US20110072961A1

US20110072961A1 - Environmental seal technology for spaced transparent armor

Info

Publication number: US20110072961A1
Application number: US12/275,142
Authority: US
Inventors: David Jungkuist; Marlowe Moncur
Original assignee: GKN Aerospace Transparency Systems Inc
Current assignee: GKN Aerospace Transparency Systems Inc
Priority date: 2008-11-20
Filing date: 2008-11-20
Publication date: 2011-03-31

Abstract

The present invention is embodied in environmental seal technology incorporated into a double-paned window, the environmental seal technology comprising an inner desiccant seal and a structural spacer. The subject invention solves the problem of moisture between the window panes by keeping the internal gap dry using a desiccant system. The invention also incorporates a durable structural spacer that will not rupture under normal military vehicle loads and environmental conditions. The spacer is bonded to the window panes using pressure-sensitive adhesives, thus allowing for easy manufacture.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to environmental seal technology for spaced transparent armor and, more particularly, to environmental seal technology incorporated into a double-paned window having an inner desiccant seal combined with a structural spacer.
Spaced armor has been used for many years in opaque armor applications. The challenge for using it in transparent armor has been related to the environmental durability of the seal. The air between the glass laminate blocks must be kept clean and dry throughout the life of the armor.
In the insulated glass market, two or more panes of glass are used, with an air space defined between the panes. The primary purpose of the air space is for insulation. The primary purpose for the air space in transparent armor is for improved ballistic protection, although the air space also improves the product's insulation.
Several approaches have been used in the insulated glass industry to keep the air between the glass panes clean and dry. None of these approaches appears to use a seal having sufficient strength for environmental and mechanical durability in military applications. In the insulated glass industry, a seal of significant strength is not required. Thus, the primary seal is typically a low modulus elastomer. In a military vehicle application, the seal needs to be able to withstand substantial environmental and mechanical loading.
A few approaches that use an air gap have been tried in ballistic applications. Many of these approaches have been designed for use in the periscope market. An example is U.S. Pat. No. 4,149,778. This patent states that the void between the spaced blocks is preferably filled with an inert gas such as dry nitrogen or may have a vacuum formed therein. Having a vacuum or inert gas in the gap, however, has been found to be cumbersome and costly in larger military applications, such as double-paned windows for military vehicles.
Transparent armor for a passenger vehicle application is disclosed in U.S. Pat. No. 4,316,404. In this patent, a polycarbonate layer is bonded to a glass laminate using a double-sided tape, thus creating a thin air gap between the polycarbonate layer and the glass laminate. This approach, however, fails to use a seal having sufficient strength for environmental and mechanical durability in military applications, and does not address the issue of moisture within the air gap.
It should thus be appreciated that there is a need for environmental seal technology for spaced transparent armor that combines a strong, durable seal with a means for keeping the air between the glass laminate blocks clean and dry. The system should function without the need for inert gas or a vacuum in the gap between the glass laminate blocks. The present invention fulfills this need and provides further related advantages.

