Coin discrimination apparatus and method

• US 5,351,798 A
• Filed: 03/08/1993
• Issued: 10/04/1994
• Est. Priority Date: 06/28/1991
• Status: Expired due to Term

• Current Assignee: Protel Incorporated (Inductotherm Group)
• Original Assignee: Protel Incorporated (Inductotherm Group)
• Inventors: Hayes, Stephen J.
• Primary Examiner(s): Bartuska, F. J.
• Application Number:
  US08/027,363
• Time in Patent Office: 575 Days
• Field of Search: 194/317, 194/318, 194/319
• US Class Current: 194/318
• CPC Class Codes: G07D 2205/001 Reconfiguration of coin testing devices
• CPC Class Codes: G07D 5/08 Testing the magnetic or electric properties

Abstract

An electronic coin detector and method for sensing the presence of a valid coin and for providing an indication of the valid coin'"'"'s type. A coin is guided into position between a first set of inductor coils. The coin is then guided through a channel surrounded by a second inductor coil. A first oscillating signal is then fed to the first set of inductor coils and a second higher frequency oscillating signal is fed to a second inductor coil. An altered signal is then provided in response to the effect of the coin passing through the inductor coils. After the coin has passed adjacent one of the inductor coils, the inductor coils are fed a calibration signal to produce a calibrated signal. This calibrated signal is then used to scale the altered signal. The frequency and amplitude of the scaled altered signal for the first set of inductor coils and the second inductor coil are combined with prestored statistical variables corresponding to frequency and amplitude values of a sample of valid coins. The combined results are then compared to determine if the deposited coin is valid. If the coin is valid, the combined results are compared with the prestored statistical variables to determine the coin'"'"'s type.

Claims

1. A coin detection method, comprising the steps of:

establishing a magnetic flux across a coin path;

passing a coin under test along the path;

detecting both the change in inductance and the change in energy loss caused by the presence of the coin under test;

utilizing both changes for the detection of plural predetermined electrical characteristics of the coin under test;

storing into memory statistical variables determined from measurements of the predetermined electrical characteristics of a plurality of coins of the same type as the coin under test;

determining for the coin under test a deviation value in relation to all of the stored statistical variables; and

providing a signal indicating acceptability of the coin under test if said deviation value is within a predetermined acceptable range.

2. The coin detection method as recited in claim 1 further comprising the steps of:

providing a first oscillating signal to establish said magnetic flux;

establishing a second magnetic flux across the coin path being generated by an oscillating signal having a frequency different than the first frequency; and

detecting both the change in inductance and change in energy loss across said second magnetic flux caused by the presence of the coin and utilizing both changes for the detection of a coin having predetermined characteristics.

3. An electronic coin detector comprising:

a path in which a coin under test travels from a first end to a second end;

a first inductor coil having a surface extending along said path, said surface being disposed adjacent said path such that when the coin travels along said path the coin passes adjacent the coils;

a longitudinal channel extending through said duct for receiving coins traveling along said path;

a second inductor coil surrounding said channel;

means for providing a first oscillation signal to said first inductor coil and for providing a first altered oscillation signal in response to the effect of a coin passing adjacent said first inductor coil;

means for providing a second oscillation signal to said second inductor coil and for providing a second altered oscillation signal in response to the effect of a coin passing through said channel;

means for storing into a memory statistical variables determined from measurements of the predetermined electrical characteristics of a plurality of coins of the same type as the coin under test; and

means responsive to said first and second altered signals for determining for the coin under tests a deviation value in relation to the stored statistical variables.

4. The coin detector as recited in claim 3 further comprising:

a third inductor coil having a surface extending along said path, said surface being disposed adjacent and parallel to said first inductor coil surface, said third inductor coil being electrically connected to said first inductor coil, and wherein said first oscillation signal providing means provides said first oscillation signal to said first and second inductor coils, and provides the first oscillation signal in response to the extent of the coin passes between said first and third inductor coils.

5. The coin detector as recited in claim 3 wherein said first oscillation signal is provided at a frequency substantially less than said second oscillation signal'"'"'s frequency.

6. The coin detector as recited in claim 3 wherein said indicating means comprises means for sensing the frequency of said first and second altered signals and means for sensing the amplitudes of said first and second altered signals.

7. The coin detector as recited in claim 4 wherein the diameter of an outside parameter of the parallel coils is greater than the diameter of the largest acceptable coin.

8. The coin detector as recited in claim 4 further comprising one or more ferrite disks disposed adjacent said parallel surfaces and mounted to said inductor coils.

