Logistics transfer conveying device

Abstract

The application discloses a logistics transfer conveying device, which comprises a transfer and distribution conveying system and a layered conveying system; the transfer and distribution conveying system comprises a fixed frame, an input end conveying table is fixedly arranged at the middle of one end of the fixed frame, an upper distribution conveying table and a lower distribution conveying table are reversibly and parallelly arranged at the other end of the fixed frame, and a turnover adjusting mechanism for driving the upper distribution conveying table and the lower distribution conveying table to synchronously turn over is arranged on the fixed frame; the layered conveying system comprises a rack, two horizontal upper conveying tables and lower conveying tables are parallelly arranged on the rack. The upper distribution conveying table and the lower distribution conveying table can be turned over, and the upper conveying tables and the lower conveying tables in the layered conveying system are matched, so that the distribution conveying in the vertical direction is realized, the horizontal land area is obviously reduced, and the problems of large land area and high site expansion cost of the existing plane arrangement type distribution device are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of logistics transportation, and more particularly to a logistics transfer and transportation device. Background Technology

[0002] With the rapid development of e-commerce and the express delivery industry, the volume of logistics transit has experienced explosive growth, placing higher demands on the cargo handling efficiency and space utilization of transit stations. As a key process in the logistics transit chain for classifying goods by destination, route, or batch, the structural layout and operational efficiency of the diversion and transportation equipment directly affect the overall logistics timeliness and site utilization.

[0003] Currently, most common logistics diversion and conveying devices adopt a horizontal layout, where the main conveyor line and all branch conveyor lines are distributed in a planar network on the same horizontal plane. This type of planar layout presents the following technical problems in practical applications: First, it requires a large footprint. To meet the needs of multi-directional and multi-batch diversion, multiple conveyor lines and corresponding turning mechanisms need to be set up on the same horizontal plane, occupying a large amount of warehousing or transfer space and limiting the throughput capacity per unit area of ​​the transfer station. Second, diversion paths often intersect or interfere. At the confluence of multiple branches or diversion nodes, the conveying paths of goods in different directions are prone to intersection or conflict, requiring additional complex avoidance or timing control mechanisms, increasing the difficulty of system control and operational risks. Third, space utilization is low. The vertical dimension of the transfer station building space is not fully utilized, and site expansion costs are high. Therefore, this paper proposes to develop a logistics transfer and conveying equipment. Summary of the Invention

[0004] The purpose of this invention is to provide a logistics transfer and conveying device to solve the technical problems mentioned in the background section.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention provides a logistics transfer and conveying device, comprising a transfer and diversion conveying system and a layered conveying system.

[0006] The transfer and diversion conveying system includes a fixed frame. An input conveyor is fixedly arranged in the middle of one end of the fixed frame. An upper diversion conveyor and a lower diversion conveyor are arranged in parallel at the other end of the fixed frame and can be flipped. The fixed frame is provided with a flipping adjustment mechanism for driving the upper and lower diversion conveyors to flip synchronously.

[0007] The layered conveying system includes a frame on which two horizontal upper and lower conveying platforms are arranged in parallel. When the flipping adjustment mechanism aligns one end of the upper diversion conveying platform with the input conveying platform, the other end of the upper diversion conveying platform aligns with the upper conveying platform. When the flipping adjustment mechanism aligns one end of the lower diversion conveying platform with the input conveying platform, the other end of the lower diversion conveying platform aligns with the lower conveying platform.

[0008] Furthermore, the input end conveyor platform includes two symmetrically fixed first mounting plates on the fixed frame. The bottoms of the two first mounting plates are respectively fixedly connected to the bottom of the fixed frame via vertical support rods. Two sets of first support roller seats are respectively fixedly installed at both ends of the two first mounting plates. A first conveyor roller is rotatably installed between the two first support roller seats located at the same end. A first conveyor belt is wound around the two first conveyor rollers together. A first motor for driving the first conveyor roller to rotate is fixedly installed at the outer end of the fixed frame.

[0009] Furthermore, two first bearing seats are symmetrically fixedly arranged on the outer side of one end of the fixed frame, and the two ends of the central shaft of one of the first conveying rollers are respectively rotatably engaged with the two first bearing seats; a first reducer is fixedly arranged on the outer side of the fixed frame, the first motor is fixedly arranged on the input end of the first reducer, and the output end of the first reducer is connected to one end of the central shaft of the corresponding first conveying roller.