SUMMARY OF THE INVENTION

The present invention is embodied in a spaced transparent armor structure comprising a desiccant system and a structural spacer. The subject invention solves the problem of moisture between the window panes of the spaced transparent armor structure by keeping the internal gap dry using the desiccant system. The invention also incorporates a durable structural spacer that will not rupture under normal military vehicle loads and environmental conditions. The spacer is bonded to the window laminates using pressure-sensitive adhesives, thus allowing for easy manufacture.
In one embodiment, the spaced transparent armor structure comprises a first transparent laminate configured as a pane having a first face, a second face, and an edge; a second transparent laminate configured as a pane having a first face, a second face, and an edge; a structural spacer bonded to the second face of the first transparent laminate and to the first face of the second transparent laminate; and a desiccant. The first and second transparent laminates are spaced in a substantially parallel relationship so that an air gap is defined therebetween. The desiccant is positioned to absorb moisture trapped in the air gap.
In one embodiment, the desiccant is contained in an inner desiccant seal that circumscribes the air gap and that extends between the second face of the first transparent laminate and the first face of the second transparent laminate. The inner desiccant seal comprises a polymer binder. The desiccant is supported in the polymer binder. The polymer binder is selected from the group consisting of silicone foam, ethylene propylene (EPM), ethylene propylene diene (EPDM) rubber, styrene-butadiene rubber (SBR), nitrile, and polyurethanes. The inner desiccant seal comprises at least twenty percent desiccant.
In one embodiment, the structural spacer has an elastic modulus greater than 300 psi. The polymer binder has an elastic modulus greater than 200 psi and less than the elastic modulus of the structural spacer. The structural spacer circumscribes the inner desiccant seal and comprises a material selected from the group consisting of polyurethanes, polymethyl methacrylate, and metals.
In one embodiment, the desiccant is embedded in the structural spacer. In another embodiment, the structural spacer is configured as a hollow tube. The desiccant is embedded within the hollow of the tube.
In one embodiment, the spaced transparent armor structure further comprises a film adhesive. The structural spacer is bonded to the second face of the first transparent laminate and to the first face of the second transparent laminate by means of the film adhesive. The film adhesive is a pressure-sensitive tape adhesive, such as acrylic foam tape.
In one embodiment, the spaced transparent armor structure further comprises a gasket bonded to the edge of the first transparent laminate and to the edge of the second transparent laminate by means of a sealant. The sealant is selected from the group consisting of silyl modified polymer sealants, urethane sealants, polysulide sealants, silyl-terminated-polyether sealants, acrylic sealants, and silicone sealants. The gasket extends from the second face of the first transparent laminate to the second face of the second transparent laminate.
In one embodiment, the spaced transparent armor structure further comprises a urethane backfill that circumscribes the structural spacer and that extends between the second face of the first transparent laminate and the first face of the second transparent laminate. The urethane backfill additionally extends at least partially between the structural spacer and the second face of the first transparent laminate, and at least partially between the structural spacer and the first face of the second transparent laminate. The urethane backfill further extends around the edge of the first transparent laminate and the edge of the second transparent laminate.
In one embodiment, the spaced transparent armor structure further comprises a frame into which the first transparent laminate and the second transparent laminate are potted.
Other features and advantages of the invention should become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a spaced transparent armor structure, in accordance with an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a spaced transparent armor structure having a desiccant-filled structural spacer, in accordance with an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a spaced transparent armor structure having a desiccant-filled structural spacer and a urethane backfill, in accordance with an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a spaced transparent armor structure having a solid structural spacer and inner desiccant seal, in accordance with an embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a spaced transparent armor structure having a solid structural spacer, inner desiccant seal, and urethane backfill, in accordance with an embodiment of the present invention.

FIG. 6 is a partial cross-sectional view of a spaced transparent armor structure having a pair of transparent laminates, a structural spacer, and a urethane backfill that extends partially between the structural spacer and the transparent laminates, in accordance with an embodiment of the present invention.

FIG. 7 is a partial cross-sectional view of a spaced transparent armor structure having a pair of transparent laminates, a structural spacer, and a urethane backfill that extends around the edges of both transparent laminates as well as partially between the structural spacer and the transparent laminates, in accordance with an embodiment of the present invention.

FIG. 8 is a partial cross-sectional view of a spaced transparent armor structure having an elastomer gasket, in accordance with an embodiment of the present invention.

