| 摘要 |
PURPOSE:To prevent the detrioration of an oil-pressure circuit for an oil-pressure shovel during the multiplex operation by a method in which when pressure oil is supplied to the rod side of a bucket cylinder through a switch valve for the bucket cylinder, provided to each oil-pressure pump, the pressure oil on the bottom side of the bucket cylinder is returned to a tank. CONSTITUTION:The first multiple valves 10 to be led to the first oil-pressure pump 12 are included with a switch valve 8a for a bucket cylinder, and the second multiple valves 11 to be led to the second oil-pressure pump 13 are included with a switch valve 8b for another bucket cylinder. The main circuits for the switch valve 8a and the switch valve 8b are led to the bottom side of the bucket cylinder 8. When the pressure oil is supplied to the rod side of the bucket cylinder 8, the pressure oil on the bottom side of the bucket cylinder 8 is returned to a tank through both the switch valve 8a and the switch valve 8b. |
