Device for manufacturing at least one hollow blade by lost-wax moulding

Abstract

The invention relates to a device (100) for manufacturing a hollow turbine engine blade by lost-wax moulding, the device comprising: - a shell mould (20) comprising an internal cavity (28) extending along an axis (A) between a first end (21) having a first surface (S1) having a plurality of first contact portions (27), and a second end (22) having a second surface (S2) having a plurality of second contact portions (29), - a core (33) arranged in the internal cavity and extending between a first platform (36) in contact with the first contact portions in first contact zones (25), and a second platform (37) in contact with the second contact portions in second contact zones (26), the first contact zones and the second contact zones being inclined and located on either side of the axis (A).

Description

[0001] DESCRIPTION

[0002] TITLE: DEVICE FOR THE LOST-WAX CASTING MANUFACTURE OF AT LEAST ONE HOLLOW BLADE

[0003] Technical field of the invention

[0004] The present invention relates to the field of manufacturing hollow turbomachine blades by lost-wax casting.

[0005] In particular, the invention relates to a device for manufacturing hollow turbomachine blades by lost-wax casting.

[0006] Technical background

[0007] The technical background includes, in particular, documents US-A-3-401-738 and US-A1-2021 / 138533.

[0008] An aircraft turbomachine, such as a turbojet, typically comprises, from upstream to downstream in the direction of gas flow, a movable fan rotating about a longitudinal axis, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, and a gas exhaust nozzle.

[0009] The blower allows the intake of an airflow that splits into a primary flow and a secondary flow. The primary flow passes through a primary channel of the turbomachine, while the secondary flow is directed towards a secondary channel surrounding the primary channel.

[0010] The primary airflow is compressed within the compressors. The compressed air is then mixed with fuel and burned in the combustion chamber. The combustion gases pass through the turbines and then escape through the nozzle, whose cross-section allows these gases to be accelerated to generate propulsion.

[0011] Turbines are typically equipped with blades evenly distributed around a disk. A blade extends radially from the disk between a root and a crest. It typically comprises a blade connected to the root by a platform. The root is arranged in a recess in the disk to retain the blade on the disk. The blade also has an aerodynamic shape and typically comprises an upper and lower surface connected by a leading edge and a trailing edge.

[0012] Because high-pressure turbine blades are located downstream of the combustion chamber, they are subjected to high temperatures. Therefore, these blades are typically made of metallic material. Although metallic materials have the advantage of withstanding high temperatures, such blades can be subjected to temperatures exceeding the maximum temperature these materials can withstand.

[0013] In this context, it was proposed to equip the blades with a cooling system. The cooling system comprises a cooling circuit arranged inside the blades, allowing air from the compressors to pass through them. The cooling circuit includes internal channels formed during the blade manufacturing process. Each channel typically extends from the tip of the blade to its root.

[0014] Such blades are typically produced using a lost-wax casting process. This manufacturing process involves a step of creating cores from ceramic material, followed by a step of molding wax or resin patterns of the blade around the respective cores. These blade patterns are then arranged in clusters around a casting mold, thereby increasing the production rate of the blades. The process then includes a step of creating shell molds for the blades. For this purpose, the clustered blade patterns and the casting mold are coated with a refractory material, for example, ceramic materials, to form a shell mold around each blade pattern and around the casting mold. This results in a lost-wax casting installation.The patterns are then removed from their respective shell molds, for example by heat treatment, thus forming an internal cavity in the shell mold that bears an imprint of the blade pattern. The molding setup is then placed in a heating chamber, such as a furnace, for pouring molten metal into the internal cavity of the shell molds. This pouring step typically includes a first step of preheating the molding setup to a temperature equal to or substantially equal to the melting temperature of the metal material, a second step of filling the shell molds of the molding setup with the molten metal material, and a third step of solidifying and cooling the metal material.

[0015] Thus, each shell mold typically includes an internal cavity for casting the metallic material and features a blade impression comprising a first impression of the root and a second impression of the blade. The core is arranged inside the internal cavity to form the internal channel of the blade during the casting of the metallic material into the shell mold. To hold the core within the internal cavity, it is typically bonded to the shell mold.

[0016] During the preheating stage of shell molds, the shell mold expands more than the core, creating a differential expansion between the core and the shell mold. This differential expansion can weaken the core's anchoring within the shell mold and reduce the cohesion between the core and the shell mold. Furthermore, the contact between the ceramic shell mold and the ceramic core during this preheating stage is difficult to measure, making the dimensioning of the bond between the core and the shell mold complex. This bond can break under the effect of external forces exerted on the core during filling after preheating. All of these phenomena occurring during the preheating stage can lead to displacement of the core within the internal cavity of the mold.

[0017] Furthermore, during the filling stage, there is also a risk of core displacement within the internal cavity of the shell mold. Indeed, when the molten metal material impacts the core, hydrodynamic and / or hydrostatic forces can cause it to move. Thus, during this filling stage, there is a dynamic phase during which the metal material fills the internal cavity and immerses the core, and a static phase during which the core is fully submerged. During the dynamic phase, the levels of metal material within the cavity may vary, generating forces in a plane perpendicular to the core's elongation axis. Such forces can also cause the core to move within the internal cavity of the shell mold.

