Image forming apparatus

Information

  • Patent Grant
  • 6268909
  • Patent Number
    6,268,909
  • Date Filed
    Thursday, May 13, 1999
    25 years ago
  • Date Issued
    Tuesday, July 31, 2001
    23 years ago
Abstract
In an image forming apparatus that folds plural sheets in folio, an image forming unit forms images an a recording area on the sheets and forms a margin between the recording area and another forming area. A projecting unit folds the sheets upon nipping the sheets between two rollers by projecting between the two rollers so as to nip a part of the sheets where the margin is formed at first. The projecting unit projects to the margin of prescribed width of images formed at an image forming apparatus body to fold the plural sheets.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




This invention relates to an image forming apparatus having a sheet processing apparatus for fetching sequentially sheets on which images are formed by an image forming means, stapling the plural sheets with a stapling means, and folding the sheets in folio.




2. Description of Related Art




Some image forming apparatus such as photocopiers or the like today can do bookbinding by stapling plural sheets and folding the sheets in folio where connected with a sheet processing apparatus. Such an apparatus forms images on double sides or the sheets at an image forming apparatus body, fetches sequentially the sheets, staples the sheets at about the center of the sheet bundle upon driving the stapler unit, and folds the sheets in folio where the sheets are conveyed to a folding means.




As a structure for folding the sheets in folio, it is structured by a folding roller means made of a roller pair, and a projecting means made of a projecting plate and so on. The projecting plate folds the sheet bundle upon projecting the stapled position of the sheet bundle between the nip portions, and the folded sheet bundle is pressed and conveyed by the roller pair to fold the bundle in folio. Therefore, the sheet bundles delivered to the delivery tray are delivered in a state that the sheet bundles are folded in folio and bound in a book form at the center stapled position of the sheets.




Where the sheet processing apparatus performs a folding operation, if the frictional coefficient between sheets is low, the sheets may slip when the sheet bundle folded in folio is pulled by a folding roller, thereby possibly generating tears at the stapling positions. Such tears tend to occur right after the start of the folding operation. At that time, if images are formed at the folding start positions and toners cling to there, the sheets located inside in a fold form when the folding roller pulls inside the sheets are easily returned, thereby causing tears easily.




This invention is made with respect to the above viewpoint and it is an object to provide an image forming apparatus capable of bookbinding sheet bundles without generating tears when the sheet bundles are pulled inside.




SUMMARY OF THE INVENTION




A representative structure of the invention to accomplish the above object is characterized in an image forming apparatus for folding plural sheets in folio including: two rollers for folding sheets in folio; and projecting means for folding the sheets upon nipping the sheets between the two rollers by projecting between the two rollers, wherein the projecting means projects to a margin of a prescribed width of images formed at an image forming apparatus body to fold the plural sheets.




In another representative structure of the invention, an image forming apparatus for folding plural sheets in folio including: an image forming apparatus body having image forming means for forming images on the sheets; and a sheet processing apparatus for stapling the plural sheets on which images are formed at the image forming apparatus body and bookbinding the sheets in folio, wherein a margin of a prescribed width is placed at a folded portion of the sheets when the images are formed at the image forming apparatus body on the sheets to be folded and made into a book in the sheet processing apparatus.




With the above structures, when the sheet bundle is pulled inside at a sheet processing apparatus, a margin is placed in advance on the sheet, so that the frictional force between the sheets will not be lowered at that location. Therefore, the plural sheets can be folded in folio surely in the sheet processing apparatus, thereby preventing tears and wrinkles from occurring due to separation of the plural sheets.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is an illustration showing the whole structure of an image forming apparatus;





FIG. 2

is an illustration showing a cross-sectional structure of a finisher unit;





FIG. 3

is an illustration showing a cross-sectional structure of a stitcher unit;





FIG. 4

is a perspective illustration showing a sheet status of a sheet delivered by an offset operation;





FIG. 5

is an illustration showing squeezing for a sheet delivered by the offset operation and a status of the delivered sheet;





FIG. 6

is an illustration showing a status in which a proceeding sheet is left over in a buffer path in a double sheet delivery control;





FIG. 7

is an illustration showing a status in which two sheets are conveyed at the same time in the double sheet delivery control;





FIG. 8

is a flowchart showing a delivery signal transmission timing for the proceeding sheet in the double sheet delivery control;





FIG. 9

is a flowchart showing a delivery signal transmission timing for the proceeding sheet in the double sheet delivery control according to this embodiment;





FIG. 10

is an illustration showing a status of a sheet in a case where a side guide top is not used as a guide for sheet delivery;





FIG. 11

is an illustration showing a status of a sheet in a case where a side guide top is used as a guide for sheet delivery according to this embodiment;





FIG. 12

is an illustration showing a status for escaping the side guide after the front end of the sheet is nipped by a downstream delivery roller pair;





FIG. 13

is a cross section showing a position of the stack tray as the essential portion;





FIG. 14

is an enlarged view showing as the essential portion a status of a rocking guide and a paddle when the sheets are pulled back;





FIG. 15

is an enlarged view showing as the essential portion a status of a rocking guide and a paddle when the sheets are pulled back;





FIG. 16

is a view showing an example of a paddle shape;





FIG. 17

is a diagram exemplifying drive times of the paddle, moving speed of the side guide, and alignment control according to the sheet size;





FIG. 18

is an illustration showing a rear end stopper,





FIG. 19

is a diagram showing a waiting position when the stapler serves as a rear end stopper,





FIG. 20

is a diagram showing a width alignment status by the side guide;





FIG. 21

is a diagram showing a width alignment status by the side guide;





FIG. 22

is a diagram showing a status of a knurled belt during the sheet width alignment by the side guide;





FIG. 23

is a view showing an example of a knurled belt shape;





FIG. 24

is a diagram showing a width alignment status by the side guide;





FIG. 25

is an illustration showing an operation status or a rocking guide and a drive mechanism of a downstream delivery roller;





FIG. 26

is an illustration showing an operation status of the rocking guide and the drive mechanism of the downstream delivery roller;





FIG. 27

is an illustration showing an operation status of the rocking guide and the drive mechanism of the downstream delivery roller;





FIG. 28

is a flowchart showing a flow of position control when the rocking guide is made closed;





FIG. 29

is a flowchart showing a flow of an extraordinary completion processing when the rocking guide is made closed;





