JP2000159393A - Paper feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the double feed of paper with high accuracy at all times to surely prevent the double feed by eliminating the influence of paper powder on a sensor for detecting the double feed. SOLUTION: In a paper feeder in which paper P loaded in a paper feed hopper 4a is delivered by a paper feed roller 5 and double feed is prevented by a separating roller 7 and a retard roller 8, a vertical path through which the paper P is fed almost vertically is provided in a portion of a conveyance path up to a portion where the paper P is subjected to image processing, and an optical or ultrasonic double-feed sensor 10 having its detecting surface opposed to each side of the paper P passing through the vertical path is disposed to prevent paper powder from the paper P from clinging to the detecting surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic paper feeder provided in an image reader such as an image scanner, and more particularly to a paper feeder having a double feed detection function capable of improving the detection accuracy of double feed of sheets. It relates to a paper feeding device.

[0002]

2. Description of the Related Art An image scanner has conventionally been used as a device for reading various documents in large quantities and performing, for example, electronic filing. This image scanner is equipped with a transport path for transporting paper as a path facing a scanning module for reading documents, and an automatic paper feeder for setting documents in a stacked state and sending them one by one to the reading unit. A device provided with an apparatus (ADF) is generally used.

FIG. 4 is a schematic diagram showing a basic configuration of an automatic paper feeder used in a conventional image scanner and other document reading devices.

[0004] As shown in the figure, the automatic paper feeder stacks and loads paper P, and a hopper 51 is elastically urged upward by a spring 51a.
A feed roller 52 that picks up and feeds out one sheet at a time, and a separation roller 53 and a retard roller 5 for preventing double feeding of the paper P immediately downstream of the feed roller 52.
4 are arranged. As is conventionally known, the retard roller 54 is provided with a torque limiter 54b around a support shaft 54a which is driven to rotate in a direction opposite to the sheet feeding direction, and one sheet P is nipped between the sheet P and the separation roller 53. When the two or more sheets P are nipped, the sheet P rotates in the direction opposite to the sheet feeding direction and returns the lower one of the overlapping sheets P to the hopper 51 side.

A transport path is provided downstream of the separation roller 53 and the retard roller 54 for feeding the fed sheet P to an image reading unit and for collecting the read sheet. The transport path includes a plurality of transport rollers. 55 are arranged. Further, immediately downstream of the separation roller 53 and the retard roller 54, a double feed detecting unit for detecting whether the sheet P is a single sheet or a double feed is provided. The double feed detecting unit is, for example, a pair of optical or ultrasonic type double feed sensors 56a, 56b.
And is disposed so as to sandwich the transport path of the paper P up and down. When the multi-feed sensors 56a and 56b are of the optical type, the multi-feed is determined based on the attenuation of the light transmittance when passing through the paper P as the light-emitting side and the light-receiving side, respectively.
Further, if it is an ultrasonic type, the double feed sensors 56a, 56
6b as ultrasonic transmitting and receiving sides, and
The double feed is determined based on the attenuation rate of the wave amplitude at the time of exiting.

[0006]

The double feed sensors 56a and 56b for detecting such double feed of the paper P
If the sheet P in the double feed state is arranged downstream of the double feed separating section and upstream of the reading section, the double feed is determined before the sheet P in the double feed state enters the reading section. If the double feed sensors 56a and 56b are disposed immediately downstream of the separation roller 53 and the retard roller 54 as in the illustrated example, the paper P that could not be separated by double feed can be detected quickly. Therefore, if the conveyance of the sheet P is stopped in accordance with this detection, the multi-feed sheet can be easily pulled out from the hopper 51 side, which is easy to cope with.

However, the distance between the separation roller 53 and the retard roller 54 and the paper feed roller 52 is restricted. This is because, for example, in order to be able to feed a manuscript sheet having a size of about a postcard, the distance between the roller shafts must be reduced in order to correspond to the shape and size of a small manuscript. Therefore, when the multi-feed sensors 56a and 56b are arranged near the separation portion of the sheet P, the distance between the multi-feed sensors 56a and 56b and the paper feed roller 52 is also reduced. On the other hand, since the hopper 51 stacks and loads a large number of sheets of paper P, it has only a degree of freedom of a substantially horizontal posture as shown in the drawing or a slightly inclined posture toward the conveyance path. For this reason, the conveyance path in which the separation roller 53 and the retard roller 54 are disposed at the entrance is also restricted to a horizontal or downward inclination in order to quickly feed the sheet P.

