| 摘要 |
<p>A pilot valve controlled fluid pressure actuated flow control valve is disclosed which includes a plunger in the flow passageway through the main valve. One end of the plunger defines a piston which is disposed in a piston chamber, and the other end of the plunger defines a valve element displacable into and out of engagement with a valve seat in the passageway. A pilot valve controls the flow of upstream fluid into and from the piston chamber to respectively close and open the main valve passageway. The pilot valve includes a pair of valve elements reciprocable together between first and second positions. In the first position, one of the valve elements closes the passage for delivery of upstream fluid to the piston chamber and the other valve opens a passageway to release upstream fluid from the piston chamber. In the second position, the one valve element opens the passageway for directing upstream fluid to the piston chamber and the other closes the passageway for release of upstream fluid from the piston chamber. Each of the pilot valve elements is biased in its closed position by the pressure of upstream fluid acting thereagainst.</p> |
