| 摘要 |
<p>A fluid flow control device suitable for controlling the flow of fluid between two chambers of a jack comprises a valve between each of the two chambers being controlled and a common chamber. The valves are controlled by pilot operated stops which, when retracted permit the valves to close fully but which, when extended hold the valves partially open. A source of make-up fluid can be connected to the common chamber, and the feed to the pilot valves can be tapped off the common chamber by way of a restriction. Alternatively, the pilot valves can be isolated from the common chamber and a separate source of pilot fluid provided. In this case, the common chamber can be permanently connected to a source of fluid under pressure which can be a fluid pressure accumulator.</p> |