[0018] In the field of the invention, this displacement of the core in the shell mold, for example under the effect of differential expansion between the core and the shell mold, or under the effect of a force imposed on the core during filling, is commonly called "core displacement".

[0019] Core offset can directly impact the dimensions of the blade walls, which may be thinner than nominal. Such undersizing can significantly degrade the blade's thermomechanical properties and thus lead to its rejection. Core offset can even cause blade perforation when the core comes into contact with the internal cavity of the blade shell.

[0020] One of the major technical difficulties of this manufacturing process is therefore to ensure the positioning of the core in the internal cavity of the shell mold throughout the manufacturing process, in particular during the preheating and filling stages, and therefore over a wide temperature range.

[0021] In this context, there is a need to provide a device for the manufacture of hollow blades by lost-wax casting which makes it possible to limit the manufacturing defects of these blades by such a process.

[0022] Summary of the invention

[0023] To overcome the drawbacks described above, the invention provides a device for manufacturing at least one hollow turbomachine blade by lost-wax casting, said device comprising:

[0024] - at least one shell mold comprising an internal cavity extending along a longitudinal axis and intended to receive molten metallic material, the internal cavity comprising a central section extending along said longitudinal axis between a first longitudinal end having a first internal surface having a plurality of first contact portions, and a second longitudinal end axially opposite to the first longitudinal end and comprising a second internal surface having a plurality of second contact portions, and

[0025] - a core arranged in the internal cavity and comprising a body extending along the longitudinal axis and between a first transverse platform and a second transverse platform, the first transverse platform being in contact in at least two first contact zones with said first contact portions of the first internal surface, and the second transverse platform being in contact in at least two second contact zones with said second contact portions of the second internal surface,

[0026] the at least two first contact zones being located on either side of said longitudinal axis or distributed around said longitudinal axis and separated from each other by a first distance H1, and said at least two first contact portions being inclined at a first angle α with respect to a transverse axis perpendicular to the longitudinal axis and converging towards each other and towards the longitudinal axis in the direction of the second transverse platform,

[0027] the at least two second contact zones being located on either side of said longitudinal axis or distributed around said longitudinal axis and separated from each other by a second distance H2, and said at least two second contact portions being inclined at a second angle p with respect to the transverse axis and converging towards each other and towards the longitudinal axis in the direction of the first transverse platform,

[0028] the second contact zones being located at a third distance L1, measured along the longitudinal axis, from the first contact zones, and the first and second angles a and P being such that: 0.9 x arctan (L1 / H1) < a < 1.1 x arctan (L1 / H1) and 0.9 x arctan (L1 / H2) < 0 < 1.1 x arctan (L1 / H2). In other words, in a device according to the invention, the values ​​of the first and second angles a and P are such that: a = arctan (L1 / H1) to plus or minus 10% and P = arctan (L1 / H2) to plus or minus 10%.

[0029] Regarding the measurement of the third distance L1 presented above, "measured along the longitudinal axis" means that the third distance L1 can be measured between a projection of any first contact zone onto the longitudinal axis A and a projection of any second contact zone onto the longitudinal axis A. Thus, even if the first distance H1 and the second distance H2 are not equal, and the first and second contact zones are therefore not aligned on the same axis parallel to the longitudinal axis A, the measurement of the third distance L1 remains the same. In other words, the third distance L1 is measured in the same way, whether the first and second contact zones are aligned on the same axis parallel to the longitudinal axis A or not, and whether the first and second distances H1 and H2 are equal or not.Therefore, the first distance H1 is measured between a projection of one of the first contact zones onto the transverse axis A, which is perpendicular to the longitudinal axis A, and a projection of another of the first contact zones onto said transverse axis A. Similarly, the second distance H2 is measured between a projection of one of the second contact zones onto the transverse axis A and a projection of another of the second contact zones onto said transverse axis A. Finally, for optimal clarity, it is specified that in case of doubt, the point projected to measure any of the distances presented above is the point in the contact zone that is closest to the longitudinal axis.

[0030] In a device with the characteristics described above, the inclination of the first and second contact portions is a function of the first distance H1 between the first contact zones, the second distance H2 between the second contact zones, and the third distance L1 between the first and second contact zones. Therefore, the proportions of such a device ensure that contact is maintained between the core platforms and the corresponding contact portions of the shell mold at the contact zones, particularly in the event of differential expansion between the shell mold and the core.

[0031] For example, in a coordinate system (x, y) where the x-axis is horizontal and parallel to the transverse axis A, and the y-axis is vertical and parallel to the longitudinal axis A, the first transverse platform is located at the top and rests on the first contact points in the first contact zones, and the second transverse platform is located at the bottom and is in contact with the second contact points in the second contact zones, thus preventing the core from swinging from side to side. Since the y-axis is vertical and parallel to the longitudinal axis A, the core therefore experiences gravity along its longitudinal axis A.The core is thus suspended from the shell mold by its first transverse platform and is thereby held in place in the vertical direction, i.e., along the longitudinal axis A, and in the horizontal direction, i.e., along the transverse axis A', by contact of its transverse platforms against the corresponding contact portions of the shell mold. The core therefore remains centered in its position relative to the shell mold, even in the event of differential expansion between the shell mold and the core.

