| 摘要 |
PURPOSE:To minimize a pressure loss of a hydraulic circuit and to prevent the rise in temperature of the hydraulic circuit, by a method wherein a parallel line is formed so that, when switching valves located in parallel are operated simultaneously, the one switching valve is reduced in load and the other is increased in load. CONSTITUTION:An arm switching valve 24 is changed over in a I-direction and a revolution switching valve 23 in a II-direction to feed a part of pressure oil in a pump 2 to a revolving motor through a discharge line b, a line Z, a port m', and a line m, and other pressure oil to an arm cylinder 40 through a pipe Zb, a relief valve F, a check valve J, a port t', and a line t. Thus, even if a load of an arm is low, the revloving motor is enoughly revolved with the pressure in the line Zb. If the arm switching valve 24 is switched in the II-direction and the revolution switching valve 23 in the I-direction, a part of the pressure oil is fed to a revolving motor 50 through a Za, a S' and a S, and this permits the revolving motor to run at a given speed. |
