Safety auxiliary device for installation and construction of anchor bolt of wind generating set

By designing wind turbine anchor bolt installation construction safety auxiliary devices, the lifting mechanism and safety rope lock are used to protect staff, the risk of falling at high places in the top of the anchor bolt is solved, and construction safety and stability are improved.

CN223280543UActive Publication Date: 2025-08-29NINGXIA KAITAI NEW ENERGY ENG TECH CO LTD
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Patent Information

Application Number
CN202422708594.3
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-11-07
Publication Date
2025-08-29
Estimated Expiration
2034-11-07

AI Technical Summary

Technical Problem

During the installation and construction of wind turbine anchor bolts, staff have the risk of falling from high places when working on the top of the anchor bolts, resulting in insufficient construction safety.

Method used

A construction safety auxiliary device for the installation of anchor bolts of wind turbines is designed, including the body, lifting mechanism, safety rope and safety lock. The height of the body is adjusted through the lifting mechanism, and the safety rope and safety lock protect the staff to prevent falling.

Benefits of technology

Effectively prevent staff from falling on the top of the anchor bolt, improve the safety and stability of the anchor bolt installation and construction, and reduce the danger during the construction process.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model discloses a wind generating set anchor bolt installation construction safety auxiliary device which comprises a machine body, and a lifting mechanism is arranged in the middle of the lower end in the machine body. The safety auxiliary equipment for installation and construction of the anchor bolt of the wind generating set can be formed, a worker can be protected when working at the top of the anchor bolt, the worker is prevented from falling from the top of the anchor bolt, the danger of the worker during working is reduced, and the working efficiency is improved. And the safety in the installation and construction process of the anchor bolt of the wind generating set is ensured.
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Description

Technical Field

[0001] The utility model relates to the technical field of anchor bolt installation and construction, in particular to a safety auxiliary device for anchor bolt installation and construction of a wind turbine generator set. Background Art

[0002] The wind power generation power supply consists of a wind turbine generator set, a frame supporting the generator set, a battery charging controller, an inverter, an unloader, a grid controller, a battery pack, etc. The wind turbine generator set includes a wind wheel and a generator. The wind wheel is composed of blades, a hub, reinforcements, etc. The blades rotate under the wind force to generate electricity. During the construction of the wind turbine anchor bolt foundation, the height of the anchor bolt cage is at least four to six meters from the ground. The staff needs to climb to the top of the anchor bolt to install the nut, adjust the height, and inspect and accept the top of the anchor bolt.

[0003] During the existing wind turbine anchor bolt installation construction process, workers are unable to provide safety assistance. Workers are prone to falling from the top of the anchor bolt when working on the top of the anchor bolt, which increases the danger of wind turbine anchor bolt installation construction, so improvement is needed. Utility Model Content

[0004] The purpose of the utility model is to overcome the problem in the prior art that during the installation and construction of anchor bolts for wind turbine generator sets, it is dangerous for workers to work on the top of the anchor bolts, and there is a great risk of workers falling from heights during the operation, thereby reducing the safety deficiency during the installation and construction of anchor bolts for wind turbine generator sets, and a safety auxiliary device for the installation and construction of anchor bolts for wind turbine generator sets is proposed.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A wind turbine generator anchor bolt installation construction safety auxiliary device comprises a body, wherein a lifting mechanism is provided at the lower middle portion of the body;

[0007] An anchor cage is correspondingly provided below the machine body, and a circular slide is provided in the middle of the lower end of the machine body. Slide blocks are slidably sleeved on both sides of the circular slide, and safety ropes are provided at the lower ends of the two slide blocks. Safety locks are provided at the lower ends of the two safety ropes. Two threaded sleeves are correspondingly provided on the lifting mechanism, and the two threaded sleeves are rotatably sleeved on both sides of the lower end of the machine body respectively. The upper ends of the two threaded sleeves are rotatably connected to both sides of the upper end of the machine body respectively. Lifting screws are threadedly sleeved in the two threaded sleeves, and the lower ends of the two lifting screws are fixedly connected to a supporting plate, and a plurality of universal wheels are evenly spaced at the lower ends of the two supporting plates.

