JPS58152741A - Device for detecting conveyance of overlapped sheets - Google Patents

Abstract

PURPOSE:To enable the long-term unmistaken detection of conveyance of overlapped sheets, by providing a light receiver on a sheet passage and retaining the level of that output signal of the light receiver which is generated when there is no sheet facing the receiver and by comparing the level with that of a new output signal to judge whether the overlapped sheets are conveyed. CONSTITUTION:A light emitter 1 and a light receiver 2 are provided so that they face each other across the passage of a sheet 4. The output signal of the light receiver 2 is amplified at 3 and then applied to one input terminal of a comparator 7. The amplified signal L is also applied to a sample hold circuit 5. When the send-out of a signal S2 from a control circuit 8 which follows up the change in the signal L has stopped, the sample hold circuit 5 is caused to retain the level of the signal L applied to the circuit just before the stoppage. The voltage level La retained by the circuit 5 is divided by a dividing resistor circuit 6, the divided voltage output of which is applied as a discrimination level LS2 to the other input terminal of the comparator 7. When the level of the signal L is not higher than the discrimination level LS2, the comparator 7 generates a signal S3 indicating the conveyance of overlapped sheets, so that prescribed measures are taken.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides equipment such as facsimile machines, optical character reading devices, and mark d capturing devices that use paper sheets as input media.
The present invention relates to a sheet double feeding detection device used for detecting double sheet feeding.

Conventional technology As a device for optically detecting the repeated feeding of paper sheets, a light emitting source such as a tungsten lamp or light emitting diode and a light receiving element such as a photodiode or phototransistor are placed facing each other across the travel path of the paper sheet. There is a method that detects duplicate feeding of paper sheets by receiving the light transmitted through the paper sheet with a light receiving element and comparing the output signal level of the light receiving element with a determination level. In other words, by taking advantage of the property that the amount of transmitted light that enters the light receiving element is different when sheets are fed normally one by one and when two or more sheets are fed at an angle of inclination equal to 1, overlap is detected. This is the book that tries to detect the feed.

However, such conventional devices have a configuration in which the output signal level (bright level) of the light receiving element is manually measured when there is no paper sheet, and the judgment level is manually set based on the measurement result. There were drawbacks such as:

First, due to errors between individual measuring instruments used to measure the brightness level and differences in the skill levels of workers, errors in setting the determination level are likely to occur, leading to false detections. Furthermore, even if the determination level is set accurately, it does not compensate for the effects of changes in the light intensity of the light emitting source and the sensitivity of the light receiving element due to changes in the surrounding layers, changes over time, and even the adhesion of dust, resulting in false detection. This is likely to occur, and it is necessary to reset the judgment level periodically.

OBJECTS OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a highly reliable sheet feeding detection device.

The paper sheet double feeding detection device according to the present invention includes a signal level holding means for holding the output signal level of the light receiving means during a period in which there is no paper between the light emitting means and the light receiving means, which are provided in the same way as in the prior art; It has a judgment level setting means for setting a judgment level according to the latest signal level held in the signal level holding means. Therefore, even if the characteristics of the light emitting means and the light receiving means change due to changes in ambient temperature, aging, dirt, etc., the changes are accurately reflected in the determination level, and the determination level is always maintained at an appropriate level. The comparison means compares the output signal level of the light-receiving element with the determination level during the sheet feeding period, and the duplicate feeding of the sheet is determined based on the result, as in the conventional method.

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

In the figure, 1 is a light emitting element, and for example, a tungsten lung or a light emitting diode is used.

This light emitting element is driven by a mold groove (not shown). 2
is a light receiving element, for example, a photoelectric conversion water element such as a photodiode or a phototransistor is used. As shown in the figure, the light emitting element 1 and the light receiving element 2 are arranged so as to face each other across the travel path of the sheet 4. Therefore, the light emitted from the light-emitting element 1 enters the light-receiving element 2 either directly or through the passing paper sheet 4, and depending on the amount of incident light, the output signal of the light-receiving element 2 is reflected in the voltage level or current level). changes. Reference numeral 8 denotes an amplifier for amplifying the output signal of the light receiving element 1, and its output voltage level L is proportional to the output signal level of the light receiving element l.

Reference numeral 5 denotes a known sample and hold circuit, which functions as the signal level holding means described above. The holding voltage level La (output voltage level) of this sample and hold circuit 5 is:
During the period when the 1d signal S2 is output from the sample control circuit 8, the output of the amplifier 8 is 1. It changes following the pressure level L, but when the signal S2 is no longer output, it is held at the previous level. The held voltage level Lα of the sample and hold circuit 5 is divided by a resistive voltage dividing circuit 6 at a predetermined voltage dividing ratio. This resistance voltage divider circuit 6 functions as the above-mentioned judgment level setting means, and its output voltage level L82 is applied to one input of the comparator 7 as a judgment level. This comparator 7 compares the level of the output voltage of the amplifier 8 applied to the other input with the determination level L=i, and outputs a signal S8 when L<L82.

