A welding fixture with back gas protection

Abstract

This invention discloses a welding fixture with back gas protection, belonging to the field of welding technology. It includes a worktable and two workpieces to be welded. The worktable has a welding port located at the bottom of the workpiece to be welded. A reduction gearbox is mounted on one side of the worktable. The input end of the reduction gearbox is connected to a motor, and the output end is connected to a lower lead screw and an upper lead screw. The workpieces to be welded are located between the lower and upper lead screws. A protective cover is connected to the lower lead screw, and a welding torch and a drive block are connected to the upper lead screw. The welding port of the welding torch is located between the two workpieces to be welded and directly above the protective cover. This welding fixture with back gas protection solves the technical problems of existing devices, such as difficulty in achieving synchronous movement between the back gas output device and the welding head, lack of versatility, and limited ability to control the flow direction of the protective gas.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a welding fixture with back gas protection. Background Technology

[0002] In modern welding processes, gas shielding on the back side of the weld is crucial to ensuring weld quality. This is especially important when welding oxidation-sensitive metals such as stainless steel, nickel-based alloys, and titanium alloys. Back-side gas shielding effectively prevents direct contact between the high-temperature molten pool and oxygen in the air, avoiding weld oxidation failure and thus ensuring the performance of the weld joint.

[0003] Currently, common back-side gas shielding methods for welding have many shortcomings. On the one hand, many existing devices struggle to synchronize the movement of the back-side shielding gas output device with the welding head. During welding, the welding head needs to move flexibly to complete various complex welds. If the shielding gas output device cannot synchronize with this movement, certain areas of the weld will not receive effective gas protection in a timely manner, leading to quality problems such as oxidation. For example, some devices use pre-positioned shielding gas hoods around the welding area or long pipelines to deliver the shielding gas. However, when the welding head moves, the shielding gas hoods are fixed and cannot follow in real time, while long pipelines are prone to gas delivery delays or instability, severely affecting the stability of welding quality.

[0004] On the other hand, existing welding fixtures are poorly adaptable to various weldments. Different weldments vary greatly in shape, size, and structure; however, most existing back gas protection devices are often designed for specific types or sizes of weldments, lacking versatility. For example, some back gas protection fixtures used for pipe welding are only suitable for pipes of specific diameters and cannot be used for weldments of other diameters or different shapes. This necessitates frequent changes of different fixtures when facing diverse welding tasks, significantly increasing production and time costs.

[0005] Furthermore, existing shielding gas output devices have limited capabilities in controlling the flow direction of the shielding gas. The flow direction of the shielding gas plays a crucial role in accurately and efficiently covering the back of the weld. If the gas flow direction is unreasonable, uneven gas distribution may occur, with some areas having excessively high gas concentrations, resulting in waste, while other areas have insufficient gas concentrations, failing to provide adequate protection. For example, some simple shielding gas injection devices have a single gas outlet design, making it impossible to adjust the gas flow direction according to the shape of the welded workpiece and the welding process requirements. This makes it difficult to ensure that all parts of the weld receive sufficient gas protection when welding complex-shaped workpieces.

[0006] In summary, it is necessary to provide a welding fixture that can realize the synchronous movement of the device for outputting back protective gas and the welding head, adapt to various welded parts, and effectively control the flow direction of the protective gas to meet the growing welding process requirements. Summary of the Invention

[0007] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a welding fixture with back gas protection to solve the problems mentioned in the background art.

[0008] The technical solution adopted by this invention to solve its technical problem is as follows: a welding fixture with back gas protection, including a worktable and two workpieces to be welded. The worktable has a welding port located at the bottom of the workpiece to be welded. A reduction gearbox is installed on one side of the worktable. The input end of the reduction gearbox is connected to a motor, and the output end of the reduction gearbox is connected to a lower lead screw and an upper lead screw. The workpieces to be welded are located between the lower lead screw and the upper lead screw. A protective cover is connected to the lower lead screw, and a welding torch and a drive block are connected to the upper lead screw. The welding port of the welding torch is located between the two workpieces to be welded and directly above the protective cover. The welding torch is located between the reduction gearbox and the drive block. A connecting rod is connected to the bottom of the drive block. One end of the connecting rod is hinged to the protective cover. The connecting rod passes through the welding port and is located between the two workpieces to be welded. The protective cover is located inside the welding port and moves along the length of the welding port. The motor transmits power to the reduction gearbox to drive the welding torch, drive block, connecting rod, and protective cover to move synchronously.

