Aircraft control surface deflection limiter

Abstract

The application relates to the technical field of airborne rocker assembly control, in particular to an aircraft control surface deflection angle limiting mechanism, which comprises a fixed component and a movable component, a turnover groove is arranged on the fixed component, the movable component is rotationally installed on the inner wall of the turnover groove, a fixed plate is fixedly installed on the inner wall of the turnover groove, a rotating plate is fixedly installed on the movable component, a connecting shaft is rotationally penetrated through the rotating plate, the connecting shaft is rotationally penetrated through the fixed plate and rotationally connected with the inner wall of the turnover groove, a sector limiting ring is fixedly installed outside the connecting shaft, an adjusting mechanism for limiting the maximum deflection angle of the sector limiting ring is arranged in the fixed plate, a double-way pipe is arranged on the movable component, and a limiting compensation mechanism for limiting and compensating the deflection angle of the movable component is arranged in the double-way pipe. Compared with the prior art, the application has a wide application range, can compensate the lifting height and turning angle of the aircraft, and reduces the influence of external wind.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of airborne rocker assembly control, in particular to an aircraft control surface deflection angle limiting mechanism. BACKGROUND

[0002] The aircraft control surface is an important part of the flight control system, which changes the airflow distribution by deflection to generate control moments to achieve attitude adjustment and stability of the aircraft. The control surface refers to a movable aerodynamic component installed on the wing or tail, which changes the local airflow characteristics by deflection to generate additional aerodynamic forces or moments for controlling the attitude of the aircraft (such as roll, pitch, and yaw) or enhancing stability. The aircraft control surface balances aerodynamic efficiency, structural strength, and control response through precise design and material selection, and is the core component to realize flight safety and performance.

[0003] For example, the application with application number CN119099845A discloses an aircraft control surface deflection angle limiting device. The load of the aircraft control surface is connected to one end of the rocker assembly through a pull rod. The device includes a body and a limiting assembly installed in the body. The limiting assembly is connected to the other end of the rocker assembly and can limit the swing angle or rotation angle of the rocker assembly. However, the application still has some deficiencies. During the process of lifting and turning, the movable component rotates to disturb the airflow on both sides of the wing, allowing the aircraft to smoothly lift and turn. When the aircraft is in a space with a large air flow, the aircraft heading is the same as the air flow direction. The turning of the movable component reduces the pressure difference between the front and rear sides of the movable component compared to the conventional method, reducing the lifting height and turning angle of the aircraft. Conversely, when the aircraft heading is opposite to the air flow direction, the turning of the movable component increases the pressure difference between the front and rear sides of the movable component compared to the conventional method, increasing the lifting height and turning angle of the aircraft, resulting in poor accuracy of aircraft control.

[0004] Therefore, based on the above problems, we have invented an aircraft control surface deflection angle limiting mechanism. SUMMARY

[0005] To overcome the deficiencies of the prior art, the present application provides an aircraft control surface deflection angle limiting mechanism to solve the problems raised in the background.

[0006] In order to achieve the above object, the present application provides the following technical scheme: a kind of aircraft control surface deflection angle limiting mechanism, including fixed component and movable component, the fixed component is provided with turnover slot, the movable component is rotatably installed with turnover slot inner wall, fixed plate is fixedly installed on the turnover slot inner wall, rotating plate is fixedly installed on the movable component, connecting shaft is rotatably penetrated in the rotating plate, the connecting shaft is rotatably penetrated fixed plate and is rotatably connected with turnover slot inner wall, sector limiting ring is fixedly installed outside the connecting shaft, adjusting mechanism for limiting the maximum deflection angle of sector limiting ring is arranged in the fixed plate, double-way pipe is installed on the movable component, limiting compensation mechanism for limiting and compensating the deflection angle of movable component is arranged in the double-way pipe.

