| 摘要 |
PROBLEM TO BE SOLVED: To simplify the structure and reduce the manufacturing cost by providing a section having a terminal part for ensuring static seal and a circular part for ensuring dynamic seal, curving the circular part in the same direction, and changing the curvature radius. SOLUTION: The upstream and/or downstream seals of a butterfly valve is ensured by a part of a gasket 14 having a circular part 15 which is a dynamic seal part designed to be held to the support part of the stepped part of a body so as to provide static seal and a collar-shaped terminal part 16 showing a radially flat part. The gasket 14 has the circular part 15 formed of three circular arcs (α,β),γ,δhaving at least two different radiuses selected from R1 , R2 , and R3 . The connection of the circular part 15 to the terminal part 16 is attained by the circular arc of a radium R4. The circular part 15 has a linear part 20 having a length suitable to the state of the usable space of a gasket housing.
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