JPS58152740A - Device for detecting conveyance of overlapped sheets - Google Patents

Abstract

PURPOSE:To secure long-term reliability, by sampling the level of the output signal of a light receiver during the passing of a sheet through between a light emitter and the light receiver and identifying it with the conveyance of overlapped sheets that the number of samples within an appropriate level range is not more than a discrimination threshold value. CONSTITUTION:When a sheet 4 is noot facing a light receiver 7, a control circuit 20 sends out a strobe signal so that the output signal of an amplifier 9 is sampled once by an A-D converter 11. The sample is applied to a calculation circuit 10 through the control circuit 20 so that the circuit 10 calculates the upper and lower limits of an appropriate level range. Comparators 14, 15 compare the samples with the upper and lower level limits set in registers 12, 13. The samples within the appropriate level range are reckoned by a counter 17. After that, the control circuit 20 sends out a gate signal to a comparator 19 so that if the number of the samples which are within the appropriate level range and reckoned by the counter 17 is not more than a threshold value set in a register 18, it is identified with the conveyance of overlapped sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for detecting duplicate feeding of paper sheets in devices that use paper sheets as input media, such as 7. axis devices, optical character reading devices, and mark reading devices. This invention relates to a duplicate feed detection device.

Conventional technology As an installation for optically detecting the repeated feeding of paper sheets, a light emitting element and a light receiving element are placed facing each other across the travel path of the paper sheet, and the output signal level of the light receiving element when the paper sheet passes is determined as a judgment level. Compared to K, there are some that detect duplicate feeding of paper sheets. In other words, it utilizes the property that the amount of light that passes through the paper sheets and enters the light-receiving element differs depending on whether the paper leaves are fed normally one by one or when two or more paper leaves are fed overlapping each other. It is something to do.

However, such a conventional device has the following glare problem that should be improved.

First, the output signal level (bright level) of the light receiving element in a state where there is no paper sheet is manually measured, and the determination level is manually set based on the measurement result. Therefore, errors in setting the determination level are likely to occur due to factors such as the accuracy of the measuring instrument and the skill level of the operator, resulting in false detection.

Furthermore, even if the determination is made and the PEL is set correctly, it does not compensate for changes in the amount of light emitted by the light emitting element or the sensitivity of the light receiving element due to changes in ambient temperature, aging, dust adhesion, etc., so the reliability of detection V is reduced. It was difficult to secure and required regular maintenance.

In addition, since the amount of transmitted light is measured only in a limited area of the paper sheet, such as in the margin area where there are no characters or binding holes, if there is dirt, dust, or eraser shavings adhering to that area, false detection may occur. is likely to occur.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a sheet double feed detection device that eliminates the drawbacks of the prior art as described above and can ensure detection reliability over a long period of time.

In the sheet double feed detection device according to the present invention, the appropriate level range and judgment darkness value are determined based on the output signal level of the light receiving element in a state where there is no sheet between the light emitting element and the light receiving element. During the period when the sheet of paper passes between the light emitting means and the light receiving means, the output signal level of the light receiving element is sequentially sampled a plurality of predetermined times, and it is determined whether each sample is within the above-mentioned appropriate level range. Then, if the number of samples determined to be within the appropriate level range in this determination is equal to or greater than the above threshold value, it is determined to be normal, and if it is less than the dark value, it is determined to be duplicate feeding.

Embodiment of the Invention FIG. 1 is a block diagram of a sheet double feeding detection device according to the present invention.

The paper sheet 4 is fed by the feed roller 21 of the feeding mechanism, and a light emitting element 8 such as a light emitting lamp or a light emitting diode, and a photoelectric conversion device such as a photodiode or phototransistor are placed on both sides of the paper sheet travel path. The light-receiving elements 7 having the same structure are provided facing each other. The output signal of the light receiving element 7 is amplified by an amplifier 9 and then input to an analog/digital (A/D) converter 11.