[0010] Furthermore, the upper diversion conveyor includes two symmetrically rotatable second mounting plates disposed in the middle of the other end of the fixed frame. Two sets of second support roller seats are fixedly disposed at both ends of the two second mounting plates. A second conveyor roller is rotatably mounted between the two second support roller seats located at the same end. A second conveyor belt is wound around the two second conveyor rollers together.

[0011] Furthermore, the lower diversion conveyor includes two symmetrically rotatable third mounting plates disposed at the lower part of the other end of the fixed frame. Two sets of third support roller seats are fixedly disposed at both ends of the two third mounting plates. A third conveyor roller is rotatably installed between the two third support roller seats located at the same end. A third conveyor belt is wound around the two third conveyor rollers together.

[0012] Furthermore, two pairs of second bearing seats are fixedly arranged at intervals on the outer side of the other end of the fixed frame. The two ends of the central shaft of the second conveying roller near the end of the fixed frame are respectively rotatably engaged with the two upper second bearing seats. The two ends of the central shaft of the third conveying roller near the end of the fixed frame are respectively rotatably engaged with the two lower second bearing seats. A second motor for driving the second conveying roller and the third conveying roller to rotate synchronously is fixedly arranged on the outer end of the fixed frame.

[0013] Furthermore, a second reducer is fixedly installed on the outer side of the other end of the fixed frame, and the second motor is fixedly installed on the input end of the second reducer. The output end of the second reducer is connected to one end of the central shaft of the third conveying roller near the end of the fixed frame. A drive sprocket is fixedly installed on the other end of the third conveying roller near the end of the fixed frame, and a driven sprocket is fixedly installed on the end of the second conveying roller near the end of the fixed frame corresponding to the drive sprocket. A tension sprocket is rotatably installed between the drive sprocket and the driven sprocket in the fixed frame. A transmission chain is wound around the drive sprocket, the driven sprocket, and the tension sprocket.

[0014] Furthermore, a crossbeam is fixedly installed in the middle of the upper part of the fixed frame. Two support frames are symmetrically fixedly installed in the fixed frame between the crossbeam and the upper diversion conveyor. A third bearing seat is fixedly installed at the bottom of each of the two support frames. The flipping adjustment mechanism includes an adjusting cylinder hinged to one end of the crossbeam and a rotating shaft rotatably installed between the two third bearing seats. The telescopic end of the adjusting cylinder is hinged to the upper end of two parallel connecting plates. The lower ends of the two connecting plates are fixedly connected to the rotating shaft. Two drive arms are symmetrically fixedly installed on the rotating shaft. Two first connecting rods are symmetrically hinged between the two drive arms and the two second mounting plates. Two second connecting rods are symmetrically hinged between the two second mounting plates and the two third mounting plates.

[0015] Furthermore, drive columns are fixedly installed on the outer sides of the two drive arms, two first connecting columns are symmetrically fixedly installed on the outer sides of the two second mounting plates, and two second connecting columns are symmetrically fixedly installed on the outer sides of the two third mounting plates; two first fisheye connectors that rotatably engage with the drive columns and the first connecting columns are fixedly installed at both ends of each first connecting rod, and two second fisheye connectors that rotatably engage with the first connecting columns and the second connecting columns are fixedly installed at both ends of each second connecting rod.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention achieves vertical diversion conveying by setting up a flip-up upper and lower diversion conveyor platform, in conjunction with the upper and lower conveyor platforms in a layered conveying system. After goods are input through the input conveyor platform, they can be selectively conveyed to the upper or lower conveying channel based on the identification result, thus transforming multiple diversion lines that originally needed to be arranged on the same horizontal plane into a two-level three-dimensional layout. This structural design makes full use of the vertical space of the transfer station building, significantly reducing the horizontal footprint while maintaining the same processing capacity, and effectively solving the problems of large footprint and high site expansion costs of existing planar diversion devices.

