ARRANGEMENT WITH A RING AND A SWIVEL SUPPORT SLEEVE FOR SCOOPER FEET WITH VARIABLE INCLINATION, TURBINE MOTOR WITH SUCH ARRANGEMENT AND METHOD FOR DISASSEMBLING SUCH ARRANGEMENT

Description

Scope of the invention

[0001] The present invention relates to the general field of aeronautics. It specifically concerns the integration of variable-pitch blades into a ring used in aircraft turbomachinery. It also relates to the corresponding turbomachine and the corresponding dismantling method. Technical background

[0002] Variable-pitch turbine blades can be fitted to unfaired turboprop propellers or ducted turbojet fans. Varying the blade pitch around their axes improves turbomachine performance while reducing the overall mass of the propulsion system. Variable-pitch blades allow for modification of the airflow through them according to the turbomachine's operating conditions and the aircraft's flight phases, whether to slow the aircraft (thrust reversal) and / or restore pumping margin on turbomachines with very high bypass ratios. Examples of variable-pitch blades are described in documents US-A-4047840, US-B2-8075270, and US-A1-2016146025.

[0003] Variable-pitch blades are generally held in a rotating hub by means of a pivot joint. This pivot joint is achieved by means of a pin on the variable-pitch blade, which is received in a housing on the hub. This type of joint allows for consideration of the relationship between the aerodynamic moment at the pin and the centrifugal force, which may be insufficient to ensure proper contact between the pin and the hub.

[0004] An example of a plot for a variable-pitch blade is shown on the figure 1The cylindrical pin 1A is rotatably mounted in a housing 2A of a ring 3A around a pitch axis A. The ring 3A is fixed to a rotor shaft 4A via a trunnion 5A and is centered on the longitudinal axis X of the turbomachine. Rotation of the pin 1A is enabled by two ball bearings 6A, which are superimposed along the pitch axis A. Each bearing 6A comprises an inner ring 7A integral with the pin 1A and an outer ring 8A integral with the ring 3A. The radially external end 9A of the pin is intended to be connected to an inner end of a blade extending radially outwards, and the radially internal end 10A of the pin is connected to a pitch control system 11A. However, such a configuration makes it difficult to remove the variable-pitch blade pin in the event of a failure.Indeed, since the outer bearing rings are fixed to the ring, the entire module, including the ring and the blades, must be removed for maintenance. Disassembly of the assembly is even more necessary when the blades are enclosed in an external housing. This increases the intervention time and results in a cost loss. Summary of the invention

[0005] The objective of the present invention is to provide a solution to facilitate the assembly and disassembly of variable pitch blades having a cylindrical base, particularly in case 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 for an aircraft, the assembly comprising a ring of axis of revolution, the assembly comprising a plurality of support sleeves each having an axis of revolution and each intended to receive a pin of a variable pitch blade, each support sleeve comprising a bore through on both sides of the support sleeve along the axis of revolution, each support sleeve being mounted pivotally on the ring along a pivot axis transverse to the radial axis and the axis of revolution.

[0007] Thus, this solution achieves the aforementioned objective. In particular, this configuration allows each variable-pitch blade to be removed individually if it is damaged and / or requires inspection. It is therefore no longer necessary to dismantle the entire hub assembly with its multiple variable-pitch blades. Furthermore, this saves time during maintenance, preventing the turbomachine from being grounded, for example, and thus resulting in cost savings. In addition, repairing the variable-pitch blades individually reduces environmental impact, as it avoids the destruction of an entire assembly.

