ASSEMBLY COMPRISING A VANE AND A VANE HOLDING SYSTEM

Abstract

The invention relates to an assembly (101) comprising a blade (103) and a system (105) for holding the blade (103), for an aircraft turbomachine. The system (105) comprises a pivot (113) configured to rotate along the axis (A) and an annular flange (117), mounted on the pivot (113) and configured to receive the root (111) therein. The root (111) has a cross-section to the axis (A) of elliptical shape and is positioned in an internal housing (119) of the pivot (113) of complementary shape. The assembly (101) further comprises a compressible device (121), positioned at the bottom of the housing (119) and compressed by a base (123) of the foot (111) and a sleeve (125), positioned in the housing (119) of the pivot (113) between the pivot (113) and the annular flange (117) on the one hand, and between the pivot (113) and the foot (111) on the other hand. Figure for the abstract: Fig. 4

Description

Title of the invention: ASSEMBLY COMPRISING A BLADE AND A BLADE HOLDING SYSTEM Technical field

[0001] The invention relates to the field of the architecture of fixed blades of aircraft turbomachines. It relates in particular to an assembly comprising a blade and a blade holding system. Prior art

[0002] In an unducted turbomachine, so-called fixed blades, i.e. blades that are not mobile in rotation around the longitudinal axis of the turbomachine, are coupled to a propeller and have the function of "straightening" the aerodynamic flow at the outlet of the propeller.

[0003] In the same way, in a ducted turbomachine, such fixed blades are coupled to a fan which is located upstream of these fixed blades in the direction of flow of the flow in the turbomachine and which comprises blades moving in rotation around the axis of the turbomachine. As in the case of the unducted turbomachine, these fixed blades also have the function of straightening the flow coming from the fan which has been accelerated by the latter. This is also referred to as an outlet guide vane or OGV (from the English “Outlet Guide Vane”).

[0004] Furthermore, these fixed blades can be variable-pitch, that is to say they can be part of an assembly which allows their rotation around their longitudinal axis so as to modify their orientation relative to the direction of flow of the stream.

[0005] [Fig.l] thus shows, by way of example, a variable-pitch blade 11 which comprises a blade 13 which is mounted on a system 15 for holding the blade 11 which is mobile in rotation around the axis A and therefore allows its orientation to be modified.

[0006] In recent turbomachines, and in particular in non-ducted turbomachines, large blades are increasingly frequently made from organic matrix composite materials to the extent that these materials allow a significant weight saving while retaining mechanical properties equivalent to those of materials used until now.

[0007] In the context of the design and manufacture of blades made of composite material, the support to which the blade is fixed is generally made of metallic material. It is this metallic part which can exert a rotation in order to orient the composite blade which is fixed above, and thus modify its incidence relative to the flow.

[0008] For such a blade, the main type of stress seen by the part concerns bending movements induced by its incidence, but also by the variation of the pressure field caused by the passage of the fan blades. Significantly larger amplitudes can also be seen in the event of impacts (pieces of propeller, bird, others...) during extreme events.

[0009] The simplest means of attachment between a metal part and a composite part is bolting. For this purpose, two types of fasteners are commonly used, as illustrated in [Fig.2a] and [Fig.2b] in sectional views perpendicular to the axis of the turbomachine of blade holding systems 15.

[0010] [Fig.2a] thus shows a clamping attachment (called a “radial attachment”) in which the composite parts 17 are shown in light gray and the screws 19 and the metal fixing part 21 are shown in dark gray.

[0011] [Fig.2b] shows a tangential attachment in which the composite part 17 is shown in light gray and the metal attachment system 19 and 21 is shown in dark gray.

[0012] In the case of fixed blades with radial type attachment, it is the lower part of the blade which is most stressed. In addition, the type of stress to which the blade is subjected produces an antisymmetrical loading of the attachment, with one side in tension and the other in compression.

[0013] In particular, it is possible to distinguish two most critical zones linked to this type of stress: - the radius of the flanges, the bending stresses of which produce radial forces, favorable to damage modes known as type I (i.e. opening (tension) and buckling (compression)); and, - the lateral part of the flanges, in correspondence with the fixings, where the forces are concentrated to be transmitted to the components located below the blade.

