Steel box girder welding device and welding method thereof

Abstract

The present application relates to the technical field of steel box girder welding, and particularly relates to a steel box girder welding device and a welding method thereof, which comprises a sliding rail table, the upper end of the sliding rail table is driven by a linear motor to have a slidingly connected sliding seat, the upper end of the sliding seat is fixedly installed with a stand column, the upper end of the stand column is fixedly installed with a guide table, the guide table is driven by a linear motor to have a slidingly connected guide seat, the front end of the guide seat is driven by a servo motor to have a rotationally connected rotating seat, the front end of the rotating seat is hingedly connected with one end of a first force arm, the other end of the first force arm is hingedly connected with one end of a second force arm, the other end of the second force arm is rotationally connected with a welding head driven by a servo motor, a steel box girder to-be-welded piece is placed below the welding head, the welding device further comprises a control mechanism and a monitoring mechanism, the control mechanism is arranged on the rotating seat, the first force arm and the second force arm, and is used for controlling the swing speed of the first force arm and the second force arm, and the monitoring mechanism is arranged in the control mechanism and is used for further reducing the swing speed.

Description

Technical Field

[0001] This invention relates to the field of steel box girder welding technology, and in particular to a steel box girder welding device and welding method. Background Technology

[0002] Steel box girders, with their core structure consisting of orthotropic plates composed of top plates, bottom plates, webs, U-shaped ribs, and transverse diaphragms, are widely used in long-span bridges. Early methods relied primarily on manual arc welding, which was inefficient and prone to quality fluctuations due to the skill of welders. Submerged arc welding gradually became more widespread, and the use of specialized welding machines and high-strength bridge steel solved the problem of efficient welding and strength matching. With the advancement of major bridge projects, robotic welding systems, BIM modeling, and finite element simulation technologies have been implemented, enabling automatic weld identification, adaptive trajectory, and precise quality control. Current mainstream processes include submerged arc welding and laser-arc hybrid welding, each adapted to different weld types. Furthermore, to address pain points such as welding deformation, confined space operations, and uncontrolled impacts, optimizations are achieved through anti-deformation tooling and collaborative robots. Technological development is progressing towards higher efficiency, intelligence, greenness, and safety.

[0003] When a robotic arm is welding a steel box girder, it may lose control and move too fast, resulting in a collision. This "runaway" phenomenon is mostly caused by servo and drive system failures (such as encoder damage, short circuit in the driver circuit, or incorrect parameter settings), control system abnormalities (such as microprocessor crashes, program overload, or unstable power supply voltage), mechanical transmission component failures (such as worn and loose joint gears or failure of limit components), as well as human operation and system configuration errors (such as incorrect setting of high-speed motion parameters or improper mode switching). After losing control, the robotic arm's speed far exceeds the normal operating speed, and it is very easy to collide with beams and other components in the complex spatial structure of the steel box girder, causing serious damage.

[0004] To address this, a steel box girder welding device and its welding method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a steel box girder welding device and welding method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a steel box girder welding device, comprising a slide rail table, a slide seat slidably connected to the upper end of the slide rail table via a linear motor, a column fixedly installed on the upper end of the slide seat, a guide table fixedly installed on the upper end of the column, a guide seat slidably connected to the guide table via a linear motor, a rotating seat rotatably connected to the front end of the guide seat via a servo motor, one end of a first lever arm hinged to the front end of the rotating seat, one end of a second lever arm hinged to the other end of the first lever arm, a welding head rotatably connected to the other end of the second lever arm via a servo motor, and a steel box girder to be welded placed below the welding head. The welding device further comprises a control mechanism and a monitoring mechanism. The control mechanism is disposed on the rotating seat, the first lever arm, and the second lever arm, and is used to control the swing speed of the first lever arm and the second lever arm. The monitoring mechanism is disposed inside the control mechanism and is used to further reduce the swing speed.

[0007] Preferably, a first servo motor is fixedly mounted on the side of the rotating base, the output shaft of the first servo motor passes through the rotating base and is fixedly connected to a first lever arm, and a second servo motor is fixedly mounted on the side of the first lever arm, the output shaft of the second servo motor passes through the first lever arm and is fixedly connected to the second lever arm.

