DRIVE SHAFT FOR AN AIRCRAFT TURBOMACHINE

Abstract

The invention relates to a transmission shaft (22) comprising: - a male cylindrical body (23), - a first splined section arranged coaxially around the male cylindrical body (23) and having longitudinal first splines (38) and comprising an alternation of first teeth (39) and first grooves (40), the first section (34) being rotationally fixed to the male cylindrical body (23), characterized in that the transmission shaft (22) further comprises: - a second splined section arranged coaxially around the male cylindrical body (23), the second section having longitudinal second splines and comprising an alternation of second teeth (44) and second grooves, the second section being stressed by an elastic element from a first position to a second position in which the second teeth (44) are angularly offset relative to the first teeth (39). (Short figure: 3)

Description

Title of the invention: DRIVE SHAFT FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The invention relates to a drive shaft for an aircraft turbomachine.

[0002] The invention relates in particular to a transmission shaft having splines. Technical background

[0003] An aircraft turbomachine generally extends along and around a longitudinal axis. It comprises a gas generator which typically includes, from upstream to downstream in the direction of gas flow in the turbomachine, a blower, a low-pressure compressor, a high-pressure compressor, a gas combustion chamber, a high-pressure turbine and a low-pressure turbine.

[0004] The rotor of the low-pressure compressor is typically connected to the rotor of the low-pressure turbine via a low-pressure shaft. The rotor of the high-pressure compressor, on the other hand, is connected to the rotor of the high-pressure turbine via a high-pressure shaft.

[0005] The blower ensures the intake of an airflow that splits into a primary airflow passing through a primary channel and a secondary airflow passing through a secondary channel surrounding the primary channel. The primary airflow passes through the low-pressure and high-pressure compressors. The compressed primary airflow then passes through the combustion chamber where it is mixed with fuel. The combustion gases thus pass through the high-pressure and low-pressure turbines. The energy of the gases is transformed by the turbine rotor of the low-pressure turbine into mechanical energy, which drives the low-pressure shaft and, consequently, the low-pressure compressor.

[0006] Furthermore, such a turbomachine includes a plurality of accessories such as lubrication pumps, fuel pumps, or electrical power supply components necessary for the operation of the turbomachine and the aircraft. These accessories must also be powered for their operation.

[0007] In this context, a portion of the turbomachine's mechanical energy is drawn to power the accessories. This drawing is typically carried out on one of the turbomachine's shafts, in particular the high-pressure shaft. Such a drawing is performed by an accessory drive train, also known by the English acronym ADT for "Accessory Drive Train". Such a drive train is also implemented for the mechanical drive of the turbomachine during the start-up phases.

[0008] The accessory drive train typically includes drive shafts which ensure the transmission of the rotational motion of the turbomachine shafts and the transfer of mechanical energy.

[0009] Each transmission shaft extends along a longitudinal axis and typically comprises a male cylindrical body extending along the longitudinal axis and a female cylindrical body in which the male cylindrical body is coaxially engaged.

[0010] The male and female cylindrical bodies cooperate together via a grooved connection. Thus, the male cylindrical body comprises a section with longitudinal grooves and the female cylindrical body comprises an internal annular housing having internal longitudinal grooves that cooperate with the grooves of the male cylindrical body.

[0011] In certain hybrid turbomachines, the accessory drive train is also used for power injection phases. In such turbomachines, the accessory drive train thus experiences alternating phases of power injection and power extraction. This alternation of extraction and injection phases generates dynamic overtorques within the accessory drive train's transmission shafts, resulting in increased mechanical clearances between the splines of the male and female cylindrical bodies. These clearances are responsible for significant rattling during the rotation of the transmission shafts. Furthermore, this alternation of power extraction and injection phases generates torque oscillations within the transmission shafts.

[0012] These phenomena, which are particularly important in hybridized turbomachinery, can severely degrade the drive shafts.

