Bridge inspection vehicle

Abstract

The application discloses a bridge maintenance vehicle, which is driven by a single motor and is supported by a three-point support structure, fundamentally solves the risk of rail clamping and rail derailment caused by the asynchronization of a double-motor system, and greatly improves operation safety. The single driving motor makes the control system more simple and light, brings economic advantages of low manufacturing cost, convenient installation and easy maintenance, avoids rail clamping and stop, ensures smooth bridge maintenance operation, and significantly improves maintenance efficiency.

Description

Technical Field

[0001] This utility model generally relates to the field of bridge maintenance equipment technology, and in particular to a bridge maintenance vehicle. Background Technology

[0002] With rapid economic development, the number of cross-river bridges is increasing, making comprehensive and multi-dimensional inspection and maintenance of these bridges, while ensuring the entire maintenance process is simple, safe, and convenient, a pressing need. Currently, there are two commonly used maintenance methods: one is to erect scaffolding for maintenance, which involves a large workload, high costs, and a long construction period, sometimes even causing traffic disruptions due to partial road closures; the other is to employ dangerous "spider-man" work, which lacks effective safety and reliability guarantees.

[0003] Therefore, researching and designing a bridge maintenance vehicle to make the entire maintenance process simple, safe, and convenient is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] This utility model provides a bridge maintenance vehicle, including: a main truss, a track assembly, a maintenance vehicle drive motor, and a pulley assembly. The main truss is located beneath the bridge, and the track assembly is installed at the bottom of the bridge. The track assembly includes a first track, a second track, and a third track arranged in parallel, with the lengths of the first track, the second track, and the third track all extending in a direction perpendicular to the length of the main truss. A pulley assembly is connected to the top of the main truss. The pulley assembly includes an active pulley structure and two driven pulley structures. The active pulley structure is driven by the maintenance vehicle drive motor. The middle track of the first track, the second track, and the third track can slide with the active pulley structure. The active pulley structure moves along the middle track, thereby causing the two outer tracks of the first track, the second track, and the third track to slide with the two driven pulley structures respectively. The driven pulley structures move along the outer tracks.

[0005] As one possible implementation, the intermediate component is an I-beam or an H-beam. The active pulley structure includes a first mounting bracket and a first drive assembly, the first drive assembly including at least one first drive wheel and at least one second drive wheel. The first and second rotating shafts are mounted on opposite sides of the first mounting bracket. The first drive wheel is mounted on the first rotating shaft, and the second drive wheel is mounted on the second rotating shaft. The first and second drive wheels are located on both sides of the web of the I-beam or the H-beam. The first drive wheel includes a first gear body and a first roller body arranged coaxially, and the second drive wheel includes a second gear body and a second roller body arranged coaxially. The first gear body and the second gear body are rotated by the maintenance vehicle drive motor, thereby the first roller body and the second roller body move on the lower flange of the I-beam or the H-beam.

[0006] As one possible implementation, the first drive group has two parallel first drive wheels and two parallel second drive wheels.

[0007] As an alternative implementation, the active pulley structure further includes an auxiliary rotating shaft mounted on the first mounting bracket. The auxiliary rotating shaft is located between two first rotating shafts or two second rotating shafts. A third gear and a fourth gear are mounted on the auxiliary rotating shaft. The third gear meshes with two first gear bodies, and the fourth gear meshes with two second gear bodies. The output shaft of the maintenance vehicle drive motor causes the auxiliary rotating shaft to rotate.

[0008] In one possible implementation, the first mounting bracket includes a first connecting plate, a second connecting plate, a first side plate, and a second side plate. The first side plate and the second side plate are located on both sides of the web of the I-beam or the H-beam, and the first connecting plate, the first side plate, the second connecting plate, and the second side plate are connected end to end in sequence. One end of the first rotating shaft is mounted on the first side plate, and the other end is mounted on the first drive wheel, with the other end not protruding from the first roller body; the second rotating shaft is mounted on the second side plate, and the other end is mounted on the second drive wheel, with the other end not protruding from the second roller body; wherein, the lowest position of the first roller body and the second roller body is higher than the highest position of the first connecting plate and the second connecting plate.

