Automatic welding equipment for outer circular seam of cylinder

Abstract

The invention provides automatic welding equipment for an outer circular seam of a cylinder, and relates to the field of automatic welding equipment.The automatic welding equipment comprises two fixed supports which are symmetrically arranged, an overturning platform is rotationally connected to the top between the two fixed supports, a lifting support is arranged at the bottom of the overturning platform, and a control motor is fixedly installed on the front side of the right side wall of the lifting support; the front end and the rear end of the transmission shaft rod are connected with two-way screw rods in a meshed mode. Cylinders with different thickness degrees are borne by adjusting the distance between anti-skid columns at the top of a bearing support, so that the adaptability of equipment is improved, clamping electric cylinders fixedly installed at the tops of two adapter shafts of an overturning platform can clamp and fix the cylinders through fixing arc pieces, the stability of the cylinders during welding is guaranteed, and the welding quality of the cylinders is improved. Manual operation is reduced, and the problems that the labor intensity of cylinder fixing, angle adjusting and manual welding is large, and the welding time is long are solved.

Description

Technical Field

[0001] The invention relates to the technical field of automatic welding equipment, and in particular to an automatic welding equipment for outer annular seams of a cylinder. Background Art

[0002] In the process of welding the cylinder skin and the connecting plate, the traditional welding method follows the steps of first internal priming and then external welding. The external welding is a multi-layer and multi-pass welding. In this process, there are a series of problems that need to be solved in terms of the fixing effect of the cylinder and the convenience of welding.

[0003] Based on the above, the existing cylinder outer ring seam automatic welding equipment has the following shortcomings: When manual welding is performed, due to the problem of fixing the cylinder, manual welding is inconvenient, and workers need to maintain a high degree of concentration and precise operating techniques. In the complex process of multi-layer and multi-pass welding, workers need to constantly adjust the welding angle, speed and supply of welding materials, which makes manual welding extremely labor-intensive. Workers are very likely to get tired after being in this high-intensity working state for a long time, which in turn affects the welding quality. In addition, workers need to have rich welding experience and superb skills to ensure the quality and stability of welding. However, it takes a long time of training and practical accumulation to master these skills, which increases the difficulty and cost of enterprises to train qualified welders. Finally, manual welding is difficult to ensure that the quality of each weld can meet high standards. During the welding process, due to the influence of human factors, such as subtle differences in operating techniques, lack of concentration caused by fatigue, etc., it is easy to cause defects such as pores, slag inclusions, and cracks in the weld, thereby affecting the overall quality and safety of the cylinder. These shortcomings seriously restrict the efficiency and quality improvement of the welding process, and also increase production costs and labor costs, which have brought many adverse effects on the production and operation of the enterprise. Summary of the invention

[0004] The disclosed embodiment relates to an automated welding device for the outer annular seam of a cylinder, which first searches for the weld according to input welding parameters through a welding robot arm, compares the weld with a preset welding program after scanning the weld, and directly starts welding through a welding machine after confirming that it is correct until the welding is completed. Operators do not need to perform high-intensity welding operations for a long time, which reduces the impact of manual fatigue on welding quality. Automated welding can more accurately control welding parameters and welding paths, effectively control weld quality, improve welding stability and consistency, reduce the generation of weld defects, and improve the welding quality of the cylinder.

[0005] In a first aspect of the present disclosure, an automatic welding device for the outer annular seam of a cylinder is provided, which specifically includes: a fixed support; two fixed supports are symmetrically arranged, and the top between the two fixed supports is rotatably connected to a flip platform, and the top end surface of the flip platform is hinged with a supporting bracket on the front and rear sides, and the supporting bracket is a scissors-type structure, and the bottom end of the supporting bracket is rotatably connected to a rotating connecting block, and a bidirectional screw is threadedly connected in the rotating connecting block, and a lifting bracket is arranged at the bottom of the flip platform, and a control motor is fixedly installed on the front side of the right side wall of the lifting bracket, and a transmission shaft is rotatably connected in the lifting bracket, and the front and rear ends of the transmission shaft are meshingly connected with a bidirectional screw.