[0007] Further, the adjusting mechanism includes a through hole provided in the fixed plate, two openings of the through hole are rotatably installed with screw rods, the two screw rods are drivingly connected by a synchronous transmission mechanism, an adjusting motor is embedded in the fixed component, a drive shaft of the adjusting motor is rotatably penetrated through the fixed component and the fixed plate and coaxially installed with one of the screw rods, an adjusting block is threadedly sleeved on the screw rod, the adjusting block is slidingly connected with the inner wall of the through hole, corrugated plates are installed at both ends of the adjusting block, one end of the corrugated plate away from the adjusting block is fixed with the inner wall of the through hole, two limiting rods are fixedly installed on the side of the adjusting block away from the inner part of the through hole, and the two limiting rods are respectively located on the upper and lower sides of the adjusting block.

[0008] Further, the synchronous transmission mechanism includes two first pulleys, the two first pulleys are coaxially installed with the two screw rods, and the two first pulleys are drivingly connected by a synchronous belt.

[0009] Further, the limiting compensation mechanism comprises a sealing sliding block in sealing sliding connection with the inner wall of the double-way pipe, two fixing rings fixed in the double-way pipe, the two fixing rings being distributed on the two sides of the sealing sliding block, the fixing rings and the sealing sliding block being fixed through return springs, an extension head provided on the lower side of the end of the double-way pipe close to the fixing part, one end of the sealing sliding block being fixed with a rack, the end of the rack away from the sealing sliding block penetrating the fixing rings and extending through the extension head, a rotating shaft rotatably installed in the double-way pipe, a gear coaxially installed on the outer side of the rotating shaft, the gear being in meshing connection with the rack, a rotating shaft provided above the rotating shaft, the rotating shaft and the rotating shaft being in transmission connection through a universal joint, the upper end of the rotating shaft penetrating the extension head and a rotating plate, a box body and a sealing frame being installed on the upper end of the rotating plate, a bidirectional screw rod rotatably installed in the box body, the rotating shaft and the bidirectional screw rod being in transmission connection through a limiting compensation transmission mechanism, two threaded blocks being sleeved on the outer thread of the bidirectional screw rod, the threaded blocks being in sliding connection with the inner wall of the box body, the box body penetratingly and slidably provided with a sliding block, a deflection plate being rotatably installed on the side of each of the two threaded blocks, the end of the deflection plate away from the threaded block being in rotating connection with the sliding block, and a telescopic rod rotatably installed on the inner wall of the deflection groove, the driving end of the telescopic rod being in rotating connection with the sliding block.

[0010] Further, the limiting compensation transmission mechanism comprises a second belt wheel and a third belt wheel, the second belt wheel is coaxially installed with the rotating shaft, the third belt wheel is coaxially installed with the bidirectional screw rod, and the second belt wheel and the third belt wheel are in transmission connection through a synchronous belt.

[0011] Further, the two threaded blocks are each provided with a threaded hole matched with the bidirectional screw rod, and the threads in the two threaded holes are in opposite directions.

[0012] Further, the inner side of the fan-shaped limiting ring is provided with a fan-shaped hole matched with the limiting rod.

[0013] Further, the opening below the double-way pipe is located on the side of the movable part away from the fixing part, and the opening above the double-way pipe is located above the side of the movable part close to the fixing part.

[0014] Further, the universal joint comprises a transition block and four connecting plates, the four connecting plates are respectively in rotating connection with the upper four sides of the transition block in the same horizontal plane, the connecting plates located on the front and back sides of the transition block are fixed with the rotating shaft, and the connecting plates located on the left and right sides of the transition block are fixed with the rotating shaft.

[0015] Compared with the prior art, the present application provides an aircraft control surface deflection angle limiting mechanism, which has the following beneficial effects:

[0016] 1. By setting the adjusting mechanism, the movable component can be turned to different positions with different maximum deflection angles, and the maximum deflection angle of the movable component can be adjusted through the sector limiting ring and the limiting rod. When the limiting rod is closer to the connecting shaft, the turning angle of the sector limiting ring is smaller. When the limiting rod is farther away from the connecting shaft, the turning angle of the sector limiting ring is larger. It is suitable for movable components at different positions and has a wide range of applications.

