Aeronautical laminated glazing with electrical heating system, use of the aeronautical laminated glazing as aircraft cockpit glazing, and associated aircraft

Abstract

The present invention relates to aeronautical laminated glazing (1) comprising a first sheet (2) on the outside and at least one second structural sheet (3a, 3b) on the inside, the aeronautical laminated glazing (1) further comprising at least one electrical heating system (9) arranged facing the internal face of the first sheet (2), the aeronautical laminated glazing (1) further comprising an isopotential layer (10) applied to the internal face of the first sheet (2).

Description

[0001] Description

[0002] Title of the invention: Laminated aeronautical glazing with electric heating system, use of laminated aeronautical glazing as aircraft cockpit glazing, and associated aircraft

[0003] The present invention relates to the field of aeronautics, and relates in particular to an aeronautical laminated glazing with an integrated electric heating system, to the use of such an aeronautical laminated glazing as aircraft cockpit glazing, and to an aircraft comprising such an aeronautical laminated glazing as cockpit glazing.

[0004] Laminated aeronautical glazing is generally made of electrically insulating materials (such as mineral glass, PMMA (poly(methyl methacrylate), PC (polycarbonate), etc.) which tend to become electrically charged in certain charging environments which can be of two types, namely:

[0005] - charges of triboelectric origin associated with the impact of particles (such as dust, snow, ice crystals, etc.) on the outer surface (facing the aircraft) of the laminated glazing, and

[0006] - charges associated with lightning (rarer).

[0007] Under these conditions, the outer surface of the laminated glazing can develop extremely high electrical potentials (relative to the mass of the aircraft) of several kV or even several tens of kV.

[0008] A surface potential of the laminated glazing is then created which is different from that of the structure of the aircraft, which is generally equipped with passive dissipators (for example, by corona effect at the points) which allow the charges accumulated on the entire electrically conductive structure of the aircraft to flow away.

[0009] In addition, laminated aeronautical aircraft cockpit glazing generally incorporates an electric heating system covering all or part of the internal face of the sheet (also called "ply") on the external side (facing the aircraft) of the laminated glazing.

[0010] There are two categories of laminated aircraft cockpit glazing with integrated heating systems: windshields or front windows on the one hand, which are equipped with an electric heating system known as anti-frost; and side windows on the other hand, which are generally only equipped with an electric heating system known as anti-fog. These two heating systems (anti-frost and anti-fog) differ in the specific power delivered, the electric field developed being weaker for anti-fog heating systems.

[0011] The high potentials developed on the outer surface of the laminated glazing generate intense electric fields which can be discharged, among other things, by dielectric breakdowns: either in the air (between the outer surface of the glazing and the conductive structure of the aircraft on the periphery of the glazing); or in the thickness of the sheet on the outer side of the laminated glazing, between its outer face and the electric heating system (for example, a heating layer) arranged on its inner face. The discharges in the air can be partial or develop surface discharges (commonly called St. Elmo's fires in the aeronautical sector).

[0012] These two mechanisms are therefore in competition with each other in such a way that the first of the two which is triggered prevents the appearance of the other by total or partial neutralization of the external surface of the external ply. Nevertheless, the consequences of a surface discharge and a dielectric breakdown in the external ply are radically different. Surface discharges generate glare and electrical transients in the electrical circuits of the glazing, but these two phenomena are accepted or managed on many aircraft. Conversely, dielectric breakdowns in the thickness of the external ply can lead to its perforation and / or its rupture which constitute modes of failure of the glazing requiring replacement.

[0013] Glazing designers therefore aim to avoid the occurrence of dielectric breakdown fields in the outer plies. This can be achieved by draining surface electric charges using an antistatic layer. In the case of glazing with a heating layer, this can naturally be managed by surface discharges. However, peak effects in heating systems locally increase the electric fields in the outer ply very strongly and can cause dielectric breakdowns in the outer ply before a surface discharge has taken place.

[0014] A first known case of electric field concentration is encountered during the implementation of heating by thin wires. The requirement of invisibility of the wires by the pilots imposes the use of wires with a diameter of typically 20pm to 30pm which, due to their small radius, strongly concentrate the electric fields and induce, in the absence of dedicated systems for minimizing surface potentials, external fold ruptures.

[0015] A second, more exceptional case of electric field concentration is encountered in the case of the edge of a heating layer. In both cases, the occurrence of dielectric breakdowns is all the higher as neutralization of the areas concerned is difficult by surface discharges. This will mainly correspond to the case of heating networks far from the metal structure of the aircraft.

[0016] Indeed, surface discharges are permitted in areas where the electrical heating system (such as a heating layer) forms a capacitor with the charged outer surface of the laminated glazing. Typically, this capacitor is similar to a plane-plane capacitor whose dielectric separating the charged planes is formed by the thickness of the outer side sheet (for example, 3 mm of glass) of the laminated glazing. The surface discharge, by neutralizing the surface, dissipates the electrical energy. This energy is used to power the propagation of the arc (by ionization of the air) until the arc resistance in the air (a function of the arc length) no longer ensures a sufficient potential difference between the arc head and the outer surface of the glazing to ionize the air.

[0017] In the absence of an electrical heating system (e.g., heating layer) indirectly linked to the aircraft mass, the capacitive coupling of the glazing surface is done with much more distant ground planes, so that the energy stored by the surface charge is significantly lower and does not allow a surface discharge to be powered.

