Patent ID: 7708029

Claim:
A coupling member of a pipe coupling having a male coupling member and a female coupling member that are couplable to each other; the coupling member comprising: a tubular member having a fluid passage, the tubular member having an annular valve seat surface formed so as to surround said fluid passage; and an on-off valve provided in the fluid passage of the tubular member, the on-off valve being movable between a closed position where it is engaged under pressure with the annular valve seat surface to close the fluid passage and an open position where the on-off valve is displaced rearward in the axial direction of the fluid passage to separate from the annular valve seat surface, thereby opening the fluid passage; the on-off valve comprising: an annular valve surface located so as to face the annular valve seat surface when the on-off valve is in the closed position; and a seal ring fitted and fixed in an annular groove formed circumferentially in the annular valve surface; the annular groove comprising a stepped bottom surface which comprises a first surface bottom having a first diameter, a second bottom surface positioned rearward of the first bottom surface and having a second diameter greater than the first diameter, and an intermediate surface connecting the first and bottom surfaces; the seal ring having a cross section complementary to a cross section of the annular groove and comprising a forward annular seal portion positioned on the first bottom surface and a rear annular seal portion position on the second bottom surface and contiguous with the forward annular seal portion, the rear annular portion having an outer diameter that is substantially same as that of the forward annular seal portion.