ELASTOMERIC GASKET HAVING A FOAM METAL SKELETAL MEMBER

Abstract

A gasket for compressible placement between a first surface and a second surface is disclosed. In one embodiment, the gasket has a cellular metal skeleton, such as a woven metallic skeleton, encapsulated in a viscoelastic, pliable, deformable tacky polymer body, which may contain graphene or other filler. The skeleton has multiple strands, which connect to form multiple interconnected cells or pores. The void space is substantially filled in the manufacture of the gasket, with the tacky uncured polymer. The uncured polymer will set up or cure, and then the gasket may be used.

Claims

1. A gasket for compressible placement between an aircraft first surface and a second aircraft surface, the gasket comprising: a viscoelastic, pliable, deformable, polymer body; and a metal skeleton comprising multiple interconnected metal strands defining multiple regular shaped cells, the metal skeleton encapsulated in the polymer body; wherein the body contains multiple graphene particles.

2. The gasket of claim 1, wherein the graphene particles are nanoparticles.

3. The gasket of claim 1, wherein the polymer body is gel.

4. The gasket of claim 1, wherein graphene particles are micron sized.

5. The gasket of claim 1, wherein graphene particles are submicron sized.

6. The gasket of claim 1, wherein the graphene particles are spheres, flakes or fibers or a combination thereof.

7. The gasket of claim 1, wherein the graphene particles is in the amounts of 20-80% of total weight of the body.

8. The gasket of claim 1, wherein the body is a cured polyurethane gel body.

9. The gasket of claim 7, wherein the body is a cured polyurethane gel body between about 40-150 (cone penetration).

10. The gasket of claim 1, wherein the skeleton has a pore density of between 15 and 250 ppi.

11. The gasket of claim 1, wherein graphene particles are micron sized or submicron sized; and wherein the graphene particles are spheres, flakes or fibers or a combination thereof.

12. The gasket of claim 1, wherein the skeletal member comprises a flexible woven nickel alloy or aluminum alloy.

13. The gasket of claim 1, wherein the resistance of the skeleton is 2.5 milliohms or less.

14. The gasket of claim 11, wherein the skeletal member comprises a flexible woven nickel alloy or aluminum alloy; and wherein the resistance of the skeleton is 2.5 milliohms or less.

15. The gasket of claim 11, wherein the body is a cured polyurethane body.

16. The gasket of claim 15, wherein the skeleton has a pore density of between 15 and 250 ppi.

17. The gasket of claim 11, wherein the graphene particles are nanoparticles.

18. An aircraft assembly comprising: a first member, the first member having a first surface; a second member having a second surface; a gasket for compressible placement between the first surface and the second surface, the gasket comprising: a viscoelastic, pliable, deformable, polymer body; and a metal skeleton comprising multiple interconnected metal strands defining multiple regular shaped cells or opening; wherein the body contains multiple graphene particles.

19. The aircraft assembly of claim 18, wherein the graphene particles are nanoparticles.

20. The aircraft assembly of claim 18, wherein graphene particles are micron sized or submicron sized.

21. The aircraft assembly of claim 18, wherein the graphene particles are spheres, flakes or fibers.

22. The aircraft assembly of claim 18, wherein graphene particles are micron sized or submicron sized; and wherein the graphene particles are spheres, flakes or fibers.

23. The aircraft assembly of claim 18, wherein the first member is an antenna mounting member.

24. The aircraft assembly of claim 18, wherein the first member is a fuel access door.

25. The aircraft assembly of claim 18, wherein the graphene particles are dispersed in the polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is an illustration of a skeleton with irregular-shaped pores.

[0050] FIG. 1A is an illustration of a skeleton with a regular structure.

[0051] FIGS. 1B and 1C are photographs of the skeleton of FIGS. 1 and 1A, respectively.

[0052] FIG. 2 is a detail perspective view of the cell structure of the skeleton.

[0053] FIGS. 2A and 2B are cross-sectional views of a small portion of the gasket, FIG. 2A showing the manner in which a gasket body may extend beyond the skeletal structure and FIG. 2B a close up of a cell of the skeleton and the manner in which it may be saturated with the body material.

