Patent Grant
8628076
1. Field of the Invention
The present invention relates to a sheet feeding device and an image forming apparatus, and more particularly to a sheet feeding device that separates and feeds sheets by blowing air on the sheets.
2. Description of the Related Art
Conventionally, as an image forming apparatus such as a copying machine or a printer, an image forming apparatus has been proposed that includes an air-blowing sheet feeding device that floats sheets by blowing air onto them so that the sheets are conveyed by suction to a suction conveyance belt.
Japanese Patent Application Laid-Open No. 2007-276910 discusses a sheet feeding device capable of reliably feeding sheets whose edge portion on the downstream side in the sheet conveyance direction has a curl that bends upward (hereinafter referred to as “upward curl”).
The sheet feeding device discussed in Japanese Patent Application Laid-Open No. 2007-276910 will now be described based on
This sheet feeding device has a detection unit 61, which is connected to a sensor lever 52 that turns a sensor unit (including a first sheet surface sensor 54 and a second sheet surface sensor 55) ON/OFF. The detection unit 61 extends toward the downstream side in the sheet conveyance direction. Sheet surface control is performed by the detection unit 61 contacting the topmost surface of the sheets stacked on an elevating tray, to position the topmost stacked sheet within an appropriate range by turning the sensor unit ON/OFF to raise or lower the elevating tray.
As illustrated in
However, in the sheet feeding device discussed in Japanese Patent Application Laid-Open No. 2007-276910, there is still room for improvement when the edge portion on the downstream side in the sheet conveyance direction has a curl that bends downward (hereinafter referred to as “downward curl”).
As illustrated in
Consequently, when trying to convey the sheets by suction, the suction can be incomplete, so that the leading edge of the fed sheets may hit a downstream guide, thereby causing problems such as paper jamming. Further, it can become impossible to convey the sheet by suction because the gap between the sheet and the suction conveyance belt is too wide.
An example of the present invention is directed to a sheet feeding device capable of reliably feeding even sheets that have upward curl or downward curl.
According to an aspect of the present invention, a sheet feeding device includes an elevating tray configured to be movable up and down and to support sheets, an air blowing unit configured to blow air onto sheets supported on the elevating tray to float the sheets, a suction and conveyance mechanism configured to suction and convey a topmost sheet of the sheets floated by air blown by the air blowing unit, and a sheet surface detection mechanism configured to detect an upper surface of the topmost sheet of the sheets supported on the elevating tray, wherein the sheet surface detection mechanism includes a sensor unit arranged on a upstream side of the suction and conveyance mechanism in a sheet conveyance direction, a sensor lever configured to turn the sensor unit ON/OFF, and a detection unit having one end connected to the sensor lever and another end that extends toward a downstream side in the sheet conveyance direction, and wherein the detection unit includes, on a downstream side in the sheet conveyance direction, a protruding member that protrudes in a downward direction and that is capable of contacting the topmost sheet supported on the elevating tray.
According to an exemplary embodiment of the present invention, since a detection unit in a sheet surface detection mechanism includes a protruding member that protrudes downward on a downstream side in a sheet conveyance direction, appropriate sheet surface control can be performed, and sheets having downward curl can be reliably fed. Further, even sheets having upward curl or no curl can be reliably fed.
Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention.
Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings.
The printer 100 illustrated in
The image forming unit 102 includes a photosensitive drum 112, a development unit 113, a laser scanner unit 111, a transfer charging device 118, and a fixing unit 114. The sheet feeding device 103 includes a plurality of sheet storage units 115, which store sheets S such as an overhead transparency (OHT) and can be attached/detached to/from the printer body 101. The sheet feeding device 103 also includes a suction conveyance belt 21 that feeds the sheets S stored in the sheet storage units 115.
Next, an image forming operation performed by the printer 100 having such a configuration will be described.
When an image read signal is output to the image reading unit 130 from a (not illustrated) control apparatus provided in the printer body 101, an image is read by the image reading unit 130. Then, laser light corresponding to this electric signal is irradiated onto the photosensitive drum 112 from the laser scanner unit 111.
At this stage, the photosensitive drum 112 has already been charged, so an electrostatic latent image is formed by the irradiation of the light. The electrostatic latent image is developed by the development unit 113, so that a toner image is formed on the photosensitive drum.
