Aerial device for harnessing energy from a wind current

Abstract

An aerial device for harnessing energy from a wind current (99) comprises a flying body (10) and a tether cable (20) The flying body (10) has a front face (11) and a rear face (12), and comprises a closed wing structure which has a substantially quadrilateral shape and which comprises two main wings (110) and two lateral joining wings (120). Motors (150) – provided with propellers – are positioned on the closed wing structure. The flying body (10) also comprises a stabilising wing (130) for stabilising the flight. The stabilising wing (130) is at a mid-sagittal plane of the flying body (10) and joins the two main wings (110) to each other. The stabilising wing (130) is at least partly outside a region contained between the two lateral joining wings (120): the stabilising wing (130) projects frontwards beyond leading edges of the two lateral joining wings (120), or the stabilising wing (130) projecting rearwards beyond trailing edges of the two lateral joining wings (120).

Description

[0001] DESCRIPTION

[0002] AERIAL DEVICE FOR HARNESSING ENERGY FROM A WIND CURRENT

[0003] This invention relates to an aerial device for harnessing energy from a wind current. A specific application for this invention is to contribute to propelling a boat (for example a ship) using the force that the aerial device receives from the wind current. In practice, in an example of application this invention is used for pulling ships.

[0004] In particular, this invention relates to an aerial device comprising a flying body which in use is kept airborne by the wind current. The aerial device also comprises a tether cable which has a first end connected to the flying body and a second end which, in use, is connected to an anchoring base. The airborne flying body receives a force from the wind current and, being constrained to the anchoring base by the tether cable, applies a pulling force to the anchoring base. Therefore, the tether cable prevents the flying body from being carried away and lost by the wind current, moreover the flying cable transfers to the anchoring base a force which can if necessary be used as a force for movement or converted into energy to be used.

[0005] The prior art already comprises for example aerial devices which are used in association with an anchoring base fixed to a vehicle, for example a boat, and which are used to propel the vehicle similarly to how a kitesurfing kite is used to pull a kite surfer: in those applications, the wind current applies to the flying body an aerodynamic force which, by means of the tether cable, is transmitted to the anchoring base and therefore to the vehicle. Some examples are described in patent applications JP 59143796 A, WO 2005 / 100148 A1, WO 2009 / 26939 A1, WO 2015 / 160697 A1. Moreover, use of such aerial devices for generating electric energy is known. In some of those aerial devices, for example, the tether cable is mounted at the anchoring base and is wound on a revolving drum associated with an electric generator: in that way, the aerodynamic force applied by the wind current to the flying body and transmitted by the tether cable causes unwinding of the cable and rotation of the revolving drum, and therefore production of electric energy by the electric generator; some examples are described in patent applications WO 2013 / 94623 A1, WO 2020 / 12430 A2, WO 2021 / 220148 A1.

[0006] Patent application EP 2 341 242 A2 relates to a type of aerial devices for generating electric energy, wherein the flying body includes inflatable wing profiles and has a net buoyancy, that is to say, it is able to remain afloat in a wind absence situation. The flying body essentially flights as a kite and is not maneuvered by on-board propulsion motors, nor by movable aerodynamic surfaces actuated by a control system. The angle of attack of the flying body is only controllable through a control box that is suspended from the flying body and is interposed between the ground base and the flying body. The control box has a motorised system that enables variation of the length of the cables connecting the control box to the flying body, thus varying the angle of attack of the flying body.

[0007] This invention instead relates to aerial devices of a type wherein the flying body comprises awinged structure, movable aerodynamic surfaces, one or more motors for manoeuvring the flying body, and an electronic flight management system. The electronic flight management system is operatively connected to the movable aerodynamic surfaces and to the one or more motors. It should be noticed that the aerial devices considered herein do not require a human pilot to be on board the flying body, basically they are a particular type of drone which is constrained to the anchoring base by the tether cable. Aerial devices of this type are already known in themselves and some examples are illustrated in patent applications WO 2020 / 12430 A2, IT 202000009280 A1 , WO 2021 / 220148 A1.

[0008] In some cases, aerial devices of this type are configured in such a way as to make the flying body follow a trajectory in which the flying body flies transversally to the line along which it applies the pulling force to the anchoring base (that is to say, along which the tether cable is pulled taut); in some stretches of the trajectory, the flying body rotates on itself according to an axis of rotation parallel to that line, thereby inverting the direction of flight. That fulfils the need to make the flying body follow a curved trajectory relative to the anchoring base in order to obtain pulling forces greater than those obtainable with “static” positioning of the flying body in the wind current; the curved trajectory may for example be circular, or elliptical, or lemniscate, including descending stretches in which the flying body increases its speed relative to the wind current and, therefore, there is also an increase in the lift generated by the winged structure of the flying body and in the pulling force on the tether cable.

[0009] In the prior art technical solutions, the flying bodies are subject to flight instability which may have catastrophic consequences for the entire aerial device, in particular in the event of sudden changes in the direction and / or strength of the wind current.

[0010] The inventor of this invention observed that this disadvantage seems to be particularly important for technical solutions in which the flying body comprises a closed wing structure having a substantially quadrilateral shape in a front view.

[0011] In this specific context, the technical purpose which forms the basis of this invention is to obtain an aerial device which at least partly overcomes that disadvantage, or which in any case offers an alternative solution to the prior art solutions.

[0012] In particular, this invention aims to obtain an aerial device whose flying body - with closed wing structure - is more stable in flight and therefore more controllable than the flying bodies of the prior art aerial devices.

[0013] The technical purpose specified and the aims indicated are substantially achieved by an aerial device as defined in independent claim 1. Particular embodiments of this invention are defined in the corresponding dependent claims.

[0014] This invention relates to a flying body with a closed wing structure which has a substantially quadrilateral shape in a front view of the flying body; the closed wing structure comprises two main wings and two lateral joining wings, each lateral joining wing joining the two main wings toeach other.

[0015] According to one aspect of this invention, the flying body comprises a stabilising wing for stabilising the flight of the flying body. The stabilising wing joins the two main wings to each other and is at a mid-sagittal plane, so that in the front view of the flying body the stabilising wing extends substantially at an equal distance from the two lateral joining wings (that stabilising wing has a thickness perpendicular to the mid-sagittal plane and a chord which extends parallel to the mid-sagittal plane). The stabilising wing is at least partly outside a region contained between the two lateral joining wings: in one embodiment the stabilising wing projects frontwards beyond the leading edges of the two lateral joining wings; in another embodiment the stabilising wing projects rearwards beyond the trailing edges of the two lateral joining wings; in yet another embodiment there is a stabilising wing which projects frontwards and a stabilising wing which projects rearwards (or a single stabilising wing which projects frontwards and rearwards).

[0016] As is better illustrated in the following description, that projecting stabilising wing makes the flying body more stable and controllable. In the flight conditions in which the weight of the flying body is supported by the lateral joining wings, the lift of the stabilising wing helps to support the weight, and the stabilising wing increases flight stability (behaving similarly to a canard, or to a tail, depending whether it projects frontwards or rearwards).

[0017] Moreover, the stabilising wing contributes to stiffening the closed wing structure, thanks to the fact that it joins the two main wings to each other around half way along their length between the two lateral joining wings.