[0017] In this invention, the upper diversion conveyor and the upper layer conveyor form the upper conveying channel, and the lower diversion conveyor and the lower layer conveyor form the lower conveying channel. The two diversion paths are completely separated in space and do not intersect. By controlling the upper and lower diversion conveyors to connect with the input conveyor through a flipping adjustment mechanism, the goods are always transported along a single and clear path during the diversion process. This avoids the problems of multiple branch paths intersecting and goods interfering with each other in traditional planar diversion devices, and eliminates the need for complex avoidance control logic, thus reducing the system control difficulty and operational risks.

[0018] This invention achieves synchronous rotation of the upper and lower distribution conveyors via a tilting adjustment mechanism. Specifically, an adjusting cylinder drives a rotating shaft through a connecting plate. The drive arm on the rotating shaft rotates the upper distribution conveyor via a first connecting rod, while the upper distribution conveyor simultaneously rotates the lower distribution conveyor via a second connecting rod. This ingenious linkage mechanism requires only one drive source to achieve synchronous switching between the upper and lower distribution conveyors, resulting in a compact structure and simple control. Furthermore, the tilting shafts of both the upper and lower distribution conveyors are located near the input end, ensuring the positional accuracy of the docking ends during tilting and guaranteeing a smooth transition in cargo transport. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 A schematic view of the overall structure; Figure 2 This is a schematic diagram of the front-end structure of the transfer and diversion conveying system of the present invention; Figure 3 This is a schematic diagram of the rear-end structure of the transfer and diversion conveying system of the present invention; Figure 4 This is a top-view structural diagram of the transfer and diversion conveying system of the present invention; Explanation of reference numerals in the attached drawings: 1. Fixed frame; 2. Input conveyor; 3. Upper diversion conveyor; 4. Lower diversion conveyor; 5. Frame; 6. Upper conveyor; 7. Lower conveyor; 8. First mounting plate; 9. 10. Support rod; 11. First support roller seat; 12. First conveyor roller; 13. First conveyor belt; 14. First bearing seat; 15. First reducer; 16. Second mounting plate; 17. Second support roller seat; 18. Second conveyor roller; 19. Second conveyor belt; 20. Third mounting plate; 21. Third support roller seat; 22. Third conveyor roller; 23. Third conveyor belt; 24. Second motor; 25. Second reducer; 26. Drive sprocket; 27. Driven sprocket; 28. Tensioning sprocket; 29. ​​Crossbeam; 30. Support frame; 31. Third bearing seat; 32. Adjusting cylinder; 33. Rotating shaft; 34. Connecting plate; 35. Drive arm; 36. First connecting rod; 37. Second connecting rod; 38. Drive column; 39. First connecting column; 40. Second connecting column; 41. First fisheye joint; 42. Second fisheye joint. Detailed Implementation

[0021] like Figures 1-4 As shown, a logistics transfer and conveying device includes a transfer and diversion conveying system and a layered conveying system.

[0022] The transfer and diversion conveying system includes a fixed frame 1. An input conveyor 2 is installed in the middle of one end of the fixed frame 1. An upper diversion conveyor 3 and a lower diversion conveyor 4 are installed in parallel at the other end of the fixed frame 1 and can be flipped. The fixed frame 1 is provided with a flipping adjustment mechanism for driving the upper and lower diversion conveyors to flip synchronously.

[0023] The layered conveying system includes a frame 5, on which two horizontal upper conveying platforms 6 and lower conveying platforms 7 are installed in parallel.

[0024] In operation, goods to be transferred are input into the transfer and diversion conveying system via the input conveyor 2. A barcode scanner or a visual recognition system with a high-definition camera is installed on the top of one end of the fixed frame where the input conveyor 2 is located (this part is existing technology with mature applications in the field and will not be described in detail here). After the goods are identified, it is confirmed that the goods are transported to the upper or lower diversion conveyor. The upper or lower diversion conveyor is switched with the input conveyor 2 via a flipping adjustment mechanism. When the flipping adjustment mechanism connects one end of the upper diversion conveyor 3 to the input conveyor 2, the other end of the upper diversion conveyor 3 connects to the upper conveyor 6; when the flipping adjustment mechanism connects one end of the lower diversion conveyor 4 to the input conveyor 2, the other end of the lower diversion conveyor 4 connects to the lower conveyor 7. Therefore, this invention enables the vertical diversion and transportation of goods during the logistics transfer process, reducing the floor space occupied by the transportation system and improving space utilization.

