GB2341709A - Coin sensing device - Google Patents

Abstract

A coin or token sensing device 2 comprises means for determining the positions adopted concurrently by at least two points on the perimeter of a coin or token travelling on a coin track, wherein at least one of said determining means comprises an optical sensor for deriving the position of a perimeter point from the amount of light sensed by the sensor. The amount of light sensed being linearly related to the area of the sensor covered by the coin. A sensor (30, Fig.4) may be provided on the base of the track (10, Fig.4) to detect a further perimeter point. A circular sensor may determine the amount of light sensed is non linearly related to the area of the sensor covered by the coin. Sensor means (40,42, Fig. 6) for determining the trajectory of the coin, and a further magnetic, optical or capacitive sensor may determine characteristics of the centre region of the coin. A star shaped array of sensors may detect a coin falling down a path (16, Fig. 9), said sensors being associated with rectangular windows (46,48,50, Fig. 9), and a further inductive sensor (52, Fig. 9) in the centre of the array. The star shaped array may identify the velocity, acceleration and trajectory of a coin.

Description

234170,9 Coin sensimdevice The invention relates to a device for sensing a

coin, and especially to a device for deriving the diameter of a coin, for use, for example, in a coin-operated Z device or system, such as a vending machine.

Z> In this specification, the term "coin" is employed to mean any coin (whether valid or counterfeit), token, slug, washer. or object or item, and especially any object or item which could be utilised by an individual in an attempt to operate a coin-operated device or system. A "valid coin" is considered to be an authentic coin, token, or the like, and especially an authentic coin of a monetary system or systems in which or with which a coin-operated device or system is intended to operate and of a denomination which such coin-operated device or system is intended selectively to receive and to treat as an item of value.

Kno"m coin mechanisms perform one or more tests on an inserted coin to assess, for example, the material, thickness and diameter of the coin, to determine whether or not it is valid.

US 5,3392,892 describes an apparatus for measuring the diameter of coins comprising two photoelectric detectors arranged along a line perpendicular to the floor of the guide channel along which a coin travels. Using a timer and the photoelectric detectors, two points on the outline of a coin are determined, and those two points and the geometry of the guide channel are used to derive the diameter of the coins.

GB 2 115 547 A also relates to an apparatus for measuring the diameter of coins. The apparatus has a pair of photo-electric converters, each extending 1 along a line towards the centre of the path along which a coin travels. A signal is output representing the total area of the photo-electric converters that is 2 obscured. The apparatus selects the largest output value, which corresponds to the diameter of the coin.

Both the arrangements described above are complicated, and require either timers or a maximum value circuit. Neither enables a diameter of a coin to be derived from a single, measurement of the coin.

The present invention provides an apparatus for sensing a coin or token comprising means for determining the positions concurrently adopted by at least two points on the perimeter of the coin or token, wherein at least one of id position determining means comprises an optical sensor for deriving the sai 1 1 cl 1 position of a perimeter point from the amount of light sensed by the sensor.

The invention also provides an apparatus comprising sensor means for 0 determining the trajectory of a coin or token and a sensor for sensing a 1 1 characteristic in the centre region of the coin or token, using the trajectory determininz means.

The invention also provides a method for sensing a coin or token comprising C, t> determining the position of at least one perimeter point of the object by measuring the amount of light sensed by an optical sensor at a particular time, 0 and determining the position of at least one other point on the perimeter of the object at that particular time.

The invention also provides a method for sensing a coin or token comprising determining the positions concurrently adopted by at least two points on the perimeter of the coin or token by deriving the position of a perimeter point from the amount of light sensed by an optical sensor.

t> The invention further provides a method of validating coins comprising determining the extent to which at least three optical sensors are contemporaneously obscured by the coin and producing therefrom a value dependent on coin diameter.

The invention further provides a method of monitoring movement of a coin by measuring the chance in the output of at least one optical sensor as a coin edge passes the sensor.

The invention further provides a method for measuring coin speed comprising determining the rate at which the output of an optical sensor changes as a coin I edge passes the sensor.