[0018] For a surface discharge to initiate, a sufficient electric field is required in the air between the periphery of the glazing and the edge of the opposite electric heating system. Thus, surface discharges initiate more easily in locations where the electric heating system is close to the periphery of the glazing than in locations where it is far from it.

[0019] Since surface discharges cannot extend over the entire surface of the glazing (due to the arc resistance increasing with the arc size), the edges of the electric heating system far from the edges of the glazing can reach higher electrical potentials compared to the rest of the glazing surface. These areas are therefore more likely to develop dielectric breakdowns in the thickness of the sheet on the outside of the laminated glazing, which can break the latter, causing the laminated glazing to fail.

[0020] In addition, the edge of the electric heating system generates a tip effect type electric field singularity promoting the occurrence of dielectric breakdown in the laminated glazing.

[0021] Typically, these problems are solved by applying an electrostatic discharge layer, called an antistatic layer, to the outer surface of the laminated glazing, which provides surface conductivity to the glazing. The electrical resistivity of this antistatic layer typically ranges from tens of kOhms to a fraction of a megaOhm. This antistatic layer is usually electrically connected to the aircraft structure to dissipate low charging currents and maintain the outer surface of the laminated glazing at the aircraft ground potential.

[0022] However, such an antistatic layer is exposed to the external environment of the aircraft (for example, impact of water drops, dust, water, aircraft ground cleaning) and may be removed from the external surface of the laminated glazing. This then results in risks of breakage in service of the sheet on the external side of the laminated glazing in a charging environment.

[0023] The present invention aims to overcome the drawbacks of the prior art, by proposing an aeronautical laminated glazing with an integrated electric heating system, incorporating an isopotential layer applied to the internal face of its exterior side sheet, so as to obtain a durable solution for preventing dielectric breakdowns of the exterior side sheet of the laminated glazing in a charging environment.

[0024] The present invention therefore relates to an aeronautical laminated glazing comprising a first sheet on the exterior side, at least one second structural sheet on the interior side and an intermediate layer arranged between the first sheet and the at least one second structural sheet, the first sheet and the at least one second structural sheet being at least one of a mineral glass and an organic glass, the aeronautical laminated glazing further comprising at least one electric heating system arranged opposite the internal face of the first sheet, characterized in that the aeronautical laminated glazing further comprises an isopotential layer applied to the internal face of the first sheet.

[0025] By "outer side sheet" is meant the sheet (or ply) of the laminated glazing arranged on the outer side with respect to the aircraft on which the laminated glazing is installed, and by "inner side sheet" is meant the sheet (or ply) of the laminated glazing arranged on the inner side with respect to the aircraft on which the laminated glazing is installed. Thus, the outer face of the first sheet on the outer side of the laminated glazing is in contact with the external environment of the aircraft. The intermediate layer of the laminated glazing serves as an interlayer between the first sheet and the at least one second structural sheet of the laminated glazing.

[0026] It should be noted that, in the case where the laminated glazing comprises several second structural sheets, an intermediate layer of the interlayer type is also arranged between each pair of adjacent second structural sheets.

[0027] The first sheet and the second structural sheet(s) of the laminated glazing may be either made of mineral glass (for example, soda-lime, borosilicate, aluminosilicate, etc.), or of organic glass (for example, PMMA (poly(methyl methacrylate), PC (polycarbonate), etc.). It should be noted that the at least one second structural sheet could also be made of organic glass of the PET (polyethylene terephthalate) film type, without departing from the scope of the present invention.

[0028] The isopotential layer applied to the inner face of the first sheet on the outer side of the laminated glazing has a uniform electrical potential over its entire surface. It should be noted that, by "isopotential", we mean a uniform electrical potential with respect to the charge potentials at several tens of kV, such that all electrical potentials between 0V and 500V will be considered uniform with respect to the tens of kV of the charge potentials (typically, on the isopotential layer, a potential of 200V will thus be considered equivalent to a potential of 0V).

[0029] The isopotential layer is encapsulated inside the laminated glazing, so it is not susceptible to erosion, dissolution or scratching.

[0030] This lower sensitivity makes it possible to consider thinner layers which may be simpler to deposit or have less optical impact.

[0031] The present invention thus makes it possible to obtain a durable solution (not subject to erosion of the antistatic layer) for eliminating the risks of breakage or perforation of the heating ply of aeronautical glazing having a heating zone reduced by dielectric breakdown in the thickness of the external sheet in a charging environment.

[0032] According to one embodiment of the invention, the at least one electrical heating system is applied to the isopotential layer and has a first real or equivalent electrical surface resistivity, the isopotential layer having a second real or equivalent electrical surface resistivity which is greater than the first real or equivalent electrical surface resistivity.

[0033] Since the isopotential layer applied to the inner face of the first sheet on the outer side up to the edges of the glazing (possibly with the exception of a peripheral edge) has a surface electrical resistivity greater than that of the at least one electric heating system applied to the isopotential layer, the isopotential layer is thus significantly less conductive than the at least one electric heating system, such that it does not disturb the flow of heating currents in the electric heating system.The interposition of the isopotential layer between the electric heating system and the internal surface of the glazing makes it possible to screen the high potentials of the external surface of the glazing (whether they come from triboelectric charges or lightning) and therefore to eliminate the field concentrations within the first sheet on the external side linked to the peak effects of the electric heating system.

