| 摘要 |
In a high pressure hydraulic system a source supplies pressurized fluid to a slave unit through a control valve operative to maintain the slave unit in a desired condition. Leakage from the slave unit past the control valve when the source is inoperative is undesirable, but it is difficult to provide durable leakproof seals and to minimize valve operating forces at high fluid pressures. The control valve therefore comprises two solenoid-operated valves oppositely acting and arranged in series between the source and the slave unit, each valve being closed to prevent flow through the valve in a direction from the other valve and opened to permit flow in both directions, under the control of a solenoid and the pressure differential acting across the valve, a seating portion on a first valve is of elastomeric material to provide a leakproof seal when that valve is closed. In the construction shown the slave unit is an hydraulic suspension strut, and the system is adapted as a vehicular suspension levelling system, with the valves and the source being manipulated as required by an electronic control system.
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