JPH11286345A - Paper feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder capable of preventing a sheet from being damaged when the sheet is double fed even if an object feeding sheet is easy to damage. SOLUTION: In a paper feeder provided with a pick-up roller 14 acting as a means for taking out one sheet 20a laid over the uppermost layer out of a plurality of sheets 20 stacked inside a paper feeding cassette 10, this device is provided with a sheet thickness sensor 19 which is provided for the sheet delivery side of the pick-up roller, and acts as a means for detecting that a double feed of the sheet 20, and with a means 9 which executes control in such a way that the pick-up roller 14 is driven in the reverse direction, and the sheet 20 is thereby returned back to its original position inside the paper feeding cassette 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device, and more particularly to a paper feeding device that can be suitably used even when a sheet to be fed is easily damaged.

[0002]

2. Description of the Related Art Conventionally, as this type of paper feeder, for example, a paper feeder as shown in FIG. 4 is known. FIG. 4A is a side sectional view of a conventional sheet feeding device, and FIG. 4B is a plan view of the sheet feeding device. In FIG. 1, reference numeral 10 denotes a paper feed cassette, 11 denotes an outlet of the paper feed cassette 10, 12 denotes a sheet guide plate which is urged upward by a spring 13 provided at a lower portion, and 14 denotes a sheet facing the aforementioned outlet 11. A pickup roller which can be moved up and down is provided. Reference numeral 15 denotes a normal rotation roller for assisting sheet feeding. Reference numeral 16 denotes a double feed prevention roller which is in pressure contact with the sheet feeding roller 15 (hereinafter referred to as a "retard roller"). Reference numerals 17 and 17 denote motors for driving the pickup roller 14 and the forward rotation roller 15, respectively. The above-described pickup roller 14 is provided with the solenoid 1
By turning on / off the switch 8, it is configured to be movable between a position (standby position) 14 indicated by a solid line and a position (operating position) 14 ′ indicated by a broken line in FIG. Also,
The pickup roller 14 and the normal rotation roller 15 are rotated clockwise in the figure by a motor 17.

Next, the configuration of the retard roller 16 will be described in detail. Although not shown, a torque limiter is set between the retard roller 16 and its shaft,
The retard roller 16 is always rotating clockwise in the figure with a small torque. Further, when a large force equal to or larger than the set value of the torque limiter is applied to the retard roller 16 in the counterclockwise direction, that is, in the sheet feeding direction, the retard roller 16 follows the normal rotation roller 15 and rotates counterclockwise. .

[0004] The operation of the device configured as described above will be described below. When a sheet is fed from the paper feed cassette 10, the solenoid 18 is turned on, the pickup roller 14 is lowered, and the outlet 1 of the paper feed cassette 10 is pulled out.
1. Touch the sheet surface located at 1. This is a state in which it has moved from a position (standby position) 14 indicated by a solid line (standby position) 14 to a position (operating position) 14 'indicated by a broken line in FIG. At the same time as the movement of the pickup roller 14 described above, the pickup roller 14 and the forward rotation roller 15 are rotated clockwise in the drawing by the motor 17. Due to the operation of the two rollers, one of the uppermost layers of the sheet 20 of the sheet cassette 10 (hereinafter referred to as 20 a) is moved by the frictional force with the pickup roller 14 to the outlet 1 of the sheet cassette 10.
1 and is sent to the next stage by the frictional force with the normal rotation roller 15. At this time, the next second sheet (hereinafter, referred to as 20b) may be taken out of the sheet cassette 10 in association with the uppermost sheet 20a of the sheets 20. This double feed phenomenon is called double feed. Hereinafter, the operation of the retard roller 16 will be described in detail for a case where only the uppermost sheet 20a is taken out and a case where the second sheet 20b is accompanied by double feeding.