[0006] Furthermore, a rotating shaft seat is fixedly installed on the top of the right side wall of the fixed support on the right side of the two fixed supports, a flipping motor is fixedly installed on the rear side of the rotating shaft seat, a flipping worm is fixedly connected to the front end of the driving shaft of the flipping motor, and the front and rear ends of the flipping worm are rotatably connected in the front and rear side walls of the rotating shaft seat.

[0007] Furthermore, an "L"-shaped fixed arm is fixedly installed on the right rear side of the fixed support on the left side of the two fixed supports, a telescopic cylinder is fixedly installed on the top front side of the fixed arm, a welding machine arm is fixedly connected to the bottom of the telescopic cylinder, and a welding machine is installed on the bottom front side of the welding machine arm.

[0008] Furthermore, a transfer shaft is fixedly installed in the middle of the left and right sides of the top end surface of the flipping platform, and the top shafts of the outer walls of the two transfer shafts are rotatably connected to the top of the side walls of the fixed support. The end of the shaft at the top of the right side wall of the transfer shaft on the right side of the flipping platform is fixedly connected to a flip worm gear, and the bottom of the flip worm gear is meshed with the top of the flip worm connected to the front side of the flip motor. An annular protective ring is fixedly connected between the tops of the opposite side walls of the two transfer shafts of the flipping platform.

[0009] Furthermore, a clamping electric cylinder is fixedly installed on the front side of the top of the side wall opposite to the two transfer shafts of the flip platform, and a fixed arc piece is fixedly connected to the telescopic end on the opposite side of the two clamping electric cylinders.

[0010] Furthermore, a hinged shaft end is fixedly installed in the middle of the front and rear sides of the top end surface of the turning platform, and a penetrating sliding guide groove is opened in the end surface of the turning platform at the bottom of the hinged shaft end.

[0011] Furthermore, the supporting bracket is connected to the top of the hinge shaft end in an "X" shape, the bottom of the supporting bracket is slidably connected in the sliding guide groove, the top of the supporting bracket is fixedly connected with an anti-skid column, and the outer surface of the anti-skid column is wrapped with high-friction rubber.

[0012] Furthermore, a control gear is fixedly connected to the left end of the driving shaft of the control motor, and the control gear is meshed at right angles with the transmission gear in the middle of the transmission shaft that is rotatably connected inside the lifting bracket, and the front and rear ends of the transmission shaft are fixedly connected with a control worm.

[0013] Furthermore, a control worm gear is fixedly connected in the middle of the bidirectional screws rotatably connected at the front and rear ends of the lifting bracket, and the control worm gears in the middle of the two bidirectional screws are respectively meshed and connected with the control worm gears at the front and rear ends of the transmission shaft.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The welding robot arm first searches for the weld according to the input welding parameters, and then compares the weld with the pre-set welding program after scanning. After confirmation, welding is started directly through the welding machine until the welding is completed. The operator does not need to perform high-intensity welding operations for a long time, which reduces the impact of manual fatigue on welding quality. Automated welding can more accurately control welding parameters and welding paths, effectively control weld quality, improve welding stability and consistency, reduce the generation of weld defects, improve the welding quality of the cylinder, and adjust the height of the welding robot arm through the telescopic cylinder to expand the activity space of the welding robot arm.

[0015] 2. By controlling the meshing of the control gear connected to the motor drive shaft end and the transmission gear on the transmission shaft, the rotation of the transmission shaft can be controlled by controlling the motor, so that the rotation of the bidirectional screw can be controlled by meshing the control worm fixedly connected at the front and rear ends of the transmission shaft with the control worm wheel in the middle of the bidirectional screw, and the positions of the two rotating connecting blocks on the bidirectional screw can be controlled, thereby adjusting the scissor angle of the supporting bracket, so that by adjusting the distance between the anti-slip columns on the top of the supporting bracket, cylinders of different thicknesses can be carried, thereby improving the adaptability of the equipment, and the clamping electric cylinder fixedly installed on the top of the two adapter shafts of the flip platform can clamp and fix the cylinder through the fixed arc piece, thereby ensuring the stability of the cylinder during welding and reducing manual operation.

