| 摘要 |
PROBLEM TO BE SOLVED: To provide a butterfly valve preventing a valve element seat from excessively biting into a valve easing seat while maintaining a totally closed state always without leakage by preventing the formation of a clearance between the valve element seat and the valve casing seat caused by the expansion of a valve casing. SOLUTION: The valve casing seat 12 is provided inside the valve casing 11, and a valve element seat 15 coming in sliding contact with the valve casing seat 12 is provided at the peripheral edge part of a valve element 14 disposed inside the valve casing 11. A valve stem 13 is disposed being radially inserted through the valve element 14, and the valve element 14 is provided to be rotatable between a totally closed position and a totally open position around the axis of the valve stem 13. The head end side 13a and foot end side 13b of the valve stem 13 are rotatably supported by both valve casing boss parts 16, 17 provided at both side parts in the radial direction of the valve casing 11. A connecting pin 18 piercing the valve element 14 in the radial direction of the valve stem 3 to connect and fix the valve element 14 and the valve stem 13 to each other is disposed in proximity to the valve casing boss 17 for holding the foot end side 13b of the valve stem 13.
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