Electromagnetic shielding sheath for an electrical cable, manufacturing process and use of said sheath.

Abstract

Electromagnetic shielding sheath (30) for an electrical cable (20), the sheath (30) comprising: elongated elements (41) of a first type, made of a first electrically conductive material, and elongated elements (42) of a second type, made of a second magnetically conductive material, and elongated elements (43) of a third type, made of a synthetic, elastic, or heat-shrinkable material, the elongated elements (41, 42, 43) being assembled in an interlaced manner and / or forming an interlacing to form a fabric (25), said fabric (25) having the shape of a tube (25) wound around an axis, a cross-section of the tube (25) in a plane transverse to the axis forming a closed circular curve, a dimension of the cross-section being variable between a maximum dimension and a minimum dimension, the tube (25) being configured to enclose the cable (20), an inner face of the tube (25) being, in the assembled state of the sheath (30), held in contact,and adjusted to a dimension, of a periphery of the cable (20) by an elastic tension of the elongated elements (43) of the third elastic type, or by a tension of the elongated elements (43) of the third heat-shrink type. Figure 1,

Description

Title of the invention: Electromagnetic shielding sheath for an electrical cable, method of manufacturing and use of said sheath.

[0001] The present invention relates to the field of electromagnetic shielding of electrically conductive cables.

[0002] It is known to protect one or more electrical conductor cables intended for the transport of electrical power requiring high voltages, by using a tubular sheath which envelops the entire periphery of the conductor cable(s).

[0003] To meet the weight, size, cost and performance requirements of the electromagnetic protection function, it is particularly necessary that the size of the tubular sheath be adjusted to the size of the bundle of conductive cables.

[0004] On the other hand, the performance of known tubular sheaths is not suitable for the electromagnetic protection of cables intended for data transmission, for example for the electromagnetic protection of electronic signal transmission cables, which carry low voltage currents, and which are particularly sensitive to the capacitive reactance effects of the shielding, against which known tubular sheaths are not very effective.

[0005] The invention therefore aims to provide a solution to all or part of these problems.

[0006] To this end, the present invention relates to an electromagnetic shielding sheath for an electrical cable, the sheath comprising: - elongated elements of a first type, made of a first electrically conductive material, and - elongated elements of a second type, made of a second, magnetically conductive material, and - elongated elements of a third type, made of a synthetic, elastic or heat-shrinkable material, the elongated elements being assembled in an interlaced manner and / or forming an interlacing to form a fabric, said fabric having the form of a tube wound around an axis, a cross-section of the tube along a plane transverse to the axis forming a closed circular curve, a dimension of the cross-section being variable between a maximum dimension and a minimum dimension, the tube being configured to enclose the cable, an inner face of the tube being, in the assembled state of the sheath, held in contact with, and adjusted to a dimension, a periphery of the cable by an elastic tension of the elongated elements of the third type elastic, or by tension of the elongated elements of the third type thermo-shrinked.

[0007] According to these provisions, the shielding sheath adapts to a wide variety of dimensions of the different wiring branches, while maintaining electrical continuity between the different wiring branches; the shielding sheath thus makes it possible to avoid the use of shielded junction boxes to operate an electrical bundle branch, the tubular electromagnetic shielding sheath retractable according to the size of the branch fulfills this function.

[0008] Furthermore, according to these provisions, the contraction of the sheath around the conductor cable, by elasticity or by heat shrinking, of the elongated elements of the third type reduces a size of the holes 60 present in the fabric of the shielding sheath formed by the assembly of the elongated elements of the first, second and third types; thus the capacitive reactance of the shielding will also be reduced, which improves the effectiveness of the shielding by reducing the disturbances of the signals transmitted by the electrical cable protected by the shielding sheath.

[0009] According to one embodiment, the invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0010] According to one embodiment, the elongated elements may have a round cross-section, or a rectangular cross-section, preferably a flattened rectangular cross-section. The elongated elements may be considered to belong to the group comprising: round cross-section wires, flat wires, laminated wires, metallic wires wrapped around a textile core, synthetic wires coated with a metallic layer, strips, and laminated strips.

[0011] The term "feuillard" refers to a narrow, flat strip.

[0012] The term "type" may refer to the material constituting the elongated elements, from which the conductivity and magnetic properties are derived. It can also refer to the structure or geometry of the elongated elements (such as the shape or diameter of these elements).

[0013] According to one embodiment, the elongated elements of the first type can be made of at least one material having a relative electrical conductivity greater than 0.5, preferably between 0.6 and 1.05, at room temperature. This material is, for example, copper or aluminum. It should be noted that the relative electrical conductivity of a material is a dimensionless number defined as the electrical conductivity of the material divided by the electrical conductivity of copper.