[0016] 3. By controlling the rotation of the flip worm at the end of the flip motor driving shaft, the flip worm can be used to control the rotation of the flip worm wheel, thereby realizing the angle change of the flip platform through the cooperation of the flip worm wheel and the adapter shaft, so that the flip platform can be tilted, and the cylindrical welding surface in the protective circle at the top of the flip platform can be directed upward to improve the convenience of welding and better complete the welding work. In addition, by controlling the flip platform through the flip motor, the automatic control can be better realized, the labor intensity of manual labor can be reduced, and the requirements for manual skills can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0018] The drawings described below are only related to some embodiments of the present invention, but are not intended to limit the present invention.

[0019] In the attached picture: Figure 1 It is a schematic diagram of the right front axial structure of the cylinder outer annular seam automatic welding equipment according to an embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of the cylinder outer annular seam automatic welding equipment as viewed from the right rear side according to an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the structure of removing the flip platform of the automatic welding equipment for the outer annular seam of the cylinder according to an embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the structure of a turning platform of the cylinder outer annular seam automatic welding equipment according to an embodiment of the present invention.

[0023] Figure 5 It is a schematic structural diagram of the bottom right side axial view of the turning platform of the automatic welding equipment for the outer annular seam of the cylinder according to an embodiment of the present invention.

[0024] Figure 6 It is a schematic diagram of the right front axial structure of the turning platform of the automatic welding equipment for the outer annular seam of the cylinder according to an embodiment of the present invention.

[0025] Figure 7 It is a schematic cross-sectional structure diagram of a lifting bracket of an automatic welding device for an outer annular seam of a cylinder according to an embodiment of the present invention.

[0026] Figure 8 It is a schematic diagram of the protective ring and clamping electric cylinder position structure of the cylinder outer annular seam automatic welding equipment of the embodiment of the present invention.

[0027] Reference numerals list 1. Fixed support; 101. Rotating shaft seat; 102. Fixed support arm; 103. Telescopic cylinder; 2. Welding machine arm; 201. Welding machine; 3. Flipping motor; 301. Flipping worm; 4. Flipping platform; 401. Adapter shaft; 40101. Flipping worm gear; 402. Articulated shaft end; 403. Sliding guide groove; 404. Protective ring; 5. Clamping electric cylinder; 501. Fixed arc piece; 6. Support bracket; 601. Anti-skid column; 7. Rotating connecting block; 8. Lifting bracket; 9. Control motor; 901. Control gear; 10. Transmission shaft; 1001. Transmission gear; 1002. Control worm; 11. Bidirectional screw; 1101. Control worm gear. DETAILED DESCRIPTION

[0028] In order to make the purpose, scheme and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in conjunction with the drawings of the specific embodiments of the present invention. Unless otherwise specified, the terms used herein have the usual meanings in the art. The same reference numerals in the drawings represent the same components.

[0029] Embodiment 1 Please refer to Figures 1 to 8 As shown, the present invention provides an automatic welding device for the outer annular seam of a cylinder, comprising a fixed support 1; two fixed supports 1 are symmetrically arranged, and the top between the two fixed supports 1 is rotatably connected with a flip platform 4, and the top end surface of the flip platform 4 is hinged with a supporting bracket 6 on the front and rear sides, and the supporting bracket 6 is a scissor-fork structure, and the bottom end of the supporting bracket 6 is rotatably connected with a rotating connecting block 7, and a bidirectional screw 11 is threadedly connected in the rotating connecting block 7, and a lifting bracket 8 is arranged at the bottom of the flip platform 4, and a control motor 9 is fixedly installed on the front side of the right side wall of the lifting bracket 8, and a transmission shaft 10 is rotatably connected in the lifting bracket 8, and the front and rear ends of the transmission shaft 10 are meshingly connected with the bidirectional screw 11.

[0030] Among them, a rotating shaft seat 101 is fixedly installed on the top of the right side wall of the fixed support 1 on the right side of the two fixed supports 1, and a flip motor 3 is fixedly installed on the rear side of the rotating shaft seat 101. The front end of the driving shaft of the flip motor 3 is fixedly connected with a flip worm 301, and the front and rear ends of the flip worm 301 are rotatably connected in the front and rear side walls of the rotating shaft seat 101.