The invention further provides a method for measuring coin acceleration comprising deten-nining the rate at which the rate of change of the output of It) ?_ an optical sensor changes as a coin edge passes the sensor.

The invention also provides a method of testing a coin or token comprising determining the position and/or trajectory of the coin or token and sensing a characteristic pattern in the center region of the coin or token.

Embodiments of the invention will be described with reference to the accompanying drawings, of which:

rp Fig. I is a diagram of a coin mechanism according to a first embodiment of the invention; Fig. 2 is a cross-section of a diameter sensor according to the first embodiment of the invention; Fig. 3 is a schematic diagram of the first embodiment; 30 Fig. 4 is a schematic diagram of a second embodiment; 4 Fig. 5 is a schematic diagram of a third embodiment; Fig. 6 is a schematic diagram of a fourth embodiment; Figs. 7A, 7B, 7C and are diagrams illustrating the operation of the fourth 0 embodiment Fig. 8 is a schematic diagram of a sixth embodiment; Fig. 9 is a schematic diagram of a seventh embodiment.

Fig. 1 shows a coin mechanism 1 in accordance with a first embodiment of the invention in outline. The coin mechanism 1 is for use, for example, in a vending machine. The coin mechanism 1 includes a coin testing section, indicated cenerally by the reference numeral 2, a coin separating section, indicated generally by the reference numeral 4, and a coin storage section indicated generally by the reference numeral 6. The mechanism is controlled by control means 8, including a microprocessor and a memory (not shown).

tP The coin testing section 2 includes a coin guide formed of a downwardly sloping ramp 10 along which an inserted coin rolls on its edge, and a pair of parallel facing walls 11 (see Fig. 2). The testing section also includes electromagnetic sensors 12, 14 for testing respectively the material and W thickness of an inserted coin, and a diameter sensor 16, which will be described in more detail below. The sensors 12, 14, 16 are connected to the control means 8. The structure and operation of the coin mechanism 1 other than the diameter sensor 16 are known and described, for example, in GB 1 3 397 083), GB 1 44-33 934, GB 2 254 948 and GB 2 094 008 the contents of which are incorporated herein by reference.

The diameter sensor 16 of the first embodiment of the invention is described with reference to Figs. 2 and 33. The diameter sensor 16 includes a first optical sensor and a second optical sensor. Referring especially to Fig. 2, the first optical sensor is made up of an LED 18 positioned on one side of the coin guide and a detector in the fonn of a photodiode 20 positioned on the other side of the coin guide. The LED 18 is positioned close to the focal point of a convergent lens 22 so that a quasi parallel or substantially parallel beam is generated, and a focusing lens 24 focuses the light beam on the photodiode 20. A pair of corresponding rectangular windows 26 are formed in the walls of the coin guide facing the LED 18 and the photodiode 20 so that light from the LED 18 passes through those windows 26 to the photodiode 220. The rectangular windows 26 are relatively narrow in comparison with their length.

?D C, In the first embodiment, the windows 26 are arranged at an obtuse angle to the coin ramp 10 in the downstream direction (see Fig. 33) and are arranged so that a coin passing along the coin ramp 10 overlaps the windows 26 during part of its travel. The second optical sensor is an optical point sensor, also formed of an LED and a detector in the fon-n of a photodiode on opposite sides of the coin guide, with corresponding holes 28 are formed in the walls of the coin guide. The rectangular windows 26 associated with the first optical sensor and the holes 28 associated with the second sensor are so arranged that when the coin interrupts the light beam from the optical point sensor the rectanorular windows 26 are always partially covered for all types of coin with which the mechanism is to be used. Fig. 3 shows schematically the relationship between the rectangular windows 26, the holes 28 and the coin ramp 10, and a notional coin 29.