[0013] For this purpose, there is a need to provide a transmission shaft which limits mechanical play within the transmission shaft and reduces torque oscillations. Summary of the invention

[0014] To this end, the invention proposes a drive shaft for an aircraft turbomachine, the drive shaft having a longitudinal axis and comprising:

[0015] - a male cylindrical body extending around and along the longitudinal axis,

[0016] - a first grooved section arranged coaxially around the male cylindrical body and having first longitudinal grooves regularly distributed around the longitudinal axis and comprising an alternation of first teeth and first grooves, the first section being rotationally fixed to the male cylindrical body.

[0017] The transmission shaft is remarkable in that it further comprises:

[0018] - a second grooved section arranged coaxially around the male cylindrical body, the second section having second longitudinal grooves regularly distributed around the longitudinal axis and comprising an alternation of second teeth and second grooves, the second section being stressed by an elastic element from a first position to a second position in which the second teeth are angularly offset with respect to the first teeth.

[0019] The invention may comprise one or more of the following features, taken individually or in combination with each other:

[0020] - the elastic element comprises at least one first spring mechanically connecting the first and second sections,

[0021] - the elastic element comprises a second spring diametrically opposite to the first spring and mechanically connecting the first and second sections,

[0022] - the first section comprises an annular lateral flank having at least one first reception accommodation of the first jurisdiction and optionally a second reception accommodation of the second jurisdiction,

[0023] - in the second position, the second teeth are angularly offset by less half a step from the first teeth, a step being the inter-tooth distance between two adjacent first teeth,

[0024] - at least one axial stop connected to the elastic means,

[0025] - a third section arranged coaxially around the male cylindrical body, the third section having longitudinal third grooves distributed around the longitudinal axis and comprising an alternation of third teeth and third grooves, the first section being arranged axially between the second and third sections, the third section being stressed by a second elastic element from a first position to a second position in which the third teeth are angularly offset with respect to the first teeth,

[0026] - in the second position, the third teeth are angularly aligned with the second teeth,

[0027] - a female cylindrical body having an internal annular housing in which The male cylindrical body and internal longitudinal grooves are inserted, cooperating with the first and second grooves. The internal grooves comprise an alternation of internal teeth and internal grooves, with the first teeth being inserted into the internal grooves and the second teeth filling a defined angular gap between the first teeth and the internal teeth.

[0028] - the second teeth are plated onto the inner teeth.

[0029] The invention also relates to a method for preparing a transmission shaft according to any one of the preceding characteristics.

[0030] The process is further remarkable in that it comprises the following steps:

[0031] (a) provide the male cylindrical body on which the first section is located,

[0032] (b) provide the second section, and

[0033] (c) to use the elastic means to drive the second section from the first position up to second position.

[0034] The invention also relates to a method of mounting a transmission shaft according to any one of the preceding characteristics.

[0035] The process is further remarkable in that it comprises the following steps:

[0036] (a') prepare the transmission shaft according to the previous preparation method,

[0037] (b') provide the female cylindrical body, and

[0038] (c') insert the male cylindrical body into the female cylindrical body, the second teeth filling the gap defined between the first teeth and the inner teeth. Brief description of the figures

[0039] Other features and advantages will become apparent from the following description of non-limiting embodiments of the invention with reference to the accompanying drawings in which:

[0040] [Fig.1] is a longitudinal cross-sectional view of an example of an aircraft turbomachine according to the invention;

[0041] [Fig.2] is a schematic longitudinal cross-sectional view of a transmission shaft according to the invention, comprising a female cylindrical body and a male cylindrical body engaged in the female cylindrical body,

[0042] [Fig.3] is a cross-sectional view of the transmission shaft of [Fig.2], along plane A-A',

[0043] [Fig.4] is a schematic longitudinal cross-sectional view of the male cylindrical body of [Fig.2] and indicating the mounting direction of the second and third grooved sections,

[0044] [Fig. 5] is a schematic perspective view of the first section of the male cylindrical body,

[0045] [Fig.6] is a schematic cross-sectional view of the second segment of the male cylindrical body,

[0046] [Fig.7] is another schematic longitudinal sectional view of the male cylindrical body,

[0047] [Fig.8] is a schematic cross-sectional view of the male cylindrical body along plane B-B',

[0048] [Fig.9] is a side view of the second section of [Fig.6]. Detailed description of the invention

[0049] An example of an aircraft turbomachine 1 according to the invention is shown very briefly in [Fig. 1]. The turbomachine 1 is, for example, a turboprop.