First, when only the uppermost sheet 20a is taken out, since the frictional force between the forward rotation roller 15 and the sheet 20a is sufficiently large, the rotational force of the forward rotation roller 15 is reduced to the sheet 2a.
The rotation of the retard roller 16 is transmitted to the retard roller 16 via the first roller 0a, and as described above, the retard roller 16 follows the normal rotation roller 15 and rotates counterclockwise to feed the sheet 20a to the next stage. On the other hand, not only the top sheet 20a but also the second sheet 20a
When b is accompanied, the driving force in the rotation direction of the normal rotation roller 15 is not sufficiently transmitted to the retard roller 16, and the retard roller 16 is stopped or rotated reversely (clockwise). Therefore, the first sheet 20a is sent out because the frictional force between the normal rotation roller 15 and the sheet 20a is large. However, compared with the frictional force between the normal rotation roller 15 and the sheet 20a, the distance between the sheet 20a and the sheet 20b is increased. Since the frictional force is small, the second sheet 20b is restrained by the retard roller 16 whose leading end is stopped or reversed, and the second sheet 20b is partially exposed from the sheet feeding cassette 10, but is not in the next stage. Will not be sent out completely.

[0006]

However, the above-described prior art apparatus has the following problems. In other words, when a sheet that is easily damaged when a frictional force is applied is used in the conventional sheet feeding device, the second sheet 20b is accompanied by the second sheet 20b.
Roller 16 and one of the uppermost layers 20
a is continually slid in contact (rubbed) with each other, causing a problem that the surface on the sensitive side of the sheet is damaged.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a sheet feeding device which can be suitably used even when a sheet to be fed is easily damaged by frictional force. To provide.

[0008]

According to a first aspect of the present invention, there is provided a pickup roller for feeding one uppermost layer sheet out of a plurality of sheets stacked in a paper feed cassette. A sheet feeding device configured to detect double feeding of sheets provided in the vicinity of the sheet feeding cassette; and a pickup roller when the sheet double feeding is detected by the sheet double feeding detecting unit. And a sheet reverse feeding control means for controlling the sheet feeding direction to return the sheet to the original position of the sheet feeding cassette. With the above-described configuration, when a double feed of sheets is detected, the removal of the sheet from the sheet feeding cassette is immediately stopped, and the sheet is temporarily returned to the sheet feeding cassette. There is a possibility that the first sheet and the second sheet may be separated, and then, a retry of sheet removal can be performed. Therefore, even when the sheet to be fed is a sheet that is easily damaged by frictional force, the removal of the sheet is immediately interrupted by the double feed detection, so that the conventional retard roller and one of the uppermost layers are continuously provided. No more rubbing.

Further, the invention according to claim 2 is characterized in that the sheet reverse feed control means controls to return the sheet to the original position of the sheet feeding cassette and further to retract the sheet by a predetermined distance. And With the above configuration, the first sheet that is in contact with the pickup roller is returned more greatly behind the second sheet, so that the rear of the first sheet is fed. Since the first sheet is further returned to the rear even after contacting the rear end of the cassette, the first sheet is bent in a bridge state, and remains in contact with the rear end of the sheet cassette. 2
Air will flow between the second sheet and the second sheet.
Therefore, if the sheet is retried afterwards, the possibility of double feeding is reduced. Further, according to a third aspect of the present invention, in the sheet feeding device according to the first or second aspect, the sheet feeding device further includes an error indication output device, and
Even if the pickup roller picks up the uppermost sheet again, the double feed still does not disappear, and if the double feed continues even if the reverse feed is repeated a predetermined number of times, the error display / output device displays or outputs an error. It is characterized by: With the above-described configuration, if a double feed still occurs even after retrying the sheet removal, the first sheet and the second sheet are in a considerably strong adhesive state for some reason. If multiple feeds are repeated even if the reverse feed is repeated a predetermined number of times, an error is displayed or output, so that the operator can be quickly notified of this fact.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described.
A specific description will be given based on the drawings. FIG. 1A is a side sectional view of a sheet feeding device according to an embodiment of the present invention.
FIG. 2B is a plan view of the sheet feeding device according to the embodiment of the present invention. The same components as those shown in FIG. 4 are denoted by the same reference numerals. That is, 10 is a paper feed cassette, 11 is an outlet of the paper feed cassette 10, 12 is a sheet guide plate which is urged upward by a spring 13 provided at a lower portion, and 14 is provided to face the above-described outlet 11. The pickup roller 17 which can be moved up and down, and 17 denotes a motor for driving the pickup roller 14.

