Title:
COIN CHECKING DEVICE
United States Patent 3738468


Abstract:
An electronic coin checking device comprising at least one window circuit for checking coin-characteristic measurement signal values caused by the movement of coins past a measuring location, wherein the window circuit arrangement possesses two window boundary circuits delimiting a window region, at least one of which window boundary circuit is constructed as an amplifier in such a manner that a portion of a measurement signal value penetrating into the window region is amplified.



Inventors:
PRUMM M
Application Number:
05/245976
Publication Date:
06/12/1973
Filing Date:
04/20/1972
Assignee:
PRUMM M,DT
Primary Class:
International Classes:
G07D5/00; G07D5/08; (IPC1-7): G07F3/02
Field of Search:
194/100,1A
View Patent Images:
US Patent References:
3682286METHOD FOR ELECTRONICALLY CHECKING COINS1972-08-08Prumm
3317016Coin selecting device1967-05-02Turillon



Primary Examiner:
Tollberg, Stanley H.
Claims:
What is claimed is

1. An electronic coin checking device comprising at least one window circuit arrangement for checking coin-characteristic measurement signal values caused by the movement of coins past a measurement location, said window circuit arrangement comprising two window boundary circuits defining a window region, at least one of such window boundary circuits being constructed as an amplifier means in such a manner that a portion of the measurement signal value penetrating into the window region is amplified.

2. The coin checking device as defined in claim 1, wherein said amplifier means comprises a transistor and wherein there is utilized the amplification of the transistor in the region between saturation and blocking or vice versa.

3. The coin checking device as defined in claim 1, wherein the amplification of the window boundary circuit is brought about by said amplifier means designed as a comparator circuit.

4. The coin checking device as defined in claim 1, wherein said amplifier means of said window boundary circuit comprises an operational amplifier.

5. The coin checking device as defined in claim 1, wherein the other window boundary circuit when activated directly or indirectly eliminates the action of the first amplifying window boundary circuit.

6. The coin checking device as defined in claim 1, further including means for delivering the actual measurement signal value to both window boundary circuits.

7. The coin checking device as defined in claim 1, further including means for delivering the actual measurement signal value to only one of the amplifying window boundary circuits and wherein the second window boundary circuit evaluates the amplified analogue signal amplified by the first window boundary circuit.

8. The coin checking device as defined in claim 6, wherein with the presence of a number of measurement regions corresponding to different coin acceptance regions there is set a different gain of the window boundary circuit constructed as amplifier means and therefore there is brought about a standardized stroke of the output signal of one of each measurement range notwithstanding different window widths.

9. The coin checking device as defined in claim 7, wherein with the presence of a number of measurement regions corresponding to different coin acceptance regions there is set a different amplification of the window boundary circuit constructed as amplifier means and therefore there is brought about a standardized stroke of the output signal of one of each measurement range notwithstanding different window widths.

10. The coin checking device as defined in claim 1, wherein the boundary voltage for the lower window boundary circuit, and upon presence of a number of window circuits the common boundary voltage, is used as a reference voltage for the null point- and/or terminal deflection compensation of an adjustment measurement device adapted to be connected to the circuit arrangement.

Description:
BACKGROUND OF THE INVENTION

The present invention relates to a new and improved electronic coin checking device of the type comprising at least one window circuit arrangement for checking coin-characteristic measurement signal values brought about by the movement of coins past a measurement location.

The heretofore known coin checking devices generally employ window circuits composed of two or more logically coupled voltage sensitive thresholds for the determination of coin-characteristic voltage measurement values, these window circuits constituting for instance thyristors, Schmitt-triggers and the like which deliver digital data.

Such window circuits only furnish information indicative of whether a coin has or has not generated a voltage value which falls into a selected acceptance region. They do not deliver information which allows determining where such voltage value is located within the selected acceptance region. Consequently, it is not possible to ascertain if the coin checking device has been optimumly adjusted. For this purpose it is necessary to formulate by means of a multiplicity of coins a quantitative-statistic or it is necessary to work with a number of specifically calculated boundary coins.

