Telescopic boom of engineering vehicle

Abstract

The invention provides a telescopic boom of an engineering vehicle. The telescopic boom comprises a cylinder body, a first piston rod, a second piston rod and an oil pipe for conveying hydraulic oil into the telescopic boom, wherein a first inner cavity which the first piston rod is sleeved in is arranged on the cylinder body, a second inner cavity which the second piston rod is sleeved in is arranged on the first piston rod, a third inner cavity which the oil pipe is sleeved in is arranged on the second piston rod, the first piston rod is provided with a first runner communicated with the first inner cavity and the third inner cavity, and the second piston rod is provided with a second runner communicated with the second inner cavity and the third inner cavity. The telescopic boom has a simple structure and easiness in being processed, effectively reduces assembling difficulty and production cost of oil cylinders, brings convenience to engineering designs and improves economic applicability of the engineering vehicle with a boom system.

Description

technical field [0001] The invention relates to the technical field of engineering vehicles, in particular to a telescopic arm of an engineering vehicle. Background technique [0002] The telescopic function of the boom of engineering vehicles such as telescopic box-arm fire trucks and aerial work vehicles can only be realized by the promotion of hydraulic cylinders. Please refer to figure 1 , figure 1 It is a schematic cross-sectional view of a typical boom telescopic arm in the prior art. In the current boom system, the telescopic boom used is mostly a double-acting oil cylinder, and its working process is described as follows: The oil enters the oil port C, and the oil inlet of the oil port B passes through the first oil pipe 18 to the rodless chamber 13, pushing the first-stage piston 11 and the first-stage piston rod 14 to extend outwards, and the oil inlet of the oil port C passes through the second oil pipe 10 to the The rodless chamber 16 pushes the second-stage pi...

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Problems solved by technology

[0002] The telescopic function of the boom of engineering vehicles such as telescopic box-arm fire trucks and aerial work vehicles can only be realized by the promotion of hydraulic cylinders. Please refer to figure 1 , figure 1 It is a schematic cross-sectional view of a typical boom telescopic arm in the prior art. In the current boom system, the telescopic boom used is mostly a double-acting oil cylinder, and its working process is described as follows: The oil enters the oil port C, and the oil inlet of the oil port B passes through the first oil pipe 18 to the rodless chamber 13, pushing the first-stage piston 11 and the first-stage piston rod 14 to extend outwards, and the oil inlet of the oil port C passes through the second oil pipe 10 to the The rodless chamber 16 pushes the second-stage piston 12 and the second piston rod 15 to extend out, and at the same time, port A returns oil; when the oil cylinder needs to be retracted, the oil enters through the oil port A, and the oil enters the rod chamber 19, and then passes through the D port, the oil Road 20, the oil port E enters the rod chamber 17, so that the two rod chambers can be filled with high-pressure oil at the same time, and the oil is returned through the oil port B and the oil port C at the same time to realize the retraction of the oil cylinder; the structure of this oil cylinder is complicated, and there are two High requirements on processing technology

Among them, since there is an oil passage 20 in the primary piston rod 14, the oil passage 20 can be processed with a deep hole drill, but the disadvantage is that the straightness of the drilling is very high, and the wall thickness of the general cylinder rod is relatively small, so it is difficult to ensure a straight line. In addition, the length of the drill bit is limited, and it is difficult to process long oil cylinders; the oil passage 20 can also be welded with two-stage sleeves, leaving a certain gap in the middle. Although this method can process long oil cylinders, it will affect the strength and stability of the cylinder rod. , while cleaning the middle cavity is more difficult

Moreover, in order to ensure that the hydraulic oil can be delivered to the rodless cavity 13, the second oil pipe 18 needs to adopt a two-stage nesting form, which requires very high straightness and coaxiality. At the same time, a device is required in the middle of the two-stage oil pipe nesting. Sealing, which means that the processing and welding requirements of the oil pipe are very strict, and it is very easy to have problems such as oil pipe bending and oil leakage in the later stage

The telescopic arms of high-lifting vehicles are generally very long, with a stroke of about 10 meters, so the above two points are difficult to meet the use requirements. Even if they are barely achieved, it will be difficult to quantitatively produce because of the complicated process; It is too complicated, so the later failure rate will be very high, and because there are many failure points, once a problem occurs, it will be difficult to judge the specific cause of the failure, which will seriously affect the production progress and quality stability of the host product; and in order to ensure its complex internal If the structure can be realized and the performance can be satisfied at the same time, the external dimensions of the oil cylinder will be relatively increased, resulting in an increase in the corresponding structural size and weight. However, once the telescopic load of the boom is too large, in order to ensure that the hydraulic system can provide the maximum pressure, the hydraulic cylinder can output Enough thrust requires increasing the size of the hydraulic cylinder, and the increase in the size of the cylinder will make it difficult to arrange the internal space of the boom structure, so it is necessary to increase the size of the boom, which in turn increases the weight of the boom. At the same time, the weight of the telescopic boom itself It will also increase, so that the telescopic load will be further increased, which will form a vicious circle, causing the product to fail to meet the design standards; moreover, since the existing boom telescopic arm is a double-acting oil cylinder, high pressure oil must enter the rod chamber when retracting However, because the area ratio of the rodless cavity and the rod cavity is generally very large, the pressure of the hydraulic system is too high when the cylinder is retracted, which cannot meet the use of existing products.

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