Rotor for an aircraft capable of hovering

Abstract

A rotor (8, 8', 106'", 106", 106'", 106'"") for an aircraft (1, 100) is described, comprising: an input shaft (10, 108) rotatable about a first axis (C, I); an output member (15, 112) rotatable about a second axis (D, J); a coupling element (20, 20', 20", 20'") functionally interposed between the input shaft (10, 108) and the output member (15, 112) and adapted to transmit motion from the input shaft (10, 108) to the output member (15, 112); The components (20, 20', 20", 20'") are configured to allow fixed or variable tilting between corresponding first and second axes (C, I, D, J) in use; the coupling element (20, 20', 20", 20') includes at least one first corrugated element (21, 22, 25, 120', 121', 120", 121", 122"") made of elastically deformable material; the first corrugated elements (21, 22, 25; 120', 121', 120", 121", 122") allow tilting by elastic deformation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority from European Patent Application No. 20182377.0, filed on June 25, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The invention relates to a vertical take-off and landing reversing aircraft.

[0004] The invention also relates to a helicopter. Background Art

[0005] In more detail, the known types of VTOL aircraft basically consist of:

[0006] - a fuselage extending along a first longitudinal axis;

[0007] a pair of half-wings projecting in cantilevered manner from respective portions of the fuselage opposite one another and having respective free ends opposite the fuselage, the free ends being aligned along a second transverse axis substantially orthogonal to the first longitudinal axis; and

[0008] - a pair of pods carrying respective power units, each power unit being formed by a respective motor and a respective propeller.

[0009] Each propeller is rotatable about an associated third axis.

[0010] VTOL aircraft can also optionally display:

[0011] - an "airplane" configuration, wherein the propellers are arranged with the respective third axis being substantially parallel to the first axis of the VTOL aircraft itself and defining the respective power unit of the VTOL aircraft itself; or

[0012] - A "helicopter" configuration, wherein the propellers are arranged so that the respective third axis is substantially vertical and transverse to the first axis of the VTOL aircraft.

[0013] Each propeller comprises, in a known manner:

[0014] a control shaft driven by an associated motor into rotation about an associated third axis;

[0015] - a hub operatively connected to the control shaft and rotatable about an associated fourth axis; and

[0016] - a plurality of blades articulated on the control shaft and carried by the hub, in particular distributed circumferentially around the free end of the control shaft protruding from the respective pod.

[0017] Each propeller also comprises an articulated joint, for example an elastomeric joint of the spherical type interposed between the control shaft and the hub.

[0018] This happens because, unlike the solutions usually used in helicopters, the hub of the VTOL aircraft is free to oscillate through the aforementioned angle relative to the control shaft.

[0019] The articulated joint allows the fourth axis of the hub and the third axis of the control shaft to swing to a certain maximum angle, for example 12 degrees.

[0020] Said oscillation is caused by asymmetrical aerodynamic forces acting on the blades, for example due to gusts of wind or due to cyclic pitch variations of the blades themselves. Alternatively, said oscillation is caused when a VTOL aircraft switches between "airplane" and "helicopter" configurations, or when a disturbance acts on the blades, generating gyroscopic forces.

[0021] In solutions of known type, for example from EP-B-1 088 755 and EP-B-276 945, the articulated joint is homokinetic, ie the ratio between the angular velocities of the hub and the control shaft does not depend on the angular positions of the hub and the control shaft.

[0022] More specifically, an articulated joint of known type comprises a plurality of rigid elements articulated to one another in such a way as to allow the transmission of high torque values ​​while allowing offsets between a respective fourth axis of the hub and a respective third axis of the control shaft.

[0023] Furthermore, there is a need felt in the art to reduce the number of articulated parts and to simplify as much as possible the co-moving joints of the rotors of a VTOL aircraft.

[0024] Helicopters are also known which basically comprise a fuselage, a main rotor situated on top of the fuselage and rotatable about its own fifth axis, and an anti-torque rotor arranged at the tail end of the fuselage.

[0025] In a known manner, the helicopter also comprises one or more motor members, for example turbines, and a transmission group interposed between the turbines and the main rotor and suitable for transmitting movement from the turbines to the main rotor itself.

[0026] In more detail, the anti-torque rotor includes:

[0027] - a control shaft rotatable about a sixth axis;

[0028] - a hub rotatable about a sixth axis; and

[0029] - a plurality of blades articulated on the hub, projecting in a cantilevered manner from the hub itself and each extending along a respective seventh axis transverse to the sixth axis.

[0030] The helicopter also includes:

[0031] an intermediate shaft connected to the power take-off of the transmission group and rotatable about an eighth axis inclined relative to the sixth axis; and

[0032] - a pair of bevel gears meshing with each other and interposed between the intermediate shaft and the control shaft of the anti-torque rotor.

[0033] There is a felt need in the art to connect the intermediate shaft and the control shaft of the anti-torque rotor with a co-moving coupling element which allows high load carrying capacity and torsional stiffness, while low bending and axial stiffness.

