Method of manufacturing corrugated tube

Abstract

A method of continuously manufacturing a corrugated tube having a corrugated outer wall and a smooth inner wall surface along the length of the tube is provided which method comprises the steps of arranging in a circular array a plurality of rollers each rotating at the same speed such that an imaginary cylinder is defined about its central axis by said rollers, the longitudinal axes of said rollers being parallel to each other but offset with respect to said central axis; continuously feeding a flat non-reinforced strip of synthetic resin material in a softened state generally perpendicularly to the length of said rollers in such a manner that said strip is helically wrapped around and advanced axially along said imaginary cylinder with portions of adjacent turns of the strip overlapping one on another and welded together; continuously feeding a flexible core member and embedding it between the overlapping portions of adjacent turns of the strip to raise the upper one of said overlapping portions so as to define spiral raised convolutions around the tube; and pressing a pressure roller against the overlappin portions of the strip having said flexible core member embedded therein; whereby a corrugated tube is formed having spiral convolutions defined by the embedded flexible core member around the outer periphery of the tube along the length thereof and a smooth inner wall surface.