ASSEMBLY COMPRISING A RING FORMED FROM SECTORIZED PORTIONS FOR VARIABLE PITCH BLADES, TURBOMACHINE EQUIPPED WITH SUCH AN ASSEMBLY AND METHOD FOR DISASSEMBLING SUCH AN ASSEMBLY

Abstract

The invention relates to an assembly for a turbomachine, in particular for an aircraft, the assembly comprising at least one variable-pitch blade (3) provided with a cylindrical-shaped stud (8), and a ring (2) with a longitudinal axis (X) provided with housings (12) each intended to receive the stud (8) of a blade, the stud (8) being mounted to pivot about a setting axis (A), the assembly further comprising pivoting elements (38) configured so as to promote free pivoting of the stud about the setting axis and in each housing (12). According to the invention, the ring (2) comprises a first annular part (43) and a second part (44) which are coaxial, the second part (44) comprising a plurality of sectored portions (44a, 44b, 44n) arranged adjacently around the longitudinal axis (X), each sectored portion (44a, 44b, 44n) being removably fixed to the first part and defining with the first part a housing (12).Figure for abstract: Figure 3.

Description

Title of the invention: ASSEMBLY COMPRISING A RING FORMED FROM SECTORIZED PORTIONS FOR BLADES VARIABLE TIMING, TURBOMACHINE EQUIPPED WITH SUCH AN ASSEMBLY AND METHOD FOR DISASSEMBLING SUCH AN ASSEMBLY TOGETHER Field of invention

[0001] The present invention relates to the general field of aeronautics. It aims in particular at the integration of variable-pitch blades in a ring which equips aircraft turbomachines. It also relates to the corresponding turbomachine and the corresponding disassembly method. Technical background

[0002] Variable pitch blades can be fitted to unducted propellers of turboprops or to ducted fans of turbojets. Varying the pitch of the blades around their axes makes it possible to improve the performance of the turbomachine while limiting the mass of the propulsion unit. Variable pitch blades make it possible to modify the flow of the flow passing through them according to the operating conditions of the turbomachine and the flight phases of the aircraft, whether to brake the aircraft (thrust reversal) and / or restore a pumping margin on turbomachines with a very high bypass ratio.

[0003] The variable-pitch blades are generally retained in a rotating hub using feet which are each pivotally mounted in a housing as shown in [Fig.l]. [Fig.l] illustrates a cylindrical-shaped foot IA which is rotatably mounted in a housing 2A of a ring 3A around a setting axis A. The ring 3A is fixed to a rotor shaft 4A via a journal 5A and is centered on the longitudinal axis X of the turbomachine. The rotation of the foot IA is permitted by means of two ball bearings 6A which are superimposed along the setting axis A. The bearings 6A each comprise an inner ring 7A secured to the foot IA and an outer ring 8A secured to the ring 3A. The radially outer end 9A of the root is intended to be connected to an inner end of a blade extending radially outwards and the radially inner end 10A of the root is connected to a pitch change system 11A.

[0004] However, such a configuration involves difficulties in dismantling the root of the variable-pitch blade following damage. Indeed, since the external rings of the bearings are fixed to the ring, it is the entire module complete with the ring and the blades that must be removed for maintenance. Disassembly of the assembly is more necessary when the blades are surrounded by an external casing. This increases the intervention time and leads to economic loss. Summary of the invention

[0005] The objective of the present invention is to provide a solution making it easier to assemble and disassemble variable-pitch blades having a cylindrical root, particularly in the event of damage, while avoiding impacting the mass of the module comprising the blades.

[0006] We achieve this objective in accordance with the invention by means of an assembly for a turbomachine, in particular an aircraft turbomachine, the assembly comprising at least one variable-pitch blade provided with a cylindrical-shaped stud, and a ring with a longitudinal axis provided with housings each intended to receive the stud of the blade, the stud being pivotally mounted about a setting axis, the assembly further comprising pivoting elements configured so as to promote free pivoting of the stud about the setting axis and in each housing, the ring comprising a first annular part and a second part which are coaxial, the second part comprising a plurality of sectored portions arranged adjacently about the longitudinal axis, each sectored portion being removably fixed to the first part and defining with the first part a housing.