[0018] Further characteristics and the advantages of this invention will be more apparent from the detailed description of several preferred, non-limiting embodiments of an aerial device for harnessing energy from a wind current. Reference will be made to the drawings of the accompanying figures, in which:

[0019] - Figure 1 is a side view of a boat equipped with an apparatus for harnessing energy from a wind current during operation of the apparatus;

[0020] - Figure 2 shows, in more detail and from a different angle, the apparatus with which the boat of Figure 1 is equipped and which comprises an aerial device according to this invention in accordance with a first embodiment;

[0021] - Figure 3 is an enlarged view of the detail III of Figure 2;

[0022] - Figures 4 to 7 show a flying body of the aerial device of Figure 2 respectively in a side view, in a rear view, in a top view and in an axonometric bottom view;

[0023] - Figure 8 is an enlarged view of the detail VIII of Figure 7;

[0024] - Figure 9 is a side view of a part of the aerial device in accordance with a second embodiment; - Figure 10 is an enlarged view of the detail X of Figure 9;

[0025] - Figures 11 to 13 show the part of the aerial device of Figure 9 respectively in a rear view, in a top view, and in an axonometric rear view;- Figures 14 to 17 show a part of the aerial device in accordance with a third embodiment respectively in a side view, in a rear view, in a top view and in an axonometric front view; - Figures 18 to 21 show a part of the aerial device in accordance with a fourth embodiment respectively in a side view, in a rear view, in a bottom view and in an axonometric front view; - Figures 22 and 23 show, respectively in a rear view and in a side view, the flying body of the aerial device in a storage configuration, in accordance with a fifth embodiment;

[0026] - Figures 24 and 25 show, respectively in an axonometric rear view and in a rear view, the flying body of the aerial device in a storage configuration, in accordance with a sixth embodiment. As already indicated above, the context for this invention is that of harnessing energy from a wind current 99, by means of an apparatus 1 which comprises an anchoring base 40 and a flying body 10 which is connected to the anchoring base 40 by a tether cable 20. The anchoring base 40 may comprise a device which, by maintaining or changing the length of the tether cable 20, is suitable for keeping the flying body 10 at a fixed distance or at a variable distance; in particular, the length of the tether cable 20 is increased during a take-off step of the flying body 10 and is reduced during a landing step of the flying body 10. For example, that device is a motor-driven revolving drum on which the tether cable 20 is wound.

[0027] The flying body 10 in use is kept airborne by the wind current 99 and also receives from the wind current 99 a force which tends to move it away from the anchoring base 40. Since the flying body 10 is constrained to the anchoring base 40 by the tether cable 20, it applies a pulling force 98 to the anchoring base 40. In other words, the tether cable 20 connects the flying body 10 to the anchoring base 40 and transmits to the latter the pulling force 98 which the flying body 10 develops, when it is airborne, thanks to the wind current 99 and to the speed of the flying body 10 itself.

[0028] The anchoring base 40 is configured to use the pulling force 98 applied to it by the flying body 10. Specifically, the pulling force 98 is usable as a force for movement (for example, for propelling a boat 2) or is convertible into energy to be used (for example into electric energy, by means of an electric generator associated with an element that is movable under the action of the pulling force 98 applied by the tether cable 20, similarly to what is described in US 2015 / 0097086 A1).

[0029] In one possible variant, the anchoring base 40 only constrains the flying body 10 and energy is harnessed directly by the flying body 10, which for example is provided with propellers connected to electric generators on board the flying body 10, those electric generators converting rotation of the propellers produced by the wind current 99 into electric energy (similarly to what is described in US 2013 / 0221154 A1). The electric energy produced may be stored in on board batteries or may be transmitted directly to the anchoring base 40 by means of an electrical cable.

[0030] This description focuses mainly on the aspects of the flying body 10 and on the aspects of an aerial device comprising the flying body 10 and the tether cable 20, whilst the aspects relating to the anchoring base 40 may be in accordance with the prior art and it does not seem necessaryto describe them in more detail.

[0031] The tether cable 20 has a first end 21 connected to the flying body 10 and a second end 22 (opposite the first end 21) which, in use, is connected to the anchoring base 40, so that the flying body 10, constrained to the anchoring base 40 by the tether cable 20, when airborne receives a force from the wind current 99 and applies the pulling force 98 to the anchoring base 40 along a pulling line, similarly to how a kitesurfing kite applies a pulling force to a kite surfer and his or her board.

[0032] In some embodiments, as described below, the first end 21 of the tether cable 20 is connected to the flying body 10 by a plurality of bridles 30 to constrain the movements of the flying body 10, stabilising its flight (as happens for example to the sail of a paraglider which is stabilised by the weight of the pilot), and to control an angle of attack of the wings of the flying body 10 relative to the wind current 99. Each bridle 30 is constrained to a respective connecting point 13 on the flying body 10 and has a respective length. For example, the aerial device comprises at least three bridles 30 which are constrained to three respective connecting points 13. That is useful for limiting the degrees of rotational freedom of the flying body 10 relative to axes of rotation transversal to the line of the tether cable 20. In particular, the plurality of bridles 30 comprises four bridles 30, of which two are longitudinal bridles 31, 32 (which determine an angle of attack of the flying body 10 relative to the wind current 99) and two are lateral bridles 33, 34 (which laterally stabilise the flying body 10 and distribute the load better).

[0033] However, in some embodiments, the first end 21 of the tether cable 20 may be mounted directly on the flying body 10.

[0034] The flying body 10 comprises a closed wing structure, a plurality of movable aerodynamic surfaces, and one or more motors 150 for manoeuvring the flying body 10. The one or more motors 150 are positioned on the closed wing structure (that is to say, they are on board the closed wing structure) and are provided with propellers. The flying body 10 also comprises an electronic system, which is operatively connected to the movable aerodynamic surfaces and to the one or more motors 150. The electronic system is configured to manage the flight of the flying body 10, that is to say, is an electronic flight management system which controls the flight (in particular, also based on information supplied by sensors as explained below) and, by moving the movable aerodynamic surfaces and / or issuing commands to the one or more motors 150, maintains or changes the trajectory and the position of the flying body 10 relative to the wind current 99, as well as (acting on the movable aerodynamic surfaces) adjusting the lift of the closed wing structure. For example, the movable aerodynamic surfaces are ailerons, flaps, slats.

[0035] As already remarked in relation to prior art, it is useful for the flying body 10 to follow a curved trajectory relative to the anchoring base 40, in order to obtain pulling forces greater than those obtainable with a static positioning of the flying body in the wind current 99. Therefore, the electronic system is configured to make the flying body 10 follow a curved trajectory, thanks tothe movement of the movable aerodynamic surfaces and / or to the one or more motors 150, appropriately commanded.

[0036] The motors 150, provided with propellers, are used in the take-off step to position the flying body 10 in the wind current 99 and in the return step to bring the flying body 10 back to the anchoring base 40. When the wing structure of the flying body 10, during flight, generates enough lift to support the weight of the flying body 10, the electronic flight management system controls the movable aerodynamic surfaces to implement and control the trajectory required for the flying body 10 supported by the wind current 99; in that condition the motors 150, also controlled by the electronic flight management system, can be switched off to save energy, or can also be used to implement and control the trajectory required for the flying body 10.

[0037] Basically, depending on the step of the flight and the operating conditions, the flying body 10 is manoeuvred by acting only on the movable aerodynamic surfaces, by acting only on the motors 150, or by acting both on the movable aerodynamic surfaces and on the motors 150.

[0038] In some flight conditions the motors 150 may be used as electric generators, harnessing the movement of the propellers produced by the wind current 99: the propellers are used into the wind as a micro wind turbine. Therefore, electric energy is produced which, for example, is useful for powering the electric components of the flying body 10.

