An aircraft frame preform, a method for manufacturing an aircraft frame and an aircraft frame assembly, particularly for unmanned aircraft

Abstract

The present invention relates to an aircraft frame preform, particularly for unmanned aircraft, comprising a central member (1) and at least two arms (2) extending from the central member (1) in an outward direction, wherein the central member (1) and / or the at least two arms (2) are formed of an inner wall (6) and an outer wall (7) made of a metal sheet, wherein the inner wall (6) and the outer wall (7) are arranged in planes relative to each other while retaining a gap, wherein the edges of the inner wall (6) and the outer wall (7) are connected and sealed by means of a seal (12), forming a closed hermetic empty inner space (3) of the aircraft frame preform, wherein a valve (8) is arranged on at least one wall (6, 7). The present invention also relates to a method for manufacturing an aircraft frame, particularly for unmanned aircraft, from the aircraft frame preform and an aircraft frame manufactured by this method, particularly for unmanned aircraft.

Description

[0001] An aircraft frame preform, a method for manufacturing an aircraft frame and an aircraft frame assembly, particularly for unmanned aircraft

[0002] The present invention relates to an aircraft frame preform, a method for manufacturing an aircraft frame and an aircraft frame assembly, particularly for unmanned aircraft. The objects of the invention are applied in the aviation industry, particularly for the construction of frames for unmanned, remotely controlled or autonomous aircraft, as well as for conventional multi-rotor manned aircraft structures.

[0003] The growing interest in unmanned aerial vehicle (UAV) technology results from its wide application in various fields, such as terrain monitoring, agriculture, rescue operations, logistics, as well as military operations. Therefore, engineers and designers continuously strive to improve parameters such as flight altitude, speed, range and payload capacity. A key aspect in achieving these objectives is the appropriate construction of the UAV frame, which directly influences the performance and operational capabilities of the drone (unmanned aircraft).

[0004] UAV frames must be characterized not only by low weight and high mechanical strength, but also by resistance to variable atmospheric conditions, vibrations and material fatigue. Important technical parameters are also structural rigidity, aerodynamic stability, as well as resistance to deformation under the influence of forces acting during flight. The frame must be designed to minimize air resistance and optimize aerodynamic flow, which translates into lower energy consumption and higher flight efficiency.

[0005] High frame rigidity is crucial for maintaining UAV stability, particularly during abrupt maneuvers or in strong wind conditions. Furthermore, frames must be designed with the possibility of integrating various components, such as batteries, sensors, cameras, or communication systems, while simultaneously ensuring easy access to these elements for service or replacement purposes.

[0006] In practice, UAV frames are often made of composite materials, such as carbon fiber, which combine low weight with high rigidity and resistance to mechanical damage. Alternatively, aluminum alloys are also used, which offer a good balance between strength and ease of machining. In some cases, glass fiber-reinforced polymers are also used, which, despite a somewhat higher weight, offer satisfactory strength at lower production costs.

[0007] The UAV frame manufacturing process typically includes techniques such as vacuum forming, autoclave forming for composites, and precision CNC machining for metal alloys. In the case of composite frames, forming begins with laying fiber layers in a mold, which are then saturated with resin and cured in an autoclave. Aluminum alloys are often subjected to CNC machining to obtain precise and lightweight components, which can then be joined using rivets, screws or welding. An important aspect of frame design is also geometry optimization for weight minimization while maintaining required rigidity and integration of mounting elements for other UAV components.

[0008] The construction of a UAV frame is therefore a foundation that determines the technological and operational capabilities of the drone. Appropriate design and manufacture of the frame is crucial for performance maximization, which is essential to meet the growing market requirements regarding UAV performance.

[0009] Document US10780970B2 discloses a frame dedicated to a heavy unmanned aircraft, which comprises a central frame part having a symmetrical shape and forming a socket area for receiving an avionics package. Upper and lower plates are attached to the central frame part and comprise four corner elements that extend diagonally outward. A plurality of boom arms is pivotally connected to the corner elements, which have the capability of changing between an extended position for flight and a retracted position for storage and transport. In one embodiment of the frame, the upper and lower plates are made of aluminum and are connected to each other via side walls that form a socket receiving the avionics package.

[0010] Document W02024015207A1 discloses an unmanned aircraft which comprises a fuselage, a pair of wings attached to the fuselage and a propulsion system mounted on the wings for providing UAV propulsion. The fuselage has an outer fuselage shell, which is a first mechanical support structure for the UAV airframe. The pair of wings is attached to the fuselage and shaped to provide aerodynamic lift. The wings have outer wing shells, which are second mechanical support structures for the airframe. The outer fuselage shell or the outer wing shells are formed from one or more formed metal sheets, such as aluminum. The metal sheets may be subjected to various operations to form a shell having the desired geometry, such as pressing, stamping, extrusion or hydroforming. Individual metal sheets forming the fuselage for the UAV are joined together by various techniques, including welding, soldering, lap joints, snap connections or sheet bending.

