| 摘要 |
PROBLEM TO BE SOLVED: To provide a boom for preventing an overstroke.SOLUTION: This boom 2 includes a plurality of stages of boom members constituted in a nesting shape, an expansion cylinder 30 for sending out the boom members while fixing the boom members by a cylinder-boom connector 31, and a boom fixing device 32 for fixing the inside boom member and the outside boom member in a set fixing position, and includes a boom excess movement preventive means 4 for preventing the inside boom member from moving by going over the fixing position. |
