Patent Grant
7213697
The present invention relates to an apparatus and method for sensing coins and other small discrete objects, and in particular to an apparatus which may be used in coin counting or handling.
A number of devices are intended to identify and/or discriminate coins or other small discrete objects. One example is coin counting or handling devices, (such as those described in U.S. patent application Ser. No. 08/255,539, now U.S. Pat. No. 5,564,546, and its continuation application Ser. Nos. 08/689,826, 08/237,186, now U.S. Pat. No. 5,620,079 and its continuation Ser. No. 08/834,952, filed Apr. 7, 1997, and Ser. No. 08/431,070, all of which are incorporated herein by reference). Other examples include vending machines, gaming devices such as slot machines, bus or subway coin or token “fare boxes,” and the like. Preferably, for such purposes, the sensors provide information which can be used to discriminate coins from non-coin objects and/or which can discriminate among different coin denominations and/or discriminate coins of one country from those of another.
Previous coin handling devices, and sensors therein, however, have suffered from a number of deficiencies. Many previous sensors have result in an undesirably large proportion of discrimination errors. At least in some cases this is believed to arise from an undesirably small signal to noise ratio in the sensor output. Accordingly, it would be useful to provide coin discrimination sensors having improved signal to noise ratio.
Many previous coin handling devices, and associated sensors, were configured to receive only one coin at a time, such as a typical vending machines which receives a single coin at a time through a coin slot. These devices typically present an easier coin handling and sensing environment because there is a lower expectation for coin throughput, an avoidance of the deposit of foreign material, an avoidance of small inter-coin spacing (or coin overlap), and because the slot naturally defines maximum coin diameter and thickness. Coin handlers and sensors that might be operable for a one-at-a-time coin environment may not be satisfactory for an environment in which a mass or plurality of coins can be received in a single location, all at once (such as a tray for receiving a mass of coins, poured into the tray from, e.g., a coin jar). Accordingly it would be useful to provide a coin handler and/or sensor which, although it might be successfully employed in a one-coin-at-a-time environment, can also function satisfactorily in a device which receives a mass of coins.
Many previous sensors and associated circuitry used for coin discrimination were configured to sense characteristics or parameters of coins (or other objects) so as to provide data relating to an average value for a coin as a whole. Such sensors and circuitry were not able to provide information specific to certain regions or levels of the coin (such as core material vs. cladding material). In some currencies, two or more denominations may have average characteristics which are so similar that it is difficult to distinguish the coins. For example, it is difficult to distinguish U.S. dimes from pre-1982 U.S. pennies, based only on average differences, the main physical difference being the difference in cladding (or absence thereof). In some previous devices, inductive coin testing is used to detect the effect of a coin on an alternating electromagnetic field produced by a coil, and specifically the coin's effect upon the coil's impedance, e.g. related to one or more of the coin's diameter, thickness, conductivity and permeability. In general, when an alternating electromagnetic field is provided to such a coil, the field will penetrate a coin to an extent that decreases with increasing frequency. Properties near the surface of a coin have a greater effect on a higher frequency field, and interior material have a lesser effect. Because certain coins, such as the United States ten and twenty-five cent coins, are laminated, this frequency dependency can be of use in coin discrimination, but, it is believed, has not previously been used in this manner. Accordingly, it would further be useful to provide a device which can provide information relating to different regions of coins or other objects.
Although there are a number of parameters which, at least theoretically, can be useful in discriminating coins and small objects (such as size, including diameter and thickness), mass, density, conductivity, magnetic permeability, homogeneity or lack thereof (such as cladded or plated coins), and the like, many previous sensors were configured to detect only a single one of such parameters. In embodiments in which only a single parameter is used, discrimination among coins and other small objects was often inaccurate, yielding both misidentification of a coin denomination (false positives), and failure to recognize a coin denomination (false negatives). In some cases, two coins which are different may be identified as the same coin because a parameter which could serve to discriminate between the coins (such as presence or absence of plating, magnetic non-magnetic character of the coin, etc.) is not detected by the sensor. Thus, using such sensors, when it is desired to use several parameters to discriminate coins and other objects, it has been necessary to provide a plurality of sensors (if such sensors are available), typically one sensor for each parameter to be detected. Multiplying the number of sensors in a device increases the cost of fabricating, designing, maintaining and repairing such apparatus. Furthermore, previous devices typically required that multiple sensors be spaced apart, usually along a linear track which the coins follow, and often the spacing must be relatively far apart in order to properly correlate sequential data from two sensors with a particular coin (and avoid attributing data from the two sensors to a single coin when the data was related, in fact, to two different coins). This spacing increases the physical size requirements for such a device, and may lead to an apparatus which is relatively slow since the path which the coins are required to traverse is longer.
Furthermore, when two or more sensors each output a single parameter, it is typically difficult or impossible to base discrimination on the relationship or profile of one parameter to a second parameter for a given coin, because of the difficulty in knowing which point in a first parameter profile corresponds to which point in a second parameter profile. If there are multiple sensors spaced along the coin path, the software for coin discrimination becomes more complicated, since it is necessary to keep track of when a coin passes by the various sensors. Timing is affected, e.g., by speed variations in the coins as they move along the coin path, such as rolling down a rail.
Even in cases where a single core is used for two different frequencies or parameters, many previous devices take measurements at two different times, typically as the coin moves through different locations, in order to measure several different parameters. For example, in some devices, a core is arranged with two spaced-apart poles with a first measurement taken at a first time and location when a coin is adjacent a first pole, and a second measurement taken at a second, later time, when the coin has moved substantially toward the second pole. It is believed that, in general, providing two or more different measurement locations or times, in order to measure two or more parameters, or in order to use two or more frequencies, leads to undesirable loss of coin throughput, occupies undesirably extended space and requires relatively complicated circuits and/or algorithms (e.g. to match up sensor outputs as a particular coin moves to different measurement locations).
Some sensors relate to the electrical or magnetic properties of the coin or other object, and may involve creation of an electromagnetic field for application to the coin. With many previous sensors, the interaction of generated magnetic flux with the coin was too low to permit the desired efficiency and accuracy of coin discrimination, and resulted in an insufficient signal-to-noise ratio.
Many previous coin handling devices and sensors had characteristics which were undesirable, especially when the devices were for use by untrained users. Such previous devices had insufficient accuracy, short service life, had an undesirably high potential for causing user injuries, were difficult to use, requiring training or extensive instruction, failed, too often, to return unprocessed coins to the user, took too long to process coins, had an undesirably low throughput, were susceptible to frequent jamming, which could not be cleared without human intervention, often requiring intervention by trained personnel, could handle only a narrow range of coin types, or denominations, were overly sensitive to wet or sticky coins or foreign or non-coin objects, either malfunctioning or placing the foreign objects in the coin bins, rejected an undesirably high portion of good coins, required frequent and/or complicated set-up, calibration or maintenance, required too large a volume or footprint, were overly-sensitive to temperature variations, were undesirably loud, were hard to upgrade or retrofit to benefit from new technologies or ideas, and/or were difficult or expensive to design and manufacture
Accordingly, it would be advantageous to provide a coin handler and/or sensor device having improved discrimination and accuracy, reduced costs or space requirements, which is faster than previous devices, easier or less expensive to design, construct, use and maintain, and/or results in improved signal-to-noise ratio.
The present invention provides a device for processing and/or discriminating coins or other objects, such as discriminating among a plurality of coins or other objects received all at once, in a mass or pile, from the user, with the coins or objects being of many different sizes, types or denominations. The device has a high degree of automation and high tolerance for foreign objects and less-than-pristine objects (such as wet, sticky, coated, bent or misshapen coins), so that the device can be readily used by members of the general public, requiring little, if any, training or instruction and little or no human manipulation or intervention, other than inputting the mass of coins.
According to one embodiment of the invention, after input and, preferably, cleaning, coins are singulated and move past a sensor for discrimination, counting and/or sorting. In general, coin slowing or adhesion is reduced by avoiding avoiding extensive flat regions in surfaces which contact coins (such as making such surfaces curved, quilted or dimpled). Coin paths are configured to flare or widen in the direction of coin travel to avoid jamming.
A singulating coin pickup assembly is preferably provided with two or more concentrically-mounted disks, one of which includes an integrated exit ledge. Movable paddles flex to avoid creating or exacerbating jams and deflect over the coin exit ledge. Vertically stacked coins tip backwards into a recess and slide over supporting coins to facilitate singulation. At the end of a transaction, coins are forced along the coin path by a rake, and debris is removed through a trap door. Coins exiting the coin pickup assembly are tipped away from the face-support rail to minimize friction.
According to one embodiment of the present invention, a sensor is provided in which nearly all the magnetic field produced by the coil interacts with the coin providing a relatively intense electromagnetic field in the region traversed by a coin or other object. Preferably, the sensor can be used to obtain information on two different parameters of a coin or other object. In one embodiment, a single sensor provides information indicative of both size, (diameter) and conductivity. In one embodiment, the sensor includes a core, such as a ferrite or other magnetically permeable material, in a curved (e.g., torroid or half-torroid) shape which defines a gap. The coin being sensed moves through the vicinity of the gap, in one embodiment, through the gap. In one embodiment, the core is shaped to reduce sensitivity of the sensor to slight deviations in the location of the coin within the gap (bounce or wobble). As a coin or the object passes through the field in the vicinity of the gap, data relating to coin parameters are sensed, such as changes in inductance (from which the diameter of the object or coin, or portions thereof, can be derived), and the quality factor (Q factor), related to the amount of energy dissipated (from which conductivity of the object or coin, or portions thereof, can be obtained).
In one embodiment, data relating to conductance of the coin (or portions thereof) as a function of diameter are analyzed (e.g. by comparing with conductance-diameter data for known coins) in order to discriminate the sensed coins. Preferably, the detection procedure uses several thresholds or window parameters to provide high recognition accuracy.
According to one aspect of the invention, a coin discrimination apparatus and method is provided in which an oscillating electromagnetic field is generated on a single sensing core. The oscillating electromagnetic field is composed of one or more frequency components. The electromagnetic field interacts with a coin, and these interactions are monitored and used to classify the coin according to its physical properties. All frequency components of the magnetic field are phase-locked to a common reference frequency. The phase relationships between the various frequencies are locked in order to avoid interference between frequencies and with any neighboring cores or sensors and to facilitate accurate determination of the interaction of each frequency component with the coin.
