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United States Patent 5178458
Douris , ê et al. January 12, 1993

Extruder screw mixing head

Hsu January 12, 1993

Abstract

An extruder screw mixing head that is adapted to be carried by an extruder screw at a downstream portion of the screw for improved distributive mixing. The mixing head includes a central body that tapers and diverges in a downstream direction to provide a progressively diminishing flow channel in an axial direction of the mixing head. Four equally spaced flights of equal pitch are provided on the outer periphery of the mixing head, and each flight has a series of peripheral recesses that are spaced from each other along the flights and that permit flow of plasticated material between adjacent flow channels defined by the spaced flights to improve homogeneity of the material. The recesses are so configured that their respective leading and trailing edges are aligned to define circumferential angles with the longitudinal axis of the mixing head, so that the inter-channel flow areas of the recesses increase in a direction toward the outlet of the extruder barrel. The taper of the center portion of the mixing head causes a reduction in the flow areas of the channels in a downstream direction, which encourages inter-channel flow to thereby promote improved mixing of the material being conveyed by the extruder screw.