[0032] In other words, in a device according to the invention, the core and the shell mold exhibit structural and dimensional complementarity, enabling the core to remain in position within the internal cavity when the dimensions of the shell mold and the core change relative to each other, particularly during temperature changes. With such a device, core displacement during the preheating and filling stages is prevented, thereby reducing the scrap rate and increasing the quality of conforming blades.

[0033] The effects shown above, and in particular the maintenance of the position of the nucleus in the internal cavity, are observed throughout the range of values ​​of plus or minus 10% of the angles a and 0.

[0034] Preferably, the first and second angles a and p are such that: a = arctan(L1 / H1) plus or minus 5% and p = arctan(L1 / H2) plus or minus 5%. In other words, the values ​​of the first and second angles a and p are such that: 0.95 x arctan(L1 / H1) < a < 1.05 x arctan(L1 / H1) and 0.95 x arctan(L1 / H2) < p < 1.05 x arctan(L1 / H2).

[0035] Even more preferably, the first and second angles α and P are such that: α = arctan(L1 / H1) ± 1% and P = arctan(L1 / H2) ± 1%. In other words, the values ​​of the first and second angles α and P are such that: 0.99 arctan(L1 / H1) < α < 1.01 arctan(L1 / H1) and 0.99 arctan(L1 / H2) < α < 1.01 arctan(L1 / H2). A device according to the invention, in which the first and second contact portions have an inclination within this range of values ​​of ± 1% of angles α and P, makes it possible to obtain blades with the most compliant proportions and generating the lowest scrap rate.

[0036] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0037] - The first and / or second contact zones are discrete and in the form of contact points. These characteristics allow better circulation of the molten metallic material in the internal cavity during filling, while maintaining sufficient support points to hold the core in its position within the internal cavity;

[0038] - The first and / or second contact zones are continuous and in the form of contact lines. With these characteristics, the core's transverse platforms have a greater surface area in contact with the contact portions of the shell mold, which increases core stability during preheating and / or filling, while maintaining good circulation of the molten metal during filling. Discrete contact points or continuous contact lines may be preferred depending on the conditions, for example, based on the viscosity of the molten metal during filling. The geometry of the core's transverse platforms is then adapted accordingly;

[0039] - The first transverse platform is in contact at four initial contact zones with the initial contact portions of the first internal surface, and the second transverse platform is in contact at four subsequent contact zones with the subsequent contact portions of the second internal surface. With four contact zones, instead of two, distributed around the longitudinal axis, the stabilizing force is better distributed, and the two transverse platforms ensure greater stability of the core in the longitudinal direction, i.e., along the longitudinal axis A, and in the transverse direction, i.e., along the transverse axis A; - The initial and / or subsequent contact portions are substantially concave. A concave curvature of the contact portions allows for greater stability of the core, particularly in response to imbalances caused by thermal expansion and filling;

[0040] - the first internal surface is substantially frustoconical and / or the second internal surface is substantially frustoconical;

[0041] - the first contact portions and / or the second contact portions are substantially flat. Flat contact portions facilitate the movement of transverse platforms on the contact portions, in particular by sliding;

[0042] - the central section has a first internal width H3, measured along the transverse axis, which is such that: H1 / 1.5 < H3 < H1 / 1.2 and / or H2 / 1.5 < H3 < H2 / 1.2, preferably such that H1 / 1.5 < H3 < H1 / 1.25 and / or H2 / 1.5 < H3 < H2 / 1.25, even more preferably such that H1 / 1.2 < H3 < H1 / 1.03 and / or H2 / 1.2 < H3 < H2 / 1.03;

[0043] - the first transverse platform includes a first polygonal base extending in a plane substantially orthogonal to the axis, and first lateral faces of general triangular shape, a first vertex of which is in contact in at least a first contact zone with a first portion of contact of the first internal surface, and the second transverse platform includes a second polygonal base extending in a plane substantially orthogonal to the axis, and second lateral faces of general triangular shape, a second vertex of which is in contact in at least a second contact zone with a second portion of contact of the second internal surface;

[0044] - The first and / or second base is / are quadrilateral. The invention also relates to a method for manufacturing a hollow turbine blade for a turbomachine, said method comprising the following steps:

[0045] (a) provide a device according to the invention as described above;

[0046] (b) cooking of said device;

[0047] (d) carry out a casting step, said casting step comprising the following substeps:

[0048] • (dO) preheating of the shell mold, and

[0049] • (d1) filling the shell mold with the molten metallic material;

[0050] (e) solidify the metallic material by cooling the internal cavity; (f) perform a shell removal step; and

[0051] (g) remove the kernel.

[0052] Step (b) of baking the device solidifies the shell mold. Optionally, between step (b) and before step (d), the process may include a step (c) of packaging the device according to the invention. This packaging is intended to prevent the molten material from cooling too quickly, particularly during solidification. This ensures a homogenized distribution of the molten material within the shell mold during casting, especially in the thinnest parts of the internal cavity.