[0034] In the event that an electric arc impacts the outer side of the laminated glazing, its surface potential rises and the electric arc quickly attaches to the structure. This rapid rise in potential can cause a risk of electric field concentration at the edge of the electric heating system, causing a dielectric breakdown in the first sheet on the outer side of the laminated glazing. By applying a significantly more resistive isopotential layer, these field concentrations are eliminated without disrupting the heating.

[0035] The isopotential layer ensures that the entire internal face of the first sheet on the external side of the laminated glazing is maintained at the potential of the aircraft mass (to within a few hundred volts).

[0036] This provides three effects preventing the occurrence of dielectric breaks in the first sheet on the exterior side of the laminated glazing:

[0037] - promotion of surface discharges;

[0038] - in the case where the electric heating system is of the resistive heating layer type, elimination of the electrostatic peak effect at the edge of the heating surface given that the neighboring layer is at a very close potential;

[0039] - in the case where the electric heating system is of the network type of thin resistive heating wires, elimination of the peak effect around each thin wire. It is relevant to compare the equivalent resistivities of the electric heating system and the isopotential layer with respect to the risks of short-circuiting of the heating currents by the isopotential layer. The notion of surface resistivity is rigorously defined only for a homogeneous conductive layer and corresponds for a homogeneous square of conductive layer to the resistance between two electrodes which would be placed on two opposite sides of the square. The equivalent surface resistivity is then defined as the resistivity of a homogeneous layer which would connect two electrodes. Thus, a wire heating system, whose wires connect two electrodes, can then be described as an equivalent homogeneous layer.Similarly, a globally homogeneous discontinuous layer can induce by tortuosity of the current flow an equivalent resistivity higher than the resistivity of the same layer where it is continuous. Finally, in the case of total opening of the continuous electrical path connecting the two electrodes, the equivalent resistivity tends towards infinity.

[0040] According to a particular characteristic of the invention, the ratio between the second real or equivalent surface electrical resistivity and the first real or equivalent surface electrical resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0041] Thus, this important ratio makes it possible not to short-circuit at least one electric heating system by the isopotential layer.

[0042] The isopotential layer thus has a surface resistivity or apparent surface resistivity (obtained for example by partial ablation of this layer) significantly higher than that of the electric heating system.

[0043] According to a particular characteristic of the invention, the isopotential layer is a transparent conductive layer configured to be connected directly or indirectly to the ground of a mounting structure of the aeronautical laminated glazing. Thus, the transparent conductive layer with isopotential and high resistivity is connected to the ground of the aircraft on which the laminated glazing is installed, either directly via electrical means such as wires, screen printing, soldering, conductive bonding, etc., or indirectly via an impedance. The connection to ground can also be made via at least one electric heating system.

[0044] According to a particular characteristic of the invention, the transparent conductive layer is one of doped oxide such as indium-tin oxide or aluminum-zinc oxide, non-stoichiometric oxide such as tin dioxide, diamond-like carbon, and silver.

[0045] According to a particular characteristic of the invention, the at least one electric heating system is one of at least one network of resistive heating wires arranged between at least two power supply electrodes and at least one resistive heating layer arranged between at least two power supply electrodes.

[0046] Thus, the at least one network of heating resistive wires or the at least one heating resistive layer allows the laminated glazing to have an anti-frost function by providing heating by the Joule effect when it is crossed by an electric current coming from the at least two power supply electrodes.

[0047] Laminated glazing may, for example, comprise a single electrical heating system (resistive wire network or resistive layer) arranged between two power supply electrodes in the case of a single-phase power supply.

[0048] The laminated glazing may also comprise three electrical heating systems (resistive wire networks or resistive layers) arranged adjacently between four supply electrodes in the case of a three-phase supply, each electrical heating system being arranged between a respective pair of supply electrodes among the four supply electrodes.

[0049] Each electrical supply electrode is, in practice, a sufficiently conductive element with respect to the electrical elements connected to it to consider that the potential is constant over this entire electrode. In the case of a network of resistive heating wires, it should be noted that the first surface electrical resistivity will not be isotropic, but will be an apparent or equivalent surface electrical resistivity. Indeed, a network of resistive wires can be likened to a conductive layer with electrical conductivity if we consider the current flow in the direction from supply electrode to supply electrode. In the orthogonal direction, there is no electrical conductivity.

[0050] The aircraft grounding of the isopotential layer can be done directly by an electric wire (possibly with an insulation impedance ensuring isopotentiality without the capacity to drain high currents), or indirectly via a power supply electrode of the electric heating system, or even via contacts between the electric heating system and the isopotential layer.

[0051] In the case of an electric heating system of the resistive heating wire network type, the isopotential layer must have a resistivity significantly higher than that of the wire network. Since wire networks are generally very low in resistivity (0.1 to a few Ohms per square), an isopotential layer having a resistivity of 100 Ohms per square to 1 mega Ohms per square can be considered. The resistive wire network is applied in contact with the isopotential layer which forms an electrical screen with respect to the potential of the resistive wires, so that the peak effects associated either with the edge of the heating network or with the size of the wires (a few tens of microns) do not generate an intensification of the electric field by peak effect in the first sheet on the outside of the laminated glazing.

[0052] In the case of an electric heating system of the heating resistive layer type, the isopotential layer must have a resistivity significantly higher than that of the heating resistive layer. The layers usually based on ITO can have resistivities of a few Ohms per square to a few hundred Ohms per square. An isopotential layer having a resistivity of a few tens of kOhms per square to a fraction of mega Ohms per square can thus be considered. The isopotential layer will thus ensure continuity of the electrical potentials in the plane of the heating resistive layer without short-circuiting the latter.

