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A gas assisted injection molding system and method in which quantity of an inert gas is applied both internally and externally to a thermoplastic material introduced into an injection mold cavity during formation of an injection molded part. The system includes first and second mold portions definin

A gas assisted injection molding system and method in which quantity of an inert gas is applied both internally and externally to a thermoplastic material introduced into an injection mold cavity during formation of an injection molded part. The system includes first and second mold portions defining a mold cavity. An injection means injects a quantity of a thermoplastic material into the mold cavity to form an injection molded part within the cavity. At least one internal gas inlet is provided for introducing a first quantity of gas into a portion the thermoplastic material to form a gas channel therein. The gas within the gas channel presses the thermoplastic material against a mold parting line defined by the intersection of the mold portions and forms a seal between the mold cavity and the mold parting line. As least one external gas inlet is located within one of the mold portions for introducing a second quantity of pressurized gas into the cavity to hold the thermoplastic material firmly against an inner surface of one of the mold portions. The system and method of the present invention thereby forms an injection molded part having a sink-free appearance side with a Class A finish.

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[ What is claimed is:] [1.] In an injection molding apparatus including stationary and movable mold portions defining a mold cavity, and mating means for moving mating faces of said mold portions into abutting contact with one another, a method for producing an injection molded part having a sink-fr

[ What is claimed is:] [1.] In an injection molding apparatus including stationary and movable mold portions defining a mold cavity, and mating means for moving mating faces of said mold portions into abutting contact with one another, a method for producing an injection molded part having a sink-free appearance side, comprising the steps of:introducing a flowable thermoplastic material into said mold cavity to form an injection molded part;introducing a first quantity of gas into said mold cavity so as to form a gas channel in said thermoplastic material in close proximity to a mold parting line formed at an intersection of said mold portion mating faces, said first quantity of gas biasing said thermoplastic material against said mold parting line to form a gas seal between said mold parting line and said mold cavity;introducing a second quantity of pressurized gas through at least one gas inlet located in a first of said mold portions, thereby allowing said second quantity of gas to be uniformly dispersed along an underside of said formed injection molded part to hold said formed injection molded part against an inner surface of a second of said mold portions; andcontaining said second quantity of pressurized gas within said mold cavity via said gas seal as said injection molded part cools to form said injection molded part having a sink-free appearance side.