ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE PROPELLER

Abstract

Assembly for an aircraft turbomachine propeller (10), this assembly comprising a variable-pitch blade (14), a blade pitch control system (76) comprising a sleeve (80) engaged in a metal body (102) forming the blade root, and a tie rod (120) passing through the sleeve (80) and the metal body (102) to connect the blade to the control system (76) and pre-stress the metal body (102). Figure for the abbreviation: Figure 4

Description

Title of the invention: ASSEMBLY FOR AN AIRCRAFT TURBO-MACHINE PROPELLER Technical field of the 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. Technical background

[0002] The state of the art includes in particular documents FR-A1-3 017 163, FR-Al-3 080 322 and WO-A1-2022 / 018353.

[0003] An aircraft turbomachine propeller may 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 which can be variable pitch. The turbomachine then comprises 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, the improvement of 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 of the FPF (Fan Pressure Ratio). Consequently, a pitch change system (variable pitch blade) is generally required for the propeller to be 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.

[0007] A propeller generally comprises a hub which carries systems for retaining the blades and for controlling the angular setting of its blades. The hub has a generally annular or polygonal shape around a first axis which is the longitudinal axis of the turbomachine, and comprises orifices distributed around this first axis and in which the roots of the blades and the aforementioned systems are housed.

[0008] Each of these orifices has a substantially radial orientation relative to the first axis and receives bearings for guiding the root of a blade around a second radial axis relative to the first axis, and which is a setting axis of the corresponding blade.

[0009] Each of the propeller blades comprises a blade connected by a stilt to a root which is centered on the pitch axis of the blade. The blade may be formed by a metal body and a fiber preform obtained by weaving fibers in three dimensions and embedded in a polymer matrix. The preform forms the blade, and the metal body forms the root and stilt as well as a spar which extends into the blade along the pitch axis.

[0010] The root of each blade is mounted in one of the holes in the hub and in the bearings of this hole, and is retained in this hole by a retaining system. Each root is also associated with a system for controlling its angular setting.

[0011] The metal body thus forms an integral part of the blade and makes it possible to create a mechanical interface with the bearings allowing variable timing of the blade.

[0012] In the event of a blade loss, its density is such that it gives them significant energy. However, the energy of the debris released on an unducted propeller is a fundamental element to optimize, because the debris can impact the fuselage of the aircraft. It is therefore a dimensioning element for the shielding of the fuselage which impacts the mass of the aircraft, and therefore the overall performance of the engine / aircraft torque.

[0013] The invention provides a solution to at least some of the problems of the prior art and aims to optimize safety in the event of blade loss, in particular in an unducted architecture. Summary of the invention

[0014] The invention relates to an assembly for an aircraft turbomachine propeller, this assembly comprising a variable-pitch blade and a system for controlling the pitch of this blade,

[0015] the blade comprising a blade connected by a stilt to a root which is centered on a setting axis of the blade, this blade being formed by a metal body and a fiber preform obtained by weaving fibers in three dimensions and embedded in a polymer matrix, the preform forming the blade, the metal body forming the root and stilt as well as a spar which extends in the blade along the setting axis, the metal body further comprising an internal recess which is centered on the setting axis and which opens axially at an end of the body opposite the blade,

[0016] the control system comprising a sleeve engaged by translation along the wedging axis inside said recess, this sleeve comprising external grooves configured to be engaged in internal grooves of the body,

[0017] characterized in that it further comprises a tie rod which extends along the wedging axis and which passes through the sleeve and the recess, this tie rod comprising a first end located on the side of the blade, which is axially supported on the spar in the direction of the root, and a second end located on the side opposite the blade, which is threaded and receives a nut which is axially supported on the sleeve in the direction of the blade, the nut being tightened so as to apply a compressive stress to the body.

[0018] The invention thus proposes to associate a tie rod with the metal body of the blade and in particular with its spar, this tie rod having the particularity of connecting the spar and therefore the blade to the control system of this blade. It is therefore understood that, in the event of breakage of the metal body for example, the tie rod still ensures the connection of the blade to the control system which then ensures the retention of the blade.

[0019] The tie rod can thus be considered as an integral part of the blade and is preferably secured to the rest of the blade during the manufacture of this blade.

[0020] The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0021] - the tie rod comprises two coaxial sections of different diameters, the section of largest diameter being located on the blade side and comprising a support shoulder on an internal bearing surface of the spar;

[0022] - the section with the largest diameter is prismatic and has a shoulder prismatic support on an internal bearing surface of complementary shape to the side member; the prismatic shape (in the form of a straight prism) prevents the tie rod from rotating around its axis when tightening the nut;

[0023] — the section with the smallest diameter is cylindrical;

[0024] - the nut is engaged inside the socket and rests on an internal rim of the socket;

[0025] - the tie rod passes through an orifice in the spar which extends from said recess to a spar cavity which is located inside the blade;

[0026] - the control system comprises a link arm which is connected to the socket and includes a connecting pin remote from the shim pin;

[0027] — the tie rod is made of metal or composite material.

[0028] The present invention also relates to a propeller for an aircraft turbomachine, this propeller comprising:

[0029] - a hub extending around a first axis and comprising distributed orifices around this first axis, each of these orifices having a substantially radial orientation relative to said first axis and passing through said hub,

[0030] - assemblies according to one of the preceding claims, the feet of the blades being respectively engaged in the orifices of the hub and the setting axis of each of the blades extending substantially radially relative to said first axis,

[0031] - guide bearings for the blade roots in the holes in the hub around said timing axes, and

[0032] - systems for retaining the blade roots in the hub holes along of said timing axes.

