| 摘要 |
PURPOSE:To prevent the lowering of the life of an oil-pressure shovel by a method in which the secondary side of overload relief valves connected to circuits between boom, arm, both cylinders, and direction switching valve is connected to the primary side of a throttle valve, and the discharge amount of pumps is regulated to a minimum. CONSTITUTION:Oil pressure is supplied to switching valves V1-V8 to control both motors for driving and slewing the crawler of a traveling device 2 and also to the cylinders 8, 4, and 6 of bucket, boom, and arm by variable discharge- type pumps P1 and P2. A bypass oil path 10 and a main relief valve 11 are connected in parallel to the discharge port of the pump P1. Overrelief valves 15 are connected to both-side oil paths between the switching valves V2-V4 and the corresponding actuators in the form of a closed-center type with check valve and them connected to the primary side of a throttle valve 13 through the valve 11 and both secondary side oil paths 16 and 17. Overmuch load can thus be automatically detected to stop excavating operation. |
