Helicopter

Abstract

Describes a helicopter (1) comprising: a motor member (3) including an output shaft (12) and a first stator (11, 29) rotatably supporting the output shaft (12) about a first axis (C); a main rotor (4) adapted to provide the lift required for the support of the helicopter (1) and the thrust required for movement; a transmission (7) inserted between the motor member (3) and the main rotor (4); the transmission (7) in turn including an input shaft (21) rotatable about a second axis (D) and a second stator (20, 30) rotatably supporting the input shaft (21) about the second axis (D); the helicopter (1) further includes a joint (35) inserted between the first and second stators (11, 29; 20, 30), the joint being fixed at an angle relative to the first axis (C) and configured to allow tilting between the first and second stators (11, 29; 20, 30) in a plane parallel to the first axis (C); the joint (35) includes a first corrugated element (36) made of an elastically deformable material, the first corrugated element being interposed between the first and second stators (11, 29; 20, 30) and adapted to allow tilting by elastic deformation.

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the priority of European Patent Application No. 20182389.5, filed on June 25, 2020, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a helicopter. Background art

[0004] As is well known, a helicopter generally includes:

[0005] - A motor member, such as a turbine;

[0006] - A main rotor; and

[0007] - A main transmission formed by a series of gears that transfer motion from the output shaft of the motor member to the main rotor at a suitable reduction ratio.

[0008] The motor member further includes an output shaft and a first stator that rotatably supports the output shaft about a first axis.

[0009] The main transmission further includes an input shaft and a second stator that rotatably supports the input shaft about a second axis.

[0010] According to known solutions, a helicopter further includes:

[0011] - A flexible rotary joint, such as a disk, which is interposed between the output shaft of the motor member and the input shaft of the main transmission to allow the transfer of a first torque from the output shaft of the motor member to the input shaft of the main transmission; and

[0012] - A static articulated joint, such as a universal joint, which is interposed between a first sleeve connected to the first stator of the motor member and a second sleeve connected to the second stator of the main transmission.

[0013] Both the flexible joint and the articulated joint must meet precise functional requirements.

[0014] More specifically, the flexible rotary joint transfers torque while allowing a few degrees of angular offset between the output shaft of the motor member and the input shaft of the main transmission. The latter is subject to angular movement due to the loads on the rotor under operating conditions and / or due to the different operating states of the drive shaft and the power take - off.

[0015] Similarly, in addition to transferring a second torque between the first sleeve and the second sleeve, the articulated joint must also allow a certain degree of angular tilt between the first sleeve and the second sleeve for the same reasons as described above with reference to the output member of the drive shaft.

[0016] Unlike the flexible joint, the articulated joint is stationary, i.e., it does not rotate about the axes of the first sleeve and the second sleeve. The articulated joint only serves as a joint that allows the above-mentioned offset.

[0017] The articulated joint is also hollow and houses the respective adjacent portions of the input shaft and the output shaft as well as the flexible joint of the drive shaft.

[0018] The flexible joint can rotate integrally with the output shaft of the motor member and the input shaft of the transmission.

[0019] The loads on the articulated joint include the torque of a variable entity obtained from the reaction of the motor torque under normal operating conditions. In a specific emergency situation, such as when the motor member jams, the torque can reach a higher value than under normal operating conditions. In addition, the articulated joint is also subject to axial and shear loads under normal and specific conditions.

[0020] For example, in the case of a collision, the axial and shear load values can be very high because the element is used to prevent the motor from collapsing onto the transmission.

[0021] The inclination between the first sleeve and the second sleeve occurs in a pair of planes that are parallel to the rotational axes of the input shaft and the output shaft, i.e., in the bending planes of the aforementioned input shaft and output shaft.

[0022] In particular, known types of articulated joints include a plurality of rigid elements articulated between them in order to allow the transmission of high torque values and to allow the necessary offset / inclination between the output shaft of the motor member and the input shaft of the transmission.

[0023] There is a felt need in the art to connect the first sleeve of the motor member and the second sleeve of the transmission with an articulated joint that allows high load-carrying capacity and torsional, axial, and shear rigidity accompanied by low bending rigidity.

