| 摘要 |
PROBLEM TO BE SOLVED: To provide a telescopic jib for a crane, especially for a mobile crane, including a main jib having a base box and a plurality of jibs telescopically going into/out of the base box, wherein the base box and the telescopic jib are made of deformed materials, the deformed materials are formed of an intermediate product or a plate material, the respective deformed materials have an upper half shell and a lower half shell, legs facing each other of the upper and lower half shells are welded each other, the weight of the jib can be restrained to minimum, and the high rigidity of the deformed material can be achieved in an usable structure space.SOLUTION: The intermediate product or the plate material is made of the plate material manufactured by rolling and partially reinforced. In the half shell, reinforcement parts 1 and 5 which are thick are formed on a terminal area of the leg, that is, an area of an abdominal part, and a reinforcement part 3 which is a thick is formed on a top area, that is, an upper chord area and a lower chord area. Intermediate areas 2 and 4 of both of them are formed to have an ordinary thickness, which is a standard thickness. |