When a coin 29 passes between the rectangular windows 26 of the first optical sensor, it obscures parts of the windows 26 and reduces the amount of light sensed by the detector 20. As the coin passes the rectangular windows 26, the position of the coin changes and the amount of overlap with the rectangular windows 26 varies so that the amount of light sensed varies in dependence on the position of the coin 29. The ratio of the amount of light sensed by the detector 20 when a coin 29 overlaps the rectangular windows 26 to the amount of light sensed by the detector 20 when the windows are not obscured 6 (which is determined in advance) is the proportion of the windows that is obscured by the coin 29. This proportion indicates how far along the rectangular window 26 the circumference of the coin 29 overlaps the window.

Because the position and orientation of the rectangular windows 26 within the fixed reference of the coin mechanism is known, the co-ordinates of a point on the circumference of the coin 29 where it overlaps the windows can be derived. (The windows are sufficiently narrow that, as an approximation, the curvature of the circumference of the coin 29 can be disregarded and the outer edge of the coin 29 can be treated as a straight line.) More specifically, , the ratio of distance x to distance y (see Fig. J3) is the same as the ratio of amount of light detected when the coin 29 is in the position shown to the amount of light detected when no coin 29 interrupts the light from the LED 18.

In operation, when a coin 29 rolls doAm the ramp 10 and reaches the diameter sensor 16, it starts to obscure the rectangular windows 26. As the coin 29 progresses fiziher down the ramp 10, eventually it interrupts the light beam of the point sensor 28, in the position shown in Fig. J35. When the light beam for the second optical sensor is interrupted, this triggers a measurement of the output from the first detector 20 representing the amount of light sensed by the detector 20 at that time. The microprocessor in the control means then uses that measured output value to derive the co-ordinates of the circumference of the coin 29 at the point at which it overlaps the rectangular windows 26.

2 5 The position of the optical point sensor and the coin ramp 10 are stored in a memory within the control means 18. Using those parameters, which represent a point on the circumference of the coin 29 and a tangent to the coin 29, and the second point on the circumference of the coin 29 derived as described above, the microprocessor calculates the radius of the coin 29. (As is well known, the equation for a circle passing through two known points and 7 having a known tangent can then be derived, using, for example, the equation A C (x-a)2 + (y-b)2 = r 2 for the circle, where (a,b) are the initially unknown co ordinates of the centre point and r is the initially unknown radius. Thus, the radius of the circle can be determined.) Either the radius, or the diameter, is then compared with stored data representing diameters of acceptable coins and used in combination with the results of other tests from the coin test section to determine whether or not the coin 29 is valid.

The diameter sensor described above is relatively simple and accurate and allows the position of a coin 29 at a given time to be measured directly, without needing to know the speed of the coin 29. Unlike the prior art, the sensor does not require a timer or a circuit for determining the maximum value of the output from a sensor. The sensor can be used with coins of all sorts of materials, and the rectangular windows provide flexibility in the variation of diameter of coins that can be measured.

The coin mechanism of the second embodiment is the same as the first embodiment, apart from the diameter sensor. The diameter sensor of the second embodiment, as shown in Fig. 4, has a first optical sensor, and a contact sensor 30 arranged in the coin ramp 10. The optical sensor is like the first optical sensor of the first embodiment with rectangular windows, except that the rectangular windows '32 are arranged at an acute angle to the coin ramp 10 in the downstream direction. The first optical sensor is downstream of the contact sensor 330. The contact sensor 30 and the optical sensor are so arranged relative to each other that whenever a coin 29 with which the mechanism is to be used is in contact with the contact sensor 330, it also obscures at least part of the optical sensor, as shown schematically in Fig. 4.

8 In operation, when a coin 29 rolling along the coin ramp hits the contact 1 sensor 30, that triggers a measurement of the output of the detector of the optical sensor, the measurement representing the amount of the windows obscured by the coin 29, as in the first embodiment. As in the first embodiment, the microprocessor uses the measurement from the sensor to derive the co-ordinates of a first point B on the circumference of the coin 29.