In one embodiment, low and high frequency coils on the core form a part of oscillator circuits. The circuits are configured to maintain oscillation of the signal through the coils at a substantially constant frequency, even as the effective inductance of the coil changes (e.g. in response to passage of a coin). The amount of change in other components of the circuit needed to offset the change in inductance (and thus maintain the frequency at a substantially constant value) is a measure of the magnitude of the change in the inductance caused by the passage of the coin, and indicative of coin diameter.
In addition to providing information related to coin diameter, the sensor can also be used to provide information related to coin conductance, preferably substantially simultaneously with providing the diameter information. As a coin moves past the coil, there will be an amount of energy loss and the amplitude of the signal in the coil will change in a manner related to the conductance of the coin (or portions thereof). For a given effective diameter of the coin, the energy loss in the eddy currents will be inversely related to the conductivity of the coin material penetrated by the magnetic field.
Preferably, the coin pickup assembly and sensor regions are configured for easy access for cleaning and maintenance, such as by providing a sensor block which slides away from the coin path and can be re-positioned without recalibration. In one embodiment, the diverter assembly is hinged to permit it to be tipped outward for access. Preferably, coins which stray from the coin path are deflected, e.g. via a ramped sensor housing and/or bypass chutes, to a customer return area.
Coins which are recognized and properly positioned or spaced are deflected out of the default (gravity-fed) coin path into an acceptance bin or trolley. Any coins or other objects which are not thus actively accepted travel along a default path to the customer return area. Preferably, information is sensed which permits an estimate of coin velocity and/or acceleration so that the deflector mechanism can be timed to deflect coins even though different coins may be traveling at different velocities (e.g. owing to stickiness or adhesion). In one embodiment, each object is individually analyzed to determine if it is a coin that should be accepted (i.e. is recognized as an acceptable coin denomination), and, if so, if it is possible to properly deflect the coin (e.g. it is sufficiently spaced from adjacent coins). By requiring that active steps be taken to accept a coin (i.e. by making the default path the “reject” path), it is more likely that all accepted objects will in fact be members of an acceptable class, and will be accurately counted.
The sensor and associated apparatus described herein can be used in connection with a number of devices and purposes. One device is illustrated in
The embodiment depicted in
Preferably, when the doors 36a, 36b are in the open position as shown, most or all of the components are accessible for cleaning and/or maintenance. In the depicted embodiment, a voucher printer 23 (
The general coin path for the embodiment depicted in
Devices that may be used in connection with the input tray are described in U.S. Ser. No. 08/255,539, now U.S. Pat. No. 5,564,546U.S. Ser. No. 08/237,486, now U.S. Pat. No. 5,620,079, supra.
Devices that may be used in connection with the coin trolleys 66a, 66b are described in Ser. No. 08/883,776, for COIN BIN WITH LOCKING LID, incorporated herein by reference.
Devices that may be used in connection with the coin chutes and the trommel 52 are described in PCT/US97/03136 Feb. 28, 1997 and its parent provisional application U.S. Ser. No. 60/012,964, both of which are incorporated by reference. In one embodiment, depicted in
Briefly, and as described more thoroughly below and in the above-noted applications, a user is provided with instructions such as on computer screen 32. The user places a mass of coins, typically of a plurality of denominations (typically accompanied by dirt or other non-coin objects and/or foreign or otherwise non-acceptable coins) in the input tray 16. The user is prompted to push a button to inform the machine that the user wishes to have coins discriminated. Thereupon, the computer causes an input gate 17 (
First and second chutes (not shown in
Preferably, some or all of the surfaces that contact the coin along the coin path, including the chutes, have no flat region large enough for a coin to contact the surface over all or substantially all of one of the faces of the coin. Some such surfaces are curved to achieve this result, such that coins make contact on, at most, two points of such surfaces. Other surfaces may have depressions or protrusions such as being provided with dimples, quilting or other textures. Preferably, the surface of the second chute is constructed such that it has a finite radius of curvature along any plane normal to its longitudinal axis, and preferably with such radii of curvature increasing in the direction of coin flow.
In one embodiment, the chutes are formed from injected molded plastic such as an acetal resin e.g. Delrin®, available from E.I. DuPont de Nemours & Co., or a polyamide polymer, such as a nylon, and the like. Other materials that can be used for the chute include metals, ceramics, fiberglass, reinforced materials, epoxies, ceramic-coated or -reinforced materials and the like. The chutes may contain devices for performing additional functions such as stops or traps, e.g., for dealing with various types of elongate objects.
The trommel 52, in the depicted embodiment is a perforated-wall, square cross-section, rotatably mounted container. Preferably, dimples protrude slightly into the interior region of the trommel to avoid adhesion and/or reduce friction between coins and the interior surface of the trommel. The trommel is rotated about its longitudinal axis. Preferably, operation of the device is monitored, such as by monitoring current draw for the trommel motor using a current sensor 21. A sudden increase or spike in current draw may be considered indicative of an undesirable load and/or jam of the trommel. The system may be configured in various ways to respond to such a sensed jam such as by turning off the trommel motor to stop attempted trommel rotation and/or reversing the motor, or altering motor direction periodically, to attempt to clear the jam. In one embodiment, when a jam or undesirable load is sensed, coin feed is stopped or discouraged, e.g., by closing the gate and/or illuminating a “stop feed” indicator. As the trommel motor 19 rotates the trommel, one or more vanes protruding into the interior of the trommel assist in providing coin-lifting/free-fall and moving the coins in a direction towards the output region. Objects smaller than the smallest acceptable coin (about 17.5 mm, in one embodiment) pass through the perforated wall as the coins tumble. In one embodiment, the holes have a diameter of about 0.61 inches (about 1.55 cm) to prevent passage of U.S. dimes. An output chute directs the (at least partially) cleaned coins exiting the trommel towards the coin pickup assembly 54. The depicted horizontal disposition of the trommel, which relies on vanes rather than trommel inclination for longitudinal coin movements, achieves a relatively small vertical space requirement for the trommel. Preferably the trommel is mounted in such a way that it may be easily removed and/or opened or disassembled for cleaning and maintenance, as described, e.g., in PCT Application US97/03136, supra.
As depicted in
As described below, the coins move into an annular coin path defined, on the outside, by the edge of a circular recess 1802 (
A circuit board 1744 for providing certain control functions, as described below, is preferably mounted on the generally accessible front surface of the chassis 1864. An electromagnetic interference (EMI) safety shield 1746 normally covers the circuit board 1744 and swings open on hinges 1748a,b for easy service access.
In the embodiment depicted in
The base plate 1810 is mounted on a chassis 1864 which is positioned within the cabinet (
A rotating main disk 1812 is configured for tight (small clearance) fit against the edge 1802 of recess 1808. Finger holes 1813a, b, c, d facilitate removal of the disk for cleaning or maintenance. Relatively loose (large clearance) fit is provided between disk holes 1814a, b, c, d and hub pins 1816a, b, c, d and between central opening 1818 and motor hub 1820. The loose fit of the holes and the tight fit of the edge of disk 1812 assist in reducing debris entrapment and motor jams. Because the main disk is received in recess 1802, it is free to flex and/or tilt, to some degree, e.g. in order to react to coin jams.
A stationary rail disk 1806 is positioned adjacent the main disk 1812 and has a central opening 1824 fitting loosely with respect to the motor hub 1820. In one embodiment, the rail disk is formed of graphite-filled phenolic.
The ledge 1804 defined by the rail disk 1806 is preferably configured so that the annular coin path flares or widens in the direction of coin travel such that spacing between the ledge and the recess edge near the bottom or beginning of the coin path (at the eight o'clock position 1876) is smaller (such as about 0.25 inches, or about 6 mm smaller) than the corresponding distance 1827 at the twelve o'clock position 1828. In one embodiment, the rail disk 1806 (and motor 2032) are mounted at a slight angle to the plane formed by the attachment edge 2042 of the hopper 1702 such that, along the coin path, the coin channel generally increases in depth (i.e. in a direction perpendicular to the face of the rail disk).
As the coins travel counterclockwise from approximately a 12:00 position 1828 of the rail disk, the ledge is thereafter substantially linear along a portion 1834 (
A tension disk 1838 is positioned adjacent the rail disk. The tension disk 1838 is mounted on the motor hub 1820 via central opening 1842 and threaded disk knob 1844. As the knob 1844 is tightened, spring fingers 1846a, b, c, d apply force to keep the disks 1838.1806, 1812 tightly together, reducing spaces or cracks in which debris could otherwise become entrapped. Preferably, the knob 1844 can be easily removed by hand, permitting removal of all the disks 1812, 1806, 1838 (e.g., for maintenance or cleaning) without the need for tools.
In one embodiment, the tension disk 1838 and main disk 1812 are formed of stainless steel while the rail disk 1806 is formed of a different material such as graphite-filled phenolic, which is believed to be helpful in reducing galling. The depicted coin disc configuration, using the described materials, can be manufactured relatively easily and inexpensively, compared to previous devices. Paddles 1704a, b, c, d are pivotally mounted on tension disk pins 1848a, b, c, d so as to permit the paddles to pivot in directions 1852a, 1852b parallel to the tension disk plane 1838. Such pivoting is useful in reducing the creation or exacerbation of coin jams since coins or other items which are stopped along the coin path will cause the paddles to flex, or to pivot around pins 1848a, b, c, d, rather than requiring the paddles to continue applying full motor-induced force on the stopped coins or other objects. Springs 1854a, b, c, d resist the pivoting 1852a, 1852b, urging the paddles to a position oriented radially outward, in the absence of resistance e.g. from a stopped coin or other object.
Preferably, sharp or irregular surfaces which may stop or entrap coins are avoided. Thus, covers 1856 are placed over the springs 1854a, b, c, d and conically-shaped washers 1858a, b, c, d protect the pivot pins 1848a, b, c, d. In a similar spirit, the edge of the tension disk 1862 is angled or chamfered to avoid coins hanging on a disk edge, potentially causing jamming.
