METHOD FOR REMOVING A FRONT EDGE SIGN ATTACHED TO A FAN SHOVEL AND ASSEMBLY WITH A FAN SHOVEL, A FRONT EDGE SIGN ATTACHED TO THE FAN SHOVEL AND A DEVICE FOR REMOVING THE SIGN

Description

Technical Field

[0001] The present invention relates to the field of aeronautical turbomachines, more precisely the repair or retouching of turbomachine fan blades, and in particular a method for removing a leading edge shield fixed to a fan blade and an assembly comprising a fan blade, a leading edge shield fixed to the fan blade, and a device for removing the shield. Prior art

[0002] In fields such as aeronautics, reducing aircraft weight is a constant concern for manufacturers. For example, in aircraft engines, it is known to replace certain metal blades with blades made of composite material, which have the advantage of being lighter.

[0003] Although these materials generally have very favorable mechanical qualities, particularly in relation to their mass, they exhibit a certain sensitivity to point impacts.

[0004] In the case of fan blades, for example, made of organic matrix composite, a metal leading edge, providing increased resistance to the point impacts to which this portion of the blades is subjected, is attached to the end of these blades. These metal leading edges act as shields, taking the form, for example, of a thin intrados fin and a thin extrados fin joined at an upstream end of the blade, the assembly matching the shape of the blade on the leading edge and the adjacent sections of the intrados and extrados.

[0005] However, the accumulation of flight hours and potential repeated impacts from foreign bodies generate wear on these metal leading edges, requiring their repair or replacement.

[0006] There are various solutions for removing the metal leading edge from the rest of the blade, such as mechanical or thermomechanical tearing. However, these solutions have the disadvantage of damaging the fibers of the composite material of the blade to which the leading edge is fixed. Conventional machining solutions are also possible, but require complex devices and computer tools, particularly due to the awkward and complex shape of the blade surface. US 7,544,112 B1, FR 3,025,735 A1, US 8,720,526 B1 and DE 195 29 749 A1 describe other examples of surface treatment methods.

[0007] There is therefore a need for a material removal process that overcomes the drawbacks mentioned above. Statement of the invention

[0008] The present disclosure relates to a method of removing a leading edge shield attached to a fan blade according to claim 1, the fan blade comprising a first material, and the leading edge shield comprising a second material different from the first material, the method comprising steps of: -Determining the thicknesses of the leading edge shield as a function of the position on the leading edge shield, -Removing the leading edge shield by means of a pressurized water jet moving over the leading edge shield as a function of the thicknesses determined in the determining step.

[0009] It is understood that the leading edge shield is a different element from the fan blade, and is related to the latter, by being fixed to it. The determination step makes it possible to map the thicknesses of the leading edge shield. In other words, this step makes it possible to determine the thickness of the leading edge shield for a given position on the external surface of the leading edge shield. This step thus makes it possible to determine the thickness of material to be removed.

[0010] The removal step removes the leading edge shield using a pressurized water jet. The high pressure of the water jet acts as a machining tool, removing the material contained in the leading edge shield. For a given position on the surface of the leading edge shield, the water jet thus removes the thickness of material from the leading edge shield determined in the determination step.

[0011] The use of a pressurized water jet, knowing the thickness of the material to be removed, allows the removal of the leading edge shield of the fan blade, without this fan blade being impacted. In other words, this process makes it possible to remove the first material of the leading edge shield, while limiting direct contact, as could be the case with a mechanical machining tool, with the second material of the fan blade. It is thus possible to spare the fan blade, by limiting the risks of degradation of the second material. The use of a pressurized water jet also has the advantage of simplifying material removal processes on parts with complex surface shapes.

[0012] In some embodiments, the first material is an organic matrix composite, and the second material is a metal.

[0013] In other words, the fan blade comprises an organic matrix composite, and the leading edge shield attached to the fan blade comprises a metal. The method makes it possible to remove the metal from the leading edge shield without damaging the organic matrix composite, in particular without damaging the fibers of said composite.

