JP2000118732A - Paper feeder - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a paper feeder capable of reliably preventing double feed regardless of the size of paper. SOLUTION: A hopper 3b which is held by a biasing force of a torsion spring 8 in a state where the surface of the stacked sheets of paper abuts against the peripheral surface of a pickup roller 5 is interlocked with a guide 10b set at a position corresponding to the size of the sheet. The balance weight 16 changes the position of the guide 10b for each paper size, and the load on the torsion spring 8 is adjusted by changing the position of the balance weight 16 when the position of the guide 10b is set for each paper size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device in an image reading device such as an image scanner, for example.
In particular, the present invention relates to a sheet feeding device in which separation performance is adjusted even when the size of a document changes so that reliable double feed prevention can be obtained.

[0002]

2. Description of the Related Art An image reading apparatus such as an image scanner is provided with a paper feeding device for feeding a sheet set on a hopper to a line. This sheet feeder feeds out stacked sheets one by one from the top, and most of the sheet feeders have a double feed prevention mechanism in which two or more sheets are sent out by friction between overlapping 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. 7 is a schematic diagram showing a typical example of a conventional double feed prevention mechanism, and the one disclosed in the above-mentioned publication has almost the same configuration.

In FIG. 7, a hopper 5 for mounting and setting paper P such as an original to be read or various documents is set.
1 is disposed at the base end of the reading line, and a pickup roller 52 that rotates in contact with the surface of the uppermost sheet P is disposed. The hopper 51 is urged toward the pickup roller 52 by a spring 51a.
By pressing the surface of the sheet P against the peripheral surface of the pickup roller 52, only the uppermost sheet P can be fed out.

In the line on the output side of the hopper 51, for example, three-stage conveying rollers 53, 54 and 55 for feeding the paper P to the image reading position are arranged, and the paper P fed from the hopper 51 is nipped. And transport it downstream while pulling it out. A separation roller 56 and a retard roller 57 are provided between the hopper 51 and the first-stage transport roller 53 as a mechanism for preventing double feeding of the paper P.

The prevention of double feeding by the separation roller 56 and the retard roller 57 is widely known in the field of an image reading apparatus, a copying apparatus and the like.
Is a motor in which a torque limiter 57b is interposed around a main shaft 57a rotated in a direction indicated by an arrow in the drawing by a drive motor (not shown). That is, by providing such a torque limiter 57b, when one sheet P is fed out from the pickup roller 52, the retard roller 57 receives the rotational torque of the separation roller 56 and rotates in the transport direction of the sheet P, When two sheets of paper P are fed and nipped, the retard roller 57 keeps rotating in the direction of the arrow, and pushes the lower-fed paper P that is being double fed back to the hopper 51 side.

[0007]

The size of the original paper P to be placed on the hopper 51 is various. For example, the size of the original paper P is such that the maximum size is A3 size and the minimum size is B5 size or smaller. It is necessary to When the size of the paper P is adjusted in this way, the load applied to the hopper 51 is large when the paper P is large, and the weight load is small when the size is small. On the other hand, since the spring constant of the spring 51a is fixed, when the size of the sheet P is large, the weight load is large, so that the pressing force F to the pickup roller 52 becomes weak, and as the size becomes small, the pressing force F becomes strong. .

As described above, even when the pressing force applied to the pickup roller 52 changes depending on the size of the sheet P, the sheet P itself cannot be fed unless a proper frictional force with the pickup roller 52 is obtained. For this reason,
Even when the largest size paper P is placed on the maximum number of hoppers 51, the spring constant of the spring 51a must be set so that the frictional force required for feeding between the paper P and the pickup roller 52 can be secured.

However, when the size of the paper P is large, the setting of the spring constant of the spring 51a as described above
Feeding using friction between the pickup roller 52 and the peripheral surface is possible, but when the size of the sheet P is small, the weight load is small, and the urging force of the spring 51a is too strong. Therefore, the pickup roller 5
2 also increases the reaction force against the sheet P, and a large frictional force acts not only on the uppermost sheet P but also on the sheet below the sheet P, so that multiple feeds of the sheets P are likely to occur.

[0010] Even if such a double feeding of the paper P occurs, it is prevented by the separation roller 56 and the retard roller 57 disposed in the immediate vicinity of the hopper 51, and the paper P overlapping below is retarded by the retard roller 57. Should push back. However, if the pressing force of the pickup roller 52 against the sheet P exceeds the return force of the retard roller 57 due to strong pressing by the spring 51a, the multi-fed sheet cannot be returned. For this reason, the lower-side sheet P that is being multi-fed is pressed in the sheet feeding direction by the pickup roller 52 and, at the same time, receives a reverse return force by the retard roller 57. Therefore, the paper P is jammed between the pickup roller 52 and the retard roller 57, and the paper P cannot be fed out.