[0008] Preferably, the control mechanism includes a flow control cylinder hinged to the middle of the outer side of the first lever arm, the flow control cylinder having a first air passage inside, one end of a control rod hinged to the outer side of the second lever arm, the other end of the control rod having the flow control cylinder inserted and a piston head threadedly connected thereto, both ends of the piston head having sealing plates fixedly installed by screws, and a first sealing ring fitted onto the middle of the outer side of the piston head.

[0009] Preferably, a floating piston is slidably connected inside the flow control cylinder, and the inside of the flow control cylinder is divided into a first chamber, a second chamber, and an air chamber by the piston head and the floating piston.

[0010] Preferably, both ends of the piston head are provided with a flow conversion chamber and a flow passage, and a flow passage is provided between the flow conversion chamber and the flow passage. The flow passage is connected to a first chamber through a first flow conversion hole, and another set of flow passages is connected to a second chamber through a second flow conversion hole. A second air passage is provided in the middle of the piston head for communication with the first air passage.

[0011] Preferably, the monitoring mechanism includes a first damping plate slidably connected to the converter chamber, one end of a first damping spring fixedly connected to the side of the first damping plate near the middle of the piston head, the other end of the first damping spring fixedly connected to the converter chamber, a second damping plate sleeved inside the first damping plate, one end of a second damping spring fixedly connected to the side of the second damping plate near the middle of the piston head, the other end of the second damping spring fixedly connected to the converter chamber, a third damping plate sleeved inside the second damping plate, one end of a third damping spring fixedly connected to the side of the third damping plate near the middle of the piston head, the other end of the third damping spring fixedly connected to the converter chamber.

[0012] Preferably, a first guide hole, a second guide hole and a third guide hole are provided on the outer side of the first damping plate, a second sealing ring is embedded in the inner wall of the first damping plate, and a sealing ring for sealing the flow passage is embedded in the inner wall of the converter chamber.

[0013] A welding method for a steel box girder welding device includes the following steps:

[0014] S1. Start the external control system, set the sliding seat and guide seat movement parameters and the speed of the first servo motor and the second servo motor according to the weld parameters of the steel box girder to be welded, then inject non-Newtonian liquid into the flow control cylinder, set the pressure gauge warning threshold and connect the alarm system.

[0015] S2. Start the welding head, and simultaneously drive the slide, guide seat and rotating seat to move in coordination according to the preset program, causing the first lever arm and the second lever arm to swing at a set speed, so as to realize the welding head moving at a constant speed along the weld seam. During this process, the swing of the first lever arm and the second lever arm will drive the control rod to push the piston head to move in the flow control cylinder. The non-Newtonian liquid flows smoothly between the first chamber and the second chamber through the flow conversion chamber, flow passage, flow cavity and the first flow conversion hole and the second flow conversion hole of the piston head, without interfering with the normal swing of the lever arm.

[0016] S3. If the first or second lever arm experiences a runaway failure during welding, the piston head will experience a sudden increase in force. Due to the limited flow capacity of the flow orifice, the flow of non-Newtonian liquid will be obstructed, directly limiting the abnormal increase in the lever arm swing speed. At the same time, the floating piston will compress the air in the air chamber to buffer the flow and prevent hard damage to the mechanism. Furthermore, when the pressure in the first or second chamber exceeds the warning threshold, the pressure gauge will promptly transmit a signal to the external system, triggering an alarm and enabling the control system to suspend the operation of the device.

[0017] S4. If a minor jerking fault occurs in the power system, causing a slight abnormal increase in the driving force of the lever arm, the pressure will overcome the restoring force of the first, second, and third damping springs, driving the first, second, and third damping plates to move step by step towards the center point of the piston head. Through the first, second, and third guide holes, the flow holes are gradually blocked, thereby achieving reverse control of the lever arm swing speed and timely warning of minor faults.

