FR3120660A1 - PROPELLER BLADE ANGULAR PITCH CONTROL SYSTEM FOR AN AIRCRAFT TURBOMACHINE - Google Patents

Abstract

System (34) for controlling the angular setting of a propeller blade (10), for an aircraft turbine engine, characterized in that it comprises: - a bowl (58) comprising an annular wall (58a) s' extending around an axis (A) intended to be a wedging axis of the blade, this annular wall (58a) comprising a lower axial end closed by a bottom wall (58b), and an upper axial end open and configured to allow mounting of a foot (14) of the blade (10) inside the bowl (58), and - an immobilizing ring (152) which extends around the said axis (A) and which is configured to be mounted around the foot (14), this immobilization ring (152) being a double dog clutch ring which comprises two annular rows of outer teeth (154, 156) of dog clutch, respectively active and safety. Figure for abstract: Figure 20

Description

PROPELLER BLADE ANGULAR PITCH CONTROL SYSTEM FOR AN AIRCRAFT TURBOMACHINE

Technical field of the invention

The present invention relates to the field of aircraft turbomachines and in particular the propulsion propellers of these turbomachines which include variable-pitch blades.

Technical background

The state of the art includes in particular documents FR-A1-3 017 163 and FR-A1-3 080 322.

An aircraft turbomachine propeller can be shrouded, as is the case with a fan for example, or not shrouded, as is the case with an architecture of the open-rotor type for example.

A propeller includes blades which can be variable pitch. The turbomachine then comprises a mechanism making it possible to modify the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

The design of a propeller blade involves several disciplines whose objectives are generally antagonistic. It must allow optimal aerodynamic performance (i.e. provide thrust while maximizing efficiency), guarantee mechanical strength of the blade (i.e. withstand the mechanical stresses resulting from static and dynamic loads ) while limiting the mass as well as the acoustic signature. In particular, the improvement in the aerodynamic performance of the propeller tends towards an increase in the BPR ( By Pass Ratio ), which results in an increase in its external diameter and therefore in the span of the blades. However, the increase in the BPR goes hand in hand with the reduction in the FPF ( Fan Pressure Ratio ). Therefore, a pitch change system (variable pitch vane) is generally required for the propeller to be operable over the entire flight envelope.

There are several technologies for attaching a variable-pitch propeller blade and several technologies for controlling the angular pitch of a propeller blade of this type. However, these technologies are relatively complex and expensive. Moreover, in the event of a problem and in particular of breakage, they do not guarantee the retention of the blades radially outwards with respect to the axis of rotation of the propeller, in particular when this propeller is not streamlined.

In the event of breakage or failure of the means for retaining a blade of the propeller, it is in fact particularly important to ensure the retention of this blade in order to prevent it from being thrown outwards and it impacts the fuselage of the aircraft equipped with the turbomachine. This safety function, called " failsafe ", is not always present in the control systems of current technologies. The control systems which include this function generally include elements which are themselves liable to detach and impact the fuselage of the aircraft. The greater the size and density of these elements, the greater the risk of damage to the fuselage and may require specific shielding, which impacts the weight of the aircraft and therefore its performance.

There is therefore a need for a control system technology that incorporates a simple and effective safety function.

The invention relates to a system for controlling the angular setting of a propeller blade, for an aircraft turbine engine, characterized in that it comprises:

- a bowl comprising an annular wall extending around an axis intended to be a wedging axis of the blade, this annular wall comprising a lower axial end closed by a bottom wall, and an upper axial end open and configured to allow the mounting of a root of the blade inside the bowl, the bottom wall being configured to cooperate by complementarity of shapes with a free end of said root so that the bowl is integral in rotation with the foot around said axis, and

- an immobilization ring which extends around said axis and which is configured to be mounted around the foot, this immobilization ring being configured to be mounted inside the bowl and to cooperate respectively with the foot and the wall ring of the bowl to ensure the axial retention of the foot in the bowl,

and in that the immobilizing ring is a double-clutch ring which comprises two annular rows of external dog clutch teeth, a first of these rows of teeth being configured to cooperate by dog clutch with first internal dog teeth complementary to the wall ring of the bowl and by axial support with these teeth to ensure the retention of the foot in the bowl, and a second of these rows of teeth being configured to cooperate by dog clutch with second internal dog teeth complementary to the annular wall of the bowl and being spaced from these teeth by an axial play to ensure safety in the event of failure of the first row of teeth

In the present application, a ring with double dog clutch means a ring which is equipped with two annular rows of external dog teeth. Each of these rows of teeth is capable of cooperating by dog clutching with a row of complementary internal teeth of the bowl of the system. Dog clutching is a type of assembly of one part in another by a double movement of the parts by translation then by rotation, one in relation to the other. One of the parts is engaged in the other of the parts by axial translation until the teeth pass from a position where they are one above the other to a position where they are one below the others. To do this, the teeth of one of the parts should be aligned with the inter-tooth spaces of the other of the parts to allow the parts to engage one in the other. The parts are then moved in rotation around their axes and relative to each other so that the teeth of the parts are substantially aligned axially and can cooperate by axial abutment with each other.

The function of the first row of dog teeth of the immobilization ring is to ensure the axial retention of the foot in the bowl and cooperates for this by axial support with the complementary internal teeth of the bowl.

The second row of dog teeth of this ring has the function of providing security of the “ failsafe ” type in the event of failure of the first row of teeth.

In other words, the retaining ring has an active or primary row of dog teeth (the first row of teeth) for blade root retention and a passive or secondary row of dog teeth (the second row of teeth) which is not operational in normal operation but used in the event of failure of the active row of teeth. This redundancy ensures optimum safety in retaining the blade root without leading to significant modification of the system and without adding parts. The safety function added to the system therefore does not lead to a significant modification of the system and its size.

The object of the invention is thus to introduce a safety element into the design of the blade root attachment. This safety element consists not only of a standby secondary force path which allows the non-release of the blade in the event of failure of the main retention system, but also of failure detection by the unbalance of the fan generated by failure of the primary retention system. Indeed, when there is a failure of the main dog clutch, the aforementioned clearance is consumed and the blade is retained by the secondary dog clutch. Since the radial position of the vane changes, this introduces an unbalance on the fan which can be detected to signal the problem.

