Stator assembly for an aircraft turbine engine

Abstract

The invention relates to an assembly (100) for an aircraft turbine engine (1) having a longitudinal axis (X), the assembly (100) comprising: - a cylindrical rotor shroud (11) intended to be rotated about the longitudinal axis (X), - a nozzle (20) which has a ring of stator blades comprising a root (403) at the radially inner nozzle end supporting a seal (22), the seal being annular and configured to sealingly cooperate without contact with the cylindrical shroud (11) that is located radially below the nozzle, wherein the cylindrical shroud (11) comprises an annular layer (12) which is located radially across from the seal (22) and is made of a first material having a hardness greater than a hardness of a material of a radially inner end (23) of the seal (22) radially across from the annular layer (12).

Description

Description Title: Stator assembly for an aircraft turbomachine Technical field [1] This disclosure relates to an annular sealing ring, such as a hydrostatic annular sealing ring. This document also relates to an assembly comprising such a ring and to a turbine or turbomachine comprising such a ring. Prior art [2] Figure 1 schematically represents a twin-flow turbomachine 1 with longitudinal axis X. The turbomachine 1 generally comprises, from upstream AM to downstream AV according to the direction of gas flow within the turbomachine 1, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, a low-pressure turbine 7, and an exhaust system downstream of the turbomachine 1. The gas flow, in particular air, entering upstream of the turbomachine 1 first flows through the fan 2 and then divides, on the one hand, into an annular circulation channel called the primary channel 8, and on the other hand, into an annular circulation channel called the secondary channel 9 surrounding the primary channel 8. The low-pressure compressor 3, the high-pressure compressor 4, the combustion chamber 5, the high-pressure turbine 6, and the low-pressure turbine 7 are spared in the primary vein 8. [3] In this document, the terms 'longitudinal', 'radial', and 'circumferential' are defined with respect to the longitudinal axis X of the turbomachine 1, the longitudinal axis X coinciding with the axis of rotation of the low-pressure and high-pressure rotors of the turbomachine 1. The terms 'inside' and 'outside', as well as 'internal' and 'external', are then defined in the radial direction with respect to the longitudinal axis X. The terms 'upstream' and 'downstream' are defined with respect to the general direction of gas flow in the turbomachine along the longitudinal axis X around which the turbomachine extends [4] Reference is now made to Figure 2A, which schematically represents a partial view of a longitudinally oriented, low-pressure turbine 7 comprising alternating annular rows of movable blades 9 arranged longitudinally with annular rows of stator blades 10. In Figure 2, only two annular rows of rotor blades 9 and one annular row of stator blades 10 are shown. annular rows of rotor blades 9 or moving blades 9 are connected to each other by a cylindrical ferrule 1 1. [5] Each of the annular rows of stator blades 10 comprises an internal radially annular platform 12 and an external radially annular platform (not shown) between which extend a plurality of blades 13. The external radially annular platform is fixed to a turbine housing. [6] Managing the seal between the end of the stator blades 10 and the rotor shell 11 is important to limit gas leakage between the rotor and the stator 10 and to control the pressure and temperature conditions on either side of said seal and also radially below the seal. To this end, it is known to provide a radial annular partition 14 extending radially inward from said annular platform, and carrying at one end a sealing element 15 intended to maintain a small clearance with the corresponding rotor shell during operation. [7] To this end and as shown in Figures 2A and 2B, the annular row of stator blades 10 carries a backlash-controlled annular seal 15 arranged radially inside the annular row of stator blades 10 and radially outside the cylindrical shell 11, the backlash-controlled annular seal 22 cooperating to seal without contact with the cylindrical shell 11 in order to limit circulation from upstream of the annular row of stator blades 10 downstream in the annular space between the seal 15 and the cylindrical shell 11. [8] In particular, such a backlash-controlled seal 15 operates with a small and controlled annular clearance between itself and the ferrule 11 when the turbine is running. Furthermore, this type of seal aims to adapt the clearance during operation. The use of the hydrostatic seal 15 thus offers the advantage of limiting leakage at the sealing point, thereby improving the performance of the turbomachine and reducing the requirements in terms of thermal and mechanical stresses when dimensioning the various components of the turbine 7. [9] As shown in Figure 2B, the hydrostatic annular seal 15 can be formed of two concentric annular walls 16, 17, and a plurality of elastically deformable elements arranged circumferentially next to each other and extending between the two walls 16, 17, and including, in particular, elastically deformable blades 18 extending circumferentially. For example, document WO 2009 / 148787 describes such a seal. This configuration makes it possible to improve the control of the radial deformation of the seal 15, and therefore the control of the clearance between the seal 15 and the ferrule 11 cooperating with the sealing gasket 15 so as to limit the passage of air.

[0010] However, the use of a hydrostatic seal requires minimizing clearances between the rotor and stator to increase turbomachine performance, which can sometimes lead to contact between the rotor and stator. For example, when the rotor is overspeeding, the shell can undergo radial expansion and come into contact with the hydrostatic seal. Such contact can compromise the mechanical integrity of the shell.

[0011] This document aims to provide a simple, reliable and economical solution to this need. Summary

[0012] More specifically, this document concerns an assembly for a longitudinally mounted aircraft turbomachine, the assembly comprising: - a cylindrical rotor shell intended to be driven in rotation around the longitudinal axis, - a distributor which has a ring of stator blades having a foot at the radially internal end of the distributor carrying a sealing gasket, the sealing gasket being annular and configured to cooperate in sealing without contact with the cylindrical shell arranged radially under the distributor, in which the cylindrical shell includes an annular layer radially opposite the sealing gasket which is made of a first material having a hardness greater than a hardness of a material of a radially internal end of the sealing gasket radially opposite the annular layer.

[0013] The use of a harder material for the annular layer improves the mechanical strength of the cylindrical shell compared to that of the hydrostatic annular seal. Thus, in the event of a turbomachine failure, and particularly when the turbomachine is overspeeding, such an assembly provides mechanical protection to the cylindrical shell in case of prolonged contact between the hydrostatic annular seal and the cylindrical shell. The mechanical integrity of the cylindrical shell can therefore be preserved. Furthermore, the assembly described in this document can potentially contribute to the braking of the cylindrical shell.

[0014] The cylindrical ferrule may have a circular cross-section of constant radius along the longitudinal axis on at least one longitudinal portion of the cylindrical ferrule. This shape allows for better control of the clearance between the hydrostatic annular seal and the cylindrical ferrule.

[0015] In particular, the cylindrical ferrule may be devoid of lugs.

[0016] Advantageously, the hydrostatic annular joint comprises a radially external annular wall, a radially internal annular wall, and a plurality of elastically deformable elements, notably distributed circumferentially around the longitudinal axis. Each of the plurality of elastically deformable elements comprises a first substantially radial base connected to the radially external annular wall, a second substantially radial base connected to the radially internal annular wall, and at least one elastically deformable blade extending circumferentially. This at least one blade is connected to the first base at one circumferential end and to the second base at an opposite circumferential end.In other words, the first base connects one of the circumferential ends of at least one blade to the radially external annular wall, and the second base connects the other circumferential end of at least one blade to the radially internal annular wall. The hydrostatic annular seal can thus deform radially thanks to the flexibility provided by the at least one blade connecting the radially internal and radially external annular walls. The radially internal and external annular walls, the bases, and the blades are specifically dimensioned to control the radial deformation of the hydrostatic annular seal, and therefore to control the clearance between the hydrostatic annular seal and the cylindrical ferrule.

[0017] The radially internal annular wall can notably support an abradable pad designed to make contact with the cylindrical ferrule. Thus, the pad, made of abradable material, ensures that, during contact between the ferrule and the pad of the hydrostatic seal, wear occurs only on the side of the pad and not on the ferrule itself, which is intended to be protected.

[0018] The first material can then exhibit a higher hardness than the hardness of the abradable pad material.

[0019] The abradable pad can in particular have an aerodynamic profile. This allows, through radial depression and overpressure phenomena on either side of the pad, an increase in clearance between the cylindrical ferrule and the hydrostatic annular seal when they move closer together, and conversely, a decrease in clearance between the cylindrical ferrule and the hydrostatic annular seal when they move away from each other.

[0020] The hydrostatic annular seal is preferably made of a metallic material.

[0021] The first material may also exhibit abrasion resistance greater than the abrasion resistance of the material of the radially inner end of the hydrostatic annular joint opposite the annular layer.

[0022] Advantageously, the assembly can comprise at least two annular rows of moving blades arranged longitudinally on either side, upstream and downstream of the distributor's longitudinal axis, and connected by a cylindrical ferrule. A portion of the cylindrical ferrule extending longitudinally from one to the other of the two annular rows of moving blades is made of a second material. In other words, the portion of the cylindrical ferrule made of the second material connects the two annular rows of moving blades. This second material can be specifically adapted to ensure the mechanical transmission of torque between the two annular rows of moving blades.

[0023] The first material may exhibit a greater hardness than the first material.

[0024] The second material may have a lower abrasion resistance than the first material.

[0025] The first material and the second material in particular exhibit mechanical resistance and temperature resistance characteristics consistent with the thermomechanical operating conditions of the turbomachine.

[0026] The annular layer may have a longitudinal dimension greater than the longitudinal dimension of the hydrostatic annular seal along the longitudinal axis. This characteristic ensures that the hydrostatic annular seal remains radially aligned with the annular layer even in the event of relative longitudinal movement between the cylindrical shell and the annular row of stator blades. This relative longitudinal movement is commonly referred to as carriage. Carriage can occur during various phases of turbomachine operation.

