| 摘要 |
PURPOSE:To make a liquid pressure device in a simple construction by allowing the pressure in a pump discharge line plus either of the pressure in a priority line of a priority type pressure compensative valve and the pressure behind a rate and direction control valve in a by-pass line to operate a load sensing valve, and thereby performing control of the pump. CONSTITUTION:When a rate and direction control valve 11 in a priority line 6 and a rate and direction control valve 14 in a by-pass line 7 are switched, a shuttle valve 27 selects either the pressure P behind the valve 14 or the pressure, which is higher than the pressure P1 behind the valve 11 by an amount corresponding to a spring force P2 of a priority type pressure compensative valve 2, and if the pressure P, for ex., is selected, it is applied to a spring chamber in a load sensing valve 63 to mate with the fluid pressure in a discharge line 8, so that a variable capacity pump 62 is controlled so that the pressure in the duscharge line 8 is held at the sum of the pressure P and the spring force P3 of said valve 63. Thus the valves 11, 14 are both pressure compensated. This liquid pressure device A does not require any alteration of the piping when flow control valves 11-13 in the priority line 6 are increased or decreased.
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