JPS5912029A - Device for detecting and preventing multi-feed of paper - Google Patents

Abstract

PURPOSE:To improve the accuracy of detecting and preventing multi-feed of paper regardless of kinds of paper and without any influence of extraneous light in a paper transport apparatus of a copier or the like by providing a pair of rollers different in driving torque, the rotational frequency or the rotating direction of one roller being changed depending upon the slide of passing paper. CONSTITUTION:When sheets 13i and 13j are overlapped and transported, slipping is caused between the sheets 13i, 13j by a difference in coefficient of friction between the sheet 13i and a rubber roller 1 and between the sheet 13j and a rubber roller 2. Accordingly, the rotation of the rubber roller is not followed by the rotation of the rubber roller 2. At that time, an ALARM signal is generated from a frequency detection circuit 10 to light an alarm lamp, and the rotation of a motor 15 is stopped to stop the rotation of a rubber roller 8. Thus, only the sheet 13i can be transported. In this arrangment, the multi-feed of paper can be detected and prevented regardless of thickness and kinds of paper and without any influence of extraneous light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting and preventing double feeding of paper in a paper conveying device such as a copying machine, a laser beam printer, an inkjet printer, or the like.

Sheet paper is often used as a printing medium in recording devices such as copying machines, laser beam printers, and printers. The sheets are fed one by one from a part of the paper hopper to the recording section. At this time, a plurality of sheets may be fed. The above-mentioned multiple paper feeds, that is, double feeding of paper, not only causes jams on the paper transport path, but also
This causes a timing lag when feeding the paper to the image transfer section.
This causes a problem of missing recorded information.

In order to prevent this, conventional methods have been used to detect double feeding based on the amount of light transmitted through the paper and stop the recording operation of the recording device. If the paper is too thick or colored paper is used, not only the amount of light transmitted through the paper changes, but also the change in the tip of the paper is subtle, resulting in malfunctions due to external light, etc. Further, there is a problem that the method cannot be applied when using preprinted paper on which a format is printed in advance.

Furthermore, conventional methods have only been designed to detect double feeds, so there has been no function to proactively prevent double feeds.

The purpose of the present invention is to eliminate the drawbacks of the prior art, and its purpose is to ensure double feeding even when the sheet thickness changes, whether it is one-color paper, or preprinted paper. It is possible to detect.

The aim is to develop a double feed detection and prevention device that is not affected by ambient light. Furthermore, another object of the present invention is to provide a double feeding prevention device that can proactively solve the occurrence of double feeding.

Next, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and in the figure, reference numerals 1.2 and 7.8 indicate rubber rollers. The rubber roller l is rotationally driven in the direction a in the figure by a motor (not shown), and its circumferential speed is equal to the paper conveyance speed. rubber roller 8
is driven to rotate reversibly in the d and e directions by the motor 15, or remains stopped. In addition, the rubber roller 8
The peripheral speed during rotation in the d direction is equal to the paper conveyance speed, that is, the peripheral speed of the rubber roller l. Further, the '-i Muro-Ruff is lightly pressed by the rubber roller 8, and is driven to rotate by the frictional force of the contact portion. The rubber roller 2 receives rotational torque in the direction C in the figure from the motor 6 via the powder clutch 5. At this time, the amount of current applied to the powder clutch 5 is controlled to control the amount of torque transmission. Therefore, torques in opposite directions are applied to the rubber rollers 1 and 2. However, since the torque of the rubber roller 1 is large, the rubber roller 2 in contact with it rotates in the direction b due to the torque due to friction.

4 is an encoder that rotates together with the rubber roller 2;
It has J.T. 4. This encoder 4 is Surin)14
generates a pulse with a frequency proportional to the rotation speed.

