Laminated aircraft glazing with electric heating system, use of laminated aircraft glazing as aircraft cockpit glazing, and associated aircraft

Abstract

Aircraft laminated glazing with electric heating system, use of aircraft laminated glazing as aircraft cockpit glazing, and associated aircraft. The present invention relates to aircraft laminated glazing (1) comprising a first sheet (2) on the outer side and at least one second structural sheet (3a, 3b) on the inner side, aircraft laminated glazing (1) further comprising at least one electric heating system (9) arranged opposite the inner face of the first sheet (2), aircraft laminated glazing (1) further comprising an isopotential layer (10) applied to the inner face of the first sheet (2). Figure to be published with the abstract: Figure 1

Description

Title of the invention: Aeronautical laminated glazing with an electric heating system, use of aeronautical laminated glazing as aircraft cockpit glazing, and associated aircraft

[0001] The present invention relates to the field of aeronautics, and in particular to an aeronautical laminated glazing with an integrated electric heating system, to the use of such aeronautical laminated glazing as aircraft cockpit glazing, and to an aircraft comprising such aeronautical laminated glazing as cockpit glazing.

[0002] Aeronautical laminated 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:

[0003] - triboelectric charges 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

[0004] - charges associated with lightning (rarer).

[0005] Under these conditions, the outer surface of the laminated glazing can develop po extremely high electrical potentials (relative to the mass of the aircraft) of several kV or even a few tens of kV.

[0006] A surface potential of the laminated glazing is then formed which is different from that of the aircraft structure which is generally equipped with passive dissipators (for example, by corona effect at the point level) which allow the charges accumulated on the entire electrically conductive structure of the aircraft to be discharged.

[0007] In addition, aircraft cockpit laminated glazing generally incorporates an electric heating system covering all or part of the inner face of the sheet (also called "ply") on the outer side (facing the aircraft) of the laminated glazing.

[0008] Two categories of laminated aircraft cockpit glazing with integrated heating systems are distinguished: windshields or frontal windows, which are equipped with an electric heating system known as anti-icing; and side windows, which are generally equipped only with an electric heating system known as anti-fog. These two heating systems (anti-icing and anti-fog) differ in the specific power delivered, with the electric field developed being weaker for anti-fog heating systems.

[0009] The high potentials developed on the outer surface of the laminated glazing in generate intense electric fields which can discharge, among other things, through dielectric breaks: either in the air (between the outer surface of the glazing and the conductive structure of the aircraft around 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.

[0010] Discharges in the air can be partial or develop surface discharges (commonly called St. Elmo's fire in the aeronautical field).

[0011] These two mechanisms are therefore in competition with each other, such that the first one triggered prevents the other from occurring by completely or partially neutralizing the external surface of the outer ply. However, the consequences of a surface discharge and a dielectric breakdown in the outer 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 outer ply can lead to its perforation and / or rupture, which constitute failure modes of the glazing requiring replacement.

[0012] Glazing designers therefore aim to prevent the occurrence of dielectric breakdown fields in the outer layers. This can be achieved by draining surface electrical charges using an antistatic layer. In the case of heated-layer glazing, this can naturally be managed by surface discharges. However, the peak effects at the heating systems locally and very strongly increase the electric fields in the outer layer and can lead to dielectric breakdowns in the outer layer before a surface discharge has occurred.

[0013] A first known case of electric field concentration is encountered during the implementation of heating with thin wires. The requirement for the wires to be invisible to the pilots necessitates the use of wires with a diameter typically of 20 µm to 30 µm, which, due to their small radius, strongly concentrate the electric fields and, in the absence of dedicated surface potential minimization systems, induce external fold breaks.

[0014] A second, more exceptional case of electric field concentration is encountered in the case of the edge of a heating layer.

[0015] In both cases, the occurrence of dielectric breakdowns is higher when neutralizing the affected areas is difficult by surface discharges. This will mainly correspond to the case of heating networks located far from the aircraft's metallic structure.

