Gate type crane
The gantry crane bridge is a bridge type crane supported on the ground track or foundation by two side legs. It runs along the ground track and can be accessed by railway vehicles or other ground vehicles below. A type of boom crane with a rotatable lifting device mounted on a portal frame. The four legs of the portal frame form four "doorways" that can be used for railway vehicles and other vehicles to pass through. Most gantry cranes run along the crane tracks on the ground or buildings for lifting, loading, and unloading operations. A crane with a "" - shaped gantry is called a semi gantry crane, with one side of its track set on the ground and the other side set on a building higher than the ground.

brief history
The gantry crane developed with the development of the port industry in 1890. It was the first time that a fixed and rotatable boom type crane with an adjustable amplitude was installed on a running half gantry crane spanning over a narrow dock, becoming an early port half gantry crane. With the increase of dock width, gantry and half gantry cranes developed side by side, and pitch boom and horizontal amplitude system were widely used. After World War II, the use of gantry cranes in ports rapidly developed to facilitate parallel work of multiple cranes on the same ship. The commonly used gantry crane is a revolving gantry crane with a rotating part connected to the column body (Figure 1 [revolving gantry crane]), or a rolling bearing type supporting rotating device with a large bearing connected to the gantry to reduce the tail diameter of the rotating part. A gantry structure with a reduced pier cover surface (the projection of the gantry body on the ground) is also adopted. In the process of development, gantry cranes have gradually been promoted and applied to shipyards and hydropower construction sites with operating conditions similar to ports.

classification
According to their purposes, they can be divided into three categories: ① Gate cranes for loading and unloading: mainly used in ports and open-air material yards, using grab buckets or hooks for loading and unloading. The lifting capacity generally does not exceed 25 tons and does not vary with the amplitude. The work speed is relatively high, so productivity is often an important indicator Shipbuilding gantry crane: mainly used for ship platforms, floating docks, and loading sites to carry out lifting work such as ship body splicing and equipment loading, using hooks as lifting devices. The maximum lifting capacity reaches 300 tons, and the lifting capacity decreases accordingly when the amplitude is large. There are multiple lifting speeds, and the lifting speed can be increased when the lifting weight is light. Some work organizations are also equipped with micro motion devices to meet installation requirements. The height of the door seat is larger, which can adapt to the requirements of large lifting heights and large-scale operations, but the working speed is lower and the work productivity is not high Portal crane for building installation: mainly used for dam pouring, equipment and prefabricated component lifting in hydropower stations, generally using hooks. The lifting capacity and working speed are generally between the first two types of cranes. It has the characteristics of good overall assembly and disassembly transportation, large depth of lifting equipment placement, and good adaptability to temporary work and work on the wharf.

form
The gantry crane has lifting, slewing, variable amplitude, and operating mechanisms. The first three mechanisms are installed on the rotating parts and participate in the operation during each cycle. The rotating part is also equipped with a tilting single arm or combination arm that can pitch, as well as a driver's cab. The operating mechanism is installed at the lower part of the gantry to adjust the working position of the crane. The gantry crane with bucket (Figure 2 [gantry crane with bucket]) is also equipped with additional equipment such as telescopic funnels and belt conveyors to improve the productivity of the gantry crane when loading and unloading bulk materials with grab buckets. In addition to electrical protection devices, safety devices such as lifting capacity or lifting torque limiters, crane rail clamps, etc. are also installed.

system
Most gantry cranes use a horizontal variable amplitude system The center of gravity of both the heavy object and the boom system experiences almost no vertical displacement during the amplitude change process. One of its methods is to balance the rise and fall of the composite center of gravity of the boom system during pitch by adding an active balance weight. This method is more convenient to arrange, reliable in operation, and widely used. The second method is to rely on the structural characteristics of the boom system to ensure that the movement trajectory of the composite center of gravity during amplitude is close to the horizontal line, without any active balance weight The suspended object moves along a trajectory close to a horizontal line during the amplitude adjustment process, and compensation method and combination arm method can be used. The compensation method is to use a special rope storage system to automatically retract and release the corresponding lifting ropes during the amplitude change process, in order to compensate for the vertical displacement of the lifting equipment caused by the lifting of the boom. The combination arm method relies on the structural characteristics of the combination arm to ensure that the arm end moves close to horizontal during the amplitude change process. Both methods have been widely applied.