[0025] The input conveyor platform 2 includes two symmetrically mounted first mounting plates 8 fixedly installed on the fixed frame 1. The bottoms of the two first mounting plates 8 are respectively fixedly connected to the bottom of the fixed frame 1 via vertical support rods 9. Two sets of first support roller seats 10 are fixedly installed at both ends of the two first mounting plates 8. A first conveyor roller 11 is rotatably installed between the two first support roller seats 10 located at the same end. A first conveyor belt 12 is wound around the two first conveyor rollers 11. A first motor 13 for driving the first conveyor roller 11 to rotate is fixedly installed at the outer end of the fixed frame 1.

[0026] Two first bearing seats 14 are symmetrically fixedly installed on the outer side of one end of the fixed frame 1. The two ends of the central shaft of the first conveying roller 11 near the end of the fixed frame 1 are respectively rotatably engaged with the two first bearing seats 14. A first reducer 15 is fixedly installed on the outer side of the fixed frame 1. The first motor 13 is fixedly installed on the input end of the first reducer 15, and the output end of the first reducer 15 is connected to one end of the central shaft of the corresponding first conveying roller 11. Therefore, when the first motor 13 starts, after being reduced in speed by the first reducer 15, the two first conveying rollers 11 rotate synchronously, driving the first conveyor belt 12 to transport the goods to be transferred to the end of the input end conveyor table 2.

[0027] The upper diversion conveyor 3 includes two symmetrical, rotatable second mounting plates 16 installed in the middle of the other end of the fixed frame 1. Two sets of second support roller seats 17 are fixedly installed at both ends of the two second mounting plates 16 respectively. A second conveying roller 18 is rotatably installed between the two second support roller seats 17 located at the same end. A second conveyor belt 19 is wound around the two second conveying rollers 18 together.

[0028] The lower diversion conveyor 4 includes two symmetrical, rotatable third mounting plates 20 installed at the lower part of the other end of the fixed frame 1. Two sets of third support roller seats 21 are fixedly installed at both ends of the two third mounting plates 20 respectively. A third conveying roller 22 is rotatably installed between the two third support roller seats 21 located at the same end. A third conveyor belt 23 is wound around the two third conveying rollers 22 together.

[0029] Two pairs of second bearing seats 43 are fixedly installed at intervals on the outer side of the other end of the fixed frame 1. The two ends of the central shaft of the second conveying roller 18 near the end of the fixed frame 1 are respectively rotatably engaged with the two upper second bearing seats 24. The two ends of the central shaft of the third conveying roller 22 near the end of the fixed frame 1 are respectively rotatably engaged with the two lower second bearing seats 24. A second motor 24 for driving the second conveying roller 18 and the third conveying roller 22 to rotate synchronously is fixedly installed on the outer end of the fixed frame 1.

[0030] Specifically: A second reducer 25 is fixedly installed on the outer side of the other end of the fixed frame 1. The second motor 24 is fixedly installed on the input end of the second reducer 25. The output end of the second reducer 25 is connected to one end of the central shaft of the third conveying roller 22 near the end of the fixed frame 1. A drive sprocket 26 is fixedly installed on the other end of the third conveying roller 22 near the end of the fixed frame 1. A driven sprocket 27 is fixedly installed on the end of the second conveying roller 18 near the end of the fixed frame 1 corresponding to the drive sprocket 26. A tensioning sprocket 28 is rotatably installed between the drive sprocket 26 and the driven sprocket 27. A transmission chain (not shown in the figure) is wound around the drive sprocket 26, the driven sprocket 27, and the tensioning sprocket 28. When the second motor 24 starts, the second reducer 25 reduces speed, causing the two third conveyor rollers 22 to drive the third conveyor belt 23. Simultaneously, the chain drive structure consisting of the driving sprocket 26 and the driven sprocket 27 causes the third conveyor rollers 22 to drive the second conveyor rollers 18 to rotate, thereby causing the two second conveyor rollers 18 to drive the second conveyor belt 19. This allows both the lower diversion conveyor belt 4 and the upper diversion conveyor platform 3 to transport the goods to be transferred outwards.