[0016] Indeed, surface landfills are permitted in areas where The electric heating system (such as a heating layer) forms a capacitor with the charged outer surface of the laminated glass. Typically, this capacitor is similar to a plate-on-plate capacitor where the dielectric separating the charged plates is the thickness of the outer layer (e.g., 3 mm of glass) of the laminated glass. The surface discharge, by neutralizing the surface, dissipates electrical energy. This energy powers the arc propagation (by ionizing the air) until the arc resistance in the air (a function of the arc length) no longer provides a sufficient potential difference between the arc tip and the outer surface of the glass to ionize the air.

[0017] In the absence of an electric heating system (for example, a heating layer) indirectly linked to the mass of the aircraft, the capacitive coupling of the surface of the glazing takes place with much more distant ground planes, so that the energy stored by the surface charge is substantially 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 where the electric heating system is close to the periphery of the glazing than where it is farther away.

[0019] Since surface discharges cannot extend over the entire surface of the glazing (due to arc resistance increasing with arc size), the edges of the electric heating system located 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 susceptible to developing dielectric breakdowns in the thickness of the outer layer of the laminated glazing, which can shatter the glazing, leading to failure of the laminated glazing.

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

[0021] Typically, these problems are solved by applying an electrostatic discharge layer, known as an antistatic layer, to the outer surface of the laminated glass, which imparts surface conductivity to the glass. The order of magnitude of the electrical resistivity of this antistatic layer typically ranges from tens of kiloohms to a fraction of a megaohm. This antistatic layer is usually electrically connected to the aircraft structure to dissipate small charging currents and maintain the outer surface of the laminated glass at the aircraft's ground potential.

[0022] However, such an antistatic layer is exposed to the external environment of The aircraft (for example, impact from water droplets, dust, water, or aircraft ground cleaning) can be affected and may be removed from the outer surface of the laminated glass. This results in a risk of breakage of the outer layer of the laminated glass during operation in a high-stress environment.

[0023] The present invention aims to overcome the disadvantages of the prior art, by proposing an aeronautical laminated glazing with an integrated electric heating system, incorporating an isopotential layer applied to the inner face of its outer-side sheet, so as to obtain a durable solution for preventing dielectric breaks of the outer-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 outside, at least one second structural sheet on the inside and an intermediate layer disposed between the first sheet and the at least one second structural sheet, the first sheet and the at least one second structural sheet being made of 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 inner face of the first sheet, characterized in that the aeronautical laminated glazing further comprises an isopotential layer applied to the inner face of the first sheet.

[0025] By "outer-side sheet" is meant the sheet (or ply) of the laminated glass arranged on the outer side with respect to the aircraft on which the laminated glass is installed, and by "inner-side sheet" is meant the sheet (or ply) of the laminated glass arranged on the inner side with respect to the aircraft on which the laminated glass is installed. Thus, the outer face of the first outer-side sheet of the laminated glass is in contact with the aircraft's external environment.

[0026] The intermediate layer of the laminated glazing serves as an interlayer between the first sheet and at least one second structural sheet of the laminated glazing.

[0027] It should be noted that, in the case where the laminated glazing comprises several structural second sheets, an intermediate layer of the intercalary type is also arranged between each pair of adjacent structural second sheets.

[0028] The first and second structural layers of the laminated glazing may be made of either mineral glass (e.g., soda-lime glass, borosilicate glass, aluminosilicate glass, etc.) or organic glass (e.g., PMMA (poly(methyl methacrylate), PC (polycarbonate), etc.). It should be noted that at least one second structural layer could also be made of organic glass such as PET (polyethylene terephthalate) film, without departing from the scope of the present invention.

[0029] 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 length surface. It should be noted that, by "isopotential", we mean a uniform electrical potential with respect to charge potentials of 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 charge potentials (typically, on the isopotential layer, a potential of 200V will thus be considered equivalent to a potential of 0V).