[0034] US-A-2018 / 023631 discloses a flexible coupling comprising a flexible diaphragm body having a first end and a second end. A member is secured to the first end of the flexible diaphragm body. A spline member is secured to the second end of the flexible diaphragm body. The spline member is configured to shift relative to a rotatable member rotatably secured to the spline member in response to axial displacement of a rotatable member interconnected by the flexible coupling. The ratio of the inner diameter to the outer diameter is selected to allow the flexible coupling to be packaged in a confined space.

[0035] US-B-10364848 discloses a drive coupling having a first coaxial end adapter and a second coaxial end adapter. A first set of at least two coaxial helical elements has a first end of each element attached to the first end adapter, and a second end of each element coupled to the second end adapter. At least one biasing device biases the end adapters relative to each other. Torque applied to one end adapter is transmitted to the other end adapter via the first set of helical elements, which allow the end adapters to deflect during operation.

[0036] GB-A-2113349 discloses a constant velocity universal joint comprising an input element connected to an output element via an intermediate member of a torque transmitting member in the form of a bellows made of a flexible filamentary material reinforced with an adhesive capable of elastically adapting to strains caused by angular displacement between the axes of rotation of the input and output elements. The joint is preferably made by a method comprising forming the bellows by applying the filamentary material around an internal bellows forming former and applying a flowable but curable reinforcing adhesive to the filamentary material. The former may be made of a corrugated flexible material that is subjected to internal fluid pressure when the filamentary material is wound thereon and remains inside the bellows after forming. The bellows may comprise a plurality of interconnected disc-like elements.

[0037] GB-A-2082730 discloses a lightweight composite coupling capable of carrying high torsional loads while accommodating angular and axial offsets between adjoining shafts. Summary of the Invention

[0038] The object of the present invention is to achieve a rotor for an aircraft capable of hovering that allows satisfying at least one of the needs indicated above in a simple and economical manner.

[0039] According to the present invention, the above-mentioned object is achieved by the vertical take-off and landing reversible aircraft of the present application.

[0040] The invention also relates to a helicopter. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] For a better understanding of the invention, seven preferred non-limiting embodiments are described below, purely by way of example and with the aid of the accompanying drawings, in which:

[0042] - Figure 1 is a side view of a vertical take-off and landing aircraft in a "helicopter" configuration, comprising a pair of rotors implemented in accordance with the requirements of a first embodiment of the present invention;

[0043] - Figure 2 Shown in enlarged and partially cutaway proportions Figure 1 Some parts of the rotor are removed for clarity;

[0044] - Figure 3 and Figure 4 The diagram is shown on a further enlarged scale in different corresponding operating positions. Figure 2 The rotor joints, with some parts removed for clarity;

[0045] - Figure 5 Shown in cross section Figure 1Some components of a second alternative embodiment of a rotor for a vertical take-off and landing reversible aircraft;

[0046] - Figure 6 Shown Figure 1 A perspective view of some components of a third embodiment of a rotor for a vertical take-off and landing reversible aircraft;

[0047] - Figure 7 Shown in perspective and to a specific enlarged scale Figures 2 to 4 Components of the rotor;

[0048] - Figure 8 is a side view of a helicopter including an anti-torque rotor according to a fourth embodiment of the present invention;

[0049] - Figure 9 Shown on a greatly enlarged scale Figure 8 some components of the drive line of the anti-torque rotor;

[0050] - Figure 10 is a side elevational view, partially in section, on a greatly enlarged scale, with portions removed for clarity, of a helicopter including an anti-torque rotor in accordance with a fourth embodiment of the present invention;

[0051] - Figure 11 shows some components of an anti-torque rotor according to a fifth embodiment of the present invention;

[0052] - Figure 12 is a side elevational view, partially in section and on a greatly enlarged scale, of a helicopter including a rotor according to a sixth embodiment of the present invention, with parts removed for clarity; and

[0053] - Figure 13 Some components of an anti-torque rotor according to a seventh embodiment of the invention are shown. DETAILED DESCRIPTION

[0054] Reference Figures 1 to 7 , 1 represents an aircraft capable of hovering, especially a vertical take-off and landing reversible aircraft.

[0055] The vertical take-off and landing reversible aircraft 1 basically comprises:

[0056] - a fuselage 2 having an axis of longitudinal extension A;

[0057] a pair of half-wings 3 extending transversely to the axis A in a cantilevered manner from respective portions of the fuselage 2 facing each other; and

[0058] a pair of nacelles 4 housing respective groups of power units 5 and capable of tilting relative to the fuselage 2 about an axis G orthogonal to the axis A.

[0059] The fuselage 2 also comprises a nose 12 and a tail portion 13 opposite each other along an axis A, the nose 12 being arranged at the front.

[0060] The half-wings 3 have respective longitudinal extensions parallel to an axis G orthogonal to the axis A.

[0061] It should be noted that the terms "front", "tail", "longitudinal", "lateral", "above" and "below" etc. in this specification refer to the normal forward direction of the VTOL aircraft 1 in forward flight.

[0062] In the remainder of this description, a single power unit group 5 is described, the power unit groups 5 being identical to one another.

