Check-actuated control mechanisms – Including means to test validity of check – By testing material composition
Patent
1998-11-16
2000-11-14
Bartuska, F. J.
Check-actuated control mechanisms
Including means to test validity of check
By testing material composition
324236, G07D 508
Patent
active
061456462
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for testing the authenticity of coins, tokens or other flat metal articles, of the kind set forth in the classifying portion of claim 1.
Such apparatuses are suitable for example as coin collection units in public telephone stations, automatic sales machines, energy meters and so forth.
An apparatus for testing the authenticity of coins, of the kind set forth in the classifying portion of claim 1, is known from DE 24 55 112 and GB 2 287 341. The apparatus has an inductive measuring element which is acted upon by two different frequencies f.sub.1 and f.sub.2, as there are coins which deliver a measurement signal that can be easily measured and distinguished from other coins when the frequency f.sub.1 is comparatively low, while there are also coins which cannot be easily distinguished from other coins at that low frequency f.sub.1, but at a higher frequency f.sub.2. The measuring element comprises an inductive transmitter and an inductive receiver which are arranged on mutually opposite sides of a coin passage. The transmitter includes a core which has two coils wound around it. The coils are excited independently of each other at different frequencies so that an alternating magnetic field oscillates at two different frequencies in the coin passage. Filters are connected downstream of the receiver which is also in the form of a coil in order to measure the amplitudes of the signals induced in the receiver at the two frequencies. Such an apparatus represents a mechanically and electrically complicated structure.
GB 2 069 211 discloses an apparatus for testing the authenticity of coins, in which the phase shift between the voltage across the measuring coil and a reference voltage is measured.
European patent application EP 704 825 which is not a prior publication discloses an apparatus for testing the authenticity of coins, in which a coil arranged in a series resonance circuit serves as an inductive measuring element for determining the alloy composition or the thickness of the coin.
The problem of the present invention is that of providing an apparatus for testing the authenticity of coins, in which it is possible to achieve a high selection capability as between different coins, with a simple inductive measuring element.
According to the invention the specified problem is solved by the features of claim 1.
The invention proposes an apparatus having an inductive measuring element, in which the coin is exposed to an alternating magnetic field at least two frequencies. The measuring element has a single coil which is fed from two sources with currents or voltages of different frequency: the coil is at the same time part of two different circuits. In at least one circuit the phase shift between the current supplied by the source and the voltage across the coil serves as the measurement signal. To increase the level of sensitivity of measurement of the phase shift, provided in the corresponding circuit is a capacitor.
According to the invention the specified problem is solved by the features of claim 1.
The invention proposes an apparatus having an inductive measuring element, in which the coin is exposed to an alternating magnetic field at least two frequencies. The measuring element has a single coil which is fed from two sources with currents or voltages of different frequency: the coil is at the same time part of two different circuits. In at least one circuit the phase shift between the current supplied by the source and the voltage across the coil serves as the measurement signal. To increase the level of sensitivity of measurement of the phase shift, provided in the corresponding circuit is a capacitor with which the zero point of the phase shift, that is to say the value when there is no coin present, can be set to a fixed value.
Embodiments of the invention are described in greater detail hereinafter with reference to the drawing, wherein the term coin M is also used hereinafter to denote tokens or other flat metal articles. In the drawing:
FIG. 1 shows a coin pass
REFERENCES:
patent: 3918563 (1975-11-01), Schwippert et al.
patent: 4086527 (1978-04-01), Cadot
patent: 4469213 (1984-09-01), Nicholson et al.
patent: 5433310 (1995-07-01), Bell
Rueff Joseph
Seitz Thomas
Bartuska F. J.
Electrowatt Technology Innovation AG
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