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United States Patent 5332314
Douris , ê et al. July 26, 1994

Extrusion apparatus with a backfeed extruder for mixing and extruding of thermo-plastic and thermo-setting materials

Geyer July 26, 1994

Abstract

An extrusion apparatus having a rotor member rotatable within a barrel member longitudinal and cross-sectionally mixes and extrudes thermo-plastic and thermo-setting materials. The apparatus is articulated into sections including a barrel entrance and forcing section, a blending section, and an end discharge section. The barrel entrance and forcing section consists of helical extrusion grooves which terminate at an abrupt rotor to barrel and barrel to rotor material transfers. The blending section recognizes that blending is volumetric i.e. three-dimensional and therefore longitudinal displacement of the material in relation to itself is one of the dimensions. Longitudinal displacement is accomplished in the blending section by providing a double extrusion capacity main extrusion rotor and a single capacity backfeed rotor arranged to recirculate half of the material processed by the main stream rotor. The blending section is followed by the end extrusion section, which at its lead end is provided with rotor to barrel and barrel to rotor material transfers to cross shear the material in two different directions to complete volumetric blending. The material transfers are followed by helical rotor extrusion grooves as required to build extrusion pressure.