L48A1 Mast Section the difference is between the two types of tower crane height limiters
The function of the amplitude limiter is to disconnect the one-way working power supply of the luffing mechanism when the luffing trolley is driven to the minimum or maximum amplitude To ensure the safe operation of the car. The principle is the same as the lifting height limiter, which is usually installed on the side of the drum of the luffing mechanism of the trolley. The amplitude limiter comprises a cam group, a power cut-off device and a speed reducer. When the luffing mechanism works, the length of the rope is known according to the number of turns of the reel recorded.
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The reel drives the speed reducer, which drives a number of CAM groups to rotate. These cams act on the micro-motion switch Thus cut off the amplitude of the corresponding control loop, the amplitude of the car at this time can only run in the opposite direction. For the boom type tower crane, it is necessary to set the limit switch of the boom low position and the boom high position, and the device to prevent the boom from rebounding and turning back. The boom type tower crane shall also be equipped with a scope indicator so that the driver can grasp the scope change in time and prevent the boom from overturning causing major damage accidents. The amplitude indicator of boom-type tower crane is installed at the intersection of the right forearm root of the tower top, which has two functions: indicating the working amplitude of the boom and preventing the boom from tilting forward and backward. The amplitude indicating and limiting device consists of a semi-circular movable turntable, a brush holder, a seat plate, a dial rod and a limit switch. The dial rod rotates with the arm frame pitching, and the electric brush connects the contact points of the indicator lamp according to different angles The different elevation angles of the crane arm are transmitted to the amplitude indicator board of the upper and lower cab by the signal of the light being put out. When the angle between the boom and the level is less than the limit angle, the electric brush turns on the Buzzer to give a warning signal, which indicates that the working range is not normal at this time and no hoisting operation is allowed. When the arm elevation reaches the Limit Angle, the upper limit switch action, amplitude circuit is cut off power, thus play a protective role. From the knowledge of the light signal on the amplitude indicator, the crane driver can know the elevation angle of the Jib, the working range and the maximum allowable lifting weight at this time. When the boom approaches the maximum and minimum elevation angles, the Stop Block in the splint pushes the lever transmission of the limit switch installed at the intersection of the boom root, thus cutting off the power supply of the luffing mechanism and stopping the luffing action of the boom. The acting process of the limiter can be adjusted by changing the length of the Stop Block.
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