[0014] According to one embodiment, the first electrically conductive material belongs to the group formed by: copper, aluminum, a copper alloy, an aluminum alloy.

[0015] According to one embodiment, the first material has a relative magnetic permeability pr between 0.999994 and 5000.

[0016] It is recalled that the relative magnetic permeability pr of a material is a dimensionless number defined as the magnetic permeability of the material divided by the magnetic permeability of free space pO.

[0017] According to one embodiment, the second magnetically conductive material belongs to the group formed by: iron, nickel, cobalt, steel, an iron alloy, a nickel alloy, a cobalt alloy.

[0018] According to one embodiment, the second material comprises neither mumetal nor permalloy.

[0019] According to these provisions, the second magnetically conductive material has magnetic properties which improve shielding against the potentially disruptive magnetic field.

[0020] According to one embodiment, the synthetic material of the elongated elements of the third type of elastics belongs for example to the group comprising the families of elastofibers, based on fibers derived from polyurethane type elastane, fibers derived from polybutylene terephthalate, fibers derived from polymethylene terephthalate, polyethylene terephthalate fibers, polyamide fibers, silicone or latex fibers.

[0021] According to one embodiment, the synthetic material of the elongated elements of the third type heat-shrinkable belongs for example to the group comprising the families of PVC, cross-linked polyolefins, polychloroprene (Neoprene), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), silicone elastomer, fluoroelastomer (Viton®), polytetrafluoroethylene (PTFE).

[0022] According to one embodiment, the assembly of the elongated elements in an interlaced manner means that the elongated elements are crossed together several times; the assembly forming an interlacing means that the elongated elements surround the cable several times, possibly with a certain degree of tightness. The assembly of the elongated elements preferably implies a certain spatial arrangement, as opposed to an entanglement or entanglement of the elongated elements.

[0023] According to one embodiment, the elongated elements of the first and second type have a diameter less than a maximum diameter determined as a function of a frequency of a disturbing electromagnetic field.

[0024] According to these provisions, the thinness of the elongated elements of the first and second types, combined with the contraction of the sheath under the effect of the elongated elements of the third type, further reduces the size of the holes present in the shielding sheath formed by the assembly of the elongated elements of the first, second, and third types; the capacitive reactance of the shielding will also be reduced, thus improving the effectiveness of the shielding by reducing interference with signals transmitted by the electrical cable protected by the shielding sheath.

[0025] According to one embodiment, the maximum diameter of the elongated elements of the first and second type is equal to 0.16 mm for a frequency of a disturbing electromagnetic field below 10 MHz

[0026] According to one embodiment, the diameter of the elongated elements of the first and second type is between 0.05 and 0.16 mm, preferably equal to 0.1 mm.

[0027] According to one embodiment, the diameter of the cross-section of the elongated elements of the first and second type is between 0.05 and 0.07 mm; according to these arrangements the protection will be more effective against disturbing electromagnetic fields of frequency greater than 10MHz.

[0028] According to one embodiment, the fabric is a woven fabric comprising a plurality of first groupings of elongated elements of the first and second type, the elongated elements of said first groupings being arranged parallel to the axis of the tube, the woven fabric further comprising a plurality of second groupings of elongated elements of the third type, the elongated elements of said second groupings being arranged transversely to the elongated elements of said first groupings, said first groupings and said second groupings being assembled in an interlaced manner and / or forming an interlacing to form the woven fabric.

[0029] According to one embodiment, the fabric is a braided fabric comprising a plurality of third groups of elongated elements of the first type and of the second type and of the third type, the elongated elements of said third groups being arranged at a braiding angle with respect to the axis of the tube, the braided fabric further comprising a plurality of fourth groups of elongated elements of the first type and of the second type and of the third type, the elongated elements of said fourth groups being arranged transversely to the elongated elements of said third groups, said third groups and said fourth groups being assembled in an interlaced manner and / or forming an interlacing to form the braided fabric.

[0030] According to one embodiment, the elongated elements of the third type are made of an elastic synthetic material, the maximum dimension of the cross-section of the fabric tube being obtained by a radial extension of the cross-section which allows the conducting cables to pass inside the tube, and in which the minimum dimension of the tube is obtained by an elastic return of the elongated elements of the third type.

[0031] According to one embodiment, the elongated elements of the third type are made of a heat-shrinkable synthetic material, the minimum dimension of the tube being obtained by heat shrinking the elongated elements of the third type.