[0011] The technical problem of the present invention is to provide such a method for manufacturing an unmanned aircraft frame that will allow the manufacture of an unmanned aircraft frame having desired properties, particularly in terms of strength, rigidity and weight, for applications as a structural element of an unmanned aircraft, while maintaining desired dimensional accuracy. It is desirable that the method for manufacturing the unmanned aircraft frame has a limited number of technological steps and is realized without the use of specialist and complicated apparatus, so as to directly provide economic benefits of a simplified, less time-consuming and thus cheaper unmanned aircraft frame manufacturing process. It is also desirable that the method for manufacturing the unmanned aircraft frame is characterized by low material-consumption and allows the manufacture of an unmanned aircraft frame having a wide range of geometrical parameters, allowing the geometry and strength of the unmanned aircraft frame to be adapted to the remaining structural elements of the unmanned aircraft. It is also important to provide a method for manufacturing the unmanned aircraft frame which would allow the shape of the unmanned aircraft frame to be easily modified within a wide range of geometrical parameters and without the need to rearrange the apparatus used in the manufacturing process. The technical problem of the present invention is also to provide an unmanned aircraft frame having the above-mentioned characteristics and desired functional parameters, as well as an unmanned aircraft frame preform, which is a semi-product enabling the manufacture of an unmanned aircraft frame, while being a semi-product providing logistic benefits consisting in easier transport and storage.

[0012] According to a first aspect of the invention, there is provided an aircraft frame preform, particularly for unmanned aircraft, comprising a central member and at least two arms extending from the central member in an outward direction, wherein the central member and / or the at least two arms are formed of an inner wall and an outer wall made of a metal sheet, wherein the innerwall and the outer wall are arranged in planes relative to each other while retaining a gap, characterized in that the edges of the inner wall and the outer wall are connected and sealed by means of a seal, forming a closed hermetic empty inner space of the aircraft frame preform, wherein a valve is arranged on at least one wall.

[0013] Preferably, a socket for receiving a utility body is formed in the central member.

[0014] Preferably, the aircraft frame preform is formed of preform components corresponding to the number of arms, wherein each preform component comprises a part of the central member and an arm and is formed of an inner wall and an outer wall made of a metal sheet, arranged in planes relative to each other while retaining a gap, connected and sealed by means of a seal, wherein a valve is arranged on at least one wall, wherein at least two preform components are connected to each other forming the aircraft frame preform. Preferably, the aircraft frame preform comprises at least three preform components, and the assembled preform components form with their corresponding parts of the central member a central member comprising a socket for receiving a utility body.

[0015] Preferably, the valve of each preform component is arranged on the wall in the area of the central member part, so that the valves are directed towards the inside of the socket.

[0016] Preferably, the preform component comprises a leg constituting a part of the landing gear.

[0017] Preferably, the leg is an integral element with the preform component and is formed of the inner wall and the outer wall.

[0018] Preferably, landing gear is attached to the outer wall.

[0019] Preferably, the seal is a fusion weld, a pressure weld, a layer of adhesive or a lap joint.

[0020] According to a second aspect of the invention, there is provided a method for manufacturing an aircraft frame, particularly for unmanned aircraft, characterized in that it comprises the following steps: a) an aircraft frame preform as defined in the first aspect of the invention is provided, b) a fluid under pressure is introduced through the valve into the inner space of the aircraft frame preform for forming a deformed aircraft frame.

[0021] Preferably, the fluid is air, water, oil, alcohol, plastic fluid or gas, particularly nitrogen, argon, helium, carbon dioxide or a mixture thereof.

[0022] Preferably, step b) is performed at room temperature or at elevated temperature. According to a third aspect of the invention, there is provided an aircraft frame assembly, particularly for unmanned aircraft, comprising at least one aircraft frame, including a central member and at least two arms extending from the central member in an outward direction, wherein the central member and / or the at least two arms are formed of an inner wall and an outer wall made of a metal sheet, wherein the inner wall and the outer wall are arranged in planes relative to each other while retaining a gap, characterized in that the edges of the inner wall and the outer wall are connected and sealed by means of a seal, forming a closed hermetic empty inner space of the aircraft frame, wherein a valve is arranged on at least one wall, wherein the inner wall and / or the outer wall is deformed by fluid under pressure introduced into the hermetic inner space.

[0023] Preferably, a socket for receiving a utility body is formed in the central member.

