A tower crane standard section welding positioning device

Abstract

The invention discloses a tower crane standard section welding positioning device, comprising a balance seat, an active unit is arranged at one end of the balance seat, and a driven unit is arranged at the other end, the active unit comprises an active end base, and a first shell with a partition arranged on the active end base, a rotatable first turntable is arranged on the surface of the first shell facing the driven unit, a first positioning block, a first positioning rod, a second positioning rod and a third positioning rod are arranged on the surface of the first turntable facing the driven unit, the driven unit comprises a positioning part and a sliding part, the positioning part comprises a second shell, a rotatable second turntable is arranged on the surface of the second shell facing the active unit, and a second positioning block, a fourth positioning rod, a fifth positioning rod and a sixth positioning rod are arranged on the surface of the second turntable facing the active unit. The device has accurate positioning, high safety, reduces the labor intensity of workers, and improves production efficiency.

Description

Technical Field

[0001] The invention relates to a welding positioning technology, in particular to a tower crane standard section welding positioning device. Background Art

[0002] Tower cranes, also known as tower cranes, are a type of lifting equipment commonly used on construction sites. They are used to lift construction materials such as steel bars, concrete, and steel pipes for construction. The supporting main structure of a tower crane is a series of sections, called standard sections. The standard section of a tower crane is the main force-bearing component. It bears axial force, bending moment, and torque during operation. When the tower crane rotates, the main body of the standard section bears alternating loads. Therefore, the quality of the main body of the standard section is directly related to the life safety of construction workers on the site.

[0003] The main body of the standard section must be welded to the casing, and finally the upper and lower standard sections are connected together by bolts. When welding, each weld on both sides of the casing and the main body must be welded three times, and the consistency of each weld must be good, such as Figure 8 shown.

[0004] In order to ensure the welding quality, the relative position between the standard section body and the sleeve must be accurate. First, in the axial direction, the end face of the standard section body and the end face of the sleeve must be flush; second, in the radial direction, the two mutually perpendicular planes of the standard section body (square tube) are used as the reference, and the size and position of the three sleeves relative to the reference must be accurate.

[0005] Current positioning methods and defects:

[0006] Through sleeve positioning.

[0007] Use three long round rods to position each side, and put the sleeve on the round rod, running through from beginning to end. Manual welding is used during welding, and three welds are welded between the sleeve and the square tube according to the welding process requirements. Because during and after welding, due to the effects of local heating expansion and local cooling contraction, the welded workpiece and the material itself will change in size, shape and position, which is usually called post-weld deformation. After welding, the relative position of the standard section body and the sleeve will change, causing the sleeve to be stuck on the positioning round rod and unable to be smoothly removed. After welding, the workpiece cannot be removed from the tooling in time, and the worker needs to knock the positioning round rod out of the sleeve one by one to complete the unloading. This method seriously affects production efficiency, and there is also a risk of damaging the workpiece when knocking.

[0008] Therefore, it is of great value and significance to design a standard section main body welding positioning device which has high positioning accuracy, is convenient for welding, and allows the workpiece to be easily unloaded after welding. Summary of the invention

[0009] The purpose of the present invention is to provide a tower crane standard section welding positioning device in view of the shortcomings of the prior art. The device has accurate positioning, high safety, reduces the labor intensity of workers, and improves production efficiency.

[0010] The technical solution for achieving the purpose of the present invention is:

[0011] A tower crane standard section welding positioning device comprises a balancing seat, one end of the balancing seat is provided with an active unit, and the other end is provided with a driven unit, the active unit and the driven unit are located on the same side of the balancing seat,

[0012] The active unit includes an active end base, and a first shell with a partition arranged on the active end base, a rotatable first turntable is arranged on the surface of the first shell facing the driven unit, a first positioning block, a first positioning rod, a second positioning rod and a third positioning rod are arranged on the surface of the first turntable facing the driven unit, a reducer is arranged in the partition of the first shell, a first motor is arranged on the outward surface of the first shell, the first motor is connected to the reducer shaft, the bearing of the reducer passes through the partition of the first shell and is connected to the first turntable shaft, a first T-shaped first gear lever hinged to the first shell is also arranged on the first shell, and a first baffle is arranged on the outward end of the first gear lever,

