| 摘要 |
A sprinkler system control valve has a "wet" valve which is maintained seated against a mains water inlet by water pressure applied to a piston of larger effective area than the wet valve. The sprinkler system downstream of the wet valve is charged with air at a relatively low pressure, this air pressure also being supplied to an actuator chamber so as to maintain a deadweight in a lifted position. Upon operation of a sprinkler head the air pressure in the system drops rapidly, causing the deadweight to descend, operating a trip valve through a self-locking cam. Once operated, the trip valve vents the pressure on the piston to an exhaust port allowing the wet valve to open, and at the same time cutting off the actuator chamber from the sprinkler system by the entry of a sealing O-ring into an internal bore in the wet valve housing.
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