[0024] Preferably, the at least one aircraft frame is formed of frame components corresponding to the number of arms, wherein each frame component comprises a part of the central member and an arm and is formed of an inner wall and an outer wall made of a metal sheet, arranged in planes relative to each other while retaining a gap, connected and sealed by means of a seal, wherein a valve is arranged on at least one wall, wherein the inner wall and / or the outer wall is deformed by fluid under pressure introduced into the hermetic inner space, wherein at least two frame components are connected to each other forming the aircraft frame preform.

[0025] Preferably, the aircraft frame assembly comprises at least three frame components, and the assembled frame components form with their corresponding parts of the central member a central member comprising a socket for receiving a utility body.

[0026] Preferably, the valve of each frame component is arranged on the wall in the area of the central member part, so that the valves are directed towards the inside of the socket. Preferably, the frame component comprises a leg constituting a part of the landing gear.

[0027] Preferably, the leg is an integral element with the frame component and is formed of the inner wall and the outer wall.

[0028] Preferably, landing gear is attached to the outer wall.

[0029] Preferably, the fluid is air, water, oil, alcohol, plastic fluid or gas, particularly nitrogen, argon, helium, carbon dioxide or a mixture thereof.

[0030] Preferably, the aircraft frame assembly comprises at least two aircraft frames, wherein the at least two aircraft frames are arranged in substantially parallel planes with a spacing maintained relative to each other and the at least two aircraft frames are connected to each other.

[0031] Preferably, the at least two aircraft frames are connected to each other by the utility body and / or a support element.

[0032] The method for manufacturing an aircraft frame, particularly for unmanned aircraft, according to the present invention allows the manufacture of an aircraft frame having desired properties, particularly in terms of rigidity and strength of the aircraft and low weight. In particular, owing to the use for manufacturing the aircraft frame of largely relatively thin sheet metal, the aircraft frame manufactured by the method according to the invention allows a significant reduction of weight compared to conventional solutions known in the art. Moreover, the method for manufacturing the aircraft frame according to the present invention is realized using uncomplicated machinery, which translates into economic benefits and significant simplification of the aircraft frame manufacturing process. The small number of seals influences the speed and reduced labor-intensiveness of the aircraft frame manufacturing process. Furthermore, the manufacturing of the aircraft frame, constituting a structural element of the aircraft, based on introducing fluid under pressure into the hermetically closed inner space of the aircraft frame preform, allows extensive modification of the parameters of the manufactured aircraft frame, and thus of the final aircraft structure, particularly in terms of its final geometry, strength of individual zones of the aircraft frame and structural rigidity. Moreover, the aircraft frame preform is an element of low height, whereby it occupies a small transport volume during transport and storage, which influences benefits in the logistic process, reducing inter alia the generated carbon footprint.

[0033] The solution according to the invention has been illustrated in the embodiment below and shown in the drawing, in which:

[0034] Fig. 1 is a top view of an unmanned aircraft frame preform according to one embodiment of the present invention;

[0035] Fig. 2 is a cross-sectional view of the unmanned aircraft frame preform of Fig. 1, with enlarged details A and B;

[0036] Fig. 3 is an axonometric view of a step of the method for manufacturing the unmanned aircraft frame according to one embodiment of the present invention;

[0037] Fig. 4 is a cross-sectional view of an unmanned aircraft frame assembly formed from the unmanned aircraft frame preform of Fig. 1;

[0038] Fig. 5 is a top axonometric view of an unmanned aircraft frame assembly according to another embodiment of the present invention;

[0039] Fig. 6 is a bottom axonometric view of the unmanned aircraft frame assembly of Fig. 5 together with a utility body;

[0040] Fig. 7 is a cross-sectional view of the unmanned aircraft frame assembly of Fig. 6;

[0041] Fig. 8 is an axonometric view of the unmanned aircraft frame assembly of Fig. 5 together with a propulsion system;

[0042] Fig. 9 is a cross-sectional view of the unmanned aircraft frame assembly of Fig. 8; Fig. 10 is a cross-sectional view of an unmanned aircraft frame assembly according to another embodiment of the present invention together with a propulsion system;

[0043] Fig. 11 is an axonometric view of an unmanned aircraft frame assembly according to another embodiment of the present invention together with a propulsion system;

[0044] Fig. 12 is a cross-sectional view of the unmanned aircraft frame assembly of Fig. 11;

[0045] Figs. 13 A)-E) are cross-sectional views of various embodiments of unmanned aircraft frame assemblies according to the present invention;

[0046] Fig. 14 is an axonometric view of an unmanned aircraft frame assembly according to another embodiment of the present invention;

[0047] Fig. 15 is a top view of the unmanned aircraft frame assembly of Fig. 14;

[0048] Fig. 16 is an axonometric view of an unmanned aircraft frame assembly according to another embodiment of the present invention;

[0049] Fig. 17 is a top view of the unmanned aircraft frame assembly of Fig. 16;

