Gasket material having a PTFE core and a method of making a using the same

BACKGROUND OF THE INVENTION

[0002] 1. Field of The Invention

[0003] Gasket material, more specifically, a gasket material comprising a resilient, pliable body having a durable, non-tacky skin.

[0004] 2. Background Information

[0005] A gasket is a sealing member for use between two mating surfaces to help prevent the movement of fluid or gas between the mating surfaces. Gaskets are often used on vehicles such as aircraft to prevent moisture from corroding the sealed off areas and the mating surfaces. For example, on the outside skin of an aircraft antenna are often mounted to assist in communications between the aircraft and a remote location. Such antennas often consist of a tabular mounting plate having an inner and outer surface, the inner surface mating to the outer skin of the aircraft and having an electrical connector projecting from the inner surface. The electrical connector is intended to fit partially into the interior of the aircraft through a small opening in the aircraft skin designed for such purpose. The electrical connector element will connect to the appropriate electrical circuit in the aircraft. On the outer surface of the mounting plate, and often incorporated with the mounting plate, is the antenna transceiving member for transmitting and/or receiving radio frequencies.

[0006] Traditionally, the antenna is removably mounted to the aircraft through typical threaded fasteners. Holes in the tabular mounting plate of the antenna support the threaded fasteners which pass into the aircraft's skin, typically threading into blind nuts mounted against the inside surface of the aircraft's skin.

[0007] Gaskets typically are provided for covering a portion of the “footprint” of the antenna against the outer surface of the aircraft. When the fasteners are tightened down, they compress the gasket typically with some deformation, between the aircraft's skin and the inner surface or face of the antenna mounting plate. This is done in an effort to prevent moisture from penetrating the gasket barrier.

[0008] However, prior art gaskets have a number of shortcomings which applicants novel gasket material overcomes. These shortcomings include allowing moisture to penetrate the area between the antenna and the aircraft's skin. Often, for example, a site of corrosion is the junction between the antenna inner surface and the electrical connective elements of the antenna. Moisture has been found to “pool” in this area, accelerating corrosion. Further shortcomings of the prior art gaskets include their moisture content or moisture absorption ability, which moisture may encourage the formation of corrosion, when the gasket is under pressure between the mating surfaces and, especially, where such gasket includes a metallic element. Further shortcomings of the prior art gaskets include their “non-selective retentivity.” This means that after the gasket has been installed and in use for a period of time, that upon an attempt to separate the antenna from the aircraft's skin, some portions of the gasket will non-selectively stick to portions of the aircraft's skin and other portions of the gasket will stick to the antenna (see FIG. 1A.). The result, often, is the destruction of the gasket.

[0009] Applicants have invented a gasket with a novel combination of properties and qualities that effectively prevent moisture from passing the sealed area while maintaining selective retentivity. This allows the effective separation between the mating surfaces upon removal of the antenna.

[0010] Flexibility, resiliency, compressibility and pliability are other favorable properties which help affect a good seal between the mating surfaces.

[0011] All of these beneficial properties should have a useful life that is reasonable in view of operating conditions and aircraft maintenance schedules. The gasket should be inert, that is non-reactive with the work pieces (typically aluminum) as well as non-reactive to water, including salt water.

[0012] Not surprisingly, it has proven to be a challenge to develop a gasket with these properties that will survive repeated heat and pressure cycling (as the aircraft climbs and descends), structural flexing, and vibration while protecting the aircraft components and having a useful life.

[0013] While some of the prior art gaskets have provided some of the favorable properties set forth above, none have provided all of these properties in an aircraft gasket with a useful life. Such typical useful life would be a minimum of greater than one year under proper torque specifications.

[0014] Applicants, however, provide for all of the above properties in an aircraft gasket and gasket tape and a novel method of manufacturing the aircraft gasket and gasket tape. Gasket tape is gasket material that is rolled into tape rather than precut to the pattern of the mating surfaces. Applicants further provide for a method of using the preformed gasket with a liquid settable gel too, in some cases, help insure a waterproof seal.

[0015] Applicants have also found a novel method of preparing a gasket material. Applicants provide a gasket with the following beneficial properties, heretofore unavailable in a preformed gasket or a gasket tape: elasticity (with memory), low water absorption, low water content, leak free (especially of silicon oil), desiccation resistant, compressibility and surface tackiness (including selective retentivity).

[0016] The elasticity and pliability helps make an effective seal between the two mating surface as compression against such elasticity helps seal over mating surface irregularities and structural flexing or vibration of the two surfaces. The maintenance of this elasticity property is important since the surfaces undergo thermal expansion and contraction during repeated altitude and temperature changes which causes relative movement (flexing) between the mating surfaces.

[0017] Low water absorption and low water content is also a beneficial quality as it is typically water or moisture that the gasket is meant to keep out.

[0018] Nor should a gasket material itself be the source of oil, as such oil can mar the finish of the aircraft surface. This oil leaching has been a problem with prior art gaskets including those silicon-based gaskets.

[0019] An additional beneficial property of an effective gasket includes a resistance to drying out. Drying out of a gasket brings the problem of shrinkage and break-up, which destroys the integrity of the gasket/mating surface.