[0050] The turbomachine 1 extends along a longitudinal axis X. An airflow F flows into the turbomachine 1.

[0051] For the purposes of the present invention, the terms "upstream" and "downstream" are understood in relation to the direction of flow of the air flow F in the turbomachine 1 along the longitudinal axis X.

[0052] The turbomachine 1 comprises, from upstream to downstream, a blower 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6 and a low-pressure turbine 7.

[0053] Each compressor 3,4 comprises a compressor rotor 3a, 4a and each turbine 6, 7 comprises a turbine rotor 6a, 7a. The compressor rotors 3a, 4a and the turbine rotors 6a, 7a are composed of a plurality of stages, each comprising a bladed wheel.

[0054] The compressor rotor 3a of the low pressure compressor 3 is connected to the turbine rotor 7a of the low pressure turbine 7 by a low pressure shaft 8. They form a low pressure body.

[0055] The compressor rotor 4a of the high-pressure compressor 4 is connected to the turbine rotor 6a of the high-pressure turbine 6 by a high-pressure shaft 9. They form a high-pressure body.

[0056] The low pressure shafts 8 and high pressure shafts 9 are centered on the longitudinal axis X and are free to rotate about the longitudinal axis X. The high pressure shaft 9 is arranged coaxially around the low pressure shaft 8.

[0057] The airflow F passes through the blower 2 and splits into a primary airflow Fl passing through a primary stream v1 and a secondary airflow F2 passing through a secondary stream v2 surrounding the primary stream. The primary airflow Fl passes through the low-pressure compressor 3 and the high-pressure compressor 4. The compressed primary airflow Fl then passes through the combustion chamber 5 where it is mixed with fuel. The combustion gases thus pass through the high-pressure turbine 6 and the low-pressure turbine 7. The energy of the gases is transformed by the turbine rotor 7a of the low-pressure turbine 7 into mechanical energy, which drives the low-pressure shaft 8 and, consequently, the low-pressure compressor 3.

[0058] The fan 2 comprises a rotating disk about the longitudinal axis X and blades 2a evenly distributed on the disk. The fan 2 is, for example, of the unshod type. Unlike a shod type fan 2, the fan 2 does not include a fan housing surrounding the blades 2a. According to another example not shown, the fan 2 is of the shod type.

[0059] The disc is driven in rotation by a blower shaft 10. Advantageously, the blower shaft 10 is connected to the low-pressure shaft 8, for example via a speed reducer 11. The speed reducer 11 is of the type mechanical. It is, for example, an epicyclic or planetary gear train. Not shown in the illustration, the speed reducer 11 conventionally comprises a sun gear and a ring gear centered on the longitudinal axis X. It also includes satellite gears that mesh with the sun gear and the ring gear. Furthermore, it includes a satellite carrier s.

[0060] The solar element is rotationally fixed to the low-pressure shaft 8 and forms the input of the speed reducer 11, while one or the other of the ring and the satellite carrier, depending on the configuration of the reducer 11, is rotationally fixed to the blower shaft 10 and forms the output of the speed reducer 11.

[0061] The speed reducer 11 allows the blower shaft 10 to be driven at a rotational speed lower than the rotational speed of the low-pressure shaft 8. This makes it possible to increase the dilution ratio of the turbomachine 1.

[0062] The turbomachine 1 further comprises an inter-compressor housing 12 arranged axially, with reference to the longitudinal axis X, between the low-pressure compressor 3 and the high-pressure compressor 4.

[0063] The turbomachine 1 may further include an inlet housing 13. The inlet housing 13 is arranged axially, with reference to the longitudinal axis X, between the blower 2 and the low-pressure compressor 3.

