| 摘要 |
A valve comprising a closure member including an annular peripheral sealing surface, a supporting shaft fixedly secured to opposing sides of the closure member, a housing including a cylindrical flow passage and means for rotatably supporting the closure member supporting shaft, means for rotating the closure member from a first position, whereat the flow passage is open, to a second position, whereat the flow passage is closed, an annular valve seat including an annular sealing surface, the housing further including an annular valve seat receiving channel selectively configured to support the annular valve seat for mating engagement with the closure member sealing surface when the closure member is at the closed position and the valve seat is at the neutral or zero pressure position, the valve seat including a recessed portion on one side thereof with a first annular groove extending axially into the valve seat from the recessed portion and a second annular groove extending axially into the other side of the valve seat, the second groove dividing the other valve seat side into upper and lower portions, the side of the receiving channel adjacent to the other side of the valve seat being spaced from the lowermost part of the upper portion and being selectively inclined relative thereto, when the valve seat is in the neutral position, to establish a spacing therebetween which linearly increases towards the uppermost part of the upper portion to permit selected rotation of the valve seat into engagement therewith, the annular closure member sealing surface extending incrementally radially outwardly from the one side to the other side of the valve seat.
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