[0024] This is to allow the transmission of torque parallel to the rotational axes of the input shaft and the output shaft and, at the same time, to allow the inclination of the first sleeve and the second sleeve in a plane parallel to the said rotational axes.

[0025] In addition, there is a felt need in the art to meet these requirements by reducing the number, weight, and total cost of the articulated components.

[0026] The object of the present invention is to implement a helicopter that allows at least one of the above-mentioned needs to be met in a simple and economical manner.

[0027] XP055753610 discloses a helicopter having a universal joint interposed between a first stator of a motor and a second stator of a transmission. The stationary universal joint allows tilting between the first and second stators in a plane parallel to the common axis of the first and second stators.

[0028] A constant velocity universal joint disclosed in GB-A-2113349 includes an input element connected to an output element through an intermediate member of a torque transmission member, the torque transmission member being in the form of a bellows made of a flexible filamentary material, the flexible filamentary material being reinforced by an adhesive capable of elastically accommodating strains caused by an angular displacement between the rotational axes of the input element and the output element. The joint is preferably made by a method which includes forming the bellows by applying the filamentary material around an internal bellows former and applying a flowable but curable reinforcing adhesive to the filamentary material. The former may be made of a corrugated flexible material which is subjected to an internal fluid pressure when the filamentary material is wound thereon and remains inside the bellows after formation. The bellows may include a plurality of interconnected disc-shaped elements.

[0029] DE-A-102015004302 discloses a hollow drive shaft for torque transmission connection of two shafts. The tubular hollow drive shaft is made of a composite material and has at least one cylindrical tubular end portion. There is a radial gap between the shaft (2) and the at least one cylindrical tubular end portion of the hollow drive shaft, and a clamping element is provided on the radial gap, which can be assembled and disassembled several times. Radial surface pressure accumulates on the surface of the shaft and the inner surface of the cylindrical tubular end portion of the hollow drive shaft, and frictional and gapless torque transmission occurs between the shaft and the hollow drive shaft by means of this surface pressure.

[0030] JP-A-2018059601 discloses a coupling having a bellows, two outer ring holding portions assembled and inserted into two end portions of the bellows, and two connecting portions assembled and inserted into the outer ring holding portions. The bellows is formed to have a hollow tubular body, the appearance of which is formed into a continuous corrugated shape by bending and curving at least one thin plate, and each of the two end portions of the bellows has a first insertion portion and a second insertion portion. The ends of the first insertion portion and the second insertion portion are both bent to form edge warping portions.

[0031] The "Accident Report Agusta Bell AW109SP" of the Australian Transport Safety Bureau, XP055753610 discloses a helicopter according to the preamble of claim 1. Summary of the Invention

[0032] According to the present invention, this object is achieved by the helicopter as claimed in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For a better understanding of the present invention, preferred non-limiting embodiments will be described below by way of example only and with the aid of the drawings, in which:

[0034] Figure 1 is a side view of a helicopter implemented according to the requirements of a first embodiment of the present invention;

[0035] Figure 2 is shown in an enlarged and partially cut-away scale Figure 1 some components of the helicopter, and for clarity, some parts have been removed;

[0036] Figure 3 shows Figure 1 and Figure 2 a further enlarged scale perspective view of some details of the stationary joint of the helicopter, and for clarity, some parts have been removed;

[0037] Figure 4 shows according to Figure 1 and Figure 2 a perspective view of a specific embodiment of the stationary joint of the helicopter in an undeformed state from a first visual angle;

[0038] Figure 5 shows in an undeformed state Figure 4 a perspective view of different embodiments of the stationary joint in an enlarged scale and from a second visual angle;

[0039] Figure 6 shows a side view of the stationary joint of Figure 5 in a bent and deformed state; and

[0040] Figure 7 shows a side view of the stationary joint of Figure 5 and Figure 6 in an undeformed state. DETAILED DESCRIPTION

[0041] Referring to the drawings, 1 represents a helicopter.

[0042] The helicopter 1 basically comprises:

[0043] - a fuselage 2;

[0044] - a motor group 3 formed, for example, by one or more turboshaft systems 10;

[0045] - a main rotor 4, which is located at the top of the fuselage 2, can rotate about an axis A, and is adapted to provide the lift and thrust required for the support and movement of the helicopter 1; and

[0046] - An anti-torque rotor 5, which is placed at the tail end 6 of the fuselage 2 in the illustrated example and is rotatable about its own axis transverse to axis B.

