CA2012133A1

CA2012133A1 - Tool for molding plastic articles

Info

Publication number: CA2012133A1
Application number: CA002012133A
Authority: CA
Inventors: William A. Martell; Colin R. Brown
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1989-06-19
Filing date: 1990-03-14
Publication date: 1990-12-19
Also published as: AU612934B2; US4955804A; JPH0334808A; EP0404319A1; AU5494690A

Abstract

TOOL FOR MOLDING PLASTIC ARTICLES

Abstract of The Disclosure This mold tooling has a hot drop assembly operatively mounted in a bore formed therein which opens to a mold face. Heated plastic material is fed to a feed tube of the hot drop assembly and this material is heated at a temperature higher than the working temperature of the mold during its transit the face of the tool by electrically energized heater bands encircling the feed tube. The space between the heater bands and bore wall accommodates tubing through which a flow of chilled cooling air is injected. The temperature and amount of the cooling air may be regulated to match the heat energy discharged by the heating bands into the bore and to the body of the tooling. The flow of cooling air transmits heat energy out of the bore so that heat sensitive plastic materials being molded is not degraded by hot drop assembly heat energy that otherwise would be conducted by the tool body to the tool face.

Description

TOOL FOP~ ~OLDING PLASTIC ARTICIIES

PIISL~D OF ~ liO II
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Thi~ invention relate~ to molding of plastics and more particularly to new and improved : ;
tooIs with internal flui~ cooling for ~olding plastic ~
... .
articles from charges of hot plastic materials fed to ;~
the tooling.

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BAC~RO~ND OF T~E I~Y~NTION

Prior to the preseint invention tooling for molding pla~tics articles from a heated supply of pla~tic material generally require a cooling system 80 that finally fini~hed articles are produced without degradation from heat build up at the mold face. For exampl~ dr$11ed line~ are provided in : in~ection mold~ng tooling around the hot drop a~sombly fixed within the tooling so that cooling liquids 10wing therethrough can transfer the high heat energy transmitted from the hot drop as6emb1y to the tool away from the face of the tool. With such cooling the part being molded will not be damaged or destroyed by migration of heat to the tool face from ~1'~

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~`~ ' 20~2133 .

the hot drop assembly. While ~uch prior art cooling systems are effective they require extensive, labor-intensive cross-drillins of liquid flow paths generally in a rectilinear pat~ern that require plugging at drill entrance holes. In such cooling systems liquids such as water can be used as the heat transfer agent which may have impuritie tha~ build up and restrict or block and such paths. The cooling water may also freeze and expand in cold weather during tool storage or shipment or during power outages to damage or destroy the mold. Cooling liquids are also susceptible to leaking through the mold and may cause marginal performance or damage of the tool or damage to the molded product. With the lS above in mind the present invention provides a new and improved molding tool rOr molding articles from heated plastic material featuring improved cooling of ;
the tool to prevent the degradation of the part molded.

~UMMARY OF THE INV~NTION

The preferred embodiment of this invention employes a hot drop assembly mounted within a bore in in~ection mold tooling to raise the temperature of the molten plastic to prevent premature hardening of ~0~2~3~

the plastic6 transiting therethrough before entering the working face o~ the mold. Generally, this hot drop as~embly has heater ele~ents extending around a feeder tube that conducts the heated charges of plastic material from a hot runner system through the tool body and to the ~old space de~ined by the tool body used to retain the mold core and mold cavity.

With this invention a new and improved cooling system is provided which eliminates the use of the bored liquid cooling pas~ages of the prior art and the requirement for cooling liquids for heat transfer. In the present invention the hot drop assembly is radially spaced from the walls of the tool that define the bore for the hot drop asse~bly and the space is advantageously used by new and improved air cooling system and structure in which chilled air is in~ected deeply within the mold core ~:
closely ad~acent to the hot drop assembly. This cooling air transfers the radiating high heat energy ~rom the hot drop as~embly and directly from tool body areas surrounding the hot drop assembly so that such heat energy will not ~igrate through the tool body to the face of the mold to degrade or destroy the article being molded.
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Accordingly, it is an object of this invention to provide new and improved tooling for molding pla~tic articles by in~ecting a flow of chilled cooling air to the areas of the mold tooling currounding a hot drop assembly to inhibit the conduction of heat ~nOErgy ~rom the hot drop assembly by the tool body to the ~old face thereof.
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It is another object of the .invention to provide a new and improved forced air cooling system for injection mold hot drop cavities in a wide range ~ ~
of tools so that internal passages for transmittal of :
cooling liquids are eliminated. ;
. ~ . . .

These and other features, objects, advantages of the present invention will become more apparent from the following detailed description and drawing in which:

DS~C~IPrSO~ O~ T~ DRA-~INa The figure i5 a diagrammatic illustration with parts in cros~ section of a injection mold tooling with a hot drop assembly with a cooling ~ystem provided therefor.

