Importance

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Abstract

An extruder for polymer melts, with an extrusion space arranged in an extruder barrel and through which at least one extruder screw shank extends so that it can be rotated by a motor. The screw shank has at least one section in the form of a cylinder casing, the extrusion space having at least one barrel section which surrounds the cylinder casing in an essentially equidistant manner to form an encircling gap as a restricted flow zone (blister), in particular to set the pressure of the melt. The clearance of the encircling gap at the restricted flow zone can be changed in a specifically selective manner by externally adjustable force, with elastic deformation of the inside surface of the extrusion space and/or of the surface of the screw shank, by a hydraulic pressure chamber provided in the region of the restricted flow zone in the wall of the barrel section and/or in the least one screw shank. The pressure chamber has on the side facing the extrusion space a considerably smaller wall thickness (membrane wall) in comparison with the wall thickness of the extrusion space. A hydraulic pressure unit supplies the force for the surface deformation.

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First Claim