Coin Testing Device For Comparing Coin To Be Tested With A Standard Coin

Abstract

The genuineness of a coin is determined by comparison of the "test" coin with a "standard" coin which are interposed between a primary coil and first and second secondary coils respectively of a transformer, the primary coil being supplied with an AC signal while the secondary coils are connected in series so that the voltages induced by said primary coil are subtracted, and said series connection being coupled to a circuit arrangement which controls a coin gate which allows the test coin to pass into a channel for accepted coins only if the signal delivered by the series connection of the secondary coils does not exceed a threshold value during a test period in which the test coin is in a test position range between the primary and said first secondary coil.

Description

BACKGROUND OF THE INVENTION

It is known to compare a test coin and a standard coin in a bridge circuit comprising a first and a second inductor into which said test coin and said standard coin are inserted. The bridge compares the impedance of the coils which depend on the coins disposed within the respective coils.

SUMMARY OF THE INVENTION

It is the main object of the present invention to provide a coin testing device which is able to discriminate between genuine coins and spurious coins or slugs having the same size both if the items to be discriminated are made of different metals or alloys, and if the items to be discriminated are made of the same alloy but having different coin devices coined thereon. The later case applies, e.g., for the distinction of British one shilling coins and German one Deutsche Mark coins.

This problem which cannot solved with the known coin testing devices is solved, as well as others, by a coin testing device according an embodiment of the invention comprising a coin chute having a coin input end and leading downwards from said end, a coin sensing device providing an electrical output signal when a coin to be tested ("test coin") travelling through said chute is in a predetermined position within said chute, testing means actuated by said electrical output signal and comprising an oscillator and a primary coil coupled to an output of said oscillator and positioned adjacent a first side of said coin chute, said primary coil having an axis extending at least substantially normal to a main plane of said coin chute, a control circuit controlled by the output of the test means, an electromagnetic relay actuated by said control circuit and having an armature steering the test coin into a channel for accepted coins ("go-channel") or a channel for rejected coins ("reject-channel") depending on the result of the test, and an energy source for supplying energy for operation of the oscillator, the test means, the control circuit and the relay.

A coin testing device of the above-defined type is characterized according to the invention by first and second secondary coils, the first secondary coil being positioned essentially coaxial to the primary coil adjacent to the coin chute and on the opposite side thereof with respect to the primary coil, said second secondary coil being positioned essentially coaxially to said primary coil at an end thereof which is opposite to the end adjacent to said first secondary coil, said first and second secondary coils having essentially the same size and number of turns, further by means for supporting a typical specimen of the coins to be accepted ("normal coin" ) between said primary coil and said second secondary coil, means for connecting the circuits of the first and second secondary coils in series so that voltages which are induced by the primary coil in the first and second secondary coils are in subtracting relationship, a threshold and amplifier circuit provided in said control circuit for activating said coin sensing device during a short period of time ("test period") during which test period the test coin is within a test range between said primary coil and said first secondary coil, said control circuit actuating said relay only if an output signal provided by said series connection during said test period does not exceed a predetermined threshold value during any time of said test period, and stop or gate means actuated or formed by the armature of said relay, adapted to extend into said coin chute, and steering said test coin into the reject channel when said relay is deenergized while allowing the test coin to travel into said go-channel when said relay is energized.

A mechanical coin-testing device or slug rejector is preferably provided between said input end of said coin chute and the coin testing device according to the invention, said mechanical device being constructed to pass only coins the diameters and thicknesses of which falling into narrow ranges. The capability of the present coin testing device to reject slugs and specially designed counterfeits is thereby greatly increased.

Further objects, features and advantages of the present invention will become more apparent if the following is taken in view of the accompanying drawings of which:

FIG. 1 is a schematic circuit diagram of a coin testing device according to a preferred embodiment of the invention;

FIG. 2 is a schematic front view (front cover and first secondary coil removed, and partly broken away) of the mechanical portion of the embodiment according to FIG. 1;

FIG. 3 is a schematic circuit diagram of the electrical portion of the coin-sensing device;

FIG. 4 is a circuit diagram of an oscillator for a somewhat modified embodiment similar to FIG. 1 and

FIG. 5 a circuit diagram of an oscillator for another modification of FIG. 1.

