Patent Application
20180016112
The present invention relates to a sheet processing apparatus for folding a sheet on which an image is formed, and an image forming apparatus using the sheet processing apparatus.
In recent years, a sheet processing apparatuses has been developed which performs post-processing for a sheet on which an image has been formed as an option of an image forming apparatus such as an electro-photographic copying machine and a laser beam printer. This type of sheet processing apparatus has been able to perform various kinds of sheet processing such as stacking and aligning of a plurality of sheets, producing a sheet bundle or a book by providing a stapler for stapling the sheets and a folding device and so on.
As a configuration of folding sheets in such a sheet processing apparatus, the configuration is widely known in which a sheet bundle is pushed into a nip of a roller pair with a thin plate-like pushing member and the sheet bundle is folded by the roller pair, thereby making a booklet as disclosed for example in Japanese Patent Application Laid-Open No. 2011-241021.
Further, in a case where a sheet bundle is pushed and folded by the pushing member as described above, especially when a thick coated paper is pushed and folded, a problem may occur that the outer back portion of the folded sheet is broken (hereinafter referred to as back cracking). In order to prevent back cracking, it is also widely known to carry out a scoring process in which the folding line portion of the sheet is squeezed linearly in advance. As shown in
In order to place the convex portion of the folding score inside the folded sheet as explained above, the convex portion of the folding score should be pushed into a roller nip by the pushing member. At this time, so-called score reversion may occur by which the convex portion of the folding score may be collapsed by being pushed by the pushing member. When the score reversion occurs, the scoring as countermeasures against the back cracking does not exhibit its effect, causing the back cracking.
A sheet processing apparatus according to the present invention, comprising:
a supporting portion on which a sheet which has been conveyed is supported;
a pushing member configured to push the sheet with an abutting portion of the pushing member in order to fold the sheet on the supporting portion; and
a setting portion configured to set a pushing position at which the pushing member pushes the sheet with a score to a position at which the sheet is to be folded at the score, wherein a center of the abutting portion does not coincide with a center of the score of the sheet.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Next, embodiments of a sheet processing apparatus according to the present invention will be explained as well as an image forming apparatus using the sheet processing apparatus.
<Overall configuration of the image forming apparatus>
As shown in
In the present embodiment, the scoring device 200 and the sheet processing apparatus 300 both of which are attachable and detachable, but these may be integrated with the image forming apparatus main body 100.
<Image forming apparatus main body> The image forming apparatus main body 100 includes the sheet storage portion 101 for storing the sheets S, the sheet feeding portion 102 for feeding the sheets S stored in the sheet storage portion 101, and the image forming portion 103 which forms an image on the sheet S fed by the sheet feeding portion 102. Further, on the upper portion of the image forming apparatus main body 100, the original document feeding device 104 for feeding an original document and the image reader 105 for reading the information of the original document fed from the original document feeding device 104 are provided.
The image forming portion 103 includes four photosensitive drums 106a to 106d on which toner images of respective colors of yellow, magenta, cyan, and black are formed. The toner image of each color formed on the photosensitive drums 106a to 106d is transferred to the sheet S. As a result, an unfixed toner image is formed on the sheet S. Thereafter, the unfixed toner image is fixed by the fixing portion 107, and the sheet S is discharged to the sheet processing apparatus 300 by the discharging roller 108.
In the case of duplex printing, the sheet S is reversed by the reverse conveyance portion 109 and is conveyed again to the image forming portion 103 where an image is formed on the reverse side.
<Scoring device> The scoring device 200 forms a folding score on the sheet S by a squeezing process. As indicated in
After the sheet has been conveyed to a predetermined position, the convex side scoring portion 202a descends in the direction of the arrow shown in
As described above, the scoring device 200 can apply a scoring process to the center of the sheet S in the conveying direction of the sheet S. The scoring device 200 operates when applying a folding score to a sheet and a sheet only passes through the scoring device 200 when not applying a folding score to the sheet.
<Sheet processing apparatus> Next, the sheet processing apparatus 300 will be explained. The sheet processing apparatus 300 is disposed on the downstream side of the image forming apparatus main body 100 and the scoring device 200 in the sheet conveying direction. The sheet processing apparatus 300 receives a plurality of sheets S fed from the image forming apparatus main body 100 and performs staple processing, saddle processing and the like on line.
As shown in
When the side registration error is detected by the side registration detecting sensor 304, the shift processing is performed in which the shift unit 307 moves the sheet by a predetermined amount in the backward direction or in the forward direction while the sheet S is being conveyed by the shift roller pairs 305, 306. By this shift processing, the sheet is aligned in the width direction (the direction orthogonal to the sheet conveying direction). When the shift processing by the shift unit 307 is completed, the sheet S is conveyed by the conveying roller pair 308 and further conveyed to the downstream side by the buffer roller pair 309.