When a sheet feeding signal is output to the sheet feeding device 103 from the control apparatus, a sheet S is fed from a sheet storage unit 115. The fed sheet S is synchronized with the toner image on the photosensitive drum by a registration roller 117, and fed to a transfer unit configured from the photosensitive drum 112 and the transfer charging device 118.
Next, the toner image is transferred onto the sheet S fed to the transfer unit, and then the sheet S is conveyed to the fixing unit 114. The fixing unit 114 applies heat and pressure on the sheet S to fix the non-fixed transfer image on the sheet S. The sheet S on which the image is fixed is then discharged from the printer body 101 to a discharge tray 119 by a discharge roller 116.
Next, the configuration of the sheet feeding device 103 according to an exemplary embodiment of the present invention will be described with reference to the schematic diagram illustrated in
The configuration illustrated in
The sheet feeding device 103 includes an air blowing unit 30 that causes the sheets to float by blowing air onto the sheets S supported on the elevating tray 12, and a suction and conveyance mechanism 50 that conveys the topmost floated sheet by suction.
The air blowing unit 30 includes a blowing nozzle 33 and a separation nozzle 34 for blowing air onto an upper edge portion of the stored sheets S, a separation fan 31, and a separation duct 32 for sending air from the separation fan 31 to the respective nozzles 33 and 24.
The suction and conveyance mechanism 50 includes the suction conveyance belt 21, which is hung around a belt drive roller 41 and conveys the sheets S in the right direction in
In the present exemplary embodiment, the suction conveyance belt 21 includes a plurality of (three) belt pieces arranged at predetermined intervals in the width direction orthogonal to the sheet conveyance direction. Suction holes are formed in each of the belt pieces of the suction conveyance belt 21.
Next, a sheet feeding operation of the thus-configured sheet feeding device 103 will be described.
First, the user pulls out the repository 11 and sets a stack of sheets S on the elevating tray 12. Then, when the stack is stored at a predetermined position in the image forming apparatus, the elevating tray 12 starts to be lifted by a drive unit. When the distance between the topmost sheet of the sheets S supported on the elevating tray 12 and the suction conveyance belt 21 reaches a predetermined position, the (not illustrated) control apparatus temporarily stops the elevating tray 12 at that position. Then, the image forming apparatus gets ready for the sheet feeding signal for starting sheet feeding.
Next, when the (not illustrated) control apparatus detects a sheet feeding signal, the control apparatus activates the separation fan 31, which suctions air in the direction of the arrow C. This air is blown onto the sheets from the directions of the arrows D and E from the blowing nozzle 33 and the separation nozzle 34, respectively. Consequently, a plurality of the top sheets among the sheets supported on the elevating tray 12 are floated. Further, the control apparatus activates the suction fan 36, and discharges air in the direction of arrow F in
Next, as illustrated in
Next, by rotating a belt drive roller 41, as illustrated in
Next, the sheet surface detection mechanism according to a first exemplary embodiment of the present invention will be described.
The sensor lever 52 includes a first detection unit 52B that shields a received light portion of the first sheet surface sensor 54 and performs position detection, and a second detection unit 52C that shields a received light portion of the second sheet surface sensor 55 and performs position detection. Further, the sensor lever 52 is supported on a support shaft 53 so that the sensor lever 52 can freely swing.
The configuration of the detection unit 65 will now be described in more detail with reference to
On the downstream side in the sheet conveyance direction of the base member 65A of the detection unit 65, a protruding member 66 is formed that protrudes in a downward direction and that can contact the topmost sheet supported on the elevating tray. This protruding member 66 is fixed to an edge portion in the downstream side of the detection unit 65. The detection unit 65 can move up and down when the topmost sheet supported on the elevating tray 12 contact the protruding member 66 or the base member 65A. Further, in conjunction with the up/down movement of the detection unit 65, the sensor lever 52 swings about the support shaft 53 to turn the first sheet surface sensor 54 and the second sheet surface sensor 55 ON/OFF.
As illustrated in
Next, a sheet surface control operation of the sheet surface detection mechanism 49 will be described.
The sheets stored in the repository 11 are lifted up by raising the elevating tray 12 so that the upper surface of the topmost sheet Sa contacts the protruding member 66 of the detection unit 65. Then, when the elevating tray 12 is subsequently raised further, the detection unit 65 rises. In conjunction with the rise of the detection unit 65, the sheet surface sensor lever 52 swings about the support shaft 53 in a direction in which the joint 52D moves upward.
