Aeronautic glazing in which the entire surface is covered by a strong, thin film encapsulated in an adhesive insert layer.

Description

[0001] The present invention relates to lightweight aeronautical glazing, such as for helicopters but also business jets with pressurized cabins, for which two important functions are required: resistance to bird strike, and the absence of dislodging of the glazing from its mounting bay in the event of breakage of the structural glass sheet (a function known in English as "fail safe").

[0002] This type of lightweight glazing typically consists of an outer glass pane (exposed to the outside atmosphere) bonded to an inner pane (in contact with the interior of the mounting structure) of a tough, transparent polymer material via an interlayer adhesive. The glass pane is made of mineral glass such as float glass, soda-lime glass, aluminosilicate glass, or borosilicate glass, possibly chemically strengthened, thermally tempered, or toughened. The polymer material pane is, for example, coated polyester (CPE), such as PET with a polysiloxane-type scratch-resistant coating on its free side exposed to the interior of the mounting structure. The interlayer adhesive is preferably made of thermoplastic polyurethane (TPU), but also polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), casting resin, or ionomer resin.An example of this type of glazing is represented by application WO 2012 085433 A1.

[0003] A possible bird strike occurs first against the outer glass sheet, but the "bird strike" function is ensured by the inner sheet of polymer material, also called "anti-shatter film" and frequently referred to in English as "spall shield": this rear polymer sheet does not tear and traps the bird.

[0004] The fail-safe function (anti-glazing detachment) is achieved by bonding the glazing to the mounting structure. This bonding is accomplished either by a composite insert in the periphery of the interlayer adhesive layer, with the composite insert extending beyond at least one of the laminated glazing components, or by the interlayer adhesive layer extending beyond at least one of the laminated glazing components. In the first case, the composite insert's extension is bonded between an outer and an inner frame fixed to the structure; the two frames can be bolted to the structure through holes provided in the composite insert's extension and in the two frames. In the second case, the extension of the interlayer adhesive layer is bonded and clamped between an outer and an inner frame bolted to the structure through holes provided in the adhesive layer's extension and in the two frames.

[0005] The mass of the type of glazing in question can be optimized while maintaining, or even improving, the desired mechanical properties. Secondly, the inner polymer sheet is difficult, if not impossible, to functionalize and is fragile. The inventors focused on reducing the mass of lightweight glazing with bird strike and fail-safe features without compromising these functionalities.

[0006] FR 3 074 721 A1 discloses an aeronautical laminated glazing, characterized in that it comprises an inner sheet of structural polymer material and an outer sheet of structural glass having a breaking strength of 350 to 1000 MPa at the stress characteristics of a bird strike.

[0007] This objective has been achieved by the invention which, consequently, relates to a laminated glazing consisting of a first transparent sheet of mineral glass with a thickness of between 0.5 and 6 mm or of polymer material with a thickness of between 1.2 and 8 mm, intended, in the glazing mounting position, to be oriented towards the outside atmosphere, and bonded to a second transparent sheet of mineral glass with a thickness of between 0.5 and 1.2 mm or of polymer material with a thickness of between 0.1 and 0.5 mm, intended to be oriented, in the glazing mounting position, towards the inner volume of the mounting structure, by means of a transparent intermediate adhesive layer with a thickness of between 0.4 and 5 mm, characterized in that a tough thin film of transparent polymer material, with a thickness of between 0.05 and 0.5 mm, is inserted within the intermediate adhesive layer over the entire surface of the laminated glazing.

[0008] Every transparent sheet of laminated glass is either flat or curved.

[0009] Mineral glass refers to glass such as float, soda-lime, aluminosilicate, borosilicate, possibly thermally tempered or chemically strengthened.

[0010] Examples of transparent polymer materials include scratch-resistant coated polyester (CPE), in particular poly(ethylene terephthalate) (PET) with a polysiloxane-type coating or equivalent, poly(methyl methacrylate) (PMMA), polycarbonate (PC), polyurethane (PU) and equivalents.

