| 摘要 |
PROBLEM TO BE SOLVED: To enable ejection from the top floor of a building by providing a maintenance crane for a facility disposed on the top floor of the building with a refuge path which has length enough to span other adjacent buildings, and a boom constituted so as to be erected and folded. SOLUTION: A main tower 5 provided with a turntable 4 on its upper end is erected on the top floor of a building 3, a radio wave tower 1 provided with a parabolic antenna 6 and maintenance crane 2 for repairing and maintaining the antenna 6 and the tower 1. The crane 2 is constituted by a boom 7 which can be erected and folded to a predetermined angle, a refuge path comprising a bottom plate and both side plates is installed in a frame of the boom 7, and a foldable ladder which is restrained to the approximately perpendicular to the bottom plate is disposed on the bottom plate of the refuge path. On the other hand, a ladder 13 is hung from the top roof of the building 3 to the turntable 4 across the main tower 5.
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