[0007] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, such a configuration makes it possible to remove each variable-pitch blade individually if it is damaged and / or needs to be checked. It is therefore no longer necessary to dismantle the entire hub with the plurality of variable-pitch blades. Furthermore, this saves time during the intervention and thus provides economic benefits. In addition, repairing the variable-pitch blades individually helps reduce the environmental impact since, on the one hand, this facilitates maintenance and avoids the destruction of an entire assembly, and on the other hand, limits the downtime on the ground of the entire turbomachine and the savings in transporting replacement turbomachines.

[0008] The assembly also includes one or more of the following features, taken alone or in combination:

[0009] - the pivoting elements comprise a first rolling bearing comprising an inner ring mounted on an external wall of the stud and an outer ring intended to bear against a cylindrical internal surface of the housing, the inner and outer rings defining rolling tracks for rolling members.

[0010] - the pivoting elements comprise a second rolling bearing comprising an inner ring mounted on the outer wall of the pad and an outer ring mounted to bear against the cylindrical internal surface, the internal and external rings defining rolling tracks for rolling members.

[0011] - the assembly comprises a first clamping nut screwed onto an external thread of the external wall of the pad so as to ensure tightening of the internal ring of the first bearing on the pad.

[0012] - the assembly comprises locking members which are configured to ensure the locking and clamping at least a portion of the pivot members in each housing, the locking members comprising an annular groove formed in the housing and a tab of the pivot members received in the annular groove.

[0013] - each housing is delimited by a cylindrical wall and each sectorized portion comprises a cylindrical half-wall intended to cooperate with a corresponding cylindrical half-wall of the first part to form the cylindrical wall.

[0014] - the first annular portion comprises first flanges which extend from a part, along the radial axis and on the other hand, along a circumferential direction around the longitudinal axis, each sectorized portion comprising second flanges intended to be fixed to the first flanges by means of first fixing members.

[0015] - each sectored portion comprises third flanges intended to be fixed on third adjacent flanges of the adjacent sectored portions around the longitudinal axis, the third flanges being fixed by means of second fixing members.

[0016] - the variable pitch vane comprises a blade which extends from the stud, the blade and the plot being formed from a single piece.

[0017] - each variable pitch blade comprises a pivot which is formed of the elements of pi voting (rolling bearings) and a stud, the pivot being configured so as to allow the variable-pitch blade to pivot around a pitch axis.

[0018] - the assembly comprises a plurality of variable-pitch blades, each blade pad with variable timing being pivotally mounted in a housing of the ring.

[0019] - the first fixing members provide an axial connection.

[0020] - the second fixing members provide a transverse connection (circumferential).

[0021] The invention also relates to a turbomachine comprising such an assembly, a pitch change system connected to the pad of the variable-pitch blade and a rotor shaft connected to the ring carrying the variable-pitch blade.

[0022] The invention further relates to an aircraft comprising a turbomachine as mentioned above.

[0023] The invention also relates to a method for dismantling an assembly as mentioned above, the method being characterized in that it comprises the following steps: - removal of at least one sectored portion of the second part of the ring, - extraction of the variable-pitch blade with the stud, the stud being equipped with the pivoting elements.

[0024] Thus, this simple method makes it possible to quickly extract a single blade which would need to be repaired or replaced without dismantling the ring as a whole as well as the plurality of blades carried by the ring. Brief description of the figures

[0025] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[0026] [Fig. 1] is an axial sectional view of an example of a cylindrical-shaped foot according to the prior art;

[0027] [Fig.2] is a perspective view of a hub of variable-pitch blades which are shrouded by an external casing according to the invention;

[0028] [Fig. 3] is a detailed view of [Fig. 2] and in partial section in which a ring is equipped with several housings which respectively receive a variable-pitch blade and elements allowing the blade stud to pivot according to a pivot connection in the corresponding housing according to the invention;

[0029] [Fig.4] represents a perspective view of a variable-pitch blade block equipped with pivoting elements allowing the block to pivot according to a pivot connection according to the invention;

[0030] [Fig.5] is a view of an embodiment of a ring intended to carry variable-pitch blades according to the invention;

[0031] [Fig.6] represents a step of a method of dismantling a variable-pitch blade according to the invention;

[0032] [Fig.7] represents another step of a method of dismantling a variable-pitch blade according to the invention; and,

[0033] [Fig.8] represents another embodiment of a ring according to the invention. Detailed description of the invention

[0034] [Fig. 1] shows a cylindrically shaped pad for a variable pitch vane which is installed in a rotating ring of a turbomachine and which has already been described previously. [Fig.l] illustrates the art prior to the present invention.