[0030] The isopotential layer is encapsulated within the laminated glass, and is therefore not susceptible to erosion, dissolution, or scratching. This reduced susceptibility allows for thinner layers that may be easier 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 the elimination of the risks of breakage or perforation of the heating ply of aeronautical glazing having a reduced heating zone by dielectric rupture in the thickness of the outer sheet in a charging environment.

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

[0033] Since the isopotential layer applied to the inner face of the first outermost sheet up to the edges of the glazing (possibly excluding a peripheral edge) has a surface electrical resistivity higher than that of the at least one electric heating system applied to the isopotential layer, the isopotential layer is thus substantially less conductive than the at least one electric heating system, such that it does not disrupt the flow of heating currents in the electric heating system. The interposition of the isopotential layer between the electric heating system and the inner surface of the glazing makes it possible to screen the high potentials on the outer surface of the glazing (whether they originate from triboelectric charging or lightning) and thus to eliminate the field concentrations within the outermost sheet related to the peak effects of the electric heating system.

[0034] In the event that an electric arc strikes the outer side of the laminated glass, its surface potential rises and the electric arc quickly adheres to the structure. This rapid potential rise can generate, at the edge of an electric heating system, a risk of electric field concentration leading to dielectric breakdown in the first layer on the outer side of the laminated glass. By applying a layer with a significantly higher resistivity at the same potential, the elimination of these field concentrations, without disrupting the heating.

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

[0036] Thus, three effects are provided that prevent the occurrence of dielectric breakdowns in the first sheet on the outer side of the laminated glazing:

[0037] - promotion of surface discharges;

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

[0039] - in the case where the electric heating system is of the thin wire network type heating resistors, eliminating the peak effect around each fine wire.

[0040] 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 the heating currents through the isopotential layer. The concept 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 placed on opposite sides of the square. The equivalent surface resistivity is then defined as the resistivity of a homogeneous layer connecting two electrodes. Thus, a heating system with wires connecting two electrodes can be described as an equivalent homogeneous layer. Similarly, a discontinuous, overall homogeneous layer can induce, due to current flow tortuosity, an equivalent resistivity higher than the resistivity of the same layer where it is continuous.Finally, if the continuous electrical path connecting the two electrodes is completely open, the equivalent resistivity tends towards infinity.

[0041] According to a particular feature of the invention, the ratio between the second actual or equivalent surface electrical resistivity and the first actual or equivalent surface electrical resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0042] Thus, this important ratio makes it possible not to short-circuit at least one electric heating system through the isopotential layer.

[0043] The isopotential layer thus exhibits 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.

[0044] According to a particular feature 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 for aeronautical laminated glazing.

[0045] Thus, the transparent, isopotential, high-resistivity conductive layer is connected to the aircraft's ground 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. Grounding can also be achieved via at least one electric heating system.

[0046] According to a particular feature of the invention, the transparent conductive layer is made of one of the following: doped oxide such as indium tin oxide or aluminum zinc oxide, non-stoichiometric oxide such as tin dioxide, diamond-type carbon, and silver.

[0047] According to a particular feature of the invention, at least one electric heating system is one of at least one network of heating resistive wires arranged between at least two supply electrodes and at least one heating resistive layer arranged between at least two supply electrodes.

[0048] Thus, at least one network of heating resistive wires or at least one heating resistive layer allows the laminated glazing to have an anti-frost function by providing heating by Joule effect when it is traversed by an electric current from at least two supply electrodes.

[0049] Laminated glazing may, for example, comprise a single electric heating system (resistive wire network or resistive layer) arranged between two supply electrodes in the case of a single-phase supply.

[0050] The laminated glazing may also include three electric heating systems (resistive wire networks or resistive layers) arranged adjacently between four supply electrodes in the case of a three-phase supply, each electric heating system being arranged between a respective pair of supply electrodes among the four supply electrodes.

[0051] Each power 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 the whole of this electrode.

[0052] In the case of a network of heating resistive 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 considered as a conductive layer with electrical conductivity if current flow is considered in the direction from supply electrode to supply electrode. In the orthogonal direction, there is no electrical conductivity.

