Flexible production robot moving mechanical structure based on magnetic adsorption

Abstract

The invention provides a flexible production robot moving mechanical structure based on magnetic attraction, and relates to the technical field of robot movement, the flexible production robot moving mechanical structure comprises a flexible robot and a moving support, the flexible robot is fixedly installed on the moving support, and the moving support is provided with a moving mechanism for assisting the flexible robot to move. The flexible robot is provided with an adjusting mechanism for adjusting the moving mechanism, the moving mechanism comprises a crawler belt and four moving wheels, the adjusting mechanism comprises a mounting block, a reducing block, a first flat tooth and a worm, and the four moving wheels are fixedly mounted at the ends of the two sides of the moving support respectively. According to the device, the moving wheels capable of achieving dynamic diameter changing during operation of the flexible robot are arranged, the device can automatically adapt to and be matched with the complex environment in the operation process, the situation that the flexible robot is difficult to transport due to the complex site environment is avoided, and the situation that due to forced transportation, the loading and unloading bearing pressure on the moving support is too large, and damage is caused is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot movement, and more specifically, particularly relates to a mobile mechanical structure of a flexible production robot based on magnetic adsorption. Background Art

[0002] The flexible production robot based on magnetic adsorption realizes stable attachment and free movement on the metal surface through a magnetic device. It can not only climb vertically and operate upside down, but also fit the curved surface to complete high-precision operations. It is especially suitable for scenarios such as large steel structure welding, inner wall inspection of storage tanks, and high-altitude equipment maintenance. Generally, it is transported in each workshop and site by a moving mechanism.

[0003] The existing robot moving mechanisms have the following disadvantages:

[0004] 1. When the existing flexible robot is transported, it will encounter terrains such as slopes or gullies. However, the existing moving mechanisms, such as fixed wheel diameter wheels or rigid tracks, cannot dynamically adjust the wheel diameter and ground contact pressure according to the terrain, resulting in frequent jamming or slipping in complex terrains such as slopes and gullies, affecting the conveying efficiency of objects and requiring manual intervention.

[0005] 2. When the existing flexible robot is actually used, the terrain it adapts to is limited. For different terrains, robots with different moving mechanisms need to be configured, such as mobile robots for climbing slopes or mobile robots for moving in gullies, resulting in an increase in transportation and conveying costs and a complicated transfer process. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a mobile mechanical structure of a flexible production robot based on magnetic adsorption to solve the above problems.

[0007] A flexible production robot mobile mechanical structure based on magnetic adsorption, including a flexible robot and a mobile support. The flexible robot is fixedly installed on the mobile support. The mobile support is provided with a mobile mechanism for assisting the flexible robot to move. The flexible robot is provided with an adjustment mechanism for adjusting the mobile mechanism. The mobile mechanism includes crawlers and mobile wheels. The adjustment mechanism includes mounting blocks, variable-diameter blocks, first flat teeth, and worm gears. The number of mobile wheels is four, and the four mobile wheels are respectively fixedly installed at both ends of the two sides of the mobile support. The number of crawlers is two, and the two crawlers are respectively sleeved on the outer side walls of the two mobile wheels. The number of mounting blocks is two, and the two mounting blocks are respectively located on both sides of the mobile support. Servo motors are fixedly installed at both ends of the two sides of each mounting block. The number of variable-diameter blocks is at least two, and each variable-diameter block is arrayed at the circumferential end of the mobile wheel. The number of the first flat teeth and worm gears is four, and each first flat tooth and worm gear is respectively located at the side end of the mobile wheel. At least two auxiliary rollers are provided at both ends of the two sides of the mobile support. Positioning disks are fixedly installed at both ends of the two sides of the mobile support. An annular groove is opened at the side end of the positioning disk. Driven rollers are provided at the side ends of the two mobile supports. Connecting rods are fixedly installed at the circumferential ends of the two driven rollers. The two driven rollers are respectively installed through and rotatably at the side ends of the positioning disks. Arc-shaped sliders are fixedly installed at the side ends of the two mounting blocks. The two arc-shaped sliders are respectively rotatably installed on the inner side wall of the annular groove. Transmission rods are fixedly installed at the output ends of the two servo motors. A first mounting roller is fixedly installed at the side end of each mobile wheel. A second mounting roller is also fixedly installed at the side end of each mobile wheel. An expansion rod is fixedly installed between each variable-diameter block and the mobile wheel. A push rod is fixedly installed at the side end of each variable-diameter block. A guide rod is fixedly installed at the side end of each push rod. Each first flat tooth is rotatably installed at the circumferential end of the first mounting roller. A damping bearing is provided between the first flat tooth and the first mounting roller. A second mounting roller is also rotatably installed at the side end of each first flat tooth. At least two arc-shaped grooves are respectively opened at the side end of each first flat tooth, and the arc-shaped grooves are distributed in an array.

