| 摘要 |
PURPOSE:To permit the smooth turning of an oil-pressure shovel by a method in which a variable sequence valve is connected to the parallel pathway of a turning direction control valve so as to give priority to the turning circuit over the arm and boom circuits during period when turning arm and boom operations are concurrently performed. CONSTITUTION:A variable sequence valve 40 is provided in the parallel pathway 32 of a turning direction control valve 21. In such a system, when the lever 51 of a turning remote control valve 50 is fallen down in the direction of arrow A, secondary pressure is directed even in the direction of arrow A3, the set pressure of the valve 40 is raised, and turning is accelerated by a turning motor M2. Then, the discharge oil of an oil-pressure pump P2 flows preferentially into the turning motor M3 and its excess oil is bleeded off by the valve 40 and directed into parallel pathways 34, 36, and 37 through the pathway 33. In short, when an arm control valve 23 is operated, said excess oil is directed in the direction of arrow A4 to actuate an arm cylinder C2. Thus, the operation of the arm cylinder C2 does not affect the operation of the turning motor M3. |