[0032] According to one embodiment, the sheath further comprises an elastic coating configured to wrap and compress the braided fabric formed with the assembled elongated elements of the braided fabric.

[0033] According to these provisions, the size of the holes present in the fabric of the shielding sheath is reduced; thus the capacitive reactance of the shielding will also be reduced, which improves the effectiveness of the shielding by reducing the disturbances of the signals transmitted by the electrical cable protected by the shielding sheath.

[0034] According to one embodiment, the elastic coating is a layer of an elastomeric material.

[0035] According to one embodiment, the elasticity of the elastic coating is defined by a value of the Young's modulus between 0.1 MPa and 100 MPa.

[0036] According to one aspect, the invention also relates to a method of manufacturing a sheath according to one of the embodiments described above, in which the elastic coating is deposited by extrusion, injection, coating or dipping, directly onto the braided tubular fabric of the sheath.

[0037] According to another aspect, the invention also relates to the use of a sheath according to any one of the embodiments described above, for the electromagnetic protection of a plurality of cables assembled into strands.

[0038] According to one embodiment, the sheath is used for the electromagnetic protection of at least two cables configured to be electrically connected to an electrical fitting, the at least two cables comprising a protected part and an unprotected terminal part configured to be electrically connected to the electrical fitting, the unprotected terminal part of the at least two cables not being protected by an electromagnetic shielding sheath, the protected part of the at least two cables being protected by an electromagnetic shielding sheath up to the unprotected terminal part, the sheath according to any one of the embodiments described above being placed around the at least two cables, so as to envelop at least a portion of the electromagnetic shielding sheath of the protected part of the at least two cables and at least a portion of the unprotected terminal part of the at least two cables.

[0039] According to one embodiment, the unprotected terminal portion of at least two cables is electrically connected to the electrical connection portion, and the sheath according to any one of the embodiments described above encloses the entire unprotected terminal portion of at least two cables and at least a portion of the electrical connection.

[0040] According to these provisions, the shielding sheath according to the invention can be used for electromagnetic protection around cables in continuity connection equipotential between a back connector fitting ("Backshell") and an electromagnetic shield of shielded cables.

[0041] According to one embodiment, the electrical connection is a branch junction.

[0042] According to these provisions, the shielding sheath according to the invention can be used for electromagnetic protection around cables at branch junctions by ensuring equipotentiality of the shields of all branches before their branches.

[0043] For the sake of clarity, an embodiment and / or implementation of the invention is described with reference to the accompanying drawings, which represent, by way of non-limiting example, an embodiment or implementation of a device and / or method according to the invention. The same reference numerals in the drawings designate similar elements or elements with similar functions.

[0044] [Fig. 1] represents a cable and a sheath according to an embodiment of the invention, placement around the cable, before shrinking the sheath.

[0045] [Fig.2] is a view of a method of assembling elongated elements in a sheath according to a woven embodiment of the invention.

[0046] [Fig.3] is a view of another method of assembling elongated elements in a sheath according to another braided embodiment of the invention.

[0047] [Fig.4] represents a cable and the sheath of [Fig.3], in the state mounted on the cable, adjusted around the cable, after the sheath has been retracted.

[0048] [Fig.5] represents a cable and a sheath according to another embodiment of the invention, adjusted after the sheath has been retracted around a cable connection area with equipment.

[0049] [Fig.6] is a schematic view of the assembly method of elongated elements in a sheath according to the braided embodiment of the invention, with visible holes.

[0050] [Fig.7] is a view of a method of assembling elongated elements in a sheath, with an elastic coating configured to wrap and compress the periphery of the fabric formed with the assembled elongated elements of the sheath.

[0051] [Fig.8] is a representation of instructions for use of the sheath according to an example of implementation of the invention, for the electromagnetic protection of two cables between a part, protected by a sheath, of each of the two cables and a part of an electrical fitting (not shown in [Fig.8]), a terminal part of the part of each of the two cables being electrically connected to the part of the electrical fitting (not shown in [Fig.8]), said terminal part of the part of the two cables not being protected by an electromagnetic shielding sheath.

[0052] [Fig.9] is a graph that shows the evolution of the transfer impedance of a shielding sheath depending on the frequency of the interfering electromagnetic field.

[0053] [Fig. 10] is another graph which shows the evolution of the transfer impedance of a shielding sheath as a function of the frequency of the interfering electromagnetic field and the compressed or stretched state of a shielding sheath according to an embodiment of the invention.

[0054] [Fig. 11] is another graph which shows the evolution of the transfer impedance of a shielding sheath as a function of the frequency of the interfering electromagnetic field and the retracted or unretracted state of a shielding sheath according to an embodiment of the invention.

