FR3071677A1 - CABLE PROTECTION DEVICE FOR AIRCRAFT - Google Patents

Abstract

The present invention relates to a protection device (10) for protecting at least one cable (5). The protective device (10) comprises an electrically conductive element (20) having at least one sector (25). This sector includes a bottom (30) extending longitudinally along an elongation line (100) along its bottom length (31) from a first end (32) to a second end (33), and transversely according to its bottom thickness (37) of a first face (38) to a second face (39). Said bottom (30) comprises a plurality of openings (50) which cross the bottom (30) transversely from one side of the first face (38) to the second face (39), each opening (50) being inscribed in a rectangular parallelepiped (60), said rectangular parallelepiped (60) having an extension length (61) and an extension width (62), said extension length (61) being greater than said extension width (62) .

Description

Cable protection device for aircraft.

The present invention relates to a cable protection device for an aircraft and to an aircraft comprising such a cable protection device.

The term "cable" usually designates a bundle of electrical wires. The term “cable” is used subsequently to denote in particular an electrically conductive wire, and / or a bundle of electrically conductive wires, and / or several bundles of electrically conductive wires.

An aircraft conventionally comprises avionic equipment linked together by cables traveling within its primary structure. Such avionic equipment is more simply referred to as "equipment" below.

This primary structure may in particular comprise an outer skin linked to frames and stringers. The outer skin is sometimes made from metallic materials. The use of a metallic skin is interesting from an electrical point of view. By way of illustration, a metal skin allows common grounding of the equipment in order to protect it. In addition, the metallic skin tends to protect the equipment from the indirect effects of a lightning strike on the aircraft by a Faraday cage effect.

However, aircraft increasingly include a primary structure made of composite materials. The use of composite materials tends to optimize the weight of the aircraft and its mechanical strength. In particular, aircraft structures are sometimes produced using composite materials comprising carbon fibers.

Although interesting, a structure made of composite materials does not in fact have the same advantages as a metallic structure from an electrical point of view, since the electrical conductivity of these composite materials is relatively low.

During a lightning strike on the aircraft, the cables and interfaces of the on-board electronic equipment are then likely to carry transient induced electric currents significantly more energetic than on an aircraft with a metallic structure.

To remedy this drawback, the equipment can be modified to withstand such high energy transient electric currents.

Alternatively or additionally, the outer skin of the primary structure can be metallized.

Alternatively or additionally, a protection device can be integrated as close as possible to the cables, in particular if a manufacturer wishes to integrate in an aircraft with a structure in composite materials equipment developed and certified initially for an aircraft with a metallic structure.

A protection device comprises an electrically conductive element to be installed along the structure of the aircraft. The cables are then arranged in a space delimited by the electrically conductive element. For example, the cables are attached not to the structure but possibly to the electrically conductive element.

Document FR 2950490 presents an electrically conductive element having U-shaped sections. Each section therefore comprises a bottom which extends longitudinally substantially parallel to the support structure, and two branches which extend transversely perpendicular to the bottom. The two branches are parallel to each other.

Each cable is arranged in a U shape between the bottom and the branches.

In addition, the U-shape tends to electrically protect cables more effectively than a simple ground plane against the indirect effects of lightning by a Faraday cage or shielding effect.

Such an electrically conductive element of a cable protection device is sometimes called "metallic ground plane" or "raceway" in English.

The electrically conductive elements can sometimes have sections having other shapes, for example but not exclusively L-shaped sections. In addition, the electrically conductive elements can include compartments for defining and segregating different cable routes.

Consequently, an aircraft can comprise a network of electrically conductive elements, this network being sometimes called "Electrical structure Network" in English.

Although interesting, the arrangement of electrically conductive elements is penalizing in terms of mass.

To minimize the mass of the network, the dimensions of the electrically conductive elements and in particular their thicknesses can be minimized. However, a minimum thickness is required for the electrically conductive element to perform an electromagnetic protection function.

In addition, the electrically conductive elements are subjected to mechanical stresses. These mechanical stresses can cause fatigue cracks which can cause partial or total local rupture of an electrically conductive element. In the presence of such a fault, an electrically conductive element then no longer fully protects against the indirect effects of lightning for the cables protected by this electrically conductive element.

The object of the present invention is therefore to propose a protection device for cables aimed at optimizing its resistance to cracks and its mass.

