Coin sorting device

In a conventional coin sorting device, sensor abnormalities tend to be overlooked as the reference value used to determine whether a coin introduced is good or bad is set by the introduction of a coin with the reference characteristics during an adjustment. In the present invention, a representative value common to a plurality of coin sorting devices of a similar type is used as the reference value. From the detection value and reference value of a coin that has been introduced into the coin sorting device, the constants of a linear regression formula related to both values are obtained and set during an adjustment. When the coins are sorted, the detection value of the coin being sorted is corrected by those constants and compared with the reference value or, in another embodiment, the sensor detection signals for the sorted coins are corrected to a value corresponding to the reference value relating to the linear formula by applying a constant in the second memory when the coins are sorted, and the peak value being derived and is used as the comparative detection value. Furthermore, a sensor abnormality can be identified by checking the aforementioned constants.

BACKGROUND OF THE INVENTION 
The present invention relates to a coin sorting device which can be mounted 
in an automatic vending machine and which is capable of facilitating 
detection of a sensor abnormality and of shortening the adjustment time. 
FIG. 6 schematically illustrates the construction of an electronic coin 
sorting device. As shown in the figure, when a coin 1 is introduced, the 
coin 1 rolls down a coin path 2 and is assessed as either good or bad, and 
has its denomination read by the coil sensor which is disposed on the coin 
path 2. The coin that is assessed as good is led to a good coin path 5A as 
a gate 4 is pulled. If the coin is assessed as bad, the coin is led to a 
bad coin path 5B as the gate 4 is not pulled. 
FIG. 7 is a construction diagram depicting the principles of the detection 
circuit 11 used to detect a change in the impedance of the coil sensor 
when the coin 1 passes the coil sensor 3; comprising a bridge circuit 
consisting of the coil sensor 3, resistors 6A and 6B, a capacitor 7, and 
an oscillator 8. The output of this bridge circuit is supplied to a 
rectification circuit 10 through a differential amplification circuit 9. 
When the coin 1 is introduced into the coin sorting device, the output 11a 
of the detection circuit 11 changes with the characteristics of the coin 1 
as shown in FIG. 8 (1A through 1C). 
FIG. 5 is a block diagram of a circuit for making adjustments and 
determinations in a conventional coin sorting device. With this system, 
when the coin sorting device is adjusted, the analog output value 11a that 
is derived from the detection circuit 11 in FIG. 7 as a result of 
introducing a coin with a reference characteristic, is converted into a 
digital value "x(t)" by means of an A/D converter 12. Furthermore, a peak 
value "x" is obtained from this digitally converted output "x(t)" by means 
of the peak detector 13, and this peak value is then adopted as a 
characteristic value. This characteristic value is stored in the memory 14 
as the reference value for a denomination. 
Next, when the coin sorting device is actually used to sort coins, the 
characteristic value of the introduced coin is compared, using a 
comparator 15, with the reference value stored in the memory 14, and if 
the difference between these two values is within a permissible range, the 
coin will be determined, by a determination circuit 16 to be a good coin 
of the denomination corresponding to the reference value. 
In the above-mentioned conventional coin sorting device, the reference 
value stored in the memory 14 is the characteristic value of a coin 
introduced during an adjustment. When the coil sensor 3 suffers from any 
abnormality, the characteristic value detected by this abnormal sensor 
will be used as the reference value; and it will be impossible to detect 
any abnormality in the coil sensor 3. 
The present invention is aimed at providing a coin sorting device capable 
of facilitating detection and/or compensation of a sensor abnormality and 
of shortening the adjustment time. 
SUMMARY OF THE INVENTION 
To detect and/or compensate for sensor abnormalities, a coin sorting device 
includes processing and memory means for applying a linear function or 
regression to a sensor signal. A desired peak value may be obtained either 
by first finding the peak value of sensor signals and then applying the 
linear function, or else by applying the linear function to sensor signals 
and then finding the peak value of the transformed signals. Linear 
regression coefficients or constants can be found in a calibration step 
prior to use of the device for sorting.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
According to the present invention, in one preferred embodiment, the coin 
sorting device is arranged so that a sensor (coil sensor 3, for example) 
is disposed on a coin path 2; wherein a comparative detection value is 
derived from a detection signal produced by the sensor after a coin that 
is placed in the device and which passes the coin path is compared with a 
reference value that is based upon a denomination of coins initially set 
in a first memory; wherein the coin that is placed in the device is 
determined to be a specie of a denomination when the comparative detection 
value is within a predetermined range relative to one of the reference 
values. The reference values to be used are values con, non to a plurality 
of coin sorting devices of a similar type as the said coin sorting device 
and there is a calculation means disposed, by which a constant (also known 
as a correction coefficient constant) for a linear regression formula is 
derived; the constant to represent an approximate relation between a peak 
value of the sensor detection signals, derived from introducing one or 
more types of true coins into the coin sorting device, and the reference 
values corresponding to the denominations of the coins initially set in 
the first memory. The constant (correction coefficient constant) is to be 
stored in a second memory when an adjustment is made. 
In this embodiment, the peak value of the sensor detection signals for the 
sorted coins is corrected to a value corresponding to the reference value 
relating to the linear regression formula by using the constants 
(correction coefficient constants) stored in the second memory, with the 
corrected value to be used as the comparative detection value when the 
coins are sorted. 