[0053] Since the i-sopotential layer and the heating resistive layer are found on the same internal face of the first sheet on the external side of the laminated glazing, they can thus be deposited during the same process step, which reduces manufacturing costs and eliminates the technical complexity associated with depositing layers on both faces of the first sheet of the laminated glazing (in particular the risk of scratches).

[0054] According to another embodiment of the invention, the at least one electric heating system is at least one heating resistive layer, having a planar geometric shape whose periphery forms a simple closed curve, arranged between at least two power supply electrodes and applied to a part of the internal face of the first sheet, and the isopotential layer is applied to the remaining part of the internal face of the first sheet and made of the same material as the at least one heating resistive layer.

[0055] In this other embodiment, the isopotential layer is applied to the areas of the internal face of the first sheet not facing the at least one heating resistive layer, and thus allows management of the electric fields present at the edge of the heating resistive layer.

[0056] According to a particular characteristic of this other embodiment of the invention, the isopotential layer is one of indium-tin oxide, gold, silver and aluminum-doped zinc oxide, (as is the at least one heating resistive layer).

[0057] According to a first variant of this other embodiment, the isopotential layer consists of at least one of: at least one zigzag strip arranged between the at least two power supply electrodes; and at least one comb-shaped arrangement, said isopotential layer being made of the same material as the at least one heating resistive layer and being electrically connected to the at least one heating resistive layer.

[0058] Thus, as an isopotential layer, we use a layer of the same nature as the heating resistive layer but artificially increasing its apparent resistivity by texturing (zigzag or comb).

[0059] For example, the isopotential layer, which is electrically linked to the heating resistive layer, can be ablated (e.g. by means of a laser) to significantly increase its electrical resistance.

[0060] According to a particular characteristic of this first variant, the at least one heating resistive layer, having a flat geometric shape whose periphery forms a simple closed curve, and the isopotential layer are created on the internal face of the first sheet by:

[0061] - application of a conductive layer on the internal face of the first sheet;

[0062] - defining at least one heating zone having a planar geometric shape whose periphery forms a simple closed curve on the conductive layer; ablation, in particular laser ablation, of the conductive layer so as to form, as a heating resistive layer, the at least one defined heating zone; and ablation, in particular laser ablation, of the conductive layer outside the at least one formed heating zone, so as to form, as an isopotential layer, at least one of at least one zigzag strip and at least one comb-shaped arrangement outside the at least one formed heating zone, such that the equivalent electrical resistivity of the isopotential layer is greater than that of the formed heating zone.

[0063] Thus, after application of the conductive layer over the entire surface of the internal face of the first sheet of the laminated glazing (possibly with the exception of a peripheral edge), a uniform heating resistive layer is created by ablation strategies (or masking prior to deposition), as well as a textured isopotential layer at the edges of the glazing. Laser ablation does not change the surface resistivity of the conductive layer. On the other hand, the texturing / tortuosity of the isopotential layer imposes a longer path and therefore a higher resistance from supply electrode to supply electrode. This area becomes equivalent to a layer of higher resistivity.

[0064] According to a second variant of this other embodiment, the isopotential layer is electrically insulated from the at least one heating resistive layer and configured to be connected directly or indirectly to the ground of a mounting structure of the aeronautical laminated glazing, and by the fact that the at least one heating resistive layer and the isopotential layer are created on the internal face of the first sheet by ablation, in particular laser ablation, of a conductive layer applied to the internal face of the first sheet.

[0065] Thus, after application of the conductive layer over the entire surface of the internal face of the first sheet of the laminated glazing (possibly with the exception of a peripheral edge), electrical insulation is provided between the heating resistive layer and the isopotential layer by ablation strategies (or masking prior to deposition). The isopotential layer at the edge of the glazing can then be connected to the aircraft ground by electrical means such as wires, screen printing, soldering, conductive bonding, etc.

[0066] The present invention also relates to the use of a laminated aeronautical glazing as described above as aircraft cockpit glazing, in particular windshield, in particular for medium and long-haul commercial aircraft, business or tourist aircraft. The present invention also relates to an aircraft, such as an airplane or a helicopter, the cockpit glazing of which is a laminated aeronautical glazing as described above.

[0067] To better illustrate the object of the present invention, preferred embodiments will be described below, by way of illustration and not limitation, with reference to the appended drawings.

[0068] On these drawings:

[0069] [Fig. 1] is a sectional view of an aeronautical laminated glazing according to a first embodiment of the present invention;

[0070] [Fig. 2] is a sectional view of an aeronautical laminated glazing according to a second embodiment of the present invention;

[0071] [Fig. 3] is a sectional view of an aeronautical laminated glazing according to a third embodiment of the present invention;

[0072] [Fig. 4] is a view of the inner face of the first glass sheet of an aeronautical laminated glazing according to a fourth embodiment of the present invention; [Fig. 5] is a view of the inner face of the first glass sheet of an aeronautical laminated glazing according to a fifth embodiment of the present invention; [Fig. 6] is a front view of a three-phase electric heating system assembly in delta mounting;

[0073] [Fig. 7] is a front view of a three-phase electric heating system assembly in star connection; and

[0074] [Fig. 8] is a schematic view of an aircraft equipped with a laminated aeronautical glazing according to the invention. If we refer to Figure 1, we can see that it represents a laminated aeronautical glazing 1 according to a first embodiment of the present invention.

