Abstract: A method for forming a corrugated tube having a smooth inner wall surface and a corrugated outer wall are provided. A first strip of resin material is wrapped around first portions of rollers arranged in a circular array and is helically wrapped around the first portions of the rollers each having equally spaced ridges therearound to form the corrugated outer wall. A second strip of resin material is fed from the interior of second portions of rollers arranged in a circular array onto the inner surface of the outer wall being manufactured and bonded thereto. The second strip bonded to the outer all is wrapped around the second portions of the rollers each having a smooth surface to form the smooth inner wall.

Abstract: A method and apparatus for forming a corrugated tube having a smooth inner wall surface and a corrugated outer wall are provided. A first strip of resin material is wrapped around first portions of rollers arranged in a circular array and is helically wrapped around the first portions of the rollers each having equally spaced ridges therearound to form the corrugated outer wall. A second strip of resin material is fed from the interior of second portions of rollers arranged in a circular array onto the inner surface of the outer wall being manufactured and bonded thereto. The second strip bonded to the outer wall is wrapped around the second portions of the rollers each having a smooth surface to form the smooth inner wall.

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