Method of making socketed pipe-fittings of synthetic plastics material by injection moulding, apparatus for carrying out said method

A method of making a pipe fitting of synthetic plastics material by injecting moulding, said pipe fitting comprising a socket including means for receiving a sealing ring, characterized by, prior to the injection moulding process, placing a sealing ring in slightly pinched condition with reduced outer diameter at the level of the means to be formed on the socket for receiving the sealing ring, and holding it in this position during the injecting moulding process, the sealing ring being isolated from the moulding cavity during the injection moulding process;

• and after sufficient, but incomplete cooling of the moulded socket, temporarily and partially deforming the means for receiving the sealing ring, and releasing the sealing ring to permit the same to spring into the partially deformed ring receiving means, which thereafter reassume their original shape, thereby gripping the sealing ring.