[0064] The turbomachine 1 may further include an inter-turbine casing 14. The inter-turbine casing 14 is arranged axially, with reference to the longitudinal axis X, between the high-pressure turbine 6 and the low-pressure turbine 7.

[0065] The turbomachine 1 may further include an inter-vein compartment v3 located between the primary vein vl and the secondary vein v2.

[0066] The turbomachine 1 includes accessories or equipment (not shown) such as a fuel pump, a lubrication pump, an electric generator, an electric pump or a starter.

[0067] To ensure the drive of these accessories, the turbomachine 1 typically includes an electric machine. The electric machine is particularly advantageously of the reversible type. The electric machine is thus configured to draw power from a shaft, such as the low-pressure shaft 8 or high-pressure shaft 9, and to inject power into another shaft, such as the low-pressure shaft 8 or high-pressure shaft 9. The electric machine can therefore be of the generator type when used in a power-drawing phase and of the motor type when used in a power-injection phase.

[0068] In order to perform power extraction or injection, the turbomachine typically includes an accessory drive train 21, also known by the English acronym ADT for "Accessory Drive Train". The accessory drive train 21 comprises a gear train including a series of gears meshing together and each mounted coaxially around a shaft of respective drive. The drive of the gears of the gear train is achieved by drawing mechanical power from the low-pressure or high-pressure shaft 8, 9 for example. The drawn mechanical power is transferred to the gear train via transmission shafts 22 coupled to one of the drive shafts. The gear train is also coupled to rotors of accessories or equipment.

[0069] With reference to figures 2 and 3, each transmission shaft 22 has a longitudinal axis Z.

[0070] In the following description, the terms "longitudinal" and "longitudinally" are extended with reference to the longitudinal axis Z of the transmission shaft 22.

[0071] The transmission shaft 22 comprises a male cylindrical body 23 and a female cylindrical body 24.

[0072] Each male and female cylindrical body 23, 24 extends along and around the longitudinal axis Z. Each male and female cylindrical body 23, 24 thus has an elongated shape along the longitudinal axis Z. By "elongated", it is understood that each male and female cylindrical body 23, 24 has a length such that, measured along the longitudinal axis Z, it is greater than its internal diameter.

[0073] The male cylindrical body 23 is mounted coaxially at least in part in the female cylindrical body 24. The male cylindrical body 23 cooperates with the female cylindrical body 24 by means of a splined connection.

[0074] The female cylindrical body 24 extends longitudinally between a first end 25 and an opposite second end 26. The first and second ends 25, 26 are annular and centered on the longitudinal axis Z. The first end 25 has a first internal diameter d1 greater than a second internal or external diameter d2 of the second end 26.

[0075] The female cylindrical body 24 includes an internal housing 27. The internal housing 27 is annular and centered on the longitudinal axis Z. In particular, the internal housing 27 is located at the first end 25. Thus, the first end 25 is hollow.

[0076] The internal housing 27 is delimited by a grooved annular internal surface 28.

[0077] With reference to [Fig. 3], the internal surface 28 thus has internal grooves 29. The internal grooves 29 are preferentially regularly distributed around the longitudinal axis Z. Each internal groove 29 extends longitudinally along the longitudinal axis Z. Each internal groove 29 thus has an elongated shape along a direction parallel to the longitudinal axis Z. Each internal groove 29 comprises an alternation of internal teeth 30 and internal grooves 31, around the longitudinal axis Z. Each internal tooth 30 has a vertex 30a extended by two lateral flanks 30b.

[0078] Each internal tooth 30 can have a profile of general triangular or rectangular shape.

[0079] Each internal groove 31 is circumferentially delimited by two adjacent internal teeth 30. The space el delimited by two internal teeth defines the width of an internal groove 31.

[0080] The male cylindrical body 23 is free to rotate about the longitudinal axis Z. It extends longitudinally between a first end 32 and an opposite second end 33. The first end 32 may include longitudinal grooves. The second end 33 is inserted into the internal housing 27 of the female cylindrical body 24. They cooperate together by means of the grooved connection.