[0053] During step (f) of shell demolding, the shell mold is removed so as to demold the blade.

[0054] At step (g), the removal of the core can be done by chemical treatment of the blade, for example by dissolving it in a soda bath.

[0055] Optionally, after step (g), the process may include a step (h) of machining and / or drilling the blade.

[0056] Another object of the invention relates to a hollow turbine blade for a turbomachine that can be obtained by the process according to the invention as described above. Finally, yet another object of the invention relates to an aircraft turbomachine equipped with at least one hollow turbine blade according to the invention as described above.

[0057] Brief description of the figures

[0058] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached drawings in which:

[0059] [Fig.1] Figure 1 is a diagram of a longitudinal cross-sectional view of a half-turbomachine of an aircraft according to the invention.

[0060] [Fig.2] Figure 2 is a three-dimensional schematic representation of a hollow blade according to the invention.

[0061] [Fig.3] Figure 3 is a schematic representation of a lost-wax casting installation placed in a heating chamber for the manufacture of the blade of Figure 2.

[0062] [Fig.4] Figure 4 is a diagram of a longitudinal cross-sectional view of a device according to the invention.

[0063] [Fig.5] Figure 5 is a schematic of a longitudinal cross-sectional view of the device in Figure 4 showing the dimensional difference of the cold and hot shell mold.

[0064] [Fig.6] Figure 6 is a three-dimensional schematic representation of a core according to a preferred embodiment of the invention.

[0065] [Fig.7] Figure 7 is a synoptic diagram of a lost-wax casting manufacturing process for a hollow blade according to the invention and implementing the foundry mold of Figure 3.

[0066] Detailed description of the invention

[0067] An example of an aircraft turbomachine 1 according to the invention is shown in Figure 1. The turbomachine 1 extends around and along a longitudinal axis B.

[0068] The turbomachine 1 comprises, from upstream to downstream with respect to the direction of gas flow in the turbomachine 1 along the longitudinal axis B, a blower 2, at least one compressor such as a low-pressure compressor 3 and a high-pressure compressor 4, a combustion chamber 5, at least one turbine such as a high-pressure turbine 6 and a low-pressure turbine 7, and a nozzle (not shown).

[0069] The blower 2 allows the intake of an airflow F which splits into a primary flow F1 and a secondary flow F2. The primary flow F1 passes through the engine of the turbomachine 1 while the secondary flow F2 is directed towards a secondary duct.

[0070] The primary flow F1 is compressed within the low-pressure compressor 3 and then the high-pressure compressor 4. The compressed air is then mixed with a fuel and burned within the combustion chamber 5. The gases formed by the combustion pass through the high-pressure turbine 6 and low-pressure turbine 7. The gases finally escape through the nozzle whose cross-section allows the acceleration of these gases to generate propulsion.

[0071] Fan 2, for example, is enclosed. It is surrounded by an annular casing 2b centered on the longitudinal axis B. The casing 2b is, for example, surrounded by a nacelle (not shown) of the turbomachine 1.

[0072] With reference to Figure 2, the high-pressure and low-pressure turbines 6, 7, and in particular the high-pressure turbine 6, comprise blades 8 extending radially with respect to the longitudinal axis B, from a disk (not shown) fixed or movable in rotation with respect to the longitudinal axis B. Each blade 8 extends between a head 10 and a foot 12. The foot 12 can be connected to a blade 9 by a platform 11.

[0073] The foot 12 is mounted in a corresponding recess in the disc to hold the blade 8 onto the disc. In cross-section with respect to the longitudinal axis B, the foot 12 has a fir tree or dovetail shape. The blade 9 has an aerodynamic shape and comprises an intrados face 9i and an extrados face 9e connected by a leading edge 9a and a trailing edge 9b.

[0074] The blade 8 is made of metallic material. Advantageously, the metallic material is chosen from single-crystal nickel-based superalloys. Such materials have the advantage of withstanding high temperatures and therefore allow the implementation of these blades 8 in close proximity to the combustion chamber 5, in an environment subjected to high temperatures.

[0075] To further improve the temperature resistance of the blades 8, each blade 8 is hollow. Each blade 8 includes a cooling system comprising at least one internal channel 13 for circulating cooling air within the blade 8. The internal channel 13 extends within the blade 8 from the tip 10 to the foot 12 of the blade 8. The cooling air is, for example, air drawn from the low-pressure compressor 3 or the high-pressure compressor 4.

[0076] Each blade 8 is manufactured in a lost-wax casting facility 14, illustrated for example in Figure 3.

[0077] Installation 14 can be arranged in a heating chamber C. Heating chamber C is advantageously a furnace, preferably a directed solidification furnace such as a Bridgman furnace.

[0078] The installation 14 includes a foundry mold 15 having a central axis Z. It includes a central barrel 16 extending along the central axis Z between a funnel 17 and a tray 18 which are centered on the central axis Z.

[0079] Installation 14 further includes blade manufacturing devices 8. Each device includes shell molds 20 regularly distributed around the central shaft 16 and connected to the funnel 17 by fixing arms 2.

[0080] Each shell mold 20 comprises a refractory material, for example a ceramic material. Each shell mold 20 has a longitudinal axis A of elongation. The longitudinal axis A is parallel to the central axis Z when the shell molds 20 are mounted in the installation 14.

