Device for stamping acoustic structures

Abstract

The invention relates to a stamping tool (500) for producing an acoustic component, the tool comprising a first part and a second part, the first part (100) having a moulding surface (130) including a plurality of cavities (150) and a punch housing suitable for accommodating the punch (240) of the second part; the second part (200) having a moulding surface (230) forming a plurality of projections, each projection further comprising, at the end thereof, a punch (240) complementary to the punch housing; the stamping tool being characterised in that the punch has a length (Lp) greater than or equal to the length of the projections (Lc), and in that the spacing (l1) between the punch and the punch housing is smaller than the spacing (l2) between the moulding surface of the first part and the moulding surface of the second part.

Description

Description Title of the invention: Device for stamping acoustic structures Technical Field

[0001] The present invention relates to the general field of acoustic attenuation structures or panels. More particularly, it concerns acoustic attenuation structures used to reduce noise produced in aircraft engines, such as gas turbines or exhaust systems. Previous technique

[0002] Acoustic attenuation structures typically consist of a plate or skin with an acoustic surface permeable to the sound waves to be attenuated, and a solid, reflective plate or skin known as a "closing plate." A cellular body, such as a honeycomb or porous structure, is placed between these two surfaces. As is well known, such panels form Helmholtz resonators, which attenuate sound waves within a specific frequency range. Acoustic attenuation structures of this type are described in US patent 5,912,442 and GB patent 2,314,526.

[0003] These acoustic attenuation structures are limited to simple cell shapes, such as the honeycomb structure of a classic NIDA® design. With this technology, the frequency treated is approximately one-quarter of the inverse of the cavity height. Therefore, treating low frequencies requires very tall cavities, which, in the case of propulsion systems, significantly increase drag. Furthermore, the acoustic performance achieved is limited to the absorption of a specific, but restricted, frequency.

[0004] One solution for adding other frequencies to the acoustic attenuation is to superimpose two cell bodies with different shapes and cell sizes. This solution has the disadvantage of significantly increasing the size and drag of the acoustic attenuation structure.

[0005] A known solution for lowering the attenuated frequency without increasing the size of the attenuation structure is to place open truncated cones in recesses as described in documents EP 0 738 865 and FR 3 082 987. While this solution reduces the size of the acoustic attenuation structure, the However, the mass of the structure remains significant and, consequently, a disadvantage for uses in aircraft where control of the overall mass is always sought.

[0006] The increasing use of such acoustic attenuation structures makes any potential improvement to their manufacturing processes commercially interesting. Description of the invention

[0007] The invention aims specifically to propose an improvement in the manufacturing processes of acoustic attenuation structures.

[0008] According to one of its aspects, it concerns a stamping tool for manufacturing an acoustic component comprising a plurality of hollow complex acoustic elements, each having a shape that gradually narrows between a base and a top, the hollow complex acoustic elements being connected to each other by one or more adjacent edges, the tool comprising a first part and a second part in relative motion with respect to each other between an open position of the tool in which it is possible to place a flat polymeric film of precursor material of the acoustic elements between the first and second parts, and a closed position of the tool in which a plurality of molding cavities in the shape of the elements to be obtained are formed between the first and second parts,The first part having a molding surface forming a plurality of cavities, each having a shape corresponding to the external surface of the hollow complex acoustic elements of the acoustic component to be manufactured, the first part further forming, in the extension of each cavity, a punch housing; the second part having a molding surface forming a plurality of protrusions corresponding to the shape of the internal surface of the hollow complex acoustic elements of the acoustic component to be manufactured, each protrusion further comprising, at its end, a punch, complementary to the punch housing; the stamping tooling being characterized in that the punch has a length greater than or equal to the length of the protrusions, and in that the spacing between the punch and the punch housing is smaller than the spacing between the molding surface of the first part and the molding surface of the second part.

[0009] It is understood that the spacing between two surfaces is measured as the smallest distance between said surfaces. For example, between two parallel surfaces, the spacing will be the distance measured between the two surfaces in the direction perpendicular to said surfaces.

[0010] The length of the punch is understood here as its extension in the main direction of extension of the tooling, for example along the vertical direction.

[0011] In one embodiment, the principal extension direction of the tooling can be determined as the direction normal to the plane in which the polymer film in precursor material of the complex hollow acoustic elements is arranged.

[0012] When a polymer film is placed between the first and second parts of a stamping tool, and the tool is gradually closed, the polymer film gradually adopts the shape of the remaining cavity between the first and second parts, which is increasingly constrained as the tool closes, until the desired shape is reached for a complete closure of the tool.

[0013] However, the relative length of the punch in relation to the length of the protrusion particularly chosen for the tooling of the invention ensures that the punch prevents the precursor material of the acoustic elements from entering the punch housing, the latter being already occupied by the punch when the precursor material of the acoustic element fills the whole of the cavity.