The invention relates to a protection device for protecting at least one cable, the protection device comprising an electrically conductive element, the electrically conductive element having at least one sector comprising a bottom, the bottom having a bottom length as well as a bottom width and bottom thickness, the bottom extending longitudinally along an extension line along its bottom length from a first end to a second end, the bottom extending in elevation perpendicular to the line of elongation from a first flank to a second flank, the bottom extending transversely perpendicular to the extension line, the bottom extending transversely along its bottom thickness of a first face intended to be opposite said at at least one cable to a second face intended to be opposite a structure carrying said protection device.

The bottom has a plurality of openings, each opening crossing the bottom transversely from the first face to the second face, at least one opening being empty, each opening being inscribed in a rectangular parallelepiped, this rectangular parallelepiped having a length extension along said extension line and an extension width perpendicular to said extension line, said extension length being greater than said extension width.

The expression "said bottom extending longitudinally along an extension line along its bottom length" refers to the extension of the bottom according to its direction of extension between the first end and the second end. The bottom indeed extends longitudinally along its bottom length along an extension line, namely a straight or curved line for example. The cables then extend parallel to this extension line. For example, the extension line is a virtual line located equidistant from the first flank and the second flank, and / or parallel to the first flank and / or to the second flank. The expression "along the extension line" refers to a direction parallel to the extension line.

The expression "said bottom extending in elevation along its bottom width" and the expression "said bottom extending transversely according to its bottom thickness >> refer to dimensions of the bottom in two perpendicular directions between them and at said extension line.

The bottom length represents the length of the largest segment extending between two ends of the bottom parallel to said extension line. This bottom length is greater than the bottom width, the bottom width being greater than its bottom thickness. This bottom thus takes the form of a plate extending along its bottom length by following a line, the width of the plate and / or its thickness being optionally scalable (s). In said sector, the bottom may have the shape of a rectangular parallelepiped having the length of the bottom length and the width of the bottom width.

The expression “each opening crossing the bottom transversely from the first face to the second face” means that each opening is an open orifice which opens onto the outside of the bottom at the level of the first face and the second face.

The expression "at least one opening being empty" means that no object fills this opening.

Each opening is further delimited by an edge describing a closed loop and belonging to the bottom. The expression "each opening being inscribed in a rectangular parallelepiped" means that said edge touches the four side walls of this rectangular parallelepiped.

Therefore, the bottom has multiple cutouts forming openings. These openings can help stop a crack. Indeed, such a crack no longer propagates in a given direction when this crack reaches an opening.

In addition, these openings tend to limit the mass of the protection device.

Any openings in the bottom of a protection device nevertheless have a negative impact on protection against the effects of lightning. In general and with reference to the following website https://leadertechinc.com/blog/how-apertures-affect-emi-shielding/, those skilled in the art believe that the largest dimension of an opening limits the effect first order electromagnetic shielding. The invention goes against this prejudice and is based on the fact that, depending on the orientation of the magnetic field with respect to the largest dimension of the opening, such a formulation is false.

Those skilled in the art consider that a large number of characteristic small openings induce a smaller loss of shielding effect than a small number of large openings. This situation can actually occur in a general case where the orientation of the electromagnetic field may be arbitrary and a priori unknown.

On the other hand, the invention goes against this prejudice by considering that the orientation of the electromagnetic field in the environment of the cables is fixed since it is determined by the orientation of the electrically conductive element along the extension line. Specific rules on the size of the openings can then be applied to improve the efficiency / mass ratio. In particular, the openings are dimensioned to be much longer than wide, namely to have a longitudinal dimension in the direction of extension of the cables greater than in a transverse direction according to a thickness of the cables. These openings thus make it possible to obtain a technical solution tending to limit the propagation of fatigue cracks by having a limited impact on the protection offered against the indirect effects of lightning. Optionally, the dimensions of the sections of the protective device can be reduced.

The protective device may further include at least one or more of the following characteristics.

Thus, the electrically conductive element can comprise at least one branch integral with the bottom.

The shapes can give the sections of the electrically conductive element L, U or other shapes to optimize a Faraday cage effect ...

In one aspect, the openings can be identical.

The openings therefore have the same shape and the same dimensions. The manufacture of the electrically conductive element can be facilitated.

Furthermore, the openings can have various shapes.

According to one aspect, at least one said opening may have an elliptical shape seen in a direction going from the second face to the first face, said extension length being equal to a major axis of the elliptical shape and said extension width being equal to a minor axis of the elliptical shape.

According to one aspect, at least one said opening may have a rectangular shape seen in a direction going from the second face to the first face.

The above forms can achieve the desired results.