[0081] Each shell mold 20 extends longitudinally along the longitudinal axis A between a first longitudinal end 21 and a second longitudinal end 22. The first longitudinal end 21 and the second longitudinal end 22 are axially opposed along the longitudinal axis A of elongation of the shell mold 20. The first longitudinal end 21 is connected to the fixing arm 24 while the second longitudinal end 22 is connected to the plate 18 by means of a baffled selector 23. Reference is now made to Figures 4 and 5 which illustrate a device 100 according to the invention in a coordinate system (x, y) in which the x-axis is horizontal and the y-axis is vertical.

[0082] The device 100 comprises at least one shell mold 20 and a core 33. The shell mold 20 includes an internal cavity 28 extending along a longitudinal axis A and intended to receive molten metallic material. The internal cavity 28 includes a central section 23 extending along the longitudinal axis A between a first longitudinal end 21 and a second longitudinal end 22. The first longitudinal end 21 has a first internal surface S1 having a plurality of first contact portions 27. The second longitudinal end 22 is axially opposite to the first longitudinal end 21 and has a second internal surface S2 having a plurality of second contact portions 29.

[0083] The core 33 is arranged in the internal cavity 28 and comprises a body 38. The body 38 extends along the longitudinal axis A and between a first transverse platform 36 and a second transverse platform 37. The first transverse platform 36 is in contact in at least two contact zones 25 with the first contact portions 27 of the first internal surface S1. The second transverse platform 37 is in contact in at least two second contact zones 26 with the second contact portions 29 of the second internal surface S2.

[0084] The first two or more contact zones 25 are located on either side of the longitudinal axis A or distributed around the longitudinal axis A. The first two or more contact zones 25 are separated from each other by a first distance H1. The first two or more contact portions 27 are inclined at a first angle α with respect to the transverse axis A” and converge towards each other and towards the longitudinal axis A in the direction of the second transverse platform 37.

[0085] The at least two second contact zones 26 are located on either side of the longitudinal axis A or distributed around the longitudinal axis A. The at least two second contact zones 26 are separated from each other by a distance H2. The at least two second contact portions 29 are inclined at a second angle P with respect to the transverse axis A” and converge towards each other and towards the longitudinal axis A in the direction of the first transverse platform 36.

[0086] The second contact zones 26 are located at a third distance L1, measured along the longitudinal axis A, from the first contact zones 25. The first and second angles α and P are such that: 0.9 arctan(L1 / H1) < α < 1.1 arctan(L1 / H1) and 0.9 arctan(L1 / H2) < 0 < 1.1 arctan(L1 / H2). In other words, the values ​​of the first and second angles α and P are such that: α = arctan(L1 / H1) ± 10% and P = arctan(L1 / H2) ± 10%.

[0087] Preferably, the first and second angles a and p can be such that: a = arctan(L1 / H1) ± 5% and P = arctan(L1 / H2) ± 5%. In other words, the values ​​of the first and second angles a and P are such that: 0.95 x arctan(L1 / H1) < a < 1.05 x arctan(L1 / H1) and 0.95 x arctan(L1 / H2) < 0 < 1.05 x arctan(L1 / H2).

[0088] Even more preferably, the first and second angles a and p can be such that: a = arctan (L1 / H1) to plus or minus 1% and P = arctan (L1 / H2) to plus or minus 1%. In other words, the values ​​of the first and second angles a and P are such that: 0.99 x arctan (L1 / H1) < a < 1.01 x arctan (L1 / H1) and 0.99 x arctan (L1 / H2) < 0 < 1.01 x arctan (L1 / H2).

[0089] As illustrated in Figures 4 and 5, the first internal surface S1 can be substantially frustoconical, and the second internal surface S2 can also be substantially frustoconical. The first internal surface S1 and the second internal surface S2 can also have the same axis of revolution, and said axis of revolution can be the longitudinal axis A. Furthermore, the first contact portions 27 can be substantially planar, and the second contact portions 29 can also be substantially planar.

[0090] The first angle of inclination of the first contact portions 27 can be formed between a first generatrix G1 of the first contact portions 27 and the transverse axis A”. The second angle of inclination P of the second contact portions 29 can be formed between a second generatrix G2 of the second contact portions 29 and the transverse axis A”. Thus, in an embodiment, not illustrated in this application, in which the first and / or second contact portions 27 and / or 29 are substantially concave, the first generatrix G1 can be tangent to the curvature of the first contact portions 27 and the second generatrix G2 can be tangent to the curvature of the second contact portions 29.

[0091] The first angle a and the second angle p can be equal.

[0092] In the embodiment illustrated in figures 4 and 5, the first internal surface S1 comprises two first planar contact portions 27.