FIG. 9 is a partial cross-sectional view of a spaced transparent armor structure 180 having a pair of transparent laminates and a metal frame into which the transparent laminates are potted, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, there is shown a cross-sectional view of a spaced transparent armor structure 10, in accordance with an embodiment of the present invention. The spaced transparent armor structure comprises a pair of transparent laminates 12, each transparent laminate configured as a substantially rectangular pane having an outer face 14, an inner face 16, and an edge 18. The transparent laminates may comprise glass and/or other transparent or translucent materials.
The inner faces 16 of the transparent laminates 12 are spaced in a substantially parallel relationship so that an air gap 20 is defined therebetween. The air gap is configured as a substantially rectangular space, the edges of which are bounded by an inner desiccant seal 22 that extends between the inner faces of the transparent laminates. Although FIG. 1 shows the spaced transparent armor structure 10 as having two transparent laminates, the present invention encompasses spaced transparent armor structures having more than two transparent laminates.
The inner desiccant seal 22 is a composition of a desiccant supported in a polymer binder. The desiccant absorbs moisture trapped between the inner faces 16 of the transparent laminates 12. An advantage to this approach is that the spaced transparent armor structure 10 can be assembled without the need for an inert gas or vacuum, which gives this approach a cost advantage over other forms of fabrication.
The desiccant material can be embedded within one of a number of elastomers to create a seal. For example, Super Spacer® Triseal™ from Edgetech I.G. of Cambridge, Ohio, is a desiccant embedded in silicone foam. Other suitable elastomers include ethylene propylene (EPM), ethylene propylene diene (EPDM) rubber, styrene-butadiene rubber (SBR), nitrile, chloroprene, Epichlorohydrin, polyacrylic, fluorosilicone, perfluroelastomers, polyether block polyamides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, thermoplastic vulcanizates, thermoplastic polyurethane (TPU), thermoplastic olefins, and polysulfide rubber. The desiccant could additionally or alternatively be embedded within one of a number of plastics, including polypropylene, polystyrene, acrylonitrile/butadiene/styrene (ABS), polyethylene terephthalate, polybutylene terephthalate, polyester alloys, nylons, poly(vinyl chloride), polyurethanes, polycarbonate, polyethylene, polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone, polyetherimide, and phenolics. In one embodiment, the desiccant is embedded within a polymer having an elastic modulus greater than 200 psi and less than the modulus of the structural spacer (described below).
Desiccants that may be used in the present invention include activated alumina, aerogel, benzophenone, bentonite clay, calcium chloride, calcium hydride, calcium sulfate, copper(II) sulfate, lithium chloride, lithium hydride, lithium bromide, magnesium, magnesium sulfate, magnesium perchlorate, sodium potassium alloy, phosphorus pentoxide, potassium carbonate, silica gel, sodium chlorate, sodium hydroxide, sodium sulfate, sodium benzophenone, and molecular sieves. In one embodiment, the inner desiccant seal 22 comprises twenty percent desiccant.
The spacing between the pair of transparent laminates 12 is maintained by a structural spacer 24, which surrounds the inner desiccant seal 22 and extends between the inner faces 16 of the transparent laminates. The structural spacer may comprise hard elastomers, composites, plastics, metals, and/or metal alloys. Suitable hard elastomers include ethylene propylene monomer (EPM) rubber, ethylene propylene diene monomer (EPDM) rubber, styrene-butadiene (SBR), nitrile, chloroprene, Epichlorohydrin, polyacrylic, fluorosilicone, perfluroelastomers, polyether block polyamides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, thermoplastic vulcanizates, thermoplastic polyurethane (TPU), thermoplastic olefins, and polysulfide rubber. Suitable plastics include polypropylene, polystyrene, acrylonitrile/butadiene/styrene (ABS), polyethylene terephthalate, polybutylene terephthalate, polyester alloys, nylons, poly(vinyl chloride), polyurethanes, polycarbonate, polyethylene, polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone, polyetherimide, and phenolics. Suitable metals and metal alloys include iron, aluminum, copper, stainless steel, nickel, magnesium, zinc, and titanium alloys. In one embodiment, the material comprising the structural spacer has an elastic modulus greater than 300 psi.
