| 摘要 |
A fluid-flow control valve comprises a valve housing bounding a chamber and defining an inlet port for entry of fluid into the chamber and a control port for egress of fluid from the chamber. The control port is of reduced cross-sectional area relative to the chamber. The valve also comprises a valve closure member disposed in the chamber. The valve closure member is less dense than the fluid that the valve is to be used to control, so that when the chamber contains that fluid and the control port is above the closure member, the valve closure member is urged toward the control port so as to obstruct the control port. The closure member can be displaced away from the control port so as to allow fluid to flow through the control port.
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