Forming a socket at the end of a softened thermoplastic pipe - by dilating it over a profiled arbor while adding fresh material

摘要

The end of the pipe is passed over an arbor bearing the inner profile of the required socket; a mould of the required outer profile is then placed round, and filled with plastic under pressure. This pressure forces the existing softened plastic pipe into the shape o the profiled arbor, while the new material adds the necessary extra wall thickness. This method avoids thickening the end of the pipe before shaping it, as was previously necessary to maintain sufficient wall thickness in the dilated pipe.