[0009] As an implementation method, at least one of the first connecting plate and the second connecting plate is provided with a first guide wheel, which contacts the web of the I-beam or the H-beam.

[0010] As an implementation method, the first connecting plate is provided with two first guide wheels, which are located on both sides of the web of the I-beam or the H-beam; the second connecting plate is provided with two first guide wheels, which are located on both sides of the web of the I-beam or the H-beam.

[0011] As a possible implementation, at least one of the first track, the second track, and the third track is an I-beam. The lower flange of the I-beam has a first inclined support surface near the first roller body and a second inclined support surface near the second roller body. The first roller body has a first conical side surface that matches the first inclined support surface, and the second roller body has a second conical side surface that matches the second inclined support surface.

[0012] As an implementation method, the outermost of the first track, the second track, and the third track is an H-beam.

[0013] As one possible implementation, the driven pulley structure includes a second mounting bracket and a second drive group, wherein the second drive group includes at least one third drive wheel and at least one fourth drive wheel. The third and fourth rotating shafts are mounted on opposite sides of the second mounting bracket. The third drive wheel is mounted on the third rotating shaft, and the fourth drive wheel is mounted on the fourth rotating shaft. The third and fourth drive wheels are located on both sides of the web of the H-beam, and the third and fourth drive wheels are in contact with the lower flange of the H-beam.

[0014] The above-mentioned solution, through a single-motor drive and a three-point support structure, fundamentally solves the risks of rail jamming and derailment caused by the asynchrony of dual-motor systems, significantly improving operational safety. The single drive motor makes the control system simpler and lighter, resulting in economic advantages such as lower manufacturing costs, convenient installation, and easy maintenance. It also avoids rail jamming and ensures smooth bridge maintenance operations, significantly improving maintenance efficiency. Attached Figure Description

[0015] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A schematic diagram of the structure of the bridge maintenance vehicle provided in this embodiment of the utility model; Figure 2 for Figure 1 A magnified view of a portion of the image; Figure 3 A schematic diagram of the active pulley structure provided in an embodiment of this utility model; Figure 4 An exploded view of the active pulley structure provided in an embodiment of this utility model; Figure 5 This is a front view of the active pulley structure provided in an embodiment of the present utility model; Figure 6 A schematic diagram of the driven pulley structure provided in an embodiment of this utility model; Bridge maintenance vehicle 10, main truss 11, track assembly 12, first track 121, first inclined support surface 1211, second inclined support surface 1212, second track 122, third track 123; Active pulley structure 13, first mounting bracket 131, first side plate 1311, second side plate 1312, first connecting plate 1313, second connecting plate 1314; First drive group 132, first drive wheel 1321, first gear body 13211, first roller body 13212, second drive wheel 1322, second gear body 13221, second roller body 13222, first conical side surface A, second conical side surface B; Auxiliary rotating shaft 133, third gear 134, fourth gear 135, first guide wheel 136; Driven pulley structure 14, second mounting bracket 141, second drive group 142, third drive wheel 1421, fourth drive wheel 1422, second guide wheel 143; Bridge 20. Detailed Implementation

[0016] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the relevant utility model and not intended to limit the scope of the utility model. Furthermore, it should be noted that, for ease of description, only the parts relevant to the utility model are shown in the accompanying drawings.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] With rapid economic development, the number of cross-river bridges is constantly increasing. Therefore, comprehensive and multi-dimensional inspection and maintenance of these bridges, while ensuring that the maintenance process is simple, safe, and convenient, has become an urgent priority. Currently, there are two commonly used maintenance methods: one is to erect scaffolding for maintenance, which involves a large amount of work, high costs, and a long construction period, and can severely disrupt traffic when sections of the road are closed; the other is to use "spider-men" (high-speed, manual laborers) for risky operations, the safety and reliability of which cannot be effectively guaranteed.

[0019] Therefore, researching and designing a bridge maintenance vehicle that can simplify, ensure safety and convenience has become a technical problem that urgently needs to be solved by those skilled in the art.

