| 摘要 |
PURPOSE:To effectuate directional control without using a directional control valve of complicated structure and high cost, by providing a three-position two- port normally-closed control valve if a hydraulic actuator is of the single-acting type but providing two such cotrol valves if the actuator is of the double-acting type and by connecting the control valve or valves to the supply and discharge ports of an oil pressure causing unit. CONSTITUTION:Actuators 19, 20, 21 are connected in parallel with each other. The first ports of normally-closed electromagnetic directional control valves 22, 23 communicate with cylinder chambers 19', 19'' and the second and third ports of the valves communicate with normally-open directional control valves 15-18. When a switch A1 is turned on, the valves 22, 23 act so that pressurized oil enters into the chamber 19' through the valves 17, 22 and oil in the other chamber 19'' returns to a tank 50 through the valves 23, 16. As a result, a piston rod 19''' is moved rightward. |