[0033] Advantageously, the root of each of the blades is configured to be engaged in the corresponding orifice of the hub by translation along the setting axis of this blade, radially from the outside towards the inside with respect to said first axis, inside the external and internal bearings, the root of each of the blades comprising:

[0034] + a stop configured to bear in the direction of the wedging axis on the external bearing to retain the blade radially inwards with respect to the first axis,

[0035] + an annular groove extending around the setting axis and oriented radially outwards relative to this setting axis, the groove being located radially inside the stop with respect to said first axis, and

[0036] and in which the system for retaining the root of each of the blades comprises:

[0037] + a ring, preferably sectored, configured to be engaged in the groove of the foot of dawn, and

[0038] + an annular screw-nut assembly comprising an internal screw comprising a thread external, and an external nut comprising an internal thread for screwing onto the external thread of the internal screw, the internal screw being configured to be mounted around the root, between the stop and the groove, and to bear in the direction of the setting axis on the ring on the side opposite the blade, and the external nut being configured to bear in the direction of the setting axis on the internal bearing on the blade side of the blade in order to retain the blade radially outwards with respect to the first axis.

[0039] The invention thus proposes a relatively simple configuration of the system which ensures the retention of the blade root in the orifice of the hub. On the side of the blade of the blade, the blade root comprises a stop which bears directly or indirectly on the external bearing which is advantageously mounted prior to the insertion of the root in the orifice of the hub. On the side opposite the blade of the blade, the blade root comprises a groove in which a ring is added, preferably sectorized. The simple cooperation by stop of the ring with the side walls of the groove, in the direction of the setting axis, is sufficient to ensure the retention of the ring in the groove. This ring can advantageously form an additional stop for the blade root, which is this time added to the root. The blade root further comprises a zone for receiving the screw-nut assembly, which can for example be in the form of an external cylindrical surface.This screw-nut assembly has the advantage of having a dual function and a limited number of parts. The internal screw is slid around the foot and cooperates by stop with the ring which ensures retention of the foot radially outwards relative to the first axis. This can also allow . to axially immobilize the ring in the groove, along the setting axis, or even to block it radially in the groove with respect to this axis. The external nut is screwed onto the internal screw and cooperates by stop with the internal bearing. The root of the blade is therefore retained by the external and internal bearings, by means of the stop on the one hand, and by means of the ring and the screw-nut assembly on the other hand.

[0040] The number of parts of the foot retention system is therefore relatively limited insofar as it can comprise only three parts, namely the ring and the two parts of the screw-nut assembly.

[0041] The propeller according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0042] — the ring is sectorized into two pieces and comprises two half-rings; - the ring comprises an internal periphery housed in the groove and an external periphery located outside the groove and on which the internal screw rests;

[0043] — the internal periphery of the ring has an annular rim located on the side of the blade which is intended to cooperate by support with the internal screw to prevent the ring from accidentally coming out of the groove;

[0044] — the internal screw comprises an annular rim which is located on the side opposite the blade and which extends around the outer periphery of the ring to prevent the ring from accidentally coming out of the groove;

[0045] — the inner screw and the outer nut each comprise a series of oriented teeth radially outward relative to the timing axis;

[0046] — the series of teeth of the external nut is located on the side of the blade of the vane, and the series of teeth of the internal screw is located on the side opposite the blade of the vane; - the propeller further comprises an internal annular cover which is mounted around the foot and at least partially covers the internal bearing and / or the screw-nut assembly; - the internal cover comprises a first axial end, located on the blade side, which bears axially on the internal bearing in the direction of the blade, and a second axial end, located on the opposite side, which bears axially on the control system in a direction opposite to the blade; - the second end of the cover is axially interposed between the control system and an axial end of the metal body; - the second end of the cover is deformable by crushing between the control system and an axial end of the metal body;

[0047] — the inner cover comprises at least two teeth which are configured to cooperate by engagement with the series of teeth of the screw-nut assembly in order to im- mobilize in rotation around the wedging axis;

[0048] — the internal cover has its external periphery which is supported in the direction of the axis of wedging on the hub, for example by means of an annular seal;

[0049] — the inner cover comprises an inner cylindrical centering surface which is configured to cooperate with a complementary external cylindrical surface of the internal bearing, and for example of an internal ring of this internal bearing;

[0050] — the centering surface is located at the inner periphery of an inner annular veil of the internal cover, this veil comprising through orifices for the passage of fluid and in particular of bearing lubrication oil; - the root of each of the blades comprises an internal recess which opens radially inwards with respect to the first axis and which comprises internal grooves extending around the setting axis, the propeller further comprising a setting control system which is associated with the root of each of the blades, the control system comprising an eccentric, a sleeve of which is engaged by translation in the direction of the setting axis inside the recess, this sleeve comprising external grooves configured to be engaged in the internal grooves of the root;

[0051] — the stop of the foot of each of the blades is in direct support on the external bearing, or is supported on the external bearing by means of an external annular cover which is mounted around the foot and which at least partially covers the external bearing;

[0052] — the outer cover has its inner periphery which is clamped between the stop and the bearing external, and its external periphery which is supported in the direction of the timing axis on the hub, for example by means of an annular seal; - the external bearing comprises an external ring which bears in the direction of the setting axis and on the side opposite the blade on a stop located in the orifice of the hub, and / or the internal bearing comprises an external ring which bears in the direction of the setting axis and on the side of the blade on a stop located in the orifice of the hub; - the external bearing comprises an internal ring which bears in the direction of the setting axis and on the side opposite the blade on a spacer mounted around the root and in the orifice of the hub, and / or the internal bearing comprises an internal ring which bears in the direction of the setting axis and on the side of the blade on a stop on the root of the blade or on the aforementioned spacer;

[0053] — the inner ring of the outer bearing is supported on the spacer by means of of an adjustable shim, and / or the internal ring of the internal bearing is supported on the stop or on the spacer by means of an adjustable shim;

[0054] — the bearings have internal diameters which increase radially from the inside outwards with respect to said first axis; thus, the internal diameter of the bearing (radially) internal has an internal diameter which is smaller than the internal diameter of the (radially) external bearing;

[0055] — the screw-nut assembly is mounted on an external cylindrical surface of the foot;

[0056] — the bearings are rolling bearings, for example ball or roller bearings; the rollers which can be tapered.

