Abstract: An anti-backflow valve for mounting on the forward end of a plasticating screw rotatably and translatably carried in a tubular barrel of an injection molding machine. The valve includes a rod-like body member that extends forwardly of the plasticating screw for rotation relative to the screw and for axial translation relative to the screw for a limited distance. A retaining sleeve is threadedly secured to the forward end of the screw to define a forward stop to limit axial outward movement of the body member relative to the screw. The outer surface of the retaining sleeve includes a valve seat that is engagable with a sealing surface on a screw tip that is carried at the forward end of the body member. The screw tip includes flow passageways extending substantially axially therethrough to provide communication between the space ahead of the screw and an area behind the screw tip and between the screw body and the screw-receiving tubular barrel.

Abstract: A nozzle shut-off valve for the plastication system of an injection molding machine. The valve includes a cylindrical body member that has axially spaced inlet and outlet passageways. Inclined passageways that extend from the inlet and outlet passageways to the outer surface of the body member to terminate in spaced openings on the periphery of the inner body member. A tubular outer member is provided with at least one recess or depression on its inner surface, the recess having a length sufficient to provide communication between a pair of the spaced peripheral openings in the inner body member when the recess is positioned in overlying relationship with the respective openings. Rotation or translation of the tubular outer member relative to the inner body member shifts the recess out of registration with the respective peripheral openings, to thereby prevent flow of material through the valve.

Abstract: An anti-backflow valve for mounting on the forward end of a plasticating screw of an injection molding machine. The valve includes a rod-like member that extends forwardly of the plasticating screw, and is relatively rotatable therewith. The rod-like member is axially retined in position relative to the screw by a retaining ring that engages with the forward end of the screw and that includes a valve seat. The outwardly extending end of the rod terminates in a stop that is spaced forwardly of the valve seat. An annular sealing ring includes an outer surface that engages the inner surface of the barrel and an inner surface that is radially spaced from the rod-like member to provide a flow passage therebetween. The ring is positioned between the forward stop and the valve seat and is freely axially movable therebetween.