[0027] The cylindrical ferrule may have an annular recess designed to receive the annular layer. In particular, the annular recess and the annular layer may be of the same thickness. In other words, the annular layer does not add any extra thickness to the cylindrical ferrule.

[0028] The annular layer can project beyond a first radially external surface of the cylindrical ferrule. This first radially external surface of the cylindrical ferrule can, in particular, correspond to a surface furthest radially inside a radially external periphery of the cylindrical ferrule.

[0029] The thickness is such that it provides sufficient mechanical resistance to the annular layer in case of contact between the cylindrical ferrule and the hydrostatic annular seal.

[0030] Also concerned is an assembly comprising a sealing joint having a plurality of sealing joint sectors distributed circumferentially around the longitudinal axis X, each sealing joint sector comprising a radially external annular wall sector and a radially internal annular wall sector connected to each other by an elastically deformable element.

[0031] According to another aspect, a turbine for an aircraft turbomachine is described, the turbine comprising a casing, an assembly and a rotor which includes the cylindrical shell, the cylindrical shell being driven in rotation around the longitudinal axis and the distributor being mounted in the casing and the cylindrical shell being arranged radially under the distributor.

[0032] According to another aspect, a turbomachine, such as a turbojet or turboprop, is described, comprising the assembly as previously described.

[0033] In another aspect, a manufacturing process for the assembly, as previously described, is outlined. The process comprises the following steps: - the application of the annular layer onto the cylindrical ferrule, - machining of a radially external face of the annular layer.

[0034] The process then makes it possible to ensure that the annular layer meets the dimensional constraints, geometric tolerances, and surface finish of the cylindrical shell. Brief description of the drawings

[0035] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which:

[0036] [Fig. 1] schematically illustrates a cross-sectional view of an example of a turbomachine;

[0037] [Fig. 2] schematically illustrates a partial view of part of a turbine, for example low pressure, figure 2B being an enlargement of the sealing joint illustrated in figure 2A;

[0038] [Fig.3] schematically illustrates an annular sealing gasket;

[0039] [Fig. 4] schematically illustrates part of an annular row of stator blades and a sealing gasket according to this document;

[0040] [Fig. 5] is a larger scale view of the sealing joint in Figure 4;

[0041] [Fig. 6] and [Fig. 7] schematically illustrate the sealing principle of the sealing joint according to this document;

[0042] [Fig. 8] schematically illustrates a first sealing joint according to this document;

[0043] [Fig. 9] schematically illustrates a second sealing joint according to this document;

[0044] [Fig. 10] to [Fig. 16] schematically illustrate a third type of sealing joint according to this document as well as variants thereof;

[0045] [Fig. 17] to [Fig. 20] schematically illustrate variants of the realization of the connecting tabs between a radially external annular wall and the radially internal annular walls for a sealing joint;

[0046] [Fig. 21] is a schematic three-dimensional view of a sector of an annular row of stator blades or distributor according to this document;

[0047] [Fig. 22] is a schematic perspective view of part of a hydrostatic annular joint;

[0048] [Fig. 23] is a schematic perspective view of the legs of a hydrostatic annular joint;

[0049] [Fig. 24] and [Fig. 25] are schematic perspective views of the radial sliding means between the hydrostatic annular joint and the annular row of stator blades;

[0050] [Fig. 26] is a cross-sectional view of an assembly according to this document;

[0051] [Fig. 27] to [Fig. 33] are schematic perspective views of an assembly comprising a hydrostatic annular joint according to this document;

[0052] [Fig. 34] and Fig. 35] including schematic perspective views of an assembly according to this document and comprising a hydrostatic annular joint connected by form cooperation with radial sliding linkage means on an annular row of stator blades;

[0053] Fig. 36] is a schematic perspective view of a circumferential edge of an annular joint as described in this document;

[0054] [Fig. 37] is a schematic illustration of an annular sealing gasket according to this document, the annular gasket having a housing on its radially internal face;

[0055] [Fig. 38] schematically illustrates a partial view of an example assembly according to this document, this assembly including an annular joint;

[0056] [Fig. 39] schematically illustrates a partial enlarged view of an example of an assembly according to figure 38;

[0057] [Fig. 40] schematically illustrates a partial enlarged view of another example of the assembly according to figure 38;

[0058] [Fig. 41] schematically illustrates respectively a partial view of an example assembly according to this document, and two enlarged partial views of the example assembly in two different configurations;

[0059] [Fig. 42] schematically illustrates a partial view of an example of a hydrostatic annular joint;

[0060] [Fig. 43] schematically illustrates a partial cross-sectional view of an example assembly according to this document;

[0061] [Fig. 44] schematically illustrates a partial cross-sectional view of another example assembly according to this document;

[0062] [Fig. 45] schematically illustrates a partial cross-sectional view of another example assembly according to this document;

[0063] [Fig. 46] schematically illustrates a partial cross-sectional view of another example assembly according to this document. Description of the embodiments

[0064] This document concerns an annular sealing ring, such as a hydrostatic annular sealing ring used in a turbomachine. It specifically covers various embodiments and integration methods for such a hydrostatic annular sealing ring.

[0065] Reference is made to Figure 3, which schematically represents a partial view of a hydrostatic annular seal 51 according to this document. Preferably, this hydrostatic annular seal 51 is integrated into a turbomachine assembly 52 with a longitudinal axis X. Such an assembly is implemented in a turbine, particularly a low-pressure turbine, of a turbomachine. This document also applies to any type of turbomachine comprising such a turbine, for example, a turboprop or turbojet engine for aircraft.

[0066] The assembly 52 comprises a cylindrical ferrule 53 intended to be driven in rotation about the longitudinal axis X and an annular row of stator blades. The assembly may also comprise two annular rows of movable blades arranged longitudinally on either side of the annular row of stator blades 54 and connected to each other by the cylindrical ferrule 53. The annular row of stator blades 54 carries the hydrostatic annular seal 51. This hydrostatic annular seal 51 is arranged radially inside the annular row of stator blades 54 and radially outside the cylindrical ferrule 53, the hydrostatic annular seal 51 cooperating to seal without contacting the cylindrical ferrule 53.

[0067] The hydrostatic annular seal 51 preferably comprises a radially external annular wall 55, a radially internal annular wall 56, and a plurality of elastically deformable members or elements 57, notably distributed circumferentially around the longitudinal axis X. The hydrostatic annular seal 51 can deform radially thanks to the flexibility offered by the elastically deformable member 57 connecting the radially internal annular wall 56 and the radially external annular wall 55. The radially internal annular walls 56 and 55, and the elastically deformable element 57, are specifically dimensioned to control the radial deformation of the hydrostatic annular seal 51, and thus control a clearance J2 between the hydrostatic annular seal 51 and the cylindrical ferrule 53.

[0068] The sealing joint may comprise a plurality of sealing sectors distributed circumferentially around the longitudinal axis, each sealing sector comprising a radially internal annular wall sector 56 and a radially external annular wall sector 55 connected to each other by an elastically deformable member 57. The radially external annular wall sectors may form a monolithic outer ferrule, i.e., of a single piece, and the radially internal annular wall sectors are distinct and arranged circumferentially end to end.

[0069] A turbine is a system that expands air, moving from a high pressure upstream to a low pressure downstream. It is essential that a maximum amount of air passes through the turbine and does not escape from the flow. A layer of air from the annular cavity located upstream of the sealing ring 51 passes between the cylindrical shell 53 and the ring 51, the radial differences in dimensions of which form the clearance J2. By maintaining a small radial clearance, the hydrostatic annular ring 51 thus achieves a seal. It is the pressure differential between the annular cavity upstream of the hydrostatic annular ring 51 and the annular cavity immediately downstream of this hydrostatic annular ring 51 that drives the resultant of the radial pressure forces applied to the radially internal annular wall 56 of the hydrostatic ring 51.

[0070] The hydrostatic annular seal 51 has an internal surface 59 arranged radially opposite the cylindrical ferrule 53. This internal surface 59 has a first, substantially cylindrical, surface portion 60 and a second, curved, surface portion 61. The concave surface has a concavity curved radially outwards to form an annular cavity opposite the cylindrical ferrule 53. It also includes a third, substantially cylindrical surface portion 62 and a fourth, frustoconical surface portion 63 with a cross-section increasing downstream. A clearance j1 exists between the first surface portion 60 and the cylindrical ferrule 53, and a clearance j2 between the third surface portion 62 and the cylindrical ferrule 53. The clearances j1 and j2 are such that j1 is greater than j2. This difference in clearance between j1 and j2 creates a restriction. This restriction accelerates the airflow and reduces static pressure in the case of a large clearance j1 (e.g., >0.6 mm). The hydrostatic annular seal 51 deforms under the resultant mechanical forces acting on the inner surface 59 and the outer surface 63 of the sectorized pad 58.This specific configuration allows for maintaining a small gap and therefore a high-performance seal, without risking contact between the sectorized pad 58 and the ferrule 53.

