SYSTEM FOR CONTROLLING THE BLADE PITCHING OF A PROPELLER FOR AN AIRCRAFT TURBINE ENGINE

Description

Domaine technique de l'invention

[0001] The present invention relates to the field of aircraft turbomachines and in particular to the propulsion propellers of these turbomachines which comprise variable-pitch blades. Arrière-plan technique

[0002] The state of the art includes in particular documents FR-A1-3 017 163, FR-A1-3 080 322, WO-A1-2020 / 169896, FR-A1-2 942 454 and WO-A1-2010 / 116080. In particular, document WO 2020 / 169896 A1 discloses according to its abstract a blade pivot with adjustable orientation, comprising a stud having retaining means and coupling means, an internal ring, a tightening nut, a timing transmission ring positioned inside the inner radial end of the stud and provided with coupling means cooperating with the coupling means of the stud, and means for locking the timing transmission ring on the stud.

[0003] An aircraft turbomachine propeller can be shrouded, as is the case with a fan for example, or unshrouded as is the case with an open-rotor type architecture for example.

[0004] A propeller comprises blades that can be variable pitch. The turbomachine then includes a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

[0005] 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 constraints resulting from static and dynamic loads) while limiting the mass as well as the acoustic signature. In particular, improving 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 FPR ( Fan Pressure Ratio ). Therefore, a pitch change system (variable pitch blade) is generally required to make the propeller operable over the entire flight envelope.

[0006] There are several technologies for attaching a variable-pitch propeller blade and several technologies for controlling the angular pitch of such a propeller blade. However, these technologies are relatively complex and expensive. Furthermore, in the event of a problem, particularly breakage, they do not guarantee that the blades will be retained radially outwardly relative to the propeller's rotational axis, particularly when the propeller is not shrouded.

[0007] In the event of failure of the retaining means of a propeller blade, it is in fact particularly important to ensure that this blade is retained in order to prevent it from being thrown outwards and impacting 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. Control systems that include this function generally include elements that are themselves likely to detach and impact the aircraft fuselage. The larger the size and density of these elements, the greater the risk of damage to the fuselage and may require specific shielding, which impacts the mass of the aircraft and therefore its performance.

[0008] There is therefore a need for a control system technology that integrates a simple and effective safety function. Summary of the invention

[0009] The invention relates to a system for controlling the angular pitch of a propeller blade, for an aircraft turbomachine, which comprises: a blade comprising a blade connected to a root, the blade comprising a setting axis and its root comprising a bulb which has two bearing surfaces, respectively lower and upper, which extend around said axis, a bowl comprising an annular wall extending around said axis, 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 the root of the blade inside the bowl, the bottom wall comprising a recess having a non-circular cross-section and configured to receive a free end of complementary shape to said root so that the bowl is secured in rotation with the root around said axis, a ring which extends around said axis and which is mounted around the root and in the bowl, this ring comprising a lower wall which is located in the bowl and which comprises an opening crossed by said free end of the root,said lower surface of the root bulb being configured to bear at least in the axial direction on this lower wall, on the side opposite the blade of the vane, the ring further comprising an openwork intermediate wall and a thread at an upper end, stops which are arranged around said axis and which are mounted around the root and in the bowl, these stops being engaged in slots in said intermediate wall and in at least one housing in the annular wall of the bowl, said upper surface of the root bulb being configured to bear at least in the axial direction on these stops, on the side of the blade of the vane, and a nut screwed onto the thread of the ring and configured to bear axially on said bowl so that tightening the nut forces the lower wall of the ring to bear on the lower surface of the root bulb, the upper surface of this bulb to bear on the stops,and the support of these stops on complementary support surfaces of said at least one housing of the bowl.

[0010] In the wedging system according to the invention, it is the bowl in which the blade root is mounted, which is configured to be moved in rotation around the wedging axis and which drives the blade in this movement. For this, the blade root is secured in rotation with the bowl, which thus forms a pivot connection for the blade.

[0011] The shimming system includes a ring, stops and a nut and this assembly allows several functions to be performed. It allows the blade root to be mounted and removed in the bowl without having to dismantle the bowl. This mounting and dismantling can be carried out from the outside, which, in the case of an unducted propeller, can allow the blade to be dismantled and removed without the need to remove the turbomachine, which can remain attached to an aircraft wing, for example. The stops provide a safety function failsafe. In the case, for example, where one of these stops is split or broken, the other stops would ensure the retention of the blade root until the damaged stop is replaced. Furthermore, tightening the nut makes it possible to apply a radial preload to the blade root, which ensures that the blade is immobilized and retained. This preload is advantageously predetermined so as not to be totally compensated by the forces induced by the centrifugal forces, the aerodynamic forces and the moments applied to the blade, during operation and rotation of the propeller.

