The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2013-007720 filed in Japan on Jan. 18, 2013 and Japanese Patent Application No. 2013-224320 filed in Japan on Oct. 29, 2013.
1. Field of the Invention
The present invention relates to a sheet processing apparatus, an image forming system, and a method of additionally folding a sheet bundle, and particularly relates to a sheet processing apparatus having a function of performing folding processing on a sheet-shaped recording medium such as paper, recording paper, and transfer paper (hereinafter simply referred to as a “sheet” in this specification), an image forming system including a sheet processing apparatus, and a method of additionally folding a sheet bundle executed by the sheet processing apparatus.
2. Description of the Related Art
A conventional post-processing apparatus used in combination with an image forming apparatus such as a copying machine binds a saddle stitched booklet by stitching a sheet or a plurality of sheets at its center part and folding the same at the center part with a pair of folding rollers arranged parallel to the direction of sheet folding. In addition, a technique is already known that carries out additional folding with a roller moving along the back of a saddle stitched booklet so as to strengthen a fold of the booklet.
Such an additionally folding technique performs additional folding on the back (a fold part) of a booklet (a sheet bundle) by putting a roller standing by on the outside of the booklet on the back of the booklet and moving the roller.
Known examples of this kind of additionally folding technique are disclosed in Japanese Patent Application Laid-open No. 2008-207964 and Japanese Patent Application Laid-open No. 2009-126685.
Japanese Patent Application Laid-open No. 2008-207964 describes a folding means for performing folding processing on a sheet or a sheet bundle with a plurality of bound sheets and a fold strengthening mechanism for strengthening a fold of the sheet or the sheet bundle folded by the folding means by pressing the fold. The fold strengthening mechanism and the folded sheet(s) move relatively to each other along the fold and intermittently stop during the move.
Japanese Patent Application Laid-open No. 2009-126685 describes a sheet folding device that includes folding means for performing folding processing on a sheet-shaped recording medium that is carried in and additional folding means for performing additional folding after the folding processing by the folding means by moving on a fold of the sheet-shaped recording medium in a direction perpendicular to a sheet-ejecting direction and pressurizing the fold. The additional folding means is inclined from the normal of a medium surface of the sheet-shaped recording medium in a direction of force generated in a moving direction when the fold is pressurized.
According to Japanese Patent Application Laid-open No. 2008-207964, the fold strengthening mechanism and the folded sheet(s) relatively move along a fold and intermittently stop during the move. Because of this, strength is increased with regard to additional folding; however, productivity is conversely decreased.
According to Japanese Patent Application Laid-open No. 2009-126685, a direction for applying an energizing force is inclined from the moving direction of an additional folding mechanism for the purpose of load reduction. In this case, because the additional folding mechanism consists of a fixed receiver opposed to a pressurizing roller, a pressuring force against a sheet bundle is generated in the thickness direction of the sheet bundle. This requires a stiffer device, which results in increased size and cost of the apparatus.
Therefore, there is a need for a sheet processing apparatus capable of performing additional folding on a fold part of a folded sheet bundle without reducing productivity or increasing the size or cost of the apparatus.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to an embodiment, there is provided a sheet processing apparatus that includes a pressing unit including a first pressing member and a second pressing member, the pressing unit being configured to sandwich and press a fold part of a folded sheet bundle between the first pressing member and the second pressing member; and a moving unit configured to move a position pressed by the pressing unit in a direction of a fold of the sheet bundle. A position pressed by the first pressing member on the sheet bundle and another position pressed by the second pressing member on the sheet bundle are shifted with respect to each other in the direction of the fold of the sheet bundle.
According to another embodiment, there is provided a sheet processing apparatus that includes a pressing unit including a first pressing member and a second pressing member, the pressing unit being configured to sandwich and press a fold part of a folded sheet bundle between the first pressing member and the second pressing member; and a moving unit configured to move a position pressed by the pressing unit in a direction of a fold of the sheet bundle. An angle between a thickness direction of the sheet bundle and a direction of a tangent line at a nip position with the sheet bundle being sandwiched between the first pressing member and the second pressing member is greater than 60 degrees but less than 90 degrees.
