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US 5,028,377 AGranted
Method for injection molding plastic article with gas-assistance
AssigneeMichael Ladney
InventorJames W. Hendry
Life of this patent
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Abstract
A method and apparatus for injection molding plastic articles with gas-assistance wherein the injected molten plastic is depressurized by a controlled amount prior to gas injection to facilitate the penetration of the gas into the molten plastic within the article-defining cavity of the mold.
Claims12
In an apparatus for injection molding, a method of injection molding a plastic article with gas-assistance, the method comprising the steps of:
- injecting a pressurized charge of molten plastic through a flow path having a volume at least partially defined by a movable part of the apparatus and into an article-defining cavity of a mold;
- then depressurizing the molten plastic in the flow path by a controlled amount after the injection step by moving the movable part;
- then introducing a charge of gas pressurized at a predetermined level into the molten plastic for assistance in molding the plastic article in conformity with the article-defining cavity;
- maintaining the gas under pressure while the plastic solidifies in the article-defining cavity;
- venting the pressurized gas;
- and
- removing the plastic article from the mold.
4 more elements
Dependencies are inferred from the claim text.