Automatic shut off nozzle for plastic extruder

A multi-position nozzle assembly for an injection molding machine operable to assume three distinct positions, namely a fully closed position, a partially open purging position and a fully open molding position, said nozzle assembly comprising:

• a housing having an internal compound transmission channel, a housing extension connected to said housing, a sleeve member received slidably in said housing extension, stop means on said housing extension for limiting relative axial motion between the sleeve member and the housing extension and for establishing the partially open purging position, a torpedo having a central through bore slidably disposed in said sleeve member, said central through bore having an inlet port and an outlet end said inlet port being operable to connect with said transmission channel, cap means carried by said torpedo for effecting operating contact with said sleeve member, and a single power means operating continuously and directly on said torpedo and on the sleeve member, said power means tending to urge the torpedo relative to the sleeve member to maintain contact between said sleeve member and said cap means whereby said sleeve member overlays and closes said inlet port to establish said fully closed position while maintaining a predetermined axially spaced condition between the torpedo and the sleeve member.