According to still another embodiment, there is provided an image forming system that includes the sheet processing apparatus according to any one of the above embodiments.
According to still another embodiment, there is provided a method of additionally folding a folded sheet bundle executed by a sheet processing apparatus that includes a pressing unit configured to sandwich and press a fold part of the folded sheet bundle between a first pressing member and a second pressing member, and a moving unit configured to move a position pressed by the pressing unit in a direction of a fold of the sheet bundle. The method includes moving the pressing unit in a state where a position pressed by the first pressing member on the sheet bundle and another position pressed by the second pressing member on the sheet bundle are shifted with respect to each other in the direction of the fold of the sheet bundle.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
According to embodiments of the present invention, when additional folding is performed on the back of a saddle stitched booklet, the back of the booklet is displaced in the thickness direction of the booklet by applying a pressurizing force of a pair of additional folding rollers, which moves in the sheet width direction of the booklet, in a direction inclined from the thickness direction of the sheet.
Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings.
The first sheet post-processing apparatus 1 has a function of making a sheet bundle by receiving sheets one by one from the image forming apparatus PR, sequentially stacking and aligning the sheets, and thereafter making a sheet bundle in a stacking unit. The first sheet post-processing apparatus ejects the sheet bundle to the second sheet processing apparatus 2 in the subsequent stage through sheet bundle ejecting rollers 10. The second sheet post-processing apparatus 2 is a saddle-stitching bookbinding apparatus that receives the conveyed sheet bundle and performs saddle stitching and center folding thereon (in this specification, the second sheet post-processing apparatus may be referred to as a “saddle-stitching bookbinding apparatus”).
The saddle-stitching bookbinding apparatus 2 directly ejects the bound booklet (the sheet bundle) or ejects it to a sheet processing apparatus in the subsequent stage. The image forming apparatus PR forms a visible image on a sheet-shaped recording medium based on input image data or image data of a read image. Examples of the apparatus include a copying machine, a printer, a facsimile, and a digital multifunction peripheral having at least two functions of these. The image forming apparatus PR uses known schemes such as electrophotography and liquid droplet ejection, and any image forming scheme is applicable.
In
The downstream side of the entrance rollers 201 of the entrance conveying path 241 has a bifurcating claw 202. In
The center folding conveying path 243 is provided with a bundle conveying upper guide plate 207 that guides a sheet bundle in the upper part of a folding plate 215 for performing center folding and a bundle conveying lower guide plate 208 that guides a sheet bundle in the lower part of the folding plate 215. The bundle conveying upper guide plate 207 is provided with, from the top, bundle conveying upper rollers 205, a trailing end slapping claw 221, and bundle conveying lower rollers 206. The trailing end slapping claw 221 is provided in a standing manner to a trailing-end slapping-claw driving belt 222 that is driven by a driving motor (not shown). The trailing end slapping claw 221 slaps (presses) the trailing end of a sheet bundle against a movable fence side, which will be described later, by a back-and-forth rotating motion of the trailing-end slapping-claw driving belt 222, and thereby performs an alignment operation on the sheet bundle. When a sheet bundle is carried in or lifted up for center folding, the trailing end slapping claw 221 recedes from the center folding conveying path 243 on the bundle conveying upper guide plate 207 (the position indicated by the dotted line in
Numeral 294 denotes a trailing-end slapping-claw HP sensor for detecting the home position of the trailing end slapping claw 221, which detects the position indicated by the dotted line in
The bundle conveying lower guide plate 208 is provided with, from the top, a saddle stitching stapler S1, saddle stitching jogger fences 225, and a movable fence 210. The bundle conveying lower guide plate 208 receives a sheet bundle conveyed through the bundle conveying upper guide plate 207. The bundle conveying lower guide plate 208 includes the pair of saddle stitching jogger fences 225 in its width direction, and the movable fence 210 that is movable up and down and abuts (supports) the leading end of a sheet bundle in its lower part.