[0071] The annular row of stator blades 54 includes a radial annular partition 64 carrying the hydrostatic annular seal 51. The hydrostatic annular seal 51 may include radial sliding means 65 in the direction of the annular row of stator blades 54. The radially external annular wall 55 is connected to an annular part 71 having an upstream annular lug 66 and a downstream annular lug 67, each having longitudinally opposite orifices 68 in which pins 69 are mounted. The external annular wall 55 and the annular part 71 may be formed of a single piece. The pins 69 are press-fitted into the holes 68 of one of the upstream 66 and downstream 67 annular lugs only so as to allow insertion into the other of the upstream 66 and downstream 67 annular lugs. Preferably, the press-fitting is done on the upstream annular lug 66.The radial annular partition 64 of the annular row of stator blades 54 comprises a plurality of preferably oblong openings 70 in which an intermediate portion of the pins 69 are mounted. Alternatively, the openings may be rectangular. This arrangement allows one degree of freedom in the radial direction of the hydrostatic annular seal 51 relative to the annular row of stator blades 54. Other means of radial movement could be considered. The radial sliding of the hydrostatic annular seal 51 can be achieved as shown in Figures 21 to 26, but also as shown in Figures 27 to 33.

[0072] Thus, a degree of freedom in the radial direction is allowed to the hydrostatic annular seal 51 when the turbomachine is in operation. Indeed, under the effect of heat, expansions occur in the annular row of stator blades 54 relative to the annular part 71. The U-shape formed by the connection between the upstream annular lug 66 and the downstream annular lug 67 facilitates the mounting and radial sliding guidance of the seal on the annular partition 64. This U-shape therefore expands radially under the effect This U-shaped design ensures that there will be no outward radial thrust. Thus, the hydrostatic annular seal 51 is guided and undergoes minimal deformation due to temperature differentials with adjacent / neighboring components in the radial, circumferential, and even longitudinal directions.

[0073] In order to have the pressure differential described above between the upstream and downstream cavity of the turbine, it is necessary to provide a secondary seal 72. This secondary seal 72 prevents leakage between the radially internal annular wall 56 and the radially external annular wall 55 and ensures that air passes only between the cylindrical shell 53 and the radially internal annular wall sectors 56.

[0074] For this purpose, reference is now made to figures 4 to 7.

[0075] Figures 4 and 5 show the hydrostatic annular seal 51 equipped with the secondary seal 72 and fixed to the annular row of stator blades 54. This hydrostatic annular seal 51 is intended to be arranged longitudinally between two annular rows of rotor blades 73 arranged on either side of an annular row of stator blades 54. As described previously, the hydrostatic annular seal 51 comprises a radially internal annular wall 56 and a radially external annular wall 55 connected to each other by elastically deformable members 57. An annular flange is arranged opposite the upstream faces 74 of the elastically deformable members 57. This flange is supported by the radially external annular wall 55. There is an annular clearance between a radially internal end 76 of the ring 75 and the radially internal annular wall. 56.This annular set is sealed by the secondary seal 72 which we will describe in more detail.

[0076] As illustrated in Figures 4 to 6, a first annular row of first sheet metal sectors 77 is arranged circumferentially end-to-end and applied to an upstream face 78 of the ring 75. A second annular row of second sheet metal sectors 79 is applied to upstream faces 80 of the first annular row of first sheet metal sectors 77. The sheet metal sectors 77, 79 have a thickness between 0.1 and 0.6 mm. The second sheet metal sectors 79 can be arranged circumferentially by being offset from the first sheet metal sectors 77 so that a second sheet metal sector 79 is arranged longitudinally opposite two circumferentially adjacent first sheet metal sectors. The inner edges 81 of the second sheet metal sectors 79 are aligned longitudinally with the inner edges 82 of the first sheet metal sectors 77.The outer edges 83 of the second sheet metal sectors 79 are aligned longitudinally with the outer edges 84 of the first sheet metal sectors 77. The circumferential edges 85,86 of the first sheet metal sectors 77 are misaligned with. the circumferential edges 87,88 of the second sectors of sheet metal 79. The misalignment of the circumferential edges 85,86,87,88 of the first 77 and second sectors 79 of sheet metal prevents leakage related to annular play.

[0077] More specifically, as illustrated in Figure 7, the radially internal ends 89 of the first sheet metal sectors 77 bear against a radial face 90 of the radially internal annular wall 56. The flange 75 includes an internal annular rim 91a extending upstream. An upstream face 92 of the ring 75 is formed at the upstream end of the internal annular rim 91a of the flange 75. The first annular row of the first sheet metal sectors 77 is arranged circumferentially end-to-end and applied to the upstream face 92 of the ring 75. The material of the first sheet metal sectors and that of the flange is determined to facilitate sliding between these two parts.

[0078] The flange 75 also includes an annular rim 91b extending downstream and formed at its radially external end. As can be seen in Figure 5, the annular rim 91b radially covers the upstream ends of the radially external annular wall sectors.

[0079] As illustrated in Figures 4 to 7, the sheet metal sectors 77, 79 are attached to the ring 75 by fastening elements 93 passing through openings 94 in the sheet metal sectors 77, 79. These fastening elements 93 secure the first 77 and second sheet metal sectors 79 together to the ring 75, which is itself supported by the radially external annular wall 66. The fastening elements may be pins. The openings 94 are such that there is some play and the sheet metal sectors 77, 79 are able to move slightly.

[0080] We now refer to Figure 8, which represents a hydrostatic annular seal 150 intended to provide a seal between an annular row of stator blades to which it is connected and a cylindrical ferrule, as described with reference to Figure 2. As illustrated in Figure 8, the annular seal 150, which is of a known type, comprises an internal annular wall 151 formed of sectors 152 arranged circumferentially end to end. It also comprises an external annular wall 153 from which at least one lug or annular wall 154 may extend, having at least one orifice 155 for the insertion of a shaft, preferably materialized by a pin, or by the smooth shank of a screw, or alternatively by a spacer, intended to cooperate with an oblong opening in a radial annular partition carried by the internal annular platform of the annular row of stator blades.

[0081] Each radially internal annular wall sector 152 is connected to the external annular wall 153 by an elastically deformable member 156. Thus, each radially internal annular wall sector is associated with an elastically deformable member 156.

[0082] Each elastically deformable element 156 comprises two elastic lamellae 159 extending circumferentially and parallel to each other. The first ends of the lamellae 159 are connected to a first radial tab 158 carried by a radially internal annular wall sector, and the second ends of the lamellae 159 are connected to a second radial tab 157 carried by the radially external annular wall 153. While this type of embodiment proves effective, it does not allow for the optimal compromise between radial flexibility and torsional strength for a given lamella thickness, as mentioned in the prior art reference at the beginning of this description.

[0083] Thus, we propose a hydrostatic annular joint 100 formed of a plurality of circumferentially distributed sealing joint sectors, only one of which is represented in figure 9.Each sealing sector 102a, 102b comprises a radially external annular wall sector 106a, 106b and a radially internal annular wall sector 110a, 110b connected to each other by an elastically deformable member 105a, 105b, in which the circumferentially adjacent sealing sectors 102a, 102b have their respective elastically deformable members 105a, 105b made monolithically as a common elastic deformable member 105, the common elastic deformable member 105 connecting two circumferentially adjacent radially internal annular wall sectors 110a, 110b of sealing sector and in which the radially external annular wall sectors 106a, 106b of the sealing sectors form a monolithic external ferrule 106.

[0084] Thus, each common elastic element 105 is elastically connected to at least two radially internal annular wall sectors 110a, 110b—here, exactly two—which are circumferentially adjacent, and to two radially external annular wall sectors 106a, 106b. The radially internal annular wall sectors 110a, 110b successively form the radially internal annular wall of the hydrostatic annular joint 100. In the embodiment shown in Figure 9, each elastically deformable element 105 is connected to two circumferentially adjacent internal sectors 110a, 110b, one 110a being designated as a primary sector and the other 110b as a secondary sector.

[0085] It is observed that each common elastic organ 105 comprises at least one first elastically deformable circumferential blade 112a, 112b and at least one second elastically deformable circumferential blade 114a, 114b connected by first circumferential ends opposite each other to the external annular wall and of which second ends 122 circumferentially opposed to each other with respect to the first ends are each connected to the primary sector 110a and to the secondary sector 110b. Said first end 116 of said at least one first blade 112a, 112b and said first end 116 of said at least one second blade 114a, 114b are arranged in a circumferential screw.

[0086] In Figure 9, it can be seen that the at least first blade 112a, 112b and the at least second blade 114a, 114b comprise two blades which are radially spaced from each other. The first blades 112a, 112b and / or the second blades 114a, 114b may be substantially parallel to each other as shown in Figure 9. The first blades 112a, 112b and / or the second blades 114a, 114b may also form an angle with each other. Among the first blades 112a, 112b, one blade 112b is an inner blade 112b and the other 112a is an outer blade 112b. Among the second blades 1 12a, 112b, one second blade 112b is an internal second blade and the other 112a is an external second blade.

[0087] The first ends 116 of the first and second elastic blades can be connected, as shown in Figure 9, to a single first leg 118, which can extend substantially radially. The first inner blade 111b and / or the second inner blade 114b can be connected to the radially inner end of the first leg 118. The first outer blade 112a and / or the second outer blade 114a can be connected in the vicinity of the radially outer end of the first leg 118, this radially outer end of the first leg 118 being connected to the radially outer annular wall.

[0088] The radially internal end of the first leg 118 lacks a direct connection to either of the two circumferentially adjacent primary 110a and secondary 110b sectors, the connection of the first leg 118 with sectors 110a, 110b being made indirectly by the first 112a, 112b and second blades 114a, 114b and the second legs 120a, 12ab, the latter being described in the following paragraphs.

[0089] In the design of figure 9, the legs are dimensioned so that they are not deformable, the deformation taking place at the level of the blades.