[0081] To this end, the transmission shaft 22 further comprises a first splined section 34. As also visible in [Fig. 4], the first section 34 is annular and centered on the longitudinal axis Z. It is located coaxially around the male cylindrical body 23 and is rotationally fixed to this male cylindrical body 23. In particular, the first section 34 is located at the second longitudinal end 33 of the male cylindrical body 23. The first section 34 may have a diameter equal to or greater than the diameter of the male cylindrical body 23.

[0082] In a particularly preferred manner, the first section 34 and the male cylindrical body 23 form a single piece and are thus made of material.

[0083] With reference to [Fig.5], the first section 34 comprises a peripheral edge 35 and lateral sides 36. The peripheral edge 35 is annular and centered on the longitudinal axis Z. The lateral sides 36 are also annular and centered on the longitudinal axis Z and are located on either side of the peripheral edge 35.

[0084] At least one of the lateral sides 36 may include at least one housing 37. Advantageously, at least one of the lateral sides 36 may include two housings 37 which are diametrically opposed along the longitudinal axis Z. Each housing 37 has a curved shape.

[0085] The first section 34 further comprises first grooves 38. The first grooves 38 extend longitudinally along the longitudinal axis Z and along the first section 34. The first grooves 38 are regularly distributed around the longitudinal axis Z. They are, for example, formed on the peripheral edge 35.

[0086] Each first groove 38 comprises an alternation around the longitudinal axis Z of first teeth 39 and first grooves 40.

[0087] Each first tooth 39 has a summit 39a extended by two lateral flanks 39b.

[0088] Each first tooth 39 can have a profile of general triangular or rectangular shape.

[0089] Each first groove 40 is circumferentially delimited by two adjacent first teeth 39.

[0090] As can be seen in [Fig.3], the first grooves 38 of the male cylindrical body 23 cooperate with the internal grooves 39 of the female cylindrical body 24. In particular, the first teeth 39 are inserted into the internal grooves 31 of the internal grooves 29.

[0091] Such cooperation by means of splines allows the rotational movement of the male cylindrical body 23 to be transmitted to the female cylindrical body 24. However, the width of the first teeth 39 is less than the width el of the internal grooves 31. There is thus a defined angular clearance j between a first tooth 39 and an adjacent internal tooth 30. This angular clearance is responsible for knocking, dynamic overtorque, and torsional dynamics, which are exacerbated by the alternating phases of power injection and extraction during which the transmission shafts 22 are used.

[0092] For this purpose, the transmission shaft 22 according to the invention further comprises a second splined section 41 and advantageously a third splined section 42.

[0093] As can be seen in [Fig.4] for example, the second and third sections 41, 42 are located coaxially around the male cylindrical body 23 and on either side of the first section 34.

[0094] With reference to [Fig. 6], the second section 41 is annular and centered on the longitudinal axis Z. It includes second splines 43. The second splines 43 extend longitudinally along the longitudinal axis Z and along the second section 41. The second splines 43 are regularly distributed around the longitudinal axis Z.

[0095] Each second groove 43 comprises an alternation around the longitudinal axis Z of second teeth 44 and second grooves 45.

[0096] Each second tooth 44 has a vertex 44a extended by two lateral flanks 44b.

[0097] Each second tooth 44 may have a generally triangular or rectangular profile. Preferably, the profile of each second tooth 44 is identical to the profile of the first teeth 39. The number of second teeth 44 is identical to the number of first teeth 39.

[0098] Each second groove 45 is circumferentially delimited by two adjacent second teeth 44.

[0099] The third section 42 is annular and centered on the longitudinal axis Z. It includes third splines 46. The third splines 46 extend longitudinally along the longitudinal axis Z and along the third section 42. The third splines 46 are regularly distributed around the longitudinal axis Z.

