CA2018683A1 - Process for production of injection molded parts from plastic material - Google Patents
Process for production of injection molded parts from plastic materialInfo
- Publication number
- CA2018683A1 CA2018683A1 CA 2018683 CA2018683A CA2018683A1 CA 2018683 A1 CA2018683 A1 CA 2018683A1 CA 2018683 CA2018683 CA 2018683 CA 2018683 A CA2018683 A CA 2018683A CA 2018683 A1 CA2018683 A1 CA 2018683A1
- Authority
- CA
- Canada
- Prior art keywords
- molding
- gas
- injection
- cavity
- pressure
- 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.)
- Abandoned
Links
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
- B29C45/1703—Introducing an auxiliary fluid into the mould
- B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
- B29C45/1711—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity
-
- 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
- B29C45/1703—Introducing an auxiliary fluid into the mould
- B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
- B29C45/1711—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity
- B29C2045/1712—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity plastic material flowing back into the injection unit
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The initial step in production of a partially hollow injection molded part, even with a complex geometry, is to completely fill an injection mold with a plasticized plastic mass. Subsequently, a pressure gas is forced through the injection mold (tool) into the cavity to be formed while simultaneously displacing the plastic material filling the cavity. the displaced plastic material is removed from the injection mold. the pressure gas is exhausted from the molding and the molding is stripped from the mold after the cavity has been formed and the molding cooled.
The initial step in production of a partially hollow injection molded part, even with a complex geometry, is to completely fill an injection mold with a plasticized plastic mass. Subsequently, a pressure gas is forced through the injection mold (tool) into the cavity to be formed while simultaneously displacing the plastic material filling the cavity. the displaced plastic material is removed from the injection mold. the pressure gas is exhausted from the molding and the molding is stripped from the mold after the cavity has been formed and the molding cooled.
Description
:
~ ~` 2n~ 3 , PROCESS FOR PRODUCTION OF INJECTION MOLDED
,` P~RTS FROM PLASTIC MATERIAL
,~
! BACKGROUND OF THE INVENTION
! 1 Field of the Invention The invention relates to a process for production of an at least partially hollow molded part from plastic material.
~ ~` 2n~ 3 , PROCESS FOR PRODUCTION OF INJECTION MOLDED
,` P~RTS FROM PLASTIC MATERIAL
,~
! BACKGROUND OF THE INVENTION
! 1 Field of the Invention The invention relates to a process for production of an at least partially hollow molded part from plastic material.
2. Description of the Related Technology .
I U.S. Patent 4,101,617 shows a process for I producing hollow plastic injection moldings. A pressure j gas is forced into the mold cavity under a high pressure together with or after injection of plasticized plastic I material. Only the mass required for the hollow molding is filled into the injection mold. The pressure gas is injected through the sprue of the injection mold and forces the plastic material against the walls of the mold ca~ity while orming a corresponding cavity in the plastic mass. The pressure gas remains in the nlold until the plas~ic material has cooled. Subse~uently the pressure -gas is discharged into the atmosphere and the finished ~ ~article is stripped from the mold. ~ Y;
EP-OS 283 207 shows pressure gas introduction of at one or more points of the injection mold. The injection of the pressure gas takes place simultaneously with the filling of the injection mold with the plasticized plastic, with again only enough of the plastic mass being introduced to form ~he partially hollow molding.
."' ' .'. ~
. ' .' ' ^ . :
2n:18683 In the known process the plastic materials cools during its displacement by the pressure gas. This is particularly so in relatively large mold cavities where only a slight internal pressure or fill resistance is present during the fill phase. In relatively rapidly solidifying plastic materials this premature cooling leads to the formation of wrinkles on the surface of the plastic masses introduced. The wrinkles cause visible surface defects of the molding upon their contact with the walls of the mold cavity, ~ -~
In complex mold cavities, such as those with sections of different widths, the sections having the lowest fill resistance are filled irst and the sections with the smallest width dimensions are filled last.