[0009] The top of the protective cover is slidably sealed to the bottom of the two workpieces to be welded, and the protective cover has multiple gas ports connected to a gas source.

[0010] Furthermore, the protective cover has an upward-opening air collection chamber, the length of the cross-section of the air collection chamber gradually decreases from high to low in the direction of travel, forming an inclined surface whose inner wall gradually slopes from the outside to the inside, and a filter plate is installed inside the protective cover, the two ends of the filter plate have chamfered portions, and the chamfered portions abut against the inclined surface.

[0011] Furthermore, the bottom of the drive block is connected to a threaded rod, the outer wall of the threaded rod has an external thread, the connecting rod has a sleeve part and a movable part, the movable part is slidably connected to the sleeve part and is located at the bottom end of the sleeve part, the sleeve part has a connecting groove with an internal thread, and the threaded rod is threadedly connected to the sleeve part.

[0012] The end of the protective cover away from the gearbox is the front end, and a hinge seat is fixedly connected to the outer wall. The end of the movable part away from the sleeve part is hinged to the hinge seat.

[0013] Furthermore, the diameter of the sleeve part is larger than the diameter of the movable part, and a connecting plate is slidably connected to the movable part. Auxiliary wheels are provided on both sides of the bottom of the connecting plate. The two auxiliary wheels correspond to a workpiece to be welded and roll on the upper surface of the workpiece to be welded.

[0014] Furthermore, a sealing gasket is installed around the top of the protective cover, and the sealing gasket abuts against the bottom of the workpiece to be welded. A grinding section extends rearward from the top of the protective cover, and rollers are rotatably connected to both sides of the grinding section via a rotating shaft. One of the rollers is rotatably connected to a lower slider via a shaft.

[0015] The protective cover is also provided with a front end interface, a side interface, a bottom interface and an exhaust port that communicate with the air collection chamber. The front end interface is located directly below the hinge seat. The exhaust port and the front end interface are symmetrically arranged. The bottom interface is located at the bottom of the protective cover. The side interface is located on one side of the protective cover. The front end interface, the side interface, the bottom interface and the exhaust port are all provided with plugs.

[0016] Furthermore, the top of the filter plate is provided with a plurality of filter holes evenly arranged in an array, and the bottom of both sides of the filter plate in the width direction are provided with chamfered portions, which abut against the inner wall slope of the protective cover.

[0017] The bottom of the filter plate is fixedly connected to a primary guide plate and a secondary guide plate. The primary guide plate has an arc-shaped primary guide surface, and the secondary guide plate has an arc-shaped secondary guide surface. The primary guide surface and the secondary guide surface are arranged facing each other, and the secondary guide plate is located in the upper middle part of the primary guide plate.

[0018] The side interface is directly opposite the first-stage guide plate, the bottom interface is located between the first-stage and second-stage guide plates in the longitudinal direction, and the side interface is located between the first-stage and second-stage guide plates in the transverse direction.

[0019] Furthermore, the bottom of the workbench is symmetrically provided with two tracks, which are located on both sides of the length of the welding joint. Each track has a sliding cavity, and the roller slides within the sliding cavity.

[0020] The bottom of the workbench is also provided with a bearing block. The end of the lower lead screw away from the gearbox is rotatably connected to the bearing block. Lower guide posts are installed on both sides of the lower lead screw. One end of the lower guide post is fixedly connected to the gearbox, and the other end is fixedly connected to the bearing block.

[0021] A lower slider is installed on the roller near the lower lead screw. The lower slider is connected to the lower lead screw and the lower guide post. The rotation of the lower lead screw drives the lower slider to slide along the lower guide post, so that the roller slides in the sliding cavity and drives the protective cover to move.

[0022] Furthermore, a positioning frame is fixedly connected to the top of the workbench, the welding joint is located between the gearbox and the positioning frame, the end of the upper screw away from the gearbox is rotatably connected to the positioning frame, and upper guide posts are installed on both sides of the upper screw, one end of the upper guide post is fixedly connected to the gearbox, and the other end is fixedly connected to the positioning frame.

[0023] An upper slider is installed on one side of the welding torch. The upper slider is connected to the upper lead screw and the upper guide post. The rotation of the upper lead screw drives the upper slider to slide along the upper guide post, so that the welding torch moves in a straight line.

