WO2001024596A1

WO2001024596A1 - Emi/rfi shielding device and gasket and method of making the same

Info

Publication number: WO2001024596A1
Application number: PCT/US2000/040853
Authority: WO
Inventors: Anthony M. Sosnowski; Frank T. Mcnally
Original assignee: Instrument Specialties Co., Inc.
Priority date: 1999-09-30
Filing date: 2000-09-08
Publication date: 2001-04-05
Also published as: AU1250701A

Abstract

A fabric for electrical shielding (12) having a plurality of warp yarns (32) including first conductive yarns and first non-conductive yarns, the first conductive yarns including non-conductive filaments which are plated, coated, or impregnated with a conductive material, the first conductive yarns defining a first percent by weight of the warp yarns; and a plurality of filling yarns (34) including second conductive yarns, the second conductive yarns including non-conductive filaments plated, coated or impregnated with a conductive material, the second conductive yarns defining a second percent by weight of the filling yarns. The second percent by weight of the second conductive yarns is greater than the first percent by weight of the first conductive yarns. The fabric defines a fabric layer which is disposed about a core (14) and adhered to the core to form a gasket structure (10) for electrical shielding.

Description

EMI/RFI SHIELDING DEVICE AND GASKET AND METHOD OF MAKING THE SAME

TECHNICAL FIELD

The present invention relates generally to EMI/RFI shielding devices, and more particularly, to an EMI/RFI shielding gasket having a plated filament fabric surface and a resilient core, and a method of making the same.

BACKGROUND OF THE INVENTION

The operation of electronic devices such as computers, business machines, communications equipment, and the like is attended by the generation of electromagnetic radiation within the electronic circuitry of the equipment. As is detailed in U.S. Pat. Nos. 5,202,536; 5,142,101; 5,105,056; 5,028,739; 4,952,448; and 4,857,668, such radiation often develops as a field or as transients within the radio frequency band of the electromagnetic spectrum, i.e., between about 10 KHz and 10. GHz, or greater, and is termed "electromagnetic interference" (EMI) or "radio frequency interference" (RFI) as being known to interfere with the operation of other proximate electronic devices. To attenuate EMI/RFI effects, shielding having the capability of absorbing and/or reflecting EMI/RFI energy may be employed both to confine the EMI/RFI energy within a source device, and to insulate that device or other "target" devices from other source devices. Such shielding is provided as a barrier which is inserted between the source and the other devices, and typically is configured as an electrically conductive and grounded housing which encloses the device. As the circuitry of the device generally must remain accessible for servicing or the like, most housings are provided with openable or removable accesses such as doors, hatches, panels, or covers. Between even the flattest of these accesses and its corresponding mating surface, however, there may be present gaps which reduce the efficiency of the shielding by presenting openings through which radiant energy may leak or otherwise pass into or out of the device. Moreover, such gaps represent discontinuities in the surface and ground conductivity of the housing or other shielding, and may even generate a secondary source of EMI/RFI radiation by functioning as a form of slot antenna. In this regard, bulk or surface currents induced within the housing develop voltage gradients across any interface gaps in the shielding, which gaps thereby function as antennas which radiate EMI/RFI noise. In general, the amplitude of the noise is proportional to the gap length, with the width of the gap having less appreciable effect.

For filling gaps within mating surfaces of housings and other EMI/RFI shielding structures, gaskets and other seals have been proposed both for maintaining electrical continuity across the structure, and for excluding from the interior of the device such contaminates as moisture and dust. Such seals are bonded or mechanically attached to, or press-fit into, one of the mating surfaces, and function to close any interface gaps to establish a continuous conductive path thereacross by conforming under an applied pressure to irregularities between the surfaces. Accordingly, seals intended for EMI/RFI shielding applications are specified to be of a construction which not only provides electrical surface conductivity even while under compression, but which also have a resiliency allowing the seals to conform to the size of the gap. The seals additionally must be wear resistant, economical to manufacture, and capability of withstanding repeated compression and relaxation cycles. Various types of EMI/RFI gaskets are known for reducing the transmission of electromagnetic interference and radio frequency interference. Among the known devices are gaskets having a resilient core surrounded by a deformable wire-mesh gasket material. Suitable known wire-mesh materials are tin-plated phosphor bronze, tin-coated copper-clad steel, silver-plated brass, Monel, beryllium copper and aluminum. Different core cross sections and materials are used depending upon the particular application. Wire-mesh gaskets are generally used to shield conventional computer or other electronic equipment by compressing the gasket around an openable access panel, door, or the like. Known wire-mesh gaskets are manufactured in various lengths and then cut to size for particular installations. In so doing, however, the wire-mesh tends to fray at the terminal ends of the gasket and thus produces an unacceptable appearance. A secondary treatment such as the in situ application of an adhesive has previously been utilized to overcome the poor appearance of the fraying ends. That treatment is a labor intensive process, however, and is not well suited for quick and cost-productive installations.