Every time a strobe signal is applied from the control circuit 20, the A/D converter 11 samples the output signal (analog signal) of the amplifier 9, converts each sample into a digital signal, and outputs the digital signal. The output signal of this ~Φ converter 11 is transmitted to comparators 14, 15 . and is input to the control circuit 20.

The comparators 14.16 compare each sample input from the A/D converter 11 with the contents of the register 12.18, and the AND circuit 16 performs a logical product on each output. In the registers 12.18, the upper and lower limit levels of the appropriate level range, which will be described later, are reset by the control circuit zO. A counter 17 is reset by a reset signal from the control circuit 20, and counts up every time a signal is output from the AND circuit 16.

18 is a register, and 1-100 million, which will be described later, is set by the control circuit zO. A comparator 19 compares the value of the color register 17 and the register 18. The output of this comparator 19 indicates the detection result of double sheet feeding.

10 is an arithmetic circuit which calculates the above-mentioned appropriate level range and darkness value.

Next, the operation of the apparatus of this embodiment will be explained.

When the paper sheet 4 is not located at the light receiving element 7, one strobe signal is emitted from the control circuit zO.

From this k, the A/D converter 11 converts the output signal of the amplifier 9 into 1
The sample (corresponding to the bright level) is converted into a digital signal and output. This sample is sent to the arithmetic circuit IO through the control circuit 20, where the upper and lower limit levels of the appropriate level range are calculated.

This will be explained in detail with reference to FIG. 2 (α).

The ratio of the output level of the amplifier 9 when there is one sheet of paper between the light emitting elements of the receiver 9 and when there is no sheet of paper can be shown by the curve in FIG. 2 (,). This curve is almost unaffected by deterioration of the receiver 1 light emitting element, ambient temperature, adhesion of dust, etc.

Therefore, once the thickness of the sheet (horizontal axis) is determined, the corresponding output level ratio is determined from this curve.

Now, if the thickness of the target paper sheet is specified as TO, the arithmetic circuit IO multiplies the output level ratio Mo determined by the above curve (registered in advance) by the level (bright level) indicated by the above sample. By doing this, the center level of the appropriate level range is found. Next, a predetermined level is added to this center level to obtain an upper limit level, and a predetermined level is subtracted to obtain a lower limit level.

Further, the arithmetic circuit IO calculates the above-mentioned dark value and the total number of samples. The total number of samples is the number of times the output signal of the amplifier 9 is sampled while the paper sheet passes between the 99 light emitting elements, and assuming that the sampling period and the paper feed speed are constant (in this example, this condition is ), is calculated by multiplying the length of the designated sheet by a pre-registered constant K. The threshold value will be explained with reference to FIG. 2(A).

When the paper sheets are fed correctly one by one, if the output signal of the amplifier 9 is sampled by the total number of samples mentioned above, the appearance W4 degree distribution of the sample values (amplifier output level) will be the curve shown in Figure 2 (A). It will be like this.

This distribution curve changes depending on the density of characters on the paper sheet, the number of binding holes, etc., but it remains almost constant for paper sheets of the same format. The darkness value above is based on this distribution curve.
This is the remaining number of samples after subtracting samples with values corresponding to the printing part and the perforation part from the total number of samples. The center level, upper limit level, and lower limit level C of the above appropriate level range correspond to the levels LO, LMMUx, and LMIM in FIG. 2(A).

Normally, the upper and lower limit levels IJMAX and LMIII can be selected at levels that are increased or decreased by about 1 m from the center level LO. Therefore, in this embodiment, the arithmetic circuit 10
Center level LoO± obtained by multiplying the clarity level by a constant
The 20% level is set to the upper and lower limit levels LM, respectively,
Calculated as LMXM.

Returning to FIG. 1, the control circuit 20 stores the upper limit level, lower limit level, and 1 value calculated by the arithmetic circuit IO in the register 12.
18 and 18, the control circuit zO activates the feeding mechanism. After a certain period of time from activation, the leading edge of the paper reaches between the receiver 1 light emitting elements 7.8. From this point on, the control circuit 20 starts sending out the strobe signal and also releases the reset of the counter 17.

