Tower cranes must have a weight limiter, a torque limiter, a height limiter, a stroke limiter, an amplitude limiter, and the like.
(1) Lifting weight limiter: also called overload limiter, is a kind of safety device that can make the crane not overloaded. When the hoisting weight exceeds the rated lifting weight, it can automatically cut off the power supply of the lifting mechanism to stop or send out. alarm. The lifting limiter is available in both mechanical and electronic versions.
(2) Torque limiter: For a luffing crane, a certain range is only allowed to lift a certain hoisting weight. If it is overweight, there is a danger of tipping over when it is stressed. The torque limiter is a protection device developed according to this feature. At a certain extent, if the hanging object exceeds its corresponding weight, the circuit is cut off, so that the lifting cannot be carried out, and the stability of the crane is ensured. Torque limiters are available in mechanical, electronic and composite versions.
(3) Height limiter: Also called hook height limiter. It is usually mounted on the head of the boom. When the hook slides to the limit position, the lever is lifted. Press the lower limit switch to cut off the circuit, and when the switch is closed, the hook can only be lowered.
(4) Stroke limiter: A safety device that prevents the crane from colliding or restricts driving within a certain range. It is usually mounted on the inside of the active trolley, mainly by installing a travel switch that can be used to toggle the handle. In addition, a fixed limit position baffle is installed at the end of the track (in the position where the operation is limited). When the tower crane runs to this position, the limit baffle touches the wrench of the travel switch, and the power supply for controlling the walking is cut off. When the gate is closed, the tower crane can only run in the opposite direction.
(5) Amplitude limiter: Also called a variable limit or amplitude indicator, an amplitude indicator is hung on the boom of a general boom crane. It consists of a fixed circular indicator disc with a vertical active pointer in the center of the disc. When swelling, the hands indicate the nominal lifting capacity at various amplitudes. When the boom is moved to the upper and lower limit positions, the lower limit switch is respectively pressed to cut off the main control circuit, and the luffing motor stops to reach the limit position.
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