| 摘要 |
<p>A supply or demand margin valve for use in hydraulic systems having at least one load provided with hydraulic fluid under pressure by a main pump, a pilot pump and at least one control valve for the load. The margin valve includes a valve body having a bore with a spool reciprocally received within the bore. A first port in the body extends to the bore and is adapted to be connected to the pilot pump. A second port in the body extends to the bore and spaced in relation to the first port and is adapted to be connected to a component of a hydraulic system other than a pilot pump. A spring is disposed in the valve body for applying a biasing force to the spool to urge the spool in one direction and a third port is in fluid communication with the pressure responsive surface and is adapted to be connected to a main pump so as to apply a force to the spool to urge the spool in the same direction as the spring. A fourth port connects with a pressure responsive surface for applying a force to the spool in bucking relation to the spring and a feedback passage in connection with an additional pressure responsive surface is in fluid communication with the second port for applying an additional force to the spool in bucking relation to the spring.</p> |
