Multi-station steel pipe welding tool

Abstract

The invention discloses a multi-station steel pipe welding tool, and relates to the technical field of steel pipe welding, the multi-station steel pipe welding tool comprises a placing plate, an exchange mechanism used for changing the position of the placing plate is arranged at the bottom of the placing plate, and a turnover mechanism used for driving the placing plate to rotate is arranged on the side face of the exchange mechanism; a positioning mechanism for preventing a steel pipe from moving is arranged on the surface of the placing plate, a jacking mechanism for separating the welded steel pipe from the placing plate is arranged in the placing plate, the exchange mechanism comprises supporting seats which are symmetrically arranged, and a first rotating shaft is horizontally connected to the top of each supporting seat. The first rotating shaft is used for driving the two placing plates to rotate, the design of the two placing plates allows steel pipes to be butted and fixed on one placing plate, meanwhile, the other placing plate can be used for welding and discharging operation, stations are switched through the first rotating shaft, the waiting time is shortened, and seamless connection of procedures is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe welding, and specifically relates to a multi-station steel pipe welding tooling. Background Art

[0002] Steel pipe welding tooling refers to tools or equipment used to fix and position steel pipes for efficient and high-quality welding operations. They are widely used in industrial manufacturing, construction, and other fields, especially in situations involving a large number of steel pipe connections. Using appropriate welding tooling can significantly improve production efficiency and ensure the consistency and reliability of welding quality.

[0003] Welding steel pipes into a rectangular frame is a common process, widely used in construction, furniture manufacturing, mechanical structures, etc. During welding, the steel pipes are first butt-jointed and then fixed in place, and finally welded and unloaded.

[0004] During the process of welding a steel pipe frame, it is necessary to perform steel pipe butt-jointing, fixing, welding, and unloading in sequence at the same station. Since each step needs to be carried out in sequence and the next step can only start after the previous step is completed, this will result in a large amount of waiting time, especially when dealing with multiple frames or large frames, the efficiency is particularly low. The entire station can only focus on one task within a period of time, and other tasks that could be carried out in parallel cannot be performed simultaneously, resulting in waste of equipment and human resources.

[0005] Therefore, the present invention proposes a multi-station steel pipe welding tooling to make up for and improve the deficiencies of the existing technology. Summary of the Invention

[0006] In view of the above problems, the invention provides a multi-station steel pipe welding tooling, which can effectively solve the problem of time waste in welding at the same station in the existing technology. To achieve the above object, the embodiments of the present application provide the following technical solutions: The present invention discloses a multi-station steel pipe welding tooling, including a placement plate. A switching mechanism for changing the position of the placement plate is provided at the bottom of the placement plate. A flipping mechanism for driving the placement plate to rotate is provided on the side of the switching mechanism. A positioning mechanism for preventing the steel pipe from moving is provided on the surface of the placement plate. A jacking mechanism for separating the welded steel pipe from the placement plate is provided inside the placement plate. A release mechanism for driving the release of the fixed state of the steel pipe is provided on the side of the placement plate away from the positioning mechanism; The switching mechanism includes symmetrically arranged support seats. A first rotating shaft is horizontally connected to the top of each support seat. Mounting frames are fixedly connected to the mutually close ends of the two first rotating shafts. Second rotating shafts are rotatably connected to both ends of each mounting frame. A placement plate for placing steel pipes is fixedly connected between the two second rotating shafts at the same end.

[0007] Furthermore, the switching mechanism further includes a worm gear fixedly connected to one end of the first rotating shaft away from the mounting bracket. A worm is rotatably connected to the side surface of the support base. The worm is engaged with the worm gear. A motor is fixedly connected to the side surface of the support base, and an output end of the motor is fixedly connected to one end of the worm.

[0008] Furthermore, the flipping mechanism includes a first pulley fixedly connected to the outside of the first rotating shaft. A second pulley is fixedly connected to one end of the second rotating shaft away from the placing plate. The second pulley and the first pulley are connected by a synchronous belt.