[0050] Fig. 18 shows a step of the method for manufacturing an unmanned aircraft frame preform according to another embodiment of the present invention;

[0051] Fig. 19 is an axonometric view of a component of the unmanned aircraft frame assembly according to the present invention manufactured from the unmanned aircraft frame preform of Fig. 18;

[0052] Fig. 20 is a cross-sectional view of the unmanned aircraft frame assembly component of Fig. 19;

[0053] Fig. 21 is an axonometric view of the unmanned aircraft frame assembly of Fig. 16 during connection with the utility body. Although the embodiments of the invention below show an implementation based on an unmanned aircraft and its components, such as the frame and frame preform, the present invention is not limited to unmanned aircraft and is also applicable to the construction of aircraft for transporting people or cargo, such as manned aircraft.

[0054] Example 1

[0055] The first embodiment of the invention in the form of an unmanned aircraft frame preform is shown in a top view in Fig. 1 and in cross-section in Fig. 2 with enlarged details A and B.

[0056] As shown in Fig. 1, the unmanned aircraft frame preform is a star-like structure, in which a central part constituting the central member 1 can be distinguished, from which four arms 2 extend radially outward. In this embodiment, the unmanned aircraft frame preform is a symmetrical structure with arms 2 arranged at an equal angular spacing of 90°. It should be emphasized, however, that the arrangement of the arms 2, as well as their number, are not limited to the embodiment shown in Fig. 2, and in alternative embodiments of the invention the unmanned aircraft frame preform may comprise a greater or smaller number of arms 2, not necessarily arranged symmetrically, on condition that there are at least two arms 2 with a geometry allowing effective arrangement of the propulsion systems of the unmanned aircraft. Alternative and non-limiting embodiments of unmanned aircraft frames (formed from corresponding unmanned aircraft preforms) are shown in Figs. 13 A)-E), where a two-arm, three-arm, four-arm, five-arm and eightarm frame are illustrated.

[0057] Returning to Figs. 1 and 2, the above-mentioned components of the unmanned aircraft frame preform are connected to each other and form an integral part made of a metal sheet such as steel sheet, defining an inner wall 6 and an outer wall 7. In this embodiment, the metal sheet has a uniform thickness over the entire surface of the unmanned aircraft frame preform, but in alternative embodiments it is possible to use a metal sheet which has areas of different thicknesses, connected to each other and forming a "patchwork" type structure.

[0058] As shown in Fig. 2, the unmanned aircraft preform was formed from two walls 6, 7 made of sheet material (in this example, stainless steel sheet), with a thickness of 0.8 mm.

[0059] The terms inner wall 6 and outer wall 7 are conventional terms and are intended to denote respectively the inner and outer side of the unmanned aircraft in which the unmanned aircraft frame according to the invention is used. The inner wall 6 and the outer wall 7 are arranged relative to each other in alignment (planar) and while retaining a gap forming a closed, hermetic inner space 3 of the unmanned aircraft frame preform. A valve 8 is arranged on one of the walls 6, 7, providing fluid communication with the inner space 3 formed between the walls 6, 7 of the unmanned aircraft frame preform. In the embodiment shown in Figs. 1 and 2, the valve 8 is arranged on the inner wall 6 in the area of the central member 1.

[0060] The valve 8 is a pneumatic or hydraulic connection and enables tight attachment of a supply conduit from an external source of fluid under pressure. In some embodiments of the invention, the valve 8 may be a check valve. The location of the valve 8 is not a limitation to the scope of the present invention, and thus the valve 8 may be arranged in any area on the metal sheet, on condition that a connection with the inner space of the aircraft frame preform is provided.

[0061] In this embodiment, the outer edges of the unmanned aircraft frame preform (the assembled inner wall 6 and outer wall 7) are sealed by means of a seal 12 forming a closed hermetic inner space 3 of the unmanned aircraft frame preform.

[0062] The sealing is performed on the edges of the metal sheet forming the walls 6, 7 of the unmanned aircraft frame preform after they are assembled together. In this embodiment, all the circumferential edges of the assembled walls 6, 7 of the unmanned aircraft frame preform are thus subjected to sealing. In this embodiment, the sealing was performed by welding corresponding edges together, forming inter alia circumferential welds. Sealing all of the mentioned edges results in the formation of a pressure-tight hermetic inner space 3 in the unmanned aircraft frame preform. The type of seal 12 is in this case not a limitation to the scope of the present invention, and it is possible in alternative embodiments to use any type of seal 12, on condition that a pressure-tight inner space is formed in the unmanned aircraft frame preform, such as that formed by pressure welding, soldering, gluing, bending, pressing.