[0017] 2. By setting the limiting compensation mechanism, the deflection angle of the movable component can be compensated according to the size of the external wind force. When the aircraft moves along the wind direction, the influence of wind force on the aircraft is reduced. Compared with the normal state, when the movable component turns the same angle, the lifting height and turning angle of the aircraft will be smaller. Through the deflection angle compensation, the turning angle of the movable component can be slightly increased, the lifting height and turning angle of the aircraft can be increased, and the influence of external wind force can be reduced. Similarly, when the aircraft moves against the wind direction, compared with the normal state, when the movable component turns the same angle, the lifting height and turning angle of the aircraft will be larger. Through the deflection angle compensation, the turning angle of the movable component can be slightly reduced, the lifting height and turning angle of the aircraft can be reduced, and the influence of external wind force can be reduced.

[0018] The application has a wide range of applications, and can compensate the lifting height and turning angle of the aircraft, and reduce the influence of external wind force. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a front structure schematic diagram of the application;

[0020] Figure 2 It is a bottom structure schematic diagram of the application;

[0021] Figure 3 It is a side structure perspective view of the movable component in the application;

[0022] Figure 4 It is Figure 3 the enlarged view of A in the figure;

[0023] Figure 5 It is a top structure perspective view of the fixed plate in the application;

[0024] Figure 6 It is a side structure perspective view of the fixed plate in the application;

[0025] Figure 7 It is a structure schematic diagram of the sector limiting ring in the application;

[0026] Figure 8 It is a structure schematic diagram of the universal joint in the application.

[0027] In the figure: 1, fixed part; 2, movable part; 3, turnover groove; 4, fixed plate; 5, rotating plate; 6, fan-shaped limiting ring; 7, adjusting mechanism; 8, through hole; 9, screw rod; 10, adjusting motor; 11, first pulley; 12, adjusting block; 13, corrugated plate; 14, double-way pipe; 15, extension head; 16, limiting compensation mechanism; 17, sealing slider; 18, fixed ring; 19, return spring; 20, rack; 21, rotating shaft; 22, gear; 23, rotating shaft; 24, connecting shaft; 25, sealing frame; 26, box body; 27, slider; 28, telescopic rod; 29, deflection plate; 30, double-way screw rod; 31, threaded block; 32, second pulley; 33, third pulley; 34, limiting compensation transmission mechanism; 35, universal joint; 36, limiting rod; 37, transition block; 38, connecting plate. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0029] As introduced in the background, there are deficiencies in the prior art. In order to solve the above technical problems, the present application provides an aircraft control surface deflection angle limiting mechanism.

[0030] As shown in Figures 1-8 An aircraft control surface deflection angle limiting mechanism includes a fixed part 1 and a movable part 2. The fixed part 1 is provided with a turnover groove 3. The movable part 2 is rotatably installed with the inner wall of the turnover groove 3. The inner wall of the turnover groove 3 is fixedly installed with a fixed plate 4. The movable part 2 is fixedly installed with a rotating plate 5. The rotating plate 5 is rotatably penetrated with a connecting shaft 24. The connecting shaft 24 is rotatably penetrated with the fixed plate 4 and rotatably connected with the inner wall of the turnover groove 3. The connecting shaft 24 is fixedly installed with a fan-shaped limiting ring 6 outside. It should be noted that the inner side of the fan-shaped limiting ring 6 is provided with a fan-shaped hole. The limiting rod 36 matches the fan-shaped hole. The fixed plate 4 is provided with an adjusting mechanism 7 for limiting the maximum deflection angle of the fan-shaped limiting ring 6. The movable part 2 is installed with a double-way pipe 14. Further, the opening below the double-way pipe 14 is located on the side of the movable part 2 away from the fixed part 1. The opening above the double-way pipe 14 is located above the side of the movable part 2 close to the fixed part 1. The double-way pipe 14 is provided with a limiting compensation mechanism 16 for limiting and compensating the deflection angle of the movable part 2.

[0031] In this invention, the adjusting mechanism 7 includes a through hole 8 disposed in the fixed plate 4. Two screws 9 are rotatably mounted at the two openings of the through hole 8. The two screws 9 are connected by a synchronous transmission mechanism. Specifically, the synchronous transmission mechanism includes two first pulleys 11, which are coaxially mounted with the two screws 9 respectively. The two first pulleys 11 are connected by a synchronous belt. An adjusting motor 10 is embedded in the fixed component 1. The drive shaft of the adjusting motor 10 rotates through the fixed component 1 and the fixed plate 4 and is coaxially mounted with one of the screws 9. An adjusting block 12 is threaded onto the external thread of the screw 9. The adjusting block 12 is slidably connected to the inner wall of the through hole 8. Corrugated plates 13 are mounted at both ends of the adjusting block 12. The end of the corrugated plate 13 away from the adjusting block 12 is fixed to the inner wall of the through hole 8. Two limiting rods 36 are fixedly mounted on the side of the adjusting block 12 away from the inside of the through hole 8, respectively located on the upper and lower sides of the adjusting block 12.