[0014] Indeed, thanks to the relative lengths of the punch and the protrusion, the punch reaches the punch housing before the polymeric film, and since the spacing between these two elements is smaller than that of the molding cavity, the punch prevents the polymeric film from entering the punch housing.

[0015] Thus, the tooling according to the invention prevents any deposit of precursor material for the acoustic elements in the punch housing. On the one hand, less material is lost, because all the precursor material for the acoustic elements is forced to remain in the molding cavity.

[0016] On the other hand, since the precursor material of the acoustic elements does not reach the punch housing, the tooling according to the invention can be immediately reused without requiring cleaning of the punch housing.

[0017] This leads to a shaping tool that ensures that all the material introduced contributes to the formation of the desired part and that requires significantly less cleaning compared to prior art tools.

[0018] Furthermore, the stamping tooling described makes it possible to obtain, through the punches and their housings, complex acoustic elements directly emerging at the end of the stamping process, without needing to machine them before or after their shaping.

[0019] In one embodiment, the length of the punch can be between one and two times the length of the protrusion.

[0020] These length ratios ensure that the punch's footprint is as small as possible but sufficient to ensure that the punch effectively prevents the polymeric film from accessing the punch housing well before the polymeric film actually reaches the end of the molding cavity.

[0021] The acoustic element is said to be "hollow" in the sense that a cavity runs through it from one side to the other.

[0022] In one embodiment, the shape of the molding cavity comprises a first portion and a second portion, the first portion having a greater narrowing than the second portion.

[0023] This geometry is indeed particularly suitable for the intended use, which concerns turbomachinery.

[0024] In one embodiment, the second portion has a narrowing of between 1° and 5°, relative to the extension direction of the acoustic component.

[0025] Such a narrowing makes it possible to avoid having a very small narrowing while avoiding having to overcome very high friction when opening the stamping tooling if the narrowing was less than 1°.

[0026] In other words, the shape of the molding cavity may include a first portion called "funnel", which has a narrowing between the beginning of the first portion and the beginning of the second portion, and the second portion called "chimney" which has a very slight narrowing.

[0027] The term "narrowing" here refers to a narrowing of the mold cavity section in a direction perpendicular to the main axis of the protrusions of the second part.

[0028] In one embodiment, the hollow complex acoustic elements are axisymmetric in the sense that there exists an axis for which any projection of the element into a plane perpendicular to the axis admits the projection of the axis into that plane as the center of symmetry.

[0029] In this respect, axisymmetry should not be reduced to revolution symmetry alone, but includes the latter.

[0030] For example, complex hollow acoustic elements can be truncated cones, cylinders, truncated square-based pyramids, or truncated hexagonal-based pyramids. Alternatively, hollow acoustic elements can comprise a first portion with a shape chosen from those mentioned above and a second portion extending from this first portion.

[0031] In one embodiment, the first and / or second part of the stamping tooling includes means for heating and / or cooling at least their molding surfaces.

[0032] These heating and / or cooling methods allow for precise adjustment of temperature conditions during the operation of the stamping tooling, so that the properties of the materials used for manufacturing the acoustic component, and in particular its viscosity, can be adapted to the stresses experienced by the stamping tooling.

[0033] In one embodiment, in a closed position of the tooling, the spacing between the molding surface of the first part and the molding surface of the second part is between 0.1 mm and 0.6 mm.

[0034] The spacing between the molding surface of the first part and the molding surface of the second part precisely defines the thickness of the acoustic elements of the component.

[0035] The particular choice of this thickness, and therefore of the spacing between the molding surface of the first part and the molding surface of the second part in the closed position, is a compromise between obtaining a robust and lightweight acoustic component.

[0036] In particular, it is understood that the thickness of the component must allow excellent mechanical fatigue resistance, adequate vibration behavior, as well as good reproducibility and reliability of the process.

[0037] In one embodiment, in a closed position, the spacing between the punch and the punch housing is less than or equal to 0.1 mm or even less than or equal to 50 pm.

[0038] This embodiment ensures that, in the closed position, the base material used for manufacturing the hollow complex acoustic element cannot become lodged in the punch housing.

[0039] In particular, such spacing is sufficient to prevent the base material used for manufacturing the complex hollow acoustic element from accessing the punch housing when that material is worked in a viscous or molten state.

[0040] In one embodiment, the punch and / or the punch housing includes at least one air communication that can be made to communicate fluidically with the outside of the stamping tooling.

[0041] This embodiment simplifies the opening of the stamping tooling by avoiding a suction effect of the hollow complex acoustic element on the first and / or second part of the stamping tooling.

[0042] Such a suction effect could lead to degradation of the complex hollow acoustic element at the time of demolding.

[0043] In one embodiment, the first part of the stamping tooling can be formed of two parts, the first part comprising the external surfaces defining the molding cavity and the second part comprising the external surfaces defining the punch housing.

[0044] Thus, the first part of the stamping tooling is formed by stacking the first and second parts. For example, the first and second parts include registration marks to ensure they are correctly positioned relative to each other.

