There are many types of underhung bridge crane, but their basic construction is the same. The main components include girder, lifting device, end beam, girder traveling mechanism, lifting device traveling mechanism, track and electrical power, control device, etc.
1) Girder structure
Generally, Overhead bridge crane for sale are constructed using a combination of two girders connected at the ends, which are called double-girder bridge cranes. Only a small number of light bridge cranes use a single-girder structure, which are called beam cranes.
The girder structure forms of bridge cranes include box structure, deflection box structure, deflection hollow box structure, single main girder box structure, four truss structure, triangular truss structure, single web beam structure, curved web Plate beam structure and prestressed box beam structure, etc. Among them, the most common is the box structure. The box beam consists of an upper cover plate, a lower cover plate and two webs to form a box. The box is also equipped with vertical and horizontal ribs. On one side of the girder, a walking platform and railings are set, and the walking track of the lifting device is laid on the upper cover plate. In order to facilitate maintenance, the beams are also equipped with walkways and railings for people to walk on.
2) Lifting device
The lifting device is used to lift heavy objects and is the most important and basic device on the overhead hoist i beam. The lifting device of the bridge crane usually uses a lifting trolley, except for a few beam cranes that use electric hoists. The lifting trolley consists of a frame, a traveling mechanism, a lifting and winding mechanism and electrical equipment.
The frame is supported on four wheels, and the traveling mechanism on the frame drives the wheels to run along the trolley track to achieve hoisting operations in the width direction of the span.
The lifting and winding mechanism is actually a combination of an electric winch and a pulley block. For bridge cranes with a lifting capacity of more than 1500kN, they are usually equipped with two sets of lifting and winding mechanisms, namely the main hook and the auxiliary hook. The main hook has a larger rated load, but the lifting speed is slower; the auxiliary hook has a smaller rated load, but the lifting speed is faster. The auxiliary hook is used to lift lighter objects or perform auxiliary work to improve work efficiency. On the nameplate of an overhead crane, the rated load is usually marked first with the rated load of the main hook, and then with the rated load of the auxiliary hook, separated by a slash “/”, such as “1600kN/500kN “.
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