An automatically cleaned horizontal grid cleaner
Patent Information
- Application Number
- CN202522453203.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-10-13
- Estimated Expiration
- 2035-11-19
AI Technical Summary
但是其工况恶劣,清理组件与格栅框之间依赖的导向结构(例如导轨、轴套之列)和运行依赖的液压缸均浸泡在污水和各种过滤污物中,易磨损变形,通常每1—3个月就需清理和维护,且经常因为动力和传动组件损坏而要更换整套设备,给运维带来较大的压力
本装置可以作为清洁机构装配在水平格栅新设备上,也可以在检修中对正在使用的水平格栅设备进行清洁机构的替换和升级,通过挑高安装在格栅上方的行走梁承担和构成传动及驱动结构,从而让易损的组件能够尽量远离恶劣的运行环境,结合采用不易损坏的机械结构,实现在运维成本上的节约,降低清洁部分组件的损坏频率。
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Figure CN224845823U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of bar screen filtration equipment, specifically an automatic cleaning horizontal bar screen cleaning device. Background Technology
[0002] A horizontal overflow bar is a solids interception device used in the inlet bar, outlet, and overflow of a regulating tank. It can effectively intercept sewage or solid particles and floating matter in sewage. Under normal circumstances, sewage flows into the overflow pipe from the discharge outlet through the horizontal bar. The intercepted pollutants need to be cleaned by the built-in rake teeth, comb teeth, or brush. The reciprocating stroke is usually driven by a hydraulic cylinder (bidirectional or unidirectional).
[0003] The cleaning device is the core of the bar screen's continuous and efficient operation. Once the rake teeth, comb teeth, or cleaning vehicle stop, dirt immediately accumulates, the water flow cross-section is drastically reduced, and the system overflows and causes pollution to get out of control. Therefore, continuous operation is essential. However, its working conditions are harsh. The guide structures (such as guide rails and bushings) that the cleaning components rely on to connect with the bar screen frame, as well as the hydraulic cylinders that rely on operation, are all immersed in sewage and various filtered dirt, making them prone to wear and deformation. They usually require cleaning and maintenance every 1-3 months, and often the entire set of equipment needs to be replaced due to damage to the power and transmission components, which puts a lot of pressure on operation and maintenance. Utility Model Content
[0004] The purpose of this invention is to provide an automatic cleaning device for horizontal bar screens, which can be installed on horizontal bar screen equipment to reduce equipment maintenance costs and damage frequency, and ensure stable and continuous operation of the bar screen.
[0005] To achieve the above objectives, this utility model employs the following technical solution: An automatic cleaning horizontal bar screen cleaning device includes a traveling beam mounted elevated along the length of the bar screen. The traveling beam is equipped with a traveling frame that has a linear reciprocating stroke along it. The traveling frame is rotatably mounted with upper rollers, lower rollers, and side rollers. There are at least two upper rollers that cooperate with the top surface of the traveling beam, at least two lower rollers that cooperate with the bottom surface of the traveling beam, and side rollers that cooperate with the sides of the traveling beam. A downwardly extending upright member is provided below the traveling frame, and a cleaning component is provided at the bottom end of the upright member.
[0006] The top side of the traveling beam is provided with a straight groove extending in the same direction as its length. A rack extending in the same direction is fixed in the straight groove. A gear located above the traveling beam is rotatably mounted on the traveling frame. The gear is driven by a motor and meshes with the rack below.
[0007] Shallow grooves are provided on both sides of the traveling beam, and the inner circumferential surface of the side rollers contacts and engages with the bottom of the shallow grooves. At least two side rollers are provided on one side of the traveling frame.
[0008] The straight groove has inclined surfaces on both sides, and the rack is detachably installed to the bottom of the straight groove.
[0009] The two ends of the walking beam are respectively fixed with portal frames, which are used to install the device on both ends of the horizontal grid.
[0010] A mounting plate is fixed to one side or the bottom of the walking frame. A vertically extending column is fixed to the mounting plate. A cleaning component is fixed to the bottom of the column. The cleaning component includes a connecting beam that is fixedly connected to the bottom of the column in the middle. Brush plates are fixedly installed at both ends of the connecting beam. The brush plates are horizontally set and perpendicular to the walking beam. The brush plates have bristles on the bottom. The column has various models based on its length.