[0055] The present invention relates to an electromagnetic shielding fabric whose dimensions can be adapted by heat shrinking or by elastic expansion and contraction, such that the size of the electromagnetic shielding sheath is perfectly matched to the size of the bundle of electrical conductors it protects. Thus, the numerous gaps usually found at the intersections of the conductors that form the shielding sheath, and which impair the sheath's electromagnetic protection performance, are reduced in size by the elastic contraction or heat shrinking of the sheath. Furthermore, the electromagnetic shielding fabric adapts to a wide variety of perimeters while maintaining electrical continuity between the different branches of the diverging bundles.It is no longer necessary to use a shielded junction box to operate a shielded electrical beam branch; the electromagnetic shielding fabric according to the invention adapts to the variable dimensions of all branches and thus fulfills the function of a shielded junction box.

[0056] Figure 1 shows an example of an embodiment of the shielding sheath 30 electromagnetic according to the invention, placed around an electrical cable 20, before the contraction of the sheath 30 to adjust to the dimension of the cross-section of the electrical cable 20. This configuration of the sheath 30 of electromagnetic shielding before contraction facilitates the passage of the electrical cable 20 inside the sheath 30 which is of tubular shape.

[0057] The sheath 30 comprises: - elongated elements 41 of a first type, made of a first material, electrically conductive, and - elongated elements 42 of a second type, made of a second, magnetically conductive material, and - elongated elements 43 of a third type, made of a synthetic, elastic or heat-shrinkable material.

[0058] For example, the elongated elements may have a round cross-section, or a rectangular cross-section, preferably a flattened rectangular cross-section. It can be foreseen that the elongated elements belong to the group comprising: round cross-section wires, flat wires, laminated wires, metallic wires wrapped around a textile core, synthetic wires covered with a metallic layer, strips, laminated strips.

[0059] The term "feuillard" refers to a narrow, flat strip.

[0060] The term "type" may refer to the material constituting the elongated elements, from which the conductivity and magnetic properties are derived. It can also refer to the structure or geometry of the elongated elements (such as the shape or diameter of these elements).

[0061] According to one embodiment, the elongated elements of the first type can be made of at least one material having a relative electrical conductivity greater than 0.5, preferably between 0.6 and 1.05, at room temperature. It should be noted that the relative electrical conductivity of a material is a dimensionless number defined as the electrical conductivity of the material divided by the electrical conductivity of copper.

[0062] In particular, the first electrically conductive material belongs to the group formed by: copper, aluminum, a copper alloy, an aluminum alloy.

[0063] More particularly, the first material, electrically conductive, has a relative magnetic permeability pr between 0.999994 and 5000.

[0064] It is recalled that the relative magnetic permeability pr of a material is a dimensionless number defined as the magnetic permeability of the material divided by the magnetic permeability of free space pO.

[0065] According to one embodiment, the second material, magnetically conductive, belongs to the group formed by: iron, nickel, cobalt, steel, an iron alloy, a nickel alloy, a cobalt alloy.

[0066] In particular, the second material does not comprise mumetal or permalloy.

[0067] Thus, the second magnetically conductive material has magnetic properties which improve shielding against the potentially disruptive magnetic field.

[0068] According to one embodiment, the synthetic material of the elongated elements of the third type, elastic, belongs to the group comprising the families of elastofibers, based on fibers derived from polyurethane type elastane, fibers derived from polybutylene terephthalate, fibers derived from polymethylene terephthalate, polyethylene terephthalate fibers, polyamide fibers, silicone or latex fibers.

[0069] According to another embodiment, the synthetic material of the elongated elements of the third type, heat-shrinkable, belongs to the group comprising the families of PVC, cross-linked polyolefins, polychloroprene (Neoprene), fluoride of Polyvinylidene (PVDF), Fluorinated Propylene Ethylene (FEP), Silicone elastomer, Fluoroelastomer (Viton®), Polytetrafluoroethylene (PTFE).

[0070] The elongated elements 41, 42, 43 are assembled in an interlaced manner and / or forming an interlacing to form a fabric 25, said fabric 25 having the form of a tube 25 wound around an axis, a section of the tube 25 according to a plane transverse to the axis forming a closed circular curve, a dimension of the section being variable between a maximum dimension and a minimum dimension, the fabric tube 25 being configured to envelop the cable 20, an inner face of the fabric tube 25 being, in the assembled state of the sheath 30, held in contact, and adjusted to a dimension, of a periphery of the cable 20 by an elastic tension of the elongated elements 43 of the third elastic type, or by a tension of the elongated elements 43 of the third heat-shrinked type.