[0014] In all cases, the stresses on the composite part associated with this type of holding system are likely to reduce the service life of the part if special arrangements are not made to avoid these drawbacks. Summary of the invention

[0015] The present invention provides a solution to these drawbacks.

[0016] Thus, one objective of the invention is to enable...

[0017] To this end, the invention according to a first aspect relates to an assembly comprising a blade and a blade holding system, for an aircraft turbomachine,

[0018] said blade extending longitudinally along an axis and comprising a blade and a root,

[0019] said system comprising a pivot configured to perform a rotation along the axis and an annular flange, mounted on said pivot and configured to receive the foot within it,

[0020] said assembly being characterized in that the foot has a cross-section to the axis of elliptical shape, and is positioned in an internal housing of the pivot, of complementary shape,

[0021] and in that the assembly further comprises:

[0022] - a compressible device, positioned at the bottom of the housing and compressed by a base of the foot so as to exert a pressure force on said base of said foot; and,

[0023] - a socket, of the bi-cone type, positioned in the housing of the pivot, at the level of an upper opening of said housing, between said pivot and the annular flange on the one hand, and between said pivot and the foot on the other hand.

[0024] The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another:

[0025] - the foot has a shoulder resting on a lower end of the socket so as to block the translation along the axis, towards the upper opening of the housing, of said foot.

[0026] - the system further comprises an O-ring positioned in a groove of the sleeve, at its circumference, so as to be compressed between said sleeve and the pivot.

[0027] - the system further comprises a support, mounted on an upper face of the flange, and configured to allow the mounting of at least one platform on its upper face.

[0028] - the support has substantially the shape of an openwork disc comprising an internal ring configured to be mounted on the upper face of the flange and an outer ring, configured to allow the mounting of at least one platform on its upper face.

[0029] - the pivot, the bushing, the flange and the internal ring of the support have orifices complementary aligned screws of the assembly used to secure said pivot, said bushing, said flange and said bracket together.

[0030] - the system further comprises at least one platform, fixed on the support, at level of holes in the outer ring of said support.

[0031] - a first platform is positioned on the extrados side of the blade and a second platform is positioned on the intrados side of the blade.

[0032] - the foot has a nipple at a lower face, said nipple being embedded in a complementary hole of the pivot.

[0033] - the system further comprises a nut, screwed onto a complementary thread of the lower part of the pivot and tightened so as to rest on the nipple.

[0034] - the compressible device is a spring, preferably a leaf spring.

[0035] - the blade is made of organic matrix composite material, for example made by three-dimensional weaving.

[0036] - the blade is an outlet guide blade.

[0037] The invention according to a second aspect further relates to a turbomachine, in particular for an aircraft, comprising at least one assembly according to the first aspect.

[0038] The invention according to a third aspect further relates to a method of assembling an assembly according to the first aspect, comprising the following steps:

[0039] - inserting the foot of the blade into the support and into the flange;

[0040] - positioning the sleeve on the foot of the blade so that the end in lower part of said socket rests on the shoulder of said foot;

[0041] - the positioning of the O-ring at the level of the groove of the socket;

[0042] - the positioning of the compressible device at the bottom of the pivot housing;

[0043] - the assembly of the assembly formed by the blade, the support, the flange, the sleeve and the O-ring with the assembly formed by the pivot and the compressible device; and,

[0044] - the securing of the support, the flange, the sleeve and the pivot, by means of screws, inserted into the complementary holes, so that the base of the foot compresses said compressible device. Brief description of the drawings

[0045] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which:

[0046] [Fig.l] is a perspective view of an assembly comprising a blade and a blade holding system according to an embodiment of the prior art;

[0047] [Fig.2a] is a schematic representation of a blade holding system according to a first embodiment of the prior art;

[0048] [Fig.2b] is a schematic representation of a system for holding a blade according to a second embodiment of the prior art;

[0049] [Fig. 3] is a perspective view of an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0050] [Fig.4] is a sectional view of an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0051] [Fig.5] is a step diagram of a method of assembling an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0052] [Fig.6] is a schematic representation of a step of a method of assembling an assembly comprising a blade and a blade holding system according to an embodiment of the invention;