[0014] In some embodiments, prior to removal of the leading edge shield, the leading edge shield is secured to the aircraft part by gluing.

[0015] By "before removal of the leading edge shield" is meant before carrying out the method, i.e. before removal of the leading edge shield, for example for replacement in the event of wear of the leading edge shield, is necessary. The leading edge shield may be fixed to the fan blade by a structural epoxy adhesive, for example. Such a method of fixing would risk, in the event of removal of the leading edge shield by mechanical tearing, for example, damaging the fibers of the composite material of the fan blade. The use of the pressurized water jet makes it possible to overcome this disadvantage.

[0016] In some embodiments, the pressure of the water jet is between 100 and 1000 bars.

[0017] This range of pressure values ​​allows for efficient removal of the leading edge shield.

[0018] In some embodiments, the injected water comprises an abrasive media.

[0019] The pressure of the water jet used, combined with the presence of the abrasive media, generates a multitude of impacts on the leading edge shield, these impacts causing the removal of particles of the second material, in particular the metal, which is contained in the leading edge shield. The presence of the abrasive media thus improves the efficiency of the leading edge shield removal process.

[0020] In some embodiments, the abrasive media has a particle size between 50µm and 1mm.

[0021] The abrasive media may contain solid particles present in the water to be injected under pressure, the diameter of these particles being between 50µm and 1mm. Values ​​lower than 50µm would limit the efficiency of the removal process, and values ​​higher than 1mm would not be compatible with the pressurized water injection tool used in this process.

[0022] In some embodiments, the abrasive media is a sand comprising one of pure silica and silicon carbide.

[0023] In some embodiments, the water jet is applied through a nozzle oriented to form an angle of between + / -15° and + / -25°, preferably equal to + / -20° relative to a normal to a plane tangent to the surface of the leading edge shield at a point to which the water jet is applied.

[0024] In the case where the leading edge shield is a flat plate for example, the nozzle, and consequently the pressurized water jet applied to the plate, has an angle of between + / -15° and + / -25°, for example an angle of + / - 20°, relative to a direction perpendicular to this plate. This inclination of the water jet makes it possible to optimize the removal of material from the leading edge shield, compared to a situation in which the water jet would be oriented perpendicular to the plate.

[0025] In some embodiments, the nozzle applying the water jet is disposed at a distance less than or equal to 20 cm from the leading edge shield.

[0026] This makes it possible to avoid direct contact between the removal device and the fan blade. Furthermore, a distance greater than twenty centimetres would result in a dispersed water jet, and therefore a loss of precision during the removal step.

[0027] In some embodiments, determining the thicknesses of the leading edge shield as a function of position on the leading edge shield is performed via ultrasound.

[0028] A scan of the entire outer surface of the leading edge shield can, for example, be carried out using an ultrasonic tool. At each position of the tool on the surface of the leading edge shield, a signal transmitted by the ultrasonic tool is converted into a thickness. This ultrasonic analysis can be carried out, in particular, by echolocation.

[0029] During use of the fan blade, the wear generated on the leading edge shield is not uniform, such that the thickness of the leading edge shield, at the time of removal thereof, is itself not uniform. Determining the thicknesses of the leading edge shield, as a function of the position on it, by means of ultrasound, thus makes it possible to know the thickness of material to be removed for each of these positions, and thus to adapt the pressurized water jet according to the thickness to be removed, for example by adapting the pressure of the water jet.

[0030] In some embodiments, during the removal step, the speed of movement of the water jet moving over the leading edge shield is constant, and the pressure of the water jet varies depending on the thickness to be removed.

[0031] According to this configuration, the thicknesses of the leading edge shield determined in the determination step are converted into pressures. During the movement at constant speed of the water jet on the external surface of the leading edge shield, when the thickness of the leading edge shield is locally smaller, for example, the pressure is then reduced. Conversely, when the thickness is locally greater, the pressure of the water jet is increased. This removal process has the advantage of being able to be carried out by varying only one parameter, here the pressure, and thus of simplifying the control of the machining.