[0011] A horizontally extending mounting plate is fixed to one side of the walking frame. A U-shaped groove is provided in the middle of the mounting plate. An outer cylinder is detachably installed in the U-shaped groove. An inner cylinder that slides through the outer cylinder is telescopically fitted with it. An upper plate is fixed to the bottom of the inner cylinder. A cleaning component is fixedly installed below the upper plate. The cleaning component includes a centrally located connecting beam. Brush plates are fixedly installed at both ends of the connecting beam by fasteners. The brush plates are horizontally arranged and perpendicular to the walking beam. Brush plates have bristles on their underside.
[0012] A horizontally extending mounting plate is fixed to one side of the walking frame. A U-shaped groove is provided in the middle of the mounting plate, and an outer cylinder is detachably installed in the U-shaped groove. An inner cylinder, which slides and extends with the outer cylinder, passes through the outer cylinder. An upper plate is fixed to the bottom of the inner cylinder. A cleaning component is provided below the upper plate. The cleaning component includes a centrally located connecting beam. Brush plates are fixed to both ends of the connecting beam by fasteners. The brush plates are horizontally arranged and perpendicular to the walking beam. Brush plates have bristles below them. A hinge plate is welded to the bottom surface of the upper plate. A lower plate is fixed to the middle of the connecting beam. A hinge seat is fixed to the top surface of the lower plate. The hinge seat has two first positioning holes. A hinge shaft, which is rotatably connected to the hinge plate, passes through the hinge seat. The hinge plate has two second positioning holes. The center distance between the first and second positioning holes corresponds to the center distance of the hinge shaft. The two first positioning holes are distributed at right angles to the hinge shaft. The two second positioning holes are distributed at right angles to the hinge shaft. Positioning pins pass through the first and second positioning holes.
[0013] The U-shaped groove has vertically extending clamping plates on both sides of the groove wall. The outer cylinder and the inner cylinder are rectangular cross-sections. The side length / width of the outer cylinder is adapted to the spacing of the clamping plates. The side walls of the outer cylinder are fixed with baffles at equal intervals along their length direction. The spacing between adjacent baffles corresponds to the height of the clamping plates. The baffles on the side walls are symmetrically arranged. The maximum spacing between baffles of equal height is greater than the width of the U-shaped groove. A pin passes through the clamping plates. The two ends of the pin are threaded with large nuts. The minimum distance from the pin to the bottom of the U-shaped groove is adapted to the side length / length of the outer cylinder.
[0014] A strip-shaped hole is opened on one side of the outer cylinder. The bottom end of the strip-shaped hole penetrates the bottom side of the outer cylinder. The strip-shaped hole is located on the side of the outer cylinder away from the traveling frame. A screw is welded to the side wall of the inner cylinder at the position corresponding to the strip-shaped hole. The outer end of the screw penetrates the strip-shaped hole and is threadedly connected to a fastening nut.
[0015] Compared with the prior art, the beneficial effects of this utility model are as follows: This device can be installed as a cleaning mechanism on new horizontal bar screen equipment, or it can be used to replace and upgrade the cleaning mechanism of existing horizontal bar screen equipment during maintenance. By raising the walking beam installed above the bar screen to bear and form the transmission and drive structure, the vulnerable components can be kept away from harsh operating environments as much as possible. Combined with the use of a non-damaging mechanical structure, it can save on operation and maintenance costs and reduce the frequency of damage to the cleaning components. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the present invention.
[0017] Figure 2 This is a schematic diagram of the structure of this utility model.
[0018] Figure 3 This is a schematic diagram of the lateral operation of this utility model.
[0019] Figure 4 This is a schematic diagram showing the components of this utility model disassembled.
[0020] The labels shown in the attached diagram: 1. Portal frame; 2. Traveling beam; 3. Shallow groove; 4. Straight groove; 5. Rack; 6. Traveling frame; 7. Side plate; 8. Edge plate; 9. Notch; 10. Upper roller; 11. Lower roller; 12. Side roller; 13. Gear; 14. Mounting plate; 15. U-shaped groove; 16. Clamping plate; 17. Outer cylinder; 18. Stop bar; 19. Inner cylinder; 20. Pin; 21. Strip hole; 22. Screw; 23. Upper plate; 24. Hinge plate; 25. Second positioning hole; 26. Lower plate; 27. Hinge plate; 28. First positioning hole; 29. Connecting beam; 30. Brush plate. Detailed Implementation
[0021] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined in this application.
