Screw extruder

Abstract

Abstract There is disclosed a screw extruder for processing synthetic plastics and other material of it consistency and, more particularly, a twin-screw extruder in which two extruder screws are rotatably mounted in a casing including two parallel cylindrical intersecting bores. The flights on each screw shaft are interrupted to form two facing sections free of flights. An inner bushing is mounted on the flight-free section of each shaft secured against rotation relative to the shaft and an outer bushing is inserted into each bore of the casing in registry with the respective inner bushing and secured against rotation relative to the casing. The outer diameter of the inner bushings and the inner diameter of the outer bushings are so correlated that a gap is defined between the two bushing walls. This gap has a uniform radial width along its length and constitutes a shear gap. The radial width of the gap can be varied while maintaining the uniform width of its by forming the inner wall of the outer bushing and the outer wall of the inner bushing with a conical configuration and axially displacing the bushings relative to each other. Each gap constitutes a shear gap generating shear forces to which the material is subjected as being conveyed through the extruder. These shear forces can be accurately controlled by varying the radial width of the shear gaps while maintaining uniformity of the shear forces along the length of the gap.

Inventors

• 👤 Hans Werner

Bibliographic Details