阅读说明：本技术 蜂窝隔音结构、相关飞行器、制造方法以及插入工具 (Honeycomb acoustic insulation structure, associated aircraft, method of manufacture and insertion tool ) 是由 A·波特 J·拉兰纳 F·拉维斯 F·多贝若尼 F·梅卡 于 2021-05-25 设计创作，主要内容包括：蜂窝隔音结构、相关飞行器、制造方法以及插入工具。本发明涉及一种蜂窝隔音结构(10)和相关飞行器,其中,所述蜂窝隔音结构的小室(11)设有隔膜(20),所述隔膜包括：膜(21),所述膜具有穿过所述膜的厚度的至少一个孔口(22)；以及封盖所述孔口(22)的至少一根管(23),管从所述膜的面延伸到小室的一个隔室中,包括形成声出口的自由端,声出口定位在距小室的基部截面的距离(p)处。本发明还涉及一种用于制造这种蜂窝隔音结构(10)的方法以及一种用于将隔膜(20)插入到小室(11)中的工具(30)。这种蜂窝结构使得能够处理较宽声学频谱,并且其声学尺寸及其制造被简化。(Honeycomb sound insulation structures, related aircraft, methods of manufacture, and insertion tools. The invention relates to a honeycomb sound-proofing structure (10) and to a related aircraft, wherein the cells (11) of the honeycomb sound-proofing structure are provided with a membrane (20) comprising: a membrane (21) having at least one aperture (22) through a thickness of the membrane; and at least one tube (23) covering the orifice (22), the tube extending from the face of the membrane into one compartment of the chamber, including a free end forming an acoustic outlet, the acoustic outlet being positioned at a distance (p) from the base section of the chamber. The invention also relates to a method for producing such a honeycomb sound-insulating structure (10) and to a tool (30) for inserting a membrane (20) into a cell (11). Such a honeycomb structure enables a wider acoustic spectrum to be processed, and its acoustic size and its manufacture are simplified.)

1. Honeycomb acoustic insulation (10) comprising at least one cell (11) having a base section (S) of arbitrary shape and a height (H), characterized in that said cell (11) comprises a membrane (20), said membrane (20) comprising a membrane (21), said membrane dividing said cell (11) along said height (H) into two compartments (14, 15), the membrane (21) comprising at least one aperture (22) through the thickness of the membrane, and the membrane (20) comprising at least one tube (23) closing the at least one orifice (22) and extending from the face of the membrane (21) into one (14) of the two compartments, the tube (23) comprises a free end forming an acoustic outlet (24) positioned at a distance (p) from the base section (S).

2. The honeycomb acoustic insulation structure (10) according to claim 1, characterized in that the distance (p) between the sound outlet (24) and the base section (S) of the cells (11) is between 20% and 80% of the height (H) of the cells (11).

3. Honeycomb sound insulating structure (10) according to any of claims 1 and 2, characterized in that the sound outlet (24) of the tube (23) comprises at least one orifice, micro-perforation and/or woven zone.

4. The honeycomb acoustical structure (10) of any of claims 1 through 3 wherein the film (21) includes at least one corrugation.

5. The honeycomb acoustic insulation structure (10) according to any one of claims 1 to 4, characterized in that it comprises a resistant sheet (12) covering the cells (11) on a first side and a closing sheet (13) covering the cells (11) on a second side, the closing sheet (13) being porous.

6. An aircraft comprising at least one propulsion unit comprising a nacelle (200), the nacelle (200) comprising an air intake (201) having a sound-absorbing panel (103), characterized in that the sound-absorbing panel (103) has a honeycomb sound-insulating structure (10) according to any one of claims 1 to 5, the sound-absorbing skin (111) of which comprises a resistant sheet (12), and the rear skin (113) of which, configured to ensure the structural strength of the sound-absorbing panel (103), comprises a closing sheet (13).

7. A method for making a honeycomb acoustical structure (10) comprising:

-a step of providing at least one cell (11) having a base section (S) of arbitrary shape and a height (H);

characterized in that the manufacturing method further comprises:

-a step of providing a diaphragm (20) comprising a membrane (21), the membrane (21) comprising at least one aperture (22) through the thickness of the membrane, and the diaphragm (20) comprising at least one tube (23) covering the at least one aperture (22), the tube comprising a free end forming an acoustic outlet (24);

-a step of picking up a membrane (20) by means of an insertion tool (30), the step of picking up the membrane comprising a step of gripping a portion of the membrane (20) by means of the insertion tool (30);

-a step of inserting the diaphragm (20) into the chamber (11) by means of the insertion tool (30) until the acoustic outlet (24) is placed at a distance (p) from the base section (S);

-a step of fixing a portion of the membrane (20) against an inner wall (16) of the chamber (11); and

-a step of releasing the septum (20) by means of the insertion tool (30).

8. The manufacturing method according to claim 7, characterized in that it comprises a step of pressing said portion of the diaphragm (20) against the inner wall (16) of the cell (11) by means of a pressure application system (36) of the insertion tool (30) so as to fix it.