[0008] The package also includes one or more of the following features, taken alone or in combination: Each support sleeve pivots between a first position in which the axis of revolution of the support sleeve is parallel to the radial axis and perpendicular to the axis of revolution, and a second position in which the axis of revolution of the support sleeve is transverse to the radial axis. The ring is provided with a plurality of orifices passing through an annular wall of the ring along a radial axis and arranged regularly around the axis of revolution, and in that the ring includes two lugs that project on either side of each orifice, each support sleeve being installed between the two lugs and pivoting on the lugs about the axis of pivot. The ring extends between an upstream end and a downstream end along the axis of revolution of the ring, the ring including two lugs that project in the vicinity of the upstream end, each support sleeve pivoting on the lugs about the axis of pivot.The ring includes mechanical reinforcement means, these mechanical reinforcement means comprising ribs extending, on the one hand, between an upstream end and a downstream end of the ring along an axis of revolution, and on the other hand along the radial axis, the ribs being arranged on either side of the openings around the axis of revolution. The assembly comprises a plurality of variable-pitch blades, each equipped with a cylindrical pin, each pin being pivotally mounted in the bore of a support sleeve about a pitching axis. Each variable-pitch blade comprises a blade extending from the pin, the blade and the pin being formed as a single piece. Each pin comprises a fastener at one radially external end, the fastener being designed to receive a blade root and comprising a groove extending along an axis perpendicular to the axis of the pin.The assembly includes fastening means configured to retain the support sleeve on the ring when the ring is in the first position. The ring has a plurality of holes through an annular wall of the ring along a radial axis and arranged regularly around the axis of revolution. The pin of each blade is designed to pass through a hole. Each support sleeve is opposite a hole in the first position. Each support sleeve passes at least partially through a hole in the second position. Each support sleeve is outside and at a distance from a hole in the second position.The assembly comprises at least two rolling bearings, each comprising an inner ring mounted on an outer wall of the block and an outer ring intended to bear against an inner cylindrical wall of the bore of the support sleeve, the inner and outer rings defining raceways for rolling elements.

[0009] The invention also relates to a turbomachine comprising such an assembly, a pitch change system connected to a radially inner end of a stud on each variable pitch blade and a rotor shaft connected to the ring.

[0010] The invention further relates to an aircraft comprising a turbomachine as mentioned above.

[0011] Finally, the invention relates to a method for dismantling an assembly such as the aforementioned, the method comprising the following steps: removal of the means of fixing the support sleeve on the ring, pivoting of the support sleeve around the pivot axis and upstream along the axis of revolution, and extraction of the support sleeve stud or the support sleeve from the ring.

[0012] According to the process, prior to the extraction step of the block, there is a step of disengaging the support sleeve from the ring at the pivot axis.

[0013] According to another characteristic of the process, it includes a step of tilting the support sleeve relative to the ring after the disengagement step. Brief description of the figures

[0014] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the detailed explanatory description that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which: There figure 1 is an axial cross-sectional view of an example of a cylindrical foot according to the prior art; The figure 2 is a perspective view of a variable-pitch blade hub enclosed by an external housing according to the invention; The figure 3 is a perspective view of a ring intended to support a plurality of blades with variable pitch according to the invention; The figure 4 is a detailed view of an example of a ring intended to support variable-pitch blades according to the invention; The figure 5represents an embodiment of a ring and a support sleeve for a variable-pitch blade according to the invention; The figure 6 is a radial cross-sectional view of the ring and support sleeve of the figure 4 according to the invention; The figure 7 represents another embodiment of a ring and a sleeve for supporting variable-pitch blades according to the invention; The figure 8 is a detailed perspective view of a support sleeve intended to carry a variable-pitch blade and located in a first position according to the invention; The figure 9 is a detailed and perspective view of a support sleeve intended to carry a variable-pitch blade and located in a second position according to the invention. Figure 10 illustrates another embodiment of a blade and support sleeve according to the invention; The figure 11 represents a step in disengaging a support sleeve from a dismantling process according to the invention; The figure 12represents a tilting step of a support sleeve in a dismantling method according to the invention; The figure 13 represents a switching step in a dismantling process according to the invention; and The figure 14 represents an extraction and separation step of a support sleeve mounted on a blade of a dismantling process according to the invention. Detailed description of the invention

[0015] There figure 1 represents a cylindrical housing for a variable-pitch blade that is installed in a rotating ring of a turbomachine and which has already been described previously. figure 1 illustrates the technique prior to the present invention.

[0016] The invention applies to variable pitch blades whose variation or pivoting is controlled by a pitch change system 40 and to all turbomachines equipped with these variable pitch blades.