[0090] The second ends 122 of the first and second elastic blades can be connected, as shown in Figure 9, to a second leg 120a, 120b which can extend substantially radially. It can be seen that there are two second legs 120a, 120b which are arranged circumferentially on either side of the first leg 118 and which can be positioned circumferentially in a substantially symmetrical manner with respect to the position of the first leg 1 18. A second leg called the second primary leg 120a is connected to the second ends of the first blades 112a, 112b and a second leg called the second secondary leg 120b is connected to the second ends of the second blades 1 14a, 114b.

[0091] According to the embodiment shown in Figure 9, the common elastically deformable member thus has a first radial leg with a circumferential end 120a connected to a circumferential end of the sector 110a of the internal annular wall of a first joint sector 102a and a second radial leg 120b with a circumferential end connected to a circumferential end of the sector of the internal annular wall 110b of a second joint sector 102b, each radial leg 120a, 120b with a circumferential end being connected to a common radial leg 118 by a first blade 112a, 112b and a second blade 114a, 114b which each extend circumferentially to connect each radial leg 120a, 120b with a circumferential end to a common radial leg 118.

[0092] The term "primary" and the term "secondary" only allow a distinction to be made between the two second legs 120a, 120b and their connection to the primary sector 110a and secondary sector 110b.

[0093] The first external blade 112a and / or the second external blade 114a may be connected to the radially external end of the second primary 120a and secondary 120b legs. The first internal blade 112b and / or the second internal blade 114b may be connected near the radially internal end of a second leg 120a, 120b, this radially internal end of a second leg 120a, 120b being connected to a pad 110a, 110b. More precisely, the radially internal end of the second primary leg 120a is connected to the primary sector 110a and, for example, near a circumferential end of it. The radially internal end of the second secondary leg 120b is connected to the secondary pad 110b and, for example, near a circumferential end of it. The two ends of the primary sector 1 10a and secondary sector 110b are opposite to their ends which are circumferentially facing each other.

[0094] Compared to Figure 8, the embodiment described above eliminates one connecting bracket for each pair of primary 110a and secondary 110b sectors, thereby lightening the structure of the hydrostatic annular joint 100. A significant reduction in circumferential dimensions is also achieved. With constant stiffness compared to the prior art, it is thus possible to use thicker blades, thereby limiting torsion. Thus, for each pair of primary 110a sectors and secondary 1 10b, it is necessary to have only three legs instead of four as in figure 8.

[0095] The annular seal 100 could include means allowing radial sliding of the hydrostatic ring seal relative to the radial annular partition of the annular row of stator blades. These means could be, for example, of the type described with reference to Figures 21 to 25 or with reference to Figures 27 to 33.

[0096] Reference is now made to figures 10 to 20.

[0097] Figures 10 to 16 schematically illustrate a third hydrostatic annular joint 201 and variants thereof.

[0098] Figure 10 shows a hydrostatic annular joint 201 comprising a radially internal annular wall 202, an elastically deformable element 203, and a radially external annular wall 204. The radially internal annular wall 202 is formed by a plurality of sectored pads 205. The sectored pad 205 shown is connected to the radially external annular wall 204 by the elastically deformable element 203. This elastically deformable element 203 has an internal tab 206 and an external tab 207. Each tab 206, 207 is substantially flat. The inner leg 206 has a radially internal end 208 to which the sectorized pad 205 is attached. The outer leg 207 has a radially external end 209 to which the radially external annular wall 204 is attached. The inner leg 206 has a radially external end 210 connected to a radially internal end 211 of the outer leg 207 by a connecting wall 215.In the embodiment of Figure 10, the inner leg 206 and the outer leg 207 extend radially so that the radially inner end 211 of the outer leg 207 is arranged radially inside the radially outer end 210 of the inner leg 206.

[0099] The hydrostatic annular seal 201 shown in Figure 11 comprises an elastically deformable element 203 made up of several elastically deformable elements. It thus includes a first elastically deformable element 212 and a second elastically deformable element 213. The first 212 and second 213 elastically deformable elements are arranged such that the inner leg 206, respectively the outer leg 207, of the first element 212 is axially adjacent to the outer leg 207, respectively the inner leg 206, of the second element 212.

[0100] The hydrostatic annular joint 201 shown in Figure 12 comprises an elastically deformable element 203 formed of three elastically deformable elements, a first organ 212, second organ 213 and third organ 214. The first 212 and second 213 organs are arranged so that the inner leg 206, respectively the outer leg 207, of the first organ 212 is axially adjacent to the outer leg 207, respectively the inner leg 206, of the second organ 213. The third organ 214 is arranged so that its outer leg 207, respectively its inner leg 206, is axially adjacent to the inner leg 206, respectively the outer leg 207, of the second organ 212.

[0101] The outer leg 207 can be inclined with respect to a tangent to the radially external annular wall 204 at the point of connection between the outer leg 207 and the radially external annular wall 204. Similarly, the inner leg 206 can be inclined with respect to a tangent to the radially internal annular wall 202 at the point of connection between the inner leg 206 and the radially internal annular wall 202. This angle can be between 10° and 150°. It is thus understood that the inner leg 206 and the outer leg 207 can have different inclinations, as clearly shown in Figure 13. Other embodiments are obviously possible. The inclination of the legs 207 and 206 with respect to the radial direction restricts the displacement of the elastically deformable element along the longitudinal direction.

[0102] Each connecting wall 215 can include a thickness, defined by the radial dimension of the connecting wall 215, between 0.5 and 10 mm and / or a width, defined by the longitudinal dimension of the connecting wall 215, between 2 and 30 mm.

[0103] Each leg 206, 207 can include at least one of the following parameters: A width along the longitudinal direction of between 2 and 30 mm, A dimension, depending on its direction of extension between its radially internal and external ends, ranging from 3 to 60 mm. - A dimension perpendicular to the direction of extension of the leg between 0.5 and 10 mm.

[0104] As illustrated in Figure 14, the hydrostatic annular joint 201 comprises first 212 and second 213 components. The connecting wall 215 restricts upstream / downstream rocking movements due to its torsional resistance. The internal and external tabs 206 and 207, which are also deformable, allow predominantly radial movement through bending of the elastically deformable component. The inclination of the tabs 206 and 207 relative to the internal 202 and external 204 annular walls limits the displacement of the pad 205 along the longitudinal axis.

[0105] As illustrated in Figure 15, the hydrostatic annular joint 201 may comprise a first 212 and a second 213 elastically deformable elements. The connecting wall 215 of the first element 212 includes a radially internal surface formed successively by a concave surface 216 and then a convex surface 217. The connecting wall 215 of the second element 213 includes a radially internal surface formed successively by a convex surface 217 and then a concave surface 216.

[0106] The hydrostatic annular seal 201 shown in Figure 16 comprises an elastically deformable element 203 consisting of a first element 212 and a second element 213. The connection between the radially external end 210 of the internal tab 206 and the connecting wall 215 of each element is at a right angle. Similarly, the connection between the radially internal end 211 of the external tab 207 and the connecting wall 215 of each element is also at a right angle. Figure 16 illustrates the oblique inclination of the elements 212 and 213.

[0107] Figures 17 to 20 schematically illustrate variant embodiments of the connecting lugs of the connecting walls 215 to the radially internal annular walls 202 and external annular walls 204 for a hydrostatic annular joint 201. Only an external lug 207 is illustrated, but the description also applies to an internal lug 206.

[0108] Figure 17 represents a leg 207 with a substantially constant cross-section between its inner and outer ends.

[0109] Figure 18 illustrates a leg 207 with a cross-section that evolves radially and increases in the particular case of Figure 18. The general shape here is triangular.

[0110] Figure 19 represents a leg 207 having a circumferential surface oriented towards the other leg which is concave and an opposite circumferential surface which is substantially flat.

[0111] Figure 20 also represents a leg 207 having concave and flat circumferential surfaces as in Figure 19. However, in this embodiment, the radially internal end of the leg has a smaller dimension than the radially external end.

[0112] The hydrostatic annular seal 201 comprises at least one material or combination of materials from the following list: steel, titanium, aluminum alloy, cobalt-based alloy, nickel-based alloy and / or any composite material.

[0113] We now refer to figures 21 to 26 which concern the radial sliding of a hydrostatic annular joint 300 on an annular partition 305 of an annular row of stator blades.

[0114] With reference to Figure 21, a sector 310 of an annular row or ring of stator blades, which is shown here as a distributor, is depicted. Such sectors are arranged circumferentially end to end to form the ring of stator blades. This ring carries a hydrostatic annular seal 300, which is shown in Figure 26. It could be of any type as described herein, for example, those described with reference to Figures 9 or 10 to 20.

[0115] All the crown sectors 310 of the distributor are identical so that the following description, which relates to one sector of Figure 21, applies to each of the other sectors 310 of the distributor.

[0116] With reference to Figure 21, the sector comprises an internal platform 312, an external platform 314 and blades 316.

[0117] The blades 316 are each connected on one side to the inner platform 312 and on the other side to the outer platform 314 so as to extend radially through a primary air stream, which is radially delimited by these platforms 312, 314.

[0118] The blades of sector 310 are circumferentially spaced from each other. The external platform 314 is configured to be fixed to a housing of the turbomachine 1.