Every time a strobe signal is output, the output signal of the amplifier 9 is sampled by the A/D converter 11.

Each sample is compared in level with the upper and lower limit levels in registers 11.18 by comparators 14.15. One comparator 1
4 sets the output signal to logic @l"III if each input sample is below the upper limit level, and the other comparator 15 sets the output signal to logic'"l if the input sample is above the lower limit level.
Therefore, each time a sample within the appropriate level range is input, the output signal of the AND circuit 16 becomes logic 11'', and the counter 17 counts up.

When sampling for the total number of samples is completed, a gate signal is sent from the control circuit 20 to the comparator 19. When the comparator 19 is supplied with this gate signal, it compares the values of the counter 17 and the register 18 and outputs the comparison result. That is, if the number of samples within the appropriate level range determined by the counter 17 is greater than or equal to the threshold set in the register 18, the comparator 19 outputs logic 10', otherwise It determines this and outputs logic @1''.

- If logic 11" is not output from the comparator 19, the control circuit 2
0 is 1- as described above, sampling the light level, calculating the upper and lower limit levels, setting registers 12 and 18, resetting the counter 17, and starting the feeding mechanism to send the next sheet. let When calculating and setting the dark value, it is desirable to always keep an eye on the light level value and calculate the threshold value based on it.

If comparator 19 outputs logic 11', control circuit 20 stops the feed mechanism. At the same time, an alarm is issued, but since this is not the gist of the present invention, the details will be omitted.

Note that the arithmetic circuit 10 that manages the arithmetic and control operations as described above
．． The control circuit 2o can be realized by hardware logic alone or by a combination K of hardware logic and microprogram logic. Regardless of the configuration, the applicable technical field! A person with average technical knowledge can easily realize the arithmetic circuit lO and the control circuit zo based on the above explanation, so specific examples of these circuits will not be presented.

Effects of the Invention As detailed above, the paper industry double feed detection device ↑d according to the present invention automatically sets the appropriate level range based on the brightness level, so there is no need to make adjustments or use a measuring device as in the prior art. It is no longer affected by errors, aging, changes in ambient temperature, dust, etc., and can maintain high reliability without regular maintenance. In addition, since the amount of transmitted light is measured at the double P point on the paper sheet to detect duplicate feeding, false detections due to dirt, dust, eraser debris, etc. on the paper sheet are less likely to occur, and the reliability of detection is significantly improved compared to conventional methods. can be increased to

The present invention can provide a sheet double feeding detection device having such features, and its effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a device configuration diagram showing an example of a sheet double feeding detection device according to the present invention, and FIGS. 2 (α) and (b) are diagrams for explaining the calculation method of the upper and lower limit levels of the appropriate level range and the threshold value. It is a graph. 4...Paper leaf? ... Light receiving element, 8... Light emitting element,
9... Amplifier, lO... Arithmetic circuit, 11... Analog/digital (A/D) converter, 12.18.18
...Register, 14, 15.19...Comparator, 16
...AND circuit, 17...Counter, 20...Control circuit, 21...Feed roller. Agent Patent Attorney Susuki 1) Yuki Toshi・, -1,
' Figure 2 ((L) (b) □ Make it the back side

Claims (1)

[Claims] +1) A light emitting means, a light receiving means provided opposite to the light emitting means and outputting a signal at a level corresponding to the amount of incident light, and a light receiving element when there is no paper between the light emitting means and the light receiving means. means for determining an appropriate level range and determination threshold based on the output signal level; and a means for determining the output signal level of the light-receiving element over a predetermined number of times during a period during which a sheet of paper exists between the nuclear light-emitting means and the light-receiving means. A determination means for sampling and determining whether each sample is within the appropriate level range, and a means for determining paper industry duplicate feeding if the number of samples determined to be within the appropriate level range by the determination means is less than the determination threshold. A paper sheet double feeding detection device.