As depicted in
The lower edge of the recess 1808 is formed by a separate piece 1872 which is mounted to act as a trap door. The trap door 1872 is configured to be moved rearwardly 2012 (
Coins which fall into the hopper 1702 from the trammel 52 are directed by the curvature of the hopper towards the 6:00 position 1877 (
Once coins are positioned along the annular path, the leading edge of the paddle heads 2028 contact the trailing edge of the coins, forcing them along the coin path, e.g. as depicted in
As the paddle heads 2028 continue to move along the circular path, they contact the linear portion 1834 (
As seen in
The terminal point 2105 of the rail disk ledge is laterally spaced a distance 2107 from the initial edge of the coin rail ledge 2104 to define a “V” gap therebetween. This gap, which extends a certain distance 2109 circumferentially, as seen in
The coin rail 56 functions to receive coins output by the coin pickup assembly 54, and transports the coins in a singulated (one-at-a-time) fashion past the sensor 58 to the diverting door 62. Singulation and separation of coins is of particular use in connection with the described sensor, although other types of sensors may also benefit from coin singulation and spacing. In general, coins are delivered to the coin rail 56 rolling or sliding on their edge or rim along the rail ledge 2104. The face of the coins as they slide or roll down the coin rail are supported, during a portion of their travel, by rails or stringers 2106a, b, c. The stringers are positioned (
The position and shape of the stringers and the width of the rail 2104 are selected depending on the range of coin sizes to be handled by the device. In one embodiment, which is able to handle U.S. coins in the size range between a U.S. dime and a U.S. half-dollar, the ledge 2104 has a depth 2111 (from the backplate 2114) of about 0.09 inches (about 23 mm). The top stringer 2106a is positioned at a height 2108a (above the ledge 2104), of about 0.825 inches (about 20 mm), (the middle stringer 2106b is positioned at a height 2108b of about 0.49 inches (about 12.4 mm), and the bottom stringer 2106c is positioned at a height of about 0.175 inches (about 4.4 mm). In one embodiment, the stringers are about 0.8 inches (about 2 mm) wide 2109 (
As seen in
Another feature contributing to singulation is the change in inclination of the coin rail from a first portion 2121a which is inclined, with respect to a horizontal plane 2124 at an angle 2126 of about 0° to about 30°, preferably about 0° to about 15° and more preferably about 10°, to a second portion 2121b which is inclined with respect to a horizontal plane 2124 by an angle of about 30° to about 60°, preferably between about 40° and about 50° and more preferably about 45° Preferably, the coin path in the transitional region 2121c between the first portion 2121a and second portion 2121b is smoothly curved, as shown. In one embodiment, the radius of curvature of the ledge 2104 in the transition region 2121c is about 1.5 inch (about 3.8 cm).
One feature of singulating coins, according to the depicted embodiment, is to primarily use gravitational forces for this purpose. Use of gravity force is believed to, in general, reduce system cost and complexity. This is accomplished by configuring the rail so that a given coin, as it approaches and then enters the second portion 2121b, will be gravitationally accelerated while the next (“following”) coin, on a shallower slope, is being accelerated to a much smaller degree, thus allowing the first coin to move away from the following coin, creating a space therebetween and effectively producing a gap between the singulated coins. Thereafter, the following coin moves into the region where it is, in turn, accelerated away from the successive coin. As a coin moves from the first region 2121a toward and into the second region 2121b, the change in rail inclination 2126, 2318 (
In one embodiment, acceleration of a coin as it moves into the second rail region 2121b is also enhanced by placement of a short, relatively tall auxiliary stringer 2132 generally in the transition region 2121c. The auxiliary stringer 2132 projects outwardly from the back surface 2114 of the coin rail, a distance 2134 (
Another feature of the coin rail contributing to acceleration is the provision of one or more free-fall regions where coins will normally be out of contact with the stringers and thus will contact, at most, only the ledge portion 2104 of the rail. In the depicted embodiment, a first free-fall region is provided at the area 2136a wherein the auxiliary stringer 2132 terminates. As noted above, coins in this region will tend to contact the coin rail only along the ledge 2104. Another free-fall region occurs just downstream of the upstream edge 2342 of the door 62. As seen in
Another free-fall region may be defined near the location 2103 where coins exit the disks 1812, 1806 and enter the rail 56, e.g., by positioning the disk 1812 to have its front surface in a plane slightly forward (e.g., about 0.3 inches, or about 7.5 mm) of the plane defined by rail stringers 2106. This free-fall region is useful not only to assist the transition from the disk onto the rail but makes it more likely that coins which may be slowed or stopped on the rail near the end of a transaction will be positioned downstream of the retract position (
The sensor 58 is positioned a distance 2304 (
The leading surface of the sensor housing is preferably ramped 2306 such that coins or other objects which do not travel into the space 2304 (such as coins or other objects which are too large or have moved partially off the coin path) will be deflected by the ramp 2306 onto a bypass chute 1722 (
In the depicted configuration, the sensor 58 is configured so that it can be moved to a position 2142 away from the coin rail 56, for cleaning or maintenance, such as by sliding along slot 2144. Preferably, the device is constructed with an interference fit so that the sensor 58 may be moved out of position only when the diverter cover 1811 has been pivoted forward 1902 (
As noted above, in the depicted embodiment, a door 62 is used to selectively deflect coins or other objects so the coins ultimately travel to either an acceptable-object or coin bin or trolley, or a reject chute 68.
In the embodiment depicted in
Preferably the device is configured such that activation of the door deflects coins to an acceptable coin bin and non-activation allows a coin to move along a default path to the reject chute 68. Such “actuate-to-accept” technique not only avoids accumulation of debris in the exit bins but improves accuracy by accepting only coins that are recognized and, further, provides a configuration which is believed superior during power failure situations. The actuate-to-accept approach also has the advantage that the actuation mechanism will be operating on an object of known characteristics (e.g. known diameter, which may be used, e.g. in connection with determining velocity and/or acceleration, or known mass, which may be used, e.g. for adjustment of forces, such as deflection forces). This affords the opportunity to adjust, e.g. the timing, duration and/or strength of the deflection to the speed and/or mass of the coin. In a system in which items to be rejected are actively deflected, it would be necessary to actuate the deflection mechanism with respect to an object which may be unrecognized or have unknown characteristics.
Although in one embodiment the door 62 is separately actuated for each acceptable coin (thus reducing solenoid 2306 duty cycle and heat generation), it would also be possible to configure a device in which, when there are one or two or more sequential accepted coins, the door 62 is maintained in its flexed position continuously until the next non-accepted coin (or other object) approaches the door 62.
An embodiment for control and timing of the door 62 deflection will be described more thoroughly below. In the depicted embodiment, the door 62 is deflected by activation of a solenoid 2306. The door 62, in one embodiment, is made of a hard resilient material, such as 301 full hard stainless steel which may be provided in a channel shape as shown. In one embodiment, the back surface of the coin-contact region of the door 2308a is substantially covered with a sound-deadening material 2334 such as a foam tape (available from 3M Company). Preferably the foam tape has a hole 2335 adjacent the region where the solenoid 2306 strikes the door 62.
In one embodiment, the door 62 is not hinged but moves outwardly from its rest position (
In some situations, particularly at the end of a coin discrimination cycle or transaction, one or more coins, especially wet or sticky coins, may reside on the first portion 2121a of the rail such that they will not spontaneously (or will only slowly) move toward the sensor 58. Thus, it may be desirable to include a mechanical or other transducer for providing energy, in response to a sensed jam, slow-up or other abnormality. One configuration for providing energy is described in U.S. Pat. No. 5,746,299, incorporated herein by reference. According to one embodiment for providing energy, a coin rake 2152, normally retracted into a rake slot 2154 (
Preferably, the rake position is sensed or monitored, such as by sensing the position of the rake motor 2502, in order to ensure proper rake operation. Preferably the system will detect (e.g. via activity sensor 1754) if the coin rake knocked coins off the rail or, via coin sensor 58, if the coin rake pushed coins down the coin rail to move past the sensor 58. In one embodiment if activation of the coin rake results in coins being knocked off the rail or moved down the rail, the coin rake will be activated at least a second time and the system may be configured to output a message indicating that the system should be cleaned or requires maintenance.
Between the time that a coin passes beneath the sensor 58 and the time it reaches the deflection door 62 (typically a period of about 30 milliseconds), control apparatus and software (described below) determine whether the coin should be diverted by the door 62. In general, it is preferred to make the time delay between sensing an object and deflecting the object (i.e., to make the distance between the sensor and the deflection door) as short as possible while still allowing sufficient time for the recognition and categorization processes to operate. The time requirements will be at least partially dependent on the speed of the processor which is used. In general, it is possible to shorten the delay by employing a higher-speed processor, albeit at increased expense. Shortening the path between the sensor and the deflector not only reduces the physical size of the device but also reduces the possibility that a coin or other object may become stuck or stray from the coin path after detection and before disposition (potentially resulting in errors, e.g. of a type in a coin is “credited” but not directed to a coin bin). Furthermore, shortening the separation reduces the chance that a faster following coin will “catch up” with a previous slow or sticky coin between the sensor and the deflector door. Shortening the separation additionally reduces the opportunity for coin acceleration or velocity to change to a significant degree between the sensor 58 and the door 62. Since the door, in one embodiment, is controlled based on velocity or acceleration measured or (calculated using data measured) at the sensor, a larger separation (and consequently larger rail length with potential variations is, e.g. friction) between the sensor 58 and the door 62 increases the potential for the measured or calculated coin velocity or acceleration to be in error (or misleading).
Because the coin deflector requires a certain minimum cycle time (i.e., the time from activation of the solenoid until the door has returned to a rest state and is capable of being reactivated), it is impossible to successfully deflect two coins which are too close together. Accordingly, when the system determines that two coins are too close together (e.g. by detecting successive “trail” times which are less than a minimum period apart), the system will refrain from activating the deflector door upon passage of one or both such coins, thus allowing one or both such coins to follow the default path to the reject chute, despite the fact that the coins may have been both successfully recognized as acceptable coins.
