Gantry cranes have become the most widely used and owned rail cranes because of their superior performance, with rated lifting capacities ranging from a few tons to several hundred tons. The most common form of gantry crane is the universal hook gantry crane, other gantry cranes are improved on this form.
Gantry crane is a heavy machinery and equipment, and its working conditions are very heavy, we want to ensure that it can have sufficient strength, rigidity and stability under the complex and changing conditions of the load, choose a metal skeleton that can carry the whole crane and connection, so as to have sufficient sex. Gantry crane working life is mainly determined by its metal skeleton, as long as the metal skeleton is not damaged, it can be used, other devices and parts will not affect its life, but once its metal skeleton is damaged, it will bring serious consequences to the gantry crane.
Metal construction forms of Gantry cranes
The metal structure of gantry cranes is divided into three categories according to the different force characteristics, one is the beam and truss is the main member to bear the bending moment; the second is the column is the main member to bear the pressure; the third is the compression bending member, mainly used to bear both pressure and bending moment members. We can design the metal structure of the gantry crane into structural, solid web and hybrid according to the way these members are stressed and the size of the structure. In the following we will mainly talk about solid web members. The so-called solid web members are mainly made of steel plates and are mainly used when the load is high and the dimensions are small. Its advantages are that it can be welded automatically, it is simple to manufacture, it has a high fatigue strength, a small stress concentration, a wide range of applications, and it is easy to install and maintain, but it also has the disadvantage of being heavy and rigid.
Components of the gantry crane operating mechanism
The running mechanism, which refers to the mechanism that makes the crane do horizontal movement, is mainly used to move the goods horizontally. The tracked running mechanism refers to the mechanism that moves on a special track, which is characterised by low running resistance and large load, with the disadvantage that the range of movement is limited, while those trackless running mechanisms, which can move on ordinary roads, have a wider range of operations. The running mechanism of a crane consists mainly of a drive unit, a running support unit and a device. The drive unit consists of the engine and drive and brake, the running support consists of the track and steel wheel set, and the device consists of wind and slip resistant devices, travel limit switches, buffers and track end stops, etc. These devices can effectively prevent the trolley from derailing and prevent the crane from being blown away by strong winds and causing it to overturn.
The working principle of the gantry crane hoisting mechanism
The motor of the crane is connected together by a coupling and a reducer. It works by rotating the low speed shaft of the reducer to bring the reel and hook together with the wire rope and so on. When the motor works, the movement is transferred to the reel by rotating it in different positive and negative directions, and then the reel rolls the wire rope in or out, causing the hook to lift or lower the weight. The basic principle is that the rotation of the motor is transformed into the lifting and lowering movement of the load. When the power is suddenly cut, the brake is applied and the load is stopped at the specified position. When the load is raised to the limit position, the limiter is touched, stopping the hook's movement.
Here we take a double main girder general purpose gantry crane as an example to discuss the working principle of gantry cranes. This type of crane is also called A-type double girder gantry crane, which is usually composed of several major parts of the bridge, large car running mechanism, trolley and electrical equipment.
The following is a brief description of the function and working principle of the gantry crane overload protection device form.
Gantry crane overload protection device form and function: overload protection device according to its different functions, can be divided into two kinds of automatic stop type and comprehensive type. According to the structure type, there are two types of electrical and mechanical type.
The overload protection device shall have a dynamic load suppression function, an automatic working function and an automatic insurance function.
Working principle of overload protection device for gantry cranes. Lifting capacity limiter, mainly used for bridge type cranes, the leading product is the electrical type. Electrical products are generally composed of two parts: load sensors and secondary instruments.
Load sensors are either resistive strain gauge or piezomagnetic sensors with special mounting accessories depending on the installation location. The sensors are available in 3 main types of construction: compression, tension and shear beam.