[0071] According to one embodiment, the assembly of the elongated elements in an interlaced manner means that the elongated elements are crossed together several times; the assembly forming an interlacing means that the elongated elements surround the cable several times, possibly with some tightness. The assembly of the elongated elements preferably implies a certain spatial arrangement, as opposed to an entanglement or entanglement of the elongated elements.

[0072] Numerous void spaces 60, located at the intersections of the elongated elements 41, 42, 43 assembled to form the fabric 25 of the shielding sheath 30, are shown in Figures 2 and 6; these void spaces 60 impair the performance of the sheath 30 in terms of electromagnetic protection by creating a capacitive reactance effect, illustrated in [Fig. 9]. Indeed, any opening created in a shield degrades its performance in terms of electromagnetic protection. The openings behave like radiation antennas whose dimensions are those of the openings. Electric and magnetic fields escape through the openings, creating areas of reduced electromagnetic protection in their vicinity. Near-field sources near the openings leak significantly through said openings. This physical phenomenon is accentuated with high-frequency waves.Shielding will be more effective if it contains many small holes instead of larger ones, even if there are fewer of them.

[0073] Reducing the size of the holes affects the capacitive reactance. The graph shown in [Fig. 9] illustrates the evolution of the transfer impedance of a shielding sheath, represented vertically on [Fig. 9] on a scale in decibels (dB) converted from measurements in Ohms / m, as a function of the frequency in MHz of a disturbing electromagnetic field, represented horizontally on [Fig. 9]. The profile of the curve showing the evolution of the transfer impedance as a function of frequency notably reveals three distinct zones, Z1, Z2, and Z3: a zone The signal consists of a resistive Z1 zone, followed by a capacitive Z2 zone, and finally an inductive Z3 zone. Although the effect of capacitive reactance tends to improve the transfer impedance, as the curve points towards a lower impedance value, capacitive reactance acts like a capacitor, accumulating an electrical charge that opposes the signal transmitted by the cable(s) protected by the shielding. The most well-known phenomenon is that of a square wave digital pulse signal that is transformed by the capacitance charges into a sawtooth wave.

[0074] In order to combat the counterproductive effect of capacitive reactance, it is necessary Choose elongated elements 41, 42 conductors of small dimensions, as thin as possible, with a diameter of 0.05 to 0.16 mm, preferably 0.10 mm and if the shielding is designed against an incident wave of frequency greater than 10 MHz a diameter between 0.05 and 0.07 mm

[0075] Optionally, the elongated elements 41, 42 of the first and second type have a diameter less than a maximum diameter determined as a function of a frequency of a disturbing electromagnetic field.

[0076] Thus, the thinness of the elongated elements 41, 42 of the first and second types, combined with the contraction of the sheath under the effect of the elongated elements of the third type, further reduces the size of the holes 60 present in the fabric 25 of the sheath 30 of shielding formed by the assembly of the elongated elements of the first, second and third types; the capacitive reactance of the shielding will also be reduced, thus improving the effectiveness of the shielding by reducing the disturbances on the signals transmitted by the electrical cable protected by the sheath 30 of shielding.

[0077] Thus, according to one embodiment, the maximum diameter of the elongated elements of the first and second type is equal to 0.16 mm for a frequency of a disturbing electromagnetic field less than 10 MHz.

[0078] In particular, the diameter of the elongated elements of the first and second type is between 0.05 and 0.16 mm, preferably equal to 0.1 mm.

[0079] In particular, the diameter of the cross-section of the elongated elements 41, 42 of the first and second type is between 0.05 and 0.07 mm; according to these arrangements, the protection will be more effective against disturbing electromagnetic fields of frequency greater than 10MHz.

[0080] The choice of elongated elements 41, 42 of the first and second types, conductive, also has the effect of optimizing the reflection and / or absorption, by the electromagnetic shielding sheath 30, of the potentially disturbing electromagnetic wave.

[0081] The tubular shape finally gives the electromagnetic shielding sheath 30 360° effectiveness around the cable(s) to be protected.

[0082] According to a first embodiment, more particularly illustrated in [Fig.2], the fabric 25 is a woven fabric 25 comprising a plurality of first groupings of elongated elements 41, 42 of the first and second type, the elongated elements of said first groupings being arranged parallel to the axis of the tube, and a plurality of second groupings of elongated elements 43 of the third type, the elongated elements 43 of said second groupings being arranged transversely to the elongated elements 41, 42 of said first groupings, said first groupings and said second groupings being assembled in an interlaced manner and / or forming an interlacing to form the woven fabric 25.