If a coin is to be diverted, when it reaches the door 62, solenoid 2306 is activated. Typically, because of the step 2136b and/or other flying-inducing features, by the time a coin reaches door 62 it will be spaced a short distance 2307 (such as 0.08 inches, or about 2 mm) above the door plane 62 and the door, as it is deflected to its activated position (
In one embodiment, the timing of deflection of the door 62 is controlled to increase the likelihood that the door will strike the coin as desired in such a fashion as to divert it to entrance to the coin tubes 1728. The preferred striking position may be selected empirically, if desired, and may depend, at least partially, on the diameter and mass of the coins and the coin mix expected in the machine as well as the size and characteristics of the door 62. In one embodiment, the machine is configured to, on average, strike the coin when the leading edge of the coin is approximately 3 mm upstream (“upstream” indicating a direction opposite the direction of coin flow 2332) of the downstream edge 2334 of the actuator door 62 (
Preferably, there is a gap between coins as they stream past the door 62. The preferred gap between adjacent coins which have different destinations (i.e., when adjacent coins include an accepted coin and a not-accepted coin) depends on whether the accepted coin is before or after the non-accepted coin (in which the “accepted coin” is a coin which will be diverted by the door and the not-accepted coin will travel past the door without being diverted). The gap behind a not-accepted coin (or other object) which reaches the door 62 before an accepted coin is referred to herein as a “leading gap”. The gap behind an accepted coin is referred to herein as a “trailing gap”. In one embodiment, the preferred leading gap is described by the following equation:
GAPlead.min=ΔdStoA.lead+ErrorPlus+a (1)
where:
The preferred minimum leading gap of approximately 12 mm applies when a non-accepted coin (or other object) precedes an accepted coin. In the common case of a string of consecutive accepted coins, this constraint need not be enforced after the first coin in the stream.
In one embodiment, the preferred trailing gap is described by the following equation:
GAPtr.min=ΔdStoA.trail+Δdontime+Errorminus+b−a−Dcoin.mi (2)
where:
A process for verifying the existence of preferred leading and trailing gaps, in appropriate situations, and/or selecting or controlling the activation of the door 62 to strike coins at the preferred position, is described below.
In the depicted embodiment, the region of the common entrance 1728 (
As best seen in
The core 2802, in the depicted embodiment, is generally U-shaped with a lower annular, semicircular, rectangular cross-sectioned portion 2808 and an upper portion defining two spaced-apart legs 2812a, 2812b. The core 2802, in the depicted embodiment, has a thickness 2814 of less than about 0.5 inches, preferably about 0.2 inches (about 5 mm), a height 2816 of about 2.09 inches (about 53 mm) and a width 2818 of about 1.44 inches (about 3.65 cm) although other dimensions can also be used, such as a thickness greater than about 0.5 inches.
Because the sensor 58 is preferably relatively thin, 2814, the magnetic field is relatively tightly focused in the longitudinal (streamwise) direction. As a result, the coin or other object must be relatively close to the sensor before the coin will have significant effect on sensor output. For this reason, it is possible to provide relatively close spacing of coins without substantial risk of undesirable influence of a leading or following coin on sensor output.
The facing surfaces 2822a, b of the legs 2812a, b are, in the depicted embodiment, substantially parallel and planar and are spaced apart a distance 2824 of about 0.3 inches (about 8 mm). The interior facing surfaces 2822a, b have a height at least equal to the width of the coin rail 2826, such as about 13 inches (about 33 mm). With the sensor positioned as depicted in
In the depicted embodiment, the faces 2822a,b extend 2816 across the entire path width 2133, to sense all metallic objects that move along the path in the region of the sensor. It is also possible to provide face extents which are larger or smaller than the path width, such as equal to the diameter of the largest acceptable coin.
It is believed that providing a core with a larger gap (i.e. with more air volume) is partially responsible for decreasing the sensitivity to coin misalignments but tends to result in a somewhat lower magnetic sensitivity and an increase in cross-talk. In one embodiment, the sensor can provide reliable sensor output despite a vertical displacement (“bounce”) of about 0.1 inch (about 2.5 mm) or more, and a sideways (away from the stringers) displacement or “wobble” of up to 0.015 inches (about 0.4 mm).
In the depicted embodiment the low frequency winding 2804 is positioned at the bottom of the semicircular portion 2808 and the high frequency winding is positioned on each leg 2806a, b of the semicircular portion. In one embodiment the low frequency winding is configured to have an inductance (in the driving and detection circuitry described below) of about 4.0 millihenrys and the high frequency winding 2806a, b to have an inductance of about 40 microhenrys. These inductance values are measured in the low frequency winding with the high frequency winding open and measured in the high frequency winding with the low frequency winding shorted together. The signals on the windings are provided to printed circuit board via leads 2704.
In the embodiment of
In the embodiment of
In addition to the toroid or torus-shaped sensors (
Although the depicted embodiments provide a sensor with a single magnetic core as a unitary piece, it is possible to configure a sensor with two spaced apart components such as providing the signal-generating magnetic means on one side of a coin and a signal-receiving magnetic means on the other side of a coin (as the coin moves past the center). It is believed, however, that such a multipart sensor will present alignment requirements and may prove to be relatively expensive or provide less uniform or reliable performance.
During normal counting operations, the system will sense that coins are streaming past the sensor 4026. The system is able to determine 4028 whether coins are being sent to the reject chute or the coin trolley. In the latter case, the system proceeds normally if the sensor in the coin tube outputs an intermittent or flickering signal. However, if the coin tube sensor is stuck on or off, indicating a jam upstream or downstream (such as an overfilled bin), operations are suspended 4036.
In one embodiment, the flow of coins through the system is managed and/or balanced. As shown in
When the coin sensor 58 (and associated circuitry and software) are used to measure or calculate coin speed, this information may be used not only to control the deflector door 62 as described herein, but to output an indication of a need for maintenance. For example as coin speeds decrease, a message (or series of messages) to that effect may be sent to the host computer 46 so that it can request preventive maintenance, potentially thereby avoiding a jam that might halt a transaction.
Once the system senses that coins are no longer streaming past the sensor, if desired a sensor may be used to determine whether coins are present e.g. near the bottom of the hopper 4042. If coins are still present, the motors continue operating 4044 until coins are no longer detected near the bottom of the hopper. Once no more coins are detected near the bottom of the hopper 4046, the system determines that the transaction is complete. The system will then activate the coin rake, and, if coins are sensed to move past the coin sensor 58 or into the hopper, the counting cycle is preferably repeated. Otherwise, the transaction will be considered finished 4028, and the system will cycle the trap door and output e.g. a voucher of a type which may be exchanged for goods, services or cash.
The coin sensor phase locked loop (PLL), which includes the sensor or transducer 58, maintains a constant frequency and responds to the presence of a coin in the gap 2824 by a change in the oscillator signal amplitude and a change in the PLL error voltage. The phase locked loop shown in the depicted embodiment requires no adjustments and typically settles in about 200 microseconds. The system is self-starting and begins oscillating and locks phase automatically. It is also possible to provide frequencies or signals for application to a sensor without using a phase lock. The winding signals (2 each for high frequency and low frequency channels) are conditioned 2904 as described below and sent to an analog-to-digital (A/D) converter 2906. The A/D converter samples and digitizes the analog signals and passes the information to the microcontroller 3202 (
Although in one embodiment the signal or signals provided to the sensor are substantially sinusoidal, it is also possible to use configurations in which non-sinusoidal signals are provided to the sensor, such as (filtered or unfiltered) substantially square wave, pulse, triangle, or similar periodic signals. Such non-sinusoidal signals, in addition to offering system cost savings, for some configurations, also typically include various harmonics. A harmonic-rich signal, such as a square wave signal is believed to be affected differently for different coins, e.g., due to the interrelationships of the various harmonics' phases and amplitudes. For example, in one embodiment, as depicted in
Although a phase locked loop (PLL) approach to providing one or more constant frequencies is depicted in
One approach provides a plurality of signals for distinguishing coin types (e.g., a different signal “tuned” for each anticipated or acceptable coin type. It is believed this approach may provide relatively high accuracy but may involve additional cost compared to providing a reduced number of signals.
Returning to the configuration of
The coin sensor phase locked loop, according to one embodiment, consists of a voltage controlled oscillator, a phase comparator, amplifier/filter for the phase comparator output, and a reference clock. The two PLL's operate at 200 KHz and 2.0 MHZ, with their reference clocks synchronized. The phase relationship between the two clock signals 3101a, b is maintained by using a divided-down clock rather than two independent clock sources 3102. The 2 MHZ clock output 3101a is also used as the master clock for the A/D converter 2906.
As a coin passes through the transducer's slot, there is a change in the magnetic circuit's reluctance. This is seen by circuitry as a decrease in the inductance value and results in a corresponding decrease in the amplitude of the PLL error voltage, providing a first coin-identifying factor. The passing coin also causes a decrease in the amplitude of the sinusoidal oscillator waveform, depending on its composition, e.g. due to an eddy current loss, and this is measured to provide a second coin-identifying factor.
The topology of the oscillators 2902a, b relies on a 180 degree phase shift for feedback to its drive circuitry and is classified as a Colpitts oscillator. The Colpitts oscillator is a symmetric topology and allows the oscillator to be isolated from ground. Drive for the oscillator is provided by a high speed comparator 3104a, b. The comparator has a fast propagation to minimize distortion due to phase delay, low input current to minimize loss, and remains stable while operating in its linear region. In the depicted embodiment, the plus and minus terminals of the inductors go directly to a high-speed comparator which autobiases the comparator so that signals convert quickly and are less susceptible to oscillation and so that there is no need to bias the comparator to a central voltage level. By tying the plus and minus Terminals of the inductor to the plus and minus terminals of the comparator, the crossing of the terminals' voltage at any arbitrary point in the voltage spectrum will cause a switch in the comparator output voltage so that it is autobiasing. This achieves a more nearly even (50%) duty cycle.
The output of the comparator drives the oscillator through resistors 3106a, b. The amplitude of the oscillating signal varies and is correlated to the change in “Q” of the tuned circuit. Without wishing to be bound by any theory, this change is believed to be due to change in eddy current when a coin passes through the transducer gap. Resistors 3108a, b, c, d work with the input capacitance of the comparator 3104a, b to provide filtering of unwanted high frequency signal components.
Voltage control of the oscillator frequency is provided by way of the varactors 3112a, b, c, d, which act as voltage controlled capacitors (or tuning diodes) These varactors change the capacitive components of the oscillator. Use of two varactors maintains balanced capacitance on each leg of windings 2804, 2806. It is also possible to provide for tuning without using varactors such as by using variable inductance. As the reverse diode voltage increases, capacitance decreases. Thus by changing the Voltage Controlled Oscillator (VCO) input voltage in accordance with the change in inductance due to the presence of a coin, the frequency of oscillation can be maintained. This VCO input voltage is the signal used to indicate change of inductance in this circuit.
