Sliding rail-based scalable cargo drone tail cargo door opening and closing mechanism and method

Abstract

The application discloses a telescopic freight unmanned aerial vehicle tail cabin door opening and closing mechanism and method based on a sliding rail, relates to the technical field of freight unmanned aerial vehicles, and comprises a fuselage frame, a bottom rail assembly, a sliding seal arranged lower sliding door, a rotary hinged upper rotary cabin door, a translation driving mechanism, a rotary driving mechanism and a anti-shaking assembly. When opening, the translation driving mechanism drives the lower sliding door to slide along the rail to the tail direction of the fuselage, and the lower sliding door is locked to the upper rotary cabin door through a hook and a hook seat; then the rotary driving mechanism drives the upper rotary cabin door to rotate upward, drives the lower sliding door to rotate synchronously, and realizes complete opening of the cabin door. When closing, the operation is performed in the reverse order. The cabin door is divided into two parts, sliding and rotating, the opening and closing track is completely located in the fuselage, the external space for cabin door storage and retrieval and the top space of the tail of the fuselage are reduced, meanwhile, the rail and the anti-shaking assembly constrain the movement track, ensure stable opening and closing, the carbon cloth wrapped foam structure is adopted to realize light weight, and is suitable for compact freight unmanned aerial vehicles.

Description

Technical Field

[0001] This invention relates to the field of cargo drone technology, and more specifically to the field of a sliding rail-based retractable cargo drone tail door opening and closing mechanism and method. Background Technology

[0002] With the rapid development of the drone logistics industry, the application scenarios for cargo drones are becoming increasingly diverse, ranging from feeder transport to last-mile delivery, and from land-based takeoffs and landings to shipboard deployments. This places increasingly higher demands on the payload capacity, loading and unloading efficiency, and environmental adaptability of cargo drones. Especially in feeder transport and last-mile delivery scenarios, drones need to take off and land frequently and adapt to cargo loading and unloading needs under different terrain and site conditions.

[0003] Currently, cargo drones primarily use either flip-top or side-opening cargo door structures. Flip-top doors typically use one edge of the door as a hinge axis, opening and closing through rotation; side-opening doors, similar to car side doors, swing open to the side of the drone. However, these traditional door structures have the following technical drawbacks in practical applications: First, they have low space utilization and are prone to external interference. Traditional side-opening or tilt-down doors require a large external swing space when opened, and the door's sweep path is located outside the fuselage. In narrow take-off and landing areas, shipboard environments, or complex terrain conditions, the doors are very likely to collide with ground obstacles, buildings, or ship equipment when opened, which not only affects loading and unloading efficiency but may also cause door damage or even flight safety accidents.

[0004] Secondly, it occupies a significant amount of space on top of the fuselage. For upward-opening hatch structures, a single, integrated hatch requires a large amount of space on top of the fuselage when opening. In cargo drones with compact fuselage structures, the limitation of top space often becomes a bottleneck in hatch design. Excessive top space requirements may force compromises in the fuselage structure design, affecting the overall aerodynamic layout and structural efficiency.

[0005] Third, the stability and reliability of the hatch opening and closing process are insufficient. Traditional hatch structures lack effective trajectory constraints and anti-sway devices during opening and closing. Especially under harsh conditions such as airdrop unloading, the hatch is prone to swaying due to wind load or turbulence, which not only affects the smoothness of hatch opening and closing, but may also cause the hatch to collide or jam with the fuselage structure, reducing the service life and reliability of the mechanism.

[0006] Fourth, the contradiction between the weight and strength of the cargo door is prominent. Traditional cargo doors mostly adopt a structure of metal skin and frame, which often requires a significant increase in weight to ensure sufficient structural strength. For cargo drones, the weight of the cargo door directly affects the effective payload capacity. How to achieve lightweight cargo doors while ensuring strength and rigidity is a technical problem that urgently needs to be solved in this field.

[0007] Fifth, the airtightness of the hatches is difficult to guarantee. In traditional hatch structures, the sealing design at the junction of the upper and lower hatches is often relatively simple, which can easily lead to water leakage and seepage under severe weather conditions, affecting the safety of the cargo inside the hold.

[0008] To address the aforementioned technical challenges, there is currently a lack of comprehensive solutions that can simultaneously resolve issues related to external space interference, top space occupation, opening and closing stability, lightweight design, and airtightness. Therefore, there is an urgent need to design a hatch opening and closing mechanism that saves external opening space, reduces top space occupation, and possesses high reliability and lightweight characteristics to address the current technical pain points. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of interference with external space, large top occupation, and poor stability of traditional cargo door. This invention provides a retractable cargo drone tail door opening and closing mechanism and method based on a sliding rail.

[0010] To achieve the above objectives, the present invention specifically adopts the following technical solution: One aspect of the present invention provides a sliding rail-based retractable cargo drone tail compartment door opening and closing mechanism, including a fuselage cargo compartment frame structure, a guide rail assembly disposed at the bottom of the fuselage cargo compartment frame structure, a sliding door slidably and sealed on the guide rail assembly, an upper rotating door rotatably hinged to the bottom front end of the fuselage cargo compartment frame structure, a translation drive mechanism for sliding the sliding door along the guide rail assembly onto the upper rotating door and locking it by a lock box assembly, a rotation drive mechanism mounted on the fuselage cargo compartment frame structure for driving the upper rotating door to rotate, and an anti-sway assembly disposed on the fuselage cargo compartment frame structure to prevent swaying when the upper rotating door and the sliding door rotate synchronously.