[0020] Tackiness has been found beneficial since there is also vibration and flexing of the mating surfaces. Tackiness and resiliency provide a better seal should there be a slight separation between the mating surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]
FIGS. 1 and 1A illustrate prior art gaskets and their use.

[0022]
FIG. 2 is a cross-sectional view of Applicants preformed gasket.

[0023]
FIG. 3 is a side elevational view of Applicants preformed gasket in use.

[0024]
FIGS. 4, 5 and 6 are elevational views of various “footprints” of Applicants preformed gaskets.

[0025]
FIG. 7 is a cross-sectional elevational view of Applicants gasket tape.

[0026]
FIG. 8 is a perspective view of a step in the manufacture of Applicants preformed gaskets.

[0027]
FIG. 9 is a perspective view of another step in the process of manufacturing Applicants preformed gaskets.

[0028]
FIG. 9A is a side elevational view of a table for use in the method of manufacturing Applicants gasket material and illustrating Applicants gasket material on the upper surface thereof.

[0029]
FIG. 10 is a perspective view of a manufacturing step in preparing Applicants gasket material.

[0030]
FIG. 11 is a perspective view of a step in the manufacturing of Applicants preformed gaskets.

[0031]
FIG. 12 is a side elevational view of a step undertaken in preparation for manufacturing Applicants gasket material.

[0032]
FIG. 13 is a side elevational view of a table for use in the manufacture of Applicants gasket tape illustrating the stretching and clamping of a woven, non-metallic fiberglass member against the upper surface of the table, the table upper surface having been covered with a release film.

[0033]
FIG. 14 is a perspective view of the cutting of gasket tape stock into tape.

[0034]
FIGS. 15, 15A and 15B illustrate a method of using Applicants preformed gasket with a liquid, curable mix with a preformed gasket to provide an effective gasket seal between an aircraft skin and an aircraft antenna.

[0035]
FIG. 16 is a top elevational view of the dry open cell foam substrate or base used in applicants alternate preferred embodiment of novel gasket material set forth with the figures described herein below.

[0036]
FIGS. 16A, 16B, 16C and 16D are three alternate preferred embodiments of Applicants novel gasket material featured in at least partially saturated foam core, these three views being side cross-sectional views.

[0037]
FIGS. 17A, 17B, 17C and 17D illustrate elevation of the use of a number of applications of Applicants alternate preferred embodiment of a gasket material.

[0038]
FIG. 18 is a side elevational view featuring one use of the alternate preferred embodiment of Applicants novel gasket material.

[0039]
FIGS. 19A, 19B, 19C, 19D, 19E, 19F, 19G and 19H illustrate a method of preparing the alternate preferred embodiment of Applicants novel gasket material.

[0040]
FIGS. 20A and 20B are perspective and side cutaway elevational views, respectively, of a novel, tabular, skinned gasket member.

[0041]
FIGS. 21A, 21B and 21C are perspective illustrations of a novel method of manufacturing the skinned gasket member.

[0042]
FIG. 21D illustrates in perspective a novel application of the skinned gasket member.

[0043]
FIG. 22 is a perspective view of a new embodiment of Applicants novel gasket material featuring a sandwiched PTFE carrier.

[0044]
FIGS. 23A and 23B are perspective views of a method for preparing Applicants PTFE carrier in the manufacture of the novel gasket material illustrated in FIG. 22.

[0045]
FIGS. 24 and 25 are perspective views illustrating a method of manufacturing Applicants novel gasket material as set forth in FIG. 22.

[0046]
FIGS. 26A, 26B and 26C are three views of a manner in which Applicants novel gasket material as illustrated in FIG. 22 may be used to repair damage to the skin of an aircraft.

[0047]
FIG. 27 illustrates a method by which Applicants novel gasket material may be used in the refurbishment of aircraft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0048]
FIGS. 1 and 2 illustrate a prior art gasket. In FIG. 1 the prior art gasket is seen to contain a woven, typically mesh member within a gel body. However, the mesh member is located in a central area of the gasket body between the two outer faces of the gasket. This is to be compared to Applicant's preformed gasket 10 as illustrated in FIG. 2. Applicant's preformed gasket 10 has a metallic skeletal member 12 ( or non-metallic skeletal member 12A, see FIG. 14) wherein the skeletal member lays close to or adjacent one of the two outer surfaces of the gasket. One beneficial result of this placement is that Applicant's gasket has selective tackiness or retentivity, unlike prior art gaskets. Without such selective retentivity or tackiness, when prior art gaskets undergo tension during the release of the mating surfaces as illustrated in FIG. 1A (Prior Art) one face of the gasket often sticks to one mating surface and the other face of the gasket to a second mating surface. Such a result may be damaging to the gasket, preventing its reusability.

[0049] As seen in FIG. 2, Applicant's preformed gasket or gasket tape (FIG. 7) includes a skeletal member which may be metallic 12 or nonmetallic 12A. A typically woven skeletal member is, more typically, a woven aluminum mesh of thickness typically between 0.11 to 0.25 mil. Non-metallic mesh 12A (see FIGS. 13 and 14) may be woven fiberglass, for example, as when used in Applicant's gasket tape 16 typically between 7 and 20 mil. Sources of 1010 aluminum wire mesh are Estey wire and woven fiberglass is available from Teague Lumber as part number 337,600.

