| 摘要 |
PROBLEM TO BE SOLVED: To provide a limiting surface detecting/alarming device capable of confirming whether a crane boom of a machine in operation projects to a limiting surface or not by a crane operator in real time and individually confirming the limiting surface, even if a plurality of cranes performs works in the same area. SOLUTION: At the same level as the height of a limiting surface at the position of a pole 1 installed at a position where the height of the limiting surface is the lowest within a construction field site, a rotary laser light emitting device 2 is installed. At an tip of a boom of each crane 4A, 4B, a level sensor 5 for detecting laser beam 3 emitted from the rotary laser light emitting device 2 is installed. When laser beam 3 emitted from the rotary laser light emitting device 2 is detected by the level sensor 5 at the tip of each crane 4A, 4B, an alarm device 6 is operated, an alarm is generated within operator houses 4a, 4b and an operator recognizes that a tip of the crane driven by himself projects to the limiting surface.
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