[0035] The invention applies to variable-pitch blades whose variation or pivoting is controlled by a pitch change system and to all turbomachines equipped with these variable-pitch blades.

[0036] The turbomachine may be a turboprop comprising a plurality of unducted variable-pitch blades known as an "open rotor" or a turbojet comprising a plurality of ducted variable-pitch blades known as a turbofan. The turbomachine is intended to be mounted on an aircraft. Of course, the variable-pitch blades may be fitted to other machines such as wind turbines.

[0037] [Fig. 2] illustrates a turbomachine 1 intended to equip an aircraft. The turbomachine generally comprises, from upstream to downstream following the circulation of the gases and along a longitudinal axis X, a set of compressors E1, an annular combustion chamber E2 and a set of turbines E3. These sets form a gas generator G. The sets of compressors and turbines respectively comprise at least one compressor stage and at least one turbine stage. In the context of a turbojet, this comprises a fan S comprising the variable-pitch blades and which is placed upstream of the set of compressors EL. In the context of a turboprop, one or more counter-rotating propellers comprising the variable-pitch blades are placed either upstream of the set of compressors (a “puller” configuration in English) or downstream of the set of turbines (a “pusher” configuration in English).

[0038] In [Fig.2], a turbomachine module, centered on the longitudinal axis X, comprises a ring 2 which carries a plurality of variable-pitch blades 3. This module is located upstream of the gas generator G, a rotor of which drives the plurality of variable-pitch blades around the longitudinal axis X. The variable-pitch blades 3 may have an inclination relative to a pitch axis A of the blade 3 and which varies according to the speeds reached so as to improve the aerodynamic performance and the efficiency of the turbomachine equipped therewith.

[0039] Advantageously, but not limitatively, the turbomachine module comprises an external casing 4 centered on the longitudinal axis and surrounding the variable-pitch blades 3. The external casing 4 comprises a cylindrical wall 4a having an internal surface 5 on which an abradable annular coating 6 is arranged. The latter is arranged opposite the free ends 7 of the blades 3 and at a short distance from them. This short distance implies that the abradable coating 6 can be worn by the friction of the blades during the rotation of the latter and limit gas leaks at the free ends 7.

[0040] Each variable-pitch blade 3 comprises a pivot 30 configured so as to allow it to pivot in a corresponding housing 12 and around the pitch axis A. In particular, each pivot 30 is formed of pivoting elements 38 and a stud 8.

[0041] Each variable-pitch blade 3 comprises a stud 8 and a blade 9 which extends along a radial axis outwards from the pad 8. The radial axis Z is perpendicular to the longitudinal axis. Each blade 9 comprises a leading edge 10a and a trailing edge 10b which are connected by intrados and extrados surfaces 11a, 11b.

[0042] With reference to Figures 3 and 4, the stud 8 of each blade 3 is mounted in a housing 12 of the ring 2. The blade 3 is mounted in the housing 12 via its stud 8 so as to resist detachment thereof during rotation of the ring 2 around the longitudinal axis. Each stud 8 extends along the radial axis Z. The stud 8 has a cylindrical shape. Advantageously, but not limitingly, the stud 8 is of straight cylindrical shape. By the expression "straight cylindrical shape" we mean a shape which is obtained by the displacement of a generating line along a directrix curve defined in a plane perpendicular to the generating line. The curve may be circular.

[0043] Each stud 8 comprises a radially outer end 13 (relative to the Z axis) which is connected to the blade 9. According to a preferred embodiment, the radially outer end 13 is integral with the blade 9. In other words, the stud 8 and the blade 9 are formed from a single piece or are non-removable. According to another embodiment, the radially outer end 13 comprises a bulb-shaped attachment which is intended to receive a root of a blade. In this way, the blade 9 and the stud 8 are formed from two separate pieces.

[0044] Each stud 8 comprises a radially inner end 14 which is opposite the radially outer end 13 along the radial axis Z. The stud 8 comprises a blind hole 15 which opens at this radially inner end 14. The blind hole 15 is centered on the longitudinal axis Z. The blind hole 15 is intended to receive a timing transmission sleeve 60. The latter is shown schematically in [Fig. 3] and is also known by the term "eccentric". The timing transmission sleeve 60 is intended to transmit the torque to the stud to change the timing of the blade 3. The timing transmission sleeve 60 is connected to the pitch change system 70 (shown schematically in [Fig. 3]).