[0031] A crossbeam 29 is fixedly installed in the middle of the upper part of the fixed frame 1. Two support frames 30 are symmetrically fixedly installed in the fixed frame 1 at the position between the crossbeam 29 and the upper diversion conveyor 3. A third bearing seat 31 is fixedly installed at the bottom of each of the two support frames 30.

[0032] In this embodiment, the tilting adjustment mechanism includes an adjusting cylinder 32 hinged to one end of the crossbeam 29 and a rotating shaft 33 rotatably mounted between the two third bearing seats 31. The telescopic end of the adjusting cylinder 32 is hinged to the upper end of two parallel connecting plates 34, and the lower ends of the two connecting plates 34 are fixedly connected to the rotating shaft 33. Two drive arms 35 are symmetrically fixedly mounted on the rotating shaft 33. Two first connecting rods 36 are symmetrically hinged between the two drive arms 35 and the two second mounting plates 16, and two second connecting rods 37 are symmetrically hinged between the two second mounting plates 16 and the two third mounting plates 20.

[0033] Specifically: a drive column 38 is fixedly installed on the outer side of each of the two drive arms 35; two first connecting columns 39 are symmetrically fixedly installed on the outer side of each of the two second mounting plates 16; and two second connecting columns 40 are symmetrically fixedly installed on the outer side of each of the two third mounting plates 20. Two first fisheye connectors 41 are fixedly installed at both ends of each of the first connecting rods 36, which are respectively rotatably engaged with the drive column 38 and the first connecting column 39; and two second fisheye connectors 42 are fixedly installed at both ends of each of the second connecting rods 37, which are respectively rotatably engaged with the first connecting column 39 and the second connecting column 40.

[0034] In this embodiment, the flipping and switching adjustment of the upper diversion conveyor 3 and the lower diversion conveyor 4 is as follows: When the adjusting cylinder 32 extends, the two connecting plates 34 drive the rotating shaft 33 to rotate counterclockwise by a certain angle. Under the action of the rotating shaft 33, the two drive arms 33 drive the two second mounting plates 16 and the third mounting plate 20 to flip counterclockwise through the first connecting rod 36 and the second connecting rod 37, so that the lower diversion conveyor 4 is connected to the input end conveyor 2. At this time, the input end conveyor 2, the lower diversion conveyor 4, and the lower layer conveyor 7 constitute a cargo conveying channel. Similarly, when the regulating cylinder 32 retracts, the two connecting plates 34 drive the rotating shaft 33 to rotate clockwise by a certain angle. Under the action of the rotating shaft 33, the two drive arms 33 drive the two second mounting plates 16 and the third mounting plate 20 to rotate clockwise through the first connecting rod 36 and the second connecting rod 37, so that the upper diversion conveyor 3 is connected to the input end conveyor 2. At this time, the input end conveyor 2, the upper diversion conveyor 3, and the upper conveyor 6 constitute a cargo conveying channel.

[0035] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A logistics transfer and conveying device, characterized in that: This includes transit and diversion conveying systems and tiered conveying systems; The transfer and diversion conveying system includes a fixed frame. An input conveyor is fixedly arranged in the middle of one end of the fixed frame. An upper diversion conveyor and a lower diversion conveyor are arranged in parallel at the other end of the fixed frame and can be flipped. The fixed frame is provided with a flipping adjustment mechanism for driving the upper diversion conveyor and the lower diversion conveyor to flip synchronously. The layered conveying system includes a frame on which two horizontal upper and lower conveying platforms are arranged in parallel. When the flipping adjustment mechanism aligns one end of the upper diversion conveying platform with the input conveying platform, the other end of the upper diversion conveying platform aligns with the upper conveying platform. When the flipping adjustment mechanism aligns one end of the lower diversion conveying platform with the input conveying platform, the other end of the lower diversion conveying platform aligns with the lower conveying platform.

2. The logistics transfer and conveying device according to claim 1, characterized in that: The input end conveyor platform includes two symmetrically fixed first mounting plates on the fixed frame. The bottoms of the two first mounting plates are respectively fixedly connected to the bottom of the fixed frame by vertical support rods. Two sets of first support roller seats are fixedly installed at both ends of the two first mounting plates. A first conveyor roller is rotatably installed between the two first support roller seats located at the same end. A first conveyor belt is wound around the two first conveyor rollers. A first motor for driving the first conveyor roller to rotate is fixedly installed at the outer end of the fixed frame.

