Patent Grant
7296793
This invention relates to a sheet processing apparatus aligning and stacking sheets and an image forming apparatus having this sheet processing apparatus.
In image forming apparatuses such as photocopiers and printers, conventionally, sheet S on which images are formed with an image forming apparatus body 300 as shown in
However, as shown in
When the sheet bundle S on which the stapling processing is made are stacked on the stacking tray 400 as shown in
It is an object of the invention to provide an apparatus preventing stacked sheet bundles from positionally shifting in the conveyance direction and improving stacking alignment property of the sheet bundles.
Further objects of the invention will be apparent from reading the following detailed description in reference to the attached drawings.
Referring to the drawings, hereinafter, the preferred embodiments of the invention are described in detail in an exemplifying manner. The sizes, materials, and shapes of structural parts set forth in the following description, correlative positions of those, and the like can be modified properly according to the structure and the various conditions of the apparatus to which this invention applies, and are not intended to render the scope of the invention limited to those only.
The embodiment of the image forming apparatus having the sheet processing apparatus according to the invention are exemplified in
In this embodiment, the sheet processing apparatus 1 as shown in
This invention, however, is not limited to the example shown in
[Brief Structure of the Image Forming Apparatus]
In
In the image forming apparatus body 30, the original document by the automatic original document reading apparatus 35 is fed automatically to the reading position as shown in
Subsequently, the laser beam reflects at a rotating polygon mirror, and is returned at a reflection mirror to be radiated onto a photosensitive drum 3 whose surface is uniformly charged, thereby forming electrostatic latent images. The electrostatic latent image on the photosensitive drum 3 is developed with a developing device 5, and is then transferred onto a sheet S such as paper or OHP sheet as a toner image.
The sheet S is properly selectively fed out of sheet cassettes 31, 32, 33, 34 with a pickup roller 38 constituting the sheet feeding means. The sheet S is conveyed one by one upon separation by a separating means 37, and after corrected with a pre-registration roller pair when fed obliquely, the sheet is fed to a transfer position in synchrony with the rotation of the photosensitive drum 3, so that the toner image formed on the photosensitive drum 3 is transferred to the sheet S via a transfer belt 11 as an intermediate transfer body.
Then, the sheet S is introduced to a fixing roller pair 6, and the toner image transferred to the sheet S is permanently fixed upon application of heat and pressure from the fixing roller pair 6. A fixing upper separation nail and a fixing lower separation nail are in contact with the fixing roller pair 6, and this separates the sheet S from the fixing roller pair 6.
The sheet S on which images are formed thus with the image forming section is further conveyed to the exterior of the image forming apparatus body 30 with a body side delivery roller pair 7, so that the sheet S is introduced into the sheet processing apparatus 1 coupled to the image forming apparatus body 30.
[Brief Structure of the Sheet Processing Apparatus]
In
A processing means capable of temporarily stacking a plural number of sheets and processing the sheet or sheet bundle is provided on an upstream side of the stacking tray 4 and the rocking roller 50 in the sheet conveyance direction. The processing means according to this embodiment includes a processing tray 40 temporarily stacking a plural number of sheets, an aligning means constituted of alignment plates 41, 42 for aligning sheets stacked on the processing tray 40, and a stapler unit 10 serving as stapling means for stapling processing of sheet bundles aligned with the aligning means. The processing means can have only the aligning means, or may have, other than the aligning means, a punching means for making holes in the sheets, a pasting means for pasting an end of the sheet bundle, and a bookmaking means such as a tape attaching means attaching a binding tape to the end of the sheet bundle.
As shown in
The rear end of the sheet S is subsequently fed along a lower guide 61 to the processing tray 40 in the opposite direction to the conveyance direction as conveyed so far by the reverse rotation of the rocking roller 50, and sheets are aligned one by one in the sheet conveyance direction and in the sheet width direction substantially perpendicular to the sheet conveyance direction by the aligning means constituted of such as a returning belt 60 and the alignment plates 41, 42 as described below.
The alignment in the conveyance direction of the sheet S is done by contacting the rear end of the sheet S to a rear end stopper 62 of the sheet S serving as a sheet reception means located at an end of the processing tray 40 for receiving the sheet S on the processing tray 40, from the self-weight force of the sheet S obtained by the inclined angle of the processing tray 40 and from the returning belt 60. The alignment in the sheet width direction is done by the alignment plates 41, 42 arranged on both sides in the sheet width direction operating by a driving means, not shown, e.g., lack and pinion gear drive source, and by the controlling means.
Where the stapling mode is selected, the stapler unit 10 makes stapling to the already aligned sheet bundle S which are aligned on the processing tray 40. The sheet bundle S thus finished with the post-processing are delivered and stacked on the stacking tray 4 arranged to extend substantially horizontally by rotation in the counterclockwise direction in
[Alignment of Sheet Rear Ends]
Referring to
First, described in reference with
As shown in
In
As shown in
As described above, while the escaped rear end alignment wall 70 is returned to the home position by the rotation of the cam 72, acceleration α of the sheet bundle (or sheet) from pressing of the rear end alignment wall 70 is required to be controlled. This is because the sheet bundle (or sheet) S may be kicked if the acceleration α is high, thereby reducing the alignment property on the stacking tray 4. Conversely, if acceleration α is low, the productivity of the sheet processing apparatus is reduced. To prevent such problems from occurring, the acceleration α of the sheet bundle S due to pressing of the rear end alignment wall 70, or namely, the acceleration α of the rear end alignment wall 70, is required to be controlled.