[0075] The aeronautical laminated glazing 1 can be used as aircraft cockpit glazing, and comprises a first sheet 2 arranged on the outside facing the aircraft, two second structural sheets 3a, 3b arranged on the inside facing the aircraft, an intermediate adhesive layer 4 of the interlayer type arranged between the first sheet 2 and the second structural sheet 3a, and another intermediate adhesive layer 5 of the interlayer type arranged between the two second structural sheets 3a and 3b.

[0076] It should be noted that the aeronautical laminated glazing 1 could also comprise a single second structural sheet or at least three second structural sheets, without departing from the scope of the present invention.

[0077] The thickness of the first sheet 2 can be between 1 and 5 mm.

[0078] The thickness of each of the second sheets 3a, 3b can be between 4 and 20 mm (in practice, between 4 and 8 mm for mineral glass, and between 6 and 20 mm for organic glass).

[0079] Thus, the first sheet 2, the external face of which is in contact with the external environment of the aircraft, is a relatively thin surfacing sheet, unlike the second sheets 3a and 3b, constituting the structural block of the laminated glazing 1, which are relatively thick so as to guarantee the mechanical properties required for the laminated glazing 1, in particular in the case where the latter must delimit a pressurized volume inside the aircraft. It should be noted that, when the structural block comprises only a single second sheet of glass 3a, it is considered that this is structural provided that its elastic modulus is at least equal to 1500 MPa for example.

[0080] Each of the first sheet 2 and the second structural sheets 3a, 3b may be either made of mineral glass (e.g., soda-lime, borosilicate, aluminosilicate, etc.) or of organic glass (e.g., PMMA (polymethyl methacrylate), PC (polycarbonate), etc.). It should be noted that the second structural sheets 3a, 3b could also be made of organic glass of the PET (polyethylene terephthalate) film type, without departing from the scope of the present invention.

[0081] Each of the interlayer-type adhesive intermediate layer 4 and the other interlayer-type adhesive intermediate layer 5 may be made of one of the following thermoplastic polymers: polyvinyl butyral (PVB), thermoplastic polyurethane (TPU), ethylene-vinyl acetate copolymer (EVA), casting resin, and ionomer resin.

[0082] The thickness of the interlayer-type adhesive intermediate layer 4 may be between 2 and 10 mm, preferably between 3 and 8 mm (this thickness depending on the aircraft manufacturer's attachment strategy and the thickness of the external ply).

[0083] The thickness of the other adhesive intermediate layer 5 of the interlayer type may be between 0.5 and 6 mm, preferably at most equal to 3 mm.

[0084] The laminated glazing 1 is supported against an internal retainer 6', which may be the structure of the aircraft, with the interposition of a shim 7. The laminated glazing 1 is fixed to the mounting structure of the aircraft by an external retainer 6 consisting of a glass press which, by being bolted to the structure of the aircraft, exerts pressure on the edge of the structural block 3a, 3b by means of a silicone seal 8.

[0085] The aeronautical laminated glazing 1 further comprises an electric heating system of the heating resistive layer type 9 arranged between the internal face of the first sheet 2 and the intermediate layer 4.

[0086] The heating resistive layer 9 is arranged between two power supply electrodes (not visible in Figure 1) and covers a (central) part of the internal face of the first sheet 2. The heating resistive layer 9 thus allows the laminated glazing 1 to have an anti-frost function by providing heating by the Joule effect when it is crossed by an electric current coming from the two power supply electrodes.

[0087] The heating resistive layer 9, which is one of indium tin oxide (ITO), gold, silver, and aluminum-doped zinc oxide, exhibits a first real surface electrical resistivity.

[0088] The heating resistive layer 9 may have a thickness of between 10 and 200 nm, and a surface electrical resistivity of between 1 and 500 Ohms per square.

[0089] The aeronautical laminated glazing 1 further comprises an isopotential layer 10 applied to the (peripheral) zones of the internal face of the first sheet 2 not facing the electric heating system of the heating resistive layer type 9.

[0090] The isopotential layer 10 is thus encapsulated inside the laminated glazing 1 and is therefore not sensitive to erosion, dissolution or scratching.

[0091] The isopotential layer 10, which is a conductive layer of the same nature as the heating resistive layer 9 (the two layers 9 and 10 thus having the same real surface electrical resistivity), is completely electrically isolated from the heating resistive layer 9 and electrically connected to the ground of the aircraft mounting structure via electrical wires 11 (possibly with an insulation impedance ensuring isopotentiality without the capacity to drain high currents).

[0092] It should be noted that the isopotential layer 10 could also be connected to the ground of the aircraft, either directly via other electrical means such as screen printing, soldering, conductive bonding, etc., or indirectly via an impedance, without departing from the scope of the present invention. The connection to ground could also be made via one of the two power supply electrodes connected to the heating resistive layer 9.

[0093] Since the isopotential layer 10 and the heating resistive layer 9 are located on the same internal face of the first sheet 2 of the laminated glazing 1, they can be deposited during the same process step, which reduces manufacturing costs and eliminates the technical complexity associated with depositing layers on both faces of the first sheet 2 of the laminated glazing 1.