[0054] FIGS. 2C and 2D illustrate cross sections thru the strands.

[0055] FIG. 3 is a perspective exploded view of an assembly that may use applicant's gasket used with an aircraft antenna. FIG. 3A is a close up cross-sectional view illustrating Applicant's gasket under compression.

[0056] FIGS. 4 and 4A are cross-sectional views showing the relationship between the skeletal member and the gasket body and some dimensions of the gasket body and skeletal member.

[0057] FIGS. 5A and 5B are cross-sectional views of two methods of manufacturing Applicant's gasket.

[0058] FIG. 5C is a perspective view of a portion of the gasket in an embodiment that includes conductive or non-conductive particulate filler.

[0059] FIGS. 5D, 5E and 5F illustrate perspective views of methods to manufacture the applicant's gasket.

[0060] FIGS. 6, 7 and 8 are top views of three different shaped gaskets made by the methods and having the structure and function disclosed herein.

[0061] FIGS. 9, 10, and 11 illustrate the use of Applicant's novel elastomeric foam metal gasket for use on an aircraft with sealing an aircraft fuel access door to the surface of an aircraft fuselage or skin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] FIG. 1 illustrates a perspective illustration of a cellular metal skeleton 12 of the type which may be used in gasket 10 (see FIG. 2A). FIGS. 2, 2A, 2B, 2C, 2D, 3A, 4 and 4A illustrate Applicant's gasket 10 comprising a metal skeleton 12 substantially saturated with a gasket body 14. Skeleton 12 may be a foam metal skeleton, in one embodiment; a reticulated open cell foam, in one embodiment, Duocel foam. The term foam metal or cellular metal skeleton may refer to an all metal skeleton or a skeleton with strands having a non-metallic core. Gasket body 14 may be a cured polyurethane, polyurea or other suitable polymer gel two component mix 11 (see FIG. 5B) that is applied with an applicator 18 and allowed to cure after saturating skeleton 12.

[0063] In FIGS. 1, 1A, B, C, 2, 2A, and 2B, skeleton 12 is seen to have a skeleton perimeter 12a, multiple open cells 12b each one that may comprise multiple struts or strands 12d that are joined at nodes 12c. Each cell (for example, see FIG. 2B) is joined to multiple other cells and they are intertwined as seen in a cross-section view, FIG. 2A. In one configuration, each cell 12b is configured generally like a bucky ball and as substantially set forth in the '841 patent incorporated herein by reference (see also FIGS. 1A and 1C). The skeletons may be as substantially set forth and may be made by the methods set forth in U.S. Pat. Nos. 6,309,742 and 3,616,841. Briefly, the foam metal body of the '841 patent may be all metal (see FIG. 2C, cross-section of a strand), whereas the foam metal body of the '742 patent may include metal deposited on a non-metallic foam substrate (see FIG. 2D). Either foam metal skeleton or any other cellular metal skeleton may be used with the pliable gasket body 14 to provide the suitable gasket 10 for use in a number of environments. FIG. 2C illustrates that the strands may be solid metal (or metal with an open core), while FIG. 2D illustrates that in cross-section, strands 12d may be a metal coated 13a, deposited on a core 13b, which may be non-metal such as a polyurethane reticulated foam core. This skeleton may sometimes be termed a metalized foam. The strands of FIG. 2D sometimes provide more give (less stiff) and resiliency than skeletons made from the solid metal strands of FIG. 2C.

[0064] FIG. 1A illustrates an embodiment of a skeletal structure 12, in which the pores are regular shaped, that is, generally defined by regularly orderly shaped cells, at least in three dimensions (see FIG. 1A), in one view being honeycomb and, in one embodiment, honeycomb shaped. In the embodiment of the skeleton set forth in FIG. 1, the pores are somewhat random in size, shape, and spacing (three dimensioned), thus deemed non-regular. Both skeletons may have the same pore density and void space.

[0065] Gasket body 14 may have a perimeter 14a as seen in FIGS. 2, 4, and 4A, which perimeter 14a may, in one embodiment, extend pass all of the outer surfaces of the metal skeleton 12 a distance of about 1 mil up to about 20 mil. In another embodiment, the perimeter 14a make extend past one, two or more faces or surfaces of the skeleton 12, depending upon the use. This is illustrated with the gap in FIGS. 4 and 4A (no gap on the lower surface in FIG. 4A).