In another embodiment, the coin sorting device is arranged so that the coil 
sensor 3 is disposed on the coin path 2; wherein a comparative detection 
value is derived from a detection signal produced by the sensor after a 
coin that is placed in the device and which passes the coin path is 
compared with a reference value that is based upon a denomination of coins 
initially set in a first memory; wherein the coin that is placed in the 
device is determined to be a specie of a denomination when the comparative 
detection value is within a predetermined range relative to one of the 
reference values. The reference values to be used are values common to a 
plurality of coin sorting devices of a similar type as the said coin 
sorting device and there is a calculation means disposed, by which a 
constant (also known as a correction coefficient constant) for a linear 
regression formula is derived; the constant to represent an approximate 
relation between a peak value of the sensor detection signals, derived 
from introducing one or more types of true coins into the coin sorting 
device, and the reference values corresponding to the denominations of the 
coins initially set in the first memory. The constant (correction 
coefficient constant) is to be stored in a second memory when an 
adjustment is made. 
In this embodiment, the sensor detection signals for the sorted coins are 
corrected to a value corresponding to the reference value relating to the 
linear regression formula by applying constants (correction coefficient 
constants) stored in the second memory when the coins are sorted, and the 
peak value of the corrected value being derived and used as the 
comparative detection value. 
As a result, in the present invention, an abnormality in the sensor during 
an adjustment can be detected by checking whether the constants 
(correction coefficient constants) are abnormal. 
Preferred embodiments of the present invention are explained with reference 
to FIGS. 1 through 4. FIG. 1 is a block diagram showing one embodiment of 
the circuit, according to the present invention, representing an 
improvement over the conventional coin sorting device corresponding to 
FIG. 5. In reference to FIG. 1, after the coin sorting device has been 
adjusted the characteristic value "x" derived from the output value 11a of 
the peak detector 13 as a result of a coin passing through the A/D 
converter 12 and the peak detector 13, is measured as x1, x2, . . . , xn 
(for n denominations). 
The memory 23a has, already contained within, the representative reference 
values y=y1, y2, . . . , yn used to indicate certain denominations. These 
values have been obtained previously, through experimentation, as the 
reference values representing many coin sorting devices of the same model. 
The calculation part 22 calculates the coefficients "a" and "b" , suitable 
for the linear regression formula y=a+bx; with the representative 
reference value y=y1, y2, . . . , yn and the measured characteristic value 
(e.g. the output of the peak detector (13)) x=x1, x2, . . . , xn. For 
example, the values of "a" and "b" are obtained using the so-called 
least-square method as the minimum value of: 
##EQU1## 
(where xm, ym are the mean values of the x's and y's, respectively) 
FIG. 3 shows an example of the relation of the representative reference 
values y=y1, y2, y3 and the measured value x=x1, x2, x3; with the linear 
regression formula y=a+bx to be derived from both values. Using this 
relation, calculations may, of course, be done with the high denominations 
weighted. The values "a" and "b" are stored in the memory 23b, as 
indicated in FIG. 1, as the correction coefficients. 
Next, according to the present invention as referenced in FIG. 1, when this 
coin sorting device is actually used to sort coins, the characteristic 
value "x", which is the output of the peak detector 13 resulting from the 
introduction of a coin to be sorted, is corrected to a+bx by the 
correction circuit 21 using the correction coefficients "a" and "b" which 
are stored in the memory 23b. This resulting corrected value is then 
compared, by the comparator 15 referenced in FIG. 1, to the reference 
values referring to the denominations of y1, y2, . . . , yn contained in 
the memory 23b that is storing a+bx, and if the corrected value is within 
the permissible range of any of the reference values y1, y2, . . . , yn, 
the coin is determined by the determination circuit 16 to be a coin of a 
denomination equivalent to this reference value. 
FIG. 2 is a block diagram of an embodiment different from that in FIG. 1. 
The operation shown in FIG. 2 is identical to the operation as indicated 
in the embodiment in FIG. 1 when the coin sorting device is being 
adjusted, but differs when the coin sorting device is actually used for 
coin sorting. In coin sorting, the output value "x(t)" of the A/D 
converter 12 is input into the correction circuit 21a and corrected to 
a+bx (t), with the peak value a+bx obtained by the peak detector 13. This 
peak value a+bx is then compared with the representative reference value 
y1, y2, . . . , yn stored in the memory 23a by the comparator 15, and the 
results of this comparison are determined by the determination circuit 16. 
As another embodiment of the method to adjust the coin sorting device, when 
the correction coefficients "a" and "b" are obtained as a function of the 
output value "xo" of the peak detector 13, when no coin is present in the 
coil sensor 3, and the characteristic value "xi" (output by the peak 
detector 13) of a particular denomination "i", with "yo and yi" as the 
representative reference values corresponding to the values "xo and xi" 
then an adjustment can be carried out by the introduction of just one coin 
of a single denomination. As a result, the adjustment of the coin sorting 
device can be simplified. 
FIG. 4 is a graph showing the relation of the representative reference 
values "yo, yi" under the above conditions and the measured values "xo xi" 
(with i=2 in this example) with the linear regression formula y=a+bx to be 
determined therefrom.