[0020] In related technologies, bridge maintenance vehicles are mostly of the under-mounted double-track, double-motor structure. However, in practical applications, unbalanced power supply voltage and external resistance factors such as wind can cause the maintenance vehicle to gradually accumulate running errors on the left and right sides, resulting in asynchronous running. This can lead to minor issues such as jamming the running mechanism and affecting maintenance efficiency, or even derailment and serious safety accidents.

[0021] To address this issue, this application proposes a novel bridge maintenance vehicle 10. This vehicle employs a design with a centrally located mobile drive crane. During movement, the motor is activated, causing the vehicle to travel along the tracks on both sides. This effectively avoids the problem of asynchronous control between the two motors, thus preventing track jamming. The maintenance vehicle uses a three-point support structure, making it lighter, less expensive to manufacture, and easier to install.

[0022] In detail, such as Figure 1 and Figure 2 As shown, the bridge maintenance vehicle 10 includes a main truss 11, a track assembly 12, a pulley assembly, and a maintenance vehicle drive motor. The main truss 11 is located below the bridge 20 and includes a main beam and guardrails on both sides of the main beam. The length extension direction of the main beam is consistent with the length extension direction of the guardrails. A step can be installed on the top of the main beam. The surface of the step has friction texture to facilitate the walking of operators or the movement of the vehicle.

[0023] The track assembly 12 is used for installation at the bottom of the bridge 20. The track assembly 12 includes a first track 121, a second track 122, and a third track 123 arranged in parallel. The lengths of the first track 121, the second track 122, and the third track 123 all extend in a direction perpendicular to the length of the main truss 11, that is, the lengths of the first track 121, the second track 122, and the third track 123 all extend in a direction perpendicular to the length of the main beam. The track material can be I-beams, H-beams, etc.

[0024] The maintenance vehicle drive motor is the only drive motor and the sole drive source for the bridge maintenance vehicle 10.

[0025] The pulley assembly is connected to the top of the main truss 11. The pulley assembly includes a driving pulley structure 13 and two driven pulley structures 14. The driving pulley structure 13 is driven by the maintenance vehicle's drive motor. The middle track of the first track 121, second track 122, and third track 123 can slide along the driving pulley structure 13, causing the driving pulley structure 13 to move along the middle track. This, in turn, causes the two outer tracks of the first track 121, second track 122, and third track 123 to slide along the two driven pulley structures 14, causing the driven pulley structures 14 to move along the outer tracks.

[0026] In practical applications, the maintenance vehicle drive motor works in conjunction with the active pulley structure 13. The maintenance vehicle drive motor causes the active pulley structure 13 to move along the middle track, that is, the main truss 11 moves along the length of the track in the middle position, thereby driving the driven pulley structure 14 to slide along the track in the outer position, realizing the overall movement of the main truss 11.

[0027] In summary, this application, through a single-motor drive and a three-point support structure, fundamentally solves the risks of rail jamming and derailment caused by asynchronous operation in dual-motor systems, significantly improving operational safety. The single drive motor makes the control system simpler and lighter, resulting in economic advantages such as lower manufacturing costs, convenient installation, and easy maintenance. It also avoids rail jamming and ensures smooth bridge maintenance operations, significantly improving maintenance efficiency.

[0028] The active pulley structure 13 includes a first mounting bracket 131 and a first drive group 132. The first drive group 132 includes at least one first drive wheel 1321 and at least one second drive wheel 1322.

[0029] The first and second rotating shafts are mounted on opposite sides of the first mounting bracket 131. The first drive wheel 1321 is mounted on the first rotating shaft, and the second drive wheel 1322 is mounted on the second rotating shaft. The first drive wheel 1321 and the second drive wheel 1322 are located on both sides of the web of the I-beam or H-beam.