[0032] In some embodiments, during the removal step, the speed of movement of the water jet moving over the leading edge shield varies depending on the thickness to be removed, the pressure of said water jet being constant.

[0033] According to this configuration, the thicknesses of the leading edge shield determined in the determination step are converted into speeds. During the movement at constant pressure of the water jet on the external surface of the leading edge shield, when the thickness of the leading edge shield is locally smaller, for example, the movement speed is then increased. Conversely, when the thickness is locally greater, the movement speed of the water jet is reduced, so that the water jet has time to remove the entire thickness of the leading edge shield at this location. This removal method has the advantage of being able to be carried out by varying only one parameter, here the speed, and thus of simplifying the control of the machining.

[0034] In some embodiments, during the removal step, the speed of movement and pressure of the water jet moving over the leading edge shield vary depending on the thickness to be removed.

[0035] According to this configuration, the thicknesses of the leading edge shield determined in the determination step are converted into pairs of speed / pressure parameters.

[0036] In some embodiments, during the removal step, the speed of movement and pressure of the water jet moving over the leading edge shield are constant, and the number of passes of the water jet varies depending on the thickness to be removed.

[0037] In this configuration, the leading edge shield thicknesses determined in the determination step are converted into the number of water jet passes required at a given position, based on the thickness at that position. For example, at constant speed and pressure, a greater thickness at a given location will result in a greater number of passes required at that location, and vice versa.

[0038] In some embodiments, a suction tool suctions the material removed during the removal step.

[0039] The device may be arranged close to the water jet injection nozzle, for example within 10 cm. The suction tool is used to suck up material debris from the leading edge shield removed by the water jet during the removal step.

[0040] In some embodiments, the water jet moves over the leading edge shield via an articulated tool comprising at least two rotational axes.

[0041] In some embodiments, the water jet moves over the leading edge shield via an articulated tool comprising only two axes of rotation.

[0042] The articulated tool may be a robot comprising at least two arms articulated relative to each other, the nozzle injecting the water jet being arranged at one end of one of the arms. The rotation of the nozzle around only two axes of rotation, by means of the articulated tool, has the advantage of simplifying the removal process, in particular for parts having a complex surface. In the case of left surfaces for example, a mechanical machining tool would require rotations around five different axes in order to adapt to this left shape, and to the variable thickness of the leading edge shield. The use of the pressurized water jet makes it possible to limit the number of axes of rotation required, and thus to simplify the removal process.

[0043] In some embodiments, the method comprises, after the removing step, a step of polishing the fan blade resulting from the removing step.

[0044] The polishing step may involve manual or mechanical sanding of the residual adhesive after the removal step. This step makes it possible to standardize and smooth the surface of the resulting fan blade, on which the leading edge shield that was attached has been removed, in order to obtain a level of roughness close to that of a new part. This notably makes it easier to attach a new leading edge shield to the fan blade.

[0045] The method makes it possible to determine the thicknesses of the metal leading edge shield according to the position on the leading edge shield, and then to remove the leading edge shield by means of the pressurized water jet, sparing the fan blade on which the leading edge is fixed, i.e. limiting the risks of damaging the fibers of the organic matrix composite that the blade comprises. In addition, the implementation of this method using a water jet oriented using a two-axis robot that scans the surface of the leading edge shield, is particularly suitable for the left shape of the fan blades.

[0046] The present disclosure also relates to an assembly according to claim 12, comprising a fan blade, a leading edge shield attached to the fan blade, and a device for removing the leading edge shield, the fan blade comprising a first material, and the leading edge shield comprising a second material different from the first material, the removal device comprising a measuring tool configured to measure the thickness of the leading edge shield as a function of the position on the leading edge shield, and a pressurized water injection tool configured to remove the leading edge shield via the pressurized water jet moving over the leading edge shield, as a function of the thicknesses determined by the measuring tool. Brief description of the drawings