FIG. 30

is an illustration showing a low speed drive control when the rotational direction of a drive motor is switched;





FIG. 31

is an illustration showing a staple operation according to this embodiment;





FIG. 32

is an illustration showing a stapler and a staple cartridge





FIG. 33

is a flowchart illustrating staple cartridge exchange processing;





FIG. 34

is a flowchart illustrating staple initialization processing;





FIG. 35

is an illustration of a conventional control when staple jamming occurs;





FIG. 36

is a diagram showing a control when staple jamming occurs according to this embodiment;





FIG. 37

is an illustration showing a stapler initialization when a stapler door is closed;





FIG. 38

is an illustration showing a setting up speed for delivery motor;





FIG. 39

is an illustration showing a status that the sheet is delivered to the stack tray and a perspective view showing a schematic structure of an essential portion of a tray unit portion;





FIG. 40

is a flowchart showing a control when full stacking is detected;





FIG. 41

is a flowchart showing a full stacking detection for special sheets;





FIG. 42

is a block diagram showing an outline of a control system for finisher unit;





FIG. 43

is a partially enlarged view showing a structure of a pickup roller;





FIG. 44

is an illustration showing operation of the pickup roller;





FIG. 45

is a view showing a shape of a vertical path;





FIG. 46

is a diagram showing a shape of staked sheets;





FIG. 47

is an illustration showing a drive mechanism for stopper;





FIG. 48

is an illustration showing a structure of the stapler unit;





FIG. 49

is an illustration showing staple filling to the staple cartridge;





FIG. 50

is an illustration showing a motor drive current waveform during the staple initialization;





FIG. 51

is an illustration showing a status that a staple fitted in a groove on the anvil is released by the pickup roller;





FIG. 52

is a flowchart in a case where the shifting amount of the stopper to the staple stopping position and folding stopping position is automatically adjustable;





FIG. 53

is an illustration showing a movable structure of a movable roller;





FIG. 54

is a side illustration showing a drive structure of the folding unit;





FIG. 55

is a plan illustration showing the drive structure of the folding unit;





FIG. 56

is an illustration showing a stopper structure of a projecting plate;





FIG. 57

is an illustration showing a structure of a cam member for adjusting the center of the projecting plate;





FIG. 58

is a state illustration when the projecting plate is pulled back;





FIG. 59

is an illustration showing mechanisms of occurrences of tears and wrinkles in sheets during the folding operation;





FIG. 60

is an illustration showing an image forming area and a margin for folding on a sheet;





FIG. 61

is a diagram showing a layout of an intermediate sensor, a stopper sensor, and a delivery sensor which detect tears in sheets;





FIG. 62

is an illustration showing a shiftingly stacking state of sheet bundles on a stack tray;





FIG. 63

is an illustration showing a stacking state of sheet bundles on a stack tray; and





FIG. 64

is a block diagram showing an outline of a control system for stitcher unit.











DESCRIPTION OF PREFERRED EMBODIMENTS




Referring to the drawings, an embodiment according to the invention is shown.





FIG. 1

is an illustration showing an inner structure of a photocopier as an example of an image forming apparatus to which this invention is applicable. This photocopier is structured having an image forming apparatus body A combined with a sheet processing apparatus B. The sheet processing apparatus B includes a finisher unit C capable of sorting the sheets on which images are recorded at the image forming apparatus body A according to the number of copies and a stitcher unit D capable of bookbinding the multiple sheets upon stapling the sheets.




Herein, the whole structure of the image forming apparatus is generally described, and subsequently, concerning the structure of the sheet processing apparatus, the finisher unit C and the stitcher unit D are described in detail.




The Whole Structure of the Image Forming Apparatus




The image forming apparatus body A reads, in an optical way with an optical means


2


, original documents automatically fed from the original document feeding apparatus


1


mounted on the top of the apparatus and transmits the read information to an image forming means


3


as digital signals for recording the information on recording sheets such as plain papers or OHP sheets




Multiple sheet cassettes


4


in which sheets of various types are contained are set at the lower portion of the image forming apparatus body A, and the image forming means


3


records images in an electrophotographic method on the sheets fed by the conveyance rollers


5


from the sheet cassettes


4


. That is, latent images are formed on a photosensitive drum


3




b


by radiating a laser beam on the photosensitive drum


3




b


from a light radiating means


3




a


based on the information read through the optical means


2


. The latent images are developed with toners and transferred onto the sheets, and the sheets are conveyed to a fixing means


6


to fix the images permanently in application of heat and pressure.




In a case of a single side recording mode, the sheet is sent to a sheet processing apparatus B, and in a case of a double side recording mode, the sheet is conveyed to a re-feeding path


7


in a switchback way, thereby sending the sheet to the sheet processing apparatus B after forming images on the other side where the sheet whose one side is recorded is conveyed to the image forming means


3


again.




It is to be noted that the sheets can be fed not only from the sheet cassettes


4


but also from the multi-tray


8


.




The finisher unit C in the sheet processing apparatus B is structured as shown in FIG.


2


. To deliver the sheets, the finisher unit C can do delivery operations according to respective modes such as, in addition to a normal delivery mode, an offset mode, a staple mode, and so on.




The offset mode here is the operation anode in which, when the sheets are delivered upon sorting them by respective copies, the first sheet of each copy is positionally shifted in a sheet width direction (a direction perpendicular to the sheet conveyance direction) by a prescribed amount by actuating a side guide


11


when delivered, and the sheets of the second or latter are delivered in the normal fashion, thereby distinctively showing the boundaries of respective copies.




It is to be noted that, where no space to which the sheets are shifted is available with respect to the size in the sheet width direction, a reference guide


37


is made to escape lower than the level of a staple tray


12


serving as a temporally stacking means, thereby ensuring the sheet shifting amount adequately.




The staple mode is an operation mode in which, when the sheets are delivered upon sorting them with respect to each copy, the sheets are stacked and aligned on the staple tray


12


and stapled with a stapler


13


to deliver them upon stapling the sheets with respect to each copy.




It is to be noted that to deliver the sheets, this apparatus can perform a double sheet delivery control capable of delivering two sheets at the same time, in addition to the normal delivery control for delivering the sheets sheet by sheet. In this double sheet delivery control, a sheet sent to the sheet processing apparatus B from the image forming apparatus body A is stored in a buffer path


14


arranged in the finisher unit C, and the sheet is overlapped with another sheet subsequently delivered to deliver the two sheets at the same time.