[0013] The driven unit includes a positioning part and a sliding part, the sliding part includes a driven end base, a first guide rail and a second guide rail are horizontally spaced apart on the driven end base, the first guide rail is in the same direction as the balance seat, a group of first sliders and second sliders are slidably provided on the first guide rail and the second guide rail, a first screw bearing seat and a second screw bearing seat are spaced apart on the driven end base between the first guide rail and the second guide rail, a screw with a screw nut assembly is provided between the first screw bearing seat and the second screw bearing seat, the screw is in the same direction as the first track, a second motor is provided on the outward surface of the driven end base, and the second motor is connected to the screw through a coupling shaft.

[0014] The positioning part includes a second shell, a plane formed by the first slider and the second slider is connected to the second shell, the bottom of the second shell is fixedly connected to the screw nut assembly, a rotatable second turntable is provided on the surface of the second shell facing the active unit, a second positioning block, a fourth positioning rod, a fifth positioning rod and a sixth positioning rod are provided on the surface of the second turntable facing the active unit, the axis of the second turntable is on the same horizontal line as the axis of the first turntable, the second shell is also provided with a T-shaped second gear rod hinged to the second shell, and a second baffle is provided on the outward end of the second gear rod.

[0015] The first rotating disk has the same specifications as the second rotating disk, the first positioning block has the same specifications as the second positioning block, and the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod have the same specifications.

[0016] The positional relationship of the first positioning block, the first positioning rod, the second positioning rod and the third positioning rod provided on the first turntable is as follows: with the center of the first turntable as the base point, the first positioning rod and the first positioning block are placed at both ends of the vertical line perpendicular to the center of the first turntable, the second positioning rod and the third positioning rod are symmetrical with the vertical line of the center of the first turntable, and the angles between the second positioning rod and the third positioning rod and the first positioning rod and the center of the first turntable are 90︒-120︒ respectively, the first positioning rod, the second positioning rod and the third positioning rod are located on a circle with a radius of 110-120mm scattering outward from the center of the first turntable, and the positional relationship of the second positioning block, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod provided on the second turntable is the same as the corresponding positional relationship of the first positioning block, the first positioning rod, the second positioning rod and the third positioning rod on the first turntable.

[0017] The first positioning block is provided with a V-shaped groove, the top of the V-shaped groove faces outward, the vertex of the V-shaped groove is in the same straight line with the center of the first rotating disk, and the angle between the two inclined surfaces of the V-shaped groove is 90°.

[0018] When the driven end base slides to the position abutting the second screw bearing seat, the length between the first turntable and the second turntable is greater than the length of the standard section of the crane. When the driven end base slides to the position abutting the first screw bearing seat, the length between the first turntable and the second turntable is less than the length of the standard section of the crane.

[0019] The first turntable and the second turntable are respectively provided with three bosses, which are integrally formed with the first turntable and the second turntable, and the six bosses are respectively used to install the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod.

[0020] The reducer is an RV reducer.

[0021] The first motor is a servo motor.

[0022] The second motor is a three-phase asynchronous motor.

[0023] In a normal state, the first positioning block is located directly below the first positioning rod, the second positioning block is located directly below the fourth positioning rod, and the first positioning block is directly opposite to the second positioning block.

[0024] The device of this technical solution can cooperate with a welding robot to realize automatic welding.

[0025] Working process:

[0026] Before welding, the standard section of the tower crane is hoisted between the active unit and the driven unit by using a workshop crane, and the two ends of the standard section are respectively placed in the V-shaped grooves of the first positioning block and the second positioning block, and the second motor is controlled to drive the screw to rotate. The rotation of the screw drives the screw nut assembly to move axially along the screw, thereby driving the driven end base to move toward the active unit, so that the two end heads of the standard section are respectively in contact with the inner bottom surfaces of the first positioning block and the second positioning block, and the sleeve is manually mounted on the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod in sequence, and then the standard section is connected to the sleeve by spot welding, wherein the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod are sequentially inserted into one-third of the sleeve, and the inner wall of the sleeve is in contact with the positioning rod part;