[0066] A range of thicknesses Ts for the skeleton 12, which in one preferred embodiment may be tabular (and may contain holes for fasteners or other items), is in the range of about 20 to 150 mil. A preferred thickness (shortest dimension) of body Tb in a preferred embodiment is tabular, essentially the same shape as the metal skeleton 12, and substantially saturating the cells thereof, Tb in one embodiment, in the range of about 30 to 200 mil.

[0067] FIG. 3 illustrates one environment or assembly in which gasket 10 may be used, that is, between two parts, here, aluminum antenna A.sub.a and aluminum outer surface A.sub.s of an aircraft. These parts A.sub.s and A.sub.a represent the skin of an aircraft A.sub.s and an aircraft antenna (A.sub.a) with an embodiment of Applicant's gasket 10 therebetween. Fasteners (not shown) are entrained in the holes illustrated and the gasket is typically compressed between the moveable workpiece (antenna) and static base (aircraft outer surface). Compression will tend to squeeze out the pliable sticky, soft body material, which may extend (uncompressed) above or below the surface of the skeleton, which squeeze out may be seen in FIG. 3A. Typically, the gasket 10 may be die cut as set forth below, such that the perimeter of the gasket conforms to the perimeter of the workpiece, here, in one embodiment, an aircraft antenna.

[0068] In FIG. 3A, squeeze out is seen extending past the edges of As and Ab, as well as past the edge of the skeletal member. This occurs under compression and may be wiped clean with an alcohol soaked cloth, if desired. The greater the compression, the greater the squeeze out. In FIGS. 4 and 4A, it is seen that there may be a perimeter 14a of gel body extending above or below one or both of the upper or lower surface of the skeleton creating a gap. Additionally, there may or may not be a gap along the perimeter. For example, FIG. 4 illustrates that prior to compression the body extends beyond the perimeter, sidewalls and the top of the skeleton, leaving a gap, but there being no gap on the bottom surface. In FIG. 4A, there is a gap that is a difference between TS, referring to skeletal thickness and TB referring to body thickness, the gap defining a perimeter 14a typically comprised of gel.

[0069] The gel or body material that is on the gasket surfaces facing the faying structures is used to create a good environmental seal between the two pieces that generate the compression on the gasket. In one embodiment, the skeleton is substantially soaked with the gel such as polyurethane gel and there is only a very thin veneer on the top surface and the bottom surface of the gasket, prior to compression, amounting to only about 1 or 2 two mil. In this embodiment there may be substantially no perimeter gap, could just a thin veneer of gel along the perimeter of the skeleton. When a very thin layer or veneer of gel is provided, there will be, when under compression, less or limited squeeze out. In one embodiment, the skeleton may be undercut; that is, cut back a few millimeters from the edge of the workpiece. In this embodiment, when compression occurs between the movable workpiece and the base, the squeeze will tend to fill the undercut.

[0070] FIGS. 5A and 5B illustrate two ways to make the gasket illustrated herein. An important objective in making the gasket is soaking the skeleton so that substantially all of the voids contain the body material. These two methods illustrated combine the uncured fluid, viscous or semi-solid mix 11 (typically in the viscosity range of 18,000 to 42,000 cps at about 24-26 C.) that will form gasket body 14 with the metal skeleton, such that there is soaking or encapsulation of the skeleton. The first illustrated cross-sectional view of FIG. 5A uses a substantially closed mold M in which is placed in (vacuum assisted) close proximity to the walls thereof, metal skeleton 12. A liquid or semi-solid curable two-part mix 11 is applied, at least sufficient to fill the skeletal voids. Closed mold (which may be used with a bag, not shown) then has a vacuum V drawn on it to draw out air and ensure investment of the skeleton with the mix prior to the mix curing.