[0050] Substantially encapsulating skeletal member 12 or 12A is a resilient body 14 typically a semisolid gel and more typically formed from a curable polyurethane mix. The resilient body includes a first surface 14A and an opposed second surface 14B, the two surfaces with parallel planes. A typical thickness of Applicant's preformed gasket 10 is 0.032 inches to 0.050 inches before compression. A typical thickness of Applicants gasket tape is between 0.032 and 0.060 inches before compression. The preformed gasket and tape share the same resilient body and both have a sticky or tacky surface typically in the range of 2 to 7 inch pounds.

[0051]
FIG. 3 illustrates Applicant's gasket as it is used to mount between two mating surfaces, here aircraft skin As and aircraft antenna Aa, with preformed gasket 10 cut to dimensions dictated by the specifications of the antenna. It is placed between the aircraft skin and antenna and fasteners are tightened down typically to between about 15 and 35 inch pounds, to compress and slightly deform (squish out along the gasket edges) the gasket.

[0052]
FIGS. 4, 5, and 6 illustrate three “footprints” available for Applicants preformed gasket.

EXAMPLE 1

[0053] Applicant provides in example 1 a preformed gasket 10 with a footprint similar to FIG. 4 with an inner diameter about 5 inches and an outer diameter of 7 inches. The gasket has a resilient body of about 40 mil thickness comprised of polyurethane from a curable mix available from KBS Chemical of Fort Worth, Tex. as part numbers P-1011 (polyol) and U-1010 (urethane). Aluminum mesh of about 22 mil thickness is used. The preformed gasket was installed on a commercial jet airliner (Boeing 737) between the aircraft skin and the aircraft antenna to between 15 and 35 inch pounds pressure. The resulting compression allowed the wire mesh to ground the antenna to the skin, with the making surfaces about 20 mil distance apart. Upon removal, after 7 months of service, there was observed clean separation of the antenna from the gasket and the gasket maintained adhesion to the aircraft skin, expanding to about 40-90% of its original thickness and shape. The gasket did not dry out, and maintained its structural integrity and other chemical and physical properties, providing an effective seal.

EXAMPLE 2

[0054] A second gasket, similar in dimensions and structure to that set forth in Example 1, was joined between two mating surfaces under conditions similar to Example 1 and underwent 1,554 hours of salt fog testing per ASTM B 117. This gasket had a central cutout area in which a high tack, self leveling, green polyurethane sealant (Part No. U-1020 and P-1021 from KBS) was injected. The gasket was subject to a specified torque of 15 and 35 inch pounds. Upon release of the two mating surfaces the gasket was seen to maintain its integrity and to release clean from one mating surface of the two mating surfaces. It was seen to retain its resiliency and memory, as did the gasket in Example 1 above making an effective environmental seal.

[0055]
FIG. 7 illustrates the use of Applicant's unique gasket material in tape form 16, rolled up and available to be cut to length for placing between a pair of mating surfaces or as a self sealing tape. Applicant's tape 16 uses, typically, the same polyurethane body as preformed gasket 10 which has surface tackiness and has a mesh, 12A, typically woven fiberglass, that is closer to one of the two tape other surfaces then to the other. This is believed to result in Applicants unique selective retentivity.

[0056]
FIGS. 8, 9, 10 and 11 illustrate a method of producing Applicant's precut gasket 10.

[0057] The first step is the flattening step. The purpose of this step is to flatten out a skeletal member 12. The way in which this is done, if the skeletal member is metallic wire mesh, is to place the wire mesh 12 between two flat weighed members 20A and 20B and then placing the weighed members with the wire mesh between them in an oven. The wire mesh is typically 18 inches by 24 inches and the weighed members are typically ¼″ stainless steel plates. The mesh and weighed member are typically laid flat in an oven and heated to 600 degrees F for about 30 minutes. This anneals the metallic wire mesh and keeps it flat. The metal plates and the wire mesh are then removed from the oven and allowed to cool. Following cooling the weighed plates are removed and the wire mesh is ready for placement onto flat table 24.

[0058] At this point it is germane to examine the nature of flat table 24 in more detail. With reference to FIG. 9A, table 24 has legs and a table top. The table top typically includes a flat transparent glass member 24A with a flat upper surface. It also includes beneath the glass member 24A longitudinal aligned fluorescent lights 24B. Before placement of wire mesh 12 onto the glass table top a release sheet, such as an FEP sheet (fluorinated ethylene propylene) film is applied to the table top. The FEP film is inert and will not stick to the polyurethane mix or the cured mix and will allow a clean removal of the cured polyurethane mix, which comprises the resilient body, from the table top. It is noted with reference to FIG. 12 the FEP film is typically applied to the flat glass table top 24A from a roll, after Windex® an ammonia based cleaner 38 is applied to the surface of a table top and a squeegee 40 is used to squeeze out any air bubbles. This is done to insure a flat, bubble free surface for gasket formation. Thus, it is seen with reference to FIGS. 9A and 12 that table top 24A has been prepared prior to the placement of the flattened wire mesh on top thereof, with an FEP or otherwise suitable release film which will lay flat to the table top, be inert to the cure mix and allow the gasket material to release therefrom.

