JPS61145054A - Overlap detecting device - Google Patents

Abstract

PURPOSE:To enable an overlap to be detected regardless of the kind of forms (material and thickness) and also enable the overlap, which occurs for the first time though, to be positively detected by arranging a thickness detecting sensors at the form passage allowing the detected thickness to be stored one after another so as to to be processed by means of a comparison means. CONSTITUTION:Sensors 34 and 35 are arranged in front of a register roller to detect the thickness of a form in such a way that they hold a form passage from the both sides. A light passing hole 37 is arranged on an upper and a lower guide plates 36 which guide the form 18 allowing a light receiving element 35 to receive light from a light sourse lamp 34. The light receiving element 35 allows its electric resistance to vary with the amount of light received. Accordingly, electric current which flows the light receiving element 35 varies with the amount of light which penetrates the form 18, allowing electric potential at a point A to be a value that corresponds to the thickness of the form. And the thickness tN of the form (thickness of the Nth form) is stored in a memory whenever the form passes through a thickness detecting unit. In case that N is 1, the thickness is stored as tmin. And the thickness TN detected in the form which comes from the second form, is compared with tmin allowing any overlap to be detected. Even if the first form causes overlapping, it is detected. And even if the first form overlaps with the second one each other, the overlap is definitely detected.

Description

[Detailed Description of the Invention] [Scope of Industrial Application] The present invention is used in a multi-feeding device, particularly in equipment that handles paper sheets such as copying machines and recording machines, to detect the thickness of paper sheets being fed and conveyed. This invention relates to a double feed detection device that has storage and comparison means and notifies that double feed has occurred.

[Conventional technology]

Conventionally, this type of device has used, for example, a method of detecting a change in thickness using a roller or a displacement amount, a method of detecting a change in the amount of transmitted light or a change in lines of magnetic force, as a means for detecting double feeding.

In order to determine whether or not there is a double feed, there is a method to detect the double feed based on the sensor level when one sheet of standard paper is fed normally, and the selection and replacement of the cassette. When the material or thickness of the paper sheets changes, double feeding is detected based on the sensor level when the paper sheets are fed to the first circle.

However, the former method has the disadvantage that it cannot handle a wide variety of paper sheets such as second original paper, thin letters, and thick letters.

Even with the latter method, if double feeding occurs during the first feeding and conveyance, there is a drawback that double feeding cannot be detected from the second time onwards.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to accurately detect double feeding without being influenced by the type of paper sheets, and even when double feeding occurs during initial feeding and conveyance.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a new double feed detection device that is improved in view of the conventional drawbacks.

Another object of the present invention is to provide a double-feed detection device that can accurately detect double-feeding of paper sheets even when double-feeding occurs for the first time.

〔Example〕

Specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a copying machine to which the present invention is applied. In FIG. ．．
Lens 9. An image is formed by a mirror 1o onto a drum 11 covered with an optical semiconductor. The drum 11 is uniformly charged by a charger 12, and after an image is exposed on the drum 11, it is visualized on the drum 11 as a toner image by a developer 13.

Then, the visible image is transferred by a transfer charger 15 onto a sheet that is conveyed in a timed manner by a register roller 14, and the latent image and toner image remaining on the drum 11 are then transferred to the drum 11 by a lamp 16 and a cleaner 17. l
removed from above.

On the other hand, C) 18 is stored in a cassette etc. 19,
The half-moon-shaped paper feed roller 2o and the register roller 4 send out the toner image in synchronization with the toner image on the drum 11, and after the toner image is transferred by the transfer charger 15, the separation roller 2
1, it is separated from the drum 11, passed through a conveying section 22, and sent to a fixing device 23 such as a heat fixing device. When copying after fixing is a normal one-sided copy, the flap 24 is at the solid line position in FIG.
The top is discharged.

In the case of double-sided copying, the sheet on which only the front side (one side of both sides) has been copied is positioned directly under the first tray 27 by rotating the flap 24 to the position shown by the two-dot chain line in FIG. The required number of sheets are stored in the second tray 28 for temporary storage, and thereafter, the sheets are sequentially separated and discharged by a pair of reversing rollers 29-30 facing each other at an appropriate timing.

The ejected sheet is simultaneously conveyed by width adjustment rollers 31-32 provided under the main body of the copying machine.

The width adjustment is performed and the paper is fed into the main body of the copying machine.

Before being fed into the main body of the copying machine, the sheet is once stopped by register rollers 14 to form a loop. This is because when the slip roller 33 sends the sheet conveyed by the width adjustment rollers 31 and 32 to the register roller 14, it once hits the register roller 14 to form a loop in order to correct the skew of the sheet. It is.

When the loop is formed, the slip roller 33 slips due to the resistance of the loop and rotates idly.

