EP2944590A2

EP2944590A2 - Sheet feeding unit

Info

Publication number: EP2944590A2
Application number: EP15167564.2A
Authority: EP
Inventors: Akira Hayashi
Original assignee: Funai Electric Co Ltd
Current assignee: Funai Electric Co Ltd
Priority date: 2014-05-14
Filing date: 2015-05-13
Publication date: 2015-11-18
Also published as: US20150329302A1; EP2944590A3; CN105082788A; JP2015231912A

Abstract

A printer which reduces feeding failure that occurs when a roller (120) is pressed against a sheet of paper by power of a driving source includes: a rotating member (114) which rotates around a first axis; a connecting member (119) which connects with the rotating member (114); a roller (120) which is disposed in the connecting member (119) and rotates around a second axis to transfer a medium; and a support member (130) disposed across from the roller (120), wherein the roller applies a force to the medium based on rotation of the rotating member (114), and the medium is transferred between the roller (120) and the support member (130).

Description

Field

The present invention relates to a printer.

Background

Printers, photocopiers, multifunction printers and the like include a document feeder to transfer in sequence a plurality of sheets of paper stacked on a loading surface. For example, the document feeder transfers the plurality of sheets of paper in sequence by repeatedly transferring the top one of the sheets stacked on top of each other.
With such a document feeder, feeding failure occurs at times. Feeding failure includes multi feeding and mispick. Multi feeding refers to transfer of two or more sheets of paper at a time. Mispick refers to transfer of no sheet of paper.
Patent Literature 1, for example, discloses a technique for preventing such feeding failure. Patent Literature 1 prevents no transfer of the last sheet of paper by allowing a roller member disposed across from a feeding roller to rotate with the feeding roller at the time of transferring the last sheet.

Citation List

Patent Literature

[Patent Literature 1]
Japanese Unexamined Patent Application Publication No. 2000-191166

Summary

Technical Problem

However, the technique of Patent Literature 1 prevents feeding failure in the case where the document feeder has a structure in which a sheet of paper is pressed against the roller by movement of the loading surface on which the paper is loaded. Thus, the technique of Patent Literature 1 cannot be easily applied to a document feeder having a structure in which the roller is pressed against a sheet of paper by power of a driving source (auto compensating document feeder).
In view of this, the present invention provides a document feeder which reduces feeding failure that occurs when the roller is pressed against a sheet of paper by power of a driving source.

Solution to Problem

A printer according to an aspect of the present invention includes a rotating member which rotates around a first axis; a connecting member which connects with the rotating member; a roller which is disposed in the connecting member and rotates around a second axis to transfer a medium; and a support member disposed across from the roller, wherein the roller applies a force to the medium based on rotation of the rotating member, and the medium is transferred between the roller and the support member.
For example, the support member may include a frictional member and an elastic member.
For example, when the medium includes a first sheet of paper and a second sheet of paper, a frictional force between the frictional member and an underside of the second sheet of paper may be (i) larger than a frictional force between an underside of the first sheet of paper and a topside of the second sheet of paper and (ii) smaller than a frictional force between the roller and a topside of the first sheet of paper.
With such a structure, an appropriate frictional force relationship is maintained even when the plurality of sheets of paper is two sheets of paper including the first sheet and the second sheet. That is to say, the elastic member and the frictional member make it possible to reduce feeding failure which occurs when the number of sheets of paper loaded on the loading surface becomes two.
For example, the elastic member may be smaller than the frictional member in hardness value.
With such a structure, the elastic member is smaller than the frictional member in hardness value. Thus, when the frictional member and the elastic member are pressed by the roller via the plurality of sheets of paper, the elastic member is deformed, causing the frictional member to move downward.
For example, the elastic member may be a spring.
With such a structure, the elastic member is a spring. Thus, when the frictional member and the elastic member are pressed by the roller via the plurality of sheets of paper, the elastic member is deformed, causing the frictional member to move downward.
For example, the elastic member may have an end connected to a loading surface on which the medium is loaded, and the elastic member may have an other end which moves downward when the frictional member and the elastic member are pressed by the roller via the medium.
With such a structure, the elastic member has an end connected to the loading surface and another end movably structured. In other words, the elastic member has a cantilever structure. Thus, when the frictional member and the elastic member are pressed by the roller via the plurality of sheets of paper, the other end of the elastic member moves downward, causing the frictional member to move downward.
For example, the printer may further include a flywheel connected to a rotation shaft of a driving source which rotates the rotating member.
With such a structure, a flywheel is connected to the rotation shaft of the driving source. This enables stable transmission of a rotary force generated by the driving source to the roller. This also enables rotation of the flywheel even when backlash of the transmission mechanism prevents transmission of power to the roller. After that, when the power can be transmitted to the roller, not only the power of the driving source but also the inertia force of the flywheel is transmitted to the roller, thereby increasing the power for driving the roller. This therefore reduces failure to feed the first sheet of paper upon increase in the frictional force between the roller and the topside of the first sheet.
For example, the driving source may be disposed between the flywheel and the rotating member.
With such a structure, the driving source can be disposed between the flywheel and the transmission mechanism. This enables rotation of the flywheel without influence of backlash of the transmission mechanism.
For example, the roller may be larger than the frictional member in width, and the roller may have an outer circumferential surface having a circumferentially extending dip across from the frictional member.
With such a structure, the roller has an outer circumferential surface having a circumferentially extending dip across from the frictional member. Therefore, selecting an appropriate dip enables adjustment of the force by which the roller presses the frictional member against the paper. That is to say, adjustment for reducing feeding failure is simplified.