[0063] The power unit group 5 basically includes ( Figure 2 ):

[0064] a motor 6 having an output shaft 7 rotatable about an axis B orthogonal to the axis G;

[0065] a propeller 8 rotatable about an axis C parallel to the axis B; and

[0066] A transmission group 11 , interposed between the output shaft 7 of the motor 6 and the control shaft 10 of the propeller 8 .

[0067] In the case shown, the axes B, C are parallel to each other and offset from each other.

[0068] The vertical take-off and landing reversible aircraft 1 can be selectively configured to:

[0069] - "Helicopter" structure (in Figure 1 ), wherein the axis of the propeller 8 is orthogonal to the axis A; and

[0070] - an “airplane” configuration (not shown) in which the axis C of the propeller 8 is parallel to the axis A.

[0071] The conversion of the VTOL aircraft 1 between the “helicopter” configuration and the “airplane” configuration is achieved by tilting the propeller 8 about the axis G.

[0072] In the case shown, the propeller 8 is tilted about the axis G integrally with the nacelle 4 and the power unit group 5 during the aforementioned conversion.

[0073] The propeller 8 further comprises:

[0074] - a joint 20 interposed between the control shaft 10 and the hub 15;

[0075] - a hub 15 having an axis D; and

[0076] Blades constrained to an element 17 , which in turn is constrained to a hub 15 , articulated on the control shaft 10 through the interposition of elastic bearings 19 .

[0077] In the case shown, the joint 20 is a co-moving joint configured to transmit driving torque only.

[0078] The joint 20 is also an elastically flexible joint configured to allow the axis D of the hub 15 to oscillate relative to the axis C of the control shaft 10 .

[0079] exist Figure 4 As can be seen in FIG, the control shaft 10 and the hub 15 have respective axes E, F that are radial and orthogonal to the respective axes C, D.

[0080] The joint 20 is configured to allow the axis D to oscillate about the axis C and thus the axis F about the axis E at a variable angle α, the variable angle α including the angles 0 degrees ( Figure 3 ) and + / - 12 degrees in the example shown ( Figure 4 )between.

[0081] Advantageously, the joint 20 is defined by at least one corrugated element made of elastically deformable material; this corrugated element allows tilting between the axes D, C by elastic deformation of the joint 20 itself.

[0082] In other words, the corrugations of the joint 20 allow elastic bending deformation capabilities to be obtained so as to allow the axis D to oscillate relative to the axis C.

[0083] Thus, although the joint 20 has no parts that are articulated to one another, it behaves like an articulated joint.

[0084] In the remainder of this description, the term "corrugation" refers to a continuous or periodic succession of annular ridges and grooves in certain stretches and around the axis C.

[0085] In the section containing the axis C ( Figure 4 and Figure 5 ), the ripples have:

[0086] - a longitudinal extension direction along which the ridges and grooves repeat periodically; and

[0087] - a transverse direction orthogonal to the direction of extension, along which the ridges and grooves extend at a distance from each other.

[0088] The maximum distance between two consecutive ridges (grooves) along the longitudinal direction is called the pitch p of the corrugations.

[0089] The distance between the ridges and grooves in the transverse direction is called the height h of the corrugation.

[0090] The joint 20 is symmetrical about the axis C.

[0091] Reference Figure 2 , the joint 20 basically comprises:

[0092] - a pair of head elements 21, 22 connected to the control shaft 10 and the hub 15 respectively; and

[0093] - an element 25 which is interposed between the elements 21 , 22 and is connected to the elements 21 , 22 themselves.

[0094] The elements 21 , 22 are disc-shaped and extend around respective axes C, D.

[0095] The elements 21 , 22 are corrugated and have respective corrugations 23 , 24 having a longitudinal extension radial to the axis C and a thickness parallel to the axis C.

[0096] The element 25 is tubular and has corrugations 26 having a longitudinal extension parallel to the axis C and a thickness radial to the axis C.

[0097] The corrugations 23, 24 of the elements 21, 22 include ( Figure 7 ) corresponding multiple rings 29, 30.

[0098] The rings 29 , 30 alternate with one another in the radial direction relative to the axis C and define respective axial ends of the corresponding corrugations 23 , 24 , facing one another.

[0099] The ring 29 is arranged at a first axial distance from the hub 15 .

[0100] The ring 30 is arranged at a second axial distance from the hub 15 , which second axial distance is smaller than the aforementioned first axial distance.

[0101] The rings 29 (30) are all arranged at the same first (second) axial distance.

[0102] The corrugations 23 , 24 each have a plurality of connecting stretches 31 , each connecting stretch 31 being interposed between a corresponding ring 29 and a corresponding ring 30 adjacent thereto.

[0103] Each stretching portion 31 extends from the corresponding ring 29 towards the corresponding ring 30 adjacent thereto at gradually increasing axial and radial distances.

[0104] In the example shown, the corrugations 23 , 24 have, in a section parallel to the axis B, the shape of a coil.

[0105] The rings 29 , 30 lie in respective planes orthogonal to the axis B.