The above-described pickup roller 14 is turned between a position (standby position) 14 indicated by a solid line and a position (operating position) 14 'indicated by a broken line in FIG. Is configured to be movable. The pickup roller 14 is rotated clockwise in the figure by a motor 17. Reference numeral 19 denotes a sheet thickness sensor to be described later. Here, a capacitance type sensor is used as an example. This sheet thickness sensor 19
The number of sheets is identified by utilizing the fact that the capacitance between the electrodes changes depending on the thickness of the sheet 20 existing between the two electrodes. In accordance with the type and thickness of the sheet to be used, the number of sheets is determined in advance. Set and use its characteristics.

In the paper feeder shown in this embodiment,
Based on the output of the sheet thickness sensor 19 described above, the operation of the pickup roller 14 is controlled as follows by program control by the control unit 9. The control unit 9 is configured by a microcomputer, and controls the motor 1 based on the rotation amount of the motor 17, the output of the sheet thickness sensor 19, and the like.
It controls the operation of the solenoid 7 and the solenoid 18 and has the function of a sheet reverse feed control means. FIG. 3 is an operation flowchart showing an example of the operation control program of the control unit 9. Less than,
The operation of the device configured as described above will be described. When feeding a sheet from the sheet cassette 10, the above-described solenoid 18 is turned on, the pickup roller 14 is lowered, and the sheet is brought into contact with the sheet surface located at the outlet 11 of the sheet cassette 10. This is a state where the position (standby position) 14 indicated by a solid line in FIG. 1A has been moved to a position (operation position) 14 ′ indicated by a broken line.

Further, at the same time as the movement of the pickup roller 14 described above, the pickup roller 14 is
Is rotated clockwise in the figure (step 31). By these two operations, the uppermost sheet 20 a of the sheets 20 in the sheet cassette 10 is taken out from the outlet 11 of the sheet cassette 10 by the frictional force with the pickup roller 14. At this time, the next second sheet 20b may be taken out of the sheet cassette 10 in a manner accompanied by the uppermost sheet 20a of the sheets 20. Below, 1 of the top layer
The case where only the sheet 20a is taken out and the second sheet 20
The operation of the paper feeder according to the present embodiment will be described in detail for the case where b is accompanied.

As a common operation, the sheet 20a (or 20a and 20b) taken out by the pickup roller 14 is supplied to the sheet thickness sensor 19, where the sheet thickness is checked (step 32). ). Then, based on the result of the sheet thickness check, a characteristic operation of the sheet feeding device according to the present embodiment is performed as follows. First, the top layer 1
When only the sheet 20a is taken out, the fact is recognized by the check by the sheet thickness sensor 19 (NO in step 32), and the result is sent to the control unit 9, and the control unit 9 controls the pickup roller 14 to Rotate forward as it is,
The sheet 20a is sent to the next stage.

On the other hand, not only the uppermost sheet 20a but also
If the second sheet 20b is accompanied, the fact is recognized by the check by the sheet thickness sensor 19 (YES in step 32), and the result is sent to the control unit 9. The control unit 9 immediately stops the pickup roller 14 based on the above information, and further rotates the pickup roller 14 backward (counterclockwise in the drawing) by a distance equal to the distance by which the sheet has been conveyed (steps 33 to 35). . As a result, the upper and lower two sheets are once returned to the paper cassette 10,
The two sheets 20a and 20b are not accompanied and sent out to the next stage.

Next, the control unit 9 controls the pickup roller 1
4 is rotated forward again, and the sheet 20 from the paper feed cassette 10 is rotated.
Is retried (step 36). In this retry, if only the uppermost one sheet 20a is taken out, it is recognized by the check by the sheet thickness sensor 19 as described above (N in step 37).
O), the control unit 9 rotates the pickup roller 14 as it is, and sends out the sheet 20a to the next stage.