[0053] [Fig.7] is a schematic representation of steps in an assembly process of an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0054] [Fig.8] is a schematic representation of steps of a method of assembling an assembly comprising a blade and a blade holding system according to one embodiment of the invention; and,

[0055] [Fig.9] is a schematic representation of steps of a method of assembling an assembly comprising a blade and a blade holding system according to one embodiment of the invention. Description of the embodiments

[0056] With reference to [Fig. 3] and [Fig. 4], we will now describe an embodiment of an assembly 101 comprising a blade 103 and a system 105 for holding the blade 103, for an aircraft turbomachine (not shown). The elements included in the assembly 101 described below are also visible in Figures 6 to 9, which illustrate an embodiment of a method of assembling an embodiment of such an assembly.

[0057] The blade 103 extends longitudinally along an axis A and comprises a blade 109 and a root 111. The axis A is orthogonal to an axis X of longitudinal extent of the turbomachine around which mobile blades of said turbomachine rotate. The blade 103 is therefore mounted in the turbomachine, typically among other identical blades which belong to a row of so-called fixed blades.

[0058] This is a so-called fixed blade in the sense that it is not rotatable about the longitudinal axis of the turbomachine in which it is mounted. However, as will become more clear in the following, the blade 103 is rotatable about the axis A and can be said to have variable pitch, that is to say that its orientation relative to the flow flowing in the turbomachine can be modified.

[0059] It may thus be, by way of non-limiting example, a blade called an outlet guide vane or OGV (from the English “Outlet Guide Vane”) belonging to a row of OGVs whose function is to straighten a flow coming from a propeller of an unducted turbomachine or from a fan of a ducted turbomachine.

[0060] In a particular embodiment, the blade 103 is made of organic matrix composite material. It may have been produced, for example, by lamination of two-dimensional fiber reinforcements, then densified by resin, or by three-dimensional weaving of a single preform which is then densified.

[0061] Advantageously, this type of material allows a significant weight gain while retaining mechanical properties equivalent to those of other heavier materials, or an improvement in mechanical properties for an equivalent weight or even a combination of the two advantages.

[0062] In the assembly 101, the system 105 for holding the blade 103 comprises a pivot 113 which is configured to perform a rotation along the axis A. Thus, by way of example, the pivot 113 can cooperate with bearings which allow its rotation along the axis A or even with rollers or any other means allowing its rotation.

[0063] The pivot 113 has substantially the shape of a hollow cylinder which further comprises an arm 115 which extends radially relative to the axis of the cylinder, and which is configured to allow connection to a mechanism for driving the rotation of the pivot 113.

[0064] The system 105 also includes an annular flange 117, mounted on the pivot 113 and configured to receive the foot 111 therein.

[0065] In the non-limiting example shown, the annular flange 117 has substantially the shape of a cover, the upper part of which covers the upper part of the pivot 113 and the lateral parts of which cover the upper lateral parts of the pivot 113. Furthermore, the annular flange 113 has an opening in its center adapted to allow the insertion of the root 111 of the blade 103.

[0066] The terms "lower" and "upper" are defined relative to the engine axis (i.e. the X axis of rotation of the moving blades of the turbomachine mentioned above). Thus, the lower parts mentioned in the following are those closest (radially) to the X axis while the upper parts mentioned in the following are those furthest (radially) from the X axis.

[0067] In the assembly 101 according to the invention, the foot 111 has a cross-section to the axis A of elliptical shape. In other words, in a section orthogonal to the axis A, the foot 111 has an elliptical shape. Furthermore, the foot 111 is positioned in an internal housing 119 of the pivot 113 of complementary shape.

[0068] Advantageously, the elliptical shape of the foot 111 and the housing 119 makes it possible to optimize the transmission of the torque and to offer indexing of the blade 103 (i.e. precise control of the orientation of said blade) relative to the pivot 113.