9. An insertion tool (30) for inserting a membrane (20) into cells (11) of a honeycomb sound-insulating structure (10), characterized in that the insertion tool (30) comprises at least one end piece (31) configured to be inserted into the cells (11), the end piece (31) comprising at least one gripping system configured to hold or release a portion of the membrane (20).

10. Insertion tool (30) according to claim 9, wherein the end piece (31) comprises a pressure application system (36) configured to flatten a portion of the membrane (20) against the inner wall (16) of the cell (11).

Technical Field

The present invention relates to a honeycomb structure, and more particularly, to a honeycomb soundproof structure. The invention also relates to an aircraft comprising such a honeycomb acoustic insulation structure.

The invention also relates to a method for producing such a honeycomb structure and to a tool for carrying out the method.

Background

The honeycomb structure may have various applications, in particular in the field of aeronautics, for example in aircraft nacelles.

Here, the honeycomb structure refers to a structure including cells (that is, juxtaposed hollow cell volumes).

Such structures may be made of various materials, for example, plastic, composite, or metal materials. The cells may have a variety of geometries. One well-known form of honeycomb has cells in the shape of a right prism with a hexagonal base. The term "honeycomb" structure is commonly used to refer to this type of structure having hexagonal cells, but such expression is sometimes used by the term misused to refer to honeycomb panels having other cell shapes.

Such a structure can be used in many technical fields, in particular in the aeronautical field.

For example, the nacelle of an aircraft propulsion unit usually comprises an air intake, which is a sound-absorbing structure intended to ensure acoustic treatment of the forward portion of the nacelle and to absorb possible sound pollution that may originate from the rotor of the engine.

Air intakes traditionally comprise sound-absorbing panels which mainly ensure acoustic treatment and most of the internal aerodynamic behaviour of the air intake.

The sound absorbing panel may be made of a composite material and made in one piece. The entire inner surface thereof can ensure the acoustic treatment.

In this context, the sound absorption panel may be dimensioned to withstand various stresses, for example, loss of blades of the rotor, aerodynamic loads (overpressure) over the entire inner periphery of the sound absorption panel, bird strikes, various thermal stresses, etc.

To this end, at least a portion of the sound-absorbing panel conventionally comprises a core made of a honeycomb (inaccurately called "honeycomb") structure, configured to suppress acoustic pollution, interposed between a sound-absorbing skin ("resistant skin") forming a first face and a structural back skin ("backing skin") forming a second face of the sound-absorbing panel.

One purpose of the sound absorbing skin is to transmit noise. It is for example made up of a plurality of layers, one of which is a porous layer, usually with pores.

The structural back skin has in particular the function of acting as a sound reflector and greatly contributing to the structural strength of the sound-absorbing panel.

By varying the thickness of the sound absorbing panel, high or low frequencies can be attenuated: the thicker the panel, the lower the attenuated frequency. Propulsion units sometimes use engines with high dilution ratios, which for a given level of thrust have wider and shorter dimensions and have larger dimensions of the fan blades, which may be associated with lower rotational speeds than conventional engines. The frequency to be attenuated is then lower.

However, the sound absorbing panels known in the prior art are generally only effective for a narrow interval of the main frequency of this type of engine.

In order to attenuate frequencies in a wide range, patent US 7857093B 2 proposes, for example, the superposition of two honeycomb layers to absorb lower frequencies.

However, this solution actually results in a large size. The thickness of the sound-absorbing panel is significantly increased, resulting in an increase in the mass and stiffness of the sound-absorbing panel.

Disclosure of Invention

The present invention therefore aims to provide a sound-absorbing structure which enables at least a wide range of frequencies to be treated, while limiting its size.

To this end, a first aspect provides a honeycomb acoustic structure comprising at least one cell having a base section S of arbitrary shape and a height H, characterized in that the cell comprises a membrane, the membrane comprising a membrane dividing the cell into two compartments along the height H, the membrane comprising at least one aperture passing through the thickness of the membrane, and the membrane comprising at least one tube enclosing the at least one aperture and extending from a face of the membrane into one of the two compartments, the tube comprising a free end forming an acoustic outlet, the acoustic outlet being positioned at a distance p from the base section S.

Such a honeycomb structure is thus configured to handle a broader acoustic spectrum, that is, high and/or low acoustic frequencies, than a honeycomb structure without a septum.

More particularly, such a tube enables lower frequencies to be processed. One of the two compartments (the compartment into which the tube extends) is then configured to handle low frequencies, while the other of the two compartments is configured to handle high frequencies.

The two compartments are then acoustically or fluidically connected to each other by a tube.

The diaphragm according to the invention thus achieves a simpler acoustic dimensioning of the structure, since the dimensions of the tube are known beforehand.

Furthermore, such a diaphragm is more robust in industry. Such a diaphragm can be adapted to a large number of cells of different shapes and sizes.

If desired, the septum may comprise a plurality of tubes, for example, one to ten tubes.

