GB2174227A - Apparatus for discriminating between different metallic articles - Google Patents

Abstract

A coin validator comprises a coin rundown path 2 along which is arranged an electrostatic coin diameter sensor 7, an electrostatic coin thickness sensor 8 and an inductive sensor 9 for determining the material from which the coin is made. Outputs from the sensors 7, 8 and 9 are processed by a microprocessor 12 and compared with stored values representative of acceptable coins and a solenoid 18 which operates an accept gate 4 is energised if the coin is acceptable. The electrostatic sensors in an alternative arrangement are replaced by optical sensors. <IMAGE>

Description

SPECIFICATION Apparatus for discriminating between different metallic articles FIELD OF THE INVENTION The invention relates to apparatus for discriminating between different metallic articles and in particular to the recognition and testing of coins e.g. in multi-coin validators as used for example in vending applications.

BACKGROUND OF THE INVENTION Current multi-coin validators rely upon either mechanical or inductive (electronic) technology.

An example of a mechanical validator is the Series 10 validator manufactured by Coin Controls Limited the assignee of the present application. An example of an inductive validator is the Coin Controls Limited Model EM5 validator. Mechanical coin testers are generally configured for particular coin sets and may often be limited in the range of coin sets to which they may be applied. In addition, their mechanical complexity leads to low reliability.

Mechanical testers are, however, the cheapest solution for coin validation.

Inductive coin validators utilise induction coils which establish an inductive coupling with a coin under test, the degree of coupling providing a characteristic signature signal indicative of the coin denomination. Inductive validators have the advantage of a great reduction in moving parts and therefore greatly increased reliability, and also offer greater security of validation. An example of an inductive validator is described in U.K. Patent Specification 2121579A.

However, inductive validators tend to be significantly more expensive then mechanical coin testers. Also, fundamental limitations of the sensing technology make inductive coin validators vulnerable to a class counterfeit coins or slugs which would be rejected by the older, cheaper mechanical validators. This is because an inductive coin signature signal is a weighted sum of the influences of material, coin thickness and coin diameter such that physically quite dissimilar metal coins and slugs can give similar or identical readings.

SUMMARY OF THE INVENTION The present invention makes use of a mix of inductive and non-mechanical non inductive sensing technology in order to maintain all the advantages of present wholly-inductive validators while offering increased security and much lower cost.

According to the present invention there is provided apparatus for discriminating between different metallic articles, comprising first and second sensor means for responding to different characteristics of an article under test, wherein the first sensor means comprises an inductive sensor responsive to the material of which the material is made, and the second sensor means is a non-inductive non-mechanical sensor responsive to a dimensional characteristic of the article under test.

The invention also provides a coin validator comprising a coin rundown path; a sensor including first and second sensing stations along said path and each for producing respective signals indicative of the duration of passage of a coin through the station; and means responsive to said signals to provide a signal indicative of coin diameter.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully understood an embodiment thereof will be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a schematic section view of a coin validator; Figure 2 is a schematic circuit diagram for the validator of Figure 1; Figure 3 is a waveform diagram for the outputs on lines 10 and 11 of Figure 2 in response to passage of a coin; and Figure 4 is a schematic view of an alternative optical sensor for detecting coin diameter.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to Figure 1, the coin validator consists of a coin entry 1, a coin rundown path 2 along which validation sensors 3 are positioned for coin validation, an accept gate 4, and accept and reject paths 5,6.

In use, a coin enters the mechanism, rolls down the rundown 2 pass the validation sensors 3 and if validated "true", causes the accept gate 4 to open and the coin to fall down the accept path 5. If the coin is validated false, the accept gate 4 does not open and the coin falls down the reject channel 6 and is returned to the punter. Entry of coins into the accept path 5 is confirmed for security reasons by means of an accept sensor (not shown) which may either be inductive or photoelectric.

The sensors 3 consist of an electrostatic diameter sensor 7, an electrostatic thickness sensor 8 and an inductive material sensor 9.

The inductive material sensor 9 creates an alternating (or pulsed) magnetic field which generates eddy currents in any conducting object placed within the field's region of influence. The amount of eddy current generated in a conductor and therefore the energy loss from the magnetic field is a function both of the type and bulk of the material within the field. If the inductive sensor 9 is suitably sized to be smaller than the coins under test and the frequency (or frequency components) of the inductive sensor's field are sufficiently high so that the field does not fully penetrate the coin, then the reading from the sensor is very strongly related to coin material type with a small residual effect due to the pattern em bossed on the surface of the coin, but is effectively independent of thickness or diameter.

The thickness sensor 8 consists basically of a parallel, 2-plate capacitor with plates 8A, 8B placed either side of the coin path 2. As the coin rolls between the plates, the capacitance of the plates is varied according to the metal thickness of the coin with a small effect due to embossed pattern. Since the dielectric constant of all metals is very similar, and is in any case swamped by the high conductivity of the metal, the capacitive thickness measurement is effectively independent of coin diameter and coin material.

