US Patent 7537248 Combination seal and restraint system for plastic pipe

An apparatus for restraining pipe against both internal and external forces at a pipe or fitting connection and to join and seal at least two pipes to form a pipeline featuring an improved restraining and sealing mechanism. The restraining and sealing mechanism includes a circumferential housing and a companion sealing ring which are received within a mating groove provided in the belled end of a female pipe. The circumferential housing has an interior region which contains a gripping ring insert. The sealing ring and housing are integrally located within a belled pipe end during belling operations.