[0012] The system according to the invention may comprise one or more of the following features, taken in isolation from one another, or in combination with one another: the number of stops is less than or equal to the number of slots in the intermediate wall of the ring, each of the stops being engaged in one of these slots; the number of stops is between 5 and 20, and preferably between 7 and 11; the lower wall of the ring has a general truncated cone shape flared on the blade side so that the support of the lower bearing surface of the root bulb on this lower wall has at all points an axial component and a radial component relative to said axis; each of the stops comprises a bearing face on the upper surface of the bulb of the foot, this bearing face being shaped so that the support has at every point an axial component and a radial component relative to said axis; the nut is screwed to the outside of the ring and / or bears axially on an upper free end of the bowl; each of the stops comprises at least one finger projecting radially outwards relative to said axis, said at least one finger comprising an upper axial bearing face on a corresponding bearing surface of said at least one housing; said at least one finger further comprises a lateral radial bearing face outwards on a corresponding bearing surface of said at least one housing; each of the stops comprises two fingers projecting radially outwards relative to said axis and arranged axially one behind the other;the bowl comprises at least one annular rib which extends around said axis and which defines said at least one housing for engaging said stops, this rib comprising at least one axial notch configured to allow the stops to be mounted one after the other. the bowl comprises two annular ribs, respectively upper and lower, which extend around said axis and which define between them said at least one housing for engaging said stops, these ribs comprising at least one axial notch configured to allow the stops to be mounted one after the other; the system further comprises at least one lock which is engaged in one of the slots of the ring and in said at least one notch, said lock being fixed to said ring; the lock is fixed by one or more screws to the ring; said lock is located on the side of an extrados of the blade of the vane, and is closer to a trailing edge of the blade than to its leading edge;Before the lock is assembled, the ring is able to rotate around said axis within the bowl, and after the lock is assembled, the ring is rotationally immobilized around this axis by circumferential abutment of the lock against the sides of the notch; -- one of the abutments forms a lock; -- the lock is independent of said abutments; -- said foot or said bulb of the foot is solid (i.e., it is free of a hollowed-out part); -- the number of lights on the intermediate wall of the ring is between 5 and 20, and preferably between 8 and 12; -- the system further comprises: a lower rolling guide bearing extending around said axis and mounted around a lower part of the bowl; an upper rolling guide bearing extending around said axis and mounted around an upper part of the bowl; -- at least one of the guide bearings has its inner ring integrated with said bowl; -- at least one of the guide bearings is an angular contact bearing;-- the recess is eccentric relative to the alignment axis. ;

[0013] The guide bearings ensure the absorption of mechanical actions resulting from aerodynamic and centrifugal forces applied to the blade during operation. The lower bearing can be configured to ensure retention of the blade in the centrifugal force and the upper bearing can be configured to ensure 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.

[0014] The present invention also relates to a turbomachine, in particular for an aircraft, comprising at least one system as described above.

[0015] The present invention finally relates to a method of mounting a system as described above, in which it comprises the steps of: a) inserting the ring into the bowl, b) inserting the foot of the blade into the ring, until the lower surface of the bulb of the foot rests on the lower wall of the ring, c) engaging the stops in the slots of the intermediate wall of the ring and in said at least one housing of the bowl, and d) screwing the nut onto the ring and tightening the nut onto the bowl so as to force the lower wall of the ring to rest on the lower surface of the bulb of the foot, the upper surface of this bulb to rest on the stops, and the stops to rest on the complementary bearing surfaces of said at least one housing of the bowl.

[0016] Advantageously, step c) comprises the following successive sub-steps: c1) engagement of one of the stops in one of the slots of the intermediate wall of the ring, by displacement of the stop in axial translation through the notch of the bowl, c2) rotational displacement of the ring and the stop inside the bowl, around the axis, c3) engagement of another of the stops in one of the slots of the intermediate wall of the ring, by displacement of the stop in axial translation through the notch of the bowl, c4) rotational displacement of the ring and the stops inside the bowl, around the axis, c5) repetition of steps c3) and c4) for the remaining stops, c6) engagement of the lock in the last free slot of the intermediate wall of the ring, by displacement of the lock in axial translation through the notch of the bowl, and c7) fixing the lock to the ring.

[0017] In one embodiment, the ring is displaced by a circumferential pitch at each of steps c2) and c4), this circumferential pitch being equal to 360° / k, k being the number of lights of the intermediate wall of the ring. Brève description des figures

[0018] Other features and advantages will emerge from the following description of a non - limiting embodiment of the invention with reference to the appended drawings on which: Fig.1 the figure 1 is a schematic perspective view of a turbomachine blade for an aircraft, Fig.2 the figure 2 is a larger - scale view of a part of the figure 1 and shows the blade root, Fig.3 the figure 3 is a schematic axial cross - sectional view of a system according to the invention for angular alignment of a turbomachine blade, according to a first embodiment of the invention, Fig.3a the figure 3a is a larger-scale detail view of part of the figure 3 , [ Fig.4 ] there figure 4 is a schematic view of a bowl of the system of the figure 3 , seen from above, [ Fig.5 ] there figure 5 is a schematic perspective view of the bowl of the system of the figure 3 , [ Fig.6 ] there figure 6 is a schematic perspective view of a ring of the system of the figure 3 , [ Fig.7 ] there figure 7 is a schematic perspective view of a stop of the system of the figure 3 , seen from above, [ Fig.8 ] there figure 8 is a schematic perspective view of a lock of the system of the figure 3 , seen from above, [ Fig.9 ] there figure 9 is a schematic view of the bowl and the ring mounted in the bowl of the system of the figure 3 , seen from above, and illustrates a step of a mounting method according to the invention, [ Fig.10 ] there figure 10 is a schematic view of the bowl, ring and a stop, seen from above, and illustrates another step of the process, [ Fig.11 ] there figure 11 is a view similar to that of the figure 10 and illustrates another step in the process, [ Fig.12 ] there figure 12 is a schematic view of the bowl, ring and stops, seen from above, and illustrates another step of the process, [ Fig.13 ] there figure 13 is a schematic view of the bowl, ring, stops and a lock, seen from above, and illustrates another step of the process, [ Fig.14 ] there figure 14 is a schematic perspective view of the ring, the stops and the lock and therefore without the bowl, [ Fig.15 ] there figure 15 is a schematic cross-sectional view of the assembly of the figure 13 , [ Fig.16 ] there figure 16 is a larger-scale detail view of part of the figure 15 , [ Fig.17 ] there figure 17 is a schematic axial sectional view of a system according to the invention for angular setting of a turbomachine propeller blade, according to an alternative embodiment of the invention, and [ Fig.17a ] there figure 17a is a larger-scale detail view of part of the figure 17 . Description détaillée de l'invention

[0019] There figure 1 shows a blade 10 for a propeller of an aircraft turbomachine, this propeller being shrouded or unshrouded.

