1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multi function mechanism. The invention also relates to a sheet processing apparatus which performs processing such as alignment, binding, and center-folding to image-formed sheets which are discharged from the image forming apparatus. The invention also relates to a sheet processing method.
2. Description of the Related Art
The image forming apparatus such as the copying machine is provided with a sheet post-processing apparatus which stacks plural image-formed sheets to perform saddle stitch or the like. The sheet bundle which is center-folded at a binding position is discharged and stacked on a discharge tray with a folded portion in the lead. When the folded sheet bundle has a thick, or when the sheet has strong stiffness, it is difficult that the sheet bundle is completely folded, and sometimes the sheet bundle becomes poor-looking because both ends are opened after the sheet bundle is folded. When the sheet bundle is loosely folded to easily open both the ends, the subsequent sheet bundle plunges into the already stacked sheet bundle in stacking the plural sheet bundles on top of another on a discharge tray. When the sheet bundles are stacked on top of another while swollen, the sheet bundles easily collapse.
In order to eliminate the defect, for example, Japanese Patent Application Laid-Open No. 11-193175 discloses a sheet bundle folding apparatus and a sheet processing apparatus. In this case, when the folded portion of the sheet bundle is delivered toward a nip between a pair of folding rollers, a pushing member plunges the folded portion of the sheet bundle between the folding rollers while being followed by motion of the sheet bundle. Therefore, the sheet bundle is completely folded by correctly and securely pushing the folded portion of the sheet bundle with the pushing member.
However, in the sheet bundle folding apparatus and sheet processing apparatus disclosed in Japanese Patent Application Laid-Open No. 11-193175, there are problems to be solved.
One of the problems is that, in the case where the folding processing is performed to the sheet bundle, the fold becomes looser in the sheet located close to the outside of the folded sheet bundle. This is attributed to the fact that a folded radius becomes larger in the sheet located close to the outside due to a thickness of the sheet bundle.
Another problem is that, during an action in a staple mode selected by a user, sometimes breakdown or wrinkle is generated in a wire-stitched portion when the sheet bundle is center-folded at the wire-stitched portion with the sheet bundle folding apparatus disclosed in Japanese Patent Application Laid-Open No. 11-193175 after stapling process is previously performed at the predetermined position where the sheet bundle is center-folded. This is because a cover sheet is broken from the wire-stitched portion to generate the wrinkle by a difference between frictional resistance which the cover sheet receives from a roller surface and frictional resistance generated by rubbing the sheets with one another inside the sheet bundle when the sheet bundle is conveyed while nipped between the rollers.
Still another problem is a defect which is generated by bringing the pushing member close to the folding roller to prevent the breakdown and wrinkle as much as possible. In the configuration disclosed in Japanese Patent Application Laid-Open No. 11-193175, when the sheet bundle is nipped between the folding rollers, the pushing member which is stopped just before the sheet bundle rubs the inside of the sheet bundle to generate a scratch and a trace.
In view of the foregoing, an object of the invention is to provide a sheet processing apparatus which obtains the folded sheet bundle having the good appearance and excellent stacking property by performing the folding processing to the sheet bundle twice in an opposite direction, and an image forming apparatus provided with the sheet processing apparatus.
In order to achieve the above object, a sheet processing apparatus according to the present invention includes a first folding unit which performs folding processing to a predetermined folding position on a sheet or a sheet bundle; and a second folding unit which folds the sheet or the sheet bundle folded by said first folding unit in an opposite direction to said first folding unit at said predetermined folding position.
An image forming apparatus according to the present invention includes an image forming portion which forms an image in a sheet; and a sheet processing apparatus having the above configuration, which performs processing to the sheet in which the image is formed by the image forming portion.
According to the sheet processing apparatus of the invention, the first folding unit tentatively center-folds the sheets to make a fold and the second folding unit folds the sheets in the opposite direction from the backside of the fold again, which enables the sheet bundle becomes good-looking in the good sheet bundle folding processing.
Furthermore, in the sheet processing apparatus of the invention, the first folding roller folds the sheets including the first pushing member. Therefore, even if the saddle stitch is performed to the sheet bundle to which the staple processing is already performed, the sheets cannot be broken in the staple portion, and rubbing is not generated inside the saddle stitch bundle.
