| 摘要 |
PURPOSE:To make a line pressure loss small in an electromagnetic valve and obviate the use of a check valve by controlling the operation speed of a hydraulic jack via the control of a pressure fluid flow with a hydraulic pump, while the electromagnetic valve is wide open during the upward and downward travel of a cage. CONSTITUTION:Upon receipt of a lifting operation instruction, a solenoid 11 is energized with an electromagnetic control device 18, thereby making an electromagnetic valve 21 wide open. Concurrently, a hydraulic pump 8 is actuated and oil in an oil tank 12 is supplied to a hydraulic jack 1 via the electromagnetic valve 21, thereby lifting a cage 5. In this case, the rotational speed of an induced electric motor 7 for driving the pump 8 is detected with a rotation sensor 16. The lifting speed of the hydraulic jack 1 is controlled via an inverter device 19, on the basis of the detected speed. According to the aforesaid construction, a line pressure loss becomes small in the electromagnetic valve 21 and a check valve is not needed. The constitution of the electromagnetic valve 21, therefore, can be made simple. |