9. The coin detector as recited in claim 3 wherein said first oscillation signal is provided at a frequency substantially less than 1 MHz and said second oscillation signal is provided at a frequency above 1 MHz.

10. The coin detector as recited in claim 9 wherein said first oscillation signal is provided at a frequency of about 120 kHz and said second oscillation signal is provided at a frequency at about 2 MHz.

11. A method of determining whether or not a coin being sampled is acceptable, the method comprising the steps of:

providing a signal having electrical characteristics corresponding to physical characteristics of the coin being sampled;

storing into memory statistical variables determined from electrical characteristics for acceptable coin types;

determining for said coin being sampled a statistical variation of said electrical characteristics of said signal from the stored statistical variables; and

providing an indication that the coin being sampled is acceptable if said statistical variation is within a predetermined range.

12. The method of determining whether or not a coin is acceptable as recited in claim 11 further comprising the step of establishing a probability that the coin being sampled is an acceptable coin type by comparing the signal corresponding to the coin being sampled with the stored statistical variables for each coin type.

13. The method of determining whether or not a coin is acceptable as recited in claim 11 further comprising the step of storing into memory as part of the statistical variables a mean and standard deviation value for each acceptable coin type.

14. The method of determining whether or not a coin is acceptable as recited in claim 11 further comprising the step of determining the probability that a coin is being sampled is an acceptable coin type by determining difference the signal and the stored mean value, for each coin type, dividing this difference by the stored standard deviation for each coin type, squaring the quotient obtained from the division and adding the resulting squared quotients for each signal.

15. The method of determining whether or not a coin is acceptable as recited in claim 12 further comprising the step of indicating which of said acceptable coin types said coin being sampled matches when said statistical variation is less than the predetermined value by comparing the probability that the coin being sampled is acceptable for each coin type;

and selecting the acceptable coin type with the highest probability.

16. The method of determining whether or not a coin is acceptable as recited in claim 15 further comprising the step of determining the coin type with the smallest statistical variation when one of said statistical variations is less than a predetermined value.

17. The method of determining whether or not a coin is acceptable as recited in claim 15 further comprising the step of determining a mean signal characteristic for each coin type.

18. The method of determining whether or not a coin is acceptable, the method comprising the steps of:

providing a signal having a plurality of electrical characteristics, each of said characteristics corresponding to an effect resulting from a coin under test passing through an inductively induced electromagnetic field;

providing variables which are statistical functions of a plurality of said electrical characteristics for each acceptable coin type;

storing said variables in a memory;

determining a statistical variation of said electrical characteristics of said signal with reference to said stored variables; and

indicating when a coin under test has a statistical variation within a predetermined limit.

19. A method for detecting the presence of a coin comprising the steps of:

passing a coin along a path from a first end to a second end;

providing an inductor coil establishing a magnetic flux along the path;

providing a correction signal that changes to a changed correction signal in response to changes in magnetic flux caused by the presence of the coin in the path;

sensing a characteristic of the correction signal before the coin is present in the path;

setting a first threshold level corresponding to the characteristic of the correction signal;

incrementing the first threshold level by a preset amount to a second threshold level;

comparing the second threshold level to the characteristic of the changed correction signal; and

indicating that the coin is passing along the path when the characteristic of the changed correction signal exceeds the second threshold level.

20. The method as recited in claim 19 wherein said characteristic is a voltage level.

21. The method as recited in claim 19 selecting the preset amount to prevent false indications due to electric noise or interference.

22. A method for discriminating between acceptable and unacceptable metal members of a given type, the method comprising the steps of:

evaluating a plurality of acceptable members of a given type with an electrical sensing means for determining statistical variables for selected electrical characteristics of the given type;

evaluating the selected electrical characteristics for a member of the given type under test and determining a deviation value in relation to a plurality of the statistical variables; and

accepting or rejecting the member under test by determining whether its deviation vale falls within a predetermined range of the statistical variables.

23. The method recited in claim 22 wherein the evaluating steps further include inducing a first electromagnetic field of a first frequency across the acceptable members and the member under test.

24. The method recited in claim 23 wherein the evaluating steps further include the step of inducing a second electromagnetic field of a second frequency across the acceptable members and the member under test.

25. The method recited in claim 22 further comprising the step of computing a standard deviation of the statistical variables and a means for the selected electrical characteristics of the acceptable members of the given type.

26. The method recited in claim 22 further comprising the steps of evaluating and determining statistical variables of selected electrical characteristics of members of a second given type, the acceptance of rejection step further comprising the step of determining whether the selected electrical characteristics of a member of the second given type under test fall within a second predetermined range of the statistical variables.