JPS5811802Y2 - Two sheet difference detection device - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a two-sheet difference detection device.

It has become common practice to use a light transmission type detector to detect the difference between two sheets of paper during printing, approval, etc.

This is mainly composed of a light emitting element and a light receiving element, and a sheet of paper is passed between them, and the difference between two sheets is detected based on the output voltage of the light receiving element at that time.

However, in conventional detection devices of this type, a sheet of paper is first passed between the light source and the light-receiving pixel element for reference setting, and the output of the light-receiving element at that time is used as the reference. The difference between the two sheets was detected by comparing the output of the light receiving element at the time with a comparator.

However, this type of detection means has the inconvenience of having to take a reference output every time the type of paper changes.
Also, at this time, the paper does not necessarily pass smoothly; for example, if it passes while jumping, the output of the light receiving element will fluctuate. It becomes necessary to correct or modify the reference output.

The purpose of this invention is to detect the difference between two sheets without using a reference output.

An embodiment of this invention will be described with reference to the drawings.

Reference numeral 1 denotes a light transmission type detector, which is mainly composed of a light emitting element (for example, a light emitting diode) and a light receiving element (for example, a phototransistor), and a sheet of paper passes between the pixel elements.

2 is an amplifier for amplifying the output based on the amount of light received by the light receiving element; 3 and 4 are storage devices such as analog memories; 5 and 6 are
is a comparator, and T is a detector that detects when the trailing edge of the paper passes between the pixel elements. To detect.

Specifically, a circuit that detects the fall of the output of amplifier 2 (
For example, a differential circuit).

8 is a delay circuit.

The operation of this configuration will be explained with reference to FIG.

When a sheet of paper passes through the detector 1, it is blocked by the sheet of paper and the amount of light reaching the light receiving element is reduced.

This reduces its output.

On the other hand, when the paper does not pass through, the output increases.

Therefore, the output A of the amplifier 1 that amplifies this output is the second
The output waveform will be as shown in the figure.

In other words, if at time T1 the leading edge of the paper enters between the light emitting and light receiving pixel elements of the detector 10, from that point onwards the output A decreases from before, and at time T2 the trailing edge of the paper emits light and passes between the light receiving pixel elements. When finished, the output A increases.

While the paper is passing between the pixel elements, if the paper is being printed, the output A will fluctuate as shown in the figure due to the printed portion.

Output A is applied to analog memory 3, comparators 5, 6 and paper passage detector I.

Comparator 5 outputs A and memory value B of analog memory 3
When memory value B is smaller than output A, output C
and give it to analog memory 3.

When the analog memory 3 receives the output C, the previous memory value is cleared and the current output A is newly stored in the memory.

When the paper finishes passing through the detector 1 at time T2, an output is output from the rear end detector T.

When this output is given to the analog memory 4, the analog memory 4 stores the memory value B stored in the analog memory 3 at that time.

Thus the best? After the paper fed to the detector 77 passes through the detector 1, it is cut off, and the memory value in the analog memory 4 becomes the lowest value of the outputs A output from the detector 1 during the process of the paper passing through.

If there is only one sheet of paper (that is, if there is a difference of two sheets), then the memory value should be larger than the output A when there is a difference of two sheets.

The output is also sent to a delay circuit 8.

Then, after a time delay, an output E is outputted and applied to the analog memory 3.

This clears the analog memory 3 of its previous memory values.

However, by then, the previous memory values have been transferred to the analog memory 4 by output.

The memory value of the analog memory 4 may be given to the comparator 6 as is, but it is divided by the resistors 9 and 10,
For example, the output F of 60% of the value is given to the comparator 6 as a reference value.

The reason why the 60% value is used as the reference value is that even if the first sheet of paper is just one sheet, the output level may fluctuate due to the movement of the sheet as it passes through detector 1. This is to prevent detection errors from occurring.

Comparator 6 compares output F and output A, and outputs G when output A is smaller than output F.

This output G becomes a two-sheet difference detection signal.

As described above, when the paper finishes passing through the detector 1 at time T2, the output A increases.

Also, the next sheet is fed and its leading edge is detected by detector 1 at time T3.
When the output A reaches between the light emitting and receiving pixels, the output A decreases again.

Then, the above-mentioned operation is repeated.

Here, it is assumed that at time T4, two sheets overlap (a so-called two-sheet difference state) and reach between the light emitting and light receiving pixel elements of the detector 10.

Note that the example of two sheets of paper overlapping at time T4 is a situation where, while one sheet of paper is passing through detector 1, the next sheet of paper overlaps from the middle of the paper and paper feeding is started. It's raining.

When a difference between the two sheets occurs at time T4, the output A decreases from that time and becomes smaller than the memory value of the analog memory 4 (to be more specific, 60% of the memory value).

Therefore, an output G is output from the comparator 6.

At this point, the difference between two sheets is detected, and specifically, an alarm is issued by the output G, or the sheet feeding operation is stopped.

Note that even when the two-sheet difference is corrected by the generation of the output G, the output B of the analog memory 3 still stores the output A when there is a two-sheet difference.

However, the time T when the paper finishes passing through detector 1
5, the analog memory 3 is output by the output E of the delay circuit 8.
will be cleared.

Also, the analog memory 4 will store the memory value of the analog memory 4 when there is a two-sheet difference at time T5, or this memory value will be changed when the operator confirms the alarm and stops the alarm. It is cleared in conjunction with.

As can be understood from the above explanation, according to this invention, it is only necessary to pass one sheet of paper to be fed first, and in that case, as in the conventional case, reading the output of the detector at that time, There is no need to set the output as a reference value in the comparator, and this idea updates the memory value in the analog memory every time a sheet of paper passes, so it is not necessary to set the output as a reference value in the comparator. This has the effect of eliminating the need for operations such as correction and correction of reference values during paper feeding operation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of this invention, and FIG. 2 is a waveform diagram for explaining the operation. 1...Detector, 3...First storage device, 4...Second storage device, 6...Comparator.

Claims (1)

[Scope of utility model registration request] A detector outputs an output according to the amount of transmitted light of the paper being fed, and the lowest level of the output during the process of the paper passing through the detector is memorized, and the output is recorded every time the paper finishes passing. a first storage device in which a memory value is cleared; and a second storage device in which the memory value of the first storage device is stored when the sheet finishes passing through the detector;
The output corresponding to the memory value of the second storage device is compared with the output of the detector, and the output of the detector is determined from the second memory value.
A two-sheet difference detection device comprising a comparator that outputs a two-sheet difference detection signal when the output is less than the output corresponding to the memory value of the storage device.