[0039] In the embodiment illustrated herein the closed wing structure, in a front view of the flying body 10, has a substantially quadrilateral shape - in which it is possible to identify four sides opposite each other in pairs and four vertices - and which comprises two main wings 110 and two lateral joining wings 120: the two main wings 110 respectively form two first opposite sides 101 of the closed wing structure (in the front view, the wing span of each main wing 110 defines one of the two first opposite sides 101), whilst the two lateral joining wings 120 respectively form two second opposite sides 102 of the closed wing structure (in the front view, the wing span of each lateral joining wing 120 defines one of the two second opposite sides 102); each lateral joining wing 120 joins the two main wings 110 to each other (at one of the two second opposite sides 102). For the purposes of this description of the closed wing structure, it makes no difference if the flying body 10 is seen from the front or from the rear, as in some of the accompanying figures.

[0040] They are rigid wings, that is to say, they keep their shape on their own (with small deformations under stress). For example the wings are made of composite material with fibreglass or carbon fibres.

[0041] The main wings 110 and the lateral joining wings 120 comprise respective wing portions which are fixed, and respective movable wing portions which at least partly define the movable aerodynamic surfaces of the flying body 10 and by means of which it is possible to change the wing profiles of the main wings 110 and of the lateral joining wings 120; the flying body 10 comprises actuators which are associated with those movable wing portions for their movement and which are controllable by the electronic flight management system. More construction detailsabout the main wings 110 and the lateral joining wings 120 are provided in the description below. The two main wings 110 are “main” since they are configured to interact with the wind current 99 in such a way as to generate all or most of the pulling force 98 applied to the anchoring base 40, therefore they are directly linked to the aim of the aerial device. It is useful for each main wing 110 to have - or in any case to be able to adopt - an overall wing profile which is asymmetrical, so that in use it generates greater lift and greater pulling forces 98 acting on the anchoring base 40.

[0042] The two lateral joining wings 120 are configured to interact with the wind current 99 in such a way as to support at least part of the weight of the flying body 10, when the main wings 110 generate the pulling force 98. It is useful for each lateral joining wing 120 to have - or in any case to be able to adopt - an overall wing profile which is symmetrical, since the flight trajectory of the flying body 10 may involve rotations such that a same surface of the lateral joining wing 120 acts as the top surface in some parts of the trajectory and acts as the bottom surface in other parts of the trajectory.

[0043] The closed wing structure has a mid-sagittal plane (an imaginary plane, not a physical component of the structure) which intersects the two main wings 110 and relative to which the two lateral joining wings 120 are arranged so that they are substantially symmetrical to each other; in particular, the mid-sagittal plane corresponds to a plane of symmetry of the closed wing structure, even more particularly it is a plane of symmetry of the entire structure of the flying body 10 (that is to say, of the assembly of structural elements of the flying body 10). Using an anatomical analogy, the mid-sagittal plane is for the closed wing structure what the sagittal anatomical plane is for the human body.

[0044] In the embodiments illustrated, the closed wing structure is a box-wing, therefore in the front view of the flying body 10 the two main wings 110 and the two lateral wings form four sides of a square, or four sides of a rectangle (depending on the wing spans of the two main wings 110 and of the two lateral joining wings 120).

[0045] The flying body 10 has a front face 11, facing an airflow which determines the lift of the wings, and a rear face 12 facing the opposite way to the front face 11. The expressions “frontwards” and “rearwards” shall be considered herein to respectively refer to a front direction, in which the front face 11 is directed, and a rear direction, in which the rear face 12 is directed.

[0046] On the front face 11 of the flying body 10, the two main wings 110 and the two lateral joining wings 120 have respective leading edges. Vice versa, on the rear face 12 the two main wings 110 and the two lateral joining wings 120 have respective trailing edges. Quoting here definitions used in the field: the “leading edge” of a wing (also called the “attack edge”) is understood to be the forward-most edge where the wing separates an airflow into two different airflows; the “trailing edge” of a wing (also called the “rear edge”) is understood to be the rear retracted edge where in use the two different airflows reunite.The two main wings 110 have respective chords which, in some embodiments, lie in two respective main planes which are parallel to each other and which are perpendicular to the mid-sagittal plane, each main wing 110 extending mainly planar in its main plane. It should be noticed that “chord” means a segment (imaginary) which, in the wing profile, joins the leading edge and the trailing edge of the wing to each other.

[0047] The two lateral joining wings 120 have respective chords which preferably lie in two respective lateral planes parallel to each other and parallel to the mid-sagittal plane.

[0048] According to an innovative aspect of the aerial device described herein, the flying body 10 comprises a stabilising wing 130 for stabilising the flight of the flying body 10, that is to say, for aerodynamically stabilising the flying body in flight. That stabilising wing 130 joins the two main wings 110 to each other and is at the mid-sagittal plane so that, in the front view of the flying body 10, the stabilising wing 130 extends substantially at an equal distance from the two lateral joining wings 120. The stabilising wing 130 has a thickness perpendicular to the mid-sagittal plane and a chord which extends parallel to the mid-sagittal plane. Specifically, the stabilising wing 130 is parallel to the two lateral joining wings 120 and is in the middle between them in the front view (or in the similar rear view of the flying body 10). In particular, since the stabilising wing 130 also extends between the two main wings 110, the length of the stabilising wing 130 is roughly equal, or at least comparable, to the length of the lateral joining wings 120.

[0049] The stabilising wing 130 is at least partly outside a region contained between the two lateral joining wings 120, that is to say, outside a space which separates the two lateral joining wings 120 from each other: in particular, the stabilising wing 130 projects frontwards beyond the leading edges of the two lateral joining wings 120 (that is to say, the leading edge of the stabilising wing 130 is positioned ahead of the leading edges of the two lateral joining wings 120) or, alternatively, it projects rearwards beyond the trailing edges of the two lateral joining wings 120 (that is to say, the trailing edge of the stabilising wing 130 is positioned behind the trailing edges of the two lateral joining wings 120). In use, in a view projected on the mid-sagittal plane in which the two lateral joining wings 120 are superposed on each other, the stabilising wing 130 is only partly superposed (or is not superposed at all) on the lateral joining wings 120.

[0050] The stabilising wing 130 shaped in this way gives the flying body 10 greater stability 10 than the stability that the closed wing structure itself has. In particular, the stabilising wing 130 increases the rotational stability relative to an axis of rotation parallel to the pulling line (that along which, in use, the flying body 10 applies the pulling force 98 to the anchoring base 40, that is to say, the line of the taut tether cable 20) and passing through the barycentre of the flying body 10. In practice, the stabilising wing 130 behaves as if it were a “tail” or a canard of the closed wing structure; thanks to its large lengthwise extent between the two main wings 110, the stabilising effect is obtained without the need to position the stabilising wing 130 at a considerable distance from the closed wing structure, that is to say, without requiring a long fuselage which connectsthe closed wing to the stabilising wing. That is useful for limiting the overall dimensions of the flying body 10.

[0051] Limiting of the overall dimensions is demonstrated by the fact that, at least in some embodiments, an orthogonal projection of the flying body 10 on the mid-sagittal plane has a depth dimension which is less than a width dimension and a height dimension - in the front view of the flying body 10 - of the substantially quadrilateral shape of the closed wing structure.

[0052] Moreover, the presence of the stabilising wing 130 which connects the two main wings 110 to each other at the mid-sagittal plane gives the rigid wing structure greater stiffness, avoiding the need for other stiffening elements which would only increase the weight.