[0024] The beneficial effects of the present invention are as follows: The present invention provides a welding fixture with back gas protection. The fixture is equipped with a speed reducer, which controls the lower slider, the upper slider and the drive block, thereby realizing the synchronous movement of the welding torch and the protective cover, and enabling the protective gas to be stably delivered to the weld.

[0025] By incorporating a threaded rod and a sleeve, the top of the protective cover can be sealed or left open with the workpiece to be welded, increasing the range of applications for the protective cover to accommodate different workpieces and enhancing its versatility.

[0026] By setting a grinding part on the protective cover, the protective cover is not in a sealed state for the workpiece to be welded. The grinding part can contact the back of the workpiece to be welded. Thus, in the case of open welding, when welding defects occur on the back of the workpiece to be welded, the grinding part can clean the defects in time by passing through the defects.

[0027] By providing front-end, side, and bottom interfaces, the number of ways in which protective gas can enter the protective cover can be increased, thereby providing gas protection for the weld from different angles.

[0028] By installing a slag filter plate, welding slag can be prevented from entering the protective cover. On the other hand, the primary and secondary guide plates can change the direction and speed of the airflow, thus providing better gas protection for the weld.

[0029] This invention solves the technical problems of existing devices, such as difficulty in achieving synchronous movement between the back protective gas output device and the welding head, lack of versatility, and limited ability of existing protective gas output devices to control the flow direction of protective gas.

[0030] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0031] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is an overall schematic diagram of the present invention;

[0033] Figure 2 This is a side view of the present invention;

[0034] Figure 3 This is a schematic diagram of the top of the workbench of the present invention;

[0035] Figure 4 For the present invention Figure 3 Enlarged diagram of area A in the middle;

[0036] Figure 5 This is a schematic diagram of the bottom of the worktable of the present invention;

[0037] Figure 6 For the present invention Figure 5 Enlarged diagram of area B in the middle;

[0038] Figure 7 This is a schematic diagram of the bottom of the protective cover of the present invention;

[0039] Figure 8 This is a schematic diagram of the top of the protective cover of the present invention;

[0040] Figure 9 This is a schematic diagram of the filter plate of the present invention;

[0041] Figure 10 This is a schematic diagram of the protective cover of the present invention tilted.

[0042] Figure 11 This is a schematic diagram of the airflow direction of the side interface of the present invention;

[0043] Figure 12 This is a schematic diagram of the airflow direction at the bottom interface of the present invention;

[0044] The following are the labeling elements in the figure:

[0045] 1. Workbench; 11. Welding joint; 12. Positioning frame; 13. Track; 131. Sliding cavity; 14. Bearing block; 2. Workpiece to be welded; 3. Gearbox; 31. Lower lead screw; 32. Lower guide post; 33. Lower slide block; 34. Upper lead screw; 35. Upper guide post; 36. Upper slide block; 4. Motor; 5. Welding torch; 6. Drive block; 61. Threaded rod; 611. External thread part; 7. Connecting rod; 71. Sleeve part; 7 2. Moving part; 73. Connecting plate; 74. Auxiliary wheel; 8. Protective cover; 81. Roller; 82. Hinge seat; 83. Front end interface; 84. Side interface; 85. Bottom end interface; 86. Exhaust port; 87. Sealing gasket; 88. Grinding part; 9. Filter plate; 91. Filter hole; 92. Primary guide plate; 921. Primary guide surface; 93. Secondary guide plate; 931. Secondary guide surface; 94. Chamfered part. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0048] like Figure 1-12 As shown, the present invention provides a technical solution: a welding fixture with back gas protection, comprising a worktable 1 and two workpieces 2 to be welded. The worktable 1 has a welding port 11 located at the bottom of the workpiece 2 to be welded. A reduction gearbox 3 is installed on one side of the worktable 1. The input end of the reduction gearbox 3 is connected to a motor 4, and the output end of the reduction gearbox 3 is connected to a lower lead screw 31 and an upper lead screw 34. The workpieces 2 to be welded are located between the lower lead screw 31 and the upper lead screw 34. The lower lead screw 31 is connected to a protective cover 8, and the upper lead screw 34 is connected to a protective cover 8. The welding gun 5 and the drive block 6 are connected. The welding port 11 of the welding gun 5 is located between the two workpieces 2 to be welded and directly above the protective cover 8. The welding gun 5 is located between the gearbox 3 and the drive block 6. The bottom of the drive block 6 is connected to the connecting rod 7. One end of the connecting rod 7 is hinged to the protective cover 8. The connecting rod 7 passes through the welding port 11 and is located between the two workpieces 2 to be welded. The protective cover 8 is located inside the welding port 11 and moves along the length of the welding port 11. The motor 4 transmits power to the gearbox 3 to drive the welding gun 5, the drive block 6, the connecting rod 7 and the protective cover 8 to move synchronously.