[0022] Example:
[0023] The system includes a traveling beam 2, the length of which corresponds to the total length of the grid to be applied. It can be manufactured by cutting profiles to a fixed length and then performing simple welding, as required. The traveling beam 2 provides constraint for the reciprocating movement of the cleaning components, facilitating the application of additional components.
[0024] Shallow grooves 3 are provided on both sides of the walking beam 2 to facilitate movement with the track wheels and improve the stability of the walking assembly. A straight groove 4 extending in the same direction as its length is provided in the center of the top side of the walking beam 2. The groove walls on both sides of the straight groove 4 are inclined at an angle of about 80 degrees to facilitate cleaning dirt upwards. A row of mounting holes is provided at the bottom of the straight groove 4 along its length to facilitate the installation of the rack 5.
[0025] A rack 5 extending in the same direction is fixed inside the straight groove 4. The rack 5 is fixed to the mounting hole by bolts, enabling quick assembly. In case of maintenance or damage, the rack 5 can be easily and quickly disassembled and removed, allowing only the damaged transmission component to be replaced, thus reducing maintenance costs.
[0026] A portal frame 1 is fixed to each end of the traveling beam 2. The portal frame 1 is used to install the device onto both ends of the horizontal grid. Specifically, the traveling beam 2 has threaded grooves at both ends, which are located on both sides of the straight groove 4. There are at least three pairs of threaded grooves on the same end. The middle part of the portal frame 1 is fixed to both ends of the traveling beam 2 by fasteners that cooperate with the threaded grooves. The bottom of the portal frame 1 is fixed to the frame at both ends of the grid to install and fix the device, thereby allowing for the replacement and upgrading of all horizontal grids with damaged cleaning components. It allows for quick adaptation and integration with existing grid equipment without the need for complete replacement.
[0027] The traveling beam 2 is provided with a traveling frame 6, which has a reciprocating travel stroke along the length of the traveling beam 2.
[0028] The walking frame 6 is made of welded metal iron plates. The frame includes two side plates 7 connected at the bottom and / or top, with the walking beam 2 passing through the middle of the two side plates 7.
[0029] The frame is rotatably equipped with: upper roller 10, lower roller 11, and side roller 12.
[0030] There are two upper rollers 10, which are rotatably installed on the upper part of the frame. The upper rollers 10 are located above the traveling beam 2, and their bottom circumference matches the top surface of the traveling beam 2. There are two lower rollers 11, which are staggered vertically from the upper rollers 10 for greater stability. They are located below the traveling beam 2, and their top circumference mates with the bottom surface of the traveling beam 2. The upper rollers 10 and lower rollers 11 are symmetrical in pairs and staggered vertically to achieve an isosceles trapezoidal layout, which can effectively stabilize the traveling trajectory.
[0031] There are four side rollers 12, two on the same side, symmetrically arranged in pairs on both sides of the traveling beam 2. A side plate 8 extends outward from the lower middle part of the side plate 7, and a vertical shaft is installed on the side plate 8. The side rollers 12 are rotatably mounted on the vertical shaft. A notch 9 is provided on the side plate 7 at the position corresponding to the side rollers 12 to allow space for them. The inner circumferential surface of the side rollers 12 contacts and engages with the bottom of the shallow groove 3.
[0032] In the above structure, the side rollers 12 clamp the traveling beam 2 horizontally on both sides, and the upper rollers 10 and lower rollers 11 clamp the traveling beam 2 vertically. This effectively constrains the linear travel trajectory of the traveling frame 6 in four directions. Furthermore, based on rolling and cooperating travel, it reduces sliding resistance and is less susceptible to the influence of dirt.
[0033] A gear 13 is provided between the two side plates 7, located above the walking beam 2. The gear 13 is located in the center of the two upper rollers 10. The lower part of the gear 13 is located in the straight groove 4 and meshes with the rack 5. A shaft is passed through the gear 13 and is rotatably mounted to the walking frame 6 based on the bearing component. One end of the shaft is driven by a motor to drive the walking frame 6 during the rotation of the gear 13.