[0030] The first drive wheel 1321 includes a first gear body 13211 and a first roller body 13212 arranged coaxially. The second drive wheel 1322 includes a second gear body 13221 and a second roller body 13222 arranged coaxially. The first gear body 13211 and the second gear body 13221 are rotated by the maintenance vehicle drive motor, so that the first roller body 13212 and the second roller body 13222 move on the lower flange of the I-beam or H-beam.

[0031] In a specific embodiment, such as Figures 3-5 As shown, the first mounting bracket 131 includes a first connecting plate 1313, a second connecting plate 1314, a first side plate 1311, and a second side plate 1312. The first side plate 1311 and the second side plate 1312 are located on both sides of the web of the I-beam or H-beam. The first connecting plate 1313, the first side plate 1311, the second connecting plate 1314, and the second side plate 1312 are connected end to end to form a frame structure. The thickness direction of the first side plate 1311 and the second side plate 1312 is perpendicular to the thickness direction of the first connecting plate 1313 and the second connecting plate 1314.

[0032] The first drive group 132 is provided with two parallel first drive wheels 1321 and two parallel second drive wheels 1322. The parallel direction of the first drive wheels 1321 is parallel to the length direction of the I-beam or H-beam, and the parallel direction of the second drive wheels 1322 is parallel to the length direction of the I-beam or H-beam.

[0033] One end of the first rotating shaft is mounted on the first side plate 1311, and the other end is mounted on the first drive wheel 1321. The first gear body 13211 is close to the first side plate 1311, and the first roller body 13212 is close to the web of the I-beam or H-beam. The other end of the first rotating shaft does not protrude from the first roller body 13212. The second rotating shaft is mounted on the second side plate 1312, and the other end is mounted on the second drive wheel 1322. The second gear body 13221 is close to the second side plate 1312, and the second roller body 13222 is close to the web of the I-beam or H-beam. The other end of the second rotating shaft does not protrude from the second roller body 13222. This design prevents the ends of the first and second rotating shafts from scraping against the web during movement, improving safety.

[0034] It should be noted that the lowest point of the first roller body 13212 and the second roller body 13222 is higher than the highest point of the first connecting plate 1313 and the second connecting plate 1314. This design ensures that the first mounting bracket 131 will not interfere with the I-beam or H-beam.

[0035] like Figure 4 As shown, the active pulley structure 13 also includes an auxiliary rotating shaft 133 mounted on the first mounting bracket 131, located between two first rotating shafts or two second rotating shafts. A third gear 134 and a fourth gear 135 are mounted on the auxiliary rotating shaft 133. The third gear 134 meshes with two first gear bodies 13211, and the fourth gear 135 meshes with two second gear bodies 13221. The output shaft of the maintenance vehicle drive motor causes the auxiliary rotating shaft 133 to rotate, thereby rotating the third gear 134 and the fourth gear 135. The third gear 134 then drives the two first drive wheels 1321 to rotate, and the fourth gear 135 drives the two second drive wheels 1322 to rotate. In this way, the first roller bodies 13212 and the second roller bodies 13222 move on the lower flange of the I-beam or H-beam, realizing the movement of the active pulley structure 13 along the I-beam or H-beam.

[0036] Therefore, the active pulley structure 13 contacts the I-beam or H-beam at four driving points through two first drive wheels 1321 and two second drive wheels 1322. This multi-point drive design significantly increases the effective driving force, ensuring that the maintenance vehicle can operate smoothly and reliably even in the presence of wind resistance or slight inclines.

[0037] Furthermore, at least one of the first connecting plate 1313 and the second connecting plate 1314 is provided with a first guide wheel 136, which contacts the web of the I-beam or H-beam.

[0038] In a specific embodiment, such as Figure 3 and Figure 4 As shown, the first connecting plate 1313 is provided with two first guide wheels 136, which are arranged perpendicular to the web of the I-beam or H-beam and located on both sides of the web of the I-beam or H-beam; the second connecting plate 1314 is provided with two first guide wheels 136, and two second guide wheels 143 are arranged perpendicular to the web of the I-beam or H-beam and located on both sides of the web of the I-beam or H-beam. This effectively counteracts lateral forces, ensuring that the active pulley structure 13 always travels along the centerline of the I-beam or H-beam without lateral deviation, thus preventing the first roller body 13212 and the second roller body 13222 from scraping or jamming with the I-beam or H-beam.

