Wood board automatic edge-finding laser cutting machine based on machine vision

Abstract

The invention provides a wood board automatic edge-finding laser cutting machine based on machine vision, which comprises a frame structure consisting of a bottom plate, a placing plate and a top plate, a control device and a cutting mechanism which are arranged on the top plate, an adsorption mechanism arranged on the placing plate, and a stabilizing mechanism positioned on the bottom plate, the cutting mechanism achieves two-dimensional movement of a laser cutting module through transmission of a dual-drive motor, a guide rail, a threaded rod and a gear, the adsorption mechanism fixes a plate through a negative pressure device, a rotary connector and a suction cup, a tray is driven by a motor to rotate to adjust the angle, and the stabilizing mechanism enhances the stability of the plate through an electric telescopic rod and a stabilizing block. The visual identification module obtains plate contour information, and the control device plans a cutting path. By means of the structure, the equipment has the advantages of achieving automatic edge searching and precise cutting of wood boards, being suitable for machining of various boards and complex shapes and the like, and the wood machining quality and the production efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of furniture manufacturing, and particularly to an automatic edge-finding laser cutting machine for wood boards based on machine vision. Background Art

[0002] In the field of wood processing, traditional cutting of wood boards mostly relies on manual scribing for positioning and mechanical tool cutting, which has problems such as low efficiency, poor accuracy, and high labor intensity. With the surging demand for customized furniture, the demand for cutting complex contours has increased, and the traditional method is difficult to meet the high-precision and diversified production requirements. Some enterprises have introduced laser cutting technology, but the existing equipment still requires manual loading and positioning, cannot automatically adapt to changes in the size and shape of the boards, and the boards are not fixed stably during the cutting process, which is likely to cause cutting deviation. In addition, traditional equipment has a single function and is difficult to be compatible with boards of multiple materials and thicknesses, restricting the processing range. Although machine vision technology has been applied in industrial inspection, in the field of wood board cutting, there is still a blank for equipment that deeply integrates visual recognition, automatic control, and laser cutting. This automatic edge-finding laser cutting machine for wood boards based on machine vision aims to solve the above pain points and achieve the automation, precision, and high efficiency of wood board cutting, meeting the urgent need for intelligent production in the modern wood processing industry. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides an automatic edge-finding laser cutting machine for wood boards based on machine vision, which solves the problems of low positioning accuracy, low processing efficiency, and insufficient flexibility.

[0004] To achieve the above objectives, the present invention is realized through the following technical solutions: An automatic edge-finding laser cutting machine for wood boards based on machine vision, comprising: a bottom plate, four ends of the upper part of the bottom plate are fixedly connected with first support rods, the upper ends of the first support rods are fixedly connected with a placement plate, four ends of the upper part of the placement plate are fixedly connected with second support rods, the upper ends of the second support rods are fixedly connected with a top plate, the upper end of the top plate is fixedly connected with a control device, a cutting mechanism is arranged at the lower end of the top plate, a suction mechanism is arranged at the lower end of the placement plate, and a stabilizing mechanism is arranged at the upper end of the bottom plate;

[0005] The cutting mechanism includes a vision recognition module, a first guide rail, a first mounting bracket, a first threaded rod, a first slider, a first driving motor, a first helical gear, a second helical gear, a second guide rail, a second driving motor, a second threaded rod, a second slider, a third mounting bracket, and a laser cutting module;

[0006] The suction mechanism includes a rotating shaft, a tray, a toothed ring, a suction cup, a first connecting pipe, a second connecting pipe, a rotary joint, a third connecting pipe, a negative pressure device, a third driving motor, a second mounting bracket, and a small gear.

[0007] Preferably, legs are fixedly connected to the lower end of the bottom plate, and the number of the legs is four and they are evenly distributed.

[0008] Preferably, the stabilizing mechanism includes a first electric telescopic rod, a guide rod, a cross-shaped bent support plate fixedly connected to a second electric telescopic rod. The center of the upper end of the bottom plate is connected to the first electric telescopic rod, the upper end of the first electric telescopic rod is fixedly connected to the cross-shaped bent support plate, the bent direction of the cross-shaped bent support plate towards the center is fixedly connected to the second electric telescopic rod, the front end of the second electric telescopic rod is fixedly connected to a stabilizing block, T-shaped grooves are provided on the four sides of the placement plate, and the inner wall of the T-shaped groove is slidably connected to the stabilizing block.

