Intermediate plate for mounting on a blade base of a turbomachine rotor, guide vane of a turbomachine rotor movable around a rotational axis, arrangement for turbomachine rotor and turbomachine rotor

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The technical field of the invention is that of turbine blades.

[0002] The present invention relates to a foil intended to be mounted on a blade root of a turbomachine rotor, a blade of a turbomachine rotor movable around an axis of rotation, an assembly for a turbomachine rotor, as well as a turbomachine rotor. ARRIERE-PLAN TECHNOLOGIQUE DE L'INVENTION

[0003] Conventionally, an axial turbine of a turbomachine consists of a succession of axial stages (along the axis of circulation of the gas flows) arranged one behind the other. Each stage comprises a bladed wheel forming the rotor and a bladed distributor forming the stator. The wheel is rotated opposite the corresponding distributor.

[0004] The moving wheel is conventionally made up of an annular disc centered on the axis of rotation of the wheel, comprising cells and a plurality of moving blades each comprising an attachment member called hereinafter a blade root in a dedicated cell-shaped housing.

[0005] In the contact zones between the root of each moving blade and the cell of the disc housing this root, several types of constraints are exerted.

[0006] We encounter in particular "fretting", that is to say contact wear, which is the consequence of the repetitive friction of one part on another, the resulting friction forces being able to cause damage to the material by different fatigue processes. This phenomenon is particularly sensitive in the case of contact between two parts, for example metal or CMC.

[0007] These areas are therefore subject to a significant tendency towards material damage, as well as wear of the blade root surfaces which are the areas in contact with the cell wall, or even deformation of these contact areas.

[0008] In addition, the level of local stresses is very high due to the coefficient of friction at the interface between the contacting walls of the blade root and the cell, formed by a metal / metal contact. In the following, this interface is called the blade root bearing surface and the cell bearing surface.

[0009] To solve these problems, we are seeking in particular to strengthen the wear resistance of the surfaces in contact and to reduce the coefficient of friction.

[0010] To do this, we generally use a protective part which can be a consumable, formed of one or more metal foils fitting the foot of the blade.

[0011] With this type of solution, we can reduce the coefficient of friction and we can change the foil instead of an entire blade.

[0012] For example, document EP2042689A1 proposes using an assembly with a metal foil between a blade root and a disc.

[0013] On turbine blades, foils are placed between the blade roots and the disc cells to prevent wear of these parts. These ensure the mechanical integrity of the parts with which they are in contact.

[0014] In the foils of the prior art, these are held in position on the blade roots by two folded tabs projecting from the base of the foil located at the bottom of the blade root.

[0015] During turbine operation, possible axial displacements of the foils have been observed in certain situations, which can damage the sensitive tabs following their folding / unfolding during the foil assembly phase. This damage can in certain cases lead to cutting and lead to possible axial disengagement of the foils. Indeed, in these situations, once the tabs have been cut, the foils can then partially or completely disengage from the blade roots.

[0016] The disengagement of the foils no longer ensures the mechanical integrity of the blade root and the turbine disk. This axial disengagement of the foil therefore results in at least a portion of the blade root being unprotected and therefore premature wear of the blade root instead of the foil produced by "fretting"

[0017] In some situations, the cut tabs can also end up in an air stream and damage the shock-sensitive blades located downstream of the turbine.

[0018] Also known in document EP1764480A1 is a foil whose tab is formed by two legs each extending from the ends of the branches, connected together by a connecting piece by welding or riveting or interlocking. Such a tab results in an additional production cost and furthermore, even if the connecting piece makes it possible to increase the strength of the tab, it does not prevent the breaking of one of the legs of the tab at the end of one of the two branches.

[0019] Foils are also known, in particular in document EP EP2042689A1 filed by the applicant, comprising a tab folded towards the rotor rather than towards the blade, however the tab is still likely to unfold or tear and cause wear of at least a portion of the blade. Furthermore, in this document, there is a shim between the foil and the bottom of the disc cell. The foil therefore comprises its base between the shim and a surface of the blade root. A lock is mounted retained between an upstream edge of the shim and the blade root, so that the retaining tab is retained between the lock and the blade root, which makes it possible to prevent axial displacement of the foil relative to the blade root.

