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1, Introduction: Types of limiters
The tower crane must have lifting capacity limiter, moment limiter, height limiter, travel limiter, amplitude limiter, etc.
(1) Lifting capacity limiter: also known as overload limiter, it is a safety device that can prevent the crane from overloading. When the lifting weight exceeds the rated lifting weight, it can automatically cut off the power supply of the lifting mechanism to stop or give an alarm. There are two kinds of lifting limiters: mechanical and electronic.
(2) Torque limiter: For luffing cranes, only a certain lifting weight is allowed within a certain range. If you are overweight, you will be in danger of tipping over. Torque limiter is a kind of protection device developed according to this characteristic. In a certain range, if the hoisted object exceeds its corresponding weight, the circuit will be cut off, which will make the lifting impossible and ensure the stability of the crane. There are three types of torque limiter: mechanical, electronic and composite.
(3) Height limiter: also called hook height limiter. Generally installed on the derrick head. When the hook slides to the limit position, it will lift the lever. Press the lower limit switch to cut off the circuit and stop. When it is closed again, the hook can only descend.
(4) Travel limiter: an insurance device to prevent the crane from colliding or limit the travel within a certain range. It is generally installed inside the mobile car, mainly by installing a travel switch that can toggle the handle. In addition, a fixed limit position baffle is installed at the end of the track (where the operation is restricted). When the tower crane runs to this position, the limit baffle touches the lever of the travel switch to cut off the power supply for controlling walking. When it is closed again, the tower crane can only run in the opposite direction.
(5) Limiter: Also known as limiter or amplitude indicator, an amplitude indicator is hung on the jib of a general jib crane. It consists of a fixed circular indicating board with a vertical movable pointer in the center. When changing the amplitude, the pointer indicates the rated lifting weight at various amplitudes. When the boom moves to the upper and lower limit positions, press the lower limit switch respectively to cut off the main control circuit and stop the luffing motor to realize the limit function.