Bridge erecting machine

Abstract

The utility model relates to the technical field of hoisting, in particular to a bridge girder erection machine which comprises a plurality of supporting legs and an upper layer mechanism arranged at the tops of the supporting legs, moving mechanisms are arranged at the bottoms of the supporting legs, the bridge girder erection machine further comprises a deviation rectifying mechanism, and the deviation rectifying mechanism comprises a speed measuring unit and a control unit. Each moving mechanism is provided with the speed measuring unit, and the speed measuring unit is used for detecting the moving speed of the corresponding moving mechanism; the control unit is in signal connection with each moving mechanism and each speed measuring unit. The moving speed of the moving mechanism is measured through the speed measuring unit, the moving stroke of each supporting leg is determined through the control unit according to the measured moving speed of the moving mechanism, the supporting legs can tend to move synchronously, the possibility of deflection of the whole upper-layer frame body is reduced, and the stability of hoisting operation of the bridge girder erection machine is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of hoisting construction, and particularly relates to a bridge erecting machine. Background Art

[0002] Existing bridge erecting machines are provided with multiple legs transversely, and a moving mechanism is arranged at the bottom of each leg, which can drive each leg to move longitudinally. The upper mechanism for suspension in the bridge erecting machine is arranged on the top of the legs, and can drive the upper mechanism to move longitudinally by synchronously moving all the legs, so as to transport the suspended components.

[0003] Among them, each leg in the bridge erecting machine can usually move transversely, thereby realizing the crawling of the bridge erecting machine (i.e., the advancing mode in which multiple legs advance alternately to drive the whole bridge erecting machine forward). Based on this, the transverse spacing between each leg may vary greatly under different working conditions; in hoisting operations, according to the different transverse positions of each leg and the suspended components, the pressures received by different legs are correspondingly different, which may lead to the phenomenon that the moving speeds of the moving mechanisms are not synchronized, and may cause a certain degree of yaw of the upper frame body as a whole, affecting the hoisting operation of the bridge erecting machine. Summary of the Utility Model

[0004] The purpose of the utility model is to overcome the technical problem in the prior art that the moving speeds of the moving mechanisms may not be synchronized, resulting in a certain degree of yaw of the upper frame body as a whole and affecting the hoisting operation of the bridge erecting machine, and to provide a bridge erecting machine.

[0005] The utility model provides a bridge erecting machine, which includes multiple legs and an upper mechanism arranged on the tops of the multiple legs. A moving mechanism is arranged at the bottom of each leg, and a deviation correction mechanism is further included. The deviation correction mechanism includes a speed measurement unit and a control unit; each moving mechanism is provided with the speed measurement unit, and the speed measurement unit is used to detect the moving speed of the corresponding moving mechanism; the control unit is respectively connected to each moving mechanism and each speed measurement unit in a signal connection.

[0006] Preferably, the moving mechanism includes a wheel box and a track; the track extends longitudinally along the bridge erecting machine; the wheel box includes a box body and a wheel body, the box body is connected to the leg, the wheel body is rotatably connected to the box body and is driven by a power device to rotate, and the wheel body cooperates with the track.

[0007] Preferably, the speed measurement unit is a modular device.

[0008] Preferably, the speed measurement unit includes a first gear, a second gear, and a speed measurement shaft; the first gear is coaxially connected to the wheel body; the second gear is coaxially connected to one end of the speed measurement shaft, the second gear meshes with the first gear, the speed measurement shaft is rotationally fitted relative to the box body, and the other end of the speed measurement shaft is exposed outside the box body for measuring the rotational speed of the shaft end of the speed measurement shaft.

