APPARATUS FOR DETECTING THE PASSAGE OF MULTIPLE DOCUMENTS

Abstract: An apparatus for detecting the passage of multiple documents (10) in a transport system, including a pair of rollers (20, 22) between which said documents (10) are arranged to pass and which are displaceable by an extend dependent on the thickness of one document or multiple documents simultaneously passing therebetween. This displacement is measured by the movement of a graded density translucent member (34) between the photodiode (46) and sensor (40) of a detector (36). Electronic circuitry associated with the detector (36) indicates the presence of a record member (10) between the rollers (20, 22), and also the presence of multiple record members (10). The graded density of the member (34) allows the circuitry to detect only the displacement from the static position of the rollers (20, 22) eliminating the necessity for adjustment due to wear, temperature, and other mechanical factors.

Description: APPARATUS FOR DETECTING THE PASSAGE OF MULTIPLE DOCUMENTS Technical Field This invention relates to an apparatus for detecting the passage of multiple documents in a trans¬ port system. The invention has application, for example, to an apparatus which monitors a currency dispenser in order to detect the simultaneous feeding of multiple bills. Background Art With the acceptance of automated financial terminals increasing rapidly, the role of .the currency dispenser is growing more significant. Today terminals of this type, such as the device disclosed in U.S. Patent No. 4,168,058, serve in an important capacity in the business and financial communities. A major function of any currency dispenser is to remove bills from a stack and present them one at a time to a transport mechanism for delivery to the cus- tomer. This function may also be deemed the most criti¬ cal, since problems in delivering the bills, such as failure to feed or the feeding of more than one bill at a time, generally begin at this stage. Because of the wide disparity in bill quality, ranging from new, crisp bills to limp, torn ones, as well as the occurrence of foreign matter between bills, preventing their separa¬ tion, it is not possible to achieve perfect performance. Therefore, it is important to detect the problem situ¬ ation and take corrective action immediately, such as the activation of a diverter gate, to capture the erron¬ eously fed bills. A number of different techniques have been used in the past for detecting the presence of multiple bills or other documents in a transport system. These systems use mechanical, electrical, or optical devices, OA'.PI or a combination thereof, to sense the presence of multiple bills. Overall performance of a doubles detec¬ tor, however, depends heavily on the means of determin¬ ing if a document has been fed, and if so, whether it was a single document. A double document detector is described in the IBM Technical Disclosure Bulletin, Vol. 7, No. 8 of January 1965, in which the documents are arranged to pass between a pair of cooperating rollers. One of the rollers has an arm attached thereto and is displaceable relative to the other by an extent dependent on the thickness of the documents passing between the rollers. If a single document passes between the rollers, the arm is moved from the home position to a position in which it will not prevent light from passing through an aperture to impinge upon a light sensitive element. When overlapped documents pass between the rollers, the arm is moved to a position to cover the aperture and prevent light from reaching the element, thereby indi- eating an overlapped document condition. A disadvantage of this arrangement is that static changes in the position of the rollers, caused by wear, elasticity or accumulation of foreign matter, may result in a drift of the operating range of the system causing erroneous operation. Disclosure of the Invention It is an object of the present invention to provide an efficient multiple document detector with a simple, low cost, design in which the above disadvantage is alleviated. Thus, according to the invention, there is provided an apparatus for detecting the passage of mul¬ tiple documents in a transport system, including a gaug¬ ing means through which documents are arranged to pass, said gauging means being displaceable by an extent de¬ pendent on the thickness of one document or multiple documents passing therethrough, characterized by detec¬ ting means which is coupled to said gauging means and which is arranged to produce an output which progres¬ sively varies in response to a displacement of said gaug- ing means, and circuit means, responsive to said detec¬ ting means, for producing an indication of whether multiple documents have simultaneously passed through said gauging