ASSEMBLY INCLUDING A BLADE AND A BLADE RETAINING SYSTEM

Abstract

The invention relates to an assembly (101) comprising a blade (103) and a blade (105) retention system for an aircraft turbomachine. The blade (103) extends longitudinally along an axis (A), and the system (105) includes a pivot (113) configured to rotate about the axis (A). The system (105) further includes a movable jaw (117) housed in the groove (113a). The groove (113a), the foot (111), and the movable jaw (117) together form a dovetail joint in which the foot (111) is held tightly between an inclined plane (113aa) of the groove (113a), the bottom (113ab) of the groove (113a), and a first inclined plane (117a) of the movable jaw (117), by means of pressure means (119) exerting pressure on a second inclined plane (117b) of the movable jaw (117), such that the first inclined plane (117a) bears against the foot (111). Figure for the abbreviation: 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 systems 15 for holding the blade 11.

[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 17a, 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 17a, 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] 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,

[0017] said blade extending longitudinally along an axis and comprising a blade and a root, and

[0018] said system comprising a pivot configured to perform a rotation along the axis, said pivot comprising a groove in which the foot is housed,

[0019] said assembly being characterized in that the system further comprises a movable jaw housed in the groove, said groove, the foot and said movable jaw together forming a dovetail assembly in which said foot is held clamped between an inclined plane of said groove, the bottom of said groove and a first inclined plane of said movable jaw, by means of pressure means exerting pressure on a second inclined plane of said movable jaw so that the first inclined plane bears on the foot.

[0020] 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:

[0021] - the pressure means are screws, screwed into one side of the groove, and coming in support on the second inclined plane of the movable jaw.

[0022] - the number of screws is between 3 and 8, preferably between 4 and 6, said screws being equally distributed along the longitudinal extent of the throat.

[0023] - the movable jaw is positioned in the groove on the extrados side of the blade.

[0024] - the maximum displacement of the movable jaw in the groove, in the transverse direction to the longitudinal extent of the throat, is less than the maximum thickness of the foot in this same transverse direction.

[0025] - the pressure means extend longitudinally in a direction forming a non-zero angle with a plane in which the bottom of the groove extends.

[0026] - the angle is between 10 degrees and 80 degrees, preferably between 20 degrees and 70 degrees or between 30 degrees and 70 degrees.

[0027] - the system further comprises at least one platform, mounted on the pivot, and of which the upper face is intended to be in contact with a flow flowing around the blade.

[0028] 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.

[0029] The invention according to a third aspect further relates to a method of disassembling an assembly having any one of the preceding characteristics, comprising the following steps:

[0030] - the loosening of the pressure means of the system;

[0031] - the translation of the movable jaw, in the groove, in the transverse direction to the longitudinal extent of said groove, so that the foot is no longer held tight in said groove;

[0032] - the translation of the foot, in the groove, in the direction transverse to the longitudinal extent tudinal of said groove, so that the foot is in contact with the system only at the level of the lower surface of said foot; and,

[0033] - extraction of the blade from the holding system. Brief description of the drawings

[0034] 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:

[0035] [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;

[0036] [Fig.2a] is a schematic representation of a blade holding system according to a first embodiment of the prior art;

[0037] [Fig.2b] is a schematic representation of a blade holding system according to a second embodiment of the prior art;

[0038] [Fig. 3] is a perspective view of an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0039] [Fig.4] is a sectional view of an assembly comprising a blade and a blade holding system according to one embodiment of the invention;

[0040] [Fig.5] is a step diagram of a method for disassembling an assembly comprising a blade and a blade holding system according to one embodiment of the invention; and,

[0041] [Fig.6] is a schematic representation of steps of disassembly of an assembly comprising a blade and a blade holding system according to one embodiment of the invention. Description of the embodiments

[0042] With reference to [Fig.3] and [Fig.4] we will now describe embodiments of an assembly 101 comprising a blade 103 and a system 105 for holding the blade 103, for an aircraft turbomachine (not shown) according to the invention. The elements of this assembly are also visible in [Fig.6] which illustrates the disassembly of such an assembly.

[0043] 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 the 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.

[0044] 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.

[0045] It may thus be, by way of non-limiting example, a vane 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.