[0059] The next step in the manufacture of the preformed gasket, may be called the “mixing and pouring” step and is best illustrated with reference to FIG. 9. In FIG. 9 it is seen that a mix applicator 28 containing a curable mix of resilient body such as a mix of polyol and urethane available from KBS Chemical as set forth above, is applied to the mesh through the applicator. The prior art applicator stores the liquid mix typically as a resin (here urethane) and hardener (here polyol) in the body thereof, but injection through the nozzle thereof allows the two compositions to mix. Thus, in the process of pouring or applying the resilient body liquid mix, the two components are typically combined. This application and pouring step is typically done at room temperature. Moreover, it is noted that the resilient body liquid mix is self leveling. This step may also be done as two separate steps. First, one could separately mix the two components of the curable mix and, before it begins to set, apply it by pouring or any other suitable manner, onto the skeletal member.

[0060] With a minimum practice and experience the proper amount of liquid mix for the mesh may be determined. That is, sufficient liquid mix should be applied to the mesh for it to sufficiently cover the mesh such that the resilient body contains the wire mesh closer one surface than the other (see FIG. 2). For example, it been determined that using a 10 ½ inch by 17 inch 22 mil aluminum wire mesh such as set forth above, one applies about 160 milliliters of mix, typically, in the crisscross or zig zag pattern as illustrated in FIG. 9. This will typically result in a gasket of about 40 mil thickness.

[0061] The next step in preparing Applicant's preformed gasket is to allow the liquid mix to cure. Typical time to curing is about 4 hours at room temperature. Upon curing a second FEP layer here 38 (see FIG. 10) is applied to the top surface of the gasket stock 10A as seen in FIG. 10. This second layer of FEP material will help protect the gasket stock in handling and also will release easily from the surface therefrom.

[0062] Further in FIG. 11 it is seen that gasket stock 10A may be cut with a die stamp machine 34 in ways known in the trade to form precut gaskets 10 to any number of suitable configurations (see for example FIGS. 4, 5 and 6).

[0063]
FIG. 13 illustrates a manner for making Applicant's gasket tape 16. This involves the step utilizing a table such as is illustrated in FIG. 9A and stretching a non-metallic skeletal member 12A from a roll or other stock of such material under tension atop the FEP layered table. Some tension and clamping is necessary to insure that the mesh 12A is maintained flat against the FEP bottom layer 30B.

[0064] The mixing and pouring step is similar to that illustrated in FIG. 9, with the same resilient body liquid mix as used in the preformed gasket 10, coating all of the skeletal member to a thickness sufficient to place the skeletal member closer to one surface of the gasket tape than the other.

[0065] Following a period of curing the resulting gasket tape stock as illustrated in FIG. 14 may be cut longitudinally, covered with a top layer of FEP and rolled into a roll resulting in the gasket tape 16 illustrated in FIG. 7.

[0066] This tape may be then used in lining aluminum structural members of the frame of aircraft such as those in cargo bays and also on aluminum mating surface beneath lavatories and galleys, where moisture may be a problem. This will help prevent access of moisture to the structural member. It is noted that use of Applicant's tape or gaskets will be self sealing around fasteners hole. This occurs when there is some defamation of the tape or gaskets at their edges under compression between the two joined mating surfaces.

[0067] In summary, it may be seen that Applicant's unique method of manufacturing either the tape or the prevent gasket includes the step of flattening the skeletal member against a flat surface, typically a table top and more typically table top against which a flat release film such as an FEP film has been placed thereon. It is seen that a curable liquid mix is combined and applied in liquid form, to cover the skeletal member to a depth sufficient to insure that the skeletal member is closer to the bottom surface of the resulting stock then to the upper surface. It is further seen that the resilient body liquid mix is typically self leveling and will cure at room temperature. The resulting stock may be then precut to a desire shape or cut to a preselected width and rolled up in a form of gasket tape. It is further seen that the gasket tape, as illustrated in FIG. 7 is provided with a first protected film 18A and a second protective film 18B, typically FEP and that after by cutting, the precut gaskets are typically covered top and bottom with the same protective FEP film.

[0068] FIGS. 15 shows Applicants preformed gasket 10 ready for installation between two mating surfaces As and Aa. FIG. 15A illustrates the use of non-preformed pliable sealant mix 13, typically a resin and a hardener, more typically a polyurethane curable mix. Mix 13 will set in place, and may fill any central cut-out areas 13A in gasket 10. This will often protect against the trapping of moisture in such area. Note that this curable mix should have the beneficial properties of the resilient body of Applicants preformed gasket 10. Such curable mixes are available from KBS Chemical of Fort Worth as U-1020 and P-1021.