[0017] A turbomachine can be a turboprop engine comprising a plurality of unfaired variable-pitch blades, known as an "open rotor," or a turbojet engine comprising a plurality of enclosed variable-pitch blades, known as a turbofan. Turbomachines are designed to be mounted on aircraft. Of course, variable-pitch blades can also be used on other machines, such as wind turbines.

[0018] There figure 2Figure 1 illustrates a turbomachine intended for use on an aircraft. The turbomachine generally comprises, from upstream to downstream along the gas flow 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 compressor and turbine sets each comprise at least one compressor stage and at least one turbine stage, respectively. In a turbojet engine, this includes a fan S with variable-pitch blades, located upstream of the compressor set E1. In a turboprop engine, one or more counter-rotating propellers with variable-pitch blades are located either upstream of the compressor set (puller configuration) or downstream of the turbine set (pusher configuration).

[0019] On the figure 2A turbomachine module 1, centered on the longitudinal axis X, comprises a ring 2 carrying 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 can be inclined relative to a pitch axis A of the blade 3, and this inclination varies according to the operating speeds reached in order to improve the aerodynamic performance and efficiency of the turbomachine equipped with them.

[0020] Advantageously, but not exclusively, the turbomachine module 1 comprises an external casing 4 centered on the longitudinal axis X and surrounding the variable-pitch blades 3. The external casing 4 includes a cylindrical wall 4a having an internal surface 5 on which an abradable annular coating 6 is disposed. This coating is positioned opposite the free ends 7 of the blades 3 and at a short distance from them. This short distance means that the abradable coating 6 can be worn away by the friction of the blades 3 during their rotation, thus limiting gas leakage at the free ends 7.

[0021] Each variable pitch blade 3 comprises a lug 8 and a blade 9 which extends outwards along a radial axis Z from the lug 8. The radial axis Z is perpendicular to the longitudinal axis X. Each blade 9 comprises a leading edge 10a and a trailing edge 10b which are connected by intrados and extrados surfaces 11a, 11b.

[0022] With reference to figures 3 And 4 The lug 8 of each variable pitch blade is carried by the ring 2 via a support sleeve 12. The support sleeve 12 is removable and also mounted to pivot about an axis of rotation relative to the ring 2. In particular, each lug 8 is pivotally mounted in a corresponding support sleeve 12 around its pitch axis A and the pivoting of each support sleeve 12 facilitates, on the one hand, the accessibility of the variable pitch blade 3 and, on the other hand, its extraction from the ring 2.

[0023] Ring 2 has an axis of revolution O which is centered on the longitudinal axis X of the turbomachine in its installed position. The ring in the embodiment of the figure 3 presents an annular wall 15 of generally frustoconical shape. Alternatively, the annular wall 15 of ring 2 has a cylindrical shape with a right circular cross-section.

[0024] Advantageously, ring 2 is mounted to rotate freely around the longitudinal axis X. For this purpose, ring 2 extends along its axis of revolution between an upstream end 13a and a downstream end 13b. The upstream end 13a is fixed to a trunnion (not shown) which is itself fixed to a rotor shaft (not shown).

[0025] Advantageously, the smaller diameter of the frustoconical wall 15 is located towards the upstream end 13a, and the larger diameter of the frustoconical wall 15 is located towards the downstream end 13b. This allows for better integration of the ring 2 into the turbomachine. The ring 2 comprises a plurality of orifices 14 that pass through the annular wall 15 of the ring 2 on either side along the radial axis. The orifices 14 are regularly distributed around the longitudinal axis X.

[0026] Advantageously, but not exclusively, each orifice 14 has a generally rectangular shape with rounded or circular portions. More precisely, each orifice 14 has four portions with large radii that are connected to four portions with small radii (the large radii being greater than the small radii).

