| 摘要 |
PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a butterfly valve by reducing turning torque required on a valve element in opening and closing the butterfly valve, matching the allowable torque of an opening and closing operator to the turning torque and realizing a turning transmission mechanism in which the operator can be miniaturized. SOLUTION: The butterfly valve 1a has a valve element 4 turnably installed in a valve casing 2. A semicircular gear 5 is mounted on one surface of the valve element 4 in a direction vertical thereto and perpendicular to a valve stem 3, and a driving gear 7 is meshed with the semicircular gear 5. The semicircular gear 5 has a larger pitch circle radius than the driving gear 7. A turning operation shaft 9 of an opening and closing operator 8 is arranged to rotate the driving gear 7, by which the valve element 4 is opened and closed. Driving torque required on the turning operation shaft 9 is thus reduced in opening and closing the valve element 4 and allowable torque is matched to the driving torque, so that the opening and closing operator 8 can be miniaturized. An opening and closing operator 8 can be selected in conformance to each butterfly valve to reduce the manufacturing cost.
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