[0011] In one embodiment, the fuselage cargo hold frame structure includes a left lower rear fuselage beam and a right lower rear fuselage beam located on the left and right sides of the bottom of the rear fuselage, and multiple transverse reinforcing frames are arranged at intervals on the upper part between the left lower rear fuselage beam and the right lower rear fuselage beam to bear the gravity load when the cargo door is closed, and cooperate with the sealing strip on the edge of the cargo door to achieve sealing. The sliding door has a sliding connection part on its edge, and a screw joint is provided on the side of the sliding door near the upper rotating door; the sliding connection part of the sliding door is in rolling engagement with the guide rail assembly, and the guide rail assembly is used to constrain the sliding trajectory of the sliding door; The front end of the upper rotating hatch is hinged to the front transverse reinforcing frame; The translation drive mechanism is a ball screw actuator, which is installed on the upper rotating hatch. The movable end of the ball screw actuator is connected to the screw joint on the lower sliding door, and is used to drive the lower sliding door to slide along the guide rail assembly to the locking position with the upper rotating hatch. The rotation drive mechanism is a piston actuator. One end of the piston actuator is hinged to the top of the fuselage cargo hold frame structure, and the other end is hinged to the upper rotating door. It is used to drive the upper rotating door to rotate upward around its hinge point, so as to drive the sliding door locked with the upper rotating door to flip open together.

[0012] In one embodiment, the lock box assembly includes hooks and hook seats that cooperate with the hooks. Multiple hooks are provided at the bottom of the sliding door, and multiple hook seats are provided at corresponding positions on the upper part of the rotating door. When the sliding door slides onto the rotating door, the hooks pass through the corresponding hook seats to lock the sliding door and the rotating door.

[0013] In one embodiment, the sliding connection includes multiple slide rail joints disposed on both sides of the sliding door, each slide rail joint being provided with a bearing, the bearing being embedded in the guide rail assembly and rollingly engaging with the guide rail assembly.

[0014] In one embodiment, the guide rail assemblies are symmetrically distributed on both sides of the interior of the fuselage cargo hold frame structure, and each side of the guide rail assembly includes a first guide rail section, a second guide rail section and a third guide rail section arranged in sequence. The first and third guide rail sections are located on the lower left and lower right beams of the rear fuselage, while the second guide rail section is located on the central transverse reinforcing frame. The first guide rail section and the second guide rail section are used to constrain the sliding trajectory of the sliding door and the rotation trajectory of the upper rotating cabin door, respectively. The third guide rail section is used to constrain the sliding trajectory of the sliding door.

[0015] In one embodiment, when the sliding door is fully closed, each slide rail joint is in the first position of the guide rail assembly; when the sliding door is fully closed and locked with the upper rotating door, some slide rail joints are in the second position of the guide rail assembly; when the upper rotating door is fully opened by rotating upwards, some slide rail joints are in the third position of the guide rail assembly.

[0016] In one embodiment, the anti-sway assembly includes anti-sway slide rails symmetrically installed on both sides of a transverse reinforcing frame in the middle and anti-sway joints provided on both sides of the upper rotating hatch. The anti-sway joints are provided with anti-sway bearings, which are in rolling contact with the anti-sway slide rails to limit the left and right swaying of the hatch when the upper rotating hatch is rotated to open and close.

[0017] In one embodiment, the anti-sway rail is fixed by an anti-sway rail joint and a transverse reinforcing frame in the middle, and the shape of the extension direction of the anti-sway rail is adapted to the rotation trajectory of the upper rotating door.

[0018] In one embodiment, the ball screw actuator includes a servo motor, a screw, and a nut seat. The nut seat is connected to the screw joint on the sliding door via a left screw connector and a right screw connector. The servo motor drives the screw to rotate, causing the nut seat to translate along the screw axis, thereby driving the sliding door to slide along the guide rail assembly via the left and right screw connectors.

[0019] In one embodiment, a cover is provided in the middle of the sliding door. When the ball screw actuator fails, the cover can be opened to manually push the sliding door along the guide rail assembly.

[0020] In one embodiment, rubber sealing strips are affixed to the four edges of both the sliding door and the rotating door; when the sliding door and the rotating door are fully closed, the outer edges of the sliding door and the rotating door with rubber sealing strips together form a complete door sealing boundary.

[0021] In one embodiment, when the sliding door and the rotating door are fully closed, the tail of the sliding door presses against the nose of the rotating door, and a rubber sealing strip is affixed to the nose of the rotating door. The tail of the sliding door achieves sealing of the mating edges of the upper and lower doors by pressing the rubber sealing strip.

[0022] In one embodiment, when the sliding door and the rotating door are fully closed, the outer edges of the sliding door and the rotating door with rubber sealing strips are pressed together with the lower beam of the rear fuselage and the transverse reinforcing frame under the action of gravity, thereby achieving a waterproof seal between the door and the fuselage.

[0023] In one embodiment, the main structures of both the sliding door and the rotating hatch are composite material structures made of carbon fiber wrapped in foam.

[0024] In one embodiment, the upper rotating hatch is hinged to a double-eared joint fixed to a third transverse reinforcing frame via a left-flipping joint and a right-flipping joint; the piston cylinder of the piston actuator is hinged to an actuator joint mounted on the fuselage frame, and the piston rod of the piston actuator is hinged to a hydraulic rod joint on the upper rotating hatch.

[0025] The second aspect of the present invention provides an opening and closing method for a sliding rail-based retractable cargo drone tail door opening and closing mechanism. The above-mentioned sliding rail-based retractable cargo drone tail door opening and closing mechanism is used, and the opening and closing method includes a door opening method and a door closing method. The hatch opening method includes the following steps: Step S1: Activate the ball screw actuator to drive the sliding door to slide along the guide rail assembly toward the tail of the aircraft until the sliding door locks with the upper rotating door; Step S2: Activate the piston actuator to drive the upper rotating hatch to rotate upward around its hinge point. The upper rotating hatch drives the lower sliding door, which is locked with it, to flip upward together, so that the hatch is fully opened. The hatch closing method includes the following steps: Step S3: Unlock and reverse the piston actuator to drive the upper rotating hatch to rotate downwards around its hinge point. The upper rotating hatch then drives the lower sliding door, which is locked with it, to flip downwards and reset. Step S4: Unlock and reverse the ball screw actuator to drive the sliding door to slide and reset along the guide rail assembly toward the nose of the aircraft until the door is completely closed.