As described above, when the multi-feed sensors 56a and 56b are provided in the vicinity of the sheet separating section, the multi-feed sensors 56a and 56b need to be opposed to each other with the conveyance path of the sheet P vertically interposed therebetween. However, when the paper P is conveyed, there is a tendency that minute paper dust is scattered due to contact with a guide or a roller, and this paper dust is generated by the double feed sensors 56a and 56.
b. In particular, paper dust easily accumulates on the detection surface facing the sheet P, which is the surface of the double feed sensor 56b below the conveyance path.

As described above, the paper powder is supplied to the double feed sensors 56a, 56
If it adheres to the surface of b, the optical transmittance fluctuates in the case of the optical system, and the attenuation rate of the wave amplitude fluctuates in the case of the ultrasonic system, and in any case, the accuracy of double feed detection decreases. Therefore, in order to maintain the detection accuracy, it is necessary to periodically clean the light emitting / receiving surface or the transmitting / receiving surface of the double feed detecting sensors 56a and 56b, and the maintenance work is troublesome.

As described above, in the conventional paper feeding apparatus, since the sensors for detecting the double feed are arranged vertically above and below the paper conveyance path, the influence of the paper dust on the sensors arranged on the lower side can be avoided. There is a risk of overlooking the double feed.

The problem to be solved in the present invention is to provide a paper feeder capable of always detecting a double feed with high accuracy and eliminating a double feed of paper without the influence of paper dust on a sensor for double feed detection. Is to do.

[0012]

According to the present invention, there is provided a paper feed hopper for stacking and loading sheets of paper, and a paper feeder disposed above the paper feed hopper for picking up and loading the loaded paper one by one from an upper layer. A sheet feeding device including a roller and a conveyance path including a double-feed prevention mechanism for the sheet and an image processing unit that performs image processing on the sheet between the sheet feeding roller and a discharge end. A vertical path for feeding the sheet in a substantially vertical direction is provided between the double feed prevention mechanism and the image processing unit on the transport path, and a detection surface is arranged facing a surface of the sheet passing through the vertical path. And a double feed detecting means for detecting the double feed of the sheet.

In such a configuration, since the detection surface of the double feed detecting means faces the surface of the paper along the upward or downward vertical path, paper dust when the paper is fed slides down even if it covers the detection surface. There is no adhesion, and high detection accuracy can be maintained.

[0014]

According to the first aspect of the present invention, there is provided a paper feed hopper on which sheets are bundled and loaded, and the loaded paper placed above the paper feed hopper is picked up one by one from an upper layer. A sheet feeding device including a feed roller that feeds out, a conveyance path including a mechanism for preventing double feed of the sheet and an image processing unit that performs image processing on the sheet between the sheet feeding roller and a discharge end. In the transport path, a vertical path for feeding the sheet in a substantially vertical direction is provided between the double feed prevention mechanism and the image processing unit, and a detection surface faces a surface of the sheet passing through the vertical path. A sheet feeder provided with a double feed detecting means arranged to detect double feed of the paper, and has an action of suppressing adhesion of the double feed detecting means to the detection surface even if paper dust scatters from the paper. .

According to a second aspect of the present invention, a head is provided between the double feed prevention mechanism and the entrance of the vertical path, and a head is provided between the double feed prevention mechanism and the entrance of the vertical path. Or as a path gently bent down, the double feed detecting means is a double feed sensor of a combination of a transmitting element and a receiving element of an ultrasonic wave arranged at a position sandwiching both front and back surfaces of a sheet passing through the vertical path. 2. The sheet feeding device according to claim 1, wherein the sheet after passing through the double feed prevention mechanism is bent and deformed along a path until it reaches the entrance of the vertical path, and the two sheets are double fed. In this case, it is peeled off from the distal end side by this bending deformation. Therefore, an air layer can be included between the sheets, and the effect of further improving the double feed detection accuracy of the double feed sensor using ultrasonic waves, in which the amplitude attenuation is increased by the presence of the air layer, is provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing an image reading apparatus provided with the automatic sheet feeding apparatus of the present invention, and FIG. 2 is a longitudinal sectional view showing a main part of an internal structure of the automatic sheet feeding apparatus.