The diameter sensor 7 consists of three plates comprising a central transmit plate TX and two spaced apart receive plates RX1, RX2. As a coin passes along the path 2 it interacts succesively with the plate pairs TX;RX1 and TX;RX2 to alter their capacitive coupling and this is used to detect coin diameter as will be explained in more detail hereinafter.

Referring now to Figure 2, the capacitor plate TX is connected to an electrostatic potential source - V and the plates RX 1,2 are connected to a potential source +V. Changes in potential on the plates RX 1,2 are detected by amplifiers Al, A2 and the electrostatic bias potential +V is blocked from the amplifiers by capacitors C1,C2. The outputs of the amplifiers A1,A2 are fed through lines 10, 11 to a microprocessor 12 for processing to determine the coin diameter.

Figure 3 shows the outputs on lines 10,11 as a coin passes through the diameter sensor 7; Figure 3A shows the output on line 10 and Figure 3B shows the output on line 11. As the coin encounters the capacitive coupling between the plates TX;RX1, the output on line 10 increases at time A in response to the leading edge of the coin, and falls at time B in response to the coin's trailing edge. Similarly, as the coin encounters the capacitive coupling between TX and RX2, the output on line 11 rises at time C and falls at time D. It will be seen that since the spacing between the plates TX; RX1;RX2 is known, the time interval A,C is indicative of the speed at which the coin travels along the path 2. This time interval is computed by the microprocessor 12 to provide a signal indicative of coin speed.Further, it will be seen that the time interval A,B is a function of both coin diameter and coin speed. The microprocessor 12 is thus programmed to compute coin diameter by computing the time interval A,B and dividing it by the coin speed signal derived from the time interval A,C. The resulting coin diameter signal is temporarily stored by the microprocessor 12.

An additional diameter computation can be performed utilising the time intervals C,B and C,D and the two results can be averaged to correct for coin acceleration along the rundown path 2.

As shown in Figure 2, the plates 8A, 8B of the thickness sensor are connected to the electrostatic potential sources +V; --V and the change in capacitance produced by passage of a coin between the plates results in a change in voltage that is detected by an amplifier A3 through a blocking capacitor C3.

The peak value of the output voltage of A3 is sampled and digitised by means of a circuit 13 and fed to the microprocessor 12.

The inductive sensor coil 9 is energised by an oscillator 14. As the coin passes the coil 9 it produces an inductive coupling with the coil which modifies the resonant characteristics of the ossillator/coil combination. This change in resonant characteristics may be manifested as a change in frequency and/or amplitude and is detected by a process circuit 15. The process circuit 15 will not be described in detail herein but may operate in accordance with the teachings of U.K. Patent Application No. 8531781 and corresponding U.S. Application Serial No.

06/812817. The output of the process circuit 15 constitutes a digital signal representative of the material of which the coin is made.

Thus, for a particular coin under test the microprocessor 12 develops a set of signals indicative of coin diameter,thickness and material type. The set of signals is compared with stored sets held in an EEPROM 16 which are representative of true coins of different denominations. If the signal set from the coin under test corresponds to stored signals for a true coin, within predetermined tolerance levels, an accept signal is produced on line 17 to energise a solenoid 18 that operates the gate 4 (Figure 1). Also, a signal may be provided on line 19 indicative of the coin denomination. Conversely, if the signal set does not correspond to a stored set from the EEPROM 16, the solenoid 18 is not energised and the coin is rejected.

An alternative form of the diameter sensor 7 is shown in Figure 4. This sensor utilises a pair of optical detector stations each comprising a light emitting diode LE01,2 and a phototransistor TR 1, TR2 on opposite sides of the rundown track 2. The outputs of the transistors To1,2 are connected to the amplifiers A1,A2 which produce on lines 10,11 outputs that are fed to the microprocessor 12. It will be seen that the outputs on lines 10,11 of Figure 4 correspond to the waveforms shown in Figure 3 as a coin 20 rolls down the track 2.

Other forms of electrostatic and optical detectors for use in the diameter and thickness sensors 7,8 can be utilised.

The electrostatic potentials +V; -V shown in Figure 2 may be pulsed or modulated under the control of the microprocessor. Many of the components shown in Figure 2 may be integrated into a customised integrated circuit.

In addition, the majority of the capacitive sensor plates may be incorporated onto PCB to produce high tolerance, highly repeatable low cost sensors. Costs may be further reduced by making these plates part of the PCB which carries the electronic components.

Expensive wound components are therefore limited to the material sensor 9 (and perhaps the accept sensor) and by means of a custom integrated circuit, extremely low component counts can be attained and hence very low cost.

