Check-actuated control mechanisms – Including noncontacting – relatively movable parts connected...
Patent
1981-10-02
1984-07-31
Rolla, Joseph J.
Check-actuated control mechanisms
Including noncontacting, relatively movable parts connected...
73163, G07F 300
Patent
active
044625138
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improvements in and relating to apparatus for testing coins.
Electronic techniques are widely known for checking the validity of coins. One common technique is to subject a coin in a test position to an inductive test, involving the use of a sensing coil or a transmit/receiver coil arrangement, and to compare the output signal produced with narrow ranges of reference values corresponding to acceptable coins of different recognized denominations.
It is possible to make such apparatus more selective so that in addition to rejecting non-metallic objects and objects of ferrous metal it will also reject some denominations of unacceptable coins. This is achieved by reducing the range of amplitudes of the high and/or low frequency components for which the mechanism will give an acceptance signal. There are however difficulties in producing a reliable coin mechanism of this kind with high selectivity. Because of the nature of the mechanism it is necessary to adjust each mechanism individually before it is released from the factory in order to compensate for variations in components within the range of manufacturing tolerances, for example, variations in the air gap between transmitter and receiving coil. There are also the long term effects of temperature drift and long term ageing of the components of the system.
In our United Kingdom patent specification No. 1443934 we described a coin mechanism in which the difference between the values of the output signal when a coin is in the test position and when no coin is present is compared wlth corresponding values for acceptable coins. These measures result in a significant improvement over the difficulties referred to, and yet can be realised in practice in a comparatively simple way.
The present invention is concerned with tackling the sample problem but in another way which can be made in some embodiments to substantially eliminate such difficulties.
According to the invention from a first aspect there is provided apparatus for testing coins, comprising a coin passageway, means for producing an electrical signal of which a parameter varies on the passage of a coin into a test position along the coin passageway in dependence on a characteristic of the coin, and means for examining the variation of said parameter as a test for coin acceptability, characterised by automatic control means operative to vary the interdependence of said parameter and the said characteristic so as to hold the value of said parameter invariant in the absence of the coin, and by means operative to stop the interdependence of said parameter and said characteristic being varied during the determination of coin acceptability.
With this arrangement the interdependence of said parameter and said characteristic is controlled so that the value of said parameter is held invariant until immediately prior to the arrival of the coin being tested. Thus, provided the circuit components have linear characteristics and are kept out of saturation the effects of long term temperature drift and ageing and mechanical changes in the coin testing apparatus will have no effect on the value of the said parameter when the coin is in the test position. Because the parameter-to-characteristic interdependence is automatically set up by the automatic control means, there is no need for initial adjustment of the apparatus.
With reference to a second aspect of the invention, in the transmit/receive coil arrangement briefly referred to above, a transmitter coil is arranged on one side of a coin passageway to transmit an oscillating magnetic field across the passageway to a receiving coil. When a coin passes between the two coils, the attenuation of the magnetic field between the coils is a function of the thickness of the article and the material from which it is made. By examining the attenuation of the signal induced in the receiver coil, it is possible to distinguish between coins of different material and/or thickness.
One convenient technique for processing the signal induced in the r
REFERENCES:
patent: 3682286 (1972-08-01), Prumm
patent: 3738468 (1973-06-01), Prumm
patent: 3870137 (1975-03-01), Fougere
patent: 3918564 (1975-11-01), Heiman et al.
patent: 3933232 (1976-01-01), Searle et al.
patent: 4385684 (1983-05-01), Sugimoto et al.
Dean Robert
Raphael Paul S.
Mars Inc.
Rolla Joseph J.
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