The saddle stitching stapler S1 stitches a sheet bundle at its center part. The movable fence 210 moves upward and downward in a state of supporting the leading end of the sheet bundle, and arranges the center part of the sheet bundle at an opposed position to the saddle stitching stapler S1, at which stapling processing, that is, saddle stitching is performed. The movable fence 210 is supported by a movable fence driving mechanism 210a, and is movable from the position of a movable fence HP sensor 292 at the upper part of the movable fence driving mechanism 210a in
The space between the bundle conveying upper guide plate 207 and the bundle conveying lower guide plate 208, which is almost the center part of the center folding conveying path 243, is provided with the folding plate 215, a pair of folding rollers 230, an additional folding roller unit 260, and paper ejecting lower rollers 231. The additional folding roller unit 260 includes additional folding rollers arranged at the upper and the lower sides of an ejected paper conveying path located between the pair of folding rollers 230 and the paper ejecting lower rollers 231. The folding plate 215 is movable back and forth in the horizontal direction in
The lower end side of the bundle conveying upper guide plate 207 has a sheet bundle detecting sensor 291 that detects the leading end of a sheet bundle carried in the center folding conveying path 243 and passing through the center folding position. The ejected paper conveying path 244 is provided with a fold part passing sensor 293 that detects the leading edge of a center folded sheet bundle and recognizes passing of the sheet bundle.
The saddle-stitching bookbinding apparatus 2, which is configured as schematically illustrated in
A sheet bundle SB carried in the center folding conveying path 243 is conveyed through the center folding conveying path 243 to its lower part by the entrance rollers 201 and the bundle conveying upper rollers 205. The sheet bundle SB is recognized of its passing by the sheet bundle detecting sensor 291, and is thereafter conveyed to the position where the leading end of the sheet bundle SB abuts the movable fence 210 by the bundle conveying lower rollers 206 as illustrated in
In this state, as illustrated in
The saddle stitching jogger fence 225 performs an alignment operation in a width direction (a direction perpendicular to the sheet conveying direction), and the movable fence 210 and the trailing end slapping claw 221 perform alignment operations in the conveying direction. Alignment operations in the width direction and the conveying direction of the sheet bundle SB are thereby completed. In this process, respective pushing amounts of the trailing end slapping claw 221 and the saddle stitching jogger fence 225 are changed to the most appropriate value for the alignment based on size information of the sheet, information on the number of sheets in the sheet bundle, and information on the thickness of the sheet bundle.
A large thickness of a bundle reduces the space in the conveying path, and therefore, a single alignment operation may not be suitable for complete alignment. In such a case, the number of alignment operations is increased, and a better alignment state is thereby achieved. A larger number of sheets require a longer time for sequentially stacking the sheets in the upstream, which takes long until the next sheet bundle SB is received. As a result, increasing the number of alignment operations does not cause any time loss as the whole system, and therefore a fine alignment state is efficiently achieved. It is therefore possible to control the number of alignment operations depending on the processing time in the upstream.
The stand-by position of the movable fence 210 is usually set at a position where the saddle stitched position of the sheet bundle SB is opposed to the stitching position of the saddle stitching stapler S1. Alignment at this position makes it possible to perform stitching processing on the sheet bundle SB immediately at a stacked position without moving the movable fence 210 to the saddle stitched position of the sheet bundle SB. At the stand-by position, a stitcher in the saddle stitching stapler S1 is driven in the direction of the arrow b toward the center part of the sheet bundle SB, saddle stitching processing is performed between the stitcher and a clincher, whereby the sheet bundle SB is saddle-stitched.
The movable fence 210 is positioned based on pulse control from the movable fence HP sensor 292, and the trailing end slapping claw 221 is positioned based on pulse control from the trailing-end slapping-claw HP sensor 294. The control for positioning the movable fence 210 and the trailing end slapping claw 221 is executed by a central processing unit (CPU) on a control circuit (not shown) for the saddle-stitching bookbinding apparatus 2.