[0047] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, on which [ Fig. 1 ] There figure 1 is a schematic perspective view of a bypass turbojet engine, [ Fig. 2 ] There figure 2 is a schematic perspective view of a rotating blade of the fan of the turbojet engine of the figure 1 , [ Fig. 3 ] there figure 3 is a cross-sectional view, along plane III-III, of the dawn of the figure 2 , [ Fig. 4 ] there figure 4 is a schematic view of the removal device according to one embodiment, [ Fig. 5 ] there figure 5 is a detailed schematic view of a removal step using the device of the figure 4 , [ Fig. 6 ] there figure 6 is a cross-sectional view of the dawn of the figure 4 , [ Fig. 7 ] there figure 7 is a diagram representing the removal process according to the present disclosure. Description of the embodiments

[0048] There figure 1 illustrates a dual-flow turbojet 1 comprising a gas generator unit 2 and a fan 3. This fan 3 comprises a plurality of rotating blades 4, arranged radially around a central axis X, and aerodynamically profiled so as to impel the air by their rotation. Thus, as illustrated in the figure 2 , each blade 4 has a leading edge, a trailing edge 6, an extrados 7 and a intrados 8.

[0049] In normal operation, the relative wind is substantially oriented towards the upstream end, according to the direction of air flow in the fan, of each blade 4. This upstream end is particularly exposed to impacts and wear. In particular when the blade 4 comprises a composite material, in particular a polymer matrix reinforced by fibers, it is therefore appropriate to protect this upstream end of the blade 4 with a leading edge shield 5 fixed to each blade 4.

[0050] The leading edge shield 5 is a part, or component, attached to the upstream end of the blade 4, according to the direction of air flow in the fan, and matching the shape of the upstream end of the blade 4. In other words, the leading edge shield 5 is assembled on the blade 4. This assembly can be carried out by gluing, by a structural epoxy adhesive for example. The leading edge shield 5 is made of a material having better resistance to point impacts than the composite material of the blade 4. More precisely, the leading edge shield 5 is mainly metallic, and more specifically made of a titanium-based alloy, such as for example TA6V (Ti-6Al-4V). The leading edge shield 5 could also be made of steel or an alloy based on iron, chromium and nickel such as for example Inconels ®< .

[0051] The outer surface 5A of the leading edge shield 5 is thus exposed to impacts and wear, consequently protecting the composite material of the blade 4. The accumulation of flight hours causes wear of this leading edge shield. This wear, and the impacts causing this wear, not being uniform, the thickness of the leading edge shield 5A is itself non-uniform. figure 3 is a cross-sectional view, along plane III-III, of the dawn of the figure 2 , and illustrates an example of variations in the thickness of the leading edge shield 5 as a function of the position on the outer surface 5A of the leading edge shield 5.

[0052] When the wear of this leading edge shield 5 is significant, it is necessary to remove the latter, in order to replace it with a new leading edge shield. This removal is possible by means of a removal device described below with reference to the figure 4 , and comprising an articulated tool 30, for example a robot, the articulated tool 30 comprising at least a first arm 31 fixed to the ground for example, at least a second arm 32 articulated relative to the first arm 31 by means of a first axis of rotation 30A, and a tool holder 33 articulated relative to the second arm 32 by means of a second axis of rotation 30B.

[0053] The removal device also comprises a control unit 40 connected to the articulated tool 30, and controlling the movements thereof. A measuring tool 20 may be fixed on the tool holder 33, and is configured to detect the thicknesses of the leading edge shield 5. The measuring tool 20 may be an ultrasonic thickness gauge. The measuring tool 20 is connected to the control unit 40. The control unit 40 may be a human-machine interface capable of translating geometric trajectories in the machine code line space to control the arms of the articulated tool 30.

[0054] The removal device also comprises a pressurized water injection tool 10. The pressurized water injection tool comprises a high-pressure pump (not shown), and an injection nozzle 12, connected to the pump. The pressurized water injection tool 10 is configured to inject a stream of water, via the injection nozzle 12, at a pressure of between 100 and 1000 bars. The water present in the pump and intended to be injected by the injection nozzle 12 may be mixed with an abrasive medium, having a particle size of between 50 µm and 1 mm. The abrasive medium may be pure silica or silicon carbide. The water injection tool 10 is connected to the control unit 40. The control unit 40 can thus regulate the pressure of the water injected by the water injection tool 10.

