Vertical forced landing protection structure for unmanned aerial vehicle

Abstract

The invention relates to the technical field of unmanned aerial vehicles, and discloses a vertical forced landing protection structure for an unmanned aerial vehicle, which comprises a spring damping module arranged at the bottom of an unmanned aerial vehicle body, the spring damping module comprises a fixed plate fixed at the bottom of the unmanned aerial vehicle body, and buffer frames are hinged to four corners of the bottom of the fixed plate; the unmanned aerial vehicle body comprises a supporting plate installed at the upper end of the fixing plate, a connecting plate is fixedly installed at the upper end of the supporting plate, and connecting boxes are installed at the four corners of the connecting plate through wing rods. A propeller protection mechanism is arranged on the outer side of the connecting box. According to the invention, when the unmanned aerial vehicle is in vertical forced landing, the whole fuselage of the unmanned aerial vehicle can be stably maintained, the hard landing phenomenon of the unmanned aerial vehicle during forced landing is avoided, and the overall protection effect on the unmanned aerial vehicle during vertical forced landing is further achieved.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) technology, specifically a vertical forced landing protection structure for UAVs. Background Technology

[0002] With the rapid iteration and maturation of drone technology, its applications have deeply penetrated into many key fields such as aerial surveying and mapping, agricultural plant protection, emergency rescue, and logistics transportation, becoming core equipment for improving operational efficiency and expanding operational boundaries. However, when drones fly in complex environments, they are easily affected by factors such as sudden drop in battery power, motor failure, GPS signal loss, strong electromagnetic interference, or sudden gusts of wind, which can easily lead to power failure or loss of attitude control. In such cases, vertical forced landing becomes a crucial emergency measure to avoid drone crashes and reduce safety risks. According to statistics, approximately 70% of drone crashes occur during takeoff and landing, with attitude imbalance during vertical forced landing being one of the main causes of equipment damage.

[0003] Currently, various drone emergency landing protection technologies have been developed in the industry, mainly focusing on optimizing the bottom buffer structure, such as absorbing vertical impact energy through components like elastic landing gear, buffer springs, or inflatable airbags. For example, some solutions disperse impact force by setting elastic rings between the landing gear, but such structures mostly focus on mitigating impact in the single vertical direction and lack effective restraint on fuselage tilt caused by uneven ground, delayed attitude correction, or initial landing point deviation during emergency landing.

[0004] More critically, existing protection technologies have significant shortcomings in providing targeted protection for the core power components of drones—the propellers and wing masts. As a key component for maintaining flight, the propellers are highly susceptible to rigid collisions with the ground before the landing gear during forced landings, and most buffer structures do not prioritize their protection. A few solutions equipped with propeller protection use fixed guardrails, which offer some protection during rollovers, but these guardrails remain constantly active. This not only increases the overall weight and wind resistance of the drone but may also interfere with the airflow during normal flight, affecting flight stability and endurance, thus limiting the practicality and reliability of the protection structure. Summary of the Invention

[0005] The purpose of this invention is to provide a vertical emergency landing protection structure for unmanned aerial vehicles (UAVs) that can balance fuselage attitude stability and propeller-specific protection, and is an efficient protection structure suitable for emergency landing scenarios, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A vertical forced landing protection structure for a drone includes a spring damping module located at the bottom of the drone body. The spring damping module includes a fixed plate fixed to the bottom of the drone body. Buffer frames are hinged at the four corners of the bottom of the fixed plate, and tilting buffer mechanisms are provided on the buffer frames. A damping shaft is fixedly installed at the center of the bottom of the fixed plate. A buffer plate vertically positioned at the bottom side of the damping shaft is installed on the damping shaft via an abutment buffer mechanism. The drone body includes a support plate installed on the upper part of the fixed plate. A connecting plate is fixedly installed on the upper part of the support plate. Connecting boxes are installed at the four corners of the connecting plate via wing rods. A drone propeller is installed on the upper part of the connecting box. A propeller protection mechanism for protecting the drone propeller is provided on the outside of the connecting box.