[0020] However, this solution is difficult to implement and is not always possible due to space requirements and the mechanical strength of the blade or disc.

[0021] Document WO 2021 / 013280 A1 constitutes the closest prior art. RESUME DE L'INVENTION

[0022] The invention provides a solution to at least one of the problems mentioned above, by allowing the foils not to disengage from the blade roots and ensuring the mechanical integrity of the blade root and the turbine disk.

[0023] A first aspect of the invention relates to a foil intended to be mounted on a blade root of a rotor comprising an axis of rotation, extending longitudinally comprising: a base, a first lateral branch and a second lateral branch connected to each other by the base, at least the first branch comprises at least one recess comprising at least two folds in two different directions, remarkable in that the recess can cooperate with a notch provided in the blade root to ensure the longitudinal retention of the foil relative to the blade root at least in one longitudinal direction. Thanks to the recess in one branch, the foil cannot dislodge from the blade root along the axis of the rotor disc; it acts as a stop. In addition, the recess is stronger than a tab formed by a single fold, due to its different folds.

[0024] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations:

[0025] According to one embodiment, the foil comprises a first lateral edge and a second lateral edge extending over the base and the branches, and the recess is located between the first lateral edge and the second lateral edge and distant from them, forming a longitudinal stop in the two axial directions of the foil in the blade root. By placing the recess between the two lateral edges, the blade is prevented from disengaging in the two axial directions. The foil therefore extends longitudinally between the two lateral edges forming its ends.

[0026] According to one embodiment, the foil comprises on each lateral branch, a longitudinal edge, a longitudinal edge being contiguous to the recess.

[0027] According to an example of this embodiment, the first lateral branch comprises a planar surface comprising the longitudinal edge and the recess extends from this planar surface towards the other branch. This makes it easy to produce the recess and a longitudinal stop without a slope.

[0028] According to a particularity of this example, the flat surface is perpendicular to the base. This allows for a recess that extends towards the other branch parallel to the base, forming a longitudinal and radial stop without slope.

[0029] According to a feature of this example, the first fold of the recess extends longitudinally from the flat surface of the first lateral branch forming a first reinforcing wall and the second fold extends from the first reinforcing wall to two opposite stop walls to each form a longitudinal stop in at least one axial direction of the foil in the blade root. Thus the recess comprises two folds each forming two surfaces extending in two different directions making it possible to increase the strength of this recess.

[0030] According to a feature of this example, the second fold extending from the first reinforcing wall further forms a second reinforcing wall perpendicular to the first reinforcing wall.

[0031] According to one embodiment, the recess comprises: two longitudinal folds extending longitudinally, two depth folds, each depth fold extending between one end of the first longitudinal fold and the other longitudinal fold and four radial folds extending radially from the longitudinal edge towards the ends of the longitudinal folds and the depth folds.

[0032] According to an example of this embodiment, the recess comprises: a first reinforcing wall delimited between: the two longitudinal folds, one of the two longitudinal folds extending longitudinally from the flat surface of the first lateral branch and each depth fold, two opposite stop walls each to ensure the longitudinal retention of the foil relative to the blade root at least in one longitudinal direction, each delimited between: one of the two depth folds, and two of the four radial folds.

[0033] In one embodiment, the first ply forms a radial bearing surface.

[0034] This also makes it possible to form a radial support of the foil on a surface of a notch of the blade root, thus being able to reduce a displacement of the foil relative to the blade root when the rotor is rotated.

[0035] In one embodiment, the recess of the first branch projects toward the other branch. This forms a stop in a notch of the blade.

[0036] In one embodiment, the foil includes a second recess on the second branch. This increases the resistance to deformation of the recesses.

[0037] According to an example of this embodiment, the second branch may be symmetrical to the first branch. This makes it possible to insert the foil in both longitudinal directions around the blade root.

[0038] According to one embodiment, the foil is flexible. The flexibility of the foil allows it to deform. When inserting the blade root between the two branches, the recess bears against a surface of the blade root until the recess fits into a notch in the blade root.