According to the image forming apparatus of the invention, the sheet bundles never collapse because the sheet bundles completely folded by the sheet processing apparatus are orderly stacked and stored in the discharge tray. And productivity can be improved as a whole because the image-formed sheet is efficiently delivered to the sheet processing apparatus.
A sheet processing apparatus and an image forming apparatus and a sheet processing method according to a preferred embodiment of the invention will be described in detail with reference to the accompanying drawings.
(Image Forming Apparatus)
The image forming apparatus will be described with reference to
The original stacked on an original feeding device 130 is sequentially conveyed onto an original base plate glass surface 121 one by one. When the original is conveyed, a lamp of a scanner portion 122 is lit to irradiate the original while a scanner unit 123 is moved. The light reflected from the original passes through mirrors 124, 125, and 126 and a lens 127 in this order, and the reflected light is inputted to an image scanner 128 which is of an image input portion with CCD (Charge Coupled Device). CCD performs photo electric conversion of the inputted image information into an electric signal. Various kinds of image processing are performed to the converted signal, and the signal is inputted to the apparatus main body 110 to form the image as the visible image. In the first embodiment, the image input device 120 which converts the original into the image data inputs the signal to the apparatus main body 110. However, the invention is not limited to the first embodiment. For example, the image data may be transmitted from a personal computer or a host computer which is of an upper-level apparatus.
The signal inputted to the apparatus main body 110 is converted into a light signal by an exposure controlling portion 101, and a photosensitive member 102 is irradiated based on the image signal. A latent image formed on the photosensitive member 102 by the irradiating light is developed by a development device 103 which constitutes an image forming portion along with the photosensitive member 102. In the sheet which is fed from sheet feeding portion 145 while timed to the development, the developed image is transferred to by a transfer portion 104, and the transferred image is fixed by a fixing portion 150. The sheet discharged from the fixing portion 150 is reversed by a reversal path 170 if needed, and the sheet is discharged to the sheet processing apparatus 2 by a discharge roller 180.
(Sheet Processing Apparatus)
Then, a configuration of the sheet processing apparatus 2 of the first embodiment will be described in each processing mode along with a sheet flow.
(Staple Sort Mode)
Referring to
The sheet directed to the second conveyance path 252 for sort conveyance is stacked on a processing tray 254 by a conveyance roller 253. The processing tray 254 is arranged with a predetermined inclined angle such that the sheet abuts on a sheet rear end regulating member 255 provided at an end portion of the processing tray 254. Accordingly, the sheet abutting on the sheet rear end regulating member 255 stand by for a given time and the sheet is aligned by a sheet alignment member (not shown) in a sheet width direction. When a sheet alignment action is finished for the predetermined number of sheets, a stapling process is performed to rear end portions of the sheets by a stapler 257. Then, the sheet bundle is discharged to and stacked on a stack tray 281 by a bundle discharge roller 256.
(Saddle Stitch Mode)
Referring to
As shown in
The conveyance roller 215 is arranged on a left side of the sheet storage portion 203 such that the subsequent sheet is conveyed onto the left side of
As shown in
In the sheet bundle S conveyed to the sheet storage portion 203, the position is adjusted by moving the movable stopper 207 by a predetermined amount in the upstream or downstream direction according to the sheet size. After the stapling process is performed if needed, the central portion in the sheet conveyance direction of the sheet bundle S (corresponds to the wire-stitched portion in the bind where the stapling process is performed) is conveyed near the nip between the first folding rollers 205, and a first pushing plate (first pushing member) 206 is caused to proceed toward the nip direction of the first folding roller 205. As shown in
At this point, the first pushing plate 206 is plunged into the nip portion of the first folding rollers 205 along with the sheet bundle S. This is because the trouble generated by the difference between a frictional coefficient between the sheets inside the sheet bundle and a frictional coefficient between the cover sheet of the sheet bundle S on the side which is in contact with the first folding roller 205 and the roller surface is eliminated. Sometimes the conveyance amount of cover sheet which comes into contact with the roller surface to receive conveyance force is larger than the conveyance amount of inside sheet of the sheet bundle S due to the difference in frictional coefficient. That is, the shift of the conveyance amount between the cover sheet and the inside sheet in the sheet bundle S causes the generation of the breakdown or wrinkle to remarkably decrease bundle fold quality or binding quality. In order to prevent the decrease in bundle fold quality or binding quality, the first pushing plate 206 is followed by the sheet bundle S and nipped between the first folding rollers 205.