As described above, the sheet P loaded on the hopper 51
Of the paper P using the frictional force between the paper P and the pickup roller 52, the strength of the spring 51a pressing the paper P against the pickup roller 52 via the hopper 51 is constant. Likely to be.

An object of the present invention is to provide a sheet feeding device capable of reliably preventing double feeding regardless of the size of a sheet.

[0013]

According to a first aspect of the present invention, there is provided a paper feeder comprising: a pickup roller disposed at a start end of a line of paper to be fed; and a pickup roller disposed below the pickup roller and stacked on the upper surface thereof. A hopper that can be moved in a direction in which the surface of the uppermost layer abuts against the peripheral surface of the pickup roller; A guide and an elastic means for urging the hopper in the direction of the pick-up roller; an urging force capable of changing the urging force of the elastic means by adjusting a load on the elastic means in conjunction with movement of the guide; And adjusting means.

[0014]

According to the first aspect of the present invention, there is provided a pickup roller disposed at a start end of a line of a sheet to be fed, and a pickup roller disposed below the pickup roller and stacked and mounted on an upper surface thereof. A hopper that can be moved in a direction in which the surface of the upper layer abuts against the peripheral surface of the pickup roller, and a pair of guides that can be moved in the width direction of the hopper according to the size of the paper mounted on the upper surface of the hopper And an elastic means for urging the hopper in the direction of the pickup roller, and adjusting the load on the elastic means in conjunction with the movement of the guide to adjust the urging force of the elastic means. Means, and the direction of the pick-up roller is adjusted by the urging force adjusting means in accordance with the respective weight load even if the size of the paper loaded on the hopper changes. Can be adjusted to the biasing force of, is prevented excessive pressing of the pickup roller against the paper, it has the effect of preventing double feeding, regardless of the paper size.

According to a second aspect of the present invention, the hopper has a free end on a side facing the pickup roller, and is rotatable toward the pickup roller with a base end as a fulcrum. The urging force adjusting means includes a pinion arranged on the bottom surface side of the hopper, a pair of racks which are arranged so that their tooth surfaces face each other and whose teeth are aligned with the moving direction of the guide, and which mesh with the pinion. A balance weight connected to a rack via a link mechanism and capable of changing the position of the hopper between the base end side and the tip end side, and when the guides approach each other, the balance weight is connected to the base of the hopper. The balance weight can be moved from the distal end side to the proximal end side of the hopper from the end side to the distal end side and when the guides are separated from each other. A sheet feeding apparatus according to claim 1 wherein comprising as, an effect that can automatically adjust the position of the balance weight in conjunction to move the guide when replacing the paper.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of an image scanner provided with the sheet feeding device of the present invention.

In FIG. 1, an image scanner is provided with a housing 1 provided with an operation section 1a standing upright on the right side as viewed from the front, and a sub-housing 2 located on the left side of the operation section 1a and connected to open and close vertically. And a paper feed unit 3 for mounting a document such as a sheet on the front side of the housing 1 and below the sub-housing 2. The housing 1 and the sub-housing 2 are provided with a paper transport mechanism and an image reading device using an optical system. After reading an image from the paper fed from the paper feeding unit 3, a collection tray 2 a formed on the upper surface of the sub-housing 2 is provided.
The paper is ejected.

The paper supply unit 3 includes a frame 3a fixed to the housing 1 and a hopper 3b contained in the frame 3a for mounting paper. The hopper 3b has a size corresponding to the size of the paper. And a pair of guides (described later) that change the distance between each other. The hopper 3b is rotatably pivoted at both ends on the distal end side to the frame 3a, and is rotatable in a vertical direction with the base end side as a free end. In other words, the frame 3a is kept in the fixed position shown in FIG. 1 with respect to the housing 1, but the hopper 3b is moved with respect to the housing 1 so that the base end thereof can freely move up and down. Assembled.

FIG. 2 is a longitudinal sectional view showing a main part of the sheet feeding device, and FIG. 3 is a plan view showing a main part of FIG.

