Abstract: Combined mould element and sealing ring suitable for sealing off a joint between a socket end and an insert end of two cooperating pipes formed from thermoplastic material and for being used as a portion of a body of a mould for both fabricating the socket end of the one pipe and simultaneously inserting the ring in an internal groove in the socket end produced thereby. The main bulk of the sealing ring is composed of elastically yielding material having within its contour at least one zone composed of relatively non-elastic material capable of rendering the zone stable as regards its shape compared with the remainder of the ring. Conveniently, such zones are formed by stiffening rings permanently connected to the main bulk of the sealing ring.

Abstract: Combined mould element and sealing ring suitable for sealing off a joint between a socket end and an insert end of two cooperating pipes formed from thermoplastic material and for being used as a portion of a body of a mould for both fabricating the socket end of the one pipe and simultaneously inserting the ring in an internal groove in the socket end produced thereby. The main bulk of the sealing ring is composed of elastically yielding material having within its contour at least one zone composed of relatively non-elastic material capable of rendering the zone stable as regards its shape compared with the remainder of the ring. Conveniently, such zones are formed by stiffening rings permanently connected to the main bulk of the sealing ring.