Tool for bonding an Anti-wear strip to a turbomachine blade

Abstract

A tool (40) for bonding at least one anti-wear strip (22) to a turbomachine blade (10), comprising: - a support (50), - at least one first fastening member (60) which is fastened to the support (50) and is able to cooperate with the root (14) of the blade (10) in order to immobilize it with respect to the support (50), and - at least one second member (70) for holding said at least one anti-wear strip (22) on the blade (10) and for heating this anti-wear strip (22) for the bonding thereof, this second member (70) being fastened to the support (50) and comprising, on the one hand, at least one expandable bag (72), and, on the other hand, at least one heating element (80) able to heat said at least one anti-wear strip (22) for the bonding thereof.

Description

[0001] DESCRIPTION

[0002] TITLE: TOOL FOR BONDING AN ANTI-WEAR STRIP ON A TURBOMACHINE BLADE

[0003] Technical field of the invention

[0004] The present invention relates to a tool for bonding at least one anti-wear strip to a turbomachine blade. It further relates to an assembly comprising a tool and a blade, as well as a bonding method using the tool.

[0005] Technical background

[0006] The technical background includes in particular documents US-A- 3,305,420, US-A1 -2018 / 009068, JP-A-H08 192484 and FR-1-3 108 940.

[0007] The use of composite materials is particularly advantageous in the aeronautics industry because these materials are relatively light and have good mechanical properties.

[0008] A composite material typically used in aeronautics comprises a fiber preform embedded in a polymer resin. The preform can be produced by three-dimensional weaving or can be obtained by draping and superimposing several fabrics.

[0009] The resin can be injected into the preform or the preform can be pre-impregnated with the resin.

[0010] The shaping of the final part is generally carried out using a tool comprising a mold. In the case where a resin is to be injected into a preform, the preform is placed in the cavity of a mold and the mold is covered with a counter-mold. The tooling includes a port for injecting resin into the mold cavity as well as a port for vacuuming the mold cavity. In the case where the preform is already impregnated with resin, the preform is placed in the cavity of a mold which can be covered with a flexible tarpaulin or a counter-mold.

[0011] The tooling also includes a resin injection port into the mold cavity as well as a mold cavity vacuum port. The countermold applies pressure to the preform by creating a vacuum between the countermold and the flexible sheet or mold. Using a countermold allows for better control of the thickness of the final part.

[0012] In the case of a blade, particularly a fan blade, after the molding operation described above, an operation of fitting anti-wear strips on the root and Péchasse of the blade must be carried out.

[0013] These strips are currently attached and secured to the foot and Péchasse of the blade, by gluing. Thus, the anti-wear strips are first impregnated with glue, generally phenolic, by hand. Then, the operator places, still manually, the anti-wear strips on the foot and Péchasse of the blade.

[0014] The blade coated with anti-wear strips is then replaced in the mold and the anti-wear strips are vacuum bonded using a counter-mold or a silicone sheet. The assembly is then placed in an autoclave to heat the strips and bond them to the blade. The adhesive used to fix the strips is in fact of the heat-curing type and requires a heating cycle to ensure its function.

[0015] This operation of bonding the anti-wear strips is therefore very manual and generates many defects in the final part. One of the difficulties encountered with the current process of bonding the anti-wear strips on a blade is the difficulty of positioning, to within several tens of millimeters, the strips, by hand, on a clump and the difficulty of maintaining this positioning of the strips during the operation of installing the blade coated with the anti-wear strips in the mold and during the vacuum bonding operation. Furthermore, there is a significant risk of leakage of the tarpaulin during the autoclave heating cycle (poor application of the seal, presence of thermocouples, micro-perforation of the waterproof tarpaulin, etc.) which can lead to non-conformities. In addition, this heating cycle generates a lot of waste because the tarpaulins are single-use consumables (several tons per year).

[0016] The overall cost of the current process is also relatively high.

[0017] Finally, the composite material of the blade can be relatively sensitive to high temperatures and can be thermally affected by the autoclave heating operation. This can impact the number of possible retouches / repairs of the blade, and in fact can generate a limitation in the time of use of the blade in service.

