Weldable pipe fittings

摘要

A method of forming a weldable pipe fitting including a thermoplastic sleeve comprising the steps of incising around the internal wall 2 of the sleeve a helical cut 3 inclined to the surface of the wall along the line of cut, the cutting tool and its angular relationship to the bore of the sleeve being chosen such that during incision an internally extending flap of thermoplastic material produced by the incision is caused to open out and deform transverse to the direction of incision whereby a helical cavity 8 is formed within the sleeve wall. An electrically conducting wire is fed into the cavity and the ends anchored. The internal surface of the sleeve is treated to hold the wire within the cavity.