[0049] The top of the protective cover 8 is slidably sealed to the bottom of the two workpieces 2 to be welded. The protective cover 8 has multiple gas ports connected to a gas source.

[0050] The protective cover 8 has an upward-opening air collection chamber. The length of the cross-section of the air collection chamber gradually decreases from high to low in the direction of travel, forming an inclined surface whose inner wall gradually slopes from the outside to the inside. A filter plate 9 is installed inside the protective cover 8. Both ends of the filter plate 9 have chamfered portions 94, which abut against the inclined surface. By abutting against the inclined surface, the position of the filter plate 9 within the protective cover 8 can be restricted, allowing the filter plate 9 to be quickly positioned and installed.

[0051] The bottom of the drive block 6 is connected to a threaded rod 61. The outer wall of the threaded rod 61 has an external thread 611. The connecting rod 7 has a sleeve part 71 and a movable part 72. The movable part 72 is slidably connected to the sleeve part 71 and is located at the bottom end of the sleeve part 71. A connecting groove with an internal thread is opened in the sleeve part 71. The threaded rod 61 is threadedly connected to the sleeve part 71.

[0052] The end of the protective cover 8 away from the gearbox 3 is the front end, and the outer wall is fixedly connected to the hinge seat 82. The end of the movable part 72 away from the sleeve part 71 is hinged to the hinge seat 82.

[0053] The diameter of the sleeve part 71 is larger than the diameter of the movable part 72. A connecting plate 73 is slidably connected to the movable part 72. Auxiliary wheels 74 are provided on both sides of the bottom of the connecting plate 73. The two auxiliary wheels 74 correspond to a workpiece 2 to be welded and roll on the upper surface of the workpiece 2 to be welded.

[0054] A sealing gasket 87 is installed around the top of the protective cover 8. The sealing gasket 87 abuts against the bottom of the workpiece 2 to be welded. A grinding part 88 extends rearward from the top of the protective cover 8. Rollers 81 are rotatably connected to both sides of the grinding part 88 via a rotating shaft. One of the rollers 81 is rotatably connected to a sliding block 33 via a shaft.

[0055] The protective cover 8 is also provided with a front end interface 83, a side interface 84, a bottom interface 85 and an exhaust port 86 that communicate with the air collection chamber. The front end interface 83 is located directly below the hinge seat 82. The exhaust port 86 and the front end interface 83 are arranged symmetrically. The bottom interface 85 is located at the bottom of the protective cover 8. The side interface 84 is located on one side of the protective cover 8. The front end interface 83, the side interface 84, the bottom interface 85 and the exhaust port 86 are all provided with plugs.

[0056] The top of the filter plate 9 is provided with a number of filter holes 91 evenly arranged, and the bottom of both sides of the filter plate 9 in the width direction are provided with chamfered parts 94, which abut against the inner wall slope of the protective cover 8.

[0057] The bottom of the filter plate 9 is fixedly connected to a primary guide plate 92 and a secondary guide plate 93. The primary guide plate 92 has an arc-shaped primary guide surface 921, and the secondary guide plate 93 has an arc-shaped secondary guide surface 931. The primary guide surface 921 and the secondary guide surface 931 are arranged facing each other, and the secondary guide plate 93 is located in the upper middle part of the primary guide plate 92.

[0058] The side interface 84 is directly opposite the first-stage guide plate 92, the bottom interface 85 is located between the first-stage guide plate 92 and the second-stage guide plate 93 in the longitudinal direction, and the side interface 84 is located between the first-stage guide plate 92 and the second-stage guide plate 93 in the transverse direction.

[0059] Two tracks 13 are symmetrically arranged at the bottom of the workbench 1. The tracks 13 are located on both sides of the length of the welding joint 11. The tracks 13 have sliding cavities 131, and the rollers 81 slide within the sliding cavities 131.

[0060] The bottom of the workbench 1 is also provided with a bearing block 14. The end of the lower lead screw 31 away from the gearbox 3 is rotatably connected to the bearing block 14. Lower guide posts 32 are installed on both sides of the lower lead screw 31. One end of the lower guide post 32 is fixedly connected to the gearbox 3, and the other end is fixedly connected to the bearing block 14.

