US20060011054A1

US20060011054A1 - Electromagnetically shielded, flexible bomb suppression device

Info

Publication number: US20060011054A1
Application number: US10/867,219
Authority: US
Inventors: Lacy Walthall; Robert Boyd
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-06-15
Filing date: 2004-06-15
Publication date: 2006-01-19

Abstract

A multi-layered flexible shield comprising an RF shielding layer and a ballistic control layer. The RF shielding layer is constructed of a conductive fabric, preferably a copper/nickel woven fabric, and a flexible conductive coating formed of an emulsion coating with high attenuating capabilities, and preferably an electrically conductive and electromagnetic radiation absorptive coating composition. The ballistic control layer has upper and lower sub-layers made of a woven ballistic material and a middle sub-layer made of sheets of a non-woven ballistic material, the ballistic materials being Aramid or high molecular weight polyethylene fibers. A detachable cover formed of a woven ballistic material covers the lower surface of the conductive fabric and protects the RF shielding layer from abrasion and environmental conditions. The outer edge of the bomb suppression device has a weighted, flexible rim that aids in securing the unit to the surrounding surface, thereby electronically isolating the explosive device.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an electromagnetically shielded, portable device for protection against remote detonation of an explosive device, and also having ballistic shielding capabilities.
2. Related Art
As used herein, “ballistic materials” means materials that provide blast-fragment mitigation. The construction of ballistic materials is well known in technology. Typical ballistic materials would consist of multiple layers of a woven or non-woven Aramid, such as Kevlar® or Twaron®, or high molecular weight polyethylene, such as Dyneema® or Spectra®, fibers or fabrics or a combination thereof. As used herein, “Aramid” means a manufactured fiber in which the fiberforming substance is a long-chain synthetic polyamide in which at least 85% of the amide (—CO—NH—) linkages are attached directly between two aromatic rings.
Most ballistic materials have been incorporated in clothing such as flak jackets for protection against ballistic rounds and fragments. Ballistic materials have also been used for the containment of explosive devices. The specific fiber and/or fabric have the ability to absorb the energy of impact of a ballistic projectile as described by Van der Loo (U.S. Pat. No. 5,569,528). Other containment systems often include a metal structure, which are of a set size and, due to the weight, not very portable.
All of the prior art to date addresses the containment of the fragments after the detonation of the blast.
In recent years, the ability to detonate an explosive device from a remote location has become easier. An electronic device as simple as the common cellular phone can be used as a detonation device, which can be activated from a remote location.
Current portable blast suppression devices do not address the protection against remote detonation by a radio frequency (RF) signal.
It is to the solution of these and other problems that the present invention is directed.