[0083] According to this first embodiment, the elongated elements 41, 42 of the first and second types are in the warp of the woven fabric 25, and the elongated elements 43 of the third type are in the weft of the woven fabric 25. Advantageously, the synthetic material of the elongated elements 43 of the third type is elastic. According to these arrangements, the tubular woven fabric 25, which is naturally not very stretchy, can be stretched more easily to facilitate the passage of the electrical cable(s) 20, before returning to its shape adjusted to the dimensions of the electrical cable(s) 20.

[0084] According to a second embodiment, more particularly illustrated in [Fig. 3] and [Fig. 6], the fabric 25 is a braided fabric comprising a plurality of third groups of elongated elements 41, 42, 43 of the first and second types, the elongated elements 41, 42, 43 of said third groups being arranged at a braiding angle with respect to the axis of the tube, the braided fabric 25 further comprising a plurality of fourth groups of elongated elements 41, 42, 43 of the first and second types, the elongated elements 41, 42, 43 of said fourth groups being arranged transversely to the elongated elements 41, 42, 43 of said third groups, said third and fourth groups being assembled in an interlaced manner and / or forming an interlacing to form the 25 braided fabric.

[0085] The advantage of this braided tubular variant is its adaptability to a wide range of tubular sheath diameters through the angular movement of the strands relative to each other, by exerting axial forces, either in tension or compression. The disadvantage of the mesh movement is the random modification of the shielding effectiveness characteristics because the shielding transparency changes. This transparency is linked to the shape of the holes left at the intersection of each mesh. These are parallelograms of varying shapes, from rhombuses to squares, depending on the deformation applied to the tubular braiding. The shielding effectiveness of the braided tubular variant is linked to the shape of the quadrilateral holes relative to the tube axis.

[0086] The elongated elements 41, 42 of the first and second type, conductive, are arranged joined with the elongated elements 43 of the third type, synthetic, whose function is to ensure the mechanical reinforcement of the braided tubular structure and also to keep the empty spaces closed to reduce the size of the holes, either by an elastic extension-retraction force, or by a thermo-retraction force.

[0087] Figure 10 shows how the shielding effectiveness is modified when compared, on the one hand, in a configuration of the tubular braid stretched to its maximum axially and, on the other hand, in a configuration of the tubular braid compressed to its maximum. The tubular product used for the measurements in Figure 10 is stretched; in this case, it covers a mandrel with a diameter of 16 mm; if it is compressed, it covers a mandrel with a diameter of 32 mm.

[0088] The graphs shown in [Fig. 10] illustrate the evolution of the transfer impedance of a shielding cladding. The impedance is represented vertically in [Fig. 10] on a scale in decibels (dB) converted from measurements in Ohm / m, as a function of the frequency (in MHz) of a disturbing electromagnetic field, represented horizontally in [Fig. 10]. The profile of the transfer impedance curve of the braided tubular cladding as a function of frequency changes between a first profile (PLE) when the diamond-shaped holes (LE) are stretched, and a second profile (PLC) when the diamond-shaped holes (LC) are compressed, depending on the radial extension of the braided fabric. [Fig. 10] shows that the shielding effectiveness is increased when the braided tubular cladding is in its maximum extension position.

[0089] As previously stated, a dimension of the cross-section of the fabric tube 25 is variable between a maximum dimension and a minimum dimension: for example, the maximum dimension of the cross-section of the fabric tube 25 is obtained by a radial extension of the cross-section which allows the conductive cables to pass inside the tube, and the minimum dimension of the fabric tube 25 is obtained by an elastic return of the elongated elements 43 of the third type, made of elastic material. Optionally, the minimum dimension of the fabric tube 25 is obtained by heat shrinking the elongated elements 43 of the third type, made of heat-shrinkable material. Whether by the effect of an elastic return or by heat shrinking the elongated elements 43 of the third type, an inner face of the fabric tube 25 is, in the assembled state of the sheath 30, held in contact with, and adjusted to the dimension of, a periphery of the cable 20, as illustrated in [Fig.4].

[0090] The graphs shown in [Fig. 1 1] illustrate the evolution of the transfer impedance of a heat-shrinkable shielding sheath, the impedance being represented vertically on [Fig. 1 1] according to a scale in decibels (dB) converted from measurements in Ohm / m, as a function of a frequency in MHz of a field The interfering electromagnetic field is shown horizontally in [Fig. 11]; the profile of the impedance transfer curve of the heat-shrinkable tubular sheath as a function of frequency changes between a PR profile when the sheath is shrunk, and a PNR profile when the sheath is not shrunk. [Fig. 11] shows that the shielding effectiveness is increased when the tubular sheath is shrunk.