[0093] Each of the first two contact portions 27 is inclined at the first angle α with respect to the transverse axis A. The first transverse platform 36 is in contact with these first two contact portions 27 at the first two contact zones 25. In other words, the first platform 36 is in contact at the first contact zone 25 with each of the first two contact portions 27. The first two contact zones 25 are located on either side of the longitudinal axis A and separated from each other by the first distance H1. Similarly, the second internal surface S2 comprises two second planar contact portions 29. Each of the two second contact portions 29 is inclined at the second angle α with respect to the transverse axis A. The second transverse platform 37 is in contact with these two second contact portions 29 at the second contact zones 26.In other words, the second platform 37 is in contact at a second contact zone 26 with each of the two second contact portions 29. The two second contact zones 26 are located on either side of the longitudinal axis A and are separated from each other by the second distance H2. The first distance H1 and the second distance H2 are equal.

[0094] The first transverse platform 36 can also be in contact in the first four contact zones 25 with the first contact portions 27 of the first internal surface S1, and the second transverse platform 37 can be in contact in the second four contact zones 26 with the second contact portions 29 of the second internal surface S2. In this case, the first four contact zones 25 are distributed around the longitudinal axis A and separated from each other by the first distance H1, and the second four contact zones 26 are distributed around the longitudinal axis A and separated from each other by the second distance H2.

[0095] Each of the first and second transverse platforms 36 and 37 can have a general parallelepiped shape and present a rectangular cross-section respectively over its first distance H1 and its second distance H2. The first transverse platform 36 has a first quadrilateral base 54 extending in a plane substantially orthogonal to the longitudinal axis A, a first internal face 50 extending in a plane substantially orthogonal to the longitudinal axis A, and first lateral faces 56 extending parallel to the longitudinal axis A. The second transverse platform 37 has a second quadrilateral base 55 extending in a plane substantially orthogonal to the longitudinal axis A, a second internal face 52 extending in a plane substantially orthogonal to the longitudinal axis A, and second lateral faces 58 extending parallel to the longitudinal axis A.

[0096] The first contact zones 25 are formed between the first contact portions 27 of the first internal surface S1 and the ends of the first internal face 50 of the first transverse platform 36. The second contact zones 26 are formed between the second contact portions 29 of the second internal surface S2 and the ends of the second internal face 52 of the second transverse platform 37. In such a device 100, filling can be carried out in different ways. According to a first example, filling can be done through the first or second longitudinal end 21, 22 of the shell mold 20. According to a second example, filling can be done either through an opening made in at least one of the transverse platforms 36, 37, or through a lateral opening made in a thickness of the shell mold 20, for example at the central section 23.

[0097] Thus, in the case where the first and second transverse platforms 36 and 37 are in linear contact with the first and second contact portions 27 and 29, respectively, and where these first and second contact portions 27 and 29 extend over a circumference of the first internal surface S1 and the second internal surface S2, respectively, the first transverse platform 36 and / or the second transverse platform 37 may include at least one opening (not shown) intended to allow the molten metallic material to flow through at least one of the transverse platforms and into the internal cavity 28 of the shell mold 20 for the filling step. Such an opening may extend through the first transverse platform 36 from the first base 54 to the first internal face 50, and / or another opening may extend through the second transverse platform 37 from the second base 55 to the second internal face 52.Alternatively or jointly, the shell mold 20 may include a lateral opening (not shown) through a thickness (not shown) of the shell mold 20 at the central section 23, and which is also intended to allow the molten metallic material to flow into the internal cavity 28 to perform the filling step.

[0098] Advantageously, the first contact zones 27 and / or the second contact zones 29 can be discrete and in the form of contact points, or continuous and in the form of contact lines. This allows the molten metal material to flow without the need for an opening through the first transverse platform 36 and / or the second transverse platform 37, or through the central section 23 of the shell mold 20.

[0099] Now, with reference to Figure 5 which illustrates the dimensional difference of the cold 20 shell mold and the hot 20” expanded shell mold in device 100 of Figure 4.

[0100] The internal cavity 28 has a first internal width H3, measured along the transverse axis A” which is perpendicular to the longitudinal axis A. Figure 5 shows that when the shell mold 20 is heated, the dimensions of the internal cavity 28 change. In particular, a second internal width H3” of the internal cavity 28 of the expanded shell mold 20” is greater than the first internal width H3 of the cold shell mold 20. The second internal width H3” of the internal cavity 28 is also measured along the transverse axis A”. Compared to the dimensional changes of the shell mold 20, the dimensions of the core 33 vary only slightly.Therefore, during this differential expansion between the core 33 and the shell mold 20, it is important that the core 33 remains centered in its initial position within the cold shell mold 20 before casting begins, particularly before preheating, to prevent core displacement during casting. To achieve this, the first and second transverse platforms 36 and 37 will slide on the first and second contact portions 27 and 29, following their respective inclinations of angles α and β, as the shell mold 20 expands. This results in a displacement of the first and second contact zones 25 and 26 onto the first and second contact portions 27 and 29. With such a device 100, the contact zones 25 and 26 between the transverse platforms 36 and 37 and the contact portions 27 and 29 are maintained, whether the shell mold 20 is dilated or not.This allows an adjustment of the position of the core 33 in the internal cavity 28 and relative to the shell mold 20, simultaneously with the thermal expansion of the shell mold 20.