Referring now to FIGS. 1 to 3, there is illustrated a preferred embodiment of the invention comprising a coin chute 10 into which the coins to be tested ("test-coins") are inserted through a coin input slot 12. A mechanical slug rejector 14 is provided behind slot 12. This slug rejector may be of a known type, e.g., a ledge-type slug rejector which allows to pass only coins the width and diameter of which lying in narrow ranges. The coin chute 10 emerging from the mechanical slug rejector 14 passes between a primary coil 18 and a first secondary coil 20. At least in this area the coin chute consists of an electrically nonconducting material or is provided with appropriate openings so that the induction field between coils 18 and 20 is not disturbed.

Primary coil 18 is connected to output terminals of an oscillator 22 which delivers an alternating current to coil 18, said AC current having a frequency preferably between about 30 and 100 kc./sec. An electronic voltage regulator 24 supplies regulated electrical energy to oscillator 22. An energy source 28 which may comprise a battery is connected by a switching device 26 to the input of energy source 28. The switching device 26 comprises a normally open contact 29 (FIG. 3) of an electromechanical relay 62 (FIG. 3) which contact is closed under the control of the coin sensing device 16 for a short period of time ("test period") when the test coin 30 travelling through coin chute 10 is between coils 18 and 20. The test period is sufficiently short, e.g., about a hundredth of a second, so that the position of the test coin 30 which is moving continuously through coin chute 10 does not vary appreciably during the test period.

A second secondary coil 32 is provided coaxial to primary coil 18 on a side thereof which is opposite to first secondary coil 20. Secondary coils 20 and 32 are at least essentially symmetrically disposed in respect to primary coil 18. Means are provided to connect the circuits of secondary coils 20 and 32 in series so that the voltages induced by primary coil 18 in the secondary coils 20 and 32 are in opposite, subtracting relationship. Preferably, coils 20 and 32 are directly connected in a series circuit which is coupled to an input of an amplifier circuit 34 which provides an amplified output signal to a full-wave rectifier circuit 36 which in turn provides a rectified voltage to the input of a Schmitt-trigger circuit 38. Schmitt-trigger circuit is activated if and when the output of the full-wave rectifier exceeds a predetermined threshold value. This means that Schmitt-trigger circuit 38 is actuated if the output signal provided by the series circuit 20, 32 exceeds a predetermined value.

The output of Schmitt-trigger circuit 38 is coupled to an input of an inverter amplifier and holding circuit 40. Circuit 40 produces an output signal only if Schmitt-trigger circuit 38 has not been triggered at any time during the entire test period. The output signal of circuit 40 activates a power amplifier 44 controlling an electromagnetical relay 42 the drop out of which being delayed. Relay 44 comprises an armature 46 which forms or controls a chute gate. Chute gate prevents when relay 44 is deenergized passing of the test coin from coin chute 10 into go-chute 10a and directs the test coin into a reject chute 10b while the test coin is allowed to pass into the go-chute 10a when relay 44 is energized.

Means 48 are provided for positioning between primary coil 18 and second secondary coil 32 a typical specimen 50 of the coins to be accepted.

A preferred embodiment of coin-sensing device 16 is shown in FIG. 2. The coin-sensing device shown in FIG. 2 comprises a lever 54 having three arms 54a, 54b and 54c. Lever 54 is pivotally supported by a pin 52. Arms 54a and 54b are lying at the lower edge of coin chute 10 so that test coin 30 moving through chute 10 from the right to the left side in FIG. 2 is straddled by arms 54a and 54b. Lever 54 is then pivoted in a counterclockwise direction by the weight and impetus of coin 30 into a position shown in dashed lines. The test coin assumes a position 30' between primary coil 18 and first secondary coil 20 when lever 54 is in the actuated position shown in dashed lines (FIG. 2). Only primary coil 18 is schematically shown in FIG. 2, first secondary coil 20 would be above the paper in FIG. 2 and attached into a cover member not shown which is hinged to the base member of the device which is partially shown in FIG. 2. A small permanent magnet 56 is fixed to the end of the third arm 54c of lever 54, said permanent magnet 56 lying adjacent a reed-contact switch 60 when lever 54 is in the actuated position.

