Pressure compensating valve, unloading pressure control valve and hydraulically operated device

Abstract

A pressure compensating valve (7) comprises a main valve (20) that is operated in such a way as to increase the area of the opening between an inlet port (24) and an outlet port (25) by means of pressure acting on a first pressure receiving component (21). The pressure compensating valve (7) is also operated in such a way as to reduce the area of the opening by means of pressure acting on a second pressure receiving component (22) and pressure acting on a third pressure receiving component (23). The pressure compensating valve (7) is designed to allow the pressure (Pa) of the pressurized oil flowing to the inlet port (24) to act on the first pressure receiving component (21) and the pressure (Pb) of the load driven by the pressurized oil flowing from the outlet port (25) to act on the second pressure receiving component (22). A control pressure producer (7B) is provided for allowing control pressure (Pe) resulting from a reduction in the pressure (Pa) of the inlet port (24) to act on the third pressure receiving component (23). An unloading pressure control valve and an variable bleed valve can also be provided. This structure allows the pressure compensated characteristics to be changed as desired. The unloading start pressure is also preset so as to improve response in terms of the hydraulic actuators. Energy loss can also be minimized, allowing the rapid start-up of the hydraulic actuators to be controlled, machines can be made smaller, and high precision control can be achieved.

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