Patent ID: 6017477
Filing Date: 2000-01-25
Classification: B29C

Abstract:
A method of manufacturing an elongated tubular element having a substantially rectilinear cross-section, which includes the steps of:providing a first work station for extruding a first material and a second material:extruding said first material to form an elongated tubular element having a circular cross-section and simultaneously extruding a strip comprising a second material, wherein the rate of shrinkage of said first material is different from the rate of shrinkage of said second material, onto the outer surface of said elongated tubular element at one or more selected points about the periphery of said elongated tubular element, wherein said circular cross-section of said elongated tubular element is forced to a moderately rectilinear cross-section due to the impingement force of said second material;providing a second work station having a means for cooling said elongated tubular element; andpassing said elongated tubular element through said second work station thereby cooling said elongated tubular element;wherein said cooling, which causes distortion of said moderately rectilinear cross-section due to a differential shrinkage force between said second material and said first material of said elongated tubular element during cooling is effective to form a non-circular cross-section of substantially rectilinear form from said moderately rectilinear cross-section.