means. Brief Description of the Drawings One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic view illustrating certain components of a currency dispenser; Fig. 2 shows a partial sectional view of the currency dispenser taken along the line 2-2 of Fig. 1; Fig. 3 is a schematic diagram of the monitoring circuitry of the currency dispenser; Fig. 4 shows the unfiltered waveform of a single bill passing through the currency dispenser with its leading edge folded over; Fig. 5 shows the unfiltered waveform of a double bill passing through the currency dispenser; Fig. 6 shows the waveforms of several bills as inputs to the doubles detection comparator; Fig. 7 shows the waveforms of several bills as » inputs to the presence detection comparator; Fig. 8 is a graph of the output voltages of several detectors versus displacement of the film strip; Fig. 9 is a graph of the normalized output voltage of several detectors versus displacement of the film strip from the energized center position. Best Mode of Carrying Out the Invention Referring now to Fig. 1, there are shown cer- tain components of a currency dispenser. Currency bills O PI ,* A , 1PO or other documents 10 are urged against a table 12 by spring 13 for feeding. A pair of spaced-apart driving wheels 14, each located between two adjacent arms of an assembly 16, are fixed to a shaft 18 to be driven there- by. During the feeding operation, currency 10 is urged by driving wheels 14 between a pair of rollers 20 and 22. Preferably, both rollers are composed of an alumi¬ num core with a polyurethane covering. Feed roller 20 is fixed at the end of a motor shaft 24, which rotates at a surface speed of 250 centimeters per second. Idler roller 22 is rotatably mounted on a short shaft 26, which freely rotates in the arms of assembly 16. Arm assembly 16 is pivotally mounted on a shaft 28 and tensioned by a spring 30, which spring is' attached to arm assembly 16 at connecting pin 32. The opposite end of spring 30 is attached to a short shaft 33. Spring 30 applies a force on arm assembly 16 such that roller 22 is urged into cooperating engagement with roller 20. For a more detailed description of the above-described structure, reference is made to the previously-mentioned U.S. Patent No. 4,168,058. As currency 10 is fed between rollers 20 and 22, roller 22 is forced away from roller 20 a distance equal to the thickness of the currency 10, causing arm assembly 16 to pivot about shaft 28, and displacing the bottom of arm assembly 16 in the direction toward roller 20. In the present embodiment, the distance between shaft 28 and the bottom of arm assembly 16 is three times greater than the distance between shaft 28 and shaft 26; therefore, the bottom of arm assembly 16 is displaced toward roller 20 three times further than roller 22 is moved away from roller 20 when currency 10 is fed between rollers 20 and .22. Consequently, when using U.S. currency, which has a normal average thickness of 0.010 centimeters, the bottom end of arm assembly 16 will travel approximately 0.030 centimeters when a single bill passes between rollers 20 and 22. O.v.P A processed photographic film strip 34 is bonded along a protrusion 35 on the end of arm assembly 16. Film strip 34 is attached to arm assembly 16 such that it moves between the light source and sensor of a detector module 36 as the bottom end of arm assembly 16 is displaced. Since film.strip 34 is processed in such a manner as to exhibit a relatively rapid change in optical density in a direction parallel to its length, the described motion of arm assembly 16 will change the amount of light activating the sensor of module.36. Thus, the electrical output of detector 36 is relative to the position of arm assembly 16. In the present embodiment, the currency dis¬ penser monitor is used to detect the presence of a single bill in addition to sensing the presence of multiple bills. However, due to several different factors, the home position of rollers 20 and 22 may change. ' Causes for the position drift may be variations in the resilience of the polyurethane surface covering of the rollers, wearing of the surfaces, ink deposits from the bills, wear in the bearings, or changes in ambient temperatures which cause expansion or contraction of the machine base and components. Experimental analy¬ sis of this home position drift indicates that it may shift plus or minus 0.075 centimeters from its initial position. Therefore, assuming a 0.075 centimeter dis¬ placement being necessary for detecting multiple bills, a linear measurement range of 0.225 centimeters is pre- ferred for satisfactory operation of the doubles detec- tor. In the preferred embodiment, for cost consid¬ erations it is desirable to use a low-cost and commer¬ cially-available component in the circuit