Sections with a large width display a low fill resistance. In the prior processes the pressure gas injected may break into narrow sections not yet filled with the plastic material. This results in unusable perforated moldings. Even in favorable cases, joining seams appear between sections filled at different ~imes of the molding. The seams affect th~ articles quality.
., ' ' ~ . .
Another difficulty is that the wall thickness of `
hollow molding sections are difficult to control, because ~ ;
of the plastic material displaced by the pressure gas is not always uni~rm, especially in molding cavities with sections of different widths.
~. . .
SUMMARY OF THE INVENTION
.. . .
An obiect of the invention is to assùre a satisfactory molding quality even with comple~ mold cavities. According to the invention improved quality parts may be obtained by introducing a plasticized plastic material and a pressure gas into an injection molding , . .
. 1196U
2n~8683 mold. The pressurizing gas is exhausted from,,~he molding following the cavity formation in the partial area and following article or molding cooling. The molding is then stripped from the mold. The injection mold may initially be completely filled with the plastic material and subsequently pressure gas is pressed into the cavity to be formed. Simultaneously the plastic material filling the cavity is displaced, whe,reupon the displaced material is removed rom the injection mold.
;The invention is based on the concept of time separation of the article forming process from the cavity forming process. This assures that all sections of geometrically complex or simple mold cavities are reliably filled with a completely plasticized mass prior to formation of desired cavities in the molded part by ~' injection of pressure gas. After injection the intended cavities are filled with a plasticized mass. The excess, , unsolidified plastic mass of the intended cavities is .-driven out from the injection mold and may be transported back into the injection molding machine by the 'introduction of the pressure gas. The returned material is maintained in the plasticized state and used in the next fill process. The complete filling of the mold cavity Wit}l plasticized plastic material is carried out by the conventional, well controlled injection technology, so ' that the qualities of the molding, such as surface conditions and mechanical strength may be accurately regulated. The surface development will be largely completed in a manner similar to a solid molding by the time the gas pressure developed and forms the cavities.
The surface quality will not be affected by the subsequent cavity ormation. The system according to the invention eliminates the wall thickness dependence on an "inflating process". The wall thickness depends only on the rate of solidification which declines from the outside to the ;, ` ~,.. :
I U.S. Patent 4,101,617 shows a process for I producing hollow plastic injection moldings. A pressure j gas is forced into the mold cavity under a high pressure together with or after injection of plasticized plastic I material. Only the mass required for the hollow molding is filled into the injection mold. The pressure gas is injected through the sprue of the injection mold and forces the plastic material against the walls of the mold ca~ity while orming a corresponding cavity in the plastic mass. The pressure gas remains in the nlold until the plas~ic material has cooled. Subse~uently the pressure -gas is discharged into the atmosphere and the finished ~ ~article is stripped from the mold. ~ Y;
EP-OS 283 207 shows pressure gas introduction of at one or more points of the injection mold. The injection of the pressure gas takes place simultaneously with the filling of the injection mold with the plasticized plastic, with again only enough of the plastic mass being introduced to form ~he partially hollow molding.
."' ' .'. ~
. ' .' ' ^ . :
2n:18683 In the known process the plastic materials cools during its displacement by the pressure gas. This is particularly so in relatively large mold cavities where only a slight internal pressure or fill resistance is present during the fill phase. In relatively rapidly solidifying plastic materials this premature cooling leads to the formation of wrinkles on the surface of the plastic masses introduced. The wrinkles cause visible surface defects of the molding upon their contact with the walls of the mold cavity, ~ -~
In complex mold cavities, such as those with sections of different widths, the sections having the lowest fill resistance are filled irst and the sections with the smallest width dimensions are filled last.
Sections with a large width display a low fill resistance. In the prior processes the pressure gas injected may break into narrow sections not yet filled with the plastic material. This results in unusable perforated moldings. Even in favorable cases, joining seams appear between sections filled at different ~imes of the molding. The seams affect th~ articles quality.
