| 摘要 |
PURPOSE:To eliminate a special control valve by a method wherein two circuit systems are provided, both a control valve and the first merging control valve are arranged in parallel in one circuit, the second merging control valve is set at the most downstream side thereof and the third merging control valve is arranged at the most downstream side and then they are properly communicated to each other. CONSTITUTION:The figure illustrates a circuit which is applied to a power shovel and one circuit communicating with the first pump 15 is provided with the normal-open control valves 18 to 20, the first merging control valve 28 is arranged in parallel with the control valve and the second merging control valve 29 is arranged at the most downstream side thereof. The other circuit communicating with the second pump 16 is provided with the cntrol valves 21 to 23 and the third merging control valve 40 is arranged at the most downstream side thereof. The merging control valves 28 and 29 are cooperatively coupled to the control valve 22 for operating the boom cylinder 32, and the merging control valve 40 is cooperatively coupled to the control valve 19 for moving the arm cylinder 44. |