[0094] The heating resistive layer 9 and the isopotential layer 10 may be deposited on the inner face of the first sheet 2 by means of physical vapor deposition, for example by magnetic field-assisted cathode sputtering - magnetron under reduced pressure, or by liquid means, for example sol-gel.

[0095] In practice, a single conductive layer is deposited on the internal face of the first sheet 2, then the isopotential layer 10 and the heating resistive layer 9 are created, by ablation of the deposited conductive layer, so that the isopotential layer 10 is completely isolated from the heating resistive layer 9.

[0096] The isopotential layer 10 has, over its entire surface, a uniform electrical potential with respect to charge potentials at several tens of kV.

[0097] If we refer to Figure 2, we can see that it shows an aeronautical laminated glazing 12 according to a second embodiment of the present invention.

[0098] The common elements between the first embodiment of the invention in Figure 1 and this second embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0099] The aeronautical laminated glazing 12 according to the second embodiment is identical to the aeronautical laminated glazing 1 according to the first embodiment, except for the fact that the isopotential layer 10 is a transparent conductive layer applied to the entire internal face of the first sheet 2 (possibly with the exception of a peripheral strip), and ensures that the entire internal face of the first sheet 2 is maintained at the potential of the aircraft mass (to within a few hundred volts), the heating resistive layer 9 being applied to a (central) part of the isopotential layer 10.

[0100] Furthermore, in this second embodiment, the transparent conductive layer type isopotential layer 10, which is one of doped oxide such as indium tin oxide or aluminum zinc oxide, non-stoichiometric oxide such as tin dioxide, diamond-like carbon, and silver, has a second actual surface electrical resistivity greater than the first actual surface electrical resistivity of the heating resistive layer 9.

[0101] The ratio of the second actual surface electrical resistivity to the first actual surface electrical resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0102] The transparent conductive layer type isopotential layer 10 may have a thickness of between 10 and 100 nm.

[0103] Since the isopotential layer 10 has a surface electrical resistivity greater than that of the heating resistive layer 9, the isopotential layer 10 is thus substantially less conductive than the heating resistive layer 9, such that the isopotential layer 10 ensures continuity of the electrical potentials in the plane of the heating resistive layer 9 without short-circuiting the latter, and makes it possible to initiate surface discharges from the entire periphery of the glazing and to eliminate the peak effects at the boundary of the heating resistive layer 9 promoting dielectric breakdowns in the first sheet 2 of the laminated glazing 1.

[0104] If we refer to Figure 3, we can see that there is shown there an aeronautical laminated glazing 13 according to a third embodiment of the present invention. The common elements between the second embodiment of the invention in Figure 2 and this third embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0105] The aeronautical laminated glazing 13 according to the third embodiment is identical to the aeronautical laminated glazing 12 according to the second embodiment, except that the electric heating system of the heating resistive layer type 9 is replaced by an electric heating system of the heating resistive wire network type 9' applied to the transparent isopotential conductive layer 10. The heating resistive wire network 9' is arranged between two power supply electrodes (not visible in Figure 3), and allows the laminated glazing 13 to have an anti-icing function by providing heating by the Joule effect when its resistive wires are crossed by an electric current coming from the two power supply electrodes. For example, one of the two power supply electrodes may be at a potential of 0V and the other of the two power supply electrodes may be at a potential of 28V.

[0106] It should be noted that the surface electrical resistivity of the network of resistive heating wires 9' will not be isotropic, but will be considered as an apparent or equivalent surface electrical resistivity whose value will be significantly lower than the surface electrical resistivity of the isopotential layer 10. The network of resistive heating wires 9' will in fact be assimilated to a conductive layer with electrical conductivity if the current flow in the supply electrode to supply electrode direction is considered. On the other hand, in the orthogonal direction, there will be no electrical conductivity.

[0107] A network of resistive wires 9' being generally very low resistivity (1 to a few Ohms per square), an isopotential layer 10 having an electrical surface resistivity ranging from 100 Ohms per square to 1 mega Ohms per square could be chosen.

[0108] The network of resistive wires 9' is applied in contact with the isopotential layer 10 which forms an electrical screen with respect to the potential of its resistive wires, such that the peak effects associated either with the edge of the heating network 9', or with the size of the wires (a few tens of microns) do not generate an intensification of the electric field by peak effect in the first sheet 2 of the laminated glazing 13.

[0109] If we refer to Figure 4, we can see that there is shown an aeronautical laminated glazing 14 according to a fourth embodiment of the present invention.

[0110] The common elements between the first embodiment of the invention in Figure 1 and this fourth embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0111] In a similar manner to the first embodiment, the aeronautical laminated glazing 14 according to the fourth embodiment comprises a heating resistive layer 9 in the shape of a simple polygon applied to a (central) part of the internal face of the first sheet 2 of the laminated glazing 14 and arranged between two single-phase power supply electrodes 15a and 15b applied in the upper and lower parts, respectively, of the internal face of the first sheet 2 of the laminated glazing 14.

[0112] It should be noted that the heating resistive layer 9 could also have any other planar geometric shape whose periphery forms a simple closed curve, without departing from the scope of the present invention.