Other prior art gaskets have attempted to overcome this problem by knitting a conductive layer over a foam core before the foam has completely cured. In such cases, the uncured foam adheres to the knitted layer to prevent the terminal ends from fraying; however, utilizing an uncured core presents problems of dimensional stability and thus limits the shapes and sizes that can be successfully manufactured. U.S. Patent No. 5,045,635, assigned to Schlegel Corporation, for example, describes a process whereby a urethane foam core expands and cures in a traveling mold that is surrounded by a sheath with a conductive surface having embedded metal fibers or the like.

In addition to aesthetic considerations, EMI/RFI leakage may also occur due to the reduced shielding coverage that occurs as a result of the fraying terminal ends of the gaskets. Further, cutting the wire-mesh gasket during installation may produce particles of metallic debris within the shielded housing. A further design consideration for EMI/RFI gaskets is galvanic compatibility in the ultimate application. More particularly, when a conductive gasket for excluding electromagnetic interference is placed between two metal flange plates or metalized plastic components, dissimilar metals having dissimilar electrochemical potentials are quite likely to be placed in contact with one another. The use of dissimilar metals or metal coating/plating in metalized plastics is expected because desirable attributes in flange plates, such as strength and rigidity, are not the same as those for gaskets, such as flexibility and maximum electrical conductivity. The difference in the electrochemical potential of the two dissimilar metals is the force that drives the movement of ions therebetween and thus causes galvanic corrosion.

SUMMARY OF THE INVENTION

The present invention is directed to an electrical shielding device for shielding against electromagnetic and radio frequency interference. The shielding device comprises a conductive filament fabric having a plurality of first yarns including first conductive yarns and first nonconductive yarns, the first conductive yarns including nonconductive filaments which are plated, coated or impregnated with a conductive material. The first conductive yarns define a first percent by weight of the first yarns. The conductive filament fabric also has a plurality of second yarns including second conductive yarns, the second conductive yarns including non-conductive filaments plated, coated or impregnated with a conductive material. The second conductive yarns define a second percent by weight of the second yarns. The second percent by weight of the second conductive yarns is greater than the first percent by weight of the first conductive yarns. The electrical shielding device further includes a core, with the conductive filament fabric being disposed around the core to form a gasket structure.

A further aspect of the invention provides a fabric for electrical shielding having a plurality of warp yarns comprising first conductive yarns and first nonconductive yarns, the first conductive yarns including non-conductive filaments which are plated, coated or impregnated with a conductive material, and the first conductive yarns defining a first percent by weight of the warp yarns. The fabric also has a plurality of filling yarns comprising second conductive yarns, the second conductive yarns including non-conductive filaments plated, coated or impregnated with a conductive material, and the second conductive yarns defining a second percent by weight of the filling yarns. In accordance with the present invention, the second percent by weight of the second conductive yarns is greater than the first percent by weight of the first conductive yarns. The fabric is preferably woven from the warp yarns and the filling yarns.

The present invention further provides a method of making an electrical shielding device including selecting a core, selecting a conductive yarn and a nonconductive yarn, forming the conductive yarn and the nonconductive yarn into a fabric having a greater percentage of conductive yarn in one orientation, selecting an adhesive, applying the adhesive to the fabric, constructing a composite structure by arranging the adhesive coated fabric around the selected core, heating the composite structure to melt the adhesive such that the fabric will adhere to the core, and after said heating step, shaping the composite structure by drawing it through a die. The method further includes, after the shaping step, cooling the composite structure. Still further, the step of forming the fabric includes weaving the conductive yarn and the nonconductive yarn, with the greater percentage of conductive yarn being in a filling direction of the fabric.