Depending on one aspect and regardless of the shape of the opening, the extension length can be at least twice the extension width.

An opening that meets this criterion makes it possible to limit the impact of the opening on the protection offered against lightning, while making it possible to combat the propagation of possible cracks.

According to one aspect, the extension length may be equal to 10 centimeters plus or minus ten percent, and / or the extension width may be less than or equal to two centimeters, and / or said rectangular parallelepiped containing an opening may have a extension thickness between 0.4 millimeter and 1.4 millimeter.

In particular, the extension width can be equal to one centimeter, and / or less than one centimeter to optimize protection against lightning. An opening having an extension width less than or equal to one centimeter and an extension length of 10 centimeters tends to induce better protection than an opening having an extension width equal to two centimeters and an extension length of 10 centimeters.

Furthermore, the density of the number of openings may depend on the expected mass gain objective and on the protection performance against the indirect effects of expected lightning.

A minimum thickness may be required to resist the mechanical stresses undergone, in particular on an aircraft.

In one aspect, the extension width is less than one centimeter.

According to one aspect, the openings can be arranged along a plurality of protection lines, each protection line extending longitudinally along said extension line, each protection line comprising said openings arranged longitudinally one after the other, a full longitudinal section of the bottom longitudinally separating two adjacent openings arranged on the same protection line, a full elevation section of the bottom separating in elevation two adjacent openings disposed respectively on two adjacent protection lines.

In one aspect, the protective lines can be parallel to each other.

In one aspect, said openings of two adjacent protection lines can be staggered.

In one aspect, the protection device may include a comb fixed to the bottom to carry at least one cable.

Furthermore, the invention also relates to an aircraft. This aircraft is provided with a structure and with a protection device according to the invention fixed to said structure, said protection device housing at least one cable, or even carrying at least one cable.

Optionally, this cable extends parallel to the bottom of the protection device, the cable having a cable length along said extension line and a cable thickness in elevation.

The invention and its advantages will appear in more detail in the context of the description which follows with examples given by way of illustration with reference to the appended figures which represent:

FIG. 1, a view of an aircraft according to the invention,

FIG. 2, a view of a protection device according to the invention,

- Figures 3, to 5, views showing protective devices according to the invention.

The elements present in several separate figures are assigned a single reference.

Three directions X, Y and Z orthogonal to each other are shown in some figures.

The first direction X is said to be longitudinal. The term "longitudinal" relates to any direction parallel to the first direction X.

The second direction Y is said to be transverse. The term "transverse" relates to any direction parallel to the second direction Y.

Finally, the third direction Z is said to be in elevation. The expression "in elevation" relates to any direction parallel to the third direction Z.

Figure 1 shows an aircraft 1 according to the invention. This aircraft comprises a structure 2 comprising at least one wall 3. The wall 3 can for example be made from metallic or composite materials. This aircraft 1 can be a rotorcraft equipped with at least one rotary wing 4.

Furthermore, the aircraft 1 comprises at least one cable 5. Each cable 5 can be provided with one or more wires 6. Such a wire 6 can be an electric wire for example. A wire can allow the flow of an electric current or data.

In addition, the aircraft 1 comprises a protection device 10 according to the invention tending to protect at least one cable 5. Such a protection device 10 can be arranged on various structures, and not exclusively on an aircraft. For example, a protective device 10 according to the invention can be arranged on a ship, an automobile, a dwelling, etc.

According to FIG. 2 and independently of its location, the protection device 10 has an electrically conductive element 20. This electrically conductive element can form a chute 1 5.

The electrically conductive element 20 has at least one sector 25 forming a protective section. The electrically conductive element can comprise only a sector 25 according to the invention. According to another variant, the electrically conductive metallic element 20 may comprise at least one sector forming a protective section and at least one transition section.

More specifically, the electrically conductive element 20 and in particular a protection sector 25 is either produced using a metal or using a metallized material. Various constituent parts of this electrically conductive element 20 thus comprise metal. In addition, at least two electrical connections 80 are fixed to the electrically conductive element 20 to electrically connect the electrically conductive element 20 to an electrical current return network of the aircraft. Such electrical connections may include a wire or even metal tabs for example.

Furthermore, each sector 25 forming a protective section extends along its length along a line called for convenience "extension line 100". The extension line followed in Figure 2 is straight. However, such an extension line can be curved.

