Expanding and conferring cup shape to terminal junction segment of biaxially oriented thermoplastic pipes

摘要

A calibration expander expands the terminal segment (2) heated to the plastic state. A circumferential annular seat is shaped for housing of the sealing gasket for the junction. The terminal segment is heated in a furnace to a temperature which increases towards the end of the segment and is controlled so the segment inner diameter reduces as the temperature increases. The calibration expander is also heated and forced inside the heated segment. The outer surface of the shaped segment is cooled and the expander is removed. The differential temperature is formed by means of a flow of cooled fluid which moves from the exterior to the interior of the furnace (44). The cold fluid flows through the ducting (35) in the rigid element (34) which is introduced inside the terminal segment. The fluid flows to the diffuser (36) and is then discharged through holes (37) along the rigid element. A probe (45) regulates the heat produced by the band resistor (56) positioned around the furnace.