[0091] Figure 5 illustrates another use of a sheath 30 according to the invention, in which the connector of the cable 20 is connected to a rear ground connection of an electrical device M, for example, a motor, and in which the tubular fabric 25 of the sheath 30, after elastic or heat-shrinking, is held in contact with the periphery of the cable 20, its connector, and the rear ground connection, all of which have different external dimensions. The sheath 30 according to the invention thus adapts perfectly to the different dimensions of the conductive elements that it must protect from potentially disruptive electromagnetic fields.

[0092] According to an example of an embodiment illustrated in [Fig.7], the sheath 30 further comprises an elastic coating 70 configured to wrap and compress the braided fabric 25 formed with the elongated elements 41, 42, 43 assembled from the braided fabric 30.

[0093] According to these provisions, the size of the holes 60 in the fabric of the shielding sheath is further reduced by compressing the coating 70; thus, the capacitive reactance of the shielding is further reduced, which further improves the shielding's effectiveness by reducing interference with the signals transmitted by the electrical cable protected by the shielding sheath 30. The external elastic coating 70 constrains the sheath 30 to its minimum diameter, the non-conductive holes are kept small to limit the transparency of the shielding, and thus increase the shielding's effectiveness.

[0094] Advantageously, the elasticity of the elastic coating 70 is defined by a value of the Young's modulus between 0.1 MPa and 100 MPa.

[0095] According to one embodiment, the elastic coating 70 is a layer of an elastomeric material.

[0096] In particular, the elastomeric material belongs to the group comprising thermoplastic elastomers (urethane-based TPE, styrene-based TPE, TPE copolyester, TPE-copolyamide, thermoplastic vulcanized TPE-V), and silicone elastomers.

[0097] According to one aspect, the invention relates to a method of manufacturing a sheath 20 according to the embodiments described above, in which the elastic coating is deposited by extrusion, by injection, by coating or by dipping, directly onto the braided tubular fabric 25 of the sheath 30.

[0098] According to another aspect, the invention relates to the use of a sheath 30 according to one of the embodiments described above, for the electromagnetic protection of a plurality of cables gathered into strands.

[0099] Figure 8 illustrates another example of the use of a sheath 30 according to one of the embodiments described above, for the electromagnetic protection of two cables between a shielded portion PB of the two cables and a portion of an electrical connection (not shown in Figure 8), an unshielded terminal portion PNB in ​​the extension of the shielded portion of the cables being electrically connected to the portion of the electrical connection (not shown in Figure 8).8]), the unshielded terminal portion PNB not being protected by an electromagnetic shielding screen, the shielded portion PB of the two cables being protected by an electromagnetic shielding screen, the tubular fabric 25 of the sheath 30 according to one of the embodiments described above being placed around the two cables, so as to envelop all or part of the shielded portion PB of the two cables; optionally the unshielded terminal portion PNB of the two cables as well as the part of the electrical connection (this alternative is not shown in [Fig. 8]) are also enveloped by the tubular fabric 25 of the sheath 30. The retracted electromagnetic shielding sheath 30 according to the invention thus ensures the electrical continuity of the two shielding screens of the shielded portions PB of the two cables, and brings the two shielding screens of the shielded portions PB of the two cables to the same electrical potential. It should be noted that, in [Fig.[8] The shielded portion PB of the two cables comprises a bare shielded portion PB, located in the figure to the left of the sheath 30, and an insulated shielded portion PB, located in the figure to the right of the sheath 30; on the bare shielded portion PB, the shielding screen is visible, represented by a braid, and on the insulated shielded portion PB, the shielding screen is masked by the insulation.

[0100] Thus, the shielding sheath 30 according to the invention can be used for electromagnetic protection around cables in equipotential continuity link between a back connector fitting ("Backshell") and an electromagnetic shield of shielded cables.

[0101] In particular, the electrical connection may be a branch junction.

[0102] Thus, the shielding sheath 30 according to the invention can be used for protection electromagnetic field around cables at branch junctions by acting by equipotentially matching the shields of all branches before their branches.