Meanwhile, the stitcher unit D in the sheet processing apparatus B is structured as shown in FIG.


3


. The sheets delivered from the image forming apparatus body A are aligned with respect to each copy and stapled by means of the staple unit, and the stapled sheets are folded in folio and bound into books. In briefly speaking, the sheets delivered from the image forming apparatus body A are conveyed to a vertical path


60


of the stitcher unit D; the sheets are stacked and aligned on a copy basis so that the lower end of the sheet hits a stopper


62


; the stacked sheets are bound upon stapling the sheets with a stapling unit


61


at two locations of a center in the sheet lengthwise direction (sheet conveyance direction).




The stopper


62


is moved downward to move the sheet bundle so that the bound portion reaches a nip position of folding rollers


78


, and where the bound position is struck by a striking plate


79


, the sheet bundle is nipped and conveyed by the nip rollers


78


as to be folded in folio at the bound position. This operation makes the sheet bundle bound at the center in the sheet lengthwise direction as well as delivered on a stacking tray


106


in a folio bound form.




Finisher Unit




The sheet P delivered to the finisher unit C from the image forming apparatus body A according to this embodiment is, in the normal mode, conveyed to a conveyance roller


15


and delivered to the stack trays


18


by means of an upstream delivery roller pair


16


and a downstream delivery roller pair


17


. The stack trays


18


are provided in a plural number as movable in a vertical direction by a driver installed at a lower side of the trays. When sheets are delivered upon sorting, the plural stack trays


18


are moved in a shifting manner step by step at the delivery opening, thereby delivering the sheets P where the sheets P are sorted with respect to each copy. In a case of the offset mode and the staple mode, sheets P can be delivered to the sole stack tray


18


in a sorted state upon offset operation or staple operation. Moreover, in a case of an interruption mode, the sheets P can be delivered on an upper tray


19


without delivered to the stack tray


18


.




Offset Delivery Processing




The finisher unit C according to this embodiment is capable of sorting the sheets in the offset mode as described above. In this mode, as shown in

FIG. 4

, all copies are delivered on the single stack tray


18


, and where the sheets are delivered on the copy basis, the first sheet P


1


is positionally shifted in the sheet width direction with respect to the sheets P of the second and latter, thereby rendering the boundaries of the copies clear.




The downstream delivery roller pair


17


is structured having a downstream delivery roller


17




a


formed at a unit body and a movable delivery roller


17




b


attached to a rocking guide


20


which is capable of rocking around a shaft with respect to the unit body. When the rocking guide


20


moves up as to open, each roller of the downstream delivery pair


17


becomes separated from one another as shown in FIG.


4


. The side guide


11


is provided movably in the sheet width direction between the upstream delivery roller pair


16


and the downstream delivery roller pair


17


, serving as an aligning means guiding one edge of the sheets P in the width direction. During the offset mode, when the first sheet of each copy to be sorted is delivered, the rocking guide


20


is moved up as to open at a time that the rear end of the sheet falls onto the staple tray


12


upon conveyed between the upstream delivery roller pair


16


and the downstream delivery roller pair


17


, and subsequently, the side guide


11


is moved in the arrow direction, thereby shifting the first sheet P


1


for a prescribed amount. The sheet P


1


is then delivered onto the stack tray


18


upon closing the rocking guide


20


. Subsequently, the sheets P of the second and latter are delivered in the normal fashion, and the sheets are delivered in a form that the first sheet P


1


of each copy is positionally shifted as shown in FIG.


4


and FIG.


5


. As described above, where no space in which the sheet is moved by the prescribed amount in the sheet width direction is available, the reference guide


37


is made to escape lower than the staple tray


12


, thereby ensuring the sheet shifting amount adequately.




Double Sheet Delivery Control During Offset




In the offset delivery, when the first sheet P


1


of each copy is delivered, the offset processing of the sheet P


1


as described above is required, and therefore, the sheets P of the second and latter cannot be delivered until that the processing finishes. Accordingly, the delivery of the second sheet has to be suspended, and the processing time is required to be longer.




The second sheet P is temporarily stored in the buffer path


14


during the offset processing in this embodiment, and the second sheet and the third sheet are delivered at the same time, thereby shortening the processing time by delivering the sheets without suspending the sheet delivery even in the offset mode.




The double sheet delivery control for such operation is described. While the first sheet is subjecting to the offset processing, when the second sheet is conveyed to the finisher unit C from the image forming apparatus body A, the second sheet is sent to the buffer path


14


by positioning upstream side ends of a first flapper


21


and a second flapper


22


downward as shown in FIG.


6


. The proceeding sheet P


2


sent to the buffer path


14


(in the case of the offset mode, the second sheet) is transferred in the shown arrow direction as to wind a buffer roller


23


by means of the buffer roller


23


which is rotatively driving and a buffer roller


24


driven rotatively in pushing the sheet to the buffer roller


23


. A third flapper


25


is driven as to send the proceeding sheet P


2


in a direction that the sheet is wound around the buffer roller


23


.




When a buffer sensor


26


detects the front end of the proceeding sheet P


2


, and when the front end of the proceeding sheet P


2


reaches the prescribed position, the buffer roller


23


is stopped to rotate, and the sheet is stopped in the buffer path


14


. As shown in

FIG. 6

, when the subsequent sheet


13


(in the case of the offset mode, the third sheet) enters, the buffer roller


23


begins to rotate, and as shown in

FIG. 7

, this unit conveys the proceeding sheet P


2


and the subsequent sheet P


3


in an overlapped manner. When the rear end of the proceeding sheet P


2


passes by the position of the third flapper


25


, the third flapper


25


rotates the two sheets P


2


, P


3


in the direction toward the upstream delivery roller pair


16


, thereby delivering the sheets P


2


, P


3


as they are stacked onto the stack tray


18


.




The double sheet delivery control as described above prevents sheets from being delivered from the upstream delivery roller pair


16


during the offset processing operation, and therefore, the operation of the image forming apparatus body is not necessarily stopped. Accordingly, in the offset mode, the processing time is made not longer, and the sheets can be quickly delivered in the offset manner.




