Patent Grant
7607655
1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus and particularly to a construction to prevent over-stacking of sheets on a sheet supporting portion.
2. Description of the Related Art
Heretofore, in an image forming apparatus such as a printer and a copying machine, a sheet feeding apparatus is provided for feeding out a sheet to an image forming portion from a sheet supporting portion on which a plurality of sheets are stacked.
In the sheet feeding apparatus constructed as above, when more than a predetermined quantity of sheets are stacked on a sheet feed tray (hereinafter referred to as over-stacking of sheets), defective sheet feeding occurs.
Methods to prevent such over-stacking of sheets include a method of putting a mark indicating an upper limit of the sheet stacking height on a width regulating member arranged on the sheet feed tray, for example.
However, when the mark 109a indicating the upper limit of stacking is provided on the width regulating member 109 in this way, the user may not notice the mark 109a and causes an over-stacking state. In this case, feeding-out of sheets by a pickup roller (not shown) cannot be carried out reliably, and defective sheet feeding might occur.
In order to prevent such over-stacking without relying on visual check by the user of the upper-limit mark of sheet stacking, there is a method of providing a member for restricting a stacking height on the width regulating member.
When the user sets the sheet bundle on the sheet feed tray, the user is supposed to prevent over-stacking of the sheet by setting the sheet in a range not exceeding this restricting member 109b for the sheet stacking height.
However, in the conventional sheet feeding apparatus provided with the restricting member 109b for the sheet stacking height on the width regulating member in this way, when the sheet bundle is to be set on the sheet feed tray, the sheet bundle might be forced to be below the restricting member 109b and set thereon. In this case, the sheets which were forced in and set are held between the restricting member 109b and the sheet feed tray. Therefore, even if the sheet is to be fed by the pickup roller, sheet feed resistance is generated to prevent feeding-out and cause defective sheet feed.
The present invention has been made in view of such circumstances and an object thereof is to provide a sheet feeding apparatus and an image forming apparatus, which can prevent over-stacking without providing an over-stack protective member on a sheet supporting portion and can stably feed sheets with low costs.
The present invention provides a sheet feeding apparatus comprising: a sheet supporting portion configured to support sheets; a sheet feeding device swingable between a sheet feeding position for feeding out a sheet supported by the sheet supporting portion and a standby position spaced from the sheet supported by the sheet supporting portion; and an over-stack protective portion configured to restrict an insertion of the sheets higher than a maximum stacking height capable of being supported by the sheet supporting portion, wherein a movement of the over-stack protective portion is regulated to restrict sheet insertion when the sheet feeding device is in the standby position, and the over-stack protective portion is released from a regulation of the movement in association with swing motion of the sheet feeding device from the standby position to the sheet feeding position.
The preferred embodiments for carrying out the present invention will hereinafter be described in detail with reference to the drawings.
A pick arm 4 as a holding portion for rotatably holding the pickup roller 5 is fixed to a feed roller shaft 6 provided at a main body (not shown) of a sheet feeding apparatus and made capable of pivotal movement in the vertical direction through this feed roller shaft 6.
This feed roller shaft 6 is rotated by a rotating mechanism (not shown) and the rotation of the feed roller shaft 6 rotates the pick arm 4 in the vertical direction. And with this pivotal movement of the pick arm 4, the pickup roller 5 moves between the sheet feeding position and the standby position.
The pickup roller 5 is held by the pick arm 4 in the standby position above the sheet feed tray 2 till a sheet feed operation is started. And when the sheet feed operation is started, the pickup roller 5 is rotated and moved to a position (sheet feeding position) abutting against the sheet stacked on the sheet feed tray 2 in association with a downward pivotal movement of the pick arm 4. Then, since the pickup roller 5 abuts against the sheet stacked on the sheet feed tray 2 while rotating, the sheet stacked on the sheet feed tray 2 is fed out.
A feed roller 7 is rotatably supported by the feed roller shaft 6. A pad arm 8 holds a separation pad 9 and is urged by an elastic member (not shown) toward the feed roller side. And the separation pad 9 is brought into pressure contact with the feed roller 7 by the pad arm 8 urged toward the feed roller side. In the sheet feeding apparatus 20 constructed in this way, when an image forming operation is started, the pick arm 4 is pivotally moved downward, and the pickup roller 5 abuts against the sheet stacked on the sheet feed tray 2 while rotating. Thereby, the sheets stacked on the sheet feed tray 2 are fed out and then, the fed-out sheets are separated by the feed roller 7 and the separation pad 9 one by one and conveyed to an image forming portion (not shown).
