Production of biaxially oriented thermoplastic tube, by periodical variation of the advancement speed ratio of the preform which is determined by the speed-control and the output of the extruder of different values

摘要

A biaxially oriented thermoplastic tube is produced by periodical variation of the advancement speed ratio of the preform which is determined by the speed-control and the output of the extruder of different values. The wall thickness of the preform is periodically changed. Production of a biaxially oriented thermoplastic tube comprises extrusion of tubular preform from thermoplastic material using an extruder which is provided with an extruder die with an inner core. The inner core defines a hollow space in the preform. The preform is temperature conditioned to reach an orientation temperature suitable for the plastics material being used. The tempered preform is forced over a mandrel. The mandrel comprises an expansion part, which brings expansion in the circumferential direction of the preform passing over it. The stretched tube is cooled and the advancement speed of the preform upstream of the mandrel is set by speed control. The periodical variation ratio of the advancement speed of the preform is determined by the speed control and the output of the extruder of different values. The wall thickness of preform is periodically changed. An Independent claim is also included for a biaxially oriented thermoplastic tube having a tube body and at one or both ends, an integrally formed socket. The axial stretching of the plastic material in the socket is equal to the axial stretching of the plastic material in the tube body.