Device for stamping acoustic structures

Abstract

Device for stamping acoustic structures Stamping tool (500) for manufacturing an acoustic component, the tool comprising a first part and a second part, the first part (100) having a molding surface (130) comprising a plurality of cavities (150) and a punch housing capable of receiving the punch (240) of the second part; the second part (200) having a molding surface (230) forming a plurality of protuberances, 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 (Lp) greater than or equal to the length of the protuberances (Lc), and in that the spacing (l1) 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. Figure for abstract: Fig. 2.

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. It relates more particularly to acoustic attenuation structures used to reduce noise produced in aircraft engines such as in gas turbines or their exhausts. Prior art

[0002] Acoustic attenuation structures are typically made up of an acoustic surface plate or skin permeable to the acoustic waves that are to be attenuated and a reflective solid plate or skin called a "closing plate", a cellular body, such as a honeycomb or a porous structure, being arranged between these two walls. In a well-known manner, such panels form Helmholtz-type resonators which make it possible to attenuate the acoustic waves in a certain frequency range. Acoustic attenuation structures of this type are described in particular in documents US 5,912,442 and GB 2,314,526.

[0003] These acoustic attenuation structures are limited to simple cell shapes such as those of the cells of a conventional NID A® type structure. With this technology, the frequency processed is of the order of a quarter of the inverse of the cavity height. To process low frequencies, very high cavities are therefore required which, in the case of propulsion systems, considerably increase their drag. In addition, the acoustic performances obtained are 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 having different cell shapes and dimensions. 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 consists of placing open truncated cones in cells as described in documents EP 0 738 865 and FR 3 082 987. If this solution makes it possible to reduce the size of the acoustic attenuation structure, the mass of the structure nevertheless remains significant and, consequently, penalizing for uses in aircraft where control of the overall mass is always sought.

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

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

[0008] For this, it relates, according to a first of its aspects, to 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 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 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 and at the end thereof a punch, complementary to the punch housing; the stamping tool 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 surfaces parallel to each other, 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 tool, for example in the vertical direction.

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

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

[0013] However, the relative length of the punch compared to the length of the protuberance particularly chosen for the tooling of the invention ensures that the punch prevents the precursor material of the acoustic elements from penetrating into the punch housing, the latter already being occupied by the punch when the precursor material of the acoustic element fills the entire cavity.

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

[0015] Thus, the tooling according to the invention makes it possible to avoid any deposition of precursor material of the acoustic elements in the punch housing. On the one hand, less material is thus lost, because all the precursor material of the acoustic elements is forced to remain in the molding cavity.

[0016] Furthermore, 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 results in a shaping tool which, on the one hand, ensures that all the material introduced contributes to the formation of the desired part and, on the other hand, the need for cleaning is greatly reduced compared to the tools of the prior art.

[0018] Furthermore, the stamping tool described makes it possible to obtain, thanks to 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 may be between one and two times the length of the protrusion.

[0020] These length ratios ensure that the punch is as compact as possible but sufficient so that the punch effectively prevents the polymer film from accessing the punch housing well before the polymer film has actually reached the end of the molding cavity.

[0021] The acoustic element is said to be “hollow” in the sense that a cavity passes through it from side to side.

[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 in fact particularly suitable for the desired use which concerns turbomachines.

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

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

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

[0027] The narrowing is understood here as a narrowing of the section of the molding cavity 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 in a plane perpendicular to the axis admits the projection of the axis in this plane as a center of symmetry.

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

[0030] For example, the hollow complex acoustic elements may be truncated cones, cylinders, truncated square-based pyramids, truncated hexagonal-based pyramids. Alternatively, the hollow acoustic elements may comprise a first portion having a shape chosen from those mentioned above and a second portion in the extension of the latter.

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

[0032] These heating and / or cooling means make it possible to precisely adapt the temperature conditions during operation of the stamping tool, 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 tool.

[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 resistance to fatigue, adequate vibration behavior as well as good reproducibility and good 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 μm.

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

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

[0040] In one embodiment, the punch and / or the punch housing comprises at least one air communication capable of being fluidly connected to the exterior of the stamping tool.

[0041] This embodiment makes it possible to simplify the opening of the stamping tool by avoiding a suction effect of the hollow complex acoustic element on the first and / or second part of the stamping tool.

[0042] Such a suction effect could lead to degradation of the hollow complex acoustic element when it is demolded.

[0043] In one embodiment, the first portion of the stamping tooling may be formed of two pieces, the first piece comprising the outer surfaces defining the mold cavity and the second piece comprising the outer surfaces defining the punch housing.

[0044] In this way, the first part of the stamping tool is formed by stacking the first and second parts. For example, the first and second parts include reference elements to ensure that they are correctly positioned relative to each other.