[0008] Preferably, a second flat tooth is fixedly installed at the circumferential end of each second mounting roller, and each second flat tooth is meshed with the first flat tooth.

[0009] Preferably, a worm wheel is also fixedly installed at the circumferential end of each second mounting roller. Each worm gear is respectively fixedly installed at the side end of the transmission rod. Each worm gear is respectively meshed with the worm wheel, and the helical lines of the two worm gears are opposite.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] In the present invention, by providing adjustable moving wheels, when it is necessary to cross a gully or climb a steep slope, the ground clearance can be increased by enlarging the diameter of the front moving wheels and reducing the diameter of the rear moving wheels, thereby avoiding jamming of the moving support. The reduction of the rear moving wheels can lower the center of gravity, enhance the grip of the rear wheels, prevent slipping during climbing, and ensure the stability of the flexible robot when transporting objects.

[0012] In the present invention, by providing moving wheels with variable diameters, when the flexible robot is going downhill, the diameter of the front moving wheels can be reduced to lower the inertia of the front part and avoid diving out of control, while the diameter of the rear moving wheels is increased to increase the contact area with the ground and enhance the braking friction force, ensuring that the flexible robot is in a state of high friction and low inertia when going downhill, reducing the impact on object transportation and ensuring stability.

[0013] In the present invention, by providing moving wheels that can achieve dynamic diameter change during the operation of the flexible robot, it can adapt to and match complex environments during operation, avoid difficulties in transporting objects by the flexible robot due to complex site environments, avoid damage caused by excessive mechanical pressure on the moving support during forced transportation, or the situation where the flexible robot loses balance and topples due to uneven terrain, ensuring the balance and safety of the flexible robot when transporting objects.

[0014] In the present invention, by providing a servo motor, a transmission rod, and a first flat tooth in cooperation, when the front and rear moving wheels are synchronously reduced or enlarged through linkage, the total length of the track remains constant, and the redundant circumference generated by the wheel diameter change is automatically compensated by the linkage mechanism, avoiding sudden changes in tension caused by adjusting the wheel diameter of a single moving wheel, and always maintaining the track pre-tightening force within the safety threshold, preventing both track derailment and overload fracture, thus achieving self-balancing tension in scenarios such as climbing slopes and crossing obstacles, and taking into account terrain adaptability and system reliability.

[0015] In the present invention, by providing a positioning disk and an annular groove in cooperation, when the driven roller rotates, it will drive the mounting block on the arc-shaped slider connected to it to rotate synchronously, thereby ensuring that the worm gears on both sides can ensure the same running track when the moving wheels on both sides rotate, providing a better supporting effect for the transmission rod and the worm gears, and ensuring the accuracy and stability of meshing when the device is in use. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the flexible robot of the present invention;

[0017] Figure 2 is a schematic structural diagram of the moving support of the present invention;

[0018] Figure 3 is a schematic structural diagram of the positioning disk of the present invention;

[0019] Figure 4It is a schematic structural diagram of the auxiliary roller of the present invention;

[0020] Figure 5 It is a schematic structural diagram of the mounting block of the present invention;

[0021] Figure 6 It is a schematic structural diagram of the moving wheel of the present invention;

[0022] Figure 7 It is a schematic structural diagram of the first flat tooth of the present invention;

[0023] Figure 8 It is a schematic structural diagram of the diameter-changing block of the present invention.