[0053] Preferably, the stabilising wing 130 has a symmetrical wing profile for which the mid-sagittal plane defines a plane of symmetry.

[0054] According to the evaluations carried out by the inventor, the alternative in which the stabilising wing 130 projects frontwards beyond the leading edges of the two lateral joining wings 120 appears to be more advantageous for a greater stabilisation of the flying body 10, the dimensions of the stabilising wing being equal. However, even the alternative in which the stabilising wing 130 projects rearwards allows effective stabilisation to be achieved.

[0055] In some embodiments, the stabilising wing 130 is completely outside the region contained between the two lateral joining wings 120: in an alternative, the stabilising wing 130 projects frontwards in its entirety beyond the leading edges of the two lateral joining wings 120, that is to say, the trailing edge of the stabilising wing 130 is positioned ahead of the leading edges of the two lateral joining wings 120, and the stabilising wing 130 therefore is frontal (it is frontally ahead with respect to the two lateral joining wings 120); in the other alternative, the stabilising wing 130 projects rearwards in its entirety beyond the trailing edges of the two lateral joining wings 120, that is to say, the leading edge of the stabilising wing 130 is positioned behind the trailing edges of the two lateral joining wings 120, and the stabilising wing 130 therefore is rear (it is rearwards retracted with respect to the two lateral joining wings 120). That allows interference between the flows generated by the different wings of the flying body 10 to be limited.

[0056] For similar reasons, in some embodiments in which the stabilising wing 130 projects frontwards beyond the lateral joining wings 120, the same stabilising wing 130 also projects frontwards beyond the leading edge of one of the two main wings 110, or beyond the leading edges of both of the two main wings 110. Similarly, in some of the embodiments in which the stabilising wing 130 projects rearwards beyond the lateral joining wings 120, the stabilising wing 130 also projects rearwards beyond the trailing edge of one of the two main wings 110, or beyond the trailing edges of both of the two main wings 110.

[0057] In some embodiments the flying body 10 comprises two stabilising wings 130: a front stabilising wing 130a which projects frontwards beyond the leading edges of the two lateral joining wings 120 (as already described above) and a rear stabilising wing 130b which projects rearwardsbeyond the trailing edges of the two lateral joining wings 120. In a way very similar to the front stabilising wing 130a, the rear stabilising wing 130b also joins the two main wings 110 to each other, is at the mid-sagittal plane, and is at least partly outside the region contained between the two lateral joining wings 120, but on the opposite side to the front stabilising wing 130a. In one embodiment, the front stabilising wing 130a and the rear stabilising wing 130b are both completely outside the region contained between the two lateral joining wings 120: one projects frontwards in its entirety, the other projects rearwards in its entirety.

[0058] In some embodiments, a tapering connecting element 140 is interposed between the stabilising wing 130 and one of the main wings 110. That tapering connecting element 140 is elongate along a sagittal line and distances the stabilising wing 130 from the closed wing structure. That is also useful for limiting the interference between the flows generated by the different wings of the flying body 10.

[0059] A tapering connecting element 140 such as that just described may also be interposed between the stabilising wing 130 and the other main wing 110, in such a way that there are two respective tapering connecting elements 140 which are interposed between the stabilising wing 130 and the two main wings 110.

[0060] In some of the embodiments comprising the front stabilising wing 130a and the rear stabilising wing 130b, each of the two respective tapering connecting elements 140 is elongate enough to distance the front stabilising wing 130a from the front of the closed wing structure, and to distance the rear stabilising wing 130b from the rear of the closed wing structure. The flying body 10 may also comprise a central tapering element which, positioned at the mid-sagittal plane across the region contained between the two lateral joining wings 120, connects the front stabilising wing 130a to the rear stabilising wing 130b.

[0061] Positioned at the joints between the main wings 110 and the lateral joining wings 120, there may be lateral tapering elements similar to the tapering connecting elements 140, for example in the case of the embodiments illustrated.

[0062] According to a possible embodiment (not illustrated), which is an alternative to that in which the flying body 10 comprises the front stabilising wing 130a and the rear stabilising wing 130b (separate from each other), the flying body 10 comprises a single stabilising wing 130 which projects both frontwards beyond the leading edges of the two lateral joining wings 120, and rearwards beyond the trailing edges of the two lateral joining wings 120; however, in accordance with evaluations carried out by the inventor of this invention, it is preferable for the flying body 10 to comprise the front stabilising wing 130a and the rear stabilising wing 130b which are separate from each other.

[0063] The following is a description of several possible variants of the closed wing structure itself, all within the scope of protection of this patent application. In fact, they are variants which do not significantly deviate from a closed wing structure with quadrilateral shape in the front view of theflying body 10, so that the closed wing structure can still be considered a box-wing similarly to the embodiments of Figures 3 to 13.

[0064] In the embodiments in which the mid-sagittal plane corresponds to a plane of symmetry of the closed wing structure, the mid-sagittal plane divides each of the two main wings 110 into two opposite half-wings which are arranged symmetrically relative to the mid-sagittal plane.

[0065] In some embodiments (for example those illustrated in Figures 14 to 17 and in Figures 18 to 21), the two opposite half-wings are arranged in a V-shape in the front view of the flying body 10; in other words, the two half-wings extend lengthwise along two respective longitudinal lines which, in the front view of the flying body 10, are oblique relative to each other, so that the two half-wings are not coplanar and, instead, they form a dihedral angle between them.

[0066] In some embodiments (for example that illustrated in Figures 18 to 21), looking at the top surface (or the bottom surface) of a main wing 110, the two opposite half-wings are arranged in a V-shape, that is to say, their leading edges extend lengthwise along lines which are oblique relative to each other, like an arrowhead; so that a region of main wing 110 at the mid-sagittal plane is further forward than the regions at the lateral joining wings 120. This particular shape may be adopted for both of the main wings 110, as is the case - for example - of the embodiment illustrated in Figures 18 to 21, or for only one of the main wings 110.

[0067] In some embodiments (see for example Figures 6 and 7), the two main wings 110 are offset from each other along the sagittal line, for greater aerodynamic efficiency: the leading edge of a first main wing 110 is positioned further forward than the leading edge of the second main wing 110; this offset can be achieved for example by means of lateral joining wings 120 which are oblique, or by means of tapering connecting elements 140 (and similar lateral tapering elements) - with appropriate length - between the main wings 110 and the lateral joining wings 120. In particular, the two main wings 110 may be completely offset from each other: the trailing edge of the first main wing 110 is positioned further forward than the leading edge of the second main wing 110 (this is the case for example of the embodiments illustrated in the accompanying figures). In other embodiments, the two main wings 110 are not offset along the sagittal line.

[0068] Some possible design details of the wings are now described.

[0069] Each main wing 110 comprises a fixed wing portion having a preferably asymmetrical wing profile, and one or more first movable wing portions for changing the overall profile of the main wing 110, especially at the leading edge (for example, slats) and / or at the trailing edge (for example, flaps). The first movable wing portions at least partly define the movable aerodynamic surfaces of the flying body 10. In particular, the main wings 110 have ailerons for carrying out flight manoeuvres, and aerodynamic appendices on the leading edge (slats) and on the trailing edge (flaps) for maximising lift and therefore the pulling force 98 on the tether cable 20; that is illustrated by way of example in Figure 8 (in particular, please notice the slat at the leading edge, and two flaps at the trailing edge). For example, the flaps and the slats of the main wings 110 are divided betweenthe respective half-wings so that, as well as serving to increase the lift of the main wings 110, they can also be used as ailerons for flight manoeuvres.