of detector 36 which is pre-aligned, and has a sufficiently high elec- trical output to provide direct drive of the associated electronic circuitry. A satisfactory component is General Electric type H13B1 photon-coupled interruptor module, which is composed of a gallium arsenide solid- state lamp illuminating a silicon photo-darlington sensor across an air gap of 0.318 centimeters. This component and the film strip provide the entire optical system for the present currency dispenser monitor. These detector units, however, have an active optical area of only 0.050 to 0.075 centimeters. There¬ fore, if the film strip contained a sharp opaque/trans¬ parent transition line, the desired range of 0.225 centi- meters could not be reached. To expand the operating range, an incrementally graded density film strip is used. A method and apparatus for producing such a film strip is disclosed in an international application filed by the present Applicants on the same day as the present application entitled "Method and Apparatus for Fabricating a Translucent Graded Density Medium" (NCR Docket No. 2905) . The film strip having a substantially linear density gradient enables the detector to operate over a greater travel distance. Any movement of the film will cause a change in the intensity of light which the sensor of the detector receives; therefore, the length of the filmstrip determines the operating range of the detector. Fig. 3 shows the electronic circuitry which, taken together with detector 36, comprises the monitor control. A phototransistor 40 contained within detector 36 acts as a variable resistor between the supply voltage 42, which is filtered by capacitors 43 and 44, and line 45. The resistance of phototransistor 40 is controlled by illumination emitted by a photodiode 46 also contained within detector 36. As the illumination from photodiode 46 increases when film strip 34 is moved in one direction within the air gap between the components of detector 36, the circuit voltage becomes more positive across a resistor 47 with respect to ground 48. The voltage on _ Q . " line 45 is also applied to a filtering combination of resistor 49 and capacitor 50. The coupling capacitor 50 blocks the DC component of the voltage at 45, which voltage is proportional to the quiescent position of film strip 34, arm assembly 16, and roller 22, allowing the circuit to respond only to changes in the position of film strip 34 between the components of detector 36. Thus, the circuit of Fig. 3 is independent of the static position of rollers 20 and 22, and reacts only to a physical movement of roller 22, which also causes move¬ ment of arm assembly 16 and film strip 34; mechanical drift of the static roller position will not affect the proper operation of the circuit. Current to operate photodiode 4'6 is supplied from a voltage regulator 51 via a potentiometer 52. Regulator 51 may be an integrated circuit chip, such as Motorola Type MC1723CL or its equivalent, and serves to insure a sufficient calibrated current supply to photo¬ diode 46 for proper operation. Regulator 51 and its associated components (resistors 54, 56, 58 and capaci¬ tor 60) may be eliminated if the power supply used to drive the circuit is sufficiently stable. The output 61 of regulator 51, which is ap¬ proximately 8 volts, is applied to another portion of the detection circuitry via resistors 62 and 64 and a diode 66. Diode 66 tends to hold the voltage across resistor 64 on the cathode of capacitor 50, which pro¬ vides a fast recovery from the charge condition on capacitor 50. The voltage at 68 is applied to the non-inver¬ ting input 69 of a differential comparator 70 via an integrating network of resistor 72 and capacitor 74. Comparator 70, which may be a Motorola type MC1414L or its equivalent, detects the presence of more than one bill between rollers 20 and 22. The reference voltage for the inverting input 75 of comparator 70 is generated when the supply voltage at 42 is transmitted across a series combination of a resistor 78 and a zener diode 80. The voltage present across zener diode 80, which is approximately 3.3 VDC, is transmitted to the strobe input 81 of comparator 70, and also to input 75 via a resistor 82 and a potentiometer 84. Potentiometer 84 makes it possible to adjust the reference voltage for input 75 to a desired level for precise detection of a single bill thickness. Thus, when the voltage at input 69 exceeds the reference voltage at 75 by a few milli- volts, indicating that a doubles condition has occurred, comparator 70 outputs a fast rising TTL compatible signal at terminal 86 across a load resistor 88. Detection of the presence of a single bill is accomplished in a similar manner. The voltage at 68 is applied to the non-inverting input 90 of a differential comparator 