[0024] In the figure, the corresponding relationship between the component names and the drawing numbers is as follows: 1. Flexible robot; 2. Moving support; 21. Auxiliary roller; 22. Crawler; 23. Positioning disk; 24. Driven roller; 25. Link; 26. Annular groove; 3. Mounting block; 31. Arc-shaped slider; 32. Servo motor; 33. Transmission rod; 4. Moving wheel; 41. First mounting roller; 42. Second mounting roller; 5. Diameter-changing block; 51. Push rod; 52. Guide rod; 53. Telescopic rod; 6. First flat tooth; 61. Arc-shaped groove; 62. Second flat tooth; 7. Worm; 71. Worm gear. Specific embodiments

[0025] The following further describes the embodiments of the present invention in detail with reference to the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0026] Please refer to Figures 1 - 8 , the present invention provides a mobile mechanical structure of a flexible production robot based on magnetic adsorption, including a flexible robot 1 and a moving support 2. The flexible robot 1 is fixedly installed on the moving support 2. A moving mechanism for assisting the flexible robot 1 to move is provided on the moving support 2. An adjusting mechanism for adjusting the moving mechanism is provided on the flexible robot 1. The flexible robot 1 realizes stable attachment and free movement on the metal surface through a magnetic device, and can not only climb vertically and work upside down, but also fit the curved surface to complete high-precision operations. It is especially suitable for scenarios such as large steel structure welding, inner wall inspection of storage tanks, and high-altitude equipment maintenance. When the flexible robot 1 is in use, the moving wheel 4 is driven to rotate through the moving support 2, so that the crawler 22 rotates synchronously, thereby assisting the flexible robot 1 to displace, and further realizing transfer movement during the transportation of goods;

[0027] The moving mechanism includes a crawler 22 and moving wheels 4, and the adjusting mechanism includes mounting blocks 3, diameter-changing blocks 5, first flat teeth 6, and a worm 7. The number of moving wheels 4 is four, and the four moving wheels 4 are respectively fixedly installed at the two side ends of the moving support 2. The number of crawlers 22 is two, and the two crawlers 22 are respectively sleeved on the outer side walls of the two moving wheels 4. The number of mounting blocks 3 is two, and the two mounting blocks 3 are respectively located on both sides of the moving support 2. Servo motors 32 are fixedly installed at the two side ends of each of the two mounting blocks 3. The number of diameter-changing blocks 5 is at least two, and each diameter-changing block 5 is arranged in an array at the circumferential end of the moving wheel 4. The number of the first flat teeth 6 and the worm 7 is four each, and each of the first flat teeth 6 and the worm 7 is respectively located at the side end of the moving wheel 4. At least two auxiliary rollers 21 are provided at the two side ends of the moving support 2. Positioning disks 23 are fixedly installed at the two side ends of the moving support 2. An annular groove 26 is formed at the side end of the positioning disk 23. Driven rollers 24 are provided at the two side ends of the two moving supports 2. Connecting rods 25 are fixedly installed at the circumferential ends of the two driven rollers 24. The two driven rollers 24 respectively penetrate and are rotatably installed at the side end of the positioning disk 23. Arc-shaped sliders 31 are fixedly installed at the two side ends of the two mounting blocks 3. The two arc-shaped sliders 31 are respectively rotatably installed on the inner side wall of the annular groove 26. Transmission rods 33 are fixedly installed at the output ends of the two servo motors 32. When the flexible robot 1 goes down a steep slope, at this time, it is necessary to reduce the diameter of the moving wheels 4 at the front side of the flexible robot 1 and increase the diameter of the moving wheels 4 at the rear side of the flexible robot 1. The user can adopt the same method as in the second step and start the two servo motors 32 to drive the two transmission rods 33 to rotate in opposite directions. At this time, the rotation of the first flat teeth 6 at the front side will drive the diameter-changing block 5 to contract through the cooperation of the arc-shaped groove 61 and the guide rod 52, and the rotation of the first flat teeth 6 at the rear side will drive the diameter-changing block 5 to expand through the cooperation of the arc-shaped groove 61 and the guide rod 52, so as to realize the reduction of the front wheel diameter and the expansion of the rear wheel diameter, and change the front and rear diameters of the moving wheels 4 when going downhill;