Advantageous Effects

The printer according to an aspect of the present invention reduces feeding failure which occurs when the roller presses a sheet of paper by power of a driving source.

Brief Description of Drawings

[FIG. 1]
FIG. 1 is a perspective view showing an external appearance of a document feeder according to Embodiment 1.
[FIG. 2]
FIG. 2 is a perspective view showing a transmission mechanism of a document feeder according to Embodiment 1.
[FIG. 3]
FIG. 3 shows enlarged cross-sectional views near a roller, a frictional member, and an elastic member of a document feeder according to Embodiment 1.
[FIG. 4]
FIG. 4 illustrates a relationship of frictional force in a document feeder according to Embodiment 1.
[FIG. 5]
FIG. 5 is an enlarged cross-sectional view near a roller, a frictional member, and an elastic member of a document feeder according to Variation 1 of Embodiment 1.
[FIG. 6]
FIG. 6 is an enlarged cross-sectional view near a roller, a frictional member, and an elastic member of a document feeder according to Variation 2 of Embodiment 1.
[FIG. 7]
FIG. 7 is an enlarged plan view of a frictional member and an elastic member according to Variation 2 of Embodiment 1.
[FIG. 8]
FIG. 8 is a perspective view showing an external appearance of a document feeder according to Embodiment 2.
[FIG. 9]
FIG. 9 is an enlarged plan view of a roller and a frictional member of a document feeder according to of Embodiment 3.

Description of Embodiments

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.
Each of the following embodiments describes a general or specific example. The numerical values, shapes, materials, structural elements, the arrangement and connection of the structural elements etc. shown in the following embodiments are mere examples, and therefore do not limit the scope of the claims. Moreover, among the structural elements in the following embodiments, structural elements not recited in any one of the independent claims are described as arbitrary structural elements.

(Embodiment 1)

A document feeder according to Embodiment 1 presses a roller against a sheet of paper and rotates the roller by power of a driving source. To prevent feeding failure caused by a change in the pressing force of the roller against the paper, the document feeder includes an elastic member which supports from below a frictional member disposed across from the roller on a loading surface.

[Structure of Document Feeder]