[0100] Each third groove 46 comprises an alternation around the longitudinal axis Z of third teeth 47 and third grooves 48.

[0101] Each third tooth 47 has a summit 47a extended by two lateral flanks 47b.

[0102] Each third tooth 47 may have a generally triangular or rectangular profile. Preferably, the profile of each third tooth 47 is identical to the profile of the first teeth 39 and the second teeth 43. The number of third teeth 47 is identical to the number of first teeth 39.

[0103] Each third groove 48 is circumferentially delimited by two adjacent third teeth 47.

[0104] The second and third sections 41, 42 are mobile in rotation around the longitudinal axis X. The second and third sections 41, 42 are mobile between a first position and a second position in which the second and third teeth 44, 47 are angularly offset with respect to the first teeth 39. By "angularly offset", it is understood that the teeth have a circumferential position which is different.

[0105] Preferably, the second and third teeth 44, 47 are angularly offset by less than half a step with respect to the first teeth 39, a step being the inter-tooth distance between two adjacent first teeth 39.

[0106] To ensure the movement of the second and third sections 41, 42 in rotation around the longitudinal axis X, the transmission shaft 22 further includes an elastic means 49 capable of stressing the second and third sections 41, 42 in rotation from the first to the second position.

[0107] The elastic means 49 comprises, for example, a first spring 49a and advantageously a second spring 49b suitable for applying stress to the second section 4L. The elastic means 49 may include third and fourth springs 49c, 49d suitable for applying stress to the third section 42. The first and second springs 49a, 49b are arranged in recesses 37 of a first lateral flank 36 of the first section 34. They are diametrically opposed. They mechanically connect the first section 34 to the second section 4L. The third and fourth springs 49c, 49d are arranged in recesses 37 of a second lateral flank 36 of the first section 34. They are diametrically opposed. They mechanically connect the first section 34 to the third section 42.

[0108] The transmission shaft 22 advantageously comprises at least one axial stop 50 connected to the first spring 49a. Advantageously, the transmission shaft 22 comprises a second axial stop 51 connected to the second spring 49b. The first and second axial stops 50, 51 are diametrically opposed and located in the housing 37.

[0109] The transmission shaft 22 advantageously comprises at least one third axial stop 52 connected to the third spring 49c and a fourth axial stop 53 connected to the fourth spring 49d. The third and fourth axial stops 52, 53 being diametrically opposed and located in the housing 37.

[0110] With reference to [Fig.7], the transmission shaft 22 may further include annular axial stops 54, 55 mounted around the male cylindrical body 23, the second and third sections 41, 42 being located axially between the first section 34 and the axial stops 54, 55 in order to maintain the second and third sections in axial position.

[0111] With reference to [Fig.3], in the mounting position of the male cylindrical body 23 in the female cylindrical body 24, the second teeth 44 and advantageously the third teeth 47 fill the gap j defined between the first teeth 39 and the internal teeth 30. Advantageously, the second teeth 44 and advantageously the third teeth 47 are pressed against the internal teeth 30.

[0112] Thanks to the second section 41 and the elastically deformable means 49, the play j between the male and female splines is filled, thus reducing rattles and torque oscillations.

[0113] The transmission shaft 22 is thus more mechanically robust, in particular to withstand an alternation of injection and power extraction phases.

[0114] A method for preparing the transmission shaft 22 will now be described.

[0115] This preparation process comprises the following steps:

[0116] (a) provide the male cylindrical body 23 with the first section 34,

[0117] (b) mount the second and optionally third section 41, 42 around the body male cylindrical 23, on either side of the first section 34,

[0118] (c) to use the elastic means to drive the second and optionally third section 41, 42 from the first position to the second position.

[0119] Advantageously, the second and third sections 41, 42 are driven in rotation about the longitudinal axis Z in opposite directions. This makes it possible to anticipate the reversals of torque in both directions of rotation.

[0120] A method for mounting the transmission shaft 22 will now be described.

[0121] This assembly method comprises the following steps:

[0122] (a') prepare the drive shaft according to steps (a) to (c),

[0123] (b') mount the male cylindrical body 23 into the female cylindrical body 24.

