Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – With internal application of fluid pressure
Patent
1997-03-12
1999-05-11
Housel, James C.
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
With internal application of fluid pressure
26432812, 26432816, 249111, 425130, 425547, B29D22/00;7/00
Patent
active
059025417
DESCRIPTION:
BRIEF SUMMARY
The instant application has been filed as a 371 of PCT application PCT/JP95/00190 filed Feb. 10, 1995 with a priority claim to national application 6/314370 filed Nov. 25, 1994 in Japan.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved method for producing a shaped, hollow resin article. More particularly, the present invention is concerned with an injection molding method for producing a shaped, hollow resin article by injecting a resin in a molten form into a mold cavity to form a molten resin mass, and introducing a pressurized fluid into the molten resin mass, wherein, during the introduction of the pressurized fluid into the molten resin mass, the temperature of at least one preselected portion of a back surface of the molten resin mass is maintained at a level which is higher by a specific temperature difference than the temperature of a front surface of the molten resin mass, causing the fluid to flow into the molten resin mass along a line substantially corresponding to a line along which the preselected portion of the back surface extends, so that the shaped, hollow resin article produced has a hollow in a position corresponding to the preselected portion of the back surface. By the method of the present invention, the flow of the pressurized fluid introduced can be surely led to an intended portion in a molten resin mass, so that the location of a hollow in the molten resin mass can be surely controlled and, therefore, a shaped, hollow resin article having a hollow of an orderly morphology can be produced. The present invention is also concerned with a mold for use in the method.
2. Discussion of Related Art
Conventionally, for the purpose of not only preventing the occurrence of sink marks of a resin on a local thick-walled section but also producing a light weight shaped resin article, there have been employed various injection molding methods (so-called gas injection molding methods) for producing a shaped, hollow resin article by injecting a resin in a molten form into a mold cavity to form a molten resin mass, and introducing a pressurized fluid into the molten resin mass (the so-called "gas injection molding methods" include not only a method in which a gas is used as the pressurized fluid but also a method in which a liquid is used as the pressurized fluid). In the field of gas injection molding, for leading the flow of the pressurized fluid to an intended portion in a molten resin mass so as to control the location of a hollow to be formed in the molten resin mass, the following methods and molds suitable therefor have conventionally been proposed.
(1) A method in which a molten resin mass having continuous thick-walled sections of rib structures connected to a gate for introducing a pressurized gas is formed, and a pressurized gas is introduced into the thick-walled sections, and a mold suitable therefor (see Unexamined Japanese Patent Application Laid-Open Specification No. 63-268611, which corresponds to U.S. Pat. No. 4,923,666).
(2) A method in which use is made of a mold provided, at a portion thereof corresponding to a thick-walled section of a shaped resin article to be produced, with a heat insulating member or heater which is capable of lowering the cooling rate of the molten resin at the thick-walled section as compared to the cooling rate of the molten resin at portions other than the thick-walled section (see Unexamined Japanese Patent Application Laid-Open Specification No. 4-62125).
(3) A method in which use is made of a mold, the overall inner wall surface (defining a mold cavity) of which is coated with a heat resisting, heat insulating resin film in a thickness of 0.001 to 2 mm (see Unexamined Japanese Patent Application Laid-Open Specification No. 5-245881). The specification describes that this method renders it possible to solve problems, such as poor reproduction of the profile of the mold inner surface on a resultant molded product and occurrence of a hesitation mark, which are likely to be caused in forming a holl
REFERENCES:
Patent Abstracts of Japan, vol. 15, No. 253 (M-1263), (Jun. 9, 1992) and JP 04 062125A (Isuzu Motors Ltd), (Feb. 27, 1992).
Patent Abstracts of Japan, vol. 95, No. 8, (Sep. 29, 1995) and JP 07 112460A (Asahi Chem Ind Co Ltd), (May 2, 1995).
Patent Abstracts of Japan, vol. 95, No. 5 (Jun. 30, 1995) and JP 07 052183A (Asahi Chem Ind. Co Ltd), (Feb. 28, 1995).
Patent Abstracts of Japan, vol. 95, No. 6 (Jul. 31, 1995) and JP 07 080883A (Asahi Chem Ind Co Ltd), (Mar. 28, 1995).
Patent Abstracts of Japan, vol. 18, No. 650 (M-1719), (Dec. 9, 1994) and JP 06 254912A (Asahi Chem Ind Co Ltd), (Sep. 13, 1994).
Horikoshi Maki
Imai Shoji
Asahi Kasei Kogyo Kabushiki Kaisha
Devi S.
Housel James C.
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