[0011] An interlayer adhesive herein refers to polyvinyl butyral (PVB), thermoplastic polyurethane (TPU), ethylene-vinyl acetate (EVA) copolymer, casting resin, ionomer resin, and equivalents. Because the tough thin film is embedded within the interlayer adhesive, the invention does not preclude it from being sandwiched between two interlayer adhesives of different materials, for example, between a layer of PVB and a layer of TPU. Each of the two interlayer adhesives sandwiching the tough thin film can provide various functions: solar control, sun protection, and acoustic insulation, notably through a laminated structure.

[0012] In the sense of the invention, the tough thin film is tear-resistant and a crack propagates with difficulty; an example of this is a poly(ethylene terephthalate) (PET) film approximately 0.2 mm thick.

[0013] The tough, thin film reinforces the mechanical bond between the mounting structure and the transparent part of the glazing. It provides resistance to bird strikes and prevents the glazing from being dislodged from its mounting frame in the event of breakage of the first and second transparent layers, while eliminating the need for a peripheral composite insert and / or reducing the thickness of a glass or organic component. This results in lower manufacturing costs and a welcome reduction in the mass of the laminated glass. The tough, thin film can also provide thermal control (solar control or low-emissivity) or be fully or partially tinted (sunshade).

[0014] The invention also makes it possible to replace the inner transparent sheet (“bird strike”) made of polymer material with a thin sheet of mineral glass, or other transparent element providing better mechanical resistance (abrasion resistance, routine maintenance), and more easily functionalized (scratch-resistant varnish, heating layers, etc.).

[0015] The functionalities sought by the invention are already achieved with a tough, thin film that does not extend beyond the first and second transparent sheets. However, according to a preferred configuration of the laminated glazing of the invention, in its mounting position, the free surface of the first transparent sheet is bonded around its periphery to an outer frame by means of adhesive, and the free surface of the second transparent sheet is bonded around its periphery to an inner frame by means of adhesive. The tough, thin film extends beyond the edge of at least one of the first and second transparent sheets so as to reach the edges of both the outer and inner frames. This arrangement increases the ability of the fastening system to hold the glazing in its opening in the event of breakage of one transparent sheet ("fail-safe") or even all of the transparent sheets ("full fail-safe"), that is, to ensure that the glazing does not become dislodged.

[0016] According to a first realization of this preferred configuration, the second transparent sheet is overhanging in relation to the first, so as to extend, in the mounting position of the laminated glazing, to the edges of the outer frame and the inner frame.

[0017] According to a second embodiment of this preferred configuration, in the laminated glass mounting position, the outer and inner frames are bolted to the mounting structure via a sleeve passing through the tough, thin film. The glass is thus clamped by pressure exerted by the outer frame on the first transparent sheet (via adhesive) on one side, and by the inner frame on the second transparent sheet (also via adhesive) on the other. This arrangement increases the degree of "fail-safe" and "full fail-safe" functionality.

[0018] Preferably, the tough thin film is made of poly(ethylene terephthalate) (PET) with a thickness between 0.1 and 0.4, preferably between 0.12 and 0.3 and particularly preferably 0.15 and 0.25 mm.

[0019] Preferably, the innermost transparent layer of the laminated structure has a heating, electrically conductive metallic or transparent conductive oxide (TCO) layer. Examples include a metallic layer of silver, gold, indium tin oxide (ITO), or fluorine-doped tin oxide (SnO₂:F). A heating layer located within the thickness of the laminated structure so close to the outer surface of the glazing primarily serves an anti-frosting function.

[0020] According to an advantageous embodiment of the laminated glazing of the invention, the second transparent sheet is made of mineral glass and carries one or more functional layers / stacks. Such an inner mineral glass sheet exhibits superior scratch resistance compared to scratch-resistant polyester. Unlike the latter, it is easy to deposit one or more thin layers in a functional stack, each layer a few nanometers thick, as produced by magnetic field-assisted sputtering (magnetron sputtering).

