Knowledge Sharing of the Excavator

一. The definition of excavator
Excavator, also known as excavating machinery, is the earth-moving machinery which digs the materials above or below the bearing surface with its bucket, and loads to transport vehicle or unloads to the stockyards. The materials excavated are mainly soil, coal, sand and also the pre-loosed soil and rock. From the development of construction machinery in recent years, the development of excavator is relatively faster. While the excavator acts as one of the most important construction machinery and aircraft engineering, the correct selection of its type will become more important.
二. The brief history of excavator
So far, it has more than 13o years’ history since the advent of the first manual excavator, and it has experienced the progressive development process from the steam-driven rotary bucket excavator to electric drive and combustion engine driven rotary excavator, and then to automatic hydraulic excavator applied the hydraulic integration during these years.
Due to the application of hydraulic technology, in the 1940s,there existed the attachment excavators equipped with the hydraulic backhoe on a tractor. In the early and mid 1950s,
full rotary hydraulic tractor-type excavator and full hydraulic track-type excavator were developed successively. Early trial hydraulic excavator was using the hydraulic technology of aircraft and machine tool, so hydraulic components which is suitable for various working conditions were shortage, manufacturing quality was not stable enough, and accessories were not complete. While, the hydraulic excavator has entered into the promoted and vigorous development stage since the 1960s, excavator factories and varieties from various countries increased rapidly, production soared. From 1968 to 1970 years, production of hydraulic excavators accounted for 83% of total output of excavator, now approaching to 100%.
三. The constitute of excavator
Common structures of excavator include power device,working equipment, slewing mechanism, control mechanism, transmission mechanism, running gear, auxiliary facilities ant etc.
From the exterior, the excavator consists of three parts: working device, the upper turntable, and running gear.
四. The development history of excavator
The initially excavator which is manual,has more than one hundred and thirty years up to now since its invention, and experienced a variety of driving ways such as steam-driven, power-driven, internal combustion engine driven and etc.
After the 1940s, hydraulic technology has been applied to excavator. Then, it has developed to fully hydraulic track type excavators today.
The three most important parameters of excavator are vehicle weight (mass), engine power and bucket capacity.
　　In 1951, the first full hydraulic backhoe excavator published in Poclain plant of Paris, so that creating a new space in the field of excavator’s technological development.
五. The classification of excavator
The common classifications are as follows:
1. According to different drive ways, there are two types, internal combustion engine driven excavators and electrically driven excavators. Besides, electric excavators are mainly used in high altitude areas and underground mines and other inflammable and explosive places.
　 2. According to different running ways, excavators can be divided into crawler excavators and wheel excavators. 　
3. According to different transmission ways, excavators can be classified into hydraulic excavators and mechanical excavators. And mechanical excavators are mainly used in some large-scale mines.
　　4. According to different purpose, excavators can be divided into different categories, such as generic excavators, mining excavators, marine excavators, special excavators and other categories.
5. According to different buckets, there are shovel excavators and backhoe excavators. The shovel type is mainly used for digging materials above the surface, while the backhoe is most used for the digging materials below the surface.
六、The development overview of Chinese excavators
Chinese excavators production started lately, in 1954 Fushun Excavator Factory produced the first single-bucket mechanical excavator with the bucket capacity of 1m3. So far, excavators largely have went through the mapping imitation, independent research and development, and development and improvement these three stages.
In Early New China, it began production history of the excavator, mainly in mapping and imitation the 1930s - 1940s W501, W502, W1001, W1002 and other models of single-bucket mechanical excavators of former Soviet Union. Because of the demand of national economic construction at that time, more than a dozen excavator production plants were established. In 1967, China began to independently develop hydraulic excavators. Early successful products mainly include WYl00 model of Shanghai Construction Machinery Factory, W4-60 model of Guiyang Mining Machinery Plant, WY60 model of Hefei Mining Machinery Plant and etc. Then, WYl60 model of Yangtze Excavator Plant and WY250 model of Hangzhou Heavy Machinery Plant were appeared. They took a very important step for the formation and development of Chinese hydraulic excavator industry.
By the late 1980s, There were more than 30 excavator production plants in China, and more than 40 kinds of models produced. Medium and small hydraulic excavators has formed series, bucket capacity has 12 levels from 0.1 to 2.5 m3, and more than 20 kinds of models. And the 0.5-4.0m3 and large mining 10m3,12m3 single-bucket mechanical transmission excavators, 1m3 tunnel excavators, 4m3 backhoe excavators, 1000m3 / h earth discharging machines were produced, marine hydraulic excavators with bucket capacity 0.25m3 developed, the underwater and land excavators with bucket capacity 0.4m3, 0.6m3, 0.8m3 and others were developed, too. But overall, China's excavator production volume was small, scattered, and there was a big gap in production processes and product quality, compared with the international advanced level.