[0018] The present invention provides a solution to at least some of the problems discussed below.

[0019] Summary of the invention

[0020] The invention relates to a tool for bonding at least one anti-wear strip to a turbomachine blade, this blade comprising a root connected to a blade and at least one anti-wear strip located on the blade, the tool comprising:

[0021] - a support,

[0022] - at least one first fixing member which is fixed to the support and which is capable of cooperating with the blade in order to immobilize it with respect to the support, characterized in that it further comprises:

[0023] - at least one second member for holding said at least one anti-wear strip on the blade and for heating this anti-wear strip with a view to bonding it, this second member being fixed to the support and comprising on the one hand at least one expandable cushion capable of adopting a first non-expanded position and a second expanded position in which said at least one cushion is capable of applying pressure to at least one anti-wear strip located on the blade, and on the other hand at least one heating element capable of heating said at least one anti-wear strip with a view to bonding it.

[0024] The invention provides several advantages. Firstly, it allows the anti-wear strip(s) to be precisely positioned and held on the blade thanks to the second holding member(s) in order to prevent it from moving during bonding. Furthermore, this or these member(s) allows a predetermined pressure to be applied to the strip(s), this pressure being a function of the expansion of the cushion(s). Each cushion is thus expandable between two positions. Finally, the heating member(s) allows the strip(s) to be locally heated, which avoids putting the entire blade in an autoclave and therefore heating the entire blade. Only the area of ​​the blade receiving the anti-wear strip(s) can be heated, for example by conduction through the strip, which limits the exposure of the blade material to the heating cycle and therefore improves its service life.Finally, the tooling is relatively simple and space-saving, and significantly less expensive than a mold designed to completely enclose the blade for the purpose of bonding anti-wear strip(s).

[0025] The tooling 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:

[0026] - said at least one second member is independent of said at least one first fixing member;

[0027] - said at least one expandable cushion is or comprises at least one inflatable bladder;

[0028] - said at least one second member comprises at least one pressurized air supply channel for said at least one inflatable bladder;

[0029] - said at least one heating element is or comprises at least one heating mat, and in particular a resistive heating mat;

[0030] - said at least one heating mat is located on or under said at least one expandable cushion; - said second member comprises a first cushion capable of extending on a first side of the blade or its root, a second cushion capable of extending on a second opposite side of the blade or its root, or even a third cushion capable of extending on an upstream or downstream edge of the blade or its root;

[0031] - said second member defines an elongated slot which is configured to receive the blade or its root by sliding and which comprises one or more cushions along its internal edges.

[0032] The present invention also relates to an assembly comprising a tool as described above and a turbomachine blade, this blade comprising a root connected to a blade and at least one anti-wear strip located on the blade.

[0033] 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:

[0034] - the or each anti-wear strip is made by weaving fibers such as aramid fibers and / or PTFE;

[0035] - the blade is made of composite material from a fiber preform whose fibers, for example carbon, are coated or impregnated with polymerizable and in particular crosslinkable resin (such as an epoxy resin). The present invention also relates to a method for bonding at least one anti-wear strip to a turbomachine blade, this blade comprising a root connected to a blade and at least one anti-wear strip located on the blade, the method using a tool as described above and comprising the following steps: a) immobilizing the blade with respect to the support of the tool, using the first fixing member, b) expanding said at least one cushion and applying pressure to said at least one anti-wear strip located on the blade, and c) heating this anti-wear strip with a view to bonding it to the blade, using said at least one heating element. Advantageously, before step a), the root of the blade is inserted into the slot of the second member.

[0036] Preferably, before step a) and the assembly of the blade in the tool, the or each anti-wear strip is coated with glue and positioned on the blade.

[0037] The glue is for example a phenolic glue.