[0045] According to an advantageous characteristic, the pitch change system 70 is configured to modify an orientation or pitch of the variable-pitch blades 3. The pitch change system 70 is advantageously connected to a full-authority electronic computer (known by the acronym FADEC for Full Authority Digital Engine Control) which is not shown. Advantageously, but not limitingly, the computer comprises an electronic regulation module (not shown) (known by the acronym ECU for Electronic Control Unit) which actuates a member of the pitch change system to change the pitch of the blades according to the flight conditions (for example the speed of the turbomachine).

[0046] Advantageously, but not limitatively, the transmission sleeve 60 is secured to the stud 8 by means of coupling means such as grooves (not shown). Other easily removable coupling or fixing means are of course conceivable.

[0047] In the example shown, each pad 8 is pivotally mounted by means of the pivoting elements 38 configured so as to promote the free rotation / pivoting of the pad 8 according to a pivot connection around the setting axis. More precisely, the pivoting elements 38 comprise at least one rolling bearing. In the present case, the pivoting elements comprise two rolling bearings called first rolling bearing 16 and second rolling bearing 17 in order to facilitate the setting of the blades 3 around their setting axis A. The bearings 16 and 17 are superimposed along the radial axis Z. Of course, other pivoting elements 38 allowing the free pivoting or rotation of the pads 8 in each housing 12 can be provided.

[0048] More precisely, the first bearing 16 comprises an inner ring 18, an outer ring 19 and rolling members 20. The inner ring 18 and the outer ring 19 define rolling tracks for the rolling members 20. The inner ring 18 is secured to an outer wall 21 of the stud 8. The outer ring 19 is mounted radially around the inner ring 18 (in a radial direction perpendicular to the setting axis). The latter comprise balls. The first bearing 16 makes it possible to take up centrifugal forces (i.e. along the radial axis Z). The inner ring 18 is mounted in transverse support against the radially outer end 13 while the outer ring 19 is intended to bear transversely against a cylindrical inner surface 22 of the housing 12.

[0049] In the illustrated embodiment, and advantageously, the inner ring 18 of the first bearing 16 is formed of two parts 18a, 18b which are distinct. The two-part inner ring 18 facilitates the mounting of the latter on the stud 8 and of the stud 8 even subsequently in the housing 12.

[0050] The stud 8 comprises a first shoulder 23 forming an annular surface 24 in a plane perpendicular to the setting axis A and against which the internal ring 18 (in particular the part 18a) is in radial support.

[0051] The second bearing 17 is mounted along the radial axis inside the first bearing. In other words, the second bearing 17, offset inwards, is closer to the longitudinal axis X than the first bearing 16. The second bearing 17 comprises an inner ring 25, an outer ring 26 and rolling members 27. The inner and outer rings 25, 26 define rolling tracks for the rolling members 27. The inner ring 25 of the second bearing 17 is mounted on the outer wall 21 of the stud 8. The outer ring 26 is mounted radially around the inner ring 25 (along the radial direction perpendicular to the setting axis). The rolling members 27 are here rollers. This second bearing 17 advantageously allows transverse forces to be absorbed (i.e. along a plane perpendicular to the radial axis ZZ). Alternatively, the rolling members 17 can also be balls. The outer ring 26 is intended to bear against the cylindrical inner surface 22 of the housing 12.

[0052] With reference to Figures 3 and 4, and advantageously, but not limitingly, retention means are provided to retain the pivoting elements 38 on the stud 8. In the present example, the stud 8 comprises an annular groove 28 which is formed in the external wall 21 of the stud 8. This groove 28 has a U shape and is open on the external wall 21. The groove 28 is positioned below the internal ring 16 of the first bearing 16 along the radial axis. The retention means comprise a retention ring 29 which is housed in the groove 28. The retention ring 29 is annular in shape or formed of two separate segments to facilitate the mounting thereof in the groove 28.The retention means further comprise a plurality of clamping pieces 49 which are each mounted on the one hand, in transverse support against the retention ring 29 in a plane / plane contact and on the other hand, in radial support against the internal ring 18 of the first bearing 16 in a plane / plane contact. The clamping pieces 49 are partly arranged in the groove 28. There are approximately six clamping pieces 49 which are regularly distributed around the wedging axis A.

