| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a telescopic jib for a crane enabling higher rated load them ever in the same boundary condition of a life and a maximum allowable axial load. SOLUTION: This a telescopic jib is for a crane, and for a moving type crane, in particular, and has a main jib. The main jib has a base box and a plurality of jib parts capable of telescopically going into/out of the base box. The base box and the telescopic jib part are made of deformed materials. Each telescopic jib part has an upper shell and a lower shell constituted in the same mode or different modes. Leg parts facing each other of the upper and lower shells are welded each other. In each telescopic jib part in which nominal wall thickness of the upper shell is equal to nominal wall thickness of the lower shell at maximum or is smaller than thereof, at least a part of the lower shell 5 is provided with two outside thin plates 8, 8' having cavity with a mutual distance 90 from the viewpoint of cross section.</p> |
