Abstract Corrugated plastic tubing is formed by producing a plastic tube in a softened condition, passing the softened tube through a rotatable disc having an axial bore with a helical groove for corrugating the wall of the tubular body and then cooling the tube to set the corrugations formed in the wall of the tube. Means is provided for rotating the die, and means synchronized with the rotating means is also provided for drawing the tubular body through the die and cooling chamber to form a helical corrugation in the tubing wall. A pressure differential is applied in the die across the wall of the tubular body to force the wall of the tube into the die groove. Means is provided for engaging the softened tubular body adjacent the entrance to the die to restrain the tubular body against rotation with the die and prevent the softened tubular body from becoming twisted or kinked before entering the die.
Apparatus for making corrugated tetrafluoroethylene tubing comprising means for axially advancing a continuous length of preformed cylindrical tetrafluoroethylene tubing, means for heating the advancing preformed tubing to a temperature above the gel point thereof to soften the tube material, means for drawing the softened tubing to a smaller diameter and simultaneously frictionally engaging the softened tubing circumferentially thereof with a predetermined restraining force to prevent rotation of said softened tubing, a die rotatable about its axis and having an axial bore provided with a helical groove for receiving the heated softened tubing, means for rotating the die at a predetermined speed, the predetermined circumferential restraining force exerted on the softened tubing by said drawing means being sufficient to restrain the tubing from rotating with the die and prevent the rotating die from twisting and kinking the softened tubing before entering the die, means operable to produce a pressure differential across the wall of said tubing in said rotating die to urge said wall into the helical groove to form a helical corrugation in the tubing wall, means synchronized with said die rotating means for drawing said tubular body axially through said rotating die to form a helical corrugation in said tubing wall, cooling means containing a cooling medium operable to cool said tubular body and set said helical corrugation in said tubing wall, and means engaging and drawing the cooled corrugated tubing axially away from the die at a predetermined linear speed to cause the softened tubing to traverse the die at a velocity synchronized with the speed of rotation of the die.