DE2603393

1477074 Injection moulding pipe couplings HEPWORTH IRON CO Ltd 19 Jan 1976 [31 Jan 1975] 4372/75 Heading B5A [Also in Division F2] A method of manufacturing a plastics pipe coupling of the sleeve or socket and spigot type comprises injection moulding a second annular member on to a preformed first annular member. The latter may also be injection moulded. The members are interconnected by a chemical and/or mechanical bond. One member may be rigid PVC polypropylene or polyethylene and the other member may be plasticised P.V.C. or a cross-linked thermoplastic rubber. The outer member 1 may be formed with axial ribs 4 provided with end undercuts 5 to provide a mechanical key with the inner member 2. The latter may have a wave-like inner surface for gripping the pipe ends. The coupling 1, 2 may be formed by double injection moulding in the mould shown in Fig. 3. The outer first member 1 is formed by injecting from a nozzle 15 into a cavity defined by a block 10, and sleeve cores 11, 12 supported on cores 7, 9. Following the moulding of the member 1, the sleeve core 12 is retracted along the core 9 the sleeve core 11 is retracted along the core 7 with the nozzle 15, and members 13a-14b are moved radially inwardly to define with the member 1 and cores 7, 9 a second mould cavity in which the second member 2 is formed by injection from a second nozzle (16, Fig. 4 not shown). The composite pipe coupling is ejected by retracting the core 9 to strip the coupling from the core 7 and then sliding the core sleeve 12 along to strip the coupling from the core 9.