Abstract: When a solenoid has been turned on by supplying current to a coil thereof, the solenoid operation is checked by temporarily ceasing the supply of current to the coil to temporarily deenergize the solenoid. The current flowing in the coil is detected while the solenoid is temporarily deenergized, and the characteristics of the thus detected current are used to discriminate the position of a movable iron core of the solenoid. On the other hand, when the solenoid has been turned off by ceasing the supply of current to the coil, the solenoid operation is checked by temporarily supplying current to the coil to thereby temporarily energize the solenoid. The current flowing in the coil while the solenoid is temporarily energized is detected, and the characteristics of the thus detected coil current are used to determine the position of the movable iron core of the solenoid.

Abstract: A proportional pressure release valve comprising a valve body incorporating a valve seat, a valve closure member mounted in the valve body and cooperable with the valve seat to control flow of fluid through the valve from an inlet pressure port to an outlet tank port, and electromagnetic control means having a push pin operable to move, via resilient means, the valve closure member in dependence upon the magnitude of a control current applied thereto, wherein the valve further comprises damper means provided between the push pin and the valve closure member. The valve may also comprise an anti-cavitation ring having a bore and disposed downstream of the valve seat, the anti-cavitation ring being apertured to provide a fluid connection between the ring core and the tank port. The valve closure member may be guided for movement towards and away from the valve seat by guide means comprising at least one linear bearing.