[0057] The present invention also relates to a turbomachine, in particular for an aircraft, comprising at least one assembly or at least one propeller as described above.

[0058] The present invention finally relates to a method for detecting a failure in a propeller as described above, in which it comprises the following steps:

[0059] a) rupture of the metal body or ring,

[0060] b) displacement of the blade radially outwards relative to the first axis,

[0061] c) retention of this blade by its tie rod and the control system which is supported by means of the retaining system and the internal bearing on the hub, and

[0062] d) detection of unbalance linked to movement.

[0063] Advantageously, the movement of the blade causes the second end of the cover to be crushed between the control system and the axial end of the metal body. Brief description of the figures

[0064] 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:

[0065] [Fig-1] [Fig.l] is a schematic axial sectional view of a propeller for a turbine aircraft engine,

[0066] [Fig.2] [Fig.2] is an enlarged view of part of [Fig.l] and shows the root of a blade mounted in an orifice of a propeller hub,

[0067] [Fig.3] [Fig.3] is an even larger scale view of part of [Fig.2] and blade root restraint and control systems,

[0068] [Fig.4] [Fig.4] is a view similar to that of [Fig.2] and illustrating a mode of realization of the invention,

[0069] [Fig.5] [Fig.5] is an enlarged view of part of [Fig.4],

[0070] [Fig.6] [Fig.6] is a view similar to that of [Fig.4] and illustrating a de failure of the propeller and in particular a rupture of the metal body of one of its blades, and

[0071] [Fig.7] [Fig.7] is a view similar to that of [Fig.4] and illustrating a de failure of the propeller and in particular a rupture of a retaining ring of one of its blades. Detailed description of the invention

[0072] [Fig.l] shows a propeller 10 for an aircraft turbomachine, this propeller 10 being shrouded or unshrouded.

[0073] The propeller 10 comprises a hub 12 and blades 14 carried by this hub 12.

[0074] The hub 12 has a generally annular or polygonal shape and extends around a first axis not shown.

[0075] In [Fig.l], one of the blades 14 of the propeller 10 is visible and the hub 12 is seen in axial section, the section plane passing through the first axis of the hub 12.

[0076] The hub 12 comprises orifices 12a distributed around the first axis, each of these orifices 12a having a substantially radial orientation relative to this first axis. Each orifice 12a passes radially through the hub 12, that is to say that each orifice 12a opens respectively radially to the outside and radially to the inside.

[0077] The blades 14 each comprise a blade 16 and a root 18. The roots 18 of the blades 14 are respectively engaged in the orifices 12a of the hub 12.

[0078] The blade 16 has an aerodynamic profile and comprises a lower surface 16a and an upper surface (not visible) which are connected by an upstream leading edge 16c and by a downstream trailing edge 16d, the terms upstream and downstream referring to the flow of gases around the blade 16 in operation.

[0079] The blade 16 has an upper end which is free, called the apex, and a lower end which is connected to the foot 18.

[0080] The blade 14 can be made of composite material by an injection process called the RTM process (acronym for Resin Transfer Molding). This process consists of preparing a fiber preform 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 16, its leading edge 16c is generally reinforced by a metal shield 20 added and fixed, for example by gluing.

[0081] The shield 20 may be made of titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 16a or even the extrados of the blade 16 may be covered with a polyurethane film 22 for protection against erosion, or even with a heating mat allowing the blade to be defrosted.

[0082] A denotes the axis of elongation of the blade 14 and of the airfoil 16 and in particular the setting axis of the blade 14, that is to say the axis around which the angular position of the blade 14 is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the first axis.

[0083] As best seen in [Fig.2], the foot 18 is hollow and includes an internal recess 18a in the example shown. The foot 18 has an elongated shape and tubular, its internal recess 18a being closed on the side of the blade 16 and open on the side opposite the blade 16.

[0084] The recess 18a of the foot 18 makes it possible to reduce its mass, the shape and dimensions of the foot 18 being optimized to ensure good mechanical strength of the blade 14 in operation.

[0085] The foot 18 comprises in its recess 18a internal grooves 24 which are configured to allow coupling of the foot 18 with a system for controlling the timing of the blade around its timing axis A (figures 2 and 3).

[0086] The grooves 24 extend around the axis A. In the example shown, they are located between two internal cylindrical surfaces 26a, 26b of the recess 18a, located respectively radially outside and inside the grooves 24 with respect to the first axis.

[0087] The root 18 of the blade 14 further comprises at its radially internal free end (with respect to the first axis), an annular surface 26c which extends in a plane perpendicular to the axis A.

[0088] The root 18 of the blade 14 comprises one or more stops 28, 30. The or each stop 28, 30 has an annular shape and extends around the axis A and radially outwards relative to this axis A.

[0089] In the example shown, the stop 28 is formed as a projection at a radially external end of the foot 18 with respect to the first axis, substantially at the level of the closed end of the recess 18a.

