Method 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 heat capacity of the note.

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method 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 a method for determining the limpness of a note and, thereby, addressing the many needs for determining this physical characteristic. 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. The note's thermal hysteresis can be measured. In this method, the performance of a worn, limp note differs from the performance of a new, stiff note. Further, the 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. US-A-4,723,072 discloses a bank note discriminating apparatus which detects light reflected by or transmitted through the note. According to one aspect of this invention there is provided a method of measuring a limpness of a note comprising the steps of heating a portion of the note to a predetermined temperature, measuring the temperature for that portion after a predetermined time, and determining the limpness of the note from the measured temperature. Preferably the method further comprises calculating a thermal conductivity for the note based upon a difference between the predetermined temperature and the measured temperature. Advantageously the method further comprises correlating the thermal conductivity of the note to a limpness value. 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 limp or worn note, respectively; and Figure 2 illustrates a method of heating a note and measuring its heat capacity to determine limpness. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The present invention relates to a method 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. The method involves a measurement of the heat capacity of the note. In other words, the note's ability to dissipate heat is a function of the notes limpness and wear. In this method, as shown in Figure 2, a portion 10c of the note 10 is heated by a thermal source 42 to a first temperature. At a predetermined time, the temperature of that same portion is measured by a thermal detector 44. The difference in temperature can be translated into a thermal conductivity or hysteresis coefficient for the note. This coefficient is related to the limpness of the note. 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. For the thermal conductivity test discussed above, the note might be heated at the beginning of the process and measured at a second location to allow time for cooling. The currency processing apparatus would have a transport mechanism, which takes the note between various test locations. Further, the 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 re-arrangements, modifications and substitutions of parts and elements without departing from the invention. Accordingly, the present invention is intended to encompass such re-arrangements, modifications and substitutions of parts and elements as fall within the scope of the appended Claims.

Claims: A method of measuring a limpness of a note (10) comprising the steps of: (a) heating a portion of the note (10) to a predetermined temperature; (b) measuring the temperature for that portion after a predetermined time; and (c) determining the limpness of the note (10) from the measured temperature. The method of Claim 1 further comprises: (d) calculating a thermal conductivity for the note (10) based upon a difference between the predetermined temperature and the measured temperature. The method of Claim 2 further comprises: (e) correlating the thermal conductivity of the note (10) to a limpness value.

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