[0106] The corrugations 26 include a respective plurality of rings 35 , 36 .

[0107] The rings 35 , 36 alternate with one another parallel to the axis C and define respective radial ends of the corrugations 26 that are opposite one another.

[0108] The ring 35 is arranged at a first radial distance from the axis C.

[0109] The ring 36 is arranged at a second radial distance from the axis C, which is smaller than the aforementioned first radial distance.

[0110] The rings 35 ( 36 ) are all arranged at the same first (second) radial distance from the axis C.

[0111] The corrugations 26 have a plurality of connecting stretches 37 , each of which is interposed between a corresponding ring 35 and a corresponding ring 36 adjacent thereto.

[0112] Each stretching portion 37 extends from the corresponding ring 35 towards the corresponding ring 36 at gradually increasing axial and radial distances.

[0113] The corrugations 26 have a coil shape in a cross section parallel to the axis C.

[0114] The corrugations 26 are symmetrical about the axis C.

[0115] The rings 35 , 36 lie in respective planes orthogonal to the axis C.

[0116] The corrugations 23 , 24 comprise respective ends 33 , 34 which are radially on the inside and are connected to the control shaft 10 and the hub 15 .

[0117] In particular, the ends 33 , 34 extend continuously and uniformly around the respective axes C, D.

[0118] The corrugations 23 , 24 also comprise respective ends 39 , 40 , which are radially external and opposite the corresponding ends 33 , 34 .

[0119] The corrugations 26 include opposite axial ends 41 , 42 that are opposite each other and that connect to the respective ends 39 , 40 of the corresponding corrugations 23 , 24 .

[0120] In particular, the joint 20 is made of a composite material, in particular a fiber-reinforced laminate material.

[0121] Alternatively, the joint 20 may be made of a different resilient material, such as metal or a combination of materials.

[0122] In use, the VTOL aircraft 1 lands and takes off in a "helicopter" configuration, and travels forward in an "airplane" configuration.

[0123] During hovering or in the "helicopter" configuration at low speed, the lift required to support the VTOL aircraft 1 is provided by the propellers 8 arranged with their respective axes C being orthogonal to the axes A, E ( Figure 1 ).

[0124] In the “airplane” configuration, not shown, the lift required to support the VTOL aircraft 1 is provided largely by the half-wings 3 .

[0125] The motor 6 drives the propeller 8 to rotate about the corresponding axis D.

[0126] More specifically, each motor 6 drives the relative control shaft 10 in rotation about the relative axis C.

[0127] The control shaft 10 drives the hub 15 to rotate about the axis D via the joint 20 .

[0128] In more detail, the joint 20 is co-rotating, i.e. the ratio between the speed of rotation of the control shaft 10 about the axis C and the speed of rotation of the hub 15 about the axis D is constant for each angular position of the control shaft 10 or of the hub 15 relative to the respective axis C, D and is equal to 1 in the example shown.

[0129] This is obtained because the ends 33 , 34 extend continuously and evenly around the respective axes B, C. Consequently, no “jerky” movements of the hub 15 relative to the shaft 10 occur.

[0130] Due to the presence of the corrugations 23, 24; 26 and the fact that the joint 20 is made of a fiber reinforced composite laminate, the joint 20 also allows the axis D to swing relative to the axis C, thereby allowing the axis E to swing relative to the axis F equal to an angle α, which is included in the range of 0 degrees ( Figure 3 ) and 12 degrees in the example shown ( Figure 4 )between.

[0131] The joint 20 allows said oscillation due to its own bending elastic deformation, while it ensures that the torque is transmitted from the shaft 10 to the hub 15 by its own torsional rigidity.

[0132] This oscillation is due to the fact that the aerodynamic forces acting on the blades 16 are almost never perfectly symmetrical, for example due to gusts of wind or due to cyclic pitch variations of the blades 16 themselves.

[0133] Such asymmetric forces also arise during the transition of the VTOL aircraft 1 between the “airplane” configuration and the “helicopter” configuration, or due to gyroscopic forces that arise when disturbances act on the blades 16 .

[0134] Reference Figure 5, 8' represents a propeller according to a second embodiment of the present invention.

[0135] The propeller 8 ′ is similar to the propeller 8 and will be described hereinafter only with respect to its differences from the propeller 8 ; where possible, identical or equivalent parts of the propellers 8 , 8 ′ will be indicated with the same reference numerals.

[0136] The propeller 8 ′ differs from the propeller 8 in that the joint 20 ′ of the hub 15 does not comprise the elements 21 , 22 and is formed solely by the element 25 .

[0137] The propeller 8 ′ also differs from the propeller 8 in that the corrugations 26 ′ are spiral-shaped.

[0138] The rings 35 , 36 of the propeller 8 ′ lie on respective planes orthogonal to the axis B.

[0139] The operation of the propeller 8' is similar to that of the propeller 8 and therefore will not be described in detail.

[0140] Reference Figure 6 , 8" represents a propeller according to a third embodiment of the present invention.

