| 摘要 |
PROBLEM TO BE SOLVED: To provide a butterfly valve in which a jumping phenomenon due to a rapid drop in rotating torque occurring at the time of opening of a valve body is prevented, control of valve opening is made easy, a secondary eccentricity is not required to set as large, design of valve proper is simplified, and a valve operating mechanism for large torque can be eliminated. SOLUTION: In the butterfly valve provided with a disc-form valve body 20 and a valve stem 22 which is arranged in parallel with the diametrical direction of the valve body 20 and is located eccentrically with respect to both of the directions, i.e., the central axis N of the valve body 20 and the direction M perpendicular to the central axis N, a width of sealing surface 20a on the outer periphery of the valve body which makes sealing contact with a seat ring 24 furnished in the inner surface of a cylindrical valve casing is formed to become wider consecutively from the near side of the valve stem to the remote side thereof when viewed in the direction of the valve stem 22, and at the time of valve opening the remote side departs from the seal ring 24 after a time lag as compared with the near side.
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