Pipe connectors

A connector for connecting pipe sections comprising a tubular pin member having a generally frusto-conical outer peripheral surface and a tubular box member having a generally frusto-conical inner peripheral surface corresponding to the frustro-conical outer peripheral surface of the pin member and which overlies the outer peripheral surface of the pin member when the members are fully engaged together, each frusto-conical surface comprising a central portion and end portions, the central portions of the surfaces being provided with a plurality of annular projections and grooves which are inter-engaged when the members are fully engaged together to axially lock the members together, means being provided for sealing a free end of one member to the other member when the members are fully engaged together, wherein end surface portions of the members adjacent the free end of the one member are radially spaced apart and a radially extending annular rib is provided intermediate the ends of each end portion, the ribs being axially aligned and radially dimensioned so that, when the members are fully engaged together, the crest surfaces of the ribs are in contact, and where there is a substantial pressure difference across the walls of the connector, the ribs serve to transfer hoop stresses in the region of the one end surface portion of one member of the connectors to the other.