuration of the cavity, it is shown here as a single section for ease of illustration. Similarly, the ejector pins which eject the produ~t 181 from the cavity 134 after it opens are not shown. The ejector pins apply enough force to the molded product 181 to sufficiently compress the undercut collar 196 and release the product from the mold platen 178. After the product has been ejected, the mold is closed again and the sequence is repeated. It is, of course, necessary that the system be sufficiently reliable to run continuously for a long period of time without a malfunction due to plugging or sticking, nor deterioration of the polymer of the product. This system, in which 1 the stationary melt during the period when the v~lve pin is in the cl.osed posi-tion is completely separated further from the cooled cavity plate, has been found to be very satisfactory in this regard.
Figures 6 and 7 illustrate another embodiment of the invention in which many items are the same as those of the embodiment shown in Figures 4 and 5 and are described and illustrated using the same reference numerals. In fact, most of the structure and the operation of this embodiment is identical to that described above, and need not be repeated. The differences are that in this embodiment the head portion 190 of the valve pin 116 is formed with a hollow well 200 extending from the tip end 118 and 15 ` a copper plug 202 is seated in it adiacent the tip end 118. This provides an insulative air space 204 adjacent the neck portion 192 of the valve pin 116 While, in this embodiment, the plug 202 is heat seated in the well 200 and is shown as having a head 206 which locates it in the well and determines the length oE
air space 204, it is apparent other structures and other highly conductive metals could be used. Xn fact, the plu~ 202 could be formed of the same metal as the valve pin 116.
In use, the air space 204 provides the valve pin with greater thermal separation between the hot nozzle 110 and the cool cavity plate 112 and mold ,~
33B~3L7 1 platen 178. Thus, in the open position shown in Figure 7, the hot neck portion 192 of the valve pin 116 extends down into a p~rtion of the cavity 134 to facilitate filling, but the air space 204 insulates this from the cooling effect of the copper plug 202. On the other hand, the higher conductivity of the plug 202 results in more rapid cooliny of the melt in the cavity adjacent the valve pin, ~ut the air space 204 prevents excessive h.eat loss from the neck portion 192. In the 10 closed position shown in Figure 6, the thermal separate provided by the air space occurs in the area where the hot melt is separated from the cooled cavity plate 112.
While the relative si~es of the plug 202 and the air space 204 may be adjusted for different applications and materials, this arrangement is particularly advantageous for large diameter valve pins, for example where the diameter o~ the head portion 190 is greater than one half inches.
Figure 8 is a view similar to Figure 7 showing another embodiment of the invention. In this embodiment, the head portion 190 of the valve pin is formed with a highly conductive heat pipe 210 received in the well 200 rather than the copper plug. As may be seen, the heat pipe 210 is formed of a hollow titanium tube 212 which is partially filled with deionized, degassed, distilled water under a partial vacuum. The tube 212 is hrazed in place in the well 200 to leave the air space 204 1 between the heat pipe 210 and the neck portion 192 of the valve pin. It is apparent that the tube 212 may be ~ormed of other suitable mat~rials and that other fluids may be sealed in it depending upon the application according to well known heat pipe technology.
In use~ the system operates generally the same as ~escribed above in regard to Figures 7 and 8.
However, in this case, the heat from the mel~t vaporizes th.e water in the tube 212 and the vapour pressure cases it to circulate towards the tip end 118 where it is cooled from the cool mold platen 178. As is well known, circulation is very rapid and results in heat being transferred quickly alons the heat pipe 210 with a m; n; mllm temperature drop along its length. Thus, m~imllm cooling is provided to the part adjacent the valve pin, and the air space 204 provides thermal separation from the neck portion of the valve pin.
.Still further variations and modifications of the invention will occur to those skilled in the art.
For example, this core ring gating system can be used with other types of valve gated in~ection molding systems.
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Claims (11)
1. In an injection molding system for filling a cavity defined between a cool cavity plate and a cool mov-able mold platen with an opening therethrough, an elongated valve pin with a tip end which extends through a gate in the cavity plate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pressurized melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the tip end which is substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, and a reduced neck portion which extends past the gate in the open position to provide for the flow of pressurized melt into the cavity, the improvement wherein a first portion of the head portion adjacent the reduced neck portion of the valve pin is hollow.