[0009] Preferably, the center of the lower end face of the top plate is fixedly connected to the vision recognition module, the side wall of the second support rod is fixedly connected to the first guide rail, the inner side of the second support rod is fixedly connected to the first mounting bracket, and the first driving motor is fixedly installed inside the first mounting bracket.

[0010] Preferably, the output end of the first driving motor is fixedly connected to a second bevel gear, the outer surface of the second bevel gear is meshed with a first bevel gear, and the inner wall of the first bevel gear is fixedly connected to a first threaded rod.

[0011] Preferably, the outer surface of the first threaded rod is threadedly connected to a first slider, and the outer surface of the first slider is slidably connected to the inner wall of the first guide rail.

[0012] Preferably, the upper end of the first slider is fixedly connected to a second guide rail, the opening of the second guide rail faces downward, the inner wall of the second guide rail is slidably connected to a second slider, the rear end of the second guide rail is fixedly connected to a second driving motor, the output end of the second driving motor is fixedly connected to a second threaded rod, and the inner wall of the second slider is threadedly connected to the second threaded rod.

[0013] Preferably, the lower end of the second slider is fixedly connected to a third mounting bracket, and the lower end of the third mounting bracket is fixedly connected to a laser cutting module.

[0014] Preferably, the center of the placement plate is rotatably connected to a rotating shaft, the upper end of the rotating shaft is fixedly connected to a tray, the lower end of the placement plate is fixedly connected to a second mounting bracket, the outer side of the lower end of the rotating shaft is fixedly connected to a toothed ring, the bottom inner wall of the second mounting bracket is fixedly connected to a third driving motor, the output end of the third driving motor is fixedly connected to a small gear, and the outer surface of the small gear is meshed with the toothed ring.

[0015] Preferably, the bottom inner wall of the second mounting bracket is fixedly connected to the negative pressure device, the front end of the negative pressure device is fixedly connected to the third connecting pipe, the upper end of the third connecting pipe is fixedly connected to the rotary joint, the upper end of the rotary joint is rotatably connected to the second connecting pipe, the outer side of the second connecting pipe is fixedly connected to the first connecting pipe, the number of the first connecting pipes is four and they are annularly distributed, and the upper ends of the first connecting pipes penetrate through the rotating shaft and extend into the interior of the tray.

[0016] The present invention provides an automatic edge-finding laser cutting machine for wood boards based on machine vision. It has the following beneficial effects: for this automatic edge-finding laser cutting machine for wood boards with machine vision, the vision recognition module accurately captures the contour information of the board and transmits it to the control device to plan the path. Cooperating with the double-axis precision transmission structure of the cutting mechanism, it realizes high-precision cutting, effectively avoiding manual measurement errors and cutting deviations. The combination of negative pressure adsorption and mechanical clamping and the stable mechanism's adaptive adjustment, and at the same time, the rotary joint ensures that the negative pressure does not cut off when the tray rotates, supporting flexible cutting at multiple angles. The modular structure design enables quick replacement of key components and greatly improves the maintenance efficiency. And in order to avoid interference during the blanking process of the material taking machine, the first electric telescopic rod drives the cross-shaped bending support plate and the second electric telescopic rod at the front end to move downward along the T-shaped groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0018] Figure 2 is a schematic diagram of the storage structure of the stabilizing block of the present invention;

[0019] Figure 3 is a schematic diagram of the storage position of the present invention;

[0020] Figure 4 is a schematic diagram of the vertical movement structure of the present invention;

[0021] Figure 5 For the present invention Figure 4 is an enlarged schematic diagram of the structure at A in the present invention;

[0022] Figure 6 is a schematic diagram of the position of the vision recognition module of the present invention;

[0023] Figure 7 is a schematic diagram of the horizontal movement structure of the present invention;

[0024] Figure 8 is a schematic diagram of the adsorption structure of the present invention.