SUMMARY OF THE INVENTION

Accordingly it is a primary object of the present invention to provide a new and improved construction of coin checking device which renders it possible to portray the analogue position of a coin within a selected acceptance region and thus by means of, for instance, a cathode ray oscilloscope to acquire a so-to-speak "insight into the window." Such coin checking device can be set rapidly and thus economically because each change of a voltage divider in front of the "window" (for instance by rotating a trimmer potentiometer) can be directly followed in terms of its affect upon the analogue position of a coin measurement value within the acceptance region. If one proceeds from the experience that the optimum enlargement of an acceptance region (window width) need only be determined once, then, with the inventive coin checking device the adjustment can occur with only a single measured-out average coin.

More specifically, the inventive coin checking device is manifested by the features that the window circuit arrangement comprises two window boundary circuits, at least one of which is constructed as an amplifier in such a manner that the portion of the measurement signal value which penetrates into the window region can be amplified.

In the simplest situation the amplifying window boundary circuit can be formed by a single transistor, wherein there is made use of its switching behavior in the region between saturation and blocking or vice versa, in other words the so-called operating region.

The second window boundary circuit which forms the threshold bounding the window towards the other side can basically possess any optional design.

In principal, it would be possible to employ per se the amplifying threshold circuit if it were desired to be able not only to differentiate between two switching conditions, for instance the voltage of the measurement signal value above the window boundary and the voltage below the window boundary, rather between its three conditions: voltage above the window region, voltage in the window region, and voltage below the window region.

Now according to a proposal which is not part of the prior art this could be basically carried out such that a high-frequency voltage of low amplitude is superimposed upon the actual rectified measurement voltage and such is only permitted to be amplified by the transistor. However, this proposal in principal is frequency-dependent and associated with stability drawbacks. Therefore it is not one which falls under consideration. Moreover, because of the subsequently connected second rectifier which is required it is furthermore more expensive than the inventive circuit. Further, with lower frequencies it cannot be used for the measurement of moving coins. Hence, in accordance with the invention there is thus employed, for instance, in the amplifying window threshold circuit a transistor which amplifies the peak value of the rectified measurement signal delivered thereto and at which there is not superimposed any high frequency signal, and the amplification of which is adjusted in accordance with the required window width, for instance by feedback. This transistor does not deliver any signal in the event the measurement voltage culminates above its operating region or range.

On the other hand, if the measurement voltage falls into the operating region of the transistor then there appears a coin-characteristic collector voltage which can be tapped-off, stored or employed for deriving pulse-like data or information.

The transistor does not however behave differently when the measurement voltage falls below a desired acceptance region. The transistor is not able to differentiate between both of the last switching conditions because it can only monitor the upper boundary of a selected window, not however, according to a feature of the invention, at the same time also the lower boundary. It is for this reason that the lower boundary of the window is monitored by a second threshold device. In principal this can likewise consist of only a transistor.

The basic concepts of this development are not altered if advantageously, for instance, in order to obtain an increased temperature stability there is employed, instead of the single amplifying transistor, a comparator or an operational amplifier or the like. Also the second threshold device is preferably constructed in this manner for highly stable circuits.

A characteristic aspect of this development resides in the features that the window circuit arrangement functioning according to the principles of amplification possesses a principal advantage in contrast to all previously known window circuits for coin checking devices which are designed according to the principals of bistable threshold circuit arrangements, and namely: as previously indicated the collector of the amplifying transistor delivers a coin-characteristic voltage curve which is directly proportional to the degree of penetration of the measurement voltage value into the window region and therefore provides a direct indication regarding the more-or-less optimum adjustment of the window with respect to a coin-characteristic measurement signal.

This occurs in that the inventive circuitry suppresses the portion of the total dampening curve which is located externally of the selected window because of the operation in saturation or blocking of the amplifying transistor and there is only represented the uppermost cup or bend of the dampening curve, although amplified, which is essential for the measurement determination.

