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United States Patent 4842414
Douris , ê et al. June 27, 1989

Mixing device for a feed screw

Dray June 27, 1989

Abstract

This invention relates to a mixing device for a feed screw for melting and conveying plasticated material of the type which rotates about a longitudinal axis in a barrel of an apparatus for melting and conveying plasticated material. The feed screw includes consecutive feed, transition, and metering sections, and further includes at least one helical main channel for conveying material in a downstream direction. The mixing device includes a cylinder having a clearance from the inside of the barrel, which cylinder rotates with the feed screw about said axis within the barrel. The outer surface of the cylinder is provided with at least one continuous mixing channel which extends over the surface of the cylinder, the channel being disposed in alternate upstream and downstream directions wherein material conveyed in the mixing channel is caused to alternately reverse its direction while proceeding through the mixing channel. An inlet is provided to admit material from the main channel of the feed screw into the mixing channel. An outlet is also provided to return said material from the mixing channel into the main channel of said feed screw. Because the material is caused to alternately reverse the direction of its flow external to the screw, improved mixing of the material being processed is obtained.