[0038] Brief description of the figures

[0039] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0040] [F ig . 1 ] Figure 1 is a schematic perspective view of a blade for an aircraft turbomachine,

[0041] [Fig. 2] Figure 2 is a larger-scale schematic view of part of the blade of Figure 1, and in particular of its root on which anti-wear strips are located,

[0042] [Fig. 3] Figure 3 is a very schematic sectional view of a tool for bonding anti-wear strips to the blade,

[0043] [Fig .4] Figure 4 is a schematic perspective view of part of the tooling of Figure 3,

[0044] [Fig. 5] Figure 5 is a schematic perspective view of a tool for bonding anti-wear strips to a blade, in accordance with one embodiment of the invention,

[0045] [Fig. 6] Figure 6 is another schematic view in perspective and by transparency of the tooling of Figure 5,

[0046] [Fig .7] Figure 7 is a schematic perspective view of a detail of the tooling of Figure 5,

[0047] [Fig .8] Figure 8 is a schematic view of another detail of the tooling of Figure 5, and

[0048] [Fig. 9] Figure 9 is another schematic perspective view of the tooling of Figure 5. Detailed description of the invention

[0049] We first refer to figures 1 and 2 which illustrate a blade 10 made of composite material for a turbomachine, in particular an aircraft one, this blade 10 being for example a propeller or fan blade.

[0050] The blade 10 comprises a blade 12 connected for example by a stilt 14 to a foot 16. The foot 16 may have a dovetail shape and is shaped to be engaged in a cell of complementary shape of a rotor disk, in order to retain the blade on this disk.

[0051] The blade 12 comprises a leading edge 12a and a trailing edge 12b for the gases flowing into the turbomachine. The blade 12 has a curved or even twisted aerodynamic profile and comprises a lower surface 18 and an upper surface 20 extending between the leading edges 12a and trailing edges 12b.

[0052] Anti-wear strips 22 made of fabric are secured to the blade 10.

[0053] In the example shown, the blade 10 comprises four anti-wear strips 22, namely two on each side of the root 16 and two others on each side of the Péchasse 14 or the blade 12.

[0054] As their name indicates, the strips 22 are configured to limit the wear of the walls on which they are secured, by contact and / or friction. These strips 22 are located on the root 16 and Péchasse 14 or the blade 12 which are likely to come into contact with bearing surfaces of the aforementioned rotor disk.

[0055] Each strip 22 has a generally elongated shape and extends substantially from the leading edge 12a to the trailing edge 12b of the blade 12. A strip 22 has, for example, a length of between 2 and 50 cm, and a width of between 2 and 7 cm.

[0056] An anti-wear strip 22 is made by weaving fibers such as aramid fibers and / or PTFE.

[0057] The blade 10 is made of composite material from a fiber preform whose fibers, for example carbon, are coated or impregnated with polymerizable and in particular crosslinkable resin (such as an epoxy resin). The tooling used to manufacture the blade 10 comprises a mold and a counter-mold, the mold and the counter-mold defining between them a cavity configured to receive the fiber preform.

[0058] When manufacturing a blade, the tool is opened and a fiber preform is placed in the cavity. This arrangement can be made with a three-dimensional woven preform or with fabrics that are draped and layered in the cavity. This step can be done manually or by robot. The tool is then closed by sealing the countermold onto the mold.

[0059] The preform is pre-impregnated with resin or resin is injected into the mold to impregnate the preform.

[0060] The tooling is heated to increase the temperature of the resin and cause it to polymerize.

[0061] After polymerization of the resin and stiffening of the blade, the strips 22 are glued, for example with a phenolic glue, onto the blade 10.

[0062] For this, the tooling 24 illustrated in Figures 3 and 4 is used in the prior art.

[0063] The tooling 24 comprises a mold 26 and a counter-mold 28 or a flexible cover, the mold 26 and the counter-mold 28 defining between them a cavity 30 configured to receive the blade 10 (figure 3).

[0064] Before installing the blade 10 in the mold, the fabric strips 22 are coated with the glue and then the strips are positioned on the blade 10. The blade 10 is then installed between the mold 26 and the counter-mold 28. The strips 22 are held on the blade 10 and applied with a certain pressure on the blade 10 thanks to the compression of the blade 10 between the mold 26 and the counter-mold 28 or the vacuuming of the tarpaulin which covers the blade 10 and the mold 26. The tooling 24 is then placed in an autoclave in order to heat the glue and ensure its polymerization. The strips 22 are then secured to the blade 10 which can be removed from the mold after the autoclave heating cycle.

