| 摘要 |
PROBLEM TO BE SOLVED: To improve workability by providing a gas chamber on the side of a rod and a pressure chamber on the opposite side to the rod partitioned by a piston and a check valve mechanism opening/closing both chambers, and setting the internal pressure of the gas chamber to a negative pressure state in the most compressed state. SOLUTION: When a hydraulic fluid is fed from a pressure port 20 for an extending action in the no-load state, a piston 2 is lifted, and the pressure of a gas chamber 4 is increased. When the pressure becomes the pressure of a piston side pressure chamber 5 or above and exceeds the set pressure of a check valve mechanism 6, the pressure of the gas chamber 4 opens a valve element 9 and is released to the pressure chamber 5 side. When the port 20 is connected to the low pressure side in the most extended state, the piston 2 is lowered by the tare weight of a piston rod 3, the gas chamber 4 is made a negative pressure state, the tare weight of the rod 3, etc., is larger than the suction force by the negative pressure to allow a shrinking action, and the pressure of the gas chamber 4 can be set to the negative pressure state. The pressure rise of the gas chamber 4 is small at the time of the extending action, no hollow section is required on the rod 3 for compensating the pressure rise, and the machining/ assembling property is improved.
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