Patent ID: 7811075
Filing Date: 2010-10-12
Classification: B29C,B29K,B29L,Y10T

Abstract:
1. A screw for use in an extruder comprising a cylinder for carrying a rubber material supplied from a hopper port at an upstream end of the cylinder by the screw, molding it into a predetermined sectional form and extruding it from a nozzle attached to a downstream end of the cylinder, wherein a height of a flight portion of that part of the screw located below the hopper port is lower than a height of a flight portion located on a downstream side, said height at said part varies continuously in a peripheral direction over a predetermined rotational angle of the screw and the predetermined rotational angle is an angle beginning 90° before a position where the height of the flight is lowest and ending 90° after the position where the height of the flight is lowest, and wherein the diameter of the screw located below the hopper port is between 2% and 6% smaller than the diameter of the screw at the downstream side owing to the reduced height of the flight at the part located below the hopper.