[0026] In one embodiment, during steps S2 and S3, when the upper rotating door rotates, the anti-sway bearing of the anti-sway joint on the upper rotating door rolls into contact with the anti-sway rail fixed to the fuselage, thereby limiting the left and right swaying of the upper rotating door.

[0027] In one embodiment, in steps S2 and S3, a portion of the sliding door's slide rail joint moves along the second guide rail section of the guide rail assembly, which constrains the rotation trajectory of the sliding door and the upper rotating cabin door.

[0028] In one embodiment, in step S1, the sliding door slides 1116 mm along the guide rail assembly toward the tail; in step S2, the upper rotating door rotates upward by 23°. In step S3, the upper rotating hatch rotates downward by an angle of 23°; In step S4, the sliding door slides 1116mm along the guide rail assembly towards the machine head.

[0029] The beneficial effects of this invention are as follows: 1. This invention designs the cargo compartment door of a cargo drone as a two-part structure consisting of a sliding lower door and an upper rotating door that work together. When opened, the lower door first slides backward along the guide rail and retracts to below the upper door and locks, and then rotates upward together with the upper door. Compared with the traditional single-piece, one-piece, upward-flipping door, this effectively reduces the space occupied on the top of the fuselage when the door is opened, reduces the space constraints of the fuselage structure design, and enables the door to be adapted to compact cargo drones with limited space on the top of the fuselage.

[0030] 2. In this invention, the sweep path of the hatch opening and closing is entirely located inside the fuselage. During the entire opening and closing process, the hatch and its movement trajectory do not exceed the fuselage outline. Compared with traditional side-opening or downward-opening hatches, there is no need to reserve space for the hatch to swing outside the fuselage, which completely avoids the risk of interference and collision with the external environment such as ground obstacles, buildings, and ship equipment when the hatch is opened. It is particularly suitable for cargo loading and unloading operations in narrow take-off and landing areas, shipboard environments, and complex terrain conditions.

[0031] 3. This invention constrains the sliding trajectory of the sliding door throughout its entire movement using a guide rail assembly. The coordinated action of the guide rail assembly and the hinge point of the upper rotating door precisely limits the rotation trajectory of the upper and lower doors. Simultaneously, the rolling contact between the anti-sway joint bearing in the anti-sway assembly and the anti-sway rail suppresses the left and right swaying of the door in real time during the door's rotation. This restricts the door's trajectory and swaying throughout the entire sliding and rotating motion, significantly improving the motion stability and reliability of the door opening and closing mechanism. It can easily cope with wind loads and turbulence interference under harsh working conditions such as airdrop unloading.

[0032] 4. In the closed state of the cargo door, the rubber sealing strips on the left and right edges of the upper cargo door and the four edges of the lower cargo door, together with the rear fuselage lower beam and fuselage frame, are pressed together under the action of gravity to form a complete and continuous sealing boundary; at the same time, the tail direction of the lower cargo door presses against the nose direction of the upper cargo door, which is covered with the sealing rubber strip, to achieve an overlapping seal between the mating edges of the upper and lower cargo doors. The double sealing structure effectively ensures the waterproof sealing performance of the entire cargo door system and prevents rainwater, dust and other external media from entering the cargo hold.

[0033] 5. The main structure of the sliding door and the rotating door in this invention adopts a composite material structure of carbon cloth wrapped in foam. Compared with the traditional door structure with metal skin and frame, it has higher specific strength and specific stiffness. Under the premise of meeting the strength and stiffness requirements of the door structure, the weight of the door is greatly reduced, which is conducive to improving the effective payload capacity and endurance of cargo drones.

[0034] 6. In this invention, the overall length of the lower hatch is shortened after it slides up, and the rotational torque acting on the fuselage frame is significantly reduced when the hatch rotates and opens with the upper hatch. This reduces the load on the fuselage structure caused by the opening and closing of the hatch, which is more favorable to the structural fatigue life of the fuselage frame and beam, and helps to improve the service life of the entire aircraft structure.

[0035] 7. The cover in the middle of the sliding door in this invention allows the operator to directly access the internal structure of the lower door and manually push it when the ball screw actuator malfunctions and cannot drive it normally. This ensures that the door can still open and close normally in the event of a power system failure, effectively improving the system's fault tolerance and emergency handling capabilities. At the same time, the cover can also serve as an inspection window and endoscopic observation channel during routine maintenance, facilitating the operator to check the status and troubleshoot internal mechanisms such as the ball screw actuator and guide rails, thus improving the maintainability of the mechanism.

[0036] 8. In this invention, the ball screw actuator is driven by a servo motor and equipped with a locking function. After the lower hatch slides to the retracted position and locks with the upper hatch, the servo motor switches to the locked state to ensure that the lower hatch will not accidentally slide due to gravity or inertia during the rotation of the upper hatch. The piston actuator also has a locking function, keeping the piston rod locked after the hatch is fully opened or fully closed. The dual locking mechanism effectively ensures the position holding capability and safety of the hatch in different working states.

[0037] 9. In this invention, the lower hatch is connected to the guide rail assembly via a bearing on the slide rail joint, and the upper hatch is connected to the fuselage frame via a flip joint. All moving parts adopt low-friction connection methods of rolling or hinge, resulting in low movement resistance and high transmission efficiency. The ball screw actuator has high transmission accuracy and repeatability, which can ensure the displacement accuracy and position repeatability of the lower hatch each time it slides, and ensure the accurate alignment and locking of the hook and hook seat, thereby improving the automation control accuracy and reliability of the hatch opening and closing mechanism.