[0090] The stop 30 is formed as a projection on a middle part of the foot 18 with respect to the first axis, located between the stop 28 and the free end of the foot 18.

[0091] The root 18 of the blade 14 further comprises an annular groove 32 which opens radially outwards and which is here formed in the vicinity of the free end of the root 18.

[0092] Between the stop 28 and the groove 32, and more particularly between the stop 30 and the groove 32, the foot 18 comprises an external cylindrical surface 34a.

[0093] The root 18 of the blade 14 comprises several external cylindrical centering surfaces S1, S2 and S3 in the example shown. The surfaces S1, S2 and S3 have decreasing diameters D1, D2 and D3 and are distributed along the axis A, radially from the outside towards the inside with respect to the first axis.

[0094] The surface SI of largest diameter Dl is located between the stops 28, 30.

[0095] The surface S2 of intermediate diameter D2 is located between the stop 30 and the surface 34a.

[0096] The surface S3 of smaller diameter D3 is located between the groove 32 and the free end of the foot 18, and more particularly between the groove 32 and an external thread 34b of the foot 18. The thread 34b has a diameter smaller than that of the surface 34a.

[0097] The stop 28 is located at the radially outer end of the surface SI relative to the first axis. The stop 30 is located at the radially outer end of the surface S2 relative to the first axis.

[0098] The hub 12 may comprise annular fixing flanges 36 at each of its axial ends, as can be seen in [Fig.2].

[0099] In the example shown, each of the orifices 12a of the hub 12 comprises stops 38, 40, 42, 44.

[0100] Each stop 38, 40, 42, 44 has an annular shape and extends around the axis A and radially inwards relative to this axis A.

[0101] The stops 38, 40, 42, 44 are respectively arranged one after the other along the setting axis A. There is thus a radially external stop 38, a radially internal stop 44 and two intermediate stops 40, 42.

[0102] The stop 38 has a larger diameter than the stop 40, and the stop 44 has a larger diameter than the stop 42.

[0103] The intermediate stops 40, 42 make it possible to accommodate bearings 46, 48 for guiding the feet 18 of the blades 14.

[0104] The bearings 46, 48 are here two in number and are mounted in the orifice 12a of the hub, being arranged radially one to the outside of the other. Thus, the external bearing 46 designates the bearing located radially to the outside, and the internal bearing 48 designates the bearing located radially to the inside.

[0105] The bearings 46, 48 are mounted inside the orifice 12a, bearing axially (with respect to the axis A) on the intermediate stops 40, 42. The bearings 46, 48 are mounted around the foot 18, and in particular around the surfaces S1 and S2, bearing axially (with respect to the axis A) on the stops 28, 30.

[0106] Advantageously, an intermediate piece is provided between the bearing 48 and the blade root 18, and in particular between the inner ring of the bearing 48 and the surface S2. This is a hoop tightly mounted on the blade root 18 which makes it possible to have a harder material than that (for example titanium) of the root 18 as a bearing surface. Indeed, the inner ring of the bearing 48 cannot have significant hooping on its axis because it is displaced during preloading. Therefore, to avoid a defretting phenomenon (tearing of material which would result in the start of a break on the blade root), this hard intermediate piece can be added.

[0107] The external bearing 46 is configured to be engaged in the orifice 12a from the outside of the hub 12, by moving it radially from the outside towards the inside, until it comes to bear on the stop 40. The bearing 46 is here a ball bearing with angular contact and it is its external ring which bears on the stop 40.

[0108] The internal bearing 48 is configured to be engaged in the orifice 12a from the inside of the hub, moving it radially from the inside to the outside, until come to bear on the stop 42. The bearing 48 is here a ball bearing, and in particular a double row of balls, and with angular contact and it is its external ring which bears on the stop 42.

[0109] As seen in Figures 2 and 3, the root 18 of the blade 14 is configured to be engaged in the orifice 12a by translation along the axis A, radially from the outside to the inside with respect to the first axis, inside the bearings 46, 48, until the stop 28 bears axially (with respect to the axis A) on the bearing 46, and in particular its inner ring, and the stop 30 bears axially (with respect to the axis A) on the bearing 48, and in particular its inner ring. The bearings 46, 48, and in particular their inner rings, are then mounted on the surfaces S1 and S2.

[0110] It is therefore understood that the external bearing 46 has an internal diameter greater than the internal diameter of the internal bearing 48 to allow the mounting of the foot 18 in the orifice 12a, insofar as the bearings 46, 48 are mounted beforehand on the foot 18 in the example shown.

[0111] The stop 28 of the foot 18 may bear directly (along the axis A) on the external bearing 46 and in particular its internal ring. In the example shown, the stop 28 bears on the external bearing 46 by means of an external annular cover 50 which is mounted around the foot and which at least partially covers the external bearing 46.

[0112] This external cover 50 has its internal periphery which is clamped between the stop 28 and the external bearing 46, and in particular its internal ring. The external periphery of the cover 50 bears in the direction of the axis A on an annular seal 52 interposed between this external periphery of the cover 50 and the hub 12, and in particular the stop 38. This assembly allows rotation of the cover relative to the hub, during rotation of the blade root.

[0113] The stop 30 of the foot 18 may bear directly (along the axis A) on the internal bearing 48 and in particular its internal ring. In the example shown, the stop 30 bears on the internal bearing 48 by means of a shim of adjustable thickness 54.

[0114] An internal annular cover 56 may also be mounted around the foot 18 and at least partially cover the internal bearing 48.