Reed-contact switch 60 comprises a normally open contact which is closed by the magnetic field produced by permanent magnet 56. The normally open contact of the reed-contact switch 60 is arranged in a series circuit connected between the live and ground terminals of energy source 28 and comprises further a driving coil of electromagnetic relay 62 and a parallel combination 64 of a capacitor and resistor. The capacitor of the parallel combination 64 is charged when reed-contact switch 60 is closed and the charging current energizes relay 62 for a predetermined period of time namely the test period.

Operation of the described embodiment of the present invention is as follows. When the test coin moving through coin chute 10 arrives at the coin-sensing device 16 and actuates lever 54 switch 28 closes for about a hundredth of a second. Hereby oscillator 22, amplifier 34, Schmitt-trigger circuit 38 and circuit 40 are provided with electrical energy from energy source 28 and activated. Oscillator 22 delivers an alternating current to primary coil 18 during the test period during which switch 28 remains closed. The position of the test coin between coils 18 and 20 does not change appreciably during the test period. A voltage is produced at the input of amplifier 34 and Schmitt-trigger circuit 38 respectively which does not exceed the threshold value during the test period if the test coin 30 is identical with standard coin 50 within given limits which may be varied by adjusting of Schmitt-trigger circuit 38. Power amplifier 42 is switched on by circuit 40 if Schmitt-trigger circuit 38 has not been triggered during the test period, and relay 44 is energized and remains energized because of the delayed dropout until the test coin has passed into go-chute 10a.

However, Schmitt-trigger circuit 38 is triggered if coin 30 is not similar to standard coin 50, and then circuit 40 does not provide an output signal for activating power amplifier. Relay 44 remains deenergized, the test coin is recoiled by armature 46 which forms a stop extending into the path of the test coin, and test coin is directed into the reject chute 10b as indicated by the dotted arrow in FIG. 2.

According to a further aspect of the present invention, the discrimination capability of the present coin testing device is greatly improved by varying, during the test period, a parameter selected from the group of signal amplitude and signal frequency, of the signal which is supplied to primary coil 18 by oscillator 22. This may be accomplished by modified oscillator means 22' and 22" shown in FIGS. 4 and 5 respectively. Oscillator means 22', 22" may be used as oscillator 22 in FIG. 1 or a portion thereof (e.g., in combination with a following buffer stage not shown).

Referring to FIG. 4 there is shown an oscillator 21' comprising a known transistor oscillator circuit having a frequency-determining parallel resonant or tank circuit 70. A series circuit comprising an additional capacitor 72 and a transistor switch 74 is connected across tank circuit 70. An input electrode (base electrode) of transistor 74 is coupled to an astable multivibrator circuit 76. Both the oscillator section and the multivibrator section of oscillator 22' are provided with energy from energy source 28 for operation during the test period and multivibrator 76 delivers to transistor 74 a square wave signal by which capacitor 72 is connected in parallel to tank circuit 70 and disconnected from tank circuit once or a number of times during the test period. The frequency of the output signal of oscillator 22' is switched thereby between two values once or a number of times during the test period.

The oscillator portion of oscillator 22' comprises a transistor 82 the emitter of which being coupled to ground by an emitter impedance 80 which is, according to a further feature of the invention, a temperature dependent resistor which is heated by the emitter current of transistor 82 so that the resistance, the degenerative effect of emitter impedance and thus the signal amplitude are varied during the test period. The output signal of oscillator 22' may be derived from output terminal 78.

