Check-actuated control mechanisms – Including means to test validity of check – By testing material composition
Patent
1993-04-28
1995-01-10
Bartuska, F. J.
Check-actuated control mechanisms
Including means to test validity of check
By testing material composition
G07D 508
Patent
active
053798767
DESCRIPTION:
BRIEF SUMMARY
This invention relates to coin discrimination apparatus with improved discrimination between true and fraudulent coins and has particular but not exclusive application to a multi-coin validator.
In a conventional multi-coin validator coins pass along a path past a number of sensor means in the form of a coils which are energised to produce an inductive coupling with the coin. The degree of interaction between the coin and the coil is a function of the relative size of the coin and coil, the material from Which the coin is made and also its surface characteristics. Thus by monitoring the change in impedence presented by each coil, data indicative of the coin under test can be provided. The data can be compared with information stored in a memory to determine coin denomination and authenticity.
Our UK Specification 2 169 429 discloses coin discrimination apparatus utilising a plurality of inductive sensor coils which are each included in a respective resonant circuit. The resonant circuits are driven by a variable frequency oscillator through a multiplexer. As the coin passes a particular coil, the natural resonant frequency of the resonant circuit is altered due to the inductive coupling between the coin and the coil. The circuit is maintained at its natural resonant frequency by means of a phase locked loop which alters the frequency of the oscillator so as to track the natural resonant frequency of the resonant circuit during passage of the coin passed the coil. As a result, the amplitude of the oscilatory signal developed across the resonant circuit varies substantially on a transitory basis. The amplitude deviation produced by passage of the coin past the coil is a function of the coin denomination. It has been found that by using three coils of different sizes and configurations, three coin signals can be provided which uniquely characterise coins of a particular coin set e.g. the UK coin set.
The amplitude deviations produced by the three coils are digitised to produce the coin signals and are then compared with reference values stored in a programmable memory in order to discriminate between coins of different denominations, and frauds.
The data stored in the programmable memory is arranged to define windows of acceptable values for the coin signals. The windows are required because true coins of a particular denomination exhibit minor deviations in the values of the coin signals from coin to coin and the windows are selected so as to encompass the range of values normally expected from coins of a particular denomination.
A coin is determined to be acceptable if the coin signals produced from the respective sensor coils each lie within the range of values defined by the windows stored in the memory.
A problem arises that certain fraudulent coins e.g. a coin of a foreign coin set may have corresponding windows which overlap the windows of an acceptable coin, making it difficult to discriminate between a fraudulent and true coin.
The present invention provides a solution to this problem. In accordance with the present invention, first and second window widths are stored for each of first and second windows associated with the coin signals from first and second of the sensor means, the first window width corresponding to the width of a distribution of coin signals associated with acceptable coins of a particular denomination, and the second window width corresponding to the width of the distribution but excluding therefrom a range of values corresponding to fraudulent coins, and a coin under test is deemed to be acceptable upon the coin signals falling within the either a first or a second acceptance condition, wherein for the first acceptance condition, the value of the first coin signal falls within the first window width of the first window, and the value of the second coin signal falls within the second window width of the second-window, and for the second acceptance condition, the value of the first coin signal falls within the second window width of the first window, and the value of the second co
REFERENCES:
patent: 4845994 (1989-07-01), Quinlan, Jr.
Bartuska F. J.
Coin Controls Limited
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