[0069] Applicants provide for a novel variation of the gasket or gasket tape heretofore disclosed. More specifically, Applicants provide in FIGS. 16A through 19H a novel gasket material (50) and a method for making the same. Applicants novel variation of the gasket material heretofore disclosed includes an open cell foam base or substrate (54) at least partially saturated (typically saturated) with a polyurethane mix (52). One such open cell foam substrate (54) is available from Reilly Foam Corporation of Conshohocken, Pa. as “100 PPI Z.”

[0070] The new gasket material may be configured in short strips, patches, washers, sheets or tape. The foam provides open cells which allows the gasket material to at least partially absorb a poured, liquid polyurethane mix which would typically cure at room temperature. The polyurethane mix (52) may be the same formulation used in the specifications set forth with the earlier embodiment. That is, the polyurethane mix (52) used in Applicants novel foam based gasket or gasket tape is available through KBS Chemical of Fort Worth, Tex. as Part No. P-1011 (Polyol) and U-1010 (Urethane). The polyurethane mix contains no silicone. Having no silicone oil means there is no silicone residue on the aircraft. Further, prior art gasket tape having a foam base (54) utilizing a silicone base mix would have a tendency to release silicone oil and thereby contaminate the substrate surrounding area and “lose” some of the actual sealing compound; especially under continuous compression and thermal cycling. Applicants novel gasket material with the polyurethane mix does not dry up or harden, even in extreme dry and cold. As such, Applicants novel gasket material using a foam base and a polyurethane mix (52) has a favorable application in the aircraft industry, as set forth in more detail below.

[0071] Applicants polyurethane mix or fill will typically at least partially saturate the foam substrate prior to curing. It will cure to form an elastomeric, solvent resistant, pliable material that will maintain its elasticity and pliability between about −65° C. and 135° C. Among the advantages of Applicants novel gasket material using a form substrate is that the material will not compression set. There is no silicone oil residue before, during or after installation or removal. Therefore, there are no problems with paint adhesion or preparation and no peripheral silicone contamination. It maintains excellent retentivity and may be stretched when applied if used in a tape form. Thus, in a tape form, it is excellent for wrapping cables such as coaxial cables. It provides a high level of tack compared to most other gasket materials and therefore is effective at corrosion protection. It is easily installed and, because it does not dry out, may be easily removed well after original installation.

[0072] Applicants novel gasket material with the foam base and the polyurethane mix is not reactive to polyethylene or aluminum. It is solvent resistant (ASTM D-543, water, polypropylene glycol/water, skydrol LD-4, MIL-H-5606, JET A) without degradation of physical properties. It passes FAR 25.853a.

[0073] All of these advantages and benefits provide for a gasket material that has numerous applications in the aviation industry, Applicants material may also be used wherever a protective wrap or gasket is needed. Indeed, numerous marine and land-borne vehicle applications are anticipated. Because Applicants gasket or sealant material is flexible and extensible, it can accommodate a number of complex forms.

[0074]
FIG. 16A illustrates Applicants dry, open cell foam substrate (54) before the mix is added. FIGS. 16B, 16C and 16D are side views cut away of Applicants gasket material (50). In FIG. 16B, it is seen that one embodiment includes a gasket material (50A) with a cured polyurethane mix (52) forming a bottom surface (52A) and a top surface (52B) to an at least partially saturated polyurethane foam core (56). In the embodiment of gasket material (50A), it is seen that core (56) is centrally located between top and bottom surfaces (52A and 52B) of cured polyurethane mix. On the other hand, it is seen with reference to FIG. 16C, that the at least partially saturated foam core (56) has a layer of cured polyurethane mix (52) on one side of the foam core and a thinner layer or, in an alternative, no layer on the other side.

[0075]
FIG. 16D illustrates a third embodiment of gasket material (50C), which gasket material is comprised of simply the at least partially saturated core (56), with no layers of cured mix on either side (“naked”). Thus, it is seen that Applicants novel gasket material (50) may come in different forms. First, it may include an at least partially saturated core (56) which may stand alone, or which may have, on one side or the other (or on both sides) a layer of cured polyurethane mix (52). Indeed, as in the mesh substrate embodiment above (see for example, FIG. 2), the core may be closer to the bottom of the gasket than to the top. That is, the core need not be centered as illustrated in FIG. 16B. Applicants have found that when the core is closer to one side of the gasket than the other (see for example FIG. 16C), there is a tackiness differential between the two surfaces. With a more tacky surface on one side, and used as a connector or cable wrap, it is found to be effective to wrap the tackier side to the inside, against the connector or cable.

[0076]
FIGS. 17A through 17D illustrate a number of forms which Applicants novel gasket material (50) may take. These include tape (58) wherein the top and bottom surfaces of the gasket material (50) may include protective sheets (58A and 58B). Applicants novel gasket material (50) may also be shaped to form a washer (60) as in FIG. 17B, a rectangular gasket (62) as in FIG. 17C and other complex shapes (64) such as illustrated in FIG. 17D. That is, Applicants novel gasket material (50) may be used a wrap and, since it is stretchable and sticks to itself as well as the work piece (such as a cable), it may hold the work piece under slight compression. On the other hand, it may be used under compression for intimate contact between two surfaces such as an antenna gasket. Some of these uses are illustrated in FIG. 18 wherein an aircraft antenna Aa is mounted to aircraft skin As and a washer (60) is provided as well as a wrap (58).