[0055] The water injection nozzle 12 and the measuring tool 20 can be attached simultaneously to the tool holder 33. Alternatively, the water injection nozzle 12 and the measuring tool 20 can be attached successively to the tool holder 33. More precisely, at the end of the first step of the method described below, the measuring tool 20 can be removed from the tool holder 33 and replaced by the water injection nozzle 12, for carrying out the second step.

[0056] The removal device may also comprise a suction tool 50 comprising a suction conduit 52, one end of which is fixed to the tool holder 33, close to the injection nozzle 12. The suction tool 50 may be a vacuum cleaner configured to suck up debris and liquid, and having a power of between 1500 and 2500 W.

[0057] The removal process is described in the remainder of the description, with reference to the figures 5 à 7 .

[0058] A first step (step S1) makes it possible to determine the thickness of the leading edge shield 5 as a function of the position on the latter, that is to say for a given point on the external surface 5A of the leading edge shield 5.

[0059] In step S1, the control unit 40 controls the articulated tool 30 so that the measuring tool 20, arranged opposite the leading edge shield 5, moves while scanning the entire outer surface 5A of the leading edge shield 5 along a predetermined trajectory, by emitting ultrasound. The data measured by the measuring tool 20 are then transmitted to the control unit 40, which converts these data into thicknesses. Thus, at the end of step S1, the thickness mapping of the leading edge shield 5, i.e. the thickness of the leading edge shield for each given point on the outer surface 5A, is known.

[0060] A second step (step S2) makes it possible to remove the leading edge shield 5 from the blade 4. To do this, the control unit 40 converts the thicknesses measured during the first step S1 into pressures. The control unit 40 then controls the articulated tool 30 so that the water injection nozzle 12, arranged opposite the leading edge shield 5, moves by sweeping the entire external surface 5A of the leading edge shield 5 following the same trajectory as the measuring tool 20 during step S1. During this sweep, the injection nozzle 12, arranged on the tool holder 33, moves at a constant speed v0, and the pressure p of water injected by the nozzle 12 varies according to the thickness of the leading edge shield 5, on the basis of the conversion carried out by the control unit 40.

[0061] In parallel with this removal step, the debris or particles from the leading edge shield 5 removed by the water jet J can be sucked up by the suction tool 50, via the suction duct 52 also arranged on the tool holder 33. Alternatively, the suction of the debris can be carried out at the end of step S2.

[0062] During step S2, in order to improve the precision of the machining by avoiding excessive dispersion of the water jet J, a distance Δ between the end of the nozzle 12 and each point of contact between the jet J and the external surface 5A of the leading edge shield 5 remains less than or equal to 20 cm, during the movement of the nozzle 12.

[0063] Furthermore, an angle β between the jet J and a straight line perpendicular to the plane P tangent to the external surface 5A at the point of contact between the jet J and the surface 5A, and passing through this point of contact, is between + / -15° and + / -25°.

[0064] Furthermore, during step S2, the scanning of the external surface 5A of the leading edge shield 5 by the water jet J is carried out by means of the articulated tool 30, controlled by the control unit 40. The control unit 40 controls in particular the axes of rotation 30A and 30B. The control of these two axes of rotation thus makes it possible to position and orient the injection nozzle 12, and therefore the water jet J, relative to the surface 5A.

[0065] The method may comprise a third step (step S3) for polishing the portion of the surface of the blade 4 on which the leading edge shield 5 was fixed, after the completion of step S2. This polishing may be carried out by manual or mechanical sanding. This step S3 makes it possible to clean the residual glue joint on the blade 4, in order to regain a level of roughness close to the new part, and thus fix a new leading edge shield 5 on the blade 4.