[0047] The helicopter 1 further includes a main transmission group 7 interposed between the motor group 3 and the control shaft 8 of the rotor 4.

[0048] The motor group 3 ( Figure 2 ) basically includes:

[0049] - A stator 11 of the accommodation system 10;

[0050] - An output shaft 12 of the system 10 rotatable about axis C.

[0051] The transmission group 7 basically includes:

[0052] - A stator 20; and

[0053] - An input shaft 21 rotatable about axis D, which coincides with axis C in the illustrated example.

[0054] The helicopter 1 further includes a joint 25 rotatable about axes C and D and interposed between the output shaft 12 and the input shaft 21.

[0055] The joint 25 is adapted to transmit the driving torque generated by the motor group 3 to the input shaft 21 of the transmission group 7.

[0056] In the illustrated example, the joint 25 includes a pair of disks 27a, 27b, which are respectively carried by opposite ends 28a, 28b adjacent to the corresponding output shaft 12 and input shaft 21.

[0057] The stators 11, 20 have respective sleeves 29, 30 fixed at an angle relative to the relevant axes C, D.

[0058] The sleeves 29, 30 are hollow and respectively accommodate portions of the output shaft 12 and the input shaft 21 that define the corresponding ends 28a, 28b.

[0059] The helicopter 1 further includes a joint 35 interposed between the sleeves 29, 30, fixed at an angle relative to axes C, D, and configured to allow the sleeves 29, 30 to tilt at a certain angle (e.g., 2 degrees) in a pair of planes parallel to axes C, D.

[0060] More specifically, the planes correspond to the elastic bending planes of the output shaft 12 and the input shaft 21.

[0061] Advantageously, the joint 35 includes a corrugated element 36 made of an elastically deformable material, which is interposed between the sleeves 29, 30 and is adapted to allow the inclination of said angle by its own elastic deformation.

[0062] In other words, the corrugations of the corrugated element 36 allow to obtain an elastic bending deformation capacity in order to allow the inclination between the sleeves 29, 30 in the aforementioned plane.

[0063] In the example shown, the corrugated element 36 extends axially symmetrically about the axis E.

[0064] When the corrugated element 36 is undeformed ( Figure 5 ), the axis E coincides with the axes C, D, and when the corrugated element 36 is bent and deformed, the axis E bends with respect to the axes C, D ( Figure 6 ).

[0065] In the following of this specification, the term "corrugation" refers to the continuous continuation or succession in certain stretches and the periodic succession of annular ridges and grooves around the axis C.

[0066] In a cross-section containing the axis E, the corrugation has:

[0067] - a longitudinal extension direction along which the ridges and grooves are periodically repeated; and

[0068] - a transverse direction orthogonal to the extension direction, along which the ridges and grooves extend at a certain distance from each other.

[0069] The distance between two consecutive ridges (grooves) along the longitudinal direction is called the pitch p of the corrugation.

[0070] The distance between the ridges and grooves along the transverse direction is called the height h of the corrugation.

[0071] Referring to Figure 2 , the joint 35 substantially includes a pair of flanges 38, 39 which project from the respective axial ends of the sleeves 29, 30 opposite to the motor group 3 and the transmission group 7 respectively.

[0072] In the example shown, the flanges 38, 39 extend orthogonally to the respective axes C, D.

[0073] The corrugated element 36 is axially interposed between the flanges 38, 39 and is connected to the flanges 38, 39 themselves.

[0074] The element 36 has corrugations 40 which have a longitudinal extension direction parallel to the axis E and a thickness in the radial direction of the axis E.

[0075] The corrugations 40 include respective multiple rings 41, 42.

[0076] The rings 41, 42 are parallel to each other between them and alternate with respect to the axis E, and define the respective radial ends of the corrugation 40 that face each other.

[0077] The ring 41 is arranged at a first radial distance from the axis E and defines the respective ridges of the corrugation 40.

[0078] The ring 42 is arranged at a second radial distance from the axis E that is less than the aforementioned first axial distance, and defines the respective grooves of the corrugation 40.

