Discussion on several key technical problems of th

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Discussion on several key technical problems of single cylinder bolt telescopic boom

with the rapid development of China's economic construction, the market demand for large tonnage wheel cranes is increasing. At present, domestic large tonnage wheel cranes basically rely on imports. In order to seize the market as soon as possible and develop national industry, it is urgent to research and develop large tonnage wheel cranes

as the main load-bearing component of wheel crane, the weight of telescopic boom generally accounts for 13 ~ 20% of the whole machine, while the proportion of large cranes is larger. Therefore, the telescopic boom technology has a crucial impact on the performance of large tonnage wheel cranes in the case of large amplitude and high lifting height, and the key technology of the telescopic boom lies in the type of telescopic mechanism. At present, the truck cranes produced in China are mainly of medium and small tonnage, and the type of telescopic mechanism with telescopic oil cylinder and rope row is generally adopted, but each has its own characteristics in details. The characteristic of the telescopic mechanism is that the last one and two telescopic arms are telescopic by steel wire rope, and the other telescopic arms are telescopic by oil cylinder. Therefore, the section of the last telescopic arm changes greatly, which greatly reduces the lifting performance of the crane under a large range. At the same time, it is difficult to apply this type to telescopic boom with more than five arms. Western developed countries mainly produce medium and large tonnage wheel cranes with more than 50 tons, and the telescopic mechanism generally adopts the single cylinder bolt type. The adoption of this type of telescopic mechanism greatly improves the lifting performance of the crane. From baumachina200, which is also the key to the significant weight reduction of iPhone 5 compared with 4S. 4 the Expo can be seen that the elliptical telescopic boom, single cylinder plug telescopic mechanism and automatic telescopic boom system constitute the core of western advanced telescopic boom technology represented by iebherr of Germany, representing the current world's highest level, and is the development direction of telescopic boom technology of wheeled cranes. At present, Xuzhou Heavy Machinery Factory of XCMG group is the only one in China that has successfully launched three tonnage all terrain cranes with single cylinder plug telescopic boom technology, qay130, qay160 and QAY200

II. Several key technologies

single cylinder plug telescopic boom technology is a typical mechanical, electrical and hydraulic integrated system. According to some of our superficial understanding and practical experience, the key technologies in the telescopic boom are briefly described as follows:

1, single cylinder telescopic mechanism

take Liebherr in Germany as an example, as the actuator of telescopic boom expansion, it is mainly composed of (see Figure 1) 1. Telescopic cylinder, 2. Pin pulling mechanism, 3. Cylinder pin, etc. in order to ensure the safety and reliability of telescopic boom expansion process, the mechanism adopts a built-in interlocking system, that is, the spring installed on the telescopic cylinder drives the cylinder pin to fix the telescopic boom, and then mechanically releases the connection between the boom and other boom. In this way, the connection between the telescopic boom and other boom can be released only after the telescopic boom and the telescopic oil cylinder are locked mutually. Liebherr places the pin pulling device above the telescopic mechanism, which has the advantages of simple structure, strong self-locking and easy realization; Grove, Demag and tadanofaun put the pin pulling device on both sides of the telescopic mechanism, which is difficult in structural layout, has high requirements for processing and assembly accuracy, and is relatively difficult to insert and remove pins. The cylinder pins are arranged on the side of the telescopic mechanism. The single cylinder telescopic mechanism requires flexible action, high reliability, fast response speed and good interlocking. Otherwise, it is difficult to realize the reliable telescopic of the boom

2. Automatic telescopic PLC control system

the system is mainly composed of controller, display, operating handle, length sensor, position detection switch and other electronic components. The reason why PLC control technology is selected is that the traditional relay control can no longer meet the complex logic control requirements of single cylinder telescopic mechanism. PLC control is easy to realize complex logic control, has strong anti-interference ability, and is suitable for the harsh working environment of mobile cranes. At present, China pays more attention to the research and application of bus technology, especially can bus. Based on practical experience, the author believes that the key to realizing the automatic expansion and contraction of the boom lies in whether the influence of vibration and impact during the expansion and contraction of the boom can be eliminated, and the length and thermal conductivity of the vacuum insulation plate are absolutely the lowest position signal in the existing thermal insulation materials for reliable detection and transmission. In addition to the communication between controller and display, can bus technology should not be the technology we urgently need to adopt at present. In addition, the implementation of automatic scaling technology must be based on a large number of experiments, and the neglect of any detail will lead to failure

3. Automatic telescopic hydraulic system

the system is mainly composed of the hydraulic circuit that controls the telescopic cylinder and the hydraulic circuit that controls the insertion and removal of the cylinder and arm pin. The hydraulic circuit controlling the telescopic oil cylinder must have a certain speed and good inching performance, so as to ensure that the telescopic of the boom can be completed in a relatively short time. At the same time, when inserting and removing the pin, it also has the key technical bottleneck that restricts the treatment of acid soil and heavy metal pollution, good smoothness and small impact. The circuit pressure can be set to different levels according to the different loads of the telescopic cylinder (see ASTM C 363) in order to make better use of the power of the variable displacement pump. The hydraulic control circuit of cylinder and arm pin should have fast response speed and reliable action switching, the pressure of control circuit should be set appropriately, and an appropriate balance point should be sought on the speed of inserting and pulling pins. In this way, the control signal output by the PLC controller can automatically control the telescopic mechanism accurately, reliably and quickly through the hydraulic circuit. Considering the safety and reliability of the whole boom telescopic, another set of emergency operation system is designed. When the automatic telescopic system fails, the boom can be safely retracted by using the emergency operation system

III. summary

we have carried out scientific research on the above key technologies for more than a year, and finally all of them have been mastered and applied to the all ground series cranes in our factory, and achieved good results. In the next step, we will conduct more in-depth research and discussion to further improve the safety, reliability and comfort of the system

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