Oscillator 22" shown in FIG. 5 produces an output signal the frequency of which varies continuously during the test period. Oscillator 22" which may be of known construction and is shown schematically in block form comprises a frequency determining tank circuit 70'. A series circuit comprising a coupling capacitor 81 and a varactor diode 83 is connected across tank circuit 70. The junction of capacitor 81 and diode 83 is coupled through an isolation impedance 84 to a capacitor 86. Capacitor 86 is charged through a resistor 88 upon closing of relay contact 28 whereby the bias of the diode 83 and the frequency of the oscillator signal are varied. Tank circuit 70' may be part of a beat-frequency oscillator circuit. Resistor 90 connected in parallel to capacitor 86 provides for discharging of capacitor 86 after opening of contact 28 at the end of the test period.

The circuits mentioned above and shown in block form or schematically are preferably transistorized circuits which may be of known construction.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

I claim:

1. A coin-testing device comprising a coin chute, a coin-sensing device producing an electrical output signal when a coin to be tested travelling through said chute is in a predetermined position within said chute; testing means actuated by said electrical output signal and comprising an oscillator and a primary coil which is coupled to an output of said oscillator and positioned adjacent a first side of said coin chute, said primary coil having an axis extending substantially normal to a plane comprising said coin chute; a control circuit responsive to the output signal of said testing means; a relay actuated by said control circuit and having an armature steering the test coin into a chute for accepted coins or a chute for rejected coins depending on the result of the test, and an energy source for providing energy for operation of the oscillator; the testing means and the control circuit characterized by first and second secondary coils, the first secondary coil being positioned essentially coaxial to the primary coil adjacent to the coin chute and on the opposite side thereof with respect to the primary coil, said secondary coil being positioned essentially coaxially to said primary coil at an end thereof which is opposite to the end adjacent to said first secondary coil, said first and second secondary coils having essentially the same size and number of turns; further by means for supporting a typical specimen of the coins to be accepted between said primary coil and said second secondary coil, means for connecting the circuits of the first and second secondary coils in series to form a series circuit so that voltages which are induced by the primary coil in the first and second secondary coils are in subtracting relationship; a threshold and amplifier circuit provided in said control circuit for activating said coin-sensing device during a short period of time ("test period") during which the test coin is within a test range between said primary coil and said first secondary coil; said amplifier circuit actuating said relay if the signal produced by said series circuit and coupled to said threshold circuit does not exceed a predetermined value at any point of time during the test period; and stop or gate means actuated or formed by an armature of said relay, which means extending into said coin chute and directing the tested coin into the reject channel when said relay is deenergized while said means allow the test coin to pass into the channel for accepted coins when the relay is energized.

2. The device defined in claim 1 characterized in that said coin sensing device comprises switching means for connecting said energy source to said oscillator and control circuits during the test period.

3. The device defined in claim 2 characterized in that said switching means comprises a pivotally supported lever having three arms, two of which being positioned in vicinity of said coin chute so that a coin moving through said chute is straddled by said arms and pivots said lever; that a magnet body is attached to the third arm, and that a reed-contact switch is provided at a position adjacent which the magnet body is positioned in the pivoted state of said lever, said reed-contact switch being actuated by a magnetic field provided by said magnet body.

4. The device defined in claim 1 characterized by means for changing at least one parameter including signal amplitude and signal frequency, of the signal supplied by said oscillator to said primary coil during the test period.

5. The device defined in claim 4 wherein said means is adapted to switch the oscillator frequency between two values during the test period.

6. The device defined in claim 4 wherein said means is adapted to vary the oscillator frequency continuously during the test period.

7. The device defined in claim 4 wherein said means varies the signal amplitude.

8. The device defined in claim 1 characterized by a mechanical slug rejector provided in the path of the test coin between the input end and the area between the primary and first secondary coils, said rejector being adapted only to pass coins the diameter and thickness of which lying in narrow ranges.

9. A coin testing device comprising at least one inductor, means for positioning a coin to be tested in the vicinity of said inductor, means for supplying an AC signal to said inductor, means responsive to the effects of said coin on a signal derived from said inductor, means for guiding the coin into one of several channels according to the effects of the coin on said signal, and means for varying a parameter including frequency and amplitude of the signal supplied to said inductor during the period of time during which said means responsive to the effects of the coin on said signal is primed to actuate said guiding means.