PRODUCTION OF SPIRALLY CORRUGATED PLASTIC TUBE

摘要

PURPOSE:To produce a resin tube with a beautiful skin and a proper mechanical property by having the resin tube intensely adhering to the mandrel with a clearance made vacuum between the tube and the mandrel until the tube is cooled and solidified to a certain extent after contacting with the mandrel. CONSTITUTION:A mandrel 16 having a spirally corrugated outer surface is arranged ahead in the extrusion direction of the mouth piece of an extruder 12 and then, mounted to the extruder 12 in such a manner as to rotate in the circumference of the mandrel in the form of a resin tube 18 and molded into a resin tube cooling the mandrel. A fine groove 26 is provided on the circumference of the mandrel near the position at which the resin tube extruded begins to come in contact with the mandrel, in such a manner that the peripheral angle thereof exceeds at least 360 deg. crossing the spiral direction thereof. The entire fine groove is communicated to a vacuum chamber to have a clearance vacuum between the resin tube and the mandrel. The resin tube runs along the circumference of the mandrel while being withdrawn by rotating in the circumferential direction matching with the extrusion speed and spiral pitch.