Abstract:
An electrically conductive assembly for providing a low electrical resistance contact between an antenna and the corrugated roof of a train. The assembly comprises a gel and skeletal gasket member which has an electrically conductive skeleton encapsulated in a tacky gel. Multiple foam and gel members, typically made up of compressible at least partially open cell foam, are laid in the troughs and are thick enough, such that the top surface of the foam and gel members is about equal to or slightly higher than the top surfaces of the ridges of the corrugated train roof. The antenna is then laid atop the gel and gasket member and bolted to the roof with fasteners in such a manner that the tacky flowable gel at least partially squeezes out the edges of the gel and gasket member as the antenna is compressed downward while the fasteners are snugged up. This compression allows the electrically conductive skeletal member to provide contact between the antenna and the roof, the roof typically metallic and that results in a decrease of EMI (electromagnetic interference).

Description:
This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/131,508, filed Mar. 11, 2015; and U.S. Provisional Application Ser. No. 62/144,619, filed Apr. 8, 2015, both of which are incorporated herein by reference 
    
    
     FIELD OF THE INVENTION 
     Gaskets, namely electronically conductive gaskets for adapting an antenna to the corrugated roof of a train car. 
     BACKGROUND OF THE INVENTION 
     Railroad trains sometimes use transmitting and/or receiving antennas mounted to the roof of a train car. In such an application, because of RF interference, conductivity is required between the antenna and the roof. Currently, due to the corrugations of the roof and the flat base of the antenna, a metal plate is machined to fit between the corrugated roof and the underside of the antenna. The machined plate has lands and bays that are the reverse of the ridges and troughs on the corrugated roof. Fasteners are applied to hold the antenna base to the plate and the plate to the roof. Then silicone gum is applied all around the base and the machined plate and fasteners. The plate provides conductivity and the silicon provides an environmental seal to prevent elements such as moisture from finding the way into the car through, for example, fastener holes. 
     There are certain shortcomings to this present method of mounting an antenna to a corrugated roof. Applicants&#39; assembly overcomes at least some of the shortcomings to provide an effective environmental seal between the antenna assembly and the roof and further to provide for effective conductivity between the antenna and the roof, so as to overcome EMI problems. 
     SUMMARY OF THE INVENTION 
     Applicants provide a novel conductive sealant assembly for interposition between an antenna assembly and a corrugated roof of a train for substantially sealing out air and moisture. 
     Railroads travel through a harsh environment. They are subject to a variety of thermal conditions, moisture conditions and harsh vibration. Moisture is a catalyst corrosion and may condense and creep in everywhere. Corrosion may attack the antenna/locomotive metallic junction and cause a breakdown in electrical conductivity, which is typically required for RF EMI inhibition. Applicants provide, in one embodiment, a conductive polyurethane gel gasket which may be used sometimes in conjunction with a sealing tape (such as a stretchable gel impregnated sticky foam tape) to moisture proof the connection between the antenna and the train. The gel of the gel skeletal member will migrate to fill surface voids and surface. The gel will remain tacky despite vibration and temperature variation. It may flow around and protect fasteners and the metallic skeleton provides an electrical ground across the antenna/roof surface. 
     A corrugated roof of a train car has ridges and troughs and side walls between the ridges and troughs. The typical antenna assembly has a flat slightly curved base to engage the tops of the ridges of the train roof. Applicants&#39; conductive sealant assembly is comprised of at least an encapsulated skeletal member that includes, in one embodiment, a metallic skeleton encapsulated with a cured, soft tacky polyurethane gel. The conductive sealant assembly may include foam/gel members where the troughs are. The foam/gel members build up the troughs until the top of foam/gel members is even with the ridges and on this even or slightly curved plane comprising the top of the foam/gel member and the ridge tops lay the encapsulated skeletal member which is usually cut to the footprint of the antenna base. 
     Fasteners compress the antenna base to the roof, such that the soft encapsulated gel is partly squeezed out and the underside of the base contacts the skeletal member and the skeletal member contacts the ridge top to provide conductivity between the antenna and the roof, so as to reduce the problem of EMI or radio frequency interference while at the same time providing a good environmental seal against moisture and other containments. 