RRTEF DESCRIPTION OF THE DRAWINGS

Many objects and advantages of the present invention will be apparent to those skilled in the art when this specification is read in conjunction with the drawings wherein like reference numerals have been applied to like elements and wherein: FIG. 1 is an elevational view of a conductive filament fabric gasket according to the present invention;

FIG. 2 is a cross-sectional view of a conductive filament fabric gasket having a circular configuration according to the present invention; FIG. 3 is cross-sectional view of a conductive filament fabric gasket having a square configuration according to the present invention;

FIG. 4 is a cross-sectional view of a conductive filament fabric gasket having a quadrilateral configuration according to the present invention;

FIG. 5 is a cross-sectional view of a conductive filament fabric gasket having an D-shaped configuration according to the present invention;

FIG. 6 is a cross-sectional view of a conductive filament fabric gasket having a L-shaped configuration according to the present invention;

FIG. 7 is a cross-sectional view of a conductive filament fabric gasket having a hollow circular configuration according to the present invention; FIG. 8 is an enlarged schematic illustration of the weaving of the filament fabric according to the present invention; and

FIG. 9 is a flow chart diagram illustrating the process of making a conductive filament fabric gasket in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a conductive filament fabric gasket in accordance with the present invention is shown generally by reference numeral 10. The gasket 10 includes a core 14 and a conductive filament fabric layer 12 which circumferentially and longitudinally envelops and surrounds the core 14. As shown in FIG. 2, the gasket 10 is illustrated as being circularly cylindrical in cross section; however, oval, elliptical, and polygonal cross-sectional shapes including square, rectangular, hexagonal and the like are also contemplated as being within the scope of the present invention. The core 14 can be selected from any one of a variety of materials. A solid core is preferred for the present invention. The core 14 may be a circularly cylindrical element preferably fashioned of an elastomeric material, such as neoprene sponge. Neoprene sponge has a melt temperature of approximately 200 °F and will not be adversely affected by heat used to melt an adhesive coating, as discussed below. Although neoprene has a slightly higher compression force than usually preferred for a gasket structure of this type, the neoprene sponge core demonstrates excellent dimensional stability during manufacture of the core. Other materials, such as urethane foam and polyurethane foam having lower compression forces, are also suitable for forming a gasket structure; however, obtaining dimensional stability with such materials is more difficult. As used herein, "solid" core material includes elastomers, foamed elastomers, composite materials, dual durometer composite materials, conductive polymers, polymers containing conductive inclusions, other resilient non-elastomeric materials and the like.

The core 14 is chosen to have a cross-sectional configuration identical to that desired for the final gasket 10. A gasket 20 having a square cross section as shown in FIG. 3, a gasket 22 having a quadrilateral or rectangular cross section as shown in FIG. 4, a gasket 24 having a D-shaped cross section as shown in FIG. 5 and a gasket 26 having a L-shaped cross section as shown in FIG. 6 must also have similarly shaped cores 14. In appropriate applications, the core 14 could possibly be hollow, as shown for gasket 28 in FIG. 7. Depending upon the application, the core could have one or more longitudinal holes running through it. Moreover, the core could be annular. Although gasket 10 is discussed in detail herein, it should be recognized by one skilled in the art that gaskets 20, 22, 24,

26, and 28 are similarly formed and that like reference numerals are being utilized to denote similar elements in each embodiment.