[0063] The method for manufacturing the unmanned aircraft frame according to one embodiment comprises a step in which an unmanned aircraft frame preform as defined in this embodiment is provided. In case the provided unmanned aircraft frame preform does not have all circumferential edges connected and sealed, the next step comprises sealing the unconnected edges of the unmanned aircraft frame preform by means of a seal 12 for forming a closed hermetic inner space 3 of the unmanned aircraft frame preform. As mentioned above, the seal 12 may be realized in any known manner ensuring the formation of a pressure-tight inner space 3.

[0064] In the next step, an external source of fluid under pressure is connected to the valve 8, via a supply conduit, as illustrated in Fig. 3. In this embodiment, the fluid is air, the source of fluid under pressure is an air compressor, and the supply conduit together with the valve 8 forms a pneumatic connection. The type of external source of fluid under pressure and connection equipment is not a limitation to the scope of the invention, and in alternative embodiments it is possible to use fluid in the form of water, machine oil, alcohol, gas particularly nitrogen, argon, helium, carbon dioxide or a mixture thereof, or fluid plastic such as one-, two- or three-component foam (e.g. flex 140 type), etc. together with the connection equipment and source of fluid under pressure appropriate for these fluids. The less compressible the fluid, the more controlled the deformation conditions of the unmanned aircraft frame preform. Importantly, the use of a less compressible fluid (than air) for deforming the unmanned aircraft frame preform, for example water, causes that during the introduction of the fluid into the inner space 3 of the unmanned aircraft frame preform, the air trapped in the inner space 3 concentrates in areas near the occurrence of the seal 12, i.e. near the welded edges of the inner wall 6 and the outer wall 7. In such a situation, the pressure increase in the inner space 3 will cause that areas around the seal 12 will be subjected to less or no plastic deformation. Limiting plastic deformation in the area of the seal 12 allows increased durability and reliability of the resulting unmanned aircraft frame due to reduced impact on the metal sheet, particularly in the heat affected zone area, resulting from welding the edges of the walls 6, 7.

[0065] In the next step of the method for manufacturing the unmanned aircraft frame according to the present invention, fluid under a defined pressure is delivered to the sealed inner space 3 of the unmanned aircraft frame preform. The technology of introducing fluid under pressure into closed sealed chamber elements made of sheet metal for its plastic deformation and providing it with the final form is known inter alia from patent application EP2110189A1. As a result of delivering fluid under pressure to the inner space of the unmanned aircraft frame preform, plastic deformation of the walls 6, 7 of the unmanned aircraft frame preform occurs, as best illustrated in Fig. 4, with enlarged details A and B, where a cross-section of the unmanned aircraft frame manufactured from the unmanned aircraft frame preform is shown. As can be observed, significant plastic deformation of the walls 6, 7 of the unmanned aircraft frame preform has occurred. Importantly, the unmanned aircraft frame deformed to the greatest extent in the area distant from the edges of the walls 6, 7 of the unmanned aircraft frame preform. In the edge areas of the walls 6, 7, i.e. at the location of the seal 12, little or no degree of plastic deformation occurs, which is related inter alia to the change in the internal structure of the metal sheet in the heat affected zone area, arising as a result of the welding of the edges. It is worth mentioning that the introduction of fluid under pressure into the inner space 3 of the unmanned aircraft frame preform is performed in cold technology (i.e. at room temperature), but this is not a limitation to the scope of the present invention, and in alternative embodiments this process may be performed at elevated or high temperatures.

[0066] In one embodiment of the present invention, the step of introducing fluid under pressure was performed with the following process parameters:

[0067] • process temperature: 20 °C,

[0068] • working pressure: 5 bars,

[0069] • deformation time: 1 minute until pressure equalization in the unmanned aircraft frame preform,

[0070] • pressure holding time: 30 seconds,

[0071] • total deformation time: 1.5 minutes.

[0072] In one embodiment of the present invention, after manufacturing, i.e., deformation of the unmanned aircraft frame, the valve 8 is opened for pressure equalization inside the unmanned aircraft frame with ambient pressure. In an alternative embodiment, elevated pressure is maintained in the inner space 3 of the unmanned aircraft frame, such as in the range from 0.5 bar to 5 bars. Maintaining elevated pressure in the inner space 3 of the unmanned aircraft frame increases its strength and resistance to external mechanical factors, such as impacts with foreign objects, by providing from the inside a counteracting force to said impacts. Additionally, it is possible to fill the inner space 3 of the formed unmanned aircraft frame with another fluid, such as gaseous helium, to provide improvement of the functional parameters of the resulting unmanned aircraft. Preferably, before introducing fluid at elevated pressure into the inner space 3 of the unmanned aircraft frame, the inner space 3 may be covered with an additional coating to increase its tightness, such as a plastic film coating applied by wet method (so-called liquid film).