[0053] Furthermore, the retention means comprise a first nut 31 which is mounted on the stud 8 so as to be able to tighten the inner ring 18 of the first bearing 16 on the stud 8. The first nut 31 is arranged radially inside the inner ring 18. The first nut 31 also makes it possible to block the inner ring 18 along the wedging axis. In particular, the outer wall 21 comprises an external thread complementary to an internal thread of the first nut 31.

[0054] According to an advantageous characteristic shown in [Fig.4], the first clamping nut 31 comprises an annular shoulder 31a which carries a frustoconical internal face 31aa coming into contact with a corresponding frustoconical face of the clamping parts 49 to produce a conical support. The corresponding frustoconical face is opposite the face producing a plane / plane contact with the retaining ring 29. Once the first nut 31 is screwed, the shoulder 31a bears against the clamping parts 49 which also bear against the internal ring 18, and the retaining ring 29 is tightened at the bottom of the groove 28 of the stud 8 which makes it possible to eliminate assembly clearances.

[0055] Still with reference to Figures 3 and 4, a locking system is provided to hold the first nut 31 in position on the stud 4. The locking system comprises an anti-rotation ring 32 (better visible in [Fig.4]) which is housed in a recess formed by a second shoulder 33 of the external wall of the stud 8. The anti-rotation ring 32 is provided with several fingers 34 which each fit into a notch 35 of the first nut 31 to prevent it from pivoting around the radial axis Z. A retaining ring 36 (“circlip” type) is mounted radially under the anti-rotation ring 32 to hold the latter in position against the second shoulder 33.

[0056] In [Fig. 3], the pad 8 comprises a third shoulder 37 forming an annular surface in a plane perpendicular to the setting axis A and against which the internal ring 25 of the second bearing 17 bears.

[0057] The outer ring 26 of the second bearing 17 comprises a cylindrical portion 26a whose inner surface forms the rolling track.

[0058] Advantageously, but not limitatively, locking members 56 are configured to ensure the locking and clamping of at least a portion of the pivoting elements 38 in each housing 12. In particular, the locking members 56 comprise an annular groove 52 and a tab 26c of the pivoting elements 38 which is housed in the annular groove 52. Preferably, the annular groove 52 is formed in the housing 12 and the second bearing 17 carries the tab 26c. More precisely still, the groove 52 is formed in the cylindrical internal surface 22 of each housing 12. The annular groove 52 extends over 360°. In addition, the annular groove 52 is oriented axially and has a U-shape whose opening opens onto the cylindrical internal surface 22 of the housing (or of the ring 2). The outer ring 26 of the second bearing comprises the lug 26c which extends radially relative to the setting axis A.The tab 26c is annular or can be sectorized around the wedging axis. The tab 26c in the present example has an annular surface defined in a plane perpendicular to the wedging axis A and which is in plane support against the outer ring 18 of the first bearing 16. This very simple configuration makes it possible to lock the outer rings of the bearings in the housing 12. In particular, this allows the outer ring 26 of the second bearing 17 to be locked radially on the ring 2 and also for the outer ring 19 of the first bearing 16 to be locked axially against an internal surface of an annular sole 39 delimiting the housing 12.

[0059] The second bearing 17 comprises a skirt 26b which extends between the lug 26c and the cylindrical portion 26a. Still in the example shown, the skirt 26c comprises a first portion of frustoconical axial section and a second portion which extends parallel to the wedging axis. The skirt 26b surrounds and protects the first nut 31.

[0060] The first and second bearings 16, 17 are arranged in the form of a cartridge around the stud 8. In other words, during the assembly and insertion of each stud 8 into its corresponding housing 12, the stud 8 is already equipped with the internal and external rings as well as the rolling members of the first and second bearings 16, 17.

[0061] The external diameter of the first bearing 16 is in this embodiment greater than the external diameter of the skirt of the external ring of the second bearing. The external diameter of the lug 26c is greater than the external diameter of the first bearing 16.

[0062] With reference to [Fig.5], the ring 2 is centered on the longitudinal axis X of the turbomachine in the installation situation. The ring 2 is fixed to a rotor shaft (not shown) via a journal and is centered on the longitudinal axis X of the turbomachine. For this purpose, the ring 2 comprises a downstream flange 40b which extends along the radial axis and here towards the inside of the turbomachine (i.e. towards the longitudinal axis). The downstream flange 40b comprises various orifices 41 intended to receive fixing elements such as a screw or stud or other. A nut makes it possible to tighten the downstream flange 40b of the ring on a flange of the journal.

