Check-actuated control mechanisms – Including means to test validity of check – By testing material composition
Patent
1994-04-28
1995-11-28
Bartuska, F. J.
Check-actuated control mechanisms
Including means to test validity of check
By testing material composition
194339, G07D 504, G07D 508
Patent
active
054699525
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to coin discrimination apparatus which has particular but not exclusive application to a multi-coin validator.
BACKGROUND OF THE INVENTION
In a conventional multi-coin validator, coins pass along a path past a number of spaced sensor coils which are each energised to produce an inductive coupling of the coin. The degree of interaction between the coil and the coin 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 impedance presented by each coil, data indicative of the coin under test can be provided. The data can be compared with information stored in the memory to determine coin denomination and authenticity. An example of such an inductive validator is disclosed in UK Patent Specification 2 169 429 (Coin Controls Limited).
It has also been proposed in the past to use optical detectors to discriminate between coins on the basis of their optical characteristics e.g. diameter.
However, it has been found that certain types of counterfeit coins such as lead discs or discs made from a lead alloy cannot readily be distinguished by conventional validators from true coins since the characteristics of the counterfeits are too similar to acceptable coins to permit effective discrimination.
Coin validators incorporating piezo electric elements for sensing the impact of the coin falling onto part of the coin path are known from International Patent Application No. PCT/DK82/00072 (GNT Automatic A/S) and GB-A-2 236 609 (Mars Incorporated).
In PCT/DK82/00072, the mechanical elasticity of the coin is determined by causing the coin to apply an impact force to a piezo electric element, the output of which is amplified and compared with a preset threshhold amplitude value to determine coin acceptability. A coin made of lead or lead alloy produces a lower output of the piezo electric device than a corresponding true coin and thus by appropriately setting the threshhold value, discrimination between true and counterfeit coins can be achieved.
GB-A-2 236 609 discloses a similar arrangement in which the signal from the piezo electric element is differentiated prior to comparison with a predetermined threshhold in order to reduce the effects of variation in coin impact velocity.
It is an object of the present invention to provide an improved coin discrimination apparatus utilising an impact responsive sensor.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided coin discrimination apparatus comprising: means defining a path for coins under test; a surface to be impacted by coins that pass along the path; sensor means for providing an electrical output signal in response to impact of a coin with the surface; means for detecting the peak maximum and minimum of said output signal within a given duration following impact; and means for determining coin acceptability in dependence upon said detected maximum and minimum of the output signal.
In accordance with the invention, it has been appreciated that when a coin impacts against the surface, the sensor means provides an osillatory signal wherein the amplitude between the peak maximum and minimum occurring over a given duration following impact, is a function of the ringing or damping, which, in turn, is dependent upon the mechanical characteristics of the material from which the coin under test is made. Thus, if the coin is formed of lead or a lead alloy, the output signal is damped in comparison to that produced by a true coin, with the result that the difference between the peak maximum and minimum is reduced. Thus, the relationship between the maximum and minimum varies as a function of the material from which the coin is made, and can be used to determine coin acceptability.
The aforesaid maximum of the output signal is a function of the impact force of the coin, which in turn is dependent upon coin mass. In accordance with the invention, a coin parameter signal may be formed from a c
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Hutton Lesley
Kershaw John
Bartuska F. J.
Coin Controls Limited
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