., ' ' ~ . .
Another difficulty is that the wall thickness of `
hollow molding sections are difficult to control, because ~ ;
of the plastic material displaced by the pressure gas is not always uni~rm, especially in molding cavities with sections of different widths.
~. . .
SUMMARY OF THE INVENTION
.. . .
An obiect of the invention is to assùre a satisfactory molding quality even with comple~ mold cavities. According to the invention improved quality parts may be obtained by introducing a plasticized plastic material and a pressure gas into an injection molding , . .
. 1196U
2n~8683 mold. The pressurizing gas is exhausted from,,~he molding following the cavity formation in the partial area and following article or molding cooling. The molding is then stripped from the mold. The injection mold may initially be completely filled with the plastic material and subsequently pressure gas is pressed into the cavity to be formed. Simultaneously the plastic material filling the cavity is displaced, whe,reupon the displaced material is removed rom the injection mold.
;The invention is based on the concept of time separation of the article forming process from the cavity forming process. This assures that all sections of geometrically complex or simple mold cavities are reliably filled with a completely plasticized mass prior to formation of desired cavities in the molded part by ~' injection of pressure gas. After injection the intended cavities are filled with a plasticized mass. The excess, , unsolidified plastic mass of the intended cavities is .-driven out from the injection mold and may be transported back into the injection molding machine by the 'introduction of the pressure gas. The returned material is maintained in the plasticized state and used in the next fill process. The complete filling of the mold cavity Wit}l plasticized plastic material is carried out by the conventional, well controlled injection technology, so ' that the qualities of the molding, such as surface conditions and mechanical strength may be accurately regulated. The surface development will be largely completed in a manner similar to a solid molding by the time the gas pressure developed and forms the cavities.
The surface quality will not be affected by the subsequent cavity ormation. The system according to the invention eliminates the wall thickness dependence on an "inflating process". The wall thickness depends only on the rate of solidification which declines from the outside to the ;, ` ~,.. :
-3- : . ::`.
1196U ' ~
;: . .: . . :: ; `: . ` .. : .: : .: . ` : , : : ~ ,. ,., ` . . . : . .
~ . 2~18683 .
inside The process according to the invention assures improved consistancy in the wall thickness. The invention will become more apparent from the drawings attached hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a schematic view of a plastic ~-processiny plant operating according to the process of the - ~-invention following plastic injection.
, Figure 2 shows a schematic view of the installation according to Fig. 1 in its condition after creating a molding cavity.
Figure 3 shows a section through a molding or article produced by~the plant according to Fig. 1 and 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT `~
, The plastic processing plant designated 10 in Fig. 1 comprises a plastic injection molding machine 10a, a two-part tool 16 and a gas pressure system 13 with the gas tanks 13a, 13b for an inert pressure gas, for example -nitrogen, that may be under a high pressure of up to 1000 bar or more, At its output and the injection molding machine 10a has a metering head 11, which is controlled by means of a hydraulic drive apparatus.
The gas tanks 13a, 13b are connected to pressure `accumulators 14, 15 which are charged by a pump 13c at a variable volume. The pressure loading circuit contains a proportional valve 17, which allows gas pressure control as a function of the pressure of the plastic mass in the gas feeder line lg. The gas feeder line 19 leads to a gas shut-off valve 18, built into the tool 16.
.: .
. . ~ ~,.
1196U ' ~
;: . .: . . :: ; `: . ` .. : .: : .: . ` : , : : ~ ,. ,., ` . . . : . .
~ . 2~18683 .
inside The process according to the invention assures improved consistancy in the wall thickness. The invention will become more apparent from the drawings attached hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a schematic view of a plastic ~-processiny plant operating according to the process of the - ~-invention following plastic injection.
, Figure 2 shows a schematic view of the installation according to Fig. 1 in its condition after creating a molding cavity.