[0027] During welding, two welding robots are used to perform the first welding on the casing near the active unit and the driven unit, that is, the first casing on the same side. After welding is completed, the first motor drives the reducer to rotate, and then drives the first turntable to rotate 90︒-120︒. The welding robot performs the first welding on the casing near its side, that is, the second casing. After welding is completed, the first motor drives the reducer to rotate again, and drives the first turntable to rotate another 90︒-120︒. The welding robot performs the first welding on the casing near its side, that is, the third casing. The first welding of the pipe is carried out. Since the active unit and the driven unit are connected by a standard joint, when the first turntable of the active unit rotates, the second turntable of the driven unit rotates following the first turntable. After all the sleeves have completed the first welding, the first motor drives the reducer to rotate so that the first turntable returns to the position before welding, and the second turntable follows the first turntable to return to the position before welding. The above welding rotation operation is repeated until the second and third weldings are completed for all the sleeves. Finally, the first motor drives the reducer to rotate so that the first turntable and the second turntable return to the positions before welding.

[0028] After welding is completed, the first gear rod and the second gear rod are twisted so that the first baffle and the second baffle are placed on the standard section where the sleeve welding is completed, and the second motor drives the screw to rotate. The rotation of the screw drives the screw nut assembly to move axially along the screw, thereby driving the driven end base to move in the opposite direction of the active unit. At this time, the sleeve on any side of the active unit or the driven unit is disengaged from the positioning rod, and the disengaged sleeve hits the first baffle or the second baffle, and the driven end base continues to move. The sleeve interacts with the first baffle or the second baffle to generate a reverse pulling force to pull the sleeve on the other side that has not been disengaged from the positioning rod, and the driven end base moves to the predetermined position and stops, and the workshop crane lifts the standard section of the completed welded sleeve away, and continues the welding of the next standard section and sleeve.

[0029] This device has accurate positioning, high safety, reduces workers' labor intensity and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an embodiment;

[0031] Figure 2 is a schematic diagram of the structure of the active unit in the embodiment;

[0032] Figure 3 It is a structural schematic diagram of the positioning part of the driven unit in the embodiment;

[0033] Figure 4 It is a structural schematic diagram of the sliding part of the driven unit in the embodiment;

[0034] Figure 5 A diagram showing the position relationship between the positioning rod and the positioning block in the embodiment;

[0035] Figure 6 Schematic diagram of the structure of the first positioning block in the embodiment

[0036] Figure 7 is a schematic structural diagram of a first positioning rod in an embodiment;

[0037] Figure 8 It is a schematic diagram of completing casing welding of a standard section in an embodiment.

[0038] In the figure, 1. balancing seat 2. active end base 3. first shell 4. first turntable 5. first positioning block 6. first positioning rod 7. second positioning rod 8. third positioning rod 9. reducer 10. first motor 11. first gear rod 12. first baffle 13. driven end base 14. first guide rail 15. second guide rail 16. first slider 17. second slider 18. first screw bearing seat 19. second screw bearing seat 20. screw 21. screw nut assembly 22. second motor 23. second shell 24. second turntable 25. second positioning block 26. fourth positioning rod 27. fifth positioning rod 28. sixth positioning rod 29. second gear rod 30. second baffle 31. boss 32. standard section 33. sleeve a is the angle between the first positioning rod and the second positioning rod, b is the angle between the first positioning rod and the third positioning rod, and r is the radius scattering outward with the center of the first turntable as the base point. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0040] Example:

[0041] Reference Figure 1A tower crane standard section welding positioning device comprises a balance seat 1, an active unit is arranged at one end of the balance seat 1, and a driven unit is arranged at the other end, and the active unit and the driven unit are located on the same side of the balance seat 1.