Two arms 4 are rotatably mounted around a support shaft 1b fixed in the housing 1, and a support roller 4a for receiving the bottom surface on the base end side of the hopper 3b is provided at the tip of these arms 4. Is rotatably mounted. On the other hand, the tip of the hopper 3b is connected to the frame 3a via a pin 3d so as to be freely rotatable in the vertical direction. Therefore, when the arm 4 is rotated from the position indicated by the alternate long and short dash line in FIG. 2 to the position indicated by the solid line, the supporting roller 4a receiving the base end of the hopper 3b lifts the hopper 3b while rotating. When the arm 4 is turned in the counterclockwise direction in FIG. 2, the base end of the hopper 3b is lowered, and the posture of the hopper 3b is set to a dashed line in the figure.

In the sub-housing 2, a pickup roller 5 is disposed at a position covering the upper surface on the base end side of the hopper 3b, and a separation roller 6 is provided at a position slightly away from the hopper 3b. The pickup roller 5 and the separation roller 6 are disposed one by one at the center in the width direction of the hopper 3b, and the drive shaft 6a passing through the separation roller 6 is connected to the output shaft of a drive motor (not shown). . A drive system is connected between the separation roller 6 and the pickup roller 5 by, for example, a gear train, and the separation roller 6 and the pickup roller 5 rotate at the same peripheral speed.

Further, a hopper 3b is provided below the separation roller 6.
The retard roller 7 for preventing double feed is disposed below the pass line of the paper fed from the printer. The retard roller 7 is provided with a torque limiter 7a, and as is well known in the art, when the torque is below the critical set torque of the torque limiter, that is, when there is a double feed of paper, the retard roller 7 pushes the paper back to the hopper 3b. When a load equal to or greater than the critical set torque is applied without the double feed of paper, the paper rotates in the reverse direction in the paper feeding direction.

A torsion spring 8 for pressing a sheet mounted on the hopper 3b against the pickup roller 5 is interposed between the arm 4 supporting the base end side of the hopper 3b and the periphery of the support shaft 1b. This torsion spring 8
As shown in FIG. 2, two hooks 8a, 8b protruding tangentially from the circumferential surface of the helical winding at both ends in the winding direction.
The hook 8a on one end is inserted into an engagement hole 4b provided in the arm 4, and the hook 8b on the other end is abutted against a restraining block 1c fixedly arranged near the support shaft 1b.

On the other hand, as shown in FIG. 3, the drive motor 4 is a drive mechanism for pushing down the arm 4 in response to the upward rotation of the arm 4 by the torsion spring 8.
1 is provided. The output shaft of the drive motor 41 has a gear train 4
A transmission shaft 42 having an axis parallel to the support shaft 1b is connected via 1a, and disk-shaped flanges 43 are attached to both ends of the transmission shaft 42 in the axial direction. As shown in FIG. 3, the two flanges 43 face each of the arms 4, and project a boss 43 a, which abuts on the upper surface of the arm 4, from the vicinity of the outer periphery of the flange 43 due to the rotation posture of the flange 43.

In the state shown in FIG. 2, the boss 43a is separated from the upper surface of the arm 4 and is not restrained downward of the arm 4.
The arm 4 is rotated clockwise around the support shaft 1b by the urging force of the torsion spring 8. Therefore, the uppermost sheet loaded on the hopper 3b is pressed against the peripheral surface of the pickup roller 5, and the pressing force at this time is determined by the strength of the urging force of the torsion spring 8. On the other hand, when the flange 43 is rotated by the drive motor 41, the boss 43a comes into contact with the upper surface of the arm 4, and the arm 4 is pushed downward by the boss 43a. When the boss 43a is located at the lowest position, the arm 4 assumes the posture shown by the one-dot chain line in FIG. 2, and the hopper 3b rotates counterclockwise around the pin 3d and tilts downward and to the right.

On the upper surface of the hopper 3b, there are provided guides 10a and 10b which can be moved integrally in the width direction of the hopper 3b (in the horizontal direction in FIG. 3) according to the size of the paper to be loaded.
In order to link these guides 10a and 10b, a pinion 11 and a guide 1 are provided on the lower surface of the hopper 3b.
It has racks 12 and 13 integrally connected to Oa and 10b. FIG. 4 is an exploded perspective view of a mechanism for adjusting the urging force of the pinion 11, the racks 12, 13 and the torsion spring 8.

The pinion 11 is rotatably supported on the lower surface substantially at the center in the width direction of the hopper 3b. Racks 12 and 13 meshing with the pinion 11 are provided with sliding grooves 3b-1 (FIG. 2) provided on the bottom surface of the hopper 3b. ). The racks 12 and 13 are arranged such that the tooth rows 12b and 13b are opposed to each other. Each of the racks 12 and 13 is passed through a guide slit 3b-2 cut into the hopper 3b to integrally connect the guides 10a and 10b. Screw 1
2a and 13a are provided. Therefore, for example, when one guide 10a is shifted laterally, the pinion 11 rotates,
This rotation causes the other guide 10b to move in conjunction with it. The direction of movement of these guides 10a and 10b is either the direction away from or approaching each other.