[0065] Alternatively, the strips 22 could be glued to the blade 10 outside the mold. The gluing operation therefore remains an essentially manual operation which is the source of numerous defects in the final part, as seen previously.

[0066] Figures 5 and following illustrate an embodiment of a tool 40 according to the invention which allows the bonding of one or more strips 22 onto a blade 10.

[0067] This tool 40 essentially comprises three parts, namely:

[0068] - a 50 support,

[0069] - at least one member 60 for fixing the blade 10,

[0070] - at least one member 70 for holding the strip(s) 22 on the blade 10. In the example shown, the support 50 is in the form of a flat plate which is intended to be placed flat on a horizontal surface such as a workshop workbench.

[0071] The support 50 thus comprises an upper surface 50a which is substantially flat and horizontal in the example.

[0072] The support 50 may comprise a plurality of tapped holes 52 for screwing screws 54.

[0073] The support 50 may include marks 56, such as positioning lines, intended to facilitate the positioning of the blade 10 during its assembly in the tooling 40.

[0074] The fixing member 60, also called the first member, is fixed to the support 50 and is capable of cooperating with the blade 10, and for example or in particular its root 16, in order to immobilize it with respect to the support 50.

[0075] In the example shown, the fixing member 60 firstly comprises a base 62 which is fixed to the support 50 and which is intended to be inserted between the blade 10 and the support 50. In other words, the blade 10 bears on the base 62 fixed to the support 50.

[0076] The base 62 has an adjustable position relative to the support 50, in particular along an axis A which is intended to extend along an axis B of elongation of the foot 16. The position of the base 62 along the axis A can thus be modified and immobilized, the aforementioned marks 56 making it possible to have a reference of the position chosen or to be adopted.

[0077] The movement of the base 62 on the support can make it possible to precisely position the blade 10 with respect to the support 50.

[0078] The movement of the base 62 on the support 50 can be made possible by means of a system 64 of the rail-slide type carried by the support 50 and intended to receive the base 62.

[0079] The fixing of the system 64 on the support 50 or the immobilization of the base 62 on the support 50 can be carried out by means of the aforementioned screws 54.

[0080] In the example shown, the fixing member 60 further comprises jaws 66 which are intended to extend on either side of the blade 10 or its root 16 and which are intended to grip it in order to immobilize it.

[0081] It is understood that the distance between the jaws 66 is adjustable, for example from a spaced apart position allowing the blade 10 to be mounted between the jaws 66, to a close position allowing the blade 10 to be clamped and immobilized between the jaws 66.

[0082] Flexible pads 68, for example made of elastomer, may be carried by the jaws 66 and rest on the blade 10 in order to avoid damaging its material. Although this is not shown in the drawings, these jaws 66 may be connected or fixed to the support 50 by suitable means.

[0083] The holding member 70, also called the second member, has a dual function. It allows the strip(s) 22 to be held on the blade 10 on the one hand, but also to heat each of these strips 22 with a view to bonding them. It is therefore no longer necessary to autoclave the tool 10.

[0084] The holding member 70 is fixed to the support 50 for example by means of the aforementioned screws 54.

[0085] As seen in the drawings and in particular in Figure 5, the members 60 and 70 are advantageously independent. This means that they are fixed to the support 50 independently of each other and can also be dismantled independently of each other. This also means that they can be handled and adjusted independently of each other. The holding member 70 comprises on the one hand at least one expandable cushion 72 capable of adopting a first non-expanded position and a second expanded position to apply a predetermined pressure to the or each strip 22 located on the blade, and on the other hand at least one heating element 80 capable of heating the or each strip 22 with a view to bonding it.

[0086] By expansion is meant a capacity to increase in volume. The or each cushion 72 therefore has the capacity to increase in volume and to move from an unexpanded position of low volume to an expanded position of greater volume.

[0087] In a preferred embodiment, the or each cushion 72 is or comprises at least one inflatable bladder. The inflation of the bladder is achieved using a fluid, such as air for example. It is therefore understood that the supply of air to the bladder causes it to inflate and therefore expand, and that the evacuation of the air contained in the bladder causes it to deflate and therefore reduce its volume.