Figure 3 shows a section through a molding or article produced by~the plant according to Fig. 1 and 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT `~
, The plastic processing plant designated 10 in Fig. 1 comprises a plastic injection molding machine 10a, a two-part tool 16 and a gas pressure system 13 with the gas tanks 13a, 13b for an inert pressure gas, for example -nitrogen, that may be under a high pressure of up to 1000 bar or more, At its output and the injection molding machine 10a has a metering head 11, which is controlled by means of a hydraulic drive apparatus.
The gas tanks 13a, 13b are connected to pressure `accumulators 14, 15 which are charged by a pump 13c at a variable volume. The pressure loading circuit contains a proportional valve 17, which allows gas pressure control as a function of the pressure of the plastic mass in the gas feeder line lg. The gas feeder line 19 leads to a gas shut-off valve 18, built into the tool 16.
.: .
. . ~ ~,.
2nl~6s3 -The plastic material plasticized in t~he plastic injection molding machine lOa is introduced through the sprue channel 16b into the mold cavity 16a of the tool 16, until the mold cavity chamber 15a is completely filled with the plasticized plastic mass (condition according to Fig. 1). During this filling process a "counter gas pressure" may be built up by low pressure gas introduction through the gas valve 18 if the mold cavity 16a, as shown, has a section 16d with a large width dimension. The low pressure may be at 10-50 bar The counter gas pressure creates an artificial fill resistance, which results in an improved surface quality of the molding. A constant pressure is established and main~ained prior to and during the continuing filling of the mold cavity, until filling is completed.
After illing of the mold cavity 16a pressure gas is introduced through the gas valve 18 at a high pressure of 50 to 400 bar into the cavity mold 16a, whereby the not yet solidified plastic material in the core area of the section 16d is displaced in the direction of the sprue channel 16b and thus from the tool 16. The plastic material displaced is moved back into the injection molding machine lOa, The material is maintained in a plastiaized state in the machine and is used in the next fill of the tool 16. By the reflux of the plastic material displaced, the plasticizer screw, not shown, of the plastic injection molding machine lOa is pressured back. The material in the core of the plastic mass filled is displaced by the pressure gas until the gas bubble 20 (Fig. 2) has been expanded to the sprue channel 16b of the tool 16, there by pressuring the plastiaizer screw of the injection~molding machine lOa into a predetermined position. When this position is attained, the reflux of the mass is discontinued by closing a shut-off valve, not shown, in the metering head 11. The continuing . ' ~ :"
--5-- ::
1196U :: ~:
n~683 introduction of the pressure gas builds a higher gas ~ 3 pressure in the gas bubble 20, which presses the molding wall of the section 16d during the subsequent cooling o ~
the plastic material against the wall of the mold cavity ~ ;
16a. After cooling, the pressure gas is returned from the gas bubble 20 into the pressure accumulators 14, 15 and the finished molding, shown in Fig. 3, stripped from the mold. The sprue of the molding 21 indicated by a broken line, is later cut from the molding 21. -.
According to an advantageous embodiment a control unit 30 may be connected to the plastic injection molding plant. The control unit may be set up to operate the injection molding machine and the gas pressure system.
The control may be an automated or computerized system which controls the injection of plasticized material into ~he mold cavity, the low pressure back pressure during the injection phase, duration of an interim cooling period to . .
control the wall thickness and still maintain a plasticized core, introduction of high pressure gas to create the molding cavity by causing material to flow out of the mold cavity and opening the tool and striping the molding. The control unit 30 may also control valves (not shown) to control plasticized material flow into and out of the molding tool and the gas shut-off valve.