[0073] Example 2

[0074] The second embodiment of the present invention is shown in a top axonometric view in Fig. 5, in a bottom axonometric view in Fig. 6 and in a side cross-sectional view in Fig. 7. The embodiment of the invention shown in the figures comprises an unmanned aircraft frame assembly formed from an appropriately prepared unmanned aircraft frame preform and comprising one unmanned aircraft frame.

[0075] Generally, the unmanned aircraft frame preform, as well as the unmanned aircraft frame manufactured from it, is a structure substantially similar to the structure of the unmanned aircraft frame preform and the structure of the unmanned aircraft frame shown in the first embodiment, therefore similar structural elements will not be repeated for clarity of the disclosure.

[0076] Importantly, the unmanned aircraft frame shown in Fig. 5 (as well as its corresponding unmanned aircraft frame preform) has a socket 4 formed in the central member 1 for receiving a utility body 5. The socket 4 shown in this embodiment takes a square shape, which is formed by the assembled parts of the central member 1 surrounding an opening constituting the socket 4. Due to the geometry of the socket 4, the valve 8 is located on the inner wall 6 in the area of the connection of the central member 1 with one of the arms 2 of the unmanned aircraft frame. It should be emphasized that the shape of the socket 4 is not limited to square, as shown in the embodiment illustrated in Figs. 5 and 6, and in alternative embodiments the socket may take a different geometry, for example circular or rectangular, such as those shown in Figs. 13 A)-E).

[0077] The socket 4 is intended to receive the utility body 5, which has a complementary shape and which for example stores avionics including power and control systems, or the utility body 5 may constitute a transport space for carrying cargo. Unlike the first embodiment of the invention, the unmanned aircraft frame assembly according to this embodiment additionally comprises landing gear 9, which is formed by four legs 11, attached to the outer wall 7 of each of the arms 2, as best illustrated in the bottom axonometric view in Fig. 6. The legs 11 form landing gear 9, which allows safe landing and takeoff of the unmanned aircraft on uneven surfaces or places with protruding elements.

[0078] Fig. 8 shows in a top axonometric view an example of an unmanned aircraft formed using the unmanned aircraft frame assembly according to the second embodiment of the invention. Fig. 9 shows the unmanned aircraft of Fig. 8 in a side cross- sectional view. Propulsion systems 15 in the form of electric motors equipped with propellers, known in the art, are mounted on each of the arms 2. Fig. 10 shows an analogous implementation of the unmanned aircraft, which is equipped with propulsion systems 15 having a dual propeller construction.

[0079] Example 3

[0080] The third embodiment of the present invention is shown in an axonometric view in Fig. 11, and in a side cross-section in Fig. 12. The embodiment of the invention shown in the figures comprises an unmanned aircraft frame assembly according to the invention supplemented with peripheral utility systems, such as propulsion systems 15.

[0081] Generally, the unmanned aircraft frame assembly, as well as the corresponding unmanned aircraft frame preform, is a structure substantially similar to the structure of the unmanned aircraft frame assembly and the structure of the unmanned aircraft frame preform shown in the second embodiment, with the difference that the unmanned aircraft frame assembly according to this embodiment comprises two unmanned aircraft frames according to the present invention. Two identical unmanned aircraft frames, described in detail in the second embodiment, were used for the construction of the unmanned aircraft frame assembly. The two unmanned aircraft frames are arranged in substantially parallel planes with a spacing maintained relative to each other and the two unmanned aircraft frames are connected to each other. In this embodiment, the unmanned aircraft frames are connected by means of the utility body 5 mounted in the sockets 4 of each of the frames. Additionally, to increase the rigidity and strength of the structure, the unmanned aircraft frames are connected to each other by means of support elements 14 arranged in the area of the arms 2 of each of the unmanned aircraft frames, taking the form of connecting posts. The support elements 14 are attached to the inner wall 6 of the lower unmanned aircraft frame and the outer wall 7 of the upper unmanned aircraft frame.

[0082] Figs. 11 and 12 show an unmanned aircraft equipped with eight propulsion systems 15, each attached to the distal end of the arm 2 of the corresponding unmanned aircraft frame, with the propulsion systems 15 in the lower unmanned aircraft frame directed with propellers downward, and the propulsion systems in the upper unmanned aircraft frame directed with propellers upward.

[0083] Example 4

[0084] The fourth embodiment of the present invention is shown in an axonometric view in Fig. 14, and in a top view in Fig. 15. The figures show an unmanned aircraft frame assembly according to the present invention.

[0085] Generally, the unmanned aircraft frame assembly, as well as the corresponding unmanned aircraft frame preform, is a structure substantially similar to the structure of the unmanned aircraft frame and the structure of the unmanned aircraft frame preform shown in the first and second embodiments, therefore similar structural features will not be described again for clarity of this disclosure.