[0018] The beneficial effects of this invention are:

[0019] 1. This invention, through a control mechanism composed of a flow control cylinder, control rod, piston head, floating piston, and pressure gauge, enables precise control and fault protection of the swing speed of the first and second lever arms. During normal welding operations, the piston head drives the non-Newtonian liquid through the flow converter chamber, flow orifice, flow cavity, and the first and second flow conversion orifices in the first and second chambers, ensuring smooth flow without interfering with the normal swing of the lever arms. When a runaway fault occurs in the first or second lever arm, the piston head experiences a sudden increase in force. Due to the limited flow capacity of the flow orifice, the flow of the non-Newtonian liquid is obstructed, directly limiting the abnormal increase in the swing speed of the lever arms and preventing collision accidents caused by runaway. Simultaneously, the floating piston compresses the air in the air chamber to buffer the system and prevent hard damage to the control mechanism. Abnormal increases in pressure in the first and second chambers can be detected in time by the pressure gauge and fed back to the external system, facilitating rapid alarm issuance and enhancing the safety protection level of the device.

[0020] 2. This invention, through a monitoring mechanism composed of a first damping plate, a first damping spring, a second damping plate, a second damping spring, a third damping plate, a third damping spring, and a sealing ring, enables early warning of minor faults in the first and second lever arms and secondary speed control. When the driving force of the lever arms experiences a slight abnormal increase, the pressure overcomes the restoring force of the first, second, and third damping springs, causing the first, second, and third damping plates to move progressively towards the center point of the piston head. Through the first, second, and third guide holes, the flow holes are gradually blocked, achieving a reverse control effect where the greater the driving force, the slower the lever arm swing speed. This allows for the determination of whether there are minor faults in the power system, such as jerking, affecting speed stability, thus achieving early warning. Even if the speed exceeds a predetermined threshold, the non-Newtonian fluid can still prevent the first and second lever arms from continuing to move due to its own properties, further ensuring the operational stability and welding accuracy of the steel box girder welded joint. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a three-dimensional schematic diagram of a steel box girder welding device and welding method according to an embodiment of the present invention;

[0023] Figure 2 This is a partial three-dimensional schematic diagram of a steel box girder welding device and welding method according to an embodiment of the present invention;

[0024] Figure 3This is a cross-sectional schematic diagram of the monitoring mechanism of a steel box girder welding device and welding method according to an embodiment of the present invention;

[0025] Figure 4 This invention relates to a steel box girder welding device and welding method. Figure 3 Enlarged view of point A in the middle;

[0026] Figure 5 This is a three-dimensional schematic diagram of the piston head of a steel box girder welding device and welding method according to an embodiment of the present invention;

[0027] Figure 6 This is a three-dimensional schematic diagram of the first damping plate of a steel box girder welding device and welding method according to an embodiment of the present invention.

[0028] The following are marked in the diagram: 1. Slide rail; 11. Slide seat; 12. Column; 13. Guide table; 14. Guide seat; 15. Rotating seat; 16. First lever arm; 161. First servo motor; 17. Second lever arm; 171. Second servo motor; 18. Welding head; 19. Steel box girder to be welded.

[0029] 2. Control mechanism; 21. Flow control tube; 211. First chamber; 212. Second chamber; 213. Air chamber; 22. Control rod; 221. First air passage; 23. Piston head; 231. Flow converter chamber; 232. Flow passage; 233. Flow passage orifice; 234. First flow exchange orifice; 235. Second flow exchange orifice; 236. Second air passage; 24. Sealing plate; 25. First sealing ring; 26. Floating piston; 27. Pressure gauge;

[0030] 3. Monitoring mechanism; 31. First damping plate; 311. First guide hole; 312. Second guide hole; 313. Third guide hole; 314. Second sealing ring; 32. First damping spring; 33. Second damping plate; 34. Second damping spring; 35. Third damping plate; 36. Third damping spring; 37. Sealing ring. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] Please see Figures 1 to 6 This invention provides a technical solution: a steel box girder welding device, including a slide rail table 1, with a sliding seat 11 slidably connected to the upper end of the slide rail table 1 via a linear motor. A column 12 is fixedly installed on the upper end of the sliding seat 11, and a guide table 13 is fixedly installed on the upper end of the column 12. A guide seat 14 is slidably connected to the guide table 13 via a linear motor. A rotating seat 15 is rotatably connected to the front end of the guide seat 14 via a servo motor. One end of a first lever arm 16 is hinged to the front end of the rotating seat 15, and one end of a second lever arm 17 is hinged to the other end of the first lever arm 16. The other end of the second lever arm 17 is rotatably connected to a welding head 18 via a servo motor. A steel box girder is placed below the welding head 18. The box girder to be welded 19, the welding device also includes a control mechanism 2 and a monitoring mechanism 3. The control mechanism 2 is set on the rotating seat 15, the first lever arm 16 and the second lever arm 17, and is used to control the swing speed of the first lever arm 16 and the second lever arm 17. The monitoring mechanism 3 is set inside the control mechanism 2 and is used to further reduce the swing speed. A first servo motor 161 is fixedly installed on the side of the rotating seat 15. The output shaft of the first servo motor 161 passes through the rotating seat 15 and is fixedly connected to the first lever arm 16. A second servo motor 171 is fixedly installed on the side of the first lever arm 16. The output shaft of the second servo motor 171 passes through the first lever arm 16 and is fixedly connected to the second lever arm 17.