[0032] Through the above technical features: by adjusting the motor 10 to drive the two screws 9 to rotate, the two screws 9 drive the two adjusting blocks 12 to move, and the adjusting blocks 12 drive the limiting rod 36 to move until the appropriate position is reached, when the movable part 2 flips, the movable part 2 drives the connecting shaft 24 to rotate through the fixed plate 4, and the connecting shaft 24 drives the fan-shaped limiting ring 6 to rotate. At this time, the limiting rod 36 can block the fan-shaped limiting ring 6. When the external wind force is too strong, the blocking effect of the limiting rod 36 can prevent the movable part 2 from deflecting too much, thereby limiting the flipping angle of the movable part 2, that is, limiting the deflection angle of the control surface, and improving the stability of the deflection angle of the control surface.

[0033] In this invention, the limiting compensation mechanism 16 includes a sealing slider 17 that slides and seals against the inner wall of the double-pass pipe 14. Two fixing rings 18 are fixed inside the double-pass pipe 14, distributed on both sides of the sealing slider 17. The fixing rings 18 and the sealing slider 17 are fixed together by a return spring 19. An extension head 15 is provided on the lower side of the end of the double-pass pipe 14 near the fixing component 1. A rack 20 is fixed to one end of the sealing slider 17. The end of the rack 20 away from the sealing slider 17 passes through the fixing ring 18 and through the extension head 15. A rotating shaft 21 is rotatably installed inside the double-through pipe 14. A gear 22 is coaxially installed outside the rotating shaft 21. The gear 22 meshes with the rack 20. A rotating shaft 23 is provided above the rotating shaft 21. The rotating shaft 23 and the rotating shaft 21 are connected by a universal joint 35. It is worth mentioning that the universal joint 35 includes a transition block 37 and four connecting plates 38. The four connecting plates 38 are rotatably connected to the four sides of the transition block 37 on the same horizontal plane. The connecting plates 38 located on the front and rear sides of the transition block 37 are fixed to the rotating shaft 21.

[0034] In this invention, the connecting plates 38 located on the left and right sides of the transition block 37 are fixed to the rotating shaft 23. The upper end of the rotating shaft 23 is rotatably connected through the extension head 15 and the rotating plate 5. The upper end of the rotating plate 5 is equipped with a box body 26 and a sealing frame 25. A bidirectional lead screw 30 is rotatably installed inside the box body 26. The rotating shaft 23 and the bidirectional lead screw 30 are connected by a limit compensation transmission mechanism 34. Further, the limit compensation transmission mechanism 34 includes a second pulley 32 and a third pulley 33. The second pulley 32 is coaxially mounted with the rotating shaft 23, and the third pulley 33 is coaxially mounted with the bidirectional lead screw 30. The second pulley 32 and the third pulley 33 are connected by a limit compensation transmission mechanism 34. The wheels 33 are connected by a synchronous belt drive. The double-acting screw 30 has two threaded blocks 31 on its external thread. It is worth mentioning that both threaded blocks 31 have threaded holes that match the double-acting screw 30. The threads in the two threaded holes have opposite directions. The threaded blocks 31 are slidably connected to the inner wall of the box 26. The box 26 is slidably connected to a slider 27. A deflection plate 29 is rotatably installed on one side of each of the two threaded blocks 31. The end of the deflection plate 29 away from the threaded block 31 is rotatably connected to the slider 27. A telescopic rod 28 is rotatably installed on the inner wall of the flip groove 3. The driving end of the telescopic rod 28 is rotatably connected to the slider 27.