Conventionally, when only the first pushing plate 206 is brought close to the nip portion of the first folding roller 205, there is generated the trouble that scratch or frictional trace occurs inside the sheet of the sheet bundle S pushed by the first pushing plate 206. However, the trouble can be eliminated by pushing the sheet bundle S into the nip portion of the first folding roller 205 along with the first pushing plate 206.
The sheet bundle S is conveyed by the predetermined conveyance amount while the first pushing plate 206 pushes the sheet bundle S into the first folding roller 205. Then, as shown in
During the conveyance of the sheet bundle S onto the downstream side, the rear end of the sheet bundle S is detected by a bundle detection sensor 240 (Step S8). The detection signal stops the conveyance performed by the rotation of the first folding roller 205 at the position where the sheet bundle S proceeds slightly toward the down stream side (Step S9). As shown in
At this point, the control device 200 performs the control such that the position of the fold F of the sheet bundle S which is folded by the first folding rollers 205 is conveyed to the nip position of the second folding rollers 209. Therefore, in a conveyance path 215 to the second folding rollers 209 on the downstream side of the bundle detection sensor 240 in
The conveyance path 215 between the first folding rollers 205 and the second folding rollers 209 is formed in a U-shape in which the path is bent by about 180°, which realizes the compact configuration of the sheet processing apparatus main body. In the first embodiment, the miniaturization of the sheet processing apparatus main body is realized by bending the conveyance path 215. However, the bent angle is not limited to 180° as long as the miniaturization is achieved by forming the conveyance path 215 in the curved shape.
A length of the conveyance path 215 between the first folding roller 205 and the second folding roller 209 is set longer than the maximum sheet size to which the saddle stitch can be performed. Therefore, when the second folding roller 209 is driven, the rear end of the sheet bundle S is located on the downstream side of the movable stopper 207 which allows the sheet storage portion 203 to become an empty state to receive the next sheet bundle S. As a result, the total productivity is not decreased as the image forming system because the conveyance can be continued without stopping the processing between the previous sheet bundle S and the subsequent sheet bundle S.
Then, as shown in
At this point, the plunging action of the second pushing plate 210 is set so as to be stopped immediately before the nip of the second folding rollers 209. The scratch or frictional trace never generates because the second pushing plate 210 is plunged from the opposite direction to the direction in which the fold F is made. The second pushing plate 210 and the sheet bundle S hardly slide because a fold habit in the direction in which the sheet bundle S is separated away from the second pushing plate 210 is made to the sheet S by the first folding unit. In the first embodiment, the second pushing plate 210 is a member which constitutes “second folding unit” along with the second folding rollers 209. Thus, the sheet bundle having good appearance can be realized in bundle good folding processing.
In the folding processing, the second pushing plate 210 is plunged toward the fold F of the sheet bundle S to which the fold is made. At this point, because a mountain peak is aimed, the front end of the second pushing plate 210 does not always correspond to the fold F at an initial stage of the plunging action. However, because the folding processing is already performed to the fold F by the first folding unit, the sheet rigidity is locally decreased in the fold F. Accordingly, as the plunging action of the second pushing plate 210 is in progress, a turnoff in the reversal direction is generated along the fold F, and the fold F corresponds to the front end of the second pushing plate 210. In order to further secure the plunging action to the fold F, the shapes of the conveyance path 215 on the upstream side and the conveyance path 216 on the downstream side are curved in the reversal direction of the direction in which the fold is made such that the sheet bundle S is stably pushed into the nip portion between the second folding rollers 209. That is, the conveyance path 215 on the upstream side and the conveyance path 216 on the downstream side are curved in the direction in which the conveyance path 215 and the conveyance path 216 are separated away from the second folding rollers 209 such that the neighbor of the fold of the sheet bundle S becomes a top of the curved portion toward the second folding roller 209.
Then, the sheet bundle S to which the folding processing is performed by the second folding rollers 209 is directly conveyed, and the sheet bundle S is discharged to and stacked on the stack tray 220. The folded sheet bundle S discharged to the stack tray 220 abuts on the movable stopper 221 (see
In the sheet bundle S finished through the above procedure, the staple leg in the wire-stitched portion of the sheet bundle S center-folded in the folding processing by the second folding rollers 209 is located inside the center-folded sheet bundle S. The folding processing is performed from the reversal direction at the position where the first-time folding processing is already performed. Therefore, as the number of sheets is increased in the sheet bundle S, the quality is improved in the folding processing, and the sheet bundle S has becomes good-looking because the both the ends of the folded portion are never opened when compared with the conventional sheet bundle to which the one-time folding processing is performed. The binding processing can orderly be performed because the disorder caused by the stacking collapse is not generated.
In the first embodiment, for example, when plain paper sheets is set to predetermined sheets or less, for example, three or less in the saddle stitch mode, the action of making the fold F in the folding processing by the first folding rollers 205 can be neglected. In this case, the folding processing is performed only by the second folding rollers 209, and the sheet bundle S can directly be saddle-stitched (
In the first embodiment, the case in which the fold is made at the predetermined position in the direction orthogonal to the sheet conveyance direction and the folding processing is reversely performed at the fold is explained. Alternatively, the fold may be made along the sheet conveyance direction and the folding processing is reversely performed at the fold.
In the first embodiment, the U-shape conveyance path 215 which is bent by about 180° is provided for the purposes of the miniaturization of the image forming apparatus 1 and the productivity improvement of the image forming system. On the other hand, in the second embodiment, the sheet processing apparatus 2 is miniaturized in the case of a type of image forming apparatus 1 having relatively low productivity per hour. For this end, the second folding rollers 209 are arranged on the downstream side of the first folding rollers 205 while brought close to the first folding rollers 205. While the folding processing is performed in either the first folding rollers 205 or the second folding rollers 209, the end portion of the sheet bundle to which the folding processing is being performed enters the folding processing position of the other sheet bundle to which the folding processing is not performed. That is, the folding processing is not simultaneously performed in the first folding rollers 205 and the second folding rollers 209. Instead the conveyance path length between the first folding rollers 205 and the second folding rollers 209 is reduced to minimal length to realize the miniaturization of the apparatus. In the second embodiment, the conveyance path is linearly provided, and thereby the miniaturization is also achieved in the direction orthogonal to the conveyance path. The miniaturization may be achieved by bending the conveyance path to further decrease the length in the conveyance direction.
Therefore, the miniaturization is realized in the sheet processing apparatus 2, the sheet bundle becomes good-looking because the folded portion is not opened, and the good binding processing can be performed.
In the first and second embodiments, the folding processing is collectively performed to the sheet bundle. On the other hand, in configuration of the third embodiment, the folding processing is performed to the sheet one by one by the first folding rollers 205 and the plural folded sheets are stacked by the sheet storage portion 203. Then, the staple processing is performed if needed, the second folding rollers 209 fold the sheet bundle S including the plural sheets toward the reversal direction of the first folding rollers 205, and thereby the folded portions becomes further good-looking and the stacking properties is improved. In the folding processing performed to the one sheet, depending the thickness of the sheet, the outside of the fold and the inside differ from each other in the folded radius. The difference becomes remarkable as the thickness is increased in the sheet. The folding processing is securely performed by folding the thick sheet one by one. Thus, after the fold is made to the sheet one by one, the folding processing is performed in the reversal direction, which allows the same effect as the first and second embodiments to be obtained even in the thick sheet. In this case, the discharge roller 242 is formed by a one-way clutch mechanism because the reversal rotation of the sheet conveyance direction is made free. That is, the sheet bundle S returned by the first folding rollers 205 is conveyed by the discharge rollers 242 again, and the sheet bundle S is delivered to the sheet storage portion 203 for the saddle stitch. Then, the front end in the sheet conveyance direction of the conveyed sheet bundle S abuts on the movable stopper 207, and the sheet width direction of the sheet bundle S is aligned by a pair of alignment plates 219 as alignment member in the sheet width direction. This processing is performed to the predetermined number of sheets.
In the first, second, and third embodiments, the two folding means are provided, and the folding processing is performed in the reversal direction in each folding means. However, the invention is not limited to the above embodiments. For example, as shown in
Thus, the preferred embodiments of the invention are described. Other embodiments, modifications, changes, and combinations thereof could be made without departing from the scope of the invention.
This application claims the benefit of priority from the prior Japanese Patent Application No. 2005-326887 filed on Nov. 11, 2005 and No. 2006-292011 filed on Oct. 27, 2006 the entire contents of which are incorporated by reference herein.
Number | Date | Country | Kind |
---|---|---|---|
2005-326887 | Nov 2005 | JP | national |
2006-292011 | Oct 2006 | JP | national |
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Number | Date | Country | |
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