The protection device further comprises at least one holding means 90 making it possible to fix the electrically conductive element 20 to the wall 3 of the structure 2. Such a holding means 90 comprises for example a rivet 91 passing through an orifice of a sector 25 of the electrically conductive element 20. Any other known system can be envisaged, such as for example a system using screws and spacers, pins provided with gripping means, etc. Holding means 90 are distributed along the length of the electrically conductive element 20, for example as a function of a regular distribution defining a maximum spacing between two holding means 90 consecutive.

Each sector 25 has a bottom 30. This bottom 30 extends longitudinally along the extension line 100 along its bottom length 31 from a first end 32 to a second end 33.

In addition, the bottom 30 extends in elevation, in a direction Z perpendicular to the extension line 100, along its bottom width 34 from a first flank 35 to a second flank 36. For example, the line of elongation 100 is located at equal distances from the first flank and the second flank.

Finally, the bottom 30 extends transversely, in a direction Y perpendicular to the extension line 100, along its bottom thickness 37 from a first face 38 to a second face 39. The first face is opposite the cables 5 to be protected, while the second face 39 faces the structure 2 carrying said protection device 10.

Optionally, the bottom 30 of one or each sector 25 has the shape of a rectangular parallelepiped.

The sector 25 can also comprise at least one branch 40, and for example two branches according to FIG. 2. Each branch 40 extends from the bottom 30, for example from the first flank 35 or the second flank 36.

Furthermore, each branch can extend only transversely in the second direction Y. In particular, the branches shown move away from the bottom 30 by extending in a transverse direction D1. Due to this only transverse extension, the branches are perpendicular to the bottom.

Optionally, at least one branch can also extend from the bottom 30 longitudinally in the third direction Z and transversely in the second direction Y. Such a branch can for example have a shape in C or in L

The bottom 30 and each branch 40 jointly delimit a space 60. This space 60 is separated from the wall 3 of the structure 2 by the electrically conductive element 20, and in particular by the bottom 30 according to FIG. 2.

At least one cable 5 is then held in this space 60. Optionally, at least one cable is carried by the electrically conductive element 20. For example, the bottom 30 carries fixing means 70 by elastic stapling. According to another example, the bottom 30 carries a comb, each cable 5 being fixed to the comb. Alternatively or additionally, a removable plug can close the space 60 to hold a cable 5 in place. The teaching of document FR 304831 1 is applicable.

In addition, each cable 5 can extend substantially parallel to the bottom 30, and parallel to the extension line 100.

According to another aspect, the bottom 30 of a protection sector 25 has a plurality of openings 50. The openings of a protection section may be identical.

Each opening 50 crosses the bottom 30 transversely in the second direction Y right through from the first face 38 to the second face 39. Each opening represents a cut-out in the bottom 30.

Furthermore, each virtual rectangular parallelepiped opening 60 indicates that geometric, rectangular 60.

is registered in

The one each opening and in particular This parallelepiped is inscribed a shape in the shape of a rectangular parallelepiped 60 extends along an extension length 61 in a direction X parallel to the extension line 100, along an extension width 62 perpendicular to the extension line 100 and in a third direction Z, and finally along an extension thickness 63 perpendicular to the extension line 100 and in a second direction Y.

Therefore, the edges of each opening are in contact against the faces of such a rectangular parallelepiped.

In addition, the extension length 61 of such a rectangular parallelepiped is greater than its extension width 62.

For example, the extension length 61 is 10 centimeters plus or minus ten percent. Furthermore, the extension width 62 is for example less than or equal to two centimeters. Furthermore, the extension thickness 63 can be between 0.4 millimeter and 1.4 millimeter.

Optionally, the extension length 61 is at least twice as large as the extension width 62, or even ten times greater.

According to another aspect, one or more openings may have a rectangular shape 51 seen in a transverse direction going from the second face 39 to the first face 38.

Optionally, the opening has the shape of a rectangular parallelepiped, this rectangular parallelepiped may have the characteristics described above.

According to the variant of FIG. 3, one or more openings can have the shape of an ellipse 52 seen in a transverse direction going from the second face 39 to the first face 38. Consequently, the extension length 61 is coincident with a major axis 53 of the elliptical shape 52. Likewise, the extension width 62 is coincident with a minor axis 54 of the elliptical shape 52.

Regardless of the shape of the openings and with reference to FIG. 4, the openings 50 can be aligned along a plurality of virtual protection lines 55. Each protective line 55 extends longitudinally parallel to the extension line 1 00.

Along the same protective line 55, openings 50 are aligned longitudinally one after the other. As a result, a solid longitudinal section 56 of the bottom 30 without an opening longitudinally separates two adjacent openings 50 arranged on the same protection line 55.