Next, a structure of the document feeder according to the present embodiment will be described. FIG. 1 is a perspective view showing an external appearance of the document feeder according to Embodiment 1. FIG. 2 is a perspective view showing a transmission mechanism of the document feeder according to Embodiment 1. FIG. 3 shows enlarged cross-sectional views near a roller, a frictional member, and an elastic member of the document feeder according to Embodiment 1. More specifically, (a) of FIG. 3 shows a state in which no sheet of paper is loaded on the loading surface, and (b) of FIG. 3 shows transfer of a sheet of paper loaded on the loading surface.
A document feeder 100 according to the present embodiment is included in a printer and transfers, one by one in sequence, media (a plurality of sheets of paper, for example) stacked on a loading surface 11a of a feed tray 11. More specifically, the document feeder 100 separates the top one of the sheets of paper stacked on the loading surface 11a of the feed tray 11 from the rest, and transfers the separated top sheet.
As shown in FIG. 1 to FIG. 3, the document feeder 100 includes a driving source 101, a transmission mechanism 110, rollers 120, a frictional member 130, and an elastic member 140.
The driving source 101 drives the rollers 120 via the transmission mechanism 110. The driving source 101 is specifically a motor, for example.
The transmission mechanism 110 transmits power of the driving source 101 to rotate the rollers 120 and press the rollers 120 against the topside of the top one of the sheets of paper.
Here, the transmission mechanism 110 includes a first gear 111, a second gear 112, a third gear 113, a first shaft 114, a fourth gear 115, a fifth gear 116, a sixth gear 117, a seventh gear 118, and a second shaft 119. It is to be noted that clockwise rotation and counterclockwise rotation hereinafter indicate rotational directions viewed from the positive direction to the negative direction of the X-axis.
The driving source 101 rotates counterclockwise to transfer a sheet of paper loaded on the loading surface 11a. The first gear 111 is connected to the rotation shaft of the driving source 101 and thus rotates counterclockwise with the rotation shaft. The second gear 112 and the third gear 113 rotate with the first gear 111. This results in counterclockwise rotation of the third gear 113.
The third gear 113 is connected to an end of the first shaft 114. Thus, counterclockwise rotation of the third gear 113 leads to counterclockwise rotation of the first shaft 114.
The first shaft 114 is an example of a rotating member which rotates around a first axis. The first shaft 114 is a rod-like member extending in the direction (X-axis direction) orthogonal to the direction of paper transfer (Y-axis direction). The first shaft 114 is disposed above the loading surface 11a.
The fourth gear 115 is connected to the other end of the first shaft 114. Thus, counterclockwise rotation of the first shaft 114 leads to counterclockwise rotation of the fourth gear 115. The fifth gear 116, the sixth gear 117, and the seventh gear 118 rotate with the fourth gear 115. This results in clockwise rotation of the seventh gear 118.
The seventh gear 118 is connected to the second shaft 119. Thus, clockwise rotation of the seventh gear 118 leads to clockwise rotation of the second shaft 119.
The combination of members including the fourth gear 115, the fifth gear 116, the sixth gear 117, the seventh gear 118, and the second shaft 119 is an example of a connecting member connecting with the rotating member.
The second shaft 119 is a rod-like member extending in the direction (X-axis direction) orthogonal to the direction of paper transfer (Y-axis direction). The second shaft 119 is disposed above the loading surface 11a and lower than the first shaft 114. Each end of the second shaft 119 is connected with a roller 120. Thus, clockwise rotation of the second shaft 119 leads to clockwise rotation of the rollers 120.
Furthermore, counterclockwise rotation of the first shaft 114 leads to counterclockwise rotation (revolution) of the second shaft 119 around the first shaft 114. As a result, the rollers 120 are pressed against the sheet of paper loaded on the loading surface 11a. More specifically, when a plurality of sheets of paper is stacked on the loading surface 11a, the rollers 120 are pressed against the topside of the top sheet.
The rollers 120 rotate around a second axis and transfer a medium (a sheet of paper, for example). The rollers 120 apply a force to the medium based on the rotation of the first shaft 114. The medium is transferred between the rollers 120 and the frictional member 130.
The rollers 120 are specifically pickup rollers. By the power of the driving source 101, the rollers 120 are pressed against the topside of the top one of the sheets of paper stacked on the loading surface 11a, and rotate while being in contact with the topside of the top sheet. As a result, the rollers 120 transfer the top sheet in Y-axis direction. That is to say, the rollers 120 separate the top sheet from the rest of the sheets of paper. In other words, the rollers 120 pick up only the top sheet from the plurality of sheets of paper. The rollers 120 then transfer the picked up sheet.
Each roller 120 specifically includes an inner circumferential member 121 and an outer circumferential member 122. The inner circumferential member 121 is connected to the second shaft 119. The inner circumferential member 121 is sometimes called wheel. A light and hard material such as resin is used for the inner circumferential member 121, for example.
The outer circumferential member 122 is a band-like member circumferentially surrounding the inner circumferential member 121. The outer circumferential member 122 is sometimes called tire. The outer circumferential member 122 generates appropriate frictional force between the outer circumferential member 122 and the topside of the top one of the sheets of paper. More specifically, a material having a high coefficient of friction such as rubber is used for the outer circumferential member 122, for example.
The frictional member 130 is disposed across from the roller 120 on the loading surface 11a, and is in contact with the underside of the bottom one of the sheets of paper. The frictional member 130 generates appropriate frictional force between the frictional member 130 and the underside of the bottom sheet.
The frictional member 130 here is a sheet-like member extending in the direction of paper transfer (Y-axis direction). The frictional member 130 has a thickness of 0.4 mm, for example.
The elastic member 140 supports the frictional member 130 from below. That is to say, the elastic member 140 is disposed below the frictional member 130. The elastic member 140 here is a sheet-like member extending in the direction of paper transfer (Y-axis direction). The elastic member 140 has a thickness of 1 mm, for example.
In the present embodiment, the elastic member 140 is smaller than the frictional member 130 in hardness value (In other words, the elastic member 140 is softer). Put it differently, the elastic member 140 is smaller than the frictional member 130 in Young's modulus in the vertical direction (Z-axis direction). Thus, application of force from above brings about a change in thickness of the elastic member 140 in the vertical direction larger than a change in thickness of the frictional member 130 in the vertical direction. As a result, when the frictional member 130 and the elastic member 140 are pressed by the roller 120 via the plurality of sheets of paper, the elastic member 140 is deformed, causing the frictional member 130 to move downward.
The elastic member 140 is specifically formed from sponge or relatively soft rubber, for example. The frictional member 130 is formed from resin, cork, or rubber, for example.
The frictional member 130 and the elastic member 140 are disposed in a concave portion 11b formed in the loading surface 11a. Here, the concave portion 11b is formed in such a manner that the topside of the frictional member 130 is higher than the loading surface 11a. The frictional member 130 and the elastic member 140 are an example of a support member.