The position of the contact sensor 350, which gives the co-ordinates of a second point on the circumference of the coin 29, are stored in the memory of the control means. From the first point B, the microprocessor derives the co ordinates of a third point A, using the fact that the perpendicular to the coin ramp passing through the co-ordinates of the contact sensor passes through the 1 C> centre of the coin 29 and so, by symmetry, the co-ordinates of a third point A correspond to the first point B but on the other side of the centre line.

is The microprocessor then calculates the radius of the coin 29 using the three points on the circumference of the coin 29, from the equation:

4Jp(p - a) -(p- b) (p - c) a, b, c are as shown on Fig. 4 and p = 1/2 (a + b + c) p = semiperimeter of triangle ABC on Fig. 4 The calculated radius is then used as described in the first embodiment to test the coin 29.

The coin 29 mechanism of the third embodiment is like the coin mechanism of the first embodiment, apart from the diameter sensor. The diameter sensor of the third embodiment, shown in Fig. 5, has two optical sensors with respective pairs of rectangular windows '34, 36. The control means 8 monitors the outputs from the detectors of both sensors, and when the outputs from 9 both detectors fall below a predetermined threshold value indicating that the coin 29 overlaps both pairs of windows, the outputs are measured simultaneously and used to derive two points on the circumference of the coin, in a similar manner to that described in relation to the first embodiment.

As in the first embodiment, the two points on the circumference and the coin ramp as a tanaent are used to derive the diameter of the coin.

The coin mechanism of the fourth embodiment is like that of the first embodiment, apart from the diameter sensor. The diameter sensor of the fourth embodiment is shown schematically in Fig. 6. The diameter sensor has a first optical sensor like the first embodiment with rectangular windows 38 arranged perpendicular to the coin ramp 10. Dowristream of the first optical sensor there are a pair of point sensors 40, 42 each point sensor being as described in the first embodiment arranged in a line parallel to the coin ramp 10. The output of the detector 20 of the first sensor is monitored by,' the control means 8, and when the output falls below a predetermined threshold, a first measurement is taken of the output of the sensor at a rate. Second and third measurements of the output of the sensor are taken at intervals of 1 ms (or less) later. The corresponding positions of the coin 29 are shown in Figs.

7A, 713 and 7C. As the coin 29 continues to travel down the ramp 10 it passes the two point sensors 40, 42 in succession. When the coin 29 interrupts the beam of the first point sensor 40, a timer is started, and when the coin 29 interrupts the beam of the second point sensor 42, the timer is stopped. Thus, the timer aives the time for the coin 29 to travel the known distance d between the two point sensors. The microprocessor then calculates the speed of the coin 29, using the time measured by the timer and the distance d, assuming that the coin 29 is travelling at a substantially constant speed. The three sampled output values from the first optical sensor give co-ordinates for points in the same manner as described above. These points are translated in accordance with the speed of the coin 29 and the times at which the corresponding values were measured, to reconstruct the position of the coi W 1 in 29 at one moment, as shown in Fig. 7D. More specifically, here the second Z measurement, of point B, was taken time t after the measurement of point C, and so point B is translated back by, distance vt, where v is the calculated velocity, of the coin 29, in the direction parallel to the ramp to point W.

Similarly', point A, measured time s after point C is translated back by distance vs in the direction of the ramp to point X. Thus, the position of the coin 229 at the time when point C was measured is reconstructed. Using points C, B' and A', the processor then calculates the radius of the coin 29, as in the second embodiment.

According to a fifth embodiment, which is a,,-ariation of the fourth embodiment, a first output from the first optical sensor is selected as the output from the sensor decreases, indicating that the first half of the coin 29 is being sensed, and the centre of the coin 29 is moving towards the sensor, and the output is monitored for the same value but when the output from the sensor is decreasing, indicating, that the second half of the coin 29 is being, sensed, and the centre of the coin 29 is moving away from the sensor. The time at which the selected value occurs for the second time is registered, and, using the speed of the coin 29 calculated from the point sensors, the two points on the circumference of the coin 29 for a single point in time are 1 reconstructed. The two points are symmetrical about the centre line and so a third point, where the centre line intersects the coin ramp, can be ascertained.

Then, again, the radius of the circle can be determined as described above.

