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United States Patent 5816698
Douris , ê et al.

Screw and plasticating apparatus and method

Durina , Ê et al. October 6, 1998

Abstract

A plasticating apparatus including a rotating screw having a helical flight disposed within and cooperating with the inner wall of a heated barrel. Solid resinous material is introduced to a helical valley extending between said flight to be heated and plasticized by said apparatus while being advanced towards an outlet opening by the rotation of said screw. The screw has a meter section for working, melting and mixing said resinous material at high temperatures. The bottom surface of the helical valley in said metering section is divided into side by side relatively shallow and relatively deep levels. Within the metering section is a transit channel having a reverse helical direction as compared with the helical direction of the flight. Because of the reverse helical direction of the transit channel, the transit channel intersects the helical flight and helical valley with the transit channel cutting therethrough. During operation, the level differential between the shallow and deep levels induces a continuous tumbling and mixing action upon the molten resin while the transit channel allows portions of the molten resin to back flow and recirculate through the mixing section.