[0039] Furthermore, such as Figure 5 As shown, at least one of the first track 121, the second track 122, and the third track 123 is an I-beam. The lower flange of the I-beam has a first inclined support surface 1211 near the first roller body 13212 and a second inclined support surface 1212 near the second roller body 13222. The first roller body 13212 has a first conical side surface A that matches the first inclined support surface 1211, and the second roller body 13222 has a second conical side surface B that matches the second inclined support surface 1212.

[0040] The conical sides of the first drive wheel 1321 and the second drive wheel 1322 can maintain continuous and stable contact with the inclined support surface of the lower flange of the I-beam, preventing slippage due to insufficient contact. This allows the driving force of the maintenance vehicle's drive motor to be converted into forward thrust most effectively, contributing to the stable movement of the active pulley structure 13 along the I-beam or H-beam. Simultaneously, it effectively counteracts lateral offset, ensuring that the active pulley structure 13 always travels along the centerline of the I-beam or H-beam.

[0041] Optionally, the outermost of the first track 121, the second track 122, and the third track 123 is an H-beam.

[0042] The first track 121, the second track 122, and the third track 123 are arranged sequentially along the length of the main truss 11. The first track 121 and the third track 123 are H-beams. The driven pulley structure 14 is in sliding engagement with the first track 121 or the third track 123.

[0043] like Figure 6 As shown, the driven pulley structure 14 includes a second mounting bracket 141 and a second drive assembly 142. The second mounting bracket 141 is identical to the first mounting bracket 131. The second drive assembly 142 includes at least one third drive wheel 1421 and at least one fourth drive wheel 1422. A third shaft and a fourth shaft are mounted on opposite sides of the second mounting bracket 141. The third drive wheel 1421 is mounted on the third shaft, and the fourth drive wheel 1422 is mounted on the fourth shaft. The third drive wheel 1421 and the fourth drive wheel 1422 are located on both sides of the web of the H-beam. The third drive wheel 1421 and the fourth drive wheel 1422 are in contact with the lower flange of the H-beam.

[0044] In addition, the driven pulley structure 14 also includes a second guide wheel 143. The mounting structure of the second guide wheel 143 on the second mounting bracket 141 is the same as the mounting structure of the first guide wheel 136 on the first mounting bracket 131, so it will not be described again.

[0045] It should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used above to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "frame" and "layout" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "frame" or "layout" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0046] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the utility model involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A bridge maintenance vehicle (10) characterized by, include: The main truss (11) is located below the bridge (20); A track assembly (12) is used for installation at the bottom of the bridge (20). The track assembly (12) includes a first track (121), a second track (122), and a third track (123) arranged in parallel. The lengths of the first track (121), the second track (122), and the third track (123) all extend in a direction perpendicular to the length of the main truss (11). Repair vehicle drive motor; A pulley assembly is connected to the top of the main truss (11). The pulley assembly includes an active pulley structure (13) and two driven pulley structures (14). The active pulley structure (13) is driven by the maintenance vehicle drive motor. The middle one of the first track (121), the second track (122), and the third track (123) can slide with the active pulley structure (13). The active pulley structure (13) moves along the middle one, thereby driving the two outer ones of the first track (121), the second track (122), and the third track (123) to slide with the two driven pulley structures (14) respectively. The driven pulley structures (14) move along the outer ones.

2. The bridge maintenance vehicle (10) according to claim 1, characterized in that, The intermediate component is either an I-beam or an H-beam. The active pulley structure (13) includes a first mounting bracket (131) and a first drive group (132), wherein the first drive group (132) includes at least one first drive wheel (1321) and at least one second drive wheel (1322). The first and second rotating shafts are mounted on opposite sides of the first mounting bracket (131), the first drive wheel (1321) is mounted on the first rotating shaft, and the second drive wheel (1322) is mounted on the second rotating shaft. The first drive wheel (1321) and the second drive wheel (1322) are located on both sides of the web of the I-beam or the H-beam. The first drive wheel (1321) includes a first gear body (13211) and a first roller body (13212) arranged coaxially. The second drive wheel (1322) includes a second gear body (13221) and a second roller body (13222) arranged coaxially. The first gear body (13211) and the second gear body (13221) are rotated by the maintenance vehicle drive motor, so that the first roller body (13212) and the second roller body (13222) move on the lower flange of the I-beam or the H-beam.