[0034] As one embodiment of the present invention, such as Figure 2 , Figure 3 and Figure 4As shown, the control mechanism 2 includes a flow control cylinder 21 hinged to the middle of the outer side of the first lever arm 16. A first air passage 221 is provided inside the flow control cylinder 21. One end of a control rod 22 is hinged to the outer side of the second lever arm 17. The other end of the control rod 22 is inserted into the flow control cylinder 21 and threadedly connected to a piston head 23. Both ends of the piston head 23 are fixedly fitted with sealing plates 24 by screws. A first sealing ring 25 is fitted onto the middle of the outer side of the piston head 23. A floating piston 26 is slidably connected inside the flow control cylinder 21. The flow control cylinder 21 is connected to the piston... The piston head 23 and the floating piston 26 are divided into a first chamber 211, a second chamber 212 and an air chamber 213. Both ends of the piston head 23 are provided with a flow-changing chamber 231 and a flow passage 232. A flow passage 233 is provided between the flow-changing chamber 231 and the flow passage 232. The flow passage 232 is connected to the first chamber 211 through a first flow-changing hole 234. Another set of flow passages 232 is connected to the second chamber 212 through a second flow-changing hole 235. A second air passage 236 is provided in the middle of the piston head 23 for communicating with the first air passage 221.

[0035] By adopting the above technical solution, firstly, since the piston head 23 can only pass through the flow passage 233, the normal swing speed of the first lever arm 16 and the second lever arm 17 is calculated so that the displacement difference caused by the flow rate of the six sets of piston heads 23 can be matched with the swing speed of the first lever arm 16 or the second lever arm 17. Then, when the first lever arm 16 or the second lever arm 17 is working normally, the first lever arm 16 or the second lever arm 17 drives the piston head 23 to move. The piston head 23 allows the non-Newtonian liquid to flow back and forth in the first chamber 211 and the second chamber 212 through the flow converter chamber 231, the flow passage 232, the flow passage 233, the first exchange passage 234, and the second exchange passage 235, without affecting the swing of the first lever arm 16 or the second lever arm 17. This causes an impact. When the first lever arm 16 or the second lever arm 17 experiences a runaway malfunction, the piston head 23 experiences increased force. Because the piston head 23 can only flow through the smaller flow hole 233, the swing speed of the first lever arm 16 or the second lever arm 17 will not increase significantly, making it easy to control. When the pressure exceeds the limit, the non-Newtonian liquid will prevent the first lever arm 16 or the second lever arm 17 from swinging, thereby avoiding a runaway collision accident. Furthermore, the floating piston 26 squeezes the air in the air chamber 213 to buffer the mechanism and prevent hard damage. Then, due to the increased pressure inside the first chamber 211 or the second chamber 212, all pressure gauges 27 promptly detect the abnormal pressure and transmit it to the external system, enabling the system to issue an alarm in a timely manner.