As illustrated in
Next, after the sheets are floated in this manner, as illustrated in
When the distance between the belt surface of the suction conveyance belt 21 and the upper surface of the topmost sheet Sa is lower than SL, as illustrated in
The elevating tray 12 is thus raised and lowered based on detection signals from the first sheet surface sensor 54 and the second sheet surface sensor 55 so that the position of the topmost sheet Sa of the sheets on the elevating tray 12 is maintained between the lower limit and the upper limit of the sheet floating region. Consequently, even when the sheet quantity gradually decreases due to feeding of the sheets, the position of the topmost sheet Sa can be maintained within the feedable range S1 by raising the elevating tray 12.
Table 1 shows the series of operations performed after the air blowing is started.
Thus, in the present exemplary embodiment, the elevating tray 12 is raised and lowered based on signals from the first and second sheet surface sensors 54 and 55. This operation enables the control apparatus to perform control such that the position of the elevating tray 12 when air is being blown is maintained at a position that allows the suction conveyance belt 21 to suction and convey only the topmost sheet Sa. Consequently, when suctioning a sheet with the suction conveyance belt 21, the sheets S can be individually separated and fed toward the image forming unit, which enables stable sheet feeding.
Further, by using the detection unit 65 that extends as far as the upstream side of the suction and conveyance region, sheet surface detection can be performed even when the first and second sheet surface sensors 54 and 55 are provided at a position that is behind the suction and conveyance region of the suction conveyance belt 21 of the suction and conveyance mechanism 50.
In addition, at the downstream side in the sheet conveyance direction, the protruding member 66 protruding in a downward direction from the base member 65A of the detection unit 65 contacts the sheet, so that sheet surface detection is performed. Thus, even downward curl sheets can be reliably fed. Specifically, when the sheets supported on the elevating tray 12 curl downward, the protruding member 66 contacts the downward curling portion (the leading edge side of the sheet) of the topmost sheet Sa. The elevating tray 12 is raised and lowered based on signals from the first and second sheet surface sensors 54 and 55 so that the leading edge side of the topmost sheet Sa is positioned at a position where a distance from the belt surface of the suction conveyance belt 21 is within the range S1. Consequently, the leading edge side of the topmost sheet Sa is at a position where the sheet can be reliably suctioned onto the suction conveyance belt 21, so that the sheet can be reliably separated by the air blown from the separation nozzle 34. Therefore, jamming and feeding problems can be prevented even for sheets that curl downward.
Next, a second exemplary embodiment of the present invention will be described. Except for the configuration of the detection unit, the second exemplary embodiment is the same as the first exemplary embodiment.
As illustrated in
The sheets curling downward contacts the leading edge 66A of the protruding member 66 or the base member 65A, lifts the detection unit 65, and raises or lowers the elevating tray 12 based on detection by the sensor unit. Thus, the topmost sheet is moved to an appropriate position. Further, the second exemplary embodiment also enjoys the same advantageous effects as the first exemplary embodiment.
A third exemplary embodiment of the present invention will now be described. Except for the configuration of the detection unit, the third exemplary embodiment is the same as the first exemplary embodiment.
In the third exemplary embodiment of the present invention illustrated in
This configuration allows the height of the joint 52D to be changed. For example, when feeding a sheet that has a large downward curl, the distance in the height direction between the leading edge 66A of the protruding member 66 and the joint 52D can be increased by replacing the sensor lever 52 with a shorter sensor lever to increase the height of the position of the joint 52D. Consequently, by causing the sheet to contact the leading edge 66A of the protruding member 66, the leading edge of the topmost sheet Sa can be moved to a position where it can be appropriately suctioned by the suction conveyance belt 21 even for sheets having a large downward curl.
The third exemplary embodiment also enjoys the same advantageous effects as the first and second exemplary embodiments.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions.
This application claims priority from Japanese Patent Application No. 2011-253960 filed Nov. 21, 2011, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-253960 | Nov 2011 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5921540 | Acquaviva et al. | Jul 1999 | A |
| 7635125 | Ikeda | Dec 2009 | B2 |
| 7744081 | Ikeda | Jun 2010 | B2 |
| 7850162 | Imai et al. | Dec 2010 | B2 |
| 8079585 | Fujita | Dec 2011 | B2 |
| 8210518 | Suzuki | Jul 2012 | B2 |
| 8444138 | Taki | May 2013 | B2 |
| Number | Date | Country |
|---|---|---|
| 2007-276910 | Oct 2007 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20130127109 A1 | May 2013 | US |
