| 摘要 |
A seal ring of an on-off valve of a pipe coupling is prevented from separating from the on-off valve even when a fluid flows at high speed around the seal ring. When an on-off valve 26 is in the closed position, a seal ring 50 is sealingly engaged under pressure with an annular valve seat surface 34. A forward annular valve surface portion 52 located forward of the seal ring and a rear annular valve surface portion 54 at the rear of the seal ring respectively have a forward annular passage limiting portion 56 and a rear annular passage limiting portion 58 that are adapted to be in contact with or close proximity to the annular valve seat surface. During the period from when the on-off valve starts to move from the closed position (FIG. 4 ) toward the open position (FIG. 7 ) until the seal ring 50 has separated from the annular valve seat surface by a predetermined distance, the forward annular passage limiting portion 56 and the rear annular passage limiting portion 58 are moved while keeping in contact with or close proximity to the annular valve seat surface 34.
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