Injection molding single nozzle valve gating

In a single cavity hot runner injection molding system having a heated nozzle with a hot runner passage which extends to convey pressurized melt from a molding machine to a gate in a temperature controlled cavity plate leading to a cavity, the nozzle being secured against rotational movement and extending into a well in the cavity plate having an inner surface, the nozzle having an outer surface with an air space between the outer surface of the nozzle and the inner surface of the well, the nozzle having a nose portion with a conical surface leading to a tip which is in alignment with the gate, the system including an actuating mechanism to drive the nozzle longitudinally between a retracted open position and a forward closed position wherein the tip of the nose portion of the nozzle is seated in the gate, the improvement wherein the actuating mechanism comprises:

• (a) an inner collar secured against rotation to the nozzle,
• (b) an outer collar extending around the inner collar in threadable engagement with the inner collar, the outer collar being secured against longitudinal movement, and,
• (c) power means connected to the outer collar to rotate the outer collar through a predetermined angle whereby the inner collar is driven longitudinally a distance sufficient to drive the nozzle from the retracted open position to the forward closed position.