| 摘要 |
PROBLEM TO BE SOLVED: To provide a coaxial-type butterfly valve having high water stopping property, comprising a valve element easy to integrate, and further highly durable. SOLUTION: This butterfly valve comprises a valve box 1, the disc-like valve element 2, and a valve rod 2 for rotating the valve element. The valve seat part 11 of the valve box 1 has an elliptic base surface 12 and a spherically recessed valve seat surface 13. The valve element 2 comprises a core body 21 the outer surface of which is lined with an elastic material such as rubber, and a valve seat part 23 made of an elastic material. Since the valve seat surface 13 of the valve box 1 is spherically recessed, and the valve seat part of the valve element is elastic, the both are in face contact to each other in a sufficient contact width, and when a hydraulic pressure is applied in valve closing, the contact pressure in a water stopping part is increased to provide high water stopping property and durability. Since the base surface 12 is elliptic, the valve element 2 is assembled by a method for inserting it in a position having a large inside diameter followed by moving to a normal position, and the attachment and detachment work of the valve element is smoothly performed.
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