Composites, including fiber reinforced composites, would be suitable for lightweight structural spacers. Suitable fiber reinforced composites may comprise glass and/or carbon fibers, and matrices of epoxy, vinyl ester, polyester, phenolics, and/or polyimides. The structural spacer 24 also acts as a moisture barrier. Low permeability materials such as polyurethanes, polymethyl methacrylate, and metals are also suitable for the structural spacer.
In one embodiment, the structural spacer 24 is an extrusion of any of the previously stated materials. The extrusion may comprise polymer, composite, elastomer, plastic, and/or metallic extrusions. A desiccant may be embedded within the extrusion. The structural spacer may have a solid cross-section or a hollow cross-section (hollow tube).
The structural spacer 24 is bonded to the inner faces 16 of the transparent laminates 12 using a film adhesive, such as pressure-sensitive tape adhesive 26. Bonding with a pressure-sensitive tape adhesive allows for a much quicker and cleaner application method than a paste adhesive, and the cleanliness of the pressure-sensitive tape adhesive eliminates a source of potential messes in the air gap 20. A pressure-sensitive tape adhesive also has near immediate bond strength, thus allowing for a quicker and easier application method. Furthermore, a pressure-sensitive tape adhesive can act as an additional moisture barrier. Suitable pressure-sensitive tape adhesives include acrylic foam tapes, such as HyperJoint H8000 series (Nitto Denko Corporation of Osaka, Japan), HyperJoint H9000 series (Nitto Denko Corporation of Osaka, Japan) and Very High Bonding (VHB) tapes (3M Company of Maplewood, Minn.). Other suitable film adhesives include urethane, polyvinyl butyral (PVB), and epoxies. Although FIG. 1 shows the use of a pressure-sensitive tape adhesive, the present invention encompasses the use of other adhesives, including paste adhesives.
In one embodiment, a pressure-sensitive tape adhesive is not used, and the structural spacer 24 is instead bonded to the inner faces 16 of the transparent laminates 12 using a hot-melt adhesive. A hot-melt adhesive allows for good control of adhesive placement, without the need for cleanup. Suitable hot-melt adhesives include Jet-melt™ Adhesive by 3M Company of Maplewood, Minn.
To mount the transparent laminates 12 into a vehicle, the transparent laminates can be potted into a frame, or a gasket 28 can be bonded to the edges 18 of the transparent laminates and the structural spacer 24 using a sealant, such as pressure-sensitive tape adhesive 26 and/or urethane adhesive 30. Either of these methods adds another sealant layer between the air gap 20 and the outside environment, and thus further improves the environmental and mechanical durability of the spaced transparent armor structure 10. Suitable sealants include silyl modified polymer sealants, urethane sealants, polysulfide sealants, silyl-terminated-polyether sealants, acrylic sealants, and silicone sealants.
The gasket 28 is configured to extend around the edges 18 of both transparent laminates 12, extending from the outer face 14 of one transparent laminate to the outer face of the other transparent laminate. In one embodiment, pressure-sensitive tape adhesive 26 is used to bond the gasket to the outer faces of the transparent laminates, while urethane adhesive 30 is used to bond the gasket to the edges 18 of the transparent laminates and the structural spacer 24. The spaced transparent armor structure 10 may comprise a single gasket or a plurality of gaskets as needed to mount the transparent laminates into a vehicle.
In some embodiments, a desiccant is embedded within the structural spacer extrusion, so that a separate inner desiccant seal is unnecessary. With reference to FIG. 2, there is shown a partial cross-sectional view of a spaced transparent armor structure 40 having a pair of transparent laminates 42, an air gap 44 defined therebetween, and a desiccant-filled structural spacer 46 bonded to the transparent laminates using pressure-sensitive tape adhesive 48, in accordance with an embodiment of the present invention. With reference to FIG. 3, there is shown a partial cross-sectional view of a spaced transparent armor structure 60 having a pair of transparent laminates 62, an air gap 64 defined therebetween, a desiccant-filled structural spacer 66 bonded to the transparent laminates using pressure-sensitive tape adhesive 68, and a urethane backfill 70, in accordance with an embodiment of the present invention. The urethane backfill 70 surrounds the outer perimeter of the desiccant-filled structural spacer 66 and extends between the transparent laminates 62 to provide additional sealing for the air gap 64.