Since the reform and opening, China has actively introduced, digested and absorbed foreign advanced technology to promote the development of excavator industry in China. And Guiyang Mining Machinery Plant, Shanghai Construction Machinery Plant, Hefei Mining Machinery Plant, Yangtze Excavator Plant and other plants introduced hydraulic excavators’ manufacturing technology of Germany Liebherr Company, these hydraulic excavators included A912, R912, R942, A922, R922, R962, R972, R982 models. A few years later, Hangzhou Heavy Machinery Plant introduced the H55 and H85 hydraulic excavators’ manufacturing technology of Germany Demag Company, and Beijing Construction Machinery Factory introduced manufacturing technology of Germany 0 & K Company’s RH6 and MH6 hydraulic excavators. At the same time, the complete set of manufacturing technology of Japan Komatsu's PC100, PC120, PC200, PC220, PC300, PC400 hydraulic mining machine ( except the engine) was introduced jointly by Shandong Bulldozer Plant, Yellow River Engineering Machinery Plant, Jiangxi Changlin Machinery Factory, Shandong Linyi Engineering Machinery Plant and etc. These plants comprehensively improved performance indicators of Chinese hydraulic excavator to the 1980s’ international standards, and also increased production year by year through several years of digestion, absorption, transplant for introduced technology. Due to the increasing Chinese demand and diverse of hydraulic excavators and the product structure’s adjustment in state-owned large and medium-sized enterprises, a number of factory from other machinery industry joined the hydraulic excavator industry. For example, China First Tractor Engineering Machinery Company, Guangxi Yuchai Co., Ltd., Liuzhou Engineering Machinery Factory and etc. These enterprises have reached a certain scale and level after several years’ efforts. For instance, the small hydraulic excavators developed by Yuchai Machinery Co., Ltd in the early 1990s, have been exported largely to Europe, America and other countries for many years, and this company has become the batch export enterprises in China's excavator industry.
Insiders pointed out that China’s Single-bucket hydraulic excavators should develop to the direction of full hydraulic, bucket capacity should be controlled within 0.1-15 m3, but for large-scale and multi-bucket excavators, they are still mainly in mechanical type due to the high accuracy requirements of hydraulic components’ manufacturing and assembly, and poor condition of construction site’s maintenance, then still mechanically based. China should start to study, apply the electro-hydraulic control technology to achieve the automation of hydraulic excavator operation.

So many worlds. But all the useful information!

七、The development overview of overseas excavators
The manufacturing of excavators in industrially developed countries is earlier, France, Germany, the United States, Russia, Japan are major producing countries of 3.5-40 m3 single-bucket hydraulic excavator, producing large excavators from the 1980s. For example, the peeling excavators with the bucket capacity of 50-150 m3 and the walk-dragline excavators with the bucket capacity of 132 m3 produced by American Marion Company, the walk-dragline excavators with the bucket capacity of 132 m3 and the peeling excavators with the bucket capacity of 107 m3 produced by B-E Company are the largest excavators around the world at present.
From the late 20th century, the international manufacturing of excavators has developed to the direction of large-scale, miniaturization, multi-functional, specialization and automation.
1) Development of excavator with multi-species, multi-function, high quality and high efficiency. To meet the needs of municipal construction and agricultural construction, mini excavators with bucket capacity of 0.25 m3 below were developed, and the smallest bucket capacity was 0.03 m3. Besides, the medium and small excavators of most quantity tended to be the machine having a variety of functions, and were equipped with multiple working devices-except shovel, backhoe, also equipped with crane, grab, flat slope bucket, loading bucket, rake teeth, crushing cone, twist drill, electromagnetic chuck, vibrators, bulldozing plate, shock shovel, container fork , high-altitude planes, winch and pull shovel and etc, to meet the needs of various construction. At the same time, special excavators of special-purpose were developed, such as low pressure, low noise, underwater dedicated and also underwater and land excavators.
2) The rapid development of fully hydraulic excavators, continuous improvement and innovation of control ways, makes the excavator operated by a simple lever to hydraulic control, pneumatic operation, hydraulic servo manipulation and electrical control, radio remote control, computer integrated process control. Applying the radio-control on dangerous areas or underwater operations, combining control receiver of computer and laser guidance to achieve a fully automation of excavator manipulation. Full hydraulic technology of excavators creates the foundation and a good premise for all of these.