Claims (14)

1. Apparatus for discriminating between different metallic articles, comprising first and second sensor means for responding to different characteristics of an article under test, wherein the first sensor means comprises an inductive sensor responsive to the material of which the material is made, and the second sensor means is a non-inductive non-mechanical sensor responsive to a dimensional characteristic of the article under test.

2. Apparatus according to claim 1 and comprising a coin validator.

3. Apparatus according to claim 2 wherein said second sensor comprises an electrostatic sensor.

4. Apparatus according to claim 3 wherein said second sensor is adapted to provide signals for determining coin diameter.

5. Apparatus according to claim 3 including a coin rundown path, and wherein the second sensor includes electrode means arranged along the path such that passage of a coin along the path affects capacitive coupling therebetween; and means responsive to said capacitive coupling to produce a signal indicative of coin diameter.

6. Apparatus according to claim 5 wherein said electrode means comprises a transmit electrode at a first potential, and receive electrodes at a second potential and arranged on opposite sides of the transmit electrode along the coin rundown path.

7. Apparatus according to claim 5 including a third sensor for sensing coin thickness.

8. Apparatus according to claim 7 wherein said third sensor comprises first and second electrode plates arranged on opposite sides of the coin rundown path to permit passage of a coin therebetween, means for applying a potential difference to the electrode plates, and means responsive to changes of potential difference between the electrode plates produced in response to passage of a coin therebetween for producing a signal indicative of coin thickness.

9. Apparatus according to claim 2 wherein said second sensor means comprises an optical sensor.

10. Apparatus according to claim 9 wherein the optical sensor comprises first and second spaced apart dectector stations, each station comprising a light source and a light detector for passage of a coin therebetween.

11. Apparatus according to claim 2 including means for comparing signals from said sensor means with stored values thereof to determine coin authenticity.

12. A coin validator comprising a coin rundown path; a sensor including first and second detector stations along said path and each for producing respective signals indicative of the duration of passage of a coin through the station; and means responsive to said signals to provide a signal indicative of coin diameter.

13. A coin validator according to claim 12 wherein said signal responsive means includes means responsive to the signals from both of the stations to derive a signal which is a function of coin speed, means responsive to the signal from one of the stations to derive an interval signal which is a function of coin speed and coin diameter, and means responsive to said interval signal and said coin speed signal to derive a signal indicative of coin diameter.

14. A coin validator substantially as herein described with reference to Figure 4 of the accompanying drawings.

14. A coin validator according to claim 12 wherein said sensor is an electrostatic sensor.

15. A coin validator according to claim 12 wherein said sensor is an optical sensor.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1-15 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A coin validator comprising a coin rundown path and first and second sensor means for sensing characteristics of a coin travelling along the path wherein: the first sensor means comprises an inductive sensor responsive to the material of which the coin is made, and the second sensor is a non-inductive non mechanical sensor responsive to coin diameter, and comprises first and second detector stations along said path for producing respective signals as the coin passes through the stations, and means responsive to said detector station signals to provide an output which is a function of the diameter of the coin.

2. A coin validator according to claim 1 wherein said detector station signal responsive means includes means responsive to the signals from both of the stations to derive a signal which is a function of coin speed, means responsive to the signal from one of the stations to derive an interval signal which is a function of coin speed and coin diameter, and means responsive to said interval signal and said coin speed signal to derive a signal indicative of coin diameter.

3. A coin validator according to claim 1 or 2 wherein said second sensor comprises an electrostatic sensor.

4. A coin validator according to claim 3 wherein the second sensor includes electrode means arranged along the path to define said detector stations such that passage of a coin along the path affects capacitive coupling therebetween for said stations respectively.

5. A coin validator according to claim 4 wherein said electrode means comprises a transmit electrode at a first potential, and receive electrodes at a second potential and arranged on opposite sides of the transmit electrode along the coin rundown path.

6. A coin validator according to any preceding claim wherein said second sensor means comprises an optical sensor.

7. A coin validator according to claim 6 wherein each said detector station comprises a light source and a light detector for passage of a coin therebetween.

8. A coin validator according to any preceding claim including a third sensor for sensing coin thickness.

9. A coin validator according to claim 8 wherein said third sensor comprises first and second electrode plates arranged on opposite sides of the coin rundown path to permit passage of a coin therebetween, means for applying a potential difference to the electrode plates, and means responsive to changes of potential difference between the electrode plates produced in response to passage of a coin therebetween for producing a signal indicative of coin thickness.

10. A coin validator according to any preceding claim including means for comparing signals from said sensor means with stored values thereof to determine coin authenticity.

11. A coin validator comprising a coin rundown path; a sensor including first and second detector stations along said path and each for producing respective signals indicative of the duration of passage of a coin through the station; and means responsive to said signals to provide a signal indicative of coin diameter.

12. A coin validator substantially as herein described with reference to Figure 1 of the accompanying drawings.

13. A coin validator substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.