[0038] 10. The hatch opening process of this invention consists of two steps: the sliding door retracts first and then rotates upwards to flip together. The closing process consists of two steps: the upper and lower hatches are lowered together and then the sliding door extends. The entire opening and closing process is logically clear and the sequence is controllable. The locking mechanism between each step achieves state maintenance and safety interlocking, avoiding damage to the mechanism or safety accidents caused by misoperation. It is easy to operate and highly safe, and is suitable for one-button automated control on the UAV ground control station or onboard control panel. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the overall structure of the tail hatch opening and closing mechanism of a retractable cargo drone based on a sliding rail in the fully closed state of the fuselage cargo hatch of the present invention. Figure 2 A schematic diagram showing the lower cargo door of the fuselage retracted and locked to the upper cargo door; Figure 3 This is a schematic diagram of the structure of a ball screw actuator; Figure 4 This is a schematic diagram of the structure of the hook and hook seat working together; Figure 5 A schematic diagram of the overall structure with the cargo hold door of the fuselage fully open; Figure 6 This is a schematic diagram of the lower hatch structure; Figure 7 This is a schematic diagram of the structure of the lower surface of the lower hatch; Figure 8 This is a schematic diagram of the upper hatch structure; Figure 9 This is a structural diagram of the lower surface of the upper hatch; Figure 10 This is a schematic diagram showing the limit of the guide rail during the opening and closing of the hatch; Figure 11 This is an enlarged view of the anti-slip bearing. Figure 12 This is a schematic diagram of the anti-sway components on both sides of the upper cabin door.

[0041] Figure label: 1. Lower left beam of the rear fuselage; 2. Lower right beam of the rear fuselage; 7. First horizontal reinforcing frame; 8. Fourth horizontal reinforcing frame; 9. Second horizontal reinforcing frame; 10. Fifth horizontal reinforcing frame; 11. Third horizontal reinforcing frame; 12. Right guide rail mounting bracket; 13. Left guide rail mounting bracket; 14. Screw connector; 15. First right slide rail joint; 16. Second right slide rail joint; 17. First left slide rail joint; 18. Second left slide rail joint; 19. Lid; 20. Hook; 21. Rubber sealing strip; 22. Right-flip connector; 23. Left-flipping connector; 24. Right hydraulic rod connector; 25. Left hydraulic rod connector; 26. Right anti-sway connector; 27. Left anti-sway connector; 28. Hook base; 29. Right actuator connector; 30. Left actuator connector; 31. Right lead screw connector; 32. Left lead screw connector; 33. Nut seat; 34. Servo motor; 35. First guide rail section; 36. Second guide rail section; 37. Third guide rail section; 38. Anti-sway bearing; 39. Right anti-sway slide rail joint; 40. Anti-sway slide rail; 100. Sliding door; 200. Upper rotating hatch; 300. Guide rail assembly; 400. Anti-sway components; 500. Translation drive mechanism; 600. Rotation drive mechanism. Detailed Implementation

[0042] To make the technical problems, technical solutions, and technical effects of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0044] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present 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 limiting the present invention.

[0046] Example 1 like Figures 1 to 12 As shown, Figure 1 This diagram shows the overall structure of the mechanism of the present invention in the fully closed state of the fuselage cargo hold door. The opening and closing mechanism of the present invention mainly includes a fuselage cargo hold frame structure, a sliding door 100, an upper rotating door 200, a guide rail assembly 300, an anti-sway assembly 400, a ball screw actuator as a translation drive mechanism 500, and a piston actuator as a rotation drive mechanism 600. The fuselage cargo hold frame structure provides the mounting base for the entire mechanism, and includes the lower left rear fuselage beam 1 and the lower right rear fuselage beam 2 (the left and right positions are relative). Figure 1 The fuselage consists of a lower left side (middle and lower right side) and multiple transverse reinforcing frames spaced laterally between the lower left and lower right beams of the aft fuselage, specifically including a first transverse reinforcing frame 7, a second transverse reinforcing frame 9, a third transverse reinforcing frame 11, a fourth transverse reinforcing frame 8, and a fifth transverse reinforcing frame 10. The lower left and lower right beams of the aft fuselage are located on the left and right sides of the bottom of the aft fuselage, respectively, and play a crucial role in bearing the gravitational load when the hatches are closed. They also work in conjunction with the sealing strips at the edges of the hatches to achieve a seal between the fuselage and the hatches. These multiple transverse reinforcing frames are arranged longitudinally along the fuselage, forming a stable frame structure.

[0047] The guide rail assembly 300 is located at the bottom of the fuselage cargo hold frame structure, and is symmetrically distributed on both sides inside the fuselage cargo hold frame structure. Please refer to the following: Figure 10 , Figure 10 A detailed schematic diagram of the guide rail's limiting position during the opening and closing of the hatch is shown. Each guide rail assembly 300 includes a first guide rail section 35, a second guide rail section 36, and a third guide rail section 37 arranged sequentially. The first guide rail section 35 and the third guide rail section 37 are fixedly mounted on the lower left beam 1 and the lower right beam 2 of the aft fuselage, while the second guide rail section 36 is fixedly mounted on the central transverse reinforcing frame (i.e., the two symmetrical second guide rail sections 36 are respectively mounted on the right guide rail mounting bracket 12 and the left guide rail mounting bracket 13). The first guide rail section 35 and the second guide rail section 36 together constrain the sliding trajectory of the lower sliding door 100 and the rotation trajectory of the upper rotating hatch 200; the third guide rail section 37 is specifically used to constrain the sliding trajectory of the lower sliding door 100.

[0048] The sliding door 100 (i.e., the lower hatch door), as the lower part of the hatch assembly, has its sliding seal mounted on the guide rail assembly 300. For details, please refer to... Figure 6 and Figure 7 The detailed structure of the sliding door 100 is shown. The sliding door 100 has a sliding connection portion at its edge, which includes multiple slide rail joints disposed on both sides of the sliding door 100, specifically a first right slide rail joint 15, a second right slide rail joint 16, a first left slide rail joint 17, and a second left slide rail joint 18. Each slide rail joint is equipped with a bearing, which is embedded in the guide rail groove of the guide rail assembly 300, forming a rolling engagement with the guide rail assembly 300, allowing the sliding door 100 to slide with low friction under the constraint of the guide rail assembly 300.