[0036] As one embodiment of the present invention, such as Figure 4 , Figure 5 and Figure 6As shown, the monitoring mechanism 3 includes a first damping plate 31 slidably connected within the converter chamber 231. One end of a first damping spring 32 is fixedly connected to the side of the first damping plate 31 near the center of the piston head 23. The other end of the first damping spring 32 is fixedly connected within the converter chamber 231. A second damping plate 33 is sleeved inside the first damping plate 31. One end of a second damping spring 34 is fixedly connected to the side of the second damping plate 33 near the center of the piston head 23. The other end of the second damping spring 34 is fixedly connected within the converter chamber 231. The second damping plate 33 is fitted with a third damping plate 35 inside. One end of the third damping spring 36 is fixedly connected to the side of the third damping plate 35 near the middle of the piston head 23. The other end of the third damping spring 36 is fixedly connected to the converter chamber 231. The outer side of the first damping plate 31 has a first guide hole 311, a second guide hole 312 and a third guide hole 313. The inner wall of the first damping plate 31 is inlaid with a second sealing ring 314. The inner wall of the converter chamber 231 is inlaid with a sealing ring 37 for sealing the flow hole 233.

[0037] By adopting the above technical solution, the sudden increase in pressure can first overcome the restoring force of the first damping spring 32, the second damping spring 34 and the third damping spring 36, driving the first damping plate 31, the second damping plate 33 and the third damping plate 35 to move towards the center point of the piston head 23 step by step, and exchange air with the outside through the first air passage 221 and the second air passage 236. Then, the first damping plate 31 gradually blocks the flow hole 233 through the first guide hole 311, the second guide hole 312 and the third guide hole 313, so that the greater the driving force on the first lever arm 16 or the second lever arm 17, the slower the swing speed, thereby judging whether there is a fault such as a jerking that affects the speed of the power system, timely detecting minor faults, and still being able to use non-Newtonian fluid to stop the first lever arm 16 or the second lever arm 17 from moving when the speed exceeds the limit.

[0038] A welding method for a steel box girder welding device includes the following steps:

[0039] S1. Start the external control system, set the movement parameters of slide 11 and guide 14 and the speed of first servo motor 161 and second servo motor 171 according to the weld parameters of steel box girder 19 to be welded, then inject non-Newtonian liquid into flow control cylinder 21, set the warning threshold of pressure gauge 27 and connect to alarm system.

[0040] S2. Start the welding head 18, and simultaneously drive the slide 11, guide seat 14, and rotating seat 15 to move in coordination according to the preset program. This causes the first lever arm 16 and the second lever arm 17 to swing at a set speed, so that the welding head 18 can move and weld at a uniform speed along the weld seam. During this process, the swing of the first lever arm 16 or the second lever arm 17 will drive the control rod 22 to push the piston head 23 to move in the flow control cylinder 21. The non-Newtonian liquid flows smoothly between the first chamber 211 and the second chamber 212 through the flow conversion chamber 231, flow passage 233, flow passage cavity 232, first exchange passage 234, and second exchange passage 235 of the piston head 23, without interfering with the normal swing of the lever arm.

[0041] S3. If the first lever arm 16 or the second lever arm 17 experiences a runaway failure during the welding process, the piston head 23 will experience a sudden increase in force. Due to the limited flow capacity of the flow passage 233, the flow of non-Newtonian liquid will be obstructed, directly limiting the abnormal increase in the lever arm swing speed. At the same time, the floating piston 26 will compress the air in the air chamber 213 to buffer the mechanism and avoid hard damage. Furthermore, when the pressure in the first chamber 211 or the second chamber 212 exceeds the warning threshold, the pressure gauge 27 will promptly transmit the signal to the external system, triggering an alarm and enabling the control system to suspend the operation of the device.

[0042] S4. If a minor jerking fault occurs in the power system, causing a slight abnormal increase in the driving force of the lever arm, the pressure will overcome the restoring force of the first damping spring 32, the second damping spring 34, and the third damping spring 36, driving the first damping plate 31, the second damping plate 33, and the third damping plate 35 to move step by step towards the center point of the piston head 23. Through the first guide hole 311, the second guide hole 312, and the third guide hole 313, the flow hole 233 is gradually blocked, thereby realizing the reverse control of the lever arm swing speed and timely warning of minor faults.

[0043] Working principle: First, since the piston head 23 can only allow fluid to pass through the flow hole 233, it is necessary to pre-calculate the normal swing speed of the first lever arm 16 and the second lever arm 17 so that the displacement difference caused by the flow rate of the piston head 23 is matched with the swing speed of the first lever arm 16 or the second lever arm 17.