Further, the balance weights 16, 1 are connected to one ends of the racks 12, 13 via link rods 14, 15, respectively.
Connect 7 The link rods 14 and 15 are connected to the rack 12,
13 along the bottom surface and pin 1
4a, 15a pivotally attached to the racks 12, 13;
Turns in the direction of the arrow. Balance weight 1
Reference numerals 6 and 17 denote weights, and pin portions 16 provided on the upper surface.
a and 17a are rotatably inserted into holding holes 14b and 15b formed in the distal ends of the link rods 14 and 15, respectively.

On the other hand, a guide rail 3b-3 for restraining and guiding the balance weights 16 and 17 is provided on the lower surface of the hopper 3b. The guide rail 3b-3 is disposed between the base end side (pin 3d side) of the hopper 3b and the front end side to a substantially intermediate position. FIG. 5 is a cross-sectional view of a connection structure between the balance weight 16 on the link rod 14 side and the guide rail 3b-3. The guide rail 3b-3 has a slit 3b-4 through which the pin portion 16a of the balance weight 16 is inserted. The incision is made and the flange portion 16b at the upper end of the pin portion 16a is stored and slidably held. The other balance weight 17 and the guide rail 3
The same applies to the relationship with b-3.

As shown in FIG. 3, the guides 10a, 1a
When the maximum size for actually handling a sheet in which 0b is the most distant positional relationship is set, the spring constant of the torsion spring 8 is determined based on the load when the maximum number of sheets is placed on the hopper 3b. This is because the pressing force of the sheet against the pickup roller 5 is based on the urging force of the torsion spring 8, so that it is necessary to obtain the desired pressing force even against the maximum load during use. After the sheet is fed out after the maximum number of sheets are loaded, the weight load gradually decreases, and the restoring force of the torsion spring 8 tends to increase. Since there is a range, the pressing force is not so large as to cause a jam with the retard roller 7.

In the above arrangement, when the pickup roller 5 and the separation roller 6 are driven to rotate, the uppermost sheet mounted on the hopper 3b is fed out by friction with the pickup roller 5, as in the prior art. . Then, the separation roller 6 and the retard roller 7 form a pair, and as described above, the transport of the paper or the pushback of the double feed is performed by the function of the torque limiter.

Here, the hopper 3b of the sheet feeding unit 3
As described above, the load varies depending on the size of the sheet. That is, if the pressing force of the sheet against the pickup roller 5 is too large, not only the sheet is easily fed out in a multi-feed state, but also the function of returning the double-feed sheet by the retard roller 7 is impaired.

On the other hand, according to the present invention, the position of the balance weights 16 and 17 disposed on the lower surface of the hopper 3b is changed in conjunction with the movement of the guides 10a and 10b for guiding the sheet in the width direction, thereby reducing the size of the paper. Even for paper, the pressing force against the pickup roller 5 can be kept in an appropriate range.

First, when the size of the paper is large, the guides 10a and 10b are moved to the farthest positions as shown in FIG. 3, and the racks 12 and 13 integrated with these guides 10a and 10b have the same orientation. Go to Therefore, the balance weights 16, 17 which are connected to the racks 12, 13 via the link rods 14, 15 and whose movement direction is regulated by the guide rails 3b-3 move to the position closest to the pins 3d. Thus, when the size of the sheet is large, the balance weights 16 and 17 approach the pin 3d side, and the moment around the pin 3d decreases.

That is, when the size of the sheet is large, the load on the hopper 3b increases, so that the force for pushing the hopper 3b around the pin 3d is strong. on the other hand,
Since the balance weights 16 and 17 are automatically set at positions where the moment around the pin 3d becomes small in conjunction with the movement of the guides 10a and 10b, the load on the arm 4 by the balance weights 16 and 17 is suppressed.

On the other hand, when the size of the sheet is small, the guides 10a and 10b move in a direction to approach each other as shown in FIG. The link rods 14 and 15 change their posture in conjunction with the movements of the guides 10a and 10b, and accordingly, the balance weights 16 and 17 move along the guide rail 3b-3 in a direction away from the pin 3d. I do. Therefore, the moment around the pin 3d by the balance weights 16 and 17 increases, and when the paper size is small, the balance weights 16 and 17 compensate for the load on the torsion spring 8. For this reason, the urging force of the torsion spring 8 is suppressed, and the pressing force of the sheet against the pickup roller 5 does not become excessive.