[0008] As an improvement of the present invention, the drone body also includes a battery pack fixed to the bottom of the support plate and a control box installed at the upper end of the connecting plate.

[0009] As an improvement of the present invention: the tilting buffer mechanism includes a telescopic shaft that is slidably installed on the inner side of the bottom of the buffer frame, a landing frame is fixedly installed on the bottom of the telescopic shaft, and guide frames are installed on both ends of the landing frame through symmetrically arranged guide parts. The upper side of the guide frame is hinged to the buffer frame. A telescopic spring is also sleeved on the outside of the telescopic shaft. One end of the telescopic spring is fixed to the bottom of the buffer frame, and the other end is fixed to the landing frame.

[0010] As an improvement of the present invention: the guide part includes a guide ring hinged to the bottom of the guide frame and guide bars symmetrically fixed on the landing frame, wherein the guide ring is slidably disposed on the guide bars.

[0011] As an improvement of the present invention: the abutting buffer mechanism includes a lifting plate slidably mounted on the shock-absorbing shaft, a limit frame is hingedly mounted on the outer side of the lifting plate, and the end of the limit frame away from the lifting plate is hingedly mounted on the buffer frame. The abutting buffer assembly also includes a limit component for limiting the position of the limit frame and an abutting component for limiting the position of the lifting plate.

[0012] As an improvement of the present invention: the limiting component includes a limiting groove disposed on the buffer plate, a limiting shaft fixedly installed between the inner walls of the limiting groove, a limiting block slidably installed on the limiting shaft, an abutment frame hingedly installed on the upper end of the limiting block, an abutment frame hingedly installed on the limiting frame at the end away from the limiting block, and a limiting spring also sleeved on the outer side of the limiting shaft.

[0013] As an improvement of the present invention: the abutting component includes an abutting spring installed on the buffer plate, the upper end of the abutting spring is fixed to the bottom of the lifting plate and sleeved on the outside of the shock-absorbing shaft, an upper magnetic block is also fixedly installed at the bottom of the shock-absorbing shaft, a lower magnetic block is also fixedly installed on the buffer plate corresponding to the position of the upper magnetic block, the polarity of the lower magnetic block and the upper magnetic block on the opposite side is the same, and multiple buffer honeycombs are also provided at the bottom of the buffer plate.

[0014] As an improvement of the present invention: the propeller protection mechanism includes a lifting shaft that is vertically slidably installed inside the connecting box. A support plate is fixedly installed on the upper end of the lifting shaft. The upper end of the support plate abuts against the top of the connecting box through a support spring. A contact plate is fixedly installed on the lower end of the lifting shaft through the bottom of the connecting box. A contact spring is sleeved on the outside of the lifting shaft between the contact plate and the bottom of the connecting box. A contact block is fixedly installed on the bottom of the contact plate. A contact switch is provided on the bottom of the contact block. The propeller protection mechanism also includes an airbag protection component disposed on the outside of the connecting box.

[0015] As an improvement of the present invention: the airbag protection assembly includes a deployment shaft that is horizontally slidably installed on the side wall of the connecting box, an annular airbag is installed on one end of the outer side of the deployment shaft through a locking ring, the annular airbag is connected to a micro air pump through an air tube, the micro air pump is installed at the bottom of the connecting box, and the airbag protection assembly also includes a trigger part.

[0016] As an improvement of the present invention: the triggering part includes a wedge block fixed to the end of the unfolding shaft away from the locking ring, the inclined side of the wedge block contacts a support ball installed on the outside of the support plate, and an unfolding spring is also sleeved on the outside of the unfolding shaft between the non-inclined side of the wedge block and the connecting box.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. By setting up an inclined buffer mechanism and an abutment buffer mechanism at the bottom of the drone body, and with the cooperation between the buffer plates, the drone body can be stabilized during vertical forced landing. This allows the drone to simultaneously offset the collision forces from the horizontal and vertical directions, avoiding a hard landing during forced landing and further protecting the drone during vertical forced landing.

