| 摘要 |
<p>PROBLEM TO BE SOLVED: To control a rising speed of a cylinder at two levels consisting of a high speed mode and a low speed mode and to prevent a lowering action in spite of a lowering operation when a key switch is in an OFF condition. SOLUTION: A piston chamber 1a and a rod chamber 1b in a cylinder 1 are connected to each other via a communication path L1 provided with the first check valve 4, and the communication path L1 is provided with a switching valve 8 carries out selection between connection to a main flow path L2 connected to an oil pressure control valve 6 via a control valve 5 and connection to a return flow path L3 opened to an oil tank 7. The main flow path L2 and the communication path L1 are connected together via a bypass path L4, and the first check valve 4 can be controlled by means of a pilot pressure generated following a lowering action. In a pilot flow path 14 transmitting the pilot pressure, a solenoid valve 13, which is opened only when a main switch 11 interlocking with a key switch is in an ON condition, is arranged.</p> |