[0115] The internal cover 56 has its external periphery which bears in the direction of the axis A on an annular seal 58 interposed between this external periphery of the cover 56 and the hub 12, and in particular the stop 44. This assembly allows rotation of the cover with respect to the hub, during rotation of the blade root.

[0116] The cover 56 has its internal periphery which bears radially with respect to the axis A on the foot 18, in the vicinity of its free end, either directly or by means of an annular seal 60, on an external cylindrical surface S3, as illustrated in the drawing.

[0117] In the example shown, the internal cover 56 comprises at least two teeth 62, 64 oriented radially towards the axis A.

[0118] The internal cover 56 may further comprise an internal cylindrical centering surface 56a which is configured to cooperate with a complementary external cylindrical surface of the internal bearing 48, and for example of the internal ring of this bearing. This surface 56a may be located at the internal periphery of an internal annular web of the cover 56. This web may comprise through-orifices 65 for the passage of fluid and in particular of lubricating oil for the bearings 46, 48 ([Fig.3]).

[0119] The foot 18 is retained in the orifice 12a of the hub 12 by a retaining system which essentially comprises a ring 66 and a screw-nut assembly 68. It is this screw-nut assembly 68 which makes it possible to apply a preload to the foot of the blade.

[0120] The ring 66 is mounted around the root 18 of the blade and extends around the axis A. The ring 66 is sectorized and therefore comprises ring sectors arranged circumferentially end to end around the axis A. The number of sectors is not limiting and can be limited to two. The ring 66 then comprises two half-rings.

[0121] Alternatively, the ring could be continuous and not be sectorized. It could then include a slot to allow elastic deformation of the ring by spreading its longitudinal ends apart.

[0122] The ring 66 is configured to be engaged in the groove 32 of the foot 18. It is understood that it is the sectorization of the ring 66 which allows it to be mounted in the groove 32. The ring 66 comprises an internal periphery housed in the groove 32 and an external periphery intended to remain outside the groove 32 to form an axial stop (with respect to the axis A).

[0123] The screw-nut assembly 68 comprises an internal screw 68a and an external nut 68b. The internal screw 68a comprises an external thread 68al and an internal cylindrical surface 68a2 which is intended to cooperate by sliding with the surface 34a of the foot during the mounting and positioning of the assembly 68 on the foot.

[0124] The external nut 68b has an internal thread 68bl for screwing onto the external thread 68al of the internal screw 68a.

[0125] The positioning (by simple sliding) of the internal screw 68a on the foot 18 makes it possible to move it axially (with respect to the axis A) on the foot 18 and to position it along the axis A. The screw 68a is able to bear in the direction of the axis A on the ring 66 on the side opposite the blade 16.

[0126] Screwing / unscrewing the external nut 68b allows it to be moved axially (with respect to the axis A) on the internal screw 68a and to be positioned along the axis A. The external nut 68b is capable of bearing in the direction of the axis A on the internal bearing 48, and in particular on its internal ring, on the side of the blade 16.

[0127] The double support of the screw-nut assembly 68, respectively on the ring 66 and the bearing 48, and the screwing of the external nut 68b onto the internal screw 68a, make it possible to apply a certain preload to the root 18 of the blade by the retaining system.

[0128] The internal screw 68a comprises an annular rim 70 which is located on the side opposite the blade 16 and which extends around the external periphery of the ring 66 to prevent the ring 66 from accidentally coming out of the groove 32.

[0129] The screw 68a and the nut 68b each comprise a series of teeth 72, 74 oriented radially outwards relative to the axis A and configured to cooperate with the teeth 62, 64 of the internal cover 56 in order to immobilize the assembly 68 in rotation around the axis A.

[0130] The series of teeth 74 of the external nut 68b is located on the blade side

[0131] 16 and is configured to cooperate with the tooth 64 of the cover 56. The series of teeth 72 of the internal screw 68a is located on the side opposite the blade 16 and is configured to cooperate with the tooth 62 of the cover 56.

[0132] In the example shown, the series of teeth 72 has an external diameter smaller than that of the series of teeth 74.

[0133] The propeller 10 further comprises a system 76 for controlling the pitch of the blade 14, which is associated with the root 18 of this blade. The propeller 10 therefore comprises as many control systems 76 as there are blades 14 of this propeller.

[0134] Each control system 76 comprises an eccentric 78 of which a sleeve 80 is engaged by translation along the axis A inside the recess 18a of the foot 18, radially from the inside to the outside with respect to the first axis.

[0135] The socket 80 comprises external grooves 82 configured to be engaged in the internal grooves 24 of the foot 18.

[0136] The sleeve 80 further comprises external cylindrical centering surfaces 80a, 80b cooperating with the surfaces 26a, 26b of the recess 18a when the sleeve 80 is inserted into the recess 18a. These surfaces 80a, 80b are located on either side of the grooves 82 along the axis A.

[0137] In the example shown, the sleeve 80 also comprises an external annular rim 84 ([Fig.3]).

[0138] A threaded ring 86 is screwed onto the thread 34b of the foot, at its free end, and comprises an internal annular rim 86a which bears in the direction of the axis A on the external rim 84 of the sleeve 80, and in the direction of the blade 16 to retain the sleeve 80 in the recess 18a of the foot 18.

[0139] The threaded ring 86 bears in the direction of the axis A on the internal periphery of the internal cover 56, directly or by means of an adjustment shim 88.

[0140] The threaded ring 86 may comprise a series of teeth 90 extending radially outwardly with respect to the axis A, to allow the ring 86 to be engaged with a tool for screwing and unscrewing the ring.