[0141] The propeller 8 ″ is similar to the propeller 8 and will be described hereinafter only with respect to its differences from the propeller 8 ; where possible, identical or equivalent parts of the propellers 8 , 8 ″ will be designated with the same reference numerals.

[0142] The propeller 8 ″ differs from the propeller 8 in that the joint 20 ″ is formed by a plurality of shaped discs 52 ″ superimposed on one another parallel to the axis C to form the corrugations.

[0143] The disks 52 ″ are connected to each other, in particular by gluing or welding.

[0144] Each tray 52" essentially comprises:

[0145] - a corresponding stretch 53 ″ defining the radially inner end edge of the disc 52 ″ itself;

[0146] - a corresponding stretch 54 ″ defining the radially outer end edge of the disc 52 ″ itself; and

[0147] - a respective stretch 55" intermediate between the stretches 53", 54"'.

[0148] The stretched portions 53", 54", 55" of each disc 52" are shaped like corresponding circular crowns.

[0149] The stretched portion 55 ″ of each disc 52 ″ has a greater radial extension than the corresponding stretched portion 53 ″, 54 ″.

[0150] The stretch portions 53 ″, 54 ″, 55 ″ are axially offset from one another.

[0151] In particular, the stretched portion 55" of each disc 52" is at a first axial distance from the stretched portion 53" of the same disc 52". The stretched portion 54" of each disc 52" is at a second axial distance from the stretched portion 53" of the same disc 52", the second axial distance being greater than the first distance.

[0152] In the example shown, each tray 52" also includes:

[0153] - a stretching portion 56 ″ which is curved and radially interposed between the relative stretching portions 53 ″, 55 ″; and

[0154] A stretch 57 ″ which is curved and radially interposed between the relative stretches 55 ″, 54 ″.

[0155] The connector 20" includes a plurality of pairs 58" of discs 52".

[0156] The stretching portions 53" of each pair 58" of discs 52" are connected to each other.

[0157] The stretched portions 54 ″ of the disks 52 ″ of adjacent pairs 58 ″ are connected to each other.

[0158] In particular, each pair 58" of discs 52" extends at gradually increasing axial distances from a respective stretch 53" to a corresponding stretch 54".

[0159] The stretched portions 53", 54", 55" of the disc 52" define corrugations 60".

[0160] The corrugations 60 ″ have a longitudinal extension parallel to the axis C and a thickness in the radial direction of the axis C.

[0161] More precisely, the interconnected stretches 55 ″ of adjacent discs 52 ″ of a continuous pair 58 ″ define the ridges of the corrugations 60 ″.

[0162] The mutually connected stretches 53 ″ of the same pair 58 ″ of discs 52 ″ define the convex portion of the corrugation 60 ″.

[0163] The h / p ratio of the corrugation 60" is greater than 1. When a particularly high h / p ratio is required (for which corrugation of a single piece of laminate is not feasible), Figure 6 The approach shown may be advantageous.

[0164] The operation of propeller 8" is similar to that of propeller 8 and therefore will not be described in detail.

[0165] Reference Figures 8 to 10, 100 denotes a helicopter including an anti-torque rotor 106 ″′ according to a fourth embodiment of the present invention.

[0166] Helicopter 100 basically comprises:

[0167] - fuselage 102;

[0168] - one or more turbines 105;

[0169] a main rotor 103 placed on top of the fuselage 105 and rotatable about a first axis; and

[0170] An anti-torque rotor 106 ′″ placed at the tail end of the fuselage 102 and rotatable about its own axis H, which is transverse to the axis of the rotor 103 .

[0171] Helicopter 100 also includes a transmission group 111 that transmits motion from turbine 105 to main rotor 103 and rotor 106.

[0172] Transmission assembly 111 is shown limitedly as auxiliary output shaft 108 rotatable about axis I and operatively connected to anti-torque rotor 106 , as will be described in greater detail below.

[0173] Rotors 106 ′″ generate thrust that produces a significant torque on fuselage 102 .

[0174] The apparent torque is directed in a direction opposite to the torque exerted by rotor 103 on fuselage 102 .

[0175] Depending on the thrust value generated by rotor 106 ′″, helicopter 100 can therefore be oriented according to a desired yaw angle, or the aforementioned yaw angle can be adjusted according to the flight maneuver to be performed.

[0176] In more detail, the rotor 106'' essentially comprises:

[0177] a control shaft 112 rotatable about axis J and operatively connected to shaft 108 ; and

[0178] a plurality of blades 109 , in the case shown two blades 109 , which are rotatable about the axis H and extend in a cantilevered manner along respective axes transverse to the axis J.

[0179] Anti-torque rotor 106 ′″ also includes a joint 20 ′″ interposed between shaft 112 and shaft 108 .

[0180] Connector 20'" is similar to connector 20 and will be described below only with respect to its differences from connector 20; where possible, identical or equivalent parts of connectors 20, 20'" will be designated with the same reference numerals.

[0181] The joint 20 ′″ is configured to transmit torque between the shaft 108 and the shaft 112 , which have respective axes I, J that are inclined at a constant angle β relative to each other.

[0182] The joint 20 ′″ is axially symmetrical along the bending axis K and connects the axes I, J.

