JP2000072267A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeding device capable of sufficiently keeping a function preventing paper sheets from being piled up, and of miniaturizing a driving mechanism for carrying the paper sheets. SOLUTION: The device is provided with a paper separation mechanism composed of a separation roller 8 and a retard roller 9 with a torque limiter, and the retard roller 9 is approached to the separation roller 8 so as to be turned out a nip during the period of time when it is drivingly rotated by a driving system, and during the period of time when the driving system is out of operation, it is separated from the separation roller 8 so as to be free from the nip for reducing the loading of carrying rollers 3, 4 and 5 at the downstream side, and thereby increasing the paper pushing and returning force of the retard roller 9 by means of the torque limiter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder having a double feed preventing mechanism, for example, and more particularly, to minimizing a drive motor for feeding paper by optimizing the timing of operation of the double feed preventing mechanism. The present invention relates to a sheet feeding device capable of increasing the capacity.

[0002]

2. Description of the Related Art For example, an image reading apparatus such as an image scanner is provided with a sheet feeding device for feeding sheets stacked and stored in a sheet feeding tray to a line. This paper feeder feeds out stacked sheets one by one from the top, and most of the paper feeders have a double feed prevention mechanism in which two or more sheets are sent out in an overlapping manner due to friction between the sheets. A paper feeder having such a double feed prevention mechanism is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-286558.

FIG. 4 is a schematic view showing a main part of a conventional paper feeder, and the one disclosed in the above publication has almost the same configuration.

In FIG. 4, a pickup roller 52 that rotates in contact with the surface of the uppermost sheet P and feeds out the sheet P by a frictional force is disposed on a tray 51 that stores sheets stacked thereon. . The line on the output side of the tray 51 has, for example, 3 lines for feeding the sheet P to the image reading position.
The conveying rollers 53, 54, 55 of the stage are arranged. The transport rollers 53 to 55 are a pair of rollers vertically sandwiching a transport line of the paper P, and are each rotated synchronously by one drive motor (not shown), and are transported by the drive motor (not shown). Nip and transport it downstream while pulling out. A separation roller 56 and a retard roller 57 are disposed between the tray 51 and the first-stage transport roller 53 as a mechanism for preventing double feeding of the paper P.

The separation roller 56 is located above the pass line of the sheet P, and the retard roller 57 is disposed below the pass line so that a nip can be formed with the sheet P together with the separation roller 56. . The separation roller 56 is driven to rotate in a direction to feed the sheet P fed from the pickup roller 52, and the retard roller 57 is provided with a torque limiter so as to rotate forward or reverse depending on the load applied to the peripheral surface thereof. It is rotatable. That is, the torque limiter 57b is interposed around the main shaft 57a connected to the drive motor and connected to the retard roller 57. If the load on the peripheral surface of the retard roller 57 is equal to or less than the set critical value of the torque limiter 57b, the retard The roller 57 continues to rotate in the same direction as the main shaft 57a, that is, in the direction opposite to the sheet feeding direction. And, when the load is the torque limiter 57b
Exceeds the set critical value, the retard roller 57
It rotates in the opposite direction to 7a, that is, in the paper feeding direction.

By providing such a torque limiter 57b, when one sheet P is fed from the pickup roller 52, the sheet P nipped between the separation roller 56 and the retard roller 57 is separated from the separation roller 56. , The load is applied to the peripheral surface of the retard roller 57 as it is. Accordingly, if the set critical value of the torque limiter 57b is substantially the same as or slightly lower than the load at this time, the retard roller 57
The sheet P rotates in the transport direction of the sheet P in response to the rotation torque.

On the other hand, when two sheets of paper P are fed and nipped, the upper sheet P receives the acting force in the feed direction by the separation roller 56 and the lower sheet P receives the retard roller 57.
In the opposite direction. Therefore, if the set critical value of the torque limiter 57b is set to be larger than the sliding friction force generated between the sheets P, the retard roller 57 keeps rotating in the direction of the arrow in FIG. The lower paper P can be pushed back to the tray 51 side.

[0008]

As described above, when only one sheet of paper P is nipped with the separation roller 56, the retard roller 57 rotates in the opposite direction to the rotation direction of the main shaft 57a driven by the motor. The paper P rotates in the same direction as the paper P is fed. That is, when only one sheet of paper P is fed, the retard roller 57 is moved to the torque limiter 57 by the rotational torque of the separation roller 56 and the friction from the sheet P.
The motor rotates reversely under a load larger than the set critical value of b.
Then, the sheet P that has passed through the separation roller 56 and the retard roller 57 is conveyed from the leading end side by the transport rollers 53, 54, 55.
The paper P is conveyed by the respective rotation drives.

However, while the transport rollers 53 to 55 are all driven by a motor, during the period in which the rear end of the sheet P is not yet released from the nip between the separation roller 56 and the retard roller 57, the transport resistance is reduced. large. That is, the first-stage transport roller 53 or the third-stage transport roller 53
When the leading edge of the sheet P is nipped by the transport rollers 55 of the step and can be transported, the rotation driving of the separation roller 56 and the retard roller 57 is temporarily stopped. Such a stop operation is performed to provide an appropriate interval between the rear end of the previously fed sheet P and the front end of the next sheet P to be fed. At a point in time after which the paper P is advanced. Therefore, there is no action force for rotating the retard roller 57 in the feeding direction of the paper P by the separation roller 56, and the retard roller 57 exerts a torque opposite to the feeding direction of the paper P of the critical set value by the torque limiter 57b. Become. For this reason, not only the frictional resistance due to the nip between the separation roller 56 and the retard roller 57 but also the reverse force of the retard roller 57 acts on the sheet P, and the transport rollers 53 to 55 exert a torque exceeding this acting force. Must be generated.

As described above, the capacity of the motor for driving the transport rollers 53 to 55 is increased or a speed reduction mechanism is provided, which increases the size of the apparatus and the power consumption.

On the other hand, in order to prevent double feeding of the sheet P, it is effective to increase the critical set value of the torque limiter 57b and increase the force for pushing back the sheet P. However, when the critical set value is increased, the reverse torque acting on one sheet of paper P increases when there is no double feed as described above, and therefore, the driving force of the transport rollers 53 to 55 is further increased. I need to raise it.

As described above, if the capacity of the driving motor is to be kept small, the critical set value of the torque limiter 57b must be reduced, so that the function of preventing double feeding is impaired. Conversely, if the critical set value is increased to ensure double feed prevention, the motor capacity must be increased. Therefore, prevention of double feed and miniaturization of the motor capacity are incompatible with each other, and there is no other choice but to design to give priority to either.

It is an object of the present invention to provide a paper feeder capable of sufficiently maintaining the function of preventing double feeding of sheets and reducing the size of a driving mechanism for conveying the sheets.

[0014]

According to the present invention, a separation roller and a retard roller are arranged as a pair with a path line for feeding stacked sheets sequentially from the uppermost layer sandwiched therebetween, and the separation roller and the retard roller are arranged in pairs. A paper feed device provided with a transport roller that nips and transports the paper downstream, wherein the paper is temporarily nipped by the transport roller until the paper passes at least the transport roller. It is characterized by comprising load adjusting means for separating the separation roller and the retard roller from each other.

[0015]

According to the first aspect of the present invention, a separation roller and a retard roller are arranged as a pair with a pass line for feeding stacked sheets sequentially from the uppermost layer sandwiched therebetween,
A paper feed device including a transport roller that nips and transports the paper downstream of the separation roller and the retard roller, wherein the paper is nipped by the transport roller and the paper passes at least the transport roller. A load adjusting means for temporarily separating the separation roller and the retard roller from each other. Since the nip is released and the transport resistance to the sheet is reduced, the load on the transport roller can be reduced.

According to a second aspect of the present invention, the load adjusting means includes a support shaft whose both ends in the axial direction orthogonal to the pass line are restrained on the apparatus main body side and are rotationally driven by a drive system of the retard roller. And a base rotatably connected around the support shaft and provided with the retard roller rotatably in conjunction with the support shaft in parallel with the support shaft, and an elasticity in a direction in which the base is separated from the pass line. An urging means for urging, a torque limiter disposed between the support shaft and the base to rotate the base around the support shaft by a rotational torque of the support shaft, 2. The sheet feeding device according to claim 1, wherein the retard roller can be set to a position where a nip is formed together with the separation roller by turning the base. An effect that it is possible to link the position change of the La.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a main part of a sheet feeding device according to the present invention, showing a configuration from a tray to a conveying roller.

In FIG. 1, similarly to the prior art, a pickup roller 2 is disposed above a tray 1 on which a sheet of paper P is loaded, and contacts and feeds out the uppermost sheet of paper P. 3 for nipping and transporting paper P
Conveying rollers 3, 4, and 5 of stages are arranged. These transport rollers 3, 4, and 5 are connected to the output shaft of the transport motor 6, and are driven to rotate synchronously. Further, a paper detection sensor 7 using an optical system for detecting the leading end of the paper P is disposed on the exit side of the first-stage transport roller 3.

A separation roller 8 and a retard roller 9 are arranged between the pickup roller 2 and the first-stage transport roller 3 with the pass line interposed therebetween. The separation roller 8 is fixedly arranged at a level for receiving the sheet P fed from the pickup roller 2 horizontally as it is, connected to an output shaft of a drive motor 10 shared with the retard roller 9 and fed in the sheet feeding direction indicated by an arrow in the drawing. It is driven to rotate. The retard roller 9 is incorporated in a base 11 disposed in the sheet feeding device and is driven to rotate by a driving motor 10. FIG. 2 is a plan view showing a retard roller and a support shaft provided on the base and a driving mechanism thereof. 2 is a longitudinal sectional view showing, together with the base, a main part when the separation roller and the retard roller are in a nip state.

The base 11 has a support shaft 12, which is rotatably mounted at both ends in the axial direction on a housing or the like of a paper feeder, corresponding to the downstream side in the transport direction of the paper P, and has a housing at the bottom on the upstream side. And a tension coil spring 13 connected thereto is attached. The support shaft 12 includes bearings 12a, 12 provided on rims 11a raised at both ends of the base 11.
b, and the base 11 can be rotated around the support shaft 12. That is, the base 11 is shown in FIG.
As shown in the figure, the retard roller 9 rotates from the position where it comes into contact with the separation roller 8 at an angle within a range where the bottom surface abuts against a stopper 14 provided in the housing or the like of the sheet feeding device. When the support shaft 12 is at rest, the bottom surface of the base 11 is
As a result, the nip between the separation roller 8 and the retard roller 9 is released.

A drive gear 12c for connecting the output shaft of the drive motor 10 and driving the retard roller 9 is provided at one end of the support shaft 12, and a torque limiter 15 is provided between the support shaft 12 and the bearing 12b at the other end. Attach. When the support shaft 12 rotates in the direction of the arrow in FIG. 3, the torque limiter 15 transmits torque to the bearing 12b, and the base 11 that integrally fixes the bearing 12b is connected to the support shaft 1.
2 to generate a torque to rotate counterclockwise. When the torque becomes equal to or greater than the critical set value, the torque limiter 15 slips, and the retard roller 9 is urged toward the separation roller 8 with an urging force corresponding to the critical set value torque. It should be noted that a commercially available torque limiter 15 can be used as it is, and its critical set value can be freely set by mechanical operation.

The retard roller 9 comprises a main shaft 9a supported by a bearing 11b provided on a rim 11a, and a torque limiter 9b interposed and connected between the main shaft 9a. It has a configuration similar to that shown in the prior art. A driven gear 9c is attached to one end of the main shaft 9a, and two pinions 11c,
The rotation from the drive gear 12c of the support shaft 12 is transmitted to the main shaft 9a via 11d. At this time, the rotation drive by the drive motor 10 is set such that the rotation direction of the support shaft 12 is counterclockwise as shown in FIG. Accordingly, the rotation direction of the main shaft 9 a of the retard roller 9 is opposite to the direction of the support shaft 12, and is a direction in which the paper P is pushed back to the tray 1.

The function of the torque limiter 9b connected between the retard roller 9 and the main shaft 9a is as described in the conventional example, and the main shaft 9a always rotates clockwise in FIG. When the torque P is below the critical set value of the torque limiter 9b, that is, when there is a double feed of the paper P, the retard roller 9 rotates together with the main shaft 9a and pushes the paper P back to the tray 1 side. When a load equal to or greater than the set value is applied, the motor rotates reversely in the direction shown by the broken line in FIG.

In the above configuration, during the period when the drive motor 10 is not operating, the rotation is not transmitted to the support shaft 12, so that even if the support shaft 12 and the base 11 are connected via the torque limiter 15, There is no acting force for rotating the base 11 around the support shaft 12. Therefore, base 1
Numeral 1 is free to rotate around the support shaft 12 via bearings 12a and 12b, and receives only tension from the coil spring 13. As a result, the base 11 is restrained from the state shown in FIG. 3 to the position where the bottom surface of the base 11 abuts against the stopper 14, and the retard roller 9 is separated from the separation roller 8.

When the paper P is fed from the pickup roller 2, the drive motor 10 and the transport motor 6 are operated together, and the separation roller 8, the retard roller 9, and the transport rollers 3, 4, and 5 are driven to rotate. At this time, only the retard roller 9 rotates in the direction opposite to the paper feeding direction, and all other members are driven to rotate in the paper feeding direction.

The operation of the drive motor 10 causes the support shaft 12
Rotates in the direction of the arrow in FIG.
The main shaft 9a of the retard roller 9 is driven to rotate via 1d and the driven gear 9c. Simultaneously with the rotation of the main shaft 9a, the rotation of the support shaft 12 is transmitted to the bearing 12b via the torque limiter 15, and the base 11 rotates around the support shaft 12 integrally with the rotation of the support shaft 12. Then, as shown in FIG. 3, the retard roller 9 contacts the separation roller 8 to form a nip portion.

After operating the drive motor 10 in this manner, the separation roller 8 and the retard roller 9 form a pair,
As described above, the transport of the paper P or the pushback of the multi-feed is performed by the function of the torque limiter 9b.

When one sheet of paper P is transported, FIG.
, The retard roller 9 is rotating in the paper feeding direction shown by the broken line. When the leading edge of the sheet P passes through the nip portion of the first-stage transport roller 3 and is detected by the sheet detection sensor 7, the operation of the drive motor 10 is performed to leave an interval between the sheet P and the succeeding sheet P. Stop temporarily. Since the rotation of the support shaft 12 is also stopped by this stop, the rotation of the retard roller 9 is stopped and at the same time, the torque limiter 15 is stopped.
No rotation load is applied to the motor. Therefore, the base 11 held in the posture shown in FIG. 3 via the torque limiter 15 becomes free around the support shaft 12 and is pulled down by the coil spring 13, and the retard roller 9 is separated from the separation roller 8. Thereby, the nip to the passing paper P is released.

As described above, after the paper P is captured by the transport roller 3, the drive motor 10 is driven at least until the rear end of the paper P passes between the separation roller 8 and the retard roller 9. If stopped, there is no nip between the separation roller 8 and the retard roller 9 during this period. Therefore, the transport roller 3 and the transport rollers 4,
5, when the sheet is pulled downstream by the retard roller 9
, The resistance of the transport motor 6 and the speed reduction mechanism for increasing the torque of each of the transport rollers 3 to 5 become unnecessary.