[0039] A second aspect of the invention relates to a blade of a turbomachine rotor movable about an axis of rotation, comprising an internal platform, a blade extending radially from the platform and a blade root extending radially from this platform opposite the blade, the blade root comprising: a first radial face, a second radial face longitudinally opposite the first radial face, a first lateral longitudinal face joining each radial face and a second lateral longitudinal face joining each radial face, at least one flank on each lateral longitudinal face, comprising a bearing surface intended to bear against a surface of a housing of the blade root, remarkable in that at least the first lateral longitudinal face has a notch comprising at least one longitudinal stop surface extending in a plane intersecting the axis of rotation and a guide surface extending in a direction other than the longitudinal stop surface, the notch being intended to receive a recess of a foil to ensure the longitudinal retention of the foil relative to the blade root at least in a longitudinal direction.

[0040] The notch allows the foil to not dislodge from the blade root along the axis of the rotor disc, it plays a role of stop with a recess of the foil. In addition, the notch includes two surfaces allowing the recess to have two folds and two surfaces of different orientations thus allowing the recess to be more solid than a tab formed by a single fold, due to its different folds.

[0041] According to one embodiment, the longitudinal stop surface extending in a plane intersecting the axis of rotation

[0042] According to one embodiment, the notch is located between each radial face and distant from them. This makes it possible to block the foil in both longitudinal directions.

[0043] According to one embodiment, the blade root comprises a lower surface connecting the two lateral longitudinal faces and the two radial faces and the lower surface is closer to the flank than to the notch.

[0044] According to an example of this embodiment, the blade root comprises a base portion comprising the bearing surfaces and a restricted portion extending between the internal platform and the base portion, the restricted portion having a width less than the narrowest part of the base portion, and the notch extends from a flat surface of the first lateral longitudinal face into the restricted portion, forming the longitudinal abutment surface and a second longitudinal abutment surface perpendicular to the lower surface and inclined relative to the flat surface to ensure longitudinal retention of the foil relative to the blade root in the other longitudinal direction.

[0045] In one example, the base portion includes the spans, this base portion flares out from the restricted portion.

[0046] The invention also relates to an assembly for a turbomachine rotor comprising: a moving blade according to the second aspect of the invention described above with or without the different combinations of the different advantages described above; a foil of the first aspect of the invention described above with or without the different combinations of the different advantages described above, the foil being mounted on the blade root such that the recess is complementary to the notch of the blade root and is housed in the notch and is in axial support against at least the longitudinal stop surface.

[0047] The invention also relates to a turbomachine rotor comprising the assembly described above and a rotor disk comprising cells formed in the external periphery of the rotor disk, the blade root being housed in one of the cells.

[0048] Advantageously, a maximum width A of the recess measured, in a direction tangential to the axis of the rotor disk, from one end of the recess to a bottom of the recess, is greater than a distance B measured on the same straight line from the end of the recess to the rotor disk. BREVE DESCRIPTION DES FIGURES

[0049] The figures are presented for information purposes only and in no way limit the invention. [ Fig.1 ] is a perspective view of an assembly comprising a blade root according to a first embodiment of the invention inserted into a foil according to an embodiment of the invention. [ Fig.2 ] is a sectional view of the entire figure 1 mounted in a cavity of a turbine disc. Fig.3 ] is an enlargement of the entire figure 1 on a recess in the foil in a notch in the foot of the blade. Fig.4a ] is a front view of an assembly comprising a blade root according to a second embodiment of the invention inserted into a foil according to a second embodiment of the invention. [ Fig.4b ] is an enlargement of the entire figure 4a on a recess in the foil in a notch in the foot of the blade. DESCRIPTION DETAILLEE

[0050] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0051] The invention relates to a foil for a root of a moving blade of a turbomachine, the moving blade as well as to an assembly for a turbomachine rotor comprising a moving blade having its root inserted in such a foil and finally the rotor comprising a rotor disk comprising cells and at least one blade root inserted in the cell.

[0052] There figure 1 presents a perspective view of an assembly 100 according to the invention comprising a foil 1 and a blade 2.

[0053] There figure 2 is a sectional view of the whole 100 of the figure 1 mounted in a socket 31 of a rotor disc 3.