[0021] The inner surface of the second transparent sheet's laminated structure preferably carries a low-emissivity or solar thermal control layer, while its surface exposed to the interior of the mounting structure carries an anti-fog coating. A solar thermal layer reflects solar radiation, preventing the temperature inside the enclosed space from rising excessively and / or reducing glare for the pilot, driver, operator, passenger, or occupant. A low-emissivity layer reflects infrared radiation corresponding to the heat of the interior space enclosed by the glazing, thus retaining a greater portion of that heat inside.An anti-fog coating consists primarily of a hydrophilic layer that prevents condensation from forming droplets. This water settles as a homogeneous film that does not obstruct vision. The coating is perfectly transparent and does not degrade the optical quality of the glass. It is a layer of mineral oxide such as silica, titanium dioxide, or a polymer such as polyurethane, polyvinylpyrrolidone, or polyvinyl alcohol, formulated as a liquid, sol-gel, or equivalent.

[0022] Preferably, the second transparent sheet is made of chemically strengthened mineral glass, in particular aluminosilicate or soda-lime glass.

[0023] According to an interesting variant, a composite insert is positioned within a peripheral part of the interlayer adhesive layer, opposite a peripheral part of the first transparent sheet (i.e., opposite this part of the first sheet) and extending to the edges of the outer frame and the inner frame.

[0024] Another object of the invention consists of the use of laminated glazing described above in aeronautics, as glazing for tourist aircraft, business jets of the Falcon F10 type from Dassault Aviation or helicopters.

[0025] The invention will be better understood in light of the following description of the attached drawings, which are schematic cross-sectional representations in which [ Fig. 1] et [Fig. 2 ] represent two state-of-the-art glazing designs; [ Fig. 3] et [Fig. 4 ] are views of two variants of laminated glazing according to the invention.

[0026] With reference to the Figure 1 A laminated glass unit consists of a 3 mm thick chemically strengthened aluminosilicate glass sheet 1 bonded to a 0.18 mm thick scratch-resistant PET sheet 3 via a 3.8 mm thick TPU interlayer 2. The PET sheet 3 and the adhesive layer 2 extend beyond the glass sheet 1. An outer frame 4 is bonded to a peripheral portion of the free surface of the glass sheet 1 and the adhesive layer 2 by adhesive 6; an inner frame 5 is bonded to a peripheral portion of the free surface of the PET sheet 3 by adhesive 7. A socket 8 is inserted into holes formed through the outer frame 4, the adhesive 6, the TPU layer 2, the adhesive 7, and the inner frame 5.This assembly is bolted via the socket 8 onto the mounting structure not shown, so that the laminated glazing is pinched with pressure exerted by the outer frame 4 on the glass sheet 1 via the glue 6, respectively by the inner frame 5 on the coated PET sheet 3 via the glue 7.

[0027] The edges of all the components of the laminated glazing of the Figure 2 On the contrary, they are all substantially aligned. A composite insert 10 is encapsulated in a peripheral strip of the TPU adhesive layer 2, extending between the adhesive 6 and the adhesive 7 to the edges of the outer frame 4 and the inner frame 5. Optionally, and not shown, a sleeve such as the one shown in the Figure 1 , socket which would pass through here the outer frame 4, the glue 6, the composite insert 10, the glue 7 and the inner frame 5, in order to accommodate the bolting of the assembly to the mounting structure.

[0028] The laminated glazing according to the invention shown in the Figure 3 differs from that of the Figure 2 by removing the composite insert 10 and replacing it with a tough, thin PET film 9, 0.18 mm thick, which, in addition to the area covered by the composite insert 10, covers the entire surface of the laminated glass. Optional bolting of the assembly, not shown, is possible as described in relation to the Figure 2 Removing the composite insert 10 simplifies the glazing manufacturing process. Compared to using this composite insert 10, using the film 9 provides the functions of "bird strike" and "fail-safe," while also allowing for thinner glass sheet 1, interlayer 2, and coated PET sheet 3, ultimately resulting in a lighter glazing unit. Even when using the same type and thickness of glass sheet 1 and coated PET sheet 3 as in the previous version, the weight is reduced. Figures 1 et 2 , the sole replacement of the intermediate adhesive layer 2 of these by a sheet of PET 0.18 mm thick (constituting the tough thin film 9) sandwiched between two layers 2 of TPU 1.25 mm thick makes it possible to reduce the surface mass of the glazing by 10%, while improving its desired mechanical properties.