Thereafter, at a certain timing, the register roller 14 rotates and feeds the sheet to the drum 11.

The rest is the same as normal copying, and the sheets are finally collected in the first tray 27.

Sensors 34 and 35 provided across the paper passage path in front of the register roller 14 are sensors for detecting the thickness of the paper.
In this embodiment, by arranging the thickness detection sensor immediately before the register roller, the thickness of the paper can be checked both when feeding the paper from the cassette 19 and when refeeding the paper from the second tray 28. This allows for thickness detection.

FIG. 2 shows an example of a thickness detecting section for the paper 18 provided in the present invention.

Here, 36 is an upper and lower guide plate that guides the paper 18 to the detection section, 37 is a light passing hole provided in the guide plate 36, and 34 is a light source lamp. Reference numeral 35 denotes a light receiving element that receives light from the lamp 34 through a light passing hole 37. For example, by using a phototransistor, the resistance value of the light receiving element 35 changes in response to changes in the amount of light received. The daily thickness of the paper being transported can be detected by changes in the amount of light that passes through it. In this example, the thickness is detected based on the amount of light that passes through the paper, so double-sided paper refeeding is not necessary. In order to avoid the influence of the image on the first side when printing, image defects due to the leading edge margin (when refeeding both sides will be the rear edge due to switchback) and the separation belt are detected using non-image areas such as copy sheets. There is a need.

FIG. 3 shows an example of a block diagram for detecting the thickness of paper and inputting it to the microcomputer. The light emitted from the light source lamp 34 passes through the light transmitting hole and reaches the light receiving element 35, but as the paper 18 is conveyed between them, the paper 18
The light, which is weakened by an amount corresponding to the thickness of the light, reaches the light receiving element 35. A phototransistor is used as the light receiving element 35, and the current flowing through the phototransistor changes depending on the amount of light transmitted through the paper 18, so that the potential at point A becomes a value corresponding to the thickness of the paper. Then, the potential difference between the potential at point A and the reference ground potential is amplified by the operational amplifier 36, and the AD
The signal is digitally converted by a converter 37 and inputted to a microcomputer 38 as a paper thickness signal.

FIG. 4 is a flowchart of double feed detection and judgment in the present invention. First, when the copy start key is pressed, the paper 18 is continuously fed, and each time the paper 18 passes through the thickness detection section, its thickness tN (thickness of the Nth sheet of paper fed) is detected. It is designed to be recorded and memorized.And,
In the case of the first paper feeding, that is, when N = 1 (N, number of copies per copy), the detected thickness t N = 1 is t□n, regardless of whether there is double feeding or not. (minimum thickness of paper fed from the start of copying),
Return to the flow for detecting the thickness of the subsequent sheets. Next, in the case of paper feeding after the second concave, that is, when N=1 is not, the detected thickness tN and t sin are compared, and if they are equal, the thickness of the subsequently fed paper is detected. Return to flow. Also, in the case where tN=tI111n does not hold, in the case of tN"twin, it is determined that all sheets up to the 8th sheet, that is, from the 1st sheet to the N-1st sheet, have been double fed,
The value of tllin is replaced from 1 to a new value tH, and the process returns to the flow of detecting the thickness tN+1 of the subsequently fed paper.

Conversely, if jmin<EN, it is determined that the eighth sheet has been fed multiple times, and the flow returns to detecting the thickness tN+1 of the subsequently fed sheet.

Double feeding can be detected using the flow explained above. The accuracy of the thickness comparison mentioned above is based on whether there is one or two sheets of paper.
Needless to say, a relatively rough level of accuracy is sufficient to determine the number of sheets (or two or more sheets).

〔Effect of the invention〕

As explained above, by installing a thickness detection sensor in the paper conveyance path and providing a means to sequentially store and compare the detected thicknesses, multi-feeding is possible without being limited to one paper type (material, thickness). Furthermore, even if the first sheet causes double feeding, it is possible to detect which sheet caused double feeding.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of a copying machine to which the present invention is applied;
FIG. 2 is a sectional view showing an example of the thickness detection section of the double feed detection device of the present invention, FIG. 3 is a circuit diagram for double feed detection, and FIG. 4 is a flowchart for determining double feed detection in the present invention. 34 is a light source lamp, 35 is a light receiving element, and 38 is a microcomputer.

Claims (1)

[Scope of Claims] A double feed detection device that detects double feeding by detecting the thickness of paper sheets being conveyed, comprising: a detection means for detecting the thickness of fed and conveyed paper sheets; a storage means for successively storing the minimum thickness detected by the means as a reference thickness; and a comparison means for successively comparing the minimum thickness stored by the storage means, the storage means and the comparison means A double feed detection device that determines double feed if the thicknesses do not match.