[0101] Thus, the ratio between the first internal width H3 and the first distance H1, as well as the ratio between the first internal width H3 and the second distance H2, will vary depending on the dilation of the internal cavity 28. The first internal width H3 can be such that: H1 / 1.5 < H3 < H1 / 1.2 and / or H2 / 1.5 < H3 < H2 / 1.2, in which H1 / 1.5 corresponds to the first internal width H3 of the internal cavity 28 when cold, and H1 / 1.2 corresponds to the second internal width H3 of the dilated internal cavity 28. Preferably, the first internal width H3 is such that: H1 / 1.5 < H3 < H1 / 1.25 and / or H2 / 1.5 < H3 < H2 / 1.25, in which H1 / 1.5 corresponds to the first internal width H3 of the internal cavity 28 when dilated. cold, and H 1 / 1 ,25 corresponds to the second internal width H3” of the dilated internal cavity 28.Even more preferably, the first internal width H3 is such that: H1 / 1.2 < H3 < H1 / 1.03 and / or H2 / 1.2 < H3 < H2 / 1.03, where H1 / 1.2 corresponds to the first internal width H3 of the internal cavity 28 when cold, and H1 / 1.03 corresponds to the second internal width H3 of the dilated internal cavity 28. In all cases, the first distance H1 must remain greater than the second internal width H3 of the dilated internal cavity 28.

[0102] Advantageously, the second distance H2 also remains greater than the second internal width H3” of the dilated internal cavity 28.

[0103] Figure 6 illustrates an advantageous embodiment of the core 33 of a device 100 according to the invention, in which the core 33 comprises first and second transverse platforms 36 and 37 having a particular geometry different from that shown in Figures 4 and 5. The first transverse platform 36 comprises a first polygonal base 54 extending in a plane substantially orthogonal to the axis A. Furthermore, the first transverse platform 36 comprises first lateral faces 56 of generally triangular shape, a first vertex 57 of which can be in contact in a first contact zone 25 with a first contact portion 27 of the first internal surface S1 of the shell mold 20 of Figures 4 and 5. In the embodiment of Figure 6, the first base 54 is quadrilateral, and the first transverse platform 36 therefore comprises four first lateral faces 56.Thus, the first four vertices 57 of the first transverse platform 36 can be in contact in the first four contact zones 25 with the first contact portions 27 of the first internal surface S1 of the shell mold 20 of figures 4 and 5. All or part of the first four contact zones 25 can be on the same first contact portion 27, or the first four contact zones 25 can be on different first contact portions 27.

[0104] The second transverse platform 37 comprises a second polygonal base 55 extending in a plane substantially orthogonal to axis A. Furthermore, the second transverse platform 37 comprises second lateral faces 58 of generally triangular shape, a second vertex 59 of which can be in contact at a second contact zone 26 with a second contact portion 29 of the second internal surface S2 of the shell mold 20 of Figures 4 and 5. In the embodiment of Figure 6, the second base 55 is quadrilateral, and the second transverse platform 37 therefore has four second lateral faces 58. Thus, four second vertices 57 of the second transverse platform 37 can be in contact at four second contact zones 26 with the second contact portions 29 of the second internal surface S2 of the shell mold 20 of Figures 4 and 5.All or part of the four second contact zones 26 may be on the same second contact portion 29, or the four second contact zones 26 may be on different second contact portions 29.

[0105] In the embodiment illustrated in Figure 6, the first and second contact zones 25 and 26 are continuous and in the form of contact lines. This shape of the first and second lateral faces 56 and 58 generates four blocks having a generally pyramidal shape on each of the first and second transverse platforms 36 and 37. The pyramidal blocks of the first transverse platform 36 form passages with the first internal surface S1, allowing the molten metal material to flow into the internal cavity 28 without requiring an opening through the first transverse platform 36 or through the central section 23 of the shell mold 20.Similarly, the pyramidal blocks of the second transverse platform 37 form passages with the second internal surface S2, allowing the molten metal material to flow into the internal cavity 28 without the need for an opening through the second transverse platform 37 or through the central section 23 of the shell mold 20. An advantage of this embodiment is that it does not require any special modification of the shell mold 20 to form one or more openings in the central section 23.

[0106] Figure 7 is a block diagram of a lost-wax casting manufacturing process for a hollow blade 8 according to the invention, which can utilize the foundry mold 15 of Figure 3. The process comprises the following steps:

[0107] (a) provide a device 100 according to the invention and as described above; (b) cook said device 100;

[0108] (d) carry out a casting step, said casting step comprising the following substeps: 11

[0109] • (dO) preheating of the shell mold 20, and

[0110] • (d1) filling the carapace mold 20 with the molten metallic material;

[0111] (e) solidify the metallic material by cooling the internal cavity 28;

[0112] (f) perform a shell removal step; and

[0113] (g) remove the kernel 33.

[0114] Step (b) of cooking the device lOO allows the carapace mold 20 to solidify.

[0115] Optionally, between optional step (b) and before step (d), the process may include a step (c) of packaging the device 100 according to the invention. This packaging prevents the molten material from cooling too rapidly, particularly during casting. This ensures a homogenized distribution of the molten material within the shell mold during casting, especially in the thinnest parts of the internal cavity 28. Such packaging may consist of a series of heat shields applied to the shell mold.