Note that the encoder 4 may be of a type that simply generates a signal representing only the direction of rotation. Reference numeral 9 denotes a transmissive photo ink converter that constitutes the encoder 4, and a slit 1
4 is detected as a pulse signal, and a pulse proportional to the rotation speed is output. This pulse is supplied to the frequency detection circuit 10 to check the driven state of the rubber rollers 1 and 2. At this point, if the rotation speed of the rubber roller 2 becomes low or if the rotation speed is reversed, the rubber roller 2 becomes the rubber roller 1.
Since the feed is not followed, it is identified that a double feed has occurred. That is, when the frequency detected by the frequency detection circuit 10 falls below a predetermined value, an ALARM signal is generated, a warning lamp (not shown) lights up, and the motor drive control unit 18
A signal is sent to the motor 15, and the rotation of the motor 15 is stopped. Next, when the paper detection photosensor 17 detects the paper 13,
The motor 15 is reversed for a certain period of time and 1. Gotrolla 8 is e in the diagram.
rotationally driven in the direction. Thereafter, the motor 15 again drives the rubber roller 8 to rotate in the direction d in the figure. In the figure, reference numeral 3 denotes a constant tension spring whose tension is adjustable and which presses the rubber roller 2 against the rubber roller l with a constant force. FIG. 6 shows a subroutine which is interrupted and started upon detection of double feed in the control flowchart stored in the motor drive control section 18 mentioned above. starts when a double feed condition is input (when the output falls below a certain level, the output goes high),
The motor 15 is stopped in step S2. Next step S
In step S3, it is determined whether or not the photosensor 17 has detected paper, and if paper has been detected, control proceeds to step S4. In step S4, the motor 15 is reversed, the roller 8 is driven, and the paper (13j in this case) held by the friction of the roller 8 is reversely conveyed in the B direction. The motor 15 must continue to rotate in reverse until the paper is dropped into the storage section 12, and this driving time is controlled by setting a timer for the reversing time in step S5 and determining whether or not a timeout has occurred (No in step S6). This is executed by step S7, which sometimes performs a countdown.

When it is determined in step S6 that a timeout has occurred, control proceeds to step S8, where the motor 15 is temporarily stopped in preparation for the next sheet feeding, and its stop rotation is controlled.

Next, the operation of the present invention will be explained.

As shown in FIG. 2(a), one sheet of paper 13 is fed between the rubber rollers 7.8 through the paper path 16.
As shown in FIG. 2(C), the sheet is fed between the rubber rollers 1.2 through the paper transport guide 11'' as shown in FIG. 2(C). Rubber rollers 1, 2, 7.8 are respectively a,
One sheet of paper 13 is conveyed by rotating in the rotational directions shown in b, f, and d.

Next, see the third section for when two sheets of paper are conveyed overlapping each other.
This will be explained with reference to FIGS. (a) to (c).

As shown in FIG. 3(a), when the sheets 13i and 13j are conveyed in an overlapping manner and reach the position of the rubber roller 1.2, the frictional resistance between the sheet 13f and the rubber roller l and the sheet 13j
Since the frictional resistance between the paper 13i and the rubber roller 2 is greater than the frictional resistance between the paper 13i and the paper 13j, the paper 13i,! :
13j, slipping occurs as shown in FIG. 5(b). Therefore, since the rotation of the rubber roller 2 does not follow the rotation of the rubber roller l, as mentioned above, the frequency detection circuit 1o
When the LARM signal is generated, a warning lamp (not shown) lights up and the rotation of the motor 15 stops +1, causing the comb roller 8 to stop rotating.
The rotation of is also stopped (steps Sl and S2 in FIG. 6). At this time, the rubber roller is rotated in the direction a, as shown in Figure 3 (
As shown in b) and (C), the paper 13i is conveyed in the direction A in the figure, and the comb roller 7 rotates in the direction f in the figure following the movement of the paper 13+. Further, since the rubber roller 8 is stopped, the paper 13i is not conveyed. Next, as shown in FIG. 4(a), when the paper 13i is conveyed three times in the A direction and detected by the photosensor 17, in step S3, a signal is sent to the motor drive circuit 18 and the motor 15 is reversely rotated.
Step S4. , :l The roller 8 rotates in the e direction in the figure. At this time, it is assumed that the paper 13+ has already passed through the rubber roller 7.8 and is released from the pressing force thereof, and is still being subjected to the pressing force by the rubber roller 1.2. Then, by rotating the rubber roller 8 in the e direction, the paper 13j is moved in the B direction, that is, in the A direction.
The paper is transported in the opposite direction and reaches the paper feed path 16 again.

However, since the gap in the paper thickness direction of the paper feed path 16 is sufficiently small, the paper 13j is deflected by the wall near the paper feed path 16, and as shown in FIG. While bending, the paper is dropped into the paper storage section 12 as shown in FIG. 4(c).

On the other hand, the paper 13i is conveyed in the incoming direction by the rubber roller 1.2. Further, the motor drive circuit 18 is connected to the paper 13.
When sufficient time has elapsed for paper storage 12 to stack paper, step S6. ff14 As shown in Figure (C), the motor 15 is rotated in reverse to rotate the rubber roller 8 in the d direction in preparation for the next sheet feeding.