[Operation of Document Feeder]

Next, an operation of the document feeder 100 having the above-described structure will be described with reference of FIG. 3 and FIG. 4. FIG. 4 illustrates a relationship of frictional force in the document feeder according to Embodiment 1. It is to be noted that the frictional force described hereinafter relates to static frictional force. The following will describe a case where a plurality of sheets of paper 20 stacked on the loading surface 11a is two sheets of paper (a first sheet 21 and a second sheet 22).
As described earlier, the power of the driving source 101 is transmitted to the rollers 120 by the transmission mechanism 110. As a result, the rollers 120 are pressed against the topside of the first sheet 21 and rotate clockwise as shown in (b) of FIG. 3.
When the plurality of sheets of paper 20 includes the first sheet 21 and the second sheet 22 only, such pressing force and frictional force as shown in FIG. 4 are generated between the roller 120, the sheets of paper 20, and the frictional member 130.
In more detail, the roller 120 is pressed against the sheets of paper 20 by pressing force Fpick. This results in generation of frictional force Ftire between the roller 120 and the topside of the first sheet 21. There is also generation of frictional force Fpaper between the underside of the first sheet 21 and the topside of the second sheet 22. There is also generation of frictional force Fpad between the underside of the second sheet 22 and the frictional member 130.
At this time, the roller 120 can transfer the first sheet 21 without idling if the frictional force Ftire is larger than the frictional force Fpaper. That is to say, the document feeder 100 can prevent transfer of no sheet of paper. In other words, the document feeder 100 can prevent mispick.
Furthermore, the first sheet 21 and the second sheet 22 can be separated if the frictional force Fpad is larger than the frictional force Fpaper. That is to say, the document feeder 100 can prevent the first sheet 21 and the second sheet 22 from being transferred together while being overlaid with each other. In other words, the document feeder 100 can prevent multi feeding.
Moreover, when only the second sheet 22 remains on the loading surface 11a after the first sheet 21 is transferred, the roller 120 can transfer the second sheet 22 without idling if the frictional force Ftire is larger than the frictional force Fpad. That is to say, the document feeder 100 can prevent no transfer of the last remaining sheet of paper. In other words, the document feeder 100 can prevent mispick of the last sheet of paper.
As described above, the document feeder 100 can prevent feeding failure (multi feeding and mispick) if the relationship of frictional force satisfies Ftire > Fpad > Fpaper.
However, in the case where the roller 120 is pressed against the sheets of paper 20 by the power of the driving source 101 as in the case of the document feeder 100 according to the present embodiment, the relationship of frictional force may not satisfy Ftire > Fpad > Fpaper when the pressing force (pressing force Fpick) of the roller 120 against the sheets of paper 20 increases due to a decrease in the height of the sheets of paper 20. More specifically, when the height of the sheets of paper 20 decreases, the roller 120 moves in the direction opposite the direction of paper transfer, causing the pressing force Fpick to increase. This phenomenon is called a bite.
When the bite occurs, the pressing force Fpick and the frictional force Ftire increase, and the driving source 101 is thus required to have high driving power. Even if the driving source 101 has high driving power, the relationship of frictional force (Ftire > Fpad > Fpaper) is not maintained due to the increase in the pressing force Fpick.
In view of this, the elastic member 140 supports the frictional member 130 from below according to the present embodiment. That is to say, when the frictional member 130 is pressed from above, the elastic member 140 is deformed, lowering the topside of the frictional member 130. More specifically, the elastic member 140 lowers the contact face of the frictional member 130 and the second sheet 22 with increase of the pressing force Fpick.
This results in reduction of increase in the pressing force Fpick when the height of the sheets of paper 20 decreases. In other words, the elastic member 140 can reduce the occurrence of the bite. More specifically, the elastic member 140 can maintain the relationship of frictional force (Ftire > Fpad > Fpaper) and reduce feeding failure.
Put it differently, with the document feeder 100, when the sheets of paper 20 are two including the first sheet 21 and the second sheet 22, the frictional force Fpad between the frictional member 130 and the underside of the second sheet 22 is (i) larger than the frictional force Fpaper between the underside of the first sheet 21 and the topside of the second sheet 22 and (ii) smaller than the frictional force Ftire between the roller 120 and the topside of the first sheet 21.

