Forming socket ends of thermoplastic pipes - by progressive mechanical and hydrostatic means to obtain close dimensional tolerances on the socket

摘要

A socket with an internal annular recess is formed on the end of a thermoplastic pipe by clamping the pipe in a split hollow sleeve having a wide mouth with a bevelled edge, then inserting a hot mandrel with an annular rib and a bevelled tip to press the pipe wall against the sleeve mouth, and then enclosing the mandrel rib with an ancillary hollow annular sleeve with an extended mouth. Fluid pressure is then applied within both hollow sleeves to conform the pipe to the mandrel profile. After cooling, the sleeves are disengaged and the mandrel is withdrawn after collapsing the segments defining the rib. Used for mfr. of sockets on the ends of straight or curved pipe or fittings to obtain close dimensional tolerances (e.g. plus-or-minus 3 mm) on the socket wall profiles and thickness, even if the pipe wall thickness originally has a greater variation (e.g. plus-or-minus 1 mm). The progressive forming and consolidation of the socket profile tends to concentrate extra material into the large dia. channel wall if necessary.