[0077]
FIGS. 19A through 19H illustrate a preferred method of making Applicants novel gasket material (50). In some respects, this method is similar to that disclosed with the previous embodiment. These steps may be broken down into three general categories. First, preparing the table (24). Second, pouring polyurethane mix (52) on to the table. Third, combining the foam and mix. The mix is then allowed to cure and the gasket material (50) is removed from the table.

[0078]
FIGS. 19A and 19B illustrate the method of preparing the table. A flattop table (24) is provided typically including a flat, transparent glass member (24A). A release sheet (36) such as a sheet of FEP is laid across the table after the tabletop is sprayed with a cleaner (38) or water. Bubbles are usually squeegeed out using a squeegee (40).

[0079]
FIG. 19C shows a sheet of dry of open cell foam substrate (54) laying on top of the table (24) and more specifically shows the step of applying a polyurethane border (70) around the sheet of foam, but typically not touching the foam edges. This border is used to define area in which the mix will be laid, which is illustrated in FIG. 19D. Turning back to FIG. 19C, after the border is applied, the sheet of foam (still dry) is removed and now the step of layering mix as illustrated in FIG. 19D is commenced. In this step, a gun or applicator (28) filled with mix (52) is used. Applicator (28) typically has a nozzle that will allow the polyol and urethane to combine as it is being applied. The crisscross action has been found to be an effective method of application of the mix on the table enclosed by border (70). The mix is typically self-leveling and the criss-cross pattern will cause it to flow together, somewhat. However, manual manipulation, such as that illustrated in FIG. 19E may assist the mix (52) to level. Note the worker manipulates the mix into the dry areas in FIG. 19E. FIG. 19F illustrates the placement step wherein the foam substrate 54 is placed on the leveled mix 52. FIG. 19G illustrates the step of soaking wherein the dry open cell foam substrate (54) becomes at least partially saturated with polyurethane mix (typically saturated). Manual pressing on the surface of the foam as well as squeegeeing (illustrated) will assist in urging the polyurethane mix (52) into the substrate (54). After desired degree of saturation is reached, the polyurethane mix (52) is allowed to cure. After curing, typically at room temperature for approximately two hours, the gasket material (52) is lifted from the table as illustrated in FIG. 19H.

[0080] If one desires that the at least partially saturated foam substrate core (56) should have a top and bottom layer of polyurethane mix (52) as illustrated in FIG. 16B (“sandwich”), then a greater volume of polyurethane mix, both above and below the core is required. That is, one can control the existence of or the thickness of a polyurethane mix layer outside the core by increasing the volume of polyurethane mix applied. If only a saturated core is desired with more substantial polyurethane mix extending beyond the boundaries of the core, then the core can be squeegeed clean of any excessive mix before curing.

[0081] For example the following procedure may be used for one desiring a “naked” saturated foam core with no layer of cured polyurethane on either side. A 12 inch by 36 inch 0.070 inch thick foam sheet of the type described above is placed on the table. About 150 cc of polyurethane mix is placed in the dispenser. The steps described above are undertaken and about 30 cc of uncured mix is squeegeed off the top of the saturated foam core, with the edge of the squeegee resting gently up against the top surface of the saturated foam core when the squeegee is drawn across the foam core. The estimate of 30 cc's may be made by placing the excess mix on a piece of FEP film and weighing it.

[0082] For preparation of a “one-sided” material one would simply squeegee off less than the excess squeegeed off to make a naked foam core. For example, if about 20 cc's is removed from the original 150 cc's applied, this would result in about a 0.005 inch layer of cured mix. The thickness may be estimated and a shinier finish results when a layer of mix is provided as compared to the “naked” foam. Removal of excess mix may be verified by weighing. Use of this procedure with the 0.070 inch thick foam results in a thickness of about 75 mil plus or minus 10%.

[0083] For the “sandwich” variety of gasket material (mix extending from both sides of the core) one would proceed as in the paragraph above but allow the top layer to cure. After the top layer is cured the work piece is flipped over and in about 30 to 40 cc's of mix is applied to the reverse side of the foam allowed to level and squeegeed to provide a total thickness of, typically about approximately 0.090 inch.

[0084]
FIGS. 20A and 20B illustrate a novel, skinned gasket member 80. Gasket member 80 is made from the same polyurethane mix as set forth in the embodiments above. The polyurethane mix is liquid curable and poured to form a base 84. The base 84 comprises the liquid curable polyurethane mix, and has a tacky side 87. A tabular body 86, includes the base and at least partially emerged therein, a fabric carrier member 88. The fabric member 88 may be woven or non-woven and may be metallic or non-metallic. The non-metallic mesh and non-metallic skin may be used when non-conductivity is desired. The metallic mesh and metallic skin may be used. when conductivity is desired.