Claims

Demands

1. Electromagnetic shielding sheath (30) for an electrical cable (20), the sheath (30) comprising: - elongated elements (41) of a first type, made of a first electrically conductive material, and - elongated elements (42) of a second type, made of a second magnetically conductive material, and - elongated elements (43) of a third type, made of a synthetic, elastic, or heat-shrinkable material, the elongated elements (41, 42, 43) being assembled in an interlaced manner and / or forming an interlacing to form a fabric (25), said fabric (25) having the shape of a tube (25) wound around an axis, a cross-section of the tube (25) in a plane transverse to the axis forming a closed circular curve, a dimension of the cross-section being variable between a maximum dimension and a minimum dimension, the tube (25) being configured to enclose the cable (20), an inner face of the tube (25) being, in the mounted state of the sheath (30),maintained in contact, and adjusted to a dimension, of a periphery of the cable (20) by an elastic tension of the elongated elements (43) of the third elastic type, or by a tension of the elongated elements (43) of the third heat-shrinked type.

2. Sheath according to claim 1, wherein the elongated elements (41, 42) of the first and second type have a diameter less than a maximum diameter determined as a function of a frequency of a disturbing electromagnetic field.

3. Sheath (30) according to any one of claims 1 or 2, wherein the fabric (25) is a woven fabric (25) comprising a plurality of first groupings of elongated elements (41, 42) of the first and second type, the elongated elements (41, 42) of said first groupings being arranged parallel to the axis of the tube (25), the woven fabric (25) further comprising a plurality of second groupings of elongated elements (43) of the third type, the elongated elements (43) of said second groupings being arranged transversely to the elongated elements (41, 42) of said first groupings, said first groupings and said second groupings being assembled in an interlaced manner and / or forming an interlacing to form the woven fabric (25).

4. Sheath (30) according to claim 1 or 2, wherein the fabric (25) is a braided fabric (25) comprising a plurality of third groups of elongated elements (41, 42, 43) of the first, second, and third types, the elongated elements (41, 42, 43) of said third groups being arranged at a braiding angle with respect to the axis of the tube (25), the braided fabric (25) further comprising a plurality of fourth groups of elongated elements (41, 42, 43) of the first, second, and third types, the elongated elements (41, 42, 43) of said fourth groups being arranged transversely to the elongated elements (41, 42, 43) of said third groups, said third groups and said fourth groups being assembled in an interlaced manner and / or forming an interlacing to form the braided fabric (25).

5. Sheath (30) according to any one of claims 1 to 4, wherein the elongated elements (43) of the third type are made of a heat-shrinkable synthetic material, the minimum dimension of the tube being obtained by heat shrinking the elongated elements of the third type.

6. Sheath (30) according to any one of claims 1 to 4, wherein the elongated elements (43) of the third type are made of an elastic synthetic material, the maximum dimension of the cross-section of the fabric tube (25) being obtained by a radial extension of the cross-section which allows the conductive cables to pass inside the tube, and wherein the minimum dimension of the tube is obtained by an elastic return of the elongated elements (43) of the third type.

7. Sheath (30) according to any one of claims 4 to 6, as it depends on claim 4, further comprising an elastic coating (70) configured to wrap and compress the braided fabric formed with the elongated elements (41, 42, 43) assembled from the braided fabric (30).

8. Sheath (30) according to claim 1, wherein an elasticity of the elastic coating (70) is defined by a value of Young's modulus between 0.1 MPa and 100 MPa.

9. Method of manufacturing a sheath 30 according to any one of claims 7 or 8, wherein the elastic coating is deposited by extrusion, injection, coating or dipping, directly onto the braided tubular fabric 25 of the sheath (30).

10. Use of a sheath (30) according to any one of the preceding claims for the electromagnetic protection of a plurality of cables bundled together.

11. Use of a sheath (30) according to any one of claims 1 to 8 for the electromagnetic protection of at least two cables configured to be electrically connected to an electrical fitting, the at least two cables comprising a shielded portion (PB), protected by an electromagnetic shielding screen, and an unshielded terminal portion (PNB), not protected by an electromagnetic shielding screen, the unshielded terminal portion (PNB) being configured to be electrically connected to the electrical fitting, the sheath (30) according to any one of claims 1 to 8 being placed around the at least two cables, so as to envelop all or part of the electromagnetic shielding screen of the shielded portion (PB) of the at least two cables.

12. Use according to the preceding claim of a sheath (30) according to any one of claims 1 to 8, wherein the unshielded terminal portion (UNP) of at least two cables is electrically connected to the electrical connection portion, and wherein the sheath (30) according to any one of claims 1 to 8 encloses the entire unshielded terminal portion (UNP) of at least two cables and at least a portion of the electrical connection.

13. Use according to any one of claims 11 or 12 of a sheath (30) according to any one of claims 1 to 8, wherein the electrical connection is a branch junction.