It is to be noted that in this embodiment, the buffer roller


23


winds a single sheet P on the roller, but the roller can wind two or more sheets to deliver three or more sheets at the same time in order to compensate more time for offset processing operation. The sheet wound on the buffer roller


23


is solely delivered or stacked even without any subsequent sheet




Although in this embodiment, an example in which the sheet subjecting to the offset is the first sheet of each copy is exemplified, this operation is not limited to such a manner, and this invention is effective even where the last sheet of each copy is positionally shifted. The sheet number subjecting to the offset is not limited to a single number and can be a plural number of sheets.




The double sheet delivery control can be executed not only in the offset processing but also in the staple processing in the staple mode as described below, so that time for the staple processing can be used in an advantageous way.




Sheet Waiting Position of Double Sheet Delivery Control




In the double sheet delivery control described above, the conveyance has to be made so that a positionally shifting amount between the front ends of the proceeding sheet P


2


waiting in the buffer path


14


and the subsequent sheet P


3


delivered from the image forming apparatus body A becomes constant. To accomplish this, the buffer roller


23


begins to rotate after the subsequent sheet P


3


passes the position of an entry sensor


27


shown in

FIG. 6

or after predetermined clocks are counted up upon passage of the subsequent sheet P


3


at the position of the entry sensor


27


, thereby rendering constant the shifting amount between the front ends of the proceeding sheet P


2


and the subsequent sheet P


3


.




However, the conveyance speed of the subsequent sheet P


3


delivered from the image forming apparatus body A is changed according to the image formation mode, kinds of sheets, and the like. If the conveyance speed is different between the proceeding sheet P


2


and the subsequent sheet P


3


, positional deviations may occur at the front ends of the proceeding sheet P


2


and the subsequent sheet P


3


because the starting timing of the buffer roller


23


is the same.




This embodiment is therefore structured in which the front end position of the proceeding sheet P


2


to be stored in the buffer path


14


is changed according to the conveyance speed of the subsequent sheet P


3


because the conveyance speed of the subsequent sheet P


3


depending on the image formation mode, kinds of sheets is retrievable from the image forming apparatus body. More specifically, in

FIG. 6

, it is set that a conveyance amount of sheets from time when the front end of the proceeding sheet passes the position of the buffer sensor to time when the sheet stops becomes much when the conveyance speed of the subsequent sheet P


3


is high and conversely, less when the speed is low. According to this operation, a period from the beginning of rotation of the buffer roller


23


to a time which the front end of the proceeding sheet P


2


reaches a meeting point with the subsequent sheet P


3


is short when the conveyance speed of the subsequent sheet P


3


is fast and long when the conveyance speed is slow. Therefore, even where the starting timing of the buffer roller


23


is constant, the proceeding sheet P


2


and the subsequent sheet P


3


can be always conveyed with constant shifting amounts between the front ends of the proceeding sheet P


2


and the subsequent sheet P


3


.




It is to be noted that, as a structure for making constant the positions of the front ends of the proceeding sheet P


2


and the subsequent sheet P


3


, this operation can be performed by changing the stating timing of the rotation of the buffer roller


23


, in addition to the method for changing the waiting position of the proceeding sheet P


2


as described above. For example, while the proceeding sheet P


2


is held at a fixed position in the buffer path


14


, the buffer roller


23


starts rotating right after the subsequent sheet P


3


passes by the entry sensor


27


where the conveyance speed of the subsequent sheet P


3


is fast and after predetermined time passes after the subsequent sheet P


3


passes by the entry sensor


27


where the conveyance speed of the subsequent sheet P


3


is slow. The positionally deviated amount between the front ends of the proceeding sheet P


2


and the subsequent sheet P


3


can be made constant by changing the conveyance starting timing of the proceeding sheet P


2


according to the conveyance speed of the subsequent sheet P


3


.




It is to be noted that although the conveyance speed of the subsequent sheet P


3


can be retrieved from the image forming apparatus body A as described above, it is retrievable by detecting the conveyance speed of the proceeding sheet P


2


because the subsequent sheet is generally conveyed with the same speed as that of the proceeding sheet P


2


.




Delivery Signal Transmission Timing in the Double Sheet Delivery Control




A sheet is transferred from the image forming apparatus body A to the sheet processing apparatus B, and the sheet delivery signal is transmitted when a prescribed processing is done. As shown by a flowchart in

FIG. 8

, in the double sheet delivery control, however, if the apparatus is structured in a way in which a sheet is detected by a loading sensor


28


(see, FIG.


2


and

FIG. 6

) (S


1


), in which a delivery signal of the proceeding sheet P


2


is transmitted at a time when the proceeding sheet P


2


is conveyed in the buffer path


14


(S


2


), in which the subsequent sheet P


3


is then conveyed to a predetermined position, and in which the delivery signal of the subsequent sheet P


3


is then transmitted after the double sheet delivery is made (S


3


to S


5


), the proceeding sheet P


2


in the buffer path


14


is removed together with the subsequent sheet P


3


by paper jam recovering process where the apparatus stops due to paper jamming or the like of the subsequent sheet P


3


after the delivery signal is transmitted (between S


2


and S


3


in FIG.


8


). Therefore, when image formation is resumed in a successive manner upon recovery from the paper jamming, though the proceeding sheet P


2


is not actually delivered in the stack tray


18


or the like, the apparatus itself recognizes it as the already delivered paper due to the transmission of the delivery signal. Therefore, the processing is made by skipping the page.




In this embodiment, as shown by a flowchart in

FIG. 9

, the delivery signal is not transmitted at a time when the proceeding sheet P


2


is brought to the buffer path


14


, the proceeding sheet P


2


is placed as to be overlapped with the subsequent sheet P


3


and delivered together from the buffer path


14


. The delivery signal of the proceeding sheet P


2


and subsequent sheet S


3


is transmitted at a time when a delivery sensor


29


(see, FIG.


2


and

FIG. 6

) located right before the upstream delivery roller pair


16


detects the front ends of both sheets P


2


, P


3


(S


1


to S


15


).




With such a structure, even where the subsequent sheet P


3


is jammed to stop the apparatus while the proceeding sheet P


2


is waiting in the buffer path


14


(between S


11


and S


12


in FIG.


9


), the delivery signal has not been transmitted yet at that time. If the image formation is resumed upon recovery from the paper jamming after the proceeding sheet P


2


is removed from the buffer path


14


during the paper jamming recovery, the images can be formed in restarting with the proceeding sheet P


2


, so that this apparatus can prevent skipping pages from occurring.