[0088] In the case where each cushion 72 is an inflatable bladder, the member 70 comprises at least one channel 74 for supplying pressurized air to each bladder as illustrated in FIG. 7.

[0089] The inflation of a bladder can be carried out in a few seconds (between 2 and 10 seconds for example), at a relative pressure between 0.1 bar and 3 bars for example (0.01 to 0.3 MPa), this relatively low pressure level allows the use of inexpensive and easily available tools.

[0090] In the example shown, the tooling 40 comprises several cushions 72 or bladders. These cushions 72 are for example three in number even if this number is not limiting.

[0091] The member 70 defines an elongated slot 76 which is configured to receive the blade 10 or its root 16 by sliding and which includes one or more cushions along its internal edges.

[0092] The member 70 has a general M shape in the example shown and comprises a middle part 78 comprising this slot 76. The sides of the member 70 and of the M shape are formed by two tabs 79 which are fixed to the support by screws 54.

[0093] The middle part 78 of the member 70 extends above the base 62. It is therefore understood that the root 16 of the blade 10 is inserted into the slot 76 and rests on the base 62 located directly under the slot 76.

[0094] The slot 76 is open at one of its longitudinal ends, opposite here the marks 56. The slot 76 thus comprises three edges, namely two lateral edges 76a intended to extend on either side of the blade 10 or its root 16, and a median edge 76b connecting these lateral edges 76a.

[0095] As can be seen in the drawings, each of these edges 76a, 76b carries a cushion 72. The cushions 72a located at the edges 76a have an elongated shape and extend over the entire length of the slot 72. These cushions 72 are intended, in the expanded position, to bear on the strips 22 applied to the blade 10, in order to apply a certain pressure to these strips.

[0096] The cushion 72b located at the edge 76b extends over the entire width of the slot 72. It bears on the blade 10 and in particular on an upstream (or leading) or downstream (or trailing) edge of the blade or its root, but is not necessarily used to bear on a strip 22 of the blade.

[0097] The or each heating element 80 may be or may comprise at least one heating mat, and in particular a resistive heating mat. This heating mat may be located on or under each pad 72. It may thus be in direct contact with the strip to be heated or heat a strip through the pad 72, by conduction and / or convection. Conduction heating makes it possible to heat more locally and to reduce the risk of thermally affecting the material of the blade 10.

[0098] Alternatively, the or each heating element 80 is formed by an electrical heating resistor integrated for example in the or each cushion 72.

[0099] The heating element 80 is preferably capable of heating the strip 22 to a temperature between 80°C and 200°C for example. The present invention also relates to the assembly formed by the tooling 40 and the blade 10.

[0100] The present invention also relates to a method of bonding at least one anti-wear strip to a turbomachine blade 10, this method using the tool 40 as described above.

[0101] The process includes the following steps, some of which are optional:

[0102] - the strips are coated with glue and are positioned on the blade 10 or its foot 16,

[0103] - the cushions 72 of the tooling are (brought) into an unexpanded position,

[0104] - the blade is mounted in the tool 40, by inserting its foot between the jaws 66, that is to say in the slot 72 of the member 70,

[0105] - the blade 10 is immobilized with respect to the support 50 thanks to the fixing member 60,

[0106] - the cushions 72 are expanded so that they adopt their expanded position and bear on the strips 22 located on the blade 10, and apply a certain pressure on these strips 22,

[0107] - the heating of the strips 22 is activated with a view to their bonding to the blade, thanks to the heating element 80 of each cushion 72; the heating can be carried out at a polymerization temperature between 80°C and 200°C for a duration of between 1 h and 4 h, depending on the glue used.

[0108] It is understood that the position of the cushions 72 of the member 70 depends on the position of the strips 22 on the blade 10. In the example shown, the strips are located at the root 16 of the blade 10 and the cushions 72 are therefore located at the root of the blade. Alternatively, the strips could be located at another area of ​​the blade, then the cushions 72 would be located at this area. The tooling 40 would therefore be adapted according to the position of the strips 22 on the blade 10 and this adaptation would be within the reach of those skilled in the art.

