Shaping thermoplastic tube into smooth socket with collar - using equipment which provides a radial space during outwards expansion of the wall

摘要

The parent patent claims the formation, in stages, of the end of a thermoplastic tube into a socket with an outer collar. The end is first heated, expanded on a mandrel with corresp. redn. in wall thickness, and then compressed to increase its thickness again so that it has at the collar at least the same compression strength as elsewhere. The collar area is then pressed out into a space, and the tube wall by the collar is increased in thickness from the outer or inner side. The improvement comprises increasing the wall thickness under pressure whilst creating further outer space for it along the whole length of the collar. The improved system prevents formation of creases even with thick tubing.