[0034] The combination of gear 13 and rollers enables walking guidance and drive, which is easier to maintain than the existing sliding connection structure. Furthermore, since this device is raised and installed above the grid in a raised manner, it is at a certain height distance from the dirt, and the transmission and drive components can avoid being immersed in sewage and dirt for a long time, thereby greatly reducing the frequency of damage.
[0035] A horizontally extending mounting plate 14 is fixed to one side of the walking frame 6. A U-shaped groove 15 is provided in the middle of the mounting plate 14. Vertically extending clamping plates 16 are provided on both sides of the groove wall of the U-shaped groove 15. A quick-release outer cylinder 17 is provided between the clamping plates 16. An inner cylinder 19 that slides and extends through the outer cylinder 17 is connected to it. The outer cylinder 17 and the inner cylinder 19 can be combined by selecting square steel fixed-length cutting inserts with matching dimensions, which is convenient for processing. The side length / width of the outer cylinder 17 is adapted to the spacing of the clamping plates 16, and can be inserted into the U-shaped groove 15. The side walls of the outer cylinder 17 are welded and fixed with baffles 18 at equal intervals along their length direction. The spacing between adjacent baffles 18 corresponds to the height of the clamping plates 16. The baffles 18 on the side walls are symmetrically arranged. The maximum spacing between baffles 18 of equal height is greater than the groove width of the U-shaped groove 15 (that is, greater than the spacing between the two clamping plates 16), thereby forming a mating position between the baffles 18 that can be located in the U-shaped groove 15. The baffles 18 above the mating position fall on the upper side of the clamping plate 16, and the baffles 18 below the mating position are close to the lower side of the clamping plate 16, thereby quickly limiting the relative height of the outer cylinder 17.
[0036] With the above structure, the outer cylinder 17 and the mounting plate 14 can be quickly height-limited by simple insertion. That is, the outer cylinder 17 is found to a suitable height and quickly inserted into the U-shaped groove 15. The upper and lower limits of the insertion position are achieved by the stop strip 18 and the clamping plate 16.
[0037] A pin 20 passes through the clamping plates 16. Both ends of the pin 20 are threaded with large nuts. The large nuts are used to install the pin 20 relative to the clamping plates 16. The minimum distance from the pin 20 to the bottom of the U-shaped groove 15 is adapted to the side length / length of the outer cylinder 17, so as to achieve quick fixation after the height of the outer cylinder 17 is positioned.
[0038] A strip-shaped hole 21 is opened on one side of the outer cylinder 17. The bottom end of the strip-shaped hole 21 penetrates the bottom side of the outer cylinder 17. The strip-shaped hole 21 is located on the side of the outer cylinder 17 away from the traveling frame 6. A screw 22 is welded to the side wall of the inner cylinder 19 corresponding to the position of the strip-shaped hole 21. The screw 22 is welded through the inner cylinder 19 perpendicularly. The outer end of the screw 22 penetrates the strip-shaped hole 21 and is threadedly connected to a fastening nut. A washer can also be added to the inside of the fastening nut. By tightening the fastening nut, the inner cylinder 19 and the outer cylinder 17 are fixed, thereby quickly limiting the extension length of the inner cylinder 19 relative to the outer cylinder 17.
[0039] The inner cylinder 19 and outer cylinder 17 can be of equal length, or the inner cylinder 19 can be slightly shorter than the outer cylinder 17. The installation height of the outer cylinder 17 relative to the traveling frame 6 is adjustable, and the extension length of the inner cylinder 19 is also adjustable, allowing for a 2x adjustment of the working height of the bottom cleaning component. In practical applications, an appropriate height combination can be selected based on the site conditions. With this structure, the cleaning component can be installed very close to the traveling beam 2, i.e., the bottom of the outer cylinder 17 is fixed to the traveling frame 6, and the inner cylinder 19 is retracted into the outer cylinder 17 for fixation. This method is suitable for situations where the height of one side of the filter is limited. If space permits, the traveling beam 2 can be installed as high as possible while maintaining stable movement, thus keeping the traveling frame 6 as far away from the filter location as possible.