In the embodiment described in Section 1, two sheets of paper are fed at the same time, but even if three or more sheets of paper are fed as shown in FIG. Even when sheets of different thickness are fed, a constant tension is applied between the rubber rollers 1 and 2, so the rubber roller 2 repeats forward and reverse rotations, preventing the second and subsequent sheets of double-fed sheets from being fed. prevent passage.

The device of the invention can be modified as follows.

That is, the top paper 13i that is double fed or the rubber roller 1.
When the photo sensor 17 detects that it has passed through 2,
The motor 15 is stopped by the ALARM signal. Therefore, the paper that is in contact with the roller 8 is held as is. In other words, only the most part of the paper (the paper that is in contact with rollers 1 and 7) is conveyed in the A direction. Here, after the photo sensor 17 detects the passage of the topmost paper, when the motor 15, which had been stopped by the ALARM signal, is rotated again in the forward direction, that is, in the d direction (step S4 in FIG. 7), the The second and subsequent sheets of paper that have been sent can be sequentially transported to the main office starting from the second most sheet.

FIG. 7 shows a control flow for performing such control, in which an interruption is started upon detection of double feeding (step 5IO), the motor 15 is stopped in step Sll, and the passage of paper is detected by the photo sensor 17 in step 512. When detected, control proceeds to step S13, and the motor 15 is rotated in the normal direction. In step S14, it is determined whether there is double feeding or not, and if YES, the control is returned to step Sll, the above-mentioned control is executed, and only the most part of the paper is transported and the other paper is held. I'll keep it. Repeating this control,
If the determination in step S14 is No, the process returns.

Accordingly, according to this embodiment, the paper storage section 12 becomes unnecessary.

In this invention, the paper is passed between rollers with different driving torques, and in the case of double feeding, slippage is caused between the sheets due to the difference in the driving torque, so that the required paper can be delivered to one sheet.
Since paper is conveyed sheet by sheet, it is not only possible to stably feed the paper regardless of differences in paper Jγ or foul rate, but also on the unloading side, there is no need to stop the printing operation because double feeding does not occur substantially. There is no. Therefore, the effect of improving the operating rate is exhibited.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the double feeding prevention device according to the present invention; Fig. 2(a) is a block diagram of an embodiment showing a state in which one sheet is fed; (b) is a block diagram of an embodiment showing a state in which one sheet of paper is supported at two locations by rubber rollers, and FIG. 2(C) shows a state in which conveyance of one sheet of paper is completed. Block Diagram of One Embodiment FIG. 3(a) is a block diagram of one embodiment showing a state in which double-fed sheets are supported at two locations by rubber rollers. FIG. 3(b) is a block diagram of an embodiment showing the rotational direction of the rubber roller and the position of the paper in a state where double feeding is detected. FIG. FIG. 4(a) is a block diagram of an embodiment showing a state in which paper is transported in reverse. FIG. FIG. 4(c) is a block diagram of an embodiment showing a state in which the fed paper is fed back to the paper storage unit. FIG. Fig. 5(a) is a partially enlarged view of an embodiment showing a state in which one sheet of paper is conveyed by two rubber rollers with different driving torques, vr, Fig. 5 In (b), two sheets of paper have different driving torques.
Figure 5 (C) is a partially enlarged view of an embodiment showing a state in which sheets of paper are fed between two rubber rollers. 6 and 7 are flowcharts of the control flow executed by the motor drive control section. Here, 1, 2, and 7.8 are rubber rollers, 4 is an encoder, 6.15 is a motor, and 17 is a photosensor. Patent Applicant: Canon Corporation Figure 1 Figure 2 Cause (a) Figure 2 City) Fang 2 Figure (C) Figure 3 (al ■ Figure 3 City) Figure 3 (CI Figure 4 (a) Figure 4 Figure 4 (C) Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) A pair of rollers each having a different drive torque is provided, and double feeding is detected by causing a change in the number of rotations or direction of rotation of one of the rollers as the paper passes between the rollers. Double feed detection device for paper. (2) The paper double feed detection device according to item 1, wherein the rotational torque of the roller that causes a change in rotational speed or rotational direction when the paper runs out is lower than the rotational torque of the pair of rollers. (3) a detection means for detecting double feeding by causing a change in the rotational speed or rotational direction of the roller with lower drive torque due to the slippage of the paper passing between the rollers, and a detection means arranged before the rollers. A paper drive roller that holds all but a few sheets of paper when double feed is detected;
A device for preventing double feeding of sheets, which has a main driving roller that is controlled to convey the sheets sequentially starting from the topmost sheet, and a driven roller that is rotated by the intervening sheet of paper.