IMPROVEMENTS IN HIGH PRESSURE HYDRAULIC SYSTEMS

摘要

In a high pressure hydraulic system a source supplies pressurized fluid to a slave unit through a control valve which maintains the slave unit in a desired condition. Leakage from the slave unit past the control valve with the source inoperative is undesirable, but it is difficult at high pressures to provide cheaply a control valve with leakproof seals which requires small valve-operating forces. The control valve therefore has first and second ports communicating with the source and the slave unit, and a valve member movable to close either port or to an open position to allow communication between the ports. Movement of the valve member is controlled by the pressure differential across it; fluid flow past it, and forces produced by valve-operating solenoids. The slave unit may be an hydraulic suspension strut, and the system may comprise a vehicle suspension levelling system, with the solenoids and the source being manipulated as required by an electronic control system.