[Advantageous Effect]

As described above, with the document feeder 100 according to the present embodiment, the elastic member 140 can support the frictional member 130 from below. The elastic member 140 can change the position of the frictional member 130 according to change in the pressing force of the roller 120 against the first sheet 21. The elastic member 140 can therefore lessen the change in the pressing force of the roller 120 against the first sheet 21. As a result, the document feeder 100 can stably rotate the roller 120. The document feeder 100 can also maintain an appropriate frictional force between the roller 120, the sheets of paper, and the frictional member 130.
Specifically, in the case where the roller 120 is pressed against the sheets of paper 20 by the power of the driving source 101, the pressing force of the roller 120 against the first sheet 21 at times increases when the height of the sheets of paper 20 decreases. Absence of the elastic member 140 in such a case would result in an increase also in the frictional force between the roller 120 and the topside of the first sheet 21, and the driving source 101 is thus required to have large power. On the other hand, the presence of the elastic member 140 lowers the position of the topside of the first sheet 21, lessening the increase in the frictional force between the roller 120 and the topside of the first sheet 21. This reduces the increase in power required of the driving source 101, thereby allowing the document feeder 100 to stably rotate the roller 120.
Moreover, an increase in the pressing force of the roller 120 against the first sheet 21 at times makes inappropriate the relationship between: the frictional force between the roller 120 and the first sheet 21; the frictional force between the plurality of sheets of paper; and the frictional force between the frictional member 130 and the second sheet 22. For example, the frictional force between the first sheet 21 and the second sheet 22 at times becomes larger than the frictional force between the frictional member 130 and the second sheet 22. In such a case, the second sheet 22 is transferred with the first sheet 21. However, the presence of the elastic member 140 lessens the increase in the pressing force of the roller 120 against the first sheet 21, thereby allowing the document feeder 100 to maintain an appropriate frictional force relationship.
As described above, the document feeder 100 can reduce feeding failure caused by a particular phenomenon (increase in the pressing force of the rollers 120 against the plurality of sheets of paper 20, caused by a decrease in the height of the sheets of paper 20) which occurs in the case where the rollers 120 are pressed against the sheets of paper 20 by the power of the driving source 101.
Furthermore, with the document feeder 100 according to the present embodiment, an appropriate frictional force relationship is maintained even in the case where the plurality of sheets of paper 20 is two sheets of paper including the first sheet 21 and the second sheet 22. More specifically, the elastic member 140 supporting the frictional member 130 from below makes it possible to reduce feeding failure which occurs when the number of sheets of paper loaded on the loading surface 11a is two.
Moreover, with the document feeder 100 according to the present embodiment, the elastic member 140 is softer than the frictional member 130. Thus, when the frictional member 130 and the elastic member 140 are pressed by the roller 120 via the plurality of sheets of paper 20, the elastic member 140 is deformed, causing the frictional member 130 to move downward.

(Variation 1)

Next, Variation 1 of Embodiment 1 will be described. A document feeder according to the present variation is different from the document feeder according to Embodiment 1 mainly in that the elastic member is a spring. Hereinafter, the document feeder according to the present variation will be described centering on the points different from Embodiment 1.
FIG. 5 is an enlarged cross-sectional view near a roller, a frictional member, and an elastic member of the document feeder according to Variation 1 of Embodiment 1. Structural components in FIG. 5 which are the same as or similar to those in FIG. 3 are given the same reference signs, and descriptions thereof will be omitted.
A document feeder 100A according to the present variation includes elastic members 140A. The elastic members 140A are springs and support the frictional member 130 from below. The elastic members 140A are smaller than the frictional member 130 in Young's modulus in Z-axis direction.
Although the elastic members 140A are coil springs in FIG. 5, the present invention is not limited to this. The elastic members 140A may be leaf springs, for example.
More specifically, the frictional member 130 is placed on a plate 141A. The plate 141A is supported by the elastic members 140A. Thus, the elastic members 140A shrink and the frictional member 130 moves downward when the frictional member 130 is pressed by the roller 120.
As described above, with the document feeder 100A according to the present variation, the elastic members 140A are springs. Thus, when the frictional member 130 and the elastic members 140A are pressed by the roller 120 via the plurality of sheets of paper 20, the elastic members 140A are deformed, causing the frictional member 130 to move downward.

(Variation 2)

Next, Variation 2 of Embodiment 1 will be described. A document feeder according to Variation 2 is different from the document feeder according to Embodiment 1 mainly in structure of the elastic member. Hereinafter, the document feeder according to the present variation will be described centering on the points different from Embodiment 1.
FIG. 6 is an enlarged cross-sectional view near a roller, a frictional member, and an elastic member of the document feeder according to Variation 2 of Embodiment 1. FIG. 7 is an enlarged plan view of a frictional member and an elastic member according to Variation 2 of Embodiment 1. Structural components in FIG. 6 which are the same as or similar to those in FIG. 3 are given the same reference signs, and descriptions thereof will be omitted.
A document feeder 100B according to the present variation includes an elastic member 140B. The elastic member 140B has a first end 141B connected to the loading surface 11a. The elastic member 140B has a second end 142B which is not connected to the loading surface 11a. In other words, the elastic member 140B has a cantilever structure. In the cantilever structure, the first end 141B is a fixed end whereas the second end 142B is a free end.
Thus, when the frictional member 130 and the elastic member 140B are pressed by the roller 120 via the plurality of sheets of paper, the second end 142B of the elastic member 140B moves downward, causing the frictional member 130 to move downward.
In more detail, the elastic member 140B is formed integrally with the loading surface 11a. A cavity 143B is formed in the area surrounding the elastic member 140B except for the first end 141B. That is to say, only the first end 141B of the elastic member 140B is connected to the loading surface 11a.
As described above, with the document feeder 100B according to the present variation, an end (the first end 141B) of the elastic member 140B is connected to the loading surface, and the other end (the second end 142B) is movably structured. In other words, the elastic member 140B has a cantilever structure. Thus, when the frictional member 130 and the elastic member 140B are pressed by the roller 120 via the plurality of sheets of paper, the other end of the elastic member 140B moves downward, causing the frictional member 130 to move downward.