[0119] The sector 310 includes a radial partition 305 forming the foot of the distributor 310 and which is connected to the internal platform 312 so as to extend radially inwards from the internal platform 312, towards a cylindrical ferrule 11 of the rotor, the cylindrical ferrule being shown in Figure 2 or Figure 38 or Figure 41. The radial partition 305 is configured to cooperate with a hydrostatic annular seal 300 (Figure 26). The hydrostatic annular seal 300 comprises a sectorized radial annular wall 320, formed of a plurality of rapidly internal annular wall sectors arranged circumferentially end to end. These are connected by elastically deformable members 322 to a radially external annular wall 325 fixed to the sealing support 324, which includes a radially external annular wall 323 and, radially outward, at least one radial annular tab 326, preferably two radial annular tabs as illustrated in Figure 22.

[0120] In this regard, figure 22 shows only a circumferential section of the sealing joint support 324.

[0121] With reference to Figure 22, the radial annular lugs 326 or flanges are substantially parallel and longitudinally spaced from each other so as to form a U-shaped section defining a space into which the radial partition 305305 of each of the sectors 310 can be inserted.

[0122] The longitudinal distance between the lugs 326 is chosen to allow for proper longitudinal positioning and retention of the sectors 310, while also permitting radial sliding of the partition 305 between the lugs 326 (see below). Specifically, an axial or longitudinal clearance J1, J2 is provided between the lugs 326 and the partition 305 to allow this radial movement. Clearance J1 extends between the upstream lug 326 and the partition 305, and clearance J2 extends between the partition 305 and the downstream lug 326.

[0123] Furthermore, the partition 305 is mounted with a radial clearance J3 relative to the bottom of the space defined by the tabs 326.

[0124] In the embodiment shown in Figure 26, the radially external annular wall 324 is formed in one piece with the elastically deformable members 322, with the radially internal annular wall 320 and with at least one of the annular legs 326.

[0125] Figure 23 shows two orifices 328 made respectively in the upstream leg 326 and the downstream leg 326.

[0126] The ports 328 share a common axis A2 and are designed to receive a pin 330 such as the one shown in the figure. The pin 330 is a cylindrical part with axis A2 having two shoulders that define an upstream portion 332, an intermediate portion 334 and a downstream portion 336.

[0127] The intermediate part 334 has a diameter smaller than the diameter of the upstream part 332 and the downstream part 336. The diameter of the upstream part is also smaller than that of the downstream part.

[0128] The orifice 328 of the upstream leg 326 of the hydrostatic annular seal 300 is sized to receive the upstream portion 332 of the pin 330 so as to form an interference fit. Similarly, the orifice 328 of the downstream leg 326 of the hydrostatic annular seal 300 is sized to receive the downstream portion 336 of the pin so as to form an interference or sliding fit.

[0129] After assembly, the pin 330 is thus supported by the upstream lugs 332 and downstream 436, forming a complete connection with it.

[0130] The 330 pawl is configured to cooperate with the distributor, in particular with the radial partition 305 of sector 310.

[0131] With reference to figure 21, the partition 310 of each of the sectors includes for this purpose an opening 338 which has an oblong shape of the groove type extending radially.

[0132] In this example, the opening 338 leads radially into the interior of the crown sector 310. It might not lead radially. This would require different geometric arrangements of the pin and different assembly steps than those shown here.

[0133] The opening 338 has a width, or circumferential dimension, allowing it to be crossed by the intermediate part 334 of the pin 330, that is to say a width greater than the diameter of the intermediate part 334 of the pin 330.

[0134] The width of the opening 338 is also less than the diameter of the upstream part 332 and the downstream part 336 of the pin 330. Thus, in the event of a break in the connection between the pin 330 and the upstream and downstream legs 326, the partition 305 of the sector 310 forms an axial stop to retain the pin 330.

[0135] The assembly of this stator element includes a pre-insertion of the pin 330 into the upstream and downstream legs 326 by passing the upstream part 332 of the pin 330 through the orifice 328 of the downstream leg 326.

[0136] The pin 330 is then fixed to the legs by forcibly inserting its upstream part 332 into the orifice 328 of the upstream leg 326 and, simultaneously, its downstream part 336 into the orifice 328 of the downstream leg 326.

[0137] The sector 310 is then moved radially inwards so as to introduce the partition 305 axially between the legs 326 and to insert the intermediate part 334 of the pin 330 into the opening 338 of the partition 305.

[0138] These assembly steps lead to the configuration illustrated in figure 25.

[0139] In this configuration, the pin 330 forms on the one hand a circumferential stop for the crown sector 310, preventing a displacement of the hydrostatic annular seal 300 and the crown sector 310 relative to each other in rotation around the axis of the sector 310 and allowing the hydrostatic annular seal 300 to be centered relative to this axis A1.

[0140] On the other hand, given the respective dimensions of the intermediate part 334 of the pin 330 and 330 of the oblong opening 338, the assembly allows a radial displacement of the hydrostatic annular joint 300 relative to the sector 310.

[0141] The stator assembly may include other pins similar to pin 330, each cooperating with partition 305 according to the principles described above.

[0142] Of course, these principles can be generalized. For example, each of the distributor's 310 sectors can cooperate with several pawns similar to pawn 330.

[0143] In general, the invention allows the hydrostatic annular seal 300 and the distributor 310 to be connected to each other according to a link defining a radial degree of freedom or radial sliding capable of compensating for differential thermal expansions within the turbine 9.

[0144] Finally, the forced mounting of the pins 330 in the orifices 328 of the upstream and downstream legs 326 contributes to the reduction of gas leaks outside the primary vein.

[0145] Reference is made to figures 27 to 33.

[0146] The embodiment shown in figures 27 to 32 is proposed of a hydrostatic annular joint 419 in which a radially external annular wall 401 is fixed by bolting to a joint support 402.

[0147] The hydrostatic annular joint 419 thus comprises a radially internal annular wall 420 sectorized and a radially external annular wall also sectorized 401.

[0148] The seal support 402 is mounted to slide radially on the radial annular partition 403 described previously with reference to Figure 21. The annular seal support 402 has an upstream annular tab 404 and a downstream annular tab 405. The upstream annular tab 404 and the downstream annular tab 405 are connected to each other by a base so as to form a U. The radial annular partition 403 has oblong openings 406 opening radially inwards.

[0149] In a particular embodiment, illustrated in Figures 27 to 31, the seal support 402 comprises longitudinal and circumferential projections 415 defining radial notches in which radial tabs 416 are engaged. These tabs are formed projecting radially outwards from the radially external annular wall sectors 401 of the hydrostatic annular seal. This arrangement of shapes prevents the annular seal from rotating on the seal support 402.

[0150] As illustrated in Figure 33, a sheet 414 can be interposed longitudinally between the radial annular partition 403 and the joint support 402. The sheet 414 comprises two radial annular arms connected to each other by a substantially cylindrical base. The arms include free end portions that are radially curved. inwards so as to form a curved portion which cooperates by form connection with a lateral outgrowth of the annular legs 404, 402 of the annular joint support.

[0151] Each elastically deformable element 407 can be elastically connected to at least two circumferentially adjacent radially internal annular wall sectors 408a, 408b. In the embodiment shown in Figures 28, 29 and 32, each elastically deformable element 407 is connected to two circumferentially adjacent radially internal annular wall sectors, one being designated as a primary sector and the other as a secondary sector.

[0152] It is observed that each elastically deformable organ 407 comprises at least one first circumferential elastically deformable blade 408 and at least one second circumferential elastically deformable blade 409 connected at a first common end to the radially external annular wall 401 and whose second ends, circumferentially opposite to each other with respect to the first common end, are each connected to a radially internal annular wall sector pad 408a, 408b.

[0153] In Figures 28, 29, and 32, it can be seen that at least one first blade 408 and at least one second blade 409 comprise two blades which are radially spaced from each other. The first blades and / or the second blades may be substantially parallel to each other, as shown in Figures 28, 29, and 32. The first blades and / or the second blades may also form an angle with each other. Among the first blades, one first blade 408 is an internal first blade 408 and the other is an external first blade 408. Among the second blades, one second blade 409 is a second internal 409 blade and the other is a second external 409 blade.

[0154] The aforementioned first ends of the first and second elastic blades can be connected, as shown in Figures 28, 29, and 32, to a single first leg 410, which can extend substantially radially. The first internal blade 408 and / or the second internal blade 409 can be connected to the radially internal end of the first leg 410. The first external blade 408 and / or the second external blade 409 can be connected in the vicinity of the radially external end of the first leg 410, this radially external end of the first leg 410 being connected to the radially external annular wall 401.

[0155] The radially inner end of the first leg 410 lacks a direct connection to either of the two circumferentially adjacent pads; the connection of the first leg 410 with the radially internal annular wall being formed indirectly by the first and second blades and second legs, the latter being described in the following paragraphs.

[0156] The second ends of the first and second elastic blades can be connected, as shown in Figures 28, 29, and 32, to a second leg 411, which can extend substantially radially. It can be seen that there are two second legs 411 arranged circumferentially on either side of the first leg 410 and which can be positioned circumferentially in a substantially symmetrical manner with respect to the position of the first leg 410. A second leg 411, called the primary second leg 411, is connected to the second ends of the first blades, and a second leg 411, called the secondary second leg 411, is connected to the second ends of the second blades.

[0157] The terms "primary" and "secondary" only allow for a distinction between the two second legs and their connection to the corresponding primary or secondary skates.

[0158] The first external blade 408 and / or the second external blade 409 may be connected to the radially external end of the second primary and secondary legs. The first internal blade 408 and / or the second internal blade 409 may be connected near the radially internal end of a second leg 411, this radially internal end of a second leg 411 being connected to a pad. More precisely, the radially internal end of the second primary leg 411 is connected to the primary pad and, for example, near a circumferential end of it. The radially internal end of the second secondary leg 411 is connected to the secondary pad and, for example, near a circumferential end of it. These two ends of the primary and secondary pads are opposite to their circumferential ends.

