| 摘要 |
PURPOSE:To prevent abnormal high pressure produced in a telescopic cylinder from being blocked even if a packing case is stopped in the middle of lowering it, to protect a hydraulic instrument by disposing a safety valve in a bypass circuit communicated with a control valve. CONSTITUTION:A discharge side of a hydraulic pump P is communicated with a telescopic cylinder 5 by a discharge circuit 7. A three position, 3-port diverter valve V1 for controlling stretching, contraction, and stop of the cylinder 5 is disposed in the discharge circuit 7, and a control valve V2 capable of selecting 1-3 positions thereof is provided in parallel to the above valve V2 is communicated with the hydraulic pump P side of (a) port branch circuit 10 of the control valve V2 via an eleventh bypass circuit 11, and further communicated with the discharge circuit 7 via a second bypass circuit 12 including a high pressure relief valve R1 being a first safety valve disposed therein. Hereby, abnormal high pressue produced with inertia caused upon rapidly stopping a packing case is bypassed via the above relief valve R1 without blocking the circuit 7. |