[0035] Through the above technical features: when the movable part 2 flips, the external wind flows at the two openings of the double-pass pipe 14, creating a certain pressure difference between the two openings. At this time, the sealing slider 17 moves under the action of the pressure difference, and the sealing slider 17 drives the rack 20 to move. The rack 20 drives the gear 22 to rotate, and the gear 22 drives the rotating shaft 21 to rotate. The rotating shaft 21 drives the rotating shaft 23 to rotate through the universal joint 35. The rotating shaft 23 drives the double-acting screw 30 to rotate. The double-acting screw 30 drives the two threaded blocks 31 to move relative to each other. The threaded blocks 31 drive the slider 27 to move through the deflection plate 29. Since the telescopic rod 28 is fixed to the fixed part 1, the slider 27 drives the box 26 to move. The angle of the movable part 2 can be limited and compensated according to the air pressure difference outside the movable part 2, so that the influence of the external airflow is minimized as much as possible when the aircraft takes off, lands, and turns.

[0036] Working principle:

[0037] 1) Adjusting the maximum steering limit of the control surface: The motor 10 drives the two screws 9 to rotate, the two screws 9 drive the two adjusting blocks 12 to move, and the adjusting blocks 12 drive the limit rod 36 to move until the appropriate position is reached. When the movable part 2 flips, the movable part 2 drives the connecting shaft 24 to rotate through the fixed plate 4. The connecting shaft 24 drives the fan-shaped limit ring 6 to rotate. At this time, the limit rod 36 can block the fan-shaped limit ring 6. When the external wind force is too strong, the blocking effect of the limit rod 36 can prevent the movable part 2 from deflecting too much, thereby limiting the flipping angle of the movable part 2, that is, limiting the control surface deflection angle, and improving the stability of the control surface deflection angle.

[0038] 2) Pressure difference limitation compensation for control surfaces: When the movable part 2 flips, the external wind flows at the two openings of the double-pass pipe 14, creating a certain pressure difference between the two openings. At this time, the sealing slider 17 moves under the action of the pressure difference. The sealing slider 17 drives the rack 20 to move, the rack 20 drives the gear 22 to rotate, the gear 22 drives the rotating shaft 21 to rotate, the rotating shaft 21 drives the rotating shaft 23 to rotate through the universal joint 35, the rotating shaft 23 drives the double-acting screw 30 to rotate, the double-acting screw 30 drives the two threaded blocks 31 to move relative to each other, and the threaded blocks 31 drive the slider 27 to move through the deflection plate 29. Since the telescopic rod 28 is fixed to the fixed part 1, the slider 27 drives the box 26 to move. Thus, the angle of the movable part 2 can be limited and compensated according to the pressure difference outside the movable part 2, so that the influence of the external airflow is minimized as much as possible when the aircraft is taking off, landing and turning.

[0039] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0040] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this invention.

Claims

1. An aircraft control surface deflection angle limiting mechanism, comprising a fixed component (1) and a movable component (2), wherein the fixed component (1) is provided with a tilting groove (3), and the movable component (2) is rotatably mounted to the inner wall of the tilting groove (3), characterized in that: A fixed plate (4) is fixedly installed on the inner wall of the flipping groove (3), and a rotating plate (5) is fixedly installed on the movable part (2). The rotating plate (5) is rotatably connected to a connecting shaft (24). The connecting shaft (24) rotatably passes through the fixed plate (4) and is rotatably connected to the inner wall of the flipping groove (3). A fan-shaped limiting ring (6) is fixedly installed on the outside of the connecting shaft (24). An adjustment mechanism (7) for limiting the maximum deflection angle of the fan-shaped limiting ring (6) is provided inside the fixed plate (4). A double-pass pipe (14) is installed on the movable part (2). A limiting compensation mechanism (16) for limiting and compensating the deflection angle of the movable part (2) is provided inside the double-pass pipe (14). The limiting compensation mechanism (16) includes a sealing slider (17) that slides and seals against the inner wall of the double-pass pipe (14). Two fixing rings (18) are fixed inside the double-pass pipe (14), and the two fixing rings (18) are distributed on both sides of the sealing slider (17). The fixing rings (18) and the sealing slider (17) are fixed by a return spring (19). An extension head (15) is provided on the lower side of one end of the double-pass pipe (14) near the fixing component (1). A rack (20) is fixed to one end of the slider (17). The end of the rack (20) away from the sealing slider (17) passes through the fixing ring (18) and through the extension head (15). A rotating shaft (21) is rotatably installed inside the double-through tube (14). A gear (22) is coaxially installed outside the rotating shaft (21). The gear (22) meshes with the rack (20). A rotating shaft (23) is provided above the rotating shaft (21). The rotating shaft (23) is connected to the rotating shaft. (21) are connected by a universal joint (35). The upper end of the rotating shaft (23) is rotatably connected through the extension head (15) and the rotating plate (5). The upper end of the rotating plate (5) is equipped with a box (26) and a sealing frame (25). A bidirectional lead screw (30) is rotatably installed inside the box (26). The rotating shaft (23) and the bidirectional lead screw (30) are connected by a limit compensation transmission mechanism (34). Two pieces are threaded on the external thread of the bidirectional lead screw (30). A threaded block (31) is slidably connected to the inner wall of the box body (26). A slider (27) is slidably provided through the box body (26). A deflection plate (29) is rotatably installed on one side of each of the two threaded blocks (31). The end of the deflection plate (29) away from the threaded block (31) is rotatably connected to the slider (27). A telescopic rod (28) is rotatably installed on the inner wall of the flip groove (3). The driving end of the telescopic rod (28) is rotatably connected to the slider (27).