[0008] Preferably, in order to adjust the height of the machine body, the lifting mechanism includes a dual-axis motor fixedly installed in the middle of the lower end of the machine body, the two output shaft ends of the dual-axis motor are fixedly connected to the transmission shaft, the other ends of the two transmission shafts are fixedly connected to worms, the other ends of the two worms are respectively rotatably connected to the relative inner walls of the machine body, one side of the two worms is engaged with a worm gear, and the two worm gears are respectively fixedly sleeved on two threaded sleeves.

[0009] Preferably, in order to support the two transmission shafts and keep them rotating smoothly in the machine body, two bearing seats are fixedly connected on both sides of the lower end of the machine body, and bearings are fixedly sleeved in the four bearing seats. The four bearings are respectively rotatably sleeved on the two ends of the two transmission shafts.

[0010] Preferably, in order to increase the stability of the body above the two supporting plates, sleeves are fixedly connected to both sides of the upper ends of the two supporting plates, and round rods are fixedly connected to the four corners of the lower end of the body, and the four round rods are slidably sleeved in the corresponding four sleeves respectively.

[0011] Preferably, in order to move the machine body to above the anchor cage, the bottoms of the two corresponding sleeves are fixedly connected to increase the stability of the bottom of the overall structure, thereby improving the stability of the machine body, the lower parts of the four sleeves are fixedly sleeved with fixed blocks, and the upper ends of the two corresponding fixed blocks are detachably connected to reinforcement rods. Bolts are provided on both sides of the upper ends of the two reinforcement rods, and the lower ends of the four bolts respectively penetrate the four fixed blocks and are threaded with nuts.

[0012] Preferably, in order to move the machine body to the corresponding position, the four bottom plates are lowered and pressed against the ground. The four bottom plates pressed against the ground can support the two supporting plates to prevent the two supporting plates from moving at will. Threaded sleeves are fixedly connected on both sides of the two supporting plates, and support screws are threadedly connected in the four threaded sleeves. The upper ends of the four support screws are fixedly connected to the rotating wheels, and the lower ends of the four support screws are rotatably connected to the bottom plates.

[0013] Preferably, in order to fix the four bottom plates on the ground when the machine is in use, the stability of the machine can be ensured by fixing the four bottom plates on the ground to prevent the machine from being blown away by the wind in windy weather. Expansion bolts are provided on both sides of the upper ends of the four bottom plates, and telescopic rods are fixedly connected on both sides of the lower ends of the two supporting plates. The lower ends of the four telescopic rods are respectively fixedly connected to the upper ends of the four bottom plates.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. Through the use of components such as the lifting mechanism, two bearing plates, multiple universal wheels, a circular slide, a safety rope and a safety lock, during the installation of the anchor bolts of the wind turbine generator set, the height of the machine body can be adjusted to the corresponding height, and then the machine body can be moved above the anchor bolts. When the workers are working on the top of the anchor bolts, the safety locks are connected to the workers, thereby protecting the workers and preventing them from falling from a height, reducing the danger to the workers and effectively ensuring the safety of the wind turbine generator set anchor bolt installation construction;

[0016] 2. By using components such as bottom plates and expansion bolts, the four bottom plates can be lowered to the ground when the machine is in use, and then the bottom plates can be fixed with expansion bolts, thereby preventing the machine from moving at will, increasing the stability of the machine during use, and then increasing the safety of the machine during the installation of anchor bolts of the wind turbine;

[0017] To sum up, the utility model can form a safety auxiliary equipment for the installation and construction of anchor bolts of wind turbine generator sets. When workers are working on the top of the anchor bolts, the equipment can protect them and prevent them from falling from the top of the anchor bolts, thereby reducing the danger of workers during operation and ensuring the safety of the wind turbine generator set anchor bolt installation and construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a connection structure diagram of a wind turbine generator anchor bolt installation construction safety auxiliary device proposed by the utility model;

[0019] Figure 2 This is a schematic diagram of the internal structure of a wind turbine generator anchor bolt installation safety auxiliary device proposed by the present invention;

[0020] Figure 3 This is an enlarged view of point A of a wind turbine generator anchor bolt installation safety auxiliary device proposed by the present invention;

[0021] Figure 4 This is an enlarged view of point B of a wind turbine generator anchor bolt installation safety auxiliary device proposed by the present invention;

[0022] Figure 5 This is an enlarged view of point C of a wind turbine generator anchor bolt installation safety auxiliary device proposed by the present invention.

