| 摘要 |
PROBLEM TO BE SOLVED: To reliably prevent an accident by preventing a load P from becoming an overload state more than a prescribed load P2 regardless of operation of a releasing means when reaching a prescribed load P2 even if an overload preventive means is put in a state of releasing the operation by the releasing means. SOLUTION: A stopping judging unit 1c makes a prescribed jugement on the basis of a load rate F determined by a load rate operation unit 1b, preset two load rates F1, F2 and a state of a releasing switch 4 to control a solenoid opening/closing valve 5 for automatically stopping operation of a crane. Automatic stopping by the releasing switch 4 can be released in a range of F1<=F<F2. While, when judged as F>=F2, even if the releasing switch 4 is turned on, a stopping signal to the solenoid opening/closing valve 5 is outputted so that the crane is automatically stopped. Thus, even if an operator tries to perform unreasonable work in a state of turning on the releasing switch, operation is automatically stopped before a load reaches a limit to prevent an overturning accident.
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