[0009] Preferably, the speed measurement unit further includes a housing, a first bearing, a spacer sleeve, a second bearing, a shaft retaining ring, and a hole retaining ring; one side of the housing is located inside the box body and has a first limiting protrusion protruding inward, the other side of the housing is located outside the box body and has a second limiting protrusion protruding outward, and the second limiting protrusion abuts against the outer surface of the box body; the speed measurement shaft has a third limiting protrusion, the shaft retaining ring is arranged on the speed measurement shaft, the first bearing, the spacer sleeve, and the second bearing are sequentially sleeved on the speed measurement shaft and are limited between the third limiting protrusion and the shaft retaining ring; the hole retaining ring is arranged inside the housing, and the first bearing, the spacer sleeve, and the second bearing are limited between the first limiting protrusion and the hole retaining ring.

[0010] Preferably, the first gear and the wheel body are connected by bolts.

[0011] Preferably, the control unit includes a total control mechanism and a plurality of frequency converters. The total control mechanism is signal-connected to the frequency converters. The frequency converters correspond to the power devices one by one, and the frequency converters are used to control the output power of the corresponding power devices.

[0012] Preferably, the number of the legs is three, and the three legs are arranged side by side along the transverse direction of the bridge erecting machine.

[0013] Preferably, the wheel box provided at the bottom of the middle leg has four wheel bodies. The four wheel bodies are grouped in pairs, and the two wheel bodies in each group are simultaneously engaged with one track; the wheel boxes provided at the bottoms of the two legs on both sides each have two wheel bodies, and the two wheel bodies are simultaneously engaged with one track.

[0014] Preferably, the same traveling speed reducer and the same power device are respectively arranged in all the wheel boxes.

[0015] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0016] 1. A bridge erecting machine provided by the present utility model measures the moving speed of a moving mechanism through a speed measuring unit, and determines the moving stroke of each leg through a control unit according to the measured moving speed of the moving mechanism; thus, when the moving speed of a certain moving mechanism is too fast and the difference between the stroke of the corresponding leg and the strokes of other legs reaches a specified value, the moving speed of this moving mechanism is slowed down, so that each leg tends to move synchronously, reducing the possibility of the overall upper frame body swaying and improving the stability of the hoisting operation of the bridge erecting machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic longitudinal structure diagram of Embodiment 1 of the present utility model.

[0018] Figure 2 It is a schematic transverse diagram of the first leg of Embodiment 1 of the present utility model.

[0019] Figure 3 It is a schematic longitudinal diagram of the first leg of Embodiment 1 of the present utility model.

[0020] Figure 4 It is a schematic transverse diagram of the second leg of Embodiment 1 of the present utility model.

[0021] Figure 5 It is a schematic longitudinal diagram of the second leg of Embodiment 1 of the present utility model.

[0022] Figure 6 It is a schematic transverse diagram of the third leg of Embodiment 1 of the present utility model.

[0023] Figure 7 It is a schematic longitudinal diagram of the third leg of Embodiment 1 of the present utility model.

[0024] Figure 8 It is a schematic transverse diagram of the wheel box of Embodiment 1 of the present utility model.

[0025] Figure 9 It is a schematic longitudinal diagram of the wheel box of Embodiment 1 of the present utility model.

[0026] Figure 10 It is a schematic longitudinal diagram of the speed measuring unit of Embodiment 1 of the present utility model.

[0027] Reference signs in the figures:

[0028] 1 - Upper mechanism; 11 - Cross beam; 12 - Hoisting mechanism; 2 - Leg; 21 - First leg; 22 - Second leg; 23 - Third leg; 24 - Wheel box; 241 - Box body; 242 - Wheel body; 243 - Double - track four - wheel box; 244 - Single - track double - wheel box; 25 - Speed - measuring unit; 251 - First gear; 252 - Second gear; 253 - Speed - measuring shaft; 2531 - Third limit projection; 254 - Housing; 2541 - First limit projection; 2542 - Second limit projection; 255 - First bearing; 256 - Sleeve; 257 - Second bearing; 258 - Shaft retaining ring; 259 - Hole retaining ring; 26 - Track. Detailed implementation mode

[0029] The following further describes the present utility model in detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the above - mentioned subject matter of the present utility model to the following embodiments. All technologies implemented based on the content of the present utility model belong to the scope of the present utility model.

[0030] In the description of the specific embodiments of the present utility model, without special explanation, the expression terms of orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product / device / equipment of this utility model is commonly used and placed. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present utility model or simplifying the description in specific embodiments, facilitating technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation or be constructed and operated in a specific positional relationship. Therefore, it should not be understood as a limitation to the present utility model.

[0031] In addition, for terms such as "horizontal", "vertical", "hanging", "parallel", etc., it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present utility model.

[0032] In addition, the expressions such as "first", "second", "third", etc. in the terms are only used to distinguish the descriptions of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0033] In addition, in the description of the embodiments of the present utility model, "several", "multiple", and "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., and even can be a situation exceeding 9.

[0034] In addition, in the description of the technical solution of the present utility model, unless otherwise clearly specified / defined / restricted, where the terms "set", "installed", "connected", "connected", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be connection means commonly used in the art such as welding, riveting, bolting, and threaded connection. Such a connection can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0035] Embodiment 1

[0036] As Figure 1 shown, a bridge erecting machine includes a plurality of legs 2 and an upper mechanism 1 provided on the tops of the plurality of legs 2. Among them, the upper mechanism 1 may include a cross beam 11 and a hoisting mechanism 12: the cross beam 11 extends along the transverse direction of the bridge erecting machine, and the plurality of legs 2 are spaced apart along the transverse direction of the bridge erecting machine and support the cross beam 11. The cross beam 11 is movably connected to at least some of the legs 2 so that the cross beam 11 and some of the legs 2 can move relative to each other along the transverse direction of the bridge erecting machine. For example, as Figure 1 shown, the rightmost leg 2 is fixedly connected to the cross beam 11, and the two left legs 2 are respectively movably connected to the cross beam 11; the hoisting mechanism 12 is provided on the top of the cross beam 11, and the hoisting part of the hoisting mechanism 12 can move relative to the cross beam 11 along the longitudinal and transverse directions of the bridge erecting machine.

[0037] A moving mechanism is provided at the bottom of the leg 2 for driving the leg 2 and the entire upper mechanism 1 to move along the longitudinal direction of the bridge erecting machine.

[0038] On this basis, the bridge erecting machine further includes a deviation correction mechanism. The deviation correction mechanism includes a control unit and a plurality of speed measurement units 25; each of the moving mechanisms is provided with the speed measurement unit 25, and the speed measurement unit 25 is used to detect the moving speed of the corresponding moving mechanism; the control unit is respectively signal-connected to each of the moving mechanisms and each speed measurement unit 25.

[0039] Among them, the moving speed of the moving mechanism is measured by the speed measurement unit 25, and the control unit determines the travel of each outrigger 2 according to the measured moving speed of the moving mechanism; thus, when the moving speed of a certain moving mechanism is too fast and the difference between the travel of the corresponding outrigger 2 and the travel of other outriggers 2 reaches a specified value, the moving speed of this moving mechanism is reduced, so that each outrigger 2 tends to move synchronously, reducing the possibility of the overall upper frame body swaying and improving the stability of the erection crane's hoisting operation.

[0040] It should be noted that the determination of the travel of an object based on the speed of the object and the adjustment of the speed of the corresponding object based on the travel difference of multiple objects are prior arts and do not involve the improvement of the program.

[0041] The moving mechanism can be a roller directly arranged at the bottom of the support foot and driven by a power device to rotate, or a matching mechanism of the wheel box 24 and the track 26.

[0042] In one or more embodiments, the moving mechanism includes a wheel box 24 and a track 26; wherein, the track 26 extends along the longitudinal direction of the erection crane (i.e., the direction perpendicular to the cross beam 11); the wheel box 24 is as Figures 8 - 9 shown, including a box body 241 and a wheel body 242, the box body 241 is connected to the outrigger 2, the wheel body 242 is rotatably connected to the box body 241 and is driven by a power device to rotate, and the wheel body 242 cooperates with the track 26.

[0043] Through the cooperation of the wheel body 242 and the track 26, the stability of the moving mechanism during movement is improved, the skew of the moving mechanism during movement is reduced, and further the possibility of the overall upper frame body swaying is reduced, improving the stability of the erection crane's hoisting operation.

[0044] For the speed measurement unit 25, it is preferably a modular device, which is convenient for replacement and maintenance, so as to improve the measurement accuracy, keep the deviation correction ability of the deviation correction mechanism accurate, further reduce the possibility of the overall upper frame body swaying, and improve the stability of the erection crane's hoisting operation.

[0045] Among them, the wheel body 242 is rotatably connected to the box body 241 of the wheel box 24 through a connecting shaft. Considering that in some wheel boxes 24, the connecting shaft is fixedly connected to the box body 241 of the wheel box 24 and is rotatably connected to the wheel body 242, it may not be possible to directly judge the rotation speed of the wheel body 242 by measuring the rotation speed of the connecting shaft.

[0046] For the speed measurement unit 25, in one or more embodiments, as Figure 10As shown, the speed measuring unit 25 may include a first gear 251, a second gear 252, and a speed measuring shaft 253; the first gear 251 is coaxially connected to the wheel body 242; the second gear 252 is coaxially connected to one end of the speed measuring shaft 253, the second gear 252 is meshed with the first gear 251, and the speed measuring shaft 253 rotates relative to the box body 241, thereby, the speed measuring shaft 253 and the wheel body 242 are connected by the first gear 251 and the second gear 252, and the rotation speed of the wheel body 242 can be calculated by the rotation speed of the speed measuring shaft 253.

[0047] On this basis, the other end of the speed measuring shaft 253 can be exposed outside the box body 241, so as to facilitate the measurement of the rotational speed of the shaft end of the speed measuring shaft 253 at the end of the speed measuring shaft 253 exposed outside.

[0048] By exposing the end of the speed measuring shaft 253 outside the housing 241, it is convenient to set up a speed measuring device (not shown in the figure) outside the housing 241 for obtaining the rotation speed of the shaft end of the speed measuring shaft 253. At the same time, when there is a problem with the measurement data, it is convenient to roughly judge the cause of the problem by observing the rotation of the exposed end of the speed measuring shaft 253, that is, whether it is a problem caused by a transmission failure between the speed measuring shaft 253 and the wheel body 242, or a problem caused by a failure of the speed measuring device, and it is convenient to complete the replacement of the speed measuring device as soon as possible when the speed measuring device fails.

[0049] Among them, the method and equipment for obtaining the rotation speed of the shaft end are existing technologies and will not be described in detail.

[0050] On this basis, if Figure 10 As shown, the speed measuring unit 25 may further include a housing 254 , a first bearing 255 , a spacer sleeve 256 , a second bearing 257 , a shaft retaining ring 258 and a hole retaining ring 259 .

[0051] The housing 241 is provided with a through hole for the housing 254 to pass through. Both sides of the housing 254 have openings for the speed measuring shaft 253 to pass through, and the first bearing 255, the spacer 256, the second bearing 257, the shaft retaining ring 258 and the hole retaining ring 259 can be put into the housing 254 from the openings. By moving the housing 254, the speed measuring shaft 253, the second gear 252, the first bearing 255, the spacer 256, the second bearing 257, the shaft retaining ring 258 and the hole retaining ring 259 can be driven to escape from the through hole, so that when a transmission failure occurs between the speed measuring shaft 253 and the wheel body 242, other components of the speed measuring unit 25 except the first gear 251 can be directly extracted and replaced in time.

[0052] One side of the housing 254 passes through the through-hole and is located inside the box body 241, and the opening of this side has a first limiting bump 2541 protruding inwards. The other side of the housing 254 does not pass through the through-hole and is located outside the box body 241, and has a second limiting bump 2542 protruding outwards. The second limiting bump 2542 abuts against the outer surface of the box body 241. At this time, the first gear 251 meshes with the second gear 252. At this time, for the fixation between the housing 254 and the box body 241, it can be bonded by colloid, or spot welding can be performed at multiple points where the housing 254 and the box body 241 meet.