The sheet bundle SB having undergone saddle stitching in the state of
When the sheet bundle SB reaches the position of
The sheet bundle SB with its center part folded in half in the state of
The additional folding roller upper unit 261 is supported by a supporting member 265b movably upward and downward against the unit moving mechanism 263, whereas the additional folding roller lower unit 262 is attached to the lower end of the supporting member 265b of the pressing mechanism 265 in a stationary manner. An additional folding upper roller 261a of the additional folding roller upper unit 261 is pressable against an additional folding lower roller 262a, and pressure is applied by sandwiching a sheet bundle SB between the nip of both. A pressurizing force is given by a pressurizing spring 265c that pressurizes the additional folding roller upper unit 261 with an elastic force. The additional folding roller unit 260 moves in the width direction of the sheet bundle SB (the direction of the arrow D1 in
The guiding pin 265a of the pressing mechanism 265 is fit into the guiding path 270 in a state of loose fit in a movable manner, whereby the pressing mechanism 265 is moved along the guiding path 270. In other words, the guiding path 270 functions as a cam groove and the guiding pin 265a functions as a cam follower that changes its position while moving along the cam groove.
The additional folding roller unit 260 starts moving forward from the initial position (
When the additional folding roller unit 260 reaches the third guiding path 273 in the vicinity of the center of the sheet bundle SB (
The additional folding roller unit 260 moves further in the direction of the arrow D2, maintained in the pressing state (
The additional folding roller unit 260 thereafter starts moving backward by the unit moving mechanism 263 (
When the pressing mechanism 265 enters the fifth guiding path 275, it turns to a complete pressing state. Then, the pressing mechanism 265 moves in the direction of the arrow D3 straight along the fifth guiding path 275 (
In this way, additional folding is performed on the sheet bundle SB by moving the additional folding roller unit 260 back and forth. Specifically, the additional folding roller unit 260 starts additional folding over a side of the sheet bundle SB from the center part of the sheet bundle SB, and gets through the end part SB2 of the sheet bundle SB. Thereafter, the additional folding roller unit 260 passes on the additionally folded sheet bundle SB, starts additional folding over the other side of the sheet bundle SB from the center part of the sheet bundle SB, and performs additional folding by the operation of getting through the other end part SB2 of the sheet bundle SB.
With this operation, when starting additional folding and when getting through one side and back to the other side, the pair of additional folding rollers 261a and 262a does not come into contact with the end part SB2 of the sheet bundle SB nor pressurize it from the outside of the sheet bundle SB. This means that the additional folding roller unit 260 is in a pressing-release state when it passes on the end part SB2 of the sheet bundle SB from the outside of the end part. As a result, no damage is caused on the end part SB2 of the sheet bundle SB. In addition, because the additional folding roller unit 260 performs additional folding from the vicinity of the center part of the sheet bundle SB through the end part SB, it runs only a short distance in a state of contacting with the sheet bundle SB in performing the additional folding. That makes twists, which may cause creases or the like, unlikely to be accumulated. Accordingly, no damage is caused on the end part SB2 of the sheet bundle SB in performing additional folding on the fold part (the back) SB1 of the sheet bundle SB, and furthermore, it is possible to prevent twists and creases on the fold part SB1 and its vicinity due to accumulation of twists.
To prevent the pair of additional folding rollers 261a and 262a from running on the end part SB2 from the outside of the end part SB2 of the sheet bundle SB, the operations illustrated in
L>La+Lb
where La denotes a distance for which the additional folding roller unit 260 moves on the sheet bundle SB in a pressing-release state in its forward movement and Lb denotes another distance for which the additional folding roller unit 260 moves on the sheet bundle SB in a pressing-release state in its backward movement (
Furthermore, it is preferable that the distances La and Lb are substantially equal and pressing is started in the vicinity of the center part in the width direction of the sheet bundle SB (
The additional folding roller unit 260 in this embodiment includes the additional folding roller lower unit 262 and performs additional folding with the pair of additional folding rollers 261a and 262a. However, instead of using the additional folding roller lower unit 262, such a configuration is applicable that includes the additional folding roller upper unit 261 and a receiver (not shown) having an abutment surface opposed to the additional folding roller upper unit 261 so as to press a sheet bundle between both.
Furthermore, the additional folding roller unit 260 in this embodiment is configured such that the additional folding roller upper unit 261 is movable up and down whereas the additional folding roller lower unit 262 is stationary upward and downward. However, the additional folding roller lower unit 262 can also be configured to be movable upward and downward. With this configuration, the pair of additional folding rollers 261a and 262a is symmetrically operated in contacting with and detaching from the same the additionally folded position. As a result, the additionally folded position is maintained constant regardless of the thickness of a sheet bundle SB, and further prevention from damage such as a scratch is achieved.
The additional folding upper roller 261a is supported rotatably by an upper roller holder 261b on the side of the additional folding roller upper unit 261. The additional folding lower roller 262a is supported rotatably by a lower roller holder 262b on the side of the additional folding roller lower unit 262. The unit moving mechanism 263 includes a slider member 263a. The slider member 263a is meshed with a timing belt (not shown) at a timing belt meshing part 263b. With this configuration, when the timing belt is driven by a motor (not shown), the unit moving mechanism 263 moves in the width direction of the sheet bundle SB in synchronization with movement of the timing belt.
As earlier described, the additional folding roller upper unit 261 is supported movably upward and downward (the thickness direction t of sheets, see
Unlike the standard configuration of the additional folding roller unit 260 illustrated in
The shift δ is a shift between the respective rotation shafts of the additional folding upper roller 261a and the additional folding lower roller 262a in the moving direction of the additional folding roller unit 260.
It is preferable that the angle θ is greater than 60 degrees but less than 90 degrees.
The direction of a pressing force F generated between the additional folding upper roller 261a and the additional folding lower roller 262a perpendicularly intersects with the direction of the tangent line G, and the direction thus inclines from the thickness direction t of the sheet bundle SB. Accordingly, as illustrated in the enlarged view of a pressed portion in
In this embodiment, the pressing force F acts along a line L that couples respective centers 261a1 and 262a1 of the additional folding upper roller 261a and the additional folding lower roller 262a. In this process, because the direction of the pressing force F shifts from the thickness direction t of the sheet bundle SB, not only the pressing force F but a force that inflects the fold part SB1, in other words, a force in a bending direction is applied on the fold part SB1. The force in a bending direction stretches some fibers of the sheets or cuts the fibers. Pressing in this state enables to make the thickness of the fold part SB1 small compared with a case where pressing is applied only in the thickness direction t (θ=90 degrees) of the sheet bundle SB.
The angle θ varies depending on the thickness of the sheet bundle SB. Provided that the shift amount δ in the width direction of the sheets is constant, the distance between the centers 261a1 and 262a1 is short when the thickness of the sheet bundle SB is small, whereas the distance is long when the thickness is large. The former case has a smaller angle θ. Accordingly, the pressing force F generated on the nip between the additional folding upper roller 261a and the additional folding lower roller 262a also varies.
In other words for the angle θ set as earlier described, the direction of the tangent line G at the nip position shifts from the conveying direction (the direction of the arrow D5) of the additional folding roller unit 260. Shifting means that the direction inclines from, that is, non-parallel to, the conveying direction (the direction of the arrow D5) of the additional folding roller unit 260.
In this embodiment, the additional folding upper roller 261a and the additional folding lower roller 262a are configured rotatably and to perform additional folding by pressurizing the sheet bundle SB as rolling on both surfaces thereof. However, a fixed member can replace such rollers for pressurizing. In such a case, to generate a pressing force F in an inclined direction from the thickness direction of a booklet, the outer shape of the fixed member needs to be a curved surface as illustrated in
In the above-described embodiment, additional folding is carried out by moving the additional folding roller unit 260 with the sheet bundle SB maintained in a stop state; however, the relation between both is relative. Such a configuration is thus possible in which the additional folding roller unit 260 is maintained in a stop state in the direction of a sheet fold, whereas the pair of additional folding rollers 261a and 262a rotates in a state of pressing the fold part SB1 of the sheet bundle SB. This example is illustrated in
In this example, as illustrated in
In
The additional folding roller unit 260 in this embodiment includes the additional folding roller lower unit 262 and performs additional folding with the pair of additional folding rollers 261a and 262a. However, instead of using the additional folding roller lower unit 262, such a configuration is applicable that involves the additional folding roller upper unit 261 and a receiver (not shown) having an abutment surface opposed to the additional folding roller upper unit 261 and presses a sheet bundle between both. Because this kind of configuration does not require the additional folding lower roller 262a, a cost reduction for this roller is achieved.
Furthermore, the additional folding roller unit 260 in this embodiment is configured such that the additional folding roller upper unit 261 is movable upward and downward, whereas the additional folding roller lower unit 262 is stationary upward and downward. However, the additional folding roller lower unit 262 can also be configured to be movable upward and downward. With this configuration, the upper roller 261a and the lower roller 262a are symmetrically operated in contacting with and detaching from the additionally folded position. As a result, the additionally folded position is maintained constant regardless of the thickness of the sheet bundle SB, and further prevention from damage such as a scratch is thus achieved.
The present embodiments can provide the following advantageous effects.
1) The saddle-stitching bookbinding apparatus 2 (the sheet processing apparatus) includes a pressing unit that sandwiches and presses the fold part SB1 of the folded sheet bundle SB between the additional folding upper roller 261a and the additional folding lower roller 262a (first and second pressing members) and the unit moving mechanism 263 (a moving unit) that moves a pressing position of the pressing unit in the direction of a fold of the sheet bundle SB. In this case, a position on the sheet bundle SB pressed by the additional folding upper roller 261a (the first pressing member) and another position on the sheet bundle SB pressed by the second pressing member are shifted in the direction of the fold of the sheet bundle by δ, for example. As a result, the pressing force F on the fold part SB1 of the sheet bundle SB is not generated in the thickness direction t of the sheet bundle. In addition, additional folding can be carried out without an intermittent stop during a movement. Consequently, it is possible to carry out additional folding without decreasing productivity or increasing the size or cost of the apparatus.
This is because the shift as earlier described makes the direction of the pressing force F generated by the additional folding roller unit 260, which moves in the sheet width direction of the sheet bundle SB in performing additional folding, inclined from the sheet thickness direction t. As a result, a force that inflects the fold part SB1 is applied. With this force, some fibers of the sheets are stretched or cut. Pressing in such a state can reduce the thickness of the fold part SB1 with small force compared with a case of pressing only in the thickness direction t of the sheet bundle SB.
2) When an angle θ between the direction of the tangent line G at a position of a nip in sandwiching the sheet bundle SB between the additional folding upper roller 261a and the lower roller 262a (the first and the second pressing members) and the thickness direction t of the sheet bundle SB is set at a value greater than 60 degrees but less than 90 degrees, the direction of the pressing force F generated by the additional folding roller unit 260 moving in the sheet width direction of the sheet bundle SB in additional folding is inclined from the sheet thickness direction t, similarly to the case of 1). As a result, a force that inflects the fold part SB1 is applied. With this force, some fibers of the sheets are stretched or cut. Pressing in such a state can reduce the thickness of the fold part SB1 with small force compared with a case of pressing only in the thickness direction t of the sheet bundle SB.
3) In a forward movement, the additional folding roller unit 260 starts pressing on the sheet bundle SB from a predetermined position in the width direction of the sheet bundle SB and releases the pressing after it gets through one end part SB2 of the sheet bundle SB. In a backward movement, it starts pressing from the front side of the predetermined position and gets through the other end part SB2 of the sheet bundle SB. As a result, its running time for additional folding is shortened, and productivity is thereby improved.
4) Because the predetermined position is located in the center part of the sheet bundle SB, additional folding in the backward movement starts from a part of the sheet bundle SB that has been additionally folded and made thin by the forward movement. This results in a reduction in a driving load, and sufficient additional folding is thus attained even at a higher speed.
5) The saddle-stitching bookbinding apparatus 2 (the sheet processing apparatus) includes the additional folding roller unit 260 (a pressing unit) that presses a fold part SB1 of a folded sheet bundle SB and performs additional folding and the unit moving mechanism 263 (a moving unit) that moves the additional folding roller unit 260 back and forth in the width direction of the sheet bundle SB. The additional folding roller unit 260 includes the additional folding upper roller 261a and the additional folding lower roller 262a (first and second pressing members). Because the direction of the tangent line G at a nip position in sandwiching the sheet bundle SB between the additional folding upper roller 261a and the additional folding lower roller 262a is shifted from the moving direction of the additional folding roller unit 260, the pressing force F on the sheet bundle is not generated in the thickness direction t of the sheet bundle. Consequently, the same advantageous effects as in 1) are achieved.
