We know that jib cranes use lifting moments to characterize load conditions. The lifting moment value is determined by the product of the lifting weight and the amplitude. The amplitude value is determined by the product of the boom length and the inclination cosine of the crane boom. In this way, whether the crane is overloaded is actually affected by the lifting weight, the arm length and the boom inclination angle. Such restrictions, but also consider the operating conditions and other parameters also have constraints, the control is more complicated.
Torque limiters are integrated safety protection devices for jib cranes. Currently widely used microcomputer-controlled torque limiter can integrate multiple situations and solves this problem well. The torque limiter consists of a load detector, an arm length detector, an angle detector, a condition selector, and a microcomputer.
When the jib crane enters the working state, the detection signal of each parameter of the actual working state is input into the computer, and after calculation, amplification, and processing, it is compared with the rated lifting torque value previously stored, and the corresponding actual numerical value is displayed on the display at the same time. come out. When the actual value reaches 90% of the rated value, it will send an early warning signal. When the actual value exceeds the rated load, an alarm signal will be issued and the crane will stop in the dangerous direction (lifting, extending, lowering arm, and turning). action.