[0183] The joint 20'' basically comprises ( Figures 8 to 10 ):

[0184] a pair of elements 120'', 121'' connected to each other and to the shaft 112 and the shaft 108 respectively; and

[0185] a plurality of support elements 115 ″′, 116 ″′, 117 ″′, three in the example shown, interposed between the joint 20 ″′ and the fuselage 102 and adapted to support the joint 20 ″′, allowing it to rotate elastically about the axis K.

[0186] Helicopter 100 also includes ( Figure 12 ):

[0187] - a joint 200 interposed between the shaft 108 and the element 120''; and

[0188] A joint 201 interposed between the element 121 ′″ and the shaft 112 .

[0189] In more detail, the elements 120'", 121'" define respective corrugations 124'", 125'".

[0190] Each corrugation 124 ′″, 125 ′″ has a longitudinal extension that is curved and parallel to the axis K and a thickness along a direction orthogonal to the axis K.

[0191] Each corrugation 124'", 125'" includes a respective plurality of rings 126'", 127'".

[0192] The rings 126 ′″, 127 ′″ alternate with one another parallel to the curvilinear axis K and define respective radial ends of the respective corrugations 124 ′″, 125 ′″, facing one another.

[0193] The ring 126 ′″ is arranged at a first radial distance from the axis K.

[0194] The ring 127 ′″ is arranged at a second radial distance from the axis K, which is smaller than the aforementioned first radial distance.

[0195] The rings 126'" (127'") are all arranged at the same first (second) radial distance from the axis K.

[0196] The corrugations 124'", 125'" have a plurality of connecting stretches 128'", each connecting stretch 128'" being interposed between a corresponding ring 126'" and a corresponding ring 127'" adjacent thereto.

[0197] Each stretching portion 128'" extends from the corresponding ring 126'" towards the corresponding ring 127'" at gradually increasing axial and radial distances.

[0198] In the example shown, the corrugations 124 ′″, 125 ′″ have, in a section taken in a plane parallel to the axis K, the shape of a coil.

[0199] The corrugations 124 ′″, 125 ′″ are symmetrical about the axis K.

[0200] The rings 126 ′″, 127 ′″ lie on respective planes orthogonal to the axis K.

[0201] The elements 120'", 121'" comprise respective flanges 129'".

[0202] In the example shown, the support element 115 ′″ comprises a double row rolling bearing 130 ′″.

[0203] The bearing 130'' basically comprises:

[0204] an inner ring capable of rotating integrally with the joint 200 and with one flange 129'' of the element 120''; and

[0205] An outer ring fixed to the fuselage 102 .

[0206] In the example shown, the support element 116 ′″ comprises a rolling bearing 131 ′″ with tapered rollers.

[0207] The bearing 131"' basically comprises:

[0208] an inner ring capable of rotating integrally with the other flange 129'' of the element 120'' and with one flange 129'' of the element 121''; and

[0209] An outer ring fixed to the fuselage 102 .

[0210] The support element 117 ′″ comprises a rolling bearing 132 ′″ which, in the example shown, has tapered rollers.

[0211] The bearing 132'' basically comprises:

[0212] an inner ring capable of rotating integrally with the other flange 129'' of the element 120'' and with the joint 201; and

[0213] An outer ring fixed to the fuselage 102 .

[0214] In use, the turbine 105 drives the transmission assembly 111 .

[0215] The transmission assembly 111 drives the main rotor 103 and the auxiliary shaft 108 to rotate around the axis I.

[0216] The auxiliary shaft 108 drives the anti-torque rotor 106 in rotation via the shaft 108 rotatable about the axis I and the joint 20 ′″.

[0217] In more detail, the elements 120'', 121'' of the joint 20'' allow the axes I, J to be offset by a fixed angle ( Figure 10 ).

[0218] The joint 20 ″′ allows said deflection due to its elastic bending deformation in a plane containing the axes I, J, K.

[0219] More precisely, due to the presence of the corrugations 124'", 125'" providing torsional rigidity and at the same time bending flexibility and the fact that the joint 20'" is made of a fiber reinforced composite laminate, the joint 20'" deforms elastically flexurally to keep the angle between the axes I, J constant.

[0220] Reference Figure 11 , 106"" represents an anti-torque rotor according to a fifth embodiment of the present invention.

[0221] Rotor 106"" is similar to rotor 106'" and will be described below only with respect to its differences from rotor 106'"; where possible, identical or equivalent parts of rotors 106'", 106"" will be identified with the same reference numerals.

[0222] Rotor 106"" differs from rotor 106'" in that it comprises three elements 120", 121", 122"" with corresponding corrugations 124", 125", 123"" and it comprises four support elements 115", 116", 117", 118"" with corresponding bearings 130", 131", 132", 133".

[0223] The operation of rotor 106"" is similar to the operation of rotor 106'" and therefore will not be described in detail.

[0224] Reference Figure 12 , 106""' represents an anti-torque rotor according to a sixth embodiment of the present invention.

