| 摘要 |
A valve actuator in which condensation is prevented. A piston (5) connected to a valve (1) is urged by a spring (16) in a predetermined direction. Also, the piston (5) is received in a cylinder (4) so as to be slidable in the opposite direction against the spring (16) by pressurized air sent from a pressurized air inlet (6a). When pressurized air inlets (4a, 6a) of the cylinder (4) and a pressurized air source (18) are being communicated with each other, a solenoid valve (11) closes a circulation tube (22) connected to air outlets (4b, 6b) of the cylinder (4). When the communication between the pressurized air inlet (4a, 6a) of the cylinder (4) and a pressurized air source (18) are shutoff, the circulation tube (22) is communicated to the pressurized air inlet (4a, 6a).
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