[0020] The blade 10 comprises a blade 12 connected to a foot 14.

[0021] The blade 12 has an aerodynamic profile and comprises a lower surface 12a and an upper 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 the blade in operation.

[0022] The blade 12 has an upper end which is free, called the apex, and a lower end which is connected to the foot 14.

[0023] In the example shown, the blade 10 is made of composite material by an injection process called the RTM process (acronym for the English Resin Transfer Molding ). This method consists of preparing a fiber preform 18 by three-dimensional weaving and then placing this preform in a mold and injecting a polymerizable resin 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 added and fixed, for example by gluing.

[0024] 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 on the side opposite the top of the blade 14 to form a part of the root 14, called body 24.

[0025] The spar 22 is preferably made of an epoxy organic matrix composite material reinforced with 3D woven carbon fibers with the warp direction predominantly oriented radially and the weft predominantly oriented along the blade chord at the aerodynamic vein height. However, the spar may also be a more mechanically advantageous assembly of different organic matrix composite materials (thermosetting, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) in several fiber arrangements (woven, braided, knitted, unidirectional).

[0026] Although not shown, the blade 12 may be hollow or solid and includes an internal cavity filled with a foam or honeycomb type filler material. This filler material is installed around the spar 22 and is covered with a skin of organic matrix composite material to increase the blade's impact resistance.

[0027] The shield 20 may be titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 12a or even the extrados 12b of the blade 12 may be covered with a polyurethane film for protection against erosion.

[0028] A denotes the axis of elongation of the blade 10 and the blade 12 and in particular the setting axis of the blade 10, that is to say the axis around which the angular position of the blade 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.

[0029] Body 24 of foot 14 has a particular shape better visible at the figure 3 . 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 12, and a bulb 32 located between the free end 28 and the stilt 30.

[0030] The free end 28 has a generally parallelepiped shape in the example shown. This end 28 is preferably off-center or offset relative to the axis A to provide keying or indexing, as will be explained in more detail below.

[0031] The stilt 30 may have a relatively complex shape and may be considered to comprise: 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, 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.

[0032] The bulb 32 has a generally swollen or domed shape, this bulge or doming extending all around the axis A.

[0033] The bulb 32 has two peripheral bearing surfaces, respectively lower 32a and upper 32b, which extend around the axis A. In the example shown, due to the shape of the bulb, the lower bearing surface 32a is oriented downwards (i.e. on the side opposite the blade 12) and radially outwards relative to the axis A, and the upper bearing surface 32b is oriented upwards (i.e. on the side of the blade 12) and radially outwards relative to the axis A.

[0034] THE figures 3 à 16 illustrate a first embodiment of a system 34 according to the invention for angular setting of a blade 10 as illustrated in figures 1 et 2 .

[0035] The system 34 essentially comprises a bowl 36, a ring 38, stops 40 and a nut 42.

[0036] Bowl 36 is represented alone in the figures 4 And 5 . Ring 38 is shown alone in the figure 6 . The stops 40 are preferably identical and one of these stops 40 is shown in the figure 7 . Nut 42 is visible at figures 3 And 9 à 14 notably.

[0037] THE figures 3 , 8 And 13-15 show other elements of the system 34 which are however optional. This is notably the case of the lock 44, and the rolling bearings 46, 48.

[0038] The bearings 46, 48 are mounted around the bowl 36, between the bowl 36 and a casing 50 of the turbomachine which may be a hub of the propeller. The bearings 46, 48 are here two in number and are respectively a lower bearing 46 and an upper bearing 48.

[0039] The bearings 46, 48 are of the ball bearing type. In the example shown, they have different diameters and their balls also have different diameters.

[0040] The bearing 46 extends substantially around the lower bearing surface 32a and / or the free end 28 of the foot 14 in the example shown. This bearing 46 has a smaller diameter than the other bearing 48, and its balls have a larger diameter than those of the other bearing 48.

[0041] The bearing 46 is an angular contact bearing. In the example shown, the bearing points or surfaces of the balls on the raceways of their rings are located on a truncated cone-shaped surface which extends along the axis A and whose largest diameter is located on the side of the tip of the blade.

[0042] The bearing 48 extends substantially around the upper bearing surface 32b of the root 14. The bearing 48 is of oblique contact. In the example shown, the bearing points or surfaces of the balls on the raceways of their rings are located on a frustoconical surface which extends along the axis A and whose largest diameter is located on the side of the free end of the root of the blade. The casing 50 carries the outer rings of the bearings 46, 48 and their inner rings are carried by the bowl 36 or integrated into the latter, as is the case in the example shown for the inner ring of the bearing 46.

[0043] The bearings 46, 48 ensure the centering and guiding of the bowl 36 around the axis A with respect to the casing 50. The bowl 36 therefore serves as a pivot for the blade 10, with respect to the casing 50.