[0009] Furthermore, the positioning mechanism includes first limit blocks symmetrically and fixedly connected to the surface of the placing plate. A moving plate is slidably connected to the surface of the placing plate on the sides of the two first limit blocks away from each other. Triangular blocks are fixedly connected to both ends of each moving plate.

[0010] Furthermore, a mounting block is fixedly connected to the side of the moving plate close to the first limit block. A sliding sleeve is slidably sleeved outside the mounting block. A spring is fixedly connected to the inner cavity of the sliding sleeve, and one end of the spring away from the sliding sleeve is fixedly connected to the mounting block.

[0011] Furthermore, the positioning mechanism further includes second limit blocks symmetrically and fixedly connected to the surface of the placing plate. A rotating rod is rotatably connected to the surface of the placing plate on the sides of the two second limit blocks away from each other. A trapezoidal block is fixedly connected to one end of each rotating rod. The inclined surfaces of the trapezoidal blocks are slidably abutted against the inclined surfaces of the triangular blocks.

[0012] Furthermore, the jacking mechanism includes longitudinal grooves symmetrically opened on the surface of the placing plate. A first connecting rod is slidably connected to each longitudinal groove. One end of the first connecting rod is fixedly connected to the bottom of the moving plate, and the other end of the first connecting rod is fixedly connected to a wedge block for jacking up the steel pipe.

[0013] Furthermore, the releasing mechanism includes through grooves symmetrically opened on the surface of the placing plate. A second connecting rod is slidably connected to each through groove. One end of the second connecting rod is fixedly connected to the bottom of the moving plate, and the other end of the second connecting rod extends to the other side of the placing plate through the through groove. The two horizontal second connecting rods are fixedly connected by a cross bar.

[0014] Furthermore, a guiding rod is fixedly connected to the bottom of the placing plate, and the guiding rod slidably penetrates through the second connecting rod.

[0015] Furthermore, a bidirectional lead screw is rotatably connected to the bottom of the placing plate. Hand wheels are fixedly connected to both ends of the bidirectional lead screw. The threaded sections outside the bidirectional lead screw are respectively threadedly connected to the two cross bars.

[0016] Beneficial effects: 1. This device is equipped with an exchange mechanism. By driving two placement plates to rotate with the first rotating shaft, the design of the two placement plates allows for the butt-jointing and fixing of steel pipes on one placement plate while welding and unloading operations can be carried out on the other placement plate. The workstations are switched through the first rotating shaft, reducing waiting time and achieving seamless connection of processes.

[0017] 2. This device is equipped with a flipping mechanism. During the rotation of the placement plate, the synchronous belt is used to drive the placement plate to rotate. While the placement plate switches workstations, it can rotate 180 degrees on its own axis, causing the welded steel pipe frame to face downward, so that the steel pipe frame can quickly separate from the placement table due to the gravity of the steel pipe. The synchronous flipping mechanism reduces the physical labor required by workers, especially for large or heavy steel pipe frames, which greatly reduces the workload of operators.

[0018] 3. This device is equipped with a jacking mechanism. When releasing the fixation of the steel pipe frame, the wedge block is synchronously driven to jack out the steel pipe frame from the placement table. The jacking mechanism can automatically perform the jacking-out action while releasing the fixation, reducing manual intervention and thus accelerating the speed of the entire demolding process.

[0019] This device is equipped with a worm gear and a worm. The transmission of the worm gear and the worm has a self-locking function. When the placement plate needs to stay at a specific angle, the self-locking characteristic of the worm gear and the worm can ensure that it can stably maintain the set position without an additional locking device. Due to the self-locking characteristic of the worm gear and worm transmission, it is usually not necessary to install an additional brake or other locking mechanism to fix the position of the placement plate, which helps to simplify the overall mechanical design. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a three-dimensional structure diagram of the first perspective of the present invention.

[0022] Figure 2 It is a three-dimensional structure diagram of the positioning mechanism in the present invention.

[0023] Figure 3 In the present invention Figure 2 The enlarged structure diagram of part A in

[0024] Figure 4 In the present invention Figure 2 The enlarged structure diagram of part B in

[0025] Figure 5 This is a sectional view of the sliding sleeve in the present invention.