In other embodiments, a separate inner desiccant seal is used. With reference to FIG. 4, there is shown a partial cross-sectional view of a spaced transparent armor structure 80 having a pair of transparent laminates 82, an air gap 84 defined therebetween, a solid structural spacer 86 bonded to the transparent laminates using pressure-sensitive tape adhesive 88, and an inner desiccant seal 90 bonded to the solid structural spacer using pressure-sensitive tape adhesive, in accordance with an embodiment of the present invention. Wither reference to FIG. 5, there is shown a partial cross-sectional view of a spaced transparent armor structure 100 having a pair of transparent laminates 102, an air gap 104 defined therebetween, a solid structural spacer 106 bonded to the transparent laminates using pressure-sensitive tape adhesive 108, and an inner desiccant seal 110 bonded to the solid structural spacer using pressure-sensitive tape adhesive, and a urethane backfill 112, in accordance with an embodiment of the present invention. The urethane backfill 112 surrounds the outer perimeter of the solid structural spacer 106 and extends between the transparent laminates 102 to provide additional sealing for the air gap 104.
In some embodiments, the urethane backfill extends partially between the structural spacer and the transparent laminates. With reference to FIG. 6, there is shown a partial cross-sectional view of a spaced transparent armor structure 120 having a pair of transparent laminates 122, an air gap 124 defined therebetween, a structural spacer 126 bonded to the transparent laminates using pressure-sensitive tape adhesive 128, an inner desiccant seal 130 bonded to the structural spacer using pressure-sensitive tape adhesive, and a urethane backfill 132 that extends partially between the structural spacer and the transparent laminates, in accordance with an embodiment of the present invention. Wither reference to FIG. 7, there is shown a partial cross-sectional view of a spaced transparent armor structure 140 having a pair of transparent laminates 142, an air gap 144 defined therebetween, a structural spacer 146 bonded to the transparent laminates using pressure-sensitive tape adhesive 148, an inner desiccant seal 150 bonded to the structural spacer using pressure-sensitive tape adhesive, and a urethane backfill 152 that extends around the edges of both transparent laminates as well as partially between the structural spacer and the transparent laminates, in accordance with an embodiment of the present invention.
As noted above, the transparent laminates can be potted into a frame, or a gasket can be bonded to the edges of the transparent laminates and the structural spacer. With reference to FIG. 8, there is shown a partial cross-sectional view of a spaced transparent armor structure 160 having a pair of transparent laminates 162, an air gap 164 defined therebetween, a structural spacer 166 bonded to the transparent laminates using pressure-sensitive tape adhesive 168, an inner desiccant seal 170 bonded to the structural spacer using pressure-sensitive tape adhesive, and an elastomer gasket 172 configured to extend around the edges of both transparent laminates and bonded thereto with a urethane adhesive 174, in accordance with an embodiment of the present invention. With reference to FIG. 9, there is shown a partial cross-sectional view of a spaced transparent armor structure 180 having a pair of transparent laminates 182, an air gap 184 defined therebetween, a structural spacer 186 bonded to the transparent laminates using pressure-sensitive tape adhesive 188, an inner desiccant seal 190 bonded to the structural spacer using pressure-sensitive tape adhesive, and a metal frame 192 into which the transparent laminates are potted using a urethane adhesive 194, in accordance with an embodiment of the present invention.
It should be appreciated from the foregoing disclosure that the present invention provides environmental seal technology for spaced transparent armor that combines a strong, durable seal with a means for keeping the air between the glass laminate blocks clean and dry, the seal functioning without the need for inert gas or a vacuum in the gap between the glass laminate blocks.
Although the invention has been disclosed with reference only to the presently preferred embodiments, those of ordinary skill in the art will appreciate that various modifications can be made without departing from the invention. Accordingly, the invention is defined only by the following claims.