[0044] When the first lever arm 16 or the second lever arm 17 is working normally, the lever arm will drive the piston head 23 to move synchronously. At this time, the non-Newtonian liquid can flow back and forth between the first chamber 211 and the second chamber 212 through the flow chamber 231, the flow cavity 232, the flow hole 233, the first flow hole 234, and the second flow hole 235 of the piston head 23, without interfering with the normal swing of the lever arm.

[0045] When the first lever arm 16 or the second lever arm 17 experiences a runaway failure, the force on the piston head 23 will suddenly increase. However, due to the structural characteristic that the piston head 23 can only pass through the flow hole 233 with a small flow area, the swing speed of the lever arm will not increase significantly, making it easy for the operator to control. If the pressure in the chamber exceeds the limit, the non-Newtonian fluid will directly prevent the lever arm from swinging, thereby avoiding a collision accident caused by runaway. At the same time, the floating piston 26 will compress the air in the air chamber 213, playing a buffering role and preventing hard damage to the mechanism.

[0046] During this process, the pressure inside the first chamber 211 or the second chamber 212 will rise sharply. Each pressure gauge 27 can capture this abnormal pressure signal in time and transmit it to the external system, prompting the system to issue an alarm quickly.

[0047] Simultaneously, the sudden increase in pressure overcomes the restoring force of the first damping spring 32, the second damping spring 34, and the third damping spring 36, causing the first damping plate 31, the second damping plate 33, and the third damping plate 35 to move step by step toward the center point of the piston head 23, and to exchange air with the outside environment through the first air passage 221 and the second air passage 236. Subsequently, the first damping plate 31 will gradually block the flow passage 233 with the help of the first guide hole 311, the second guide hole 312, and the third guide hole 313. This design ensures that the greater the driving force on the first lever arm 16 or the second lever arm 17, the slower the swing speed, thereby allowing for the determination of whether there are faults such as speed jerks in the power system, enabling timely detection of minor faults; even when the speed exceeds the limit, the non-Newtonian fluid can still be used to stop the movement of the lever arm, ensuring system safety.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0049] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A steel box girder welding device, comprising a slide rail table (1), wherein the upper end of the slide rail table (1) is driven by a linear motor to a sliding seat (11) with sliding connection, a column (12) is fixedly installed on the upper end of the sliding seat (11), a guide table (13) is fixedly installed on the upper end of the column (12), a guide table (13) is driven by a linear motor to a sliding guide seat (14), a rotating seat (15) is driven by a servo motor at the front end of the guide seat (14) with rotational connection, one end of a first lever arm (16) is hinged to the front end of the rotating seat (15), one end of a second lever arm (17) is hinged to the other end of the first lever arm (16), and a welding head (18) is driven by a servo motor at the other end of the second lever arm (17) with rotational connection, wherein a steel box girder to be welded (19) is placed below the welding head (18), characterized in that: The welding device further includes a control mechanism (2) and a monitoring mechanism (3). The control mechanism (2) is disposed on the rotating seat (15), the first lever arm (16), and the second lever arm (17), and is used to control the swing speed of the first lever arm (16) and the second lever arm (17). The monitoring mechanism (3) is disposed inside the control mechanism (2) and is used to further reduce the swing speed. A first servo motor (161) is fixedly installed on the side of the rotating seat (15). The output shaft of the first servo motor (161) passes through the rotating seat (15) and is fixedly connected to the first lever arm (16). A second servo motor (171) is fixedly installed on the side of the first lever arm (16). The output shaft of the second servo motor (171) passes through the first lever arm (16) and is fixedly connected to the second lever arm (17). 7); The control mechanism (2) includes a flow control cylinder (21) hinged to the middle of the outer side of the first lever arm (16). The flow control cylinder (21) has a first air passage (221) inside. One end of the control rod (22) is hinged to the outer side of the second lever arm (17). The other end of the control rod (22) is inserted into the flow control cylinder (21) and threadedly connected to a piston head (23). Both ends of the piston head (23) are fixedly installed with sealing plates (24) by screws. A first sealing ring (25) is sleeved on the middle of the outer side of the piston head (23). A floating piston (26) is slidably connected inside the flow control cylinder (21). The inside of the flow control cylinder (21) is divided into a first chamber (211), a second chamber (212), and an air chamber (213) by the piston head (23) and the floating piston (26).