[0070] First actuators, controllable by the electronic flight management system, are associated with those one or more first movable wing portions for moving them into the positions set by the electronic flight management system.

[0071] In some embodiments, for example those illustrated in the figures, the two main wings 110 are wings with a constant chord. In some embodiments, for example that illustrated in Figure 7 and that illustrated in Figure 13, the two main wings 110 are straight wings which extend lengthwise parallel to each other.

[0072] Each lateral joining wing 120 has a fixed portion, having a preferably symmetrical wing profile of which one of the two lateral planes defines a plane of symmetry. Each lateral joining wing 120 also comprises one or more second movable wing portions for changing the overall profile of the lateral joining wing 120 and for manoeuvring the flying body 10 (in particular for making the flying body 10 follow the curved trajectory 109 already commented on above with reference to the prior art). The second movable wing portions at least partly define the movable aerodynamic surfaces of the flying body 10. In particular, the lateral joining wings 120 have second movable wing portions on the trailing edge whose function is that of both ailerons and of flaps. For example, the second movable wing portions are ailerons which may also be used as flaps to increase the lift of the lateral joining wings 120 (whose fixed portions have a symmetrical wing profile by themselves).

[0073] Second actuators 151, controllable by the electronic flight management system, are associated with those one or more second movable wing portions for moving them into the positions set by the electronic flight management system. Specifically, the one or more second movable wing portions are at the trailing edge, that is to say, they are rear movable portions, and are movable between two limit positions which are specular relative to the plane of symmetry of the wing profile of the fixed portion. In practice, the lateral joining wings 120 have symmetrical profiles, which become asymmetrical thanks to flaps (that is to say, said rear movable portions) which can tilt on both sides. That is illustrated in detail in Figure 8, where the following are visible: a fixed portion, at the leading edge of the lateral joining wing 120 (on the propeller side of the motor 150), and, at the trailing edge (on the side that is opposite to the propeller), two respective rear movable portions associated with two respective second actuators 151. In the figures, for simplicity of illustration, the second movable wing portions of the lateral joining wings 120 are only illustrated in the embodiment to which Figures 3 to 8 refer; however, it shall be understood that the second movable wing portions are also present in the other embodiments illustrated.

[0074] Preferably, the two lateral joining wings 120 are straight wings - preferably with a constant chord - which extend lengthwise parallel to each other. In some embodiments, the two lateral joining wings 120 extend lengthwise parallel to a line which is oblique relative to the main planes of thetwo main wings 110 (those embodiments include for example that to which Figures 9 to 13 refer); that allows an increase in the lift achievable by the two lateral joining wings 120 to counter the weight of the flying body 10. In other embodiments, the two lateral joining wings 120 extend lengthwise parallel to a line which is substantially perpendicular to the main planes of the two main wings 110 (for example the embodiment shown in Figures 4 to 8); that allows the obtainment of a closed wing structure which is structurally more rigid and easier to build and to assemble. Regarding the stabilising wing 130, it is also rigid and can be made of the same composite material already mentioned for the main wings 110 and for the lateral joining wings 120.

[0075] In some embodiments, the stabilising wing 130 comprises one or more third movable wing portions (and one or more relative third actuators, controllable by the electronic flight management system) for changing the profile of the stabilising wing 130, similarly to what was described relative to the lateral joining wings 120.

[0076] The following is a description of several details about the motors 150, the electronic flight management system, and the tether cable 20.

[0077] The flying body 10 preferably comprises four motors 150, which are positioned at the four vertices of the substantially quadrilateral shape of the closed wing structure.

[0078] In the embodiments illustrated, each motor 150 is an electric motor equipped with a propeller mounted at the front so that, when the motor 150 is activated, the propeller directs - onto the neighbouring parts of the main wings 110 and of the lateral joining wings 120 - an accelerated airflow which increases the lift generated by the wings. The flying body 10 also comprises an electricity storage battery (such as a rechargeable electric battery) from which the one or more motors 150 draw energy in order to operate; in flight conditions in which the motors 150 may be used as electric generators by harnessing the movement of the propellers produced by the wind current 99, the electric energy produced is used to charge the electricity storage battery. In other words, the flying body 10 is equipped with an active system having electric motors with propellers and which is used for taking off, landing, in-flight manoeuvring, and charging the electric battery. The electronic flight management system (in other words: an on board computer), which is operatively connected to the one or more motors 150 and which manages the flight of the flying body 10, is also connected to the actuators of the movable aerodynamic surfaces (that is to say, of the movable wing portions) and to on board sensors of the flying body 10. Specifically, the electronic flight management system is capable of making the flying body 10 fly completely autonomously: a human operator only has to decide to activate and switch off, whereas the electronic flight management system decides if the correct conditions exist for operation (wind speed and direction, system functionality not compromised, etc.).

[0079] In particular, the on board sensors of the flying body 10 comprise sensors for identifying the wind speed (anemometer), the position and trajectory of the flying body 10 (GPS), the pulling force on the tether cable 20 (load cell). Thanks to them, the electronic flight management system receivesdata about the flying body 10, for example the position and the speed of the flying body 10, data about the wind current 99 and / or data about the pulling force 98 generated. The on board sensors also comprise sensors for feedback on the proper operation of all components.

[0080] That plurality of sensors is useful for allowing the electronic flight management system an operational autonomy, however a manual control by an operator is possible (for example, by means of a remote control), full or only partial (for example, only for carrying out take-off and / or landing manoeuvres).

[0081] Regarding the tether cable 20, for example it is made of Dyneema. This material is advantageous because it has a specific weight which is around eight times less than steel, a tensile strength similar to that of steel, low stretch when pulled, and high resistance to wear caused by bad weather. The tether cable 20 has a length such that it allows the flying body 10 to reach altitudes where the wind is stronger, for example altitudes greater than 200 metres.

[0082] The following is a description of some example details about the operating principle.

[0083] The flying body 10 takes off vertically and moves away from the anchoring base 40 in the direction of the wind current 99, with the tether cable 20 kept taut by the revolving drum of the anchoring base 40. Take-off is performed using the motors 150. In particular, the electronic flight management system is configured to make the flying body 10 adopt a take-off set-up in which the two main wings 110 and the two lateral joining wings 120 have the respective chords arranged substantially vertical and in which the one or more motors 150 are activated and manoeuvre the flying body 10 in flight by generating a supporting force opposite to the force of the weight of the flying body 10. The tether cable 20 is gradually unwound from the revolving drum, in such a way that the tether cable 20 is always slightly taut.