[0025] Among them, 1. bottom plate; 2. support leg; 3. first electric telescopic rod; 4. guide rod; 5. cross-shaped bent support plate; 6. second electric telescopic rod; 7. stabilizing block; 8. placement plate; 9. T-shaped groove; 10. first support rod; 11. second support rod; 12. top plate; 13. control device; 14. visual recognition module; 15. first guide rail; 16. first mounting bracket; 17. first threaded rod; 18. first slider; 19. first driving motor; 20. first helical gear; 21. second helical gear; 22. second guide rail; 23. second driving motor; 24. second threaded rod; 25. second slider; 26. third mounting bracket; 27. laser cutting module; 28. rotating shaft; 29. tray; 30. toothed ring; 31. suction cup; 32. first connecting pipe; 33. second connecting pipe; 34. rotary joint; 35. third connecting pipe; 36. negative pressure device; 37. third driving motor; 38. pinion; 39. second mounting bracket. Specific embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment 1

[0028] As Figures 1-8 shown, the embodiment of the present invention provides an automatic edge-finding laser cutting machine for wood boards based on machine vision, including a bottom plate 1. Four ends of the upper part of the bottom plate 1 are fixedly connected with first support rods 10. The upper ends of the first support rods 10 are fixedly connected with a placement plate 8. Four ends of the upper part of the placement plate 8 are fixedly connected with second support rods 11. The upper ends of the second support rods 11 are fixedly connected with a top plate 12. The upper end of the top plate 12 is fixedly connected with a control device 13. A cutting mechanism is arranged at the lower end of the top plate 12. An adsorption mechanism is arranged at the lower end of the placement plate 8. A stabilizing mechanism is arranged at the upper end of the bottom plate 1. Four support legs 2 are fixedly connected to the lower end of the bottom plate 1 and are evenly distributed to prevent the equipment from shaking due to unstable support and provide a stable foundation for operations such as cutting and adsorption.

[0029] The cutting mechanism includes a visual recognition module 14, a first guide rail 15, a first mounting bracket 16, a first threaded rod 17, a first slider 18, a first driving motor 19, a first helical gear 20, a second helical gear 21, a second guide rail 22, a second driving motor 23, a second threaded rod 24, a second slider 25, a third mounting bracket 26 and a laser cutting module 27.

[0030] The stabilizing mechanism includes a first electric telescopic rod 3, a guide rod 4, a cross-shaped bending support plate 5 fixedly connected to a second electric telescopic rod 6. The center of the upper end of the bottom plate 1 is connected to the first electric telescopic rod 3, the upper end of the first electric telescopic rod 3 is fixedly connected to the cross-shaped bending support plate 5, the bending direction of the cross-shaped bending support plate 5 towards the center is fixedly connected to the second electric telescopic rod 6, the front end of the second electric telescopic rod 6 is fixedly connected to a stabilizing block 7. T-shaped grooves 9 are provided on the four sides of the placing plate 8, and the inner wall of the T-shaped groove 9 is slidably connected to the stabilizing block 7, facilitating the free lifting of the stabilizing block 7 and reducing interference with material taking and placing. The center of the lower end face of the top plate 12 is fixedly connected to a visual recognition module 14. The side wall of the second support rod 11 is fixedly connected to a first guide rail 15, and the inner side of the second support rod 11 is fixedly connected to a first mounting bracket 16. The first drive motor 19 is fixedly installed inside the first mounting bracket 16, and the visual recognition module 14 is installed at the center of the lower end face of the top plate 12, capable of comprehensively and accurately obtaining the image information of the wood board.

