Shielded Money Clip
Kind Code:

A money clip is disclosed with RF shielding characteristics to prevent skimming of stored magnetic and/or digital data in credit cards, quick pay devices, and other items that include magnetically stored personal data. The clip is formed of multiple layers of carbon cloth arranged to prevent transmission of radio frequencies in the range used to acquire the data. The layers are formed using a resin to bind the layers and the formation process resists the introduction of air into the device. The clip is strong enough to resiliently hold money, credit cards, and the like without losing its shape, and the shielding properties protect the contents for unauthorized data acquisition.

Styron, Glenn (Long Beach, CA, US)
Cox, Morgan (Long Beach, CA, US)
Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
24/67.3, 24/67.9, 150/131, 150/147
International Classes:
A45C1/00; A45C11/18
View Patent Images:
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Primary Examiner:
Attorney, Agent or Firm:
We claim:

1. A clip for retaining money, credit cards, and the like, comprising a single plate folded into a clip structure having a first and second ends opposed to one another, said first and second ends resiliently biased to form a small gap therebetween for retaining said materials with magnetically and/or digitally stored information, said plate having: a first layer of carbon cloth having a cross hatch pattern of carbon fibers; a second layer of carbon tape having a unidirectional orientation of carbon fibers; and a third layer of carbon cloth having a cross hatch pattern of carbon fibers.

2. The clip of claim 1 further comprising a fourth layer of copper wire mesh disposed between said first and third layers.

3. The clip of claim 1 wherein said first layer of carbon cloth and third layer of carbon cloth have a density of 200 grams per square meter.

4. The clip of claim 1 wherein the first layer of carbon cloth and the third layer of carbon cloth are arranged in a twill pattern having two weft and two warp threads.

5. The clip of claim 1 wherein the second layer of carbon fiber tape has a density of 150 grams per meter squared to 250 grams per meter squared.

6. The clip of claim 1 wherein a combined weight of the first, second, and third layers combined have a density in a range of 600 grams per meter squared to 650 grams per meter squared.

7. The clip of claim 1, wherein the plate comprises no more than four layers.

8. The clip of claim 1, wherein an orientation of carbon fibers in said second layer is perpendicular to a longitudinal direction of the spine.

9. The clip of claim 1, further comprising a resin layer disposed between said first and second layers and between said second and third layers.

10. The clip of claim 9 wherein the resin is selected from epoxy and polyester.

11. The clip of claim 9 wherein the concentration of resin to carbon cloth is in a range of 25 to 45 percent.

12. The clip of claim 1 further comprising an absence of trapped air between said first and third layers.



The present invention is related to clips carried in pockets or the like and used to store cash, credit cards, and other valuables, and more particularly to a clip that uses one or more protective carbon and RF shielding sheets to shield the data held in the contents of the clip from unauthorized pirating while protecting the contents with a sturdy, robust structure.

Money clips are well known in the art. Favored by men who prefer a slim profile without the bulk of a wallet, money clips are typically carried in a front or back pocket and used to hold cash, credit cards, and other valuables. The clip has a resilient tongue member that presses against a spine to capture currency. Examples of such clips can be seen in U.S. Pat. No. D283,844, U.S. Pat. No. 4,674,953, U.S. Pat. No. D400,466, and U.S. Pat. No. 6,327,749.

Security issues have arisen in connection with the storage of newer generation credit cards. These credit cards have personal data magnetically and digitally stored on the card, including the owner's name, credit card number, expiration data, and even the address or social security number of the card holder. Because this information is stored magnetically and digitally, the information can be acquired or stolen by a device placed in proximity with the credit card using radio frequency (RF) waves, called “skimming.” The RF waves can pass through clothing and even leather to skim information from credit cards or other cards carried in a wallet or purse without the owner's consent or even knowledge. This stolen information can then be used to purchase items over the internet and the like, and the card holder is unaware that his or her information has been stolen until the bill arrives sometime later.