The conductive filament fabric 12 is preferably formed from a combination of nonconductive yarns and conductive yarns having high electrical conductivity. High electrical conductivity is particularly desirable in EMI/RFI gaskets. In order to provide the gasket 10 with both longitudinal and transverse compliance, the conductive filament fabric 12 is preferably formed by a suitable weaving process, although braiding, warp knitting, and circular knitting could also be adapted in accordance with the present invention. A conventional weave, as shown in FIG. 8 for example, may include a plurality of first yarns disposed in the lengthwise or machine direction of the fabric, and thereby defining the warp yarns 32. A plurality of second yarns are then woven in an over and under pattern across the width of the warp yarns 32, thereby defining the filling or weft yarns 34 of the fabric 12. The warp yarns thus interengage the filling yarns and result in a structure that has a substantial length in comparison to its transverse dimension. In a preferred embodiment, both the warp yarns and the filling yarns are a multifilament yarn which has been twisted to improve strength and abrasion resistance, as well as lower resistance. Tightly twisting the individual conductive filaments together, approximately fourteen turns per inch, for example, improves the shielding capability thereof and the likelihood of leakage through the fabric is lessened. The twisting of the filaments holds the filaments together without the use of a sizing. In the prior art, a sizing was used to hold the filament bundle together. However, the sizing generally disappeared during fabric finishing and/or plating processes such that the finished filament bundle tended to separate. This separation of the filament bundle in the yarn made the fabric subject to "picking" or filament breakage. The twisting of the filament bundles in the present invention provides a more durable fabric which is less likely to have problems of filamentation, i.e. , the breaking of individual filaments which have separated from the bundle. It is also within the purview of the present invention to provide twisted yarns for only one of the warp and filling yarns or to twist the yarns with more or less turns per inch as required by the specific application. Depending upon the needs of the specific application for gasket 10, a combination or blend of conductive and nonconductive yarns may be used. In a preferred embodiment of the present invention, the first yarns or warp yarns comprise a majority percentage by weight of natural polyester or nylon filaments or any other nonconductive natural or synthetic yarns such as, for example, cotton, wool, silk, cellulose, polyamide, and the like. However, interspersed within the nonconductive warp yarns are a number of conductive warp yarns. By way of example, the preferred fabric 12 has a thread count including on the order of approximately 135 - 137 nonconductive threads per inch and 8 conductive threads per inch in the warp direction. The warp yarn is thus approximately 3.5 - 5.0 percent by weight conductive yarns, and most preferably approximately 4.0 percent by weight. A majority of the filling yarns are conductive yarns and, most preferably, one hundred percent are conductive yarns. Alternatively, however, it is possible within the scope of the present invention to alternate the conductive and nonconductive yarns in the filling direction. In a preferred embodiment, the fabric 12 includes a total of 80- 83 conductive threads per inch in the filling direction, although higher and lower thread counts within the general range of 60-90 threads per inch, or greater, can be used. The weft or filling yarns are thus approximately 50 - 100 percent by weight conductive yarns, and most preferably 100 percent by weight conductive yarns.

The conductive yarns in the present invention are preferably a nylon or polyester filament plated with silver, but other conductive filaments could of course also be used, such as, for example, conductive filaments made from carbon, graphite or a conductive polymer, non-metallic filaments, metal coated polymeric filaments, or other nonconductive filaments which can be plated, coated or impregnated with a conductive material and be able to retain that material for the length of time and under service conditions to be encountered by the fabric 12 and the final gasket 10. Other possible materials include aluminum-, tin- or nickel- plated nylon yarn or any other conductive yarn conventionally used in the production of gaskets. A tin-plated yarn may be preferred in some instances due to the increased galvanic compatibility that is obtained. Generally speaking, yarns with a denier in the range of 30-200, or even greater, are suitable for weaving fabric 12, while a denier of about 40 - 100 is preferred. Most preferably, the warp yarns include nonconductive and conductive yarns with a denier of approximately 40 while the filling yarns include conductive yarns with a denier of approximately 100. In most applications, the conductive yarns used as the warp yarns and the filling yarns will be the same, silver plated nylon or polyester, for instance. It is, however, within the scope of this invention to utilize different conductive yarns in the warp and filling yarns to thus weave fabric 12.