[0061] A lower slider 33 is installed on the roller 81 near the lower lead screw 31. The lower slider 33 is connected to the lower lead screw 31 and the lower guide post 32. The rotation of the lower lead screw 31 drives the lower slider 33 to slide along the lower guide post 32, so that the roller 81 slides in the sliding cavity 131 and drives the protective cover 8 to move.

[0062] A positioning frame 12 is fixedly connected to the top of the workbench 1. The welding joint 11 is located between the gearbox 3 and the positioning frame 12. The end of the upper lead screw 34 away from the gearbox 3 is rotatably connected to the positioning frame 12. Upper guide posts 35 are installed on both sides of the upper lead screw 34. One end of the upper guide post 35 is fixedly connected to the gearbox 3, and the other end is fixedly connected to the positioning frame 12.

[0063] An upper slider 36 is installed on one side of the welding torch 5. The upper slider 36 is connected to the upper lead screw 34 and the upper guide post 35. The rotation of the upper lead screw 34 drives the upper slider 36 to slide along the upper guide post 35, so that the welding torch 5 can move in a straight line.

[0064] In one embodiment, how does the device provide backplate gas protection for the tooling?

[0065] Specifically, place two workpieces 2 to be welded on the upper surface of the workbench 1, so that their welding position is above the welding port 11. Adjust the position of the protective cover 8 by using the drive block 6 and the lower slider 33 so that the center of the protective cover 8 is located at the center of the welding gun 5. Move the welding gun 5 to one end of the workpiece 2 to be welded, and the connecting rod 7 is located in front of the welding gun 5 in the forward direction.

[0066] Rotate the sleeve part 71, and the sleeve part 71 will fit the threaded rod 61 inside. The total length of the connecting rod 7 gradually decreases. The protective cover 8 uses the roller 81 as an axis to make its upper surface gradually approach the workpiece 2 to be welded. When the sealing gasket 87 is in contact with the lower surface of the workpiece 2 to be welded, the protective cover 8 is in a horizontal position. At this time, stop rotating the sleeve part 71.

[0067] Remove the plugs from the front end interface 83 and the exhaust port 86, and connect the pipe of the protective gas release device to the front end interface 83. Discharge the gas into the gas collection chamber of the protective cover 8, and discharge the air from the exhaust port 86. At this time, the protective gas fills the protective cover 8 and contacts the back of the workpiece 2 to be welded.

[0068] Turn on the welding torch 5 to weld the workpiece 2, then turn on the motor 4. The lower lead screw 31 and the upper lead screw 34 rotate through the gearbox. The upper slider 36 drives the welding torch 5 to move linearly. The drive block 6 drives the protective cover 8 to move through the connecting rod 7. The lower slider 33 also drives the protective cover 8 to move through the rotation of the lower lead screw 31, improving the stability of the movement of the protective cover 8. The roller 81 slides in the sliding cavity 131. The slag filter plate 9 receives the welding slag that falls off during welding. The auxiliary wheel 74 rolls on the upper surface of the workpiece 2 to be welded.

[0069] The welding torch 5 completes the welding of the workpiece 2 until the drive block 6 reaches the positioning frame 12.

[0070] When grinding is required again at the welding point of the workpiece 2 to be welded according to the processing technology, the speed reducer 3 can be controlled so that the lower screw 31 does not rotate, and the threaded rod 61 is separated from the connecting rod 7, so that the welding gun 5 can move back and forth at the welding point of the workpiece 2 to be welded for welding.

[0071] In another embodiment, gas protection can also be carried out in a variety of different ways.

[0072] Specifically, referring to the above embodiments, some workpieces 2 do not need to be sealed and welded. Before starting the welding gun 5, rotate the sleeve part 71 so that the protective cover 8 gradually moves away from the workpiece 2 with the roller 81 as the axis. Then the sealing gasket 87 does not contact the workpiece 2, and at the same time, one end with the grinding part 88 is raised and contacts the back of the workpiece 2.

[0073] Welding begins at this point. Shielding gas is discharged from the opening of the shield 8 into the workpiece 2 to be welded. Since it is an open shield, there is a certain probability that defects will appear at the weld. At this time, when the grinding part 88 moves synchronously with the welding gun 5, it can grind the weld of the workpiece 2 to be welded and deal with the defects in time.

