Injection molding valve member sealing bushing with a thin collar portion

In a valve gated injection molding apparatus having at least one heated nozzle seated in a mold, the heated nozzle having a rear end and a central bore extending therethrough in alignment with a gate in the mold leading to a cavity, a melt passage extending through a manifold and the central bore in the heated nozzle to convey melt to the gate, an elongated valve member having a front end and a rear end extending through the central bore of the nozzle, the rear end of the valve member being driven to reciprocate the valve member between a retracted open position and a forward closed position in which the front end of the valve member is seated in the gate, and a valve member sealing bushing being mounted rearwardly of the heated nozzle and having a valve member bore extending therethrough in alignment with the central bore of the nozzle whereby the elongated valve member extends through the valve member bore in the sealing bushing into the melt passage in alignment with the gate, the improvement wherein;

• the valve member sealing bushing has a thin collar portion which extends a predetermined distance forwardly into the melt passage in the manifold and fits around the valve member, the collar portion of the sealing bushing being sufficiently thin whereby injection pressure of the surrounding melt in the melt passage in the manifold compresses the collar portion of the sealing bushing around the valve member to form a seal against substantial leakage of melt rearwardly along the reciprocating valve member.