[0044] The bowl 36 comprises an annular wall 36a extending around the axis A. This wall 36a comprises a lower axial end closed by a bottom wall 36b, and an upper axial end open and configured to allow the mounting of the root 14 of the blade 10 inside the bowl 36. It is considered here that the axis A of the bowl 36 is that of the blade 10 corresponding to the axis of rotation for the change of angular setting of the blade, substantially radially relative to the rotation of the propeller.

[0045] The bottom wall 36b 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 36 is secured in rotation with the foot 12 around the axis.

[0046] In the present case, it is understood that the bottom wall 36b comprises a recess 52 having a non-circular, and in particular rectangular, cross-section, and configured to receive the end 28 ( figure 3 ). As seen in the figure 4 , this recess 52 is eccentric relative to the axis A in a similar manner to the end 28. This eccentricity allows indexing and keying during insertion and assembly of the foot 12 in the bowl 36, only one position of engagement of the end 28 in the recess 52 being possible.

[0047] The recess 52 is located on an upper or internal face of the bottom wall 36b of the bowl 36, which is therefore located inside the bowl 36 and oriented towards the side of the foot 12.

[0048] The system 34 generates a torque at the blade root which opposes the torsional moment resulting from the aerodynamic forces and the centrifugal forces. The transmission of forces between the bowl 36 and the root 12 is direct, the torsional moment being applied directly to the body of the root.

[0049] The bottom wall 36b comprises a lower or external face, which is located on the side opposite the foot 14, and which comprises a cylindrical extension 54 extending along the axis A and comprising an external thread or external rectilinear grooves 56 for the rotational coupling of the system with a pitch change mechanism which is not illustrated and which is common to the different systems 34 and blades 10 of the propeller (cf. figure 3 ).

[0050] The wall 36a of the bowl 36 comprises at its external periphery a raceway on which the balls of the bearing 46 roll directly. This raceway comprises an annular surface with a concave curved section. This raceway is here located at the lower end of the bowl 36 and of the wall 36a.

[0051] The inner ring of the bearing 48 is engaged on and around the free upper end 36c of the bowl 36 and the wall 36a. This end of the wall 36a comprises an external cylindrical surface for mounting this inner ring as well as an external thread for screwing a nut 58 intended to bear axially on the inner ring of the bearing 48 to keep it axially tightened against an external cylindrical shoulder of the bowl 36.

[0052] The free upper end 36c of the bowl 36 comprises a surface 36c1 which extends in a plane perpendicular to the axis A ( figures 3 à 5 ).

[0053] In the example shown, the wall 36a of the bowl 36 comprises at its internal periphery two annular ribs 60, 62 which extend around the axis A and which are therefore coaxial. The ribs 60, 62 are arranged at an axial distance from each other and one above the other, and are therefore respectively upper ribs 60 and lower ribs 62.

[0054] The upper rib 60 ensures the radial retention of the stops 40 and therefore of the root 14 of the blade 10, and the rib 62 forms a redundancy of these retention means and ensures the function failsafe of the assembly.

[0055] The ribs 60, 62 define between them a first annular housing 64 which extends around the axis A. Furthermore, the upper rib 60 can be considered as delimiting another housing 66, called upper, located above the rib 60, and the lower rib 62 can be considered as also delimiting another housing 68, called lower, located below the rib 62 ( figures 3 And 5 ).

[0056] The ribs 60, 62 extend continuously over less than 360° because they are interrupted by at least one axial notch 70, as can be seen in figures 4 And 5 . The notch 70 has for example an angular extent around the axis A of between 20 and 60°, and preferably between 30 and 50°. The ribs 60, 62 therefore preferably each have an angular extent around the axis A of between 300 and 340°, and preferably between 310 and 330°.

[0057] The notch 70 comprises side walls 70a which face each other and which are connected to each other by a bottom wall 70b which is oriented towards the axis A.

[0058] As seen in the figure 3a , the upper rib 60 comprises at its internal periphery an internal cylindrical surface 60a and at its lower end an annular surface 60b extending in a plane perpendicular to the axis A.

[0059] The lower rib 62 comprises at its internal periphery an internal cylindrical surface 62a, at its lower end an annular surface 62b extending in a plane perpendicular to the axis A, and at its upper end a frustoconical surface 62c flared on the side of the blade 12 of the vane 10.

[0060] Between the ribs 60, 62, the housing 64 comprises at the bottom an internal cylindrical surface 64a. The housing 68 comprises at the bottom an internal cylindrical surface 68a.

[0061] The ring 38 comprises an intermediate wall 72 of generally cylindrical shape which is connected at its lower end to a lower annular wall 74.

[0062] The intermediate wall 72 is perforated and comprises through-holes 76. In the example shown, the wall 72 comprises an annular row of holes 76 which are identical and regularly spaced and distributed around the axis A.

[0063] The slots 76 are configured to allow the mounting of the stops 40 and are therefore sized in this regard. Furthermore, the number of slots 76 is at least equal to the number of stops 40 so that each of the stops 40 can be mounted in one of these slots 76.

[0064] The lights 76 here have a generally rectangular shape and have a generally elongated shape along the axis A. The lights 76 are separated from each other by columns 72a of the wall 72. The columns 72a are rectilinear and parallel to each other and to the axis A.

[0065] The lower wall 74 comprises a central orifice 74a intended to be crossed by the lower end 28 of the foot of the blade, as can be seen in the figure 3 .

[0066] The wall 74 is configured to receive as support the lower bearing surface 32a of the bulb 32 of the foot 14 of the blade 10. As can be seen in the figure 3 , the wall 74 is preferably shaped to match the shape of the bulb 32 and of this bearing surface 32a. The wall 32 here has a generally truncated cone shape which is flared on the side of the blade 12 of the vane 10.

