Gas assisted injection molding apparatus utilizing sleeve and pin arrangement

An apparatus for use in fluid assisted injection molding of plastic material so as to form an injection molded product includes a pair of mold members defining when closed the sealed cavity, a first opening provided in one of the mold members for allowing the injection of plastic material into the cavity and the second opening provided in one of the mold members, and spaced from the first opening, for allowing the injection of the fluid into the cavity. A sleeve extends through the second opening. The sleeve has a longitudinally extending bore with an open first end. Preferably, the sleeve is rigidly secured in relation to the one of the mold members through which it extends. A pin extends through the sleeve with the pin having a first end, located adjacent the sleeve first end, and a second end. Preferably the pin in rigidly secured in relation to the sleeve. A fluid flow passage is defined between the pin and the sleeve. In another embodiment, the fluid flow passage is defined between a tube and a pin. The tube is secured at one end to a bushing body. The busing is, in turn, positioned between a nozzle of an injection molding machine and a sprue of a mold cavity. In yet another embodiment, the pin is allowed to reciprocate in relation to the sleeve so as to selectively open and close a fluid flow passage defined between the pin and the sleeve.