[0054] The blade 2 comprises a blade (not visible) extending radially between a radially outer end and a radially inner end. At its radially outer end, the blade 2 comprises a heel (not shown). At its radially inner end, the blade 2 comprises an internal platform 29 (partially shown in the figures 1 et 2 ) whose foot 21 extends radially towards the bottom of the cell 31. The foot 21 makes it possible to fix the blade 2 to the rotor disc 3 while being retained by bearing surfaces of the cell 31 of the disc 3.

[0055] The foot 21 of blade 2 comprises a first radial face 23a and a second radial face 23b on either side longitudinally of the foot 21.

[0056] The foot 21 radially comprises a base portion 21l comprising the bearing surfaces and a restricted portion 21h extending between the internal platform 29 and the base portion 21l. Dotted lines on the figure 1 represents the boundary between the restricted portion 21h and the base portion 21l. The base portion 21l flares out from the restricted portion 21h, widening to form the bearing surfaces and then thinning down to an inner surface 27 to face the bottom of the cell 31 of the disc 3.

[0057] The foot 21 further comprises two lateral longitudinal faces 24c, 24d of the base portion 21l and of the restricted portion 21h each connecting the first radial face 23a and the second radial face 23b.

[0058] Each lateral longitudinal face 24c, 24d therefore comprises in the base portion 21l at least one flank intended to form a bearing surface of the foot 21 against a bearing surface of the cell 31.

[0059] In this example, each lateral longitudinal face 24c, 24d comprises in the restricted portion a flat surface 28c, 28d extending from the base portion 211 and in this example a surface widening towards the internal platform.

[0060] The foil 1 includes a complementary shape with the foot 21.

[0061] A first aspect of the invention concerns the foil 1 shown in the figures surrounding the root 21 of the blade 2 of corresponding shape and a second aspect of the invention concerns the blade 2 comprising the root 21. In particular the foil 1 surrounds the base portion 21l of the root 21 and at least partially the restricted portion 21h of the root 21.

[0062] The foil 1 comprises a base 17 covering a lower surface 27 of the foot 21 as well as a first lateral branch 12c and a second lateral branch 12d visible on the figure 2 . On the figure 1 , only the first lateral branch 12c is visible. The two lateral branches 12c, 12d are connected to each other via the base 17. The first and second lateral branches 12c, 12d each cover one of the two corresponding longitudinal faces 24c, 24d of the foot 21. The lateral branches 12c, 12d form means of protection, for example against fretting, of the longitudinal faces 24c, 24d of the foot 21 in a cell 31 of the disc 3 shown in the figure 2 .

[0063] In this example, the foil 1 comprises on each lateral branch 12c, 12d, a flat surface 18 surrounding the flat surface 28c of the restricted portion.

[0064] The foil 1 comprises a first and a second lateral edge 15a, 15b extending over one end of the base 17 and lateral branches 12c, 12d forming the opposite longitudinal ends of the foil 1. The foil 1 also comprises at the end of each of its lateral branches 12c, 12d, a longitudinal edge 16c, 16d extending longitudinally along the flat surface 18 and connecting the two lateral edges 15a, 15b. The longitudinal edge 16d of the second lateral branch 12d is shown in the figure 2 and that of the first lateral branch 12c is referenced on the figure 1 .

[0065] In order to block the relative movements between the foil 1 and the foot 21, the foot 21 comprises at least one notch 22 on one of the two lateral longitudinal faces 24c, 24d and the foil 1 comprises at least one recess 13 in the notch 22 of the foot 21, located on a lateral branch 12c, 12d.

[0066] A recess means a hollow shape projecting from a surface.

[0067] By notch is meant a part hollowed out in the mass of the foot 21 of blade 2.

[0068] In this case, in this example, each longitudinal lateral face 24c, 24d comprises a notch 22 and the foil 1 comprises two recesses 13, which are visible on the figure 2 . In this case, each recess 13 is located on the longitudinal edge 16c, 16d. By “located on the longitudinal edge 16c, 16d” is meant that the recess 13 comprises a portion of the longitudinal edge 16c, 16d, in other words the deformation of the recess 13 has deformed the longitudinal edge 16c, 16d. Each notch 22 has a shape similar to the corresponding recess 13 of the foil 1.