[0086] Unlike the previous embodiments of the invention, the unmanned aircraft frame assembly according to this embodiment is formed from three frame components 13, with the assembled frame components 13 forming with their corresponding parts of the central member 1 a central member 1 comprising a socket 4 for receiving a utility body 5. In this embodiment of the invention, the connection of the three frame components 13 forms a triangular-shaped socket 4, receiving a utility body 4 with a complementary triangular shape.

[0087] In this embodiment of the invention, each frame component 13 is formed individually from a unmanned aircraft frame preform component 10. The steps of manufacturing the unmanned aircraft frame preform component 10 are shown schematically in Fig. 18. The inner wall 6 and the outer wall 7 are assembled together in planes, the valve 8 is mounted on the inner wall 6, and the walls 6, 7 are connected to each other by means of a seal 12, constituting for example a circumferential weld. This results in the unmanned aircraft frame preform component 10, which in the next operation is subjected to plastic deformation by means of fluid under pressure introduced into the hermetic inner space 3 of the unmanned aircraft frame preform component 10. After plastic deformation of the unmanned aircraft frame preform component 10, the unmanned aircraft frame component 13 shown in an axonometricview in Fig. 19 and in a side cross-sectional view in Fig. 20 is formed.

[0088] The thus formed unmanned aircraft frame components 13 are assembled together in a triangular geometry, as shown in Figs. 14 and 15, so that the parts of the central member 1 form a triangular socket 4. The end areas of the central member 1 parts of each unmanned aircraft frame component 13 are connected with the corresponding area of the central member 1 part of the adjacent unmanned aircraft frame component 13, for example by welding operations, thus forming the unmanned aircraft frame assembly according to the present invention.

[0089] It is worth adding that in this embodiment, the valves 8 on each unmanned aircraft frame component 13 (and the corresponding unmanned aircraft frame preform component 10) are arranged on the inner wall 6 in the area of the central member 1 part, so that after assembly the valves 8 are turned towards the inside of the socket 4, thus forming an additional support structure for the received utility body 5.

[0090] Furthermore, each unmanned aircraft frame component 13 (and the corresponding unmanned aircraft frame preform component 10) comprises a leg 11 constituting a part of the landing gear 9. In this embodiment, the leg 11 is an integral part of the unmanned aircraft frame component 13 and is manufactured using uniform metal sheets used for the inner wall 6 and the outer wall 7.

[0091] In the embodiment of the invention illustrated in Figs. 14 and 15, the unmanned aircraft frame assembly comprises three unmanned aircraft frame components 13 forming a triangular structure, but this is not a limitation to the scope of the present invention and in alternative embodiments it is possible to use a greater number of unmanned aircraft frame components 13 to form the unmanned aircraft frame assembly. A non-limiting example embodiment of the unmanned aircraft frame assembly, in which four connected unmanned aircraft frame components 13 were used, is shown in an axonometric view in Fig. 16, where the socket 4 formed by means of the central member 1 parts takes a square shape. Additionally, Fig. 21 shows the step of placing the utility body 5 in the thus formed socket 4.

[0092] List of reference numerals:

[0093] 1 - central member

[0094] 2 - arm

[0095] 3 - hermetic inner space of the preform

[0096] 4 - socket

[0097] 5 - utility body 6 - inner wall

[0098] 7 - outer wall

[0099] 8 - valve

[0100] 9 - landing gear 10 - preform component

[0101] 11 - leg

[0102] 12 - seal

[0103] 13 - frame component

[0104] 14 - support element 15 - propulsion system

Claims

Claims1. An aircraft frame preform, particularly for unmanned aircraft, comprising a central member (1) and at least two arms (2) extending from the central member (1) in an outward direction, wherein the central member (1) and / or the at least two arms (2) are formed of an inner wall (6) and an outer wall (7) made of a metal sheet, wherein the inner wall (6) and the outer wall (7) are arranged in planes relative to each other while retaining a gap, characterized in that the edges of the inner wall (6) and the outer wall (7) are connected and sealed by means of a seal (12), forming a closed hermetic empty inner space (3) of the aircraft frame preform, wherein a valve (8) is arranged on at least one wall (6, 7).

2. The aircraft frame preform according to claim 1, characterized in that a socket (4) for receiving a utility body (5) is formed in the central member (1).

3. The aircraft frame preform according to claim 1 or 2, characterized in that it is formed of preform components (10) corresponding to the number of arms (2), wherein each preform component (10) comprises a part of the central member (1) and an arm (2) and is formed of an inner wall (6) and an outer wall (7) made of a metal sheet, arranged in planes relative to each other while retaining a gap, connected and sealed by means of a seal (12), wherein a valve (8) is arranged on at least one wall (6, 7), wherein at least two preform components (10) are connected to each other forming the aircraft frame preform.