The sample control circuit 8 calculates, from the output voltage level L of the amplifier 8 and the holding voltage level Lα of the sample hold circuit 5,
This is a circuit that detects that the paper sheet 4 has passed between the light receiving element 2 and the light emitting element 10, and outputs No. 8 82 only for a time T from that point. The gear period d is determined to be sufficiently shorter than the time from when the leading edge of the next sheet passes through until the leading edge of the next sheet reaches the position of the light receiving element 2 (gear period d).

To explain the configuration of the sample control circuit 8, the voltage level LSI obtained by dividing the held voltage of the sample and hold circuit 5 at a predetermined voltage division ratio using the resistor voltage divider circuit 1O, and the output 'direct' of the amplifier 8. The comparator 9 compares the pressure level L with the pressure level L, and when L<LSl, the comparator 9 outputs a signal S1. The monostable multivibrator circuit 11 is triggered by the rise of this signal S1, and the signal 82 is
Output.

FIG. 2 shows changes in the signal level in the troughs in FIG. 1 when paper sheets are continuously fed. However, for convenience of explanation, the illustration is made on the assumption that the output voltage level of the amplifier 8 (referred to as the bright level) during a period when there is no paper work is sequentially lowered each time one paper sheet passes.

When the trailing edge of a certain sheet of paper passes directly under the light receiving element 2 and enters the gap period (1), the light from the light emitting element 1 reaches the light receiving element 2.
Since the output voltage level L of the amplifier 8 is directly input to
rises to the bright level L (11).As a result, the signal s1 is output from the comparator 9 and the monostable multivibrator circuit 1
1 and the signal S2 is output. Therefore, the holding voltage level La of the sample and hold circuit 5 changes to follow the bright level LmK at that time, and is held at the level Lα(1) from the time the signal 82 falls. Judgment level L8gi
It is set to level L82(1).

When the next sheet of paper is sent, the light transmitted through the sheet enters the light receiving element 2, so that the output voltage level L of the amplifier 8 drops to the level LD(1). If only one sheet of paper is sent correctly, L D+1) > L 8 Z (1) as shown in the figure (the voltage division ratio of the resistor voltage divider circuit 6 is determined in this way). ), so
Comparator 7 does not output signal S8.

When the sheet passes and the gap period begins, the sample and hold circuit 5 sets the current bright level L(2) as described above.
sample and retain. In the figure, the light level L (2
) is lower than the bright level L(1) of the previous gap period. Such a decrease in brightness level may occur due to deterioration of the light emitting element 1 or the light receiving element 2, pollution, fluctuations in the voltage, changes in ambient temperature, etc.

Therefore, each voltage level Lα, LSI, L82H is a lower level than before (Lα+2), LS 1+21. L
It decreases to S z+21.

When the next sheet of paper is sent, the output direct pressure level L of the amplifier 8 drops to level Ll]2). When two or more sheets overlap, the transmitted light that enters the light receiving element 2 becomes weaker than when there is only one sheet, so the level LD+2) becomes LD+2)<LS2(2) as shown in the figure. ) (The voltage division ratio of the resistor voltage divider circuit 6 is determined so as to be like this). So, a comparator? No. 18 S
8 is output, and double initial feed is detected and 1 is output.

As is clear from the above, in the present embodiment 11, the determination level is automatically re-established according to the light level of each gap period between the paper business and the paper sheet. Therefore, even if the characteristics of the light-emitting element and light-receiving element change due to factors such as aging, changes in ambient temperature, fluctuations in power supply, and dust adhesion, the determination level is automatically optimized, which prevents false detection of duplicate feeds. It doesn't happen.

Effects of the Invention Since the present invention has been described in detail above, it is possible to perform a stable double feeding detection operation over a long period of time without requiring manual adjustment of the discrimination level, and without the drawbacks of the prior art. It is possible to provide a device for detecting the speed of repeated nine sheets of paper, and its effects are great.

[Brief explanation of the drawing]

FIG. 1 is an apparatus configuration diagram showing one embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the same embodiment. ■... Light emitting element, 2... Light receiving element, 8... Amplifier, 4... Paper leaf, 5... Sample and hold circuit, 6.
10... Resistor voltage divider circuit, 7.9... Comparator, 11.
... Monostable multivibrator circuit. Agent Patent Attorney Susuki 1) Li, ``Happy''

Claims (1)

[Claims] (1) A light emitting means provided on one side of the paper travel path;
- A light receiving means that is provided facing the other aK# light emitting means on the sheet travel path and outputs a signal at a level corresponding to the amount of incident light, and there is no paper sheet between the light emitting means and the light receiving means. A signal level holding means for holding the level of the output signal of one light receiving means during a period, a judgment level setting means for setting a judgment level according to the latest signal level held in the signal level holding means, and the light receiving means. and comparing means for comparing the level of the output signal of the output signal with the determination level, and from the result of the level comparison by the comparing means at the time when a sheet of paper is present between the light receiving means and the light emitting means, Paper leaf Ii double feeding detection device that detects double feeding of leaves.