The system according to the invention may comprise one or more of the following characteristics, taken separately from each other, or in combination with each other:

- in which the first row of teeth is an upper row of teeth intended to be located on the blade blade side, and the second row of teeth is a lower row of teeth; the second row of teeth is thus intended to be located on the side of the root of the blade;

- the second row of teeth is an upper row of teeth intended to be located on the blade blade side, and the first row of teeth is a lower row of teeth; the first row of teeth is thus intended to be located on the blade root side;

- the first and second rows of teeth are spaced axially from each other by a space which is intended to accommodate said first or second internal teeth and which has an axial dimension greater than an axial thickness of these internal teeth.

- the teeth of the first row of teeth have an axial thickness greater than that of the teeth of the second row of teeth;

- The first and second rows of teeth have substantially the same internal diameter and the same external diameter;

- the immobilization ring comprises an internal cylindrical surface at its internal periphery, this internal cylindrical surface being configured to cooperate by sliding with an external cylindrical surface complementary to the root of the blade or of an element attached to this root during the double interconnection, and this internal cylindrical surface being situated inside the first row of teeth or even also the second row of teeth;

- the internal cylindrical surface has an axial dimension which is between 90% and 100% of an axial thickness of the teeth of the first row of teeth or of a maximum axial thickness of the immobilization ring;

- the upper part of the annular wall around which the upper bearing is mounted comprises said first and second teeth at its inner periphery and a thread at its outer periphery, a nut being screwed onto this thread and bearing axially on an outer ring of this landing;

- the ring comprises at its inner periphery a frustoconical surface at least partially complementary to the shape of the foot;

- the ring is divided into sectors and comprises a plurality of angular sectors arranged next to each other around said axis;

-- the system also includes:

- a lower rolling guide bearing extending around said axis and mounted around a lower part of the annular wall;

- an upper rolling guide bearing extending around said axis and mounted around an upper part of the annular wall;

-- at least one of the guide bearings has its inner ring which is integrated into said bowl;

-- at least one of the guide bearings has angular contact;

-- the recess is eccentric with respect to the wedging axis;

-- the system further comprises an elastically deformable member extending around the wedging axis and mounted inside the bowl, this member bearing axially on the bottom wall and being configured to axially urge the foot of the dawn out of the bowl;

-- the system further comprises a locking ring and an annular snap ring, the locking ring being configured to be axially engaged between the internal and external dog teeth to prevent rotation of the dog dog ring inside the bowl , and the annular ring being mounted in the bowl to axially block the locking ring in the bowl;

-- the barrel is made of two half-shells attached and fixed to the body, the half-shells being joined at a joint plane which passes through said wedging axis;

-- the drum is glued to the body;

-- at least one shrink ring is mounted around the half-shells to keep them tight against the body, this shrink ring extending around the wedging axis;

-- a lower shrink ring is mounted on a low cylindrical surface of the barrel, and extends around at least part of the free end of the body;

-- an upper shrink ring is mounted on a high cylindrical surface of the barrel, and extends around part of a bulb of the body;

- the dog clutch ring is configured to be mounted on the upper cylindrical surface of the barrel;

-- the first guide bearing extends at least partly around the lower shrink ring, and the second guide bearing extends at least partly around the upper shrink ring.

The guide bearings take up the mechanical actions resulting from the aerodynamic and centrifugal forces applied to the blade in operation. The lower bearing can be configured to ensure the retention of the centrifugal blade and the upper bearing can be configured to ensure the absorption of bending moments resulting from aerodynamic and centrifugal forces. The distance between the bearings, along the pitch axis, generates a sufficient lever arm to prevent the blade from rotating, whatever the phase of flight.

The present invention also relates to an assembly comprising a system as described above and a variable-pitch propeller blade, this blade comprising a blade connected to a root, the root comprising a body housed in an annular shaft which extends around a blade setting axis

The present invention also relates to a turbine engine, in particular for an aircraft, comprising at least one system or an assembly as described above.

The present invention finally relates to a method for mounting a system as described above:

a) insertion of the root of the blade inside the bowl of the system, by moving the blade in a direction parallel to the pitch axis,

b) engagement of the free end of the root in the recess in the bottom wall of the bowl so as to secure the bowl in rotation with the root of the blade, and

c) engagement of the immobilization ring, previously mounted or present around the root of the blade, in the bowl and mounting of this ring by double clutching in the bowl and on the root of the blade so as to ensure retention axial of the foot in the bowl.

Advantageously, during steps a) and/or b), the root of the blade bears against the elastically deformable member and compresses it axially.

Brief description of figures

Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

there is a schematic perspective view of a propeller blade for an aircraft turbomachine,

there is a larger scale view of part of the and shows the foot of dawn,

there is a schematic view in perspective and with partial exploded view of the foot of the blade of the ,

there is a schematic perspective view of the blade root body of the ,

there is another schematic view in axial section of the root of the blade of the and guide bearings, the cutting plane extending along a chord of the blade of the blade,

there is a schematic view in axial section of the foot of the blade of the and guide bearings, the cutting plane extending transversely to the chord of the blade of the blade,

there is another schematic sectional view along line VII-VII of the ,

there is a schematic view in axial section of the foot of the blade of the and a system for controlling the angular setting of this blade,

there is a schematic perspective view of a bowl of the system of the ,

there is a schematic perspective view of a clutch ring of the system of the ,

there is a schematic perspective view of a locking ring of the system of the ,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a first assembly step,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a second assembly step,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a third assembly step,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a fourth assembly step,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a fifth assembly step,

there is a schematic view in perspective and in partial axial section of the root of the blade and of the system of the , and shows a sixth assembly step, and

there is a schematic perspective view of an immobilizing ring with a double row of dog clutch teeth for a system according to the invention for controlling the angular setting of a blade;

FIGS. 19a and 19b are very schematic views of assembly kinematics of a double dog clutch immobilizing ring;

there is a partial schematic view in axial section of a first embodiment of a system according to the invention;

there is a partial schematic view in axial section of a second embodiment of a system according to the invention;

there is a partial schematic view in axial section of a third embodiment of a system according to the invention.

Detailed description of the invention

There shows a blade 10 for a propeller of an aircraft turbine engine, this propeller being ducted or unducted.

The dawn 10 comprises a blade 12 connected to a foot 14.

The blade 12 has an aerodynamic profile and comprises a lower surface 12a and a lower surface 12b which are connected by an upstream leading edge 12c and by a downstream trailing edge 12d, the terms upstream and downstream referring to the flow of gases around of the blade in operation.