[0028] A first mounting roller 41 is fixedly installed at the side end of each moving wheel 4, and a second mounting roller 42 is also fixedly installed at the side end of each moving wheel 4. A telescopic rod 53 is fixedly installed between each variable diameter block 5 and the moving wheel 4 respectively. A push rod 51 is fixedly installed at the side end of each variable diameter block 5, and a guide rod 52 is fixedly installed at the side end of each push rod 51. Each first flat tooth 6 is rotatably installed at the circumferential end of the first mounting roller 41, and a damping bearing is provided between the first flat tooth 6 and the first mounting roller 41. A second mounting roller 42 is also rotatably installed at the side end of each first flat tooth 6. At least two arc-shaped grooves 61 are formed through the side end of each first flat tooth 6, and the arc-shaped grooves 61 are distributed in an array. A second flat tooth 62 is fixedly installed at the circumferential end of each second mounting roller 42, and each second flat tooth 62 meshes with the first flat tooth 6. When the second flat tooth 62 rotates, it drives the first flat tooth 6 to rotate. When the first flat tooth 6 rotates, it drives the guide rod 52 in the arc-shaped groove 61 to slide. The sliding of the guide rod 52 drives the push rod 51 to move, driving each variable diameter block 5 to expand. At this time, because the spiral lines of the worm 7 on the other side are opposite to those on the front side, when the worm 7 rotates, it drives each variable diameter block 5 to contract. At this time, the diameter of the front wheels becomes larger, and the diameter of the rear wheels becomes smaller. The increase in the front moving wheels 4 can increase the ground clearance and prevent the moving support 2 from getting stuck. The reduction of the rear moving wheels 4 can lower the center of gravity and enhance the grip of the rear wheels, preventing slipping when climbing slopes;

[0029] A worm gear 71 is also fixedly installed at the circumferential end of each second mounting roller 42. Each worm 7 is fixedly installed at the side end of the transmission rod 33 respectively. Each worm 7 meshes with the worm gear 71 respectively. The spiral lines of the two worms 7 on both sides are opposite. When the flexible robot 1 needs to cross a gully or climb a steep slope, during the actual movement at this time, it is necessary to change the diameter of the front and rear groups of moving wheels 4 to assist the flexible robot 1 in moving. At this time, it is necessary to increase the diameter of the front wheels close to the gully or steep slope. The user can start the servo motors 32 on both sides. The start of the two servo motors 32 drives the two transmission rods 33 to rotate simultaneously. The rotation of the two transmission rods 33 drives the worm 7 to rotate. The spiral lines on the two worms 7 on both sides are opposite. The rotation of the worm 7 on the front wheels close to the gully or steep slope drives the worm gear 71 to rotate. The rotation of the worm gear 71 drives the second flat tooth 62 on the second mounting roller 42 to rotate.

[0030] Working principle:

[0031] In the first step, the flexible robot 1 realizes stable attachment and free movement on the metal surface through the magnetic device. It can not only climb vertically and operate upside down, but also fit the curved surface to complete high-precision operations. It is especially suitable for scenarios such as large steel structure welding, inner wall inspection of storage tanks, and high-altitude equipment maintenance. When the flexible robot 1 is in use, the moving wheels 4 are driven to rotate through the moving support 2, so that the crawler 22 rotates synchronously, thereby assisting the flexible robot 1 in displacement, and then realizing transfer movement during the transportation of goods;