The phase/frequency detector 3114a, b performs certain control functions in this circuit, It compares the output frequency of the comparator 3104a, b to a synchronized reference clock signal and has an output that varies as the two signals diverge. The output stage of the device amplifies and filters this phase comparator output signal. This amplified and filtered output provides the VCO control signal used to indicate change of inductance in this circuit.
In addition, the depicted device has an output 3116a, b which, when appropriately conditioned, can be used to determine whether the PLL is “in lock”. In one embodiment, a lock-fail signal is sent to the microprocessor on the Control PCBA as an error indication, and an LED is provided to indicate when both high and low frequency PLL are in a locked state.
Because the sensor 58 receives excitation at two frequencies through two coils wrapped on the same ferrite core, there is a potential for the coupling of signals which may result in undesired amplitude modulation on the individual signals that are being monitored. Filters 2912a, b remove the undesired spectral component while maintaining the desired signal, prior to amplitude measurement. In this way, the measured amplitude of each signal is not influenced by an independent change in the amplitude of the other oscillator circuit signals.
The filtered output signals are level-shifted to center them at 3.0 VDC in order to control the measurement of the signal amplitude by downstream circuitry.
In the depicted embodiment, the active highpass and lowpass filters are implemented as Sallen-Key Butterworth two-pole filter circuits 2916a, b. DC offset adjustment of the output signals is accomplished by using a buffered voltage divider as a reference. Input buffers 2914a, b are provided to minimize losses of the oscillator circuit by maintaining a high input impedance to the filter stage.
The lowpass filter 2916a is designed to provide more than 30 dB of attenuation at 2 MHZ while maintaining integrity of the 200 KHz signal, wish less that 0.5 dB of loss at that frequency. The cutoff frequency is 355 KHz. Highpass filtering of the output from the lowpass filter is provided 2918a with a cutoff frequency of 20 KHz. Tying to a DC reference 2922a provides an adjusted output that centers the 200 KHz signal at 3.0 VDC. This output offset adjustment is desired for subsequent amplitude measurement.
The highpass filter 2916b is designed to provide more than 30 dB of attenuation at 200 KHz while maintaining integrity of the 2.0 MHZ signal, with less that 0.5 dB of loss at that frequency. The cutoff frequency is 1.125 MHz.
Amplitude measurement of the sinusoidal oscillator waveform is accomplished by demodulating the signal with a negative peak detecting circuit, and measuring the difference between this value and the DC reference voltage at which the sinusoidal signal is centered. This comparison measurement is then scaled to utilize a significant portion of the A/D converter's input range. The input to the circuit is a filtered sinusoidal signal centered at a known DC reference voltage output of the highpass or lowpass active filter.
The input signal is demodulated by a closed-loop diode peak detector circuit. The time constant of the network, e.g. 20 msec, is long compared to the period of the sinusoidal input, but short when compared to the time elapsed as a coin passes through the sensor. This relationship allows the peak detector to react quickly to a change in amplitude caused by a coin event. The circuit is implemented as a negative peak detector rather than a positive peak detector because the comparator is more predictable in its ability to drive the signal to ground than to drive it high. Comparators 3126a, b, such as model LT1016CS8, available from Linear Technology, provide a high slew rate and maintain stability while in the linear region. The analog closed-loop peak detector avoids the potential phase error problems that filter-stage phase lag and dynamic PLL phase shifts might create for a sample-and-hold implementation, and eliminates the need for a sampling clock.
The negative peak detector output is compared to the DC reference voltage, then scaled and filtered, by using an op amp 3124a, b implemented as a difference amplifier. The difference amp is configured to subtract the negative peak from the DC reference and multiply the difference by a scaling factor. In one embodiment, for the low frequency channel, the scaling factor is 4.02, and the high frequency channel scales the output by 5.11. The output of the difference amplifier has a lowpass filter on the feedback with a corner frequency at approximately 160 Hz. In the depicted embodiment, there is a snubber at the output to filter high frequency transients caused by switching in the A/D converter.
The error voltage measurement, scaling, and filtering circuit 3128a, b is designed to subtract 3.0 VDC from the PLL error voltage and amplify the resulting difference by a factor of 1.4. The PLL error voltage input signal will be in the 3.0‘6.0 VDC range, and in order to maximize the use of the A/D converter's input range, the offset voltage is subtracted and the signal is amplified.
The input signal is pre-filtered with a lowpass corner frequency of 174 Hz, and the output is filtered in the feedback loop, with a cut-off frequency 340 Hz. A filter at the output filters high frequency transients caused by switching in the A/D converter.
In an interface circuit, 2922 data and control signals are pulled up and pass through series termination resistors. In addition, the data signal DATA–DATA15 are buffered by bi-directional registers. These bidirectional buffers isolate the A/D converter from direct connection to the data bus and associated interconnect cabling.
The A/D converter 2906 is a single supply, 8-channel, 12-bit sampling converter (such as model AD7859AP available from Analog Devices). The A/D transactions are directly controlled by the microprocessor on the Control PCBA.
An overview of control provided for various hardware components is depicted in
The microcontroller 3202 communicates with and is, to some degree, controlled by, the host computer 46. The host computer 46 can be any of a number of computers. In one embodiment, computer 46 is a computer employing an Intel 486 or Pentium® processor or equivalent. The host computer 46 and microcontroller 3202 communicate over serial line 3208 via respective serial ports 3212, 3214. The microcontroller 3202, in the depicted embodiment, has a second serial port 3216 which may be used for purposes such as debugging, field service 3218 and the like.
During normal operation, programming and data for the microcontroller are stored in memory which may include normal random access memory (RAM) 3222, non-volatile random access memory such as flash memory, static memory and the like 3224, and read-only memory 3226 which may include programmable and/or electronically erasable programmable read-only memory (EEPROM). In one embodiment, microprocessor firmware can be downloaded from a remote location via the host computer.
Applications software 3228 for controlling operation of the host computer 46 may be stored in, e.g., hard disk memory, nonvolatile RAM memory and the like.
Although a number of items are described as being implemented in software, in general it is also possible to provide a hardware implementation such as by using hard wired control logic and/or an application specific integrated circuit (ASIC).
An input/output (I/O) interface on the microcontroller 3232 facilitates communication such as bus communication, direct I/O, interrupt requests and/or direct memory access (DMA) requests. Since, as described more thoroughly below, DMA is used for much of the sensor communications, the coin sensor circuitry includes DMA logic circuitry 3234 as well as circuitry for status and control signals 3236. Although, in the described embodiment, only a single sensor is provided for coin sensing, it is possible to configure an operable device having additional sensors 3238.
In addition to the motors 2502, 2032, solenoids 2014, 1734, 2306 and sensors 1738, 1754 described above in connection with coin transport, controlling latches, gates and drivers of a type that will be understood by those of skill in the art, after understanding the present invention, are provided 3242.
A method for deriving, from the four sensor signals (
In the depicted embodiment, the base line value 3312 associated with the LFD signal 3302 is used to define a descent threshold 3324 (equal to the LFD baseline 3312 minus a predefined descent offset 3326, and a predefined gap threshold 3328 equal to the LFD baseline 3312 minus a gap offset 3332).
In one embodiment, the system will remain in an idle loop 3402 (
In the depicted embodiment, the beginning of a coin passage past the sensor is signaled by the LFD signal 3302 becoming less 4212 than the descent threshold 3324 (3406) which, in the embodiment of
During the time that the window is open 3322, the minimum-holding variables LFDMIN, LFQMIN, HFDMIN and HFQMIN will be updated, as needed, to reflect the minimum value thus-far achieved. In the depicted embodiment, the four values are updated serially and cyclically, once every clock signal. Updating of values can be distributed in a different fashion if it is desired, for example, to provide greater time resolution for some variables than for others. It is believed that, by over sampling specific channels, recognition and accuracy can be improved. As the LFD value is being tested and, if necessary, updated, a value for an ascent threshold 3336 (which will be used to define the end of the window 3322, as described below) is calculated or updated 3414. The value for the ascent threshold 3336 is calculated or updated as a value equal to the current value for LFDMIN 3342 plus a predefined ascent hysteresis 3352.
Whenever the LFDMIN value 3342 must be updated (i.e., when the value of LFD descends below the previously-stored minimum value 3412), the “peak” time value is also updated by being made equal to the current clock value. In this way, at the end 4226 of the window 3322, the “peak” variable will hold a value indicating the time at which LFD 3302 reached its minimum value within the window 3322.
As a coin passes through the arms of a sensor, the four signal values 3302, 3304, 3306, 3308 will, in general, reach a minimum value and then begin once more to ascend toward the baseline value 3312, 3314, 3316, 3318. In the depicted embodiment, the window 3322 is declared “closed” when the LFD value 3302 raises to a point that it equals the current value for the ascent value threshold 3336. In the illustration of
The other portion of the signature for the coin which was just detected (in addition to the three time variables) are values indicating the minimum achieved, within the window 3332, for each of the variables 3302, 3304, 3306, 3308. These values are calculated 3422 by subtracting the minimum values at time T33342, 3344, 3346, 3348 from the respective baseline values 3312, 3314, 3316, 3318 to yield four difference or delta values, ΔLFD 3362, ΔLFQ 3364, ΔHFD 3366 and ΔHFQ 3368. Providing output which is relative to the baseline value for each signal is useful in avoiding sensitivity to temperature changes.
Although, at time t3 3356, all the values required for the coin signature have been obtained, in the depicted embodiment, the system is not yet placed in a “ready” state. This is because it is desired to assure that there is at least a minimum gap between the coin which was just detected and any following coin. It is also desirable to maintain at least a minimum distance or gap from any preceding coin. In general, it is believed useful to provide at least some spacing between coins for accurate sensor reading, since coins which are touching can result in eddy current passing between coins. Maintaining a minimum gap as coins move toward the door 62 is useful in making sure that door 62 will strike the coin at the desired time and location. Striking too soon or too late may result in deflecting an accepted coin other than into the acceptance bin, degrading system accuracy.