[0067] When mounting the root 14 of the blade 10 in the ring 38, the lower bearing surface 32a of the bulb 32 bears axially on the wall 74. Due to the truncated cone shape of this wall 74 in the example shown, it is understood that this support has at every point an axial component and a radial component relative to the axis A.

[0068] At the connection of the lower end of the wall 72 to the external periphery of the wall 74, the ring 38 comprises an annular bearing surface 75 ( figures 3 And 6 ).

[0069] At its upper end, the wall 72 comprises a thread 78 for screwing the nut 42. This thread 78 is here located at the external periphery of the ring 38 and more particularly at the external periphery of the free upper end of the ring 38.

[0070] There figure 6 shows that this free upper end of the ring 38 comprises an annular toothing 80 which is configured to cooperate with a tool (not shown) for driving the ring 38 in rotation around the axis A.

[0071] There figure 6 also shows that the ring 38 can comprise, at the upper end of the wall 72 and at its internal periphery, elements 82 for fixing the lock 44. These fixing elements 82 can be in the form of two tabs arranged on either side of one of the slots 76, at the upper end thereof. The tabs are parallel to each other and to the axis A and each comprise an orifice for mounting a screw or a bolt 84 (cf. figures 13-14 ). The holes in the legs are substantially aligned and extend in a plane perpendicular to the axis A.

[0072] As can be seen in the figure 3 , the ring 38 is mounted in the bowl 36 so that its walls 72, 74 are located in the bowl 36 and its free upper end is located just above the upper end 36c of the bowl 36 and its surface 36c1.

[0073] The nut 42 comprises an internal thread and can be screwed, or at least pre-screwed, onto the thread 78 of the ring 38, preferably before its insertion into the bowl 36. The nut 42 is able to bear axially on the surface 36c1 of the bowl 36.

[0074] Pre-screwing the nut 42 onto the ring 38 can allow the nut 42 to come into axial support on the surface 36c1 in order to prevent the lower wall 74 of the ring 38 from coming into contact with the bowl 36 and its bottom wall 36b, during the insertion of the ring 38. However, preferably, the aforementioned bearing surface 75 of the ring 38 is configured to come into contact with the bowl 36 in order to avoid this axial support of the nut 42 on the surface 36c1.

[0075] When inserting the ring 38 into the bowl 36, the intermediate wall 72 and in particular the radially external surfaces of the aforementioned columns 72a, can cooperate by sliding with the internal cylindrical surfaces 60a, 62a of the ribs 60, 62, in order to center and guide the ring 38 in the bowl 36.

[0076] THE figures 3 And 9 à 14 show that the nut 42 can comprise at its upper end an annular toothing 81 which is configured to cooperate with a tool (not shown) for driving the nut 42 in rotation around the axis A. It can be seen that the teeth 80, 81 are similar.

[0077] The number of stops 40 is at most equal to the number of slots 76 in the ring 38. In the example shown, the number of stops 40 is equal to the number of slots 76 minus one, because one of the stops 40 is replaced by the lock 44. The number of stops 40 is between 5 and 20, and preferably between 7 and 11. It is 9 in the example shown. It is therefore understood that there are nine slots 76 in the ring 38.

[0078] The stops 40 are arranged around the axis A and are mounted around the foot 14 and in the bowl 36. These stops 40 are engaged in the slots 76 and in at least one of the housings 64, 66, 68, and are intended to bear on the upper bearing surface 32b of the bulb 32 of the foot 14, at least in the axial direction.

[0079] Each of the stops 40 comprises a bearing face 40a on the upper bearing surface 32b of the bulb 32 of the foot. This bearing face 40a is shaped so that the support has at every point an axial component and a radial component relative to the axis A.

[0080] Furthermore, each of the stops 40 comprises at least one finger projecting radially outwards relative to the axis A and comprises two fingers 86, 88 of this type in the example shown. The fingers 86, 88 are preferably spaced apart from each other and arranged one above the other. It is understood that one of the fingers 86 is intended to be engaged in the housing 64, the other of the fingers 88 being intended to be engaged in the housing 68 in the example shown in figure 3 .

[0081] Each stop 40 comprises an upper finger 86 which has an upper face 86a, a lateral face 86b, and a lower face 86c. The faces 86a and 86b are complementary to the surfaces 60b, 64a and are configured to bear on these surfaces, respectively in the axial and radial direction, during the assembly of the stop 40, as can be seen in FIG. figure 3a . Face 86c and surface 62c may be complementary but may be separated by a clearance during assembly or after tightening nut 42.

[0082] Each stop 40 comprises a lower finger 88 which has an upper face 88a, a lateral face 88b, and a lower face 88c. The face 88b is complementary to the surface 68a and is configured to bear on this surface 68a, in the radial direction, during the assembly of the stop 40, as can be seen in FIG. figure 3a . Face 88a and surface 62b may be complementary but may be separated by a clearance during assembly or after tightening the nut.

[0083] The lower finger 88 of each stop 40 is therefore not intended to bear axially on the lower rib 62, due to the presence of this clearance. In the event of breakage of the stop 40, its lower finger 88 can come into axial support on the lower rib 62, which makes it possible to ensure the radial retention of the blade 10 and forms the function failsafe aforementioned.

[0084] Advantageously, the play at the level of the lower finger 88 of each stop 40 is sufficient so that the imbalance generated by the movement of the blade 10 in the event of breakage of the upper finger 86 of one or more stops 40 can be detected.

