Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1994-05-02
1995-08-15
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 51, 264 85, 264572, 2643281, 26432813, 425 4R, 425146, 425546, B29C 4534
Patent
active
054416809
ABSTRACT:
A method of injection molding for use with an injection molding machine includes: (a) generating pressurized gas and pressurized moisture within molten plastic as plastic pellets are plasticized in the injection molding machine, the pressurized gas and the pressurized moisture having a total pressure defining an internal counterpressure within the molten plastic; (b) pressuring air within a cavity of a mold in the injection molding machine to an air pressure level which is substantially equal to the internal counterpressure in order to counterbalance the internal counterpressure as the molten plastic is injected into the cavity, thus providing a substantially pressure balanced molding environment for the plastic; and (c) maintaining the air pressure level in the cavity substantially constant as the molten plastic is injected into the cavity. A mold apparatus for use with the method of injection molding includes selectively sealed venting of the mold cavity, the vents being configured to maintain a substantially constant air pressure within the cavity as the cavity is filled with molten plastic.
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patent: 4208368 (1980-06-01), Egli
patent: 4333901 (1982-06-01), Young et al.
patent: 4675141 (1987-06-01), Kumazaki
patent: 4685872 (1987-08-01), Erlenbach
patent: 4942006 (1990-07-01), Loren
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