Introduction to excavating machinery

Excavating machinery

Excavating machinery is a type of earthmoving equipment that uses a bucket to dig materials above or below the working surface and load them into transport vehicles or unload them into stockpiles. The main materials excavated are soil, coal, silt and sand, as well as rocks and ores that have been pre-loosened.

In general engineering, approximately 60% of the earthwork volume, 80% of the stripping volume and mining volume in open-pit mines are accomplished by excavating machinery. Excavating machinery is classified into two types: single-bucket excavators and multi-bucket excavators. The operation of single-bucket excavators is periodic, while that of multi-bucket excavators is continuous.

The earliest excavators were dredgers powered by human or animal power, used to dig deep into the riverbed. Their bucket capacity generally did not exceed 0.2 to 0.3 cubic meters. Between 1833 and 1836, the American Otis designed and manufactured the first single-bucket excavator driven by a steam engine, with a hybrid structure of iron and wood, semi-rotating and rail-mounted, with a production rate of 35 cubic meters per hour. However, due to poor economy, it was not applied. In the 1970s, improved steam shovels were officially produced and applied in open-pit mine stripping. In 1880, the first batch of semi-rotary steam shovels based on tractors appeared.

From the early 20th century to the late 1940s, excavators entered a stage of diversification in power and traveling devices. In 1910, the first motor-driven single-bucket excavator emerged. In 1912, fully rotating single-bucket excavators driven by gasoline and kerosene engines emerged. In 1916, a single-bucket excavator driven by a diesel generator was produced. In 1924, diesel direct drive began to be used in single-bucket excavators. The crawler walking device was adopted in 1910. With the development of the automotive industry, tire-type walking devices have been widely used in small excavators. In the 1930s, walking devices emerged. In the mid-1950s, Germany and France successively developed fully rotating hydraulic excavators, and since then, the development of excavators has entered a new stage.

The multi-bucket excavator also has a history of over 100 years. In 1860, France produced the world's earliest multi-bucket excavator with a relatively mature structure, which was used in the excavation project of the Suez Canal. In 1889, the multi-bucket trencher produced in the United States could dig ditches that were 0.29 meters wide and 1.4 meters deep. At the end of the 19th century, bucket wheel excavators were widely used in the mining of lignite in Germany. By 1958, the capacity of each bucket had reached 3,600 liters. In 1977, the Federal Republic of Germany manufactured the world's largest bucket wheel excavator, with a production rate of 240,000 cubic meters per day.

Excavating machinery is generally composed of power units, transmission units, traveling units and working units, etc. Single-bucket excavators and bucket-wheel excavators also have turntables, while multi-bucket excavators are equipped with material conveying devices.

The power unit includes diesel engines, electric motors, diesel generator sets or external power converter units. Diesel engines and electric motors are mostly used in medium and small-sized excavators, which are centrally driven by one prime mover and can be interchanged. Diesel generator sets and external power converter units are used in large and medium-sized excavating machinery, driven by multiple motors in a decentralized manner.

The walking device is mainly used to support the machine, change the working position of the machine and transfer the working site. In addition, the buckets of bucket chain excavators and ring wheel excavators cut the soil as the traveling device moves continuously. There are several types of walking devices, including crawler type, tire type, walking type, rail type, floating type and towing type.

When the work site is fixed and a relatively low grounding specific voltage is required, a crawler type should be used. When the working site is changeable, use the tire-type. When it is necessary to set up dedicated tracks due to special construction conditions, the rail type should be used. The floating type is used for digging underwater soil. When there is no power source for the traveling device of a small single-bucket excavator, a towable type is used. When the work site is fixed and the machine is heavy, the walking type should be used. Walking-type walking devices are mostly used in large and medium-sized drag-shovel excavators and bucket wheel excavators in single-bucket excavators