[0085] The stops 40 are intended to be mounted in the slots 76 and in the housings 64, 68 one after the other, thanks to the notch 70 formed in the ribs 60, 62. The stops 40 therefore have dimensions such that they can be engaged in the slots 76, preferably in an adjusted manner, as well as in the notch 70.

[0086] For this, as represented in the figure 9 , it is appropriate to axially align one of the lights 76 with the notch 70. A first stop 40 is then inserted by axial translation from top to bottom in this light 76 and the notch 70 so that the upper finger 86 is located in a plane perpendicular to the axis A which passes through the housing 64, and that the lower finger 88 is located in a plane perpendicular to the axis A which passes through the housing 68 ( figure 10 ). Due to the circumferential stop cooperation between the sides of the stop 40 and the columns 72a of the ring 38, the stop 40 is made integral in rotation with the ring 38. It is therefore understood that a rotation of the ring 38 in the bowl 36, by means of the aforementioned tool, makes it possible to move the stop 40 around the axis A so as to move it away from the notch 70 ( figure 11 ). The other stops are mounted in the same way in the slots 76 of the ring 38 and in the housings 64, 68 ( figure 12 ).

[0087] The lock 44 is intended to be mounted in the last free slot 76 of the ring 38, after mounting the stops 40 ( figures 12 à 15 ). It is also intended to be mounted in the notch 70 of the ring 38. It is configured and in particular dimensioned to be mounted in a fitted manner in the notch 70 so that its sides can cooperate by circumferential abutment with the side walls 70a of the notch 70. It is also noted at figure 15 that the lock 44 is intended to be pressed radially against the bottom wall surface 70b of the notch 70.

[0088] The lock 44 is here configured to be fixed to the ring 38 and comprises in the example shown lateral tabs 44a positioned on the tabs 82 of the ring 38. The tabs 44a comprise orifices aligned with the orifices of the tabs and intended to receive the bolts 84. The fixing of the lock 44 to the ring 38 makes it possible to immobilize them relative to each other. Furthermore, the engagement of the lock 44 in the notch 70 makes it possible to immobilize the ring 38 in rotation in the bowl 36.

[0089] After mounting the lock 44, it is therefore understood that it is no longer possible to move the ring 38 in the bowl 36. The position of the lock 44 around the root 14 of the blade 10 can be chosen. It is advantageous to position it on the side of the extrados 12b of the blade 12 of the blade 10, and closer to the trailing edge 12d of the blade than to its leading edge 12c.

[0090] After mounting the lock 44, the screwing of the nut 42 can be continued and in particular the tightening of the nut 42 on the surface 36c1 can be carried out so as to force: the support of the lower wall 74 of the ring 38 on the lower bearing surface 32a of the bulb 32 of the foot 14, the support of the upper bearing surface 32b of this bulb 32 on the faces 40a of the stops 40, and the support of these stops 40 on the surfaces 60b, 64a and 68a of the housings 64, 68 of the bowl 36.

[0091] There figure 16 shows that relief grooves 90 can be formed on the surface 64a of the bowl 36, opposite each of the columns 72. These grooves 90 generate discontinuities in the internal cylindrical surface 64a of the bowl 36.

[0092] There figure 3a shows that relief grooves 92 can be provided at the connections between the surfaces 60b and 64a, between the surfaces 64a and 62c, and / or between the surfaces 62b and 68a, so that the connecting radii allow for better distribution of the mechanical forces and stresses during operation. In this way, the contact surfaces 60b, 64a, 68a of the bowl 36 are always a little smaller than the faces 86a, 86b, 88b of the stops 40 opposite each other. This makes it possible to avoid a local force peak at the end of the bearing surface on the bowl 36 (radial and axial support).

[0093] THE figures 17 et 17a represent an alternative embodiment of the system 34 and in particular of the stops 40' which here additionally comprise an additional finger 94 which extends axially on the side of the blade 12 of the vane 10 in the mounting position, and which comprises a lateral face 94a for bearing radially outwards.

[0094] As can be seen in the figure 17a , when mounting the stops 40', the faces 86a are intended to be applied axially to the surface 60b of the rib 60, and the faces 94a are intended to be applied axially to the surface 60a of this same rib 60. The other faces of the stops 40' are separated by clearances from the surfaces facing the bowl 36.

[0095] This variant makes it possible to limit the constraints in the bowl 36 and ensure good robustness. It differs from the initial solution in that the stops 40' are not centered in the bowl 38 on their largest external diameter, but on the internal diameter of the upper finger 86 of the bowl 36.

[0096] The radial support (expansion work) of the stops 40' is made on the inside diameter of the upper rib 60. Thus, the area of ​​the bowl 36 working in traction (retaining the blade 10 in centrifugal) is not exposed to this force. Furthermore, since the radial support is made on a thicker part of the bowl 36, the deformation of the bowl 36 is less, benefiting the operation of the upper bearing 48.

[0097] The axial support of the stops 40' is made on the lower surface 60b of the upper rib 60 of the bowl 36, isolating the critical zone of this support from the critical traction zone of the bowl 36 by a sufficient distance.

[0098] The present invention also relates to a method of mounting a system 34 as described in the above, which comprises the steps of: a) insertion of the ring 38 into the bowl 36, b) insertion of the root 14 of the blade 10 into the ring 38, until the lower bearing surface 32a of the bulb 32 of the root 14 is pressed against the lower wall 74 of the ring 38, c) engagement of the stops 40, 40' in the slots 76 of the intermediate wall 72 of the ring 38 and of their fingers 86, 88 in the housings 64, 68 of the bowl 36, and d) screwing the nut 42 onto the ring 38 and tightening the nut 42 onto the bowl 36, and in particular onto the surface 36c1, so as to force the lower wall 74 of the ring 36 to bear on the lower bearing surface 32a of the bulb 32 of the root 14, the upper bearing surface 32b of this bulb 32 on the stops 40, 40', and the support of these stops 40, 40' on the surfaces 60b, 64a, 68a or 60a, 60b of the ribs of the bowl 36.