[0069] Furthermore, the insertion depth of the root 111 in the housing 119 can be adapted to better distribute the forces undergone by the blade 103 during its use. For example, the root 111 of the blade can be inserted into the housing 119 to a height of between 100 and 200 millimeters. A sufficient insertion depth makes it possible, for example, to descend inside the bearings of the pivot 113 (not shown), which has the consequence of better distributing the forces.

[0070] In addition to the elements described so far, the system 105 also comprises a compressible device 121 which is positioned at the bottom of the housing 119 and compressed by a base 123 of the foot 111 so as to exert a pressure force on said base 123. In this example, the compressible device 121 is a spring, and more particularly a leaf spring. In other embodiments, it could be a elastomer, a coil spring or even a compressed air piston.

[0071] As can be seen in particular in [Fig.4], the spring 121 is crushed between the base 123 of the foot 111 and the bottom of the housing 119 so that in return it exerts a force on this base 123 and consequently on the foot 111.

[0072] The term “base” here designates the lower surface of the foot 111 against which the spring 121 comes to bear so that the pressure is exerted on the foot 111, in the direction of the axis A, from the bottom to the top in the figures, which causes a radial thrust (relative to the motor axis) on the foot 111.

[0073] The system 105 also comprises a socket 125, of the bi-cone type, positioned in the housing 119 of the pivot 113, at the level of an upper opening 127 of the housing 119, between the pivot 113 and the annular flange 117 on the one hand, and between the pivot 113 and the foot 111 on the other hand.

[0074] In the non-limiting example described, as can be seen in particular in [Fig.9], an upper part 125a of the sleeve 125 extends perpendicular to the axis A and is compressed between the flange 117 above and the pivot 113 below while a lower part 125b of the sleeve 125 extends parallel to the axis A and is compressed between the foot 111 on its internal part and the pivot 113 on its external part.

[0075] Advantageously, the shape of the bi-conical bushing 125 (in particular its conical bearing surface) can be adapted to optimize the contact in the outlet zone (i.e. at the level of the upper opening 127 of the housing 119), to avoid creating areas of concentration of forces between the bushing 125 and the blade 103 and to avoid creating areas of crack initiation. It can also be optimized, at the level of the zone 153 also visible in [Fig.9], to ensure good pinching of the blade 103.

[0076] Also advantageously, the assembly 101 according to the invention makes it possible to obtain an aerodynamic connection for a fixed blade which results in a reduction in the stress on its critical zones, better mechanical strength, and a significant reduction in mass.

[0077] Furthermore, in the non-limiting example shown, the foot 111 comprises a shoulder 129 bearing on a lower end 131 of the sleeve 125 so as to block the translation along the axis A, towards the upper opening 127 of the housing 119, of the foot 111. The contact between the foot 111 and the sleeve 125 is ensured by the pressure force exerted by the spring 121.

[0078] In the non-limiting example also shown, the system 105 further comprises an O-ring 133 positioned in a groove 135 of the sleeve 125, at its circumference, so as to be compressed between the sleeve 125 and the pivot 113, to participate in keeping said sleeve 125 tight against the foot 111 and to avoid the presence of play in the area concerned. The O-ring 133 tightens the sleeve 125 at this groove 135 and is also compressed between the sleeve 125 on the one hand, and pivot 113 on the other hand.

[0079] In the non-limiting example also shown, the system 105 further comprises a support 137, mounted on an upper face of the flange 117, and configured to allow the mounting of at least one platform 139 on its upper face.

[0080] Furthermore, in this example, as can be seen in particular in [Fig. 6], the support 137 has substantially the shape of an openwork disc which comprises an inner ring 137a configured to be mounted on the upper face of the flange 117 and an outer ring 137b, configured to allow the mounting of at least one platform 139 on its upper face. In particular, the outer ring 137b is a partial ring in the sense that it covers a total angular sector (in two distinct parts in this example) less than 360 degrees.

[0081] Advantageously, the use of such a support also makes it possible to reduce the mass and size of the assembly 101 while maintaining simplicity of assembly (or disassembly).

[0082] Thus, in this non-limiting example also, the pivot 113, the bushing 125, the flange 117 and the internal ring 137a of the support 137 have aligned orifices 141 which are complementary to screws 143 included in the system 105 and used to fix the pivot 113, the bushing 125, the flange 117 and the support 137 together.