[0046] Also by way of example, the blade 103 may be made of an organic matrix composite material. It may have been produced, for example, by lamination of two-dimensional fiber reinforcements, then densified with resin, or by three-dimensional weaving of a single preform which is then densified.

[0047] 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.

[0048] In the assembly 101, the system 105 for holding the blade 103 comprises a pivot 113 which is configured to rotate along the axis A. Thus, in the example shown, the pivot 113 cooperates with ball bearings 114 which allow it to rotate along the axis A. In other embodiments, it could be rollers or any other means allowing the pivot 113 to rotate.

[0049] In the non-limiting example shown, the pivot 113 is a single piece, that is to say it is not an assembly of several separate pieces. Furthermore, the pivot 113 comprises a cylindrical lower part (which is hollow in this example), and an upper part which has substantially the shape of a plate which comprises a groove 113a in which the foot 111 is housed.

[0050] 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 this are those furthest (radially) from the X axis.

[0051] The system 105 further comprises a movable jaw 117 which is also housed in the groove 113a. The movable jaw 117 is a separate part from the foot 111 and the pivot 113. In this sense, it is said to be “movable” insofar as it can be moved, for example in the groove 113a, independently of the pivot 113 and the foot 111.

[0052] Furthermore, the groove 113a, the foot 111 and the movable jaw 117 together form a dovetail assembly in which the foot 111 is held clamped between an inclined plane 113aa of the groove 113a, the bottom 113ab of the groove 113ba and a first inclined plane 117a of the movable jaw 117.

[0053] In the non-limiting example shown, the inclined plane 113aa of the groove 113a has a curvature, however, in other embodiments it can be flat, just like the corresponding face of the root 111 of the blade 103.

[0054] The foot 111 is held tight in the groove 113a by means of pressure means 119 which exert pressure on a second inclined plane 117b of the movable jaw. 117 so that the first inclined plane 117a rests on the foot 111, this support being an immobilizing clamping support.

[0055] Similarly, in other embodiments, the inclined plane 117b of the movable jaw 117 may be flat, as may the corresponding face of the root 111 of the blade 103.

[0056] In other words, the foot 111 is connected to the system 105 by a sliding connection in which the three faces indicated above (the two inclined planes and the bottom of the groove) are supported on three complementary faces of the foot 111 when the assembly 101 is assembled so that the foot 111 is clamped in the system 105.

[0057] Advantageously, this arrangement prevents the loss of the blade 103 once the assembly of the assembly 101 has been completed.

[0058] Furthermore, thanks to this arrangement also, the forces undergone by the blade 103, in particular at the level of its root 111, are diffused to the rest of the structure, in particular via the bearings, which avoids their local concentration and the associated risks.

[0059] In the non-limiting example shown, the pressure means 119 are screws, which are screwed into a side 113ac of the groove 113a, laterally opposite the foot, and which come to bear on the second inclined plane 117b of the movable jaw 117. In particular, the movable jaw 117 being free to move in the groove 133a in a direction transverse (i.e. perpendicular) to its longitudinal extent (that of the groove 113a), the role of the screws 119 (or of the pressure means in general) is to push the movable jaw 117 so that it comes to bear on a face of the foot 111 which has a complementary inclined plane.

[0060] Furthermore, the number of screws 119 used is typically between 3 and 8, and preferably between 4 and 6 (5 in the example shown). These screws 119 are equally distributed along the longitudinal extent of the groove 113a.

[0061] Generally speaking, a person skilled in the art will know how to adapt the number and spatial distribution of the pressure means 119 of the movable jaw 117 as a function of a desired pressure (and distribution of this pressure).

[0062] Thus, adjusting the level of clamping of the movable jaw 117, by the screws 119, makes it possible to determine the intensity of the pressure which is exerted on the complementary inclined plane of the movable jaw 117 and therefore contributes to clamping the foot 111 in the groove 113a in fine.

[0063] In the non-limiting example also shown, the movable jaw 117 is positioned in the groove 113a on the extrados side of the blade 103. In other embodiments, it could be positioned on the intrados side.