[0027] Ring 2 is equipped with mechanical reinforcement means configured to improve its mechanical strength. These mechanical reinforcement means comprise several ribs 16 extending, on the one hand, along the radial axis Z and, on the other hand, along the longitudinal axis. Following the example shown in the figure 4Each rib 16 extends between an annular flange 17 and the upstream end 13a. The annular flange 17 also provides mechanical reinforcement to the ring 2. Alternatively, the ribs 16 may also extend inwards towards the annular wall. In this case, an inner ring would be mounted inside the ring 2, with the portion of the inner ribs connecting the ring walls.

[0028] Advantageously, but not exclusively, the annular flange 17 is centered on the axis of revolution O and extends along the radial axis. The annular flange 17 is also located upstream of the downstream end 13b of the ring 2.

[0029] Still referring to the figure 4We see that ring 2 includes a reinforcing structure 18 which is annular and centered on the longitudinal axis X. This reinforcing structure 18 comprises a radial U-shaped cross-section whose two arms are connected to the wall 15 of ring 2. The opening of the U-shaped cross-section is oriented towards the interior of ring 2. This reinforcing structure is part of the mechanical reinforcement means of ring 2.

[0030] Thus, each orifice 14 is surrounded by ribs 16 which face each other in a circumferential direction around the longitudinal axis of the annular flange 17 and the reinforcing structure 18. The flanges, ribs, and reinforcing structure form a reinforcing box for the wall of the ring 2. The ribs 16 are arranged axisymmetrically (or regularly around the axis of the turbomachine) so as to maintain sufficient stiffness during the operation of the turbomachine. Tangential forces pass through the ribs 16 during the pivoting of the variable-pitch blades 3 around their pitch axis A.

[0031] With reference to figures 3 , 5 And 6Each support sleeve 12 is designed to receive the pin 8 of a variable-pitch blade. Each support sleeve 12 comprises a cylindrical body 21 having an axis of revolution D. The axis of revolution is coaxial with the pitching axis A of each variable-pitch blade 3 in the installed position. Each support sleeve 12 is pivotally mounted on the ring 2 about a pivot axis C between a first position in which the axis of revolution D of the support sleeve is parallel to the radial axis Z and a second position in which the axis of revolution D of the support sleeve 12 is transverse to the radial axis Z.

[0032] In this embodiment, the pivot axis C is transverse to the axis of revolution D. Advantageously, the pivot axis C is also transverse to the pitch axis A of each variable-pitch blade 3. To this end, the ring 2 comprises two lugs 19 arranged opposite each other along the circumferential direction. The lugs 19 project substantially (plus or minus 10° of inclination) along the radial axis. In particular, the lugs 19 are located respectively on either side of each opening 14 of the ring 2 along the circumferential direction. Each ear 19 includes a bore 20 passing through its wall on both sides along an axis transverse to the radial axis Z. The bores 20 of the ears define the pivot axis C of the support sleeve 12. In the present example, the ears 19 are made as a single piece with the wall 15 of the ring 2.

[0033] Regarding the method of implementation of Figures 5 And 6 The support sleeve 12 includes two nipples 25 (visible on the figure 3 ) which extend radially from a cylindrical outer wall 22a of the support sleeve 12. The pins 25 have coaxial axes. Each pin 25 is designed to engage in a corresponding bore 20 via a pivot joint to allow the support sleeve 12 to pivot about the pivot axis C. The axes of the pins 25 are defined in a median plane of the support sleeve 12, this median plane being perpendicular to the pitching axis. Each support sleeve 12 can pivot or tilt upstream and downstream about the pivot axis C when the extraction of the pitching blade 3 is necessary. To extract the variable pitching blade, the support sleeve 12 is pivoted upstream.

[0034] Advantageously, but not exclusively, the support sleeve 12 is operated manually by an operator.

[0035] Each orifice 14 is large enough to allow passage of the pin 8 and part of the kinematic mechanism, which can be activated from the inside. These same orifices 14 are also large enough to allow the support sleeve 12 and the blade 9 to pivot upstream. Advantageously, the support sleeve 12 is arranged at least partially above the corresponding orifice 14 along the axis of the orifice (substantially coaxial with the radial axis), regardless of the position of the support sleeve 12. Alternatively, a portion of the body of the sleeve 12 can extend inside the corresponding orifice 14 in either the first or second position.