Radio-Frequency Identification (RFID) is a general term for small, wireless devices that emit unique identifiers upon interrogation by RFID readers. One form of an RFID device that is expected to gain popularity in the near future is known as an EPC (Electronic Product Code) tag. They are sometimes viewed in effect as wireless barcodes, i.e., they provide identification, but not digital authentication. The term RFID, however, denotes not just EPC tags, but a spectrum of wireless devices of varying capabilities. More sophisticated and expensive RFID devices can offer cryptographic functionality and therefore support authentication protocols. One of the most popular of such devices is known as a Digital Signature Transponder (DST). Manufactured by Texas Instruments, DSTs are deployed in several applications that are notable for wide-scale deployment and the high costs (financial and otherwise) of a large-scale security breach. These include electronic payment devices such as in the Exxon-Mobil SpeedPass™ system, Mastercard's Paypass™ system, American Express' ExpressPay™ system, and Visa's payWave™ system.

A DST consists of a small microchip and antenna coil encapsulated in a plastic or glass capsule, or implanted into a credit card. It is a passive device, which is to say that it does not contain an onboard source of power, but rather receives its power via electromagnetic inductance from the interrogation signal transmitted by the reading device. This design choice allows for a compact design and long transponder life. A DST contains, for example, a secret, 40-bit cryptographic key that is field-programmable via RF command. In its interaction with a reader, a DST emits a factory-set (24-bit) identifier, and then authenticates itself by engaging in a challenge-response protocol. The reader initiates the protocol by transmitting a 40-bit challenge. The DST encrypts this challenge under its key and, truncating the resulting ciphertext, returns a 24-bit response. It is thus the secrecy of the key that ultimately protects the DST against cloning and simulation.

Recent developments in the field of cryptology have allowed the reverse engineering of the key, enabling anyone with a scanner to retrieve the information off the DST and use the information for improper purposes. This can lead to identity theft, larceny, and other assorted events that the user would like to avoid. The present invention is directed to a device for diminishing the risk of skimming and other forms of illicit data acquisition by blocking the radio frequency energy that powers the DST or other data storage device, preventing the transmission of personal data.


The present invention is a money clip that resists skimming and other forms of data acquisition using a combination of carbon layers with or without RF blockers such as a copper wire mesh, to block RF transmission. A carbon fiber matrix is created in a vacuum environment to prevent air voids from impregnating the material. Alternating layers having strands or fibers offset from the surrounding layers to create a barrier that resists the transmission of radio waves. A unidirectional carbon fiber cloth is preferably sandwiched between adjoining cover layers using a resin such as epoxy or polyester to bind the layers. The number of layers is preferably between three and four, where more than four layers can detrimentally affect the tightness of the clip's “spring.” An RF blocker such as a copper screen or wire mesh may also preferably be incorporated into the structure to further resist penetration of RF waves. The resultant composite money clip is lightweight, strong, and resists skimming of information on cards and other devices held therein.


FIG. 1a is an elevated, perspective view of a first preferred embodiment of the present invention;

FIG. 1b is a cross-sectional view of a first preferred embodiment of the present invention;

FIG. 2a is a diagram of an arrangement of carbon layers in a first preferred embodiment;

FIG. 2b is a diagram of an arrangement of a second preferred embodiment including a copper mesh screen layer;

FIG. 3 is a chart showing various results of a load spring test for different material compositions;

FIG. 4 is a plot of the shielding effectiveness for a sample material and sample frequency range; and

FIG. 5 is a plot of the shielding effectiveness of a copper wire mesh for various radio frequencies.


The money clip 10 of the present invention is preferably formed of a single planar member of material that is substantially impenetrable to radio frequency waves in a specified frequency range. The material is formed into a clip 10 having a spine 12 and a tongue 14, as shown in FIGS. 1a and 1b. The tongue 14 is preferably in the range of two to two and one half inches long, and more preferably in the range of two and an eighth to two and a quarter inches. The tongue 14 includes an upwardly turned lip 16 that facilitates the sliding of paper bills, credit cards, and the like into the clip 10. The upwardly turned lip 16 has a distal end 18 having a of slight radial curvature of approximately one third of an inch. The spine 12 is preferably formed of a relatively flat, planar section in proximity with the bottom surface of the tongue 14, and curved slightly toward a juncture 13 between the spine 12 and tongue 14. The juncture 13 is preferably a smooth transition from the respective ends of the spine 12 and tongue 14 to form a radial curvature. The shape of the clip can be stamped from a die out of a single sheet of carbon material, or formed through other known shaping methods.