[0029] The glazing of the Figure 4 differs from that of the Figure 1 by encapsulating, within the TPU 2 layer, the same PET 9 film as in the Figure 3 , also covering the entire surface of the glazing. Compared to the glazing of the Figure 1 that of the Figure 4 can implement thinner layers of glass sheet 1, adhesive layer 2 and coated PET sheet 3.

Claims

1. A laminated glazing consisting of a first transparent sheet (1) of mineral glass with a thickness of between 0.5 and 6 mm or of polymer material with a thickness of between 1.2 and 8 mm, intended, in the glazing mounting position, to be oriented towards the external atmosphere, and bonded to a second transparent sheet (3) of mineral glass with a thickness of between 0.5 and 1.2 mm or of polymer material with a thickness of between 0.1 and 0.5 mm, intended to be oriented, in the glazing mounting position, towards the interior volume of the mounting structure, by means of a transparent adhesive insert layer (2) with a thickness of between 0.4 and 5 mm, characterized in that a strong thin film (9) of transparent polymer material with a thickness of between 0.05 and 0.5 mm is inserted within the adhesive insert layer (2) over the whole surface of the laminated glazing.

2. The laminated glazing according to claim 1, characterized in that in the mounting position thereof, the free surface of the first transparent sheet (1) is bonded at its periphery to an outer frame (4) by means of adhesive (6) and the free surface of the second transparent sheet (3) is bonded at its periphery to an inner frame (5) by means of adhesive (7), and the strong thin film (9) extends beyond the edge of at least one of the first and second transparent sheets (1, 3) so as to extend to the edges of the outer frame (4) and the inner frame (5).

3. The laminated glazing according to claim 2, characterized in that the second transparent sheet (3) overhangs the first (1) so as to extend, in the mounting position of the laminated glazing, up to the edges of the outer frame (4) and the inner frame (5).

4. The laminated glazing according to claim 2, characterized in that in the mounting position thereof, the outer frame (4) and the inner frame (5) are bolted to the mounting structure by means of a bush (8) passing through the strong thin film (9), so that the glazing is clamped by the exertion of pressure by the outer frame (4) on the first transparent sheet (1) on the one hand, and by the inner frame (5) on the second transparent sheet (3) on the other.

5. The laminated glazing according to one of the preceding claims, characterized in that the strong thin film (9) is made of polyethylene terephthalate (PET) with a thickness of between 0.1 and 0.4, preferably between 0.12 and 0.3 and particularly preferably 0.15 and 0.25 mm.

6. The laminated glazing according to one of the preceding claims, characterized in that the face of the first transparent sheet (1) facing the laminated structure bears an electrically conductive heating layer of metal or transparent conductive oxide.

7. The laminated glazing according to one of the preceding claims, characterized in that the second transparent sheet (3) is made from mineral glass and carries one or more functional layer(s) / stack(s).

8. The laminated glazing according to claim 7, characterized in that the face of the second transparent sheet (3) facing the laminated structure carries a sun protection or low emissivity thermal control stack, and its face facing the interior volume of the mounting structure carries an anti-fog coating.

9. The laminated glazing according to one of the preceding claims, characterized in that the second transparent sheet (3) is made from chemically strengthened mineral glass.

10. The laminated glazing according to one of claims 2 to 9, characterized in that a composite insert (10) is positioned within a peripheral portion of the adhesive insert layer (2), facing a peripheral portion of the first transparent sheet (1) and extending to the edges of the outer frame (4) and the inner frame (5).

11. A use of a laminated glazing according to one of the preceding claims in aeronautics, as a business jet or helicopter glazing.