[0141] Figures 4 and following illustrate an embodiment of the invention. The elements visible in these drawings and already described in the above are designated by the same references. The foregoing description made in relation to Figures 1 to 3 can therefore be used to describe at least part of the invention.

[0142] A first particularity of the propeller comes from the assembly formed by the blade 14 and its control system 76.

[0143] The blade 14 comprises a blade 16 connected by a stilt 100 to a foot 18

[0144] which is centered on the setting axis A of the blade 14.

[0145] The blade 14 is formed by a metal body 102 and a fiber preform 104 obtained by weaving fibers in three dimensions and embedded in a polymer matrix.

[0146] The preform 104 forms the blade 16.

[0147] The metal body 102 forms the foot 18 and Péchasse 100 as well as a spar 106 which extends into the blade 16 along the pitch axis A.

[0148] The metal body 102 further comprises the internal recess 18a which is centered on the setting axis A and which opens axially at one end of the body 102 and of the root 18 opposite the blade 16.

[0149] In the example shown, the recess 18a comprises a first portion 18al located on the side of the blade 16, which has in axial section a generally elliptical shape and elongated along the setting axis A, and a second portion 18a2 located on the side opposite the blade 16, which has a generally cylindrical shape.

[0150] An annular shoulder 110 is located in the recess 18a, at the junction of the portions 18a1 and 18a2. The portion 18a2 comprises the internal grooves 24. The recess 18a comprises surfaces 26a, 26b similar to those described above, the surface 26a being formed by the shoulder 110.

[0151] The spar 106 comprises an orifice 112 which extends towards the blade 16, along the axis A, from the recess 18a. The orifice 112 therefore opens into the recess 18a. This orifice 112 extends into a cavity 114 of the spar 106 which preferably has a transverse dimension greater than that of the orifice 112.

[0152] In the case where the orifice 112 and the cavity 114 each have a generally cylindrical shape, the cavity 114 would preferably have an internal diameter U1 greater than that U2 of the orifice 112.

[0153] At the junction between the orifice 112 and the cavity 114, the spar 106 comprises an internal cylindrical bearing surface 116.

[0154] As in the example shown, the orifice 112 and the recess 18a, or even the cavity 114, are preferably aligned and centered on the wedging axis A.

[0155] In the example shown, it can be seen that the recess 18a is formed in the root 14 and that the orifice 112 extends to the level of Péchasse 100 and into the blade 16. The cavity 114 is located at the level of the blade 16.

[0156] It is also noted that the first part of the recess 18al is located at level of the hub 12, while the orifice 112 is located radially outside the hub and the second portion 18a2 of the recess is located radially inside the hub.

[0157] The control system 76 comprises a sleeve 80 engaged by translation along the wedging axis A inside the recess 18a, and more particularly in its second portion 18a2.

[0158] The socket 80 has external grooves 82 configured to be engaged in the internal grooves 24 of the body 102.

[0159] In the example shown, the control system 76 and in particular the socket 80 also comprises an external annular rim 84.

[0160] The control system 76 or its eccentric 78 may further comprise a connecting arm 76a which is connected to the bushing 80 and comprises a connecting axis B at a distance from, and for example parallel to, the setting axis A.

[0161] The assembly according to the invention further comprises a tie rod 120 which can form an integral part of the blade 14.

[0162] The tie rod 120 extends along the wedging axis A and passes through the sleeve 80 and the recess 18a.

[0163] The tie rod 120 has a first end 120a located on the side of the blade 16, which bears axially on the spar 106 and therefore the body 102 in the direction of the root 18.

[0164] The tie rod 120 has a second end 120b located on the side opposite the blade 16, which comprises a thread 122 and which receives a nut 124. This nut 124 bears axially on the sleeve 80 in the direction of the blade 16 and is advantageously tightened so as to apply a compressive stress to the body 102.

[0165] The tie rod 120 may be entirely metallic. Alternatively, it could be made of composite material.

[0166] In the example shown, it can be seen that the nut 124 bears on a shoulder 80c of the sleeve 80. It can also be seen that the nut 124 may include a coupling toothing 126 to allow a screwing / unscrewing tool to be engaged with this nut. This toothing 126 is located on the side opposite the blade 16.

[0167] The nut 124 can be engaged inside the socket 80 as in the example shown.

[0168] Tightening the nut 124 alone may be sufficient to apply the aforementioned compressive stress, this stress being for example of the order of three to four tonnes.

[0169] In the example shown, it can be seen that the tie rod 120 successively passes through the sleeve 80, and therefore the portion 18a2 of the recess 18a, and also passes through the portion 18al of the recess 18a and the orifice 112.

[0170] In the example shown, in the tight mounting position illustrated in [Fig. 4], the external cylindrical surfaces 80a, 80b of the sleeve 80 cooperate by centering with the surfaces 26a, 26b of the recess 18a when the sleeve 80 is inserted into the recess 18a. The external grooves 82 of the sleeve 80 are engaged in the internal grooves 24 of the foot 18. The external rim 84 of the sleeve is preferably axially spaced from the annular surface 26c of the foot 18 located at its free radially internal end, unlike the previous case of FIGS. 1 to 3. There is thus an axial clearance in this zone, between the rim 84 and the end of the foot 18.

[0171] As in the example shown, the tie rod 120 may comprise two coaxial sections 120c, 120d of different diameters, the section 120c of larger diameter being located on the side of the blade 16 and comprising said end 120a which comprises a shoulder 127 for bearing on the internal bearing surface 116 of the spar 106.

[0172] Preferably, the larger diameter section 120c is prismatic and its shoulder 127 is prismatic and comes to bear on the bearing surface 116 which is also prismatic to ensure anti-rotation of the tie rod 120 during its use.