An exemplary clip will have a width of 1½″ to 2″, measured along the spine and the leading edge of the tongue. The tongue is preferably about 2⅛″ to 2¼″ in length, whereas the upper extension is approximately 1¾″ to 2″ in length. The upturned lip 16 has an angular extension of approximately forty-five degrees from horizontal, and the distance from the upper surface 20 of the spine to the bottom of the lip 16 is approximately 1-4 mm. The radius of the juncture 13 is approximately one sixth of an inch.

A series of carbon laminate sheets are stacked to form the sheet that is shaped into the present invention. The carbon sheets are held together with a resin (not shown) such as polyester or epoxy, where epoxy has more preferable traits. The formation of the sheet can be by a wet laminate process whereby dry carbon fiber cloth is coated with resin that is applied to the material at the time of formation or pre-impregnated with the resin. In a preferred embodiment, the resin concentration is approximately 25%-45%, maintaining the preferred fiber arrangement set forth below.

The layers of woven carbon fiber cloth have been shown to provide sufficient shielding of radio frequency waves for frequencies common to the application at hand. As shown in FIG. 2a, a preferred orientation of a woven cloth 40 includes a first row of fibers 44 arranged in a parallel configuration, adjacent a second row of fibers 46 arranged perpendicular to the first row of fibers. Other woven patterns can include alternating fibers in perpendicular directions, or variations thereof. The clip 10 of the present invention preferably includes two such layers 40, 60. This cross-hatched pattern incorporates a 200 g/M2 twill weave (two weft, two warp threads). A preferred construction of the clip 10 of the present invention also includes a unidirectional carbon fiber tape 22 sandwiched between two layers of carbon cloth 24, or “twill.” The unidirectional tape 22 is preferably oriented traverse to the longitudinal direction of the spine 12 of the clip 10, and further serves to reinforce the shape of the clip. The unidirectional carbon fiber cloth can be 150 g/M2 to 250 g/M2, but can be lower if the surrounding cloth is heavier to offset the heavier twill or vice versa. The arrangement of the outside cloth 40, 60 in a cross-hatch pattern in combination with the unidirectional tape 22 serves to block the malicious radio frequency waves from penetrating the clip 10.

It is preferred that no more than four layers of carbon fiber are used to form the sheet, as the resiliency of the clip becomes compromised as it becomes thicker with excess layers. That is, the ability to slip money and credit cards into the clip becomes more difficult as the number of layers exceeds four due to the rigidity of the clip. Where four layers of material are used, it is preferred that the cloth weight is reduced to between 600-650 g/M2 for the carbon fiber matrix weight.

An alternative embodiment of the clip is shown in FIG. 2b, where a layer of copper wire mesh 70 is incorporated into the composite. The copper wire mesh 70 is a further RF inhibitor, and further restricts the intrusion of RF waves. The copper mesh can be, for example, described as RCMS 1002 nickel metalized non woven mesh sold by Real Carbon LLC of Hood River, Oreg. FIG. 5 illustrates a plot of shielding effectiveness for the wire mesh versus various radio frequencies between 1 kHz and 10 GHz. The plot reflects a greater than 100 dB reduction in transmission for three different wire mesh configurations (16 mesh 0.011 copper, 22 mesh 0.015 copper, and 100 mesh 0.0045 copper) for frequencies less than 1 MHz. Above 1 MHz, the reduction in dB is approximately linear between 1 MHz and 10 GHz, where a 20-30 dB reduction is measured at 10 GHz.

The carbon fiber composite matrix is preferably formed such that no air is introduced into the layers. To ensure that the sheet is free of air voids, the part is subject to pressure during the molding process. Methods for applying pressure include vacuum bag, autoclave, or compression bladder mold, and other such methods that can suitably withstand the necessary strength requirements for shaping the part.

FIG. 3 is a chart showing the failure analysis for several different matrix compositions. Five different samples were tested, including: (a) 200 gram twill/unidirectional tape 949/twill; (b) 200 gram twill/Unidirectional tape/twill; (c) twill/twill, Uni, 200 gram Twill; (d) Twill, uni, Twill Dry (spray glue); and (e) Twill, uni, Twill (wet laminate). The materials were manufactured and tested by Pirate Carbon, Inc. of Long Beach, Calif. Various loads were applied to the five materials to demonstrate the strength and flexibility of the materials, as reflecting in the cracking load and the failure load, where failure is deemed to be permanent deformation or breakage of the part. The twill/unidirectional tape/twill configuration, with or without a fourth twill layer, was shown to be the most effective at resisting cracking and failure. The test also demonstrated that the materials tested in FIG. 3 exceeded that of present day clips by a substantial amount, establishing the effectiveness and suitability of the materials set forth therein for its intended purpose.

