Abstract: A feedscrew for an extruder or molding apparatus has an elongated body with a helical thread formed thereon defining a first channel "A ". At the start of a mixing section, a channel "B " is cut in the center of the channel "A " and both channels are of the same pitch. The channels start at the same depth, but the channel A decreases in depth to a minimum and the channel B increases in depth to a maximum. The channel B then decreases in depth to a minimum and the channel A increases in depth to a maximum where the channels are again at the same depth. This channel within a channel configuration is repeated along the mixing section. The purpose of the arrangement is to compress and decompress the material being fed through the assembly to obtain the desired mixing action for low shear homogenization of the viscous plastic polymer.

Abstract: A check valve for use in controlling the flow of thermoplastic material in an injection molding apparatus includes a valve body having an axially extending chamber formed therein with an inlet opening and an outlet opening through which the material can flow. An poppet is slidably movable in the chamber between a valve closed position and a selected valve open position. The poppet has an inlet end with a conical shape and the chamber has a complementary taper portion adjacent the inlet opening, the inlet end and the taper portion sealingly cooperating for preventing flow of material through said chamber when said poppet is in the valve closed position. An adjusting ring is positioned in the chamber for selective movement between a minimum open position and a maximum open position, the adjusting ring being externally threaded for threadably engaging an internal thread formed in the chamber.