Information gathered by the sensor 58 may also be used in connection with assuring the existence of a preferred minimum gap between coins. In this way, if coins are too closely spaced, one or more coins which might otherwise be an accepted coin, will not be deflected (and will not be “counted” as an accepted coin). Similarly, in one embodiment, a coin having an acceleration less than a threshold (such as less than half a maximum acceleration) will not be accepted.
Accordingly, in order to assure an adequate leading gap, the system is not placed in a “ready” state until the LFD signal 3302 has reached a value equal to the gap threshold 3328. After the system verifies 3424 that this event 3372 has occurred, the status is set equal to “ready” 3326 and the system returns to an idle state 3401 to await passage of the next coin.
To provide for a minimum preferred trailing gap, in one embodiment, the software monitors the LFD signal 3302 for a short time after the ascending hysteresis criterion has been satisfied 4236. If the signal has moved sufficiently back towards the baseline 3312 (measured either with respect to the baseline or with respect to the peak) after a predetermined time period, then an adequate trailing gap exists and the door, if the coin is an accepted coin, will be actuated 4244. If the trailing gap is not achieved, the actuation pulse is canceled 4244, and normally the coin will be returned to the user. In all cases, software thresholds are preferably calibrated using the smallest coins (e.g., a U.S. dime in the case of a U.S. coin mix).
Because the occurrence of events such as the crossing of thresholds 3338, 3354, 3372 are only tested at discrete time intervals 3411a, 3411b, 3411c, 3411d, in most cases the event will not be detected until some time after it has occurred. For example, it may happen that, with regard to the ascent-crossing event 3354, the previous event-test at time T43374 occurs before the crossing event 3354 and the next event-test occurs at time T5, a period of time 3378 after the crossing event 3354. Accordingly, in one embodiment, once a test determines that a crossing event has occurred, interpolation such as linear interpolation, spline-fit interpolation or the like, is used to provide a more accurate estimate of the actual time of the event 3354.
As noted above, by time t3 3356, all the values required for the coin signature have been obtained. Also, by time t3, the information which can be used for calculating the time at which the door 62 should be activated (assuming the coin is identified as an accepted coin) is available. Because the distance from the sensor to the door is constant and known, the amount of time required for a coin to travel to the preferred position with respect to the door can be calculated exactly if the acceleration of the coin along the rail is known (and constant) and a velocity, such as the velocity at the sensor is known. According to one method, acceleration is calculated by comparing the velocity of the coin as it moves past the sensor 58 with the velocity of the coin as it passes over the “knee” in the transition region 2121C. In one embodiment, the initial “knee” velocity is assumed to be a single value for all coins, in one case, 0.5 meters/second. Knowing the velocity at two locations (the knee 2121C and the sensor location 58) and knowing the distance from the knee 2121C to the sensor location 58, the acceleration experienced by the coin can be calculated. Based on this calculated acceleration, it is then possible to calculate how long it will be, continuing at that acceleration, before the coin is positioned at the preferred location over the actuator. This system essentially operates on a principle of assuming an initial velocity and using measurements of the sensor to ultimately calculate how friction (or other factors such as surface tension) affects the acceleration being experienced by each coin. Another approach might be used in which an effective friction was assumed as a constant value and the data gathered at the sensor was used to calculate the initial (“knee”) velocity.
In any case, the calculation of the time when the coin will reach the preferred position can be expected to have some amount of error (i.e., difference between calculated position and actual position at the door activation time). The error can arise from 2 number of factors including departures from the assumption regarding the knee velocity, non-constant values for friction along the rail, and the like. In one embodiment it has been found that, using the described procedure, and for the depicted and described design, the worst-case error occurs with the smallest coin (e.g., amount 17.5 mm in diameter) and amounts to approximately 6 mm in either direction. It is believed that, in at least some environments, an error window of 6 mm is tolerable (i.e., results in a relatively low rate of misdirecting coins or other objects).
In order to implement this procedure, data obtained at the sensor 58 is used to calculate a velocity. According to one scheme, time t1 3336 is taken as the time when the coin first enters the sensor and time t2 (the “peak” time) is taken as the time when the coin is (entered on the sensor, and thus has traveled a distance approximately equal to a coin radius. Because, once the coin has been recognized (e.g. as described below in connection with
The procedure illustrated in
As illustrated in
In the embodiment of
The results of the categorization 3508 are stored in a category buffer 3512 and are provided to the relegator process 3514. The difference between categorization and relegation relates, in part, to the difference between a coin category and a coin denomination. Not all coins of a given denomination will have similar structure, and thus two coins of the same denomination may have substantially different signatures. For example, pennies minted before 1982 have a structure (copper core) substantially different from that of pennies minted after that date (zinc core). Some previous devices have attempted to define a coin discrimination based on coin denomination, which would thus require a device which recognizes two physically different types of penny as a single category.
According to one embodiment, coins or other objects are discriminated not necessarily on the basis of denomination but on the basis of coin catagories (in which a single denomination may have two or more categories). Thus, according to one embodiment, pennies minted before 1982 and pennies minted after 1982 belong to two different coin categories 3704. This use of categories, based on physical characteristics of coins (or other objects), rather than attempting to define on the basis of denominations, is advantageous since it is believed that this approach leads to better discrimination accuracy. In particular, by defining separate categories e.g. for pre-1982 and post-1982 pennies, it becomes easier to discriminate all pennies from other objects, whereas if an attempt was made to define a single category embracing both types of pennies, it is believed that the recognition windows or thresholds would have to be so broadly defined that there would be a substantial risk of mis-discrimination. By providing a system in which coin categories rather than coin denominations are recognized, coin destinations may be easily configured and changed.
Furthermore, in addition to improving discrimination accuracy, the present invention provides an opportunity to count coins and sort coins or other objects on a basis other than denomination. For example, if desired, the device could be configured to place “real silver” coins in a separate coin bin so that the machine operator can benefit from their potentially greater value.
Once a relegator process 3514 receives information from a category buffer regarding the category of a coin (or other object), the relegator outputs a destination indicator, corresponding to that coin, to a destination buffer 3516. The data from the destination buffer is provided to a director process 3518 whose function is to provide appropriate control signals at the appropriate time in order to send the coin to a desired destination, e.g. to provide signals causing the deflector door to activate at the proper time if the coin is destined for an acceptance bin. In the embodiment of
In one embodiment, the solenoid is controlled in such a manner as to not only control the time at which the door is activated 4234, 4244 but also the amount of force to be used (such as the strength and/or duration of the solenoid activation Volts). In one embodiment, the amount of force is varied depending on the mass of the coin, which can be determined, e.g., from a look-up table, based on recognition of the coin category.
Preferably, information from the destination buffer 3516 is also provided to a counter 3528 which retains a tally of at least the number of coins of each denomination sent to the coin bins. If desired, a number of counters can be provided so that the system can keep track not only of each coin denomination, but of each coin category and/or, which coin bin the coin was destined for.
In general, the flow of data depicted in
As depicted in
In the preferred embodiment, the DMA interface does not limit the ability of the software to independently read or write to the A-to-D converter. It is possible, however, that writing to the control register of the A-to-D converter in the middle of a DMA transfer may cause the wrong channel to be read.
Preferably the DMA process takes advantage of the DMA channels to configure a multiple word table in memory with the desired A-to-D controller register data. Preferably the table length (number of words in the table) is configurable, permitting a balance to be struck between reducing microcontroller overhead (by using a longer table), and reducing memory requirements (by using a shorter table). The DMA process sets up DMA0 for writing these words to a fixed I/O address. Next, DMA1 is set up for reading the same number of words from the same I/O address to a data buffer in memory. DMA1 is preferably set up to interrupt the processor when all words have been read 3812. Preferably hardware DMA decoder logic controls the timing between DMA0 and DMA1.
Another embodiment of a gapped torroid sensor, and its use, is depicted in
The core 214 may be made from a number of materials provided that the material is capable of providing a substantial magnetic field in the gap 216. In one embodiment, the core 214 consists of, or includes, a ferrite material, such as formed by fusing ferric oxide with another material such as a carbonate hydroxide or alkaline metal chloride, a ceramic ferrite, and the like. If the core is driven by an alternating current, the material chosen for the core of the inductor, should be normal-loss or low-loss at the frequency of oscillation such that the “no-coin” Q of the LC circuit is substantially higher than the Q of the LC circuit with a coin adjacent the sensor. This ratio determines, in part, the signal-to-noise ratio for the coin's conductivity measurement. The lower the losses in the core and the winding, the greater the change in eddy current losses, when the coin is placed in or passes by the gap, and thus the greater the sensitivity of the device. In the depicted embodiment, a conductive wire 220 is wound about a portion of the core 214 so as to form an inductive device. Although
The embodiment of
When an electrical potential or voltage is applied to the coil 220, a magnetic field is created in the vicinity of the gap 216, 316 (i.e. created in and near the gap 216, 316). The interaction of the coin or other object with such a magnetic field (or lack thereof) yields data which provides information about parameters of the coin or object which can be used for discrimination, e.g. as described more thoroughly below.
In one embodiment, current in the form of a variable or alternating current (AC) is supplied to the coil 220. Although the form of the current may be substantially sinusoidal as used herein “AC” is meant to include any variable (non-constant) wave form, including ramp, sawtooth, square waves, and complex waves such as wave forms which are the sum or two or more sinusoidal waves. Because of the configuration of the sensor, and the positional relationship of the coin or object to the gap, the coin can be exposed to a significant magnetic field, which can be significantly affected by the presence of the coin. The sensor can be used to detect these changes in the electromagnetic field, as the coin passes over or through the gap, preferably in such as way as to provide data indicative of at least two different parameters of the coin or object. In one embodiment, a parameter such as the size or diameter of the coin or object is indicated by a change in inductance, due to the passage of the coin, and the conductivity of the coin or object is (inversely) related to the energy loss (which may be indicated by the quality factor or “Q.”)