[0071] FIG. 5B illustrates a gravity displacement method with an open mold in which skeleton 12 is laid, the skeleton closely configured to the floor and side walls of the mold. An applicator 18 with a forcing element 18d and two compartments 18a/18b applies a two-part mix 11, which mixes in nozzle 18c of the applicator. Under the impetus of gravity, and/or with the assistance of a roller 22 or weight 26 (see FIGS. 5E and 5F), the uncured liquid or syrupy semi-solid mix will settle (or be forced) into the voids and, over time (typically between about 30 and 120 minutes), will cure in place. In an alternate embodiment, some of the voids may have some air trapped (which may be forced out with a squeegee roller 22 or other tool prior to curing), but at least the majority of the cells will be at least partially and preferably completely filled upon curing with the mix.

[0072] FIGS. 5D and 5E illustrate a moldless use of gravity or gravity assisted (tool 22) method. Here skeleton 12 is placed on release film 24 and uncured mix 11 is applied. It will soak in under its weight, and may be assisted by using tool 22 to force the uncured mix into the voids of skeleton 12. The skeleton may be cut to shape first, before application of mix or cut later, after curing. Following curing of mix, the edges may be trimmed to the skeleton shape. FIG. 5F illustrates another method, moldless, of making a cellular metal gasket encapsulated with polymer gel. Here, like FIG. 5D, the uncured mix is applied. A second release film 24 is laid over top the uncured mix and, on top of the second release film, a weight 26 is applied, to force uncured mix into the voids of the skeleton. Upon curing, weight 26 and release paper 24 are removed. The skeleton is then cut to shape (of workpiece, for example) before adding the polymer (encapsulated) or after curing.

[0073] FIGS. 6, 7 and 8 illustrate various patterns of gaskets that may be diecut from the gasket stock that is removed from the mold following curing. FIG. 6 illustrates a generally circular gasket, FIG. 7 a generally rectangular gasket, and FIG. 8 a generally straight-sided oval shape. These gaskets may be used in aircraft assemblies or other suitable environments, including EMI shielding applications. They typically have fastener holes that may have large internal openings, in one embodiment, for carrying electrical conductors to an external antenna.

[0074] In addition to the body preferably comprising a gel, such as a polymer gel, the body may also have dispersed throughout thereof, many thousands of tiny electrically conductive particles or filler 20 (see the dots in FIG. 5C). Conductive parties may be all or partially metallic particles, such as those set forth in Publication US 2013/0068519 (U.S. application Ser. No. 13/643,331, filed May 10, 2011), the contents of which are incorporated herein by reference. These at least partly conductive particles may be mixed with gel to form a top 21c and/or bottom 21d layer on the body. The conductive particulate filler 20 may include carbon, Graphenol, Graphene, and conductive metals, such as copper, nickel, silver, aluminum, tin, and alloys thereof, in one embodiment, nanoparticles; in another, macro-particles with diameters in the nano range. The conductive filler may be in amounts of 20-80% of total weight of the body (polymer gel) and may be any shape and size in the micron, submicron or other suitable range. Suitable shapes may be micron-size spheres, flakes, and fibers. In the '519 publication, elastomeric polymers are set forth and any of those listed in that publication may be used as all or part of the body 14 set forth herein.

[0075] The manufacturing of the cellular metal skeleton, in one embodiment, may start with an open cell polyurethane foam that is being metallized. Subsequently, the polyurethane is removed by pyrolosis. A cellular metal skeleton and the gaskets set forth herein may be used in applications where high electrical and thermal conductivity are of importance. In addition, where high strength and rigidity are required, the metal may be further chromised and further treated. The result is a three-dimensional, extremely porous (so as to take up the gasket body), electrically conductive (low resistance) structure of unexpected strength and wear resistance, and high corrosion resistance.

[0076] Cellular metal can be cut with a shear knife or with circular saws; it may be laser cut, EDW machined, rolled, drilled, braised, etc. In one embodiment, it may include a pre-compressed thickness and may be compressed prior to application to the workpiece, to a desired thickness. While nickel foam may be used as a skeletal structure, copper foam and even titanium foam may be used or non-foam cellular metal skeleton of the same metals may be used. The nickel may be alloyed with chromium to form a nickel chromium skeleton material or further alloyed with aluminum to form a nickel chromium aluminum to improve oxidation resistance at high temperatures in other embodiments.