[0023] In the figure: 1 anchor cage, 2 machine body, 3 circular slide, 4 slider, 5 safety rope, 6 safety lock, 7 dual-axis motor, 8 transmission shaft, 9 bearing seat, 10 bearing, 11 worm, 12 worm wheel, 13 threaded sleeve, 14 lifting screw, 15 bearing plate, 16 sleeve, 17 round rod, 18 fixing block, 19 reinforcement rod, 20 bolt, 21 nut, 22 threaded sleeve, 23 support screw, 24 rotating wheel, 25 bottom plate, 26 telescopic rod, 27 expansion bolt, 28 universal wheel. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0025] Reference Figure 1-5 , a wind turbine generator set anchor bolt installation construction safety auxiliary device, including a machine body 2, and an anchor cage 1 is correspondingly arranged under the machine body 2. The anchor cage 1 is a basic structural object for the construction of a wind turbine generator set, and the anchor cage 1 is a protective cover for fixing the anchor bolts of the wind turbine generator set. During the construction of the wind turbine generator set foundation, the anchor cage 1 needs to be installed first. During the installation and construction of the anchor cage 1, in order to ensure the safety of the workers on the top of the anchor cage 1, the machine body 2 needs to be moved to the top of the anchor cage 1. The machine body 2 is used for the safety assistance of the workers during the installation and construction of the anchor bolts of the wind turbine generator set through the supporting components on the machine body 2 to prevent the workers from falling from the top of the anchor cage 1, thereby reducing the danger of the workers during the installation and construction of the anchor bolts of the wind turbine generator set and ensuring the safety of the workers during the installation and construction of the anchor bolts of the wind turbine generator set. A circular slide 3 is provided in the middle part of the lower end of the machine body 2, and both sides of the circular slide 3 are slidably sleeved with The diameter of the slider 4 and the circular slide 3 is the same as the diameter of the anchor cage 1. When the machine body 2 moves to the top of the anchor cage 1, the circular slide 3 will be located above the anchor cage 1, and the slider 4 can move in the circular slide 3. The lower ends of the two sliders 4 are provided with safety ropes 5, and the lower ends of the two safety ropes 5 are provided with safety locks 6. The safety locks 6 are connected to the matching parts on the staff. The safety locks 6 can be connected to the slider 4 through the safety rope 5. When the staff is working on the top of the anchor cage 1, the staff needs to connect the safety locks 6 to their bodies. Through the structure of the circular slide 3, slider 4, safety rope 5 and safety locks 6, the staff working on the top of the anchor cage 1 can be protected to prevent the staff from falling when working on the top of the anchor cage 1, and the staff will not be restricted in their movement when moving on the top of the anchor cage 1, thereby ensuring the safety of the staff during the installation and construction of the wind turbine anchor bolts.

[0026] Reference Figure 1-3, a lifting mechanism is provided in the middle of the lower end of the body 2, and two threaded sleeves 13 are correspondingly provided on the lifting mechanism. The two threaded sleeves 13 are respectively rotatably sleeved on both sides of the lower end of the body 2. The operation of the lifting mechanism can drive the two threaded sleeves 13 to rotate. The threaded sleeves 13 are provided with internal threads. The rotation of the two threaded sleeves 13 can push the components connected thereto to extend and retract in the two threaded sleeves 13. The lifting mechanism includes a dual-axis motor 7 fixedly installed in the middle of the lower end of the body 2. The two output shaft ends of the dual-axis motor 7 are fixedly connected to the transmission shaft 8. The dual-axis motor 7 is connected to the supporting components for stable operation and can set the program Sequence, automatic operation, the dual-axis motor 7 is a device with two output shafts. The operation of the dual-axis motor 7 will drive the two transmission shafts 8 to rotate. The structure of the transmission shaft 8 is to increase the transmission length of the dual-axis motor 7. Two bearing seats 9 are fixedly connected to both sides of the lower end of the body 2. Bearings 10 are fixedly sleeved in the four bearing seats 9. The four bearings 10 are respectively rotatably sleeved on the two ends of the two transmission shafts 8. The four bearing seats 9 can be used to fix the four bearings 10 in the body 2. Through the structure of the four bearing seats 9 and the four bearings 10, the two transmission shafts 8 can be installed in the body 2, so that the two transmission shafts 8 can keep rotating smoothly in the body 2.