According to another embodiment of the present invention, after the multi-fed sheet is returned to the sheet cassette 10 by the pickup roller 14, the sheet is continuously fed backward for a predetermined distance (for example, 1 cm). ing. By doing so, the first sheet 20a and the second sheet 20b that have been double-fed earlier have a positional relationship as shown in FIG. That is, the first sheet 20a that is in contact with the pickup roller 14 is returned more greatly behind the second sheet 20b, so that the rear of the first sheet is located at the rear end of the sheet cassette. After the contact, the first sheet 20a is further returned to the rear.
a is curved in a bridge state, and air enters between the second sheet 20b and the second sheet 20b which is kept in contact with the rear end of the sheet cassette. Therefore, if the sheet is retried afterwards, the possibility of double feeding is reduced because air enters between the two sheets 20a and 20b and is loosened. From this state, by retrying the above-described removal operation, the probability that the sheets 20a and 20b are separated is improved, and the probability that the second sheet 20b is removed accompanying the uppermost sheet 20a is greatly increased. Has the effect of decreasing.

According to another embodiment of the present invention,
Separately, an error display output device (not shown) is provided in the vicinity of the sheet feeding device. If the double feed is not solved even if the above-mentioned retry is repeated several times (steps 33 to 38), the sheet 20 has no information. Since there is a high possibility that such a problem exists, a threshold (for example, 5) is set for the number of retries, and if the number of retries exceeds this threshold (NO in step 38), It is preferable to output a signal to the error display output device, notify by an alarm, display an error message, or the like (step 39), contact the operator, and stop the device.

According to the above embodiment, when the double feed of the sheets 20 is detected, the sheet cassette 1 for the sheets 20 is detected.
0 is immediately stopped, the sheet 20 is returned to the sheet cassette 10 once, and the sheet is retried again. For example, when the sheet 20 to be fed receives a frictional force. In the case where the sheet is easily damaged, etc., there is an effect that a sheet feeding device that can be suitably used can be realized. Examples of the sheet that is easily damaged when the above-described frictional force is applied include, in addition to the thermal transfer sheet,
Various transfer sheets can be mentioned.

The above embodiment is an example of the present invention, and it goes without saying that the present invention is not limited to this. For example, in the above-described embodiment, an example in which a capacitance type sensor is used as the sheet thickness sensor 19 has been described. In addition, a transmitted light amount sensor (a combination of an LED and a PD), an optical distance sensor Various types of detection means such as detection means using a mechanical lever can be used. It goes without saying that various changes can be made to the control program used for the control unit 9.

[0021]

As described in detail above, according to the present invention, even if the sheet to be fed is easily damaged when a frictional force is applied, the sheet can be suitably used. This has a remarkable effect that a paper device can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main part of a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a characteristic operation of the sheet feeding device according to the embodiment.

FIG. 3 is an operation flowchart illustrating a characteristic operation of the sheet feeding apparatus according to the embodiment;

FIG. 4 is a diagram illustrating a main part of a conventional sheet feeding device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 9 control unit 10 paper feed cassette 11 outlet of paper feed cassette 10 12 sheet guide plate 14 pickup roller 17 motor driving pickup roller 14 18 solenoid driving pickup roller 14 19 sheet thickness sensor 20 sheet

Claims (3)

[Claims] 1. A sheet feeding device provided with a pickup roller for feeding one sheet of an uppermost layer from a plurality of sheets stacked in a sheet feeding cassette, wherein a multi-feed of sheets provided near the sheet feeding cassette is performed. The sheet double feed detecting means for detecting, and when the double feed of the sheet is detected by the sheet double feed detecting means, the pickup roller is driven in the reverse direction to move the sheet to the original position of the sheet cassette. A sheet feeding device, comprising: sheet reversing control means for controlling return. 2. The sheet feeding apparatus according to claim 1, wherein said sheet reverse feed control means controls the sheet to return to an original position of said sheet feeding cassette and then to further retract the sheet by a predetermined distance. Paper equipment. 3. The sheet feeding device according to claim 1, further comprising an error display output device, wherein, after the sheet is reversely fed, the pickup roller again picks up the uppermost sheet. A sheet feeder characterized by displaying or outputting an error on the error display / output device when the double feed is not resolved and the double feed continues even if the reverse feed is repeated a predetermined number of times.