[0036] According to an advantageous feature, the dimensions of each orifice 14 are greater than the diameter of the support sleeve 12 (delimited by the cylindrical outer wall 22a). The perimeter of each orifice 14 is, for example, 5 times greater than the diameter of the support sleeve 12.

[0037] As shown by figure 5Fastening means are configured to retain the support sleeve 12 on the ring 2 and prevent it from pivoting during operation. The fastening is located downstream of the ring 2. More specifically, the fastening can be achieved by a threaded connection or a bayonet connection. The fastening means are advantageously located at two points downstream to ensure proper positioning of the support sleeve 12 and the variable-pitch blade, as well as retention on the ring 2. In the example shown, the fastening means include two through-holes 23 formed in the wall 15 of the ring 2. The openings 23 pass through the wall 15 along the radial axis. The support sleeve 12 here includes two bases 24 that project from the cylindrical outer wall 22a of the support sleeve 12.These bases and openings are intended to be passed through by screws, studs or threaded rods intended to cooperate with a nut for example to tighten the assembly.

[0038] As appears from the above and with reference to the figure 6Each support sleeve 12 includes a bore 30 that passes through it on both sides along its axis of revolution D. The bore 30 forms a housing for the pin 8 of the blade 3. The pin 8 of each blade 3 is pivotally mounted in the bore 30 along the alignment axis A. The pin 8 is mounted in the support sleeve 12, and the latter is mounted on the ring 2 so as to resist detachment of the blade 3 during rotation of the ring 2 about the longitudinal axis. Each pin 8 extends along the alignment axis A. The pin 8 advantageously has a cylindrical shape. Advantageously, but not exclusively, the pin 8 is a right cylindrical shape. By the expression "right cylindrical shape," we mean a shape obtained by moving a generating line along a direction curve defined in a plane perpendicular to the generating line. The curve may be circular.

[0039] Each block 8 includes a radially external end 31 (relative to the alignment axis A) which is connected to the blade 9. According to the embodiments illustrated on the figures 3 , 5 , And 6 The radially outer end 31 is integral with the blade 9, which is not shown in these figures. In other words, the block 8 and the blade 9 are formed from a single piece (or from a single piece of material).

[0040] Each pin 8 comprises a radially internal end 32 opposite the radially external end 31. The pin 8 includes a hole 34 opening at this radially internal end 32. Advantageously, the hole 34 opens into a cavity via a slot 35. The hole 34 is centered on the pitch axis A. In this example, the hole 34 is intended to receive a pitch transmission sleeve (not shown) for transmitting the torque to the pin 8 to change the pitch of the blade 3. The transmission sleeve is connected to the pitch change system 40 and is fixed to the pin 8 by means of fasteners. The fasteners include, for example, a screw centered (passing through the slot 35) on the longitudinal axis and a nut tightened onto the screw. Other threaded fasteners, for example, are of course possible.

[0041] To achieve the alignment of the blades 3 around their alignment axis A, each block 8 is pivotally mounted by means of at least two roller bearings 36, 37. The bearings 36, 37 are superimposed along the alignment axis A. More precisely, each bearing 36, 37 comprises an inner ring fixed to an outer wall 8a of the block and an outer ring fixed to a cylindrical inner wall 22b of the support sleeve 12. The cylindrical inner wall 22b is radially opposed to the cylindrical outer wall 22a. The inner and outer rings define raceways for rolling elements. These rolling elements include balls or rollers. The bearings 36, 37 can withstand centrifugal forces (either along the alignment axis A) and / or transverse forces (either along a plane perpendicular to the alignment axis A). Alternatively, the rolling elements can also be balls.Retention means are provided to hold the bearings 36, 37 in the bore 30 and on the foot, and a locking system is provided to hold these retention means in position.

[0042] Bearings 36, 37 and block 8 form a pivot for each variable pitch blade.