As described above, the positions of the balance weights 16 and 17 are automatically set in conjunction with the guides 10a and 10b that move according to the size of the paper placed on the hopper 3b.
The urging force of the torsion spring 8 is adjusted according to the paper size. Therefore, the contact pressure between the pickup roller 5 and the sheet can be made appropriate, and the double feed by the pickup roller 5 can be effectively prevented. If the biasing force of the torsion spring 8 is made appropriate, the pressing reaction force from the pickup roller 5 can be suppressed to a level that does not interfere with the sheet returning force of the retard roller 7. Also, even if the double feed occurs due to the influence of the type of paper, humidity, etc., only the upper sheet during the double feed is fed out by the separation roller 6 and the lower sheet is fed by the retard roller 7.
, It is immediately returned to the hopper 3b side. As a result, jamming of multi-feed paper is not caused between the pickup roller 5 and the retard roller 7, and efficient image reading can be performed without causing trouble in paper feeding.

[0038]

According to the first aspect of the present invention, even if the weight load on the hopper changes variously depending on the size of the paper,
Since the pressing force applied to the sheet from the pickup roller can be appropriately set by the urging force adjusting means, it is possible to reliably prevent the double feed of the sheet, which tends to occur particularly when switching to the small size sheet. In addition, in the case where a separation roller and a retard roller for preventing double feed are provided downstream of the pickup roller, the paper returned by the retard roller can be promptly received by the hopper side, and the occurrence of paper jam is effectively suppressed. Can be

According to the second aspect of the present invention, since the position of the balance weight is automatically set in conjunction with the movement of the guide according to the size of the sheet, there is no need to adjust the pressing force on the pickup roller. Usability is improved.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an image scanner provided with a sheet feeding device of the present invention.

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

FIG. 3 is a plan view showing a main part of FIG. 2;

FIG. 4 is an exploded perspective view of a pin, a rack, a link rod, and a balance weight.

FIG. 5 is a longitudinal sectional view of a main part showing a structure in which a balance weight is connected to a guide rail provided on a bottom surface of the hopper.

FIG. 6 is a plan view of a main part showing movement of a balance weight when a distance between guides is reduced.

FIG. 7 is a schematic view showing a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 1a Operation part 1b Support shaft 2 Sub-housing 2a Collection tray 3 Paper feed unit 3a Frame 3b Hopper 3b-1 Sliding groove 3b-2 Guide slit 3b-3 Guide rail 3b-4 Slit 3d Pin 4 Arm 4a Support roller 4b Engagement hole 5 Pickup roller 6 Separation roller 6a Drive shaft 7 Retard roller 7a Torque limiter 8 Torsion spring 8a, 8b Hook 10a, 10b Guide 11 Pinion 12, 13 Rack 12a, 13a Screw 12b, 13b Tooth row 14, 15 Link rod 14a , 15a Pins 14b, 15b Holding holes 16, 17 Balance weights 16a, 17a Pin portion 16b Flange portion 41 Drive motor 41a Gear train 42 Transmission shaft 43 Flange 43a Boss

Claims (2)

[Claims] A pickup roller disposed at a starting end of a line of a sheet to be fed; and a top surface of a sheet disposed below the pickup roller and stacked and mounted on an upper surface of the pickup roller. A hopper that can be moved in the abutting direction, a pair of guides that can be moved in the width direction of the hopper according to the size of the paper loaded on the upper surface of the hopper, and the hopper that is attached to the pickup roller. And a biasing force adjusting means capable of adjusting the load on the elastic means in response to the movement of the guide and changing the biasing force of the elastic means. apparatus. 2. The apparatus according to claim 1, wherein the hopper has a free end on a tip side opposite to the pickup roller and is rotatable toward the pickup roller with a base end as a fulcrum. A pinion disposed on the bottom side of the hopper, a pair of racks having tooth surfaces opposed to each other and having the teeth aligned with the moving direction of the guide and meshing with the pinion, and a link mechanism connected to these racks; A balance weight that is connected and can change the position between the base end side and the tip end side of the hopper, and when the guides approach each other, the balance weight is moved from the base end side of the hopper to the tip end side, When the guides are separated from each other, the balance weight can be moved from the distal end side to the proximal end side of the hopper, respectively. Sheet feeding apparatus according to claim 1, wherein that.