| 摘要 |
A valve comprises a valve body having an inlet and an outlet defining a flow passage through the valve body. A piston is mounted in a bore intersecting the flow passage and the piston divides the bore into first and second chambers. The piston remains substantially motionless during upstream pressure fluctuations after the desired fluid flow rate through the valve has been established. Springs in the second chamber bias the piston against the fluid pressure from the first chamber. A sleeve on the piston is configured to variably sheath a cover over the outlet such that reciprocation of the piston during initiation of fluid flow through the valve varies the effective area of openings in the cover to achieve the desired differential pressure across the flow control throttle, thus setting the flow rate constant unless the throttle position is changed. The equilibrium flow rate can be altered through variation of fluid flow between the piston and the valve body by a bladder ring which is inflated or deflated by an elastomeric ring which is deformed by liquid or structural forces, or by a metal or plastic ring that is circumferentially variable by mechanical actuators.
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