     In one embodiment, applicants&#39; provide an electrically conductive assembly for providing a low resistance electrical contact between an antenna, the antenna having an underside, a footprint, and an antenna cable extending from the underside, and a corrugated train roof having multiple ridges with top surfaces and multiple troughs with floors. The assembly may comprise a gel and skeletal gasket member comprising an electrically conductive skeletal member encapsulated in a tacky gel, the gel and skeletal gasket member dimensioned to have a perimeter about the same as the footprint of the antenna; at least one foam/gel member dimensioned to fit between the underside of the gel and skeletal gasket member and the floor of the troughs; and the gel and skeletal gasket member for laying atop the foam/gel member and the top surfaces of the ridges and beneath the underside of the antenna such that compression between the antenna and the roof will cause some of the gel of the gel and skeletal gasket member to squeeze out and will cause contact between the skeletal member and the roof and the skeletal member and the underside of the antenna and will cause contact, and sometimes compression between the underside of the antenna and the top of the foam/gel member. 
     In one embodiment, applicants&#39; provide an electrically conductive assembly for providing a low resistance electrical contact between an antenna, the antenna having an underside, a footprint, and an antenna cable, and a corrugated train roof having multiple ridges with top surfaces and multiple troughs with floors. The assembly may comprise a gel and skeletal gasket member comprising a metallic or electrically conductive member encapsulated in a tacky gel, the gel and skeletal gasket member dimensioned to have a perimeter about the same as the footprint of the antenna; at least one foam/gel member dimensioned for a contact fit between the underside of the antenna and the underside of the gel and skeletal gasket member and the floor of the troughs; the gel and skeletal gasket member for laying atop the foam/gel member and the top surfaces of the ridges and beneath the underside of the antenna such that compression between the antenna and the roof will cause some of the gel of the gel and skeletal member to squeeze out and will cause contact between the skeletal member and the roof, and the skeletal member and the underside of the antenna; and further comprising a perimeter seal; wherein the gel is polyurethane; wherein the gel is cured; and wherein the foam is compressible and at least partly saturated with gel. 
     In one embodiment, applicants provide an electrically conductive assembly for providing a low resistance electrical contact between an antenna, the antenna having an underside, a footprint, and an antenna cable, and a corrugated train roof having multiple ridges with top surfaces and multiple troughs with floors. The assembly may comprise a gel and skeletal gasket member comprising a metallic member encapsulated in a tacky gel, the gel and skeletal gasket member dimensioned to have a perimeter about the same as the footprint of the antenna; at least one foam/gel member dimensional to fit between the underside of the gel/skeletal gasket member and the floor of the troughs; the skeletal gasket member for laying atop the foam/gel member and top surfaces of the ridges and beneath the underside of the antenna such that compression between the antenna and the roof will cause some of the gel to squeeze out and will cause contact between the electrically conductive skeletal member and the roof and the electrically conductive skeletal member and an underside of the antenna; and further comprising a perimeter seal; wherein the gel is polyurethane; wherein the gel is cured; wherein the foam of the foam/gel member is compressible and at least partly saturated with gel; and further comprising a gasket tape wrap for wrapping the antenna cable; and, wherein the electrically conductive skeletal member is woven metal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of the prior art machined plate and antenna. 
         FIG. 2  is a perspective view of the antenna assembly comprising an antenna mounted to a train roof. 
         FIG. 2A  is a cutaway cross-section of  FIG. 1 . 
         FIG. 2B  is a cross-section of applicants antenna assembly showing the encapsulated skeletal member, the foam gel member sandwiched under compression between the ridges and troughs of the corrugated train roof and the base of the antenna. 
         FIG. 2C  illustrates an alternate manner in which the troughs may be built up, while avoiding air pockets and insuring a good environmental seal between the antenna and roof. 
         FIG. 3  is a side view showing a perimeter seal coating the exterior of the conductive sealant assembly from the edges of the base of the antenna to the surface of the train roof. 
         FIG. 4  shows the manner in which the foam gel member is fitted into the troughs between the ridges of the corrugated roof. 
