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Crane development history and classification

by:Laike     2020-07-18
Crane (Crane) is a kind of hoisting machinery, is a machine for circulating, intermittent movement. A working cycle includes: the picking device lifts the item from the picking place, then moves horizontally to the designated place to lower the item, and then performs a reverse movement to return the picking device to the original position for the next cycle.

Generally, a lifting machine consists of a lifting mechanism (moving the item up and down), a running mechanism (moving the lifting machine), a luffing mechanism and a slewing mechanism (making the item move horizontally), plus a metal mechanism, power device, and operation control And necessary auxiliary equipment. Type     Lifting machinery used in the construction of bridges can be divided into three major categories of light and small lifting equipment, bridge type lifting machinery and boom type cranes according to their different structures and performances. Light and small lifting equipment such as jacks, hoists, hoists, etc. Bridge type lifting machinery such as beam cranes, gantry cranes, etc.

Boom type cranes such as fixed slewing cranes, tower cranes, truck cranes, tires, crawler cranes, etc.

A multi-action hoisting machinery that vertically lifts and transports heavy objects within a certain range. Also called crane. Belongs to material handling machinery. The working characteristic of the crane is to do intermittent movements, that is, the corresponding mechanisms of the actions of taking, moving, unloading, etc. in a working cycle are alternately working. The prototype of the crane     The orange used for irrigating farmland in ancient China is the prototype of the jib crane. In the 14th century, there was a boom-type crane driven by human and animal power in Western Europe. In the early 19th century, bridge cranes appeared; important wear parts of cranes such as shafts, gears and spreaders began to be made of metal materials and began to be driven by hydraulic power. In the late 19th century, steam-driven cranes gradually replaced hydraulic-driven cranes. Since the 1920s, due to the rapid development of the electrical industry and the internal combustion engine industry, various cranes based on electric motors or internal combustion engines have been basically formed.

The crane mainly includes lifting mechanism, running mechanism, luffing mechanism, slewing mechanism and metal structure. The hoisting mechanism is the basic working mechanism of the crane. Most of them are composed of the hanging system and the winch, and some of them also lift heavy objects through the hydraulic system. The operating mechanism is used to move heavy objects horizontally and horizontally or adjust the working position of the crane. It is generally composed of electric motors, speed reducers, brakes and wheels. The luffing mechanism is only equipped on the jib crane. The amplitude of the jib decreases when it is raised and increases when it is lowered. There are two types: balanced luffing and unbalance luffing. The slewing mechanism is used to rotate the boom and is composed of a driving device and a slewing bearing device. The metal structure is the skeleton of the crane. The main load-bearing parts such as bridges, booms, and portals can be box-shaped or trussed, or can also be web-shaped. Some steel sections can be used as support beams. Cranes are classified according to different structures:    

Beam crane   1. Beam crane. It can be operated on the rectangular site and above it, and it is mostly used for loading and unloading items in workshops, warehouses, open yards, etc. There are beam cranes, bridge cranes, gantry cranes, cable cranes, carrier bridges, etc.

①Beam crane: The beam crane mainly includes a single beam bridge crane and a double beam bridge crane

The main beam of the single-girder bridge crane mostly adopts I-shaped steel or a combined section of steel and steel plate. Lifting trolleys are often assembled from hand hoist, electric hoist or using hoist as part of lifting mechanism.

According to bridge support type and suspension type. The former bridge runs along the crane track on the vehicle beam; the latter bridge runs along the crane track suspended under the factory frame. There are two types of single beam bridge cranes, manual and electric. The working speed of each mechanism of the manual single-beam bridge crane is low, and the lifting weight is also small, but its own mass is small, which is convenient for the organization of production, and the cost is low. When it is used without power, the handling capacity is not large, and the speed and productivity are not high Occasions.

The manual single-beam bridge crane uses a manual monorail trolley as a running trolley, a hand hoist as a lifting mechanism, and the bridge frame is composed of a main beam and an end beam. The main beam is generally made of a single I-beam, and the end beams are welded with profiled steel or press-formed steel plates.

The working speed and productivity of the electric single-beam bridge crane are higher than those of the manual, and the lifting capacity is also larger. The electric single-beam bridge crane is composed of a bridge frame, a truck operating mechanism, an electric hoist and electrical equipment.

② Bridge crane:

A bridge crane is a bridge-type crane whose bridge runs on an elevated track, also known as a crane. The bridge frame of the bridge crane runs longitudinally along the rails laid on the elevated side of the two sides, and the lifting trolley runs laterally along the rails laid on the bridge, forming a rectangular working range, you can make full use of the space under the bridge to lift materials, not Obstructed by ground equipment.