[0084] Once a predetermined distance from the anchoring base 40 has been reached, the flying body 10 starts to fly using the lift of the wings and consequently the motors 150 begin operating less and less until they stop. The flying body 10 moves on a curved trajectory 109 that is lemniscate I figure-of-eight shaped (Figure 2), in such a way as to increase its speed and therefore to increase the lift of the main wings 110, thereby increasing the pulling force 98 which the tether cable 20 applies to the anchoring base 40. Said curved trajectory 109 is substantially perpendicular to the axis of the tether cable 20 (Figure 1). During the pulling step, the flying body 10 flies with the main wings 110 orthogonal to the tether cable 20, whilst the lift of the lateral joining wings 120 supports the weight of the flying body 10 itself. The electronic flight management system is configured to make the flying body 10 adopt this transversal flight set-up in which the flying body 10 travels along the lemniscate curved trajectory 109. In practice, along the lemniscate trajectory the flying body 10 repeatedly follows a semi-straight stretch in a first direction, a 180° turn, a semi-straight stretch in a second direction substantially opposite to the first direction, a new 180° turn, and so on. To make the turns, the flying body 10 uses the ailerons of the lateral joining wings 120 and of the main wings 110, appropriately operated by the electronic flight management system. Duringthe flight, the flying body 10 therefore consumes energy present in the on board electricity storage battery. When the charge level of the electricity storage battery drops below a threshold value, the electronic flight management system activates the “micro wind turbine” mode of the propellers of the motors 150, generating energy but slowing the flying body 10. Therefore, during the charging step of the electricity storage battery the pulling force 98 on the tether cable 20 is lower. When a return to the anchoring base 40 and landing are necessary, they can be carried out in a similar manner to the take-off operations but performed in reverse. The electronic flight management system issues commands for the return flight of the flying body 10, and the revolving drum gradually winds in the tether cable 20.

[0085] Basically, the aerial device described herein may be seen as a combination of a drone, a glider, and a paraglider.

[0086] This invention also relates to the apparatus 1 for harnessing energy from a wind current 99: that apparatus 1 comprises the aerial device (in turn comprising the flying body 10 and the tether cable 20, whose first end 21 is connected to the flying body 10) and the anchoring base 40 to which the second end 22 of the tether cable 20 is connected. As already mentioned, the anchoring base 40 is configured to use the pulling force 98 applied to the anchoring base 40 by the flying body 10. In possible embodiments not shown in the figures, the pulling force 98 is convertible into energy to be used, for example it is convertible into electric energy by means of an electric generator associated with a movable element on which the second end 22 of the tether cable 20 is mounted. In the embodiment shown in Figure 1, the pulling force 98 is usable as a force for movement, in particular for propelling a boat 2, for example a ship. In other words, it is a system for pulling ships which harnesses wind power.

[0087] In fact, this invention also relates to a boat 2 equipped with said apparatus 1, wherein the anchoring base 40 is fixed to the boat 2 and the pulling force 98 contributes to propel the boat 2. That is useful for reducing the use of fuel for propelling the boat 2.

[0088] In general, it is advisable for the flying body 10 to reach the maximum height possible above the ground or above the sea, so as to be able to harness the greater strength of the wind higher up. At the same time, for the specific use as a system for pulling ships it is useful for the flying body 10 to fly in such a way as to maintain an angle between the horizon and the axis of the tether cable 20 which is not greater than 35°; in fact, at greater angles, the pulling in the direction of movement of the boat 2 (that is to say, the horizontal component of the pulling force 98 applied by the tether cable 20) is considerably reduced and therefore the pulling system loses efficiency. Depending on requirements, the flying body 10 may be made with dimensions ranging from several metres to tens of metres. For example, if the system is used for pulling ships, it is useful for the quadrangular shape of the flying body 10 to have sides with lengths which are roughly 20 metres.

[0089] In some embodiments, the flying body 10 comprises wings which are foldable, in order to reducethe dimensions of the flying body 10 when the device is not used and the flying body 10 is in a warehouse, in a storage unit, or is being transported. It should be noticed that the aspects relating to the foldable wings are also applicable to a flying body 10 without the stabilising wing 130 and may form a separate invention independent from the invention relating to the stabilising wing. The Applicant reserves the right to separately protect the invention relating to the foldable wings through a divisional patent application or a further patent application which claims the priority of this patent application.

[0090] Specifically, the wings of the flying body 10 may be divided into a first group of wings, of which the two main wings 110 are part, and into a second group of wings, of which the two lateral joining wings 120 are part. In the embodiments provided with a stabilising wing 130, the stabilising wing 130 (or the front stabilising wing 130a and the rear stabilising wing 130b, if both are present) are part of the second group of wings.

[0091] In the embodiments illustrated there are no other wings, other than those mentioned above; therefore, the first group of wings is formed by the two main wings 110, and the second group of wings is formed by the two lateral joining wings 120 and by the stabilising wing 130 (or by the stabilising wings 130).

[0092] The foldable wings are the wings of the first group of wings, or the wings of the second group of wings. In a possible embodiment not shown herein, the wings of both of the groups are foldable. Each foldable wing has at least one hinge 160 having a hinge axis which is transversal to a line of lengthwise extension of the foldable wing. The hinge 160 allows a relative rotation of stretches of foldable wing: the hinge 160 is interposed between two consecutive stretches of wing and, thanks to the hinge 160, a first stretch can rotate around the hinge axis relative to the second stretch. In that way the foldable wing is switchable between an operating condition, in which the foldable wing is spread out with maximum length (for example, the first stretch and the second stretch are aligned with each other and are coplanar), and a folded condition, in which the stretches of foldable wing are rotated towards each other. Specifically, the hinge axes of the foldable wings are parallel to each other, so that the foldable wings can all be folded in a coordinated way.

[0093] Thanks to the foldable wings, the flying body 10 is switchable between a flight configuration, in which the foldable wings are in the operating condition and are spread out to form the closed wing structure (having the substantially quadrilateral shape in the front view), and a storage configuration, in which the foldable wings are in the folded condition and the wings of the other group of wings are drawn near each other, thereby reducing a dimension in the front view of the closed wing structure. For example, the flying body 10 in the storage configuration is folded closed (Figure 25). Considering the need to put the flying body 10 somewhere sheltered - when it is not in use - in a hangar with dimensions suitable for the dimensions of the flying body 10, the possibility of switching the flying body 10 from the operating configuration to the storageconfiguration allows the use of hangars with smaller dimensions, the working wing surface area of the flying body 10 being equal. That is particularly useful in the case of the system for pulling ships, since on a ship the areas available for sheltering the flying body 10 are obviously limited. Figures 22 and 23 show an embodiment in which the flying body is in the storage configuration and in which the foldable wings are the main wings 110. It should be noticed that each foldable wing is divided into three stretches (of which one is central, across the mid-sagittal plane) and is provided with four hinges 160. One wing is folded inwards towards the inside of the quadrilateral shape, whilst the other wing is folded outwards. In the storage configuration, the lateral joining wings 120 are drawn near each other and the width of the flying body 10 is considerably reduced compared with the flight configuration.

[0094] Figures 24 and 25 show an embodiment in which the foldable wings are the lateral joining wings 120 and the stabilising wing 130. Each foldable wing is divided into two stretches, which are hinged to each other; each stretch is also hinged to the respective main wing 110 (or, for the stabilising wing 130, to the respective tapering connecting element 140). The lateral joining wings 120 are folded outwards from the quadrilateral shape; however, in one variant, both of the lateral joining wings 120 may be folded inwards towards the inside of the quadrilateral shape. In the storage configuration, the main wings 110 are drawn near each other and the height of the flying body 10 is considerably reduced compared with the flight configuration.

[0095] To switch the foldable wings between the operating condition and the folded condition (and vice versa), the aerial device (more specifically, the flying body 10) comprises switching actuators operatively connected to the electronic flight management system. In the flight configuration the foldable wings are kept in the operating condition by the switching actuators themselves, which are configured to apply a force such that it counters the forces which, during the flight of the flying body 10, would tend to cause the stretches of foldable wing to rotate relative to each other. Since the main wings 110 may be subjected to greater stresses than the lateral joining wings 120 (and the stabilising wing 130) during generation of the pulling force 98, in some cases it is preferable that, for the purposes of greater structural stiffness of the main wings 110, the two lateral joining wings 120 (and the stabilising wing 130) are foldable but not the two main wings 110.