, --6-- ~:
1196U :
After illing of the mold cavity 16a pressure gas is introduced through the gas valve 18 at a high pressure of 50 to 400 bar into the cavity mold 16a, whereby the not yet solidified plastic material in the core area of the section 16d is displaced in the direction of the sprue channel 16b and thus from the tool 16. The plastic material displaced is moved back into the injection molding machine lOa, The material is maintained in a plastiaized state in the machine and is used in the next fill of the tool 16. By the reflux of the plastic material displaced, the plasticizer screw, not shown, of the plastic injection molding machine lOa is pressured back. The material in the core of the plastic mass filled is displaced by the pressure gas until the gas bubble 20 (Fig. 2) has been expanded to the sprue channel 16b of the tool 16, there by pressuring the plastiaizer screw of the injection~molding machine lOa into a predetermined position. When this position is attained, the reflux of the mass is discontinued by closing a shut-off valve, not shown, in the metering head 11. The continuing . ' ~ :"
--5-- ::
1196U :: ~:
n~683 introduction of the pressure gas builds a higher gas ~ 3 pressure in the gas bubble 20, which presses the molding wall of the section 16d during the subsequent cooling o ~
the plastic material against the wall of the mold cavity ~ ;
16a. After cooling, the pressure gas is returned from the gas bubble 20 into the pressure accumulators 14, 15 and the finished molding, shown in Fig. 3, stripped from the mold. The sprue of the molding 21 indicated by a broken line, is later cut from the molding 21. -.
According to an advantageous embodiment a control unit 30 may be connected to the plastic injection molding plant. The control unit may be set up to operate the injection molding machine and the gas pressure system.
The control may be an automated or computerized system which controls the injection of plasticized material into ~he mold cavity, the low pressure back pressure during the injection phase, duration of an interim cooling period to . .
control the wall thickness and still maintain a plasticized core, introduction of high pressure gas to create the molding cavity by causing material to flow out of the mold cavity and opening the tool and striping the molding. The control unit 30 may also control valves (not shown) to control plasticized material flow into and out of the molding tool and the gas shut-off valve.
, --6-- ~:
1196U :
Claims (10)
1. An injection molding process comprising the steps of:
substantially filling a mold cavity with injected plasticized material;
introducing pressure gas to the mold cavity thereby creating a molding cavity and forcing material out of said mold cavity.
substantially filling a mold cavity with injected plasticized material;
introducing pressure gas to the mold cavity thereby creating a molding cavity and forcing material out of said mold cavity.
2. A process according to claim 1 further comprising the step of providing a low counter gas pressure during the step of substantially filling.
3. A process according to claim 1 wherein said pressure gas is introduced at a gas feeder point spaced from a plastic material injection point.
4. A process according to claim 1 wherein said step of introducing pressure gas creates a molding cavity in only a portion of the molding.
5. A process according to claim 1 further comprising the step of cooling a wall of said molding prior to said step of introducing pressure gas.
6. An injection molding plant comprising:
a molding tool;
a gas pressure system connected to said molding tool;
a plastic injection molding machine connected to said molding tool;
means for controlling connected to said gas pressure system and said plastic injection molding machine, wherein said means for controlling is configured to cause injection of plasticized material in an amount to substantially fill a mold cavity of said molding tool and to cause gas injection in an amount to partially empty said plastic material from said mold cavity.
a molding tool;
a gas pressure system connected to said molding tool;
a plastic injection molding machine connected to said molding tool;
means for controlling connected to said gas pressure system and said plastic injection molding machine, wherein said means for controlling is configured to cause injection of plasticized material in an amount to substantially fill a mold cavity of said molding tool and to cause gas injection in an amount to partially empty said plastic material from said mold cavity.
7. An injection molding plant according to claim 6 further comprising a gas shut-off valve located between said gas pressure system and said mold cavity.
8. An injection molding plant according to claim 7 wherein said molding machine displays a metering head connected to a sprue cavity of said molding tool spaced from an inlet of said gas shut-off valve.
