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 de

Abstract: A method and apparatus for continuously forming a corrugated tube from a strip of synthetic resin in a softened state by the use of a plurality of rotating rollers arranged in a circular array such that said rollers define an imaginary cylinder about its central axis with the axes of said rollers being parallel to each other but angled relative to the central axis of the imaginary cylinder whereby as the rollers rotate the strip is helically wrapped around and advanced axially along said imaginary cylinder with portions of adjacent turns of the strip overlapping and joined together to form a continuous tube; characterized in that each of said rollers is provided with a plurality of axially spaced annular ridges therearound, said ridges of the respective rollers being so arranged that the associated successive ridges of each adjacent rollers are aligned in a spiral path around said imaginary cylinder.