[0042] like Figure 2 As shown, the active unit includes an active end base 2, and a first shell 3 with a partition arranged on the active end base 2, a rotatable first turntable 4 is arranged on the surface of the first shell 3 facing the driven unit, a first positioning block 5, a first positioning rod 6, a second positioning rod 7 and a third positioning rod 8 are arranged on the surface of the first turntable 4 facing the driven unit, a reducer 9 is arranged in the partition of the first shell 3, a first motor 10 is arranged on the outward surface of the first shell 3, the first motor 10 is axially connected to the reducer 9, a bearing of the reducer 9 passes through the partition of the first shell 3 and is axially connected to the first turntable 4, a first T-shaped first gear rod 11 hinged to the first shell 3 is further arranged on the first shell 3, and a first baffle 12 is arranged on the outward end of the first gear rod 11,

[0043] The driven unit includes a positioning part and a sliding part, such as Figure 4 As shown, the sliding part includes a driven end base 13, on which a first guide rail 14 and a second guide rail 15 are horizontally spaced apart, the first guide rail 14 is in the same direction as the balance seat 1, and a group of first sliders 16 and second sliders 17 are slidably provided on the first guide rail 14 and the second guide rail 15, respectively, and a first screw bearing seat 18 and a second screw bearing seat 19 are spaced apart on the driven end base 13 between the first guide rail 14 and the second guide rail 15, and a screw 20 with a screw nut assembly 21 is provided between the first screw bearing seat 18 and the second screw bearing seat 19, and the screw 20 is in the same direction as the first rail 14, and a second motor 22 is provided on the outward surface of the driven end base 13, and the second motor 22 is connected to the screw 20 through a coupling shaft.

[0044] like Figure 3 As shown, the positioning part includes a second shell 23, a plane formed by the first slider 16 and the second slider 17 is connected to the second shell 23, the bottom of the second shell 23 is fixedly connected to the screw nut assembly 21, a rotatable second turntable 24 is provided on the surface of the second shell 23 facing the active unit, a second positioning block 25, a fourth positioning rod 26, a fifth positioning rod 27 and a sixth positioning rod 28 are provided on the surface of the second turntable 24 facing the active unit, the axis of the second turntable 24 is on the same horizontal line as the axis of the first turntable 4, and the second shell 23 is also provided with a T-shaped second gear rod 29 hinged to the second shell 23, and a second baffle 30 is provided at the outward end of the second gear rod 29.

[0045] The first rotating disk 4 has the same specifications as the second rotating disk 24, the first positioning block 5 has the same specifications as the second positioning block 25, the first positioning rod 6, the second positioning rod 7, the third positioning rod 8, the fourth positioning rod 26, the fifth positioning rod 27 and the sixth positioning rod 28 have the same specifications. Figure 7 shown.

[0046] The positional relationship of the first positioning block 5, the first positioning rod 6, the second positioning rod 7 and the third positioning rod 8 provided on the first rotating disk 4 is as follows: Figure 5 As shown: with the center of the first turntable 4 as the base point, the first positioning rod 6 and the first positioning block 5 are placed at both ends of the vertical line perpendicular to the center of the first turntable 4, the second positioning rod 7 and the third positioning rod 8 are symmetrical with the vertical line of the center of the first turntable 4, and the angles a and b between the second positioning rod 7 and the third positioning rod 8 and the first positioning rod 6 to the center of the first turntable 4 are 90︒-120︒, which is 103︒ in this case. The first positioning rod 6, the second positioning rod 7 and the third positioning rod 8 are located on a circle with a radius r of 110-120mm scattering outward from the center of the first turntable 4 as the base point, which is 118mm in this case. The positional relationship of the second positioning block 25, the fourth positioning rod 26, the fifth positioning rod 27 and the sixth positioning rod 28 provided on the second turntable 24 is the same as the corresponding positional relationship of the first positioning block 5, the first positioning rod 6, the second positioning rod 7 and the third positioning rod 8 on the first turntable 4.

[0047] like Figure 6 As shown, the first positioning block 5 is provided with a V-shaped groove, the top of the V-shaped groove faces outward, the vertex of the V-shaped groove is in the same straight line with the center of the first rotating disk 4, and the angle between the two inclined surfaces of the V-shaped groove is 90°.

[0048] When the driven end base 13 slides to the position abutting the second screw bearing seat 19, the length between the first turntable 4 and the second turntable 24 is greater than the length of the crane standard section 32. When the driven end base 13 slides to the position abutting the first screw bearing seat 18, the length between the first turntable 4 and the second turntable 24 is less than the length of the crane standard section 31.