This coin-characteristic amplified signal can be very easily represented, if desired, by introducing an isolating or disconnection transistor in that, for instance, a measurement capacitor is charged in analogue fashion with the amplified signal.

In the event that these signals leave the window region then the second employed threshold means directly or indirectly switches-off the amplifying transistor and discharges the measuring capacitor.

The window circuit arrangement of the inventive coin checking device exhibits still further advantages in contrast to the known circuits: for the purpose of determining exact and closely neighboring measurement values both window boundaries must be designed to be absolutely and highly stable with regard to one another. The window circuit arrangement of the inventive coin checking device affords these requirements as to accuracy, however only at the upper amplifying window boundary circuit and not also at the lower window boundary circuit. Such has delivered thereto an already amplified measurement voltage and accordingly its accuracy can be poorer by the amount of such gain or amplification if for both systems there is desired to be obtained the same measuring accuracy. It is for this reason that as a general rule it is sufficient to design only the upper threshold value circuit as a comparator or operational amplifier. At this point it is however further mentioned that the concepts of the invention are not changed if there is also delivered a non-amplified signal to the second window threshold circuit.

As far as the concepts of this invention are concerned it is without significance how the window width of the window circuit arrangement is adjusted. This can occur through appropriate change of a voltage divider, for instance by means of a trimmer potentiometer or, however, according to a further concept of the invention in a particularly advantageous manner by variably adjusting the gain or amplification of the amplifying threshold value circuit for the momentary type of coin which is to be measured.

This is of particular advantage if a number of measuring regions are to be monitored, in other words for coin checking devices which check different coins. Hence it is possible to maintain constant and uniform in known manner the boundary level of all windows and therefore there is realized for the subsequently connected analogue indicating- and/or evaluation devices, notwithstanding possible different window widths, a standardized output deviation or stroke of the output signal and therefore, for instance in the case of indication instruments, for all measuring ranges (coin types) uniform acceptance regions or boundary excursions or deflections.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 graphically illustrates dampening curves for two "incorrect" coins and a "correct" coin below the idling or no-load amplitude as well as the selected acceptance region for the "correct" coin;

FIG. 2 is an enlarged detail of the portion of the acceptance region of the graphic showing of FIG. 1 as well as further depicting additional typical curve envelopes for "correct" coins which are produced by exemplary scattering or stray effects:

FIG. 3 is a circuit diagram of an exemplary embodiment of window circuit arrangement for the inventive coin checking device including the corresponding signal generating means for the upper (amplifying) window boundary circuit and the lower window boundary circuit; and

FIGS. 4 to 9 are graphs depicting different other measurement signal images .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, in FIG. 1 there is graphically illustrated the so-called idling or no-load amplitude 1, whereas reference character 2 designates the base region or base line. The acceptance region for a certain coin has been indicated by reference character 3 and both of the window boundaries by reference characters 31 and 32. The dampening curve 40 represents a coin having two slight dampening properties and therefore an incorrect or false coin. On the other hand, the curve designated by reference character 60 represents a coin with two strong dampening properties. Finally, a "correct" coin-characteristic dampening curve has been indicated by reference character 50.

Now in FIG. 2 there is shown on an enlarged scale the window region of FIG. 1, wherein the same reference characters have again been conveniently employed. Additional dampening curves which fall within the confines of the coin acceptance region between the boundary lines 31 and 32 and generated by different "correct" coins have been designated by reference characters 51, 52, 53, 54 and 55.

All of these "correct" measurement values are also identified as being correct by the heretofore known window circuits. However, the exact position of each individual dampening curve within the coin acceptance region 3 cannot be ascertained by the prior art coin checking devices. FIG. 2 illustrates an ideal course of the dampening curves within the window region or window; the so-called "stray curves" 51 and 55 are disposed approximately the same distance from the window boundaries. Any occurring drift owing to temperature or extended time has the same safety margin spacing to both sides. With a conventional window circuit it would not be possible to ascertain that, for instance, the curve 51 only slightly penetrates into the window region. Thus during even slight temperature drift this could have the consequence that a one hundred percent acceptance of all correct coins is no longer ensured for. In order to avoid this uncertainty it was necessary for the heretofore known coin checking devices to carry out cumbersome quantative statistical operations while also resorting to temperature trials.

With the foregoing background in mind and considering now the circuitry of FIG. 3, it is to be understood that reference numeral 4 designates the conductor or line carrying the operating voltage, reference numeral 5 the conductor or line which is connected to ground (minus), and reference character 6 the input line for the measurement probe signal which, if desired, can be pre-amplified. The circuit arrangement also incorporates the amplifying transistor 7 of the window boundary circuit forming the upper window boundary 31. Electrically coupled with this transistor 7 is the input resistor 8 and the collector resistor 9. The relationship of the resistance value of the resistor 9 to that of the resistor 8 approximately determines the degree of amplification or gain. By means of the trimmer potentiometer 10 there is adjusted the voltage-related position of the amplifying window boundary circuit for the upper window boundary 31 for the input signal. Depending upon the magnitude of the introduced measurement signal the collector output 11 provides information which can be utilized to arrive at different determinations.

In FIG. 4 there is represented by reference character 20 the operating voltage which at the same time forms the upper window boundary, corresponding to the blocking condition of the transistor 7. Reference character 21 represents the lower window boundary which can be adjusted by means of the trimmer potentiometer 12 or, if desired, by a fixed voltage divider.

FIG. 4 illustrates that the transistor 7 remains in a blocking state. In the case of a "correct" coin the input signal received via the conductor 6 is so low that the transistor 7 is switched or controlled into its operating range and specifically in a manner analogous to the magnitude of the input signal. This has been graphically depicted in FIG. 5.

If the measurement voltage drops below the prescribed acceptance region, as shown in FIG. 6, because of an improper or false coin and owing to a pronounced dampening, then, the base-emitter path of the transistor 13 becomes conductive and the collector voltage of the transistor 7 can no longer drop further than determined by the potentiometer 12.

In this embodiment it is assumed that the resistor 12 is negligibly small in relation to resistor 9. Furthermore, the base-emitter threshold voltage of the transistor 13 has not been taken into account. Consequently, in principle there appears the curve envelope illustrated in FIG. 6.

If the base-emitter path of the transistor 13 is conductive, then there appears an appropriate collector current which causes a voltage drop across the resistor 14 as indicated in FIG. 7. If the measurement voltage does not drop to the lower window boundary then at the conductor 15 there does not appear any signal. This has been graphically portrayed in FIG. 8.

The signal graphically portrayed in FIG. 7 can now be employed in known manner either for a forward logic switching operation or a backward logic switching operation in order to render retroactive or eliminate the switching behavior of the first amplifying window boundary circuit. The switching operation has not been depicted in the drawing. In the case of a backward switching operation there appears at the conductor 11 a curve of the type depicted in FIG. 9.

The analogue and amplified measurement signal appearing at the collector of the transistor 7 can be tapped-off via the conductor 16 in order to provide a qualitative determination.

With the presence of a number of measurement regions or window circuits it is particularly advantageous to connect all transistors 13 and their emitters at the same reference voltage and to deliver such as well as the operating voltage of a connectable measurement device (adjustment device) as reference voltages for the purpose of carrying out a null point- or terminal deflection-compensation or adjustment.

Since with the circuit arrangement illustrated in FIG. 3 the acceptance region 3 depicted in FIG. 1 is simultaneously amplified from, for instance, two hundred millivolts to a range of, for instance, five volts the position of the measurement signal value can be exactly and simply determined in the acceptance region.

The examples given heretofore relate to the monitoring of descending measurement voltages wherein the "upper" window boundary circuit first responds and thereafter, when necessary, the lower window boundary circuit. With ascending measurement voltages the circuit arrangement behaves in the reverse manner without changing the basic concepts of this development.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,