Electrically operated hydraulic valve
An electrically operated hydraulic valve comprises a valve assembly that provides a common valve passageway, an inlet port, an outlet port and a return port connected to the passageway and an axially movable valve device 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 provides a restoring force urging the valve device to its first position. An electrically operated actuator coupled to the valve device comprises a permanent magnet and a cooperating electrical coil 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.
1. An electrically operated hydraulic valve comprising:
a valve assembly that provides a common valve passageway, an inlet port, an outlet port and a return port connected to the passageway, and an axially movable valve device which allows in a first position fluid flow between the outlet port and the return port while closing the inlet port 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;
means providing a restoring force urging the valve device to its first position; and
an electrically operated actuator coupled to the valve device and comprising a permanent magnet and a cooperating electrical coil 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, and disposed for operation by an electrical supply which provides a unidirectional current pulse to the coil;
wherein the valve device comprises a valve spool having a lateral valve chamber and the ports intersect the valve passageway at locations spaced apart along the passageway, and
wherein the valve passageway is a blind bore and the valve device has an internal relief passage extending between its ends.
2. A valve according to claim 1 , in which the outlet port intersects the valve passageway at a location between and substantially equidistant from the locations where the return port and the inlet port intersect the valve passageway.
3. A valve according to claim 1 , in which the valve chamber has end surfaces of different effective area whereby fluid pressure in the valve chamber can urge the valve device towards the first position.
4. A valve according to claim 1 , in which the permanent magnet is a cylindrical magnet and the permanent magnet, the coil and a cylindrical magnetic core are coaxially arranged.
5. A valve according to claim 1 , in which the coil and the permanent magnet are both disposed within an annular space between outer and inner parts of the magnetic core.