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United States Patent 5439633
Douris , ê et al. August 8, 1995

Plastic extruder having a mixing valve with automatic shut-off

Durina , Ê et al. August 8, 1995

Abstract

An apparatus and method for controlling thermoplastic mixing in a plastic extrusion machines used for injection molding, blow molding or other reciprocating molding process. The plastic extruder having a rotating helical screw within a cylindrical shell with an automatic shut-off and mixing valve secured to the helical screw at the downstream end of the screw. The automatic shut-off and mixing valve includes a unitary valve body with a poppet. A plurality of mixing groove pairs are arranged extending substantially longitudinally on the surface of the valve body. Select angular bores extend from the groove pairs to the poppet. The poppet is axially movable within and rotatable relative the valve body. The poppet has an axial stem extending into a longitudinal axial bore within the valve body. An elastic means is positioned on the rearward end of the poppet maintaining the valve in a normally closed position against a seating surface of the valve body when there is no rotation of the helical screw.