| 摘要 |
<p>A fluid flow control valve in which communication between respective inlet, outlet and exhaust ducts is controlled by movement of an axially reciprocable spool relative to an annular sealing member co-operating with respective seat means on the spool and on the housing of the valve, in which movement of the spool in one direction first effects sealing engagement between the spool seat and the sealing member to close one line of communication, and then moves the member off the other seat means to open another line of communication. The sealing member may, for example, be a flexible diaphragm or a piston.</p> |