[0225] Rotor 106'"" is similar to rotor 106'" and will be described below only with respect to its differences from rotor 106'"; where possible, identical or equivalent parts of rotors 106'"" and 106'" are labeled with the same reference numerals.

[0226] The rotor 106 ″″′ differs from the rotor 106 ″′ in that the corrugations 124 ″″′, 125 ″″′ are helical relative to the axis K and that the rings 126 ″″′, 127 ″″′ lie in respective planes orthogonal to the axis K.

[0227] Reference Figure 13 , 106""" represents the anti-torque rotor according to the seventh embodiment of the present invention.

[0228] Rotor 106""" is similar to rotor 106"" and will be described below only with respect to its differences from rotor 106""; where possible, identical or equivalent parts of rotors 106""", 106"" are labeled with the same reference numerals.

[0229] The rotor 106 ″″ differs from the rotor 106 ″″ in that the corrugations 124 ″′, 125 ″′, 123 ″′ are helical relative to the axis K and the rings 126 ″′, 127 ″′ lie in respective planes orthogonal to the axis K.

[0230] In further embodiments not shown, the elements 120'", 121'"; 120", 121"" of the joint 20'" may be made of metal (eg titanium) and optionally coated with a sheath of fiberglass or other fiber reinforcement material.

[0231] The aforementioned elements 120'', 121''; 120", 121"' of said further embodiment can also be easily manufactured by means of additive manufacturing techniques. In this way, the problem of removing internal mandrels, which is necessary for other methods of manufacturing composite products, is avoided.

[0232] The advantages that can be obtained by the present invention are obvious from the characteristics of the propellers 8, 8', 8" of the VTOL aircraft 1 and the anti-torque rotors 106'", 106", 106"'", 106""" of the helicopter 100 according to the present invention.

[0233] In particular, the propellers 8, 8', 8" and the anti-torque rotors 106'", 106", 106""" respectively comprise joints 20, 20', 20"; 20'" having corresponding corrugations 23, 24, 26, 26'; 124'", 125'", 124", 125", 123'; 124'"', 125'"'; 124'""", 125'""", 123'""".

[0234] The corrugations 23, 24, 26, 26'; 124"', 125"', 124"", 125"", 123"'; 124""', 125""'; 124""", 125""", 123""" give the joints 20, 20', 20", 20"' a high bending elastic deformation capacity associated with a high transmission capacity of torsional loads.

[0235] In other words, the corrugations 23, 24, 26, 26'; 124"', 125"', 124"", 125"", 123"'; 124""', 125""'; 124""", 125""", 123""" allow for separation of stiffness and load paths.

[0236] The ends 33 , 34 extend continuously and uniformly around the respective axes C, D, K. This allows to ensure simultaneous operation of the joints 20 , 20 ′, 20 ″, 20 ′″.

[0237] It is important to emphasize that, unlike solutions of the known type discussed in the introductory part of this description, these characteristics are obtained without requiring the use of multiple parts articulated to one another, with the advantages of significant weight savings and constructional simplification.

[0238] In this way, the joints 20 , 20 ′, 20 ″ allow the transmission of movement between the control shaft 10 and the hub 15 , thereby enabling a variable oscillation between the axes E, F during operation of the VTOL aircraft 1 , which in the example shown is between 0 and 12 degrees.

[0239] In more detail, the corrugations 23, 24, 26, 26' give the joints 20, 20', 20" a very high torsional load capacity (i.e. a very high ability to transmit the torque moments of the axis B from the control shaft 10 to the hub 15), while having a high bending flexibility in the plane containing the axes C, D and an axial flexibility that allows the aforementioned swinging motion between the axes C, D.

[0240] The joint 20 ′″ allows the transmission of movement between the shafts 12 , 16 having respective axes I, J that are inclined at a constant angle relative to each other.

[0241] In other words, joint 20'" allows the bevel gears typically provided between the aforementioned shafts 108, 112 of anti-torque rotors 106'", 106", 106'", 106"" to be replaced efficiently and with reduced weight / cost.

[0242] The helical configuration of the corrugations 23, 26'; 124""', 125""'; 124""", 125""", 123""" can increase the torsional resistance in one direction. This is particularly advantageous since the maximum torque acting on the joint 20, 20'; 20", 20"' always points in one direction.

[0243] In a further embodiment, the elements 120'", 121'"; 120", 121"" may be made of metal (e.g. titanium) and coated with a sheath of fiberglass or fiber reinforced composite material. In this way, catastrophic failure of the joint 20'" will be avoided in the event of the generation of cracks that would lead to failure.

[0244] Finally, the joint 20 ″ allows obtaining a particularly high h / p ratio due to the fact that the joint 20 ″ formed from the disk 52 ″ does not create the problem of removing the internal mandrel necessary for other manufacturing methods.

[0245] Said properties of the joint 20 , 20 ′, 20 ″, 20 ′″ can be optimized by appropriately choosing the lamination sequence of the fiber reinforcement materials of the elements 21 , 22 , 25 , 120 ′″, 121 ′″, 120 ″″, 121 ″″.