2. The aircraft control surface deflection angle limiting mechanism according to claim 1, characterized in that: The adjustment mechanism (7) includes a through hole (8) in the fixed plate (4). A screw (9) is rotatably installed at both openings of the through hole (8). The two screws (9) are connected by a synchronous transmission mechanism. An adjustment motor (10) is embedded in the fixed component (1). The drive shaft of the adjustment motor (10) rotates through the fixed component (1) and the fixed plate (4) and is coaxially installed with one of the screws (9). An adjustment block (12) is threaded on the external thread of the screw (9). The adjustment block (12) is slidably connected to the inner wall of the through hole (8). Corrugated plates (13) are installed at both ends of the adjustment block (12). The end of the corrugated plate (13) away from the adjustment block (12) is fixed to the inner wall of the through hole (8). Two limiting rods (36) are fixedly installed on the side of the adjustment block (12) away from the inside of the through hole (8). The two limiting rods (36) are located on the upper and lower sides of the adjustment block (12) respectively.

3. The aircraft control surface deflection angle limiting mechanism according to claim 2, characterized in that: The synchronous transmission mechanism includes two first pulleys (11), which are coaxially mounted with two screws (9) respectively, and are connected to each other by a synchronous belt drive.

4. The aircraft control surface deflection angle limiting mechanism according to claim 1, characterized in that: The limiting compensation transmission mechanism (34) includes a second pulley (32) and a third pulley (33). The second pulley (32) is coaxially mounted with the rotating shaft (23), and the third pulley (33) is coaxially mounted with the bidirectional lead screw (30). The second pulley (32) and the third pulley (33) are connected by a synchronous belt drive.

5. The aircraft control surface deflection angle limiting mechanism according to claim 1, characterized in that: Both of the threaded blocks (31) are provided with threaded holes that match the bidirectional lead screw (30), and the threads in the two threaded holes are in opposite directions.

6. The aircraft control surface deflection angle limiting mechanism according to claim 2, characterized in that: The fan-shaped limiting ring (6) has a fan-shaped hole on its inner side, and the limiting rod (36) matches the fan-shaped hole.

7. The aircraft control surface deflection angle limiting mechanism according to claim 1, characterized in that: The opening below the double-through pipe (14) is located on the side of the movable part (2) away from the fixed part (1), and the opening above the double-through pipe (14) is located above the side of the movable part (2) closer to the fixed part (1).

8. The aircraft control surface deflection angle limiting mechanism according to claim 1, characterized in that: The universal joint (35) includes a transition block (37) and four connecting plates (38). The four connecting plates (38) are rotatably connected to the four sides of the transition block (37) on the same horizontal plane. The connecting plates (38) on the front and rear sides of the transition block (37) are fixed to the rotating shaft (21), and the connecting plates (38) on the left and right sides of the transition block (37) are fixed to the rotating shaft (23).

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