| 摘要 |
<p>A directional control valve comprises a spool which is movable in a chamber and which carries shear seals urged against a respective wall of the chamber, the spool being movable between a first position in which a fluid supply inlet is in communication with a functional outlet and a second position in which the fluid supply inlet is cut off from the functional outlet, and a safety piston which is spring-loaded towards engagement with the spool in a sense to move the spool to the second position. An intermediate piston is interposed between the spool and the safety piston so that the intermediate piston can allow relative movement between itself and the spool. The chamber includes a port coupled to a pressure transducer which can monitor the position of the valve spool or the function line pressure.</p> |