Since a separation mechanism of the sheet bundle by the feed roller 7 and the separation pad 9 is in a general construction, its description will be omitted. Next, after an image is formed in this image forming portion, the sheets are discharged to the outside of the image forming apparatus via a fixing process.
In
Here, when the user is to set a sheet bundle PA onto the sheet feed tray 2, the pick arm 4 swings so that the pickup roller 5 comes to the standby position as shown in
Moreover, an upper part of the rotating end of the sheet stopper 3 is restrained by a restraining portion 4a provided on the end on the downstream side of the pick arm 4 at this time, and thereby, the sheet stopper 3 cannot be pivotally moved upward (clockwise direction). In this way, since the sheet stopper 3 is restrained from being pivotally moved in the vertical direction, the leading edge of the sheet bundle can be surely restricted on the upstream side of the feed roller 7 by a bottom surface 3c of the sheet stopper 3 when the user inserts the sheet bundle PA into the sheet feed tray 2. Thereby, the sheet bundle is not forced into the nip portion between the feed roller 7 and the separation pad 9. As a result, occurrence of defective separation can be avoided.
On the other hand, in the sheet feeding state, the pick arm 4 is pivotally moved downward as shown in
Here, when the pick arm 4 is pivotally moved downward in this way, the restraining portion 4a of the pick arm 4 having been restrained by the sheet stopper 3 is separated from the sheet stopper 3 and releases regulation on the pivotal movement by the sheet stopper 3. That is, the sheet stopper 3 is held in the regulating position for regulating the leading edge of the sheet P when the pickup roller 5 is in the standby position, while regulation on the sheet leading edge is released when the pickup roller 5 is in the sheet feeding position.
Thereby, thereafter, when the sheet P1 is fed by the pickup roller 5, the sheet stopper 3 is pushed up by the fed-out sheet P1. Then, thereafter, the sheet P1 which pushed up the sheet stopper 3 is fed to the image forming portion through a separation portion comprised of the feed roller 7 and the separation pad 9.
Next, the construction to prevent over-stacking of the sheets on the sheet feed tray 2 in the sheet feeding apparatus 20 provided with the sheet stopper 3 constructed as above will be described.
In
Here, till the feeding operation is started, as mentioned above, since the sheet stopper 3 cannot be pivotally moved upward by being regulated by the pick arm 4, the leading edge of the sheet can be surely regulated. Moreover, since the over-stack protective wall 3d is arranged on the upstream side with respect to the pickup roller 5, the sheets PB exceeding the maximum stacking height cannot be inserted below the pickup roller 5, and defective feeding or the like cannot be occur.
Also, when the sheet stopper 3 is in the regulating position as shown in
However, when the pickup roller 5 is moved to the sheet feeding position as shown in
According to this embodiment, since a mechanism for preventing over-stacking of the sheets is provided integrally with the sheet stopper 3, the over-stacking of the sheets can be prevented without providing an over-stack protective member on the sheet feed tray 2, and the sheets can be fed stably with low costs. Moreover, reduction of the number of parts and space can be promoted, and over-stacking of the sheets can be surely prevented without relying on visual check by the user of the sheet stacking upper-limit mark.
Next, a second embodiment of the present invention will be described.
In
By regulating the position of the sheet in the sheet width direction as well as the sheet bundle leading edge and the stacking height, not only the accurate positioning of the sheet leading edge portion and the prevention of over-stacking but also the skew feed of the sheet in a feeding operation can be prevented by regulation in the sheet width direction. By preventing the skew feed of the sheets in this way, image positions can be accurately aligned with the sheets, and the image formation is achieved with accuracy.
Heretofore, the sheet feeding apparatus having a manual feed tray was described as an example of the sheet feeding apparatus, but the present invention can be also applied to the sheet feeding apparatus of a general image reading apparatus such as an ADF (Automatic Document Feeder).
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 such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2005-373556, filed Dec. 26, 2005 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-373556 | Dec 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5433428 | Akashi | Jul 1995 | A |
| 6050565 | Fetherolf | Apr 2000 | A |
| 20040071486 | Manabe et al. | Apr 2004 | A1 |
| 20050179192 | Miura et al. | Aug 2005 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20070145672 A1 | Jun 2007 | US |