[0040] Under the above circumstances, the above structure can be widely used for the cleaning and upgrading of horizontal grids in various working environments. It can cope with various installation environments, has a wide range of applications, and is highly versatile.
[0041] The bottom end of the inner cylinder 19 is welded with an upper plate 23, and a cleaning component is installed below the upper plate 23.
[0042] The cleaning assembly adopts an I-beam structure, including a centrally located connecting beam 29. Brush plates 30 are fixedly mounted at both ends of the connecting beam 29 using fasteners. The brush plates 30 are horizontally positioned and perpendicular to the traveling beam 2, and have bristles at their base. The bristles clean the gaps in the grille.
[0043] Since the mounting plate 14 is located on one side of the walking frame 6, the two ends of the connecting beam 29 are fixed at a slightly off-center position in the middle of the brush plate 30, so that the walking beam 2 is located in the center of the brush plate 30 after fixing.
[0044] In practical use, the following two structures can be used: (1) The middle part of the connecting beam 29 of the cleaning component can be directly fixed to the upper plate 23, which is only used for horizontal grids used for flat installation. This reduces the degree of freedom of the components and the vulnerable positions. The overall structure is simple and the combination is durable and reliable.
[0045] (2) A hinge plate 2724 is welded to the bottom surface of the upper plate 23. There are two hinge plates 2724. A lower plate 26 is fixed to the middle of the connecting beam 29. A hinge seat is fixed to the top surface of the lower plate 26. The hinge seat is provided with two first positioning holes 28. A hinge shaft rotatably connected to the hinge plate 2724 passes through the hinge seat. The hinge plate 2724 is provided with two second positioning holes 25. The center distance between the first positioning holes 28 and the second positioning holes 25 corresponds to the center distance of the hinge shaft. The two first positioning holes 28 and the two second positioning holes 25 are distributed at right angles relative to the hinge shaft. Positioning pins pass through the first positioning holes 28 and the second positioning holes 25. The positioning pins can lock the swing state of the hinge seat and the cleaning component, so that the cleaning component can clean horizontally downward or laterally upright, which can cope with the grid equipment installed in different situations. It can be applied to a wider range of installation environments.
[0046] With the above structure, when a horizontal bar needs to be installed on an upright barrier, the cleaning component can be swung to one side to engage with the bar. By adjusting the height, the brush plate 30 can be positioned at the bar location. The approach position can be adjusted via the installation positions of the traveling beam 2 and the gantry frame 1. Regardless of the operating condition of the bar, both the traveling beam 2 and the traveling frame 6 are elevated, making them easy to maneuver in harsh wastewater environments.
[0047] Not limited to the optimal design in this example, a length-limited column can also be fixed to the mounting plate 14, with the cleaning components directly installed at the bottom. This also achieves the desired installation, but the column needs to be adjusted to the required height based on the site conditions. Columns of different lengths can be cut to different lengths to differentiate models. The appropriate model can be selected as needed, and the top of the column is fixed to the mounting plate 14 using fasteners. This structure is simple, low-cost, and the components are fixed with no room for flexible assembly, making it more robust and durable.
Claims
1. An automatic cleaning horizontal bar screen decontamination device, characterized in that, The device includes a traveling beam that is mounted elevated along the length of the grid. The traveling beam is equipped with a traveling frame that has a linear reciprocating stroke. The traveling frame is rotatably equipped with upper rollers, lower rollers, and side rollers. There are at least two upper rollers that cooperate with the top surface of the traveling beam, at least two lower rollers that cooperate with the bottom surface of the traveling beam, and side rollers that cooperate with the sides of the traveling beam. A downwardly extending upright member is provided below the traveling frame, and a cleaning component is provided at the bottom end of the upright member.
2. The automatic cleaning horizontal bar screen decontamination device according to claim 1, characterized in that, The top side of the traveling beam is provided with a straight groove extending in the same direction as its length. A rack extending in the same direction is fixed in the straight groove. A gear located above the traveling beam is rotatably mounted on the traveling frame. The gear is driven by a motor and meshes with the rack below.
3. The automatic cleaning horizontal bar decontamination device according to claim 1, characterized in that, Shallow grooves are provided on both sides of the traveling beam, and the inner circumferential surface of the side rollers contacts and engages with the bottom of the shallow grooves. At least two side rollers are provided on one side of the traveling frame.