[0083] Here again, advantageously, thanks to this, the assembly or disassembly of all the elements which constitute the assembly 101 can be carried out simply.

[0084] Furthermore, in the non-limiting example shown, six orifices 141 and six screws 143, in this case screws with a diameter of 12.7 millimeters, are used for fixing the elements listed above.

[0085] In the non-limiting example also shown, the system 105 also comprises at least one platform 139 which is fixed to the support 137, at the level of orifices 145 of the external ring 137b of said support 137. For example by means of screws (not shown). More precisely, a first platform 139a is positioned on the extrados side of the blade 103 and a second platform 139b is positioned on the intrados side of the blade 103.

[0086] Advantageously, the use of several platforms facilitates the assembly of the assembly 101 and those skilled in the art will know how to adapt their number, greater than or equal to 1, to the specific geometry of an assembly used.

[0087] Furthermore, the platform(s) used have an aerodynamic role in the sense that their shape (in the example shown, a convex shape) is designed to optimize the flow of the stream in contact with them while limiting their mass (for example via hollow spaces within them).

[0088] In the non-limiting example shown again, the foot 111 comprises a stud 147 (i.e. a cylindrical protrusion) at its lower face. The stud 147 is embedded in a complementary orifice 149 of the pivot 113. In addition, the assembly 101 also comprises a nut 151, which is screwed onto a complementary thread of the lower part of the pivot 113 and tightened so as to come into contact with the stud 147.

[0089] Advantageously, the stud 147 makes it possible to ensure good positioning (i.e. precise positioning) of the foot 111 relative to the pivot 113.

[0090] In this configuration, the spring 121 has a central orifice into which the stud 147 is inserted. However, in other embodiments, the spring 121 could also be positioned at the lower face of the stud 147.

[0091] With reference to figures 5 to 9, we will now describe an embodiment of a method 501 for assembling the assembly 101 as illustrated in [Fig.3] and [Fig.4],

[0092] The first step 503 consists of inserting the root 111 of the blade 103 into the support 137 and into the flange 117. As can be seen in [Fig.6], the support 137 is positioned above the flange 117 and the root 111 is inserted into an aligned central orifice of the flange 117 and the support 137.

[0093] Step 505 then consists of positioning the sleeve 125 on the root 111 of the blade 103 so that the lower end 131 of the sleeve 125 rests on the shoulder 129 of the root 111. In this way, the sleeve 125 is blocked in translation along the root 111 and retains the sleeve 125 and the flange 117.

[0094] Step 507 then consists of positioning the O-ring 133 at the level of the groove 135 of the sleeve 125. The sleeve 125 is then tightened against the foot 111 under the effect of the O-ring 133.

[0095] Step 509 then consists of positioning the spring 121 at the bottom of the housing 119 of the pivot 113. The shape of the spring 121 is adapted to be able to be inserted simply into the housing 119 and up to the bottom of the pivot 113.

[0096] Step 511 then consists of assembling the assembly formed by the blade 103, the support 137, the flange 117, the bushing 125 and the O-ring 133 with the assembly formed by the pivot 113 and the spring 121. During this assembly, the foot 111 is inserted into the housing 119 of the pivot 113 and the flange 117 covers the upper part (with the exception of the arm 115) of the pivot 113.

[0097] Finally, step 513 consists of securing the support 137, the flange 117, the sleeve 125 and the pivot 113, by means of the screws 143, inserted into the complementary orifices 141, so that the base 123 of the foot 111 compresses the spring 121. In other words, the tightening of the screws 143 determines the level of compression of the spring 121 and the pressure force of this spring 121 exerted in return on the base 123 of the foot 111.

[0098] Finally, thanks to the pressure force exerted by the spring 121 on the foot 111, the forces of the radius of the blade 103 are straightened towards the component A (i.e. along the axis A) and to its 105 maintenance system.

