| 摘要 |
PURPOSE:To reduce tilt-up force at the time of tilt-up by enabling the free connection of the operation oil receiving part in a gas chamber to the middle of a communicating passage for mutually communicating respective chambers in a cylinder rotating a swivel bracket through a manual opening and closing valve. CONSTITUTION:A cylinder 20 for vertically rotating a swivel bracket is partitioned into a first chamber 23 and a second chamber 24 by a main piston 22, and the oil as an operation fluid is received in each chamber 23, 24. A free piston 25 is received in the second chamber 24, whereby the second chamber 24 is partitioned into two chambers 24A, 24B. The respective chambers 23, 24B are communicated to each other by communicating passages 30, 31, and a first opening and closing valve 32 is interposed in the communicating passage 30. A communicating passage 34 and a gas chamber 35 are communicated to the chamber 24B through the communicating passage 31, and the gas chamber 35 is partitioned into an operation oil receiving part 36A for receiving the operation oil and an operation gas receiving part 36 on the anti- communicating passage 34 side by a separating piston 36. A second opening and closing valve 37 which is opened when the operation oil in the chamber 24B is compressed to a determined pressure value or more is interposed in the communicating passage 34. |