[0031] The output end of the first drive motor 19 is fixedly connected to a second bevel gear 21, the outer surface of the second bevel gear 21 is meshed with a first bevel gear 20, and the inner wall of the first bevel gear 20 is fixedly connected to a first threaded rod 17, realizing the movement of the cutting mechanism in the horizontal direction, enabling the laser cutting module 27 to perform precise position adjustment in the horizontal direction to meet the horizontal displacement requirements under different cutting needs. The outer surface of the first threaded rod 17 is threadedly connected to a first slider 18, the outer surface of the first slider 18 is slidably connected to the inner wall of the first guide rail 15, the upper end of the first slider 18 is fixedly connected to a second guide rail 22, the opening of the second guide rail 22 faces downward, the inner wall of the second guide rail 22 is slidably connected to a second slider 25, the rear end of the second guide rail 22 is fixedly connected to a second drive motor 23, the output end of the second drive motor 23 is fixedly connected to a second threaded rod 24, the inner wall of the second slider 25 is threadedly connected to the second threaded rod 24. The first slider 18 drives the second guide rail 22 to move, and the second drive motor 23 drives the second slider 25 to slide in the second guide rail 22 through the second threaded rod 24, realizing the movement of the laser cutting module 27 in the longitudinal direction. The lower end of the second slider 25 is fixedly connected to a third mounting bracket 26, and the lower end of the third mounting bracket 26 is fixedly connected to the laser cutting module 27.

[0032] The adsorption mechanism includes a rotating shaft 28, a tray 29, a toothed ring 30, a suction cup 31, a first connecting pipe 32, a second connecting pipe 33, a rotary joint 34, a third connecting pipe 35, a negative pressure device 36, a third drive motor 37, a second mounting bracket 39 and a small gear 38.

[0033] Embodiment 2

[0034] As Figures 1-8As shown in the figure, an embodiment of the present invention provides an automatic edge-seeking laser cutting machine for wood boards based on machine vision, including a bottom plate 1. Four ends of the upper part of the bottom plate 1 are fixedly connected with first support rods 10. The upper ends of the first support rods 10 are fixedly connected with a placement plate 8. Four ends of the upper part of the placement plate 8 are fixedly connected with second support rods 11. The upper ends of the second support rods 11 are fixedly connected with a top plate 12. The upper end of the top plate 12 is fixedly connected with a control device 13. A cutting mechanism is arranged at the lower end of the top plate 12. An adsorption mechanism is arranged at the lower end of the placement plate 8. A stabilizing mechanism is arranged at the upper end of the bottom plate 1. Four legs 2 are fixedly connected to the lower end of the bottom plate 1 and are evenly distributed to prevent the equipment from shaking due to unstable support, providing a stable foundation for operations such as cutting and adsorption.

[0035] The cutting mechanism includes a vision recognition module 14, a first guide rail 15, a first mounting frame 16, a first threaded rod 17, a first slider 18, a first driving motor 19, a first helical gear 20, a second helical gear 21, a second guide rail 22, a second driving motor 23, a second threaded rod 24, a second slider 25, a third mounting frame 26, and a laser cutting module 27.

[0036] The adsorption mechanism includes a rotating shaft 28, a tray 29, a toothed ring 30, a suction cup 31, a first connecting pipe 32, a second connecting pipe 33, a rotary joint 34, a third connecting pipe 35, a negative pressure device 36, a third driving motor 37, a second mounting frame 39, and a small gear 38. The center of the placement plate 8 is rotatably connected to the rotating shaft 28. The upper end of the rotating shaft 28 is fixedly connected to the tray 29. The lower end of the placement plate 8 is fixedly connected to the second mounting frame 39. The outer side of the lower end of the rotating shaft 28 is fixedly connected to the toothed ring 30. The bottom inner wall of the second mounting frame 39 is fixedly connected to the third driving motor 37. The output end of the third driving motor 37 is fixedly connected to the small gear 38. The outer surface of the small gear 38 is meshed with the toothed ring 30. The third driving motor 37 drives the rotating shaft 28 and the tray 29 to rotate through the meshing of the small gear 38 and the toothed ring 30. This enables the wood board to be conveniently adjusted in angle to adapt to cutting requirements at different angles. At the same time, it is also convenient for the vision recognition module 14 to obtain information of the wood board from different angles, improving the flexibility and adaptability of the equipment during the processing process and meeting diverse processing requirements.