Here, a tube means a conduit having any type of cross-section, which may or may not have a constant dimension over the height of the tube, and which forms a ridge with respect to the membrane. The tube may be cylindrical or frustoconical, having a polygonal or circular cross-section.

The acoustic outlet is a portion of the diaphragm configured to transmit acoustic waves.

In one exemplary embodiment, the acoustic outlet of the tube comprises at least one orifice, microperforation and/or woven region.

Thus, starting from a chosen basic honeycomb structure, which may even be standard (that is to say initially without membrane), the membrane is arranged in the honeycomb according to the frequency to be treated. Thus, different ranges of frequencies can be handled by the same basic honeycomb structure and the same membrane depending on the arrangement of the membrane in the cells of the honeycomb structure.

In other words, the volume of each of the compartments is determined according to the desired frequency.

Optionally, the basic honeycomb structure is selected according to the volume of the desired cells, for example by varying the height of the honeycomb structure.

For example, the cells are monolithic cells.

The cells may be made of synthetic material, paper or fabric coated or covered with resin or another product that increases rigidity and impermeability, composite material (e.g., thermoplastic), or metal, etc., depending on the intended application.

The cells are formed, for example, by right circular cylinders (that is to say cylinders whose generatrices are orthogonal to the base section).

The shape of the base section may vary. Which is determined, for example, based on the desired mechanical properties of the honeycomb structure.

For example, the base section has a circular or hexagonal shape. In the case of hexagonal cells, the honeycomb structure then corresponds in the strict sense to a honeycomb structure.

In an exemplary embodiment, the distance p between the sound outlet and the base section S of the cell is between 20% and 80% of the height H of the cell.

In one exemplary embodiment, the membrane comprises at least one corrugation.

In one exemplary embodiment, the honeycomb acoustic insulation structure includes a resistive sheet covering the cells on a first side.

In one exemplary embodiment, the honeycomb acoustic insulation structure includes a closure sheet covering the cells on a second side.

For example, the closure flap may be perforated.

Another aspect also provides an aircraft comprising at least one propulsion unit comprising a nacelle.

For example, the nacelle includes an air intake having a sound absorbing panel.

For example, the sound absorbing panel has a honeycomb acoustical structure as described above.

For example, the sound absorbing skin of the sound absorbing panel comprises a resistive sheet of the honeycomb acoustical structure.

For example, a back skin of the sound absorbing panel configured to ensure structural strength of the sound absorbing panel comprises a closed sheet of the honeycomb acoustical structure.

Another aspect provides a method for manufacturing a honeycomb sound insulating structure, comprising:

-a step of providing at least one cell having a base section S of arbitrary shape and a height H;

-a step of providing a diaphragm comprising a membrane, the membrane comprising at least one aperture through a thickness of the membrane, and the diaphragm comprising at least one tube covering the at least one aperture, the tube comprising a free end forming an acoustic outlet;

-a step of picking up a membrane by means of an insertion tool, the step of picking up a membrane comprising a step of gripping a portion of the membrane by means of the insertion tool;

-a step of inserting the diaphragm into the cell by means of the insertion tool until the acoustic outlet is placed at a distance p from the base section S;

-a step of fixing a portion of the diaphragm against the inner wall of the chamber; and

-a step of releasing the septum by the insertion tool.

This method enables different types of septums to be inserted into cells of different configurations and the septums to be fixed therein.

In particular, the cells of the honeycomb structure may vary widely between honeycomb structures, particularly in cross-sectional shape and size.

At the same time, the septum to be inserted may also vary depending on the acoustic frequency to be treated and its intended honeycomb structure.

In this context, this method for producing a honeycomb soundproofing structure formed by at least one honeycomb structure into which a membrane is inserted into at least one cell of the honeycomb structure can be applied to cells and membranes of different shapes.

Thus, starting from a chosen elementary honeycomb structure, which may even be standard (that is to say initially without membrane), the membrane is arranged in the honeycomb according to the frequency to be treated, that is to say at a predetermined distance from the base section of the cell. Thus, different ranges of frequencies can be handled by the same basic honeycomb structure and the same membrane depending on the arrangement of the membrane in the cells of the honeycomb structure.

In one exemplary embodiment, the step of gripping a portion of the septum includes the step of drawing through the insertion tool.

In an exemplary embodiment, the releasing step includes the step of ending the suction of the portion of the septum by the insertion tool.

In one exemplary embodiment, the manufacturing method comprises the step of pressing said portion of the diaphragm against the inner wall of the chamber by means of the pressure application system of the insertion tool so as to fix it.

Yet another aspect provides an insertion tool for inserting a septum into a cell of a honeycomb sound insulating structure.

For example, the insertion tool comprises at least one end piece configured to be inserted into the chamber.

For example, the end piece includes at least one gripping system configured to hold or release a portion of the septum.

In one exemplary embodiment, the gripping system includes a suction channel configured to be depressurized and hold a portion of the septum.

In an exemplary embodiment, the end piece comprises a pressure application system configured to flatten a portion of the diaphragm against an inner wall of the chamber.