In FIG. 1, the image reading apparatus includes a main body 1 movably containing an optical scanning module 1a, a document cover 2 openably and closably mounted on an upper surface of the main body 1, and a document sheet mounted thereon for automatic feeding. Paper and scanning module 1a
And an automatic paper feeder 3 for passing the reading unit around the reading unit.

The main body 1 has an operation panel 1b at the front thereof, a built-in controller (not shown) for controlling all the operating devices, and a platen 1c for reading a large-sized sheet disposed on the upper surface thereof. is there. The document cover 2 is opened, the paper is manually placed on the platen 1c, and the scanning module 1a is moved in the direction of the arrow in FIG. 1 to scan, thereby reading the image of the paper on the platen 1c.

The automatic paper feeder 3 comprises a housing 3a and a hopper unit 4 mounted on the upper end side. The hopper unit 4 includes a paper feed hopper 4a one end of which is rotatably supported by a pin 4b and the other end of which is urged upward by a spring 4c. The paper feed end of the paper hopper 4a (FIG. 2) A paper feed roller 5 that picks up and feeds out a sheet is disposed above (left end in FIG. 1). A guide 6 for transporting the paper picked up by the paper feed roller 5 is provided inside the housing 3a.

The guide 6 is disposed, for example, with a gap large enough to allow paper to pass through two metal plates or the like, or the housing 3a can be divided into two parts with the paper conveyance path as a boundary. What is necessary is just what was formed by the gap between two. In the present invention, as shown in FIG. 2, the guide 6 is connected to the paper feed hopper 4a in which the feeding end side of the paper is inclined slightly downward diagonally, and is gradually bent obliquely downward. This is a combination of a vertical portion 6b formed almost directly below the leading portion, and a reading / discharging portion 6c having a concave arc shape upward from the lower end of the vertical portion 6b.

At the entrance of the introduction portion 6a of the guide 6, a separation roller 7 and a retard roller 8 with a built-in torque limiter are provided above and below the sheet transport path. The separation roller 7 and the retard roller 8 have the same function as that of the conventional example. When one sheet is fed by the sheet feeding roller 5 from the sheet feeding hopper 4a, the retard roller 8 rotates in the sheet feeding direction to rotate the sheet. Is passed, and when two or more sheets are multi-fed, only the top one of the overlapping sheets is allowed to pass, and the multi-fed sheets are returned to the paper feed hopper 4a. In addition, two sets of transport rollers 9a are arranged in the introduction section 6a on the downstream side of the separation roller 7 and the retard roller 8, and three sets of transport rollers 9b are incorporated in the reading / discharging section 6c. The paper nipped by the transport roller 9b is the document cover 2
Is discharged onto a collection tray 2a provided on the upper surface of the tray.

The scanning module 1a has a built-in reduced optical image reading system using a CCD like the conventional image reading apparatus, and is of a carriage type movable within the main body 1. When the automatic document feeder 3 automatically feeds the document, it is held at the position shown in FIG. 2, and the guide 6 is located at the lowest position between the first and second conveying rollers 9b of the reading / discharging section 6c. The image is read by scanning the paper as it passes.

Here, the paper fed from the paper feed hopper 4a is prevented from being double fed by the separation roller 7 and the retard roller 8. However, when feeding a sheet in which sheets having different thicknesses and friction coefficients are mixed, a double feed may occur without separating the sheets depending on the conditions. In preparation for such a double feed, in the present invention, the double feed sensor 10 for detecting the double feed is provided not on the downstream of the separation roller 7 and the retard roller 8 but on the vertical portion 6b of the guide 6. The double feed sensor 10 utilizes an ultrasonic sensor, and is a combination of a transmitting element 10a disposed on the left side of the vertical portion 6b and a receiving element 10b disposed on the right side.