(Embodiment 2)

Next, Embodiment 2 will be described. A document feeder according to the present embodiment is different from the document feeder according to Embodiment 1 mainly in that the document feeder includes a flywheel connected to the rotation shaft of the driving source. Hereinafter, the document feeder according to the present embodiment will be described centering on the points different from Embodiment 1.
FIG. 8 is a perspective view showing an external appearance of the document feeder according to Embodiment 2. Structural components in FIG. 8 which are the same as or similar to those in FIG. 1 are given the same reference signs, and descriptions thereof will be omitted.
A document feeder 200 according to the present embodiment includes a flywheel 103 connected to a rotation shaft 102 of the driving source 101.
The flywheel 103 has a circular cylindrical shape in the present embodiment. The rotation shaft 102 of the driving source 101 penetrates the central shaft of the flywheel 103. The flywheel 103 is disposed opposite to the side on which the transmission mechanism 110 is connected. That is to say, the driving source 101 is disposed between the flywheel 103 and the transmission mechanism 110. Furthermore, the flywheel 103 is disposed near the driving source 101.
As described above, with the document feeder 200 according to the present embodiment, the flywheel 103 is connected to the rotation shaft 102 of the driving source 101. This enables stable transmission of the rotary force generated by the driving source 101 to the rollers 120. This also enables rotation of the flywheel 103 even while backlash of the transmission mechanism 110 prevents transmission of power to the rollers 120. After that, when the power can be transmitted to the rollers 120, not only the power of the driving source 101 but also the inertia force of the flywheel 103 is transmitted to the rollers 120, thereby increasing the power for driving the rollers 120. This therefore reduces failure to feed the first sheet upon increase in the frictional force between the rollers 120 and the topside of the first sheet.
Moreover, with the document feeder 200 according to the present embodiment, the driving source 101 can be disposed between the flywheel 103 and the transmission mechanism 110. This enables rotation of the flywheel 103 without influence of backlash of the transmission mechanism 110.

(Embodiment 3)

Next, Embodiment 3 will be described. The present embodiment is different from Embodiments 1 and 2 in that the roller has an outer circumferential surface having a circumferentially extending dip. Hereinafter, a document feeder according to the present embodiment will be described centering on the points different from Embodiments 1 and 2.
FIG. 9 is an enlarged plan view of a roller 320 and a frictional member 130 of a document feeder 300 according to Embodiment 3. Structural components in FIG. 9 which are the same as or similar to those in the other figures are given the same reference signs, and descriptions thereof will be omitted.
The roller 320 has an outer circumferential surface 320a having a circumferentially extending dip 320b across from the frictional member 130. Conversely, the outer circumferential surface 320a of the roller 320 has circumferentially extending bumps 320c not across from the frictional member 130. The dip 320b is smaller than the bumps 320c in diameter.
For example, changing the thickness of an outer circumferential member 322 of the roller 320 in the direction of the rotation axis (X-axis direction) forms the dip 320b and the bumps 320c on the outer circumferential surface 320a of the roller 320. Another example way of forming the dip 320b and the bumps 320c on the outer circumferential surface 320a of the roller 320 is by forming a dip and bumps on an inner circumferential member 321 of the roller 320.
As described above, with the document feeder 300 according to the present embodiment, the circumferentially extending dip 320b can be formed across from the frictional member 130 on the outer circumferential surface 320a of the roller 320. Therefore, selecting an appropriate dip 320b enables adjustment of the force by which the roller 320 presses the frictional member 130 against the paper. That is to say, adjustment for reducing feeding failure is simplified. For example, changing the outer circumferential member 322 of the roller 320 to alter the shape or size of the dip enables adaptation to factors such as the type of paper and the surrounding environment (temperature, humidity, for example) of the document feeder 300. As a result, feeding failure can be reduced.

(Other Embodiments)