2. A system as claimed in claim 1 wherein the valve pin is formed of steel.
3. A system as claimed in claim 2 wherein the head portion of the valve pin has a central portion between the hollow portion and the tip end formed of a highly conductive metal.
4. A system as claimed in claim 3 wherein the highly conductive metal is a beryllium copper alloy.
5. A system as claimed in claim 3 wherein the head portion of the valve pin has a central well extending from the tip end, and a beryllium copper plug is seated in the well adjacent the tip end.
6. A system as claimed in claim 5 wherein the plug is heat seated in the well.
7. A system as claimed in claim 6 wherein the diameter of the head portion of the valve pin is greater than one third inches.
8. A system as claimed in claim 7 further including adjustable stop means to limit the rearward travel of the valve pin to the closed position, whereby the amount of heat loss through the head portion of the valve pin may be varied.
9. A system as claimed in claim 7 wherein the stop means comprises an abutment sleeve of a particular height located in the actuator means.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
10. In an injection molding system for filling a cavity defined between a cool cavity plate and a cool movable mold platen with an opening therethrough, an elong-ated valve pin with a tip end which extends through a gate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pres-surized melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the tip end which extends from a reduced neck portion, the head portion being substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, the reduced neck portion extending past the gate in the open position to provide for the flow of pressured melt into the cavity,
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
10. In an injection molding system for filling a cavity defined between a cool cavity plate and a cool movable mold platen with an opening therethrough, an elong-ated valve pin with a tip end which extends through a gate leading to the cavity, through the cavity, and into a bore in the movable mold platen, the gate, the opening through the cavity, and the bore in the movable mold platen being in alignment and substantially equal in diameter, valve pin actuating mechanism which reciprocates the valve pin between a rearward closed position and a forward open position in which the valve pin extends further through the opening through the cavity, a melt passage which extends through a manifold and around the valve pin to convey pres-surized melt from a molding machine to the gate, the valve pin having an elongated head portion adjacent the tip end which extends from a reduced neck portion, the head portion being substantially equal in diameter to the gate, the opening through the cavity, and the bore in the movable mold platen, the reduced neck portion extending past the gate in the open position to provide for the flow of pressured melt into the cavity,
Claim 10 continued...
the improvement wherein the head portion of the valve pin extends a considerable distance into the bore in the movable mold platen in the retracted closed position to provide sufficient cooling from the cool mold platen to rapidly cool the melt in the cavity adjacent the valve pin.
the improvement wherein the head portion of the valve pin extends a considerable distance into the bore in the movable mold platen in the retracted closed position to provide sufficient cooling from the cool mold platen to rapidly cool the melt in the cavity adjacent the valve pin.
11. A system as claimed in claim 1 wherein the head portion of the valve pin has a central portion extending between the hollow portion and the tip end formed of a highly conductive heat pipe.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000422305A CA1193817A (en) | 1983-02-24 | 1983-02-24 | Injection molding core ring gate system |
| US06/568,048 US4521179A (en) | 1983-02-24 | 1984-01-04 | Injection molding core ring gate system |
| JP59029661A JPS59188417A (en) | 1983-02-24 | 1984-02-21 | Core ring gate device for injection molding |
| DE8484101799T DE3468645D1 (en) | 1983-02-24 | 1984-02-21 | Injection molding core ring gate system |
| EP84101799A EP0117510B1 (en) | 1983-02-24 | 1984-02-21 | Injection molding core ring gate system |