It is to be noted that the double sheet delivery control described above is effective during the offset processing and the staple processing as described below, this double sheet delivery control can be done at processings other than the above. Processings without the double sheet delivery control can be executed as a matter of course.




Shape of the Side Guide




In the double sheet delivery control thus described, or in the normal delivery mode, the sheet is delivered on the stack tray


18


by the upstream delivery roller pair


16


and the downstream delivery roller pair


17


shown in

FIG. 2

, and the staple tray


12


located between both roller pairs


16


,


17


is moved downward (see, FIG.


2


). Therefore, the front end of the sheet P to be delivered may hang over the staple tray


12


if curled downward as shown in FIG.


10


(


a


), and if the sheet is continuously conveyed as it is, the front end of the sheet may be pulled upon being folded as shown in FIG.


10


(


b


) when nipped by the downstream delivery roller pair


17


.




In this embodiment, as shown in

FIG. 11

, the shape of the side guide


11


is structured in an approximately triangle shape so that the top does not fall in the staple tray


12


. This side guide


11


is made to wait at a position (sheet delivery region) more inside than the width of the sheet to be delivered, thereby conveying the delivered sheet P to the downstream delivery roller pair


17


through guided at a top of the side guide


11


without hanging over the staple tray


12


as shown in FIG.


11


. Therefore, the sheet is delivered where the front end of the sheet is without being folded by the downstream delivery roller pair


17


as described above.




It is to be noted that if the side guide is in a shape with a cut in front of the downstream delivery roller pair


17


, the sheet P may hang over the staple tray


12


after guiding the sheet P ends at the side guide


500


even where the sheet P is guided at the top of the side guide


500


. It is therefore desirable to make the guide, like the side guide


11


in this embodiment, in a shape capable of guiding the sheets P from the upstream delivery roller pair


16


to the downstream delivery roller pair


17


(see, FIG.


11


).




It is also to be noted that if an auxiliary guide


30


is provided for guiding the sheet P between the upstream delivery roller pair


16


and the side guide


11


, it is effective for preventing sheets from hanging




It is to be noted that although the side guide


11


as described above guides the sheets P by positioning itself at the delivery region of the sheets P, the sheets P are required to be dropped in the staple tray


12


and aligned by pushing the edges in the sheet width direction in the offset mode and the staple mode. Therefore, in the offset mode and the staple mode, the side guide


11


is moved to escape more outside than the sheet width (outside the sheet delivery region) as shown in

FIG. 12

right after the front end of the first sheet is nipped by the downstream delivery roller pair


17


(state shown in FIG.


11


). This operation also prevents the front end of the sheet from being folded and pulled because the front end of the first sheet has already passed by the downstream delivery roller pair


17


, and the side guide


11


can be placed at a position for waiting and aligning the subsequent sheet.




Stacking Operation on the Staple Tray




In the staple mode, as shown in

FIG. 14

, after the rocking guide


20


is made open to deliver the sheet P to the staple tray


12


by the upstream delivery roller pair


16


, the sheet P is moved back until the rear end of the sheet P hits a rear end stopper


33


by rotating a knurled teething or knurled belt


32


in the arrow direction which is rotated by drive of a paddle


31


formed on the rocking guide


20


and drive of the upstream delivery roller pair


16


. The side guide


11


then pushes the sheet P toward one side to align the sheet P, and the stapler


13


makes the stapling operation.




When the sheet P is delivered to the staple tray


12


, if the delivery speed of the upstream delivery roller pair


16


is high, the sheet P may be delivered as projecting after passing by the upstream delivery roller pair


16


because the rocking guide


20


is open, may excessively proceed forward, and may take time for coming back. If the sheet proceeds forward overly, the sheet may not move back to the knurled belt


32


even by pulling the sheet through hitting with the paddle


31


, and the sheets may not be aligned on the staple tray


12


.




To solve this problem, in this embodiment, the rotation speed of the upstream delivery roller pair


16


is controlled to be a low speed while the rear end of the sheet passes by the upstream delivery roller pair


16


in the staple mode. This operation makes the rear end of the sheet delivered on the staple tray


12


fall near the knurled belt


32


, thereby ensuring the sheet P to be pulled by drives of the paddle


31


and the knurled belt


32


, and performing the alignment of the rear ends;.




It is to be noted that whether the rear end of the sheet passes by the upstream delivery roller pair


16


can be distinguished by detecting predetermined time after the sheet passes by a prescribed sensor or the motor rotation speed.




After the rear end of the sheet falls in the staple tray


12


, the upstream delivery roller pair


16


, which has been switched to drive with a low speed, is changed to rotatively drive with a high speed. Because this upstream delivery roller pair


16


is also a drive source for rotating the knurled belt


32


, the sheet P fallen on the staple tray


12


is promptly pulled back by the knurled belt


32


, and the rear end of the sheet is made to hit the rear end stopper


33


.




In the staple mode, as described above, this apparatus can align sheets quickly as a whole by rendering the conveyance speed slower only when the rear end of the sheet passes by the upstream delivery roller pair


16


.




Rocking Guide




Referring to

FIG. 13

, the rocking guide


20


is described briefly. The rocking guide


20


rotatively holds the movable delivery roller


17




b


, rocks around a rocking shaft


20




a


as a center by means of a drive mechanism


39


as described below during delivery of the sheet, and pushes the movable delivery roller


17




b


to press the downstream delivery roller


17




a


. In the staple mode, the rocking guide


20


is swingingly moved up around the rocking shaft


20


as the center, thereby moving the movable delivery roller


17




b


away from the downstream delivery roller pair


17


. That is, the rocking guide


20


serves as means for switching states for allowing sheet delivery and for inhibiting sheet delivery with the downstream delivery roller pair


17


composed of the movable delivery roller


17




b


and the downstream delivery roller


17




a.






In

FIG. 13

, numeral


34


is a stopper having a shutter portion


34




a


. The shutter portion


34




a


formed on the edge is lifted up by a link


35


which is moved pivotally upward around the pivotal shaft


35




a


as a pivotal center during transfer of the stack tray, and thereby, the sheets(sheet bundle) stacked on the stack tray


18


are prevented from going reversely into a delivery opening


36


by covering the delivery opening


36


when the stack tray


18


passes by the delivery opening


36


. This stopper


34


opens the delivery opening


36


by moving the link


35


pivotally downward around the pivotal shaft


35




a


as the pivotal center during the delivery of the sheets.




