Tool for automatically forming, on thermoplastic pipes, bellings of considerable longitudinal extension

摘要

The invention relates to a tool for automatically forming, on thermoplastic pipes, bellings of considerable longitudinal extension for sealingly joining pipes subject to high stresses, comprising a special mandrel (1) on which there is axially inserted the heated end (21) of the thermoplastic pipe (2) which is plastically deformed in the region of a shaped portion (11) of the mandrel designed to form the annular seat (22) for the sealing gasket of the pipe (2) and comprising, in combination, two annular chambers (3 and 4), one acting with a pressurized fluid from the outside towards the inside of the pipe and towards the underlying shaped portion (11), so as to form an extremely precise annular seat (22), and the other one acting with a pressurized fluid from the inside of the pipe towards the outside, for the formation of a belling of any length downstream of the annular seat, the adoption of the two chambers allowing the use of a mandrel preventing collapse of the heated end of the pipe during insertion of the latter onto the mandrel itself.