[0109] The invention thus provides several advantages, including: - a limitation of the exposure of the blade to the heating and polymerization cycle of the glue (which reduces the impact on the number of possible retouches / repairs of the blade),

[0110] - reliable positioning and maintenance of the blade during the bonding and polymerization stage,

[0111] - maintaining pressure on the strips on the blade,

[0112] - reduction of the time and cost of implementing the bonding: in particular by simplifying the tools,

[0113] - the elimination of the risk of non-compliance linked to a leak in the vacuum tank of the prior art,

[0114] - reduction of waste from the autoclave bonding process,

[0115] - the use of tools for the manufacture of the blade but also for its possible repair with a view to changing its anti-wear strips.

Claims

CLAIMS 1. Tooling (40) for bonding at least one anti-wear strip (22) to a turbomachine blade (10), this blade (10) comprising a root (16) connected to a blade (12) and at least one anti-wear strip (22) located on the blade (10), the tooling (40) comprising: - a support (50), - at least one first fixing member (60) which is fixed to the support (50) and which is capable of cooperating with the blade (10) in order to immobilize it with respect to the support (50), characterized in that it further comprises: - at least one second member (70) for holding said at least one anti-wear strip (22) on the blade (10) and for heating this anti-wear strip (22) with a view to bonding it, this second member (70) being fixed to the support (50) and comprising on the one hand at least one expandable cushion (72) capable of adopting a first non-expanded position and a second expanded position in which said at least one cushion (72) is capable of applying pressure to at least one anti-wear strip (22) located on the blade (10), and on the other hand at least one heating element (80) capable of heating said at least one anti-wear strip (22) with a view to bonding it.

2. Tooling (40) according to claim 1, wherein said at least one second member (70) is independent of said at least one first fixing member (60).

3. Tooling (40) according to claim 1 or 2, wherein said at least one expandable cushion (72) is or comprises at least one inflatable bladder.

4. Tooling (40) according to claim 3, wherein said at least one second member (70) comprises at least one channel (74) for supplying pressurized air to said at least one inflatable bladder.

5. Tooling (40) according to one of claims 1 to 4, wherein said at least one heating element (80) is or comprises at least one heating mat, and in particular a resistive heating mat.

6. The tooling (40) of claim 5, wherein said at least one heating mat is located on or under said at least one expanding pad (72).

7. Tooling (40) according to one of claims 1 to 6, wherein said second member (70) comprises a first cushion (72a) capable of extending on a first side of the blade (10) or its root (16), a second cushion (72a) capable of extending on a second opposite side of the blade (10) or its root (16), or even a third cushion (72c) capable of extending on an upstream or downstream edge of the blade (10) or its root (16).

8. Tooling (40) according to one of claims 1 to 7, wherein said second member (70) defines an elongated slot (76) which is configured to receive the blade (10) or its root (16) by sliding and which comprises one or more cushions (72a, 72b) along its internal edges.

9. Assembly comprising a tool (40) according to one of the preceding claims and a turbomachine blade (10), this blade (10) comprising a root (16) connected to a blade (12) and at least one anti-wear strip (22) located on the blade.

10. Assembly according to claim 9, in which the or each anti-wear strip is made by weaving fibers such as aramid fibers and / or PTFE.

11. Assembly according to claim 9 or 10, in which the blade is made of composite material from a fiber preform whose fibers, for example carbon, are coated or impregnated with polymerizable and in particular crosslinkable resin.

12. Method for bonding at least one anti-wear strip (22) to a turbomachine blade (10), this blade (10) comprising a root (16) connected to a blade (12) and at least one anti-wear strip (22) located on the blade (10), the method using a tool (40) according to one of claims 1 to 8 and comprising the following steps: a) immobilizing the blade (10) with respect to the support (50) of the tool (40), using the first fixing member (60), b) expanding said at least one cushion (72) and applying pressure to said at least one anti-wear strip (22) located on the blade (10), and c) heating this anti-wear strip (22) with a view to bonding it to the blade (10), using said at least one heating element (80).

13. Method according to the preceding claim, in which the tool (40) is as defined in claim 8 and in which, before step a), the root (16) of the blade (10) is inserted into the slot (76) of the second member (70).

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