[0113] Each of the two supply electrodes 15a and 15b is, in practice, a bar-shaped element sufficiently conductive with respect to the electrical elements connected to it to consider that the potential is constant across this entire electrode. Furthermore, in this fourth embodiment, the isopotential layer 10 is applied to the remaining part of the internal face of the first sheet 2 (with the exception of a peripheral edge of the internal face of the first sheet 2) and is made up of two continuous zigzag (or serpentine) strips 16a and 16b arranged between the two power supply electrodes 15a and 15b, on either side of the heating resistive layer 9, and forming a continuous path between the power supply electrodes 15a and 15b, longer in distance than the path between the two power supply electrodes 15a and 15b at the level of the heating resistive layer 9 and therefore of greater resistivity.It is understood that this embodiment is not the only way to form a path of higher resistivity through the isopotential layer and that other embodiments are contemplated in the present invention, for example a different or additional layer modifying the resistivity of the isopotential layer with respect to the heating resistive layer. The two zigzag strips 16a and 16b forming the isopotential layer 10 are made of the same material as the heating resistive layer 9 (namely, one of indium-tin oxide, gold, silver and aluminum-doped zinc oxide) and are electrically connected to the heating resistive layer 9.

[0114] Thus, in this fourth embodiment, a layer of the same nature as the heating resistive layer 9 is used as isopotential layer 10, but artificially increasing its apparent resistivity by zigzag texturing.

[0115] In practice, the heating resistive layer 9 and the textured isopotential layer 10 can be created on the internal face of the first sheet 2 by: - ​​application of a conductive layer on the internal face of the first sheet 2;

[0116] - definition of a heating zone (corresponding to the future heating resistive layer 9) on the applied conductive layer; ablation, in particular laser ablation, of the conductive layer so as to form, as heating resistive layer 9, the defined heating zone; and ablation, in particular laser ablation, of the conductive layer outside the formed heating zone, so as to form, as isopotential layer 10, the two zigzag strips 16a and 16b on either side of the heating resistive layer 9, such that the equivalent electrical resistivity of the zigzag strips 16a and 16b is greater than that of the heating resistive layer 9.

[0117] Thus, total or partial electrical insulation between the heating resistive layer 9 and the isopotential layer 10 (namely, the two zigzag strips 16a and 16b) is provided by laser ablation of the initial conductive layer.

[0118] Laser ablation does not change the surface resistivity of the conductive layer. On the other hand, the tortuosity (zigzag shape) imposes a longer path and therefore a higher resistance from feed electrode 15a to feed electrode 15b for the isopotential layer 10 which thus becomes equivalent to a layer of higher resistivity.

[0119] If we refer to Figure 5, we can see that it shows an aeronautical laminated glazing 17 according to a fifth embodiment of the present invention.

[0120] The common elements between the fourth embodiment of the invention in Figure 4 and this fifth embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0121] In this fifth embodiment, the textured isopotential layer 10 is no longer made up of the two zigzag strips 16a and 16b, but rather of two comb-shaped arrangements 18a and 18b extending on either side of the heating resistive layer 9, the comb-shaped textured isopotential layer 10 thus being equivalent to a higher resistivity layer. In practice, the textured isopotential layer 10 can be created on the inner face of the first sheet 2 by:

[0122] - application of a conductive layer on the internal face of the first sheet 2;

[0123] - definition of a heating zone (corresponding to the future heating resistive layer 9) on the applied conductive layer; and ablation, in particular laser ablation, of the conductive layer outside the defined heating zone, so as to form, as an isopotential layer 10, the two comb-shaped arrangements 18a and 18b extending on either side of the heating resistive layer 9, such that the equivalent electrical resistivity of the comb-shaped arrangements 18a and 18b is greater than that of the heating resistive layer 9.

[0124] Although, in each of the first to fifth embodiments shown in Figures 1 to 5, a single electric heating system 9 or 9' with single-phase power supply has been shown, each of these embodiments could also include several electric heating systems (of the heating resistive layer type 9 or network of heating resistive wires 9') with three-phase power supply, without departing from the scope of the present invention.

[0125] As an example, Figure 6 shows such a three-phase electric heating system assembly 19 in delta connection comprising three electric heating systems 9a, 9b and 9c (for example, three heating resistive layers) arranged adjacently between four power electrodes 20a, 20b, 20c and 20d.

[0126] The first electrode 20a is connected to the lower portion of the first electric heating system 9a. The second electrode 20b is connected to the upper portions of the first and second electric heating systems 9a and 9b. The third electrode 20c is connected to the lower portions of the second and third electric heating systems 9b and 9c. The fourth electrode 20d is connected to the upper portion of the third electric heating system 9c. And, the first electrode and the fourth electrode are electrically connected by an electric wire 21.

[0127] Also by way of example, Figure 7 shows another three-phase electric heating system assembly 22 in star connection comprising three electric heating systems 9a, 9b and 9c (e.g., three heating resistive layers) arranged adjacently between four power electrodes 23a, 23b, 23c and 23d.

[0128] The first electrode 23a is connected to the lower part of the first electric heating system 9a. The second electrode 23b is connected to the lower part of the second electric heating system 9b. The third electrode 23c is connected to the lower part of the third electric heating system 9c. And, the fourth electrode 23d is connected to the upper parts of the three electric heating systems 9a, 9b and 9c.

[0129] The present invention also relates to the use of one of the laminated aeronautical glazings 1, 12, 13, 14 and 17 described above as aircraft cockpit glazing, in particular windshield, in particular for medium and long-haul commercial aircraft, business or tourist aircraft.

[0130] The present invention further relates to an aircraft, such as an airplane or a helicopter, the cockpit glazing of which is one of the laminated aeronautical glazings 1, 12, 13, 14 and 17 described above.