In this embodiment, where acceleration of the sheet bundle S by pressing of the rear end alignment wall 70 at a time that the rear end alignment wall 70 presses the rear ends of the sheet bundle (or sheet) S to align the rear ends, is denoted as α, where gravitational acceleration is denoted as g, where coefficient of kinetic friction between the sheet bundle (or sheet) S pressed by the rear end alignment wall 70 and the stacking tray 4 is denoted as μ1′, and where coefficient of kinetic friction between the sheet bundle (or sheet) S pressed by the rear end alignment wall 70 and the sheet bundle (or sheet) S already stacked on the stacking tray 4 is denoted as μ2′, the operation of the rear end alignment wall 70 is controlled, as shown in
α≦−μ1′g and α≦−μ2′g
The sheet bundle (or sheet) S to be pressed moves upon receiving frictional resistance from the stacking tray 4 or the already stacked sheet bundle (or sheet). That is, where the rear end alignment wall 70 is operated with acceleration α satisfying the above relation, the rear end of the sheet bundle (or sheet) S does not become separated from the rear end alignment wall 70 by the frictional resistance, and the sheets are stacked on the stacking tray 4 as keeping a good alignment state. The relationship in amounts of coefficient of kinetic friction μ1′ between the sheet bundle S and the stacking tray 4 and the coefficient of kinetic friction μ2′ between the sheet bundle S and the sheet bundle already stacked on the stacking tray 4 is determined with kinds of the stacked sheets, toner amounts carried on the stacked sheets, materials of the tray, etc.
In
Thus, the operation of the rear end alignment wall 70 is controlled so that the acceleration α of sheet bundle (or sheet) S from pressing of the rear end alignment wall 70 satisfies the above conditions, and therefore, this apparatus can prevent the sheets from positionally shifting in the conveyance direction at the front and rear ends of the sheet bundle (or sheet) S on the stacking tray 4, thereby allowing the sheet bundle (or sheet) S to be delivered and stacked on the stacking tray 4.
It is to be noted that although in this embodiment, the sheet stacking surface 4a of the stacking tray 4 is set to extend substantially horizontally, the rear end alignment wall 70 effectively operates even where the sheet stacking surface 4a is inclined, and where the sheet stacking surface 4a is extending substantially horizontally, the effects itself increase more. Where the sheet stacking surface 4a is set with an inclined angle of eighteen degrees or less inclined to the lower side toward the rear end alignment wall 70, a smaller size of the apparatus can be realized as avoiding interference between the rear ends of the sheet bundles already stacked on the stacking tray 4 and the subsequent sheet bundle delivered out of the processing tray 40.
The stacking tray 4 is structured to be movable up and down by a driving means not shown to keep the height of the top surface of the stacked sheet bundles S at a constant level.
As described above, according to this embodiment, the sheets are aligned in the conveyance direction of the sheet bundle (rear end alignment) while delivered and stacked on the stacking tray 4, by conveying the sheets until that the rear end of the sheet bundle (or sheet) reaches the top end of the rear end alignment wall, subsequently by rendering the sheet bundle rear end contact with the rear end alignment wall 70 as escaping the rear end alignment wall 70, and by pressing the rear ends of the sheet bundle with the rear end alignment wall 70. At that time, by controlling the operation of the rear end alignment wall 70 with the finisher CPU 79 so that the acceleration α of sheet bundle from pressing of the rear end alignment wall 70 satisfies the relation of α≦−μ1′g and α≦−μ2′g, the apparatus can prevent sheets from positionally shifting in the conveyance direction at the front or rear ends of the sheet bundles, and can improve the stacking alignment property of the sheet bundle on the stacking tray 4.
The sheet alignment property on the stacking tray 4 can be improved even where the stacking tray 4 is placed as substantially horizontally extend, and because the space for inclined portion of the stacking tray 4 can be converted to an up and down moving stroke of the stacking tray 4, the number of the sheets stacked on the stacking tray 4 can be made larger without rendering the apparatus body in a larger size.
Moreover, because the inclination of the stacking tray 4 can be made gentle, folding of the sheet due to the self-weight of the sheet bundle subjecting to lower curling or having low rigidity caused by steep inclination of the stacking tray 4, can be prevented.
Because the rear ends of the sheet bundle delivered on the basis of the bundles are aligned on an upstream side in the delivery direction with respect to the sheet bundles already stacked, this apparatus can prevent the sheets from positionally shifting in the conveyance direction upon engagement of the staple of the already stacked sheet bundles on which the stapling processing is made with the rear end of the sheet bundle delivered on the basis of the bundle.
With the embodiment described above, the photocopier is exemplified as an image forming apparatus. This invention is not limited to this, and this invention can be for other image forming apparatuses such as printers or facsimile machines or other image forming apparatuses such as combined machines combining those functions. Substantially the same effects can be obtained upon application of this invention to the sheet processing apparatus used in such an image forming apparatus.
In the embodiment described above, exemplified is the sheet processing apparatus installed in the image forming apparatus body (space portion), but this invention is not limited to this. For example, the sheet processing apparatus can be arranged at the exterior of the image forming apparatus body and can be formed as detachably attached to the image forming apparatus body or formed unitedly with the image forming apparatus body. Substantially the same effects can be obtained upon application of this invention to such a sheet processing apparatus.
In the embodiment described above, the exemplified recording method is an electrophotographic method, but this invention is not limited to this. This invention can use other recording method such as, e.g., inkjet method or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-116768 | Apr 2003 | JP | national |
| 2004-020857 | Jan 2004 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20040212136 A1 | Oct 2004 | US |