[0027] Reference Figure 1-3The other ends of the two transmission shafts 8 are fixedly connected to worms 11, and the other ends of the two worms 11 are respectively rotatably connected to the opposite inner walls of the body 2. The rotation of the two transmission shafts 8 will drive the two worms 11 to rotate. The surface of the worm 11 is provided with an external spiral pattern. The rotation of the two worms 11 can drive the parts connected to it on both sides of the body 2 to operate. One side of the two worms 11 is engaged with a worm wheel 12. The two worm wheels 12 are respectively fixedly sleeved on two threaded sleeves 13. The upper ends of the two threaded sleeves 13 are respectively rotatably connected to the upper ends of the body 2. The two worms 11 rotate The two worm gears 12 will be driven to rotate, and the rotation of the two worm gears 12 will drive the two threaded sleeves 13 to rotate. The two threaded sleeves 13 are threaded with lifting screws 14. The lower ends of the two lifting screws 14 are fixedly connected with a bearing plate 15. The surface of the lifting screw 14 is provided with an external thread. The internal threads in the two threaded sleeves 13 are screwed with the external threads of the two lifting screws 14. Therefore, the rotation of the two threaded sleeves 13 will drive the two lifting screws 14 to rise and fall, and the two lifting screws 14 will drive the two bearing plates 15 to rise and fall. The bearing plates 15 are used to carry some components. The lower end of the plate 15 is evenly spaced with a plurality of universal wheels 28, which are in contact with the ground. When the machine body 2 is in use, the height of the machine body 2 is adjusted according to the height of the anchor cage 1. The supporting control device controls the operation of the dual-axis motor 7, which drives the two transmission shafts 8 to rotate, and the two transmission shafts 8 drive the two worms 11 to rotate. The two worms 11 drive the two worm wheels 12 to rotate, and the two worm wheels 12 drive the two threaded sleeves 13 to rotate. The two threaded sleeves 13 drive the two lifting screws 14 to extend and retract. When the two lifting screws 14 are pushed, the two threaded sleeves 13 will rise and fall, and the two threaded sleeves 13 will rise and fall. The sleeve 13 will drive the body 2 to rise and fall. After the height of the body 2 is adjusted to the corresponding height, the universal wheel 28 is a wheel that can change the direction at will. The universal wheel 28 can make the carrying plate 15 more convenient to move. The movement of the two carrying plates 15 will drive the two lifting screws 14 to move. The two lifting screws 14 will drive the two threaded sleeves 13 to move. The two threaded sleeves 13 will drive the body 2 to move. Therefore, when the body 2 is moved above the anchor cage 1, the multiple universal wheels 28 can make the body 2 move more conveniently and quickly, which can effectively improve the convenience of the body 2.