[0074] Plug the front end interface 83 with a plug, open the plug of the bottom end interface 85, and then connect the bottom end interface 85 to the protective gas device. At this time, the protective gas is directly sprayed from the bottom end interface 85 to the welding area of ​​the workpiece 2 to be welded, so that the flow of the protective gas is in a high flow state.

[0075] Plug the bottom interface 85 with a plug, open the plug of the side interface 84, and then connect the side interface 84 to the protective gas device. At this time, the protective gas is sprayed out from the side interface 84. The protective gas first contacts the first-stage guide plate 92. The gas is transferred to the second-stage guide plate 93 along the first-stage guide surface 921. The gas is then transported upward along the second-stage guide surface 931 to the welding point of the workpiece 2 to be welded, so that the airflow of the protective gas is slowed down.

[0076] When the protective gas is input using the bottom port 85 and the side port 84, it is applicable for both sealed and open protection.

[0077] In summary, this fixture, by incorporating a reduction gearbox 3, controls the lower slider 33, upper slider 36, and drive block 6, achieving synchronous movement of the welding torch 5 and the protective cover 8, ensuring stable delivery of shielding gas to the weld. The threaded rod 61 and sleeve 71 allow the top of the protective cover 8 to be sealed or open with the workpiece 2 to be welded, increasing its versatility and adaptability to different workpieces. Furthermore, the grinding section 88 on the protective cover 8 allows it to be in a non-sealed state with the workpiece 2, enabling it to interact with the workpiece. The back of the workpiece 2 is in contact, so that in open welding, when welding defects occur on the back of the workpiece 2, the grinding part 88 can promptly clean the defects by passing over them. The front interface 83, side interface 84, and bottom interface 85 increase the ways in which protective gas enters the protective cover 8, thus providing gas protection for the weld from different angles. The slag filter plate 9 prevents welding slag from entering the protective cover 8, and the primary guide plate 92 and secondary guide plate 93 change the direction and velocity of the airflow, providing better gas protection for the weld. This solves the technical problems of existing devices, such as difficulty in achieving synchronous movement between the back protective gas output device and the welding head, lack of versatility, and limited ability to control the flow direction of the protective gas.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding fixture with back gas protection, characterized in that: The assembly includes a workbench (1) and two workpieces (2) to be welded. The workbench (1) has a welding port (11) located at the bottom of the workpiece (2) to be welded. A gearbox (3) is installed on one side of the workbench (1). The input end of the gearbox (3) is connected to a motor (4). The output end of the gearbox (3) is connected to a lower lead screw (31) and an upper lead screw (34). The workpieces (2) to be welded are located between the lower lead screw (31) and the upper lead screw (34). The lower lead screw (31) is connected to a protective cover (8). The upper lead screw (34) is connected to a welding torch (5) and a drive block (6). The welding joint (11) of 5) is located between two workpieces (2) to be welded and directly above the protective cover (8). The welding gun (5) is located between the gearbox (3) and the drive block (6). The bottom of the drive block (6) is connected to a connecting rod (7). One end of the connecting rod (7) is hinged to the protective cover (8). The connecting rod (7) passes through the welding joint (11) and is located between the two workpieces (2) to be welded. The protective cover (8) is located inside the welding joint (11) and moves along the length of the welding joint (11). The motor (4) transmits power to the gearbox (3) to drive the welding gun (5), drive block (6), connecting rod (7) and protective cover (8) to move synchronously. The top of the protective cover (8) is slidably sealed to the bottom of the two workpieces (2) to be welded. The protective cover (8) has multiple gas interfaces connected to a gas source. The top perimeter of the protective cover (8) is fitted with sealing gaskets (87), which abut against the bottom of the workpiece (2) to be welded. A grinding section (88) extends rearward from the top of the protective cover (8), and rollers (81) are rotatably connected to both sides of the grinding section (88) via a rotating shaft. One of the rollers (81) is rotatably connected to a sliding block (33) via a shaft. The protective cover (8) is also provided with a front end interface (83), a side interface (84), a bottom interface (85) and an exhaust port (86) that communicate with the air collection chamber. The front end interface (83) is located directly below the hinge seat (82). The exhaust port (86) and the front end interface (83) are symmetrically arranged. The bottom interface (85) is located at the bottom of the protective cover (8). The side interface (84) is located on one side of the protective cover (8). The front end interface (83), the side interface (84), the bottom interface (85) and the exhaust port (86) are all provided with plugs.