2. The steel box girder welding device according to claim 1, characterized in that, Both ends of the piston head (23) are provided with a flow-changing chamber (231) and a flow-through chamber (232). A flow-through hole (233) is provided between the flow-changing chamber (231) and the flow-through chamber (232). The flow-through chamber (232) is connected to the first chamber (211) through the first flow-changing hole (234). Another set of the flow-through chambers (232) is connected to the second chamber (212) through the second flow-changing hole (235). A second air passage (236) is provided in the middle of the piston head (23) for communicating with the first air passage (221).

3. The steel box girder welding device according to claim 2, characterized in that, The monitoring mechanism (3) includes a first damping plate (31) slidably connected in the converter chamber (231). The first damping plate (31) is fixedly connected to one end of a first damping spring (32) on the side near the middle of the piston head (23). The other end of the first damping spring (32) is fixedly connected in the converter chamber (231). A second damping plate (33) is sleeved inside the first damping plate (31). The second damping plate (33) is fixedly connected to one end of a second damping spring (34) on the side near the middle of the piston head (23). The other end of the second damping spring (34) is fixedly connected in the converter chamber (231). A third damping plate (35) is sleeved inside the second damping plate (33). The third damping plate (35) is fixedly connected to one end of a third damping spring (36) on the side near the middle of the piston head (23). The other end of the third damping spring (36) is fixedly connected in the converter chamber (231).

4. The steel box girder welding device according to claim 3, characterized in that, The first damping plate (31) has a first guide hole (311), a second guide hole (312) and a third guide hole (313) on its outer side. The inner wall of the first damping plate (31) is inlaid with a second sealing ring (314). The inner wall of the converter chamber (231) is inlaid with a sealing ring (37) for sealing the flow passage (233).

5. A welding method applicable to the steel box girder welding device according to any one of claims 1-4, characterized in that: The process includes the following steps: S1. Start the external control system, set the movement parameters of the slide (11) and guide (14) and the speed of the first servo motor (161) and the second servo motor (171) according to the weld parameters of the steel box girder to be welded (19), then inject non-Newtonian liquid into the flow control cylinder (21), set the warning threshold of the pressure gauge (27) and connect the alarm system; S2. Start the welding head (18), and simultaneously drive the slide (11), guide (14) and rotating seat (15) to move in coordination according to the preset program, driving the first lever arm (16) and the second lever arm (17) to move according to the preset program. The constant speed oscillation enables the welding head (18) to move at a uniform speed along the weld seam. During this process, the oscillation of the first lever arm (16) and the second lever arm (17) will drive the control rod (22) to push the piston head (23) to move within the flow control cylinder (21). The non-Newtonian liquid flows smoothly between the first chamber (211) and the second chamber (212) through the flow conversion chamber (231), the flow passage (233), the flow cavity (232), the first exchange passage (234), and the second exchange passage (235) of the piston head (23), without interfering with the normal oscillation of the lever arm; S3, if welding During the connection process, if the first lever arm (16) or the second lever arm (17) experiences a runaway malfunction, the piston head (23) experiences a sudden increase in force. Due to the limited flow capacity of the flow passage (233), the flow of non-Newtonian liquid is obstructed, directly limiting the abnormal increase in the swing speed of the lever arm. At the same time, the floating piston (26) compresses the air in the air chamber (213) to buffer the mechanism and prevent hard damage. Furthermore, when the pressure in the first chamber (211) or the second chamber (212) exceeds the warning threshold, the pressure gauge (27) will promptly transmit a signal to the external system, triggering an alarm and enabling the control system to suspend the operation of the device. S4. If a minor jerking fault occurs in the power system, causing a slight abnormal increase in the driving force of the lever arm, the pressure will overcome the restoring force of the first damping spring (32), the second damping spring (34), and the third damping spring (36), driving the first damping plate (31), the second damping plate (33), and the third damping plate (35) to move towards the center point of the piston head (23) step by step. Through the first guide hole (311), the second guide hole (312), and the third guide hole (313), the flow hole (233) is gradually blocked, thereby realizing the reverse control of the lever arm swing speed and timely warning of minor faults.

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