Methods of measuring currency limpness

Abstract: Measuring the limpness of a note is necessary to separate a worn note out of circulation. A method of measuring the limpness of a note is disclosed which measures the response of the note to an acoustic wave.

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to methods of measuring the limpness of currency. Specifically, the currency, in the form of paper notes, is subjected to a test or a series of tests to determine if it has worn beyond an acceptable level of limpness. BACKGROUND OF THE INVENTION Automated, high-volume currency processing is a growing international industry affecting numerous aspects of the distribution, collection, and accounting of paper currency. Currency processing machines can be designed to detect numerous features of currency notes that pass several detectors on a conveyor in order to sort the currency and identify counterfeit or reject notes. For example, prior art currency processing machines are capable of detecting various physical characteristics of notes such as soiling level, optical quality, rips and tears, and can quantify missing portions of the notes. Data collected by detecting one or more of these physical characteristics can be compared to a set fitness standard when determining if an individual note should be rejected, and thereby taken out of circulation, or sorted for future distribution. Currency notes are typically embedded with fibers, for example cotton fibers and wood pulp, giving the note a certain level of rigidity or stiffness. As the note is placed in circulation and manipulated while in use, the fibers gradually break down and the note loses its rigidity, or, conversely, the limpness of the note increases with use. Limp notes pose a number of problems in commerce. For example, limp notes can jam or tear in automatic currency handling devices. Likewise, torn currency poses a problem for merchants who do not want to risk accepting currency that is not negotiable. It may be more difficult to detect counterfeit notes from authentic currency if the notes are badly worn and limp. Therefore, a need exists for a method of testing currency for limpness. By developing a method for determining the limpness of a single note, a currency processing machine could be used to incorporate this method with other tests for physical characteristics of a note to more accurately determine if a note should be pulled from circulation. The single parameter of a note limpness could also provide a standard for rejecting a note. With this new detection method of quantifying the limpness of a note, currency distributors would also have a tool for monitoring the average lifespan of notes in circulation by comparing limpness measurements with the date of initial circulation of notes processed. The present invention provides various methods for determining the limpness of a note and, thereby, addressing the many needs for determining this physical characteristic. US 4 519 249 discloses an apparatus for detecting the condition of a sheet or web. It makes use of acoustic waves directed on the sheet and a detector detecting reflected waves. It is also disclosed an arrangement that measures acoustic waves in transmission. The focus is primarily on detection of tears or pins, but also crinkles can be detected. The detected signals pass through a differentiator, a spike filter, an integrator and a threshold comparator. SUMMARY OF INVENTION Several methods have been developed to measure the relative limpness of a note. There is no absolute value for limpness above which an issuing authority will pull a note from circulation. Instead, a value can be determined which is relative to a new note or some other standard. Its ability to reflect or transmit acoustic waves can be measured. In each of these methods, the performance of a worn, limp note differs from the performance of a new, stiff note. These methods can be used alone or in combination. Further, any single test can be applied several times to different areas of the same note. By accumulating more than a single test result, the likelihood of separating an acceptable note or passing a limp note will be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: Figures 1a and 1b illustrate a new and stiff note of currency and a worn note, respectively; and Figure 2 illustrates the use of an acoustic source and detector to measure the limpness of a note; DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The present invention relates to methods of determining the limpness of currency. The currency of many nations is commonly printed on special papers which are resilient and difficult to duplicate. The paper currency, when initially printed, is very stiff. This stiffness is the result of long fibers embedded in the paper. For example, many currencies use papers with cotton fiber content. These cotton fibers provide much of the strength and stiffness to the note. However, during use, the note will be folded and crumpled and otherwise handled roughly. This rough handling will over time break down the embedded fiber, resulting in a note that is noticeably limper than new currency. Figure 1a illustrates a new, stiff note 10. The note contains fibers which are mixed throughout the thickness of the note. The fibers are not necessarily oriented in any particular direction. But, the sum of their individual stiffness results in the overall stiffness of the note. Figure 1b illustrates a similar note 10a which has been used in circulation. Over time the note will develop crinkles 11 along which embedded fibers have become weakened or broken. Eventually, the entire note may become soft and limp as numerous embedded fibers are worn down and broken. The limpness of the note makes it less suitable for use in commerce. It is more likely to tear or jam in automatic currency handling devices. Limp notes are also more susceptible to tearing in ordinary use and are generally less durable than stiff notes. Thus, it is desirable to remove limp notes from circulation. Figure 2 illustrates a method of measuring limpness by testing the response of the note 10 to an acoustic source 24. The acoustic source 24 will produce an acoustic output wave 26 which will impact the surface of the note 10. The wave will be partly absorbed, and also partly reflected. The reflected portion 28 can be detected by a detector 30. The limper a note, the more energy it will absorb from the acoustic wave 26. This results in a lower relative output from the acoustic detector 30. A suitable acoustic wave source would be a piezoelectric transmitter receiver pair. A currency processing apparatus for measuring the limpness of notes would necessarily transport the notes from a first location to a second location while performing the tests and separating the limp notes from the stiff notes. The currency processing apparatus would have a transport mechanism, which takes the note between various test locations. The apparatus could utilize any single one of the above mentioned tests by itself or in combination with any of the other tests. For example, a deflection test could be coupled with the acoustic response test. A combination of tests could produce a more complete separation of limp notes. Further, any one of these test could be performed on more than one test area on the note. This would take into account variations across the surface of the note. Although preferred embodiments of the present invention have been described in the foregoing Detailed Description and illustrated in the accompanying drawings, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention. Accordingly, the present invention is intended to encompass such rearrangements, modifications, and substitutions of parts and elements as fall within the scope of the appended claims.

Claims: A method of measuring the limpness of a currency note comprising the steps of: (a) emitting an acoustic wave so that the wave is incident on the note; (b) measuring a portion of the acoustic wave reflected off the note; and (c) determining the limpness of the note from the measured portion of the acoustic wave. The method of Claim 1 wherein step (a) comprises emitting an acoustic wave with a piezoelectric transmitter. The method of Claim 1 or 2 wherein step (b) comprises measuring the reflected portion with an acoustic receiver.

Inventors: KAYANI SOHAIL, KAYANI, SOHAIL
Applicants: CURRENCY SYS INT INC, CURRENCY SYSTEMS INTERNATIONAL, INC.
Application year: 1997
Main classification: G07D7
IPC codes: G01N25, G07D7, G01N29, G01N27