[0085] The skin is typically non-sticky to the work piece, opaque or non-opaque, about 2-5 mil thick. In a preferred embodiment, it is a PTFE sheet, which is non-abrasive, non-tacky to the work piece, durable and will adhere to body 86. The PTFE sheet is abrasion resistant and is useful in aviation or marine environments for the skin of a gasket member, especially where that gasket member is used in aviation or marine environments. The PTFE is often used with a fiberglass woven carrier or an open cell foam carrier (see FIG. 16A) to form a non-conductive gasket. A metallic mesh carrier may be used with a skin made of aluminum foil, such as 2-5 mil aluminum foil to form a conductive gasket material.

[0086] As seen in FIGS. 20A and 20B, one side of base 84 will be “skinned” with a durable skin 82 and the other side of base 84 will have a tacky surface to adhere to a work piece. The entire skinned gasket member is typically between 40 and 60 mil thick and may be cut in a variety of shapes, including round, rectangular or in the form of tape.

[0087] When used as a tape, applicants have discovered that it is useful and certain applications in the aircraft manufacture, repair and maintenance industries. One specific application that has proved beneficial is the placement of the skin gasket member, in tape form, along a perimeter of an access opening in an aircraft body. This use is illustrated in FIG. 21D. Aircraft typically has a fuselage F. Access openings Ao are provided for access to certain portions of the interior of the aircraft, such as hydraulic cables, valves and the like, for inspection or repair purposes. The access openings Ao have a perimeter P thereto which allows an access panel Ap to be removeably attached to the access opening to seal it off. Applicants provide skin gasket material 80 in the form of tape 94 which is useful for application to the perimeter P of the access opening Ao. It is typically applied with the skin 82 facing out and the tacky side 87 of the base against the perimeter, holding the tape in place. Applicants have found that repeated attachment and removal of the Access panel against the skin of the gasket member has not destroyed the effectiveness of the panel/opening seal along perimeter P.

[0088] Applicants novel skinned gasket member may be prepared generally as set forth with respect to FIGS. 19A though 19H above. In a preferred embodiment some of the steps are illustrated in FIGS. 21A through 21C. FIG. 21A shows a flat sheet of skin 82 on the surface of a flat, level, glass top table, with any bubbles worked out of the skin (see FIG. 19A). A release sheet of FEP typically is not used. In a first layering of polyurethane liquid mix 90 the familiar criss cross pattern is preferably used and a body is allowed to form level and co-terminus with the borders of the skin 82. As illustrated in FIG. 21B, fabric 88 may be then laid on to first layer 90. Note fabric 88 is typically cut to the same shape as skin 82. Furthermore, first layer 90 has typically formed a level surface prior to applying the fabric.

[0089] Depending on the thickness of the body desired, a second layer 92 of liquid polyurethane mix may be applied as illustrated in FIG. 21C. Following curing, the skin gasket member 80 is lifted off the table and then may be die cut or sliced to form tape 94.

[0090]
FIGS. 22 through 27 illustrate a novel gasket material, a method of making the novel gasket material and a method for using the novel gasket material in the manufacture or refurbishment of an aircraft or the repair of a rupture in the skin of an aircraft.

[0091] Applicants' novel gasket material 100, as illustrated in FIG. 22, includes a thin, durable carrier sheet 102, typically PTFE, sandwiched by a first pliable polyurethane layer 104 and a second pliable polyurethane layer 106. The thickness “T” of Applicants' novel gasket material 100 maybe materially less than most other prior art gasket materials, especially those used in the repair of aircraft, the thickness “T” being generally between 10 and 25 mil, preferably between 13 and 17 mil.

[0092] Applicants' novel gasket material 100 includes all the advantages and features of the polyurethane mix set forth hereinabove, including the advantage that the polyurethane mix does not leave silicone oil stain or other oil leachate which may have deleterious effects, especially in an aviation environment. Another advantage of Applicants' novel gasket material 100 is in the use of the sandwiched PTFE carrier sheet.

[0093] The PTFE is a fluoropolymer sheet which has a number of advantages when used as a gasket material. It has a wide temperature range over which it will maintain its physical and chemical properties. It has a high melting point. Its friction and wear characteristics include a low coefficient of friction and good abrasion resistance. It contains no additives and is inert. It is resistant to attack by most chemicals including solvents, acids, organics and inorganics. Further, it is inert to attack by most microorganisms and related enzymes. It tends not to break down in ultra violet light, resists oxidation, discoloration and embrittlement. It is resistant to hydrolysis and a good barrier to water permeation.

[0094] Applicants make novel use of PTFE as a gasket material in providing a thin gasket combining PTFE and a pair of polyurethane layers bonded to either side of the PTFE sheet, especially when used in an aircraft environment.

[0095] In Applicants' novel gasket material 100, the total thickness of the gasket is given above. This is typically achieved by using a 5 mil PTFE sheet (approximate, range 2-8 mil) sandwiched in thin polyurethane layers, each of the polyurethane layers typically between 3 and 7 mil (approximate). The such dimensions, especially when used in aircraft manufacture, remanufacture or repair are designed to feature an effective, inert, leachate-free environmental seal between two portions of the aircraft to be joined, typically under compression. Further, the gasket material may be used in tape form to wrap connectors. The polyurethane layers provide sufficient tackiness to adhere not only to an aircraft surface such as aluminum metal, but to another polyurethane surface.

