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A gas injection apparatus for use with a gas assisted injection molding system. The gas injection apparatus includes a mold part defining an elongated bore communicating upstream with a source of gas and downstream with a mold cavity, and an elongated pin positioned in the bore and coacting with the

A gas injection apparatus for use with a gas assisted injection molding system. The gas injection apparatus includes a mold part defining an elongated bore communicating upstream with a source of gas and downstream with a mold cavity, and an elongated pin positioned in the bore and coacting with the bore to define a gas flow passage therebetween for movement of gas from the gas source to the mold cavity. The bore and pin include first, second and third corresponding portions. The pin and bore define an annular axial clearance in the first portion, a close fit with an axial linear passage in the second portion and an annular axial passage in the third portion. This arrangement ensures that the pin will remain concentric with respect to the bore so as to discourage entry of resin into the annular axial passage.

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[ What is claimed is:] [1.] A gas injection apparatus for use with a gas assisted injection molding system, the gas injection apparatus including means defining a bore communicating upstream with a source of gas and downstream with a mold cavity, and a pin positioned in the bore and coacting with th

[ What is claimed is:] [1.] A gas injection apparatus for use with a gas assisted injection molding system, the gas injection apparatus including means defining a bore communicating upstream with a source of gas and downstream with a mold cavity, and a pin positioned in the bore and coacting with the bore to define a gas flow passage therebetween for movement of gas from the gas source to the mold cavity, characterized in thatthe bore includes a downstream bore portion and an upstream bore portion adjoining the downstream portion;the pin includes a downstream pin portion positioned in the downstream bore portion and an upstream pin portion adjoining the downstream pin portion and positioned in the upstream bore portion;the downstream bore portion has a diameter greater than the downstream pin portion so as to define an annular axial passage between the downstream bore portion and the downstream pin portion;the upstream bore portion has a diameter generally corresponding to the diameter of the upstream pin portion;the annular interface of the upstream bore portion and the upstream pin portion includes a radial recess at at least one circumferential location around the annular interface defining a linear axial passage extending axially through the annular interface and communicating with the annular axial passage;the generally corresponding diameters of the upstream bore portion and the upstream pin portion define a close fit which is operative to substantially preclude radial migration of said upstream pin Portion with respect to said upstream bore portion to maintain the downstream pin portion concentrically positioned in the downstream bore portion so as to maintain a substantially uniform radial clearance dimension throughout the circumferential extent of the annular axial passage to allow free flow of gas through said annular axial passage into said cavity while resisting entry of resin into the annular axial passage.