SUMMARY OF THE INVENTION

It is accordingly a primary object of the present invention to provide a portable ballistic shield that is lightweight, flexible, and can be easily placed over an explosive device.
It is another object of the present invention to provide a ballistic shield that will give radio frequency (RF) shielding for the prevention of remote detonation.
It is still another object of the present invention to mitigate the use of RF signals to detonate an explosive device.
It is still another object of the present invention to provide a ballistic shield that will have some fragment control capabilities in the instance that an explosive device is not detonated by a RF signal.
These and other objects of the invention are achieved by a multi-layered flexible shield comprising two main components, a RF shielding layer and a ballistic control layer.
The RF shielding layer is constructed using a conductive fabric, preferably a copper/nickel coated polyester woven fabric. A flexible conductive coating is applied to the conductive fabric. The flexible conductive coating is preferably an emulsion coating with high attenuating capabilities, and more preferably, is an electrically conductive and electromagnetic radiation absorptive coating composition.
The ballistic control layer comprises upper and lower sub-layers and a middle sub-layer between the upper and lower sub-layers. The upper and lower sub-layers are made of a woven ballistic material such as a woven Aramid or ultra high molecular weight polyethylene fibers. The middle sub-layer comprises sheets of a non-woven ballistic material such as Aramid or ultra high molecular weight polyethylene fibers in a random orientation.
A thin, protective cover formed of a woven ballistic material is provided as a third component to cover the lower surface of the conductive fabric and protect the RF shielding layer from abrasion and environmental conditions.
The outer edge of the bomb suppression device has a weighted, flexible rim that aids in securing the unit to the surrounding surface, thereby electronically isolating the explosive device.
Other objects, features and advantages of the present invention will be apparent to those skilled in the art upon a reading of this specification including the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which:
FIG. 1 is a diagrammatic, cross-sectional view of a bomb suppression device in accordance with the present invention.
FIG. 2 is a graph of the data in Table 1, illustrating RF attenuation of a conductive coating, and a copper/nickel polyester fabric coated with the flexible conductive emulsion coating, in accordance with the present invention.
FIG. 3A is a top view of a bomb suppression device in accordance with the present invention, with a mock explosive device positioned thereon.
FIG. 3B is a top view of the bomb suppression device of FIG. 3A covering the mock explosive device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.
The present invention relates to an electromagnetically-shielded bomb suppression device 10 that serves as a portable ballistic shield that is lightweight, flexible, and can be easily placed over an explosive device. The invention also provides a ballistic shield that will give radio frequency (RF) shielding for the prevention of remote detonation of an explosive device. In the instance that the explosive device is not detonated by a RF signal, the ballistic shield will have some fragment control capabilities.
Referring to FIG. 1, the bomb suppression device 10 is a multi-layered flexible shield comprising two main components, a RF shielding layer 20 and a ballistic control layer 30.
The RF shielding layer 20 comprises upper and lower sub-layers 22 and 24 (“upper” and “lower” being used herein relative to the orientation of the bomb suppression device 10 when in use). The lower sub-layer 24 is constructed of a conductive fabric, preferably a copper/nickel polyester woven fabric. The upper sub-layer 22 is a flexible conductive coating, preferably an emulsion coating with high attenuating capabilities, applied to the conductive fabric. This conductive coating enhances the RF attenuating properties of the lower sub-layer 24.
The flexible conductive coating for the present invention can be formed of an electrically conductive and electromagnetic radiation absorptive coating composition as disclosed in U.S. Pat. No. 6,576,336, which is incorporated herein by reference as if set forth in its entirety. The conductive coating composition disclosed in U.S. Pat. No. 6,576,336 comprises an emulsion polymer binder, which is a blend of a first emulsion containing a conjugated diene monomer or comonomer, and a second emulsion containing an acrylic polymer. It also contains an effective amount of electrically conductive particles dispersed in the binder, and water as a carrier. The electrically conductive particles include a combination of graphite particles and metal-containing particles, the graphite particles preferably being natural flake graphite and the metal-containing particles preferably being silver or nickel containing particles.
The flexible conductive coating can also be formed of a composition as disclosed in International application Serial No. PCT/US02/07039, filed Mar. 8, 2002 (International Publication No. WO 03/078531), which corresponds to U.S. application Ser. No. 10/358,375, filed Feb. 5, 2003 (U.S. Published Appl. No. 20040028859), both of which are incorporated herein by reference as if set forth in their entirety. As disclosed in International Publication No. WO 03/078531 and U.S. Published Appl. No. 20040028859, the second emulsion of the polymer binder for the conductive coating can be selected from any of an acrylic, aliphatic or aromatic polyurethane, polyester urethane, polyester, epoxy, polyamide, polyimide, vinyl, modified acrylic, fluoropolymer, and silicone polymer, or a combination thereof. Also, the electrically conductive particles for the conductive coating composition can be selected from any of graphite particles, carbon nanotubes, and metal containing particles, or a combination thereof. The graphite particles are preferably natural flake graphite. The carbon nanotubes are preferably 10 to 60 nanometers in diameter and from less than 1 micron to 40 microns in length. The metal containing particles are preferably silver or nickel containing particles; however, other metals may also be employed such as gold, platinum, copper, aluminum, iron or iron compounds and palladium. The metal containing particles are more preferably metal coated ceramic microspheres or metal coated ceramic fibers; however, other metal coated particles may also be employed such as metal coated glass flake, glass spheres, glass fibers, boron nitride powder or flake, mica flakes, and copper flakes.
Preferably, the flexible conductive coating for the present invention includes as the first emulsion a butadiene-acrylonitrile latex. A preferred polymer is a highly saturated butadiene/acrylonitrile copolymer latex available from the Goodyear Tire and Rubber Company, Akron, Ohio (“Goodyear”) as Chemisat LCH-7302X latex. Another preferred polymer is a highly saturated carboxylated butadiene/acrylonitrile latex available from Goodyear as Chemisat LCH-7505X latex. For the second emulsion, a urethane in water emulsion is selected. A preferred urethane in water emulsion is a dispersion of aliphatic polyester urethane polymer in water available from Bayer Corporation. The electrically conductive particles are in the form of silver coated microspheres. Miscellaneous additives comprise water, ethylene glycol monobutyl ether, and dimethylpolysiloxane (defoamer).
The components of the conductive coating composition for the present invention is composed of 30%-50% by weight, and preferably 35%-40% by weight of the urethane emulsion, 5%-20% by weight, and preferably 10%-15% by weight, of the carboxylated butadiene-acrylonitrile, and 15%-25% by weight, and preferably 18%-22% by weight of the silver coated microspheres. The resistivity of the conductive coating composition is 0.1 to 0.5 Ohm/square, and its viscosity is 35-45 seconds #2 Zahn Cup ASTM D 4212.