[0032] In the second step, when the flexible robot 1 is transported to different workshops and transportation sites, there are some special terrains on the transportation site. When the flexible robot 1 needs to cross a gully or climb a steep slope, during the actual movement, it is necessary to change the diameter of the front and rear groups of moving wheels 4 to assist the flexible robot 1 in moving. At this time, it is necessary to increase the diameter of the front wheels close to the gully or steep slope. The user can start the servo motors 32 on both sides. The start of the two servo motors 32 will drive the two transmission rods 33 to rotate simultaneously. The rotation of the two transmission rods 33 will drive the worm 7 to rotate. The helical lines on the two worms 7 are opposite. The rotation of the worm 7 on the front wheels close to the gully or steep slope will drive the worm gear 71 to rotate. The rotation of the worm gear 71 will drive the second flat teeth 62 on the second mounting roller 42 to rotate. The rotation of the second flat teeth 62 will drive the first flat teeth 6 to rotate. When the first flat teeth 6 rotate, it will drive the guide rod 52 in the arc-shaped groove 61 to slide. The sliding of the guide rod 52 drives the push rod 51 to move and drives each diameter-changing block 5 to expand. At this time, the other worm 7, due to the opposite helical line to the front side, will drive each diameter-changing block 5 to contract under the rotation of the worm 7. At this time, the diameter of the front wheels is increased, and the diameter of the rear wheels is reduced. The increase in the front moving wheels 4 can increase the ground clearance and avoid jamming of the moving support 2. The reduction of the rear moving wheels 4 can lower the center of gravity and enhance the rear-wheel grip to prevent slipping when climbing slopes;

[0033] By setting the adjustable moving wheels 4, when it is necessary to cross a gully or climb a steep slope, the ground clearance can be increased by expanding the diameter of the front moving wheels 4 and reducing the diameter of the rear moving wheels 4. The reduction of the rear moving wheels 4 can lower the center of gravity and enhance the rear-wheel grip to prevent slipping when climbing slopes, ensuring the stability of the flexible robot 1 when transporting objects;

[0034] In the third step, when the flexible robot 1 walks down a steep slope, at this time, it is necessary to reduce the diameter of the front moving wheels 4 of the flexible robot 1 and increase the diameter of the rear moving wheels 4 of the flexible robot 1. The user can adopt the same method as in the second step, start the two servo motors 32 to drive the two transmission rods 33 to rotate in opposite directions. At this time, the rotation of the first flat teeth 6 on the front side will drive the diameter-changing block 5 to contract through the cooperation of the arc-shaped groove 61 and the guide rod 52, while the rotation of the first flat teeth 6 on the rear side will drive the diameter-changing block 5 to expand through the cooperation of the arc-shaped groove 61 and the guide rod 52, so as to realize the reduction of the front-wheel diameter and the expansion of the rear-wheel diameter, and change the front and rear diameters of the moving wheels 4 when going downhill;

[0035] By setting the moving wheels 4 with variable diameters, when the flexible robot 1 is going downhill, the diameter of the front moving wheels 4 can be reduced to reduce the front inertia and avoid diving out of control, while increasing the diameter of the rear moving wheels 4 can increase the contact area with the ground and enhance the braking friction force, ensuring that the flexible robot 1 is in a state of high friction and low inertia when going downhill, reducing the impact on object transportation and ensuring stability;

[0036] By providing a moving wheel 4 that can achieve dynamic diameter variation during the operation of the flexible robot 1, this device can adapt to and match complex environments during operation, avoiding difficulties in transporting the flexible robot 1 due to complex site environments, preventing damage caused by excessive unloading pressure on the moving support 2 due to forced transportation, or preventing the flexible robot 1 from tipping over due to uneven terrain, thus ensuring the balance and safety of the flexible robot 1 during object transportation.

[0037] By providing a servo motor 32, a transmission rod 33, and a first flat tooth 6 that cooperate with each other, when the front and rear moving wheels 4 are synchronously reduced or enlarged through linkage, the total length of the crawler 22 remains constant, and the redundant circumference generated by the wheel diameter change is automatically compensated by the linkage mechanism, avoiding sudden changes in tension caused by the adjustment of the wheel diameter of the single-sided moving wheel 4, and always maintaining the pre-tightening force of the crawler 22 within the safety threshold, preventing the crawler 22 from derailing and avoiding overload fracture, so that self-balancing tensioning can be achieved in scenarios such as climbing slopes and crossing obstacles, taking into account terrain adaptability and system reliability.