[0049] The upper rotating hatch 200 (i.e., the upper door) is located in the nose direction (i.e., forward) of the lower sliding door 100. Its front end is hinged to a double-eared joint fixed to the third transverse reinforcing frame 11 via a right-flip joint 22 and a left-flip joint 23, allowing the upper rotating hatch 200 to rotate upward or downward around its hinge point. Please refer to... Figure 8 and Figure 9 The detailed structure of the upper rotating hatch 200 is shown.

[0050] In this embodiment, the translation drive mechanism 500 is specifically a ball screw actuator. Its main function is to drive the sliding door 100 to slide along the guide rail assembly 300 towards the tail (i.e., rearward), so that it moves to below the upper rotating door 200 and is locked by the lock box assembly. The ball screw actuator includes a servo motor 34, a lead screw, and a nut seat 33. The servo motor 34, as a power source, is installed at an appropriate position on the upper rotating door 200. The lead screw is connected to the output end of the servo motor 34, and the nut seat 33 is sleeved on the lead screw. The nut seat 33 is fixedly connected to the lead screw joint 14 on the sliding door 100 through the left lead screw connector 32 and the right lead screw connector 31. When the servo motor 34 starts in the forward direction, it drives the lead screw to rotate. The rotational motion of the lead screw is converted into the linear translational motion of the nut seat 33 along the lead screw axis. The nut seat 33 then drives the sliding door 100 to slide along the guide rail assembly 300 towards the tail of the machine through the left lead screw connector 32 and the right lead screw connector 31.

[0051] In this embodiment, the rotation drive mechanism 600 is specifically a piston actuator, whose function is to drive the upper rotating hatch 200 to rotate upward about its hinge point. One end of the piston actuator (actuator end) is hinged to the transverse reinforcing frame (e.g., the fifth transverse reinforcing frame 10) at the top of the fuselage cargo hold frame structure via the left actuator joint 30 and the right actuator joint 29, while the other end (piston rod end) is hinged to the upper rotating hatch 200 via the right hydraulic rod joint 24 and the left hydraulic rod joint 25. When the piston rod of the piston actuator retracts, it drives the upper rotating hatch 200 to rotate upward about its hinge point.

[0052] The anti-sway assembly 400 prevents the hatches from swaying left and right when the upper rotating hatch 200 and the lower sliding hatch 100 rotate synchronously. Figure 12 As shown, the anti-sway assembly 400 includes an anti-sway rail 40 and an anti-sway connector. Specifically, the anti-sway rail 40 is fixedly installed on both sides of the central transverse reinforcing frame (e.g., the second transverse reinforcing frame 9) via a right anti-sway rail connector 39 (the installation method on the left side is symmetrical to it). The extension direction and shape of the anti-sway rail 40 are adapted to the rotation trajectory of the upper rotating hatch 200. A right anti-sway connector 26 and a left anti-sway connector 27 are correspondingly provided on both sides of the upper rotating hatch 200. These anti-sway connectors are also equipped with anti-sway bearings 38, which form rolling contact with the anti-sway rail 40.

[0053] The working principle and process of the mechanism of this invention are described in detail below: (a) The hatch opening process: First, step S1 is executed: the ball screw actuator is activated. Specifically, the ground control station or the onboard control panel sends a command to the servo motor 34, which begins to rotate forward, driving the ball screw to rotate. The rotation of the ball screw causes the nut seat 33 to move along the ball screw towards the tail of the machine. Since the nut seat 33 is fixedly connected to the ball screw joint 14 of the sliding door 100 through the left ball screw connector 32 and the right ball screw connector 31, the sliding door 100 is driven to slide along the guide rail assembly 300 towards the tail of the machine. During the sliding process, the bearings on the first right slide rail joint 15, the second right slide rail joint 16, the first left slide rail joint 17, and the second left slide rail joint 18 on the sliding door 100 roll within the corresponding first guide rail section 35, second guide rail section 36, and third guide rail section 37, respectively, providing precise guidance for the sliding. When the sliding door 100 slides to the point where its upper surface in the tail direction overlaps with the lower surface of the upper rotating door 200, multiple hooks 20 at the bottom of the sliding door 100 pass through multiple hook seats 28 at corresponding positions on the upper part of the upper rotating door 200, achieving a mechanical lock between the sliding door 100 and the upper rotating door 200. At this time, as... Figures 2 to 4 As shown, the sliding door 100 has closed and locked with the upper rotating door 200. In this position, the servo motor 34 switches to the locked state to ensure that the sliding door 100 will not slide accidentally.

[0054] Subsequently, step S2 is executed: the piston actuator is activated. A control signal is sent to the piston actuator, causing the high-pressure oil in its actuator cylinder to push the piston, thereby driving the piston rod to retract. Since the piston rod is hinged to the right hydraulic rod joint 24 and the left hydraulic rod joint 25 on the upper rotating hatch 200, the retraction of the piston rod pushes the upper rotating hatch 200 to rotate upward around the hinge point between its front end and the third transverse reinforcing frame 11. At this time, since the lower sliding door 100 has been locked to the upper rotating hatch 200 by the hook 20 and the hook seat 28, the rotation of the upper rotating hatch 200 causes the lower sliding door 100 to flip upward together. During the flipping process, the first slide rail joint (first right slide rail joint 15 and first left slide rail joint 17) on the lower sliding door 100 moves along the second guide rail section 36 of the guide rail assembly 300. The trajectory of the second guide rail section 36 is adapted to the rotation trajectory of the upper rotating hatch 200, thereby constraining the rotation path of the upper and lower hatch assembly. Meanwhile, the anti-sway bearings 38 on the right anti-sway joint 26 and left anti-sway joint 27 on both sides of the upper rotating hatch 200 roll in contact within the anti-sway slide rail 40 fixed to the fuselage. The shape of the anti-sway slide rail 40 restricts any left or right displacement of the upper rotating hatch 200 during rotation, thereby ensuring the stability and smoothness of the entire hatch assembly during the tilting process. Figure 5 and Figure 6 As shown, when the upper rotating hatch 200 rotates upward by approximately 23°, the hatch reaches the fully open state. At this point, the entire hatch opening action is completed, and the rear of the cargo hold is completely open, facilitating cargo loading, unloading, or airdrop operations.