[0019] 2. By setting a propeller protection mechanism on the outside of the connecting box, the purpose of protecting the UAV propeller during vertical forced landing is achieved, preventing it from colliding with the ground when tilted and causing damage to the UAV. Furthermore, the propeller protection mechanism will not be triggered during normal takeoff and landing, further ensuring the reliability of the entire protection structure. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the overall front view of the present invention;

[0021] Figure 2 This is a schematic diagram of the overall bottom view of the present invention;

[0022] Figure 3 This is a schematic diagram of the overall structure of the spring damping module in this invention;

[0023] Figure 4 This is a schematic diagram of the tilting buffer mechanism in this invention;

[0024] Figure 5 This is a schematic diagram of the abutment buffer mechanism in this invention;

[0025] Figure 6 for Figure 5 A magnified schematic diagram of the structure of part A in the diagram;

[0026] Figure 7 for Figure 5 A magnified schematic diagram of the partial structure of B in the diagram;

[0027] Figure 8 This is a top view of the UAV body in this invention.

[0028] Figure 9 This is a schematic diagram of the UAV body from below in this invention;

[0029] Figure 10 This is a schematic diagram of the overall structure of the propeller protection mechanism in this invention;

[0030] Figure 11 This is a schematic diagram of the internal structure of the propeller protection mechanism in this invention.

[0031] In the diagram: 1. Support plate; 2. Connecting plate; 3. Control box; 4. Wing rod; 5. Connecting box; 6. UAV propeller; 7. Fixing plate; 8. Buffer plate; 9. Buffer honeycomb; 10. Buffer frame; 11. Telescopic shaft; 12. Telescopic spring; 13. Forced landing frame; 14. Guide strip; 15. Guide ring; 16. Guide frame; 17. Shock-absorbing shaft; 18. Limiting frame; 19. Abutment frame; 20. Lifting plate; 21. Limiting groove; 22. Limiting block; 2 3. Limiting shaft; 24. Limiting spring; 25. Abutment spring; 26. Upper magnet; 27. Lower magnet; 28. Battery pack; 29. ​​Annular airbag; 30. Deployment shaft; 31. Locking ring; 32. Air tube; 33. Miniature air pump; 34. Lifting shaft; 35. Contact spring; 36. Contact block; 37. Contact switch; 38. Contact plate; 39. Wedge block; 40. Support plate; 41. Support ball; 42. Support spring; 43. Deployment spring. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0033] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection", and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood through the specific circumstances.

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] Example 1: See Figures 1-9 In this embodiment of the invention, a vertical forced landing protection structure for a drone includes a spring damping module located at the bottom of the drone body. The spring damping module includes a fixed plate 7 fixed to the bottom of the drone body. Buffer frames 10 are hinged at the four corners of the bottom of the fixed plate 7. An inclined buffer mechanism is provided on the buffer frame 10. A damping shaft 17 is fixedly installed at the center of the bottom of the fixed plate 7. A buffer plate 8 is vertically installed on the bottom side of the damping shaft 17 via an abutment buffer mechanism. The drone body includes a support plate 1 installed on the upper end of the fixed plate 7. A connecting plate 2 is fixedly installed on the upper end of the support plate 1. Connecting boxes 5 are installed at the four corners of the connecting plate 2 via wing rods 4. A drone rotor 6 is installed on the upper end of the connecting box 5 to provide a power source for the flight of the entire drone. A rotor protection mechanism for protecting the drone rotor 6 is provided on the outside of the connecting box 5.

[0037] Specifically, the drone body in this embodiment also includes a battery pack 28 fixed to the bottom of the support plate 1 and a control box 3 installed at the upper end of the connecting plate 2. By setting up the battery pack 28 and the control box 3, the basic flight operations of the drone can be effectively guaranteed.

