This application claims the benefit of the French patent application No. 1662821 filed on Dec. 20, 2016, the entire disclosures of which are incorporated herein by way of reference.
The present invention relates to a structure establishing a sound insulator, a method for manufacturing such a structure, and a machine used in the context of said manufacturing method.
When operating, an aircraft engine generates noise. The engine is housed in a nacelle and to reduce this noise, it is known to install structures establishing a sound insulator around the engine in the structure of the nacelle.
Such structures establishing a sound insulator have, for example, the form of honeycomb structures. Such a honeycomb structure includes two parallel plates, one of which is perforated, and between which hexagonal cells placed side-by-side are arranged.
To increase the effectiveness of the low frequency sound treatments of the honeycomb structure, it is known to incline each rectangular cell with respect to the normal to the plates. Such a honeycomb inclined structure is described in the document U.S. Pat. No. 3,821,999.
Although, from a sound point of view, such a honeycomb inclined structure provides good results, the structural behavior, in particular during compression, of such a structure is reduced with respect to the structural behavior of a structure having cells that are not inclined. Moreover, since such a honeycomb inclined structure is produced by cutting a honeycomb non-inclined structure, this results in large material losses during the manufacture thereof.
An object of the present invention is to propose a structure establishing a sound insulator which, in particular, makes it possible to obtain a more mechanically robust structure.
To this end, a structure establishing a sound insulator is proposed which includes:
each folded strip is arranged between two successive intermediate strips, where every other crease line is stuck to one of the two intermediate strips and the other crease lines are stuck to the other of the two intermediate strips, where the two folds of the folded strip which are on either side of a crease line establish two faces of a triangular prism and the zone of the intermediate strip which is stuck to the two crease lines adjacent to the crease line which is between said two folds establishes the third face of the triangular prism,
where, for two folded strips on either side of a same intermediate strip, the generator of the triangular prism of one of the folded strips forms an acute angle with respect to the first plate, and the generator of the triangular prism of the other folded strip forms an obtuse angle with respect to the first plate.
The triangular structure with two reverse inclines makes it possible to obtain a structure establishing an effective sound insulator and having a reinforced mechanical structure, and to limit the losses during the manufacture thereof.
Advantageously, the intermediate strips undergo a first folding and a stacked second folding, and the two foldings take place with different folding angles.
Advantageously, the folding line corresponding to the first folding and the folding line corresponding to the second folding intersect at a point located on an edge of the intermediate strip.
The invention also proposes a method for manufacturing a structure establishing a sound insulator, the manufacturing method including:
the folding method including, when the first plate is between a fold and the rollers:
The invention also proposes a folding machine including:
Advantageously, each plate is rotatable about an axis normal to the surface thereof, and the folding machine comprises, for each plate, an actuator commanded by the control unit in order to rotate said plate.
The features of the invention which are mentioned above, as well as others, will emerge more clearly upon reading the following description of an exemplary embodiment, said description being given with reference to the appended drawings, wherein:
A web 108 is placed between the first plate 102 and the second plate 104, which web is stuck to the first plate 102 and to the second plate 104.
The web is established from a plurality of intermediate strips 110 and from a plurality of folded strips 112a and 112b.
The intermediate strips 110 are perpendicular at least to one plate from the first plate 102 and from the second plate 104 and extend between the two plates 102 and 104. Each intermediate strip 110 is stuck via one of the sidewalls thereof to the first plate 102 and by the other sidewall thereof to the second plate 104.
In the invention embodiment shown in
Each folded strip 112a-b is arranged between two successive intermediate strips 110 and each folded strip 112a, 112b is folded in a zig-zag formation. Each folded strip 112a-b is stuck to the first plate 102 and to the second plate 104. The manner in which the strips and plates are stuck to each other may depend on the materials from which the strips and plates are made, in that, with thermoplastic materials, a pressing engagement between the strips and plates at an elevated temperature would cause the strips and plates to be stuck or bound together. With other materials, an adhesive could be used to cause the strips and plates to be stuck or bound together.
Each folded strip 112a-b is, thus, a series of crease lines 114 and of folds 116.
For a folded strip 112a-b, every other crease line 114 is stuck to one of the intermediate strips 110 and the other crease lines 114 are stuck to the other intermediate strip 110.
The two folds 116 of the folded strip 112a-b which are on either side of a crease line 114 form two faces of a triangular prism and the zone of the intermediate strip 110 which is stuck to the two crease lines 114 adjacent to the crease line 114 which is between said two folds 116 establishes the third face of the triangular prism. In a section parallel with the two plates 102 and 104, the folds 116 of the folded strip 112a-b and the intermediate strips 110 form triangles.
The web 108 thus forms an isogrid shape.
For each folded strip 112a, 112b, the generator of the triangular prism is not perpendicular to the plates 102 and 104, and each folded strip 112a, 112b and the intermediate strips 110 thus create an oblique triangular prism.
Sticking the triangular prisms to each plate 102, 104 seals each triangular prism.
For two adjacent folded strips 112a-b, i.e., on either side of a same intermediate strip 110, the generator of the triangular prism of one of the folded strips 112a has, seen from a direction perpendicular to the intermediate strips 110, an acute angle α with respect to the first plate 102, and the generator of the triangular prism of the other folded strip 112b has, seen from the same perpendicular direction, an obtuse angle β with respect to the first plate 102. In other words, for two adjacent folded strips 112a-b seen from a same direction perpendicular to the intermediate strips 110, one is tilted one way and the other is tilted the other way with respect to the direction normal to the first plate 102.