[0043] THE figures 7 to 9These figures illustrate another embodiment of the ring 2 and the support sleeve 12 of the variable-pitch blades. In this embodiment, the radially outer end 31 of the pin 8 includes a fastener 33 for receiving a blade foot (not shown). The blade 3 (formed as a single piece with its foot) and the pin 8 are formed of two separate pieces. Following this example, the fastener 33 includes a groove 38 extending along an axis perpendicular to the axis of the pin 8. The groove 38 advantageously, but not exclusively, has a bulbous cross-section. The groove 38 opens upstream and downstream of the fastener 33 so that the foot of the variable-pitch blade can be inserted into the groove 38 from the upstream side and slide within it.

[0044] This embodiment also differs from the embodiment of figures 3 to 6in that the position of the pivot axis C' is different. The pivot axis C' here is located upstream of the ring 2. More precisely, the pivot axis is defined by the bore 20' of the two lugs 19' which project substantially radially from the wall 15 of the ring and in the vicinity of the upstream end 13a. Here the projections are located on the reinforcing structure 18. The support sleeve 12 includes a bridge 39 which extends radially from the cylindrical outer wall 22a of the support sleeve 12. The bridge 39 includes at its free end a bore 42 (shown in dashed lines on the figure 11) which extends transversely on both sides. In the installation position, the axis of the bore 42 of the bridge 39 is coaxial with the bore 20' of the lugs 19'. A transverse shaft (not shown) is provided to pass through the bores 20', 42 of the lugs and the free end. Such a configuration is easily disassembled. In this way, the support sleeve 12 can pivot between a first position in which the alignment axis is coaxial with the radial axis (cf. figure 8 ) and a second position in which the alignment axis is transverse to the radial axis (cf. figure 9 ). In the first position, the support sleeve 12 is at least partly inside the orifice 14, while in the second position, the support sleeve 12 is outside the orifice 14 and upstream of the ring 2.

[0045] According to one embodiment variant, the free end of the bridge 39 includes pins (not shown) which extend transversely and which are each intended to engage in a bore 20' of the lugs 19' for the pivoting of the corresponding support sleeve.

[0046] This embodiment also differs in the arrangement of the fastening means. We can see on the figures 8 and 9 The axis of the fastening means extends along the longitudinal axis. In particular, the fastening means include two through openings 23' which pass through the radial flange 17 on either side along the longitudinal axis. The support sleeve 12 includes two bases 24' which project from the cylindrical outer wall 22a of the support sleeve 12. These bases and openings are intended to be traversed by screws, studs, or threaded rods intended to cooperate with a nut, for example, for tightening the assembly.

[0047] Each blade can be individually removed by extracting its base from the support block within the support sleeve 12 if only the blade needs repair and / or inspection. Of course, if the support block 8 is damaged, it can be removed from the support sleeve 12 by disengaging the transverse shafts from the lugs. The fastening means are also removed beforehand to allow for pivoting.

[0048] The following is a variant of the previous embodiment, illustrated on the Figure 10 In this variant, the lug 8 and the blade 9 are formed from a single piece of material. The blade 9 extends radially from the lug 8. The lug 8 is inserted into the support means 12, which is connected to the ring 2 with similar fastening means (screws and nuts or threaded elements) to the embodiments described above.

[0049] We will now describe an example of a method for mounting a blade block on ring 2.

[0050] The process includes an assembly step of the block 8 and the support sleeve 12. For this, the inner rings of the two bearings are mounted on the block 8 (for example, by shrink fitting). The outer ring of the outermost bearing relative to the axis of the block 8 is mounted transversely inside the bore 30 of the support sleeve 12. This is, for example, shrink-fitted onto the cylindrical inner wall 22b of the support sleeve 12. The rolling elements are then mounted onto the outer ring.

[0051] The process includes a step of inserting the stud 8 into the support sleeve 12. During this insertion, the stud 8 is introduced along the axis of the support sleeve 12 inside the corresponding bore 30.

[0052] The process then includes mounting the rolling elements of the innermost bearing and its outer ring. The respective outer rings of the two bearings are locked by tightening the retaining devices. Anti-rotation systems are also mounted to prevent displacement of the retaining devices. Another retaining device for the outer ring of the second bearing and its anti-rotation system are also mounted.

