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Classification of lifting machinery: Based on their structural type, lifting machinery can be divided into three main categories: lightweight lifting equipment, cranes, and elevators. 1. Light and small lifting equipment: Light and small lifting equipment generally has only one lifting mechanism; common examples include jacks, electric or hand-cranked winches, winches, and pulleys. 2. Cranes When a lifting device has not only a lifting mechanism but also other moving mechanisms, its structural complexity is inevitably much greater than that of compact lifting devices with a single mechanism; such lifting devices are referred to as cranes. Depending on the type of metal structure, cranes can be divided into two main categories: bridge-type cranes and boom-type cranes. 3. Elevators: Common types include vertical elevators and lifts. Lift-type lifting equipment has only one lifting mechanism. Due to safety considerations, elevators are equipped with sophisticated safety devices and other auxiliary systems, and their complexity is unmatched by small lifting equipment; therefore, they are classified as a separate category. Among all types of lifting machinery, bridge-type cranes and boom-type cranes are the most widely used and most functional main lifting devices. Now, let’s take a closer look at this major category of lifting machinery. 1. Bridge-type crane: The main feature of a bridge-type crane is that it uses a bridge-shaped metal structure as its primary load-bearing element, with the lifting mechanism suspended on a trolley that can move along the main beam. Bridge-type cranes carry out material handling tasks within a rectangular three-dimensional space through the vertical movement of the lifting mechanism, as well as the horizontal movements of the trolley moving mechanism and the main frame moving mechanism. Crane types based on their structural design can be further divided into bridge cranes (commonly known as overhead cranes or gantry cranes), gantry cranes (also referred to as bridge cranes with legs, including loading/unloading cranes and container gantry cranes), and cable cranes (in which cables are used in place of a bridge-shaped main beam due to extremely large spans). 2. Jib-type cranes: The structural feature of jib-type cranes is that they all have a protruding, rotatable jib as the main load-bearing component. In addition to the lifting mechanism, its operating mechanisms usually include a rotating mechanism and a luffing mechanism. Through the combined movement of these four mechanisms – the lifting mechanism, the luffing mechanism, the rotating mechanism, and the traveling mechanism – loading and unloading operations can be carried out in circular or oval-shaped areas. For example, mobile cranes (truck cranes, wheel loaders, crawler cranes), tower cranes, portal cranes, etc. In addition to being classified by construction type, cranes can also be divided into track-mounted cranes and trackless cranes based on their mobility. Tracked cranes are equipped with wheels and can operate within a limited area on paved tracks; examples include various types of bridge cranes, tower cranes, and gantry cranes. The running units of trackless cranes are equipped with rubber tires or tracks. The various types of mobile cranes available are highly mobile, capable of traveling long distances on different types of surfaces and allowing for flexible changes in working locations. Most cranes are general-purpose and widely used in workshops, warehouses, open storage areas, and other such places. There are also many cranes that are designed specifically for particular work sites or certain types of processes. For example, there are metallurgical cranes such as molten iron handling cranes and ingot removal cranes, cranes used for hot processing such as casting cranes and forging cranes, cranes specifically designed for port loading and unloading operations such as gantry cranes and ship unloaders, stacker cranes used in warehouses, and floating cranes intended for offshore operations. Cranes are widely used in many key sectors of the national economy, and have become one of the essential equipment for organizing production in modern logistics and manufacturing industries. The future development direction of cranes is to further enhance their lifting capacity, move toward larger sizes, and expand their operational range ； Increase the technological content, achieve mechatronics, and improve the level of computer technology application ； Enhance safety, reliability, and operational comfort.