First, the boom structure of the truck crane
The boom of a truck crane generally includes two parts, a main arm and a jib. There are two main types of main crane booms, one is a truss structure boom made of profiles and pipes, and the other is a box-type boom with various sections. With the development of truck cranes, most of the main crane booms are now box-type structures, and only a small part is a truss structure.
The function of the jib of the truck crane is that when the height of the main arm cannot meet the needs, the jib can be connected at the end of the main arm to achieve the purpose of lifting the object to a height. The jib can only lift lighter objects. The jib generally has only one arm, and there are two or more folding jibs or telescopic jibs, of which the jib of the folded truss structure is the most common.
Second, the crane telescopic principle
(1) There are several types of boom extensions for truck cranes:
1.Sequential telescopic mechanism--The arms of the telescopic arm are telescoped in a certain order.
2. Synchronous telescopic mechanism - Each arm of the telescopic arm is telescoped at the same relative speed.
3. Independent telescopic mechanism - the mechanism that each arm can independently expand and contract
4. Combination telescopic mechanism--When the telescopic arm exceeds three sections, it can simultaneously use any two types of expansion and contraction methods to expand and contract.
(2) According to the technical division of the telescopic mechanism, the truck crane can be divided into a non-pin full hydraulic expansion mechanism and an automatic bolt type telescopic mechanism.
1. The advantage of the non-pin full hydraulic telescopic mechanism is that the arm length changes easily, the working arm length is many, and the utility is very strong. The disadvantage is that it is self-important and has a great impact on the stability of the whole machine.
The non-pin full hydraulic retractable mechanism has different combinations, which can be a multi-hydraulic cylinder plus a first-row rope row, and can be a single hydraulic cylinder or a multi-hydraulic cylinder plus a two-stage rope row.
The multi-hydraulic cylinder plus the first-row rope row is characterized in that the last section of the telescopic arm is telescopically stretched with a steel wire rope, and the other telescopic arms are directly expanded and contracted by the oil cylinder by using a multi-stage cylinder or a plurality of single-stage cylinders or a multi-stage cylinder and a single-stage cylinder sleeve. Therefore, the cross section of the last telescopic arm changes greatly, and the change of the cross section of the other arm sections is small.
The single or multi-cylinder plus two-stage rope row features a single or double cylinder plus two-stage rope row for four or five-section arms. This type of telescopic is the most advanced in the country, but it is very difficult to solve the telescopic expansion of the boom above five arms.
1, 7-guide pulley; 2-stretch steel wire rope; 3, 4, 6-fixed rope card; 5--retractor wire rope; 8, 9-cylinder fixed rope; 10-balance pulley
2. The automatic bolt-type telescopic mechanism adopts single-cylinder, interlocking cylinder pin and arm pin, and accurate length measuring electronic technology. Its advantages are light weight, minimal impact on the stability of the whole machine, faster telescopic speed and change of the cross-section of the boom. Small, heavy lifting stiffness, but technically difficult, high cost, less arm length. (sequentially stretched from the inside out)
The automatic latch type telescopic mechanism has interlocking cylinder pins and arm pins, and the cylinder pins are designed on both sides of the boom, and the arm pins are designed on the upper surface of the boom. The utility model has the advantages that the structure is simple, the self-locking property is strong, and the disadvantage is that the large deformation of the arm pin is laborious, and it needs to be retracted and retracted to be pulled out.
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Fever L.//SMC Editor