[0055] (II) Door closing process: The closing process of the hatch is the reverse of the opening process described above.

[0056] First, execute step S3: unlock and reverse the piston actuator. Control the piston actuator to extend its piston rod, driving the upper rotating hatch 200 to rotate downwards around its hinge point. The upper rotating hatch 200, together with its locked lower sliding door 100, flips downwards and resets. During this process, the anti-sway component 400 continues to function, ensuring a smooth and wobbly reset. After the upper rotating hatch 200 has rotated downwards by approximately 23°, the upper and lower hatch assembly returns to the horizontal position.

[0057] Subsequently, step S4 is executed: the ball screw actuator is unlocked and activated in reverse. The servo motor 34 rotates in reverse, driving the nut seat 33 to move along the screw towards the machine head, and via the screw connector, causing the sliding door 100 to slide and reset along the guide rail assembly 300 towards the machine head. When the hook 20 is fully disengaged from the hook seat 28 and slides back to its initial position, as... Figure 1 As shown, the hatch is completely closed.

[0058] In the fully closed state, rubber sealing strips 21 are affixed to the four edges of both the sliding door 100 and the upper rotating door 200. When the sliding door 100 and the upper rotating door 200 are fully closed, the tail of the sliding door 100 presses against the nose of the upper rotating door 200, and the nose of the upper rotating door 200 is affixed with the rubber sealing strip 21. The tail of the sliding door 100 achieves a seal between the upper and lower door mating edges by pressing the rubber sealing strip 21. Simultaneously, the outer edges of the entire door with the rubber sealing strip together form a complete door sealing boundary, which, under the action of gravity, cooperates with and presses against the rear fuselage lower beam and the transverse reinforcing frame, achieving a waterproof seal between the door and the fuselage.

[0059] Example 2 This embodiment has a basically the same structure as Embodiment 1, the difference being that the specific structure and installation method of some components have been further optimized and limited.

[0060] Preferably, to further reduce the overall weight of the hatch while ensuring sufficient structural strength, the main structures of both the sliding door 100 and the rotating door 200 are made of carbon fiber-clad foam composite materials. Compared to the traditional metal skin and frame structure, this structure has higher specific strength and specific stiffness, significantly reducing the hatch weight while meeting the structural strength and stiffness requirements, which is beneficial for improving the effective payload capacity and endurance of cargo drones.

[0061] Preferably, such as Figure 6 and Figure 7 As shown, a cover 19 is provided in the middle of the sliding door 100. Under normal conditions, the cover 19 remains closed. When the ball screw actuator malfunctions (e.g., the servo motor 34 loses power or the screw is jammed) and cannot drive the sliding door 100 normally, the operator can manually open the cover 19 to directly contact the transmission mechanism inside the sliding door 100 and manually push the sliding door 100 along the guide rail assembly 300, thereby opening or closing the door in an emergency. Furthermore, the cover 19 can also serve as an inspection window during routine maintenance, facilitating the operator's inspection and troubleshooting of the ball screw actuator, guide rail, and other internal mechanisms.

[0062] Preferably, to further improve the reliability of the hatch under harsh operating conditions, the servo motor 34 in the ball screw actuator is equipped with an electromagnetic brake. When the motor is powered off or receives a locking command, the brake engages the motor shaft to prevent the screw from rotating under external force, thereby ensuring the position of the sliding door 100 is maintained. Similarly, the piston actuator also has a hydraulic lock function. After the piston rod is fully extended or retracted, the hydraulic lock closes, keeping the piston rod in a fixed position and preventing the hatch from moving unexpectedly due to its own weight or pneumatic load.

[0063] Example 3 This embodiment is basically the same as the structure of embodiment 1 or 2, the difference being that the specific fit relationship of each kinematic pair and the sealing structure are explained in more detail.

[0064] In this embodiment, to ensure the sealing performance of the upper and lower hatches when fully closed, in addition to affixing rubber sealing strips 21 to the edges of the hatches, sealing grooves or sealing protrusions adapted to the rubber sealing strips 21 are also provided on the upper surfaces of the lower left and lower right aft fuselage beams 1 and 2, as well as at corresponding positions of the transverse reinforcing frames that contact the hatch edges. When the hatches are closed, the rubber sealing strips 21 are pressed into the sealing grooves or tightly fitted with the sealing protrusions under the action of gravity and the weight of the hatches themselves, forming multiple labyrinthine sealing paths, effectively preventing rainwater, dust, and other external media from entering the cargo hold.

[0065] Furthermore, regarding the sliding fit between the sliding door 100 and the guide rail assembly 300, since the bearing is embedded in the guide rail groove, and the guide rail groove has a certain depth, this structure itself also plays a role in preventing dust and foreign objects from entering. Optionally, a dust brush or dust cover can also be installed at the opening of the guide rail assembly 300 to further prevent dust and impurities from accumulating in the guide rail groove and affecting the rolling performance of the bearing.

[0066] Example 4 This embodiment provides an opening and closing method for the tail hatch opening and closing mechanism of a retractable cargo drone based on a sliding rail, as described in any of the above embodiments. The method includes a hatch opening method and a hatch closing method.

[0067] The method for opening the hatch includes the following steps: Step S1: Activate the ball screw actuator to drive the sliding door 100 to slide along the guide rail assembly 300 towards the tail of the aircraft until the sliding door 100 locks with the upper rotating door 200. In this step, the precise distance the sliding door 100 slides along the guide rail assembly 300 towards the tail is 1116mm. This distance ensures the accurate alignment and locking of the hook 20 and the hook seat 28.

[0068] Step S2: Activate the piston actuator to drive the upper rotating hatch 200 to rotate upwards around its hinge point. The upper rotating hatch 200, together with the lower sliding door 100 which is locked to it, flips upwards, thus fully opening the hatch. In this step, the upper rotating hatch 200 rotates upwards by an angle of 23°, which ensures that the hatch is fully opened to the predetermined position, providing maximum unobstructed passage for cargo loading and unloading.

[0069] The hatch closing method includes the following steps: Step S3: Unlock and reverse the piston actuator to drive the upper rotating hatch 200 to rotate downwards around its hinge point. The upper rotating hatch 200, together with the locked lower sliding door 100, flips downwards and resets. In this step, the upper rotating hatch 200 rotates downwards by an angle of 23°, returning it from the fully open state to the horizontally closed position.

[0070] Step S4: Unlock and reverse the ball screw actuator to drive the sliding door 100 to slide back along the guide rail assembly 300 towards the nose of the aircraft until the door is fully closed. In this step, the sliding door 100 slides precisely 1116mm along the guide rail assembly 300 towards the nose of the aircraft, returning it to its initial closed position.

[0071] In steps S2 and S3, i.e., throughout the rotation of the upper rotating door 200, the anti-sway bearings 38 of the anti-sway joints (right anti-sway joint 26 and left anti-sway joint 27) on the upper rotating door 200 maintain rolling contact with the anti-sway slide rail 40 fixed to the fuselage, thereby effectively limiting the left and right swaying of the upper rotating door 200. Simultaneously, some slide rail joints of the lower sliding door 100 (i.e., the first right slide rail joint 15 and the first left slide rail joint 17) move along the second guide rail section 36 of the guide rail assembly 300. The trajectory of this second guide rail section 36 is consistent with the rotation trajectory, thereby ensuring that the guide rail assembly 300 can always constrain the rotation trajectory of the lower sliding door 100 and the upper rotating door 200 during rotation, guaranteeing motion accuracy.

[0072] Example 5 This embodiment provides a more detailed description of the lock box assembly (the cooperation between the hook 20 and the hook seat 28) in this invention.

[0073] In this embodiment, four hooks 20 are fixedly installed at the bottom of the sliding door 100 in the tail direction, evenly distributed along the width of the sliding door 100. Correspondingly, hook seats 28 are fixedly installed at the upper part of the upper rotating door 200 in the nose direction, with their positions and numbers corresponding one-to-one with the hooks 20. The hook seat 28 is a seat structure with an open slot, the opening of which faces the tail direction, and the internal shape of the slot is adapted to the shape of the hook head of the hook 20.

[0074] As the sliding door 100 slides towards the tail and approaches the upper rotating door 200 under the drive of the ball screw actuator, the hook head of the hook 20 first enters the opening slot of the hook seat 28. As the sliding door 100 continues to move towards the tail, the hook head of the hook 20 completely passes through the opening slot of the hook seat 28, and under the limiting action of the rear side wall of the hook seat 28, the hook 20 and the hook seat 28 form a firm hook connection. The locking of the upper and lower doors also relies on the self-locking of the ball screw device.

[0075] In addition, to achieve automatic locking, a resilient reset claw can be set inside the hook seat 28. When the hook 20 is fully inserted into the hook seat 28, the claw will automatically pop out and lock the root of the hook head of the hook 20, preventing the hook 20 from coming out of the hook seat 28 without the action of a control force.

[0076] During the unlocking process, when it is necessary to separate the sliding door 100 from the upper rotating door 200, the claws are first disengaged by an unlocking mechanism (such as an electromagnet or a lever driven by a micro motor) to release the restriction on the hook 20. Then, the ball screw actuator is activated in the reverse direction to drive the sliding door 100 to move towards the machine head, so that the hook 20 is disengaged from the hook seat 28.

[0077] Through the cooperation structure of the hook 20 and the hook seat 28, the sliding door 100 and the upper rotating door 200 can be locked and unlocked quickly and reliably. Moreover, the locking structure can withstand the weight of the door itself and the inertial load during the rotation of the upper rotating door 200, ensuring a safe and reliable connection.

Claims

1. A retractable cargo drone tail door opening and closing mechanism based on a sliding rail, characterized in that, The system includes a fuselage cargo hold frame structure, a guide rail assembly (300) disposed at the bottom of the fuselage cargo hold frame structure, a sliding door (100) that is slidably sealed on the guide rail assembly (300), an upper rotating door (200) that is rotatably hinged to the front end of the bottom of the fuselage cargo hold frame structure, a translation drive mechanism (500) that causes the sliding door (100) to slide along the guide rail assembly (300) onto the upper rotating door (200) and is locked by a lock box assembly, a rotation drive mechanism (600) mounted on the fuselage cargo hold frame structure to drive the upper rotating door (200) to rotate, and an anti-sway assembly (400) disposed on the fuselage cargo hold frame structure to prevent swaying when the upper rotating door (200) and the sliding door (100) rotate synchronously.

2. The sliding rail-based retractable cargo drone tail door opening and closing mechanism according to claim 1, characterized in that, The fuselage cargo hold frame structure includes a left lower rear fuselage beam (1) and a right lower rear fuselage beam (2) located on the left and right sides of the bottom of the rear fuselage, and multiple transverse reinforcing frames are arranged at intervals on the upper part between the left lower rear fuselage beam (1) and the right lower rear fuselage beam (2). The sliding door (100) has a sliding connection part on its edge, and a screw joint (14) is provided on the side of the sliding door (100) near the upper rotating door (200); the sliding connection part of the sliding door (100) is in rolling cooperation with the guide rail assembly (300), and the guide rail assembly (300) is used to constrain the sliding trajectory of the sliding door (100); The front end of the upper rotating hatch (200) is hinged to the front transverse reinforcing frame; The translation drive mechanism (500) is a ball screw actuator, which is installed on the upper rotating door (200). The movable end of the ball screw actuator is connected to the screw joint (14) on the lower sliding door (100) and is used to drive the lower sliding door (100) to slide along the guide rail assembly (300) to the locking position with the upper rotating door (200). The rotation drive mechanism (600) is a piston actuator. One end of the piston actuator is hinged to the top of the fuselage cargo hold frame structure, and the other end is hinged to the upper rotating door (200). It is used to drive the upper rotating door (200) to rotate upward around its hinge point, so as to drive the sliding door (100) locked with the upper rotating door (200) to flip open together.