[0053] Of course, the outer rings can be mounted beforehand in the bore 30, then the inner rings on the stud 8. Similarly, it is possible to mount first the rolling elements of the innermost bearing, then those of the outermost bearing.

[0054] The method includes assembling the support sleeve 12 onto the ring 2. As part of the embodiment of the figures 3 to 6The nipples 25 are arranged to correspond with the bores 20 of the ears 19. The nipples 25 are inserted into the bores to achieve pivoting. As part of the embodiment of the figures 7 to 10 The bore 42 of the free end of the bridge 39 is positioned to correspond with the bore 20' of the lugs 19', and then the transverse shaft is inserted through the bores for each support sleeve 12 to allow it to pivot. In the other embodiment of the figures 7 to 10 , the nipples are inserted into the bores of the ears 19 19' in order to allow the pivoting of the support sleeve 12 relative to the ring 2.

[0055] The method then includes a step of removably fixing the support sleeve 12 onto the ring 2. Advantageously, threaded elements are inserted into the openings, and clamping elements are then mounted on the threaded elements to retain the support sleeve 12 on the ring 2, particularly during the commissioning and operation of the turbomachine. In this step, the support sleeve 12 is in its initial position and is at least partially inside the orifice 14. Each stud 8 passes through a corresponding orifice 14 in the ring 2. Similarly, the radially inner end of the stud 8 is located inside the ring 2, towards the axis of revolution of the ring 2 and the longitudinal axis X of the turbomachine in its installed position. The axis of revolution D of the support sleeve 12 is parallel to the radial axis in the initial position.

[0056] When the lug 8 is equipped with a fastener 33, the foot of the blade is inserted into the groove 38 before the support sleeve 12 is fixed onto the ring 2.

[0057] Once the support sleeve 12 is fixed, each blade is connected to the pitch change system 40. For this, the pitch transmission sleeve is inserted into the hole 34 of the stud 8 and then fixed in the stud 8. The pitch transmission sleeve is then fixed to the pitch change system 40 by suitable means to generate the rotation of the variable pitch blades around the pitch axis A.

[0058] The assembly is disassembled by reversing the steps described above. Specifically, the disassembly process involves removing the fasteners that secure the support sleeve 12 to the ring 2. In this example, simply unscrew the screws and nuts of the first fasteners 45. The support sleeve 12 is then tilted upstream to allow easy access to the pin 8. After tilting, the support sleeve 12 is in its second position, outside the opening 14, upstream of the ring 2.

[0059] The dismantling process then includes the extraction of the pin 8 from the support sleeve 12 with the variable pitch blade.

[0060] In the case of the implementation method of the figure 9The process may include a step of extracting the blade from the attachment 33 prior to the pivoting step or even the step of removing the fastening means. Of course, the blade and its base can be extracted from the attachment after the pivoting step of the support sleeve 12.

[0061] In the case of the implementation method of the Figure 10 (blade and block in one piece), the process includes a step of disengaging the support sleeve 12 from the ring 2 at the pivot axis C. This disengagement step is carried out by performing a translational movement of the support sleeve 12 upstream along the arrow 43 as illustrated in the figure 11To do this, the transverse shaft is first extracted from the bores of the lugs 19 and from that of the bridge 39, or by removing the studs from the bores of the lugs 19'. This disengagement step is followed by a tilting (rotation approximately around an axis transverse to the axis of the orifices 14) of the support sleeve 12 upstream, as shown in the diagrams. Figures 12 and 13 We see on the figure 14 that the support sleeve 12 and the blade (stud 8 and blade) are then separated from the ring 12 for inspection or possible repair. Similarly, the stud can be separated from the support sleeve.

Claims

1. An assembly for a turbine engine, in particular of an aircraft, the assembly comprising a ring (2) with an axis of revolution (O), the assembly comprising a plurality of support sleeves (12) each having an axis of revolution (D) and each configured to receive a stud (8) of a variable pitch vane (3), each support sleeve (12) comprising a bore (30) passing through both sides of the support sleeve (12) along the axis of revolution (D), characterized in that each support sleeve (12) is mounted so as to pivot on the ring (2) about a pivot axis (C, C') transverse to the radial axis (Z) and to the axis of revolution (O).