Operation of Stack Tray During the Double Sheet Delivery Control




Referring to

FIG. 13

, operation of the stack tray


18


when only two sheets P are stapled is described next.

FIG. 13

is a cross section showing a position of the stack tray


18


as the essential portion




When the staple processing is performed, the plural sheets S delivered sheet by sheet onto the staple tray


12


are normally moved back by the paddle described below and the knurled belt


32


in the reverse direction to the delivery direction and are aligned by the rear end stopper


33


described below upon hit by the stopper


33


. The stack tray


18


is lifted up at that time so that the front end side of the sheets P come above the rear end side of the sheets on the staple tray


12


(broken line position in FIG.


13


), thereby easily making the sheets pulled back in the aid of the gravity force.




However, if only two sheets P are to be stapled (including the situation of the double sheet delivery control), the lower sheet is pulled back in a direction opposite to the delivery direction on the staple tray


12


by the downstream delivery roller


17




a


which is rotated reversely together with rocking movement of the rocking guide


20


by the drive mechanism


39


described below, and the upper sheet is pulled back similarly in the direction opposite to the delivery direction by the paddle


31


described below and the knurled belt


32


. Accordingly, a sole sheet or double sheets can be pulled back and aligned without aid of the gravity force, so that the front end of the sheet is not necessarily lifted up by moving the stack tray


18


up.




Therefore, in this embodiment, if only two sheets P are to be stapled (including the situation of the double sheet delivery control), the stack tray


18


is not moved up. That is, if the three or more sheets are to be stapled, the stack tray


18


is moved up from a solid line position to a broken line position in

FIG. 13

, but if the sheets P are only two, the stack tray


18


is not lifted up and remains in the solid line position in

FIG. 13

to perform the pulling back operation described above.




This apparatus thus structured does not have to move up and down the stack tray


18


when the bundle of two sheets are to be stapled, and therefore, can save time for moving up the stack tray


18


and reduce the processing time greatly.




Rocking Amount of the Rocking Guide and Paddle Shape




Referring to

FIGS. 14

to


16


, the paddle


31


for pulling back the sheet P delivered on the staple tray


12


in a direction opposed to the delivery direction, and a rocking amount of the rocking guide


20


supporting the paddle pivotally are described. FIG.


14


and

FIG. 15

are enlarged views showing states of the rocking guide and paddle as essential portions in the sheet pulling back operation.

FIG. 16

is an illustration showing a shape of the paddle.




The rocking guide


20


has the paddle


31


mounted rotatively for pulling back the sheet P delivered on the staple tray


12


in a direction opposite to the delivery direction. The paddle


31


rotates in the direction opposite to the delivery direction at each delivery of a sheet P on the staple tray


12


where the rocking guide


20


is open, transforms elastically upon contacting to the rear end of the sheet P placed on the staple tray


12


, and pulls back the sheet P by frictional force created between the sheet P and itself.




If the paddle


31


pulls back each sheet at every delivery while the rocking guide


20


is swung up and held at a prescribed position, the sheet P may be excessively returned since the contact area and contact pressure of the paddle


31


in contact with the topmost sheet P may change according to the height (level) of the sheets P on the staple tray


12


because the sheets are successively delivered on the staple tray


12


.




In this embodiment, to solve this problem, the paddle


31


is structured to keep the contact pressure to the topmost sheet delivered on the staple tray


12


approximately constant. More specifically, the shape of the paddle


31


is formed or molded in a tapered shape whose tip


31




a


is narrowed as shown in FIG.


16


. FIG.


16


(


a


) indicates a case where the paddle


31


is in a tapered shape with stepwise portions on opposite sides of the tip


31




a


of the paddle


31


; FIG.


16


(


b


) indicates a case where the paddle


31


is in a tapered shape with a stepwise portion on one surface (sheet contact surface) of the tip


31




a


of the paddle


31


; FIG.


16


(


c


) indicates a case where the paddle


31


is in a tapered shape with a stepwise portion on the other surface (sheet noncontact surface) of the tip


31




a


of the paddle


31


It is to be noted that the tapered shape of the tip


31




a


of the paddle


31


is Dot limited to those shown in FIGS.


16


(


a


) to


16


(


c


)




Where the paddle


31


is thus formed, the paddle tip serving as a portion contacting to the sheet becomes easily elastically transformed when contacting with the sheet, so that the apparatus can obtain stable returning force notwithstanding the number of the accumulated sheets and have an improved durability.




In this embodiment, the plural paddles


31


are provided in the rotational direction, and the paddles


31


come in contact with the sole sheet multiple times per rotation. This structure allows one time rotation of the paddles


31


, when the paddles


31


pull back a relatively large sheet by contacting to the sheet twice, to pull back adequately the sheet, and therefore, the processing time can be shortened in comparison with two time rotation of a single paddle


31


. It is to be noted that in FIG.


16


(


a


), a case where two paddles


31


are arranged in the rotational direction or a case of a twin paddle, the feature is not limited to this. The paddle


31


can be formed in shapes shown in FIG.


16


(


d


), FIG.


16


(


e


), FIG.


16


(


f


), and FIG.


16


(


g


) to obtain substantially the same effects.




The paddle


31


can be so structured that the contact area of the paddle


31


with the sheet P delivered on the staple tray


12


is kept constant. More specifically, the apparatus is structured so as to change the swinging amount when the rocking guide


20


is opened (swung upward) according to the height (level) change of the sheets P on the staple tray


12


. Further specifically, for example, according to increase of the number of the delivered sheets P on the staple tray


12


, the rocking guide


20


is swung upward to keep the contact area of the paddle


31


to the topmost sheet P constant.




As shown in

FIG. 15

, a thickness I of the bundle of the sheets P is expressed by “t=r sin θ” wherein: “r” denotes the distance between the rocking center (rocking shaft


20




a


) of the rocking guide


20


and the rotary center of the paddle


31


; “θ” denotes the rocking angle of the rocking guide


20


; “t” denotes the thickness of the bundle of the sheets P. Based on this formula, it is suitable that the rocking amount (rocking angle θ) of the rocking guide


20


is changed according to the change of the thickness t of the bundle of the sheets P.




This structure keeps the contact area between the topmost sheet P on the staple tray


12


and the paddle


31


always constant notwithstanding the number of stacked sheets P, so that the apparatus can gain stable returning force, and so that the apparatus can prevent the sheets P from being excessively returned due to changes of the contact area of the paddle


31


to the sheet P.




