| 摘要 |
PROBLEM TO BE SOLVED: To lift up a heavy cargo again smoothly after lifting and suspending once the heavy cargo in a halfway. SOLUTION: When a heavy cargo 8 is lifted up and down, a first change-over valve 10 is set to a position that communicates a high pressure port 6a of a second fluid machine 6 and a port 7a of a hydraulic pressure cylinder 7, and a second change-over valve 20 is set to a position that shuts off a liquid flow from the high pressure port 6a of the second fluid machine 6 to a tank 9. When the heavy cargo 8 is lifted up to an intermediate position, is suspended once, and then is lifted up again, the first change-over valve 10 is set to a position that shuts off a liquid flow from the port 7a of the hydraulic pressure cylinder 7 to the high pressure port 6a of the second fluid machine 6, and the second change-over valve 20 is set to a position that communicates the high pressure port 6a of the second fluid machine 6 to the tank 9. |
