Tower Crane Luffing Mechanism
Tower Crane Luffing Mechanism
The luffing mechanism is used to change the working radius of the tower crane to expand its working range. According to the luffing method, it can be divided into trolley luffing mechanism and boom luffing mechanism.
Classification and Characteristics
01 Single Trolley Variable Multiplier
Features: When using a single trolley variable multiplier, the hook pulley block of the luffing trolley consists of an upper movable pulley and a lower double pulley hook group. When the upper movable pulley is fastened to the luffing trolley by its own locking device, the tower crane uses the lower double pulley hook group at a 2-times rate. When changing from a 2-times rate to a 4-times rate, the lower double pulley hook group rises to the luffing trolley and is connected with the upper movable pulley by a pin shaft, and the tower crane realizes 4-times rate operation.
02 Double Trolley Variable Multiplier
Features: When using a double trolley variable multiplier, the luffing trolley consists of main and auxiliary trolleys. During 2-times rate operation, the auxiliary trolley stays at the root of the boom, and the main trolley is equipped with a set of pulley hooks for operation, as shown in Figure 2a. When changing from a 2-times rate to a 4-times rate, the main trolley is connected with the auxiliary trolley to form a double trolley. At the same time, the two sets of hook pulley blocks are lowered to the ground and connected into one body with a pin shaft, as shown in Figure 2b. The combined hook pulley system can realize 4-times rate operation.
03 Boom Luffing Mechanism
Features: The boom luffing mechanism realizes luffing by the pitching and swinging of the boom. According to the different structural forms of the transmission parts between the lifting arm and the driving device, the boom luffing mechanism can be divided into two types: flexible luffing and rigid luffing. Flexible luffing changes the elevation angle of the boom through a wire rope pulley block, which is usually composed of a motor, coupling, brake, drum, wire rope, and pulley block. Rigid luffing performs luffing through a hydraulic cylinder, which is usually composed of a motor, hydraulic pump, oil tank, valve, and hydraulic cylinder. At present, most boom luffing mechanisms are flexible luffing mechanisms. Compared with the small car luffing mechanism of the same level, the flexible luffing mechanism has the advantages of large lifting height, convenient installation and disassembly, good stress condition of the boom structure, and avoiding interference with surrounding buildings. However, the flexible luffing mechanism has a low effective utilization rate of amplitude, uneven luffing speed, large luffing power, and it is difficult to achieve horizontal movement of heavy objects during the luffing process.
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