[0124] During step (b'), the second teeth 44 and advantageously the third teeth 47 fill the gap defined between the first teeth 39 and the internal teeth 30.

Claims

Demands

1. A drive shaft (22) for an aircraft turbomachine (1), the drive shaft (22) having a longitudinal axis (Z) and comprising: - a male cylindrical body (23) extending around and along the longitudinal axis (Z), - a first splined section (34) arranged coaxially around the male cylindrical body (23) and having longitudinal first splines (38) regularly distributed around the longitudinal axis (Z) and comprising an alternation of first teeth (39) and first grooves (40), the first section (34) being rotationally fixed to the male cylindrical body (23), characterized in that the drive shaft (22) further comprises: - a second splined section (41) arranged coaxially around the male cylindrical body (23), the second section (41) having longitudinal second splines (43) regularly distributed around the longitudinal axis (Z) and comprising an alternation of second teeth (44) and second gorges (45),the second section (41) being stressed by an elastic element (49) from a first position to a second position in which the second teeth (44) are angularly offset relative to the first teeth (39).

2. Shaft according to the preceding claim, characterized in that the elastic element (49) comprises at least one first spring (49a) mechanically connecting the first and second sections (34, 41).

3. Shaft according to the preceding claim, characterized in that the elastic element (49) comprises a second spring (49b) diametrically opposed to the first spring (49a) and mechanically connecting the first and second sections (34, 41).

4. Shaft according to any one of claims 2 or 3, characterized in that the first section (34) comprises an annular lateral flank (36) having at least a first housing (37) for receiving the first spring (49a) and optionally a second housing (37) for receiving the second spring (49b).

5. A shaft according to any one of the preceding claims, characterized in that in the second position, the second teeth (44) are angularly offset by less than half a pitch relative to of the first teeth (39), a step being the inter-tooth distance between two adjacent first teeth (39).

6. Shaft according to any one of the preceding claims, characterized in that it comprises at least one axial stop (50) connected to the elastic means (49).

7. Shaft according to any one of the preceding claims, characterized in that it comprises a third section (42) arranged coaxially around the male cylindrical body (23), the third section (42) having longitudinal third grooves (46) distributed around the longitudinal axis (Z) and comprising an alternation of third teeth (47) and third grooves (48), the first section (34) being arranged axially between the second and third sections (41, 42), the third section (42) being stressed by a second elastic element (49b) from a first position to a second position in which the third teeth (47) are angularly offset with respect to the first teeth (39).

8. Tree according to the preceding claim, characterized in that in the second position, the third teeth (47) are angularly aligned with the second teeth (44).

9. Shaft according to any one of the preceding claims, characterized in that it comprises a female cylindrical body (24) having an annular internal housing (27) into which the male cylindrical body (23) is inserted and longitudinal internal grooves (29) cooperating with the first and second grooves (39, 44), the internal grooves (29) comprising an alternation of internal teeth (30) and internal grooves (31), the first teeth (39) being inserted into the internal grooves (30) and the second teeth (44) filling a defined angular gap (j) between the first teeth (39) and the internal teeth (30).

10. Tree according to the preceding claim, characterized in that the second teeth (44) are plated on the internal teeth (30).

11. A method for preparing a transmission shaft (22) according to any one of the preceding claims, characterized in that it comprises the following steps: (a) providing the male cylindrical body (23) on which the first section (34) is located, (b) providing the second section (41), and (c) to use the elastic means to move the second section (41) from the first position to the second position.

12. Method of mounting a transmission shaft (22) according to any one of claims 1 to 8 in combination with claim 9, characterized in that it comprises the following steps: (a') preparing the transmission shaft (22) according to the preparation method of claim 11, (b') providing the female cylindrical body (24), and (c') inserting the male cylindrical body (23) into the female cylindrical body (24), the second teeth (44) filling the gap (j) defined between the first teeth (39) and the internal teeth (30).

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