[0031] Among them, a transfer shaft 401 is fixedly installed in the middle of the left and right sides of the top end surface of the flip platform 4, and the top shafts of the outer walls of the two transfer shafts 401 are rotatably connected to the top of the side wall of the fixed support 1. The end of the shaft at the top of the right side wall of the transfer shaft 401 on the right side of the flip platform 4 is fixedly connected with a flip worm gear 40101, and the bottom of the flip worm gear 40101 is meshed with the top of the flip worm 301 connected to the front side of the flip motor 3. A circular protective ring 404 is fixedly connected between the tops of the opposite side walls of the two transfer shafts 401 of the flip platform 4.

[0032] By adopting the above technical scheme, by controlling the rotation of the flip worm 301 at the end of the driving shaft of the flip motor 3, the flip worm gear 40101 can be controlled to rotate through the flip worm 301, so that the angle change of the flip platform 4 can be achieved through the cooperation of the flip worm gear 40101 and the adapter shaft 401, so that the flip platform 4 is in an inclined state, and the cylindrical welding surface in the top protective ring 404 of the flip platform 4 is facing obliquely upward, so as to improve the convenience of welding and better complete the welding work, and by controlling the flip platform 4 through the flip motor 3, the automatic control can be better realized, and the labor intensity of manual labor can be reduced while reducing the requirements for manual skills.

[0033] Embodiment 2 Based on an automatic welding equipment for the outer annular seam of a cylinder provided in Example 1, the device controls the rotation of the flip worm 301 at the end of the driving shaft of the flip motor 3, and can control the rotation of the flip worm wheel 40101 through the flip worm 301, so that the angle change of the flip platform 4 is achieved through the cooperation of the flip worm wheel 40101 and the adapter shaft 401, so that the flip platform 4 is tilted, and the cylindrical welding surface in the top protective ring 404 of the flip platform 4 is facing obliquely upward, so as to improve the convenience of welding and better complete the welding work. The automatic welding equipment for the outer annular seam of the cylinder also includes: a clamping electric cylinder 5 is fixedly installed on the front side of the top of the side wall opposite to the two adapter shafts 401 of the flip platform 4, and the telescopic ends of the two clamping electric cylinders 5 on the opposite side are fixedly connected with a fixed arc piece 501.

[0034] Among them, a hinge shaft end 402 is fixedly installed in the middle of the front and rear sides of the top end face of the flip platform 4, and a penetrating sliding guide groove 403 is opened in the end face of the flip platform 4 at the bottom of the hinge shaft end 402. The supporting bracket 6 is connected to the top of the hinge shaft end 402 in an "X" shape, and the bottom of the supporting bracket 6 is slidably connected in the sliding guide groove 403. The top of the supporting bracket 6 is fixedly connected with an anti-skid column 601, and the outer surface of the anti-skid column 601 is wrapped with high-friction rubber.

[0035] Among them, the left end of the driving shaft of the control motor 9 is fixedly connected with a control gear 901, and the control gear 901 and the transmission shaft 10 that is rotatably connected inside the lifting bracket 8 are meshed at a right angle with a transmission gear 1001 in the middle, and the front and rear ends of the transmission shaft 10 are fixedly connected with a control worm 1002.

[0036] Among them, a control worm gear 1101 is fixedly connected in the middle of the bidirectional screw 11 rotatably connected at the front and rear ends of the lifting bracket 8, and the control worm gear 1101 in the middle of the two bidirectional screws 11 is respectively meshed and connected with the control worms 1002 at the front and rear ends of the transmission shaft 10.

