Production of thermoplastic e.g. tube with wound heating element - e.g. by injection moulding cylinder, opening mould and winding element round it, placing in another mould and injecting main tube round it

摘要

A moulding which is at least partly thermoplastic is produced with a heating wire winding, and in partic. it is a welding sleeve for use in joining together the ends of plastic tubes. The wire is placed inside a mask in one winding operation; the mask plus wire are then integrated into the moulding by injecting polymer behind them. Pref. a welding sleeve has an i.d. (2) partly covered by the bare wire winding (3) which is about half embedded in the tube wall. The remaining half of the wire cross-section remains bare. Parts of the tube wall (8) stand up between the bare windings (6) and thus insulate them. ADVANTAGE - The method can provide bare heating wires in the assembly.