US Patent 7410174 Restraining mechanical joint gasket for ductile iron pipe

A restraining gasket for both sealing and preventing separation of a pipe joint used to join a bell end of a female ductile iron pipe to the male end of a mating ductile iron pipe. The gasket has a body formed from a compressible elastomeric material having a hardened metal ring located therein with gripping teeth. The hardened ring has an opening at one point in its circumference which is filled with rubber. The rubber-filled gap ensures that the gasket body seals first prior to engagement of the gripping teeth as the pipe joint is assembled.