[0037] By adopting the above technical scheme, the control gear 901 connected to the drive shaft end of the control motor 9 is meshed with the transmission gear 1001 on the transmission shaft 10, and the rotation of the transmission shaft 10 can be controlled by controlling the motor 9, so that the control worm 1002 fixedly connected at the front and rear ends of the transmission shaft 10 and the control worm wheel 1101 at the middle of the bidirectional screw 11 are meshed to control the rotation of the bidirectional screw 11, and the positions of the two rotating connecting blocks 7 on the bidirectional screw 11 can be controlled, so as to adjust the scissor angle of the supporting bracket 6, so as to carry cylinders of different thicknesses by adjusting the distance between the anti-slip columns 601 at the top of the supporting bracket 6, thereby improving the adaptability of the equipment, and the clamping electric cylinder 5 fixedly installed on the top of the two adapter shafts 401 of the flip platform 4 can clamp and fix the cylinder through the fixed arc piece 501, thereby ensuring the stability of the cylinder during welding and reducing manual operation.

[0038] Embodiment 3 Based on an automatic welding equipment for the outer annular seam of a cylinder provided in Example 1, the device controls the rotation of the flip worm 301 at the end of the driving shaft of the flip motor 3, and can control the rotation of the flip worm wheel 40101 through the flip worm 301, so that the angle change of the flip platform 4 is achieved through the cooperation of the flip worm wheel 40101 and the adapter shaft 401, so that the flip platform 4 is tilted, and the cylindrical welding surface in the top protective ring 404 of the flip platform 4 is facing obliquely upward, so as to improve the convenience of welding and better complete the welding work. The automatic welding equipment for the outer annular seam of the cylinder also includes: an "L"-shaped fixed support arm 102 is fixedly installed on the right side of the fixed support 1 on the left side of the two fixed supports 1, and a telescopic cylinder 103 is fixedly installed on the top front side of the fixed support arm 102, and a welding machine arm 2 is fixedly connected to the bottom of the telescopic cylinder 103, and a welding machine arm 2 is installed on the bottom front side of the welding machine arm 2. A welding machine 201 is installed on the front side of the bottom.

[0039] By adopting the above technical scheme, the welding robot arm 2 first searches for the weld according to the input welding parameters, and compares the weld with the pre-set welding program after scanning the weld. After confirming that it is correct, welding is directly started by the welding machine 201 until the welding is completed. The operator does not need to perform high-intensity welding operations for a long time, which reduces the impact of manual fatigue on welding quality. Automated welding can more accurately control welding parameters and welding paths, effectively control weld quality, improve welding stability and consistency, reduce the occurrence of weld defects, improve the welding quality of the cylinder, and adjust the height of the welding robot arm 2 by the telescopic cylinder 103 to expand the activity space of the welding robot arm 2.

[0040] Specific usage and function of this embodiment: In the present invention, first, the operator accurately measures the outer diameter, thickness and length of the cylinder before welding, and inputs these data into the operating system. The operating system generates a welding program suitable for the cylinder according to the built-in algorithm, and then passes the cylinder through the protective ring 404 of the flip platform 4. At this time, the control gear 901 connected to the drive shaft end of the control motor 9 is engaged with the transmission gear 1001 on the transmission shaft 10, and the rotation of the transmission shaft 10 can be controlled by controlling the motor 9, so that the control worm 1002 fixedly connected to the front and rear ends of the transmission shaft 10 and the control worm wheel 1101 in the middle of the bidirectional screw 11 are engaged, and the rotation of the bidirectional screw 11 is controlled, so that the position of the two rotating connecting blocks 7 on the bidirectional screw 11 can be controlled, thereby adjusting the scissor angle of the supporting bracket 6, so that By adjusting the distance between the anti-skid columns 601 at the top of the supporting bracket 6, cylinders of different thicknesses can be carried, and then by controlling the rotation of the flip worm 301 at the end of the driving shaft of the flip motor 3, the flip worm 301 can be used to control the rotation of the flip worm wheel 40101, so that the angle of the flip platform 4 can be changed by the cooperation of the flip worm wheel 40101 and the adapter shaft 401, so that the flip platform 4 is tilted, and the welding surface of the cylinder in the protective ring 404 at the top of the flip platform 4 is facing obliquely upward. Finally, the welding robot arm 2 first searches for the weld according to the input welding parameters, and compares the weld with the pre-set welding program after scanning the weld. After confirmation, welding is started directly through the welding machine 201 until the welding is completed. The operator does not need to perform high-intensity welding operations for a long time, reducing the influence of manual fatigue on the welding quality.