The coin mechanism of the sixth embodiment of the invention is like that of the first embodiment, apart from the diameter sensor. The diameter sensor, shown schematically in Fig. 8, has a single optical sensor with rectangular windows 44 extending parallel to the coin ramp 10. The output of the detector of the sensor is monitored and as soon as the output falls below a 11 predetermined threshold value, the output is sampled at a rate of 1000 times per second. The sampled output values are converted into position values and are plotted against time. The resulting curve shows the movement of the coin 29 with time, and can be used to derive the velocity curve, by differentiating the movement curve, and the acceleration curve, by differentiating the 0 velocity,' curve.

Fig. 9 shows a seventh embodiment of the invention. Unlike the earlier embodiments, in this embodiment, the coin does not roll along a ramp but falls under gravity, along a path defined by, two parallel facing walls. Three optical sensors with associated pairs of rectangular windows 46, 48, 50 are arranged along the coin path in the walls. In this embodiment, first respective ends of the rectangular windows in the walls point towards the middle of the walls and the other ends point outwardly so that the windows form a star shape. In the centre, between the windows, there is a further, inductive, sensor 5? As in the third embodiment, the outputs from the detectors of the sensors are monitored, and as soon as the outputs from all three sensors simultaneously fall below a predetermined threshold, indicating the outputs are sampled, at a rate of 1000 times per second. Each set of sampled outputs is converted into a set of points on the circumference of the coin 29, in the manner already, described, and each set of points identifies the position of the coin 29 at a given lime. Hence, the sequence of sets of samples identifies the trajectory of the coin 29, and also the velocity and acceleration of the coin 29.

The central sensor 52 is for measuring properties of the centre of the coin 29, such as embossed patterns, in this example. Outputs from the central sensor 52 are associated with the position of the coin 29 at that time as determined by 12 the optical sensors and used with pattern classification for testing embossing in the centre of the coin 29.

Instead of an inductive sensor 52, the embossing of a coin 29 may be tested using a laser beam aimed at the centre of the coin 29 and a detector for detecting modulation of a reflected beam. Alternatively, a magnetic or capacitative sensor could be used.

In the embodiments described above, a single LED is used as the light source for the optical sensors. Instead, several LEDs in a mounting may be used.

Instead of a single lens for producing a parallel beam, a condenser lens and a focusing lens may be used. When more than one optical sensor is required, a light pipe may be used to split the light from an LED source. For example, an LED source system with enough energy, for example, red, blue and/or IR wavelength sources, can be grouped together and fed to the same splitting pipe.

Regarding the detectors, instead of a photodiode as described above, a light collecting device, such as a light pipe collector, or a charge coupled device (CCD) array, or other photosensitive devices, may be used. Where more than one optical sensor is in use, a single detector component with an n-way light collecting pipe and n distinct sources may be used. Separation can be achieved by turning each source on and off, or by using modulation and a different frequency for each source, allowing simultaneous measurement.

The optical point sensors may instead, for example, be magnetic or electromagnetic proximity sensors.

Instead of the contact sensor in the second embodiment, other means can be used to sense the arrival of the coin at the required position. Such means may be, for example, a reflective optical sensor, an inductive sensor, or a Hall effect sensor.

The rectangular windows of the embodiments may be arranged in various positions, although it is prefer-red that they are either parallel to the ramp, or at a non-perpendicular angle relative to the ramp, because those arrangements can give greater accuracy. Instead of rectangular windows, other shapes may be used in the optical sensors, for example, circles. However, in the case of, for example, a circle, the relationship between the area of the circle covered and a linear measurement is not linear, which makes the calculations more complicated and more of an approximation. The position can however be deten-nined by interpolation, for example using a look-up table relating to the C 1 amount of received light to the edge position.