92 via an integrating network of a resistor 94 and a capacitor 96. Comparator 92 may be a Motorola type MC1414L or its equivalent. The reference voltage across zener diode 80 is applied to the strobe input 97 of comparator 92, and also to the inverting input 98 via a resistor 100 and a potentiometer 102. Potentiometer 102 adjusts the reference voltage for input 98 to a desired level such that the signal received at input 90 exceeding this reference voltage is indicative of one or more bills passing between rollers 20 and 22. Thus, when the voltage at input 90 exceeds the reference voltage at 98 by a few millivolts, comparator 92 outputs a signal to terminal 104 across a load resistor 106, indicating the presence of at least a single bill between rollers 20 and 22. The necessity for the integrating network of resistor 72/capacitor 74 is illustrated by the waveforms shown in Figs. 4 and 5. Fig. 4 shows the waveform of the voltage at 68 when a single bill with the leading edge folded back approximately one-half inch is inserted between rollers 20 and 22. The initial bounce caused as the bill enters rollers 20 and 22 is of sufficient "BURE O PΪ amplitude to trigger comparator 70, which would output a false double detection signal. As a comparison, Fig. 5 shows the waveform of the voltage at 68 when a double bill travels between rollers 20 and 22. The signal in Fig. 5 shows the initial bounce caused by the double bill entering rollers 20 and 22, but the signal also remains at a sufficient level for triggering comparator 70 for a longer time period, due to the extra thickness along the entire length of the bill. When the inte- grating network is used, the initial bounce is softened, allowing comparator 70 to detect only true double bills. Fig. 6 shows waveforms of the signals gener¬ ated by various bills at input 69 to comparator 70, which signals have been smoothed by the integrating network of resistor 72/ capacitor 74. Line 110 repre¬ sents the double detection threshold; any signal rising above this will trigger comparator 70. Signal 112 represents a double bill with its leading edge folded back approximately one-half inch; it is readily detected by comparator 70. Signal 114 shows a double bill; it is also detected by comparator 70. Signal 116 represents a single bill with its leading edge folded back approximately one-half inch; the inte¬ grating network has filtered the signal so that it will not cause comparator 70 to falsely trigger. Signal 118 shows the waveform for an unfolded single bill; it also is not great enough to activate comparator 70. Finally, the idle noise of the circuitry is represented by signal 120. A lesser degree of integration is provided by the integrating network of resistor 94/capacitor 96, which balances the signal to eliminate noise pulses from mechanical shock, and yet preserve the pulse width as a means of detecting the time of bill entry and removal from rollers 20 and 22. Fig. 7 shows waveforms of the signals generated by various bills at input 90 to com¬ parator 92, which signals have been smoothed by the integrating network of resistor 94/capacitor 96. Line 121 indicates the present detect threshold; any signal rising above this will trigger comparator 92. Signal 122 represents a double bill, signal 124 represents a single bill with the leading edge folded back one-half inch, and signal 126 represents an unfolded single bill. As shown in Fig. 7, these three signals are sufficiently high enough to surpass the present detection threshold, triggering comparator 92. Signal 128 represents idle noise picked up by the cir¬ cuitry; it is not strong enough to activate comparator 92. Due to the fact that commercially available pre-aligned detector modules do not necessarily exhibit precisely identical characteristics, the operating curves of different detectors may vary. Fig. 8 is a graph showing curves 140 and 142 representing the output voltages of two detectors with respect to the displace¬ ment of the graded density film strip which is used in the currency dispensor monitor. The graphs show that as the distance from the dark-to-light transition area of the film strip increases the output voltages of the detectors increase in a linear fashion. To achieve uniform results from the monitor using commercially available detectors, it is necessary to normalize the output of the detector at a known point in the linear region of its operating curve. Referring to Fig. 8, it can be seen that if the film strip is "centered" at a displacement of 0.317 centimeters, a linear operating range of 0.254 centimeters can be easily obtained from curves 140 and 142. Using the displacement of 0.317 centimeters, each detector can be normalized in the circuitry of Fig. 3 by adjusting potentiometer 52 until the current through