[0037] The bottom inner wall of the second mounting bracket 39 is fixedly connected to the negative pressure device 36. The front end of the negative pressure device 36 is fixedly connected to the third connecting pipe 35. The upper end of the third connecting pipe 35 is fixedly connected to the rotary joint 34. The upper end of the rotary joint 34 is rotatably connected to the second connecting pipe 33. The outer side of the second connecting pipe 33 is fixedly connected to the first connecting pipe 32. The number of the first connecting pipes 32 is four and they are annularly distributed. The upper ends of the first connecting pipes 32 penetrate through the rotating shaft 28 and extend into the interior of the tray 29. The setting of the rotary joint 34 ensures the connectivity of the negative pressure pipeline during the rotation of the tray 29, ensures the continuous effectiveness of the adsorption function, can firmly fix the wood board, prevent the board from shifting during the cutting process, and ensure the stability of the cutting process and the cutting quality.

[0038] Working principle: The working principle of this machine vision-based automatic edge-finding laser cutting machine for wood boards is as follows: The vision recognition module 14 is installed at the center of the lower end face of the top plate 12, performs vision recognition on the wood board placed on the tray 29, obtains information such as the edge contour of the board and transmits it to the control device 13. The control device 13 plans the cutting path according to the recognition information. In the cutting mechanism, the first driving motor 19 is installed in the first mounting bracket 16, and its output end drives the second helical gear 21 to rotate. The first helical gear 20 meshing with the second helical gear 21 rotates accordingly, so that the first threaded rod 17 rotates. The first slider 18 threadedly connected to the first threaded rod 17 slides in the first guide rail 15, realizing the movement of the cutting mechanism in one dimension in the horizontal direction. At the same time, the second driving motor 23 is fixed at the rear end of the second guide rail 22, and its output end drives the second threaded rod 24 to rotate. The second slider 25 threadedly connected to the second threaded rod 24 slides in the second guide rail 22. The third mounting bracket 26 and the laser cutting module 27 at the lower end of the second slider 25 move accordingly. Combining with the movement of the first slider 18, the two-dimensional movement of the laser cutting module 27 in the plane is realized to perform laser cutting according to the planned path.

[0039] In the adsorption mechanism, the third driving motor 37 is installed on the bottom inner wall of the second mounting bracket 39. The small gear 38 at its output end meshes with the toothed ring 30, driving the rotating shaft 28 and the tray 29 to rotate, facilitating the adjustment of the angle of the wood board. The negative pressure device 36 makes the suction cups 31 in the tray 29 generate negative pressure through the third connecting pipe 35, the rotary joint 34, the second connecting pipe 33 and the four annularly distributed first connecting pipes 32 to adsorb and fix the wood board. In the stabilizing mechanism, the first electric telescopic rod 3 at the center of the upper end of the bottom plate 1 can drive the cruciform bending support plate 5 to lift and lower. The second electric telescopic rod 6 with the cruciform bending support plate 5 bent towards the center pushes the stabilizing block 7 to fix the wood on the upper end of the placing plate 8. When it is necessary to remove or re-place the wood board, the cruciform bending support plate 5 is lowered by the first electric telescopic rod 3, and the stabilizing block 7 slides downward through the T-shaped grooves 9 on the four sides, so as to facilitate the placement or removal of the wood board. The legs 2 support the entire equipment to maintain stability.

[0040] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An automatic edge-finding laser cutting machine for wood boards based on machine vision, characterized in that, Comprising: A bottom plate (1), four ends of the upper part of the bottom plate (1) are fixedly connected with first support rods (10), upper ends of the first support rods (10) are fixedly connected with a placement plate (8), four ends of the upper part of the placement plate (8) are fixedly connected with second support rods (11), upper ends of the second support rods (11) are fixedly connected with a top plate (12), an upper end of the top plate (12) is fixedly connected with a control device (13), a cutting mechanism is arranged at the lower end of the top plate (12), an adsorption mechanism is arranged at the lower end of the placement plate (8), and a stabilizing mechanism is arranged at the upper end of the bottom plate (1); The cutting mechanism includes a vision recognition module (14), a first guide rail (15), a first mounting frame (16), a first threaded rod (17), a first slider (18), a first driving motor (19), a first bevel gear (20), a second bevel gear (21), a second guide rail (22), a second driving motor (23), a second threaded rod (24), a second slider (25), a third mounting frame (26) and a laser cutting module (27); The adsorption mechanism includes a rotating shaft (28), a tray (29), a toothed ring (30), a suction cup (31), a first connecting pipe (32), a second connecting pipe (33), a rotary joint (34), a third connecting pipe (35), a negative pressure device (36), a third driving motor (37), a second mounting frame (39) and a pinion gear (38).

