US Patent 7708029 Coupling member of pipe coupling

A coupling member is provided that comprises a valve movable between a closed position and an opening position. The valve is provided with a seal ring fixed in an annular groove formed in the valve and urged against a valve seat in the closed position. The groove has a forward annular groove portion and a rear annular groove portion shallower than the forward annular groove portion. The seal ring has forward and rear annular seal portions fitted in the forward and rear annular groove portions, respectively. The rear ring portion has substantially the same diameter as the forward seal portion.