[0069] In this case, the restricted portion 21h comprises on either side the two notches 22 extending from the corresponding flat surface 28c in the material of the restricted portion 21h. By “in the material” is meant towards the center of the restricted portion.

[0070] In the following, only the recess 13 of the first branch 12c and the notch 22 of the first lateral longitudinal face 24c will be described to simplify the description because in this example the branches 12c, 12d (including the recesses 13) as well as the lateral longitudinal faces 24c, 24d (including the notches 22) are in this case identical.

[0071] There figure 3 presents an enlargement of the figure 1 , on a recess 13 of the first lateral branch 12c of the foil 1 in a notch 22 of the foot 21 having finer lines than that of the foil 1.

[0072] The recess 13 comprises at least a first fold 131 and a second fold 132 of different direction. In this example, the recess 13 comprises eight folds forming edges of the recess 13.

[0073] In the eight folds, recess 13 includes: two longitudinal folds extending longitudinally, one of which is hereinafter called the first fold referenced 131, two other depth folds, one of which is hereinafter called the second fold referenced 132, each depth fold extending between one end of the first longitudinal fold 131 and the other longitudinal fold and four radial folds extending radially from the longitudinal edge 16c towards the ends of the longitudinal folds 131 and the depth folds, one of which is hereinafter called the third fold referenced 133.

[0074] The recess 13 extends from the flat surface 18 towards the other branch 12d.

[0075] In this example, the notch 22 is located between each radial face 23a, 23b and distant from them and the recess 13 is therefore also located between the first lateral edge 15a and the second lateral edge 15b and distant from them.

[0076] According to another embodiment, an example of which is shown and explained below in figure 4a And 4b, the notch 22 is in the angle between one of the two radial faces 23a, 23b and a lateral longitudinal face 24c, 24d forming at least two distinct surfaces and the recess 13 is formed on a lateral edge 15a, 15b comprising at least two folds 131, 132 in different orientations forming at least two surfaces corresponding to the notch 22. For example, one of the two lateral branches 12c, 12d comprises a first recess 13 on one side of one of the two radial faces 23a, 23b and the other lateral branch 12d, 12c comprises a second recess 13 on one side of the other radial face, thus making it possible to form a longitudinal stop in both directions.

[0077] In this example, the foil 1 is mounted on the root 21, in such a way that the recess 13 fits the notch 22 to ensure the axial retention of the foil 1 relative to the root 21 of the blade 2, in this case in both directions of the axial (or longitudinal) direction of the foil 1 relative to the root 21. The recess 13 and the notch 22 make it possible to maintain the foil 1 relative to the root 21 by the contact between a stop surface 223a, 223b of the notch 22 and a stop wall 132a, 132b of the recess 13 formed by folds of the foil 1 of different orientation.

[0078] In this case, each notch 22 comprises two longitudinal stop surfaces 223a, 223b extending in a plane intersecting the axis of rotation and the recess 13 comprises two stop walls 132a, 132b formed by three folds, one of the depth folds 132, and two radial folds 133 to come into contact against the corresponding stop surface 223a, 223b thus making it possible to form a stop in the two axial directions of the foil 1 in the notch 22 of the root 21 of the blade 2.

[0079] By "two longitudinal stop surfaces 223a, 223b extending in a plane intersecting the axis of rotation" is meant that they extend substantially perpendicular to the lower surface 27 of the foot 21 but may be inclined or parallel to the radial faces 23a, 23b. By substantially perpendicular is meant between 70 and 110°.

[0080] In this example, the recess 13 comprises a first reinforcing wall 131c formed between the two longitudinal folds 131 and the two depth folds 132. This first recess wall 131c can make it possible to form a radial stop, against a wall 231c of the notch 22. This first reinforcing wall 131c makes it possible to reinforce the two stop walls 132a, 132b.

[0081] The two folds of depth 132 therefore extend along this first reinforcing wall 131c and each extend along the two abutment walls 132a, 132b. In this case the reinforcing wall 131c is inclined relative to the surface of the base 17 but could be parallel.