photodiode 46 of the detector module 36 reaches a prescribed level while the output voltage of the phototransistor 40 is held at a fixed level. The current level was analytical¬ ly and experimentally determined to be 590 microamps using a 4 volt output across phototransistor 40. The normalized operating curves 140a and 142a of the detec¬ tors used in Fig. 8 are shown in Fig 9. The graph of Fig. 9 plots the normalized detector output against the "centered" or normalized position of the film strip. Curves 140a and 142a show that, over a 0.254 centimeter range (+_ 0.127 centimeters from the normalized position), the output voltages of two commercial detectors can be normalized to obtain a uniform response. Typical values of the components of the cir¬ cuit of Fig. 3 may be as follows: Resistors Value 82,88,100,106 . IK ohms 72,47,94,58 6.8K ohms 78 390 ohms 49 33K ohms 64 750 ohms 62 7.5K ohms 54 680 ohms 56 820 ohms Capacitors Value 43 .01 microfarads 44,74 4.7 microfarads 50 15 microfarads 96 1 microfarad 50 100 picofarads Potentiometers Value 52, 84, 102 500 ohms Diodes Value 80 1N748A 66 1N906

Claims: CLAIMS : 1. An apparatus for detecting the passage of multiple documents (10) in a transport system, in¬ cluding gauging means (16, 20, 22) through which docu¬ ments (10) are arranged to pass, said gauging means (16, 20, 22) being displaceable by an extent dependent on the thickness of one document or multiple documents passing therethrough, characterized by detecting means (34, 36) which is coupled to said gauging means (16, 20, 22) and which is arranged to produce an output (45) which progressively varies in response to a displacement of said gauging means (16, 20, 22), and circuit means (70, 92), responsive to said detecting means (34, 36), for producing an indication of whether multiple documents (10) have simultaneously passed through said gauging means (16, 20, 22). 2. An apparatus according to claim 1, char¬ acterized in that said detecting means (34, 36) includes control means (34) which is attached to said gauging means (16, 20, 22) and which is arranged to vary the output (45) of said detecting means (34, 36) in depen¬ dence on the magnitude of displacement of said gauging means (16, 20, 22). 3. An apparatus according to claim 2, char¬ acterized in that said gauging means (16, 20, 22) in¬ cludes a pair of cooperating rollers, between which the documents (10) are arranged to pass, comprising a first fixed roller (20) and a second roller (22) movable with respect to said first roller (20), said control means (34) being mechanically coupled to an arm (16) carrying, and movable with, said second roller (22). 4. An apparatus according to claim 2, char¬ acterized in that said control means (34) is a member of ""BUK A PI 4. ( concluded ) varying translucency and is arranged for movement between a light source (46) and a light sensing means (40) in¬ cluded in said detecting means, in dependence on dis¬ placement of said gauging means (16, 20, 22), the arrangement being such that said light sensing means (40) produces an output (45) the magnitude of which varies in response to movement of said control means (34). 5. An apparatus according to claim 4, char¬ acterized in that said control means (34) is a trans¬ lucent member of graded optical density. 6. An apparatus according to claim 5, char¬ acterized in that the optical density of said control means (34) is graded linearly. 7. An apparatus according to claim 4, charac¬ terized in that said light source (46) is a photodiode, said light sensing means (40) is a phototransistor and said control means (34) is a strip of photographic film having a graded optical density. 8. An apparatus according to claim 1, char¬ acterized in that said circuit means (70, 92) is res¬ ponsive to said output (45) from said detecting means (34, 36) for generating a plurality of signals (86, 104) indicative of certain conditions as the documents (10) pass through said gauging means (16, 20, 22). 9. An apparatus according to claim 8, char¬ acterized in that said circuit means (70, 92) generates a first signal (86) corresponding to a condition wherein multiple documents (10) simultaneously pass through said gauging means (16, 20, 22), and a second signal (106) corresponding to a condition wherein at least a single OKPI_ _. WWiiPPOO 9. ( concluded ) document (10) passes through said gauging means (16, 20, 22). 10. A currency dispenser incorporating an apparatus according to any one of the preceding claims, characterized in that said circuit means (70, 92) is arranged to give an indication of whether multiple cur¬ rency bills have simultaneously passed through said gauging means (16, 20, 22). '

Inventors: GRANZOW R, HORST W
Applicants: NCR CO, NCR CORP
Application year: 1980
Main classification: B65H7
IPC codes: B65H7