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.- --5--DE:TAILiSD DB8~RIp~rso~ OF TB DR~ -I~G

Referring now in greater detail to the .
drawing there is shown in the Figure a two p~ate mold 10 assembl~d for op~rating at a predetermined temperatur~ range ~or ~olding article~ fro~ molt~n pla~tics mater1al supplied thereto from an in~ection molding machine through a conventional hot runner 8y8t~m 12. Th2 hot runner sycte~ furth~r heats the plastics material being conducted therethrough and directs this material through a discharge opening 14 into a hot drop assembly 16, that is, operatively mounted within a tool 18 of the assembled mold 10. :~
The tool 18 includes a mold cavity 20 which may be a separate part or integral with the face of the to~
As shown, the hot drop assembly extends in an opening through tool 18 ~ormed by bore 22 and counter bore 24. ~he hot drop asse~bly 16 includes a feeder tube with a cylindrical main body 26 and a reduced diameter nozzle 2a that fit~ within the counter bore 24 and extend~ to the f2se 30 of the tool. .

That feeder tube of the hot drop assem~ly :-has a longitudinally extending feed pas6age 32 :~
25 therethrough with an entrance 34 in a flanged lower . :
end 35 communicating with the discharge opening 14 of ~ :
the hot runner system and with a reduced diameter 291~13~
- \ ~

ejector passage 36 which ter~inates in an annular opening 38 for discharging the molten plastics material being fed through the feed passage. The discharge opening 3~ co~municates with a channel 40 formed in the ~ace 30 of cavi~y retainer tool 18 and in the face of a core retainer tool 42 of mold 10 that has a core 43 separate or integral with the tool that mates with the cavity 20 to define a mold space 44 therebetween for receiving the mclt~n plastics and ;
lo for shaping the article when the plastics material cools and solidifies.

As illustrated, the large diameter portion of the feeder tube is encircled with heater bands 46 which are energized through an electrical control system not illustrated. These heater bands operate in a temperature range significantly higher than mold 10 to prevent ~freeze up~ of the material while being in~ected into the mold space. The heater bands 46 are radially spaced ~rom the annular wall d~fining the borQ 22. This gen~rally cylindrical spac qenerally indicated àt 50 is in usual practice a dead space to provide insulation for reducing the transfer of heat energy from the energized heater bands to the wall of bore 22 and the body of tool 18 and the subsequent conduction of this heat energy to tool face 30. This insulation and the water cooling 2~ 2~33 , /
.

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passages in many ~olding tools a~cordingly aScists in preventing heat sensitive plastics articles in the mold from being damaged or destroyed by the high heat enorgy of the heater bands required to ke~p the molten plastic~ material flowing through the hot drop assembly.

The present invention i~portantly utilizes :
space 50 with greater effectiveness to improve the cooling of the core space 50 and tool 18 by providing ~or efficient heat transfer deep within the bore for ~transmittal of heat from the space 50 and from areas ~ ~:
of the tool body around core 22. In accordance with a preferred e~bod~ment o~ this ~nvention there is a pres~ure regulated ~upply of air from a compre~sor 54 or other source which is fed through line 56 to an :
air chiller 58 for lowering the temperature of air supplied thereto. -~ ~

Th~ sir chiller has a manifold 60 with : ~ :
outlets 62,64 from which copper air transmitting chlll pips~ 66 and 68 respQctively extend. From outlet 62 chill pipe 66 routs in a pas~age 69 between a mold baso plat~ 72 that supports cavity retainer tool 18 and a base plate 74 that supports the flanged end 35 of the hot drop assembly, manifold 60 and the chiller 58. Pipe 66 make~ an angular bend at 78 into . .

_ ~O~.h L33 ~ .~
. . -8-bore 22 and terminake~ in an open air end 80 deep within the ~ore 22 for di~charging chilled air therein. Chill pipe 68 extend~ beneath the mani~old mounting plate 74 and i8 routed upwardly through a vertical opening 82 therethrough and into a reverse bend to extQnd in pa~age 69 back toward the chiller.
At the hot drop a~sembly the chiller pipe 68 bends upwardly through the opening 71 in the mold base plate and into the bore 22 to a terminal end 84 that lo also opens deep inside the bore 22 to deliver cooling air within the mold for the i~ternal cooling thereof. ~:
The chiller 58 has manually operable controls 86,88 which control and vary the temperature of the cooling air and the volumeric output thereof. : ;
:
This forced cooling air will flow over the :~
wall~ of bore 50 in paths leading to the bore opening c- .... ~, :.
and exhaust out of the mold in the passage 69 between the mold bas~ and the manifold mounting base to tran~mit heat energy fro~ tool 18. This importantly lower~ the temperature of the tool particularly around the hot drop a~3emb1y to eliminate the need for an int~rnal liquid cooling systems and effectively removes the high heat energy near its sourc~. This heat energy which would otherwise be transmitted from the heater coils of the hot drop assembly into the tool body and then conducted by the r }