[0053] Aircraft grounding of the isopotential layer can be achieved directly by means of an electrical 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 again via contacts between the electric heating system and the isopotential layer.

[0054] In the case of an electric heating system of the resistive heating wire array type, the isopotential layer must have a significantly higher resistivity than the wire array. Since wire arrays are generally very low resistivity (0.1 to a few Ohms per square), an isopotential layer with a resistivity of 100 Ohms per square to 1 megaOhm per square can be considered. The resistive wire array is applied in contact with the isopotential layer, which forms an electrical shield against the potential of the resistive wires, such that the point effects associated either with the edge of the heating array or with the size of the wires (a few tens of microns) do not generate an intensification of the electric field by point effect in the first sheet on the outer side of the laminated glass.

[0055] In the case of an electric heating system of the resistive heating layer type, the isopotential layer must have a significantly higher resistivity than the resistive heating layer. Layers typically based on ITO can have resistivities ranging from a few ohms per square to a few hundred ohms per square. An isopotential layer with a resistivity of a few tens of kiloohms per square to a fraction of a megaohm per square can therefore be considered. The isopotential layer will thus ensure continuity of electrical potentials in the plane of the resistive heating layer without short-circuiting the latter.

[0056] Since the isopotential layer and the heating resistive layer are located on the same inner face of the first sheet on the outer 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).

[0057] According to another embodiment of the invention, 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 supply electrodes and applied to a part of the inner face of the first sheet, and the isopotential layer is applied to the remaining part of the inner face of the first sheet and made of the same material as the at least one heating resistive layer.

[0058] In this other embodiment, the isopotential layer is applied to the areas of the inner face of the first sheet not opposite at least one heating resistive layer, and thus allows management of the electric fields present at the edge of the heating resistive layer.

[0059] According to a particular feature of this other embodiment of the invention, the isopotential layer is made of one of indium tin oxide, gold, silver and aluminum-doped zinc oxide, (as is at least one heating resistive layer).

[0060] According to a first variant of this other embodiment, the isopotential layer consists of at least one of: at least one zigzag band arranged between at least two supply electrodes; and at least one comb-shaped arrangement, said isopotential layer being made of the same material as at least one heating resistive layer and being electrically connected to at least one heating resistive layer.

[0061] Thus, as an isopotential layer, a layer of the same nature as the heating resistive layer is used, but its apparent resistivity is artificially increased by texturing (zigzag or comb).

[0062] For example, the isopotential layer, which is electrically linked to the heating resistive layer, can be ablated (for example by means of a laser) to substantially increase its electrical resistance.

[0063] According to a particular feature of this first variant, at least one heating resistive layer, having a planar geometric shape whose periphery forms a simple closed curve, and the isopotential layer are created on the inner face of the first sheet by:

[0064] - application of a conductive layer on the inner face of the first sheet;

[0065] - definition of at least one heating zone having a planar geometric shape whose periphery forms a simple closed curve on the conductive layer;

[0066] - ablation, in particular laser ablation, of the conductive layer so as to form, as a resistive heating layer, at least one defined heating zone; and

[0067] - ablation, in particular laser ablation, of the conductive layer outside the at least one heating zone formed, so as to form, as an isopotential layer, at least one of at least one zigzag band and at least one comb-like arrangement out of the at least one heating zone formed, such that the equivalent electrical resistivity of the isopotential layer is greater than that of the heating zone formed.

[0068] Thus, after application of the conductive layer over the entire surface of the inner 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 pre-deposition masking), as well as a textured isopotential layer at the edges of the glazing.

[0069] Laser ablation does not change the surface resistivity of the conductive layer. On the other hand, the texture / tortuosity of the isopotential layer imposes a longer path and therefore a higher resistance from feed electrode to electrode power supply. This zone then becomes equivalent to a layer of higher resistivity.

