Process for producing tubes

摘要

The invention relates to a process for producing tubes from polymeric materials. The tubes have annular thickenings in certain sections, these thickenings being produced by bulging the tube wall cross-section in the still deformable state during the taking-off operation. The invention is regarded as being constituted by performing the bulging by a brief, jerky displacement of the take-off unit counter to the direction of extrusion. This displacement is used to the effect that, at the end of the short travel of the take-off unit, the speed of the tube tends towards zero. At the end of the travel, the take-off unit is returned again into the starting position in a jerky counter-displacement, with the take-off speed remaining the same throughout the entire operation.