[0082] In this case, in this example the recess 13 comprises a second reinforcing wall 132c extending longitudinally between these two abutment walls 132a, 132b and along the other longitudinal fold. The second reinforcing wall 132c can come against the bottom of the notch 22, however in this example there is a clearance between the bottom of the notch 22 and this second recess wall 132c makes it possible to reinforce the two abutment walls 132a, 132b to prevent them from bending when they undergo an axial force by holding the foil 1 relative to the foot 21.

[0083] The notch 22 therefore extends from the flat surface 28c of the lateral longitudinal face 24 in the restricted portion 21h, forming the two longitudinal stop surfaces 223a, 223b which are in this example perpendicular to the lower surface 27 and inclined towards each other relative to the flat surface 28c to form a longitudinal stop of a recess 13 of a foil 1.

[0084] The notch 22 further forms a guide surface 231c opposite the first recess wall 131c to enable the recess 13 to be guided in the notch 22 when the foot 21 is inserted into the foil 1.

[0085] Advantageously, the recess 13 is obtained by stamping.

[0086] The lateral branches 12c, 12d of the foil 1 have elastic flexibility such that the lateral branches 12c, 12d can move apart or move closer together. Without constraints on the branches 12, they return to their initial shapes. This flexibility allows, by moving the branches 12 apart, to insert the foil 1 on the root 21 of the blade 2. This flexibility is necessary to insert the foil 1 on the root 21. When inserting the root 21 between the two lateral branches 12c, 12d, each recess 13 bears against the corresponding flat surface 28c, 28d of the restricted portion 21h of the root 21 of the blade 2, until each recess 13 fits into the corresponding notch 22.

[0087] Advantageously, the foil 1 has two tabs 14 projecting relative to the base 17 at the first and second lateral edges 15a, 15b. Thus, the tabs 14 form stops which are axially supported against the radial faces 23 of the foot 21 so as to block, with each recess 13 in the corresponding notch 22, the relative movements between the foot 21 and the foil 1 and thus increases the resistance of the foil 1 against deformation of its recess 13 or its tabs 14. According to another example, the foil 1 is devoid of these tabs 14 or has only one.

[0088] Advantageously, the notch 22 is obtained by molding or by machining.

[0089] There figure 2 represents a radial section of the foil 1 at the level of the recess 13 and the root 21 of the moving blade 2 engaged in a cell 31 formed in the external periphery of the disc 3 and held radially in the cell 31 by the bearing surfaces by a shape cooperation between the root 21 and the cell 31. Advantageously, the root 21 of the moving blade 2 is in the shape of a dovetail.

[0090] When the rotor disc 3 is rotated, the moving blades 2 are subjected to centrifugal forces and the bearing surfaces of the feet 21 come into abutment against the bearing surfaces of the cells 31 of the disc 3.

[0091] In order to limit the wear of the feet 21, the foil 1 is positioned at the contact interface between the feet 21 and the cells 31 of the disc 3.

[0092] In reference to the figure 2 , so that the recess 13 does not come out of the notch 22 when the latter is positioned in a cell 31 of the disc 3, a maximum width A of the recess 13 measured, in a direction tangential to the axis of the disc 3, from one end of the recess 13 is greater than a distance B measured on the same straight line between the end of the recess 13 and the disc of the rotor 3. In other words, in this example, the maximum width A of the recess 13 is measured between the second reinforcing wall 132c and the first or second fold 131, 132 at the level of the flat surface 18 and the distance B is measured between the first or second fold 131, 132 at the level of the flat surface 18 and a surface of the cell 31. Thus, the recess 13 cannot be dislodged from the notch 22 by space requirement when the foot 21 is positioned in a cell 31 of the disc 3.

[0093] There figure 4a represents a front view of the first radial face 23a' of a foot 21' of a blade 2' of a second embodiment and of a foil 1' according to a second embodiment inserted around the foot 21'. The figure 4b represents an enlargement of the figure 4a at the level of the 13' recess and the 22' notch.

