Crane is a kind of mechanical equipment that works intermittently and repeatedly to achieve vertical lifting and horizontal transportation of heavy objects hanging on hooks or other picking devices within a certain space range.
Classification of cranes
Cranes are classified according to their structure and can be divided into bridge cranes, jib cranes, and rope cranes. Bridge cranes can be divided into bridge cranes, gantry cranes, loading and unloading bridges, and other small categories. Jib cranes can be divided into tower cranes, gantry cranes, mobile cranes, jib cranes, mast cranes, and other small categories. Our daily more common are bridge cranes, tower cranes, and mobile cranes.
Various types of construction cranes are usually composed of four parts: working mechanism, metal structure, power device, and control system.
The working mechanism of the crane includes four major parts: the hoisting mechanism, the luffing mechanism, the slewing mechanism, and the traveling mechanism. The lifting structure consists of a prime mover, drum, wire rope, pulley block, and hook. Lifting methods include mechanical and hydraulic transmission. Crane luffing refers to changing the distance between the hook center and the axis of the crane’s rotation center. The form of luffing mechanism depends on the type of mobile crane boom. For the truss crane with constant length, the luffing mechanism adopts a wire rope luffing mechanism. The luffing mechanism of a mobile crane with a telescopic boom adopts a hydraulic cylinder luffing mechanism. The slewing mechanism consists of a slewing drive device and a slewing bearing. The slewing bearing device of a mobile crane usually adopts a rolling bearing type. The traveling mechanism of the mobile crane is the chassis of the crane, the wheeled crane adopts a general or special car chassis, or a chassis specially designed for the crane, and the crawler crane adopts a crawler chassis. The running gear of tower and bridge cranes is generally a specially designed running track.
The power plant of mobile cranes is an internal combustion engine, and the power plant of towers and other types of cranes is an electric motor.
The metal structure of the crane includes the boom, the slewing platform, the herringbone frame, the underframe and the tower body of the tower crane, etc. The metal structure bears the crane’s own weight and various loads during operation. The strength, stiffness, and stability of metal structures are three important indicators.
The control system of the crane includes control devices and safety devices, and the control system is provided with various control valves in the hydraulic transmission of clutches, brakes, and stoppers.