[0173] The smaller diameter section 120d may be cylindrical.

[0174] The smaller diameter section 120d includes the end 120b and the thread 122.

[0175] As regards the hub 12 and the bearings 46, 48, they are similar to those described in the above.

[0176] With respect to the foot retention system, the ring 66 and the screw-nut assembly 68 are also similar, and cooperate as indicated in the above with the bearing 48 and the foot 18.

[0177] The outer annular cover 50 is similar to that described above.

[0178] The inner annular cover 130 of the restraint system differs from the cover 56 described in the above essentially by the following characteristics.

[0179] The internal cover 130 is better visible in [Fig. 5]. Its external periphery or external end 130a bears in the direction of the axis A on an annular seal 58 interposed between this external periphery of the cover 56 and the hub 12, and in particular the stop 44 or the bearing 48. This assembly allows rotation of the cover relative to the hub, during rotation of the blade root.

[0180] The cover 130 has its internal periphery or internal end 130b which bears radially with respect to the axis A on the foot 18, and in particular on its surface 26c, either directly or by means of an annular wedge 138 as illustrated in the drawing.

[0181] This internal end 130b is engaged in the aforementioned clearance J and is thus axially interposed between the free end of the foot 18 and the annular rim 84 of the control system 76.

[0182] As can be better seen in [Fig.5], this internal end 130b is of preferably axially compressible, that is to say it has a capacity for plastic deformation in the axial direction, that is to say along the wedging axis A.

[0183] In the example shown, this deformation capacity is obtained by a particular shape of the end 130b which comprises two annular support pads, respectively internal 132 and external 134, connected together by a frustoconical web 136. The internal pad 132 bears on the free end of the root 18 (and therefore its surface 26c), for example by the wedge 138, in the direction of the blade 16. The external pad 134 bears on the rim 84, in the direction opposite to the blade 16.

[0184] In the non-free, unstressed state, the web 136 is frustoconical and the pads 132, 134 are at distinct axial positions along the axis A, i.e. they are axially spaced apart from each other. In the compressed and deformed state, the web 136 becomes flat and the pads 132, 134 are in the same plane as the web 136, which is perpendicular to the axis A.

[0185] Figures 6 and 7 show two distinct cases of failure of a propeller and illustrate a method according to the invention for detecting this failure.

[0186] The method comprises the following steps:

[0187] a) rupture of the metal body 102 or of the ring 66,

[0188] b) displacement of the blade 14 radially outwards relative to the first axis (of rotation of the propeller),

[0189] c) retention of this blade 14 by its tie rod 120 and the control system 76 which is supported by means of the retaining system and the internal bearing 48 on the hub 12,

[0190] d) detection of the imbalance linked to the movement, for example by at least one vibration sensor.

[0191] [Fig. 6] illustrates the first scenario of step a), i.e. the case where it is the metal body 102 which breaks. In this figure, a break 140 of the metal body 102 occurs at the bottom of the groove 32 for receiving the ring 66. In this case, due to the centrifugal forces in operation, the blade 14 is stressed radially outwards and is retained by the tie rod 120 and the control system 76. The retention forces can reach nearly thirty tonnes and are taken up by the hub 12, these forces passing through the ring 66, the screw-nut assembly 68 and the internal bearing 48 in the example shown (see Arrow F1). The rupture of the metal body 102 causes the reduction of the aforementioned clearance J and the crushing of the end 130b of the cover 130 between the control system 76 and the end of the foot 18, and in particular between the rim 84 and the surface 26c.

[0192] [Fig.7] illustrates the second scenario of step a), i.e. the case where it is the ring 66 which breaks. In this figure, after the breakage 142 of the ring 66, it is divided into two, its internal peripheral part mounted in the groove 32 being dissociated of its external peripheral part located outside the groove 32.

[0193] In this case, due to the centrifugal forces in operation, the blade 14 is stressed radially outwards and is retained by the tie rod 120 and the control system 76. The retention forces can reach nearly thirty tonnes and are taken up by the hub 12, these forces passing through the cover 130 and the internal bearing 48 in the example shown (see Arrow F2).

[0194] In yet another variant not shown, the bearings 46, 48 could be angular contact rolling bearings such as tapered roller bearings.

[0195] The present invention makes it possible to provide emergency force paths in the event of rupture of a part of the blade, so as not to release the most massive parts of this blade.

[0196] The invention thus makes it possible to minimize the mass of the released blade part, which makes it possible to minimize the mass of the shielding to be installed on the aircraft, to the benefit of the performance of the engine / aircraft torque.

[0197] The integration of the assembly according to the invention was carried out in the environment of the already existing parts, by optimizing their geometry and by using the rare spaces available (no impact on the overall volume of the blade root and on the hub ratio of the engine).