3. The retractable cargo drone tail door opening and closing mechanism based on a slide rail according to claim 2, characterized in that, The lock box assembly includes a hook (20) and a hook seat (28) that cooperates with the hook (20). The bottom of the sliding door (100) is provided with multiple hooks (20), and the upper rotating door (200) is provided with multiple hook seats (28) at corresponding positions on the upper part. When the sliding door (100) slides onto the upper rotating door (200), the hook (20) passes through the corresponding hook seat (28) to lock the sliding door (100) and the upper rotating door (200). The sliding door (100) has a cover (19) in the middle. When the ball screw actuator fails, the cover (19) can be opened to manually push the sliding door (100) to slide along the guide rail assembly (300). Rubber sealing strips (21) are affixed to the four edges of the sliding door (100) and the four edges of the rotating hatch (200); when the sliding door (100) and the rotating hatch (200) are in the fully closed state, the outer edges of the sliding door (100) and the rotating hatch (200) with the rubber sealing strips (21) together form a complete hatch sealing boundary.

4. The retractable cargo drone tail door opening and closing mechanism based on a slide rail according to claim 3, characterized in that, The sliding connection includes multiple slide rail joints disposed on both sides of the sliding door (100), each slide rail joint being provided with a bearing, the bearing being embedded in the guide rail assembly (300) and rollingly engaging with the guide rail assembly (300).

5. The retractable cargo drone tail door opening and closing mechanism based on a slide rail according to claim 2, characterized in that, The guide rail assembly (300) is symmetrically distributed on both sides of the interior of the fuselage cargo hold frame structure. Each side of the guide rail assembly (300) includes a first guide rail section (35), a second guide rail section (36) and a third guide rail section (37) arranged in sequence. The first guide rail segment (35) and the third guide rail segment (37) are located on the lower left beam (1) and the lower right beam (2) of the rear fuselage, and the second guide rail segment (36) is located on the middle transverse reinforcing frame; The first guide rail segment (35) and the second guide rail segment (36) are respectively used to constrain the sliding trajectory of the sliding door (100) and the rotation trajectory of the upper rotating door (200); The third guide rail segment (37) is used to constrain the sliding trajectory of the sliding door (100).

6. The sliding rail-based retractable cargo drone tail door opening and closing mechanism according to claim 2, characterized in that, The anti-sway assembly (400) includes anti-sway slide rails (40) symmetrically installed on both sides of the transverse reinforcing frame in the middle and anti-sway joints provided on both sides of the upper rotating hatch (200). The anti-sway joints are provided with anti-sway bearings (38), which roll in contact with the anti-sway slide rails (40) to limit the left and right swaying of the hatch when the upper rotating hatch (200) is rotated open and closed.

7. The retractable cargo drone tail door opening and closing mechanism based on a slide rail according to claim 6, characterized in that, The anti-sway slide rail (40) is fixed by an anti-sway slide rail joint and a transverse reinforcing frame in the middle. The shape of the extension direction of the anti-sway slide rail (40) is adapted to the rotation trajectory of the upper rotating cabin door (200).

8. The retractable cargo drone tail door opening and closing mechanism based on a slide rail according to claim 2, characterized in that, The ball screw actuator includes a servo motor (34), a screw, and a nut seat (33). The nut seat (33) is connected to the screw joint (14) on the sliding door (100) via a left screw connector (32) and a right screw connector (31). The servo motor (34) drives the screw to rotate, causing the nut seat (33) to translate along the screw axis, thereby causing the sliding door (100) to slide along the guide rail assembly (300) via the left screw connector (32) and the right screw connector (31).

9. A method for opening and closing a sliding rail-based retractable cargo drone tail door opening and closing mechanism, employing the sliding rail-based retractable cargo drone tail door opening and closing mechanism as described in any one of claims 1 to 8, characterized in that, The opening and closing method includes a hatch opening method and a hatch closing method; The method for opening the hatch includes the following steps: Step S1: Activate the ball screw actuator to drive the sliding door (100) to slide along the guide rail assembly (300) toward the tail of the machine until the sliding door (100) locks with the upper rotating door (200); Step S2: Activate the piston actuator to drive the upper rotating hatch (200) to rotate upward around its hinge point. The upper rotating hatch (200) drives the lower sliding door (100) locked with it to flip upward together, so as to fully open the hatch. The hatch closing method includes the following steps: Step S3: Unlock and reverse the piston actuator to drive the upper rotating hatch (200) to rotate downward around its hinge point. The upper rotating hatch (200) drives the lower sliding door (100) locked with it to flip downward and reset. Step S4: Unlock and reverse the ball screw actuator to drive the sliding door (100) to slide and reset along the guide rail assembly (300) toward the machine head until the door is completely closed.

10. The opening and closing method of the slide rail-based retractable cargo drone tail compartment door opening and closing mechanism according to claim 9, characterized in that, In steps S2 and S3, when the upper rotating door (200) rotates, the anti-sway bearing (38) of the anti-sway joint on the upper rotating door (200) rolls into contact with the anti-sway slide rail (40) fixed to the fuselage, thereby restricting the left and right swaying of the upper rotating door (200).

11. The opening and closing method of the slide rail-based retractable cargo drone tail compartment door opening and closing mechanism according to claim 9, characterized in that, In steps S2 and S3, a portion of the sliding rail joint of the sliding door (100) moves along the second guide rail segment (36) of the guide rail assembly (300), which constrains the rotation trajectory of the sliding door (100) and the upper rotating cabin door (200).

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