| 摘要 |
PROBLEM TO BE SOLVED: To previously prevent damage to a working jib and a swing lever by provide a detecting means of detecting the presence or absence of a weight for preventing the working jib from swinging and a warning means by the output from the detecting means. SOLUTION: This safety device is provided with a detecting means of detecting the presence or absence of a weight for preventing swinging mounted on the front end part of a working jib 7, and a warning means operated by the output from the detecting means. When the detecting means detects that the weight for preventing swinging at a bracket at the front end of a front-end jib 72 of the working jib 7 through warning display, the warning indication that the weight is not mounted is made to an operator in a operation room. Before standing operation, the safety device can give warning to the operator in an operation room, so that warning is made that the standing operation of the working jib should not be conducted. It is thus possible to prevent the jib 7 from being swung more backward even if the jib is raised to the limit of a derrick angle of the jib.
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