The function of the crane is lifting and moving goods and materials, usually in the presence of gradients, barriers or ground obstacles which make it difficult or impossible to move them in another way.
The mobile crane is a heavy motor vehicle that can handle materials in locations where a fixed installation is not available. It is essentially a wheeled vehicle with a large extendable arm that works like a crane. This particular structure allows the crane to lift weights further and reach greater heights. The mobile crane is not intended to load the vehicle on which it is positioned. Among the most used cranes may be included some of the tow trucks that perform emergency services to cars in difficulty, and that take transport the damaged vehicles to the repair workshops.
Also in the field of transport of goods are used trucks with cranes positioned immediately behind the cockpit, usually with a capacity of lifting up to 5 tons, and able to offer a complete and self- loading service, transport and unloading of materials. This type of service is often required during exhibitions or opening of new work sites.
All types of mobile cranes are provided with safety installations that ensure handling of materials in a safe environment. During the operations of loading and unloading, for example, stabilizing arms on the sides of the crane are extended to ensure the stability of the ground plane and avoid the risks of possible rollover.
They are the cranes that are applied to trucks for the movement and the subsequent transportation of cargoes. They are composed of a base that is anchored to a subframe (interposed between the truck and the crane base), which also contains the base system of rotation that can be with a rack or a scrape. Engaged in the base rack or screwed to the scrape, there is a column in which there is a joint to which it is attached the main arm, driven by the piston or cylinder anchored to the base of the column. The thrust on the arm is on pins or rods and fork.
From the main part, with the same systems of articulation, develops the secondary part (this also raised by a piston), in which are contained the extensions of the crane, or the telescopically extensible parts that allow to translate the loads at a greater distance from that made by the arms. The hook is applied at the end of the last extension.
The simplest form of a tower crane is a pulley-operated arms, fixed at the top to a beam, with a hook at the other end of the rope. There is also a particular type of crane, called quick mounting crane, where the assembly is particularly simple and thoroughly studied in order to perform all the operations in complete safety
The crawler crane is made of a rigid hydraulic arm with a hook at the end. It has tracks for traveling on rough terrain, where boom trucks cannot work (e.g. sand, peat, etc.) and it requires no stabilizer arm, as the weight (which can exceed 100 tons) is distributed over the entire crawled surface that downloads little pressure in the soil. Crawler cranes are used to handle heavy loads, construction and demolition work. Crawler cranes have difficulty in moving on roads and, because of their size, are unlikely to be transported by trucks.