[0038] The tilting buffer mechanism in this protective structure includes a telescopic shaft 11 that is slidably installed on the inner side of the bottom of the buffer frame 10. A landing frame 13 is fixedly installed on the bottom of the telescopic shaft 11. Guide frames 16 are installed at both ends of the landing frame 13 through symmetrically arranged guide parts. One side of the upper end of the guide frame 16 is hinged to the buffer frame 10. A telescopic spring 12 is also sleeved on the outside of the telescopic shaft 11. One end of the telescopic spring 12 is fixed to the bottom of the buffer frame 10, and the other end is fixed to the landing frame 13.

[0039] In order to achieve the buffering effect between the landing gear 13 and the ground, the guide part includes a guide ring 15 hinged to the bottom of the guide frame 16 and a guide bar 14 symmetrically fixed on the landing gear 13. The guide ring 15 is slidably disposed on the guide bar 14.

[0040] The entire buffer frame 10 is installed at an angle at the bottom of the fixed plate 7. When the buffer frame 10 is subjected to a vertical force, on the one hand, the position between the landing frame 13 and the buffer frame 10 will be buffered by the action of the telescopic spring 12 and the telescopic shaft 11. On the other hand, the impact force on the landing frame 13 is further reduced by the action of the guide part and the guide frame 16, thereby achieving the purpose of protecting the bottom position of the entire UAV body.

[0041] In addition, to further ensure the support of the buffer plate 8 for the entire UAV during forced landing, the abutment buffer mechanism in this protective structure includes a lifting plate 20 that is slidably mounted on the shock-absorbing shaft 17. Limiting frames 18 are respectively hinged to the outside of the lifting plate 20. The end of the limiting frame 18 away from the lifting plate 20 is hinged to the buffer frame 10. The abutment buffer assembly also includes a limiting component for limiting the position of the limiting frame 18 and an abutment component for limiting the position of the lifting plate 20.

[0042] The limiting component includes a limiting groove 21 on the buffer plate 8, a limiting shaft 23 fixedly installed between the inner walls of the limiting groove 21, a limiting block 22 slidably installed on the limiting shaft 23, an abutment frame 19 hinged to the upper end of the limiting block 22, and a limiting frame 18 hinged to the end of the abutment frame 19 away from the limiting block 22. A limiting spring 24 is also sleeved on the outside of the limiting shaft 23. By using the limiting shaft 23 and the limiting spring 24, the position of the limiting block 22 inside the buffer plate 8 can be changed. On the one hand, the buffer plate 8 can be effectively limited; on the other hand, under the action of the abutment frame 19, the position of the limiting frame 18 can be limited, ultimately changing the position of the buffer frame 10. This allows the tilting buffer mechanism to better resist impact forces from both the horizontal and vertical directions.

[0043] In addition, the abutting component includes an abutting spring 25 installed on the buffer plate 8. The upper end of the abutting spring 25 is fixed to the bottom of the lifting plate 20 and sleeved on the outside of the shock-absorbing shaft 17. An upper magnetic block 26 is also fixedly installed at the bottom of the shock-absorbing shaft 17. A lower magnetic block 27 is also fixedly installed on the buffer plate 8 at the position corresponding to the upper magnetic block 26. The polarity of the lower magnetic block 27 and the upper magnetic block 26 on the opposite side is the same.

[0044] Under the action of the abutment spring 25, the position of the lifting plate 20 on the shock-absorbing shaft 17 is changed to reduce shock. Under the same pole repulsion between the upper magnetic block 26 and the lower magnetic block 27, the position of the buffer plate 8 is also limited. At the same time, multiple buffer honeycomb 9 are provided at the bottom of the buffer plate 8, which can effectively increase the impact resistance of the buffer plate 8.

[0045] Example 2: See Figures 10-11 In another embodiment of the present invention, the difference between this embodiment and the above embodiment is that the propeller protection mechanism includes a lifting shaft 34 that is vertically slidably installed inside the connecting box 5. A support plate 40 is fixedly installed on the upper end of the lifting shaft 34. The upper end of the support plate 1 abuts against the top of the inside of the connecting box 5 through a support spring 42. A contact plate 38 is fixedly installed on the lower end of the lifting shaft 34 through the bottom of the connecting box 5. A contact spring 35 is sleeved on the outside of the lifting shaft 34 between the contact plate 38 and the bottom of the connecting box 5. A contact block 36 is fixedly installed on the bottom of the contact plate 38. A contact switch 37 is provided on the bottom of the contact block 36. The propeller protection mechanism also includes an airbag protection component provided on the outside of the connecting box 5.