2. The welding fixture with back gas protection according to claim 1, characterized in that: The protective cover (8) has an upward-opening air collection chamber. The length of the cross-section of the air collection chamber in the direction of travel gradually decreases from high to low, forming an inclined surface whose inner wall gradually slopes from the outside to the inside. A filter plate (9) is installed inside the protective cover (8). Both ends of the filter plate (9) have chamfered portions (94), and the chamfered portions (94) abut against the inclined surface.

3. The welding fixture with back gas protection according to claim 2, characterized in that: The bottom of the drive block (6) is connected to a threaded rod (61), the outer wall of the threaded rod (61) has an external thread (611), the connecting rod (7) has a sleeve part (71) and a movable part (72), the movable part (72) is slidably connected to the sleeve part (71) and located at the bottom end of the sleeve part (71), a connecting groove with an internal thread is opened in the sleeve part (71), and the threaded rod (61) is threadedly connected to the sleeve part (71); The protective cover (8) has a front end away from the gearbox (3) and a hinge seat (82) is fixedly connected to its outer wall. The movable part (72) is hinged to the hinge seat (82) at the end away from the sleeve part (71).

4. The welding fixture with back gas protection according to claim 3, characterized in that: The diameter of the sleeve part (71) is larger than the diameter of the movable part (72). A connecting plate (73) is slidably connected to the movable part (72). Auxiliary wheels (74) are provided on both sides of the bottom of the connecting plate (73). The two auxiliary wheels (74) correspond to a workpiece (2) to be welded and roll on the upper surface of the workpiece (2).

5. The welding fixture with back gas protection according to claim 2, characterized in that: The top of the filter plate (9) is provided with a plurality of filter holes (91) evenly arranged in an array. Both sides of the bottom of the filter plate (9) in the width direction are provided with chamfered portions (94), and the chamfered portions (94) abut against the inner wall slope of the protective cover (8). The bottom of the filter plate (9) is fixedly connected to a primary guide plate (92) and a secondary guide plate (93). The primary guide plate (92) has an arc-shaped primary guide surface (921), and the secondary guide plate (93) has an arc-shaped secondary guide surface (931). The primary guide surface (921) and the secondary guide surface (931) are arranged facing each other, and the secondary guide plate (93) is located in the upper middle part of the primary guide plate (92). The side interface (84) is directly opposite the first-stage guide plate (92), the bottom interface (85) is located between the first-stage guide plate (92) and the second-stage guide plate (93) in the longitudinal direction, and the side interface (84) is located between the first-stage guide plate (92) and the second-stage guide plate (93) in the transverse direction.

6. The welding fixture with back gas protection according to claim 1, characterized in that: The bottom of the workbench (1) is symmetrically provided with two tracks (13). The tracks (13) are located on both sides of the length direction of the welding joint (11). The tracks (13) have sliding cavities (131) and the rollers (81) slide within the sliding cavities (131). The bottom of the workbench (1) is also provided with a bearing block (14). The end of the lower screw (31) away from the gearbox (3) is rotatably connected to the bearing block (14). Lower guide posts (32) are installed on both sides of the lower screw (31). One end of the lower guide post (32) is fixedly connected to the gearbox (3), and the other end is fixedly connected to the bearing block (14). A lower slider (33) is installed on the roller (81) near the lower screw (31). The lower slider (33) is connected to the lower screw (31) and the lower guide post (32) in a transmission manner. The rotation of the lower screw (31) drives the lower slider (33) to slide along the lower guide post (32), so that the roller (81) slides in the sliding cavity (131) and drives the protective cover (8) to move.

7. The welding fixture with back gas protection according to claim 6, characterized in that: The top of the workbench (1) is fixedly connected to a positioning frame (12). The welding joint (11) is located between the gearbox (3) and the positioning frame (12). The end of the upper screw (34) away from the gearbox (3) is rotatably connected to the positioning frame (12). Upper guide posts (35) are installed on both sides of the upper screw (34). One end of the upper guide post (35) is fixedly connected to the gearbox (3), and the other end is fixedly connected to the positioning frame (12). The welding torch (5) is equipped with an upper slider (36) on one side. The upper slider (36) is connected to the upper screw (34) and the upper guide post (35) for transmission. The rotation of the upper screw (34) drives the upper slider (36) to slide along the upper guide post (35) so that the welding torch (5) can move in a straight line.

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