| 摘要 |
A butterfly valve, in which fluid leakage inside a valve disc and from a shaft seal part between through holes of a seat ring and a stem is prevented, when the valve disc is displaced under fluid pressure with the valve closed. Without increasing the operation torque of the stem, the fluid leakage is prevented even after continuous on/off (open/close) operations over a long period of time. The butterfly valve includes the seat ring fitted to the inner peripheral surface of the hollow cylindrical valve body, the stem supported on the valve body via the through holes of the seat ring, and the discal valve disc with the stem mounted and supported in the valve shaft hole. The annular protrusion having the tapered surface with the outer periphery thereof inclined with respect to the valve axis is formed radially inward of the peripheral edge of the through holes on the inner periphery of the seat ring. The bowl-shaped annular depression engaged with the tapered surface is formed on the inner periphery at the opening end of the valve shaft hole of the valve disc.
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