[0026] Figure 6 This is a three-dimensional structure diagram of the release mechanism in the present invention.

[0027] Figure 7 This is a three-dimensional structure diagram of the worm gear and the worm in the present invention.

[0028] The reference numerals in the figure respectively represent: 10, placement plate; 20, exchange mechanism; 201, support base; 202, first rotating shaft; 203, mounting bracket; 204, second rotating shaft; 205, worm gear; 206, worm; 207, motor; 30, flipping mechanism; 301, first pulley; 302, second pulley; 303, synchronous belt; 40, positioning mechanism; 401, first limiting block; 402, second limiting block; 403, moving plate; 404, mounting block; 405, sliding sleeve; 406, spring; 407, triangular block; 408, rotating rod; 409, trapezoidal block; 50, lifting mechanism; 501, longitudinal groove; 502, first connecting rod; 503, wedge block; 60, release mechanism; 601, through groove; 602, second connecting rod; 603, cross bar; 604, guide rod; 605, bidirectional lead screw; 606, hand wheel. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The present invention will be further described below with reference to the embodiments.

[0031] Refer to Figures 1 to 7 , a multi-station steel pipe welding tooling in this embodiment includes a placement plate 10. A exchange mechanism 20 for changing the position of the placement plate 10 is provided at the bottom of the placement plate 10. A flipping mechanism 30 for driving the placement plate 10 to rotate is provided on the side of the exchange mechanism 20. A positioning mechanism 40 for preventing the steel pipe from moving is provided on the surface of the placement plate 10. A lifting mechanism 50 for separating the welded steel pipe from the placement plate 10 is provided inside the placement plate 10. A release mechanism 60 for driving to release the fixed state of the steel pipe is provided on one side of the placement plate 10 away from the positioning mechanism 40.

[0032] The switching mechanism 20 includes support seats 201 arranged symmetrically. A first rotating shaft 202 is horizontally connected to the top of each support seat 201. Mounting brackets 203 are fixedly connected to the mutually approaching ends of the two first rotating shafts 202. Second rotating shafts 204 are rotatably connected to both ends of each mounting bracket 203. A placing plate 10 for placing steel pipes is fixedly connected between the two second rotating shafts 204 at the same end. Placing plates 10 are installed at both ends of the mounting bracket 203, and the two placing plates 10 are flipped 180 degrees relative to each other.

[0033] The switching mechanism 20 further includes a worm gear 205 fixedly connected to the end of the first rotating shaft 202 away from the mounting bracket 203. A worm 206 is rotatably connected to the side of the support seat 201. The worm 206 meshes with the worm gear 205. A motor 207 is fixedly connected to the side of the support seat 201. The output end of the motor 207 is fixedly connected to one end of the worm 206.

[0034] During specific operation, after the steel pipes are placed on the surface of the placing plate 10, the positioning mechanism 40 is used to align and fix the steel pipes. After welding is completed, the motor 207 drives the worm 206 to rotate. The worm 206 drives the worm gear 205 to rotate. The worm gear 205 drives the first rotating shaft 202 to rotate. Due to the self-locking function of the transmission between the worm gear 205 and the worm 206, when the placing plate 10 needs to stay at a specific angle, the self-locking characteristics of the worm gear 205 and the worm 206 can ensure that it can stably maintain the set position without an additional locking device. Utilizing the self-locking characteristics inherent in the transmission of the worm gear 205 and the worm 206, generally, there is no need to additionally install a brake or other locking mechanism to fix the position of the placing plate 10. The first rotating shaft 202 drives the placing plate 10 to rotate 180 degrees through the mounting bracket 203, so that the placing plates 10 at both ends of the mounting bracket 203 exchange positions with each other. Then welding is carried out. Workers only need to place the steel pipes on the newly rotated placing plate 10 and then carry out welding, reducing the steps of workers removing the welded steel pipe frames from the placing plate 10. The design of the two placing plates 10 allows for the butt-jointing and fixing of steel pipes on one placing plate 10 while the other placing plate 10 can carry out welding and unloading operations. By switching the working positions through the first rotating shaft 202, the waiting time is reduced, achieving seamless connection of the processes.