The blade 12 has an upper end which is free, called tip, and a lower end which is connected to the root 14.

In the example shown, the blade 10 is made of composite material by an injection process called the RTM process (acronym for Resin Transfer Molding ). This method consists in preparing a fibrous preform 18 by three-dimensional weaving and then in placing this preform in a mold and injecting a polymerizable resin therein, such as an epoxy resin, which will impregnate the preform. After polymerization and hardening of the blade 12, its leading edge 12c is generally reinforced by a metal shield 20 attached and fixed, for example by gluing.

The blade 10 here comprises a spar 22 which comprises a part forming a core of the blade 12 and which is intended to be inserted into the preform 18 before the injection of resin, and a part which extends from the side opposite the tip of the blade 14 to form part of the foot 14, called the body 24.

The spar 22 is preferably made of a composite material with an epoxy organic matrix reinforced with 3D woven carbon fibers with the warp direction mainly oriented radially and the weft mainly oriented along the chord of the blade at the height of the aerodynamic vein. However, the spar can also be a mechanically more advantageous assembly of different composite materials with an organic matrix (thermosetting, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) according to several fiber arrangements (woven, braided, knitted, unidirectional).

Although not shown, the blade 12 can be hollow or solid and includes an internal cavity filled with a filling material of the foam or honeycomb type. This filler material is installed around the spar 22 and it is covered with a skin of organic matrix composite material to increase the resistance of the blade to impact.

The shield 20 can be titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 12a or even the extrados 12b of the blade 12 can be covered with a polyurethane film for erosion protection.

The foot 14 essentially comprises two parts, namely this body 24 and an annular barrel 26 which extends around the body 24 and an axis A of the blade.

The axis A is an axis of elongation of the blade 10 and of the blade 12 and in particular a pitch axis of the blade, that is to say the axis around which the angular position of the dawn is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the axis of rotation of the propeller equipped with this blade.

The body 24 of the foot 14 has a particular shape best seen in Figures 3 to 7.

The body 24 essentially comprises three parts, namely:

- a free end 28 located on the side opposite the blade 12,

- a stilt 30 located on the side of the blade, and

- a bulb 32 located between the free end and the stilt.

The free end 28 has a generally parallelepipedal shape in the example shown. As can be seen at the , this end 28 is off-axis or offset with respect to the axis A to achieve keying or indexing, as will be explained in more detail below.

We define Pb as a transverse plane, that is to say a plane perpendicular to the axis A, passing substantially through the middle of the end 28, measured along the axis A. This plane Pb is called plane low or lower. There shows the shape in section of the end 28 in this plane Pb. This section, called the bottom section, has a value or an area, for example maximum, denoted Sb and has a generally rectangular shape in the example shown.

As will also be described below, the end 28 is configured to cooperate with a system 34 for controlling the pitch of the blade.

The stilt 30 has a relatively complex shape and can be considered to include:

- two lateral flanks 30a, 30b, located respectively on the side of the intrados 12a and the extrados 12b of the blade 12, which converge towards each other along the axis A and in the direction of the top of the blade 12 (see figures 4 and 6), and

- two edges, respectively upstream 30c and downstream 30d, which on the contrary diverge from each other along the axis A and in the direction of the top of the blade 12 (cf. figures 4 and 5).

We define Ph as a transverse plane passing through the stilt 30, and in particular its lower end. This Ph plane is called the high or superior plane. In this plane, the stilt can have a non-circular cross-section and for example oval, oblong, square or rectangular. This section, called the upper section, has a value or an area, for example maximum, denoted Sh.

The bulge 32 has a generally swollen or domed shape, this bulge or bulge extending all around the axis A.

Pm is defined as a median plane passing through the bulb 32, and in particular in its part of greatest cross-section, which is denoted Sm. This Pm plane is called the mean plane. In this plane, the bulb 32 can have a circular section in section although this section is not limiting.

It is understood that the plane Pm is located between the planes Pb and Ph. The cross section of the bulb 32 decreases from the plane Pm (Sm) to the plane Ph, as well as from the plane Pm, to the plane Pb. that Sm is greater than Sb and Sh. Moreover, in the example represented, Sh is greater than Sb.

The barrel 26 is made of two half-shells 26a, 26b, as can be seen in , which are attached and fixed to the body 24, for example one on the side of the intrados 12a of the blade and the other on the side of the extrados 12b of the blade 12. The half-shells 26a, 26b are thus joined at the level of a joint plane which passes through the axis A and which extends substantially parallel to a chord of the blade 12.

Barrel 26 is advantageously fixed to body 24, preferably by gluing. The glue extends between the barrel and the body, all around the A axis.

The barrel 26 is preferably metallic (steel, titanium or titanium alloy such as TA6V). The glue is for example an epoxy glue charged with thermoplastic or elastomeric nodules or reinforced with a fabric. This assembly process by bonding is particularly suitable due to the large contact surface between the cavity of the barrel and the body, which can be composite. The presence of a glue joint is advantageous because it makes it possible to compensate for slight defects in shape. The glue joint also prevents friction at the metal/composite interface and therefore increases the life of the blade.

Several possibilities are envisaged for attaching the barrel 26 to the body 24. A first possibility is to deliberately leave a clearance between the two half-shells 26a, 26b of the barrel 26 once attached so as to properly apply the pressure during the polymerization of the glue joint. The polymerization phase can be done in an autoclave with the entire blade inside a vacuum tank. But, it is also possible to carry out this operation in press. However, the disadvantage of leaving a clearance between the two half-shells 26a, 26b is less control over their positioning and therefore having to carry out a re-machining of the outer surface. A second possibility is to bring the half-shells against each other around the body with no existing play. This strategy is possible, for example by machining a blank already cut into two parts and held together during the machining operation in order to ensure the geometry of the external surfaces once the half-shells are reassembled. This makes it possible to control the positioning and the geometry of the outer surface of the barrel 26 without the need for additional machining after bonding. In all cases, positioning pins or stops can be considered to ensure the relative position of the half-shells of the barrel.

The presence of a glue joint between the body and the barrel is however not mandatory although it is very advantageous. An alternative is to use preload washers (or springs) between the shaft and the composite body in order to push the body radially and press it against the shaft bearing surfaces. You can also play on the geometry of the barrel to ensure that the body is slightly "pinched" when the two half-shells of the barrel are attached around the bulb. In this case, it is the deformation of the shaft that generates a prestress. It is therefore necessary to provide tools to maintain this position before final assembly.