2. The assembly according to the preceding claim, characterized in that each support sleeve (12) pivots between a first position wherein the axis of revolution (D) of the support sleeve (12) is parallel to the radial axis and perpendicular to the axis of revolution (O), and a second position wherein the axis of revolution (D) of the support sleeve (12) is transverse to the radial axis (Z).

3. The assembly according to one of the preceding claims, characterized in that the ring (2) is equipped with a plurality of orifices (14) passing through an annular wall (15) of the ring (2) along a radial axis (Z) and arranged regularly around the axis of revolution (O) and in that the ring (2) comprises two ears (19) which project on either side of each orifice (14), each support sleeve (12) being installed between the two ears (19) and pivoting on the ears (19) along the pivot axis (C).

4. The assembly according to one of claims 1 to 2, characterized in that the ring (2) extends between an upstream end (13a) and a downstream end (13b) along the axis of revolution (O) of the ring (2), the ring (2) comprising two ears (19') which project in the vicinity of the upstream end (13), each support sleeve (12) pivoting on the ears (19') along the pivot axis (C').

5. The assembly according to any one of the preceding claims, characterized in that the ring (2) comprises mechanical reinforcement means, the mechanical reinforcement means comprising ribs (16) which extend, on the one hand, between an upstream end (13a) and a downstream end (13b) of the ring along an axis of revolution (O) and, on the other hand, along the radial axis (Z), the ribs (16) being disposed on either side of the orifices (14) around the axis of revolution O.

6. The assembly according to any one of the preceding claims, characterized in that it comprises a plurality of variable pitch vanes (3) each equipped with a cylindrical stud (8), each stud (8) being mounted so as to pivot in the bore (30) of a support sleeve (12) about a pitch axis (A).

7. The assembly according to the preceding claim, characterized in that each variable pitch vane (3) comprises a blade (9) which extends from the stud (8), the blade (9) and the stud (8) being formed in one-part.

8. The assembly according to claim 6, characterized in that each stud (8) comprises an attachment (33) at a radially outer end (31), the attachment (33) being configured to receive a vane root (3) and comprising a groove (38) which extends along an axis perpendicular to the axis of the stud (8).

9. The assembly according to any one of claims 2 to 8, characterized in that it comprises attachment means (23; 23') configured so as to retain the support sleeve (12) on the ring 2 when the latter is in the first position.

10. The assembly according to claim 2 and any one of claims 3 to 9, characterized in that each support sleeve (12) faces an orifice (14) in the first position and at least partially passes through an orifice (14) in the second position.

11. The assembly according to claim 2 and any one of claims 3 to 9, characterized in that each support sleeve (12) is outside and spaced from an orifice in the second position.

12. The assembly according to any one of the preceding claims, characterized in that the assembly comprises at least two rolling bearings (36, 37) each comprising an inner ring mounted on an outer wall of the stud (8) and an outer ring configured to bear against a cylindrical inner wall (22b) of the bore of the support sleeve (12), the inner and outer rings defining raceways for rolling members.

13. A turbine engine (1) comprising an assembly according to any one of the preceding claims, a pitch change system (40) connected to a radially inner end (32) of a stud (8) of each variable pitch vane (3) and a rotor shaft connected to the ring (2).

14. A method for dismantling an assembly according to any one of claims 1 to 12, the method being characterized in that it comprises the following steps: - removing the attachment means for attaching the support sleeve (12) to the ring (2), - pivoting the support sleeve (12) along the pivot axis (C, C') and upstream along the axis of revolution (O), and - extracting the stud (8) from the support sleeve (12).

15. The method for dismantling an assembly according to the preceding claim, characterized in that prior to the step of extracting the stud, the method comprises a step of disengaging the support sleeve (12) relative to the ring (2) at the level of the pivot axis (C).