Claims

1. A spaced transparent armor structure comprising:

a first transparent laminate configured as a pane having a first face, a second face, and an edge;

a second transparent laminate configured as a pane having a first face, a second face, and an edge;

a structural spacer bonded to the second face of the first transparent laminate and to the first face of the second transparent laminate; and

a desiccant;

wherein the structural spacer has an elastic modulus greater than 300 psi;

wherein the first and second transparent laminates are spaced in a substantially parallel relationship so that an air gap is defined therebetween; and

wherein the desiccant is positioned to absorb moisture trapped in the air gap.

2. The spaced transparent armor structure of claim 1, wherein the desiccant is contained in an inner desiccant seal that circumscribes the air gap and that extends between the second face of the first transparent laminate and the first face of the second transparent laminate.

3. The spaced transparent armor structure of claim 2, wherein:

the inner desiccant seal comprises a polymer binder; and

the desiccant is supported in the polymer binder.

4. The spaced transparent armor structure of claim 3, wherein the polymer binder is selected from the group consisting of silicone foam, ethylene propylene (EPM), ethylene propylene diene (EPDM) rubber, styrene-butadiene rubber (SBR), nitrile, and polyurethanes.

5. The spaced transparent armor structure of claim 4, wherein the polymer binder is silicone foam.

6. The spaced transparent armor structure of claim 1, wherein the polymer binder has an elastic modulus greater than 200 psi and less than the elastic modulus of the structural spacer.

7. The spaced transparent armor structure of claim 2, wherein the inner desiccant seal comprises at least twenty percent desiccant.

8. The spaced transparent armor structure of claim 2, wherein the structural spacer circumscribes the inner desiccant seal.

9. The spaced transparent armor structure of claim 1, wherein the structural spacer comprises a material selected from the group consisting of polyurethanes, polymethyl methacrylate, and metals.

10. The spaced transparent armor structure of claim 1, wherein the desiccant is embedded in the structural spacer.

11. The spaced transparent an nor structure of claim 1, wherein:

the structural spacer is configured as a hollow tube; and

the desiccant is embedded within the hollow of the tube.

12. The spaced transparent armor structure of claim 1, further comprising a film adhesive, and wherein the structural spacer is bonded to the second face of the first transparent laminate and to the first face of the second transparent laminate by means of the film adhesive.

13. The spaced transparent armor structure of claim 12, wherein the film adhesive is a pressure-sensitive tape adhesive.

14. The spaced transparent armor structure of claim 13, wherein the pressure-sensitive tape adhesive is an acrylic foam tape.

15. The spaced transparent armor structure of claim 1, further comprising a gasket bonded to the edge of the first transparent laminate and to the edge of the second transparent laminate.

16. The spaced transparent armor structure of claim 15, further comprising a sealant, and wherein the gasket is bonded to the edge of the first transparent laminate and to the edge of the second transparent laminate by means of the sealant.

17. The spaced transparent armor structure of claim 16, wherein the sealant is selected from the group consisting of silyl modified polymer sealants, urethane sealants, polysulide sealants, silyl-terminated-polyether sealants, acrylic sealants, and silicone sealants.

18. The spaced transparent armor structure of claim 17, wherein the sealant is a urethane sealant.

19. The spaced transparent armor structure of claim 15, wherein the gasket extends from the second face of the first transparent laminate to the second face of the second transparent laminate.

20. The spaced transparent armor structure of claim 1, further comprising a urethane backfill that circumscribes the structural spacer and that extends between the second face of the first transparent laminate and the first face of the second transparent laminate.

21. The spaced transparent armor structure of claim 20, wherein the urethane backfill further extends at least partially between the structural spacer and the second face of the first transparent laminate, and at least partially between the structural spacer and the first face of the second transparent laminate.

22. The spaced transparent armor structure of claim 20, wherein the urethane backfill further extends around the edge of the first transparent laminate and the edge of the second transparent laminate.

23. The spaced transparent armor structure of claim 1, further comprising a frame into which the first transparent laminate and the second transparent laminate are potted.