[0035] The flipping mechanism 30 includes a first belt pulley 301 fixedly connected to the outside of the first rotating shaft 202. A second belt pulley 302 is fixedly connected to the end of the second rotating shaft 204 away from the placing plate 10. The second belt pulley 302 and the first belt pulley 301 are drivingly connected through a synchronous belt 303.

[0036] During specific operation, when the first rotating shaft 202 rotates, it drives the first pulley 301 to rotate, and the first pulley 301 drives the second pulley 302 to rotate through the synchronous belt 303. The rotating second pulley 302 drives the placement plate 10 to rotate synchronously through the second rotating shaft 204, so that when the two placement plates 10 exchange positions, the two placement plates 10 rotate 180 degrees and flip the side fixed with the steel pipe frame downward. Then, the positioning mechanism 40 releases the fixation of the steel pipe frame, and the steel pipe frame is accelerated to separate from the surface of the placement plate 10 under the push of the jacking mechanism 50. The synchronous flipping mechanism reduces the physical labor that workers need to perform, especially for large or heavy steel pipe frames, which greatly reduces the workload of operators.

[0037] The positioning mechanism 40 includes a first limit block 401 symmetrically fixedly connected to the surface of the placement plate 10, and a movable plate 403 is slidably connected to the surface of the placement plate 10 on one side away from the two first limit blocks 401, and each movable plate 403 is fixedly connected to a triangular block 407 at both ends.

[0038] The movable plate 403 is fixedly connected to a mounting block 404 on one side close to the first limiting block 401 . A sliding sleeve 405 is slidably sleeved on the outside of the mounting block 404 . A spring 406 is fixedly connected to the cavity of the sliding sleeve 405 . The spring 406 is fixedly connected to the mounting block 404 at one end away from the sliding sleeve 405 .

[0039] The positioning mechanism 40 also includes a second limit block 402 symmetrically fixedly connected to the surface of the placement plate 10. The two second limit blocks 402 are rotatably connected to the surface of the placement plate 10 on one side away from each other, and each rotation rod 408 is fixedly connected to a trapezoidal block 409 at one end. The inclined surface of the trapezoidal block 409 slides against the inclined surface of the triangular block 407.

[0040] During specific work, before welding, the two transverse steel pipes to be used are placed in the area between the first limit block 401 and the movable plate 403, and the spring 406 is used to push the sliding sleeve 405 to clamp the steel pipe on the side of the first limit block 401. Then, the two longitudinal steel pipes are placed on the side of the second limit block 402 and the rotating rod 408, and then the movable plate 403 is pushed toward the first limit block 401. At this time, the inclined surfaces of the triangular blocks 407 at both ends of the movable plate 403 squeeze the inclined surfaces of the trapezoidal blocks 409, thereby rotating the rotating rod 408, so that the end of the rotating rod 408 away from the trapezoidal block 409 pushes the longitudinal steel pipe to be clamped on the side of the second limit block 402. At the same time, the movable plate 403 drives the mounting block 404 to further squeeze the spring 406, so that the transverse steel pipe is further clamped and fixed on the side of the first limit block 401. After the steel pipes are docked and fixed, the exchange mechanism 20 is used to drive the two placement plates 10 to exchange positions to complete welding and unloading.

[0041] After welding is completed, at this time, the steel pipe is located at the bottom of the placement plate 10. Push the moving plate 403 in the reverse direction to drive the mounting block 404 and the sliding sleeve 405 to release the clamping of the horizontal steel pipe. While the moving plate 403 moves in the reverse direction, the triangular block 407 also releases the extrusion of the trapezoidal block 409 synchronously, so that the rotating rod 408 releases the clamping effect on the vertical steel pipe. After welding is completed, the steel pipe frame detaches from the bottom of the placement plate 10. Finally, the continuously moving moving plate 403 moving in the reverse direction can drive the lifting mechanism 50 to separate the auxiliary steel pipe frame from the surface of the placement plate 10.