[0049] Three bosses 31 are respectively provided on the first turntable 4 and the second turntable 24. The bosses 31 are integrally formed with the first turntable 4 and the second turntable 24. The six bosses 31 are respectively used to install the first positioning rod 6, the second positioning rod 7, the third positioning rod 8, the fourth positioning rod 26, the fifth positioning rod 27 and the sixth positioning rod 28.

[0050] The reducer 9 is an RV reducer.

[0051] The first motor 10 is a servo motor.

[0052] The second motor 22 is a three-phase asynchronous motor.

[0053] In a normal state, the first positioning block 5 is located directly below the first positioning rod 6 , the second positioning block 25 is located directly below the fourth positioning rod 26 , and the first positioning block 5 is directly opposite to the second positioning block 25 .

[0054] The device of this technical solution can cooperate with a welding robot to realize automatic welding.

[0055] Working process:

[0056] Before welding, the standard section 32 of the tower crane is hoisted between the active unit and the driven unit by a workshop crane, and the two ends of the standard section 32 are respectively placed in the V-shaped grooves of the first positioning block 5 and the second positioning block 25, and the second motor 22 is controlled to drive the screw 20 to rotate. The rotation of the screw 20 drives the screw nut assembly 21 to move axially along the screw 20, thereby driving the driven end base 13 to move toward the active unit, so that the two end heads of the standard section 32 are respectively in contact with the inner bottom surfaces of the first positioning block 5 and the second positioning block 25, and the sleeve 33 is manually mounted on the first positioning rod 6, the second positioning rod 7, the third positioning rod 8, the fourth positioning rod 26, the fifth positioning rod 27 and the sixth positioning rod 28 in sequence, and then the standard section 32 is connected to the sleeve 33 by spot welding, wherein the first positioning rod 6, the second positioning rod 7, the third positioning rod 8, the fourth positioning rod 26, the fifth positioning rod 27 and the sixth positioning rod 28 are sequentially inserted into one-third of the sleeve 33, and the inner wall of the sleeve 33 is in contact with the positioning rod part;

[0057] During welding, two welding robots are used to perform the first welding on the sleeve 33 near the active unit and the driven unit, that is, the first sleeve on the same side. After welding is completed, the first motor 10 works to drive the reducer 9 to rotate, and then drives the first turntable 4 to rotate 90︒-120︒, in this case 103︒, and the welding robot performs the first welding on the sleeve 33 near its side, that is, the second sleeve. After welding is completed, the first motor 10 works to drive the reducer 9 to rotate again, and drives the first turntable 4 to rotate 90︒-120︒, in this case 103︒, and the welding robot performs the first welding on the sleeve 33 near its side, that is, the second sleeve. The first welding is performed on the third sleeve. Since the active unit and the driven unit are connected by a standard joint 32, when the first turntable 4 of the active unit rotates, the second turntable 24 of the driven unit rotates following the first turntable 4. After the first welding of all sleeves 33 is completed, the first motor 10 drives the reducer 9 to rotate so that the first turntable 4 returns to the position before welding, and the second turntable 24 follows the first turntable 4 and also returns to the position before welding. The above welding rotation operation is repeated until the second and third weldings are completed for all sleeves 33. Finally, the first motor 10 drives the reducer 9 to rotate so that the first turntable 4 and the second turntable 24 return to the positions before welding.

[0058] After welding is completed, the first gear rod 11 and the second gear rod 29 are twisted so that the first baffle plate 12 and the second baffle plate 30 are placed on the standard section 32 of the welded sleeve, and the second motor 22 drives the screw rod 20 to rotate. The rotation of the screw rod 20 drives the screw nut assembly 21 to move axially along the screw rod 20, thereby driving the driven end base 13 to move in the opposite direction of the active unit. At this time, the sleeve 33 on any side of the active unit or the driven unit is disengaged from the positioning rod, and the disengaged sleeve 33 hits the first baffle plate 12 or the second baffle plate 30, and the driven end base 13 continues to move. The sleeve 33 interacts with the first baffle plate 12 or the second baffle plate 30 to generate a reverse pulling force to pull the sleeve 33 on the other side that has not been disengaged from the positioning rod. The driven end base 13 moves to the predetermined position and stops, and the workshop crane lifts the standard section 32 of the welded sleeve away, and continues the welding of the next standard section 32 and sleeve 33.