Bridge cranes are widely used in indoor and outdoor warehouses, workshops, wharves and open storage areas. Bridge cranes can be divided into ordinary bridge cranes, simple beam bridge cranes and metallurgical bridge cranes.

The ordinary bridge crane is generally composed of a lifting trolley, a bridge operating mechanism, and a bridge metal structure. The lifting trolley is composed of three parts: a lifting mechanism, a trolley running mechanism and a trolley frame.

The lifting mechanism includes electric motor, brake, reducer, drum and pulley block. The motor drives the drum to rotate through the speed reducer, so that the wire rope is wound around the drum or lowered from the drum to raise and lower heavy objects. The trolley frame is a frame that supports and installs components such as the lifting mechanism and trolley running mechanism, and is usually a welded structure.

2. Cantilever crane (rotating arm crane)

There are three types of cantilever cranes: upright, wall-mounted and balanced cranes.

①The column type cantilever crane is a cantilever crane composed of a vertical column and a cantilever that can rotate around a fixed column fixed on the base, or the cantilever and the rotating column are just connected and rotate relative to the vertical center line together in the base support. It is suitable for occasions where the lifting capacity is not large and the service scope of the operation is round or sector. It is generally used for clamping and handling of workpieces such as machine tools.

Column type cantilever cranes mostly use ring chain electric hoist as lifting mechanism and running mechanism, and less use wire rope electric hoist and chain hoist. Rotation and horizontal movement operations are mostly manual, and electric operation is only used when the lifting capacity is large.

②Wall crane is a cantilever crane fixed on the wall, or a cantilever crane that can run along the elevated track on the wall or other supporting structure.

The wall crane is used in a workshop or warehouse with a large span and a large building height. It is most suitable when the lifting operation near the wall is more frequent. Wall cranes are mostly used in conjunction with beam or bridge cranes above, serving a rectangular space near the wall, responsible for lifting light and small objects, and large parts are borne by beam or bridge cranes.

③Balance crane is commonly called balance crane. It uses the principle of four-bar linkage to make the load and balance weight form a balance system. It can use a variety of spreaders to flexibly and easily lift the load in three-dimensional space. The balance crane is light and flexible, it is an ideal lifting equipment for lifting small items. It is widely used in the loading and unloading of machine tools on the factory floor, between the process, automatic line, production line work piece, sand box lifting, parts assembly, and The driving methods of the crane operating mechanism in various occasions such as stations, docks, warehouses, etc. can be divided into two categories: one is centralized driving, that is, a long drive shaft is driven by a motor to drive the active wheels on both sides; the other is separately driven, That is, the driving wheels on both sides are driven by an electric motor. Medium and small bridge cranes mostly use the 'three-in-one' drive method in which brakes, reducers and motors are integrated. For large bridge cranes with common lifting capacity, universal couplings are often used for the drive device . The operating mechanism of a crane generally uses only four driving and driven wheels. If the lifting weight is large, the method of increasing the wheels is often used to reduce the wheel pressure. When there are more than four wheels, a hinged equalizing frame device must be used to evenly distribute the load of the crane on each wheel.

The metal structure of the bridge is composed of main beams and end beams, and is divided into two types: single main beam bridge and double beam bridge. The single main beam bridge consists of a single main beam and end beams on both sides of the span, and the double main beam bridge consists of two main beams and end beams.

The main beam is rigidly connected with the end beam, and wheels are installed at both ends of the end beam to support the bridge running on the elevated frame. Rails are welded on the main beam for the operation of the lifting trolley. There are many types of bridge girder structures, which are typically box-shaped, four-truss and open-web truss.

The box-shaped structure can be divided into two types: normal-rail box-shaped double beam, off-track box-shaped double beam, and off-track box-shaped single main beam. The box rail double beam is a basic form widely used. The main beam is composed of upper and lower flange plates and vertical webs on both sides. The trolley rail is arranged on the center line of the upper flange plate. Its structure is simple. It is easy to manufacture and suitable for batch production, but it has a large weight.

The section of the offset box double beam and the offset box single main beam are composed of upper and lower flange plates and main and auxiliary webs of unequal thickness. The trolley rail is arranged above the main web and the short stiffening in the box body The slab can be omitted, in which the deviated box-shaped single main girder is replaced by a wide flange box-shaped main girder with two main girders. The four-truss structure is composed of four flat truss into a closed space structure. The upper horizontal truss is generally covered with a walking platform, which has light weight and high rigidity. However, compared with other structures, it has a large outer size, more complicated manufacturing, and fatigue. The intensity is lower and production has been less.