[0131] Figure 8 schematically represents an aircraft 24 (here an airplane but the invention is also applicable to helicopters) equipped with laminated glazing 1 according to the invention at its windshield.

[0132] Of course, the invention is not limited in this respect and the laminated glazing according to the invention can be applied to one or more of the openings (windshield, portholes, door windows) or optical (lights) of the aircraft without departing from the scope of the invention.

[0133] It is understood that the particular embodiments which have just been described have been given for informational and non-limiting purposes, and that modifications may be made without departing from the present invention.

Claims

Claims

1. Laminated aeronautical glazing (1; 12; 13; 14; 17) comprising a first sheet (2) on the outer side, at least one second structural sheet (3a, 3b) on the inner side and an intermediate layer (4) arranged between the first sheet (2) and the at least one second structural sheet (3a, 3b), the first sheet (2) and the at least one second structural sheet (3a, 3b) being at least one of a mineral glass and an organic glass, the aeronautical laminated glazing (1; 12; 13; 14; 17) further comprising at least one electric heating system (9; 9') arranged opposite the internal face of the first sheet (2), characterized in that the aeronautical laminated glazing (1; 12; 13; 14; 17) further comprises an isopotential layer (10) applied to the internal face of the first sheet (2).

2. Laminated aeronautical glazing (12; 13) according to claim 1, characterized in that the at least one electric heating system (9; 9') is applied to the isopotential layer (10) and has a first real or equivalent electrical surface resistivity, the isopotential layer (10) having a second real or equivalent electrical surface resistivity which is greater than the first real or equivalent electrical surface resistivity.

3. Laminated aeronautical glazing (12; 13) according to claim 2, characterized in that the ratio between the second real or equivalent surface electrical resistivity and the first electrical resistivity of actual or equivalent surface area is greater than or equal to 10, preferably greater than or equal to 100.

4. Laminated aeronautical glazing (12; 13) according to one of claims 2 and 3, characterized in that the isopotential layer (10) is a transparent conductive layer configured to be connected directly or indirectly to the ground of a mounting structure of the laminated aeronautical glazing (12; 13).

5. Laminated aeronautical glazing (12; 13) according to claim 4, characterized in that the transparent conductive layer is one of doped oxide such as indium-tin oxide or aluminum-zinc oxide, non-stoichiometric oxide such as tin dioxide, diamond-type carbon, and silver.

6. Laminated aeronautical glazing (12; 13) according to one of claims 2 to 5, characterized in that the at least one electric heating system is one of at least one network of heating resistive wires (9') arranged between at least two power supply electrodes (15a, 15b) and at least one heating resistive layer (9) arranged between at least two power supply electrodes (15a, 15b).

7. Laminated aeronautical glazing (1; 14; 17) according to claim 1, characterized in that the at least one electric heating system is at least one heating resistive layer (9), having a flat geometric shape whose periphery forms a simple closed curve, arranged between at least two electrodes supply (15a, 15b) and applied to a part of the inner face of the first sheet (2), and the isopotential layer (10) is applied to the remaining part of the inner face of the first sheet (2) and made of the same material as the at least one heating resistive layer (9).

8. Laminated aeronautical glazing (1; 14; 17) according to claim 7, characterized in that the isopotential layer (10) is one of indium-tin oxide, gold, silver and zinc oxide doped with aluminum.

9. Laminated aeronautical glazing (14; 17) according to claim 7 or 8, characterized in that the isopotential layer (10) consists of at least one of: at least one zigzag strip (16a, 16b) arranged between the at least two power supply electrodes (15a, 15b); and at least one comb-shaped arrangement (18a, 18b), said isopotential layer (10) being electrically connected to the at least one heating resistive layer (9).

10. Laminated aeronautical glazing (14; 17) according to claim 9, characterized in that the at least one heating resistive layer (9), having a flat geometric shape whose periphery forms a simple closed curve, and the isopotential layer (10) are created on the internal face of the first sheet (2) by: - application of a conductive layer on the internal face of the first sheet (2); - defining at least one heating zone having a planar geometric shape whose periphery forms a simple closed curve on the conductive layer; ablation, in particular laser ablation, of the conductive layer so as to form, as a heating resistive layer (9), the at least one defined heating zone; and ablation, in particular laser ablation, of the conductive layer outside the at least one formed heating zone, so as to form, as an isopotential layer (10), at least one of at least one zigzag strip (16a, 16b) and at least one comb-shaped arrangement (18a, 18b) outside the at least one formed heating zone, such that the equivalent electrical resistivity of the isopotential layer (10) is greater than that of the formed heating zone.

11. Laminated aeronautical glazing (1) according to claim 7 or 8, characterized in that the isopotential layer (10) is electrically insulated from the at least one heating resistive layer (9) and configured to be connected directly or indirectly to the ground of a mounting structure of the laminated aeronautical glazing (1), and in that the at least one heating resistive layer (9) and the isopotential layer (10) are created on the internal face of the first sheet (2) by ablation, in particular laser ablation, of a conductive layer applied to the internal face of the first sheet (2).

12. Use of an aeronautical laminated glazing (1; 12; 13; 14; 17) according to one of claims 1 to 11 as aircraft cockpit glazing, including windshields, particularly for medium and long-haul commercial aircraft, business or tourist aircraft.

13. Aircraft whose cockpit glazing is a laminated aeronautical glazing (1; 12; 13; 14; 17) according to one of claims 1 to 11.

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