As can be seen in Figures 5 and 6, the shaft 26 covers and hugs at least a part of the bulb 32 and of the stilt 30, and has a complementary shape in section of the bulb 32, at the level of the middle section Sm, and of the stilt 30, at the level of the upper section Sh.

More specifically, the barrel 26 comprises three parts in the example shown,

- a lower end 36 which has a generally annular shape (see figures 5-7) and which extends at and around the free end 28 of the foot,

- an upper end 38 which extends at the level of the plane Ph and which comprises two lateral lips 40 applied to the sides 30a, 30b of the stilt 30, and

- A middle part 42 applied to the bulb 32 and closely matching its shape.

The lips 40 rest on the sides 30a, 30b of the stilt 30 and make it possible to stiffen the root 14 of the blade and to reinforce its resistance to torsion around the wedging axis A.

They also make it possible to absorb energy in the event of an impact on the blade 10, such as for example the ingestion of a bird. Fillets may be present on these lips to prevent wear or local damage to the body.

The internal surfaces of the barrel 26 which are in contact with the body 24 serve as bearing surfaces. Compared to a broached attachment, the bearing surface is maximized by exploiting the entire circumference of the bottom of the blade. On a broached attachment, only two distinct surfaces of the blade root, respectively located on the lower surface and on the upper surface, bear against bearing surfaces, whereas the surfaces of the blade root located on the leading edge and on the leakage are free. Still in comparison with a broached attachment, the height of the bearing surfaces in the radial direction is much greater, which also contributes to considerably increasing their surface. This large bearing surface makes it possible to reduce the contact pressure whatever the case of operation.

The barrel 26 comprises two cylindrical surfaces 44, 46a for mounting shrink rings 48, 50. The shrink rings 48, 50 make it possible to hold the half-shells 26a, 26b tight against each other and on the body 24 The shrinking rings 48, 50 extend around the axis A.

The surface 44 is located on the lower end 36 and is oriented radially outwards with respect to the axis A. It receives the ring 48 by shrinking which is engaged from the bottom and bears axially on a cylindrical surface located at the junction of the end 36 and the middle part 42 of the barrel 26.

The surface 46a is located on the middle part 42 and is oriented radially outwards with respect to the axis A. It receives the ring 50 by shrinking which is engaged from the top and bears axially on a cylindrical surface located near of the PM plane.

It can be seen that the surface 46a is located just next to a cylindrical surface 46b which is intended to receive an immobilizing ring 52, as will be described below.

The surfaces 44, 46a, as well as the rings 48, 50, have different diameters in the example shown. Surface 46a has a larger diameter than surface 44 and therefore ring 50 has a larger diameter than ring 48.

The surfaces 46a, 46b can have identical or different diameters. The surface 46b can for example have a diameter slightly smaller than that of the surface 46a. This is particularly the case where the ring 50 should be mounted with a predetermined radial play with respect to this surface 46b.

Figures 5 and 6 show that the ring 50 is located between the Ph and Pm planes, and that the ring 48 is located between the Pm and Ps planes.

Figures 5 and 6 also show the position of the rings 48, 50 and the planes Pm, Ph, Ps with respect to rolling bearings 54, 56 which extend around the axis A and the foot 14.

The bearings 54, 56 are here two in number and are respectively a lower bearing 54 and an upper bearing 56.

The bearings 54, 56 are of the ball bearing type. In the example shown, they have different diameters and their balls also have different diameters.

The bearing 54 extends substantially between the planes Pm and Pb and therefore around a lower part of the bulb 32. It also extends around the ring 48. This bearing 54 has a smaller diameter than the other bearing 56 , and its balls have a larger diameter than those of the other bearing 56.

The bearing 54 is also in oblique contact. In the example shown, the bearing points or surfaces of the balls on the raceways of their rings 54a, 54b are located on a frustoconical surface S1 which extends along the axis A and whose largest diameter is located on the side of the dawn summit.

The bearing 56 extends substantially between the planes Pm and Ph and therefore around an upper part of the bulb 32. It also extends around the ring 50. The bearing 56 is also in oblique contact. In the example shown, the bearing points or surfaces of the balls on the raceways of their rings 56a, 56b are located on a frustoconical surface S2 which extends along the axis A and whose largest diameter is located on the side of the free end of the foot of the blade.

The position of the middle section between the two bearings 54, 56 is very advantageous in terms of radial size because part of the bearing height between the middle section and the upper section is located inside the bowl 58, unlike the state of the art on broached attachments integrated into a pivot. This contributes to reducing the radial size of the control system 34.

Figures 8 to 17 illustrate an embodiment of the system and in particular of the immobilization ring 52.

The system 34 comprises a bowl 58 comprising an annular wall 58a extending around the axis A. This wall 58a comprises a lower axial end closed by a bottom wall 58b, and an open upper axial end configured to allow mounting from the 14 foot of the dawn inside the bowl.

The bottom wall 58b is configured to cooperate by complementarity of shapes with the free end of the foot 14, and therefore with the end 28 of the body 24, so that the bowl is integral in rotation with the foot around the 'axis.

In the present case, it is understood that the bottom wall 58b comprises a recess 60 having a non-circular cross-section, and in particular rectangular, and configured to receive the end 28 ( ). As we see at the , this recess 60 is eccentric with respect to the axis A in a manner analogous to the end 28 (cf. ). This eccentricity allows indexing and keying when inserting and mounting the foot in the bowl 58, only one position of engagement of the end 28 in the recess 60 being possible.

The recess 60 is located on an upper or inner face of the bottom wall 58b of the bowl 58, which is therefore located inside the bowl and oriented towards the side of the foot.

System 34 generates a torque at the blade root which opposes the twisting moment resulting from aerodynamic forces and centrifugal forces. The end 28 of the foot 14 could be enveloped in the barrel 26, like the rest of the body 24 of the foot 14. In this case, the latter would also have a non-circular shape in order to constrain its rotation. However, it is advantageous to let this end of the body come out of the barrel, as mentioned above, in order to directly constrain the rotation of the body. This results in a more direct force path, with the torque applied directly to the body. The lower section has dimensions strictly smaller than the maximum dimension of the middle section in order to limit the circumferential bulk at this height. As a result, the shaft also has a smaller circumferential bulk at this height than at the middle section. This makes it possible to reduce the diameter of the lower bearing which is located under the middle section. Therefore, the blade root can be integrated lower radially, which greatly reduces the theoretical hub ratio associated with the integration of the root. However, the person skilled in the art knows that a low hub ratio improves the performance of the engine, in particular because it is more compact and therefore lighter. This last point is a very important advantage of the technical solution compared to the competition which conventionally offers drums with a cylindrical external shape.