[0066] The method described above presents an embodiment according to which the removal of the leading edge is carried out by sweeping the surface 5A by the nozzle 12 moving at a constant speed v0, the pressure p of the water jet varying according to the position on the surface 5A, and on the basis of the conversion carried out by the control unit 40. However, other embodiments are conceivable.

[0067] For example, during step S2, the control unit 40 can convert the thicknesses measured during step S1 into speeds v of movement of the nozzle 12. The step of removing the leading edge is thus carried out by sweeping the surface 5A by the nozzle 12 at a constant pressure p0, the nozzle 12 moving at a speed varying as a function of the position on the surface 5A, and on the basis of the conversion carried out by the control unit 40.

[0068] According to another example, both the speed of movement of the nozzle 12 and the pressure of the water jet J can vary depending on the thickness of the leading edge shield 5. To do this, the thicknesses determined in step S1 are converted into a speed / pressure pair (v, p).

[0069] According to yet another example, the removal step can also be carried out at constant speed and pressure. To do this, the removal thicknesses determined in step S1 are converted into the number of passes, i.e. the number of passes of the water jet J required, at constant speed v0 and pressure p0, for a given point on the surface 5A, depending on the thickness of the leading edge shield 5 at this point.

[0070] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense. It is also obvious that all features described with reference to a method are transposable, alone or in combination, to a device, and conversely, all features described with reference to a device are transposable, alone or in combination, to a method.

Claims

1. A method for removing a leading edge shield (5) fixed to a fan blade (4), the fan blade (4) comprising a first material, and the leading edge shield (5) comprising a second material different from the first material, the method being characterized in that it comprises steps of: - Determining the thicknesses of the leading edge shield (5) as a function of the position on the leading edge shield (5) - Removing the leading edge shield (5) by means of a pressurized water jet (J) moving over the leading edge shield (5) as a function of the thicknesses determined in the determination step.

2. The method according to claim 1, wherein the first material is an organic matrix composite, and the second material is a metal.

3. The method according to claim 1 or 2, wherein the pressure of the water jet (J) is comprised between 100 and 1,000 bars.

4. The method according to any one of claims 1 to 3, wherein the injected water includes an abrasive media.

5. The method according to any one of claims 1 to 4, wherein the water jet (J) is applied by means of a nozzle (12) oriented so as to form an angle (β) comprised between + / -15° and + / -25°, preferably equal to + / - 20° relative to a normal to a plane (P) tangent to the surface (5A) of the leading edge shield (5) at a point on which the water jet (J) is applied.

6. The method according to any one of claims 1 to 5, wherein the determination of the thicknesses of the leading edge shield (5) as a function of the position on the leading edge shield (5) is performed via ultrasound.

7. The method according to any one of claims 1 to 6, wherein during the removal step, the speed of displacement of the water jet (J) moving over the leading edge shield (5) is constant, and the pressure of the water jet (J) varies as a function of the thickness to be removed.

8. The method according to any one of claims 1 to 6, wherein during the removal step, the speed of displacement of the water jet (J) moving over the leading edge shield (5) varies as a function of the thickness to be removed, the pressure of said water jet (J) being constant.

9. The method according to any one of claims 1 to 7, wherein a suction tool (50) sucks the material removed during the removal step.

10. The method according to any one of claims 1 to 9, wherein the water jet (J) moves over the leading edge shield (5) by means of an articulating tool (30) comprising at least two axes of rotation (30A, 30B).

11. The method according to any one of claims 1 to 10, comprising, after the removal step, a step of polishing the fan blade (4) resulting from the removal step.

12. An assembly comprising a fan blade (4), a leading edge shield (5) fixed to the fan blade (4), and a device for removing the leading edge (5), the fan blade (4) comprising a first material, and the leading edge shield (5) comprising a second material different from the first material, characterized in that the removal device comprises a measuring tool (20) configured to measure the thickness of the leading edge shield (5) as a function of the position on the leading edge shield (5), and a pressurized water injection tool (10) configured to remove the leading edge shield (5) by means of the pressurized water jet (J) moving over the leading edge shield (5), as a function of the thicknesses determined by the measuring tool (20).