3. The logistics transfer and conveying device according to claim 2, characterized in that: Two first bearing seats are symmetrically fixed on the outer side of one end of the fixed frame, and the two ends of the central shaft of one of the first conveying rollers are respectively rotatably engaged with the two first bearing seats; a first reducer is fixedly installed on the outer side of the fixed frame, the first motor is fixedly installed on the input end of the first reducer, and the output end of the first reducer is connected to one end of the central shaft of the corresponding first conveying roller.

4. The logistics transfer and conveying device according to claim 1, characterized in that: The upper diversion conveyor platform includes two symmetrical, flip-mounted second mounting plates located at the middle of the other end of the fixed frame. Two sets of second support roller seats are fixedly installed at both ends of the two second mounting plates. A second conveyor roller is rotatably installed between the two second support roller seats located at the same end. A second conveyor belt is wound around the two second conveyor rollers together.

5. The logistics transfer and conveying device according to claim 4, characterized in that: The lower diversion conveyor includes two symmetrical, flip-up third mounting plates located at the lower part of the other end of the fixed frame. Two sets of third support roller seats are fixedly installed at both ends of the two third mounting plates. A third conveyor roller is rotatably installed between the two third support roller seats located at the same end. A third conveyor belt is wound around the two third conveyor rollers together.

6. The logistics transfer and conveying device according to claim 5, characterized in that: Two pairs of second bearing seats are fixedly arranged at intervals on the outer side of the other end of the fixed frame. The two ends of the central shaft of the second conveying roller near the end of the fixed frame are respectively rotatably engaged with the two upper second bearing seats. The two ends of the central shaft of the third conveying roller near the end of the fixed frame are respectively rotatably engaged with the two lower second bearing seats. A second motor for driving the second and third conveying rollers to rotate synchronously is fixedly arranged on the outer end of the fixed frame.

7. The logistics transfer and conveying device according to claim 6, characterized in that: A second reducer is fixedly installed on the outer side of the other end of the fixed frame. The second motor is fixedly installed on the input end of the second reducer. The output end of the second reducer is connected to one end of the central shaft of the third conveying roller near the end of the fixed frame. A drive sprocket is fixedly installed on the other end of the third conveying roller near the end of the fixed frame. A driven sprocket is fixedly installed on the end of the second conveying roller near the end of the fixed frame corresponding to the drive sprocket. A tension sprocket is rotatably installed between the drive sprocket and the driven sprocket in the fixed frame. A transmission chain is wound around the drive sprocket, the driven sprocket, and the tension sprocket.

8. The logistics transfer and conveying device according to claim 7, characterized in that: A crossbeam is fixedly installed in the middle of the upper part of the fixed frame. Two support frames are symmetrically fixedly installed in the fixed frame between the crossbeam and the upper diversion conveyor. A third bearing seat is fixedly installed at the bottom of each of the two support frames. The flipping adjustment mechanism includes an adjusting cylinder hinged to one end of the crossbeam and a rotating shaft rotatably installed between the two third bearing seats. The telescopic end of the adjusting cylinder is hinged to the upper end of two parallel connecting plates. The lower ends of the two connecting plates are fixedly connected to the rotating shaft. Two drive arms are symmetrically fixedly installed on the rotating shaft. Two first connecting rods are symmetrically hinged between the two drive arms and the two second mounting plates. Two second connecting rods are symmetrically hinged between the two second mounting plates and the two third mounting plates.

9. The logistics transfer and conveying device according to claim 8, characterized in that: Two drive arms are respectively fixedly provided with drive columns on their outer sides; two first connecting columns are symmetrically fixedly provided on the outer sides of the two second mounting plates; two second connecting columns are symmetrically fixedly provided on the outer sides of the two third mounting plates; two first fisheye connectors that rotatably engage with the drive columns and the first connecting columns are fixedly provided at both ends of each first connecting rod; and two second fisheye connectors that rotatably engage with the first connecting columns and the second connecting columns are fixedly provided at both ends of each second connecting rod.

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