[0042] The lifting mechanism 50 includes longitudinal grooves 501 symmetrically opened on the surface of the placement plate 10. A first connecting rod 502 is slidably connected inside each longitudinal groove 501. One end of the first connecting rod 502 is fixedly connected to the bottom of the moving plate 403, and the other end of the first connecting rod 502 is fixedly connected to a wedge block 503 for lifting the steel pipe.

[0043] During specific operation, after the steel pipe frame is welded, the continuously moving moving plate 403 continues to move. The moving plate 403 drives the first connecting rod 502 to slide in the longitudinal groove 501, and the first connecting rod 502 drives the wedge block 503 to move synchronously. The inclined surface of the wedge block 503 enters the gap between the steel pipe and the placement plate 10, and the steel pipe frame is separated from the surface of the placement plate 10 by using the wedge block 503. The ejection action can be automatically performed while releasing the fixation, reducing manual intervention, and thus accelerating the speed of the entire demoulding process.

[0044] The release mechanism 60 includes through grooves 601 symmetrically opened on the surface of the placement plate 10. A second connecting rod 602 is slidably connected inside each through groove 601. One end of the second connecting rod 602 is fixedly connected to the bottom of the moving plate 403, and the other end of the second connecting rod 602 penetrates through the through groove 601 and extends to the other side of the placement plate 10. Two transverse second connecting rods 602 are fixedly connected by a cross bar 603.

[0045] A guide rod 604 is fixedly connected to the bottom of the placement plate 10, and the guide rod 604 slidably penetrates through the second connecting rod 602.

[0046] A bidirectional lead screw 605 is also rotatably connected to the bottom of the placement plate 10. Hand wheels 606 are fixedly connected to both ends of the bidirectional lead screw 605, and the threaded sections outside the bidirectional lead screw 605 are respectively threadedly connected to the two cross bars 603.

[0047] During specific operation, before welding, when fixing the steel pipe placed on the placement plate 10, rotate the hand wheel 606 to drive the bidirectional lead screw 605 to rotate. The rotating bidirectional lead screw 605 simultaneously drives the two cross bars 603 to approach each other. The two cross bars 603 drive the two moving plates 403 to approach the side of the first limit block 401 through the second connecting rods 602 respectively, so as to clamp and fix the steel pipe on the side of the placement plate 10.

[0048] After welding is completed, reverse-rotate the handwheel 606 to drive the bidirectional lead screw 605 to rotate. The rotating bidirectional lead screw 605 simultaneously drives the two cross bars 603 to move away from each other. The two cross bars 603 respectively drive the two moving plates 403 to move away from the side of the first limit block 401 through the second connecting rods 602, thereby releasing the clamping of the steel pipe, and finally separating the steel pipe frame from the surface of the placement plate 10.

[0049] Working principle: Before welding, use the release mechanism 60 to drive the positioning mechanism 40 to fix the steel pipe on the surface of the placement plate 10, realizing the butt joint and fixation of the steel pipe. Then, drive the placement plate 10 to exchange positions through the exchange mechanism 20 to complete welding and unloading. After welding is completed, reverse-operate the release mechanism 60 to drive the positioning mechanism 40 to release the fixation of the welded steel pipe frame. Under the action of gravity, the welded steel pipe frame falls. At the same time, use the moving plate 403 of the positioning mechanism 40 to drive the lifting mechanism 50 to assist the steel pipe frame to separate from the surface of the placement plate 10.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-station steel pipe welding tool, characterized in that: The placing plate (10) comprises a placing plate (10), wherein a switching mechanism (20) for changing the position of the placing plate (10) is arranged at the bottom of the placing plate (10), a flipping mechanism (30) for driving the placing plate (10) to rotate is arranged on the side of the switching mechanism (20), a positioning mechanism (40) for preventing the steel pipe from moving is arranged on the surface of the placing plate (10), a lifting mechanism (50) for detaching the welded steel pipe from the placing plate (10) is arranged inside the placing plate (10), and a releasing mechanism (60) for driving the steel pipe to be released from the fixed state is arranged on the side of the placing plate (10) away from the positioning mechanism (40); The exchange mechanism (20) comprises symmetrically arranged support seats (201), each support seat (201) having a first rotating shaft (202) horizontally connected to the top, two first rotating shafts (202) being fixedly connected to a mounting frame (203) at one end close to each other, and each mounting frame (203) having a second rotating shaft (204) being rotatably connected at both ends, and a placement plate (10) for placing steel pipes being fixedly connected between the two second rotating shafts (204) at the same end.