[0094] The foot 21' and the foil 1' of this second embodiment are identical respectively to the foot 21 and the foil 1 of the first embodiment except with regard to the following characteristics: In this second embodiment, the notch 22' extends as in the first embodiment on the flat surface 28c' of the first lateral longitudinal face 24 in the restricted portion 21h but unlike the first embodiment this notch 22' opens onto the first radial face 23a'. Of course, the notch 22' can extend over a length of the first lateral longitudinal face 24c less than half of the total length of the first lateral longitudinal face 24c, for example a quarter of this length.

[0095] The foil 1' of this second embodiment therefore comprises on the first lateral branch 12c', a recess 13' in the notch 22' of the foot 21. The recess 13' of this foil 1' according to the second embodiment is therefore contiguous to the first lateral edge 15a'. In other words, the recess 13' is different from the first embodiment in that two longitudinal folds 131', 135 (referenced on the figure 4b ) each extend from the first lateral edge 15a' longitudinally forming the recess wall 131c'.

[0096] The recess 13' therefore comprises only one stop wall 132b'.

[0097] The recess 13' therefore comprises five folds: two longitudinal folds 131', 135, two radial folds 133', 136 and a single fold of depth 132'.

[0098] Further in this example of this second embodiment, as in the first embodiment, the recess 13' is contiguous to the first longitudinal edge 16c' and the recess 13' extends from the planar surface 18' to the other branch 12d'. In an alternative embodiment, the recess 13 may be located on the second longitudinal edge 16d and the lateral branch 12d.

[0099] Furthermore, in a variant of these examples of this second embodiment, the recess 13 is still located on the first lateral branch 12c' but distant from the first longitudinal edge 16c', the recess 13 then comprises two other longitudinal folds and another deep fold forming another reinforcing wall.

[0100] Thus, the foil 1' is mounted on the foot 21', in such a way that the recess 13' shown on the figures 4a And 4bfits the notch 22' to ensure the longitudinal retention of the foil 1' relative to the foot 21' in a single axial direction of the foil 1' relative to the foot 21'.

[0101] The stop between the recess 13' and the notch 22' is formed on the one hand by a stop surface 223b' and a stop wall 132b' formed by the depth fold 132' and the two radial folds 133', 136 of the foil 1'.

[0102] The foil 1' can therefore comprise another recess in another notch to ensure the longitudinal retention of the foil 1' relative to the foot 21' in the other axial direction of the foil 1 relative to the foot 21. For example, the first and / or second branch 12c, 12d', comprises a recess similar to the recess 13' but contiguous to the second lateral edges 15b and the foot comprises a second notch opening onto its second radial face 23b.

[0103] According to yet another example not shown of another embodiment, the second branch 12d' and the flat surface 28d' of the second lateral longitudinal face are identical to that of the first embodiment by comprising a recess 13 and a notch as in the first embodiment ensuring support in both longitudinal directions.

Claims

1. A foil (1, 1') for being mounted to a root (21, 21') of a blade (2, 2') of a turbomachine rotor and comprising: - a base (17), - a first side leg (12c, 12c') and a second side leg (12d, 12d') connected together through the base (17), at least the first leg (12c, 12c') comprises at least one recess (13, 13') comprising at least two folds (131, 132, 133, 131', 132', 133', 135, 136) in two different directions, characterised in that the recess (13, 13') is able to cooperate with a notch (22, 22') provided in the root (21, 21') of the blade (2, 2') to ensure that the foil (1, 1') is longitudinally held relative to the root (21, 21') of the blade (2, 2') at least in one longitudinal direction.

2. The foil (1) according to the preceding claim, characterised in that it comprises a first side edge (15a) and a second side edge (15b) extending over the base (17) and the legs (12c, 12d), and in that the recess (13) is located between and distant from the first side edge (15a) and the second side edge (15b), forming a longitudinal stop in both axial directions of the foil (1) in the root (21) of the blade (2).

3. The foil (1, 1') according to any of the preceding claims, characterised in that it comprises on each side leg (12c, 12d, 12c', 12d') a longitudinal edge (16c, 16d, 16c'), one longitudinal edge (16c, 16d, 16c') being contiguous with the recess (13, 13').