[0096] In some embodiments, a first bridle 31 and a second bridle 32 of the plurality of bridles 30 are length-adjustable, and the flying body 10 comprises an adjusting device 170 which is activatable (and is controlled) by the electronic flight management system.

[0097] It should be noticed that the aspects relating to the adjustable bridles are also applicable to a flying body 10 without the stabilising wing 130 and may form a separate invention independent from the invention relating to the stabilising wing. The Applicant reserves the right to separately protect the invention relating to the adjustable bridles through a divisional patent application or a further patent application which claims the priority of this patent application.The adjusting device 170 is configured to adjust the respective lengths of the first bridle 31 and of the second bridle 32 by means of a coordinated adjustment such that a lengthening of one, of either the first bridle 31 or the second bridle 32, corresponds to a shortening of the other, of either the first bridle 31 or the second bridle 32.

[0098] The coordinated adjustment of the length of the first bridle 31 and of the length of the second bridle 32 allows adjustment and changing of the angular position of the flying body 10. Specifically, the two respective connecting points 13 on the flying body 10 to which the first bridle 31 and the second bridle 32 are constrained are selected in such a way as to have control of the angle of incidence (also known as the angle of attack) with which the two main wings 110 split the wind current 99; in this configuration, the first bridle 31 and the second bridle 32 are the two longitudinal bridles already previously mentioned. For example, the two respective connecting points 13 are at the two first opposite sides 101 of the closed wing structure, in particular at the tapering connecting elements 140 interposed between each main wing 110 and the stabilising wing 130 (or, in another embodiment, between the front stabilising wing 130a and the rear stabilising wing 130b).

[0099] Regarding the lateral bridles 33 and 34, in the embodiments illustrated they have the same length; in other embodiments if necessary even the lateral bridles 33 and 34 may be length-adjustable in a coordinated way, similarly to what was described herein for the longitudinal bridles 31 , 32. In the embodiment shown in Figures 9 to 13, the first bridle 31 and the second bridle 32 are respectively part of a first cable 310 and of a second cable 320 which are slidable relative to the flying body 10. In particular, the first cable 310 and the second cable 320 each extend from the tether cable 20 to the adjusting device 170 and are constrained to the adjusting device 170. The first cable 310 has a portion, between the tether cable 20 and its respective connecting point 13 (first connecting point) on the flying body 10, which defines the first bridle 31: the first connecting point 13 acts as a channelling point at which the first cable 310 is channelled into a guided path towards the adjusting device 170 (for example, a pulley 172 is present at the connecting point 13); the portion of the first cable 310 which extends between the first connecting point 13 and the tether cable 20 is that which defines the first bridle 31.

[0100] Similarly, the second cable 320 has a portion, between the tether cable 20 and its respective connecting point 13 (second connecting point) on the flying body 10, which defines the second bridle 32. In this case too, the second connecting point 13 acts as a channelling point at which the second cable 320 is channelled into a guided path towards the adjusting device 170 (for example, a pulley 172 is present at the connecting point 13); the portion of the second cable 320 which extends between the second connecting point 13 and the tether cable 20 is that which defines the second bridle 32.

[0101] It should be noticed that the first cable 310 and the second cable 320 may be separate cables (each having one end constrained to the adjusting device 170), or they may be consecutiveportions of a single cable (arranged in a ring between the tether cable 20 and the adjusting device 170); that does not form a substantial technical difference for the way in which they are adjusted as described herein.

[0102] The coordinated adjustment corresponds to a release of one of either the first cable 310 or the second cable 320, and to a retraction of the other of either the first cable 310 or the second cable 320, so that the first cable 310 and the second cable 320 slide relative to the connecting points 13 (points which are fixed relative to the rest of the flying body 10) and the lengths of the first bridle 31 and of the second bridle 32 (the respective lengths of the portions of the first cable 310 and of the second cable 320 which define the first bridle 31 and the second bridle 32) are changed. In the specific embodiment illustrated in Figures 9 to 13, the respective connecting points 13 to which the first bridle 31 and the second bridle 32 are constrained are at the opposite sides formed by the two main wings 110 (the two first opposite sides 101, see for example Figure 5), and at least one of the two cables (or the single cable arranged in a ring shape) is slidable inside the rear stabilising wing 130b (in other embodiments, which may or may not comprise the rear stabilising wing 130b, at least one of the two cables or the single cable arranged in a ring shape is slidable inside the stabilising wing 130).

[0103] Moreover, the adjusting device 170 may comprise a winch (for example, positioned inside one of the two tapering connecting elements 140), having a motor-driven revolving drum 171 on which respective portions of the first cable 310 and of the second cable 320 are wound (or rather, a stretch of the individual cable, if the first cable 310 and the second cable 320 are not physically separate cables). In those embodiments, a rotation of the motor-driven revolving drum 171 corresponds to a further winding of one of either the first cable 310 or the second cable 320, and to an unwinding of the other of either the first cable 310 or the second cable 320, thereby implementing the coordinated adjustment.

[0104] The adjusting device 170 may however differ from the one described above: in a possible variant, for example, the first cable 310 and the second cable 320 have two respective ends mounted on two opposite ends of a chain, or of a belt (preferably toothed), which is partly wound on a motor-driven pulley responsible for the coordinated adjustment.

[0105] Resuming what was already mentioned above, the change in the relative length of the first bridle 31 and of the second bridle 32 (which are connected to the sides of the main wings 110, that is to say, are longitudinal bridles) allows a change in the angle of attack of the main wings 110, thereby changing their lift and drag. In particular, the range for change of the angle of attack may be very wide (for example, roughly 90°).

[0106] The possibility of changing the angle of attack is useful in particular for the return step of the flying body 10 towards the anchoring base 40. During the pulling step the first bridle 31 and the second bridle 32 have lengths which are very different from each other in order to position the flying body 10 in such a way that the pulling force 98 is maximised, whilst during the return step it is usefulfor the first bridle 31 and the second bridle 32 to have roughly the same length (thereby reducing the pulling force 98 which counters the return of the flying body 10). Adjustment of the angle of attack and of the lift during the pulling step, in contrast, is faster and easier using the movable wing portions of the main wings 110.

[0107] The invention described above may be modified and adapted in several ways, all falling within the scope of the attached claims.

[0108] All details may be substituted with other technically equivalent elements and the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements.