Drawings

The invention will be better understood and its advantages will become clearer from reading the following detailed description, given by way of indication and without any limitation, with reference to the accompanying drawings, in which:

figure 1 shows a honeycomb soundproofing structure in a schematic perspective view;

figure 2 presents a series of cells enabling the formation of a honeycomb structure (e.g. the honeycomb structure of figure 1), implementing an exemplary embodiment according to the present invention;

figure 3 shows in cross-section cells of a honeycomb structure according to an exemplary embodiment of the invention as illustrated in figure 2;

FIG. 4 is a perspective view of an aircraft comprising a nacelle with an air intake;

FIG. 5 schematically shows an exploded view of the nacelle air intake as represented in FIG. 4;

figure 6 is a lateral section of the sound absorbing panel of the air intake as illustrated in figure 5;

figure 7 schematically shows a cross-sectional view of a cell of a basic honeycomb structure, for example as illustrated in figure 1;

figure 8 illustrates the step of picking up the membrane by means of an insertion tool according to an exemplary embodiment of the present invention;

figures 9a) and 9b) schematically show two exemplary embodiments of an insertion tool according to the present invention;

figure 10 illustrates the step of inserting the septum into the chamber while holding the septum by the insertion tool, according to the embodiment of figure 8;

figure 11 schematically shows the diaphragm in position in the cell;

figure 12 illustrates a step of inserting the septum into the chamber while holding the septum by an insertion tool, according to another exemplary embodiment; and

figure 13 shows a septum and an insertion tool according to other exemplary embodiments of the invention.

Like elements represented in the foregoing figures are identified by like reference numerals.

Detailed Description

Fig. 1 schematically illustrates a conventional or basic honeycomb acoustical structure 10.

The honeycomb acoustic insulation structure includes cells (also referred to as cavities) 11 juxtaposed to each other in two mutually orthogonal directions. The third direction, orthogonal to the first two, corresponds to the thickness of the honeycomb structure, which is also defined by the height H of the cells 11.

In the example represented in fig. 1, the honeycomb is provided with a resistant sheet 12 covering the cells 11 on a first side of the honeycomb. The resistive patch 12 is optionally perforated. It forms a resistant surface allowing the chamber 11 to communicate with the external environment.

On the second side of the honeycomb structure, the honeycomb structure is provided with a closing sheet (back skin) 13 closing the cells 11.

The closure tab 13 may be a solid tab. However, it may be a sheet with perforations. Solid sheets are typically used for simple acoustic processing known as SDOF (single degree of freedom) and form a back skin configured to reflect sound waves. Perforated closing sheets are commonly used for so-called DDOF (two degree of freedom) acoustic treatment, for which purpose a stack of two honeycomb levels is produced, these levels being separated by a porous intermediate skin formed by said closing sheet 13.

In fig. 1, to more clearly show the honeycomb structure, a resistive sheet or layer 12 is shown covering only some of the cells 11.

The cells 11 of the honeycomb structure 10 represented here are so-called hexagonal cells, the volume of which is that of a right circular cylinder with a hexagonal base section S, these hexagonal cells extending with a height H between the resistant sheet 12 and the closing sheet 13.

Furthermore, the cells are arranged in a quincunx, nested within each other, where no dead volume is defined.

Fig. 2 presents a series of cells 11 that enable the formation of a honeycomb structure 10 (similar to that of fig. 1) that embodies an exemplary embodiment according to the present invention.

For example, the cell 11 is a monolithic cell.

The cells 11 here have a hexagonal base section S (as in the hexagonal base section of fig. 1), but they may have any other shape, in particular an at least partially circular shape.

Here, the base section S represents a section of the cell at one end of the cell.

Furthermore, the cell 11 here comprises, by definition, an inner wall 16 (shown in fig. 3).

The cells 11 may be made of a synthetic material, for example, a thermoplastic matrix, paper or resin-coated fabric, or of metal or the like, depending on the intended application.

According to the invention, the cell 11 of fig. 2 comprises a membrane 20 arranged along a cross-section of the cell 11.

Septum 20 is made, for example, at least in part, of an elastomer (e.g., silicone, etc.), metal, thermoplastic, resin, or the like.

The diaphragm 20 includes at least one membrane 21.

The membrane 21 is for example bonded (by means of an adhesive or resin) or brazed or welded into the cell 11, in particular at the inner wall 16 of the cell or at the boundary thereof.

The membrane may have a profile of any shape (e.g., circular), which allows it to be adapted to a large number of honeycomb cross-sectional shapes.

For example, the septum 20 blocks, by itself or in cooperation with an adhesive or another material filling a possible gap between at least part of the contour of the membrane 21 and the inner wall 16 of the cell, the entire cross section of the cell 11 in which it is arranged, so that the septum 20 divides the cell 11 into two compartments 14, 15 (shown in fig. 3).

In one exemplary embodiment, the membrane may have a lateral dimension (e.g., diagonal or diameter if the membrane has a circular profile) that is less than or equal to a corresponding dimension of a cross-section of the cell in which the membrane is disposed, thus possibly leaving a gap between at least a portion of the profile of the membrane 21 and the inner wall 16 of the cell, which may then be filled with an adhesive or the like.