This double incline structure makes it possible to have an increased mechanical strength. In particular, it has a better mechanical strength during compression.
The first plate 102 and the second plate 104 are produced, for example, from carbon fiber, from metal materials of titanium or aluminum alloy type, or also from thermoplastic composites of PEI (polyetherimide), PEAK (polyaryletherketone) or PEEK (polyether ether ketone) type.
The intermediate strips 110 and the folded strips 112a and 112b are produced, for example, from paper, of aramid paper type, from metal materials of titanium or aluminum alloy type, but also from thermoplastic composites of PEI (polyetherimide), PEAK (polyaryletherketone) or PEEK (polyether ether ketone) type.
According to a particular embodiment, the angle α of inclination of a folded strip 112a is between 10° and 80°, preferably between 40° and 60° and, the angle β of inclination of the adjacent folded strip 112b is between 100° and 170°, preferably between 120° and 140°.
When the plates 102 and 104 are not planar but curved, for example to follow the curvature of the nacelle of an engine, the intermediate strips 110 must follow this curvature. For this purpose, each intermediate strip 110 is folded as is explained hereafter such that the folded zone is flattened, i.e., in the plane of the intermediate strip 110.
In an advantageous embodiment, the folding line corresponding to the first folding and the folding line corresponding to the second folding intersect at a point located on an edge of the intermediate strip 110.
Of course, the folding angles can be changed according to the curvature to be obtained, and generally, each intermediate strip 110 undergoes a first folding and a second folding stacked on the first folding, the two foldings taking place with different folding angles.
The operation for folding the intermediate strip 110 can be repeated according to the geometry to be obtained.
The folding machine 200 comprises two rollers 202a-b and two plates 204a-b.
Each roller 202a-b is rotatably mounted about the axis thereof, and the two axes are parallel. The two rollers 202a-b are used to supply the folding machine 200 with strip 201 and are motorized in order to drive and guide the strip 201 which is placed therebetween toward the plates 204a-b.
After folding, the strip 201 will become a folded strip 112a-b.
The axes of the two rollers 202a-b are parallel with the midplane in which the strip 201 falls, i.e., the plane equidistant from the two axes.
Each plate 204a-b has a leading edge 206a-b which attacks the strip 201 in order to fold it.
Each plate 204a-b is translatable, firstly, in a plane perpendicular (first directions 20 and 21) to the midplane, and, secondly, parallel (second directions 22 and 23) with the midplane, i.e., with the strip 201 coming from the rollers 202a-b.
To this end, the folding machine 200 has actuators for moving each plate 204a-b in each of the directions. Each actuator is motorized and comprises, for example, for each direction, slides translating each plate 204a-b, and an activator such as a motor, a jack, etc., for moving the plates 204a-b along the slides one way or the other way.
The folding machine 200 also includes a control unit, such as a processor, which commands each actuator in order to provide the appropriate movements of each plate 204a-b as are described hereafter.
The control unit also controls the actuator of each roller 202a-b in order to rotate it.
A folding method for obtaining a folded strip 112a-b, which method is implemented by the folding machine 200, is explained hereafter, taking into consideration that at least one folding has already been carried out (
When the folding of the strip has ended, the folded strip 112a-b is obtained.
A method for manufacturing the structure 100 comprises producing folded strips 112a-b according to the folding method described above, then in carrying out a step for sticking intermediate strips 110 and folded strips 112a-b between the plates 102 and 104, by inserting a folded strip 112a-b between two intermediate strips 110, and positioning them such as to produce reverse incline generators.
In this case, each plate 204a-b is also a rotatable about an axis normal to the surface thereof, and for this purpose, the folding machine 200 comprises, for each plate 204a-b, an actuator, such as a motor, commanded by the control unit to rotate said plate.
A folding method for obtaining a folded intermediate strip 110, which method is implemented by the folding machine 200, is explained hereafter, the intermediate strip 110 being transported between the rollers 202a-b up to the plates 204a-b:
When the folding of the strip has ended, the folded intermediate strip 110 is obtained.
Of course, depending on the shape to be obtained for the intermediate strip, the angles of the plates 204a-b with respect to the midplane can be different.
The aforementioned manufacturing method makes it possible to manufacture the structure 100 while minimizing material losses.
The folded strips 112a-b can be produced from a thermosetting composite, for example of epoxy resin type, and the folds are then produced by compression in a mold in an autoclave, or by forging in a dedicated mold outside an autoclave. These two methods are carried out at temperatures and pressures that are normal for thermosetting resins, namely 2 to 7 bar and 180° C. in an autoclave, or 10 to 50 bar and 180° C. in the case of forging.
It is also possible to produce the intermediate strips 110 and/or the folded strips 112a-b by additive material 3D printing (ALM: Additive Layer Manufacturing), in particular in the cases of using metal materials or composites.
In a specific embodiment, notches are cut at ends of the folded strips 112a-b in contact with the plate 102 and/or the plate 104 and at ends of the intermediate strips 110 in contact with the plate 102 and/or the plate 104. These notches allow drainage of liquid which could build up in the structure 100. According to a first alternative, these notches are cut after sticking the folded strips 112a-b onto the intermediate strips 110 and before sticking the plates 102 and/or 104. In a second alternative, these notches are cut before folding the folded strips 112a-b.
While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
Number | Date | Country | Kind |
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1662821 | Dec 2016 | FR | national |