[0063] Advantageously, but not limitatively, the ring 2 comprises an upstream flange 40a which extends along the radial axis and also towards the inside of the turbomachine. The upstream flange 40a is fixed to a flange of an upstream cowl (not shown). The upstream flange 40a and the flange of the cowl comprise axial orifices 41 which receive screws and are tightened with nuts. Alternatively, the upstream flange 40a can be fixed to the journal secured to the rotor shaft.

[0064] Each housing 12 passes through the ring 2 on either side along the radial axis Z (in the installation situation). The housings 12 are distributed regularly around the longitudinal axis X. Each housing 12 is delimited by a cylindrical wall 42 which extends along the radial axis Z. The cylindrical wall 42 extends between a free radially internal end and a radially external end. The annular sole 39 is connected to the radially external end and extends towards the radial axis Z. The cylindrical wall 42 is intended to surround the pad 8.

[0065] The ring 2 is formed of two distinct parts which are called first part 43 and a second part 44. The first part 43 and the second part 44 are coaxial. These have an identical internal diameter delimited by an internal surface 45. The first part 43 is annular (360°) and is formed in a single piece (monobloc). The first part 43 and the second part 44 are separated at a median plane of the ring 2 which is perpendicular to the longitudinal axis.

[0066] The second part 44 comprises a plurality of sectored portions 44a, 44b, 44n. Each sectored portion 44a, 44b, 44n extends over a predetermined angular sector which is less than 360°. In other words, the sectored portions 44a, 44b, 44n are distinct from one another. However, the sectored portions are identical so as to facilitate their assembly and to save time during assembly.

[0067] Each sectored portion 44a, 44b, 44n is removably fixed to the first part 43 and defines with the first part 43 a housing 12. Each sectored portion 44a, 44b, 44n comprises a cylindrical half-wall 42b intended to cooperate with a corresponding half cylindrical wall 42a of the first part 43. Each half cylindrical wall 42b of a sectorized portion and half cylindrical wall 42a of the first part 43 forms the cylindrical wall 42 of a single housing.

[0068] The cylindrical half-walls 42a, 42b are intended to cover at least the first bearing 16. In particular, the outer ring 19 of the first bearing 16 is intended to bear against the cylindrical inner surface 22 of the housing 12 but is not secured to it. In particular, these are the inner surfaces of the cylindrical half-portion of each sectored portion and the cylindrical half-portion of the first part 43. The outer ring 19 of the first bearing 16 and the outer ring of the second bearing 17 are held on the cylindrical wall 42 at least by means of the locking members 56 (system of tabs 26c and annular groove 52 or any element making it possible to perform the same function and rapid disassembly without destruction). Given that the ring is formed of two annular parts, the annular groove 52 is also formed of at least two parts.In other words, each internal surface of the first part 43 and of the second part 44 comprises a sector of the groove 52. The external ring 26 of each second bearing 17 is mounted to bear against the internal surface of a sectored portion 44a, 44b, 44n and of the internal surface of the first part (internal surface of the cylindrical half-portions).

[0069] In Figures 6 and 7, and advantageously, but not limitingly, the fixing of each sectored portion 44a, 44b, 44n on the first part 43 is carried out using first fixing members 50. The first fixing members 50 are here screws and nuts. Of course, the first fixing members 50 can be studs or any element allowing easy disassembly without destruction of the different parts. For this purpose, the first part 43 comprises several first flanges 46 which extend on the one hand, along the radial axis Z and on the other hand along a circumferential direction around the longitudinal axis X. Each first flange 46 comprises an internal surface 46a (see [Fig.6]) defined in the median plane of the ring 2. The first flanges 46 extend between each cylindrical half-wall 42a of the first annular part 43 along the circumferential direction.

[0070] Each sectored portion 44a, 44b, 44n also comprises second flanges 47 which extend on the one hand, along the radial axis Z and on the other hand, along the circumferential direction. These second flanges 47 extend on either side of each cylindrical half-wall 42b. Each second flange 47 comprises an internal surface complementary to the internal surface 46a of the first flange 46. The internal surfaces of the second flanges 47 are here planar and provide a plane support connection with the internal surface 46a of the flanges 46 in the installation situation.