4. The automatic cleaning horizontal bar decontamination device according to claim 2, characterized in that, The straight groove has inclined surfaces on both sides, and the rack is detachably installed to the bottom of the straight groove.
5. The automatic cleaning horizontal bar decontamination device according to claim 1, characterized in that, The two ends of the walking beam are respectively fixed with portal frames, which are used to install the device on both ends of the horizontal grid.
6. The automatic cleaning horizontal bar decontamination device according to claim 1, characterized in that, A mounting plate is fixed to one side or the bottom of the walking frame. A vertically extending column is fixed to the mounting plate. A cleaning component is fixed to the bottom of the column. The cleaning component includes a connecting beam that is fixedly connected to the bottom of the column in the middle. Brush plates are fixedly installed at both ends of the connecting beam. The brush plates are horizontally set and perpendicular to the walking beam. The brush plates have bristles on the bottom. The column has various models based on its length.
7. The automatic cleaning horizontal bar decontamination device according to claim 1, characterized in that, A horizontally extending mounting plate is fixed to one side of the walking frame. A U-shaped groove is provided in the middle of the mounting plate. An outer cylinder is detachably installed in the U-shaped groove. An inner cylinder that slides through the outer cylinder is telescopically fitted with it. An upper plate is fixed to the bottom of the inner cylinder. A cleaning component is fixedly installed below the upper plate. The cleaning component includes a centrally located connecting beam. Brush plates are fixedly installed at both ends of the connecting beam by fasteners. The brush plates are horizontally arranged and perpendicular to the walking beam. Brush plates have bristles on their underside.
8. The automatic cleaning horizontal bar decontamination device according to claim 1, characterized in that, A horizontally extending mounting plate is fixed to one side of the walking frame. A U-shaped groove is provided in the middle of the mounting plate, and an outer cylinder is detachably installed in the U-shaped groove. An inner cylinder, which slides and extends with the outer cylinder, passes through the outer cylinder. An upper plate is fixed to the bottom of the inner cylinder. A cleaning component is provided below the upper plate. The cleaning component includes a centrally located connecting beam. Brush plates are fixed to both ends of the connecting beam by fasteners. The brush plates are horizontally arranged and perpendicular to the walking beam. Brush plates have bristles below them. A hinge plate is welded to the bottom surface of the upper plate. A lower plate is fixed to the middle of the connecting beam. A hinge seat is fixed to the top surface of the lower plate. The hinge seat has two first positioning holes. A hinge shaft, which is rotatably connected to the hinge plate, passes through the hinge seat. The hinge plate has two second positioning holes. The center distance between the first and second positioning holes corresponds to the center distance of the hinge shaft. The two first positioning holes are distributed at right angles to the hinge shaft. The two second positioning holes are distributed at right angles to the hinge shaft. Positioning pins pass through the first and second positioning holes.
9. An automatic cleaning horizontal bar decontamination device according to claim 7 or 8, characterized in that, The U-shaped groove has vertically extending clamping plates on both sides of the groove wall. The outer cylinder and the inner cylinder are rectangular cross-sections. The side length / width of the outer cylinder is adapted to the spacing of the clamping plates. The side walls of the outer cylinder are fixed with baffles at equal intervals along their length direction. The spacing between adjacent baffles corresponds to the height of the clamping plates. The baffles on the side walls are symmetrically arranged. The maximum spacing between baffles of equal height is greater than the width of the U-shaped groove. A pin passes through the clamping plates. The two ends of the pin are threaded with large nuts. The minimum distance from the pin to the bottom of the U-shaped groove is adapted to the side length / length of the outer cylinder.
10. An automatic cleaning horizontal bar decontamination device according to claim 7 or 8, characterized in that, A strip-shaped hole is opened on one side of the outer cylinder. The bottom end of the strip-shaped hole penetrates the bottom side of the outer cylinder. The strip-shaped hole is located on the side of the outer cylinder away from the traveling frame. A screw is welded to the side wall of the inner cylinder at the position corresponding to the strip-shaped hole. The outer end of the screw penetrates the strip-shaped hole and is threadedly connected to a fastening nut.