4. The aircraft frame preform according to claim 3, characterized in that it comprises at least three preform components (10), and the assembled preform components (10) form with their corresponding parts of thecentral member (1) the central member (1) comprising the socket (4) for receiving a utility body (5).

5. The aircraft frame preform according to claim 4, characterized in that the valve (8) of each preform component (10) is arranged on the wall (6, 7) in the area of the part of the central member (1), so that the valves (8) are directed towards the inside of the socket (4).

6. The aircraft frame preform according to any of claims 3 - 5, characterized in that the preform component (10) comprises a leg (11) constituting a part of the landing gear (9).

7. The aircraft frame preform according to claim 6, characterized in that the leg (11) is an integral element with the preform component (10) and is formed of the inner wall (6) and the outer wall (7).

8. The aircraft frame preform according to claim 1 or 2, characterized in that landing gear (9) is attached to the outer wall (7).

9. The aircraft frame preform according to any of claims 1 - 8, characterized in that the seal (12) is a fusion weld, a pressure weld, a layer of adhesive or a lap joint.

10. A method for manufacturing an aircraft frame, particularly for unmanned aircraft, characterized in that it comprises the following steps: a) an aircraft frame preform as defined in any of claims 1 - 9 is provided, b) a fluid under pressure is introduced through the valve (8) into the inner space (3) of the aircraft frame preform for forming a deformed aircraft frame.

11. The method for manufacturing an aircraft frame according to claim 10, characterized in that the fluid is air, water, oil, alcohol, plastic fluid, gas, particularly nitrogen, argon, helium, carbon dioxide or a mixture thereof.

12. The method for manufacturing an aircraft frame according to claim 10 or 11, characterized in that step b) is performed at room temperature or at elevated temperature.

13. An aircraft frame assembly, particularly for unmanned aircraft, comprising at least one aircraft frame, including a central member (1) and at least two arms (2) extending from the central member (1) in an outward direction, wherein the central member (1) and / or the at least two arms (2) are formed of an inner wall (6) and an outer wall (7) made of a metal sheet, wherein the inner wall (6) and the outer wall (7) are arranged in planes relative to each other while retaining a gap, characterized in that the edges of the inner wall (6) and the outer wall (7) are connected and sealed by means of a seal (12), forming a closed hermetic empty inner space (3) of the aircraft frame, wherein a valve (8) is arranged on at least one wall (6, 7), wherein the inner wall (6) and / or the outer wall (7) is deformed by fluid under pressure introduced into the hermetic inner space (3).

14. The aircraft frame assembly according to claim 13, characterized in that a socket (4) for receiving a utility body (5) is formed in the central member (1).

15. The aircraft frame assembly according to claim 13 or 14, characterized in that the at least one aircraft frame is formed of frame components (13) corresponding to the number of arms (2), wherein each frame component (13) comprises a part of the central member (1) and an arm (2) and is formed of an inner wall (6) and an outer wall (7) made of a metal sheet, arranged in planes relative to each other while retaining a gap, connected and sealed by means of a seal (12), wherein a valve (8) is arranged on at least one wall (6, 7), wherein the inner wall (6) and / or the outer wall (7) is deformed by fluid under pressure introduced into the hermetic inner space(3), wherein at least two frame components (13) are connected to each other forming the aircraft frame preform.

16. The aircraft frame assembly according to claim 15, characterized in that it comprises at least three frame components (13), and the assembled frame components (13) form with their corresponding parts of the central member (1) the central member (1) comprising the socket (4) for receiving a utility body (5).

17. The aircraft frame assembly according to claim 16, characterized in that the valve (8) of each frame component (13) is arranged on the wall (6, 7) in the area of the part of the central member (1), so that the valves (8) are directed towards the inside of the socket (4).

18. The aircraft frame assembly according to any of claims 15 - 17, characterized in that the frame component (13) comprises a leg (11) constituting a part of the landing gear (9).

19. The aircraft frame assembly according to claim 25, characterized in that the leg (11) is an integral element with the frame component (13) and is formed of the inner wall (6) and the outer wall (7).

20. The aircraft frame assembly according to claim 13 or 14, characterized in that landing gear (9) is attached to the outer wall (7).

21. The aircraft frame assembly according to any of claims 13 - 20, characterized in that the fluid is air, water, oil, alcohol, fluid plastic or gas, particularly nitrogen, argon, helium, carbon dioxide or a mixture thereof.

22. The aircraft frame assembly according to any of claims 13 - 21, characterized in that it comprises at least two aircraft frames, wherein the at least two aircraft frames are arranged in substantially parallel planes with a spacing maintained relative to each other and the at least two aircraft frames are connected to each other.

23. The aircraft frame assembly according to claim 22, characterized in that the at least two aircraft frames are connected to each other by the utility body (5) and / or a support element (14).

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