[0053] One end of the speed measurement shaft 253 close to the second gear 252 has a third limiting bump 2531 protruding outwards. The shaft retaining ring 258 is arranged on the speed measurement shaft 253. The first bearing 255, the spacer sleeve 256 and the second bearing 257 are sequentially sleeved on the speed measurement shaft 253 and are limited between the third limiting bump 2531 and the shaft retaining ring 258. The hole retaining ring 259 is arranged inside the housing 254. The first bearing 255, the spacer sleeve 256 and the second bearing 257 are limited between the first limiting bump 2541 and the hole retaining ring 259. Through the cooperation of the first limiting bump 2541 and the hole retaining ring 259, the relative positions of the housing 254, the first bearing 255, the spacer sleeve 256 and the second bearing 257 are kept stable. And through the cooperation of the third limiting bump 2531 and the shaft retaining ring 258, the relative positions of the speed measurement shaft 253, the first bearing 255, the spacer sleeve 256 and the second bearing 257 are kept stable. Thereby ensuring the stability of the relative position of the speed measurement shaft 253 inside the housing 254 and improving the stability of the meshing of the second gear 252 with the first gear 251.

[0054] The wheel body 242 is rotatably connected to the box body 241 of the wheel box 24 through a connecting shaft. When the connecting shaft is fixedly connected to the wheel body 242, the first gear 251 can be directly connected to the connecting shaft or the wheel body 242. When the connecting shaft is rotatably connected to the wheel body 242, the first gear 251 can be directly connected to the wheel body 242.

[0055] In one or more embodiments, the first gear 251 abuts against the wheel surface of one of the wheel bodies 242 in the wheel box 24, and the first gear 251 and the wheel body 242 are connected by a plurality of bolts. Thereby ensuring that the first gear 251 and the wheel body 242 rotate synchronously, so as to improve the measurement accuracy, further reduce the possibility of the overall upper frame body having yaw, and improve the stability of the hoisting operation of the bridge erecting machine.

[0056] In one or more embodiments, the control unit includes a master control mechanism and a plurality of frequency converters. The master control mechanism is signal-connected to the frequency converters. The frequency converters correspond to the power devices one by one. The frequency converters are used to control the output power of the corresponding power devices, and thus control the rotation speed of the wheel body 242.

[0057] Among them, the master control mechanism can be a computer or a single-chip microcomputer.

[0058] In one or more embodiments, the number of the outriggers 2 is three. The three outriggers 2 are arranged side by side along the transverse direction of the bridge erecting machine, as Figure 1 shown. Among them, the three outriggers 2 are, from left to right, the first outrigger 21, the second outrigger 22, and the third outrigger 23. Among them, the first outrigger 21 is as Figures 2 - 3 shown, the second outrigger 22 is as Figures 4 - 5 shown, and the third outrigger 23 is as Figures 6 - 7 shown.

[0059] Among them, the wheel box 24 provided at the bottom of the middle outrigger 2 (i.e., the second outrigger 22) can be a double-rail four-wheel box 243. The double-rail four-wheel box 243 means that the wheel box 24 has four wheel bodies 242. The four wheel bodies 242 are grouped in pairs, and the two wheel bodies 242 in each group are simultaneously engaged with one Figure 5 rail 26, as Figure 3 and Figure 7 shown; the wheel boxes 24 provided at the bottoms of the two outriggers 2 (i.e., the first outrigger 21 and the third outrigger 23) on both sides can both be single-rail double-wheel boxes 244. The single-rail double-wheel box 244 means that the wheel box 24 has two wheel bodies 242. The two wheel bodies 242 are simultaneously engaged with one

[0060] rail 26, as

[0061] Among them, the second outrigger 22 often needs to bear a relatively large pressure. Therefore, through the setting of the double-rail four-wheel box 243, the load-bearing capacity of the moving mechanism of the middle outrigger 2 can be improved; the first outrigger 21 and the third outrigger 23 need to bear relatively small pressures. Therefore, through the setting of the single-rail double-wheel box 244, the cost can be saved.