Furthermore, a section in elevation 57 full of the bottom 30 devoid of openings can separate in elevation two adjacent openings 96, 97 arranged respectively in two adjacent protective lines 58, 59.

In one aspect, the protective lines 55 are parallel to each other.

According to the embodiment of FIG. 4, the openings present on a protection line 58 correspond to the translation in elevation in the third direction Z of the openings of an adjacent protection line 50.

According to the embodiment of Figure 5, the openings 50 of two adjacent protective lines 55 are arranged in staggered rows.

The openings on a protection line correspond to the elevation translation in the third direction Z and to the longitudinal translation in the first direction X of the openings of an adjacent protection line.

Naturally, the present invention is subject to numerous variations as to its implementation. Although 5 several embodiments have been described, it is understood that it is not conceivable to identify exhaustively all the possible modes. It is of course conceivable to replace a means described by an equivalent means without departing from the scope of the present invention.

Claims (12)

1. Protection device (10) for protecting at least one cable (5), said protection device (10) comprising an electrically conductive element (20), said electrically conductive element (20) having at least one sector (25) comprising a bottom (30), said bottom (30) having a bottom length (31) as well as a bottom width (34) and a bottom thickness (37), said bottom (30) extending longitudinally along an extension line (100) along its bottom length (31) from a first end (32) to a second end (33), said bottom (30) extending in elevation perpendicular to said extension line (100) along its bottom width (34) from a first flank (35) to a second flank (36), said bottom (30) extending transversely perpendicular to said extension line (100) according to its thickness of bottom (37) of a first face (38) intended to be opposite said at least one cable (5) to a second face (39) intended to be opposite a structure (2) carrying said protection device (10), characterized in that said bottom (30) has a plurality of openings (50), each opening (50 ) crossing the bottom (30) transversely from the first face (38) to the second face (39), at least one opening (50) being empty, each opening (50) being inscribed in a rectangular parallelepiped (60 ), said rectangular parallelepiped (60) having an extension length (61) along said extension line (100) and an extension width (62) perpendicular to said extension line (100), said length of extension (61) being greater than said extension width (62). 2. Protection device according to claim 1, characterized in that said electrically conductive element (20) comprises at least one branch (40) secured to the bottom (30). 3. Protection device according to any one of claims 1 to 2, characterized in that said openings (50) are identical. 4. Protective device according to any one of claims 1 to 3, characterized in that at least one said opening (50) has an elliptical shape (52) seen in a direction going from the second face (39) to the first face (38), said extension length (61) being equal to a major axis (53) of the elliptical shape (52) and said extension width (62) being equal to a minor axis (54) of the elliptical shape (52). 5. Protection device according to any one of claims 1 to 4, characterized in that at least one said opening (50) has a rectangular shape (51) seen in a direction going from the second face (39) to the first face (38). 6. Protective device according to any one of claims 1 to 5, characterized in that said extension length (61) is at least twice greater than said extension width (62). 7. Protective device according to any one of claims 1 to 5, characterized in that said extension length (61) is equal to 10 centimeters plus or minus ten percent, said extension width (62) is less than or equal to two centimeters, said rectangular parallelepiped (60) having an extension thickness (63) of between 0.4 millimeter and 1.4 millimeter. 8. Protection device according to any one of claims 1 to 7, characterized in that said openings (50) are arranged along a plurality of protection lines (55), each protection line (55) s' extending longitudinally along said extension line (100), each protection line (55) comprising said openings (50) arranged longitudinally one after the other, a solid longitudinal section (56) of the bottom (30) longitudinally separating two openings ( 50) adjacent disposed on the same protection line (55), an elevation section (57) full of the bottom (30) separating in elevation two adjacent openings (50) arranged respectively in two adjacent protection lines (55). 9. Protection device according to claim 8, characterized in that said protection lines (55) are mutually parallel. 10. Protection device according to any one of claims 8 to 9, characterized in that said openings (50) of two adjacent protection lines (55) are arranged in staggered rows. 11. Aircraft (1) provided with a structure (2) and with a protection device (10) fixed to said structure (2), said protection device (10) accommodating at least one cable (5), characterized in that said protection device (10) is according to any one of claims 1 to 10. 12. aircraft (1) according to claim 11 characterized in that said cable (5) extends parallel to the bottom (30) of the protection device (10), said cable (5) having a cable length (5) according to said extension line (100) and a thickness of cable (5) in elevation.