[0064] In the non-limiting example also shown, the maximum displacement d of the movable jaw 117 in the groove 113a, in the direction transverse to the longitudinal extent of the groove 113a, is less than the maximum thickness e of the root 111 (which may be on the leading edge side or on the trailing edge side of the blade 103) in this same transverse direction.

[0065] Indeed, this distance (the maximum displacement d) must be minimal and just sufficient to allow the blade to come out of its attachment. An excess of travel (possible displacement) would result in an excess of material on the pivot which would have a negative impact on its mass.

[0066] In a particular embodiment, the pressure means 119 extend longitudinally in a direction which forms a non-zero angle 0 (visible in [Fig.4]) with a plane P in which the bottom 113ab of the groove 113a extends.

[0067] Furthermore, the angle 0 is typically between 10 degrees and 80 degrees, and preferably between 20 degrees and 70 degrees or between 30 degrees and 70 degrees.

[0068] Advantageously, the orientation of the fixing means 119 allows easy access to these means for possible disassembly linked to maintenance of the blade 103. In addition, this orientation also prevents the fixing means 119 from working in shear.

[0069] Furthermore, in a particular embodiment also, the screws 119 have their axis which is substantially perpendicular to the side of the foot 111 which is at the bearing face opposite the movable jaw 117. In addition, the heads of the screws 119 push on the second inclined plane 117b of the movable jaw 117 which is substantially parallel to the side of the foot 111 and to the first inclined plane 117a of the movable jaw 117. The inclined plane 113aa of the groove 113a, the inclined plane 117b of the movable jaw 117 and the corresponding faces of the foot 111 are parallel.

[0070] Furthermore, in the embodiment described, the movable jaw 117 can slide in the groove 113a parallel to the surface of the bottom of said groove 113a on which the lower radial end face of the foot 111 rests.

[0071] Finally, in a particular embodiment, the system 105 may also comprise at least one platform 121 which is mounted on the pivot 113 and the upper face of which is intended to be in contact with a flow F (typically an air flow) which flows around the blade 109 during use of the aircraft turbomachine. The mounting system of the at least one platform is not described here, but may be, for example, screws complementary to orifices of the pivot 113 or an intermediate support itself mounted on the pivot 113.

[0072] In the assembly shown in [Fig.4], the system 105 comprises a first platform 121a which is positioned on the extrados side of the blade 103 and a second platform 121b which is positioned on the intrados side of the blade 103.

[0073] Generally speaking, 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 over their surface while limiting their mass (for example via hollow zones within them).

[0074] Advantageously, the use of several platforms facilitates the assembly of the assembly 101 and the person skilled in the art will know how to adapt their number, greater than or equal to 1, to the specific geometry of a used assembly.

[0075] 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 and good mechanical strength, while reducing the mass of the assembly.

[0076] Furthermore, those skilled in the art will know how to adapt the shape of the different parts to avoid the concentration of stresses in a given area.

[0077] Furthermore, a person skilled in the art will know how to adapt the contact surface between the root 111 and the various elements of the system 105 to optimize the distribution of the forces undergone by the blade 103 during its use, for example by increasing the embedding height of the root 111 in the system 105 (i.e. in the groove 113a in particular).

[0078] With reference to [Fig.5] and [Fig.6], we will now describe an embodiment of a method 501 for disassembling an assembly 101 such as that shown in [Fig.3].

[0079] The first step 503 consists of loosening the pressure means 119 of the system 105. Loosening here means any operation making it possible to remove the pressure force exerted by the pressure means 119 on the foot 111.

[0080] The following step 505 consists of the translation of the movable jaw 117, in the groove 113a, in the direction transverse to the longitudinal extent of the groove 113a, so that the foot 111 is no longer held tight in the groove 113a. As can be seen in [Fig.6], the movable jaw 117 can be, for example, translated until it comes into contact with the side 113ac (which is opposite the inclined plane 113aa) of the groove 113a.

[0081] The following step 507 then consists of the translation of the foot 111, in the groove 113a, in the direction transverse to the longitudinal extent of the groove 113a, so that the foot 111 is only in contact with the system 105 at the level of the lower surface of the foot 111.

