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United States Patent 5573332
Douris , ê et al.

Screw element for a screw-like extrusion machine

Weihrich , Ê et al. November 12, 1996

Abstract

In a screw element for the conditioning and/or processing of plastics or elastomers in a screw-type extruding machine having screw shafts drivable to rotate in the same direction and at least one pair of meshing screw elements, each screw element having a land of which the enveloping curve extends radially at a constant distance away from the respective shaft and, in the longitudinal direction, is of linear extension in parallel to the longitudinal axis of the shaft, a radially external screw land section near the housing running parallel to the inside wall of the housing with little play relative to the latter, for the purpose of moderate recirculation without stress points accompanied by strong axial and transverse mixing in a defined volume, it is provided that the enveloping curve encloses a blade land of reduced cross-sectional area referred to the enveloping curve, in that starting from the one axial end of the screw element and the first, in the circumferential direction external, end of the section, near the housing, of the enveloping curve, the blade ridge of the land, seen in the circumferential direction of an angle .rho., extends along part of this section, near the housing, of the enveloping curve and in that, in the axial direction, the blade ridge extends towards the second, in the circumferential direction external, end of the section, near the housing, of the enveloping curve.