The bottom wall 58b comprises a lower or outer face, which is located on the side opposite the foot 14, and which comprises a cylindrical extension 62 extending along the axis A and comprising an external thread or external rectilinear splines 64 for the rotational coupling of the system with a pitch change mechanism which is not illustrated and which is common to the various systems 34 and blades 10 of the propeller.

An elastically deformable member 66, such as a coil spring, extends around the axis A and is mounted inside the bowl 58. This member 66 bears axially on the upper surface of the bottom wall 58b, at the outer periphery of this surface in the example shown, and is configured to axially urge the root of the blade towards the outside of the bowl, that is to say on the side of the tip of the blade.

The member 66 is supported on a cylindrical surface 68 of the barrel 26. In the example shown, the member 66 is centered by engagement of its upper end on and around a cylindrical rim 70 of the barrel, and by engagement of its lower end on and around a cylindrical flange 72 of the bowl located at the outer periphery of the bottom wall 58b.

The member 66 here extends around the shrink ring 48.

As we see at the , the bowl 58 is designed to support the bearings 54, 56 which ensure the centering and the guiding of the bowl around the axis A vis-à-vis a casing 74 or a fixed structure of the turbomachine.

The bearings 54, 56 can be part of the control system. In particular, at least one of the guide bearings can have its internal ring which is integrated into the bowl.

This is the case here of the lower bearing 54 which has its internal ring 54a integrated into the bowl 58. In practice, this means that the bowl comprises a raceway 54aa at its outer periphery on which the ball bearings of the bearing 54 roll directly. raceway comprises an annular surface with a concave curved section. This raceway is here located at the lower end of the bowl and of the wall 58a. The outer ring 54b of the bearing 54 is fixed to the casing 74, for example by shrink fitting. Furthermore, the bowl 58 is advantageously designed to apply a prestress to the bearing 54.

The outer ring 56b of the bearing 56 is fixed to the casing 74, for example by shrink fitting. Its inner ring 56a is engaged on and around the free upper end of bowl 58 and wall 58a. This end of the wall 58a comprises an outer cylindrical surface 76 for mounting the inner ring 56a as well as an outer thread for screwing a nut 78 intended to bear axially on the inner ring 56a to hold it axially tight against a shoulder external cylindrical 80 of the bowl 58.

The wall 58a of the bowl further comprises at its inner periphery means configured to cooperate with the immobilization ring 52 mentioned above.

The immobilization ring 52 extends around the axis A and is configured to be mounted around the foot 14. This immobilization ring 52 is configured to be mounted inside the bowl and to cooperate respectively with the foot 14 and the annular wall 58a of the bowl 58 in order to ensure the axial retention of the foot in the bowl.

In the embodiment of Figures 8 to 17, this immobilization ring 52 is a dog clutch ring which comprises external dog teeth 84 configured to cooperate with internal dog teeth 82 complementary to the annular wall 58a of the bowl 58 .

The teeth 82 of the bowl 58 are better visible at the . These teeth are regularly spaced around the axis A. They are six in number in the non-limiting example shown. They each have, for example, an angular extension around the axis A, comprised between approximately 20 and 30°.

Each of the teeth 82 comprises at its inner periphery a groove 86 oriented circumferentially with respect to the axis A. The grooves 86 of the teeth 82 form a discontinuous groove around the axis A.

The dog clutch ring is better visible at the . Its teeth 84 are regularly spaced around the axis A. They are six in number in the non-limiting example shown. They each have, for example, an angular extension around the axis A, comprised between approximately 20 and 30°.

The teeth 84 are complementary to the teeth 82 and are configured to cooperate by interconnection with these teeth. Dog clutching is a method of assembly well known in the aeronautical field and which will be illustrated by FIGS. 12 to 17 illustrating an assembly method.

The ring 52 comprises an internal cylindrical surface 52a intended to cooperate by sliding with the aforementioned surface 76 of the bowl 58.

The ring 52 comprises a second series of teeth 88, which extend axially upwards, on the side of the tip of the blade 10. These teeth 88 are also regularly spaced around the axis A. They are six in number. in the example shown. They can be arranged in staggered rows vis-à-vis the teeth 84, that is to say that the teeth 88 are aligned axially with the circumferential spaces located between the teeth 84. By way of non-limiting example, the teeth 88 each have an angular extension around the axis A, comprised between approximately 10 and 20°.

Each of the teeth 88 comprises at its inner periphery a groove 90 oriented circumferentially with respect to the axis A. The grooves 90 of the teeth 88 form a discontinuous groove around the axis A.

There shows a locking ring 92 which is configured to be axially engaged between dog teeth 82, 84 to prevent rotation of ring 52 within bowl 58.

This ring 92 comprises pads 94, here six in number in the non-limiting example shown, intended to be engaged in the inter-tooth spaces extending between the teeth 82 and 84. It is therefore understood that these pads 94 have shapes complementary to those of these spaces and are regularly spaced around the axis A.

In the example shown, the pads 94 are secured to each other by bridges 96 extending circumferentially between the pads 94. The bridges 96 are five in number and each extend between two adjacent pads 94. Two of the pads 94 are deliberately not connected together by a bridge so that the ring 92 is open. This can simplify assembly by spacing or bringing these pads closer to each other when mounting the ring in the 34 system.

Each of the pads 94 comprises at its inner periphery a groove 98 oriented circumferentially with respect to the axis A. The grooves 98 of the pads 94 form a discontinuous groove around the axis A.

The system further comprises an annular bead 100 which is only visible at the .

The ring 100 is mounted in the bowl 58 to axially block the locking ring 92 in the bowl 58. The ring 100 can also be split or opened to facilitate its assembly and is intended to be engaged in the grooves 86 of the teeth 82 of the bowl as well as the grooves 98 of the pads 94 of the ring 92, when these grooves 86, 98 are all located in the same plane perpendicular to the axis A and are arranged circumferentially with respect to each other to form a complete groove around of axis A (see figures 16 and 17).