In the embodiment of
Many methods and/or devices can be used for analyzing the signals 512, 612, including visual inspection of an oscilloscope trace or graph (e.g. as shown in
In some cases, it is desired to separately obtain information about coin parameters for the interior or core portion of the coin and the exterior or skin portion, particularly in cases where some or all of the coins to be discriminated may be cladded, plated or coated coins. For example, in some cases it may be that the most efficient and reliable way to discriminate between two types of coins is to determine the presence or absence of cladding or plating, or compare a skin or core parameter with a corresponding skin or core parameter of a known coin. In one embodiment, different frequencies are used to probe different depths in the thickness of the coin. This method is effective because, in terms of the interaction between a coin and a magnetic field, the frequency of a variable magnetic field defines a “skin depth,” which is the effective depth of the portion of the coin or other object which interacts with the variable magnetic field. Thus, in this embodiment, a first frequency is provided which is relatively low to provide for a larger skin depth, and thus interaction with the core of the coin or other object, and a second, higher frequency is provided, high enough to result in a skin depth substantially less than the thickness of the coin. In this way, rather than a single sensor providing two parameters, the sensor is able to provide four parameters: core conductivity; cladding or coating conductivity; core diameter; and cladding or coating diameter (although it is anticipated that, in many instances, the core and cladding diameters will be similar). Preferably, the low-frequency skin depth is greater than the thickness of the plating or lamination, and the high frequency skin depth is less than, or about equal to, the plating or lamination thickness (or the range of lamination depths, for the anticipated coin population). Thus the frequency which is chosen depends on the characteristics of the coins or other objects expected to be input. In one embodiment, the low frequency is between about 50 KHz and about 500 KHz, preferably about 200 KHz and the high frequency is between about 0.5 MHZ and about 10 MHZ, preferably about 2 MHz.
In some situations, it may be necessary to provide a first driving signal frequency component in order to achieve a second, different frequency sensor signal component. In particular, it is found that if the sensor 212 (
Multiple frequencies can be provided in a number of ways. In one embodiment, a single continuous wave form 702 (
As can be seen from
The crystal oscillator circuit 806 (
The high frequency phase locked loop circuit 802b, depicted in
Low frequency phase locked loop circuit 802a is similar to that depicted in
Considering the circuit of
In order to obtain a measure of the amplitude of the voltage, it is necessary to sample the voltage at a peak and a trough of the signal. In the embodiment of
In addition to providing an output 612 which is related to coin conductance, the same circuit 802b also provides an output 512 related to coin diameter. In the embodiment of
In one embodiment, the output signals 882a, 882b, 882a′, 882b′ are provided to a computer for coin discrimination or other analysis. Before describing examples of such analysis, it is believed useful to describe the typical profiles of the output signals 882a, 882b, 882a′, 882b′.
The signals 882a, 882b, 882a′, 882b′ can be used in a number of fashions to characterize coins or other objects as described below. The magnitude of changes 902a, 902a′ of the low frequency and high frequency D values as the coin passes the sensor and the absolute values 904, 904 of the low and high frequency Q signals 882a′, 882a, respectively, at the time t1 when the coin or other object is most nearly aligned with the sensor (as determined e.g. by the time of the local maximum in the D signals 882b, 882b′) are useful in characterizing coins. Both the low and high frequency Q values are useful for discrimination. Laminated coins show significant differences in the Q reading for low vs. high frequency. The low and high frequency “D” values are also useful for discrimination. It has been found that some of all of these values are, at least for some coin populations, sufficiently characteristic of various coin denominations that coins can be discriminated with high accuracy.
In one embodiment, values 902a, 902a′, 904, 904′ are obtained for a large number of coins so as to define standard value characteristic of each coin denomination.
One method of using standard reference data of the type depicted in
As will be apparent from the above discussion, the error rate that will occur in regard to such an analysis will partially depend on the size of the regions 1002a–1002e, 1002a′–1002e′ which are defined. Regions which are too large will tend to result in an unacceptably large number of false positives (i.e. identifying the coin as being a particular denomination when it is not) while defining regions which are too small will result in an unacceptably large number of false negatives (i.e., failing to identify a legitimate coin denomination). Thus, the size and shape of the various regions may be defined or adjusted, e.g. empirically, to achieve error rates which are no greater than desired error rates. In one embodiment, the windows 2002a–2002e, 2002a′–2002e′ have a size and shape determined on the basis of a statistical analysis of the Q, D values for a standard or sample coin population, such as being equal to 2 or 3 standard deviations from the mean Q, D values for known coins. The size and shape of the regions 1002a–1002e, 1002a′–1002e′ may be different from one another, i.e., different for different denominations and/or different for the low frequency and high frequency graphs. Furthermore, the size and shape of the regions may be adjusted depending on the anticipated coin population (e.g., in regions near national borders, regions may need to be defined so as to discriminate foreign coins, even at the cost of raising the false negative error rate whereas such adjustment of the size or shape of the regions may not be necessary at locations in the interior of a country where foreign coins may be relatively rare).
If desired, the computer can be configured to obtain statistics regarding the Q, D values of the coins which are discriminated by the device in the field. This data can be useful to detect changes, e.g., changes in the coin population over time, or changes in the average Q, D values such as may result from aging or wear of the sensors or other components. Such information may be used to adjust the software or hardware, perform maintenance on the device and the like. In one embodiment, the apparatus in which the coin discrimination device is used may be provided with a communication device such as a modem 25 (
In light of the above description, a number advantages of the present invention can be seen. Embodiments of the present invention can provide a device with increased accuracy and service life, ease and safety of use, requiring little or no training and little or no instruction, which reliably returns unprocessed coins to the user, rapidly processes coins, has a high throughput, a reduced incidence of jamming, in which some or all jams can be reliably cleared without human intervention, which has reduced need for intervention by trained personnel, can handle a broad range of coin types, or denominations, can handle wet or sticky coins or foreign or non-coin objects, has reduced incidence of malfunctioning or placing foreign objects in the coin bins, has reduced incidence of rejecting good coins, has simplified and/or reduced requirements for set-up, calibration or maintenance, has relatively small volume or footprint requirements, is tolerant of temperature variations, is relatively quiet, and/or enhanced ease of upgrading or retrofitting.
In one embodiment, the apparatus achieves singulation of a randomly-oriented mass of coins with reduced jamming and high throughput. In one embodiment, coins are effectively separated from one another prior to sensing and/or deflection. In one embodiment, deflection parameters, such as force and/or timing of deflection can be adjusted to take into account characteristics of coins or other objects, such as mass, speed, and/or acceleration, to assist in accuracy of coin handling. In one embodiment, slow or stuck coins are automatically moved (such as by a pin or rake), or otherwise provided with kinetic energy. In one embodiment items including those which are not recognized as valuable, acceptable or desirable coins or other objects are allowed to follow a non-diverted, default path (preferably, under the force of gravity), while at least some recognized and/or accepted coins are diverted from the default path to move such items into an acceptance bin or other location.
In one embodiment, the device provides for ease of application (e.g. multiple measurements done simultaneously and/or at one location), increased performance, such as improved throughput and reduced jams (that prematurely end transactions and risk losing coins), more accurate discrimination, and reduced cost and/or size. One or more torroidal cores can be used for sensing properties of coins or other objects passing through a magnetic field, created in or adjacent a gap in the torroid, thus allowing coins, disks, spherical, round or other objects, to be measured for their physical, dimensional, or metallic properties (preferably two or more properties, in a single pass over or through one sensor). The device facilitates rapid coin movement and high throughput. The device provides for better discrimination among coins and other objects than many previous devices, particularly with respect to U.S. dimes and pennies, while requiring fewer sensors and/or a smaller sensor region to achieve this result. Preferably, multiple parameters of a coin are measured substantially simultaneously and with the coin located in the same position, e.g., multiple sensors are co-located at a position on the coin path, such as on a rail. In a number of cases, components are provided which produce more than one function, in order to reduce part count and maintenance. For example, certain sensors, as described below, are used for sensing two or more items and/or provide data which are used for two or more functions. Coin handling apparatus having a lower cost of design, fabrication, shipping, maintenance or repair can be achieved. In one embodiment, a single sensor exposes a coin to two different electromagnetic frequencies substantially simultaneously, and substantially without the need to move the coin to achieve the desired two-frequency measurement. In this context, “substantially” means that, while there may be some minor departure from simultaneity or minor coin movement during the exposure to two different frequencies, the departure from simultaneity or movement is not so great as to interfere with certain purposes of the invention such as reducing space requirements, increasing coin throughput and the like, as compared to previous devices. For example, preferably, during detection of the results of exposure to the two frequencies, a coin will move less than a diameter of the largest-diameter coin to be detected, more preferably less than about ¾ a largest-coin diameter and even more preferably less than about ½ of a coin diameter.
The present invention makes possible improved discrimination, lower cost, simpler circuit implementation, smaller size, and ease of use in a practical system Preferably, all parameters needed to identify a coin are obtained at the same time and with the coin in the same physical location, so software and other discrimination algorithms are simplified.
Other door configurations than those depicted can be used. The door 62 may have a laminated structure, such as two steel or other sheets coupled by, e.g., adhesive foam tape.
A number of variations and modifications of the invention can be used. It is possible to use some aspects of the invention without using others. For example, the described techniques and devices for providing multiple frequencies at a single sensor location can be advantageously employed without necessarily using the sensor geometry depicted. It is possible to use the described torroid-core sensors, while using analysis, devices or techniques different from those described herein and vice versa. It is possible to use the sensor and or coin rail configuration described herein without using the described coin pickup assembly. For example it is possible to use the sensor described herein in connection with the coin pickup assembly described in Ser. No. 08/883,655, for POSITIVE DRIVE COIN DISCRIMINATING APPARATUS AND METHOD, and incorporated herein by reference. It is possible to use aspects of the singulation and/or discrimination portion of the apparatus without using a trammel. Although the invention has been described in the context of a machine which receives a plurality of coins in a mass, a number of features of the invention can be used in connection with devices which receive coins one at a time, such as through a coin slot.
