| 摘要 |
PROBLEM TO BE SOLVED: To improve efficiency of work and safety by easily and quickly performing the jib folding operation. SOLUTION: A guide roller 42 is provided on either a base end boom 37 or a jib 40, a guide 41 which collaborates with the guide roller is provided on the other one, and the guide roller and the guide are so arranged that a jib may be fixed in the folding position after the guide roller and the guide are engaged with each other in the contracting operation of a telescopic boom at the specified derricking angle of the telescopic boom 35. Moreover, the jib projecting and storing device is constituted of a jib projecting and storing mode input means for inputting the jib projecting and storing operation state, a boom angle detecting means for detecting the derricking angle of the telescopic boom 35, a derricking operation stopping means for stopping the derricking operation of the telescopic boom 35, and a control means composed of a controller for receiving an input signal from the jib projecting and storing mode input means and a boom angle signal from the boom angle detecting means and for outputting a stop signal to the derricking operation stopping means at the specified derricking angle.
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