[0082] In other words, only this lower surface of the root 111 is in contact with the bottom 113ab of the groove. In the example shown in [Fig.6], the root 111 (and therefore the blade 103 as a whole) is translated so as to be placed in the center (transversely) of the space left free in the groove 113a.

[0083] Finally, step 509 consists of extracting the blade 103 from the holding system 105. As can also be seen in [Fig.6], the blade 103 can be translated along the axis A to be extracted from the system 105 easily.

[0084] Advantageously, the assembly according to the invention can therefore be disassembled in a very simple manner, even when said assembly is itself mounted in a turbomachine. Maintenance of the blade is therefore simplified thanks to its easy disassembly.

[0085] Furthermore, the assembly according to the invention can also be assembled in a very simple manner by reversing the steps described above. Thus, by way of example, the assembly of the assembly can comprise the following steps:

[0086] - the installation of the pressure means 119 of the system 105 so as to be loosened sufficiently to allow the translation of the movable jaw 117, in the groove 113a, in the direction transverse to the longitudinal extent of the groove 113a, the foot 111 then not being held tight in the groove 113a;

[0087] - the insertion of the blade 103 into the groove 113a with the foot 111 located between the pivot 113 and the jaw 117, including the translation of the foot 111, in the groove 113a, in the direction transverse to the longitudinal extent of the groove 113a, while the foot 111 is only in contact with the system 105 at the level of the lower surface of the foot 111; and,

[0088] - the clamping to immobilization of the blade 103 in the holding system 105 via the tightening of the pressure means 119 of the system 105, by tightening the foot 111 between the jaw 117 and the groove 113a of the pivot 113.

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), and said system (105) comprising a pivot (113) configured to rotate along the axis (A), said pivot (113) comprising a groove (113a) in which the root (111) is housed, said assembly (101) being characterized in that the system (105) further comprises a movable jaw (117) housed in the groove (113a), said groove (113a), the root (111) and said movable jaw (117) together forming a dovetail assembly in which said root (111) is held clamped between an inclined plane (113aa) of said groove (113a), the bottom (113ab) of said groove (113a) and a first inclined plane (117a) of said movable jaw (117),by means of pressure means (119) exerting pressure on a second inclined plane (117b) of said movable jaw (117) so that the first inclined plane (117a) rests on the foot (111).,

2. Assembly (101) according to claim 1, in which the pressure means (119) are screws (119), screwed into one side (113ac) of the groove (113a), and bearing on the second inclined plane (117b) of the movable jaw (117).

3. Assembly (101) according to claim 2, in which the number of screws (119) is between 3 and 8, preferably between 4 and 6, said screws (119) being equally distributed along the longitudinal extent of the groove (113a).

4. An assembly (101) according to any preceding claim, wherein the movable jaw (117) is positioned in the groove (113a) on the extrados side of the blade (103).

5. Assembly (101) according to any one of the preceding claims, in which the maximum displacement (d) of the movable jaw (117) in the groove (113a), in the direction transverse to the longitudinal extent of the groove (113a), is less than the maximum thickness (e) of the foot (111) in this same transverse direction.

6. Assembly (101) according to any one of the preceding claims, in which the pressure means (119) extend longitudinally in a direction forming a non-zero angle (0) with a plane (P) in which extends the bottom (113ab) of the throat (113a).

7. An assembly (101) according to claim 6, wherein the angle (0) is between 10 degrees and 80 degrees, preferably between 20 degrees and 70 degrees or between 30 degrees and 70 degrees.

8. Assembly (101) according to any one of the preceding claims, in which the system (105) further comprises at least one platform, mounted on the pivot (113), and the upper face of which is intended to be in contact with a flow (F) flowing around the blade (109).

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

10. Method (501) for disassembling an assembly (101) according to any one of claims 1 to 8, comprising the following steps: - loosening (503) the pressure means (119) of the system (105); - translating (505) the movable jaw (117), in the groove (113a), in the direction transverse to the longitudinal extent of said groove (113a), so that the foot (111) is no longer held tight in said groove (H3a); - translating (507) the foot (111), in the groove (113a), in the direction transverse to the longitudinal extent of said groove (113a), so that the foot (111) is in contact with the system (105) only at the lower surface of said foot (111); and, - the extraction (509) of the blade (103) from the holding system (105).

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