[0071] The first flanges 46 and the second flanges 47 comprise orifices 48 through which each extend along an axis parallel to the longitudinal axis. These orifices 48 are intended to be crossed by screws or studs or threaded rods which cooperate with nuts to fix together the sectored portions 44a, 44b, 44n and the first part 43. Here are shown two screws and nuts for each flange 47 of a sectored portion but a greater number of screws can be provided.

[0072] According to another embodiment illustrated in [Fig.8], the sectored portions are also fixed to each other. In particular, each sectored portion 44a, 44b, 44n comprises third flanges 51 which are intended to be fixed to adjacent third flanges of an adjacent sectored portion in the circumferential direction. The third flanges 51 extend transversely to the second flanges of each sectored portion. More precisely, each sectored portion 44a, 44b, 44n comprises third flanges 51 (here two) which are opposite in the circumferential direction. Each third flange 51 has a flat surface intended to provide a flat support connection with an adjacent complementary internal surface of a flange 51. The internal surfaces are each defined in a plane containing the radial axis and the longitudinal axis.The internal surfaces of the flanges 51 are flush with or extend the lateral surfaces (which circumferentially delimit the sector of a sectorized portion) of the sectorized portions. The fixing of the sectorized portions is carried out using fixing members 53. These fixing members 53 also comprise screws, studs, threaded rods or other suitable fixings. Here the flanges 51 extend along the longitudinal axis. Each third flange 51 comprises orifices 54 passing through it on either side in the circumferential direction. The orifices 54 of the third flanges 51 of the sectorized portions are respectively opposite the orifices 54 of the adjacent sectorized portions. Two screws and nuts make it possible in this example to fix the flanges 50 together, but a single screw may be sufficient or a number greater than two screws.

[0073] We will now describe an example of a method for mounting the pads 8 of the variable-pitch blades in each housing.

[0074] The method comprises a step of mounting the pivoting elements 38 and the means for retaining the pivoting elements on the pad 8.

[0075] This assembly step comprises, in accordance with the examples shown, a sub-step of assembly of the first bearing 16 on the pad 8. During this sub-step, the inner ring 18 is fixed on the pad 8, for example by shrink fitting, then the rolling members are mounted, and finally the outer ring is mounted on the rolling members. When the inner ring is fixed, the first part 18a thereof is first mounted on the pad 8 then the second part 18b.

[0076] The mounting step also comprises a sub-step of retaining the inner ring of the first bearing 16 in order to retain it on the pad 8. The retention ring 29 is for this purpose installed in the groove 28 of the stud 8 to support the second part of the internal ring 18, the clamping parts 49 are arranged one by one around the retention ring 29, at the level of the groove 28, and the first clamping nut 31 is screwed onto the thread of the stud 8.

[0077] The mounting step comprises a sub-step of mounting the locking system on the pad 8. In particular, the anti-rotation ring 32 of the anti-locking system is installed on the pad 8 then the stop ring 36 is mounted thereon so as to hold the anti-rotation ring 32 in place.

[0078] The assembly step comprises a sub-step of assembly of the second bearing 17 on the pad 8. For this, the inner ring 25 of the second bearing 17 is fixed on the pad 8 (by shrinking for example), then the rollers 27 and the outer ring 26 are installed around the inner ring.

[0079] The method comprises a step of inserting the stud 8 equipped with the pivoting elements 38, here at least one of the first and second bearings 16, 17 into a part of the housing 12 formed by the first part 43. The stud 8 is engaged against the cylindrical half-wall 42a of the first part 43. During this step, the tab 26c is partially engaged in the groove sector 52 of the first part 43.

[0080] The method comprises a step of fixing the second part 44 of the ring 2 to the first part 43 of the ring 2. Each sectored portion 44a, 44b, 44n is fixed to the first part 43 by means of the first fixing members 50. When mounting each sectored portion, a part of the tab 26c is inserted into the groove sector of the sectored portion. In the case of the embodiment of [Fig.8], the sectored portions are also fixed to each other by means of the second fixing members 53.

[0081] Once the ring 2 is formed and the stud 8 is held between the first and second parts 43, 44, the timing transmission sleeve 60 is inserted and coupled into the blind hole 15 of the stud 8. The timing transmission sleeve 60 is then connected to the pitch change system 70.