[0079] In the example shown, all of the rings 41 (42) are arranged at the same first (second) radial distance from the axis E.

[0080] The corrugation 40 has a plurality of connecting annular stretching portions 47, and each connecting annular stretching portion 47 is interposed between a corresponding ring 41 and the corresponding adjacent ring 42.

[0081] Each stretching portion 47 extends from the corresponding ring 41 towards the corresponding ring 42 with a gradually increasing axial and radial distance.

[0082] In the example shown, the corrugation 40 has a coil shape in a cross-section parallel to the axis E.

[0083] The corrugation 40 is symmetric about the axis E.

[0084] The rings 41, 42 are located in corresponding planes orthogonal to the axis E.

[0085] The corrugation 40 further includes axial ends 43, 44 that face each other and have an annular shape.

[0086] The ends 43, 44 are connected to the respective radially outer ends 45, 46 of the corresponding flanges 38, 39.

[0087] Referring Figures 3 to 7 , the joint 35 further includes a plurality of ribs 69, 70 that are connected to the element 36 and are adapted to give the joint 35 its own axial rigidity.

[0088] The ribs 69, 70 are arranged outside the element 36 with reference to the axis E and are arranged eccentrically with respect to the axis E itself.

[0089] Each rib 69, 70 extends along the axis E and extends in an arc around the axis E, and the width of the arc is less than the length of the rib 69, 70 along the axis E.

[0090] Furthermore, each rib 69, 70 has a total dimension in the radial direction of the axis E that is greater than its extension in the circumferential direction of the axis E itself.

[0091] Each rib 69, 70 is axially delimited by a pair of stretching portions 81, 82 that face each other and are shaped like circular arcs( Figure 7 ).

[0092] Each rib 69, 70 is also delimited at a radially outer position with respect to the axis E by a straight stretching portion 89 parallel to the axis E.

[0093] Furthermore, each rib 69, 70 is delimited at a radially inner position with respect to the axis E by a corresponding corrugation 71 coupled to a corresponding portion 48 of the corrugation 40 of the element 36.

[0094] The stretching portion 89 and the corrugation 71 are radially opposite to each other and extend between the stretching portions 81, 82.

[0095] The corrugation 71 has a longitudinal extension direction parallel to the axis E and a thickness in the radial direction with respect to the axis E.

[0096] In the example shown, the corrugation 71 includes a corresponding plurality of ridges 72 and grooves 73.

[0097] The ridges 72 and the grooves 73 alternate with each other parallel to the axis E therebetween, and define corresponding radially opposite ends of the corrugation 40.

[0098] The ridges 72 are provided at a first radial distance from the axis E.

[0099] The grooves 73 are provided at a second radial distance from the axis E, and the second radial distance is less than the aforementioned first radial distance.

[0100] In the example shown, all of the ridges 72 (grooves 73) are provided at the same first (second) radial distance from the axis E.

[0101] In particular, the ridges 72 and the grooves 73 respectively define the points of the maximum distance and the minimum distance of each rib 69, 70 from the axis E.

[0102] The corrugation 71 has a plurality of connecting stretching portions 74, and each connecting stretching portion 74 is interposed between a corresponding ridge 72 and a corresponding adjacent groove 73.

[0103] Each stretching portion 74 extends from the corresponding ridge 72 toward the corresponding groove 73 at gradually increasing axial and radial distances.

[0104] In the example shown, the corrugation 71 has a coil shape in a cross-section parallel to the axis E.

[0105] Each rib 69 is connected (glued in the example shown) to the relevant portion of the corrugation 40 such that the corresponding ridges 72 and the corresponding grooves 73 are radially connected to the corresponding rings 41, 42 of the corrugation 40, and the stretching portions 74 are radially connected to the corresponding stretching portions 47 of the corrugation 40(Figure 3 )。

[0106] In the example shown, each corrugation 71 includes two ridges 72 and a groove 73 axially interposed between the ridges 72.

[0107] In the example shown, the ridges 72 define opposite axial ends 75, 76 of the corrugation 71.