[0246] Obviously, modifications and variations can be made to the propellers 8, 8', 8" of the VTOL aircraft 1 and the anti-torque rotors 106'", 106", 106'" of the helicopter 100 described and illustrated herein without departing from the scope of protection defined by the claims.

[0247] In particular, the corrugations 23 , 24 , 26 can also be spiral-shaped.

[0248] Anti-torque rotor 106 ′″ may include joint 20 ″ in place of joint 20 ′″ interposed between shaft 112 and shaft 108 .

[0249] One or more of the corrugations 23, 24, 26, 26'; 124"', 125"', 124"", 125"", 123"'; 124""', 125""'; 124""", 125""", 123""" can be at least partially formed into multiple disconnected segments that are joined to each other and / or have curved stretched sections, or they can be formed into an arc.

Claims

1. A vertical take-off and landing reversible aircraft (1), comprising: a fuselage (2) extending along a first axis (A); a pair of half-wings (3) extending from respective side strips of the fuselage (2) opposite to each other along respective second axes (B); a pair of rotors (8, 8', 8") associated with the half-wings (3, 3'), rotatable about respective third axes (D) and tiltable about a fourth axis (G) orthogonal to the second axis (B) and the first axis (A) between the following positions: a first position in which the third axis (D) is parallel to the first axis (A), the first position being reached when the VTOL aircraft (1) is in the aircraft configuration in use; as well as a second position in which the third axis (D) is orthogonal to the first axis (A), the second position being reached when the VTOL aircraft (1) is in use in a helicopter configuration; Each of the rotors (8, 8', 8") comprises: an input shaft (10) rotatable about a corresponding fifth axis (C); an output member (15) rotatable about a respective said third axis (D); a coupling element (20, 20', 20") functionally interposed between the input shaft (10) and the output member (15) and adapted to transmit motion from the input shaft (10) to the output member (15); The coupling elements (20, 20', 20") are configured to allow, in use, the respective third axis (D) to be tilted at a variable angle relative to the respective fifth axis (C); Characterized in that the coupling element (20, 20', 20") comprises at least one first corrugated element (21, 22, 25) made of elastically deformable material; The first corrugated elements (21, 22, 25) allow the tilting to be performed by elastic deformation; The input shaft (10) is a control shaft of the corresponding rotor (8, 8', 8") rotatable about the corresponding fifth axis (C); The output member (15) is a hub, and the corresponding plurality of blades (16) are hinged to the hub (15) and can rotate around the corresponding third axis (D); The coupling element is configured to allow, in use, the respective third axis (D) to oscillate at the variable angle relative to the respective fifth axis (C), The coupling elements (20, 20', 20") are co-moving; and / or The coupling element (20, 20', 20") is torsionally rigid in a plane orthogonal to the fifth axis (C) and the third axis (D), and yields in bending in at least one plane parallel to the fifth axis (C) and the third axis (D).

2. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: The first corrugated element (25) is axially symmetrical about a sixth axis and has first corrugations (26, 26'); The first corrugations (26, 26') have an extension direction parallel to the sixth axis and a radial thickness relative to the sixth axis.

3. The vertical take-off and landing reversible aircraft according to claim 2, characterized in that: said first corrugation (26, 26') comprising at least one first ring (35) radially external relative to said sixth axis and axially interposed between two second rings (36) radially internal relative to said fifth axis (C) itself; The first ring (35) and the second ring (36) are defined by a single first corrugated element (25).

4. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: It comprises at least one second corrugated element (21, 22); The second corrugated element (21, 22) is disc-shaped and comprises second corrugations (23, 24) having an extension direction radial to the fifth axis (C) and a thickness parallel to the fifth axis (C).

5. The vertical take-off and landing reversible aircraft according to claim 2, characterized in that: The first corrugation (26') is spiral; and / or the fifth axis (C) and the sixth axis coincide with each other.

6. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: The coupling element (20") comprises a plurality of axially corrugated disks (52") superimposed on each other and connected to each other; The disc (52") includes a first radially inner end (53") and a second radially outer end (54") axially offset relative to the first radially inner end (53").

7. The vertical take-off and landing reversible aircraft according to claim 6, characterized in that: Each of the discs (52") includes a stretched portion (55") radially and axially interposed between a respective first radially inner end portion (53") and a respective second radially outer end portion (54").

8. The vertical take-off and landing reversible aircraft according to claim 6, characterized in that: The plates (52") axially continuous with each other comprise respective first radially inner ends (53") connected to each other and / or respective second radially outer ends (54") connected to each other.

9. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: The at least one first corrugated element (21, 22, 25) is made of a fiber-reinforced composite material.

10. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: The coupling element (20, 20', 20") comprises a first end edge (33) and a second end edge (34) connected to the input shaft (10) and the output member (15), respectively; The first end edge (33) and the second end edge (34) are circular and circumferentially continuous so that the coupling elements (20, 20', 20") are co-movable.

11. The vertical take-off and landing reversible aircraft according to claim 1, characterized in that: The at least one first corrugated element (21, 22, 25) is made of a metal material coated with a glass fiber sheath.

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