2. The multi-station steel pipe welding tool according to claim 1, characterized in that: The exchange mechanism (20) further comprises a worm wheel (205) fixedly connected to one end of the first rotating shaft (202) away from the mounting frame (203); a worm (206) is rotatably connected to the side of the support seat (201); the worm (206) is meshed with the worm wheel (205); a motor (207) is fixedly connected to the side of the support seat (201); and an output end of the motor (207) is fixedly connected to one end of the worm (206).

3. The multi-station steel pipe welding tool according to claim 1, characterized in that: The turnover mechanism (30) comprises a first pulley (301) fixedly connected to the outside of the first rotating shaft (202); the second rotating shaft (204) is fixedly connected to one end thereof away from the placement plate (10); the second pulley (302) and the first pulley (301) are connected in transmission via a synchronous belt (303).

4. The multi-station steel pipe welding tool according to claim 1, characterized in that: The positioning mechanism (40) comprises first limit blocks (401) symmetrically fixedly connected to the surface of the placement plate (10), two first limit blocks (401) being slidably connected to a movable plate (403) on the surface of the placement plate (10) on a side away from each other, and each of the movable plates (403) having triangular blocks (407) fixedly connected at both ends.

5. The multi-station steel pipe welding tool according to claim 4, characterized in that: A mounting block (404) is fixedly connected to one side of the movable plate (403) close to the first limit block (401); a sliding sleeve (405) is slidably sleeved on the outside of the mounting block (404); a spring (406) is fixedly connected to the inside of the cavity of the sliding sleeve (405); and one end of the spring (406) away from the sliding sleeve (405) is fixedly connected to the mounting block (404).

6. The multi-station steel pipe welding tool according to claim 4, characterized in that: The positioning mechanism (40) further comprises a second limit block (402) symmetrically fixedly connected to the surface of the placement plate (10); two second limit blocks (402) are rotatably connected to the surface of the placement plate (10) on a side away from each other, and a rotating rod (408) is rotatably connected to each other; one end of each rotating rod (408) is fixedly connected to a trapezoidal block (409); the inclined surface of the trapezoidal block (409) and the inclined surface of the triangular block (407) slide against each other.

7. The multi-station steel pipe welding tool according to claim 1, characterized in that: The lifting mechanism (50) comprises longitudinal grooves (501) symmetrically arranged on the surface of the placement plate (10), each of the longitudinal grooves (501) being slidably connected with a first connecting rod (502), one end of the first connecting rod (502) being fixedly connected to the bottom of the movable plate (403), and the other end of the first connecting rod (502) being fixedly connected with a wedge block (503) for lifting the steel pipe.

8. The multi-station steel pipe welding tool according to claim 1, characterized in that: The release mechanism (60) comprises through slots (601) symmetrically arranged on the surface of the placement plate (10), each of the through slots (601) being slidably connected with a second connecting rod (602), one end of the second connecting rod (602) being fixedly connected to the bottom of the movable plate (403), and the other end of the second connecting rod (602) passing through the through slot (601) and extending to the other side of the placement plate (10), and two transverse second connecting rods (602) being fixedly connected via a cross bar (603).

9. The multi-station steel pipe welding tool according to claim 8, characterized in that: A guide rod (604) is fixedly connected to the bottom of the placement plate (10), and the guide rod (604) slides through the second connecting rod (602).

10. The multi-station steel pipe welding tool according to claim 8, characterized in that: The bottom of the placement plate (10) is also rotatably connected to a bidirectional screw rod (605), both ends of which are fixedly connected to hand wheels (606), and the threaded sections outside the bidirectional screw rod (605) are respectively threadedly connected to the two cross bars (603).

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