[0108] Referring Figure 3 , each rib 40 also includes:

[0109] - A pair of flanges 180, 181, which are respectively carried by the ridges 72 and respectively fixed to the ring 41;

[0110] - A flange 182, which is carried by the groove 73 and fixed to the ring 42; and

[0111] - A plurality of flanges 183, 183, two flanges 183 in the example shown, which are carried by the stretching portion 47 and interposed between the flanges 180, 182 and 182, 181 and fixed to the corresponding stretching portion 47.

[0112] In the example shown, the flanges 180, 181, 182, 183 extend like circular arcs over a length extending circumferentially more than that of the ribs 69, 70.

[0113] Each of the flanges 180, 181 includes a surface 184 orthogonal to the axis E and a surface 185 protruding from the surface 184 parallel to the axis E in a cantilever manner.

[0114] The surface 185 of the flange 180 extends in a cantilever manner from the relevant surface 184 towards the surface 185 of the flange 181.

[0115] The element 36 also includes a plurality of strips 100, which serve as joint covers associated with the corresponding ribs 69, 70.

[0116] More specifically, the strips 100 are received within the element 36.

[0117] In particular, the element 36 is obtained by approaching and joining a pair of half-elements 37 (only one of which is partially visible in Figure 3 ), each of the pair of half-elements 37 extending one hundred and eighty degrees in a cross-section obtained by a plane orthogonal to the axis E.

[0118] The flanges 180, 181, 182, 183 and the strips 100 connect the aforementioned half-elements 37 between positions radially external and radially internal to the axis E, respectively.

[0119] The flanges 180, 181, 182, 183 help to react to loads parallel to the axis E, while the strip 100 substantially performs the function of the joint cover.

[0120] The corrugations 40 are radially interposed between each strip 100 and the associated ribs 69, 70.

[0121] Each strip 100 is bounded in the axial direction by two arched tension portions 101 provided at the respective flanges 180, 181.

[0122] Each strip 100 is bounded in the circumferential direction by a pair of tension portions 103 which are parallel to each other and axially interposed between the tension portions 101.

[0123] Each strip 100 defines an associated corrugation 104 which has a longitudinal extension direction parallel to the axis E and a thickness in the radial direction of the axis E.

[0124] The corrugation 104 includes a respective plurality of ridges 105 and grooves 106 shaped as arc-shaped sections surrounding the axis E.

[0125] The ridges 105 and the grooves 106 alternate with each other parallel to the axis E and define the respective radial ends of the respective corrugation 104 which face each other.

[0126] The ridges 105 are provided at a first radial distance from the axis E.

[0127] The grooves 106 are provided at a second radial distance from the axis E, which second radial distance is less than the aforementioned first axial distance.

[0128] In the example shown, the ridges 105 (grooves 106) are all provided at the same first (second) radial distance from the axis E.

[0129] In particular, the ridges 105 and the grooves 106 respectively define the points of the maximum distance and the minimum distance of the corrugation 104 from the axis E.

[0130] The ridges 105 and the grooves 106 are shaped as respective circumferential arcs centered on the axis E.

[0131] The corrugation 104 has a plurality of connecting tension portions 107 shaped as arcs, each connecting tension portion 107 being interposed between a respective ridge 105 and the respective adjacent groove 106.

[0132] Each tension portion 107 extends from the respective ridge 105 towards the respective groove 106 at gradually increasing axial and radial distances.

[0133] In the example shown, the corrugation 104 has a coil shape in a section parallel to the axis E.

[0134] In the example shown, each strip 100 is made of aluminum or a composite material.

[0135] With reference Figures 4 to 7 , the joint 35 includes multiple pairs of ribs 69, 70 that are coupled to the element 36 and axially continuous with each other.

[0136] In the example shown, each pair of ribs 69, 70 are angularly spaced apart by one hundred and eighty degrees.

[0137] Each pair of ribs 69, 70 are arranged at the same axial position with respect to the axis E.

[0138] In the example shown, the pairs of ribs 69, 70 that are continuous along the axis E between them are angularly offset by one hundred and eighty degrees.

[0139] Preferably, each rib 69, 70 includes an associated tension portion 90 that is received within the element 36 and is radially opposite to the corresponding tension portion 89 ( Figure 5 ).

