Mixing and kneading device

Claim 1

A mixing and kneading apparatus for producing homogeneous mixtures of powdered plastic material such as polyvinyl chloride, polyolefin and finely divided rubber with liquid plasticizer, comprising: a. an elongated kneading shaft; b. a horizontal casing about said kneading shaft; c. a feeding hopper at one end of said shaft and said casing for introducing powder and liquid; d. a receiver at the other end of said shaft and said casing where the plasticized mixture is discharged, said receiver having a neck for attachment to a vacuum; e. said kneading shaft having, in sequence, four longitudinal zones between said hopper and said receiver, namely, a conveying zone formed by continuous spiral flights on the shaft, a kneading zone formed by interrupted threads on said shaft, a homogenizing zone formed by widely spaced helical flights of forwardly angled configuration on said shaft, and a degassing zone; f. said degassing zone being formed by symmetrical deformation in said kneading shaft; g. said symmetrical deformations forming damming surfaces which are spaced from the interior wall of said casing by a plurality of wedge-shaped spaces symmetrically disposed about said shaft; h. said shaft having a plurality of bores and rills, said rills communicating with said bores and said bores being adapted for evacuation by vacuum means to withdraw gases is said wedge-shaped spaces which pass therefrom to said rills and thereby degas the stream of plasticized mixture being kneaded in said wedge-shaped spaces; and, i. motor, gear and drive means to reciprocate the shaft backward and forward for each revolution of said shaft.