The hollow-web truss structure is similar to a deviated box-shaped main beam. It consists of four steel plates to form a closed structure. Except that the main web is a solid-web I-beam, the remaining three steel plates are cut into many windows according to the design requirements to form a diagonal bar. The hollow web truss is covered with walking decks on the upper and lower horizontal truss surfaces. The crane operating mechanism and electrical equipment are installed inside the bridge frame. The weight is light and the overall rigidity is large. This is a type widely used in China.

Ordinary bridge cranes are mainly driven by electricity, and are generally operated in the driver's cab, but also controlled from a distance. The lifting weight can reach 500 tons and the span can reach 60 meters.

The simple beam bridge crane is also called a beam crane, and its structural composition is similar to that of an ordinary bridge crane, with a small lifting weight, span and working speed.

The main beam of the bridge frame is a simple cross-section beam composed of I-beam or other section steel and sheet steel. The hand hoist or electric hoist is equipped with a simple trolley as a lifting trolley. The trolley generally runs on the lower flange of the I-beam. The bridge frame can run along the track on the elevated frame or along the track suspended under the elevated frame. This type of crane is called a suspended beam crane.

Metallurgical bridge cranes can participate in specific technological operations during the steel production process. Their basic structure is similar to ordinary bridge cranes, but special working mechanisms or devices are also installed on the lifting trolley. The working characteristics of this crane are frequent use, bad conditions, and high working level. There are five main types.

Types of simple beam bridge cranes Casting cranes   Casting cranes: For lifting molten iron into a mixed iron furnace, steel making furnace, and lifting molten steel into a continuous ingot casting equipment or steel ingot mold. The main trolley lifts the barrel, and the auxiliary trolley carries out auxiliary work such as turning over the barrel.

Clamp crane: Use the clamp to lift the high temperature steel ingot vertically into the deep pit soaking furnace, or take it out and put it on the ingot truck.

Spinning crane: used to force the steel ingot out of the steel ingot mold. There is a special debonding device on the trolley. The debonding method depends on the shape of the ingot mold: some of the ingot cranes use the bar to press the steel ingot and lift the ingot mold with large tongs; some use the tongs to press the ingot mold, use Small pliers lift the steel ingot.

Feeding crane: used to add the charge to the open hearth furnace. The lower end of the column of the main trolley is equipped with a pick lever, which is used to stir the material box and send it into the furnace. The main column can rotate around the vertical axis, and the lever can swing up and down. The auxiliary trolley is used for auxiliary operations such as furnace repair.

Forging crane: It is used to forge large workpieces with the hydraulic press. The special trolley is hung on the hook of the main trolley to support and turn over the workpiece; the auxiliary trolley is used to lift the workpiece.   

Gantry crane: a bridge type crane with a horizontal bridge set on two legs to form the shape of a gantry. This crane runs on the ground track and is mainly used in open storage yards, docks, power stations, ports, and railway cargo stations for handling and installation operations. The lifting mechanism, trolley running mechanism and bridge structure of the gantry crane are basically the same as the bridge crane. Due to the large span, most crane operating mechanisms use separate drive methods to prevent the crane from skewing and increasing resistance, or even an accident. The lifting trolley of the gantry crane runs on the bridge frame, and some of the lifting trolley is a jib crane. The legs on both sides of the bridge are generally rigid legs; when the span exceeds 30 meters, it is usually a rigid leg on one side, and a flexible leg connected to the bridge through a ball hinge on the other side, making the portal a statically determinate system In this way, it can avoid the additional stress caused by the lateral thrust under the external load, and it can also compensate for the temperature deformation of the longitudinal direction of the bridge. The gantry crane has a large wind receiving area. To prevent sliding or tipping under strong wind, an anemometer and Crane rail clamp interlocked with running mechanism. The bridge frame can be cantilevered at both ends; it can also be cantilevered at one end or cantilevered at both ends to expand the working range. The semi-gantry crane bridge has legs at one end and no legs at the other end, and runs directly on the high gantry. Gantry cranes are divided into 4 types.

①Ordinary gantry crane: This crane is the most versatile. It can handle various pieces and bulk materials, with a lifting capacity of less than 100 tons and a span of 4 to 35 meters. The working level of ordinary gantry crane with grab is higher.

②Gantry crane of hydropower station: It is mainly used for lifting and opening and closing the gate, and can also be installed. The lifting weight is 80-500 tons, the span is small, 8-16 meters; the lifting speed is low, 1-5 meters/minute. Although this kind of crane is not often lifted, but once it is used, it is very heavy, so it is necessary to appropriately increase the working level.
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