[0159] As illustrated in figure 30, a ring or spacer 413 acts as an axis for the free expansion of the joint support 402.

[0160] In a particular embodiment illustrated in figure 32, the radially external annular wall 401 is formed by a radial ring 417.

[0161] Reference is made to figures 34 and 35 illustrating a hydrostatic annular joint 501. This hydrostatic annular joint 501 comprises a radially external sectorized annular wall 502, a radially internal sectorized annular wall 503 and an elastically deformable element 504 arranged between said two internal and external walls.

[0162] As illustrated in Figure 34A, the radially external annular wall 502 is fixed in a joint support 505. Each sector of the radially external annular wall 502 carries a coupling member 506 engaged circumferentially and retained radially in a circumferential groove of the joint support 505. The coupling member 506 has a dovetail shape extending circumferentially. The seal support 505 includes an upstream wall 507 extending radially inwards and formed opposite the upstream face of the hydrostatic annular seal 501 so as to contribute to the sealing of the elastically deformable member 504. The annular part 505 has an upstream annular tab 508 and a downstream annular tab 509. The upstream annular tab 508 and the downstream annular tab 509 form a U adapted to slide radially on a radial annular partition of an annular row of stator blades as illustrated in figure 21.The radial annular partition may have oblong or rectangular openings radiating inwards and in which are engaged fasteners passing through the upstream and downstream tabs of the joint support 505. The fasteners may include pins as described with reference to figures 24 and 25.

[0163] Figure 34B illustrates the presence of a locking element for the radially external annular wall sector on the joint support 505. The locking is achieved here by a pin 513 engaged and shrink-fitted through the support and the coupling element 506 of the joint 501.

[0164] As illustrated in Figure 35A, the seal support can be a 360° part which has a lateral opening 509 leading into the circumferential groove of the seal support. This makes the circumferential groove accessible, allowing each seal to be mounted by longitudinal translation into the lateral opening and then by rotation.

[0165] The annular joint could be of any type. For example, it could be of the type described with reference to Figure 9 and comprise two radially internal annular wall sectors 510a, 510b, each monolithically formed with a radial tab 515. Each radial tab 515 is connected to a common tab 514 arranged circumferentially between the two tabs 515. Details of the joint's construction can be found with reference to Figure 9. The coupling of the joint support 505 and the joint 401 can be achieved with other joints of this document, such as the joint described with reference to Figures 10 to 15.

[0166] After all the seal sectors have been assembled, an annular flange 519 is mounted on the downstream face of the seal to block the lateral opening. The flange thus includes projections 517 bolted onto the seal support 505.

[0167] Figure 36 illustrates a particular embodiment of a 600 annular hydrostatic sealing joint.

[0168] As described previously, a hydrostatic annular joint 600 comprises a radially internal annular wall and a radially external annular wall between which elastically deformable elements are formed. The present description, in relation to Figure 36, is applicable to any of the annular joints described with reference to the figures. The elastically deformable joint could be of the type described with reference to Figure 9, or one of Figures 10 to 15. In Figure 36, a radial tab 618 and an elastically deformable blade or lamella 620 can be seen.

[0169] The radially internal annular wall is sectorized and comprises a plurality of sectors 610 arranged circumferentially end to end. Each sector 610 comprises a first circumferential edge 612 and a second circumferential edge (not shown) circumferentially opposite the first edge 612. The first circumferential edge 612 of a sector 610 is circumferentially end to end with a second circumferential edge of a circumferentially adjacent sector 610.

[0170] As illustrated in Figure 36, in relation to a first circumferential edge 612 of a sector 610, a slot 614 is formed in the thickness of the sector 610 and in its first circumferential edge 612. This slot 614 opens circumferentially and may have a substantially rectangular cross-section. A similar slot 614 is formed in the second circumferential edge of each sector skate.

[0171] According to this document, a tongue 616 is mounted partly in a slot 614 of a first circumferential edge 612 and in a circumferentially opposite slot 614 of a second circumferential edge of a circumferentially adjacent pad 610.

[0172] As described with reference to Figure 36, each internal sector 610 may comprise a radially internal surface having a first part 610a with a substantially cylindrical surface, a second part 610b with a surface formed by a recess, a third part 610c with a substantially cylindrical surface, and preferably a fourth part 610c with a frustoconical surface whose cross-section increases downstream. The recess extends from one circumferential end to the other of the sector 610 and has a concave curved shape which may be formed from a longitudinal succession of flat surfaces. A housing as shown in Figure 37 could also be formed in the recess.

[0173] It is observed that the slot 614 is formed substantially radially outside the recess so that a plane perpendicular to the longitudinal axis intercepts both the slot 614 and the recess.

[0174] In one particular embodiment, the slot extends to the third part 61 Oc. The slot is open circumferentially and axially upstream. The upstream opening is sealed by a gasket (not shown) which prevents airflow at the upstream outlet. A gasket such as that described with reference to Figures 5 to 7 can be used.

[0175] Reference is now made to Figure 37, which depicts a hydrostatic annular seal 700 comprising a radially external annular wall 710 and a radially internal annular wall 712, which is sectored and formed from a plurality of sectors 714 arranged circumferentially end to end. Elastically deformable elements 716 are arranged radially between the internal wall 712 and the external wall 710. This seal 700 can be mounted at the radially internal end of an annular row of stator blades in a turbomachine. It could be mounted at any other location where it could perform the same function, for example, at a radially external end of an annular row of stator blades or at the interface between any rotating and stationary part in a turbomachine.

[0176] As can be seen, the sector in Figure 37 has the same shape as the sector in Figure 8. However, what is described below with reference to Figure 37 is also applicable to the other joints in this document, in particular to the joint as shown in Figures 9 to 12.

[0177] Each elastically deformable organ 716 can include two substantially radial legs 718, 720, a first 720 of which is connected to the sector 714 and a second 718 is connected to the outer annular wall 710. The two legs 718, 720 are connected to each other by elastic blades 722.

[0178] It is proposed here to form a housing 724 on the radially internal face of each sector 714, this housing 724 opening radially inwards, this housing 724 having upstream and downstream faces 724a, and circumferential faces 724b formed within the thickness of the sector 714. The housing also includes a bottom wall 724c connecting the radially external ends of the circumferential walls 724b, upstream and downstream 724a. Parts A, B, C and D of Figure 37 represent different orientations of the joint and are shown in cross-section for parts B, C and D.

[0179] It is observed that the housing 724 can have a substantially parallelepiped shape, that is to say, whose lateral or circumferential walls 724b, upstream and downstream walls 714a, and bottom wall 724c are substantially flat, if we disregard the radii of connection between said walls. The housing 724 can be substantially circumferentially centered on the circumferential extent of the sector 714.

[0180] The housing 724 thus created does not open circumferentially or longitudinally since the circumferential faces 724b opposite and the upstream and downstream faces 724a opposite are formed in the thickness of the sector 714.

[0181] Dwelling 724 may extend circumferentially over a distance less than 80% of the circumferential extent of the sector. Similarly, dwelling 724 may extend longitudinally over a distance less than 50% of the longitudinal extent of sector 714.

[0182] In a particular embodiment of the joint 700, each housing 724 has a depth of at least 50% of the maximum radial dimension of the sector 714.

[0183] In figure 37D, we observe that the radially internal surface of sector 714 comprises a first part of surface 726a substantially cylindrical, a second part 716b of surface forming a recess, a third part of surface 726c substantially cylindrical and a fourth part of surface 726d frustoconical with section increasing towards the downstream.

[0184] According to this document, the housing 724 is formed in the annular recess 726b. The recess 726 may have a concave curved shape. Here, it is composed of a succession of conical surfaces.

[0185] The elastic elements 716 could have the shape of those described with reference to Figures 9 to 12. In this case, the primary and secondary sectors are each provided with a housing 724 formed within its thickness. For the remaining characteristics of the elastic element, reference should be made to the description given with reference to Figures 9 to 12.

[0186] The integration of a 724 housing as described with reference to Figure 37 could be carried out on any of the annular joints and assemblies described in this document.

[0187] The annular seal 700 could further include slots formed in the circumferential edges of each sector for receiving a sealing tab as described with reference to Figure 36.

[0188] Reference is now made to Figure 38, which schematically represents a partial view of an assembly 800 for a longitudinally mounted turbomachine according to this document. Preferably, such an assembly is implemented in a turbine, particularly a low-pressure turbine, of a turbomachine as previously described with reference to Figure 1. This document also applies to any type of turbomachine. including such a turbine, for example a turboprop or a turbojet for an aircraft.

[0189] The assembly 800 comprises a cylindrical ferrule 811 intended to be driven in rotation about the longitudinal axis and an annular row of stator blades 820. The assembly 800 may also comprise two annular rows of movable blades 810 arranged longitudinally on either side of the annular row of stator blades 820 and connected to each other by the cylindrical ferrule 811. The annular row of stator blades 820 carries a hydrostatic annular seal 822 arranged radially inside the annular row of stator blades 820 and radially outside the cylindrical ferrule 811, the hydrostatic annular seal 822 cooperating to seal without contacting the cylindrical ferrule 811.

[0190] Furthermore, the cylindrical ferrule 811 includes an annular layer 812 opposite the hydrostatic annular seal 822, which is made of a first material having a hardness greater than that of a material of a radially internal end 823 of the hydrostatic annular seal 822 opposite the annular layer 812.

