Acoustic panel
The acoustic panel design with folded sheet cells and perforated walls addresses the challenges of frequency attenuation, temperature resistance, and curvature, achieving effective soundproofing and industrial scalability.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-06-12
- Publication Date
- 2026-03-13
AI Technical Summary
Existing acoustic panels fail to meet requirements of attenuating specific frequency ranges, withstanding extreme temperatures and chemicals, resisting corrosion, and being manufacturable with curvature while maintaining industrial efficiency.
The acoustic panel design features cells with multiple chambers separated by a diaphragm, formed from a folded sheet, and includes perforated walls for fluid communication, allowing for absorption of a wide frequency range and structural integrity across varying temperatures and environments.
The panel effectively attenuates sound frequencies from 500 to 3000 Hz, withstands extreme temperatures, resists corrosion, and is easily manufacturable with single or double curvature, enhancing industrial production efficiency.
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Abstract
Description
Title of the invention: Acoustic panel
[0001] The present invention relates to the field of acoustic panels, in particular intended for soundproofing engines.
[0002] Such a panel must be able to attenuate frequencies between 500 and 3000 Hertz. It must also be able to withstand temperatures between -55°C and 135°C, resist numerous chemicals, and resist corrosion in a humid and hot environment. Furthermore, it must be able to be manufactured with a single or double curvature.
[0003] Also, such a panel must be able to be produced at sustained industrial frequencies.
[0004] Such panels are known in particular from document FR 3 098 143 and from document WO 2021 / 260286.
[0005] One object of the invention is to provide an acoustic panel meeting the above requirements.
[0006] According to a first object of the invention, a cell for an acoustic panel extends along a cell axis and comprises at least two chambers arranged in series along this axis and a diaphragm substantially transverse to this axis which separates the two chambers from each other.
[0007] Advantageously, such a cell is formed from a single sheet folded upon itself. The sheet may comprise a first row of folds to form the sides of a first chamber of the two chambers, a second row of folds to form the diaphragm, and a third row of folds to form the second chamber, the second row of folds being separated from each of the other rows by a respective transverse fold, the folds of the second row forming a pattern suitable for forming said diaphragm by folding the sheet upon itself. The pattern of the second row is preferably of the "Kresling" or "Chicken wire tessellation" type.
[0008] The cell preferably has a polygonal cross-section forming a regular hexagon. The chambers may have different heights, these heights being measured axially.
[0009] Preferably, the diaphragm forms a diaphragm opening which connects the two chambers.
[0010] According to a second object of the invention, an acoustic panel comprises several cells according to the invention, arranged side by side and whose axis extends substantially along a local direction through the thickness of the panel. Such a panel preferably comprises an acoustic wall to which a free edge of a first chamber of each of the cells is attached, the wall comprising perforations for communication the interior of the chamber with an exterior middle of the panel. Also, the panel may include a facing wall to which a free edge of another chamber axially opposite to the first of each of the cells is glued, the edge including cutouts forming, with the wall, drains. Brief description of the figures
[0011] Embodiments and variants will be described below by way of non-limiting examples, with reference to the accompanying drawings in which:
[0012] [Fig-1] is a schematic, elevational, exploded perspective view according to its thickness, of an acoustic panel according to the invention;
[0013] [Fig.2] is an isolated, schematic, cross-sectional and elevational view of a cell of a first type present on the panel of [Fig.1], according to the section plan II-II indicated in [Fig.3];
[0014] [Fig.3] is an axial and perspective view of the cell of [Fig.2], according to the direction II indicated in [Fig.2];
[0015] [Fig.4] is a bottom and perspective view of a cell similar to the cell of the [Fig.3];
[0016] [Fig.5] is a developed view of a sheet for the realization of the cell of figures 2 to 4;
[0017] [Fig.6] is a schematic, elevation and perspective view of a panel acoustics of a group of three cells according to the invention assembled on a cladding wall;
[0018] [Fig.7] is a schematic axial view of a group of three cells according to the invention joined together by a coupling;
[0019] [Fig.8] is a schematic elevation and perspective view of the group of the [Fig.7], thus harnessed.
[0020] [Fig.9] is a schematic perspective view of the coupling in Figures 7 and 8; and,
[0021] [Fig. 10] is a schematic view illustrating several inserts that can be used to furnish a cell according to the invention, each insert being represented therein both in perspective and in axial view. Detailed description
[0022] In this description, in particular the terms "top", "bottom", "upper" and "lower", "horizontal" and "vertical" and other terms of the same type may be used arbitrarily in this description and generally refer to the positions illustrated in the figures.
[0023] Figure 1 illustrates schematically and partially an acoustic panel 1 according to the invention. Such an acoustic panel is intended to attenuate or dampen a sound produced by a transmitter in a first environment E1 in order to protect a second environment E2. Such an emitter is not shown in the figures; it may be a motor, for example an aircraft engine, an orchestra or any other sound emitter.
[0024] In the illustrated example, the panel comprises a layer 200 of cells 2 functioning as sound traps; the layer 200 of cells is sandwiched between two walls 3, 4. A first wall 3 of these walls, hereinafter referred to as the "sound wall," is intended to be positioned between the sound emitter and the cell layer. A second wall, hereinafter referred to as the "cladding," is then arranged beyond the cell layer relative to the emitter. Each cell 2 extends between the walls, substantially along a direction DE locally perpendicular to the walls, substantially along a local thickness of the panel 1.
[0025] Each wall comprises a structural sheet 5, which contributes to giving the panel its shape and rigidity, and an adhesive film 6 that ensures the cohesion of the wall with the cell layer. The acoustic wall 3 comprises perforations 8, formed in both the sheet and the film, in a corresponding manner such that these perforations 8 establish fluidic and vibratory communication between an interior N of each cell and the first environment El in which the emitter is located. The casing does not include perforations.
[0026] In [Fig. 1], three cells are illustrated. Of course, a panel generally comprises a very large number of cells, for example several hundred or several thousand cells. Here, each of the cells is of a different type; one is of a first type 21, another of a second type 22, and the third of a third type 23.
[0027] We will now describe the cell of the first type 21, with reference to Figures 2 to 5. In [Fig. 1], the walls 3, 4 are partially shown. The cell 2 extends substantially around an axis X2 parallel to the local direction DE of the thickness El of the panel 1.
[0028] In this first type 21, the cell comprises two chambers 11, 12 separated by a diaphragm 10. In the illustrated example, one of the two chambers 11 has a height H11 greater than the height H12 of the second chamber 12. The diaphragm 10 has a height H10. Thus, the height H2 of cell 2 is equal to the sum H11 + H12 + H10 of these heights. The total thickness of the panel E1 = H2 + E3 + E4 further includes the respective thicknesses E3, E4 of the walls 3, 4.
[0029] As particularly illustrated in [Fig. 3], the cell 2 has a regular hexagonal cross-section. A free edge 15 of the first chamber, opposite the diaphragm 10, forms an opening closed by the sound-absorbing wall 3. A free edge 16 of the second chamber forms an opening closed by the casing 4.
[0030] The diaphragm 10 has an aperture 18, which allows fluid communication chambers 11, 12 between them. In axial view, the opening 18 of the diaphragm 10 is itself hexagonal.
[0031] In the example illustrated in the figures, each cell 2 is made from a sheet folded over itself. Such a sheet 25, adapted to form a cell of the first type 21, is shown flat in [Fig. 5].
[0032] The sheet comprises a multitude of folds defining three rows. A first transverse fold PA separates a first row RI from a second row R2; a second transverse fold PA separates a second row R2 from a third row R3.
[0033] The first row RI is formed of first rectangles separated from each other by first vertical folds PV of length H11; each of the first rectangles corresponds to one of the six sides 26 of the first chamber 11. In the same way, the third row is formed of second rectangles separated from each other by second vertical folds PV of length H12; each of the rectangles corresponds to one of the six sides 26 of the second chamber 12.
[0034] The second row comprises folds A, B, and C, forming a pattern of a type known as the "Kresling pattern." This pattern is formed from non-rectangular parallelepipeds, two opposite horizontal sides A of length LA of which together form the horizontal folds PA. The other two sides are formed by first diagonal folds B of length LB, parallel to each other and connecting the horizontal folds PA. The pattern further comprises diagonal folds C of length LC, each extending along the long diagonal of each of the non-rectangular parallelepipeds.
[0035] A free longitudinal edge of the first row RI, parallel to the horizontal folds PA, forms the free edge 15 of the first chamber. A free longitudinal edge of the third row R3, parallel to the horizontal folds PA, forms the free edge 16 of the second chamber.
[0036] The second row R2, because it is of a Kresling pattern, is able to fold back on itself so that, once folded, it forms the diaphragm. Because it is made up of several superimposed folds, the diaphragm maintains a spacing of height H10 between the two chambers 11, 12; thus, the chambers are not stuck together; they can vibrate independently of each other.
[0037] The dimensions of the aperture 18 of the diaphragm and its thickness H10 depend on the ratio of the dimensions LA, LB, LC of the folds A, B and C of the second row R2.
[0038] Typically, for LB = 2 x LA, the diaphragm can be completely closed, meaning that its opening 18 has a zero cross-section. To obtain an opening with a desired cross-section, for example, one with a cross-section close to that of a corresponding perforation 8, such a diaphragm can be punched. During cell shaping, the diaphragm can also be folded around a rod serving as a template; the degree to which the diaphragm is folded back on itself can also be adjusted. that is to say, over its height H10.
[0039] Cutouts D16 in the free edge 16 of the second chamber together with the casing 4 form drains 27. This arrangement is particularly visible in figures 2 and 6. Such drains are useful for circulating fluids, in particular condensation fluids that may form in the panel 1.
[0040] If the cell of the first type 21 described above comprises two chambers 11, 12 separated by a diaphragm 10, the cells of the second and third types comprise a third chamber 13 separated from the second by a second diaphragm 10. In the second type 22, the second chamber is tall, while the first and third are of reduced height. In the third type 23, the first and second chambers are of intermediate height, while the third is of reduced height.
[0041] Of course, other types of cells can be used. For example, cells containing only one chamber, or a number of chambers greater than 3, can be used.
[0042] It appears that, for a given larger transverse dimension of the cell, i.e., the diameter D of the circle circumscribed about the hexagonal section of the cell, the band of sound frequencies that is absorbed varies with the height H, H11, H12 of the chamber. Thus, a single cell comprising several chambers of different heights can absorb as many frequency bands as there are different heights. Therefore, a panel comprising a suitable arrangement of cells of different types can absorb a very wide frequency band composed of the narrower frequency bands absorbed by the different chambers that make up this panel. Furthermore, a panel can be designed to absorb different frequencies at different locations on the panel; this is particularly useful for a panel used in the fairing of an aircraft engine, where the emitted frequencies vary from the front to the rear of the engine.
[0043] Thus, with a diameter D = 35 millimeters, for the following different heights H: - if H = 25 mm, a chamber absorbs frequencies close to 500 Hz - if H = 15 mm, a chamber absorbs frequencies close to 700 Hz - If H = 7 mm, a chamber absorbs frequencies close to 1000 Hz; - If H = 3 mm, a chamber absorbs frequencies close to 1500 Hz; and, - if H = 1 mm a chamber absorbs frequencies close to 2500 Hz.
[0044] Preferably the diameter D is greater than 27 millimeters, preferably between 32 and 40 millimeters.
[0045] Typically, the cells can be formed from sheets 25 of aramid paper, for example known under the brand name Nomex®, in thicknesses ranging from 0.13 millimeters to 0.58 millimeters. Impregnation is then advantageously carried out after the cells have been formed.
[0046] Figures 1 to 6 illustrate cells juxtaposed with each other, which can be glued together.
[0047] Figures 7 to 9 illustrate another embodiment in which the cells 2 are held apart from each other by a coupling 30. The coupling forms recesses 32, each of which can receive a corresponding cell 2. In the illustrated example, the coupling comprises only two recesses; of course, in industrial practice, a coupling advantageously comprises several hundred or several thousand recesses.
[0048] Here, the coupling 31 is intended to hold two sides 26 of two adjacent cells opposite each other at a distance D30. The coupling has a constant height H30. In the figures, the height H30 is significantly less than the height H2 of the cells 2. A coupling with a height close to or equal to that of the cells can also be provided.
[0049] Such a coupling is useful, for example, to compensate for angular offsets between different chambers 11,12 of the same cell 2 around its axis X2. It also allows for the production of panels with curved walls of single or double curvature.
[0050] With reference to [Fig. 10], we will now describe five different inserts usable with a cell 2 according to the invention, for example of the first type 21 previously described. A first row illustrates perspective views of each of the five inserts. A second row illustrates axial views of these same inserts.
[0051] A first insert 41 is provided to close the opening 18 of a diaphragm, except that it includes an axial cylindrical air passage 48, with a cross-section substantially equal to that of the corresponding perforation 8; this passage 48 allows two adjacent chambers to be connected. The insert 41 is made of a solid material, for example foam or cork, and of constant thickness E41.
[0052] A second insert 42 differs from the first in that it is made of a rigid plastic and includes recesses 51, separated by ribs, which make it possible to lighten this insert 42.
[0053] A third insert 43 differs from the second insert 42 in that it is designed to fit into a chamber and does not have an air passage.
[0054] A fourth insert 44 has the shape of a hexagonal ring; it is designed to fit into a chamber, against the sides 26 of that chamber.
[0055] The fifth insert 45 differs from the second insert 42 in that it is designed to fit into a chamber and does not have an air passage.
[0056] Of course, the invention is not limited to the examples just described. On the contrary, the invention is defined by the following claims.
[0057] It will indeed appear to the person skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to him.
[0058] Thus, other folding patterns can be used to form a diaphragm. For example, a pattern known as "Chicken wire tessellation" can be used.
[0059] Instead of a hexagonal section, a cell can be made on the basis of a polygon, preferably regular, comprising a number of sides other than six, for example it can comprise eight.
[0060] A coupling can be provided not to isolate individual cells, but groups of cells. For example, a socket in such a coupling can be provided to receive a group of three cells glued together.
[0061] A panel manufactured according to the invention is particularly advantageous. It is easy to industrialize. Furthermore, it allows for the absorption of a wider frequency spectrum with a reduced mass compared to prior art panels.
Claims
Demands
1. Cell (2) for an acoustic panel (1), characterized in that it is formed of a single sheet (25) folded over itself and in that it extends along a cell axis (X2) and comprises at least two chambers (11, 12) arranged in series along said axis and a diaphragm (10) substantially transverse to said axis which separates said two chambers from each other.
2. Cell according to claim 1, characterized in that the sheet comprises a first row (RI) of folds to form sides (26) of a first chamber (11) among the two chambers, a second row of folds (R2) to form the diaphragm, and a third row of folds (R3) to form the second chamber (12), the second row of folds being separated from each of the other rows by a respective transverse fold (PA), the folds (A, B, C) of said second row forming a pattern adapted to form said diaphragm by folding the sheet over itself.
3. Cell according to claim 2, characterized in that the pattern of the second row is of the "Kresling" type or of the "Chicken wire tes-sellation" type.
4. Cell according to any one of claims 1 to 3, characterized in that it has a polygonal cross-section preferably forming a regular hexagon.
5. Cell according to any one of claims 1 to 4, characterized in that the chambers have different heights (H11, H12), said heights being measured axially.
6. Cell according to any one of claims 1 to 5, characterized in that the diaphragm forms a diaphragm opening (18) which connects the two chambers to each other.
7. Acoustic panel (1), characterized in that it comprises several cells according to any one of the preceding claims arranged side by side and whose axis extends substantially along a local direction (DE) of the thickness of said panel.
8. Acoustic panel (1) according to claim 7, characterized in that it comprises an acoustic wall (3) for gluing a free edge (15) of a first chamber (11) of each of the cells, said wall comprising perforations (8) for communicating the interior of said chamber with an external environment (El) of said panel.
9. Acoustic panel (1) according to claim 8, characterized in that it comprises a covering wall (4) for gluing a free edge (16) of another chamber (12) axially opposed to the first of each of the cells, said edge (16) comprising cutouts (DI6) forming, with said wall (4), drains (27).