METHOD FOR MANUFACTURING AN AIRCRAFT TURBOMACHINE HOUSING

Abstract

The invention relates to a method (400) for manufacturing a housing (102) for a turbomachine (10), this housing (102) comprising a skin (102a) of annular shape about an axis (A) and having tubular chimneys (106) projecting from an external annular face (102e) of the skin (102a) and oriented radially with respect to the axis, the method (400) comprising the following steps: preparation (402) of an annular skin of thermoplastic-based material, this skin having radially through holes (102h), preparation (404) of tubular chimneys of thermoplastic-based material, attachment (406) of the tubular chimneys to the skin, the attachment step (406) comprising, for each chimney (106): welding (406a) of a support (200) onto the skin, at one of the orifices, and the welding (406b) of a socket (202) onto the support and / or the skin, the assembly formed by the support and the socket forming said chimney. Figure for the abbreviation: Fig. 3

Description

Title of the invention: METHOD FOR MANUFACTURING AN AIRCRAFT TURBOMACHINE HOUSING Technical field of the invention

[0001] The present invention relates to a method for manufacturing a turbomachine casing, in particular for an aircraft, a turbomachine casing obtained via said method and a stage and a turbomachine comprising said casing. Technological background

[0002] In a turbomachine, variable-pitch stator vane stages are mounted between the rotating wheels of a compressor. More specifically, within a low-pressure or high-pressure compressor of a turbomachine, the stator vanes have variable pitch (also called VSV, an acronym for "Variable Stator Vane") so as to adapt the angle of incidence on the compressor blades according to the rotational speed of the turbomachine.

[0003] These variable-pitch stator (rectifier) ​​blades are carried by an external annular housing and are adjustable in position around their axes of rotation, or pitch axes) to optimize the flow of gases in the turbomachine engine.

[0004] These blades can be arranged in the form of an annular row in one or more stages, generally of a compressor, of the turbomachine.

[0005] Fig. 1 illustrates an example of a stage 100 of variable-pitch stator blades 108a of a turbomachine 10. The stage 100 comprises at least one annular row of variable-pitch blades 108a, a casing 102 of annular shape around a longitudinal axis A and tubular-shaped stacks 106 mounted on an external face of a skin of the annular casing 102.

[0006] Each blade 108a comprises a blade 110 which is connected at its outer radial end by a plate with a substantially circular contour to a radial cylindrical pivot 116 which defines the alignment axis of the blade 108a and which is guided in rotation within a corresponding orifice in the outer housing. The orifice in which the radial cylindrical pivot is guided in rotation is machined in the chimney 106.

[0007] The radially internal end of the blade 110 of each blade 108a generally includes a second cylindrical pivot extending along the blade's pitching axis and guided in rotation in an orifice of an internal housing of the compressor.

[0008] The radially external end of the radial cylindrical pivot 116 of each blade is connected by a lever 124 (or a connecting rod) to a control ring 120 which is rotated around the external housing 102 by means of a hydraulic cylinder or analogous. The rotation of the control ring 120 is transmitted by the levers 124 to the cylindrical pivots 116 of the blades 108a and makes them rotate around their axes.

[0009] The stage 100 may also include an annular row of movable blades 108b carried by a rotor (not shown) of the turbomachine 10 and an abradable layer on a radially internal face of the casing and opposite a radially external end of a movable blade 108b.

[0010] The mounting or assembly of the chimneys 106 on the skin of the casing 102 can however prove complex when the casing 102 and the chimneys 106 are made, for example, of thermoplastic composite material.

[0011] For example, a housing with directly integrated chimneys can be manufactured. However, this method is complex due to the relatively complex and compact geometry of the areas where the chimneys are located. Indeed, the distance between the pivots of two successive variable-pitch blades is on the order of 20 to 30 mm.

[0012] The chimneys can also be assembled by bonding them to the casing. However, this type of assembly may have a short lifespan over time due to aging phenomena and the potentially high temperature in this environment.

[0013] As for assembly by clamping using rivets or screws, it is not feasible due to the size of the parts, which are generally too small, and the limited space.