Although the document feeders according to only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
For example, the structure of the transmission mechanism in each embodiment above is an example, and the present invention is not limited to this. That is to say, the power of the driving source may be transmitted in any manner as long as it is by the power of the driving source that the roller is pressed against the sheets of paper and rotates.
Furthermore, although the document feeder is included in a printer in the above embodiments, the present invention is not limited to this. The document feeder may be included in a facsimile machine, a photocopier, or a multifunction printer, for example.
Moreover, although the printer is a laser printer in the above embodiments, the present invention is not limited to this. For example, the printer including the document feeder may be an ink-jet printer.
It is to be noted that although the frictional member in the above embodiments is a sheet-like member extending in the direction of paper transfer (Y-axis direction), the present invention is not limited to this. That is to say, the frictional member may be in any shape as long as the frictional member faces the roller on the loading surface. For example, the frictional member may be a plurality of circular members arranged in the direction of paper transfer.
Although the frictional member in the above embodiments is disposed in the concave portion formed in the loading surface, it is not necessary to be disposed in the concave portion. For example, the frictional member may be disposed on the loading surface.
Furthermore, although the document feeder in the above embodiments includes two rollers, the number of rollers is not limited to this. For example, the number of rollers may be one, three, or more.
Although one frictional member is disposed for one roller in the above embodiments, a plurality of frictional members may be disposed for one roller. In this case, the roller may have an outer circumferential surface having a plurality of dips across from the plurality of frictional members. For example, in the case where two frictional members are each disposed across from one of two ends of the roller in the direction of the rotation axis (X-axis direction), it is sufficient as long as one dip is formed on each of two ends of the outer circumferential surface of the roller. Put it differently, it is sufficient as long as a bump is formed in the middle of the outer circumferential surface of the roller.
The shape of the dip in Embodiment 3 is one example, and the present invention is not limited to this. For example, although a bump is formed on each side of the dip in Embodiment 3, a bump may be formed on only one side of the dip.
The structure of the outer circumferential member of the roller in the above embodiments is one example, and the present invention is not limited to this. For example, the outer circumferential member of the roller does not necessarily cover the entire circumference of the inner circumferential member of the roller. That is to say, the outer circumferential member of the roller may partially lack in circumference. More specifically, the outer circumferential member of the roller is not limited to an endless-belt shape. Moreover, another member may be disposed around the outer circumferential member of the roller to form a dip on the outer circumferential surface of the roller.
The shape of the outer circumferential surface of the roller in the above embodiments is one example, and the present invention is not limited to this. For example, the outer circumferential surface of the roller may have a plurality of grooves extending in the direction of the rotation axis for increasing the coefficient of friction.
The above embodiments have illustrated the example of the case where a plurality of sheets of paper is loaded on the loading surface. However, even in the case where a single sheet of paper is loaded on the loading surface, the document feeder can transfer the sheet.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Industrial Applicability

A document feeder according to an aspect of the present invention can be used as a document feeder included in a printer, a facsimile machine, a photocopier, and a multifunction printer, for example.

Reference Signs List

11: Feed tray
11a: Loading surface
11b: Concave portion
20: Plurality of sheets of paper
21: First sheet of paper
22: Second sheet of paper
100, 100A, 100B, 200, 300: Document feeder
101: Driving source
102: Rotation shaft
103: Flywheel
110: Transmission mechanism
111: First gear
112: Second gear
113: Third gear
114: First shaft
115: Fourth gear
116: Fifth gear
117: Sixth gear
118: Seventh gear
119: Second shaft
120: Roller
121, 321: Inner circumferential member
122, 322: Outer circumferential member
130: Frictional member
140, 140A, 140B: Elastic member
141A: Plate
141B: First end
142B: Second end
143B: Cavity
320a: Outer circumferential surface
320b: Dip
320c: Bump

Claims

A printer comprising:
a rotating member which rotates around a first axis;

a connecting member which connects with the rotating member;

a roller which is disposed in the connecting member and rotates around a second axis to transfer a medium; and

a support member disposed across from the roller,

wherein the roller applies a force to the medium based on rotation of the rotating member, and

the medium is transferred between the roller and the support member.
The printer according to claim 1,
wherein the support member includes a frictional member and an elastic member.
The printer according to claim 2,
wherein when the medium includes a first sheet of paper and a second sheet of paper, a frictional force between the frictional member and an underside of the second sheet of paper is (i) larger than a frictional force between an underside of the first sheet of paper and a topside of the second sheet of paper and (ii) smaller than a frictional force between the roller and a topside of the first sheet of paper.
The printer according to claim 2 or claim 3,
wherein the elastic member is smaller than the frictional member in hardness value.
The printer according to claim 2 or claim 3,
wherein the elastic member is a spring.
The printer according to claim 2 or claim 3,
wherein the elastic member has an end connected to a loading surface on which the medium is loaded, and
the elastic member has an other end which moves downward when the frictional member and the elastic member are pressed by the roller via the medium.
The printer according to any one of claims 1 to 6, further comprising
a flywheel connected to a rotation shaft of a driving source which rotates the rotating member.
The printer according to claim 7,
wherein the driving source is disposed between the flywheel and the rotating member.
The printer according to any one of claims 2 to 8,
wherein the roller is larger than the frictional member in width, and
the roller has an outer circumferential surface having a circumferentially extending dip across from the frictional member.