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United States Patent 5698235
Douris , ê et al.

Extrusion screw for extruder

Satoh , Ê et al. December 16, 1997

Abstract

An extrusion screw for an extruder includes a screw shaft which is rotatably arranged in a cylinder barrel. A main flight and an auxiliary flight are helically provided on the outer peripheral surface of the screw shaft. The trailing ends of these flights are spaced from each other by a half turn in the circumferential direction of the screw shaft. A main flight groove is formed between the front wall surface of the main flight and the rear wall surface of the auxiliary flight. An auxiliary flight groove is formed between the front wall surface of the auxiliary flight and the rear wall surface of the main flight to have a second cross-sectional area. The cross-sectional area of the auxiliary flight groove decreases in a direction from the leading end to the trailing end of the auxiliary flight.