For example, the membrane 21 may be relatively non-deformable and rigid, and in turn, it may have a small thickness, thereby making it light in weight.

Such a membrane is for example made of a composite material.

In another exemplary embodiment, septum 20 may have a lateral dimension (e.g., diameter) that is greater than a corresponding dimension of a cross-section of the cell in which the septum is disposed, such that the septum itself blocks the entire cross-section.

In particular, in order to introduce the membrane into the cell, the membrane is then for example configured to be compressed so as to penetrate therethrough.

In this case, the membrane may comprise at least one corrugation.

The at least one corrugation may be preformed in the membrane 21 and/or may be induced by compression of the membrane when positioned in the cell 11.

One advantage of the pre-formed corrugations is that, in addition to facilitating and directing compressive deformation as required, it allows the membrane to extend relative to its rest position.

According to an exemplary embodiment, at least one of the corrugations may be static.

According to another exemplary embodiment, the at least one corrugation may be configured to allow the membrane to unfold.

This enables the diaphragm to be manufactured and stored, in particular at a small height, which enables space savings.

The adhesion between the membrane 20 and the cells 11 of the honeycomb structure 10 is produced, for example, by using an adhesive, this adhesion being supplemented by the natural pressure effect provided by the membrane 21 on the inner walls 16 of the cells (once inserted in the cells, the membrane tries to return to its free state).

In case the cells 11 are made of thermoplastic material and the membrane 20 is also made of thermoplastic material, the connection between them can be produced by welding without the need for adhesives.

Thus, in one exemplary embodiment, the membrane 21 has a flexibility and a deformability configured to accommodate shape and tolerance variations (i.e., variations of about 1 to 3mm in radius, for example) of the honeycomb structure.

The diaphragm 20 also comprises a central area that is acoustically open and here, in particular, a tube 23 extending from one face of the membrane 21.

Here, the tube 23 denotes a duct having any type of cross section, which may have constant or non-constant dimensions over the height of the tube and which forms a bulge with respect to the membrane. The tube may be cylindrical or frustoconical, having a polygonal or circular cross-section.

The polygonal cross-section is for example hexagonal.

For example, in a honeycomb structure with hexagonal cells (conventional honeycomb), the tubes have in particular a circular or hexagonal cross section.

On the other hand, in cells with a non-hexagonal cross-section (for example, in a honeycomb structure with a flexible core (commonly referred to as "flex core")), the tube more particularly has a circular cross-section and is instead frustoconical.

The two compartments are in acoustic communication with each other only through the tube 23, the membrane 21 being sealed in its contour to the inner wall 16 of the cell 11.

The free end of the tube forming the sound outlet may for example have a fully open cross-section, a bore, as represented in fig. 3 or as represented in fig. 13 for the tube 23 ", or the tube may comprise a porous wall, a set of microperforations or a fabric, e.g. a metal fabric, e.g. as illustrated in fig. 13 with reference numerals 23 'and 23"'.

Such a tube 23 is configured to maintain an undeformable region and tends to have a deformable region surrounding this undeformable region. It enables the definition of a physical interface that enhances the adaptability of the membrane while protecting the acoustic zone.

Thus, the acoustic outlet may not be deformed, since it is assumed here that the acoustic zone is not deformed within a tolerance of less than 10% of the cross-sectional variation of the acoustic outlet (which corresponds to a pressure drop of about 10%).

According to one characteristic of the diaphragm according to this embodiment, the stiffness of the acoustically open central region (i.e. the tube 23) is at least equal to the stiffness of the membrane 21.

This can be achieved, for example, by the open central area (in particular the tube 23) being thicker than the membrane 21 when the open central area and the membrane are made of the same material.

Fig. 3 shows a cell 11, such as the cell of fig. 2, in a cross-sectional view.

This figure shows that the septum 20 divides the chamber 11 into two compartments 14, 15. The peripheral edge of the membrane is fixed to the inner wall 16 of the cell 11 between the two ends of said wall 16 in the direction of the height H, so as to be able to divide it into two compartments 14, 15.

Starting from the selected honeycomb structure, the membrane 21 is arranged in the cells 11 according to the acoustic frequency to be treated.

For example, the membrane 21 is arranged along a cross section of the cell.

In an exemplary embodiment, the intersection between the membrane 21 and the inner wall of the cell 11 is arranged parallel to the base section S and at a distance from the base section S.

The membrane 21 includes at least one open central portion, e.g., an orifice 22.

Here, the orifice 22 is centered with respect to the cross section of the cell in which the membrane 21 is arranged.

Here, a tube 23 closes the aperture 22 and extends into the compartment 14.

In particular, the tube 23 extends from the edge of the orifice 22, so that the diameter of the orifice 22 is equal to the internal diameter d of the tube 23.

Thus, the tube 23 is also centred with respect to the cross section of the cell.

The free end of the tube 23 forming the acoustic outlet 24 may comprise a hole (as shown in fig. 3 or as shown in fig. 13 for the tube 23 ") or a set of micro-perforations or a fabric, e.g. a metal fabric, e.g. as illustrated in fig. 13 (indicated with reference numerals 23 'and 23"').

The cross-section of the tube 23 and in particular of the acoustic outlet 24 is not deformable, for example under the stresses induced during the step of inserting the diaphragm into the cell. For example, the cross-section of the acoustic outlet 24 remains constant between the free state and when the diaphragm is inserted into the cell, within a tolerance of 10% of the cross-sectional variation of the acoustic outlet (which corresponds to about 10% of the pressure drop).

The conformability of the diaphragm is provided by a membrane configured to deform according to the size and shape of the chamber, if desired.

The two compartments 14, 15 are then in acoustic or fluid communication with each other through the tube 23.

The compartment 14 into which the tube 23 extends is thus configured to handle low frequencies, while the compartment 15 in the cell 11 on the other side of the membrane 20 is configured to handle high frequencies.

The tube 23 is here cylindrical, for example with a circular cross section. According to another advantageous exemplary embodiment, it may have a hexagonal cross-section.

The height e of the tube 23 is equal to at least three times its diameter and in particular at least three times the diameter of the cross section of the acoustic outlet 24 of the tube 23.

Starting from the sound outlet 24, the tube 23 has an internal cross-sectional diameter which is constant over its entire height e or, for example, over at least 50% of the height e.

The diaphragm 20 is arranged in the chamber 11 according to the frequency to be treated. Thus, starting from the chosen honeycomb structure, the diaphragm is for example arranged so that the acoustic outlet 24 is at a distance p from the base section S, which is determined according to the frequency to be treated.

For example, the distance p is between 20% and 80% of the height H.

Depending on the given acoustic specifications and dimensions (height and cross-section) of the cells of the honeycomb in question, the membrane is arranged such that the acoustic outlet 24 is, for example, at one third of the height or at two thirds or half of the height.

In the present example illustrated in the figures, the membrane 21 is located at about half of the cell, i.e. at about 50% of the height H from the base section S, and the acoustic outlet 24 is here at about 25% of the height.

Thus, the volume of each of the compartments 14, 15 varies accordingly, and here they are substantially equal.

Thus, such a honeycomb structure with a septum enables a wider range of acoustic frequencies to be processed than the same honeycomb structure without a septum.

The diaphragm according to the invention thus allows a simpler acoustic dimensioning. The sound waves are guided by the tube. Such a diaphragm is more robust in industry, since it is easier to ensure that the sound waves are absorbed by the tube, which is less dependent on the shape and size of the cross-section of the cell. Furthermore, such a diaphragm may be suitable for a large number of cells of different shapes and sizes.

Fig. 4 shows a twin jet aircraft with two nacelles 200 with air intakes 201.

Fig. 5 shows an exploded view of the air intake 201 of the nacelle 200 of the propulsion unit of the aircraft as represented in fig. 4.

The air intake 201 includes structural elements, such as a front frame 101 and a rear frame 104, and from an upstream end to a downstream end of the nacelle 200, includes a lip 100 carried by the front frame 101, an outer panel 102 that extends beyond the nacelle 200 to continue the lip 100 (and forms an outer wall of the air intake), an inner wall 103 that extends within the nacelle to continue the lip and defines a central duct for directing air in the direction of the engine, the outer panel and the inner wall being carried by the front frame 101 and the rear frame 104.

The shape of the air intake and the system equipped with it must be such as to avoid the formation and/or accumulation of ice or frost, ensure aerodynamic functions, prevent birds from entering the fan chamber containing the engine system and limit the effects of noise pollution.

To perform the latter function, the inner wall 103 is a sound-absorbing panel, which is shown in cross-section, for example, in fig. 6.

The sound absorbing panel 103 then comprises a honeycomb structure as described above, i.e. for example:

a porous, perforated or micro-perforated so-called acoustic or resistant skin 111 forming, for example, the visible face of the panel (that is to say the face turned towards the inside of the central duct of the air intake); the purpose of such a resistant skin is to transmit the sound waves, and possibly also to dissipate the energy of the sound waves at least partly in the form of heat,

a rear skin 113 having substantially the function of ensuring the structural strength of the sound-absorbing panel, an

A core 112, a resistive skin 111 and a rear skin 113 are fixed on both sides of the core, which core contributes to both mechanical strength and acoustic suppression, the main function of the core being to capture and suppress sound waves.

Here, the core 112 includes a cell with a septum according to an exemplary embodiment of the present invention.

In the case where the sound absorbing panel is an area capable of picking up ice or water, the panel may incorporate a heating element, for example in the form of a heating tube or wire.

However, since the sound-absorbing panel can be formed from various basic honeycomb structures, the cells of which can be provided with various membranes, it is advantageous to be able to provide a method for producing at least a honeycomb sound-insulating structure and a membrane insertion tool that can be adapted to different configurations.

Fig. 7 schematically shows a cross-sectional view of cells 11 of a basic honeycomb structure, for example as illustrated in fig. 1 or having a base section S or height H of any other shape.

Each cell 11 has an inner wall 16.

To position septum 20 in chamber 11 as illustrated in fig. 7, fig. 8 illustrates the step of picking up septum 20 by insertion tool 30 according to an exemplary embodiment of the present invention.

Such an insertion tool 30 is illustrated, for example, in fig. 9a) and 9b) according to two alternative embodiments.

The insertion tool 30 according to the invention comprises at least one end piece 31 configured to be inserted into the chamber 11 together with the septum 20.

End piece 31 includes, for example, a gripping system configured to hold and release a portion of septum 20.

In the exemplary embodiment illustrated in the figures, the grasping system includes at least one channel 32, referred to as a suction channel 32, which is configured to be at least depressurized.

The suction channel 32 is thus configured to hold the diaphragm 20 by suction, by the suction cup effect.

In these figures, the end piece 31 includes an internal bore 34 extending from the end of the end piece 31.

Such an internal bore 34 is configured to receive a tube of a septum, such as tube 23 of septum 20 as represented in fig. 2 and 3.

With such a membrane, it may then be particularly convenient to hold the membrane by means of a tube.

For this purpose, the suction channel 32 opens into the inner bore 34.

In particular, the suction channel 32 opens into a groove 33 dug in the wall of the inner bore 34, where the groove is dug out completely around the inner bore 34, so that suction can be performed completely around a portion of the tube.

In order to retain the septum 20, in particular at the interface between the tube and the membrane (which may be produced jointly in a single piece or produced separately and subsequently assembled), which limits the risk of damage to the septum 20, the internal bore 34 comprises a deep cylindrical portion and an open flared portion, here for example frustoconical.

In the exemplary embodiment of fig. 9a), the groove 33 is hollowed out in the deep cylindrical part so that it faces the side wall of the tube when the membrane is picked up by the tool.

In the exemplary embodiment of fig. 9b), the groove 33 is dug out in the frustoconical opening portion, so that when the membrane is picked up by the tool, the groove then faces the end of the tube, or the groove is dug out at the interface between the tube and the membrane. Such a configuration is beneficial, for example, for diaphragms having small height tubes.

Externally, the end piece 31 comprises a side wall 35.

The outer side wall 35 is for example cylindrical in order to be easily insertable into all types of cells.

According to an advantageous option, the end piece 31 here comprises a pressure application system 36 arranged on the outer side wall 35.

Such a pressure application system 36 is mainly configured to flatten and press a portion of the diaphragm 20 against the inner wall 16 of the cell 11, in particular to fix a portion of the diaphragm thereto.

In the exemplary embodiment illustrated in fig. 9a) and 9b), the pressure application system 36 comprises an inflatable balloon 37.

The inflatable balloon 37 is then configured to inflate so as to press a portion of the diaphragm 20 against the wall 16 of the cell when the diaphragm is positioned in the cell 11, otherwise the inflatable balloon is configured to deflate.

According to another exemplary embodiment represented in fig. 13, the pressure application system may include an injection channel 38 configured to deliver pressurized air.

Alternatively, in this exemplary embodiment, the injection channel 38 and the suction channel 32 are formed by the same channel, which is selectively depressurized or supplied with pressurized air.

Thus, in a first step, insertion tool 30 is configured to pick up and hold septum 20 by sucking a portion of septum 20 using suction channel 32 that creates a suction cup effect.

Fig. 10 then shows the step of inserting the membrane 20 into the cell 11 by means of an insertion tool 30 which holds the membrane in the suction channel 32 by means of reduced pressure.

In this example, the step of inserting the septum 20 into the chamber 11 includes the step of pushing the septum 20 into the chamber 11 by the insertion tool 30.

As demonstrated herein, when the membrane is larger than the corresponding cross section of the cell, a portion of the membrane of the septum is then folded onto the same side as the tube, thus covering the top of the insertion tool 30.

Once the membrane 20 is in the desired position in the cell 11, the method may comprise the step of pressing a portion of the membrane 20 against the wall 16 of the cell 11 to fix it.

When the membrane is larger than the cross-section of the cell, it can naturally flatten against the inner wall 16 of the cell by elasticity.

The pressure is generated here, for example, by a pressure application system 36 of the insertion tool 30, which presses a portion of the diaphragm 20 flat against the wall 16 of the cell 11.

In the illustrated example, the inflatable bladder 37 inflates and flattens a portion of the membrane 21 against the wall 16 of the cell 11.

Simultaneously or subsequently, the method comprises a step of fixing a portion of the membrane 20, optionally pressed against the wall 16 of the cell 11.

The fixing may be performed by bonding (e.g. by an adhesive comprising e.g. a resin) or e.g. by welding or any other means.

The adhesive is for example an epoxy type adhesive.

If the size of the membrane is smaller than the corresponding cross-section of the cell, the method may comprise the step of injecting an adhesive filling possible gaps between the contour of the membrane and the inner wall 16 of the cell and fixing the membrane in the cell.

The adhesive is for example an epoxy type adhesive, a flexible adhesive or an elastomer, which enables filling of such gaps.

The adhesive may be advantageously added to the outer surface of the membrane 21 by spraying or dipping.

Before or after the securing step, the method includes the step of releasing the septum 20, for example, by the insertion tool 30.

To this end, this step comprises at least a step of ending the suction of the insertion tool 30 and, optionally, of pressure application by the pressure application system 36; for example, the inflatable balloon 37 is deflated.

The suction channel 32 is then returned to ambient pressure, for example.

Optionally, the suction channel 32 may also be configured to blow in a slight air pressure in order to release the membrane faster or to avoid adhesion between the membrane 20 and the insertion tool 30.

Figure 11 schematically shows septum 20 in place in chamber 11 released from insertion tool 30.

In this way, it is possible in particular to insert more than one diaphragm (whatever it is) into the same chamber 11.

The production of the honeycomb sound-insulating structure can then be continued.

For example, the method then comprises the step of laying a resistant sheet 12 covering the cells 11 (containing the membranes) on a first side of the honeycomb structure 10.

The resistive patch 12 may optionally be perforated. It forms a resistant surface allowing the chamber 11 to communicate with the external environment.

The method may further comprise the step of laying a closing sheet 13 closing the cells 11 on the second side of the honeycomb structure.

The closure tab 13 may be a solid tab. However, it may be a sheet with perforations. Solid sheets are typically used for simple acoustic processing known as SDOF (single degree of freedom) and form a back skin configured to reflect sound waves. Perforated closing sheets are commonly used for so-called DDOF (two degree of freedom) acoustic treatment, for which purpose a stack of two honeycomb levels is produced, these levels being separated by a porous intermediate skin formed by said closing sheet 13.

Fig. 12 shows another exemplary embodiment of the present invention.

In this figure, the outer side wall 35 of the end piece 31 of the insertion tool 30 comprises a frustoconical portion 39, the cross section of which narrows in the direction of the tip of the insertion tool 30.

Furthermore, the end piece 31 of the insertion tool 30 differs from fig. 9a) -9b) in that the suction channel 32 opens out to a part of the outer side wall 35, that is to say towards the outside instead of towards the inside as in fig. 9a) -9b), and in particular the suction channel 32 opens out here to the frustoconical portion 39.

A tool, such as the one represented in fig. 12, for example, is used to pick up and hold the membrane 20 on the side of the membrane 21 opposite to the side on which the tube 23 extends.

The frustoconical portion 39 is then configured to be placed below one end of the tube 23 at the interface with the membrane 21, for example, around the orifice 22.

The insertion tool 30 then holds the septum 20 by suction of a portion of the septum 20 surrounding the orifice 22.

In the example represented, the insertion tool 30 enables the septum 20 to be inserted into the chamber 11 by traction.

Optionally, the suction channel 32 may also be configured to blow air pressure in order to release the septum 20 faster or to avoid adhesion between the septum 20 and the insertion tool 30.

Finally, fig. 13 shows a septum 20 ', 20 "' and an insertion tool 30 according to other exemplary embodiments of the invention.

Here, for example, the diaphragm 20 'comprises a membrane 21' and a tube 23 ', the free end of which, forming the acoustic outlet 24', here comprises a plurality of microperforations.

The diaphragm 20 "here comprises, for example, a membrane 21" (which membrane comprises corrugations) and a tube 23 "(here similar to the tube 23 described above), the acoustic outlet 24" of which comprises a hole of a size equal to the diameter of the tube 23 ".

The diaphragm 20 "' here comprises a membrane 21" ' (e.g. membrane 21 "comprising corrugations) and a tube 23" ' whose acoustic outlet 24 "' comprises a plurality of microperforations in a similar manner to the tube 23 '.

According to an exemplary embodiment, not represented, the acoustic outlet of the tube may comprise a braided zone.

Each of these membranes 20 ', 20 "' may be inserted into cell 11 by an insertion tool 30 according to the invention, for example as illustrated herein.

Furthermore, in this example, the end piece 31 is configured to hold the membrane 20 ', 20 "' by a portion of the membrane 21 ', 21"' of the membrane, in particular close to its periphery, for example.

For this purpose, as in the example of fig. 12, the suction channel 32 here opens into a part of the outer side wall 35.

As previously mentioned, the suction channel 32 may also optionally be configured to blow air pressure in order to release the membrane 20 ', 20 "' relatively quickly or to avoid adhesion between the membrane 20 ', 20"' and the insertion tool 30.

Furthermore, the suction channel 32 may also be configured to enable a stronger injection (e.g. high pressure air) and thus form an injection channel 38 of a pressure application system configured to deliver pressurized air in order to press a portion of the membranes 21 ', 21 "' against the wall 16 of the chamber 11.

According to an exemplary embodiment, at least one of the corrugations may be static.

According to another exemplary embodiment, the at least one corrugation may be configured to allow the membrane to unfold.

In this case, the method may for example comprise a suction step during the baking step, in order to unfold the membrane.

This enables the diaphragm to be manufactured and stored, in particular at a small height, which enables space savings.