[0191] Using a harder material for the annular layer improves the mechanical strength of the cylindrical shell compared to the hydrostatic annular seal. Therefore, in the event of rotor misalignment due to a sudden maneuver or failure, this assembly mechanically protects the cylindrical shell from prolonged contact between the hydrostatic annular seal and the cylindrical shell. The mechanical integrity of the cylindrical shell is thus preserved.

[0192] The cylindrical ferrule 811 features a circular cross-section with a constant radius along its longitudinal axis on at least one longitudinal portion. This shape allows for better control of the clearance between the hydrostatic annular seal and the cylindrical ferrule. In particular, the cylindrical ferrule 811 is free of flanges.

[0193] The hydrostatic annular joint preferably comprises a radially external annular wall, a radially internal annular wall, and a plurality of elastically deformable elements, notably distributed circumferentially around the longitudinal axis. Each of the plurality of elastically deformable elements has a first substantially radial leg connected to the radially external annular wall, a second substantially radial leg connected to the radially internal annular wall, and at least one elastically deformable blade extending circumferentially. This at least one blade is connected to the first leg at one circumferential end and to the second leg at an opposite circumferential end. In other words, the first leg The first lug connects one circumferential end of at least one blade to the radially external annular wall, and the second lug connects the other circumferential end of at least one blade to the radially internal annular wall. The hydrostatic annular seal can thus deform radially thanks to the flexibility provided by the at least one blade connecting the radially internal and radially external annular walls. The radially internal and external annular walls, the lugs, and the blades are specifically dimensioned to control the radial deformation of the hydrostatic annular seal, and therefore to control the clearance between the hydrostatic annular seal and the cylindrical ferrule. Such a deformable component is illustrated in Figure 8.

[0194] The elastically deformable organ could also be of the type described with reference to figures 9 to 12.

[0195] The first material must then have a greater hardness than the material of the skate.

[0196] The pad, made of a material with greater abradability than the shell coating, ensures that wear during contact between the shell and the pad of the hydrostatic seal occurs only on the pad and not on the shell.

[0197] The pad can in particular have an aerodynamic shape. This allows, through phenomena of depression and overpressure on either side of the pad, an increase in clearance between the cylindrical ferrule and the hydrostatic annular seal when they move closer together, and conversely, a decrease in clearance between the cylindrical ferrule and the hydrostatic annular seal when they move away from each other.

[0198] The hydrostatic annular seal is preferably made of a metallic material.

[0199] The first material may also exhibit abrasion resistance greater than the abrasion resistance of the material of the radially internal end 823 of the hydrostatic annular joint 822 opposite the annular layer 812.

[0200] A portion 814 of the cylindrical ferrule 811, extending longitudinally from one to the other of the two annular rows of moving blades 810, is made of a first material having a greater hardness than the second material. In other words, the portion 814 of the cylindrical ferrule 811 made of the second material connects the two annular rows of moving blades. The second material can be adapted, in particular, to ensure the mechanical transmission of torque between the two annular rows of moving blades 810.

[0201] The second material may have a lower abrasion resistance than the first material.

[0202] The second material can include steel, a nickel-based alloy, or a cobalt-based alloy.

[0203] The first material and the second material in particular exhibit mechanical resistance and temperature resistance characteristics consistent with the thermomechanical operating conditions of the turbomachine.

[0204] The annular layer 812 may have a longitudinal dimension L1 greater than a longitudinal dimension L2 of the hydrostatic annular seal 822 along the longitudinal axis X. This feature ensures that the hydrostatic annular seal 822 can remain radially aligned with the annular layer 812 even in the event of relative longitudinal movement between the cylindrical shell 811 and the annular row of stator blades 820. This relative longitudinal movement is commonly referred to as carriage. Carriage can occur during various phases of turbomachine operation.

[0205] With reference to Figure 39, the cylindrical ferrule 811 may have an annular recess 813 intended to receive the annular layer 812. In particular, the annular recess 813 and the annular layer 812 may be of the same thickness. In other words, the annular layer 812 may not add any extra thickness to the cylindrical ferrule 811.

[0206] Referring to Figure 40, the annular layer 812 can project from a first radially external surface 815 of the cylindrical ferrule 811. This first radially external surface 815 of the cylindrical ferrule 811 can, in particular, correspond to a surface located most radially inside a radially external periphery of the cylindrical ferrule 811. For example, the annular layer 812 can form a ring, i.e., extend over 360°. The layer could be partially housed within the ferrule and partially project from its external surface.

[0207] The annular layer 812 may have a radial thickness h so as to provide sufficient mechanical resistance to the annular layer in case of contact between the cylindrical shell and the hydrostatic annular seal.

[0208] In another aspect, a manufacturing process for assembly 100, as previously described, is outlined. The process comprises the following steps: - the placement of the annular layer 812 on the cylindrical ferrule 811, - machining of a radially external face 816 of the annular layer 812.

[0209] The process then makes it possible to ensure that the annular layer 812 meets the dimensional constraints, geometric tolerances, and surface finish of the cylindrical ferrule 811.

[0210] Reference is now made to Figure 41, which schematically represents a partial cross-section of a 900 assembly for a longitudinally mounted turbomachine according to this document, and two enlarged views of the assembly. Preferably, such an assembly is implemented in a turbine, particularly a low-pressure turbine, of a turbomachine as previously described with reference to Figure 1. This document also covers any type of turbomachine incorporating such a turbine, for example, a turboprop or turbojet engine for aircraft.

[0211] The assembly 900 comprises a ferrule 931 designed to be driven in rotation about the longitudinal axis X and a stator stage 920 extending around the longitudinal axis X and radially outside the ferrule 931. The ferrule 931 may, in particular, have a cylindrical shape, at least along a longitudinal portion of the ferrule. The ferrule 931 is specifically devoid of blades. The assembly 900 may also comprise two annular rows of movable blades 930 designed to be driven in rotation about the longitudinal axis X, the two annular rows of movable blades 930 being arranged longitudinally on either side of the annular row of stator blades 920 and connected to each other by the ferrule 931.

[0212] The stator stage 920 comprises an annular row of stator blades 921. More precisely, the annular row of stator blades 921 includes a radially external annular platform and a radially internal annular platform 922 between which a plurality of blades extend. The annular row of stator blades 921 includes a radial partition 923 which extends radially inward from the radially internal annular platform 922.

[0213] The stator assembly 920 also includes a hydrostatic annular seal 950 carried by the annular row of stator blades 921 and radially opposite the ferrule 931, the hydrostatic annular seal 950 being configured to cooperate in non-contact sealing with the ferrule 931.

[0214] Furthermore, the stator stage 920 and more particularly the annular seal includes a stop system capable of coming into contact directly or indirectly with the ferrule 931 and allowing to limit the radial displacement of the seal.

[0215] In the context of an overspeed start of a turbine rotor including the shell, the hydrostatic annular seal can come into contact with the shell, under the effect of a The radial expansion of the latter occurs during overspeed. The thrust bearing system advantageously reinforces the contact between the stator stage 920 and the ferrule 931, thus contributing to rotor braking in case of overspeed. Such an assembly 910 allows for passive braking of the rotor. The assembly therefore protects the mechanical integrity of the rotor in case of overspeed.

[0216] More specifically, with reference to Figure 42, the hydrostatic annular seal 950 comprises a radially external annular wall 951, a radially internal annular wall 952, and a plurality of elastically deformable elements, notably distributed circumferentially around the longitudinal axis. The hydrostatic annular seal 950 preferably includes a ring 959 extending radially outward from the radially external annular wall 951. For example, the ring may have a U-shaped cross-section, with the two arms of the U positioned on either side of the radial partition. The two arms of the U and the radial partition can be positioned using centering pins.

[0217] The radially internal annular wall 952 and the radially external annular wall 951 can, in particular, be formed respectively of a plurality of internal wall sectors arranged circumferentially end to end and of a plurality of external wall sectors arranged circumferentially end to end. Each of the internal and external wall sectors is, in particular, connected to an elastically deformable element of the plurality of elastically deformable elements.

[0218] With reference to Figures 43, 44, and 45, each of the plurality of elastically deformable organs 953 comprises a first substantially radial leg 955 connected to the radially external annular wall 951, a second substantially radial leg 956 connected to the radially internal annular wall 952, and at least one elastically deformable blade 954 extending circumferentially. As such, only the blades 954 are capable of deformation; the legs 955 and 956 are undeformable.

[0219] Said at least one blade 954 is connected to the first leg 955 at one circumferential end and to the second leg 956 at an opposite circumferential end. In other words, the first leg 955 provides the connection between one of the circumferential ends of said at least one blade 954 and the radially external annular wall 951, and the second leg 956 establishes the connection between the other of the circumferential ends of said at least one blade 954 and the radially internal annular wall 952. The hydrostatic annular joint can thus deform radially thanks to the flexibility offered by said at least one blade connecting together the radially internal annular wall and the radially external annular wall.

[0220] The radially internal and external annular walls, the tabs, and the blades are specifically dimensioned to control the radial deformation of the hydrostatic annular seal, and thus to control the clearance between the hydrostatic annular seal and the shell. A first clearance J1 (shown in Figure 41) is defined between the hydrostatic annular seal 950 and the shell 931, corresponding to the nominal operating clearance between the hydrostatic annular seal and the shell. Alternatively, the first clearance can be defined as the cold-start clearance of the turbine.

