Patent ID: 6854873
Filing Date: 2005-02-15
Classification: B29C,B29K

Abstract:
1. An extruder for processing a rubber mixture, comprising: a cylinder; a screw rotatably supported in the cylinder for uptake, transport, mixing and extruding a rubber mixture; and a head with incorporated extrusion tool, wherein the screw for advancing a rubber mixture to the extrusion tool has a longitudinal dimension extending from a screw entry zone to a screw exit zone and defined by a helix angle and a thread depth, wherein the dimension varies from the screw entry zone to the screw exit zone so that a rise of the helix angle and the depth of thread are decreasing across the longitudinal dimension from the screw entry zone to the screw exit zone thereby increasing pressure on the advancing rubber mixture near the entry zone, wherein the increased pressure on the advancing rubber mixture has a heat dissipation effect so that the rubber mixture is subjected to a temperature rise during advance to the extrusion tool as a consequence of the heat dissipation and at a constant or decreasing pressure, whereby an extrudate can be obtained at a temperature which approximates a vulcanizing temperature for the extrudate.