9. An injection molding plant according to claim 8 wherein said molding machine comprises a displaceable screw.
10. An injection molding plant according to claim 7 further comprising means for generating injection back pressure connected to said molding tool.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3919333.0 | 1989-06-13 | ||
| DE19893919333 DE3919333A1 (en) | 1989-06-13 | 1989-06-13 | METHOD FOR PRODUCING INJECTION MOLDED PARTS FROM PLASTIC MATERIAL |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2018683A1 true CA2018683A1 (en) | 1990-12-13 |
Family
ID=6382685
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2018683 Abandoned CA2018683A1 (en) | 1989-06-13 | 1990-06-11 | Process for production of injection molded parts from plastic material |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0402730A3 (en) |
| CA (1) | CA2018683A1 (en) |
| DE (1) | DE3919333A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT402363B (en) * | 1993-08-19 | 1997-04-25 | Koeflach Sportgeraete Gmbh | Ski, mountain, ice-skating or roller-skating shoe with a plastic shell and method for producing the said shoe |
| ATE177676T1 (en) * | 1994-04-21 | 1999-04-15 | Schoeller Plast Ag | METHOD FOR SERIAL PRODUCTION OF ARTICLES USING THE GAS FORMING PROCESS AND DEVICE FOR IMPLEMENTING THE PROCESS |
| DE4414258C2 (en) * | 1994-04-23 | 1996-07-25 | Battenfeld Gmbh | Process for injection molding objects consisting of at least two different layers |
| US5607640A (en) * | 1995-06-21 | 1997-03-04 | Melea Limited | Method for injection molding of plastic article |
| DE19531709A1 (en) * | 1995-08-30 | 1997-03-06 | Battenfeld Gmbh | Method and device for manufacturing plastic objects |
| FR2763275B1 (en) * | 1997-05-15 | 1999-06-18 | Sommer Allibert | PROCESS FOR INJECTION MOLDING OF A PART IN PLASTIC MATERIAL (S) HAVING DIFFERENT INTERIOR AND EXTERIOR CONSTITUTIONS |
| DE19852123B4 (en) * | 1998-11-12 | 2008-07-31 | Vereinigung zur Förderung des Instituts für Kunststoffverarbeitung in Industrie und Handwerk an der Rhein.-Westf. Technischen Hochschule Aachen eV | Process for producing hollow bodies by gas injection technique |
| US6767487B2 (en) | 2001-07-10 | 2004-07-27 | Cinpres Gas Injection Ltd. | Plastic expulsion process |
| TW548173B (en) * | 2001-07-10 | 2003-08-21 | Cinpres Gas Injection Ltd | Process and apparatus for injection moulding a hollow plastics article |
| US6890477B2 (en) | 2003-03-25 | 2005-05-10 | Lear Corporation | Plastic injection molded articles with hollow rib members |
| US6899843B2 (en) | 2003-03-25 | 2005-05-31 | Lear Corporation | Plastic injection molding with moveable mold members forming speaker grill |
| GB2519816B (en) | 2013-10-31 | 2016-05-25 | Subsea 7 Ltd | Techniques for coating pipes |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2257408B1 (en) * | 1973-09-25 | 1978-01-13 | Billion Sa | |
| JPH0788025B2 (en) * | 1987-04-28 | 1995-09-27 | 三菱瓦斯化学株式会社 | Manufacturing method of synthetic resin molded product having uneven wall reinforcement structure |
| EP0321117B2 (en) * | 1987-12-16 | 2005-07-13 | Melea Limited | Method and system for localized fluid-assisted injection molding and body formed thereby |
-
1989
- 1989-06-13 DE DE19893919333 patent/DE3919333A1/en not_active Withdrawn
-
1990
- 1990-06-05 EP EP19900110565 patent/EP0402730A3/en not_active Withdrawn
- 1990-06-11 CA CA 2018683 patent/CA2018683A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE3919333A1 (en) | 1990-12-20 |
| EP0402730A3 (en) | 1991-06-12 |
| EP0402730A2 (en) | 1990-12-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |