Self-contained gas injector

A gas assisted injection molding machine comprising a clamping plate, a core supported on said clamping plate in spaced relation thereto, a cavity plate juxtaposed on said core and movable relative thereto between a closed position in which a mold cavity is defined between said core and said cavity plate and an open position to allow removal of a molded component from said cavity, an ejector mechanism movable relative to said core to eject molded components from said cavity and including a sleeve slidably supported in said core and movable with said ejector mechanism relative to said core, and at least one gas injector valve assembly to inject gas into said mold cavity, said valve assembly comprising a manifold including a body mounted on said clamping plate on an opposite side thereof to said core and having an internal passageway connected to a source of pressurized gas, a supply duct secured to said manifold and extending from said passageway through said sleeve and into said cavity to provide a conduit extending from said passageway and into said cavity and a valve member slidably mounted in said conduit and having biasing means to bias said valve member to a closed position in which flow through said conduit is inhibited.