Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including hydrostatic or liquid pressure
Reexamination Certificate
2000-06-30
2003-06-17
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including hydrostatic or liquid pressure
C264S572000
Reexamination Certificate
active
06579489
ABSTRACT:
BACKGROUND OF THE INVENTION
Gas injection molding of plastic has long been known in the industry. During gas assisted injection molding molten plastic is forced into an enclosed mold, and gas is injected into the mold within the plastic material. The gas will raise the internal pressure and create an expanding gas pocket which will force the cooling plastic to the extreme recesses of the mold, giving a better fill out of the mold surface and reducing the sag of the plastic from the mold surface as the plastic shrinks during cooling, thus producing a better finished surface.
There are two main methods of injecting gas into the mold cavity. The first is directly injecting the gas mold into the cavity, known as in-article. The second is injecting the gas into a channel leading into the mold, which is known as in-runner. The injection of gas from molten into the cavities generally is preferred over the channel method.
Gas assisted injection molding uses some plastics that have a long cycle time i.e. cooling time in the mold. However, these plastics are still used in order to get specific shaped parts as needed. However, it should be noted that in the current art the use of TPO resin will only allow the outside of the part to cool while in the mold itself. The inside of the molded part remains hot and makes for a difficult molding cycle and/or ruined molded parts. Therefore, there is a need in the art for a process that will reduce the temperature of the molded product on the inside while cooling the outside at a precise time internal and temperature to allow for a smooth finished plastic product.
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Alliance Gas Systems, Inc.
Dinnin & Dunn P.C.
McDowell Suzanne E.
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