[0070] According to a second variant of this other embodiment, the isopotential layer is electrically isolated from at least one heating resistive layer and configured to be connected directly or indirectly to the ground of a mounting structure for the aeronautical laminated glazing, and by the fact that the at least one heating resistive layer and the isopotential layer are created on the inner face of the first sheet by ablation, in particular laser ablation, of a conductive layer applied to the inner face of the first sheet.

[0071] Thus, after applying the conductive layer to the entire surface of the inner face of the first sheet of laminated glass (possibly with the exception of a peripheral edge), electrical insulation is provided between the heating resistive layer and the isopotential layer by means of ablation strategies (or masking prior to deposition). The isopotential layer at the edge of the glass can then be connected to the aircraft ground by means of electrical connections such as wires, screen printing, brazing, conductive bonding, etc.

[0072] The present invention also relates to the use of aeronautical laminated glazing as described above as aircraft cockpit glazing, in particular windshields, in particular for medium and long-haul commercial aircraft, business or tourist aircraft.

[0073] The present invention further relates to an aircraft, such as an airplane or a helicopter, whose cockpit glazing is aeronautical laminated glazing as described above.

[0074] To better illustrate the object of the present invention, we will describe below, by way of illustration and not limitation, preferred embodiments, with reference to the attached drawings.

[0075] On these drawings:

[0076] [Fig.1] is a cross-sectional view of an aeronautical laminated glazing according to a first embodiment of the present invention;

[0077] [Fig.2] is a cross-sectional view of an aeronautical laminated glazing according to a second embodiment of the present invention;

[0078] [Fig.3] is a cross-sectional view of an aeronautical laminated glazing according to a third embodiment of the present invention;

[0079] [Fig.4] is a view of the inner face of the first sheet of glass of an aeronautical laminated glazing according to a fourth embodiment of the present invention;

[0080] [Fig.5] is a view of the inner face of the first sheet of glass of an aeronautical laminated glazing according to a fifth embodiment of the present invention;

[0081] [Fig.6] is a front view of an assembly of a three-phase powered electric heating system in delta connection;

[0082] [Fig.7] is a front view of an assembled electric heating system with an ali three-phase power supply in a star connection; and

[0083] [Fig.8] is a schematic view of an aircraft equipped with aeronautical laminated glazing according to the invention.

[0084] If we refer to [Fig. 1], we can see that it represents an aeronautical laminated glazing 1 according to a first embodiment of the present invention.

[0085] 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 disposed between the first sheet 2 and the second structural sheet 3a, and another intermediate adhesive layer 5 of the interlayer type disposed between the two second structural sheets 3a and 3b.

[0086] 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.

[0087] The thickness of the first sheet 2 can be between 1 and 5 mm.

[0088] 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).

[0089] Thus, the first sheet 2, whose outer face is in contact with the aircraft's external environment, is a relatively thin surfacing sheet, unlike the second sheets 3a and 3b, which constitute the structural block of the laminated glazing 1. These second sheets are relatively thick in order to guarantee the mechanical properties required for the laminated glazing 1, particularly when it is intended to 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 structural provided that its elastic modulus is at least equal to 1500 MPa, for example.

[0090] Each of the first sheet 2 and the second structural sheets 3a, 3b can be made of either mineral glass (e.g., soda-lime glass, borosilicate glass, aluminosilicate glass, etc.) or organic glass (e.g., PMMA (poly(methyl methacrylate), PC (polycarbonate), etc.). It should be noted that the second structural sheets 3a, 3b could also be made of organic glass such as PET (polyethylene terephthalate) film, without departing from the scope of the present invention.

[0091] Each of the intermediate adhesive layer of interlayer type 4 and the other The intermediate adhesive layer 5 of the interlayer type can be made of a thermoplastic polymer from among: poly(vinyl butyral) (PVB), thermoplastic polyurethane (TPU), ethylene-vinyl acetate copolymer (EVA), casting resin and ionomer resin.

[0092] The thickness of the intermediate adhesive layer 4 of the interlayer type can 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).