The distance between the support shaft 12 and the main shaft 9a is represented by r, the torque transmitted by the torque limiter 15 to the base 11 when the rotation of the support shaft 12 is received is represented by T, and the rotation around the support shaft 12 of the base 11 by the coil spring 13 Is set to Fs, the retard roller 9 is pressed against the separation roller 8 by a force of F = (T / r) -Fs. Since the pressing force F is a factor that determines the nip force of the paper P and the torque required for the rotation of the base 11 by the torque limiter 9b, the related members are set so that r, T, and Fs become appropriate values. Is designed, the nip between the separation roller 8 and the retard roller 9 when the drive motor 10 is stopped can be released.

In the transport period of the paper P by the transport rollers 3 to 5, the paper P passes through the stopped separation roller 8 and the retard roller 9 without resistance, and the retard roller 9 moves the paper P. Does not interfere at all. Therefore, even if the torque in the returning direction of the sheet P applied to the retard roller 9 by the torque limiter 9b is set to be large, the conveyance of the sheet P is not affected. For this reason, the torque for pushing back the paper P in the multi-feed state can be further increased, and the multi-feed of the paper P can be more reliably prevented.

[0032]

According to the present invention, after the paper is nipped by the transport roller, the separation roller and the retard roller are temporarily separated from each other to release the nip for the paper passing between the two rollers. The transport load is reduced, the capacity of the driving motor can be reduced, and a reduction mechanism is not required, so that the apparatus can be downsized. Even if the torque for pushing back multi-feed paper by the retard roller is set high, the load on the transport side is not affected, so the push-back force of the paper can be increased and the double feed of paper can be reliably prevented. Is done.

When a retard roller is provided on a base that is rotatable around a support shaft and the support shaft and the retard roller are linked to each other, the rotation of the retard roller and the setting and release of the nip can be performed through the base. The number of constituent members can be reduced, and the size can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of a sheet feeding device according to the present invention and showing a configuration from a tray to a conveying roller.

FIG. 2 is a plan view showing a retard roller, a support shaft, and a driving mechanism provided on the base.

FIG. 3 is a longitudinal sectional view showing a main part together with a base when a separation roller and a retard roller are in a nip state;

FIG. 4 is a schematic view showing a main part of a conventional sheet feeding device.

[Explanation of symbols]

 Reference Signs List 1 tray 2 pickup roller 3, 4, 5 transport roller 6 transport motor 7 paper detection sensor 8 separation roller 9 retard roller 9a main shaft 9b torque limiter 9c driven gear 10 drive motor 11 base 11a rim 11b bearing 11c, 11d pinion 12 support shaft 12a, 12b Bearing 12c Drive gear 13 Coil spring 14 Stopper 15 Torque limiter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C059 AA05 AA26 AA38 2H072 BA03 CA01 EA15 3F343 FA02 FB03 FC01 GA01 GB01 GC01 GD01 HA12 HB01 JA01 JD03 JD09 JD33 LA04 LA14 LC11 LD10 LD30

Claims (2)

[Claims] 1. A separating roller and a retard roller are arranged as a pair with a path line for feeding stacked sheets sequentially from the uppermost layer sandwiched therebetween, and the sheet is nipped downstream of the separating roller and the retard roller. A paper feeder having a transport roller for transporting, wherein the separation roller and the retard roller are temporarily moved together until the paper is nipped by the transport roller and the paper passes at least the transport roller. A sheet feeding device including a load adjusting unit for separating the sheet. 2. The apparatus according to claim 1, wherein said load adjusting means comprises: a support shaft whose both ends in the axial direction are orthogonal to said pass line and which are constrained on the apparatus main body side and are rotationally driven by a drive system of said retard roller; A base rotatably connected to and rotatably connecting the retard roller to the support shaft in parallel with the support shaft, and biasing means for elastically biasing the base in a direction away from the pass line; A torque limiter disposed between the support shaft and the base and configured to rotate the base around the support shaft by a rotational torque of the support shaft, wherein the rotation of the base around the support shaft 2. The sheet feeding device according to claim 1, wherein the roller can be set at a position where a nip is formed together with the separation roller.