[0077] The pore size of the cellular skeleton may be indicated by a pore range number or ppi (pores per linear inch) which may be termed pore density. Some embodiments of Applicant's skeleton has a ppi range of about 17 to 63, with an average pore diameter in a first range of about 0.01 to 0.025 and a second range of about 0.01 to 0.125. The gasket may have a thickness of about 0.055 to 0.150 inches in a first range of about 0.0125 to about 0.50 in a second range (compressed or uncompressed). Other embodiments of Applicant's cellular metal skeleton may have a ppi range of about 47-53 and an average pore diameter of about 0.4 mm and a thickness in the range of about 0.055 inches to 0.063 inches. Other embodiments may have a ppi range of about 27-33 and a thickness of about 0.125 inches. Yet another embodiment of Applicant's skeleton is nickel or aluminum with a ppi range of about 57-63, average pore diameter of about 0.35 mm and a thickness of about 0.055 inches. The pore density is typically uniform whether measured from x, y or z axis or any other orientation.

[0078] Any of the aforementioned foams or any cellular metal may be compressed to a thickness of between about 70 to 90% of original thickness (reduced by 10-30% of original thickness cause by squashing cells) (up to 50% for Al) prior to application of the gel to form the gasket in a thickness range of about 0.0125 inches to 0.020 inches. This reduction is produced by a psi application of between about 30-350 psi. In one embodiment, the metal cellular skeleton produces a resistance of 2.5 milliohms or less when used in a polyurethane gel body, with the metallized skeleton pre-crushed to a thickness of between about 12.5 and 20 mil. In another embodiment, the metallized cellular skeleton is annealed before application of the gel.

[0079] In one embodiment, a skeleton has an open cell structure of struts 12d, a three-dimensional hollow skeletal metal where the cavities or voids cover more than in one embodiment about 90% of the total volume. It is very strong, yet has a low density compared to solid material. The densities may fall in the range of about 0.3 to 0.6 grams per cubic centimeter. The relative density indicates the mass ratio between the porous metal foam and the mass of the same volume of the basic solid material. Relative density (void/solid) may be, in one embodiment, less than about 5%, in another embodiment, less than 30%, in yet another embodiment about 2-25%.

[0080] The skeleton may be metal foam (also called cellular metal) and can be any metal or alloy. The skeleton may be made from a number of processes. In one embodiment, aluminum is foamed in a liquid state and then cooled quickly to maintain its shape, and provide an effective skeleton when used with a polyurethane gel body.

[0081] Compressive strength is proportional to the density of the metal. In one embodiment, an aluminum alloy of AA6061 is used for the metal. It may be heat treated to adjust strength and ductility. Ductility can be increased via annealingat the cost of strength. Annealing is meant to increase ductility and eliminate, if desired, the effects of string hardening and cold work components or prior heat treatments, and to avoid any hardening effects through natural aging.

[0082] FIGS. 9, 10, and 11 illustrate the use of Applicant's novel cellular metal elastomeric gasket 10 on an aircraft fuel access door 106. An aircraft fuel access door 106 may be mounted on a wing 102 of an aircraft using a retainer ring 108. Removal of access door 106 provides access fuel tank 104, typically located within the wing, for refueling of an aircraft. Access door 106 may be engaged with fasteners 112 to captured blind nuts 114 for fastening or free nuts 116 to hold the retainer ring 108 in place. Other fasteners may fasten through fuel access door 106 into retainer ring 108.

[0083] Between a shoulder on the perimeter of fuel access door 106, Applicant's gasket 10 may be placed such that threading fasteners 112 through fuel access door 106 into the retainer ring provides compression between wing 102 and the shoulder of the fuel access door as seen in FIG. 11. In one embodiment, fasteners 112 fastening the door to the retainer ring is sufficient to compress the gasket until there is contact between the elements on top and on bottom (shoulder and wing), so that there is metal (access door)/metal (metal foam)/metal (metal ring) contact, generally caused by squeeze-out of the gel body during the process of fastening and compressing the fastener that is fastening the door to the retainer ring. In some instances, psi may be as high as about 2000 psi.

[0084] Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. The skeletons are cellular metal, either metal foam or solid metal (which may have an open, unfilled core). On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention.