| 摘要 |
<p>PURPOSE:To suppress the quantity of leakage, by joining together the streams of pressure oil from a plurality of hydraulic pumps to drive a hydraulic cylinder, and to let holding pressure affect only a first direction control valve if the holding pressure is produced in the rod chamber of the hydraulic cylinder. CONSTITUTION:The bottom chamber 30 of a hydraulic cylinder 7 is connected to a first and a second direction switching valves 24, 29. The rod chamber 32 of the hydraulic cylinder 7 is connected to the first direction switching valve 24. A passage, which connects a first check valve 37 and the first direction switching valve 24 to each other, is connected to a passage which connects a second check valve 39 and the second direction switching valve 29 to each other. As a result, the streams of pressure oil from a plurality of hydraulic pumps 20, 21 are joined together to drive the hydraulic cylinder 7, and to let holding pressure affect only the first direction switching valve 24 if the holding pressure is produced in the rod chamber 32 of the hydraulic cylinder. The quantity of leakage is thus suppressed.</p> |