         FIG. 5  is an isometric view showing the encapsulated skeletal member and illustrating the manner in which the perimeter of the encapsulated skeletal member is cut to the footprint of the base of the antenna and lays on top of the surface of the ridges of the roof. 
         FIG. 6  is a side view of the corrugated roof showing some dimensions. 
         FIGS. 6A and 6B  are cross-sections of two embodiments of a foam gel tape member shaped to fit in the troughs. 
         FIG. 6C  is a schematic illustration of roof dimensions for use with Applicant&#39;s assembly. 
         FIG. 7  illustrates a gasket wrap for use at or near a co-axial connection or other electrical connection. 
         FIG. 8  illustrates a cure-in-place gel seal in a recess about the co-ax cable/antenna junction. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates prior art machined plate for mounting an antenna gasket to a corrugated roof of a train. 
       FIGS. 2, 2A, 2B and 2   c  illustrate the manner in which an encapsulated gel/skeletal member  18  of an electrically conductive sealant assembly  16  lays atop a corrugated train roof  14  and includes multiple foam/gel members  24  or foam only members sandwiched between, and typically under compression between the underside of an antenna  12  and train roof  14 . Antenna  12  is seen to have a base  12   a , and upstanding mast  12   c , and multiple fasteners  12   b  to fasten the base to the train roof with applicants conductive sealant assembly  16  under compression therebetween. The antenna is seen to have generally flat base  12   a  with a flat underside. Train roof  14  is seen to be corrugated and to have multiple ridges  14   a  separated by multiple troughs  14   b  with sidewalls  14   c  between the ridges and the troughs. Applicants&#39; conductive sealant assembly  16  is seen to comprise at least encapsulated gel/skeletom member  18 , which may include a metallic skeleton  20  (in one embodiment, a woven skeleton member) or other suitable metallic membrane and a soft, sticky, polyurethane gel  22  (typically cured) or other suitable material in which skeleton  20  is embedded or encapsulated. Typically, there is little or no water or air bubbles in the gel or the encapsulated skeleton member  18 . 
     Applicants&#39; conductive sealant assembly  16  may also include one or more foam/gel members  24 , which is seen in one embodiment to comprise a foam  26 , such as an open or partly open cell foam at least partially saturated with or covered by a gel  28 , such as a polyurethane gel, which may be cured. A perimeter seal  30 , such as Av-DEC Thixoflex®, is seen to cover and enclose the perimeter of gel/skeletal member  18 , the perimeter seal with an upper boundary  30   a  for engaging the perimeter of antenna base  12   a  and a lower boundary  30   b  engaging the roof, and in a preferred embodiment substantially enclosing the gel/skeletal member  18 . 
     Applicants&#39; gel/skeletal member  18  may include metallic skeleton  20 , such as in a woven skeleton made of a conductive metal such as aluminum, aluminum alloy or other suitable conductor. Gel  22  may be a cured two part polyurethane gel that, uncured, encapsulates and fills the voids in the woven, metallic skeleton  20  so that there are no air bubbles in the encapsulated gel/skeleton member  18  and then cures, after which the gel/skeleton member may be used as disclosed. One such encapsulated conductive gel/skeleton member is available from Av-DEC, Mony St., Fort Worth, Tex., as Hi-Tak polyurethane conductive gasket, Part No. AD2740X. The encapsulated gel/skeleton member, the method of manufacturing and a further description of its structure, function and properties may be found in U.S. Pat. Nos. 6,530,577 and 6,695,320, both of which are incorporated herein by reference. 
     Some details of Applicants&#39; foam/gel member  24 , its structure, function and properties may be found in U.S. Pat. No. 7,229,516, incorporated herein by reference. Foam  26  may be an open cell foam, a semi open cell foam, or even a closed cell foam, which is coated with the gel. FIG. 14 of the &#39;516 patent shows the manner in which a knife is used to cut an at least partially saturated open cell foam into a strip which may be dimensional to fit troughs  14   b .  FIGS. 6A and 6B  illustrate that the sidewalls  24   c  of the foam may be generally perpendicular or angled to match the sidewall profile of the trough in which the foam/gel is placed. The angled relationship may be achieved by holding the knife at an angle when cutting the gel foam into strips. 
     Corrugated roofs of trains often have profiles with different dimensions from one brand to another. The depth of the corrugations may differ from one model train to the next, as may the width of the troughs and the angles of the sidewalls. In one method, applicant uses multiple thin foam/gel members layered, one with the least width at the bottom, followed by the same width or sequentially wider foam gel members (shown) until the top of the last of the multiple members is about equal to or slightly above the ridge top (see  FIG. 2B ).  FIG. 2B  shows one such trough built up with three foam/gel layers:  24   a / 24   b / 24   c  (the right side one of the two troughs illustrated in  FIG. 2B ). Each layer is usually sticky and has a sticky outer surface which will allow it to tightly sealed against the corrugated roof and against the adjacent foam/gel layer, with the top of the uppermost layer  24   c  having a tacky gel contact with the underside of gel/skeletal member  18 .  FIG. 2B  illustrates single foam/gel member  24 . 
       FIG. 2C  illustrates a method in which trough  14   b  may be built up using one or combination of foam/gel layers  24  (here  24   a / 24   b ) along with a cure in place injectable gel sealant  34 . The injectable cure in place sealant may be injected as “make up gel” or “gap filler” in any gaps left between the side walls of the layered foam gel and the trough sidewalls  14   c , as illustrated in  FIG. 2C . An injector  32  having a mixing nozzle  32   a  and two compartments  32   b / 32   c  may be provided along with a forcing element  32   d . In each of the two compartments  32   b / 32   c , there are the two parts of injectable sealant  34 . When forcing element  32   d  is pushed in the direction indicated, the two parts will mix in nozzle  32   a  and, in one embodiment, in a gel form, fill the gap between the sidewalls of the foam/gel member and the sidewalls of the trough, and after a few minutes will cure. Injectors and two component cure-in-place polyurethane systems are available from Avdec, an injectable sealant sold under the mark Self-leveling Green. This product is a two component polyurethane designed to produce a water-tight, flexible seal. 
     In the embodiment set forth in  FIG. 6A , sidewalls  24   c  are beveled at an angle, so as to sit flush against sidewalls  14   c  of the roof. In  FIG. 6B , the straight cut sidewalls  24   c  may be used, even where sidewalls  14   c  of the roof are angled, due to the compressibility and deformability of the foam, the embodiment illustrated in  FIG. 6B  having a width about equal to the ridge to ridge dimension (see RTR in  FIGS. 6 and 6C ). 
       FIG. 6C  illustrates an example of the dimensions found in a train roof  14  as stated above. These dimensions may vary, but typically include multiple ridges  14   a , multiple troughs  14   b , and canted sidewalls  14   c . As can be seen in  FIGS. 5 and 6C , the thickness of applicants foam/gel member  24  may be in one embodiment, about 375 mil and the width RTR may be about 1.10 inches. With such dimensions the foam/gel member will substantially fill the trough area sealing out air and moisture as the gel acts as an effective sealant and the foam is a compressible substrate to carry the deformable, flowable, tacky gel (see  FIG. 3 ). 
       FIGS. 2 and 5  illustrate the manner in which the encapsulated gel/skeleton member  18  of Applicants&#39; conductive sealant assembly  16  is cut or otherwise shaped to fit the footprint or perimeter of base  12   a  of antenna  12 . The gel/skeletal member  18  may be die cut by the methods set forth in the patents incorporated herein by reference. Foam/gel member  24  may be manufactured and dimensioned according to the methods set forth in the patents incorporated herein by reference in the dimensions set forth herein. The foam/gel member may be cut with scissors or a knife to conform to the curved perimeter of the base  12   a.    