Here, when the sheet S is to be discharged to the upper stacking tray 310, the sheet S is discharged to the upper stacking tray 310 by switching of the upper path switching member 311. On the other hand, when the sheet S is not to be discharged to the upper stacking tray 310, the sheet S passes through the bundle conveying path 314 by the buffer roller pair 312 and the bundle conveying roller pair 313.
In the case of saddle bind processing, the sheet S sent to the bundle conveying path 314 is conveyed to the saddle path by switching the saddle path switching member 315, and is introduced to the saddle unit 800 by the saddle entrance roller pair 316 where saddle bind processing is performed. The saddle unit 800 will be explained later in detail.
On the other hand, when the saddle bind processing is not to be performed, the sheet S is sent to the processing tray 317 by the switching of the saddle path switching member 315. At this time, when bind processing is to be performed, the bind processing is performed by the stapling portion 318. When the bind processing is not to be performed by the stapling portion 318, the sheet S is discharged to the lower stacking tray 319 without passing through the processing tray 317.
<Control portion> Next, the configuration of the control portion for controlling the image forming apparatus A according to the present embodiment will be explained with reference to the block diagram of
As shown in
Further, the CPU 401 sends driving signals to the scoring device control portion 411 which controls the driving of the scoring device 200, and to the sheet processing apparatus control portion 412 which controls the driving of the sheet processing apparatus 300 to control them.
Further, the sheet processing apparatus control portion 412 controls driving sources such as a motor for moving the pushing member which will be explained later, a motor for driving the folding roller and a motor for driving the sheet conveying roller, and a sensor for detecting the position of a conveyed sheet.
<Saddle unit> Next, the configuration of the saddle unit 800 will be explained with the operations of the saddle unit 800 with reference to
The tip stopper 805 serves as a regulating portion which supports the tip (lower tip) of the conveyed sheet and positions the sheet in the sheet conveying direction. As shown in
The pushing plate 803 (pushing member) for folding the sheet is provided at a position substantially at the center of the sheet stacked on the processing tray 883 in the conveying direction. As shown in
The pushing drive gear 822 is engaged with the pushing link plate 825. The pushing link plate 825 has the link engagement portion 825a engaged with the pushing drive gear 822 and the pushing plate engagement portion 825b engaged with the pushing plate 803. The pushing plate engagement portion 825b is guided by the guide portion 826a of the pushing frame 826. Thus, the pushing plate 803 is reciprocated by the pushing drive motor 858 while being guided by the guide portion 826a.
The folding rollers 819 are provided in the region in which the pushing plate 803 moves. The folding rollers 819 are constituted by a roller pair driven by a drive motor which is not shown. As shown in
Then, the rear end holding member 881 is opened as shown in
Thereafter, as in the case of the first sheet S1, the alignment in the conveying direction/orthogonal direction is performed, and the holding member 881 is opened, and the sheet S2 is biased toward the processing tray 883 side by the tapping member 882, and then the holding member 881 is closed. After aligning a sheet, biasing a sheet toward the processing tray, and holding the rear end of a sheet are repeated until the last sheet Sn of the sheet bundle is completed, the bind processing is performed by the stapler 820. The tip stopper 805 waits at a position where the distance between the stapling position and the stopper is half the sheet length and receives the sheet, so that the staple processing is performed at the center of the sheet.
Thereafter, the stapled sheet bundle S is lowered to a predetermined position which is explained later. Then, the sheet bundle S is guided to the nip of the folding rollers 819 by the pushing plate 803, and at the same time, the folding rollers 819 are rotated to create a saddle-processed sheet bundle S as shown in
<Pushing position adjustment> In the sheet processing apparatus according to the present embodiment, when pushing and folding a sheet, the pushing position is changed depending on whether a folding score is provided on a sheet or not. Then, when pushing and folding a sheet on which a folding score is formed, the pushing position of the pushing plate 803 is deviated from the center of the folding score. The configuration of the pushing position adjustment will be explained next.
As shown in the flowchart of
Next, the tip stopper 805 is moved based on the presence/absence of a score. First, it is confirmed whether the folding score S-C as shown in
In the present embodiment, as explained above, the relative position of the pushing plate 803 with respect to the sheet is changed depending on whether the folding score S-C exists on the cover sheet or not. The pushing position setting mechanism is constituted which sets the pushing position of the pushing plate 803 with respect to the sheet by the position control of the tip stopper 805.
Thereafter, the prepared booklet is conveyed as a bundle and discharged to the tray (step S210). The above operations are continued up to the final bundle and then the job is completed (steps S210, S211 and S212).
The first position is a position where the distance between the center of the pushing plate 803 and the tip stopper 805 is half the sheet length.
The second position is a position where the distance between the center of the pushing plate 803 and the tip stopper 805 is half the sheet length±deviation amount (hereinafter the deviation amount is the distance between the center of the sheet abutting portion of the pushing plate 803 and the center of the folding score S-C). Considering the following two conditions, the folding score pushing position which is a position at which the pushing plate 803 pushes the folding score S-C depending on the deviation amount.
The first condition is that half the thickness of the abutting portion at which the pushing plate 803 abuts against the sheet is less than the deviation amount. That is, the center line of the abutting portion and the center line of the folding score of the sheet are separated from each other by not less than ½ of the thickness of the abutting portion. The abutting portion of the pushing plate 803 is a portion which abuts against the sheet when the pushing plate 803 abuts against the sheet and which is an abutting tip portion of the pushing plate 803.
The reason why the first condition should be met will be explained with reference to
On the other hand, when the centers are displaced from each other, the force Y for compressing the sheet is generated and the force X for bending the sheet decreases for that amount as shown in
In general, the sheet-like object is stronger against a force in the compression direction than a force in the bending direction. That is, the deformation of the sheet can be suppressed and score reversion can be reduced by shifting the center of the abutting portion of the pushing plate 803 from the center of the folding score S-C so as to change the force in the bending direction which is transmitted to the sheet into a force in the compression direction thereby reducing the force in the bending direction. In order to shift the collision point of the pushing plate 803 from the center of the folding score S-C, it is necessary to that the amount of deviation should be half the thickness of the abutting portion of the pushing plate 803 or more.
Next, the second condition is that the deviation amount should be less than half the width of the folding S-C+half the thickness of the abutting portion of the pushing plate 803.
The reason why the second condition should be met will be explained with reference to
On the other hand, as shown in
That is, by taking the collision point within the folding range of the folding score S-C, the center of the folding score S-C can be a folding position. In order to take the collision point within the folding range of the folding score S-C, it is desirable that the deviation amount should be less than half the width of the folding score S-C+half the thickness of the abutting portion of the pushing plate 803.
Further, as shown in
In summary, given that the thickness of the abutting portion of the pushing plate 803 is t, the width of the folding score S-C is b and the thickness of the sheet is tp, the score reversion can be reduced when t/2 is less than the deviation amount. The misalignment of folding position can be reduced when the deviation amount is less than b/2+t/2+tp. Therefore, the range of the deviation amount in which both problems can be reduced is:
t/2<deviation amount<b/2+t/2+tp (formula 1).
However, in the case of a thin sheet, the thickness tp of the sheet can be neglected.
Next, a result of a test in which a sheet with as folding score is pushed and folded using the sheet processing apparatus in the present configuration will be explained with reference to
Therefore, for the purpose of making the control easier, the control may be made so that the deviation amount increases as the basis weight of the sheet increases. The deviation amount does not necessarily have to be strictly within the range of the formula 1, and fluctuation up to the range of about a few tenths of millimeter is within an allowable range. For example, according to the test indicated in
By setting the deviation amount such that a part of the pushing member falls within the range of the score as explained above, occurrences of the score reversion and folding position misalignment are suppressed so that a booklet which is folded at a folding score can be obtained.
<Other examples of pushing position setting mechanism> In the above embodiment, an example in which the position of the tip stopper 805 is adjusted is shown as a pushing position setting mechanism for setting the pushing position of the pushing plate 803 with respect to the sheet. By adjusting the position of the tip stopper 805 so that the position of the sheet with respect to the pushing plate 803 is adjusted, the relative position of the butting portion of the pushing plate 803 and the folding score of the sheet is adjusted.
However, as the pushing position setting mechanism, as shown in
As shown in
Further, as another example of the pushing position setting mechanism, the configuration can be adopted in which the position of the folding score S-C with respect to the sheet is adjusted. Even with this configuration, the folding score S-C and the pushing plate 803 are shifted thereby obtaining the same effect. In the previously explained example, it is assumed that the folding score S-C is formed at the center portion of the sheet in the sheet conveying direction. However, in the case of changing the position of the folding score S-C, a booklet which is folded at a position deviated from the center is obtained.
When realizing this embodiment, the configuration can be adopted in which the sheet S is stopped at a position at which the center of the sheet S is deviated from the center of the scoring portion 202 by the deviation amount based on the sheet detecting result of the position sensor 203 and the conveying length of the sheet S, and a score is formed by the scoring portion 202 in the scoring device 200 shown in
In the embodiment in which the position of the folding score is adjusted, the score processing is performed on the sheet by the scoring device 200 and the information of this score processing is transmitted to the sheet processing apparatus 300 via the CPU 401, thereby switching the control. However, it is also possible to provide a scoring unit in the sheet processing apparatus 300, and to switch the presence/absence of the score processing in the sheet processing apparatus and the position of the pushing and folding.
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 the benefit of Japanese Patent Application No. 2016-138153, filed Jul. 13, 2016, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-138153 | Jul 2016 | JP | national |
