| 摘要 |
<p>A hydraulic valve comprises a plurality of ports, which communicate with a passageway, and a valve member movable in the passageway to control the communication between the ports. The valve member carries a lateral shear seal which is integral with the valve member and engages the passageway. In one position, the valve member isolates a first port from a second port. In another position of the valve member, the shear seal communicates with the first port and provides communication between the first port and the second port by way of a passage within the valve member. The valve member has first and second portions of different effective cross-section areas and on each portion an integral sealing member makes a radial seal between the valve member and the passageway. A supply port supplies pressure to the outside of the valve member so as to produce by virtue of the different cross-sectional areas a force tending to move the valve member towards a closed position.</p> |