[0028] Reference Figure 1 、 2, 4. Both sides of the upper ends of the two supporting plates 15 are fixedly connected with sleeves 16, and the four corners of the lower end of the body 2 are fixedly connected with round rods 17. The four round rods 17 are slidably sleeved in the corresponding four sleeves 16 respectively. When the body 2 is lifted, it can drive the four round rods 17 to lift and lower. The four round rods 17 will slide in the four sleeves 16. Through the structure of the four sleeves 16 and the four round rods 17, the stability of the body 2 on the two supporting plates 15 can be increased, and the body 2 can be restricted from shaking left and right above the two supporting plates 15. The lower parts of the four sleeves 16 are fixedly sleeved with fixed blocks 18, and the upper ends of the corresponding two fixed blocks 18 are detachably connected with reinforcement rods 19. After the machine body 2 is moved above the anchor cage 1, the two reinforcement rods 19 are installed on the four fixed blocks 18. The two reinforcement rods 19 can increase the stability of the bottom connection of the four sleeves 16, so that the overall structure of the bottom of the machine body 2 can be reinforced, and the stability of the machine body 2 is improved. Bolts 20 are provided on both sides of the upper ends of the two reinforcement rods 19, and the lower ends of the four bolts 20 respectively penetrate the four fixed blocks 18 and are threaded with nuts 21. When fixing the reinforcement rods 19, the reinforcement rods 19 need to be fixed to the fixed blocks 18 by the bolts 20 and the nuts 21. The reinforcement rods 19 can be easily disassembled and assembled by the bolts 20 and the nuts 21.

[0029] Reference Figure 1 、 25. Both sides of the two bearing plates 15 are fixedly sleeved with threaded sleeves 22, and the four threaded sleeves 22 are threadedly sleeved with support screws 23. The threaded sleeve 22 is a component with an internal thread. The surface of the support screw 23 is provided with an external thread. Through the internal thread of the threaded sleeve 22 and the external thread structure of the support screw 23, the support screw 23 can be raised and lowered in the threaded sleeve 22 by rotating the support screw 23. The upper ends of the four support screws 23 are fixedly connected with a rotating wheel. 24. The lower ends of the four support screws 23 are rotatably connected to the bottom plate 25. The support screws 23 can be easily driven to rotate by the rotating wheel 24. The support screws 23 can rotate at the upper end of the bottom plate 25. The lifting of the support screws 23 will drive the bottom plate 25 to lift. After the body 2 moves to the top of the anchor cage 1, the four support screws 23 are driven to rotate by the four rotating wheels 24. The four support screws 23 drive the four bottom plates 25 to lift. After the four bottom plates 25 fall and contact the ground, the two bearing plates 1 can be supported. 5 is supported to prevent the two supporting plates 15 from moving at will. After the two supporting plates 15 are restricted from moving, the movement of the machine body 2 will be restricted, so that the machine body 2 can remain stable when in use. Expansion bolts 27 are provided on both sides of the upper ends of the four bottom plates 25. Telescopic rods 26 are fixedly connected on both sides of the lower ends of the two supporting plates 15. The lower ends of the four telescopic rods 26 are respectively fixedly connected to the upper ends of the four bottom plates 25. After the four bottom plates 25 are pressed against the ground, in order to prevent the machine body 2 from being blown away in strong winds, the bottom plates 25 can be fixed to the ground by expansion bolts 27. After the bottom plates 25 are fixed, the movement of the two supporting plates 15 can be restricted. The restricted movement of the two supporting plates 15 will restrict the movement of the machine body 2, so that the machine body 2 can be prevented from being blown away in strong winds. The telescopic rod 26 is a retractable rod. The rotation of the bottom plate 25 can be restricted by the telescopic rod 26, so that the bottom plate 25 can be kept vertically lifted when driven, and at the same time, the bottom plate 25 can be prevented from rotating when the support screw 23 is rotated.

[0030] In the present invention, when in use: the supporting control device controls the operation of the dual-axis motor 7, the dual-axis motor 7 drives the two transmission shafts 8 to rotate, the two transmission shafts 8 drive the two worms 11 to rotate, the two worms 11 drive the two worm wheels 12 to rotate, the two worm wheels 12 drive the two threaded sleeves 13 to rotate, the two threaded sleeves 13 drive the two lifting screws 14 to extend and retract, and when the two lifting screws 14 are pushed, the two threaded sleeves 13 will rise and fall, and the two threaded sleeves 13 will drive the machine body 2 to rise and fall. After adjusting the height of the machine body 2 to the corresponding height, the machine body 2 is moved to the top of the anchor cage 1 through multiple universal wheels 28 and two bearing plates 15, and then the four rotating wheels 24 are rotated. The four rotating wheels 24 drive the four supporting screws 23 to rotate. The rotation of the four supporting screws 23 will lift and lower in the four threaded sleeves 22. The four supporting screws 23 will drive the four base plates 25 to lift and lower. After the four base plates 25 descend and hit the ground, the four base plates 25 are fixed to the ground by eight expansion bolts 27, which can prevent the two bearing plates 15 from moving. The movement of the two bearing plates 15 is restricted, and the movement of the machine body 2 is restricted by the four sleeves 16 and the four round rods 17, so that the machine body 2 remains stable above the anchor cage 1. When the staff is working on the top of the anchor cage 1, the safety lock 6 is connected to the staff to prevent the staff from falling from above the anchor cage 1.

