Lifting machinery refers to electromechanical equipment used for vertical lifting or vertical lifting and horizontal movement of heavy objects. Its scope is defined as elevators with a rated lifting capacity greater than or equal to 0.5t; cranes with a rated lifting capacity greater than or equal to 1t and a lifting height greater than or equal to 2m; and electric hoists with fixed load-bearing forms, etc.
I. Introduction to Lifting
Crane operation is an industrial process of transporting machinery or other objects from one place to another. Most cranes begin their vertical or combined vertical and horizontal working stroke after the lifting device picks up the material. Upon reaching the destination, they unload, then travel empty back to the picking location, completing one work cycle, before starting the next lifting operation. Generally, during crane operation, picking, moving, and unloading are performed sequentially, with the operation of each corresponding mechanism intermittent. Cranes are mainly used for handling packaged goods; equipped with grab buckets, they can handle bulk materials such as coal, ore, and grain; equipped with buckets, they can lift molten steel and other liquid materials. Some cranes, such as elevators, can also be used to carry people. In certain applications, cranes are the primary working machinery; for example, cranes used for loading and unloading materials in ports and railway stations are the main working machinery.
II. Working Principle
Lifting machinery uses a lifting hook or other lifting device to lift or move heavy objects. The working process of lifting machinery generally includes steps such as lifting, traveling, lowering, and returning to the original position. The lifting mechanism lifts the heavy object from the pick-up point using the lifting device, moves the heavy object to the designated location via the traveling, slewing, or luffing mechanism, and then returns the heavy object to its original position after lowering it to the designated location.
III. Composition and Structure
The working mechanisms include: hoisting mechanism, traveling mechanism, luffing mechanism, and slewing mechanism, which are known as the four major mechanisms of a crane.
(1) The hoisting mechanism is a mechanism used to realize the vertical lifting of materials. It is an indispensable part of any crane and is therefore the most important and basic mechanism of the crane.
(2) The running mechanism is a mechanism that uses a crane or trolley to move materials horizontally. It can be divided into trackless running and tracked running, and according to its driving method, it can be divided into self-propelled and traction types.
(3) The luffing mechanism is a working mechanism unique to boom cranes. The luffing mechanism changes the working radius by changing the length and elevation angle of the boom.
(4) The rotating mechanism is used to make the boom rotate around the vertical axis of the crane to move materials in the annular space. The crane achieves the purpose of moving materials through the individual movement of a certain mechanism or the combined movement of multiple mechanisms.
IV. Main Uses
Basic structure of lifting machinery
Various types of lifting machinery have different uses and significant differences in their construction, but they all possess a lifting mechanism to achieve the basic action of lifting and lowering. Some lifting machinery also has a traveling mechanism, a luffing mechanism, a slewing mechanism, or other specialized working mechanisms. Materials can be lifted and lowered by flexible components such as wire ropes or lifting chains, or by jacking with screws or other rigid components.
Lifting machinery is a type of spatial transportation equipment whose main function is to move heavy objects. It can reduce labor intensity and increase labor productivity. Lifting machinery is an indispensable component of modern production; some types of lifting machinery can also perform certain special technological operations during production, enabling the mechanization and automation of the production process.
Lifting machinery has helped humanity in its efforts to conquer and transform nature, enabling the lifting and movement of large objects that were previously impossible, such as the segmented assembly of heavy ships, the overall lifting of chemical reaction towers, and the overall lifting of steel roof trusses for stadiums.
There is a huge market demand and good economic benefits for the use of lifting machinery. In recent years, the lifting machinery manufacturing industry has developed rapidly, with an average annual growth rate of about 20%. This is because, in the production process from raw materials to finished products, the amount of material handled by lifting and transportation machinery is often tens or even hundreds of times the weight of the product. Statistics show that in the machining industry, 50 tons of materials need to be loaded, unloaded, and handled during the processing of one ton of product, and 80 tons of materials need to be handled during the casting process. In the metallurgical industry, 9 tons of raw materials need to be handled for every ton of steel smelted, with 63 tons transferred between workshops and 160 tons transferred within workshops. Lifting and transportation costs also account for a high proportion in traditional industries. For example, in the machinery manufacturing industry, lifting and transportation costs account for 15-30% of total production costs, and in the metallurgical industry, they account for 35-45%. The transportation industry relies heavily on lifting and transportation machinery for loading, unloading, and storage of goods; statistics show that loading and unloading costs account for 30-60% of total freight costs in maritime shipping.
V. Variety Classification
Lifting machinery can be categorized into several types based on its structure, including light and small lifting equipment, hoists, cranes, and overhead monorail systems. Light and small lifting equipment mainly includes lifting pulleys, slings, jacks, manual hoists, electric hoists, and ordinary winches. Most are small in size, lightweight, and easy to use. Except for electric hoists and winches, the vast majority are manually driven and suitable for light workloads. They can be used independently, or some can be used as lifting mechanisms for cranes. Some light and small lifting equipment have very large lifting capacities; for example, hydraulic jacks can lift up to 750 tons. Hoists mainly perform vertical or near-vertical lifting movements and have fixed lifting routes. These include elevators, lifting platforms, mine hoists, and bucket elevators. Cranes are multi-action lifting machinery that vertically lifts and horizontally moves heavy objects within a certain range. Overhead monorail systems have a rigid suspended track forming a line that can transport materials to various parts of a factory building and can also be extended to the outside of the factory building.
