SHEET FEEDING DEVICE AND IMAGE FORMING APPARATUS
The present invention relates to a sheet feeding device includes a sheet tray 2 to place sheets thereon, a nozzle 9 which blows air onto the sheets supported by the sheet tray 2, a conveyance belt 10 to adsorb and convey a sheet floated by blowing air by the nozzle 9, a pulling roller pair 16 which is arranged on a downstream side of the conveyance belt in a sheet conveyance direction and conveys the sheet conveyed by the conveyance belt 10, and a conveyance guide 17 which guides the sheet conveyed from the conveyance belt 10 to the pulling roller pair 16. The conveyance guide 17 has slope portions 17a, 17b which are sloped from an upstream side in the sheet conveyance direction to the downstream side to extend from a central portion in a sheet width direction perpendicular to the sheet conveyance direction to both the end portions.
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1. Field of the Invention
The present invention relates to a sheet feeding device including an air paper-feeding mechanism which adsorbs an uppermost sheet of a placed sheet stack on a conveyance belt to separately feed the sheets.
2. Description of the Related Art
Some conventional image forming apparatus such as a printer or a copying machine has a sheet feeding device which blows air on an end portion of a sheet stack stored in a sheet storing portion to loosen the sheets and adsorbs the uppermost sheet of the loosened sheets by a conveyance belt to convey the sheets one by one. An example of the sheet feeding device will be described below with reference to
However, in the sheet feeding device which adsorbs a sheet on the conveyance belt 103 to convey the sheet, a portion of the sheet which is not adsorbed by the conveyance belt 103 is hanged down, so that defective conveyance may occur. This phenomenon will be described below with reference to
When feeding is started, as shown in
If the curling-up of the sheet is eliminated in midstream, the sheet delays due to conveyance resistance generated between the sheet and the conveyance guide 104 on a side on which the curling-up occurs, so that the sheet may be skew-fed. At this time, an image forming apparatus may be deteriorated in accuracy to the sheet, or paper jam may be caused.
SUMMARY OF THE INVENTIONThe present invention is made in consideration of the above circumstances. It is an object of the present invention to provide a sheet feeding device which can reliably convey a sheet even if a level difference is generated between a central portion of the sheet in a direction of width and an end portion of the sheet when the sheet is adsorbed and conveyed by a conveyance belt.
In order to solve the above problem, there is provided a sheet feeding device having a mechanism which blows air onto stacked sheets and floats the sheets to loosen the sheets, including:
a sheet storing portion to store sheets;
an air blowing portion which blows air onto the sheets stored in the sheet storing portion;
an adsorption/conveyance portion to adsorb and convey a sheet floated by blowing air by the air blowing portion;
a sheet conveyance portion which is arranged on a downstream side of the adsorption/conveyance portion in a sheet conveyance direction and which conveys the sheet conveyed by the adsorption/conveyance portion to the downstream side; and
a conveyance guide which guides the sheet conveyed from the adsorption/conveyance portion to the sheet conveyance portion; and
wherein a conveyance guide has a slope portion which is sloped from the upstream side in the sheet conveyance direction to the downstream side according to extend from a sheet conveyance center in a sheet width direction perpendicular to the sheet conveyance direction to both the end portions.
A sheet feeding device according to an embodiment of the present invention and an image forming apparatus including the sheet feeding device will be described below with reference to the accompanying drawings.
[Entire Configuration of Image Forming Apparatus]
An entire configuration of the image forming apparatus will be described below together with an image forming operation.
In image formation, an image signal read by the image reading portion C is transmitted to the image forming portion B serving as an image forming means, and an image is formed on the sheet on the basis of the signal. The image formation in the embodiment is of electrophotographic type. More specifically, when the image forming signal is input, a photosensitive drum 50 rotates, and a surface of the photosensitive drum 50 is electrically charged by a charger 51. A laser beam from a laser scanner 52 is irradiated on the surface-charged photosensitive drum 50 on the basis of the read image signal, and an electrostatic latent image is formed on the photosensitive drum 50. The electrostatic latent image on the photosensitive drum 50 is developed with toner and then made visual image.
On the other hand, in synchronism with the formation of the toner image, a sheet supplied from a sheet feeding device A (will be described later) is conveyed between the photosensitive drum 50 and a transfer charger 54. The toner image on the photosensitive drum 50 is transferred on the sheet by bias application to a transfer charger 54. The sheet on which the toner image is transferred is conveyed to a fixing unit 55 and heated and pressured to permanently fix the toner image on the sheet. Thereafter, the sheet is discharged to a discharge tray 57 by the discharge roller pair 56.
[Sheet Feeding Device]A configuration of the sheet feeding device A according to the embodiment will be described below together with a sheet separating/feeding operation.
In
In
As shown in
In the air blowing portion, when a feeding signal is detected, the separating fan 6 operates to draw air in a direction of an arrow C in
On the other hand, an adsorption/conveyance portion to adsorb and convey an uppermost sheet of the floated sheets by the air blown by the air blowing portion is arranged above the sheet stack. This adsorption/conveyance portion is arranged such that an endless conveyance belt 10 having sucking holes 10a (see
Immediately after the sheets are floated by the air blown by the air blowing portion, the adsorption shutter 15 is still closed. When floating of the sheets S1 becomes stable a predetermined period of time after a feeding signal is detected, as shown in
On the downstream side of the conveyance portion, a pulling roller pair 16 serving as a sheet conveyance portion which conveys a sheet conveyed by the conveyance belt 10 is arranged. The sheet adsorbed and conveyed by the adsorption/conveyance belt 10 is sent by the pulling roller pair 16 toward the downstream side and conveyed to an image forming portion.
[Conveyance Guide]In the sheet feeding device A according to the embodiment, a conveyance guide 17 which guides a sheet conveyed from the conveyance belt 10 to the pulling roller pair 16 is arranged. A configuration of the conveyance guide 17 will be described below with reference to
The uppermost-stream-side end portion of the conveyance guide 17 is located on the lower side of the conveyance belt 10 and an upstream side of the downstream-side end portion of the conveyance belt 10. In this manner, a portion of a sheet adsorbed by the conveyance belt 10 can be reliably guided.
The conveyance guide 17 is made of steel plates, and the upstream-side end portions of the slope portions 17a and 17b are subjected to a bending process such that end portions of the steel plates are bent downward. The slope portions 17a and 17b, as will be described later, guides a hanged-down portion of a sheet runs on the conveyance guide 17. However, at this time, in order to reduce a load (friction) generated when the sheet is slid on the slope portions 17a and 17b, the bending process is effective. Even the slope portions 17a and 17b have simple edges, the effect that causes the sheet to run on the slope portions 17a and 17b does not change. However, in this case, debarring or the like must be sufficiently performed to prevent the sheet from jamming. For this reason, as in the embodiment, the bending process is desirably performed.
The slope portions 17a and 17b have shapes which are symmetrical about the sheet conveyance center (sheet conveyance reference) in the sheet width direction. The conveyance guide 17 is located such that the end portions of the slope portions 17a and 17b are arranged outside a maximum sheet width in which a sheet can be conveyed by the device in the sheet width direction and arranged an upstream side of the pulling roller pair 16.
More specifically, when the sheet is conveyed, the contact point between the sheet and the slope portion 17a gradually moves to outer sides 17a2 and 17a3 of the sheet, and the sheet gradually changes into forms indicated by S22 and S23. That is, the hanged-down portion of the sheet is guided to the downstream pulling roller pair 16 while being lifted up by the slope portion 17a of the conveyance guide 17. Although the above explanation about only the slope portion 17a which is one of the slope portions is performed. However, a sheet is similarly guided by the slope portion 17b serving as the other slope portion. As a result, even a hanged-down sheet is guided without being bent at the front end to run on the conveyance guide 17. For this reason, even a sheet which is fed while being hanged down can be conveyed to the image forming portion without causing paper jam.
In the embodiment, since the slope portions 17a and 17b have shapes which are symmetrical about the sheet conveyance center in the sheet width direction, a load generated when the hanged-down sheet runs on the conveyance guide 17 is horizontally symmetrical. For this reason, the sheet is conveyed without skew feeding.
A conventional conveyance guide guides a sheet such that a front end of the sheet adsorbed and conveyed by the conveyance belt is in line contact with the guide. On the contrary, the conveyance guide 17 according to the present invention guides a sheet such that the front end of the conveyed sheet is in point contact with the slope portions 17a and 17b. For this reason, in the conventional conveyance guide, a sheet curls when the sheet is guided because a resistance applied to the front end of the sheet is large. However, in the conveyance guide according to the embodiment, since a sheet and the guides are in point contact with each other, a resistance of the front end of the sheet against the guide is low, and the sheet is smoothly guided. Therefore, in the conveyance guide of the embodiment does not cause a defect unlike a conventional conveyance guide.
The sheet feeding device according to the embodiment is particularly effective in an environment in which a thin and large-size sheet having low rigidity or a wet sheet largely hanged down is used.
In the embodiment, the slope portions 17a and 17b of the upstream-side end portion of the conveyance guide 17 have straight shapes. However, the present invention is not limited to the shapes, and the slope portions 17a and 17b may be curved in a concave shape or a convex shape.
This application claims the benefit of priority from the prior Japanese Patent Application No. 2006-085121 filed on Mar. 27, 2006 the entire contents of which are incorporated by reference herein.
Claims
1. A sheet feeding device having a mechanism which blows air onto stacked sheets and floats the sheets to loosen the sheets, comprising:
- a sheet storing portion to store sheets;
- an air blowing portion which blows air onto the sheets stored in the sheet storing portion;
- an adsorption/conveyance portion to adsorb and convey a sheet floated by blowing air by the air blowing portion;
- a sheet conveyance portion which is arranged on a downstream side of the adsorption/conveyance portion in a sheet conveyance direction and which conveys the sheet conveyed by the adsorption/conveyance portion to the downstream side; and
- a conveyance guide which guides the sheet conveyed from the adsorption/conveyance portion to the sheet conveyance portion;
- wherein the conveyance guide has a slope portion which is sloped from the upstream side in the sheet conveyance direction to the downstream side according to extend from a sheet conveyance center in a sheet width direction perpendicular to the sheet conveyance direction to both side end portions.
2. The sheet feeding device according to claim 1,
- wherein a level of an upstream-side end portion of the conveyance guide in the sheet conveyance direction is set to be lower than a sheet conveyance surface which is adsorbed and conveyed by the adsorption/conveyance portion.
3. The sheet feeding device according to claim 1,
- wherein an end portion of the slope portion of the conveyance guide which is in contact with the sheet is formed symmetrically about a sheet conveyance center in the sheet width direction.
4. The sheet feeding device according to claim 1,
- wherein the conveyance guide is arranged almost horizontally.
5. The sheet feeding device according to claim 1,
- wherein both end portions of the slope portion of the conveyance guide are located outside a maximum sheet width in which the sheet can be conveyed in the sheet width direction.
6. The sheet feeding device according to claim 1,
- wherein the slope portion of the conveyance guide is formed in a straight shape.
7. The sheet feeding device according to claim 1,
- wherein the upstream-side end portion of the slope portion in the sheet conveyance direction is subjected to a bending process.
8. An image forming apparatus including a sheet feeding device having a mechanism which blows air onto stacked sheets and floats the sheets to loosen the sheets, comprising:
- a sheet storing portion to store sheets;
- an air blowing portion which blows air onto the sheets stored in the sheet storing portion;
- an adsorption/conveyance portion to adsorb and convey a sheet floated by blowing air by the air blowing portion;
- a sheet conveyance portion which is arranged on a downstream side of the adsorption/conveyance portion in a sheet conveyance direction and which conveys the sheet conveyed by the adsorption/conveyance portion to the downstream side; and
- a conveyance guide which guides the sheet conveyed from the adsorption/conveyance portion to the sheet conveyance portion; and
- wherein the conveyance guide has a slope portion which is sloped from the upstream side in the sheet conveyance direction to the downstream side according to extend from a sheet conveyance center in a sheet width direction perpendicular to the sheet conveyance direction to both side end portions.
Type: Application
Filed: Sep 11, 2006
Publication Date: Sep 27, 2007
Applicant: CANON KABUSHIKI KAISHA (TOKYO)
Inventor: TARO IKEDA (Tokyo)
Application Number: 11/530,590
International Classification: B65H 5/08 (20060101);