Reference is now made to FIGS. 12 to 17 which illustrate a method for mounting the assembly formed by a blade 10 as illustrated in and a system 34 as shown in .

In the first step illustrated in , the root 14 of the blade 10 is engaged in the bowl 58 of the system 34 by axial translation along the axis A, until the end 28 of the body 24 of the root engages in the recess 60 of the bowl 58. As seen in the drawing, the ring 52 is already mounted prisoner around the stilt 30 of the body of the foot. Although not shown in this figure, member 66 ( ) is compressed when the foot 14 is inserted into the bowl 58.

In the second step illustrated by FIGS. 12 and 13, the ring 52 is positioned angularly around the axis A so that its teeth 84 are aligned with the spaces located between the teeth 82 of the bowl. The ring 52 is then moved in axial translation inside the bowl 58 until the ring 52 is engaged on the surface 46b of the barrel 26 and the teeth 84 are located just below the teeth 82, as illustrated in there . The grooves 90 provided on the teeth can be used for gripping the ring 52 by a suitable tool.

In the third step illustrated by Figures 13 and 14, the ring 52 is moved in rotation around the axis A so that these teeth 82, 84 are aligned axially with each other. Due to the angular extension of the teeth in the example shown, this angular displacement is here of the order of 25-30°. The teeth 88 can be used to grip the ring 52 and its rotation by the aforementioned tool. The member 66, not shown, axially urges the foot towards the outside of the bowl, which causes the axial support of the teeth 84 on the teeth 82. The foot is thus maintained axially inside the bowl and the system 34 In operation, the centrifugal forces applied to the blade are transmitted by the teeth 82, 84 to the bowl 58, these forces being taken up directly by the bearing 54 whose inner ring 54a is integrated into the bowl 58.

In the fourth step illustrated by Figures 15 and 16, the ring 92 is positioned angularly around the axis A so that its pads 94 are aligned with the spaces located between the teeth 82, 84. The ring 92 is then moved in axial translation inside the bowl 58 until the pads 94 are engaged in these spaces. The bridges 96 can then rest on the teeth 84 of the ring 52. The ring 92 thus prevents any rotation of the ring 52 inside the bowl 58.

In the last step illustrated by the , the rod 100 is engaged in the grooves 86, 98 aligned circumferentially with each other. The ring 100 prevents accidental dismantling of the ring 92.

It is understood that the dismantling of the blade is carried out by carrying out the aforementioned steps in the reverse order. It is also understood that one of the essential steps in the assembly and disassembly of the foot concerns the immobilization ring 52. This ring 52 can be manipulated from outside a turbomachine, which is particularly advantageous during a maintenance operation. . A blade can be disassembled and removed from the propeller by dismantling and removing a minimum number of parts.

We now refer to the which illustrates an embodiment of a ring 152 with double dog clutch for a control system 34 according to the invention.

The ring 152 comprises an annular body which comprises at its internal periphery an internal cylindrical surface 152a and at its external periphery two annular rows of external dog clutch teeth, referenced 154 and 156.

The row of teeth 154 is located at an upper end of the ring 152 and intended to be located on the side of the blade 12 of the blade 10 in the mounting position around the root 14 of the blade 10.

The row of teeth 156 is located at a lower end of the ring 152.

The rows of teeth 154, 156 are separated from each other by a space E which has an axial dimension denoted E1. This dimension E1 is measured along the axis of revolution of the ring 152 which coincides with the axis A of wedging of the blade 10 in the mounting position.

The row of teeth 154 has an axial thickness E2 measured along this axis and the row of teeth 156 has an axial thickness E3 measured along this axis.

The teeth of the two rows 154, 156 can extend radially outwards with respect to the axis A from the same external cylindrical surface 152b. The rows of teeth 154, 156 then have identical or similar internal diameters Dint. The rows of teeth 154, 156 can also have identical or similar external diameters Dext.

The number of teeth of each row 154, 156 and their angular extent can be chosen according in particular to the desired mechanical strength of the ring 152.

The angular position of the teeth of one row relative to the teeth of the other row depends on the type of mounting of the ring 152 envisaged.

FIG. 19a illustrates a first assembly kinematics of the ring 152 when the teeth of the two rows 154, 156 are aligned axially, as is the case in the example of the .

In this case, the double dog clutch is achieved by a single translation of the ring 152 in the bowl 58 and by a single rotation of the ring 152 inside the bowl 58.

As schematically shown in Figure 19a, bowl 58 also includes two annular rows of internal teeth 158, 160. This figure shows only two teeth from each row 158, 160 and one tooth from each row 154, 156 for clarity. .

The row of teeth 158 is located at an upper end of the bowl 58 and intended to cooperate by dog clutch with the row of teeth 154, and the row of teeth 160 is located just below the row 158 and is intended to cooperate by dog clutch with row of teeth 156.

The rows of teeth 158, 160 are separated from each other by a space H which has an axial dimension denoted H1. This dimension is measured along the axis A. This dimension H1 is greater than the thickness E2 of the teeth of row 154 so that these teeth can be engaged between two teeth of rows 158, 160 of the bowl.

The arrow F1 illustrates the movement in translation of the ring 152 inside the bowl 58 along the axis A. The teeth of the two rows 154, 156 of the ring 152 are aligned with the inter-tooth spaces of the rows 158 , 160. The movement is carried out until the teeth of the row 154 are aligned transversely with the space H.

The arrow F2 illustrates the rotational displacement of the ring 152 inside the bowl 58 around the axis A. The displacement is carried out until the teeth of the rows 154, 156 are aligned axially with the teeth of the rows 158, 160.

As will be described in more detail below with reference to Figures 20 and 21, the teeth of one of the rows 154, 156 are configured to bear axially G against the teeth of one of the rows 158, 160 to ensure the axial retention of the blade 10 in the bowl 58. This is the case of the rows 154, 158 in the illustrated schematic example.

The teeth of the other of the rows 154, 156 are configured to be separated by a predetermined axial play J from the teeth of one of the rows 158, 160 to ensure safety in this restraint in the event of failure. This is the case for rows 156, 160 in the schematic example shown.

A locking ring 92 or pads 94 of the type described above can then be used to immobilize the ring 152 in rotation in the bowl.

