| 摘要 |
PROBLEM TO BE SOLVED: To provide a valve element seat for a metal seat butterfly valve capable of ensuring sufficient water stopping performance at the time of loading water pressure by making the valve element seat properly engage into a valve casing seat, widely setting a rotating angle range of the valve element capable of keeping a fully closed state, and reducing a necessary operating torque for opening/closing operation. SOLUTION: In this butterfly valve, a thin-wall cylindrical valve casing seat 31 capable of elastically deforming in a diametrical direction is concentrically provided in the inside of a valve casing at specified intervals, and a valve element 22 rotating about an axis of a valve rod 18 radially inserted in the valve casing and the valve casing seat 31 is disposed in the inside of the valve casing seat 31. A valve element seat 32 sliding with the valve casing seat 31 is provided on an outer periphery of the valve element 22. The valve element seat 32 has an outer peripheral diameter larger than the inner peripheral diameter of the valve casing seat 31, and is shaped in an ellipse having a short axis in the axial direction of the valve rod 18 and a long axis in a direction orthogonal to the valve rod 18. A valve element seat surface 32a is linearly contacted with a valve casing seat surface 13a with making a curved surface.
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