[0062] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A bridge erecting machine, comprising a plurality of outriggers (2) and an upper mechanism (1) arranged on top of the plurality of outriggers (2), wherein a moving mechanism is provided at the bottom of the outriggers (2), and is characterized in that, It also includes a rectification mechanism, and the rectification mechanism includes a speed measurement unit (25) and a control unit; Each of the moving mechanisms is provided with the speed measurement unit (25), and the speed measurement unit (25) is used to detect the moving speed of the corresponding moving mechanism; The control unit is respectively in signal connection with each of the moving mechanisms and each speed measurement unit (25).

2. A bridge erector according to claim 1, characterized in that, The moving mechanism includes a wheel box (24) and a track (26); The track (26) extends along the longitudinal direction of the bridge erecting machine; The wheel box (24) includes a box body (241) and a wheel body (242). The box body (241) is connected to the support leg (2), the wheel body (242) is rotatably connected to the box body (241), is driven to rotate by a power device, and the wheel body (242) cooperates with the track (26).

3. A bridge erecting machine according to claim 2, characterized in that, The speed measurement unit (25) is a modular device.

4. A bridge erecting machine according to any one of claims 2-3, characterized in that, The speed measurement unit (25) includes a first gear (251), a second gear (252), and a speed measurement shaft (253); The first gear (251) is coaxially connected to the wheel body (242); the second gear (252) is coaxially connected to one end of the speed measurement shaft (253), the second gear (252) meshes with the first gear (251), the speed measurement shaft (253) is rotatably fitted relative to the box body (241), and the other end of the speed measurement shaft (253) is exposed outside the box body (241) for measuring the rotational speed of the shaft end of the speed measurement shaft (253).

5. A bridge erector according to claim 4, characterized in that, The speed measurement unit (25) further includes a housing (254), a first bearing (255), a spacer sleeve (256), a second bearing (257), a shaft retaining ring (258), and a hole retaining ring (259); One side of the housing (254) is located inside the box body (241) and has a first limiting convex block (2541) protruding inward. The other side of the housing (254) is located outside the box body (241) and has a second limiting convex block (2542) protruding outward. The second limiting convex block (2542) abuts against the outer surface of the box body (241); The speed measurement shaft (253) has a third limiting convex block (2531). The shaft retaining ring (258) is arranged on the speed measurement shaft (253). The first bearing (255), the spacer sleeve (256), and the second bearing (257) are sequentially sleeved on the speed measurement shaft (253) and are limited between the third limiting convex block (2531) and the shaft retaining ring (258); The hole retaining ring (259) is arranged inside the housing (254). The first bearing (255), the spacer sleeve (256), and the second bearing (257) are limited between the first limiting convex block (2541) and the hole retaining ring (259).

6. A bridge erector according to claim 4, characterized in that, The first gear (251) and the wheel body (242) are connected by bolts.

7. A bridge erector according to claim 2, characterized in that, The control unit includes a master control mechanism and a plurality of frequency converters. The master control mechanism is in signal connection with the frequency converters. The frequency converters correspond to the power devices one by one, and the frequency converters are used to control the output power of the corresponding power devices.

8. A bridge erector according to claim 2, characterized in that, The number of the outriggers (2) is three, and the three outriggers (2) are arranged side by side along the transverse direction of the girder erecting machine.

9. A bridge erector according to claim 8, characterized in that, The wheel box (24) arranged at the bottom of the middle outrigger (2) has four wheel bodies (242). The four wheel bodies (242) are grouped in pairs, and the two wheel bodies (242) in each group are simultaneously engaged with one of the tracks (26); The wheel boxes (24) arranged at the bottoms of the two outriggers (2) on both sides each have two wheel bodies (242), and the two wheel bodies (242) are simultaneously engaged with one of the tracks (26).

10. A bridge erector according to claim 2, characterized in that, The same traveling speed reducers and the same power equipment are respectively arranged in all the wheel boxes (24).

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