Double feed sensor 10 using ultrasonic sensor
Transmits the ultrasonic wave transmitted from the transmitting element 10a to the receiving element 1
0b receives the output signal and inputs the output signal to the controller, and determines non-multi feed or double feed based on the attenuation degree of the output waveform of the transmitted ultrasonic wave. For example, based on the magnitude of the amplitude of the output waveform when one sheet has passed, it is possible to determine in advance how much the amplitude is attenuated from this reference when two sheets are multi-fed. The double feed can be detected based on the degree of attenuation. Then, the transmitting surface of the transmitting element 10a and the receiving surface of the receiving element 10b are respectively coaxially opposed to the front and back surfaces of the sheet passing along the guide 6, so that the ultrasonic wave is transmitted from the transmitting element 10a in a direction orthogonal to the sheet. Can be transmitted and applied to the receiving element 10b.

In the above configuration, as shown in the schematic diagram of FIG. 3, a bundle of sheets P is mounted on the sheet feeding hopper 4a,
The top sheet P is pressed against the peripheral surface of the sheet feeding roller 5. When the automatic paper feed mode is set by the operation panel 1b, the scanning module 1a moves to the position shown in FIG. 2 and stops, and all the rollers 7, 8, 9a, up to the paper feed roller 5 and the collection tray 2a. 9b is driven to rotate. By this rotation, only one sheet P in contact with the sheet feeding roller 5 is fed out, and the separation roller 7
The sheet is conveyed by conveying rollers 9a and 9b after passing through a nip portion between the sheet and the retard roller 8. When the sheet P passes through a scanning point (indicated by a symbol S in FIG. 3), the image is scanned by the scanning module 1a and an image on the surface of the sheet P is read. Is discharged.

During the transport of the sheet P, ultrasonic waves are continuously transmitted from the transmitting element 10a of the double feed sensor 10 arranged along the vertical portion 6b of the guide 6, and transmitted through the passing sheet P. The ultrasonic wave corresponding to the amount reaches the receiving element 10b, and the output waveform is input to the controller. Then, as described above, two or more sheets P that could not be stopped by the separation roller 7 and the retard roller 8
Is determined based on the attenuation of the output waveform signal from the receiving element 10b. When this double feed determination is made, for example, each of the rollers 5, 7, 8, 9a, 9
The driving of b is stopped, the paper P in the multi-feed state is pulled out to the paper feeding hopper 4a side, and after the paper P is reset, the paper feeding is resumed.

Here, in the double feed sensor 10 using the combination of the transmitting element 10a and the receiving element 10b using the ultrasonic sensor, the transmitting surface and the receiving surface facing the front and back surfaces of the paper P are not coated with foreign matter. Is very important in maintaining high accuracy detection. The largest cause of the film is minute paper dust that is scattered when the sheet P is conveyed as described above.

The generation of such paper dust and the double feed sensor 10
In the present invention, since the transmitting element 10a and the receiving element 10b are provided in a portion where the paper P is guided by the vertical portion 6b, the adhesion of paper dust is suppressed against the decrease in detection accuracy due to adhesion to the paper. In other words, both the transmitting surface and the receiving surface of the transmitting element 10a and the receiving element 10b are portions where the paper P advances directly below, and have a relationship substantially orthogonal to the paper surface of the paper P. Therefore, even if the paper dust from the paper P is scattered, the paper dust hardly adheres to the transmitting surface and the receiving surface, and the paper dust is hardly attached to the surface like the double feed sensor 56b located below the paper P shown in the conventional example. Paper dust does not accumulate. Even if paper dust adheres to the transmitting surface of the transmitting element 10a and the receiving surface of the receiving element 10b, when the paper P passes between the transmitting surface and the receiving surface, the surrounding air is agitated. Therefore, the adhered portion is scraped off by the air flow, and the clean transmitting and receiving surfaces are maintained.

As described above, the transmitting element 1 of the double feed sensor 10
By providing 0a and the receiving element 10b in a portion where the paper P proceeds substantially directly below by the vertical portion 6b, it is possible to prevent adhesion and accumulation of paper dust. Therefore, non-multifeed and double-feed of the paper P can always be detected with high accuracy, and trouble caused by double-feed can be avoided.

Here, if there is a uniform straight line from the sheet feeding unit to the conveyance path as in the conventional example when the sheets P are multi-fed, the sheets P are often in close contact with each other. The air layer hardly intervenes between the sheets P. On the other hand, in the present invention, the sheet P fed from the sheet feed hopper 4a is
After passing through the sheet separating section, the sheet is bent in a bow shape so as to project upward while going from the introduction section 6a of the guide 6 to the vertical section 6b. For this reason, the bending when the two sheets of paper P move while being overlapped acts, and the sheets of paper P are easily peeled off from the leading end side of the sheets of paper P, whereby an air layer is included between the sheets of paper P. Can be made. Therefore, even when the sheet P reaches the portion directly below by the vertical portion 6b, the sheet P is sent to the double feed sensor 10 as a double feed of the air layer interposed.