| AT84101799T ATE31893T1 (en) | 1983-02-24 | 1984-02-21 | RING CLOSURE DEVICE FOR INJECTION MOLDING TOOLS. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000422305A CA1193817A (en) | 1983-02-24 | 1983-02-24 | Injection molding core ring gate system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1193817A true CA1193817A (en) | 1985-09-24 |
Family
ID=4124631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000422305A Expired CA1193817A (en) | 1983-02-24 | 1983-02-24 | Injection molding core ring gate system |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4521179A (en) |
| EP (1) | EP0117510B1 (en) |
| JP (1) | JPS59188417A (en) |
| AT (1) | ATE31893T1 (en) |
| CA (1) | CA1193817A (en) |
| DE (1) | DE3468645D1 (en) |
Families Citing this family (52)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4530654A (en) * | 1984-05-29 | 1985-07-23 | Mold-Masters Limited | Injection molding peripheral opening core ring gate |
| US4806301A (en) * | 1984-08-15 | 1989-02-21 | American Safety Closure Corp. | Process of removing a plastic cap from a mold |
| US4622001A (en) * | 1985-03-12 | 1986-11-11 | Electra Form, Inc. | Cavity cooling system |
| CA1239515A (en) * | 1985-09-13 | 1988-07-26 | Jobst U. Gellert | Injection molding manifold system having balanced bridging manifold |
| JPS62196115A (en) * | 1986-02-21 | 1987-08-29 | Honda Motor Co Ltd | Molding of molded hole and molding equipment thereof |
| US4938681A (en) * | 1989-01-03 | 1990-07-03 | Gellert Jobst U | Injection molding system having offset valve pin biasing mechanism |
| CA1292848C (en) * | 1989-02-14 | 1991-12-10 | Jobst Ulrich Gellert | Injection molding system having a valve member with a ribbed insulative portion |
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| CA2409785C (en) * | 2002-10-25 | 2010-09-07 | Harald Schmidt | Apparatus for heating injection molding fluid |
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| JP2005254480A (en) * | 2004-03-09 | 2005-09-22 | Nippon Densan Corp | Valve gate type injection molding machine and injection-molding method using it |
| US20050255187A1 (en) * | 2004-05-14 | 2005-11-17 | University Of Massachusetts | Methods and devices for melt pressure regulation |
| US7226283B2 (en) * | 2004-10-13 | 2007-06-05 | Mold-Masters Limited | Injection molding apparatus with a melt channel in valve pin |
| US8091202B2 (en) | 2009-05-06 | 2012-01-10 | Synventive Molding Solutions, Inc. | Method and apparatus for coupling and uncoupling an injection valve pin |
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| US2940123A (en) * | 1957-07-17 | 1960-06-14 | Basf Ag | Shut-off nozzle for injection molding of thermoplastic materials |
| DE1529930A1 (en) * | 1965-07-21 | 1969-10-30 | Wolfgang Feine | Method and device for the production of injection molded bodies |
| JPS5227181B1 (en) * | 1971-02-17 | 1977-07-19 | ||
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| CA1029162A (en) * | 1975-04-10 | 1978-04-11 | Jobst U. Gellert | Bushing seal for valve-gated injection mold |
| CA1086014A (en) * | 1977-04-29 | 1980-09-23 | Jobst U. Gellert | Thermal valve pin |
| US4268240A (en) * | 1978-01-06 | 1981-05-19 | Husky Injection Molding Systems | Actuating mechanism for gate valve of injection nozzle |
| JPS5561438A (en) * | 1978-11-02 | 1980-05-09 | Hokoku Jushi Kogyo Kk | Hot runner system injection molding method and nozzle used for the said injection molding |
| US4279582A (en) * | 1979-04-02 | 1981-07-21 | Incoe Corporation | Method and apparatus for individual control of injection mold shut-off bushings |
| CA1149568A (en) * | 1980-05-21 | 1983-07-12 | Jobst U. Gellert | Melt spinning nozzle tip |
| CA1167222A (en) * | 1981-07-15 | 1984-05-15 | Jobst U. Gellert | Valve pin and method of manufacture |
| JPS61438A (en) * | 1984-06-14 | 1986-01-06 | Jujo Paper Co Ltd | Removal of excessive formaldehyde in microcapsule dispersion |
-
1983
- 1983-02-24 CA CA000422305A patent/CA1193817A/en not_active Expired
-
1984
- 1984-01-04 US US06/568,048 patent/US4521179A/en not_active Expired - Lifetime
- 1984-02-21 EP EP84101799A patent/EP0117510B1/en not_active Expired
- 1984-02-21 DE DE8484101799T patent/DE3468645D1/en not_active Expired
- 1984-02-21 JP JP59029661A patent/JPS59188417A/en active Granted
- 1984-02-21 AT AT84101799T patent/ATE31893T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3468645D1 (en) | 1988-02-18 |
| JPS59188417A (en) | 1984-10-25 |
| EP0117510B1 (en) | 1988-01-13 |
| ATE31893T1 (en) | 1988-01-15 |
| EP0117510A1 (en) | 1984-09-05 |
| US4521179A (en) | 1985-06-04 |
| JPH0338096B2 (en) | 1991-06-07 |
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