Claims

1. A tower crane standard section welding positioning device, characterized in that: The invention comprises a balancing seat, wherein a driving unit is arranged at one end of the balancing seat and a driven unit is arranged at the other end, and the driving unit and the driven unit are located on the same side of the balancing seat. The active unit includes an active end base, and a first shell with a partition arranged on the active end base, a rotatable first turntable is arranged on the surface of the first shell facing the driven unit, a first positioning block, a first positioning rod, a second positioning rod and a third positioning rod are arranged on the surface of the first turntable facing the driven unit, a reducer is arranged in the partition of the first shell, a first motor is arranged on the outward surface of the first shell, the first motor is connected to the reducer shaft, the bearing of the reducer passes through the partition of the first shell and is connected to the first turntable shaft, a first T-shaped first gear lever hinged to the first shell is also arranged on the first shell, and a first baffle is arranged on the outward end of the first gear lever, The driven unit includes a positioning part and a sliding part, the sliding part includes a driven end base, a first guide rail and a second guide rail are horizontally spaced apart on the driven end base, the first guide rail is in the same direction as the balance seat, a group of first sliders and second sliders are slidably provided on the first guide rail and the second guide rail, a first screw bearing seat and a second screw bearing seat are spaced apart on the driven end base between the first guide rail and the second guide rail, a screw with a screw nut assembly is provided between the first screw bearing seat and the second screw bearing seat, the screw is in the same direction as the first track, a second motor is provided on the outward surface of the driven end base, and the second motor is connected to the screw through a coupling shaft. The positioning part includes a second shell, a plane formed by the first slider and the second slider is connected to the second shell, the bottom of the second shell is fixedly connected to the screw nut assembly, a rotatable second turntable is provided on the surface of the second shell facing the active unit, a second positioning block, a fourth positioning rod, a fifth positioning rod and a sixth positioning rod are provided on the surface of the second turntable facing the active unit, the axis of the second turntable is on the same horizontal line as the axis of the first turntable, the second shell is also provided with a T-shaped second gear lever hinged with the second shell, and a second baffle is provided at the outward end of the second gear lever; The first rotating disk has the same specifications as the second rotating disk, the first positioning block has the same specifications as the second positioning block, and the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod have the same specifications; The first positioning block is provided with a V-shaped groove, the top of the V-shaped groove faces outward, the vertex of the V-shaped groove is in the same straight line with the center of the first rotating disk, and the angle between the two inclined surfaces of the V-shaped groove is 90°.

2. The tower crane standard section welding positioning device according to claim 1 is characterized in that: The positional relationship of the first positioning block, the first positioning rod, the second positioning rod and the third positioning rod provided on the first turntable is as follows: with the center of the first turntable as the base point, the first positioning rod and the first positioning block are placed at both ends of the vertical line perpendicular to the center of the first turntable, the second positioning rod and the third positioning rod are symmetrical with the vertical line of the center of the first turntable, and the angles between the second positioning rod and the third positioning rod and the first positioning rod and the center of the first turntable are 90︒-120︒ respectively, the first positioning rod, the second positioning rod and the third positioning rod are located on a circle with a radius of 110-120mm scattering outward from the center of the first turntable, and the positional relationship of the second positioning block, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod provided on the second turntable is the same as the corresponding positional relationship of the first positioning block, the first positioning rod, the second positioning rod and the third positioning rod on the first turntable.

3. The tower crane standard section welding positioning device according to claim 1 is characterized in that: When the driven end base slides to the position abutting the second screw bearing seat, the length between the first turntable and the second turntable is greater than the length of the standard section of the crane. When the driven end base slides to the position abutting the first screw bearing seat, the length between the first turntable and the second turntable is less than the length of the standard section of the crane.

4. The tower crane standard section welding positioning device according to claim 1 is characterized in that: The first turntable and the second turntable are respectively provided with three bosses, which are integrally formed with the first turntable and the second turntable, and the six bosses are respectively used to install the first positioning rod, the second positioning rod, the third positioning rod, the fourth positioning rod, the fifth positioning rod and the sixth positioning rod.

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