3. The bridge maintenance vehicle (10) according to claim 2, characterized in that The first drive group (132) is provided with two parallel first drive wheels (1321) and two parallel second drive wheels (1322).

4. The bridge maintenance vehicle (10) according to claim 3, characterized in that The active pulley structure (13) also includes an auxiliary rotating shaft (133) mounted on the first mounting bracket (131). The auxiliary shaft (133) is located between the two first shafts or the second shafts. A third gear (134) and a fourth gear (135) are mounted on the auxiliary shaft (133). The third gear (134) meshes with the two first gear bodies (13211), and the fourth gear (135) meshes with the two second gear bodies (13221). The output shaft of the maintenance vehicle drive motor causes the auxiliary rotating shaft (133) to rotate.

5. The bridge maintenance vehicle (10) according to claim 2, characterized in that The first mounting bracket (131) includes a first connecting plate (1313), a second connecting plate (1314), a first side plate (1311), and a second side plate (1312). The first side plate (1311) and the second side plate (1312) are located on both sides of the web of the I-beam or the H-beam. The first connecting plate (1313), the first side plate (1311), the second connecting plate (1314), and the second side plate (1312) are connected end to end in sequence. One end of the first rotating shaft is mounted on the first side plate (1311), and the other end is mounted on the first drive wheel (1321), and the other end does not protrude from the first roller body (13212); the second rotating shaft is mounted on the second side plate (1312), and the other end is mounted on the second drive wheel (1322), and the other end does not protrude from the second roller body (13222). The lowest position of the first roller body (13212) and the second roller body (13222) is higher than the highest position of the first connecting plate (1313) and the second connecting plate (1314).

6. The bridge maintenance vehicle (10) according to claim 5, characterized in that At least one of the first connecting plate (1313) and the second connecting plate (1314) is provided with a first guide wheel (136), and the first guide wheel (136) contacts the web of the I-beam or the H-beam.

7. The bridge maintenance vehicle (10) according to claim 6, characterized in that The first connecting plate (1313) is provided with two first guide wheels (136), which are located on both sides of the web of the I-beam or the H-beam; The second connecting plate (1314) is provided with two first guide wheels (136), which are located on both sides of the web of the I-beam or the H-beam.

8. The bridge maintenance vehicle (10) according to any one of claims 2-7, characterized in that, At least one of the first track (121), the second track (122), and the third track (123) is an I-beam. The lower flange of the I-beam has a first inclined support surface (1211) near the first roller body (13212) and a second inclined support surface (1212) near the second roller body (13222). The first roller body (13212) is provided with a first conical side surface (A) that matches the first inclined support surface (1211), and the second roller body (13222) is provided with a second conical side surface (B) that matches the second inclined support surface (1212).

9. The bridge maintenance vehicle (10) according to claim 8, characterized in that The outermost of the first track (121), the second track (122) and the third track (123) is an H-beam.

10. The bridge maintenance vehicle (10) according to claim 9, characterized in that The driven pulley structure (14) includes a second mounting bracket (141) and a second drive group (142), the second drive group (142) including at least one third drive wheel (1421) and at least one fourth drive wheel (1422). The third and fourth rotating shafts are mounted on opposite sides of the second mounting bracket (141), the third drive wheel (1421) is mounted on the third rotating shaft, the fourth drive wheel (1422) is mounted on the fourth rotating shaft, and the third drive wheel (1421) and the fourth drive wheel (1422) are located on both sides of the web of the H-beam. The third drive wheel (1421) and the fourth drive wheel (1422) are in contact with the lower wing plate of the H-beam.

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