2. The automatic edge-finding laser cutting machine for wood boards based on machine vision according to claim 1, wherein: Lower ends of the bottom plate (1) are fixedly connected with legs (2), and the number of the legs (2) is four and they are evenly distributed.

3. The automatic edge-seeking laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The stabilizing mechanism includes a first electric telescopic rod (3), a guide rod (4), a cross-shaped bent support plate (5) fixedly connected with a second electric telescopic rod (6), the center of the upper end of the bottom plate (1) is connected with the first electric telescopic rod (3), the upper end of the first electric telescopic rod (3) is fixedly connected with the cross-shaped bent support plate (5), the bent direction of the cross-shaped bent support plate (5) towards the center is fixedly connected with the second electric telescopic rod (6), the front end of the second electric telescopic rod (6) is fixedly connected with a stabilizing block (7), T-shaped grooves (9) are arranged on four sides of the placement plate (8), and inner walls of the T-shaped grooves (9) are slidably connected with the stabilizing blocks (7).

4. The automatic edge-finding laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The center of the lower end face of the top plate (12) is fixedly connected with the vision recognition module (14), the side wall of the second support rod (11) is fixedly connected with the first guide rail (15), the inner side of the second support rod (11) is fixedly connected with the first mounting frame (16), and the first driving motor (19) is fixedly installed inside the first mounting frame (16).

5. An automatic edge - finding laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: An output end of the first driving motor (19) is fixedly connected with the second bevel gear (21), an outer surface of the second bevel gear (21) is meshed with the first bevel gear (20), and an inner wall of the first bevel gear (20) is fixedly connected with the first threaded rod (17).

6. The automatic edge-seeking laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: An outer surface of the first threaded rod (17) is threadedly connected with the first slider (18), and an outer surface of the first slider (18) is slidably connected with an inner wall of the first guide rail (15).

7. An automatic edge - seeking laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The upper end of the first slider (18) is fixedly connected to the second guide rail (22). The opening of the second guide rail (22) faces downward. The inner wall of the second guide rail (22) is slidably connected to the second slider (25). The rear end of the second guide rail (22) is fixedly connected to the second driving motor (23). The output end of the second driving motor (23) is fixedly connected to the second threaded rod (24). The inner wall of the second slider (25) is threadedly connected to the second threaded rod (24).

8. An automatic edge-finding laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The lower end of the second slider (25) is fixedly connected to the third mounting bracket (26). The lower end of the third mounting bracket (26) is fixedly connected to the laser cutting module (27).

9. The automatic edge - searching laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The center of the placement plate (8) is rotatably connected to the rotating shaft (28). The upper end of the rotating shaft (28) is fixedly connected to the tray (29). The lower end of the placement plate (8) is fixedly connected to the second mounting bracket (39). The outer side of the lower end of the rotating shaft (28) is fixedly connected to the toothed ring (30). The bottom inner wall of the second mounting bracket (39) is fixedly connected to the third driving motor (37). The output end of the third driving motor (37) is fixedly connected to the small gear (38). The outer surface of the small gear (38) is meshed with the toothed ring (30).

10. The automatic edge - finding laser cutting machine for wood boards based on machine vision according to claim 1, characterized in that: The bottom inner wall of the second mounting bracket (39) is fixedly connected to the negative pressure device (36). The front end of the negative pressure device (36) is fixedly connected to the third connecting pipe (35). The upper end of the third connecting pipe (35) is fixedly connected to the rotary joint (34). The upper end of the rotary joint (34) is rotatably connected to the second connecting pipe (33). The outer side of the second connecting pipe (33) is fixedly connected to the first connecting pipe (32). The number of the first connecting pipes (32) is four and they are annularly distributed. The upper ends of the first connecting pipes (32) penetrate through the rotating shaft (28) and extend into the interior of the tray (29).

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