The materials tested in the failure analysis were then tested for RF transmittance to determine their effectiveness as RF blockers. The shielding effectiveness (SE) test is used to quantify the shielding characteristics for each material over the frequency range of 1 MHz to 1 GHz. The testing was performed by Stork Garwood Labs, Inc. of Pico Rivera, Calif. 90660. During the SE test, each material was held in place in a pre-cut precision milled aluminum frame with the edges sealed using industrial tape to prevent RF leakage around the edges. The aluminum frame was assembled in an accommodating access port in the bulkhead shared by two adjoining EMC shielded enclosures with ambient RF attenuation (shielding) properties of 70 to 80 dB.

The SE test effort was performed on each material sample from 1 MHz to 1 GHz in the following stages:

    • 1 MHz-25 MHz
    • 13 MHz-14 MHz (RFID scanner critical frequency range)
    • 22 MHz-24 MHz
    • 20 MHz-100 MHz
    • 100 MHz-200 MHz
    • 200 MHz-1 GHz

To determine the SE characteristics of each material sample in numeric terms of decibels (dB) over each frequency range, a reference was first established through the precision milled aluminum frame with no material sample in it. For the frequency range of 1 MHz-25 MHz, two 41″ monopole antennas with matched architecture properties were used: a passive one as a transmitting antenna connected to an RF power amplifier connected to a signal generator; and an active one as a receiving antenna connected to a spectrum analyzer, connected to an x-y plotter. Both antennas were vertically polarized throughout the test effort.

The RF output of the signal generator was adjusted to a fixed power output setting producing a maximum dynamic range (signal to noise ratio) into the RF power amplifier and programmed to sweep continuously and repetitively in 1 MHz resolution increments from 1 MHz to 25 MHz. Each antenna was positioned with its center beam width axis at the geometric center of the hole in the plate accommodating each sample at a distance of approximately one half meter from the plate, thus approximately one meter from the leading edge of each antenna.

The settings on the spectrum analyzer were adjusted to display a usable trace (using continuous and repetitively swept peak maximum hold weighting) expressed in terms of dB μV represented by the dashed line in FIG. 4. Once this standard reference was established and recorded, all signal generator, power amplifier, spectrum analyzer and antenna settings were fixed. Then, each material sample was secured in the aluminum frame, and the resulting signal was displayed (represented by the solid line in the plot of FIG. 4).

The shielding effectiveness (SE) of each material sample was thus calculated using the form:

SE(dB)=Standard Reference Trace(dBμV)−Material Sample Trace(dBμV)

The test was repeated for frequency ranges 13 MHz-14 MHz and 22 MHz-24 MHz.

The test was also repeated in the same way for the frequency ranges of 20 MHz-100 MHz and 100 MHz-200 MHz, using two passive biconical antennas with matched architecture properties: one as a transmitting antenna connected to the RF power amplifier connected to the signal generator; and the other as a receiving antenna connected to the spectrum analyzer connected to the x-y plotter. Both antennas were vertically polarized throughout the test effort. The test was repeated again as above for the frequency ranges of 200 MHz-1 GHz.

The graph above shows the shielding effectiveness for the embodiment of FIG. 2a for frequencies between 2.5 MHz and 1 GHz. It can be seen from the graph that the shielding effectiveness ranges from approximately 25 dB at the lower frequencies to a peak of about 55 dB at the intermediate frequencies, and dropping to about 42 dB at the highest frequencies. The resultant shielding effectiveness reflects a dramatic attenuation of RF frequency intrusion into the clip of the present invention, which is further enhanced by including the copper mesh screen as illustrated in FIG. 2b.

The foregoing descriptions of the preferred embodiments are intended to fulfill the inventor's obligation to disclose the best modes for carrying out the invention, but are not intended to limit the invention to any disclosed embodiment or depictions. Rather, the scope of the invention is properly determined by the appended claims, using the ordinary and customary meaning of the words therein, consistent with the foregoing disclosure. It is recognized that those of ordinary skill in the art would readily come up with modifications and alterations to the above-described embodiments, and such modifications and alterations are properly deemed within the scope of the invention.


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