[0045] In this embodiment, it is possible to modify one part of one tooling section without modifying the other. This embodiment is advantageous because it allows the desired thickness of the acoustic element to be adjusted by modifying only the first part of the first section, without having to modify either the second part of the first section or the second section itself.

[0046] Furthermore, such an embodiment ensures that, even if the precursor material of the acoustic elements were to be deposited in the punch housing, the tooling would be much simpler to clean than prior art tooling.

[0047] In an embodiment where the first part comprises two parts, communication channels can be provided at the junction of the first part and the second part of the first part of the tooling.

[0048] In one embodiment, one and / or the other of the external surfaces of the first and second parts may be coated with a hardening agent.

[0049] For example, a hardening agent could be a chrome coating available under the trade name BALINIT® CROMA PLUS. This improves the service life of the stamping element.

[0050] According to another aspect, the invention also relates to a method for stamping an acoustic component comprising a plurality of hollow complex acoustic elements, each having a shape that gradually narrows between a base and a vertex, the hollow complex acoustic elements being connected to each other by one or more adjacent edges, the method comprising: - the positioning of a preform made of thermoplastic material between the first and second part of a stamping tool as described above, the tool being in the open position; - shaping the preform in thermoplastic material by closing the tooling.

[0051] In such a manufacturing process, the tooling alone ensures that the formed acoustic element is directly usable without requiring further machining, and this with a wide range of possible materials for the acoustic element and independently of the closing speed of the tooling.

[0052] In one embodiment, the preform can be a film of thermoplastic material comprising openings, which are positioned opposite the punches of the second part of the tooling.

[0053] In one embodiment, the thermoplastic material of the preform may comprise a compound selected from polyaryletherketones (PAEKs) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyetherimides (PEI), polycarbonate (PC), polyphenylene sulfide (PPS), polysulfones (PSU) or a mixture of two or more of these compounds.

[0054] For the purposes of the invention, it should be understood that a mixture of these compounds can also mean a compound comprising several distinct layers, each comprising a unique compound from the preceding list.

[0055] In one embodiment, the process may include at least one step of heating one and / or the other of the molding surfaces of the first and second parts.

[0056] In one embodiment, a heating step is performed during the closing of the stamping tool. For example, such a step can be carried out at a temperature above the glass transition temperature of the polymeric material.

[0057] Heating the external surfaces of the stamping tooling during its closure facilitates the deformation of the thermoplastic material, so that it perfectly conforms to the external surfaces of the first and second parts of the stamping tooling during the stamping of the preform.

[0058] In one embodiment, the process may or may not include a heating step to aid in demolding the acoustic component. For example, such a step may be carried out at a temperature below the glass transition temperature.

[0059] According to another aspect, the invention relates to a method for manufacturing a sound attenuation structure comprising the following steps: - the production of an acoustic component according to the process described above; - the production of a complex multi-element acoustic panel comprising the acoustic component and a plurality of partitions forming acoustic cavities, each complex acoustic element of the acoustic component being housed in an acoustic cavity so as to form an acoustic cell, - the assembly of one face of the complex multi-element acoustic panel with an assembly face of an acoustic skin.

[0060] Such a manufacturing process makes it possible to produce acoustic attenuation structures more quickly than prior art processes. Brief description of the drawings

[0061] [Fig. 1] Figure 1 schematically represents a cavity and a protrusion of a stamping tool according to an embodiment presented in an open position.

[0062] [Fig. 2] Figure 2 schematically represents a cavity and a protrusion of a stamping tool according to an embodiment presented in an intermediate position between open and closed.

[0063] [Fig. 3] Figure 3 schematically represents a cavity and a protrusion of a stamping tool according to an embodiment shown in a closed position.

[0064] [Fig. 4] Figure 4 schematically represents a complex hollow acoustic element.

[0065] [Fig. 5] Figure 5 schematically represents a polymeric film that can be introduced into a stamping tool in one embodiment of a process of the invention.

[0066] [Fig. 6] Figure 6 schematically represents a stamping tool in an open position in one embodiment.

[0067] [Fig. 7] Figure 7 schematically shows a stamping tool in a closed position in one embodiment.

[0068] [Fig. 8] Figure 8 schematically represents an acoustic attenuation structure in one embodiment. Description of the implementation methods

[0069] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0070] As described, the stamping tooling as a whole comprises a first part and a second part which include several molding cavities and respectively several protrusions, complementary to the molding cavities.

[0071] Preferably, the complex hollow acoustic elements of an acoustic component are identical, and the molding cavities and protrusions are therefore identical.

[0072] For simplicity, Figure 1 describes only one of these cavities 150 and a single protrusion 250, allowing the formation of a complex hollow acoustic element.

[0073] Figure 1 thus represents a first part 100 and a second part 200.

[0074] The first part 100 includes two shoulders 110 and 120 intended to remain opposite two shoulders 210 and 220 of the second part 200 in a tooling closure position.

[0075] In the closed position, which will be described in more detail with figure 3, the shoulders 110, 120 of the first part are not in contact with the second part, but remain distant from the latter by a distance equal to the desired thickness for the acoustic elements, more precisely the thickness of the connecting portions between an acoustic element and its neighbors.

[0076] In one embodiment, the tooling includes a stop at the edge of the tooling and not shown, which ensures that the closing position cannot be exceeded.

[0077] The first part 100 includes a molding surface 130 defining a cavity 150.

[0078] The second part 200 includes a molding surface 230 defining a protrusion 250.

[0079] The cavity 150 and the protrusion 250 are made in such a way that the space left vacant between the molding surface 130 of the first piece and the molding space 230 of the second piece in a closed position corresponds to the molding cavity, having the desired shape for the hollow complex acoustic element, as will be more visible in Figure 3.

[0080] In the embodiment shown, the molding surface 130 of the first part 100 can include a first portion 130a narrowing from the base to the top, and then a second part 130b whose section narrows less or does not narrow.

[0081] This shape of the molding cavity makes it possible to form a complex hollow acoustic element 400 having a portion of cone 430a and a portion of chimney 430b, which will be described in relation to figure 4.

[0082] For example, the first portion 130a of the molding surface 130 may have an angle with the main extension dimension of the tooling between 45° and 80°.

[0083] This embodiment allows for the selection of cones of varying widths depending on the desired size for the acoustic cells and for obtaining the desired length for acoustic cells, which is a function of the frequencies that one wishes to attenuate.

[0084] In one embodiment, the second portion 130b of the molding surface 130 may have an angle with the main extension dimension of the tooling between 0° and 5°.

[0085] Preferably, the angle is between 1° and 5°. Indeed, such an angle makes it easier to open the tool by reducing the friction that exists for a second portion which would have an angle of 0°.

[0086] In the tooling described, the cavity 150 is extended by a punch housing 140.

[0087] In other words, the punch housing 140 is an extension of the cavity 150, but it does not form a molded face of it. It represents an area that will not be reached by the material constituting the hollow acoustic element.

[0088] In one embodiment, which is that shown in Figure 1, the second portion of the molding surface 130b may have a shoulder 160 before the punch housing 140.

[0089] This shoulder allows for optimal control of the spacing h present between the punch 240 and the punch housing 140 in a closed position of the tooling.

[0090] The second part 200 includes a protrusion 250 whose molding surface 230 is complementary to the molding surface 130 in order to form the complex hollow acoustic element.

[0091] As described, the protuberance 250 is extended by a punch 240 at its free end, that is to say at the end furthest from the shoulders 210, 220.

[0092] The protrusion 250 includes a molding surface 230 which may include a first portion 230a and a second portion 230b, these molding surfaces being arranged opposite the first 130a and second 130b portions of the molding surface of the first part 100.

[0093] Figure 1 also represents the length L p of the punch 240 and the length L c of the protuberance 250.

[0094] The portion of punch 240 is delimited for the diagram by dotted lines, which are only intended to facilitate understanding, and which are not associated with a physical delimitation between the molding surface 230 and the punch 240.

[0095] Similarly, the length of the protuberance L cis understood as being counted from the portion at the right of the shoulders 210 of the second piece 200.

[0096] Figure 1 illustrates the direction in which the length of the punch or protrusion is understood, namely the direction of extension of punch 240, i.e. in the figure the vertical direction.

[0097] In one embodiment, it is possible that the tooling opens more than its opening position shown in Figure 1, in particular to facilitate the placement of the polymeric film between the first and second part of the tooling, as can be seen in Figure 6.

[0098] Figure 2 represents the same part of the tooling as in Figure 1 but in an intermediate position.

[0099] Figure 2 illustrates the advantage of the invention of the feature according to which the length of the protrusion L cis greater than or equal to, and in this case equal to, the length of the punch L p .

[0100] Indeed, this embodiment ensures, for the purposes of the invention, that the punch 240 reaches the punch housing 140 before the polymeric film 610 reaches it itself.

[0101] As can be seen in Figure 2, the punch 240 and more generally the protrusion 250 of the second part 200 of the tooling drives the precursor of the complex hollow acoustic elements, here the polymeric film 610.

[0102] Accordingly, in one embodiment, the polymeric film 610 can be placed in conditions improving the malleability of said polymeric film, for example by heating.

[0103] As shown in Figure 2, at the moment when the punch 240 enters the punch housing 140, the polymeric film 610, which forms the complex hollow acoustic element, has begun to take the shape of the molding cavity but has not yet reached the punch housing 140.

[0104] Figure 3 shows the tooling in its closed position.

[0105] As shown, in its closed position, the shoulders 110, 120 of the first piece 100 are at a distance from the shoulders 210, 220 which corresponds to the desired thickness for this portion of the acoustic element.

[0106] Still in the closed position, the cavity between the molding surfaces 130, 230 of the first and second piece, takes precisely the shape of the desired hollow complex acoustic element.

[0107] Moreover, in Figure 3, the entirety of this space is filled by the polymeric film 610, which has been forced by the protrusion 250 to take the shape of the cavity of molding, i.e. the space left free between the molding surfaces 130, 230 in the closed position.

[0108] In the figurative embodiment, the hollow acoustic element has a shape that narrows between the base 301 and the top 302.

[0109] Figure 3 also allows us to represent the spacing l2 between the molding surface of the first part 130 and the molding surface of the second part 230, and the spacing R between the punch 240 and the punch housing 140.

[0110] The figures are not to scale, nor even to relative scale.

[0111] The spacing l2 will define the thickness of the hollow complex acoustic element 400 obtained by the stamping tool 500.

[0112] The spacing h ensures a minimum clearance between the punch 240 and the punch housing 140 so that the material introduced into the molding cavity to form the hollow complex acoustic element cannot lodge in the punch housing.

[0113] Thus, it is understood that the shoulder 160 of the first part 100 will reduce the spacing from l2 to h so that the material 610 forming the complex hollow acoustic element cannot penetrate into the punch housing 140.

[0114] Thus, from the stamping stage, a complex hollow acoustic element with the desired shape is formed.

[0115] In an embodiment not shown, the punch 240 and / or the housing of the punch 140 include at least one air communication that can be made to communicate fluidically with the outside of the stamping tool 500.

[0116] For example, such air communication could be a vent or a removable seal. This simply ensures that the hollow, complex acoustic element is brought back to atmospheric pressure once formed in the tooling, and facilitates its removal from the 500 stamping tool.

[0117] In particular, this prevents any suction effect that could occur due to the shaping of the complex hollow acoustic element and any temperature variations during the process.

[0118] For example, and as shown in Figure 3, we can have a first part 100 which is broken down into a first part 1100 and a second part 1200 independent of each other.

[0119] This separation of the first part 100 into two pieces 1100, 1200 then makes it easy to have an air communication channel between the two, not shown.

[0120] Although this is only represented in the case of Figure 3, it should be understood that if an embodiment is chosen where the first part 100 is decomposed into a first part 1100 and a second part 1200, the whole process will be carried out in tooling including such a decomposition (and therefore such a decomposition would then make sense for Figures 1 and 2).

[0121] Furthermore, Figure 3 illustrates what is meant by the fact that the molding surface 130 of the first part 100 has a shape corresponding to the external surface of the hollow complex acoustic elements of the acoustic component to be manufactured and that the molding surface 230 of the second part 200 has a shape corresponding to the internal surface of the hollow complex acoustic elements of the acoustic component to be manufactured.

[0122] Indeed, the acoustic element is formed between these molding surfaces and its two faces therefore take on their shapes.

[0123] Figure 4 presents a hollow complex acoustic element 400 obtained in one embodiment of the invention.

[0124] The complex hollow acoustic element has a shape that gradually narrows between a base 401 and a top 402.

[0125] The complex hollow acoustic element comprises a portion of cone 430a and a portion of chimney 430b.

[0126] In one embodiment, the base 401 of the hollow complex acoustic element can be inscribed in a circle of 9.5 mm, 12.7 mm or 25.4 mm (i.e. the SI unit equivalents of 3 / 8 inch, half an inch or one inch in Anglo-Saxon units).

[0127] These dimensions correspond advantageously to the dimensions of commercially available honeycomb structures and therefore facilitate the manufacture of an acoustic structure.

[0128] In one embodiment, the inlet area of ​​the chimney portion 403b defined for optimal acoustic performance can be between 1.0 mm 2 and 25 mm 2 for example between 3.0 mm 2 and 10 mm 2 .

[0129] In one embodiment, the height of the portion of cone 430a measured in the direction from the base 401 to the apex 402 can be between 10 mm and 50 mm, or even between 15 mm and 30 mm.

[0130] In one embodiment, the height of the chimney portion 430b measured in the direction from the base 401 to the top 402 can be between 1.0 mm and 20 mm, or even between 3.0 mm and 10 mm.

[0131] In one embodiment, the dimensions of the molding surfaces 130a, 130b and the first part 100 and those 230a, 230b of the second part have similar dimensions.

[0132] These values ​​allow for optimal acoustic performance, particularly for applications in turbomachinery noise reduction.

[0133] It is understood that the numerical values ​​defined for the hollow complex acoustic element are also understood as preferred values ​​for the corresponding elements of the corresponding parts of the 500 stamping tooling described above.

[0134] Figure 4 further shows the lower end 450 of the cavity of a hollow acoustic element.

[0135] In one embodiment, which is also the one shown, the hollow complex acoustic element is axisymmetric.

[0136] Figure 5 describes a polymeric film that can be used in one embodiment of the invention.

[0137] The thermoplastic 610 film used to manufacture the acoustic component can also have a variable thickness, as illustrated in Figure 5.

[0138] More specifically, the thermoplastic material film 610 has a surface comprising through holes 450.

[0139] For example, the film may include portions of excess thickness 22, constituting a surplus of material which, once stretched or flowed into the molding cavities during the closing of the stamping tooling, will allow the formation of complex hollow acoustic elements.

[0140] The volume of material present in each portion of the extra thickness is defined according to the wall thickness of each complex acoustic element to be manufactured.

[0141] The portions of extra thickness 22 can have a circular, annular or hexagonal shape, as shown in figure 5, and be distributed evenly over the film.

[0142] In the example described here, each portion of extra thickness 22 extends between connecting portions 21 and an opening or cavity 550 present in the center of the portion of extra thickness.

[0143] In one embodiment, the opening 550 may have a diameter less than or equal to the diameter of the punch 240, as described in connection with Figure 1.

[0144] In one embodiment, the opening 550 may have a diameter greater than the diameter of the punch 240. This embodiment is preferred since it ensures that it is the first portion 230a of the molding surface 230 that presses on the film 610. This further minimizes the risk of the film 610 reaching the punch housing 140 before the punch 240 itself.

[0145] The connecting portions 21 can be intended to be arranged between the shoulders 110, 120 of the first part 100 and the shoulders 210, 220 of the second part 200.

[0146] In this way, the connecting portions 21 link the hollow acoustic elements together to form an acoustic component.

[0147] Figures 6 and 7 together illustrate a method for manufacturing an acoustic component according to an embodiment of the invention.

[0148] Figure 6 illustrates an open stamping tool 500, in a position where the first part 100 is away from the second part 200 beyond the previously defined opening position.

[0149] The first part 100 and the second part 200 are mobile relative to each other.

[0150] In the embodiment shown, the first part 100 is fixed and the second part 200 is mobile along a double direction D, but we do not depart from the scope of the invention if the first part 100 is mobile and the second 200 is fixed, or if both parts are mobile.

[0151] Figure 6 represents a tool, equipped with side clamps 641 and 642 to hold a thermoplastic material film 610 during the formation steps of an acoustic component.

[0152] The 610 thermoplastic film can also be applied to the tooling either automatically or manually. It can also be delivered via a conveyor system.

[0153] The first part 100 includes molding cavities 150 intended to cooperate with protrusions 250 of the second part 200 for the formation of the acoustic component from the thermoplastic material film 610.

[0154] The 250 molding cavities have a shape corresponding to the shape of the complex hollow acoustic elements of the acoustic component to be manufactured.

[0155] The process can begin by heating the thermoplastic 610 film to a first temperature above the glass transition or melting temperature of the thermoplastic film material.

[0156] More specifically, in the case of an amorphous thermoplastic material, the film can be heated to a temperature above the glass transition temperature of the material, while in the case of a semi-crystalline thermoplastic material, the film can be heated to a temperature above the melting temperature of the material.

[0157] This allows the thermoplastic material to have excellent deformability properties so that it can be shaped.

[0158] Heating can be achieved by means of heating known as such, and disposed in the first part 100 and the second part 200 of the stamping tooling 500.

[0159] According to one embodiment variant, the thermoplastic material film 610 can be heated to a first temperature above the glass transition or melting temperature of the thermoplastic material of the film before it is placed above the first part 100, for example by heating the side of the film in an infrared oven.

[0160] The film can be heated to the first temperature preferably after it has been placed above the first part 100 because this allows better positioning of the thermoplastic material film 610 in the stamping tooling 500.

[0161] Once this first temperature is reached by the film, the film can be shaped into thermoplastic material 610. For this purpose, the second part 200 can be moved towards the first part 100 until the protrusions 250 cooperate completely with the cavities 150 as illustrated in figure 7, i.e. until the tooling is closed.

[0162] The heated thermoplastic film can be shaped locally in each of the molding cavities, i.e. in the space left free between the molding surfaces 130, 230 of the two parts 100, 200.

[0163] During this shaping step, the first 100 and / or the second 200 part of the tooling are preferably maintained at a second temperature higher than the glass transition or melting temperature of the thermoplastic material and lower than the first temperature.

[0164] Due to the tooling properties described above, the polymeric material film 610 is deformed by stamping, particularly under the effect of the protrusions 250, but the punch 240 and the punch housing 140 ensure that it is possible to obtain a complex hollow acoustic component at the tooling output, without the need for a subsequent machining step.

[0165] In a process of the invention, the tooling as defined is sufficient to ensure that, for the materials considered at the temperatures considered, and even taking into account the effect of gravity, the punch 240 will reach the punch housing 140 before the thermoplastic material film 610 itself reaches the bottom of the cavity.

[0166] This allows the formation of complex hollow acoustic elements 400 with very thin walls, and the obtaining of complex hollow acoustic elements 400 directly drilled.

[0167] Furthermore, by maintaining the stamping tooling at a temperature above the glass transition or melting temperature of the thermoplastic material, material flow is facilitated during film stamping.

[0168] This avoids tearing the thermoplastic film, which may initially have a relatively thin thickness, for example, on the order of 1.0 mm to 2.0 mm.

[0169] Indeed, the size and shape of the punches 240 make it possible to maintain the perforation 450 present in the film in polymeric material 610 throughout the stamping process, and this without the tear propagating, in particular in the vertical direction of the thermoplastic film.

[0170] Once the thermoplastic material film 610 has been completely deformed in the cavities 150 as illustrated in Figure 7, the first 100 and / or the second 200 part of the tooling are cooled to a third temperature below the glass transition or melting temperature of the thermoplastic material, allowing said material to solidify into the shape of an acoustic component to be manufactured.

[0171] Once the temperature of the thermoforming tooling is at least 10°C lower than the glass transition or melting temperature of the thermoplastic material, the formed acoustic component can be demolded.

[0172] The inset in Figure 7, which reproduces a detail from Figure 3, illustrates this precisely: the punch 240 at the bottom of the molding cavity formed by the molding surfaces 130, 230 facing each other, prevents the thermoplastic material 610 from accessing the punch housing 140.

[0173] Thus, the punch 240 passes through the thermoplastic film 610 during the closing of the stamping tool 500 and the hollow complex acoustic element then forms around the protrusion, without being able to close.

[0174] The acoustic component is then demolded by moving one of the two parts of the tooling 100, 200 in a direction opposite to the other 200, 100 and by opening the side clamps 641, 642 in order to release the acoustic component.

[0175] In the example described here, the molding cavities have a pyramidal shape allowing the formation of complex hollow acoustic elements of the same shape.

[0176] The molding cavities and, consequently, the resulting hollow complex acoustic elements can have other shapes such as conical, spiral, funnel or hopper shape.

[0177] In one embodiment, the thermoplastic material film 610 is chosen to match the shape of the acoustic elements to be obtained.

[0178] The manufacturing process of an acoustic component has just been described with the first part 100 arranged below the second part 200 as shown in figures 6 and 7.

[0179] In one embodiment, the first part 100 can be arranged above the second part 200. This embodiment ensures that the force of gravity further prevents the polymeric material film 610 from accessing the punch housing.

[0180] A method for manufacturing a sound-attenuating structure according to an embodiment of the invention is now described with reference to Figure 8. The sound-attenuating structure 1000 comprises an acoustic skin or plate 1110, an acoustic component 1120 manufactured as described previously, a plurality of partitions 1131, and a closing skin or plate 1140.

[0181] The closing skin 1140 corresponds to a solid surface designed to reflect sound waves entering the acoustic attenuation structure. The closing skin 1140 can be a component of the acoustic attenuation structure 1000, as in the example described here, or it can be part of the structure of an object, for example, an aircraft engine. In the latter case, the acoustic attenuation structure 1000 of the invention does not have a closing skin and can be mounted directly onto the structure of the object.

[0182] The acoustic skin 1110 has the function of allowing the sound waves to be attenuated to pass through inside the acoustic attenuation structure 1000. For this purpose and in the example described here, the acoustic skin 1110 comprises a plurality of perforations 1111.

[0183] The acoustic component 1120 is formed in a single piece and extends lengthwise and widthwise along a horizontal direction D H and vertically along a direction D v The acoustic component comprises a plurality of complex hollow acoustic elements 1121 each having a shape that gradually narrows between a base 1122 and a top 1123.

[0184] In the example described here, the complex acoustic elements 1121 have a pyramidal shape. The base 1122 of each hollow complex acoustic element 1121 is in continuous contact with the base of the adjacent complex acoustic elements so as to form a continuous network of edges 1124.

[0185] In another embodiment, the acoustic elements can be 400 cones conforming to the embodiment described above, in connection with figure 3.

[0186] In the embodiment described here, the plurality of partitions 1131 is made in one piece, namely a network of ribs 1130 which, once assembled with the hollow complex acoustic multi-element panel 1120, forms the partitions around the hollow complex acoustic elements 1121.

[0187] Alternatively, and particularly when the hollow complex acoustic elements 1121 are of the form shown in Figure 3, the rib network 1130 can be a honeycomb tiling, i.e. with partitions 1131 forming a network of hexagonal cavities rather than square, as shown here.

[0188] Continuing with the example described here, the acoustic attenuation structure 1000 is made by assembling the hollow complex acoustic multi-element panel 1120 with the plurality of partitions 1131 in a single piece, the upper edge of the partitions 1131 being fixed, for example by gluing or welding, to the lower portion of the bases 1122 of the complex hollow acoustic elements 1121. The plurality of complex hollow acoustic elements being formed in one piece within the complex hollow acoustic multi-element panel and the plurality of partitions also being formed in one piece, the assembly between these two elements is greatly facilitated by the self-positioning of the complex hollow acoustic elements 1121 with the partitions 1131.

[0189] The closing skin 1140 is fixed, for example by gluing or welding, to the lower edge of the partitions 1131, while the acoustic skin 1110 is fixed, by gluing or welding, to the upper portion of the bases 1122 of the hollow complex acoustic elements 1121 corresponding to the exposed surface of the edges 1124. Thus, the acoustic skin and the closing skin are each fixed to a perfectly flat support along the horizontal direction D H This ensures a very good seal between the skins and the assembly of the complex multi-element acoustic panel with the plurality of partitions.

[0190] Once assembled, the attenuation structure 1000 comprises a plurality of acoustic cells each formed by a hollow complex acoustic element 1121 and the partitions 1131 that surround it.

[0191] The acoustic skin, the plurality of partitions and the closing skin can be made by injection of a thermoplastic or thermosetting material, filled or unfilled, by injection-compression of a thermoplastic or thermosetting material, filled or unfilled, or by injection with temperature control of the tooling of a thermoplastic or thermosetting material, filled or unfilled.

[0192] The plurality of partitions, acoustic and closing skins, as well as assemblies combining in a single piece the plurality of partitions and the complex multi-element acoustic panel or the plurality of partitions and one of the skins, can also be made by injection of a thermoplastic or thermosetting material, filled or unfilled.

Claims

Claims

1. Stamping tool (500) for manufacturing an acoustic component (1120) comprising a plurality of hollow complex acoustic elements (400) each having a shape gradually narrowing between a base (401) and a top (402), the hollow complex acoustic elements being connected to each other by one or more adjacent edges, the tool comprising a first part (100) and a second part (200) in relative movement with respect to each other between an open position of the tool in which it is possible to arrange a flat polymeric film made of precursor material of the acoustic elements between the first and the second part, and a closed position of the tool, in which a plurality of molding cavities in the shape of the elements to be obtained are formed between the first and the second part,the first part (100) having a molding surface (130) forming a plurality of cavities (150) each having a shape corresponding to the external surface of the hollow complex acoustic elements of the acoustic component to be manufactured, the first part further forming, in the extension of each cavity, a punch housing (140); the second part (200) having a molding surface (230) forming a plurality of protuberances corresponding to the shape of the internal surface of the hollow complex acoustic elements of the acoustic component to be manufactured, each protuberance further comprising and at the end thereof a punch (240), complementary to the punch housing; the stamping tool being characterized in that the punch has a length (L, p ) greater than or equal to the length of the protrusions (L c), and in that the spacing (h) between the punch and the punch housing is smaller than the spacing (l2) between the molding surface of the first part and the molding surface of the second part.

2. The stamping tool (500) of claim 1, wherein the shape of the molding cavity (150) comprises a first portion (130a) and a second portion (130b), the first portion having a greater narrowing than that of the second portion.

3. Stamping tool (500) according to claim 2, wherein the second portion (230b) has a narrowing of between 1° and 5°, relative to the direction of extension of the acoustic component.

4. Stamping tool (500) according to any one of claims 1 to 3, wherein the first (100) and / or the second part (200) comprise means for heating and / or cooling at least their molding surfaces (130, 230).

5. Stamping tool (500) according to any one of claims 1 to 4, wherein, in the closed position, the spacing (l2) between the molding surface of the first part (130) and the molding surface of the second part (230) is between 0.1 mm and 0.6 mm.

6. Stamping tool (500) according to any one of claims 1 to 5, wherein, in the closed position, the spacing (I) between the punch (240) and the punch housing (140) is less than or equal to 50 μm.

7. The stamping tool (500) of any one of claims 1 to 6, wherein the punch (240) and / or the punch housing (140) comprise at least one air communication capable of being fluidly connected to the exterior of the stamping tool.

8. A stamping tool (500) according to any one of claims 1 to 7, wherein the first part (100) of the tooling is formed of two pieces (1100, 1200), the first piece (1100) comprising the external surfaces defining the molding cavity (130a, 130b) and the second piece (1200) comprising the external surfaces defining the punch housing (140).

9. Stamping tooling according to claim 8, wherein communication channels are provided at the junction of the first part (1100) and the second part (1200) of the first part of the tooling (100).

10. A method of stamping an acoustic component (1120) comprising a plurality of hollow complex acoustic elements (400) each having a shape gradually tapering between a base (401) and a top (402), the hollow complex acoustic elements being connected to each other by one or more adjacent edges, the method comprising: - positioning a preform made of thermoplastic material (610) between the first (200) and the second (100) part of a stamping tool (500) according to any one of claims 1 to 9, the tool being in the open position; - shaping the preform made of thermoplastic material by closing the tool.

11. Method for manufacturing an acoustic attenuation structure (1000) comprising the following steps: - producing an acoustic component (1120) according to the method of claim 10; - the production of a hollow complex acoustic multi-element panel comprising the acoustic component and a plurality of partitions forming acoustic cavities, each complex acoustic element of the acoustic component being housed in an acoustic cavity so as to form an acoustic cell, - the assembly of one face of the complex acoustic multi-element panel with an assembly face of an acoustic skin (1110).

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