OVERLOAD PREVENTING DEVICE FOR CRANE

摘要

PROBLEM TO BE SOLVED: To improve the operability and safety of a crane by lowering a derricking member to an erection quantity of the prescribed lower limit value or below without taking a release action when the derricking member is relatively short and no cargo is suspended. SOLUTION: The boom work radius R is calculated by the work radius computing unit 131 of an overload prevention section 13 based on the erection angleθof a boom detected by a boom angle detector 5, and the maximum limit load Wa capable of being suspended in response to the boom erection angleθis calculated by a limit load computing unit 132 based on the calculation result. The suspension load (actual load) W applied to the boom is calculated by a suspension load computing unit 133 from the guy cable tension F detected by a tension detector 12. A load factor W/Wa is calculated by a load factor computing unit 134 based on the calculated limit load Wa and suspension load W, and a warning is generated or boom erection drive is stopped based on the load factor.