[0041] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. An automatic welding equipment for outer annular seam of a cylinder, characterized by: The invention comprises a fixed support (1), wherein two fixed supports (1) are symmetrically arranged, and the tops between the two fixed supports (1) are both rotatably connected to a flip platform (4), and a supporting bracket (6) is hingedly connected to the front and rear sides of the top end face of the flip platform (4), and the bottom end of the supporting bracket (6) is rotatably connected to a rotating connection block (7), and a bidirectional screw (11) is threadedly connected in the rotating connection block (7), and a lifting bracket (8) is arranged at the bottom of the flip platform (4), and a control motor (9) is fixedly installed on the front side of the right side wall of the lifting bracket (8), and a transmission shaft (10) is rotatably connected in the lifting bracket (8), and the front and rear ends of the transmission shaft (10) are meshingly connected with the bidirectional screw (11).

2. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A rotating shaft seat (101) is fixedly mounted on the top of the right side wall of the fixed support (1) on the right side of the two fixed supports (1), a flip motor (3) is fixedly mounted on the rear side of the rotating shaft seat (101), a front end of the driving shaft of the flip motor (3) is fixedly connected to a flip worm (301), and front and rear ends of the flip worm (301) are rotatably connected to the front and rear side walls of the rotating shaft seat (101).

3. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A fixed support arm (102) is fixedly mounted on the right rear side of the fixed support (1) on the left side of the two fixed supports (1), a telescopic cylinder (103) is fixedly mounted on the top front side of the fixed support arm (102), a welding machine arm (2) is fixedly connected to the bottom of the telescopic cylinder (103), and a welding machine (201) is mounted on the bottom front side of the welding machine arm (2).

4. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A transfer shaft (401) is fixedly installed in the middle of the left and right sides of the top end surface of the flip platform (4); the top shafts of the outer walls of the two transfer shafts (401) are rotatably connected to the top of the side wall of the fixed support (1); the end of the shaft at the top of the right side wall of the transfer shaft (401) on the right side of the flip platform (4) is fixedly connected to a flip worm gear (40101); the bottom of the flip worm gear (40101) is meshedly connected to the top of the flip worm (301) connected to the front side of the flip motor (3); and a circular ring-shaped protective ring (404) is fixedly connected between the tops of the opposite side walls of the two transfer shafts (401) of the flip platform (4).

5. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A clamping electric cylinder (5) is fixedly mounted on the front side of the top of the side wall opposite to the two transfer shafts (401) of the turning platform (4), and a fixed arc piece (501) is fixedly connected to the telescopic ends on the opposite side of the two clamping electric cylinders (5).

6. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A hinged shaft end (402) is fixedly mounted in the middle of the front and rear sides of the top end surface of the turning platform (4), and a penetrating sliding guide groove (403) is provided in the end surface of the turning platform (4) at the bottom of the hinged shaft end (402).

7. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 6, characterized in that: The support bracket (6) is connected to the top of the hinge shaft end (402) in an "X" shape, the bottom of the support bracket (6) is slidably connected to the sliding guide groove (403), and the top of the support bracket (6) is fixedly connected to an anti-skid column (601), and the outer surface of the anti-skid column (601) is wrapped with high-friction rubber.

8. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: The left end of the driving shaft of the control motor (9) is fixedly connected to a control gear (901), and the control gear (901) is meshed with a transmission gear (1001) at a right angle in the middle of a transmission shaft (10) that is rotatably connected inside the lifting bracket (8), and the front and rear ends of the transmission shaft (10) are fixedly connected to a control worm (1002).

9. The automatic welding equipment for outer annular seam of a cylinder as claimed in claim 1, characterized in that: A control worm gear (1101) is fixedly connected in the middle of the bidirectional screw rods (11) rotatably connected at the front and rear ends of the lifting bracket (8), and the control worm gears (1101) in the middle of the two bidirectional screw rods (11) are respectively meshed and connected with the control worm gears (1002) at the front and rear ends of the transmission shaft (10).

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