The data in Table 1, which are represented graphically in FIG. 2, show the RF attenuation of a conductive coating, and a copper/nickel fabric coated with the flexible conductive emulsion coating, in accordance with the present invention. The frequency shielding testing was conducted according to ASTM D4935-99.

TABLE 1


	Coating	Coated Fabric
Frequency (Hz)	SE (dB)	SE (dB)

30000000	60.76275	58.06238
101412500	57.00528	63.62686
201143800	56.22693	60.01981
300875000	55.53969	68.93812
399375000	55.84046	66.08271
500337500	55.67454	69.89711
601300000	59.85375	68.17653
701031300	57.34368	74.29801
800762500	56.11692	64.57983
901725000	59.70403	71.75521
1001456000	55.39363	69.87521
1102419000	59.04003	69.15003
1202150000	59.11301	69.56802
1300650000	59.00401	82.29104
1400381000	58.01009	61.09758
1500113000	58.66769	68.98509
1601075000	65.09308	81.69582
1700806000	57.90765	69.10004
1803000000	63.14693	63.05803
1900269000	66.99431	65.81694
2000000000	61.84815	69.23119

On average, the shielding effectiveness of the enhanced material is greater than 60 dB, which relates to a 1000:1 reduction in signal strength.
The RF shielding layer 20 can be provided with a thin protective cover 40 that covers the lower sub-layer 24. The protective cover 40 preferably comprises a woven ballistic material such as an Aramid or high molecular weight polyethylene. The cover 40 is preferably designed to protect the RF shielding layer 20, and more particularly, the lower surface of the conductive fabric lower sub-layer 24, from abrasion and environmental conditions. It is removably attachable to the lower sub-layer 24 by means of fasteners (not shown), such as hook and loop fasteners, for easy repair or replacement.
The ballistic control layer 30 of the invention preferably comprises a multi-layer construction of upper and lower sub-layers 32 and 34 and a middle sub-layer 36 between the upper and lower sub-layers 32 and 34. The upper, lower, and middle sub-layers 32, 34, and 36 are attached to each other, for example by sewing.
The upper and lower sub-layers 32 and 34 each comprise a woven ballistic material such as Aramid or ultra high molecular weight polyethylene fibers. The middle sub-layer 36 comprises sheets of a non-woven ballistic material such as Aramid or ultra high molecular weight polyethylene fibers in a random orientation, similar to a felt fabric construction. The number of non-woven sheets can vary from one to 40, depending upon the amount of ballistic control desired.
Referring now to FIGS. 3A and 3B, the outer edge of the bomb suppression device 10 has a weighted, flexible rim 50 that aids in securing the bomb suppression device 10 to the surrounding surface, thereby electronically isolating an explosive device 60 placed under it. The rim 50 can be in the form of a sand-filled channel, which is attached to the perimeters of the ballistic control layer 30 and the RF shielding layer 20. The upper surface of the upper sub-layer 32 of the ballistic control layer 30 is preferably reinforced by strong nylon ribbing 32 a with a center sewn loop handle 32 b for easy of use. Preferably, the upper sub-layer 32 of the ballistic control layer 30 is a highly visible color, for example, bright orange, to help identify the system from a distance.
As shown in FIGS. 3A and 3B, because of its flexibility, the bomb suppression device 10 can be draped over an explosive device 60, while the rim 50 secures the RF shielding layer 20 and the ballistic control layer 20 to the surrounding surface.
The bomb suppression device 10 in accordance with the present invention was tested for electromagnetic shielding effectiveness. Testing was conducted on a concrete surface, an asphalt surface, and earth. Testing was conducted with a Portable Attenuation Measurement Set. The Portable Attenuation Measurement Set includes a transmitter to produce a calibrated signal transmission at 900 MHz and a receiver to measure the signal strength or reduction in strength. In each substrate tested, the bomb suppression device 10 in accordance with the invention demonstrated a minimum −40 dB attenuation from a distance of 25 feet. Additional tests were conducted with a Motorola® brand cellular phone being placed under the bomb suppression device 10 and a call being placed to the cell phone. Tests conducted on each substrate showed the bomb suppression device 10 blocked the signal from reaching the cell phone under it and prevented a signal from connecting. When retrieving the cellular phone from underneath the bomb suppression device 10, the display read “no service” in all instances.
Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.