The weaving of conductive filling yarns enables the fabric 12 and the resulting gasket 10 to have a predetermined or "designed" resistivity. That is, the fabric is woven with a multifilament yarn where the resistance of the yarn can be accurately measured and the individual filaments of the yarn are plated with a known resistance. The placement of the conductive yarns in a filling orientation and the amount used thus determine the resistance of the fabric. Accordingly, for applications where a higher density of conductors is desired, i.e., lower resistivity, a greater number of conductive yarns or different conductive yarns may be used for the filling yarns to lower the resistivity and obtain the desired shielding effectiveness. In a preferred embodiment of the invention, the resistivity of the warp yarns is less than 0.8 ohms per square and the resistivity of the weft yarns is less than 0.5 ohms per square, and the resulting shielding effectiveness is 120+ DB at 1 GHz. Other resistivities can of course also be used to obtain the desired shielding effectiveness for a given application.

Once woven, the fabric layer 12 is attached to the core 14 preferably with an adhesive layer 18, which may be a pressure sensitive variety, and which is disposed on one surface 30 of fabric layer 12. In this way, the fabric layer 12 can be advantageously wrapped around and bonded to the circumferential surface 16 of core member 14. The fabric layer 12 is preferably wrapped around the core 14 such that the edges thereof are adjoining edge to edge; however, it is also possible to wrap the fabric layer 12 so as to obtain an overlapping of the fabric edges along -lithe longitudinal axis of the core. Adhesive layer 18 is preferably substantially continuously applied to coat the entirety of surface 30 of fabric layer 12, and thereby prevent fraying of the ends when the gasket is cut. The adhesive must also be compatible with and capable of adhering to both the selected core material and the selected material of fabric layer 12, whether it be woven from silver- plated nylon or polyester, tin-plated nylon or another conductive yarn. A preferred adhesive in the present invention is polyurethane or an acrylic, which can be applied using conventional coating techniques. Other adhesives could of course also be used, such as, any adhesive suitable for EMI shielding applications, including formulations based on silicones, neoprene, styrene butadiene copolymers, acrylates, poly vinyl ethers, poly vinyl acetate copolymers, polyisobutylenes, and mixtures, blends, and copolymers thereof, as well as epoxies and urethanes. Heat-fusible adhesives such a hot-melts and thermoplastic films additionally may find applicability. The adhesive layer in the present invention should dry in approximately 1-3 minutes, and using the preferred polyurethane in approximately one minute, to thus produces an adhesive coated fabric layer 12.

Turning now to the method of making a conductive filament fabric gasket according to the present invention, as shown in the diagram of FIG. 9., a suitable elastomeric core is selected. The core may be selected from any elastomer that is stable and capable of withstanding the activation temperature of the selected adhesive without significant degradation. As discussed above, neoprene sponge provides the required dimensional stability and demonstrates suitable compression characteristics when subjected to the heating parameters necessary for melting the selected adhesive of the present invention. Other elastomers and elastomer sponges could of course also be used with this invention.

Referring to the second step in the FIG. 9 diagram, a conductive and a nonconductive yarn is then chosen, such as a natural nylon yarn and the preferred silver-plated nylon yarn. The selected conductive yarn and nonconductive yarn are then woven to form fabric layer 12, having the composition and orientation parameters discussed above.

An adhesive is then chosen and applied to the fabric layer 12. Preferably, the adhesive is a polyurethane layer 18 which is applied to one surface 30 of the fabric layer 12. The adhesive must be selected such that the temperature and time of exposure required to melt the adhesive will not adversely affect either the selected core 14 or the fabric layer 12 formed from the selected conductive and nonconductive yarns. If a heavier adhesive is used, the heating time may need to be increased in order to achieve a thorough activation of the adhesive. On the other hand, if a lighter adhesive is used, there may not be enough adhesive to securely adhere the fabric layer to the core. Thus, a polyurethane adhesive layer having a 0.004 inch thickness is best suited for the present invention.

The fabric layer 12 is then wrapped around the core member 14 with the adhesive coated surface 30 contacting the core member 14, and preferably, with the conductive weft yarns being disposed circumferentially about the core. A composite structure is thus formed including core 14, adhesive layer 18, and conductive fabric layer 12.

The composite structure is then passed through a heating tunnel in order to activate the adhesive on fabric layer 12. Using the preferred adhesive, core material and conductive yarn as described herein, the composite tubular structure is heated to approximately 285-300 °F for about 5-7 seconds, and most preferably to approximately 300 °F for about 5 seconds, such that the adhesive is sufficiently melted to adhere the conductive fabric layer to the core. The fabric layer is thus bonded to a pre-formed core member 14 to form gasket 10 through the application of heat, which thereby activates the adhesive layer 18.

It will be apparent to one skilled in the art that adjustments to the time of exposure and the temperature will need to be made based upon the particular type of adhesive that is used, as well as the type of nonconductive and conductive yarn used to form fabric layer 12. After heating, the still warm composite structure is drawn through a TEFLON^® (polytetrafluro-ethylene) die shaped to the desired final configuration of the gasket. That is, if the final gasket will have a circular cross section as shown in FIG. 2, then the die must also have a circular cross section, respectively. Similarly, if the final gasket has a D-shaped cross section, as shown in FIG. 5, then the die must also have a D-shaped cross section, respectively. As the assembled core, heated adhesive, and fabric layer move through the die, the die presses or irons the conductive fabric onto the core such that it adheres to the core and conforms to the shape of the core. The die is either TEFLON^® coated or solid TEFLON^® in order to prevent the still warm gasket from adhering thereto; however, it will be apparent to one skilled in the art that other types of anti- adhesion coatings and/or materials could be used as well.

After being shaped in the die, the gasket is allowed to air cool either at room temperature or with forced air such as a fan or the like. In addition, the finished gasket, or the fabric itself prior to being wrapped around the core, may be coated with a polymer coating to provide increased galvanic protection. That is, the gasket may be coated so as to improve the galvanic compatibility of the gasket in a wide range of applications. Finally, the finished gasket 10 may cut to the desired length, further treated with a pressure sensitive adhesive tape for use in the ultimate installation, packaged for shipping, or further fabricated for a particular installation.

While the shaping step is described above in connection with several particular cross sections, it is within the scope of the invention to shape the gasket to any desired cross section or angle. Likewise, it is within the scope of the invention to shape the gasket to any curved shape that may be desired.

Further, while the present invention has been described as providing separate processing steps for applying heat to bond the fabric layer 12 to the core member 14 and then shaping the composite structure, it is also within the scope of the invention to perform these processing steps simultaneously using a heated die having a shape corresponding to the final desired shape of the gasket, such that the core member is shaped simultaneously with the bonding of the fabric layer 12 to the core member 14.

One skilled in the art will recognize that a certain heating requirement or heat flux (J/s) is necessary in order to heat the composite structure in the heating tunnel and thereby melt the selected adhesive. The temperature in the heat tunnel to which the composite structure is heated and the duration of time for which the structure is exposed to this temperature must be chosen based upon at least two parameters. First, the tunnel temperature and time of duration must be great enough to cause the selected adhesive to fully melt. Second, however, the temperature and time must be less than that required to melt or otherwise adversely affect either the core or the conductive filament fabric. Thus, the linear speed at which the present invention can be produced is that speed at which the length of time in the heating tunnel produces the required heat flux subject to the above two parameters.

Referring to FIG. 8, the fabric layer 12 is adhered to core 14 by the adhesive layer 18 at a plurality of contact points extending over the entire surface thereof. In so doing, the present invention substantially prevents fraying of the terminal ends of gasket 10 when it is cut or otherwise sized for a particular installation; thus, gasket 10 is "self-terminating". The terminal ends of gasket 10 are thus prevented from unraveling when cut, there is no debris that occurs within the shielded structure, and no secondary treatments are required to obtain an aesthetically pleasing surface when the gasket is installed on enclosure frames. In addition, the smooth, soft surface obtained from a woven fabric insures against the scratching of metalized coatings on plastic interfaces.

It should now be apparent that a new useful and unobvious conductive filament fabric EMI/RFI shielding gasket has been described which overcomes problems of the type noted in connection with the prior art. It will also be apparent to those skilled in the art that numerous modifications, variations, substitutions, and equivalents exist for elements of the conductive filament fabric EMI/RFI shielding gasket described above. Accordingly, it is expressly intended that all such modifications, variations, substitutions, and equivalents for features of the invention as defined in the appended claims be embraced thereby.