[0093] The thickness of the other intermediate adhesive layer 5 of the interlayer type can be between 0.5 and 6 mm, preferably not more than 3 mm.

[0094] The laminated glazing 1 is supported against an internal retainer 6', which may be the aircraft structure, with an interposition of a wedge 7. The laminated glazing 1 is fixed to the aircraft mounting structure by an external retainer 6 consisting of a glass press which, by being bolted to the aircraft structure, exerts pressure on the edge of the structural block 3a, 3b via a silicone seal 8.

[0095] The aeronautical laminated glazing 1 further comprises an electric heating system of the resistive heating layer type 9 arranged between the inner face of the first sheet 2 and the intermediate layer 4.

[0096] The heating resistive layer 9 is arranged between two supply electrodes (not visible on [Fig. 1]) and covers a (central) part of the inner face of the first sheet 2. The heating resistive layer 9 thus enables the laminated glazing 1 to have an anti-frost function by providing heating by Joule effect when it is traversed by an electric current from the two supply electrodes.

[0097] The heating resistive layer 9, which is made of one of indium tin oxide (ITO), gold, silver and aluminum-doped zinc oxide, exhibits a first real surface electrical resistivity.

[0098] The heating resistive layer 9 can have a thickness of between 10 and 200 nm, and a surface electrical resistivity of between 1 and 500 Ohms per square.

[0099] The aeronautical laminated glazing 1 further comprises an isopotential layer 10 applied to the (peripheral) areas of the inner face of the first sheet 2 not opposite the electrical heating system of the resistive heating layer type 9.

[0100] The isopotential layer 10 is thus encapsulated inside the laminated glazing 1 and is therefore not sensitive to erosion, dissolution or scratching.

[0101] 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 actual 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 (optionally with an insulation impedance ensuring isopotentiality without the capacity to drain strong currents). currents).

[0102] It should be noted that the isopotential layer 10 could also be connected to the aircraft ground, either directly via other electrical means such as screen printing, brazing, 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.

[0103] Since the isopotential layer 10 and the heating resistive layer 9 are located on the same inner 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.

[0104] The heating resistive layer 9 and the isopotential layer 10 can be deposited on the inner face of the first sheet 2 by means of a physical vapor phase deposition, for example by magnetic field-magnetron assisted sputtering under reduced pressure, or by liquid means, for example sol-gel.

[0105] In practice, a single conductive layer is deposited on the inner 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 insulated from the heating resistive layer 9.

[0106] The isopotential layer 10 has, over its entire surface, a uniform electric potential with respect to charge potentials at several tens of kV.

[0107] If we refer to [Fig.2], we can see that it represents an aeronautical laminated glazing 12 according to a second embodiment of the present invention.

[0108] The common elements between the first embodiment of the invention in [Fig.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.

[0109] The aeronautical laminated glazing 12 according to the second embodiment is identical to the aeronautical laminated glazing 1 according to the first embodiment, except that the isopotential layer 10 is a transparent conductive layer applied over the entire inner face of the first sheet 2 (possibly with the exception of a peripheral band), and ensures that the entire inner face of the first sheet 2 is maintained at the potential of the aircraft mass (within a few hundred volts), the heating resistive layer 9 being applied over a (central) part of the isopotential layer 10.

[0110] Furthermore, in this second embodiment, the isopotential layer of the transparent conducting layer type 10, which is in one of the doped oxide such that Indium tin oxide or aluminum zinc oxide, non-stoichiometric oxide such as tin dioxide, diamond-like carbon, and silver, exhibit a second actual surface electrical resistivity greater than the first actual surface electrical resistivity of the heating resistive layer 9.

[0111] The ratio between the second actual surface electrical resistivity and the first actual surface electrical resistivity is greater than or equal to 10, preferably greater than or equal to 100.

[0112] The isopotential layer of the transparent conductive layer type 10 can have a thickness between 10 and 100 nm.