[0099] As mentioned above, step c) preferably comprises the following successive sub-steps: c1) engagement of one of the stops 40, 40' in one of the slots 76 of the intermediate wall 72 of the ring 38, by displacement of the stop 40, 40' in axial translation through the notch 70 of the bowl 36, c2) rotational displacement of the ring 38 and of the stop 40, 40' inside the bowl 36, around the axis A, c3) engagement of another of the stops 40, 40' in one of the slots 76 of the intermediate wall 72 of the ring 38, by displacement of the stop 40, 40' in axial translation through the notch 70 of the bowl 36, c4) rotational displacement of the ring 38 and of the stops 40, 40' inside the bowl 36, around the axis A, c5) repetition of steps c3) and c4) for the remaining stops 40, 40', c6) engagement of the lock 44 in the last free slot 76 of the intermediate wall 72 of the ring 38, by displacement of the lock 44 in axial translation through the notch 70 of the bowl 36, and c7) fixing of the lock 44 to the ring 38.

[0100] It is thus understood that the stops 40, 40' are mounted one after the other by a dog-type assembly in the bowl 36. Furthermore, it is also understood that the stops 40, 40' are mounted one after the other in the bowl 36 in the same manner as the loading of bullets into the rotating barrel of a firearm, the bowl 36 here forming the barrel.

[0101] At each of steps c2) and c4), the ring 38 is preferably moved by a circumferential pitch, this circumferential pitch being equal to 360° / k, k being the number of slots 76 of the intermediate wall 72 of the ring 38. In the aforementioned particular case where k is equal to 9, it is therefore understood that the circumferential pitch represents 40° around the axis A.

[0102] Other embodiments not shown are possible, including: the lock 44 can be replaced by a locking and rotational blocking device between the ring 38 and the bowl 36, and located for example between the upper free ends of the ring 38 and the bowl 36; the lock 44 could also be configured to bear on the blade root 14 in order to participate in its retention and to participate in the absorption of forces on the blade in operation, which is not the case in the previous embodiments; the lock 44 could thus be formed by one of the stops 40, 40' which would be associated with means of fixing to the ring 38 and / or to the bowl 36.

[0103] The present invention has many advantages, including: simple and rapid assembly of the system in order to be able to replace the blade 10 without dismantling the motor or the bowl 36; a highly secure and robust solution: in the event of breakage of the upper rib of the bowl 36, the blade 10 is retained by the lower rib 62 (failsafe) and the upper end 36c of the bowl 36 is further retained by the nut 42; in the event of breakage of all the columns 72a of the ring 38, the blade 10 remains retained by the upper rib 60 (without pre-tightening) and the upper end of the ring 38 remains captive around the blade root 14; in the event of breakage of one of the stops 40, 40', there are still enough stops to retain the blade 10 (redundancy); the design details (grooves 90, 92 and relief grooves for example, positioned) contribute to the robustness of the assembly; the blade 10 is well held in all phases of operation.

Claims

1. A system (34) for controlling the pitch setting of a propeller vane (10) for an aircraft turbine engine, comprising: - a vane (10) comprising a blade (12) connected to a root (14), the vane (10) comprising a pitch axis (A) and its root (14) comprising a bulb (32) which has two bearing surfaces, a lower bearing surface (32a) and an upper bearing surface (32b) respectively, which extend around said axis (A), and - a hub (36) comprising an annular wall (36a) extending about said axis (A), this annular wall (36a) comprising a lower axial end closed by a bottom wall (36b), and an upper axial end open and configured to allow the root (14) of the vane (10) to be mounted inside the hub (36), the bottom wall (36b) comprising a recess (52) having a non-circular cross-section and configured to receive a free end (28) of complementary shape to said root (14) so that the hub (36) is secured in rotation to the root (14) about said axis (A), the system further comprising: - a ring (38) which extends around said axis (A) and which is mounted around the root (14) and in the hub (36), this ring (38) comprising a lower wall (74) which is located in the hub (36) and which comprises an aperture (74a) through which said free end (28) of the root (14) passes, said lower bearing surface (32a) of the bulb (32) of the root (14) being configured so as to bear at least in the axial direction on this lower wall (74), on the side opposite the blade (12) of the vane (10), the ring (38) further comprising a perforated intermediate wall (72) and a thread (78) at an upper end, - abutments (40, 40') which are arranged around said axis (A) and which are mounted around the root (14) and in the hub (36), these abutments (40, 40') being engaged in openings (76) in said intermediate wall (72) and in at least one housing (64, 68) of the annular wall (36a) of the hub (36), said upper bearing surface (32b) of the bulb (32) of the root (14) being configured to bear at least in the axial direction on these abutments (40, 40'), on the same side as the blade (12) of the vane (10), and - a nut (42) screwed onto the thread (78) of the ring (38) and configured to bear axially on said hub (36) so that the tightening of the nut (42) forces the lower wall (74) of the ring (38) to bear on the lower bearing surface (32a) of the bulb (32) of the root (14), the upper bearing surface (32b) of this bulb (32) to bear on the abutments (40, 40'), and these abutments (40, 40') to bear on complementary support surfaces (60a, 60b, 64a, 68a) of said at least one housing (64, 68) of the hub (36).