     When applicants encapsulated gel/skeletal member  18  is layered up and the antenna and fasteners engage the roof, compression generated by the fasteners will cause the base of the antenna to pull towards the roof and squeeze out some of the soft gel and generate contact and electrical conductivity between the underside of the base from the top of the ridges through metallic skeleton  20  thus providing electrical conductivity, but with the gel assuring a good environmental seal to keep out moisture and other harmful matter which could cause corrosion. After compression has been placed on the gel/skeletal member  18  and the underlaying foam/gel layer or layers, excess squeeze out at the edge of the perimeter may be wiped away as with an alcohol soaked rag and optionally perimeter seal  30  may be applied, perimeter seal  30  such as available from Av-DEC as Thixoflex Orange or Gray, a two-part form and cure in place tacky, soft injectable sealant. Perimeter seal  30  may be a two-part mix applied, shaped (if necessary) and then cured in place around the perimeter of the assembly  6  from the top edge  30   a  engaging an outer sidewall of the antenna base typically all the way around and a bottom edge  30   b  engaging the roof (see the exterior view in  FIG. 2 ). Another such perimeter seal is Thixoblack a hard non-tacky, non-gel durable elastomer available from Av-DEC. 
       FIG. 7  shows a gasket tape wrap  35  provided at and/or near the location where the co-ax cable leaves the bottom of the antenna, through hole or opening  37  (see  FIG. 5  for example). One tape  39  that may be used for gasket tape wrap  35  is Av-DEC StretchSeal®, a foam tape at least partly saturated with tacky, pre-cured, polyurethane elastomeric sealant for sealing and moisture proofing at or near electrical connections and/or on electrical cable and co-axial connectors. It is rectangular, stretchable, and is typically stretched slightly when applied, in an overlapping manner (as illustrated with courses overlapping) to provide for a tight, moisture-proof seal—even around irregular shaped things. 
       FIG. 8  illustrates another manner of environmentally sealing the area around the underside of the antenna plate or adapter plate. (The antenna with a built-in base may be affixed directly to the sealing assembly or there may be an adapter plate to which the antenna is fixed, as by fasteners, which adapter plate is the base of the antenna and lays on the sealing assembly.) In any case, whatever piece is placed on the upper surface of the conductive sealant assembly  16 , there may be a recess  40 , the recess where the underside of the antenna/base lays against the conductive sealant assembly, recess  40  as seen in  FIG. 8 . If this recess is left unfilled, it may act as a pocket of air and moisture, which may, over time, cause corrosion. In one embodiment, where there is a recess on the underside of the base/antenna, Applicant provides a two-part cure-in-place injectable, which may be the same as makeup gel  34 . This flowable gel is injected into recess  40  (typically to fill it up) and allowed to cure in place forming a water-tight, flexible gel seal  42 , substantially surrounding the co-ax cable and its junction at the base of the antenna, and filling the recess. Gel seal  40  may be used with or without gasket wrap  35  as seen in  FIG. 7 . Applicator  32  may be used with nozzle  32   a  and two compartments  32   b / 32   c  for containing two parts of a mix that will cure upon mixing and in forcing element  32   d . In the few minutes that it takes to cure the injectable will typically self-level, when the antenna is held horizontal upon curing, then inverted and placed against assembly  16  as set forth herein. 
     Applicant&#39;s assembly is, in one embodiment, an environmental sealing assembly for use with vehicles or articles, such as tractor trailers, intermodal shipping containers (seacans), and corrugated roofs of homes or other buildings. Moreover, the corrugations may be R-panel, corrugated tin roofs or the like or any other shaped corrugations. Corrugations may be part of a side wall of a structure. Finally, the gasket assembly may be provided for more electrically conductive applications where any workpiece needs to be environmentally sealed and conductivity is not needed. These applications may include gaskets with molded nylon web or fiberglass mesh skeletons to provide structural integrity to the gel. Articles that may be mounted to corrugated members with Applicant&#39;s novel gasket assembly, including air vents, transponders, tracking antennas, any type of transmitting and/or receiving antennas. 
     Although the invention has been described in connection with the preferred embodiment, it is not intended to limit the invention&#39;s particular form set forth, but on the contrary, it is intended to cover such alterations, modifications, and equivalences that may be included in the spirit and scope of the invention as defined by the appended claims. For example, vehicles or articles, such as tractor trailer, intermodal shipping containers (seacons), and corrugated roofs of homes or other builds