| 摘要 |
PROBLEM TO BE SOLVED: To reduce the pressure loss at the passage release time by arranging the long axis side of a vane type section parallelly in the flow direction of a fluid at the release position of the passage. SOLUTION: When the gate 2 of a butterfly valve is rotated by 90 deg. from the close position of a passage 1 through a rotary shaft 30 from a drive part 4 and switched to the release position of the passage 1, the flow of a fluid is generated through the passage 1. The axis vertical section of the rotary shaft 30 is formed by a vane type section and as the long axis side of the vane type section is arranged in parallel with the flow of the fluid at the release position of this passage 1, the projection area orthogonally crossing with the flow direction of the fluid at the vertical section of the passage 1 is minified. Therefore, the area contacting to the rotary shaft 30 for the fluid flowing in the passage 1 is minified and the passage resistance against the fluid is reduced and the pressure loss taking place to the fluid passing the gate 2 of a butterfly valve can be minified.
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