| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent a tip boom from being extended even if an extension mode is not switched to an extension incapable position in multiple hooking. SOLUTION: This device is provided with a first bracket 41 having a hole 41c in the specified position of a tip boom 5, a second bracket 51 having a hole 51a to be matched to the hole 41c of the first bracket 41 in most contracting of the boom and provided on a boom 4 just before the tip boom 5 by one stage, and a plate having its base end rotatably attached to the first bracket 41 and for blocking the hole 41c of the first bracket 41 in the time except for the time of most contracting of the boom. The positions of both holes 41c, 51a of the first and second brackets 41, 51 are made to coincide with each other by rotating the plate by the second bracket 51 in most extracting of the boom and the rope end 34 of a suspending wire rope 33 is inserted in both holes and fixed by a fixing pin 42.</p> |