Claims

1. An electromagnetically shielded, flexible bomb suppression device comprising:

a RF shielding layer and

a ballistic control layer.

2. The bomb suppression device of claim 1, wherein:

the RF shielding layer includes a conductive fabric lower sub-layer and a flexible conductive coating upper sub-layer applied to the conductive fabric; and

the ballistic control layer includes upper and lower sub-layers of woven ballistic material and a middle sub-layer of at least one sheet of non-woven ballistic material between the upper and lower sub-layers.

3. The bomb suppression device of claim 2, wherein the conductive fabric is a copper/nickel coated polyester woven fabric.

4. The bomb suppression device of claim 2, wherein the flexible conductive coating is an emulsion coating with high attenuating capabilities.

5. The bomb suppression device of claim 4, wherein the flexible conductive coating is formed of an electrically conductive and electromagnetic radiation absorptive coating composition.

6. The bomb suppression device of claim 2, wherein the woven ballistic material is a material of woven Aramid or ultra high molecular weight polyethylene fibers.

7. The bomb suppression device of claim 2, wherein the non-woven ballistic material is a material of non-woven Aramid or ultra high molecular weight polyethylene fibers in a random orientation.

8. The bomb suppression device of claim 2, wherein the number of sheets of non-woven ballistic material is between one and 40.

9. The bomb suppression device of claim 2, further comprising a thin protective cover of a woven ballistic material covering the flexible conductive coating.

10. The bomb suppression device of claim 9, wherein the cover woven ballistic material is a material of woven Aramid or ultra high molecular weight polyethylene fibers.

11. The bomb suppression device of claim 9, wherein the cover is detachable from the RF shielding layer.

12. The bomb suppression device of claim 1, further comprising a weighted, flexible rim.

13. The bomb suppression device of claim 12, wherein the rim comprises a sand-filled channel.

14. The bomb suppression device of claim 2, wherein the flexible conductive coating includes a first emulsion formed of a butadiene-acrylonitrile latex, a second emulsion formed of urethane in water and silver-coated microspheres.

15. The bomb suppression device of claim 13, wherein said butadiene-acrylonitrile latex, said urethane emulsion, and said silver-coated microspheres are present in the following percentages by weight, 5%-20%, 30%-50% and 15%-25%, respectively.

16. The bomb suppression device of claim 14, wherein said butadiene-acrylonitrile latex, said urethane emulsion, and said silver-coated microspheres are present in the following percentages by weight, 10%-15%, 35%-40% and 18%-22%, respectively.

17. A flexible conductive coating composition for a bomb suppression device, comprising: (1) a butadiene-acrylonitrile latex emulsion; (2) a urethane in water emulsion; (3) silver-coated microspheres; (4) a defoamer; and (5) water.

18. The flexible conductive coating composition of claim 17 comprising: (1) about 5%-20% of said butadiene-acrylonitrile latex emulsion; (2) about 30%-50% of said urethane emulsion; (3) about 15%-25% of said silver-coated microspheres; (4) a defoamer; and (5) about 5.0% to about 25.0% water.

19. The flexible conductive coating composition of claim 18 comprising: (1) about 10%-15% of said butadiene-acrylonitrile latex emulsion; (2) about 35%-40% of said urethane emulsion; (3) about 18%-22% of said silver-coated microspheres; (4) a defoamer, and (5) about 5.0% to about 25.0% water.

20. A method of making an electromagnetically-shielded, conductive fabric which comprises applying a continuous coating to the conductive fabric to be shielded, said coating including the composition of claim 17.

21. A method of making an electromagnetically-shielded, conductive fabric which comprises applying a continuous coating to the conductive fabric to be shielded, said coating including the composition of claim 16, and wherein said fabric is comprised of a combination of woven copper and nickel fibers.