| 摘要 |
<p>PROBLEM TO BE SOLVED: To always manage extension operation with the repetition of the same operation by always keeping the extension stroke of a hydraulic cylinder constant. SOLUTION: A one-stage returning hydraulic cylinder 7 having a cylinder tube 7B extended near the base part of a rod 7A pivotally supported on a base boom 1 is used, a connecting device 8 is provided so as to be moved in parallel with the extending and contracting direction of a boom within a range occupied by the base part of each boom in the elongation/contraction direction of the cylinder tube during the full contraction of the boom, and the connecting device is provided with a cylinder boom connecting means 9, an inter-boom fixing means 10 and a positioning means 12, which are united. Modes for keeping the elongation/contraction stroke of the one-stage returning hydraulic cylinder always constant, for moving the connecting device between the contracted booms to position the same in the base part of the selected boom, for operating the boom associatively with the cylinder tube and for releasing the fixing between the adjacent booms are respectively set.</p> |