[0113] 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, so that the isopotential layer 10 ensures continuity of electrical potentials in the plane of the heating resistive layer 9 without short-circuiting the latter, and allows surface discharges to be initiated from the entire periphery of the glazing and eliminates the edge effects of the heating resistive layer 9 which promote dielectric breaks in the first sheet 2 of the laminated glazing 1.

[0114] If we refer to [Fig.3], we can see that it represents an aeronautical laminated glazing 13 according to a third embodiment of the present invention.

[0115] The common elements between the second embodiment of the invention in [Fig.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.

[0116] 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 resistive heating layer 9 is replaced by an electric heating system of the resistive heating wire network 9' applied to the transparent, isopotentially conductive layer 10. The resistive heating wire network 9' is arranged between two supply electrodes (not visible in [Fig. 3]), and enables the laminated glazing 13 to have an anti-frost function by providing Joule heating when its resistive wires are traversed by an electric current from the two supply electrodes. By way of example, one of the two supply electrodes may be at a potential of 0V and the other of the two supply electrodes may be at a potential of 28V.

[0117] It should be noted that the surface electrical resistivity of the network of heating resistive wires 9' will not be isotropic, but will be considered as an apparent or equivalent surface electrical resistivity whose value will be substantially lower than the surface electrical resistivity of the isopotential layer 10. The network The heating resistive wire 9' will indeed be considered a conductive layer with electrical conductivity if current flow is considered in the direction from feed electrode to feed electrode. Conversely, in the orthogonal direction, there will be no electrical conductivity.

[0118] Since a network of resistive wires 9' is generally very low resistance (here a few Ohms per square), an isopotential layer 10 having a surface electrical resistivity ranging from 100 Ohms per square to 1 mega Ohms per square may be chosen.

[0119] The resistive wire network 9' is applied in contact with the isopotential layer 10 which forms an electrical screen with respect to the potential of its resistive wires, so that the point 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 point effect in the first sheet 2 of the laminated glazing 13.

[0120] Referring to [Fig.4], one can see that it represents an aeronautical laminated glazing 14 according to a fourth embodiment of the present invention.

[0121] The common elements between the first embodiment of the invention in [Fig.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.

[0122] Similar to the first embodiment, the aeronautical laminated glazing 14 according to the fourth embodiment comprises a heating resistive layer 9 in the form of a simple polygon applied to a (central) part of the inner face of the first sheet 2 of the laminated glazing 14 and arranged between two single-phase supply electrodes 15a and 15b applied to the upper and lower parts, respectively, of the inner face of the first sheet 2 of the laminated glazing 14.

[0123] 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.

[0124] 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 over the whole of this electrode.

[0125] Furthermore, in this fourth embodiment, the isopotential layer 10 is applied to the remaining part of the inner face of the first sheet 2 (with the exception of a peripheral edge of the inner face of the first sheet 2) and consists of two continuous zigzag (or serpentine) bands 16a and 16b arranged between the two supply electrodes 15a and 15b, on either side of the heating resistive layer 9, and forming a continuous path between the supply electrodes 15a and 15b, which is longer in distance than the path between the two 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 greater resistivity through the isopotential layer and that other embodiments are envisaged 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.

[0126] The two zigzag bands 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.

[0127] Thus, in this fourth embodiment, a layer of the same nature as the heating resistive layer 9 is used as an isopotential layer 10, but its apparent resistivity is artificially increased by zigzag texturing.

[0128] In practice, the heating resistive layer 9 and the textured isopotential layer 10 can be created on the inner face of the first sheet 2 by:

[0129] - application of a conductive layer on the inner face of the first sheet 2;

[0130] - definition of a heating zone (corresponding to the future resistive layer) heating 9) on the applied conductive layer;

[0131] - ablation, in particular laser ablation, of the conductive layer so as to form, as a resistive heating layer 9, the defined heating zone; and

[0132] - ablation, in particular laser ablation, of the conductive layer outside the area heating formed, so as to form, as an isopotential layer 10, the two zigzag bands 16a and 16b on either side of the heating resistive layer 9, such that the equivalent electrical resistivity of the zigzag bands 16a and 16b is greater than that of the heating resistive layer 9.