[0116] During step (f) of shell demolding, the shell mold 20 is removed so as to demold the blade 8.

[0117] At step (g), the removal of the core 33 can be done by chemical treatment of the blade 8, for example by dissolution in a soda bath.

[0118] Optionally, after step (g), the process may include a step (h) of machining and / or drilling the blade 8.

Claims

DEMANDS 1. Device (100) for manufacturing by lost-wax casting at least one hollow turbine blade (8) of a turbomachine (1), said device (100) comprising: - at least one shell mold (20) comprising an internal cavity (28) extending along a longitudinal axis (A) and intended to receive molten metallic material, the internal cavity (28) comprising a central section (23) extending along said axis (A) between a first longitudinal end (21) having a first internal surface (S1) having a plurality of first contact portions (27), and a second longitudinal end (22) axially opposite to the first longitudinal end (21) and comprising a second internal surface (S2) having a plurality of second contact portions (29), and - a core (33) arranged in the internal cavity (28) and comprising a body (38) extending along the longitudinal axis (A) and between a first transverse platform (36) and a second transverse platform (37), the first transverse platform (36) being in contact in at least two first contact zones (25) with said first contact portions (27) of the first internal surface (S1), and the second transverse platform (37) being in contact in at least two second contact zones (26) with said second contact portions (29) of the second internal surface (S2), the at least two first contact zones (25) being located on either side of said longitudinal axis (A) or distributed around said longitudinal axis (A) and separated from each other by a first distance (H1), and said at least two first contact portions (27) being inclined at a first angle (a) with respect to a transverse axis (A”) perpendicular to the longitudinal axis (A) and converging towards each other and towards the longitudinal axis (A) in the direction of the second transverse platform (37), the at least two second contact zones (26) being located on either side of said longitudinal axis (A) or distributed around said longitudinal axis (A) and separated from each other by a second distance (H2), and said at least two second contact portions (29) being inclined at a second angle (P) with respect to the transverse axis (A”) and converging towards each other and towards the longitudinal axis (A) in the direction of the first transverse platform (36), the second contact zones (26) being located at a third distance (L1), measured along the longitudinal axis (A), from the first contact zones (25), and the first and second angles (a) and (0) being such that: 0.9 x arctan (L1 / H1) < a < 1.1 x arctan (L1 / H1) and 0.9 x arctan (L1 / H2) < p < 1.1 x arctan (L1 / H2).

2. Device (100) according to claim 1, wherein the first contact zones (25) and / or the second contact zones (26) are discrete and in the form of contact points.

3. Device (100) according to claim 1, wherein the first contact zones (25) and / or the second contact zones (26) are continuous and in the form of contact lines.

4. A device (100) according to any one of claims, wherein the first transverse platform (36) is in contact at four initial contact zones (25) with the initial contact portions (27) of the first internal surface (S1), and the second transverse platform (37) is in contact at four subsequent contact zones (26) with the subsequent contact portions (29) of the second internal surface (S2).

5. A device (100) according to any one of the preceding claims, wherein the initial contact portions (27) and / or the subsequent contact portions (29) are substantially concave.

6. Device (100) according to any one of the preceding claims, wherein the first contact portions (27) and / or the second contact portions (29) are substantially flat.

7. Device (100) according to any one of the preceding claims, wherein the central section (23) has a first internal width (H3), measured along the transverse axis (A”), which is such that H1 / 1.5 < H3 < H1 / 1.2 and / or H2 / 1.5 < H3 < H2 / 1.2, preferably such that H1 / 1.5 < H3 < H1 / 1.25 and / or H2 / 1.5 < H3 < H2 / 1.25, even more preferably such that: H1 / 1.2 < H3 < H1 / 1.03 and / or H2 / 1.2 < H3 < H2 / 1.

03.

8. Device (100) according to any one of the preceding claims, wherein: - the first transverse platform (36) comprises a first polygonal base (54) extending in a plane substantially orthogonal to the axis (A), and first lateral faces (56) of generally triangular shape, a first vertex (57) of which is in contact in at least a first contact zone (25) with a first contact portion (27) of the first internal surface (S1), and - the second transverse platform (37) includes a second polygonal base (55) extending in a plane substantially orthogonal to the axis (A), and second lateral faces (58) of general triangular shape of which a second vertex (59) is in contact in at least a second contact zone (26) with a second contact portion (29) of the second internal surface (S2).

9. Device (100) according to claim 8, wherein the first base (54) and / or the second base (56) is / are quadrilateral(s).

10. Method for manufacturing a hollow blade (8) for a turbomachine (1), said method comprising the following steps: (a) provide a device (100) according to any one of claims 1 to 9; (b) cooking of said device (100); (d) carry out a casting step, said casting step comprising the following substeps: • (dO) preheating of the shell mold (20), and • (d1) filling the shell mold (20) with the molten metallic material; (e) solidify the metallic material by cooling the internal cavity (28); (f) perform a shell removal step; and (g) remove the core (33).

11. Hollow blade (8) for turbomachine (1) capable of being obtained by the process according to claim 10.

12. Aircraft turbomachine (1) equipped with at least one hollow blade (8) according to claim 11.

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