FIG. 19b illustrates a second mounting kinematics of the ring 152 when the teeth of the two rows 154, 156 are angularly offset and are therefore not aligned axially. The example shown shows the case of an angular shift of one step, this step representing the angular extent of a tooth.

In this case, the double dog clutch is achieved by two translations of the ring 152 in the bowl 58 and by two rotations of the ring 152 inside the bowl 58.

Arrow F1 illustrates the translational movement of ring 152 inside bowl 58 along axis A. The teeth of row 156 of the ring are aligned with the inter-tooth spaces of row 158. The movement is made until the teeth of row 156 are located below the teeth of row 158.

The arrow F2 illustrates the rotational movement of the ring 152 inside the bowl 58 around the axis A. The movement is carried out until the teeth of the row 156 are aligned axially with the inter-tooth spaces of row 160.

The arrow F3 illustrates the movement in translation of the ring 152 inside the bowl 58 along the axis A. The movement is carried out until the teeth of the row 156 are located under the teeth of the row 160.

The arrow F4 illustrates the rotational displacement of the ring 152 inside the bowl 58 around the axis A. The displacement is carried out until the teeth of the row 156 are aligned axially with the teeth of the row 160 and the teeth in row 154 are axially aligned with the teeth in row 158.

As mentioned above, the teeth of one of the rows 154, 156 are configured to bear axially G against the teeth of one of the rows 158, 160 to ensure the axial retention of the blade in the bowl. . The teeth of the other of the rows 154, 156 are configured to be separated by a predetermined axial play J from the teeth of one of the rows 158, 160 to ensure safety in this restraint in the event of failure.

A locking ring 92 or pads 94 of the type described above can then be used to immobilize the ring 152 in rotation in the bowl.

Figures 20 to 22 illustrate more concrete embodiments of the ring 152 with double dog clutch according to the invention.

Each of these rings 152 is used in an environment similar to that described above in relation to the notably. The foregoing description therefore applies to the embodiments of FIGS. 20 to 22 insofar as it does not contradict what follows.

Regarding the , the upper axial end of the wall 58a of the bowl 58 comprises at its internal periphery the two rows of teeth 158, 160. The teeth of the rows 158, 160 have substantially identical internal and external diameters. The outer periphery of the upper axial end of the wall 58a includes the external screw thread of the nut 78 which bears on the inner ring 56a of the bearing 56.

In this embodiment, the row of active teeth is row of teeth 156, i.e. the lower row of teeth. This row of teeth 156 is intended to cooperate by axial support G towards the outside with the teeth 160 of the bowl 58. The row of passive teeth is the row of teeth 154, that is to say the upper row of teeth. This row of teeth 154 is separated by an axial play J from the row of teeth 158.

The ring 152 bears axially inwards on the hooping ring 50 and its external cylindrical surface 152a cooperates by sliding with the cylindrical surface 46a during the double clutching of the ring. This surface 152a extends here over only part of the axial dimension of the ring 152. The axial dimension of the surface 152a represents approximately between 90% and 100% of the maximum axial dimension of the teeth of the row 156 or of the ring 152.

The embodiment of the represents a relatively simple solution in which the passive dog teeth 154 are not subjected to particular forces and are therefore isolated, unless the active dog teeth 156 fail. However, it is to be feared that following the breakage of the active dog clutch, the force path of the passive dog clutch could also be damaged, which would reduce its effectiveness.

About the , the row of active teeth is the row of teeth 154, that is to say the upper row of teeth. This row of teeth 154 is intended to cooperate by axial bearing G towards the outside with the teeth 158 of the bowl 58. The row of passive teeth is the row of teeth 156, that is to say the lower row of teeth. This row of teeth 156 is separated by an axial play J from the row of teeth 160.

The ring 152 bears axially inwards on the hooping ring 50 and its external cylindrical surface 152a cooperates by sliding with the cylindrical surface 46a during the double clutching of the ring. This surface 152a extends here over a major part of the axial dimension of the ring 152. The axial dimension of the surface 152a represents approximately between 90% and 100% of the maximum axial dimension of the ring.

The embodiment of the represents a compact solution. This solution also has the advantage of better reliability of the passive dog, since there is less chance that the breakage of the active dog has damaged the force path of the passive dog.

In the variant embodiment of the , the ring 152 differs from that of FIGS. 20 and 21 in particular in that its inner periphery has a frustoconical shape flared inwards and which is complementary at least in part to the bulb of the foot. The aforementioned barrel 26 can then be eliminated or even considered as integrated into the ring 152 (on the outer side of the bulb).

Furthermore, the ring 152 can be sectorized and comprise a plurality of angular sectors arranged next to each other around the axis A. Although the ring sectors 152 are independent, they can be mounted individually in the same way as 'a one-piece ring, by double clutching with one of the kinematics of Figures 19a and 19b.

Advantageously, the aforementioned play J is determined so as to generate an imbalance when the propeller equipped with the system 34 is set in rotation. This imbalance is generated by the radial displacement of the blade 10 after the primary dog clutch breaks and can be detected by an appropriate sensor fitted to the propeller. Detection of this imbalance can trigger the engine to stop to limit the impact force during contact after the primary dog clutch has broken.

Whatever the embodiment, the passive dog clutch teeth can have dimensions, and in particular axial thicknesses, that are smaller than those of the active dog dog teeth, because unlike the active dog dog, the passive dog dog is not dimensioned in fatigue and can accept higher stress.

The invention also proposes a method for mounting the system 34, which comprises the following steps:

a) insertion of the root 14 of the blade 10 inside the bowl 58 of the system 34, by moving the blade 10 in a direction parallel to the setting axis A,

b) engagement of the free end 28 of the foot 14 in the recess 60 of the bottom wall 58b of the bowl 58 so as to secure the bowl 58 in rotation with the foot 14 of the blade 10, and

c) engagement of the immobilization ring 52, previously mounted or present around the root 14 of the blade 10, in the bowl 58 and assembly by dog clutching of this ring 52 in the bowl 58 and on the root 14 of the blade 10 so as to ensure the axial retention of the foot 14 in the bowl 58. The kinematics of Figure 19a or Figure 19b is adopted depending on the type of double dog clutch, as mentioned in the foregoing. Thus, in step c), there is engagement of the ring 152 in the bowl 58 and on the root 14 of the blade 10 so as to ensure the axial retention of the root 14 in the bowl 58, in particular by being able consider the sectors of the ring 152. It is possible to provide an insertion notch in the bowl 58 to facilitate the mounting of the ring and, if necessary, of its sectors, or it is possible to adapt the geometry of the sectors to allow assembly without insertion notch.