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g tool body 18 to face 30 thereof. Accordingly the high heat energy of the hot drop a~sembly which may operate in a temperature range up to 500 F will not migrate to the faca of the tool which operates in a temperature range up to 200 F. With this invention, thi8 heat energy will not degradate the molded pla~tic articles while solidifying in the mold space. This cooling arrangement is such that the temperature and volume output of the c~iller can be controlled through the manual controls to optimize the cooling of the tool body 18 and usage o~ energy. ;
This cooling arrangement is also adaptable to tooling made ~rom a wide range of materialc such as Zinc aL~, P20 Steel, epoxy resin~ and applies to a wide range of in~ection type tool that inject molding materials to a mold face.

While a preferred embodiment of the present invention has been shown and described, other embodiments will be apparent to thos~ skilled in the art. Accordingly, the invention is defined by the ~
following claims.

Claims

1. A mold for molding objects from a heated charge of plastic material fed thereto comprising the tool body one side of which defines a mold face, a passage in said mold body extended into said face bounded by internal wall means within said body, cooling a gas exhaust associated with said passage a hot drop assembly operative mounted within said opening for conducting and heating said charge of plastic material fed thereto for delivery thereof to said face of said mold, said hot drop assembly having an elongated injector body mounted within said tool body and having an opening therethrough for said charge of plastics material, heater means associated with said body for further heating of the heated charge of plastics material within said hot drop assembly, said hot drop assembly being spaced at least in part of its extent from said internal wall means defining said opening, and gas cooling means for forcing a flow of cooling gas directly into said opening and between said hot drop assembly and said wall means to effect the internal cooling of said mold by transferring heat energy from said opening and from areas of said tool surrounding said opening to an exhaust passage to thereby lower the operating temperature of said tooling so that high heat energy will not be conducted by said tooling to said face and damage the object being molded.

2. A mold for molding objects from a heated charge of plastic material comprising a tool body one side of which defines at least in part mold face, an opening in said mold bounded by internal wall means with in said body, a hot drop assembly operatively mounted within said opening for conducting and heating said charge of plastic material fed thereto for delivery to said mold face, said hot drop assembly having an elongated charge conducting injector mounted within said body and having an opening therethrough for transmitting said heated plastic material fed thereto to said mold face, heater means associated with said injector body to effect the heating thereof and the heating of the charge of plastic material fed therethrough, said heater element of said hot drop assembly being spaced at least in part of its extent from said wall means, and means for supplying a flow of cooling air directly to said opening and between said hot drop assembly and said wall means to effect the internal cooling of said mold and the transfer of heat energy from said tool body to an exhaust passage defined by the entrance of said bore.

3. The tool defined by claim 2 wherein an air chiller is provided for supplying cooling air for said bore and tubular feed means for transmitting said cooling air from said chiller to said bore and away from the working face of said mold.

4. A tool operable in a first temperature range for molding plastic articles from heated plastics material fed thereto comprising a tool body having a mold face, bore means formed in said body defined by wall means therein which has an inlet in said body and which opens to said mold face, elongated feed tube means for feeding molten plastics material to said face operatively mounted in said bore and having at least a portion thereof spaced from said wall means, energizible heater means associated with said feed tube means and spaced from said wall means for heating the plastics material within said feed tube means above said first temperature range and as the plastic material is forced therethrough to the face of said tool, pneumatic cooling means for injecting a flow of cooling gas to said chamber to effect the transfer of heat energy radiating from said heater means to said body out of said bore means and said inlet to thereby limit and reduce the amount of heat energy transferred from said heater means to the said mold face by conduction of heat energy through said mold body.

5. A tool operable in a first range of temperatures for molding articles from heated plastics material fed thereto comprising a tool body having a mold face, a bore formed in said body defined by wall means therein which has an inlet in said body and which opens to said mold face, feed tube means for feeding said heated plastics material to said face operatively mounted in said bore and having at least a portion thereof spaced from said wall means, energizible heater means associated with said feed tube means and spaced from said wall means for heating the plastics material within said feed tube means to a second range of temperature higher than said first range of temperatures and as the plastic material is forced through said tube means to said face of said tool, air chiller means for supplying a flow of cooling air to said chamber to effect the transfer of heat energy from said body through said wall means and said heater means to said out of said bore to thereby limit and reduce the amount of heat energy transferred from said heater means to the said mold face by conduction of heat energy through said mold body.