[0031] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A wind turbine generator anchor bolt installation construction safety auxiliary device, comprising a body (2), characterized in that: A lifting mechanism is provided at the middle of the lower end of the machine body (2); An anchor cage (1) is correspondingly provided below the machine body (2), a circular slideway (3) is provided in the middle of the lower end of the machine body (2), sliders (4) are slidably sleeved on both sides of the circular slideway (3), safety ropes (5) are provided at the lower ends of the two sliders (4), and safety locks (6) are provided at the lower ends of the two safety ropes (5), and two threaded sleeves (13) are correspondingly provided on the lifting mechanism, the two threaded sleeves (13) are respectively rotatably sleeved on both sides of the lower end of the machine body (2), the upper ends of the two threaded sleeves (13) are respectively rotatably connected to both sides of the upper end of the machine body (2), the two threaded sleeves (13) are threadedly sleeved in the two threaded sleeves (13), the lower ends of the two lifting screws (14) are fixedly connected to the supporting plate (15), and the lower ends of the two supporting plates (15) are evenly spaced with a plurality of universal wheels (28).

2. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 1, characterized in that: The lifting mechanism comprises a dual-axis motor (7) fixedly mounted in the middle of the lower end of the machine body (2); the ends of the two output shafts of the dual-axis motor (7) are fixedly connected to a transmission shaft (8); the other ends of the two transmission shafts (8) are fixedly connected to a worm (11); the other ends of the two worms (11) are rotatably connected to opposite inner walls of the machine body (2); one side of the two worms (11) is meshed with a worm wheel (12); the two worm wheels (12) are fixedly sleeved on two threaded sleeves (13) respectively.

3. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 2, characterized in that: Two bearing seats (9) are fixedly connected to both sides of the lower end of the body (2), and bearings (10) are fixedly sleeved in the four bearing seats (9). The four bearings (10) are rotatably sleeved on the two ends of the two transmission shafts (8).

4. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 1, characterized in that: Both sides of the upper ends of the two supporting plates (15) are fixedly connected with sleeves (16), and the four corners of the lower end of the body (2) are fixedly connected with round rods (17), and the four round rods (17) are respectively slidably sleeved in the corresponding four sleeves (16).

5. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 4, characterized in that: The lower parts of the four sleeves (16) are all fixedly sleeved with fixed blocks (18), and the upper ends of the corresponding two fixed blocks (18) are detachably connected to a reinforcement rod (19). Bolts (20) are provided on both sides of the upper ends of the two reinforcement rods (19), and the lower ends of the four bolts (20) respectively penetrate the four fixed blocks (18) and are all threadedly sleeved with nuts (21).

6. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 1, characterized in that: Threaded sleeves (22) are fixedly sleeved on both sides of the two bearing plates (15), support screws (23) are threadedly sleeved in the four threaded sleeves (22), the upper ends of the four support screws (23) are fixedly connected to the rotating wheels (24), and the lower ends of the four support screws (23) are rotatably connected to the bottom plate (25).

7. A wind turbine generator anchor bolt installation safety auxiliary device according to claim 6, characterized in that: Expansion bolts (27) are provided on both sides of the upper ends of the four bottom plates (25), telescopic rods (26) are fixedly connected to both sides of the lower ends of the two bearing plates (15), and the lower ends of the four telescopic rods (26) are respectively fixedly connected to the upper ends of the four bottom plates (25).