| 摘要 |
PURPOSE:To support load positively by one check valve even when the other check valve gets trouble, and to improve safety by mounting the two check valves operating separately to the control circuit of a cylinder device. CONSTITUTION:The first check valve 53 is set at a position (d) and brought to the state of a closed circuit to a tank 43, and the volume of the first and second cylinder chambers 28, 29 of an external cylinder 25 is not varied. Accordingly, load is supported. Likewise, load can be supported by setting the second check valve 54 at a position (d). The first and second check valves 53, 54 are changed over to positions (e), and brought to the state of an opened circuit to the tank 43, the second direction control valve 48 is changed over to a position (a), and a liquid is supplied to the first cylinder 37 in an external rod 33. Consequently, the cylinder device 24 can be stretched at high speed. When the direction control valve 48 is changed over to a position (b), the length of the cylinder device 24 can be shortened at high speed. |