Claims

CLAIMS1. An aerial device for harnessing energy from a wind current (99), the aerial device comprising a flying body (10), which in use is kept airborne by the wind current (99), and a tether cable (20) having a first end (21) connected to the flying body (10) and a second end (22) which, in use, is connected to an anchoring base (40), so that the airborne flying body (10) receives a force from the wind current (99) and, being constrained to the anchoring base (40) by the tether cable (20), applies a pulling force (98) to the anchoring base (40),wherein:the flying body (10) comprises a closed wing structure, a plurality of movable aerodynamic surfaces, one or more motors (150) for manoeuvring the flying body (10), and an electronic system which is operatively connected to the plurality of movable aerodynamic surfaces and to the one or more motors (150), the one or more motors (150) being positioned on the closed wing structure and being provided with propellers;the electronic system is configured to manage the flight of the flying body (10) and to make the flying body (10) follow a curved trajectory, by moving the movable aerodynamic surfaces and / or issuing commands to the one or more motors (150), so as to maintain or change the trajectory and the position of the flying body (10) relative to the wind current (99);the closed wing structure has a substantially quadrilateral shape in a front view of the flying body (10) and comprises two main wings (110) and two lateral joining wings (120), the two main wings (110) respectively forming two first opposite sides (101) of the closed wing structure and the two lateral joining wings (120) respectively forming two second opposite sides (102) of the closed wing structure, each lateral joining wing (120) joining the two main wings (110) to each other;the flying body (10) has a front face (11), on which the two main wings (110) and the two lateral joining wings (120) have respective leading edges, a rear face (12), on which the two main wings (110) and the two lateral joining wings (120) have respective trailing edges, and a mid-sagittal plane which intersects the two main wings (110) and relative to which the two lateral joining wings (120) are arranged so that they are substantially symmetrical to each other;characterised in that the flying body (10) comprises a stabilising wing (130) for stabilising the flight of the flying body (10),wherein the stabilising wing (130) joins the two main wings (110) to each other and is at the mid-sagittal plane, so that in the front view of the flying body (10) the stabilising wing (130) extends substantially at an equal distance from the two lateral joining wings (120), the stabilising wing (130) having a thickness perpendicular to the mid-sagittal plane and a chord which extends parallel to the mid-sagittal plane; andwherein the stabilising wing (130) is at least partly outside a region contained between thetwo lateral joining wings (120),the stabilising wing (130) projecting frontwards beyond the leading edges of the two lateral joining wings (120), or the stabilising wing (130) projecting rearwards beyond the trailing edges of the two lateral joining wings (120).

2. The aerial device according to claim 1, wherein the stabilising wing (130) projects frontwards in its entirety beyond the leading edges of the two lateral joining wings (120), so that the stabilising wing (130) is frontal and is completely outside the region contained between the two lateral joining wings (120),or wherein the stabilising wing (130) projects rearwards in its entirety beyond the trailing edges of the two lateral joining wings (120), so that the stabilising wing (130) is rear and is completely outside the region contained between the two lateral joining wings (120).

3. The aerial device according to claim 1 or 2, wherein:the stabilising wing (130) projects frontwards beyond the leading edge of one of the two main wings (110), or beyond the leading edges of the two main wings (110); orthe stabilising wing (130) projects rearwards beyond the trailing edge of one of the two main wings (110), or beyond the trailing edges of the two main wings (110).

4. The aerial device according to any one of claims 1 to 3, said stabilising wing (130) being a front stabilising wing (130a) which projects frontwards beyond the leading edges of the two lateral joining wings (120),wherein the flying body (10) comprises a rear stabilising wing (130b) which joins the two main wings (110) to each other and which is at the mid-sagittal plane, so that in a rear view of the flying body (10) the rear stabilising wing (130b) extends substantially at an equal distance from the two lateral joining wings (120), the rear stabilising wing (130b) having a thickness perpendicular to the mid-sagittal plane and a chord which extends parallel to the mid-sagittal plane,and wherein the rear stabilising wing (130b) is at least partly outside the region contained between the two lateral joining wings (120), the rear stabilising wing (130b) projecting rearwards beyond the trailing edges of the two lateral joining wings (120).

5. The aerial device according to any one of claims 1 to 4, wherein the closed wing structure is a box-wing.

6. The aerial device according to any one of claims 1 to 5, wherein the mid-sagittal plane divides each of the two main wings (110) into two opposite wing portions which are arrangedsymmetrically relative to the mid-sagittal plane, wherein, in the front view of the flying body (10), the two opposite wing portions of at least one of the two main wings (110) are arranged in a V-shape.

7. The aerial device according to any one of claims 1 to 6, wherein a tapering connecting element (140) is interposed between the stabilising wing (130) and one of the main wings (110), the tapering connecting element (140) being elongate along a sagittal line and distancing the stabilising wing (130) from the closed wing structure.

8. The aerial device according to any one of claims 1 to 7, comprising a plurality of bridles (30) which connect the first end (21) of the tether cable (20) to the flying body (10), each bridle (30) being constrained to a respective connecting point (13) on the flying body (10) and having a respective length,wherein a first bridle (31) and a second bridle (32) of said plurality of bridles (30) are length-adjustable,wherein the flying body (10) comprises an adjusting device (170) for adjusting the respective lengths of the first bridle (31) and of the second bridle (32) by means of a coordinated adjustment such that a lengthening of one, of either the first bridle (31) or the second bridle (32), corresponds to a shortening of the other, of either the first bridle (31) or the second bridle (32),the adjusting device (170) being activatable and controlled by the electronic system.

9. The aerial device according to claim 8, the first bridle (31) and the second bridle (32) respectively being part of a first cable (310) and of a second cable (320) which are slidable relative to the flying body (10), the first cable (310) and the second cable (320) each extending from the tether cable (20) to the adjusting device (170) and being constrained to the adjusting device (170), the first cable (310) and the second cable (320) being separate cables or being consecutive portions of a single cable, wherein:the first cable (310) has a portion between the tether cable (20) and its respective connecting point (13) on the flying body (10), said portion defining the first bridle (31); andthe second cable (320) has a portion between the tether cable (20) and its respective connecting point (13) on the flying body (10), said portion defining the second bridle (32); the coordinated adjustment corresponding to a release of one, of either the first cable (310) or the second cable (320), and a retraction of the other, of either the first cable (310) or the second cable (320), so that the first cable (310) and the second cable (320) slide relative to the connecting points (13), and the lengths of the first bridle (31) and of the second bridle (32) are changed.

10. The aerial device according to claim 9, wherein the adjusting device (170) comprises a winch having a motor-driven revolving drum (171) on which portions of the first cable (310) and of the second cable (320) are wound, a rotation of the motor-driven revolving drum (171) corresponding to a further winding of one, of either the first cable (310) or the second cable (320), and to an unwinding of the other, of either the first cable (310) or the second cable (320), thereby implementing the coordinated adjustment.

11. The aerial device according to any one of claims 1 to 10, wherein:the two main wings (110) are part of a first group of wings;the two lateral joining wings (120) and the stabilising wing (130) are part of a second group of wings;the wings of one, of either the first group of wings or the second group of wings, are foldable, each foldable wing has at least one hinge (160) having a hinge axis which is transversal to a line of lengthwise extension of the foldable wing, the hinge (160) allowing a relative rotation of stretches of foldable wing, so that the foldable wing is switchable between an operating condition, in which the foldable wing is spread out with maximum length, and a folded condition, in which the stretches of foldable wing are rotated towards each other;the hinge axes of the foldable wings are parallel to each other; andthe flying body (10) is switchable between a flight configuration, in which the foldable wings are in the operating condition and are spread out to form the closed wing structure having the substantially quadrilateral shape in the front view, and a storage configuration, in which the foldable wings are in the folded condition and the wings of the other, of either the first group of wings or the second group of wings, are drawn near each other, thereby reducing a dimension in the front view of the closed wing structure.

12. The aerial device according to claim 11, comprising switching actuators for switching the foldable wings between the operating condition and the folded condition, the switching actuators being operatively connected to the electronic system.

13. An apparatus (1) for harnessing energy from a wind current (99), comprising the aerial device according to any one of claims 1 to 12 and an anchoring base (40), the second end (22) of the tether cable (20) being connected to the anchoring base (40),wherein the anchoring base (40) is configured to use the pulling force (98) applied to the anchoring base (40), said pulling force (98) being usable as a force for movement or being convertible into energy to be used.

14. A boat (2) equipped with the apparatus (1) according to claim 13, wherein the anchoring base (40) is fixed to the boat (2) and the pulling force (98) contributes to propel the boat (2).

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