Operation Timing of the Paddle




The operation timing of the paddle


31


starts as shown in

FIG. 15

after the rear end of the sheet P gets settled as shown in

FIG. 14

where as shown in

FIG. 14

the upstream delivery roller pair


16


on the upstream side over the staple tray


12


releases the rear end of the sheet P. More specifically, the paddle


31


is rotated in the reverse direction to the sheet delivery direction after a prescribe time passes after the rear end of the sheet P passes by the delivery sensor provided on the upstream side of the upstream delivery roller pair


16


.




Rotation Number of the Paddle According to the Sheet Size




The drive number of the paddle


31


is described next. For example, with a structure that the paddle


31


is drive to rotate at a fixed rate regardless the size of the sheets, a large size sheet is not easily pulled back due to its large mass, and therefore in some case, cannot be pulled back to the knurled belt


32


even if hit in the same manner as done for small size sheets, thereby inviting failures in alignment of sheets.




In the embodiment, the drive number of the paddle


31


varies according to sheet sizes. More specifically, the drive number of the paddle


31


is made larger when the sheet has a relatively long length in the sheet conveyance direction. That is, for example, as shown in

FIG. 17

, in the cases of sheets having relatively larger sizes such as A


3


, B


4


, LGL, and LDR, the paddle


31


is driven two times, and in the case of sheets having relatively smaller sizes such as A


4


, LTR, B


5


, A


4


R, and LTRR, the paddle


31


is driven one time.




This structure surely pulls back the sheet to the knurled belt


32


even though having a large mass, thereby improving the alignment of the sheets.




It is to be noted that although in this embodiment the rotation number is changed according to the sheet size, substantially the same control can be done for designation of thicker papers or special papers (e.g., having a low surface frictional coefficient).




Traveling Speed of the Side Guide According to the Sheet Size




The traveling speed of the side guide for performing alignment of the sheets in the sheet width direction is described next. Where the sheet P is stacked on a staple tray


12


, the sheets are aligned in the sheet conveyance direction by the paddle


31


and the knurled belt


32


as described above, and concurrently, the sheets P are aligned in the sheet width direction by moving the sheets P in the width direction toward the reference guide


37


located on the opposite side with respect to the sheets by pushing the rear end of the sheets (side edges on a side of the rear end stopper


33


) by means of the side guide


11


. If the sheets have a larger size, because the center of the gravity is far from the pushing position by the side guide


11


and because the sheets have a high inertial moment where having a large mass, the front ends of the sheets cannot follow travelling of the side guide


11


in the sheet width direction, so that alignment failure of the sheets may be invited.




In this embodiment, to solve this problem, the side guide


11


changes the traveling speed in the sheet width direction according to the sheet size. More specifically, the side guide


11


is moved with a low speed where the sheet has a relatively long length in a direction (sheet conveyance direction) perpendicular to the traveling direction (sheet width direction) of the side guide


11


. That is, for example, as shown in

FIG. 17

, in the cases of sheets having a relatively short length in the sheet conveyance direction such as A


4


, LTR, B


5


, and sheets in which the guide moves in a smaller amount in the sheet width direction such as A


3


, and LDR, the side guide is made to travel with a high speed, and in the case of sheets other than above, having a relatively longer length such as B


4


, LGL, and sheets in which the guide moves in a larger amount in the sheet width direction such as A


4


R, and LTRR, the side guide


11


is made to travel with a low speed.




With such a structure, the apparatus can reduce influence of the inertial moment, and can improve alignment operation in the width direction even though it is a sheet having a large size (having a long size in the conveyance direction). This is also effective for sheet sizes needing a large traveling amount in the sheet width direction.




Rear End Stopper




Referring to

FIGS. 18

,


19


, the rear end stopper


33


for hitting the rear end of the sheets P when the sheets P are aligned in the conveyance direction is described next. The sheets P delivered on the staple tray


12


are conveyed in the direction opposite to the delivery direction by the paddle


31


and the knurled belt


32


and the like as described above, and the sheets are aligned in the sheet conveyance direction upon hit by the rear end stopper


33


arranged with a predetermined space in the sheet width direction.




For example, if a sheet hitting surface


501




a


of the rear end stopper


501


is flat as shown in FIG.


18


(


a


), the sheet P may be bent or go below the surface when the sheet P enters more or less in an oblique manner with respect to the sheet hitting surface


501




a


, or the sheet end may be damaged by hit with the corner (edge) in the width direction of the sheet hitting surface


501




a.






In this embodiment, as shown in FIG.


18


(


b


), the opposite side portions in the width direction of the sheet hitting surface


33




a


of the rear end stopper


33


are formed in a tapered shape (tapered portion


33




b


).




This structure as shown in FIG.


18


(


c


) can prevent the sheets P from bending (or going below) by both tapered portions


33




b


even if the sheets P enter obliquely with respect to the sheet hitting surface


33




a


, and further can prevent the sheet ends from sustaining damages.




As shown in

FIG. 19

, although the one rear end stopper


33


L corresponds to the knurled belt


32


L on one side of the sheet width direction, since the other knurled belt


32


R corresponds to the other rear end stopper


33


R with a slight shift in the width direction, the sheet end between the rear end stoppers may be pulled overly by the other knurled belt


32


R where the sheet corner vicinity is hit by the other rear end stopper


33


R (particularly, in the case of the R (Reduction) type sheets, in which sheet longitudinal direction is the sheet conveyance direction.), and the sheet corner vicinity may become flexible and be bend.




During the sorting processing in the offset mode, though the side guide


11


is needed to travel in the sheet width direction, since the movable area is near the knurled belt


32


R, and as shown in

FIG. 19

, the other knurled belt


32


R and the rear end stopper


33


R as described above are structured to be shifted to each other in the sheet width direction




With such a structure, the sheets of the B


5


R size having a shorter length in the sheet width direction can be subjecting to the offset processing, and the entire apparatus can be made compact.




In this embodiment, as shown in

FIG. 19

, the stapled


13


is made to wait between the rear end stopper


33


L,


33


R (or the center in this embodiment) for aligning the sheets upon hitting the rear end of the sheet bundle during the stapling operation for sheet bundles (particularly, stapling at a single portion of the R type sheets), thereby functioning the stapler


13


in the same way as the rear end stoppers


33


L,


33


R. More specifically, a rib


38


is formed to limit the rear end of the sheet bundle at a cover member


38


of the stapler


13


.