Claims

WHAT IS CLAIMED IS:

1. A fabric for electrical shielding comprising: a plurality of warp yarns comprising first conductive yarns and first non-conductive yarns, the first conductive yarns including non-conductive filaments which are plated, coated or impregnated with a conductive material, said first conductive yarns defining a first percent by weight of the warp yarns; and a plurality of filling yarns comprising second conductive yarns, the second conductive yarns including non-conductive filaments plated, coated or impregnated with a conductive material, said second conductive yarns defining a second percent by weight of the filling yarns; wherein said second percent by weight of said second conductive yarns is greater than said first percent by weight of said first conductive yarns.

2. The fabric according to claim 1, wherein said fabric is woven from said warp yarns and said filling yarns.

3. The fabric according to claim 1, wherein said first conductive yarns are approximately five percent or less of said warp yarns and said second conductive yarns are approximately fifty percent or more of said filling yarns.

4. The fabric according to claim 1, wherein each of said plurality of filling yarns includes a plurality of conductive filaments.

5. The fabric according to claim 4, wherein said conductive filaments are selected from the group consisting of silver-, aluminum-, tin-, and nickel- plated nylon.

6. The fabric according to claim 4, wherein said plurality of conductive filaments are twisted together.

7. The fabric according to claim 1, wherein said filling yarns further comprise nonconductive yarns.

8. The fabric according to claim 1, wherein said second conductive yarns define one hundred percent by weight of the filling yarns.

9. A gasket structure for electrical shielding comprising: a core; a fabric layer comprising said fabric according to claim 1 , said fabric layer being disposed about said core; and an adhesive layer adhering said fabric layer to said core.

10. The gasket structure according to claim 9, wherein said core includes a neoprene sponge.

11. The gasket structure according to claim 9, wherein said conductive yarns include a nylon yarn plated with silver.

12. The gasket structure according to claim 9, wherein said conductive yarns includes a nylon yarn plated with aluminum.

13. The gasket structure according to claim 9, wherein said core includes an elastomer foam.

14. The gasket structure according to claim 9, wherein said core has a

L-shaped cross-sectional configuration.

15. The gasket structure according to claim 9, wherein said core has a D-shaped cross-sectional configuration.

16. The gasket structure according to claim 9, wherein said core has a quadrilateral cross-sectional configuration.

17. An electrical shielding device comprising: a conductive filament fabric comprising: a plurality of first yams comprising first conductive yarns and first non-conductive yarns, the first conductive yarns including non-conductive filaments which are plated, coated or impregnated with a conductive material, said first conductive yarns defining a first percent by weight of the first yams; and a plurality of second yarns comprising second conductive yarns, the second conductive yarns including non-conductive filaments plated, coated or impregnated with a conductive material, said second conductive yams defining a second percent by weight of the second yams; wherein said second percent by weight of said second conductive yarns is greater than said first percent by weight of said first conductive yarns.

18. The electrical shielding device according to claim 17, wherein said plurality of second yarns comprise only said second conductive yarns such that said second percent by weight of said second conductive yarns is 100 percent.

19. The electrical shielding device according to claim 17, further comprising a core, said conductive filament fabric being disposed around said core.

20. The electrical shielding device according to claim 19, wherein said conductive filament fabric is oriented such that said plurality of second yarns are disposed circumferentially around said core.

21. The electrical shielding device according to claim 19, wherein an adhesive layer adheres said conductive filament fabric to said core.

22. The electrical shielding device according to claim 19, wherein said plurality of second yarns comprise only said second conductive yarns such that said second percent by weight of said second conductive yarns is 100 percent.

23. A method of making an electrical shielding device comprising: selecting a core; selecting a conductive yarn and a nonconductive yam; forming the conductive yarn and the nonconductive yarn into a fabric having a greater percentage of conductive yarn in one orientation; selecting an adhesive; applying the adhesive to the fabric; constructing a composite structure by arranging the adhesive coated fabric around the selected core; heating the composite structure to melt the adhesive such that the fabric will adhere to the core; and after said heating step, shaping the composite structure by drawing it through a die.

24. The method according to claim 23, further comprising, after said shaping step, cooling the composite structure.

25. The method according to claim 23, wherein forming the fabric includes weaving the conductive yarn and the nonconductive yarn, the greater percentage of conductive yarn being in a filling direction of the fabric.