Claims

Claims

1. Assembly (101) comprising a blade (103) and a system (105) for holding the blade (103), for an aircraft turbomachine, said blade (103) extending longitudinally along an axis (A) and comprising a blade (109) and a root (111), said system (105) comprising a pivot (113) configured to rotate along the axis (A) and an annular flange (117), mounted on said pivot (113) and configured to receive the root (111) within it, said assembly (101) being characterized in that the root (111) has a cross-section to the axis (A) of elliptical shape, and is positioned in an internal housing (119) of the pivot (113), of complementary shape, and in that the assembly (101) further comprises: - a compressible device (121), positioned at the bottom of the housing (119) and compressed by a base (123) of the foot (111) so as to exert a pressure force on said base (123) of said foot (111);and, - a socket (125), of the bi-cone type, positioned in the housing (119) of the pivot (113), at the level of an upper opening (127) of said housing (119), between said pivot (113) and the annular flange (117) on the one hand, and between said pivot (113) and the foot (111) on the other hand.;

2. Assembly (101) according to claim 1, in which the foot (111) comprises a shoulder (129) bearing on a lower end (131) of the sleeve (125) so as to block the translation along the axis (A), towards the upper opening (127) of the housing (119), of said foot (111).

3. An assembly (101) according to claim 1 or claim 2, wherein the system (105) further comprises an O-ring (133) positioned in a groove (135) of the sleeve (125), at its circumference, so as to be compressed between said sleeve (125) and the pivot (113).

4. An assembly (101) according to any preceding claim, wherein the system (105) further comprises a support (137), mounted on an upper face of the flange (117), and configured to allow the mounting of at least one platform (139) on its upper face.

5. An assembly (101) according to claim 4, wherein the support (137) has substantially the shape of an openwork disc comprising an internal ring (137a) configured to be mounted on the upper face of the flange (117) and an outer ring (137b), configured to allow the mounting of at least one platform (139) on its upper face.

6. An assembly (101) according to claim 5, wherein the pivot (113), the bushing (125), the flange (117) and the inner ring (137a) of the support (137) have complementary aligned holes (141) for screws (143) of the assembly (101) used to secure said pivot (113), said bushing (125), said flange (117) and said support (137) together.

7. Assembly (101) according to any one of claims 4 to 6, wherein the system (105) further comprises at least one platform (139), fixed on the support (137), at the level of orifices (145) of the external ring (137b) of said support (137).

8. An assembly (101) according to claim 7, wherein a first platform (139a) is positioned on the extrados side of the blade (103) and a second platform (139b) is positioned on the intrados side of the blade (103).

9. Assembly (101) according to any one of the preceding claims, in which the foot (111) comprises a stud (147) at a lower face, said stud (147) being embedded in a complementary orifice (149) of the pivot (113).

10. Assembly (101) according to claim 9, in which the system (105) further comprises a nut (151), screwed onto a complementary thread of the lower part of the pivot (113) and tightened so as to come into contact with the stud (147).

11. An assembly (101) according to any preceding claim, wherein the compressible device (121) is a spring, preferably a leaf spring.

12. Assembly (101) according to any one of the preceding claims, in which the blade (103) is made of organic matrix composite material, for example produced by three-dimensional weaving.

13. An assembly (101) according to any preceding claim, wherein the vane (103) is an outlet guide vane.

14. Turbomachine, in particular for an aircraft, comprising at least one assembly (101) according to any one of the preceding claims.

15. Method (501) of assembling an assembly (101) according to all of claims 1 to 13, comprising the following steps: - inserting (503) the root (111) of the blade (103) into the support (137) and into the flange (117); - the positioning (505) of the sleeve (125) on the root (111) of the blade (103) so that the lower end (131) of said sleeve (125) rests on the shoulder (129) of said root (111); - the positioning (507) of the O-ring (133) at the level of the groove (135) of the sleeve (125); - the positioning (509) of the compressible device (121) at the bottom of the housing (119) of the pivot (113); - the assembly (511) of the assembly formed by the blade (103), the support (137), the flange (117), the sleeve (125) and the O-ring (133) with the assembly formed by the pivot (113) and the compressible device (121); and, - the securing (513) of the support (137), the flange (117), the sleeve (125) and the pivot (113), by means of the screws (143), inserted into the complementary orifices (141), so that the base (123) of the foot (111) compresses said compressible device (121).

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