[0140] In particular, the element 36 is made of a composite material, especially a fiber-reinforced laminate, while the ribs 69, 70 are made of aluminum or other metal or a composite material or a combination of metal and composite material.

[0141] The element 36 houses the disks 27a, 27b and the portions of the output shafts 12 and 21 that are connected to the respective flanges 38, 39 ( Figure 2 ).

[0142] In use, the motor set 3 causes the output shaft 11 to rotate about the axis C.

[0143] The output shaft 12 drives the input shaft 21 of the transmission 7 to rotate about the axis D.

[0144] The transmission 7 drives the control shaft 8 of the rotor 4 to rotate about the axis A.

[0145] The corrugated element 36 of the joint 35 connects the sleeves 29, 30 that are respectively carried by the stator 11 of the motor set 3 and the stator 20 of the transmission 7.

[0146] More precisely, due to the torsional rigidity of the corrugated element 36, the corrugated element 36 allows the torque that is guided along the axis E and transmitted from the output shaft 12 to the sleeve 29 to be transmitted to the sleeve 30.

[0147] Due to the bending elastic deformation ability of the corrugated element 36 itself, the corrugated element 36 allows an inclination between the axes C, D in a pair of planes parallel to the axes C, D, E themselves.

[0148] This inclination is achieved through the bending elastic deformation ability of the corrugated element 36 ( Figure 6) and is allowed.

[0149] Due to the presence of the corrugations 40 and the fact that the corrugated element 36 is made of a fiber-reinforced composite laminate, this elastic bending deformation ability is obtained.

[0150] The ribs 69, 70 make the joint 35 axially rigid, thus allowing loads parallel to the axes C, D, E to be transmitted between the sleeves 29, 30.

[0151] From the characteristics of the helicopter 1 according to the present invention, the advantages that can be obtained are obvious.

[0152] In particular, the joint 35 interposed between the output shaft 12 of the motor group 3 and the input shaft 21 of the transmission 7 includes a corrugated element 36 having high torsional rigidity and bending deformation ability.

[0153] The torsional rigidity and bending deformation ability are determined by the corrugations 40, which have a length parallel to the axis E and a thickness transverse to the axis E.

[0154] Due to the aforementioned torsional rigidity, the joint 35 allows the effective transmission of the reaction torque from the output shaft 12 under normal operating conditions between the sleeves 29, 30, and also allows the transmission of the torque generated due to specific operating conditions (such as in the case of a jam of the motor group 3).

[0155] At the same time, due to the aforementioned bending elastic deformation ability, the joint 35 allows the inclination between the sleeves 29, 30 in a pair of planes parallel to the axes C, D, E.

[0156] In other words, the corrugations 40 allow the separation of rigidity and load path.

[0157] It is important to emphasize that, different from the known types of solutions discussed in the introductory part of this specification, these characteristics are obtained without the need to use multiple components hinged between them, with the obvious advantages of significant weight reduction and construction simplification.

[0158] The ribs 69, 70 make the joint 35 have the required axial rigidity, which is suitable for allowing the transmission of forces between the sleeves 29, 30 parallel to the axes E, C, D without significantly impairing the bending flexibility of the joint.

[0159] In other words, the ribs 69, 70 further help to separate the rigidity and load path of the joint 35.

[0160] The corrugations 71 of the ribs 69, 70 are axially constrained to the corrugations 40 of the element 36. This allows the ribs 69, 70 to be significantly stabilized, thus increasing the maximum peak load stress that can be supported by the ribs 69, 70 themselves.

[0161] The foregoing characteristics of the joint 35 can be optimized by appropriately selecting the lamination sequence of the fiber-reinforced materials of the elements 36 and the ribs 69, 70.

[0162] Obviously, the helicopter 1 described and shown herein can be modified and varied without thereby departing from the scope of protection defined by the claims.

[0163] In particular, the corrugations 40, 71, 104 can be at least partially shaped to engage with each other and / or have a discontinuous segment with a curved tensile portion.

[0164] Furthermore, the corrugated element 36 may not be axially symmetric about the axis E. For example, the corrugated element 36 may have an elliptical cross-section in order to obtain different bending rigidities from each other in different planes parallel to the axis E. Alternatively, the corrugated element 36 may have a conical or cylindrical shape.