[0133] Thus, total or partial electrical insulation between the heating resistive layer 9 and the isopotential layer 10 (namely, the two zigzag bands 16a and 16b) is provided by laser ablation of the initial conductive layer.

[0134] 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.

[0135] Referring to [Fig.5], one can see that it represents an aeronautical laminated glazing 17 according to a fifth embodiment of the present invention.

[0136] The common elements between the fourth embodiment of the invention in [Fig.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.

[0137] In this fifth embodiment, the textured isopotential layer 10 is no longer made up of the two zigzag bands 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 layer of higher resistivity.

[0138] In practice, the textured isopotential layer 10 can be created on the inner face of the first sheet 2 by:

[0139] - application of a conductive layer on the inner face of the first sheet 2;

[0140] - definition of a heating zone (corresponding to the future resistive layer) heating 9) on the applied conductive layer; and

[0141] - ablation, in particular laser ablation, of the conductive layer outside the area defined heating, 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.

[0142] Although, in each of the first to fifth embodiments shown in Figures 1 to 5, a single single-phase powered electric heating system 9 or 9' has been shown, each of these embodiments could also include several three-phase powered electric heating systems (of the type resistive heating layer 9 or resistive heating wire network 9'), without departing from the scope of the present invention.

[0143] By way of example, [Fig.6] represents such a three-phase powered electric heating system 19 in delta arrangement comprising three electric heating systems 9a, 9b and 9c (for example, three resistive heating layers) arranged adjacently between four supply electrodes 20a, 20b, 20c and 20d.

[0144] The first electrode 20a is connected to the lower part of the first electric heating system 9a. The second electrode 20b is connected to the upper parts of the first and second electric heating systems 9a and 9b. The third electrode 20c is connected to the lower parts of the second and third electric heating systems 9b and 9c. The fourth electrode 20d is connected to the upper part of the third electric heating system 9c. The first and fourth electrodes are electrically connected by an electrical wire 21.

[0145] Also by way of example, [Fig.7] represents another three-phase powered electric heating system assembly 22 in star connection comprising three electric heating systems 9a, 9b and 9c (for example, three resistive heating layers) arranged adjacently between four supply electrodes 23a, 23b, 23c and 23d.

[0146] 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.

[0147] The present invention also relates to the use of one of the aeronautical laminated glazings 1, 12, 13, 14 and 17 described above as aircraft cockpit glazing, in particular windshield, in particular of medium and long-haul commercial aircraft, business or tourist aircraft.

[0148] The present invention further relates to an aircraft, such as an airplane or a helicopter, whose cockpit glazing is one of the aeronautical laminated glazings 1, 12, 13, 14 and 17 described above.

[0149] Fig. 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 the level of its windscreen.

[0150] 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 optics (lights) of the aircraft without departing from the scope of the invention.

[0151] It is understood that the particular embodiments which have just been described have been given by way of indication and not limitation, and that modifications may be made without departing from the present invention.

Claims

Demands

1. Aircraft laminated 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) disposed 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 made of at least one of mineral glass and organic glass, the aircraft laminated glazing (1; 12; 13; 14; 17) further comprising at least one electric heating system (9; 9') arranged opposite the inner face of the first sheet (2), characterized in that the aircraft laminated glazing (1; 12; 13; 14; 17) further comprises an isopotential layer (10) applied to the inner face of the first sheet (2).

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

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

4. Aeronautical laminated glazing (12; 13) according to any 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 for the aeronautical laminated glazing (12; 13).

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

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

7. Aeronautical laminated glazing (1; 14; 17) according to claim 1, characterized in that at least one electric heating system is at least one resistive heating layer (9), having a planar geometric shape whose periphery forms a simple closed curve, arranged between at least two supply electrodes (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 resistive heating layer (9).

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

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

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

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

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

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

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