Although the sensors have been described in connection with the coin counting or handling device, sensors can also be used in connection with coin activated devices, such as vending machines, telephones, gaming devices, and the like. In addition to using information about discriminated coins for outputting a printed voucher, the information can be used in connection with making electronic funds transfers, e.g. to the bank account of the user (e.g. in accordance with information read from a bank card, credit card or the like) and/or to an account of a third party, such as the retail location where the apparatus is placed, to a utility company, to a government agency, such as the U.S. Postal Service, or to a charitable, non-profit or political organization (e.g. as described in U.S. application Ser. No. 08/852,328, filed May 7, 1997 for Donation Transaction method and apparatus, incorporated herein by reference. In addition to discriminating among coins, devices can be used for discriminating and/or quality control on other devices such as for small, discrete metallic parts such as ball bearings, bolts and the like. Although the depicted embodiments show a single sensor, it is possible to provide adjacent or spaced multiple sensors (e.g., to detect one or more properties or parameters at different skin depths). The sensors of the present invention can be combined with other sensors, known in the art such as optical sensors, mass sensors, and the like. In the depicted embodiment, the coil 242 is positioned on both a first side 244a of the gap and a second side 244b of the gap. It is believed that as the coin 224 moves down the rail 232, it will be typically positioned very close to the second portion 244b of the coil 242. If it is found that this close positioning results in an undesirably high sensitivity of the sensor inductance to the coin position (e.g. an undesirably large variation in inductance when coins “fly” or are otherwise somewhat spaced from the back wall of the rail 232), it may be desirable to place the high frequency coil 242 only on the second portion 244a (
Although it is possible to provide a sensor in which the core is driven by a direct current, preferably, the core is driven by an alternating or varying current.
In one embodiment two or more frequencies are used. Preferably, to reduce the number of sensors in the devices, both frequencies drive a single core. In this way, a first frequency can be selected to obtain parameters relating to the core of a coin and a second frequency selected to obtain parameters relating to the skin region of the coin, e.g., to characterize plated or laminated coins. One difficulty in using two or more frequencies on a single core is the potential for interference. In one embodiment, to avoid such interference both frequencies are phase locked to a single reference frequency. In one approach, the sensor forms an inductor of an L-C oscillator, whose frequency is maintained by a Phase-Locked Loop (PLL) to define an error signal (related to Q) and amplitude which change as the coin moves past the sensor.
As seen in
A relatively straightforward approach would be to use the coil as an inductor in a resonant circuit such as an LC oscillator circuit and detect changes in the resonant frequency of the circuit as the coin moved past or through the gap. Although this approach has been found to be operable and to provide information which may be used to sense certain characteristics of the coin (such as its diameter) a more preferred embodiment is shown, in general form, in
In the embodiment of
Without wishing to be bound by any theory, it is believed that the presence of the coin affects energy loss, as indicated by the Q factor in the following manner. As noted above, as the coin moves past or through the gap, eddy currents flow causing an energy loss, which is related to both the amplitude of the current and the resistance of the coin. The amplitude of the current is substantially independent of coin conductivity (since the magnitude of the current is always enough to cancel the magnetic field that is prevented by the presence of the coin). Therefore, for a given effective diameter of the coin, the energy loss in the eddy currents will be inversely related to the conductivity of the coin. The relationship can be complicated by such factors as the skin depth, which affects the area of current flow with the skin depth being related to conductivity.
Thus, for a coil 502 driven at a first, e.g. sinusoidal, frequency, the amplitude can be determined by using timing signals 602 (
In one embodiment, the invention involves combining two or more frequencies on one core by phase-locking all the frequencies to the same reference. Because the frequencies are phase-locked to each other, the interference effect of one frequency on the others becomes a common-mode signal, which is removed, e.g., with a differential amplifier.
In one embodiment, a coin discrimination apparatus and method is provided in which an oscillating electromagnetic field is generated on a single sensing core. The oscillating electromagnetic field is composed of one or more frequency components. The electromagnetic field interacts with a coin, and these interactions are monitored and used to classify the coin according to its physical properties. All frequency components of the magnetic field are phase-locked to a common reference frequency. The phase relationships between the various frequencies are fixed, and the interaction of each frequency component with the coin can be accurately determined without the need for complicated electrical filters or special geometric shaping of the sensing core. In one embodiment, a sensor having a core, preferably ferrite, which is curved (or otherwise non-linear), such as in a U-shape or in the shape of a section of a torus, and defining a gap, is provided with a wire winding for excitation and/or detection. The sensor can be used for simultaneously obtaining data relating to two or more parameters of a coin or other object, such as size and conductivity of the object. Two or more frequencies can be used to sense core and/or cladding properties.
In the embodiment depicted in
The phase locked loop circuits described above use very high (theoretically infinite) DC gain such as about 100 dB or more on the feedback path, so as to maintain a very small phase error. In some situations this may lead to difficulty in achieving phase lock up, upon initiating the circuits and thus it may be desirable to relax, somewhat, the small phase error requirements in order to achieve initial phase lock up more readily.
Although the embodiment of
Additionally, rather than providing two or more discrete frequencies, the apparatus could be configured to sweep or “chirp” through a frequency range. In one embodiment, in order to achieve swept-frequency data it would be useful to provide an extremely rapid frequency sweep (so that the coin does not move a large distance during the time required for the frequency to sweep) or to maintain the coin stationary during the frequency sweep.
In some embodiments in place of or in addition to analyzing values obtained at a single time (t1
In some embodiments the output data is influenced by relatively small-scale coin characteristics such as plating thickness or surface relief. In some circumstances it is believed that surface relief information can be used, e.g., to distinguish the face of the coin, (to distinguish “heads” from “tails”) to distinguish old coins from new coins of the same denomination and the like. In order to prevent rotational orientation of the coin from interfering with proper surface relief analysis, it is preferable to construct sensors to provide data which is averaged over annular regions such as a radially symmetric sensor or array of sensors configured to provide data averaged in annular regions centered on the coin face center.
Although
In another embodiment, depicted in
Although one manner of analyzing D and Q signals using a microprocessor is described above, a microprocessor can use the data in a number of other ways Although it would be possible to use formulas or statistical regressions to calculate or obtain the numerical values for diameter (e.g., in inches) and/or conductivity (e.g., in mhos), it is contemplated that a frequent use of the present invention will be in connection with a coin counter or handler, which is intended to 1) discriminate coins from non-coin objects, 2) discriminate domestic from foreign coins and/or 3) discriminate one coin denomination from another. Accordingly, in one embodiment, the microprocessor compares the diameter-indicating data, and conductivity-indicating data, with standard data indicative of conductivity and diameter for various known coins. Although it would be possible to use the microprocessor to convert detected data to standard diameter and conductivity values or units (such as inches or mhos), and compare with data which is stored in memory in standard values or units, the conversion step can be avoided by storing in memory, data characteristic of various coins in the same values or units as the data received by the microprocessor. For example, when the detector of
Although in one embodiment it is possible to use data from a single point in time, such as when the coin is centered on the gap 216, (as indicated, e.g., by a relative maximum, or minimum, in a signal), in another embodiment a plurality of values or a continuous signal of the values obtained as the coin moves past or through the gap 216 is preferably used.
An example of a single point of comparison for each of the in-phase and delayed detector, is depicted in
As noted, rather than using single-point comparisons, it is possible to use multiple data points (or a continuous curve) generated as the coin moves past or through the gap 216, 316. Profiles of data of this type can be used in several different ways. In the example of
In one embodiment, the in-phase and out-of-phase data are correlated to provide a table or graph of in-phase amplitude versus 90-degree delayed amplitude for the sensed coin (similar to the Q versus D data depicted in figs 10A and 10B), which can then be compared with standard in-phase versus delayed profiles obtained for various coin denominations in a manner similar to that discussed above in connection with
Although coin acceptance regions are depicted (
In both the configuration of
Although certain sensor shapes have been described herein, the techniques disclosed for applying multiple frequencies on a single core could be applied to and of a number of sensor shapes, or other means of forming an inductor to subject a coin to an alternating magnetic field.
Although an embodiment described above provides two AC frequencies to a single sensor core at the same time, other approaches are possible. One approach is a time division approach, in which different frequencies are generated during different, small time periods, as the coin moves past the sensor. This approach presents the difficulty of controlling the oscillator in a “time-slice” fashion, and correlating time periods with frequencies for achieving the desired analysis. Another potential problem with time-multiplexing is the inherent time it takes to accurately measure Q in a resonant circuit. The higher the Q, the longer it takes for the oscillator's amplitude to settle to a stable value. This will limit the rate of switching and ultimately the coin throughput. In another embodiment, two separate sensor cores (1142a,b
In one embodiment, a sensor includes first and second ferrite cores, each substantially in the shape of a section of a torus 282a, b (
In another embodiment, current provided to the coil is a substantially constant or DC current. This configuration is useful for detecting magnetic (ferromagnetic) v. non-magnetic coins. As the coin moves through or past the gap, there will be eddy current effects, as well as permeability effects. As discussed above, these effects can be used to obtain, e.g., information regarding conductivity, such as core conductivity. Thus, in this configuration such a sensor can provide not only information about the ferromagnetic or non-magnetic nature of the coin, but also regarding the conductivity. Such a configuration can be combined with a high-frequency (skin effect) excitation of the core and, since there would be no low-frequency (and thus no low-frequency harmonics) interference problems would be avoided. It is also possible to use two (or more) cores, one driven with DC, and another with AC. The DC-driven sensor provides another parameter for discrimination (permeability). Permeability measurement can be useful in, for example, discriminating between U.S. coins and certain foreign coins or slugs. Preferably, computer processing is performed in order to remove “speed effects.”
Although the invention has been described by way of a preferred embodiment and certain variations and modifications, other variations and modifications can also be used, the invention being defined by the following claims.
The present application is a continuation of U.S. application Ser. No. 10/336,617 filed Jan. 2, 2003 now U.S. Pat. No. 6,766,892, which is a continuation of U.S. application Ser. No. 09/703,946 filed Oct. 31, 2000 now U.S. Pat. No. 6,520,308, which is a continuation of U.S. application Ser. No. 09/105,403 filed Jun. 26, 1998 (now U.S. Pat. No. 6,196,371), which is a continuation-in-part of U.S. application Ser. No. 08/883,780 filed Jun. 27, 1997 (now U.S. Pat. No. 5,988,348), which is a continuation-in-part of U.S. application Ser. No. 08/807,046 filed Feb. 24, 1997, now abandoned, which is a continuation of U.S. application Ser. No. 08/672,639 filed Jun. 28, 1996, now abandoned: all are incorporated herein in their entireties by reference.
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| Parent | 10336617 | Jan 2003 | US |
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| Parent | 09703946 | Oct 2000 | US |
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| Parent | 08883780 | Jun 1997 | US |
| Child | 09105403 | US | |
| Parent | 08807046 | Feb 1997 | US |
| Child | 08883780 | US |