[0046] The airbag protection assembly includes a horizontally sliding deployment shaft 30 mounted on the side wall of the connecting box 5. An annular airbag 29 is mounted on one end of the outer side of the deployment shaft 30 via a locking ring 31. The annular airbag 29 is connected to a miniature air pump 33 via an air tube 32. The miniature air pump 33 is mounted at the bottom of the connecting box 5. The airbag protection assembly also includes a trigger unit.

[0047] In addition, the triggering part includes a wedge block 39 fixed to the end of the unfolding shaft 30 away from the locking ring 31. The inclined side of the wedge block 39 contacts a support ball 41 installed on the outside of the support plate 40. An unfolding spring 43 is also sleeved on the outside of the unfolding shaft 30 between the non-inclined side of the wedge block 39 and the connecting box 5.

[0048] When the entire drone body fails to make an effective vertical landing on the ground, the entire drone body will tilt and fall in a certain direction along the direction of the drone propeller 6. At this time, the contact switch 37 located at that position will contact the ground, triggering the micro air pump 33 to introduce gas into the corresponding annular airbag 29 through the air pipe 32, thereby causing the annular airbag 29 to fill with gas and expand, thus protecting the drone propeller 6. At the same time, when the drone tilts and falls, the lifting shaft 34 at the bottom of the connecting box 5 will move upward, and under the action of the support ball 41 set on the outside of the support plate 40, the wedge block 39 will move towards the side wall. Finally, under the action of the unfolding shaft 30, the annular airbag 29 will continuously unfold outward, thereby protecting the drone propeller 6 over a wider range and preventing it from being damaged during the collision with the ground.

[0049] In summary, during the vertical forced landing of the UAV, on the one hand, the cooperation between the impact buffer mechanism and the tilting buffer mechanism effectively supports and protects the entire UAV with the landing gear 13 and the buffer plate 8; on the other hand, with the cooperation of the propeller protection mechanism, the entire UAV propeller 6 is protected from the outside, further ensuring the protection of the entire UAV during the forced landing.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vertical forced landing protection structure for unmanned aerial vehicles (UAVs), characterized in that, The device includes a spring damping module located at the bottom of the drone body. The spring damping module includes a fixed plate (7) fixed to the bottom of the drone body. A buffer frame (10) is hinged at the four corners of the bottom of the fixed plate (7). An inclined buffer mechanism is provided on the buffer frame (10). A damping shaft (17) is fixedly installed at the center of the bottom of the fixed plate (7). A buffer plate (8) is installed on the damping shaft (17) through an abutment buffer mechanism. The drone body includes a support plate (1) installed on the upper end of the fixed plate (7). A connecting plate (2) is fixedly installed on the upper end of the support plate (1). A connecting box (5) is installed at the four corners of the connecting plate (2) through a wing rod (4). A drone propeller (6) is installed on the upper end of the connecting box (5). A propeller protection mechanism for protecting the drone propeller (6) is provided on the outside of the connecting box (5).

2. The vertical forced landing protection structure for a UAV according to claim 1, characterized in that, The drone body also includes a battery pack (28) fixed to the bottom of the support plate (1) and a control box (3) installed at the upper end of the connecting plate (2).

3. The vertical forced landing protection structure for a UAV according to claim 1, characterized in that, The tilting buffer mechanism includes a telescopic shaft (11) that is slidably installed on the inner side of the bottom of the buffer frame (10). A landing frame (13) is fixedly installed on the bottom of the telescopic shaft (11). Guide frames (16) are installed on both ends of the landing frame (13) through symmetrically arranged guide parts. The upper side of the guide frame (16) is hinged to the buffer frame (10). A telescopic spring (12) is also sleeved on the outside of the telescopic shaft (11). One end of the telescopic spring (12) is fixed to the bottom of the buffer frame (10), and the other end is fixed to the landing frame (13).

4. The vertical forced landing protection structure for a UAV according to claim 3, characterized in that, The guide section includes a guide ring (15) hinged to the bottom of the guide frame (16) and a guide bar (14) symmetrically fixed on the landing frame (13), wherein the guide ring (15) is slidably disposed on the guide bar (14).

5. A vertical forced landing protection structure for a UAV according to claim 1, characterized in that, The abutment buffer mechanism includes a lifting plate (20) slidably mounted on a shock-absorbing shaft (17). A limit frame (18) is hinged to the outside of the lifting plate (20). The end of the limit frame (18) away from the lifting plate (20) is hinged to a buffer frame (10). The abutment buffer assembly also includes a limit component for limiting the position of the limit frame (18) and an abutment component for limiting the position of the lifting plate (20).

6. A vertical forced landing protection structure for a UAV according to claim 5, characterized in that, The limiting assembly includes a limiting groove (21) set on the buffer plate (8), a limiting shaft (23) fixedly installed between the inner walls of the limiting groove (21), a limiting block (22) slidably installed on the limiting shaft (23), an abutment frame (19) hinged to the upper end of the limiting block (22), and the end of the abutment frame (19) away from the limiting block (22) hinged to the limiting frame (18). A limiting spring (24) is also sleeved on the outside of the limiting shaft (23).

7. A vertical forced landing protection structure for a UAV according to claim 6, characterized in that, The abutting assembly includes an abutting spring (25) installed on the buffer plate (8). The upper end of the abutting spring (25) is fixed to the bottom of the lifting plate (20) and sleeved on the outside of the shock-absorbing shaft (17). An upper magnetic block (26) is also fixedly installed at the bottom of the shock-absorbing shaft (17). A lower magnetic block (27) is also fixedly installed on the buffer plate (8) at the position corresponding to the upper magnetic block (26). The polarity of the lower magnetic block (27) and the upper magnetic block (26) is the same on the opposite side. A plurality of buffer honeycombs (9) are also provided at the bottom of the buffer plate (8).

8. A vertical forced landing protection structure for a UAV according to claim 1, characterized in that, The propeller protection mechanism includes a lifting shaft (34) that is vertically slidably installed inside the connecting box (5). A support plate (40) is fixedly installed on the upper end of the lifting shaft (34). The upper end of the support plate (1) is abutted against the top of the connecting box (5) by a support spring (42). A contact plate (38) is fixedly installed on the lower end of the lifting shaft (34) through the bottom of the connecting box (5). A contact spring (35) is sleeved on the outside of the lifting shaft (34) between the contact plate (38) and the bottom of the connecting box (5). A contact block (36) is fixedly installed on the bottom of the contact plate (38). A contact switch (37) is provided on the bottom of the contact block (36). The propeller protection mechanism also includes an airbag protection component provided on the outside of the connecting box (5).

9. A vertical forced landing protection structure for a UAV according to claim 8, characterized in that, The airbag protection assembly includes a horizontally sliding deployment shaft (30) mounted on the side wall of the connecting box (5). An annular airbag (29) is mounted on one end of the outer side of the deployment shaft (30) via a locking ring (31). The annular airbag (29) is connected to a miniature air pump (33) via an air tube (32). The miniature air pump (33) is mounted at the bottom of the connecting box (5). The airbag protection assembly also includes a trigger unit.

10. A vertical forced landing protection structure for a UAV according to claim 9, characterized in that, The triggering part includes a wedge block (39) fixed at the end of the unfolding shaft (30) away from the locking ring (31). The inclined side of the wedge block (39) contacts a support ball (41) installed on the outside of the support plate (40). An unfolding spring (43) is also sleeved on the outside of the unfolding shaft (30) between the non-inclined side of the wedge block (39) and the connecting box (5).

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