Methods and installations for manufacturing biaxially oriented tubing and the tubing itself

摘要

An installation to produce bi-axially oriented tubing of thermoplastic material is provided with an expansion device 20 including a non-deformable expansion part 20b having a gradually increasing diameter to a maximum diameter at a downstream end, the expansion part being contacted by the preform tube 10 and exerting an expanding force on the tube to expand the tempered tube circumferentially as the tube is drawn through the installation from the preform extruder by a tractor device downstream of the expansion device. The expansion device includes a run-off part 20c following downstream from the expansion part 20b and that has a section with a smaller diameter than the maximum diameter of the expansion part. At least one outer diameter ring 90, 91 is arranged at the location of the reduced diameter section and around the reduced diameter section. The bi-axially oriented expanded tube passes through and in contact with the outer diameter rings which in conjunction with the reduced diameter section are dimensioned so that seizing of the oriented tube between the outer diameter rings and the run-off part is prevented and the inside of the oriented tube is radially spaced from the reduced diameter section. The oriented tube is cooled by the water sprays 60 in the region of the reduced diameter section.