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United States Patent 4639143
Douris , ê et al. January 27, 1987

Extrusion screw

Frankland, Jr. January 27, 1987

Abstract

An extruder of the variety including a body having a cylindrical bore therethrough, and a shaft rotatably supported within the bore. The shaft includes at least a first helical flight means defining a main channel. The shaft is divided along its length into a feed section, an intermediate melt section, and at least one metering section. A portion is included in one of the sections which has a plurality of discrete grooves arranged in a discontinuous helix cut into the main channel. There is preferably a plurality of staggered rows of grooves within the main channel, the axis of each row being substantially parallel to the helical axis of the adjacent first helical flight means. The grooves are adapted to so receive the material forced through the extruder that the average shear force exerted against the material, and thus, the average temperature of the material, is reduced while the output of the material is maintained at a predetermined level.