Other embodiments not shown are possible, including:

• the half-shells 26a, 26b of the shaft 26 can be attached to the body 24 by bolting, riveting, welding, etc. ;
• the glue connecting the barrel 26 to the body 24 can be an epoxy glue but it can also be an elastomer or a thermoplastic glue. It is also possible to use a non-stick film to leave the possibility of relative movement by limiting wear by friction;
• Still with regard to the shaft/body interface, several technical solutions can also be combined together from those proposed (gluing, prestressing by washers or springs, prestressing by the geometry of the shaft); these solutions can be combined independently of the existence of a clearance between the two parts of the barrel;
• although this is less advantageous, the radial position of the bearing ensuring the centrifugal retention of the blade can be reversed with the radial position of the bearing which ensures the absorption of bending moments resulting from aerodynamic and centrifugal forces.

Claims (15)

System (34) for controlling the angular setting of a propeller blade (10), for an aircraft turbine engine, characterized in that it comprises:
- a bowl (58) comprising an annular wall (58a) extending around an axis (A) intended to be a wedging axis of the blade, this annular wall (58a) comprising a lower axial end closed by a bottom wall (58b), and an open upper axial end configured to allow mounting of a foot (14) of the blade (10) inside the bowl (58), the bottom wall (58b) being configured to cooperate by complementarity of shapes with a free end (28) of said foot (14) so that the bowl (58) is integral in rotation with the foot (14) around said axis (A), and
- an immobilization ring (152) which extends around said axis (A) and which is configured to be mounted around the foot (14), this immobilization ring (152) being configured to be mounted inside of the bowl (58) and to cooperate respectively with the foot (14) and the annular wall (58a) of the bowl (58) in order to ensure the axial retention of the foot (14) in the bowl (58),
and in that the locking ring (152) is a double-clutch ring which comprises two annular rows of outer dog teeth (154, 156), a first of these rows of teeth (154, 156) being configured to cooperate by dog clutching with first internal dog teeth (158, 160) complementary to the annular wall (58a) of the bowl (58) and by axial support (G) with these teeth to ensure the retention of the foot (14) in the bowl ( 58), and a second of these rows of teeth (156, 154) being configured to cooperate by dog clutch with second internal dog teeth (160, 158) complementary to the annular wall (58a) of the bowl (58) and being spaced of these teeth by an axial clearance (J) to ensure safety in the event of failure of the first row of teeth. System (34) according to claim 1, in which the first row of teeth (154) is an upper row of teeth intended to be located on the side of the blade (12) of the vane (10), and the second row of teeth (156) is a lower row of teeth. A system (34) according to claim 1, wherein the second row of teeth (154) is an upper row of teeth to be located on the blade blade side of the blade, and the first row of teeth (156) is a lower row of teeth. System (34) according to one of the preceding claims, in which the first and second rows of teeth (154, 156) are spaced axially from each other by a space (E) which is intended to receive said first or second internal teeth (158, 160) and which has an axial dimension (E1) greater than an axial thickness of these internal teeth. System (34) according to one of the preceding claims, in which the teeth of the first row of teeth (154, 156) have an axial thickness (E2, E3) greater than that of the teeth of the second row of teeth. System (34) according to one of the preceding claims, in which the first and second rows of teeth (154, 156) have substantially the same internal diameter (Dint) and the same external diameter (Dext). System (34) according to one of the preceding claims, in which the securing ring (152) comprises an internal cylindrical surface (152a) at its internal periphery, this internal cylindrical surface (152a) being configured to cooperate by sliding with a external cylindrical surface (46a) complementary to the root (14) of the blade (10) or to an element attached to this root during the double dog clutch, and this internal cylindrical surface being located inside the first row of teeth (154, 156) or even the second row of teeth. System (34) according to the preceding claim, in which the internal cylindrical surface (152a) has an axial dimension which is between 90% and 100% of an axial thickness (E2, E3) of the teeth of the first row of teeth ( 154, 156) or a maximum axial thickness of the immobilizing ring. System (34) according to one of the preceding claims, in which it further comprises:
- a lower rolling guide bearing (54) extending around said axis (A) and mounted around a lower part of the annular wall (58a),
- an upper rolling guide bearing (56) extending around said axis (A) and mounted around an upper part of the annular wall (58a). System (34) according to the preceding claim, in which at least one of the guide bearings (54, 56) has its inner ring (54a, 56a) which is integrated with said bowl (58). A system (34) according to claim 9 or 10, wherein the upper portion of the annular wall (58a) around which the upper bearing (56) is mounted includes said first and second teeth (158, 160) at its inner periphery and a thread at its outer periphery, a nut (78) being screwed onto this thread and bearing axially on an outer ring (56a) of this bearing (56). System (34) according to one of the preceding claims, in which it further comprises a locking ring (92) and an annular ring (100), the locking ring (92) being configured to be engaged axially between the teeth internal (82) and external (84) dog clutch to prevent rotation of the dog clutch ring (152) inside the bowl (58), and the annular ring (100) being mounted in the bowl (58) to block axially the locking ring (92) in the bowl (58). Assembly comprising a system (34) according to one of the preceding claims and a variable-pitch propeller blade (10), this blade (10) comprising a blade (12) connected to a root (14), the root (14 ) comprising a body (24) housed in an annular barrel (26) which extends around an axis (A) for wedging the blade. Turbomachine, in particular aircraft, comprising at least one system (34) according to one of Claims 1 to 12 or an assembly according to Claim 13. Method for mounting a system according to one of claims 1 to 12, in which it comprises the steps of:
a) inserting the root (14) of the blade (10) inside the bowl (58) of the system (34), by moving the blade (10) in a direction parallel to the setting axis ( AT),
b) engagement of the free end (28) of the foot (14) in the recess (60) of the bottom wall (58b) of the bowl (58) so as to secure the bowl (58) in rotation with the foot (14) dawn (10), and
c) engagement of the immobilization ring (152), previously mounted or present around the root (14) of the blade (10), in the bowl (58) and mounting of this ring (152) by double clutching in the bowl (58) and on the root (14) of the blade (10) so as to ensure the axial retention of the root (14) in the bowl (58).