　　3) Pay attention to the application of new technologies, new processes, new structure, accelerating the development speed of standardization, serialization, generalization. For example, German Atlas Company’s excavators, which were equipped with the new engine speed regulation devices, adjusted a best speed suited to their operational requirements to work; New*C*Series* LS-5800*model hydraulic*excavators of Lincoln's Belt*Company installed automatic hydraulic control*system that automatically*regulates the flow,*avoiding the*waste of drive power, and also installed CAPS (Computer Aided Power System) to improve the excavators’ working power and exert function of the hydraulic system better；Japanese Sumitomo company’s five new models of FJ series excavators were equipped with a computer-aided power control system connected with the hydraulic circuit, using precision control mode to select system to reduce the consumption of fuel, engine power and hydraulic power and extend the components’ life; the oil pump regulation system of Germany O & K Company's excavators had confluence characteristics, enabling the pump to have maximum efficiency; Kobelco applied intelligent control systems to hydraulic excavator of these new 904,905,907,909 types, even inexperienced driver can perform complex operations; German*Liebherr Company*developed*ECO (Electronic Control*jobs)*operating device which can adjusted the work*performance*of excavators*according to* operational requirements, and achieved*the high efficiency, low fuel consumption; US Caterpillar Company adopted the latest 3114T diesel engine, torque load-sensing pressure system, power mode selector and others in the new B system excavator, further improving the operating efficiency and stability of the excavator. South Korea's Daewoo Company used the EPOS( electronic power optimization system） in DH280 excavator according to the engine’s load changes and the power absorbed by the automatically adjust hydraulic pump, making the engine rotational speed always maintain near the rated speed, that is, the engine was always operating at full power. Which not only made full use of engine power, improves operational efficiency of excavators, but also prevented engine flameout due to overload.
　　4)Update the design theory, increase reliability and service life. United States, Britain, Japan and other countries promoted the use of finite life design theory as an alternative to the traditional infinite life design theory and method, and applied the advanced technologies such as the fatigue damage accumulation theory, fracture mechanics, finite element methods, optimum design, electro-hydraulic servo fatigue testing technology controlled by computer, fatigue strength analysis methods and others to the strength study of the hydraulic excavator, promoting the high quality, high efficiency and competitiveness of products. The United States put forward dynamic design analysis methods of dynamic strength evaluation, and created a theory of predicting product failure and update. Japan formulated the strength assessment procedures of hydraulic excavator s’ components, and developed the information processing system of the reliability. Under the guidance of the basic theory above, by means of a large number of experiments, it shortened the research cycle of new products, accelerated the upgrading process of the hydraulic excavators, and improved their reliability and durability. For example, the operating rate of the hydraulic excavator was up to 85% to 95%, and the service life was over 10,000 hours.
　　5)Strengthen labor protection for the driver, and improve the driver's working conditions. Hydraulic excavators used the cab with falling object protective structures and rollover protection structure, installed an adjustable elastic seat and reduce noise with soundproofing measures .
　　6)Further improvement of the hydraulic system.The hydraulic system of medium and small hydraulic excavators has a clear trend towards variable system. Because the variable system increases the traffic to compensate in the working process of the oil pump, making the hydraulic pump power remains constant when the pressure decreases, that is, hydraulic excavator equipped with a variable displacement pump can regularly take advantage of the maximum power of the oil pump. When the external resistance increases, decreasing the flow (reduce speed) to double digging force; using the three-circuit hydraulic system generates three independently of each other working movements, achieving the power match with the rotating mechanism. Turning the third pump on other working movements, then becomes the second independent fast motion of the open circuit. In addition, the widespread use of hydraulic technology in excavators creates the conditions for application and promotion of electronic technology, automatic control technology to the excavator.
7) The rapid development of electronic technology, automation technology using in the excavator. In the 1970s, in order to save energy consumption and reduce environmental pollution, and also get easy operation and safe operations of excavators, lower excavators’ noise and improve drivers’ working conditions, the electronics and automatic control technology was gradually used in mining. With the improvement of all kinds of excavators’ performance requirements such as the working efficiency, energy saving and environmental protection, easy operation, safety and comfort, reliability and durability and other aspects, it prompted the application of the hydraulic integration on the excavator, and made all kinds of performance a qualitative leap .
8) In the 1980s, the high-tech taking the microelectronics technology as the core, in particular the application of computer, microprocessor, sensors and examination measuring appliance on the excavator, has promoted the application and promotion of the electronic control technology in the excavator, and has became an important symbol of excavators modernization. That is to say, there are engine automatic idle speed, throttle control system, power-optimized system, mode control systems, monitoring systems and other electronic control systems equipped in advanced excavators currently.


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