[0221] More specifically, the first leg 955 comprises a radially external end directly connected to a radially internal face of the radially external annular wall and a radially internal end that lacks a direct connection to the radially internal annular wall. Similarly, the second leg 956 comprises a radially internal end directly connected to a radially external face of the radially internal annular wall and a radially external end that lacks a direct connection to the radially external annular wall.

[0222] Furthermore, the first leg 955 and the second leg 956 are specifically adapted to avoid radial deformation. Only leg 956 is capable of radial movement with the radially internal annular wall and of moving towards (or away from) the radially external annular wall.

[0223] Each of the plurality of elastically deformable organs 953 may in particular comprise a plurality of radially spaced blades 954, for example two blades. The blades are in particular substantially parallel to each other.

[0224] The radially internal annular wall can carry an abradable pad 958 arranged radially opposite the ferrule 931 and capable of wearing down in case of contact with the ferrule 931.

[0225] The 958 abradable pad can have, in particular, an aerodynamic shape. This allows, through phenomena of depression and overpressure on either side of the pad, an increase in clearance between the ferrule and the hydrostatic annular seal when they move closer together, and conversely, a decrease in clearance between the ferrule and the hydrostatic annular seal when they move away from each other.

[0226] With reference to Figure 43, which schematically represents an example of an embodiment of the assembly according to this document, the thrust bearing system 940 comprises at least one first radial thrust element 941 carried by the radially external annular wall 951 opposite the second leg 956 of one of the plurality of elastically deformable members 953. Thus, the first radial thrust element can abut against the second leg. The thrust elements are here radial projections.

[0227] The said at least first radial stop element 941 can also be carried by the radially internal annular wall 952 opposite radially the first leg 955 of one of the plurality of elastically deformable members 953. Thus, the first radial stop element can come against the first leg.

[0228] Said at least first radial stop element 941 can also be carried by the second leg 956 of one of the plurality of elastically deformable members 953 opposite radially the external radial annular wall 951, or carried by the first leg 955 of one of the plurality of elastically deformable members 953 opposite radially the internal radial annular wall 952. Thus, the first radial stop element 941 can come against the internal radial annular wall when it is carried by the first leg, or against the external radial annular wall when it is carried by the second leg.

[0229] The stop system 940 can also include at least two first radial stop elements 941, one being carried by the second lug 956 radially opposite the external radially annular wall 951 or vice versa, and the other being carried by the first lug 955 radially opposite the internal radially annular wall 952 or vice versa.

[0230] This at least one first radial thrust bearing element 941 strengthens the radial contact between the hydrostatic annular seal and the ferrule, thereby improving the ferrule's braking capacity in case of overspeed. Furthermore, the first radial thrust bearing element is advantageously integrated directly into the hydrostatic annular seal, simplifying its implementation from a manufacturing perspective. In particular, the first radial thrust bearing element 941 can be formed from a single piece of the hydrostatic annular seal.

[0231] The first radial stop element 941 can form a radial protrusion.

[0232] The first radial stop element 941 may have a first stop surface 945 substantially parallel to a face against which the first stop surface is able to come to rest.

[0233] As shown in Figure 43, a second clearance J2 between the first abutment surface 945 and the face against which the first abutment surface is able to abut must be less than or equal to the first clearance J1. As shown in Figure 43, a second clearance J2 between the first abutment surface 945 and the face against which the first abutment surface is able to abut can be 0.2 mm or more. Thus, when the ferrule deforms radially outwards under the effect of an overspeed, the radial outward movement of the internal radial annular wall of the seal is limited, which ensures contact between this wall and the 931 ferrule.

[0234] The first radial stop element 941 can extend over part or all of the longitudinal dimension of the hydrostatic annular joint 950.

[0235] In particular, the stop system 940 preferably comprises a plurality of first radial stop elements 941. For example, each of the plurality of elastically deformable members may comprise one of the plurality of first radial stop elements 941.

[0236] Figures 44 and 45 show examples of embodiments of the assembly according to this document. The assembly may include at least one second radial thrust element 942, 943 forming a finger extending radially inward from the annular row of stator blades. Said at least one second radial thrust element 942, 943 is adapted to abut radially with the radially internal annular wall 952 (as shown in Figure 45) and / or with the second leg 956 of one of the plurality of elastically deformable members 953 (as shown in Figure 44).

[0237] The second radial stop element 942, 943 can be connected to the radial partition 923 at a first end. The second radial stop element 942, 943 can include a second end opposite the first end facing the radially external face of the radially internal annular wall 952 or the radially external end of the second leg 956 of one of the plurality of elastically deformable members.

[0238] The second radial stop element 942, 943 can in particular extend over part or all of the longitudinal dimension of the radial partition 923.

[0239] The second radial stop element can radially pass through at least one opening 957a, 957b, 957b' provided in the hydrostatic annular joint.

[0240] With reference to figure 44, the second radial stop element 942 is able to come into radial contact with the second leg 956. A first opening 957a is in particular provided in the radially external annular wall 951, the first opening 957a being opposite the radially external end of the second leg 56. Thus, the second radial stop element 942 passes through the first opening 957a.

[0241] With reference to Figure 45, the second radial stop element 943 is adapted to come into radial contact with the radially internal annular wall 952, in particular with the radially external face of the radially internal annular wall 952. The second radial stop element 943 passes through a first opening 957a provided in the radially external annular wall 951, and a second opening 957b, 957b' provided in each blade of said at least one blade 954. The second radial stop element 943 can in particular be circumferentially positioned between the first leg 955 and the second leg 956, in particular substantially in the middle of the first leg 955 and the second leg 956.

[0242] The second radial stop element 942, 943 may have a second stop surface 946 substantially parallel to a face against which the second stop surface is able to come to rest.

[0243] A third clearance between the second abutment surface and the face against which the second abutment surface is designed to abut can preferably be of the same order of magnitude as the first clearance. This technical feature ensures that, when the ferrule expands radially under the effect of overspeed, and the hydrostatic annular seal and the ferrule then come into contact, the hydrostatic annular seal cannot deform radially sufficiently to allow a gas flow between the hydrostatic annular seal and the ferrule.

[0244] The assembly may include a plurality of second radial stop elements 942, 943. For example, each of the plurality of elastically deformable members may include one of the plurality of second radial stop elements.

[0245] With reference to Figure 46, at least one third longitudinal thrust bearing element 944 of the thrust bearing system 940 may advantageously extend longitudinally from the hydrostatic annular seal 950. This at least third longitudinal thrust bearing element 944 is adapted to engage longitudinally with a radial portion 932 of the annular ferrule 931 facing longitudinally. This feature ensures contact between the ferrule and the hydrostatic annular seal in the event of relative longitudinal movement between the ferrule and the stator stage, and in particular in the event of rotor shaft failure. Thus, this at least third longitudinal thrust bearing element can advantageously contribute to rotor braking in the event of overspeed.

[0246] Said at least a third longitudinal stop element 944 may preferably have an annular shape.

[0247] The thrust bearing elements have been presented individually in a non-limiting manner in the preceding description, the assembly being able to include a combination of said at least one first radial thrust bearing element, said at least one second radial thrust bearing element and said at least one third longitudinal thrust bearing element.

Claims

Claims

1. Assembly (800) for an aircraft turbomachine (1) with a longitudinal axis (X), the assembly (800) comprising: - a cylindrical rotor shell (81 1 ) intended to be driven in rotation around the longitudinal axis (X), - a distributor (20) which has a crown of stator vanes comprising a root (403) at the radially inner end of the distributor carrying a seal (822), the seal being annular and configured to cooperate in a contactless sealing manner with the cylindrical shell (811) arranged radially under the distributor, in which the cylindrical shell (811) comprises an annular layer (812) radially facing the seal (822), the annular layer (812) being made of a first material having a hardness greater than a hardness of a material of a radially inner end (823) of the seal (822) radially facing the annular layer (812).

2. Assembly (800) according to claim 1, comprising two annular rows of moving blades (810) arranged longitudinally on either side, upstream and downstream of the longitudinal axis (X), of the distributor (20) and connected to each other by the cylindrical ferrule (811), in which a part (814) of the cylindrical ferrule (811) extending longitudinally from one to the other of the two annular rows of moving blades (810) is made of a second material having a hardness lower than the hardness of the first material.

3. Assembly (800) according to claims 1 or 2, wherein the annular layer (812) has a longitudinal dimension (L1) greater than a longitudinal dimension (L2) of the seal (822) along the longitudinal axis (X).

4. Assembly (800) according to one of claims 1 to 3, in which the cylindrical ferrule (811) has an annular recess (813) intended to receive the annular layer (812).

5. Assembly (800) according to one of claims 1 to 4, in which the annular layer (812) projects relative to a first radially external surface (815) of the cylindrical ferrule (81 1).

6. An assembly according to one of the preceding claims, wherein the seal comprises a plurality of seal sectors distributed circumferentially around the longitudinal axis (X), each seal sector comprising a radially outer annular wall sector (106) and a wall sector radially internal annular (1 10) connected to each other by an elastically deformable member (105).

7. Turbine for an aircraft turbomachine, the turbine comprising a casing, an assembly according to any one of the preceding claims and a rotor which comprises the cylindrical shroud, the cylindrical shroud being driven in rotation about the longitudinal axis (X) and, the distributor being mounted in the casing and the cylindrical shroud being arranged radially under the distributor.

8. Method of manufacturing an assembly (800) according to one of claims 1 to 6, the method comprising the following steps: - placing the annular layer (812) on the cylindrical ferrule (811), - machining of a radially external face (816) of the annular layer (812).

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