4. The foil (1, 1') according to any of the preceding claims, characterised in that the first side leg (12c, 12c') comprises a planar surface (18, 18') including the longitudinal edge (16c, 16c') and in that the recess (13, 13') extends from that planar surface (18, 18') towards the other leg (12d, 12d').

5. The foil (1) according to any of the preceding claims, characterised in that the recess (13) comprises: - two longitudinal folds (131) extending longitudinally, - two depth folds (132), each depth fold (132) extending between one end of the first longitudinal fold (131) and the other longitudinal fold, and - four radial folds (133) extend radially from the longitudinal edge (16c) towards the ends of the longitudinal folds (131) and the depth folds (132).

6. The foil (1) according to claim 5, characterised in that the recess (13) comprises: - a first reinforcing wall (131c) delimited between: ∘ both longitudinal folds (131), one of both longitudinal folds (131) longitudinally extends from the planar surface (18) of the first side leg (12), and ∘ each depth fold (132), - two opposite stop walls (132a, 132b) each to ensure that the foil (1) is longitudinally held relative to the root (21) of the blade (2), at least in one longitudinal direction, each delimited between: ∘ one of both depth folds (132), and ∘ two of the four radial folds (133).

7. A blade (2, 2') of a turbomachine rotor movable about an axis of rotation, comprising an inner platform (29), a vane radially extending from the inner platform (29) and a root (21, 21') of the blade (2, 2') radially extending from this inner platform (29) opposite to the vane, the root (21, 21') of the blade (2, 2') comprising: - a first radial face (23a, 23a'), - a second radial face (23b) opposite to the first radial face (23a, 23a') longitudinally - a first side longitudinal face (24c) joining each radial face (23a, 23b, 23a') - a second side longitudinal face (24d) joining each radial face (23a, 23b, 23a'), - at least one flank on each side longitudinal face (24c, 24d), comprising a seat for bearing against a surface of a housing of the root (21, 21') of the blade (2, 2'), - characterised in that at least the first side longitudinal face (24c) has a notch (22, 22') comprising at least one longitudinal stop surface (223a, 223b, 223b') extending in a plane intersecting the axis of rotation and a guide surface (231c) extending in a direction other than the longitudinal stop surface (223a, 223b), the notch (22, 22') being intended to receive a recess (13, 13') of a foil (1) to ensure that the foil (1, 1') is longitudinally held relative to the root (21, 21') of the blade (2, 2') at least in a longitudinal direction.

8. The blade (2) according to the preceding claim, wherein the notch (22) is located between and distant from each radial face (23a, 23b).

9. The blade (2) according to claim 8, wherein the root (21) of the blade (2) comprises a base portion (211) comprising the seats and a restricted portion (21h) extending between the inner platform (29) and the base portion (211), the restricted portion (21h) having a width less than the least least width of the base portion (211), and the notch (22) extending from a planar surface (28c) of the side longitudinal face (24) into the restricted portion (21h), forming the longitudinal stop surface (223a) and a second longitudinal stop surface (223b) perpendicular to the lower surface (27) and tilted with respect to the planar surface (28c) to ensure that the foil (1, 1') is longitudinally held relative to the root (21, 21') of the blade (2, 2') in the other longitudinal direction.

10. A turbomachine rotor assembly, characterised in that it includes: - a moving blade (2, 2') according to one of claims 7 to 9; - a foil (1, 1') according to one of claims 1 to 6, mounted to the root (21, 21') of the blade (2, 2'), and in that the recess (13, 13') is complementary to the notch (22, 22') in the root (21, 21') of the blade (2, 2') and is housed in the notch (22, 22') and axially bears against at least the longitudinal stop surface (223a, 223b, 223b').

11. A turbomachine rotor comprising the assembly according to the preceding claim and a rotor disc (3) including cells (31) formed in the outer periphery of the rotor disc (3), the root (21, 21') of the blade (2, 2') being housed in one of the cells (31), characterised in that a maximum width A of the recess (13, 13'), measured in a direction tangential to the axis of the rotor disc (3), from an end of the recess (13, 13') to a bottom of the recess (13, 13'), is greater than a distance B measured on the same straight line from the end of the recess (13, 13') to the rotor disc (3).