| 摘要 |
PROBLEM TO BE SOLVED: To eliminate loads and pains from an operator though much loads and pains inflicted to the operator because the operator depresses a switch button every time a telescopic arm for construction machinery for caisson type pile excavation is lowered and penetrated into an underground excavated pit through an opening, when a deep ditch is excavated by using the construction machinery for caisson type pile excavation and an alarm is sounded to a worker working, by using a mini-shovel or the like in the excavated pit by an alarm. SOLUTION: The first ground movement of lowering and penetration into the excavated pit of the telescopic arm is detected, by measuring the current states or the like of the telescopic arm and a boom (for example, the measurement of the telescopic arm within a range±γof a fixed vertical angle and the boom within the range±αof a fixed slewing angle), and the alarm is sounded to the worker working in the excavated pit by the alarm installed into the excavated pit.
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