| 摘要 |
<p>An electrically operated hydraulic valve comprises a valve assembly that provides a common valve passageway, an inlet port (20), an outlet port (22) and a return port (23) connected to the passageway and an axially movable valve device (8, 15; 33) which allows in a first position fluid flow between the outlet port and the return port while closing the inlet and in a second position, axially displaced from the first position, fluid flow between the inlet port and the outlet port while closing the return port. A spring (13; 34) provides a restoring force urging the valve device to its first position. An electrically operated actuator (19) coupled to the valve device comprises a permanent magnet (24) and a cooperating electrical coil (25) having an associated magnetic core, one or other of the magnet and the coil constituting a stator and the other constituting an armature which is coupled to the valve device to move it from the first position to the second position. The actuator is disposed for operation by an electrical supply which provides a unidirectional current pulse to the coil.</p> |