[0165] Finally, the axes C, D can be inclined or skewed relative to each other.

Claims

1. A helicopter (1), comprising: at least one motor member (3), which includes an output shaft (12) and a first stator (11, 29) that rotatably supports the output shaft (12) about a first axis (C); a main rotor (4), which is adapted to provide the lift required for the support of the helicopter (1) itself and the thrust required for movement; a transmission (7) interposed between the motor member (3) and the main rotor (4); the transmission (7) in turn includes an input shaft (21) rotatable about a second axis (D) and a second stator (20, 30) that rotatably supports the input shaft (21) about the second axis (D); and a joint (35), which is interposed between the first stator (11, 29) and the second stator (20, 30), is fixed at an angle relative to the first axis (C), and is configured to allow tilting between the first stator (11, 29) and the second stator (20, 30) in at least one plane parallel to the first axis (C); characterized in that the joint (35) includes a first corrugated element (36) made of an elastically deformable material, the first corrugated element being interposed between the first stator (11, 29) and the second stator (20, 30) and being adapted to allow said tilting by elastic deformation; the first corrugated element (36) is torsionally rigid parallel to a third axis (E) and elastically bends and yields in at least one plane parallel to the third axis (E); the joint (35) includes at least one axial second corrugated element (69, 70) coupled to the first corrugated element (36); the second corrugated element (69, 70) has a shape similar to ribs (69, 70) that extend parallel to the third axis (E) and are eccentric with respect to the third axis (E).

2. The helicopter according to claim 1, characterized in that, At least when the first corrugated element (36) is not deformed in use, the first corrugated element (36) extends along its own third axis (E), and the third axis (E) joins the first axis (C) and the second axis (D).

3. The helicopter according to claim 2, characterized in that, The first corrugated element (36) is axially symmetric about the third axis (E).

4. The helicopter according to claim 1, characterized in that, The first axis (C), the second axis (D), and the third axis (E) coincide.

5. The helicopter according to claim 1, characterized in that, The first corrugated element (36) has a first corrugation (40), the first corrugation having an extension direction parallel to the third axis (E) and a radial thickness with respect to the third axis (E).

6. The helicopter according to claim 1, characterized in that, The second corrugated element (69, 70) has a second corrugation (71), the second corrugation having an extension direction parallel to the third axis (E) and a radial thickness with respect to the third axis (E); the first corrugation (40) and the second corrugation (71) are coupled between them so as to constrain the second corrugated element (69, 70) to the first corrugated element (36) at least in a direction parallel to the third axis (E).

7. The helicopter according to claim 1, characterized in that, It includes multiple pairs of the second corrugated elements (69, 70); Each of the second corrugated elements (69, 70) of each pair is angularly offset relative to the third axis (E) therebetween and is axially disposed relative to one another; The axially continuous pairs of corrugated elements (69, 70) are angularly offset relative to one another.

8. The helicopter according to claim 1, wherein With reference to the third axis (E), the second corrugated elements (69, 70) are axially rigid and flexurally yielding.

9. The helicopter according to claim 1, characterized in that, The second corrugation (71) is disposed radially externally relative to the first corrugation (40).

10. The helicopter according to claim 1, characterized in that, For each of the second corrugated elements (69, 70), the joint (35) includes a strip (100) defining a third corrugation (104) having an extension direction parallel to the third axis (E) and a radial thickness relative to the third axis (E); The first corrugation (40) is radially interposed between the strip (100) and the second corrugation (71).

11. The helicopter according to claim 10, characterized in that, The first corrugated element (36) includes a pair of half elements (37) that are connected to one another by the strip (100) at a radially inner position relative to the third axis (E) and are connected to one another by the second corrugated elements (69, 70) at a radially outer position relative to the third axis (E).

12. The helicopter according to claim 1, characterized in that, The first corrugated element (36) and / or the second corrugated elements (69, 70) are made of a fiber-reinforced composite material.

13. The helicopter according to claim 1, wherein It includes a further joint (25) that is rotatable and is interposed between the output shaft (12) and the input shaft (21); The further joint (25) is received within the first corrugated element (36).

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