In all of the embodiments described above, it is assumed that the coin is perpendicular to the ramp, so that all the points identified by the sensors lie on a circle in a common plane perpendicular to the coin ramp, which enables the diameter of the coin to be calculated easily. However, the coin may be at an angle that is not a right angle to the coin ramp. In such a case, the sensors used in the embodiments described above provide information about positions on the perimeter of the coin in two dimensions, that is, in a plane perpendicular to the coin ramp, but not in a third dimension, perpendicular to that plane. In such a case, the points lying in a plane derived from the sensors should be adjusted to arrive at a circle corresponding to the perimeter of the coin. This may be done, for example, by selecting a curve of best fit through the derived points in the plane, and transforming the curve to arrive at a circle in a plane, for example, using suitable computer software. If necessary, more sensors to derive more points on the perimeter of the coin can be used to achieve sufficient accuracy and uniqueness.

14 Various modifications of the apparatus and methods described above are possible.

Claims (24)

1 An apparatus for sensing a coin or token comprising means for determining the positions concurrently adopted by at least two points on the perimeter of the coin or token, wherein at least one of said position determining means comprises an optical sensor for deriving the position of a perimeter point from the amount of light sensed by the sensor.

2. An apparatus as claimed in claim 1, comprising means for determining a value dependent on the diameter of the coin or token from information including the perimeter points.

c)

3. An apparatus as claimed in claim 1 or 2, comprising means for 0 determining the position concurrently adopted by at least three points on the perimeter of the coin.

4. An apparatus as claimed in any one of claims 1 to 3, comprising a second optical sensor for determining a second perimeter point from the amount of light sensed.

5. An apparatus as claimed in claim 4, comprising a third optical sensor for determining a third perimeter point from the amount of light CI sensed.

6. An apparatus as claimed in any one of claims 1 to 5, comprising a ramp along which a coin or token rolls in use and a sensor for determining the position of a perimeter point of the coin or token in contact with the ramp.

16

7. An apparatus as claimed in any one of claims 1 to 6, wherein at least one of the optical sensors is rectangular so that the amount of light sensed is substantially linearly related to the area of the sensor covered by a coin or token.

8. An apparatus as claimed in any one of claims 1 to 7, wherein for at least one of the optical sensors the amount of light sensed is nonlinearly related to the area of the sensor covered by a coin or token.

9. An apparatus as claimed in claim 8, wherein the optical sensor is circular.

10. An apparatus as claimed in any one of claims 1 to 9 comprising a sensor for sensing a characteristic in the centre region of a coin.

11. An apparatus comprising sensor means for determining the trajectory of a coin or token and a sensor for sensing a characteristic in the centre region of the coin or token, using the trajectory determining means.

12. An apparatus as claimed in claim 10 or claim 11, wherein the sensor for sensing a characteristic in the centre region of the coin or token is a magnetic, optical or capacitative sensor.

13. A method for sensing a coin or token comprising determining the position of at least one perimeter point of the object by measuring the amount of light sensed by an optical sensor, at a particular time, and determining the position of at least one other point on the perimeter of the object at that particular time.

17

14. A method for sensing a coin or token comprising determining the positions concurrently adopted by at least two points on the perimeter of the coin or token by deriving the position of a perimeter point from the amount of light sensed by an optical sensor.

15. A method as claimed in claim 13 or claim 14, comprising deriving a value dependent on the diameter of the coin or token from the determined perimeter points.

16. A method as claimed in any one of claims B to 15, comprising determining the position of at least one further point on the perimeter of the coin.

17. A method of validating coins comprising determining the extent to which at least three optical sensors are contemporaneously obscured by the coin and producing therefrom a value dependent on coin diameter.

18. A method of monitoring movement of a coin by measuring the change in the output of at least one optical sensor as a coin edge passes the sensor.

19. A method for measuring coin speed comprising determining the rate at which the output of an optical sensor changes as a coin edge passes the sensor.

20. A method for measuring coin acceleration comprising determining the rate at which the rate of change of the output of an optical sensor changes as a coin edge passes the sensor.

21, A method of testing a coin or token comprising determining the position and/or trajectory of the coin or token and sensing a characteristic pattem in the center region of the coin or token.

22. An apparatus adapted to perform a method as claimed in any one of claims 13 to 14.

23. Apparatus substantially as hereiribefore described with reference to the accompanying drawings.

24. A method substantially as hereinbefore described with reference to the accompanying drawings.