6) The additional folding roller unit 260 (a pressing unit) includes the pressurizing spring 265c (an elastic member) that generates a pressing force between the additional folding upper roller 261a and the additional folding lower roller 262a (between the first and the second pressing members). This means that no driving sources for pressing are required, and downsizing of the apparatus and a cost reduction are thereby achieved.
7) The additional folding roller unit 260 applies the pressing force F in the thickness direction t of the sheet bundle SB with the pressurizing spring 265c. In this process, the direction in which the pressing force F is applied coincides with a direction that passes through the respective rotation shafts of the additional folding upper roller 261a and the additional folding lower roller 262a (
8) The additional folding roller unit 260 applies the pressing force F in the thickness direction t of the sheet bundle SB with the pressurizing spring 265c. In this process, respective rotation shafts of the additional folding upper roller 261a and the additional folding lower roller 262a are shifted in a direction in which the additional folding roller unit 260 is moved by the unit moving mechanism 263 (
9) In a state where one of the additional folding upper roller 261a and the additional folding lower roller 262a is fixed in the sheet thickness direction, the additional folding roller unit 260 applies the elastic force to the other one of the first and the second pressing member with the elastic member. Downsizing of the apparatus and a cost reduction are thereby achieved.
10) The additional folding roller unit 260 applies a pressing force on both the additional folding upper roller 261a and the additional folding lower roller 262a with a pressurizing spring to make them movable in the sheet thickness direction t. This enables even additional folding, and forming the fold part SB1 in high quality is thereby achieved.
11) The saddle-stitching bookbinding apparatus 2 includes the guiding member 264 (a guiding unit) that determines a pressing start and release of the additional folding roller unit 260, and the additional folding roller unit 260 (a pressing unit) is moved along the guiding path 270 of the guiding member 264 by the unit moving mechanism 263. This enables a pressing start and pressing release in the course of the movement.
12) The guiding member 264 (a guiding unit) includes the first and the second path switching claws 277 and 278 (switching units) that switch a path. Pressing and pressing release are switched from each other in response to a path switch by the first and the second path switching claws 277 and 278. This means that merely moving along the path makes it possible to switch operations of a pressing start and a pressing release.
13) The guiding path 270 (a path) includes the first to the sixth guiding paths 271 to 276. The guiding paths 271 to 276 function as a cam groove, and operations of a pressing start and release are thereby performed at a stable position in a stable timing.
14) The additional folding upper roller 261a and the additional folding lower roller 262a (first and second pressing members) each include a roller (a rotating member) that rolls on the surface of the sheet bundle SB, which enables movement of the sheet bundle SB in the width direction with a small load. Energy efficiency is thereby improved.
A sheet bundle is denoted by SB in the present embodiments. Likewise, a fold part is denoted by SB1, the additional folding roller unit 260 corresponds to a pressing unit, the unit moving mechanism 263 corresponds to a moving unit, the saddle-stitching bookbinding apparatus 2 corresponds to a sheet processing apparatus, the additional folding upper roller 261a corresponds to a first pressing member, the additional folding lower roller 262a corresponds to a second pressing member, a nip is denoted by N, a tangent line is denoted by G, the width direction of a sheet bundle is denoted by t, the pressurizing spring 265c corresponds to an elastic member, a pressing force is denoted by F, shift of the pressing unit in a moving direction is denoted by δ, the guiding member 264 corresponds to a guiding unit, the first and the second path switching claws 277 and 278 correspond to a switching unit, the path includes the guiding path 270 and the first to the sixth guiding paths 271 to 276, and the saddle-stitching bookbinding apparatus 2 and/or the image forming apparatus PR are included in an image forming system.
According to the embodiments, it is possible to perform additional folding on a fold part of a folded sheet bundle without reducing productivity or increasing the size or cost of the apparatus.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
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