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

[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 may 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 hardness-enhancing agent.

[0049] For example, a hardness enhancing agent may 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 of its aspects, the invention also relates to a method of stamping an acoustic component comprising a plurality of hollow complex acoustic elements each having a shape gradually narrowing between a base and a top, 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 between the first and second parts of a stamping tool as described above, the tool being in the open position; - shaping the preform in thermoplastic material by closing the tool.

[0051] In such a manufacturing method, the tooling alone ensures that the formed acoustic element is directly usable without requiring subsequent 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 may 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 (PAEK) 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 single compound from the preceding list.

[0055] In one embodiment, the method may comprise 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 may be performed at a temperature above the glass transition temperature of the polymeric material.

[0057] Heating the external surfaces of the stamping tool during closing thereof facilitates the deformation of the thermoplastic material, so that it perfectly matches the external surfaces of the first and second parts of the stamping tool during stamping of the preform.

[0058] In one embodiment, the method may independently or not include a heating step to assist in demolding the acoustic component. For example, such a step may be performed at a temperature below the glass transition temperature.

[0059] According to another of its aspects, the invention relates to a method of manufacturing an acoustic attenuation structure comprising the following steps: - the production of an acoustic component according to the process described above; - the production of a 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.

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

[0061] [Fig-1] [Fig.l] schematically represents a cavity and a protuberance of a stamping tool according to an embodiment shown in an open position.

[0062] [Fig.2] [Fig.2] schematically represents a cavity and a protuberance of a stamping tool according to an embodiment presented in an intermediate position between opening and closing.

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

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

[0065] [Fig.5] [Fig.5] schematically represents a polymeric film which can be introduced into a stamping tool in an embodiment of a method of the invention.

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

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

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

[0069] The invention is now described by means of figures, present 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 comprise several molding cavities and respectively several protrusions, complementary to the molding cavities.

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

[0072] For simplicity, [Fig.l] describes only one of these cavities 150 and a single protuberance 250, making it possible to form a hollow complex acoustic element.

[0073] [Fig.l] thus represents a first part 100 and a second part 200.

[0074] The first part 100 comprises two shoulders 110 and 120 intended to remain opposite two shoulders 210 and 220 of the second part 200 in a position for closing the tool.

[0075] In the closed position, which will be described in more detail with [Fig. 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 comprises a stop at the edge of the tooling and not shown, which ensures that the closed position cannot be exceeded.

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

[0078] The second portion 200 comprises 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 part and the molding space 230 of the second part 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 [Fig.3].

[0080] In the embodiment shown, the molding surface 130 of the first part 100 may comprise a first portion 130a narrowing from the base towards the top, then a second part 130b whose section narrows less or even does not narrow at all.

[0081] This shape of the molding cavity makes it possible to form a hollow complex acoustic element 400 having a cone portion 430a and a chimney portion 430b, which will be described in connection with [Fig.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 of between 45° and 80°.

[0083] This embodiment makes it possible to choose more or less narrow cones depending on the desired size for the acoustic cells and to obtain the desired length for the 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 of 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 constitute a molding face thereof. It represents an area which will not be reached by the material constituting the hollow acoustic element.

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

[0089] This shoulder makes it possible to better control the spacing 11 present between the punch 240 and the punch housing 140 in a closed position of the tool.

[0090] The second part 200 comprises 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 protrusion 250 is extended by a punch 240 in its free end, that is to say at the end furthest from the shoulders 210, 220.

[0092] The protrusion 250 comprises a molding surface 230 which may comprise 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] [Fig. 1] also represents the length Lp of the punch 240 and the length Lc of the protuberance 250.

[0094] The punch portion 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 Lc is understood as being counted from the portion at right angles to the shoulders 210 of the second part 200.

[0096] [Fig. 1] illustrates the direction in which the length of the punch or protuberance is understood, namely the direction of extension of the punch 240, or in the figure the vertical direction.

[0097] In one embodiment, it is not excluded that the tool opens more than its open position shown in [Fig. 1], in particular to facilitate the placement of the polymer film between the first and second parts of the tool, as can be seen in [Fig. 6].

[0098] [Fig.2] represents the same part of the tooling as that of [Fig.l] but in an intermediate position.

[0099] [Fig.2] illustrates the advantage of the invention of the feature that the length of the protuberance Lc is greater than or equal to, and in this case equal to, the length of the punch Lp.

[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 [Fig.2], the punch 240 and more generally the protuberance 250 of the second part 200 of the tooling drives the precursor of the complex hollow acoustic elements, here the polymeric film 610.

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

[0103] As shown in [Fig.2], at the time when the punch 240 enters the punch housing 140, the polymeric film 610 for forming the complex hollow acoustic element has begun to take the shape of the mold cavity but has not yet reached the punch housing 140.

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

[0105] As shown, in its closed position, the shoulders 110, 120 of the first part 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 parts precisely takes the shape of the desired hollow complex acoustic element.

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

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

[0109] [Fig. 3] also makes it possible to represent the spacing 12 between the molding surface of the first part 130 and the molding surface of the second part 230, and the spacing between the punch 240 and the punch housing 140.

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

[0111] The spacing 12 will define the thickness of the hollow complex acoustic element 400 obtained by the stamping tool 500.

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

[0113] In this way, it is understood that the shoulder 160 of the first part 100 will make it possible to reduce the spacing from 12 to 11 so that the material 610 forming the complex hollow acoustic element cannot penetrate into the punch housing 140.

[0114] A complex hollow acoustic element with the desired shape is thus formed from the stamping step.

[0115] In an embodiment that is not shown, 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 tooling 500.

[0116] For example, such air communication may be a vent, or a removable seal. In this way, the hollow complex acoustic element is simply returned to atmospheric pressure once it has been formed in the tool, and its extraction from the stamping tool 500 is facilitated.

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

[0118] For example, and as shown in [Fig.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 arrange an air communication channel between the two, not shown.

[0120] Although this is only shown in the case of [Fig.3], it must 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 entire process will be carried out in a tool comprising such a decomposition (and therefore such a decomposition would then have its meaning for figures 1 and 2).

[0121] Further, [Fig.3] illustrates what is meant by the fact that the molding surface 130 of the first part 100 has a shape corresponding to the outer 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 inner surface of the hollow complex acoustic elements of the acoustic component to be manufactured.

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

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

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

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

[0126] In one embodiment, the base 401 of the hollow complex acoustic element may fit within a circle of 9.5 mm, 12.7 mm, or 25.4 mm (the SI unit equivalents of 3 / 8 inch, half an inch, or one inch in Imperial units).

[0127] These dimensions advantageously correspond 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 may be between 1.0 mm2 and 25 mm2, for example between 3.0 mm2 and 10 mm2.

[0129] In one embodiment, the height of the cone portion 430a measured in the direction from the base 401 to the apex 402 may 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 may 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 ​​make it possible to obtain optimal acoustic performance, in particular for an application to the noise reduction of turbomachines.

[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 stamping tool 500 described above.

[0134] [Fig.4] further shows the lower end 450 of the cavity of an element hollow acoustics.

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

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

[0137] The thermoplastic material film 610 used to manufacture the acoustic component may also have a variable thickness such as the film 610 illustrated in [Fig.5].

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

[0139] For example, the film may comprise portions of excess thickness 22, constituting a surplus of material which, once stretched or flowed into the molding cavities when closing the stamping tool, will make it possible to form complex hollow acoustic elements.

[0140] The volume of material present in each portion of excess thickness is defined as a function of the wall thickness of each complex acoustic element to be manufactured.

[0141] The portions of excess thickness 22 may have a circular, annular or hexagonal shape, as shown in [Fig.5], and be distributed uniformly 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 [Fig.l].

[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 indeed the first portion 230a of the molding surface 230 which presses on the film 610. This further minimizes the risk of the film 610 reaching the punch housing 140 before punch 240 itself.

[0145] The connecting portions 21 may 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 connect the hollow acoustic elements together to form an acoustic component.

[0147] Figures 6 and 7 together illustrate a method of manufacturing an acoustic component in accordance with one embodiment of the invention.

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

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

[0150] In the embodiment shown, the first part 100 is stationary and the second part 200 is mobile in a double direction D, but it does not go beyond the scope of the invention if the first part 100 is mobile and the second 200 is stationary, or if both parts are mobile.

[0151] [Fig.6] represents a tool, provided with hold-down clamps 641 and 642 for holding a film of thermoplastic material 610 during the stages of forming an acoustic component.

[0152] The thermoplastic material film 610 can also be deposited on the tooling by an automaton or manually. It can also be supplied by a conveyor system.

[0153] The first part 100 comprises 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 molding cavities 250 have a shape corresponding to the shape of the hollow complex acoustic elements of the acoustic component to be manufactured.

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

[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 makes it possible to give the thermoplastic material excellent deformability properties so that it can be shaped.

[0158] The heating can be carried out by heating means known as such, and arranged in the first part 100 and the second part 200 of the tooling. 500 stamping.

[0159] According to an alternative implementation, the thermoplastic material film 610 may be heated to a first temperature higher than the glass transition or melting temperature of the thermoplastic material of the film before its placement above the first part 100, for example by heating the side of the film in an infrared oven.

[0160] The film may be heated to the first temperature preferably after its placement above the first portion 100 because this allows for better positioning of the thermoplastic material film 610 in the stamping tooling 500.

[0161] Once this first temperature has been reached by the film, the film can be shaped in thermoplastic material 610. For this purpose, the second part 200 can be moved towards the first part 100 until the protuberances 250 cooperate completely with the cavities 150 as illustrated in [Fig.7], that is to say until a position for closing the tool.

[0162] The heated thermoplastic material 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 properties of the tooling described above, the polymeric material film 610 is deformed by the stamping, in particular under the effect of the protuberances 250, but the punch 240 and the punch housing 140 ensure that it is possible to obtain a complex hollow acoustic component at the outlet of the tooling, and this without the need for a subsequent machining step.

[0165] In a method 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 film of thermoplastic material 610 itself reaches the bottom of the cavity.

[0166] This makes it possible to form hollow complex acoustic elements 400 with very thin walls, and to obtain directly drilled hollow complex acoustic elements 400.

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

[0168] This avoids tearing the film made of thermoplastic material which may initially have a relatively low thickness, for example of 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 polymeric material film 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 is completely deformed in the cavities 150 as illustrated in [Fig.7], the first 100 and / or the second 200 part of the tooling are cooled to a third temperature lower than the glass transition or melting temperature of the thermoplastic material making it possible to set said material in the shape of an acoustic component to be manufactured.

[0171] As long as the temperature of the thermoforming tool 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 insert of [Fig.7] showing a detail of [Fig.3] makes it possible to illustrate 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 material film 610 during the closing of the stamping tool 500 and the hollow complex acoustic element then forms around the protuberance, without being able to close.

[0174] The acoustic component is then demolded by moving one of the two parts of the tool 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 making it possible to form hollow complex acoustic elements 400 of the same shape.

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

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

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

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

[0180] There is now described, in relation to [Fig.8], a method of manufacturing a acoustic attenuation structure according to one embodiment of the invention. The acoustic attenuation structure 1000 here comprises an acoustic skin or plate 1110, an acoustic component 1120 manufactured as described above, a plurality of partitions 1131 and a closing skin or plate 1140.

[0181] The closing skin 1140 corresponds to a solid surface intended to reflect the sound waves entering the acoustic attenuation structure. The closing skin 1140 may be a constituent element of the acoustic attenuation structure 1000 as in the example described here or correspond to a structure of an object, for example an aircraft engine. In the latter case, the acoustic attenuation structure 1000 of the invention does not comprise a closing skin and may be directly mounted on the structure of the object.

[0182] The acoustic skin 1110 has the function of allowing the sound waves to be attenuated to pass 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 in length and width along a horizontal direction DH and in height along a vertical direction Dv. The acoustic component comprises a plurality of hollow complex acoustic elements 1121 each having a shape gradually narrowing 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 may be cones 400 conforming to the embodiment described above, in connection with [Fig.3].

[0186] In the embodiment described here, the plurality of partitions 1131 is made in a single 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 shape shown in [Fig.3], the network of ribs 1130 may be a honeycomb tiling, i.e. with partitions 1131 forming a network of hexagonal cavities rather than square, as shown here.

[0188] Still in the example described here, the acoustic attenuation structure 1000 is produced 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, on the lower portion of the bases 1122 of the hollow complex acoustic elements 1121. The plurality of hollow complex acoustic elements being formed in a single piece within the hollow complex acoustic multi-element panel and the plurality of partitions also being formed in a single piece, the assembly between these two elements is greatly facilitated by the self-positioning of the hollow complex acoustic elements 1121 with the partitions 1131.

[0189] The closing skin 1140 is fixed, for example by gluing or welding, on the lower edge of the partitions 1131 while the acoustic skin 1110 is fixed, by gluing or welding, on 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 on a perfectly flat support in the horizontal direction DH, which makes it possible to ensure very good sealing between the skins and the assembly of the complex acoustic multi-element 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 which surround it.

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

[0192] The plurality of partitions, the acoustic and closing skins as well as the assemblies joining in a single piece the plurality of partitions and the complex acoustic multi-element panel or the plurality of partitions and one of the skins can also be produced by injection of a thermoplastic or thermosetting material, loaded or not.

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 (Lp) greater than or equal to the length of the protuberances (Lc),and in that the spacing (h) between the punch and the punch housing is smaller than the spacing (12) 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 mold cavity (150) comprises a first portion (130a) and a second portion (130b), the first portion having a greater taper than the second portion.

3. The stamping tool (500) of claim 2, wherein the second portion (230b) has a taper 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 (12) 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. 111111. Stamping tool (500) according to any one of claims 1 to 5, wherein, in the closed position, the spacing (IJ between the punch (240) and the punch housing (140) is less than or equal to 50 pm.

7. A stamping tool (500) according to any one of claims 1 to 6, wherein the punch (240) and / or the punch housing (140) comprises 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 tool 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 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 in thermoplastic material by closing the tool.

11. A method of 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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