Claims

Claims

1. Assembly for a propeller (10) of an aircraft turbomachine, this assembly comprising a variable-pitch blade (14) and a system (76) for controlling the pitch of this blade, the blade (14) comprising a blade (16) connected by a stilt (100) to a root (18) which is centered on a pitch axis (A) of the blade, this blade (14) being formed by a metal body (102) and a fiber preform (104) obtained by three-dimensional weaving of fibers and embedded in a polymer matrix, the preform (104) forming the blade (16), the metal body (102) forming the root (18) and the stilt (100) as well as a spar (106) which extends in the blade (16) along the pitch axis (A), the metal body (102) further comprising an internal recess (18a) which is centered on the setting axis (A) and which opens axially at one end of the body (102) opposite the blade (16),the control system (76) comprising a sleeve (80) engaged by translation along the setting axis (A) inside said recess (18a), this sleeve (80) comprising external grooves (82) configured to be engaged in internal grooves (24) of the body, characterized in that it further comprises a tie rod (120) which extends along the setting axis (A) and which passes through the sleeve (80) and the recess (18a), this tie rod (120) comprising a first end (120a) located on the side of the blade (16), which is in axial support on the spar (106) in the direction of the root (18), and a second end (120b) located on the side opposite the blade (16), which is threaded and receives a nut (124) which is in axial support on the sleeve (80) in the direction of the blade (16), the nut (124) being tightened so as to apply a compressive stress to the body (102).,

2. Assembly according to claim 1, in which the tie rod (120) comprises two coaxial sections (120c, 120d) of different diameters, the section (120c) of larger diameter being located on the side of the blade (16) and comprising a shoulder (127) for bearing on an internal bearing surface (116) of the spar (106).

3. Assembly according to claim 2, in which the section (120c) of larger diameter is prismatic and comprises a prismatic shoulder (127) for bearing on an internal bearing surface (116) of complementary shape to the spar (106).

4. Assembly according to one of the preceding claims, in which the nut (124) is engaged inside the socket (80) and bears on an internal rim (84) of the socket (80).

5. An assembly according to one of the preceding claims, wherein the tie rod (120) passes through an orifice (112) of the spar (106) which extends from said recess (18a) to a cavity (114) of the spar which is located inside the blade (16).

6. Assembly according to one of the preceding claims, in which the control system (76) comprises a connecting arm (76a) which is connected to the bushing (80) and comprises a connecting axis (B) at a distance from the wedging axis (A).

7. Propeller (10) for an aircraft turbomachine, this propeller (10) comprising: - a hub (12) extending around a first axis and comprising orifices (12a) distributed around this first axis, each of these orifices (12a) having a substantially radial orientation relative to said first axis and passing through said hub (12), - assemblies according to one of the preceding claims, the roots (18) of the blades (14) being respectively engaged in the orifices (12a) of the hub (12) and the setting axis (A) of each of the blades (14) extending substantially radially relative to said first axis, - bearings (46, 48) for guiding the roots (18) of the blades (14) in the orifices (12a) of the hub (12) around said setting axes (A), and - systems for retaining the roots (18) of the blades (14) in the orifices (12a) of the hub (12) along said timing axes (A).

8. Propeller (10) according to the preceding claim, in which the root (18) of each of the blades (14) is configured to be engaged in the corresponding orifice (12a) of the hub (12) by translation along the setting axis (A) of this blade (14), radially from the outside towards the inside with respect to said first axis, inside the external and internal bearings (46, 48), the root of each of the blades (14) comprising: + a stop (28) configured to bear in the direction of the setting axis (A) on the external bearing (48) in order to retain the blade (14) radially towards the inside with respect to the first axis, + an annular groove (32) extending around the setting axis (A) and oriented radially towards the outside with respect to this setting axis (A), the groove (32) being located radially inside the stop (28) with respect to said first axis, and and wherein the system for retaining the root (18) of each of the blades (14) comprises: + a ring (66), preferably sectored, configured to be engaged in the groove (32) of the root (18) of the blade (14), and + an annular screw-nut assembly (68) comprising an internal screw (68a) comprising an external thread (68al), and an external nut (68b) comprising an internal thread (68b 1) for screwing onto the external thread (68al) of the internal screw (68a), the internal screw (68a) being configured to be mounted around the root (18), between the stop (28) and the groove (32), and to bear in the direction of the setting axis (A) on the ring (66) on the side opposite the blade (16), and the external nut (68b) being configured to bear in the direction of the setting axis (A) on the internal bearing (48) on the side of the blade (16) of the vane (14) in order to retain the vane (14) radially outwards with respect to the first axis.

9. Propeller (10) according to claim 8, in which the ring (66) comprises an inner periphery housed in the groove (32) and an outer periphery located outside the groove (32) and on which the inner screw (68a) bears.

10. A propeller (10) according to claim 8 or 9, wherein it further comprises an inner annular cover (56) which is mounted around the root (18) and at least partially covers the inner bearing (48) and / or the screw-nut assembly (68).

11. Propeller (10) according to the preceding claim, in which the internal cover (130) comprises a first axial end (130a), located on the side of the blade (16), which bears axially on the internal bearing (48) in the direction of the blade, and a second axial end (130b), located on the opposite side, which bears axially on the control system (76) in a direction opposite to the blade (16).

12. Propeller (10) according to the preceding claim, in which the second end (130b) of the cover (130) is axially interposed between the control system (76) and an axial end of the metal body (102).

13. Propeller (10) according to claim 11 or 12, in which the second end (130b) of the cover (130) is deformable by crushing between the control system (76) and an axial end of the metal body (102).

14. Turbomachine, in particular for an aircraft, comprising at least one assembly according to one of claims 1 to 6, or a propeller (10) according to one of claims 7 to 13.

15. Method for detecting a failure in a propeller according to one of claims 7 to 13, in which it comprises the following steps: a) rupture of the metal body (102) or of the ring (66), b) displacement of the blade (14) radially outwards relative to the first axis, c) retention of this blade (14) by its tie rod (120) and the control system (76) which is supported by means of the retention system and the internal bearing (48) on the hub (12), and d) detection of the imbalance linked to the displacement.

16. A method according to claim 15, the propeller (10) being as defined in claim 13, wherein the movement of the blade (14) causes the second end (130b) of the cowl (130) to be crushed between the control system (76) and the axial end of the metal body (102).

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