[0082] The disassembly of the assembly is obtained by carrying out the steps in reverse order. In particular, the disassembly method comprises the removal of at least one sectorized portion of the second part 44 of the ring 2. For this, it is sufficient to unscrew in this example the screws and nuts of the first fixing members 50. When the sectorized portions are also fixed together, the fixing members 53 are also extracted. The disassembly method then comprises the extraction of the variable-pitch blade 3 with the stud 8, the stud 8 being equipped with the pivoting elements 38. The first part 43 and the other sectorized portions 44a, 44b, 44n remain fixed. Once the variable-pitch blade 3 is repaired or replaced, it is installed in the module following the steps set out above. 14

Claims

Claims

1. Assembly for a turbomachine, in particular for an aircraft, the assembly comprising at least one variable-pitch blade (3) provided with a cylindrical-shaped stud (8), and a ring (2) with a longitudinal axis (X) provided with housings (12) each intended to receive the stud (8) of a blade (3), the stud (8) being pivotally mounted about a setting axis (A), the assembly further comprising pivoting elements (38) configured so as to promote the free pivoting of the stud (8) about the setting axis (A) and in each housing (12), characterized in that the ring (2) comprises a first annular part (43) and a second part (44) which are coaxial, the first annular part (43) being formed in one piece and the second part (44) comprising a plurality of sectorized portions (44a, 44b, 44n) arranged adjacently around the longitudinal axis (X), each sectorized portion (44a, 44b,44n) being removably fixed on the first part (43) and defining with the first part (43) one of the housings (12) of the ring (2).,

2. Assembly according to the preceding claim, characterized in that the pivoting elements (38) comprise a first rolling bearing (16) comprising an internal ring (18) mounted on an external wall (22) of the stud (8) and an external ring (19) intended to bear against a cylindrical internal surface (22) of the housing (12), the internal and external rings defining rolling tracks for rolling members (20).

3. Assembly according to the preceding claim, characterized in that the pivoting elements (38) comprise a second rolling bearing (17) comprising an internal ring mounted on the external wall of the stud (8) and an external ring (26) mounted to bear against the cylindrical internal surface (22), the internal and external rings defining rolling tracks for rolling members.

4. Assembly according to the preceding claim, characterized in that it comprises a first tightening nut (31) screwed onto an external thread of the external wall (21) of the stud (8) so as to ensure tightening of the internal ring (18) of the first bearing (16) on the stud (8).

5. Assembly according to any one of the preceding claims, characterized in that it comprises locking members (56) which are configured to ensure the locking and tightening of at least one part of the pivoting elements (38) in each housing 12, the locking members (56) comprising an annular groove (52) formed in the housing (12) and a tab (26c) of the pivoting elements (38) received in the annular groove (52).

6. Assembly according to one of the preceding claims, characterized in that each housing (12) is delimited by a cylindrical wall (42) and each sectorized portion (44a, 44b, 44n) comprises a half cylindrical wall (42b) intended to cooperate with a corresponding half cylindrical wall (42a) of the first part (43) to form the cylindrical wall (42).

7. Assembly according to one of the preceding claims, characterized in that the first annular part (43) comprises first flanges (46) which extend on the one hand, along the radial axis and on the other hand, in a circumferential direction around the longitudinal axis, each sectorized portion (44a, 44b, 44c) comprising second flanges (47) intended to be fixed to the first flanges (46) by means of first fixing members (50).

8. Assembly according to any one of the preceding claims, characterized in that each sectored portion (44a, 44b, 44n) comprises third flanges (51) intended to be fixed on third flanges (51) adjacent to the adjacent sectored portions around the longitudinal axis (X), the third flanges (51) being fixed by means of second fixing members (53).

9. Assembly according to any one of the preceding claims, characterized in that the variable-pitch vane (3) comprises a blade (9) which extends from the stud (8), the blade (9) and the stud (8) being formed from a single piece.

10. Turbomachine (1) comprising an assembly according to any one of the preceding claims, a pitch change system (70) connected to the stud (8) of each variable-pitch blade (3) and a rotor shaft connected to the ring (2) carrying the variable-pitch blade (3).

11. Method for dismantling an assembly according to any one of claims 1 to 8, the method being characterized in that it comprises the following steps: - removal of at least one sectorized portion (44a, 44b, 44c) of the second part (44) of the ring (2), - extraction of the variable-pitch blade (3) with the stud (8), the stud (8) being equipped with the pivoting elements (38). 17

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