Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – With internal application of fluid pressure
Patent
1990-11-07
1992-05-05
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
With internal application of fluid pressure
2643288, 26432812, 26432813, 425812, B29C, B29C, B29D 2200
Patent
active
051105330
ABSTRACT:
A method of gas-assisted injection molding in which: (1) a first amount of plastic is injected into an article-defining cavity of a mold so that it flows therein; (2) a second amount of plastic continues to be injected into the cavity simultaneous with the injection of a charge of pressurized gas wherein the pressurized gas prevents the flow of plastic in the cavity from stopping; and (3) the charge of pressurized gas continues to be injected after the second amount of plastic is injected to distribute the total amount of molten plastic resin in the cavity. The ratio for the first amount of plastic to the total amount of plastic required for the preparation of the article is in the range of 0.2 to 0.7. Also, the pressurized gas has a pressure between approximately 1000 psi and 5000 psi. These steps prevent imperfections on the exterior surface of the plastic article. The gas charge is maintained under pressure within the article until the article has set up in the article-defining cavity. Finally, the gas pressure is relieved in the article and the finished article is removed from the mold. The method is particularly useful in molding articles having a relative large cross-section.
REFERENCES:
patent: 4101617 (1978-07-01), Friederich
patent: 4474717 (1984-10-01), Hendry
patent: 4935191 (1990-06-01), Baxi
patent: 4943407 (1990-07-01), Hendry
Eckardt, H., "The Airmould Process-A New Gas-Assisted Injection Moulding Process"(Apr. 1990).
Rusch, K. C., "Gas-Assisted Injection Molding-The New Thermoplastic Molding Technology for Exterior Body Panels"(Mar. 1989).
Milad Limited Partnership
Tentoni Leo B.
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