[0096] The PTFE carrier sheet of Applicants' novel gasket material 100 is typically treated, as by mechanically roughing or chemical etching (see FIGS. 23A and 23B) in the step of manufacturing the gasket material. The purpose of the treatment of the surface of the PTFE carrier sheet 102 is to promote the adherence of the polyurethane layer to the sheet.

[0097]
FIG. 23A illustrates the use of sanding as a method of treatment of PTFE carrier sheet 102. Sandpaper 108 may be used such as 400 grade sandpaper on a sanding block, wherein the PTFE sheet is laid on a flat surface.

[0098]
FIG. 23B illustrates an etching solution 110, typically a liquid, applied to a surface carrier sheet 102. Chemically etching, such as with sodium ammonia or sodium naphthalene, changes the etched surface from a non-wetable to a wetable surface.

[0099] Following the treatment step, the PTFE sheet may be rinsed, dried and laid on a flattop table 112, as illustrated in FIG. 24. A dispersing agent 114 is then applied to a first side of sheet 102. The dispersing agent may be, for example Zonyl® 3667N. The function of the dispersing agent is to assist in spreading thin polyurethane mix, illustrated being applied in FIG. 25, into a thin layer. Zonyl® 3667N fluoroadditive is a negatively charged, hydrophobic colloid containing about 60% of 0.05 to 0.5 micrometers polytetrafluoroethylene resin particles suspended in water and about 6% of a non-ionic wetting agent and stabilizer. It can be applied to surfaces such as a PTFE sheet using conventional coating techniques such as spray, roll, dip or spin coating.

[0100] Following the application of dispersing agent to the treated surface of the PTFE sheet, the step of applying the polyurethane mix from an applicator 116 is performed. This is illustrated in FIG. 25 and is done on a smooth, flattop table 112. The liquid polyurethane mix 118 is applied to the treated surface in an amount determined as set forth with earlier embodiments, to cover the first surface of the PTFE sheet to the desired thickness. It is then allowed to cure and flipped over where the opposite side, again having already been treated, has the dispersing agent applied and then the polyurethane mix to the desired thickness.

[0101] From time to time, it may be desired that a differential in tackiness between the two surfaces of the gasket material be provided. In such a case, the polyurethane layers may be varied in thickness in the manner described in earlier embodiments in this application. In other words, one of the two polyurethane layers will be thicker than the other.

[0102]
FIGS. 26A, 26B and 26C illustrate a manner of using Applicants' novel gasket material 100 in the repair of a rupture or hole 130 in the skin SK of the fuselage of an aircraft. Hole 130 has a perimeter area 136 having an edge 134, the hole, area and edge defining a damaged area 130 of the aircraft skin. Perimeter areas typically 5 to 20 cm wide, or extended out to about 1.5-3.0 times the longest diameter of the hole. The perimeter area should be clean and dry. It should also conform to the desired shape of the aircraft skin SK. Edge 134 may be treated by removing bends, burrs or otherwise, such as by filing or grinding. In any case, damaged area 130 is shaped to conform to the desired shape and is clean and dry. A patch 138 typically approximately the same gauge thickness as skin “SK” is provided that will cover at least the hole and the damaged perimeter. Gasket material 100 is shaped to cover the perimeter area. Gasket material 100 may be used in the form of a tape and may cover one or both sides of the aircraft skin (covering both sides of the aircraft skin illustrated in FIG. 26C). When using to cover both sides of the aircraft skin, a pair of similarly dimensioned patches 138 are used and fasteners applied to fasten the two patches and the gasket material under compression to the skin in a structure that has an outer patch, an outer gasket material of the skin, an inner gasket material and inner patch covering the damaged area 130. The gasket material and the patch are thin and therefore avoid providing an additional thickness to the aircraft skin. Sufficient compression allows for defamation and squeezing of the gasket material to a thickness of about 70% of the starting (non-compressed) thickness.

[0103]
FIG. 27 illustrates a manner in which Applicants' novel gasket material 100 maybe used in the manufacture or refurbishing of planes. Specifically, aircraft having multiple panels often overlap (“lap joint”) the panels to fasten them at the paired panels or overlap them with a longitudinal stringer. The points of overlap of the panels are often weak points in terms of environmental sealing. Applicants have found that their novel gasket material is beneficial in the manufacture or refurbishing of aircraft, especially aircraft fuselage where the panels overlap. FIG. 27 illustrates three panels, Panel A, Panel B and Panel C. At one point, Panel A and Panel B overlap and, during the manufacture or refurbishing at the point of overlap, Applicants' novel gasket material 100, for example as a tape, may be applied before fastening of the two overlapping panels order compression. During the fastening process, the panels will compress Applicant's gasket material and provide an effective environmental seal. Likewise, if the overlap occurs along a stringer ST, such as illustrated in FIG. 27 where Panel A and Panel C overlap, Applicants' novel sealant material may be used between the panels and/or between the stringer and Panel C.

[0104] Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.

	Number	Date	Country
Parent	10607432	Jun 2003	US
Child	10652692	Aug 2003	US
Parent	09569793	May 2000	US
Child	10607432	Jun 2003	US

Gasket material having a PTFE core and a method of making a using the same

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