[0014] It may therefore be desirable to provide a method of assembling the casing, and in particular of mounting the chimneys on the casing, which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0015] A method for manufacturing a turbomachine casing is therefore proposed, this casing comprising an annular skin around an axis and having tubular chimneys projecting on an external annular face of the skin and oriented radially with respect to the axis, the method comprising the following steps: - preparation of an annular skin made of thermoplastic-based material, this skin having radially passing orifices; - preparation of tubular chimneys made of thermoplastic-based material; - fixing the tubular chimneys to the skin, these chimneys being attached at the level of the skin orifices, the fixing step comprising, for each chimney: • the welding of a support onto the skin, at the level of one of the orifices, and, • the welding of a socket onto the support and / or the skin, the assembly formed by the support and the socket forming said chimney.

[0016] Thus, thanks to the invention, it is possible to assemble a housing and chimneys made of thermoplastic material by increasing, through welding, the interface surfaces between the chimneys and the housing skin. This solution allows for a durable, long-term bond of the assembly.

[0017] The invention also allows a mass saving via the use of thermoplastic composite material for the preparation of the casing skin and the preparation of the chimneys.

[0018] The invention may further include one or more of the following optional features, in any technically feasible combination: - the tubular portion is frustoconical - the socket has a shape complementary to the support; - the socket includes a truncated conical orifice; - the skin is intercalated radially between the collar and the socket; - the skin is welded respectively to the collar and the socket; - the socket is mounted around the tubular portion; and - the support is fixed to the skin by a sonotrode; - the support includes a tubular portion which is mounted in a way passing through, in a radial direction, inside the corresponding orifice; - the support is attached and welded to the skin radially from the inside of the skin; - the support includes an annular collar which is pressed against an inner face of the skin, opposite the outer face, the support being welded to the skin via its collar; - the socket is attached and fixed from the outside of the skin; - the socket is mounted around the support and fixed to the support by welding; - a resistive film is placed on at least part of the faces of the socket resting on the support before it is fixed by welding to the support; - the skin is intercalated radially between the collar and the socket; - the skin (102a) is welded respectively to the collar (200b) and to the socket; - the process further includes a step of crushing a free end of the support against the socket, said free end passing radially through an orifice of the socket and emerging above this orifice; - the socket and / or support is / are made of thermoplastic composite material preferably fiber-reinforced.

[0019] The invention also relates to a housing for an aircraft turbomachine, this housing comprising: - a skin of annular shape around an axis, comprising an inner annular face and an outer annular face; - tubular chimneys projecting from the outer annular face of the skin and oriented radially with respect to the axis, each of these chimneys being formed by a support fixed by welding in a radial orifice of the skin and by a socket fixed by welding to the support and / or to the skin.

[0020] The casing, according to the invention, may further comprise one or more of the following optional features, in any technically feasible combination: - The support includes: • a tubular portion inside the radial orifice, the tubular portion passing through the orifice in a radial direction; and • a collar fixed to the inner annular surface of the skin; - the socket includes a resistive film on at least part of its faces in contact with the support.

[0021] The invention also relates to a stage for an aircraft turbomachine, the stage comprising: - an annular casing as described above; - an annular row of variable-pitch blades, each variable-pitch blade comprising a blade including a cylindrical pivot at its radially external end, this pivot being mounted in a tubular chimney of the casing and defining a blade pitch axis; and - a control ring for the blade timing, this ring extending around the casing and being connected to the blade pivots.

[0022] The invention also relates to a stage for an aircraft turbomachine comprising a stage as described above. Brief description of the figures

[0023] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig.1] is a schematic representation of a cross-sectional view of a variable-pitch stage of an aircraft turbomachine according to the prior art; - [Fig.2] is a schematic representation of a partial view of the floor of [Fig.1]; - [Fig.3] is a schematic representation of a chimney of an aircraft turbomachine casing according to the invention; - [Fig.4] is a schematic representation of the manufacturing process of the housing of [Fig.3]; - [Fig. 5] is a schematic representation of the chimney support assembly of [Fig. 3]; and - [Fig.6] is a schematic representation of the chimney socket assembly of [Fig.3]; - [Fig.7] is a schematic representation of the crushing of a free end of the support against the socket of [Fig.3]; - [Fig.8] is a schematic representation of the chimney of [Fig.3] after crushing the free end of the support. Detailed description of the invention

[0024] Generally, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis. This axis can be considered the axis of rotation of a turbomachine rotor. The term "radial" refers to the orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner" and "outer," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the axis has an inner face facing the axis and an outer surface opposite its inner surface. Similarly, the terms "upstream" and "downstream" are defined with respect to the direction of airflow in the turbomachine.

[0025] With reference to [Fig. 2], a (non-limiting) example of a variable-pitch blade stage 100 of an aircraft turbomachine 100 in which the invention is implemented will now be described. The turbomachine 10 can be a turbojet or a turboprop.

[0026] The stage 100, which is for example a stage 100 of a high-pressure compressor of the turbomachine 10, comprises an annular row of variable-pitch blades 108a, an annular housing 102 having an axis of revolution A, and a control ring 120 for the pitching of the blades 108a.

[0027] Stage 100 may also include an annular row of movable blades 108b carried by a rotor (not shown) of the turbomachine.

[0028] Each variable-pitch blade 108a comprises a blade 110 having a cylindrical pivot 116 at its radially external end. The cylindrical pivot 116 defines a pitch axis C of the variable-pitch blade 108a.

[0029] The angular orientation of the variable-pitch blades 108a can be adjusted to optimize gas flow in the compressor. In particular, the variable-pitch blades 108a can be rotated about their axes C between a closed or near-closed position and an open or fully open position.

[0030] In the closed position, the blades 110 of the vanes are inclined with respect to a longitudinal axis X of the turbomachine 10 and define between them a minimum air passage cross-section in the duct. The longitudinal axis X of the turbomachine 10 corresponds substantially to the axis A of the annular casing 102. The variable-pitch vanes 108a are brought into this closed position when the turbomachine is at low speed or idle, the air flow into the compressor then having a minimum value. In the open position, the blades 110 of the variable-pitch vanes 108a extend substantially parallel to the axis of the turbomachine 10 so that the air passage cross-section between the blades is maximized. The variable pitch 108a blades are brought into this open position when the turbomachine 10 is at full throttle, the air flow into the compressor then having a maximum value.

[0031] The blade 110 and the cylindrical pivot 116 can be connected by a disc or "plate" 118 extending perpendicularly to the pitch axis C, of ​​the variable pitch blade 108a, in a corresponding housing 114 of the annular housing 102. A radially internal surface 112 of the disc 118 can be aligned with an internal wall 102i of the annular housing 102 so as not to oppose the gas flow.

[0032] A radially external end of the cylindrical pivot 116 of each variable pitch blade 108a can be connected to the control ring 120 by a connecting rod 124, the connecting rod 124 being connected to a linking member 122 to the cylindrical pivot 116. This control ring 120 extends around the annular housing 102 on the [Fig.1].

[0033] The distance between adjacent cylindrical pivots of variable pitch blades 108a is for example between 20 and 30 mm.

[0034] The housing 102 comprises at least one annular skin 102a about the axis of revolution A, comprising an inner annular face 102i and an outer annular face 102e, and tubular chimneys 106 projecting from the outer annular face 102e of the skin 102a. The tubular chimneys 106 are oriented radially with respect to the axis A. The cylindrical pivot 116 of each blade 108a can extend inside each tubular chimney 106.

[0035] With reference to [Fig.3], each tubular chimney 106 comprises a support 200 which is fixed by welding in a radial orifice 102h of the skin 102a and a sleeve 202 which is also fixed by welding to the support 200 and / or to the skin 102a of the housing 102.

[0036] The support 200 comprises a tubular portion 200a inside the radial orifice 102h, the tubular portion 200a passing through the orifice 102h in a radially outward direction. The tubular portion 200a of the support 200 is preferably frustoconical.

[0037] The support also includes an annular collar 200b fixed to the inner annular face 102i of the skin 102a of the annular housing 102.

[0038] The support further includes a cylindrical passage 200i provided for the passage of the pivot 116 of the variable pitch blade 108a.

[0039] Preferably, the support is made of a thermoplastic material and preferably of a thermoplastic composite material reinforced with short fibers.

[0040] The sleeve 202, which is mounted around the tubular portion 200a of the support 200, has a shape complementary to the support 200 and more specifically to the tubular portion 200a. Thus, in the case where the tubular portion has a frustoconical shape, the sleeve 202 includes a frustoconical orifice 202h in which the tubular portion 200a of the support 200 extends, the wall of the orifice 202h conforming to the frustoconical shape of the tubular portion 202a.

[0041] The sleeve 202 further comprises a resistive film 204 on at least a portion of its faces bearing against the support 200 (or on the tubular portion 202a of the support 200). The sleeve 202 may also comprise a resistive film 204 on at least a portion of its faces bearing against the skin 102a of the housing 102 as illustrated in [Fig. 3]. The resistive film 204 may be in the form of a grid or a single filament.

[0042] With reference to [Fig.4], a method 400 for manufacturing a housing 102 for a variable pitch blade stage 100 of an aircraft turbomachine 100 will now be described.

[0043] The process 400 includes the preparation 402 of an annular skin 102a made of a thermoplastic-based material. During this preparation 402, at least orifices 102h are machined in the annular skin 102a. The machined orifices 102h are through-holes in the radial direction.

[0044] Preferably, the annular skin 102a is made of a thermoplastic-based material and preferably of a continuous fiber-reinforced thermoplastic composite material

[0045] The process 400 for manufacturing the housing further includes the preparation 404 of tubular chimneys 106. During the preparation 404 of tubular chimneys 106, supports 200 and bushings 202 are machined.

[0046] Machining each support includes producing the tubular portion 200a and the flange 200b, the tubular portion 200a being configured to pass in a radially external direction through one of the orifices 102h machined in the annular skin 102a. The support can be made in one block comprising the tubular portion 200a and the flange 200b fixed to one end of the tubular portion 200a or, in two blocks that can be assembled, the first block comprising the tubular portion 200a and the second the flange 200b.

[0047] Machining each bushing 202 includes at least the creation of an orifice 202h having a shape complementary to that of the tubular portion 200a of the support 200 machined. Thus, in the case where the tubular portion has a frustoconical shape, the machined orifice 202h is frustoconical in shape.

[0048] Preferably, the support 200 and the sleeve 202 are made of a thermoplastic-based material and preferably of a thermoplastic composite material reinforced with short fibers. For example, the short fibers are carbon microfibers (microfillers) with a concentration of between 20 and 30% and preferably between 25 and 30%.

[0049] Still with reference to [Fig.4], following the preparations 402 and 404 respectively of the annular skin 102a and the chimneys 106, the tubular chimneys 406 are fixed onto the annular skin 102a.

[0050] The fixing 406 of the tubular chimneys 106 includes the welding 406a of each support 200 on the annular skin 102a at the level of one of the orifices 102h of the annular skin 102a.

[0051] During the welding 406a of the support 200, the tubular portion 200a is mounted through the tubing in a radially outward direction, that is, from the inner face 102i of the skin 102a to the outer face of the skin (moving away from the axis A of the skin 102a of the housing 102), inside the corresponding opening. In this way, the annular flange 200 is pressed against an inner face 102i of the annular skin 102a, opposite the outer face 102e of the skin 102a. The support 200 is then attached and welded to the skin from the inside of the skin, via its flange 200b.

[0052] The support 200 is ultrasonically welded to the skin 102a via a sonotrode 500 as illustrated in [Fig. 5]. The ultrasound is generated by a piezoelectric effect. The sonotrode 500 is applied, in the S500 direction, to the entire surface of the collar 200b opposite the surface in contact with the inner face 102i of the skin 102a. The sonotrode is shaped like a flat disk to be in contact with the entire collar. Variable shapes 200c, which can be conical, crenellated, or trapezoidal, can be provided on the face of the collar 200b in contact with the inner face 102i of the skin 102a, serving as energy directors. This shape can be obtained by 3D printing or by injection molding. These energy directors can also be brought to the interface via a rough thermoplastic film with similar shapes.

[0053] During the welding 406a of the support 200, a cylindrical metal component 300, for example a steel or aluminum shaft, is inserted into the through-hole 200i of the support 200 to support the geometry of the support. To allow the passage of the metal component 300, a hole 500i is provided in the center of the sonotrode.

[0054] A metallic holding tool 302, for example a steel or aluminum counter-mold, is also arranged around the tubular portion 200a (as illustrated in [Fig. 5]) and resting on the outer face 102e of the skin 102a. Advantageously, The support tooling 302 prevents the deconsolidation of the tubular portion 200a of the support and the skin 102a, the skin also being made of thermoplastic composite material.

[0055] The welding 406a of the support 200, and more specifically of the collar 200b of the support 200, on the skin 102a is on the order of a few seconds, for example between one and four second(s) (including the time of holding under pressure).

[0056] Following the welding 406a of the support 200 on the skin 102a, the socket 202 is welded 406b on the support 200 and / or the skin 102a.

[0057] In this welding step 406b of the bushing 202, the bushing is mounted around the support 200 and more specifically around the tubular portion 200a. The bushing 202 is attached to the support 200, and in particular to its tubular portion 200a, in a radially inward direction (approaching the axis A of the skin 102a of the housing 102). The skin 102a is then radially interposed between the bushing 202 and the flange 200b, as illustrated in [Fig. 6]. Thus, the bushing 202 is attached and fixed from the outside of the skin 102a. A free end 200e of the support 200, and specifically of its tubular portion 200a, opposite the end of the support 200 comprising the collar 200b, passes through the frustoconical orifice 202h of the socket 202 and has a portion opening above this orifice 202h. This portion of the free end 200e has a radial dimension dR (see [Fig. 7]) which can be, for example, on the order of 5 to 10 mm.

[0058] A resistive film 204 is disposed, beforehand, on at least part of the faces of the socket 202 resting on the support and / or on the skin 102a before its fixing by welding 406b on the support 200 and / or the skin 102a.

[0059] Applying a vertical force or pressure S700 then allows the interface between the sleeve 202 and the tubular portion 200a and / or between the sleeve 202 and the skin 102a to be welded 406b. In the case where a resistive film 204 is also present between the sleeve 202 and the skin 102a, the interfaces between the sleeve 202 and the tubular portion 200a and between the sleeve 202 and the skin 102a are welded simultaneously.

[0060] Advantageously, the presence of a resistive film at the interface between the sleeve 202 and the tubular portion 200a and / or the skin 102a greatly simplifies the welding tooling by assigning to it only the dimensional problem of reducing gaps at the interfaces (between the sleeve 202 and the tubular portion 200a and / or between the sleeve 202 and the skin 102a) by applying pressure to the parts, and without any heat quality requirements, unlike a conduction welding process, for example. The frustoconical shape of the tubular portion 200a of the support 200 and of the sleeve 202 allows pressure forces to be transferred to the inclined plane with a single vertical force.

[0061] Thus after the welding steps 406a and 406b, the skin 102a is welded respectively to the collar 200b and the sleeve 202. The assembly including the support 200 and the sleeve 202 then forms the chimney 106.

[0062] Still with reference to [Fig.4], the manufacturing process 400 can further include, following the fixing 406 of the chimney to the skin 102, a crushing step 408 of the free end 200e of the support 200, which opens above the orifice 202h of the sleeve 202, against the sleeve 202.

[0063] In this crushing step 408, a metal plate 800 is first heated and then applied to the portion of the free end 200e of the support 200 that opens above the orifice 202h of the sleeve 202. Pressure is then applied to the free end 200e, from top to bottom, in the direction S900 as illustrated in [Fig. 7]. The application of the heated plate 800 melts the free end 200e of the support 200, which spreads and solidifies onto the sleeve 202 as illustrated in [Fig. 8]. The crushing 408 is controlled so that the orifice 200i of the tubular portion 200a of the support 200 is not obstructed by a portion of the molten free end 200e.

[0064] The person skilled in the art will understand that the crushing 408 of the free end 200e of the support 200 against the sleeve 202 makes it possible to make the free end 200e of the support 200 and the sleeve 202 fixed together and therefore, to reinforce the fixing of the sleeve 202 to the support 200. Thus the risk of loss of the sleeve 202 is considerably reduced or prevented.

[0065] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands

1. A method (400) for manufacturing a housing (102) for a turbomachine (10), said housing (102) comprising a skin (102a) of annular shape about an axis (A) and comprising tubular chimneys (106) projecting on an external annular face (102e) of the skin (102a) and oriented radially with respect to the axis (A), the method (400) comprising the following steps: - preparation (402) of an annular skin (102a) of thermoplastic-based material, this skin (102a) having radially through orifices (102h), - preparation (404) of tubular chimneys (106) of thermoplastic-based material, - attachment (406) of the tubular chimneys (106) to the skin (102a), these chimneys being attached at the level of the orifices (102h) of the skin (102a), the fixing step (406) comprising, for each chimney (106): • the welding (406a) of a support (200) onto the skin (102a), at the level of one of the orifices (102h),and • the welding (406b) of a socket (202) onto the support (200) and / or the skin (102a), the assembly formed by the support and the socket forming said chimney (106).

2. Method (400) of manufacturing a housing (102) according to claim 1, in which the support (200) comprises a tubular portion (200a) which is mounted through, in a radial direction, inside the corresponding orifice (102h).

3. Method (400) of manufacturing a housing (102) according to claim 1 or 2, wherein the support (200) is attached and welded to the skin (102a) radially from the inside of the skin (102a).

4. Method (400) of manufacturing a housing (102) according to any one of claims 1 to 3, wherein the support (200) comprises an annular collar (200b) which is pressed against an inner face (102i) of the skin (102a), opposite the outer face (102e), the support (200) being welded to the skin (102a) via its collar (200b).

5. Method (400) of manufacturing a housing (102) according to any one of claims 1 to 4, wherein the bushing (202) is attached and fixed from outside the skin (102a).

6. Method (400) of manufacturing a housing (102) according to any one of claims 1 to 5, wherein the bushing (202) is mounted around the support (200) and fixed to the support (200) by welding.

7. Method (400) of manufacturing a housing (102) according to claim 6, in which a resistive film (204) is disposed on at least a part of the faces of the sleeve (202) bearing on the support (200) before its fixing by welding on the support (200).

8. Method of manufacturing a housing (102) according to any one of claims 4 to 7, wherein the skin (102a) is welded respectively to the collar (200b) and to the bushing (202).

9. Method of manufacturing a housing (102) according to any one of claims 1 to 8, further comprising a step of crushing (408) a free end (200e) of the support (200) against the sleeve (202), said free end (200e) passing radially through an orifice (202h) of the sleeve (202) and emerging above this orifice (202h).

10. Method (400) of manufacturing a housing (102) according to any one of claims 1 to 9, wherein the bushing (202) and / or the support (200) is / are made of thermoplastic composite material preferably fiber-reinforced.

11. Annular housing (102) for an aircraft turbomachine (10), this housing (102) comprising: - a skin (102a) of annular shape about an axis (A), comprising an inner annular face (102i) and an outer annular face (102e), - tubular chimneys (106) projecting on the outer annular face (102e) of the skin (102a) and oriented radially with respect to the axis (A), each of these chimneys (106) being formed by a thermoplastic support (200) fixed by welding in a radial orifice (102h) of the skin (102a) and by a thermoplastic bushing (202) fixed by welding to the support (200) and / or to the skin (102a).

12. Annular housing (102) for an aircraft turbomachine (10), according to the preceding claim, wherein the support (200) comprises: - a tubular portion (200a) inside the radial orifice (102h), the tubular portion (200a) passing through the orifice (102h) in a radial direction; and - a collar (200b) fixed to the inner annular face (102i) of the skin (102a).

13. Annular housing (102) for an aircraft turbomachine (10), according to any one of claims 11 and 12, wherein the sleeve (202) comprises a resistive film (204) on at least a portion of its faces bearing on the support (200).

14. Stage (100) for an aircraft turbomachine (10), comprising at least: - an annular casing (102) according to any one of claims 11 to 13; - an annular row of variable-pitch blades (108a), each variable-pitch blade (108a) having a blade (110) comprising a cylindrical pivot (116) at its radially external end, this pivot (116) being mounted in a tubular chimney (106) of the casing (102) and defining a pitch axis (C) of the blade (108a); and - a blade pitch control ring (120), this ring extending around the casing and being connected to the blade pivots.

15. Aircraft turbomachine (10) comprising at least one stage (100) according to the preceding claim.