On the other hand, a double feed sensor 10 using an ultrasonic sensor transmits a signal from a transmitting element 10a and receives a signal from a receiving element 10b.
The multifeed is determined based on the attenuation of the ultrasonic wave received in step (1). The degree of attenuation is much greater when an air layer is included than when two sheets of paper P are in close contact with each other. Therefore, even if the sheets P are in close contact with each other during the period between the separation roller 7 and the retard roller 8 and the downstream side, even if the sheets P
Since the air layer is included by utilizing the change in the guide direction of, the detection accuracy of the double feed sensor 10 can be improved.

In the above description, an ultrasonic sensor is used as the double feed sensor 10, but an optical sensor using a light emitting element and a light receiving element may be used. Even when this optical sensor is used, the light emitting element and the light receiving element may be provided at the same position as the transmitting element 10a and the receiving element 10b in correspondence with the vertical portion 6b of the guide 6, as shown in FIGS. Then, in the optical sensor, since the degree of attenuation of the amount of light received by the light receiving element after the light from the light emitting element passes through the paper is used as a criterion for the double feed determination, if the light emitting surface and the light receiving surface are directed toward the paper, As in the previous example, the adhesion of paper dust to the light emitting surface and the light receiving surface is prevented, and high detection accuracy is maintained.

[0033]

According to the present invention, it is possible to prevent the paper dust or the like from adhering to the detection surface of the double feed detecting means for detecting the double feed of the paper. it can. Therefore, even if papers with various thicknesses and friction coefficients are mixed, reliable double feed detection can be performed, and if the equipment is attached to an image reading device for important documents, etc., operation without reading errors can be performed. Become.

Also, if the paper transport path from the double feed prevention mechanism to the double feed detecting means is bent, the double feed paper can be separated from the leading end side by bending during the transport to include an air layer. it can. Therefore, if an ultrasonic sensor is used as the double feed detecting means, the accuracy of double feed detection can be further improved by the presence of an air space.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an image reading apparatus equipped with a sheet feeding device of the present invention.

FIG. 2 is a schematic longitudinal sectional view showing a main part of an internal structure of the sheet feeding device.

FIG. 3 is a skeleton diagram showing an outline of a paper transport path by a guide from a paper feed hopper.

FIG. 4 is a schematic diagram of a conventional sheet feeding device provided with a double feed detecting unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 1a Scanning module 1b Operation panel 1c Platen 2 Document cover 2a Collection tray 3 Automatic paper feeder 3a Housing 4 Hopper unit 4a Paper feed hopper 4b Pin 4c Spring 5 Paper feed roller 6 Guide 6a Introducing part 6b Vertical part 6c Reading / discharging Part 7 Separation roller 8 Retard roller 9a, 9b Conveyance roller 10 Double feed sensor 10a Transmitting element 10b Receiving element P Paper

Claims (2)

[Claims] A sheet feed hopper for stacking and loading sheets of paper; a sheet feed roller disposed above the sheet feed hopper for picking up and loading the loaded sheets one by one from an upper layer;
A sheet feeding device including a transport path including a mechanism for preventing double feed of the sheet and an image processing unit that performs image processing on the sheet between the sheet and a discharge end disposed downstream of the sheet feed roller. A vertical path for feeding the sheet in a substantially vertical direction is provided between the double feed prevention mechanism and the image processing unit, and the sheet is disposed with a detection surface facing a surface of the sheet passing through the vertical path. A sheet feeder comprising double feed detecting means for detecting double feed. 2. A drop is provided between the double feed prevention mechanism and the entrance of the vertical path, and the space between the double feed prevention mechanism and the entrance of the vertical path is gently bent upward or downward. 2. The feeder according to claim 1, wherein the double feed detecting means is a double feed sensor of a combination of a transmitting element and a receiving element of an ultrasonic wave disposed at a position sandwiching both front and back surfaces of the sheet passing through the vertical path. 3. Paper equipment.