[0038] By providing a positioning disk 23 and an annular groove 26 that cooperate with each other, when the driven roller 24 rotates, it will drive the mounting block 3 on the arc-shaped slider 31 connected to it to rotate synchronously, thereby ensuring that the worm gears 7 on both sides can maintain the same running track when the moving wheels 4 on both sides rotate and move, providing a better supporting effect for the transmission rod 33 and the worm gears 7, and ensuring the accuracy and stability of meshing during device use.

[0039] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical applications, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for specific purposes.

Claims

1. A flexible production robot mobile mechanical structure based on magnetic adsorption, comprising a flexible robot (1) and a mobile support (2), wherein the flexible robot (1) is fixedly installed on the mobile support (2), and is characterized in that: The moving support (2) is provided with a moving mechanism for assisting the flexible robot (1) to move, and the flexible robot (1) is provided with an adjusting mechanism for adjusting the moving mechanism; Among them, the moving mechanism includes a crawler (22) and moving wheels (4), the adjusting mechanism includes mounting blocks (3), diameter-changing blocks (5), first flat teeth (6) and worm gears (7). The number of the moving wheels (4) is four, and the four moving wheels (4) are respectively fixedly installed at both end parts of the moving support (2). The number of the crawlers (22) is two, and the two crawlers (22) are respectively sleeved and installed on the outer side walls of the two moving wheels (4). The number of the mounting blocks (3) is two, and the two mounting blocks (3) are respectively located on both sides of the moving support (2). Servo motors (32) are fixedly installed at both end parts of the two mounting blocks (3). The number of the diameter-changing blocks (5) is at least two, and each diameter-changing block (5) is arrayed at the circumferential end part of the moving wheel (4). The number of the first flat teeth (6) and worm gears (7) is four, and each first flat tooth (6) and worm gear (7) is respectively located at the side end part of the moving wheel (4).

2. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 1, characterized in that At least two auxiliary rollers (21) are provided at both end parts of the moving support (2), positioning disks (23) are fixedly installed at both end parts of the moving support (2), and an annular groove (26) is formed at the side end part of the positioning disk (23).

3. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 2, characterized in that, Driven rollers (24) are provided at the side end parts of the two moving supports (2), connecting rods (25) are fixedly installed at the circumferential end parts of the two driven rollers (24), and the two driven rollers (24) respectively penetrate and are rotatably installed at the side end parts of the positioning disks (23).

4. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 3, characterized in that, Arc-shaped sliders (31) are fixedly installed at the side end parts of the two mounting blocks (3), the two arc-shaped sliders (31) are respectively rotatably installed on the inner side wall of the annular groove (26), and transmission rods (33) are fixedly installed at the output end parts of the two servo motors (32).

5. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 4, characterized in that A first mounting roller (41) is fixedly installed at the side end part of each moving wheel (4), and a second mounting roller (42) is also fixedly installed at the side end part of each moving wheel (4).

6. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 5, wherein, A telescopic rod (53) is fixedly installed between each diameter-changing block (5) and the moving wheel (4), a push rod (51) is fixedly installed at the side end part of each diameter-changing block (5), and a guide rod (52) is fixedly installed at the side end part of each push rod (51).

7. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 6, characterized in that, Each first flat tooth (6) is rotatably installed at the circumferential end part of the first mounting roller (41), a damping bearing is arranged between the first flat tooth (6) and the first mounting roller (41), and a second mounting roller (42) is also rotatably installed at the side end part of each first flat tooth (6).

8. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 7, wherein At least two arc-shaped grooves (61) are formed through the side end part of each first flat tooth (6), and the arc-shaped grooves (61) are distributed in an array.

9. The mobile mechanical structure of a flexible production robot based on magnetic adsorption according to claim 8, characterized in that A second flat tooth (62) is fixedly installed at the circumferential end part of each second mounting roller (42), and each second flat tooth (62) is meshed with the first flat tooth (6).

10. The mobile mechanical structure of a flexible production robot based on magnetic adsorption as described in claim 9, wherein, A worm gear (71) is also fixedly installed at the circumferential end of each of the second mounting rollers (42). Each of the worm shafts (7) is fixedly installed at the side end of the transmission rod (33). Each of the worm shafts (7) is meshed with the worm gear (71) respectively, and the helical lines of the worm shafts (7) on both sides are opposite.

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