2. The system (34) according to claim 1, wherein the number of abutments (40, 40') is less than or equal to the number of openings (76) in the intermediate wall (72) of the ring (38), each of the abutments (40, 40') being engaged in one of these openings (76).

3. The system (34) according to claim 2, wherein the number of abutments (40, 40') is between 5 and 20.

4. The system (34) according to one of the preceding claims, wherein the lower wall (74) of the ring (38) has a generally frustoconical shape flared towards the blade (14) so that the bearing of the lower bearing surface (32a) of the bulb (32) of the root (14) on this lower wall (74) has at every point an axial component and a radial component with respect to said axis (A).

5. The system (34) according to one of the preceding claims, wherein each of the abutments (40, 40') comprises a bearing face (40a) on the upper bearing surface (32b) of the bulb (32) of the root (14), this bearing face (40a) being shaped so that the bearing has at any point an axial component and a radial component with respect to said axis (A).

6. The system (34) according to one of the preceding claims, wherein the nut (42) is screwed to the outside of the ring (38) and / or bears axially on an upper free end (36c) of the hub (36).

7. The system (34) according to one of the preceding claims, wherein each of the abutments (40, 40') comprises at least one finger (86, 88) projecting radially outwards with respect to said axis (A), said at least one finger (86, 88) comprising an upper face (86a) bearing axially on a corresponding support surface (60b) of said at least one housing (64).

8. The system (34) according to the preceding claim, wherein said at least one finger (86, 88) further comprises a lateral face (86b) bearing radially outwards on a corresponding support surface (64a) of said at least one housing (64).

9. The system (34) according to claim 7 or 8, wherein each of the abutments (40, 40') comprises two fingers (86, 88) projecting radially outwards with respect to said axis (A) and arranged axially one behind the other.

10. The system (34) according to one of the preceding claims, wherein the hub (36) comprises at least one annular rib (60, 62) which extends around said axis (A) and which defines said at least one housing (64, 68) for engaging said abutments (40, 40'), this rib (60, 62) comprising at least one axial notch (70) configured to allow the abutments (40, 40') to be mounted one after the other.

11. The system (34) according to claim 10, wherein the hub (36) comprises two annular ribs, respectively upper (60) and lower (62), which extend around said axis (A) and which define between them said at least one housing (64) for engaging said abutments (40, 40'), these ribs (60, 62) comprising at least one axial notch (70) configured to allow the abutments (40, 40') to be mounted one after the other.

12. The system (34) according to claim 10 or 11, wherein it further comprises at least one bolt (44) which is engaged in one of the openings (76) of the ring (38) and in said at least one notch (70), said bolt (44) being attached to said ring (38).

13. The system (34) as claimed in claim 12, wherein the bolt (44) is attached by one or more screws (84) to the ring (38).

14. The system (34) according to claim 12 or 13, wherein said bolt (44) is located on the side of a suction side (12b) of the blade (12) of the vane (10), and is closer to a trailing edge (12d) of the blade (12) than to its leading edge (12a).

15. The system (34) according to one of claims 12 to 14, wherein, before mounting the bolt (44), the ring (38) is able to move in rotation about said axis (A) in the hub (36), and after mounting the bolt (44), the ring (38) is prevented from rotating about this axis (A) by circumferential abutment of the bolt (44) on sides of the notch (70).

16. A turbine engine, in particular for an aircraft, comprising at least one system (34) according to one of the preceding claims.

17. A method for mounting a system (34) according to one of claims 1 to 15, wherein it comprises the steps of: a) inserting the ring (38) into the hub (36), b) inserting the root (14) of the vane (10) into the ring (38) until the lower bearing surface (32a) of the bulb (32) of the root (14) bears on the lower wall (74) of the ring (38), c) engaging the abutments (40, 40') in the openings (76) in the intermediate wall (72) of the ring (38) and in said at least one housing (64, 68) of the hub (36), and d) screwing the nut (42) onto the ring (38) and tightening the nut (42) on the hub (36) so as to force the lower wall (74) of the ring (38) to bear on the lower bearing surface (32a) of the bulb (32) of the root (14), the upper bearing surface (32b) of this bulb (32) to bear on the abutments (40, 40'), and these abutments (40, 40') to bear on the complementary support surfaces (60a, 60b, 64a, 68a) of said at least one housing (64, 68) of the hub (36).

18. The method as claimed in claim 17, the system being as defined in claim 15, wherein step c) comprises the following successive sub-steps: c1) engaging one of the abutments (40, 40') in one of the openings (76) in the intermediate wall (72) of the ring (38), by moving the abutment (40, 40') in axial translation through the notch (70) in the hub (36), c2) moving in rotation the ring (38) and the abutment (40, 40') inside the hub (36), about the axis (A), c3) engaging another of the abutments (40, 40') in one of the openings (76) in the intermediate wall (72) of the ring (38), by moving the abutment (40, 40') in axial translation through the notch (70) in the hub (36), c4) moving in rotation the ring (38) and the abutments (40, 40') inside the hub (36), about the axis (A), c5) repeating steps c3) and c4) for the remaining abutments (40, 40'), c6) engaging the bolt (44) in the last free opening (76) in the intermediate wall (72) of the ring, by moving the bolt (44) in axial translation through the notch (70) in the hub (36), and c7) attaching the bolt (44) to the ring (38).

19. The method according to claim 18, wherein the ring (38) is moved by one circumferential pitch in each of steps c2) and c4), this circumferential pitch being equal to 360° / k, k being the number of openings (76) in the intermediate wall (72) of the ring (38).