This structure prevents the sheet from being pulled excessively because the sheets are regulated by the stapler


13


(or rib


38




a


) waiting between the rear end stoppers even if the sheet is pulled inside by the other knurled belt


32


R when the sheet corner vicinity hits the other rear end stopper


33


R, so that this apparatus prevents sheets from being bent.




Pressing Control of the Side Guide




Alignment of the sheets P in the sheet width direction by the side guide


11


is described next. The alignment of the sheets P in the sheet width direction is performed as described above by moving the sheets in the width direction in pushing the one edge on a rear end side of the sheets by means of the side guide


11


and by hitting the other side ends of sheets onto the reference guide


37


on the opposite side. At that time, the sheets P moved in the width direction by the side guide


11


are in contact with the knurled belt


32


. Therefore, the knurled belt


32


may be twisted according to the sheets P transferred in the width direction by the side guide


11


, and the sheets P may not reach the reference guide


37


by influence with the knurled belt


32


, thereby possibly causing failure of alignments.




In this embodiment, as shown in FIG.


20


and

FIG. 21

, when the side guide


11


aligns the sheets P in the width direction (particularly in a case of sheets of the R type having a large width alignment amount), the side guide


11


is pushed stepwise, and the sheets are aligned in releasing influences from the knurled belt


32


. That is, where the side guide


11


is pushed stepwise, the twisted width of the knurled belt


32


can be a minimum even the knurled belt


32


is twisted during pressing, and thereby the knurled belt


32


can back easily to the normal position (situation shown in the drawing) as well as with a shorter returning time.




Moreover, the stepwise pressing control for sheets by the side guide


11


. during the alignment in the sheet width direction is changed according to the sheet size. More specifically, the first sheet of A


4


, LTR, B


4


, and LGL sizes and the sheet of the second or latter of LTR and B


5


sizes are pushed by two-time pressing.




The two-time pressing herein means operation in which pressing temporally stops after the first pressing and the second pressing is made subsequently. It is to be noted that the number of pressing times is not limited to this. The side guide


11


after the last pressing, as described below, has a structure functioning as a guide located at the pressing position until when the front end of the subsequent sheet comes over the downstream delivery roller pair


17


or for a prescribed period, and more specifically, the sheets are in a state that the sheets are pressed by the side guide


11


.




The side guide


11


temporally stops at each pressing of the sheets when the sheets are pushed multiple times stepwise and starts pressing the subsequent sheets after a prescribed time passes for returning the knurled belt


32


to the normal position (recovery of twists).




Therefore, the alignment in the width direction by pressing the sheets stepwise by means of the side guide


11


as described below makes the influence from the knurled belt


32


release quickly and is done quickly and precisely.




Shape of the Knurled Belt




Referring to

FIGS. 22

to


24


, the shape of the knurled belt


32


is described. The knurled belt


32


pulls further back the sheets, which are pulled back by the paddle


31


as described above in the opposite direction to the sheet delivery direction, and aligns the sheets in the sheet conveyance direction by hitting the sheets P to the rear end stopper


33


. As shown in

FIG. 22

, if the contact surface of the knurled belt


502


with the sheets P are molded to be flat, an edge


502




a


of the knurled belt


502


may be trapped at the sheets S traveling in the width direction, thereby possibly causing failures in alignment of sheets.




In this embodiment, as shown in FIG.


23


(


a


), an edge portion


32




a


of the knurled belt


32


is molded in a tapered shape, or as shown in FIG.


23


(


b


), an outer round surface of the knurled belt


32


is molded in a shape having a cross section with curvature.




Those molded shapes make small resistance to the sheets P travelling in the width direction by the side guide


11


during the alignment, thereby being capable of reducing failures in alignment of the sheets due to trapping at the edge portion.




Recovery of the Knurled Belt




As described above, the alignment of the sheets in the width direction is performed by moving the sheets in the width direction upon pressing the one side end on the rear end side of the sheets by means of the side guide


11


and by hitting the other side end of the sheets to the reference guide


37


located on the other side. At that time, the sheets P moved in the width direction by the side guide


11


are in contact with the knurled belt


32


. Consequently, the knurled belt


32


may be twisted according to the sheets P moved in the width direction by the side guide


11


, the sheets P may be moved in association with recovery of the twist in the knurled belt


32


when the side guide


11


moves (escapes) in a direction opposite to the sheet pressing direction, thereby possibly causing failures in alignment.




With this embodiment, after the sheets are pressed by the side guide


11


, the side guide


11


continuously presses the sheets until the knurled belt


32


returns to the normal position (recovering the twist) and releases the pressing on the sheets after the knurled belt


32


returns to the normal position.




The side guide


11


functions as a guide for the subsequent sheet upon continuously pressing the sheets at a position shown in

FIG. 21

, but the knurled belt


32


returns to the normal position during this continuous pressing even if twisted as described above. After the front end of the sheet P under being guided comes over the downstream delivery roller pair


17


, the side guide


11


escapes to an escape position outside the sheet delivery region.




With this structure, failures in alignment of the sheet due to influence from the knurled belt


32


can be prevented.




At a Time when the Downstream Delivery Roller Rotates in the Reverse Direction while the Rocking Guide is Open




The state of the downstream delivery roller


17




a


when the rocking guide


20


is open and the state of the side guide


11


are described. The downstream delivery roller


17




a


is structured to rotate in a direction opposite to the sheet delivery direction by the drive mechanism


39


as described below when the rocking guide


20


is opened. The side guide


11


usually aligns the sheets in the sheet width direction upon finishing the reverse conveyance of the downstream delivery roller


17




a.






However, the first sheet (or the second sheet during the double sheet delivery control) is in contact with the downstream delivery roller


17




a


by the weight of itself, and this may become resistance during alignment in the width direction and cause failures in alignment of sheets. The frictional resistance between the sheet and the downstream delivery roller


17




a


is smaller when the roller rotates than that when the roller is still.




In this embodiment, the side guide


11


finishes the alignment operation in the sheet width direction by the end of the reverse operation of the downstream delivery roller


17




a


for pulling back the first sheet.




This structure allows the influence from the frictional resistance between the first sheet and the downstream delivery roller


17




a


to be reduced at a time that the first sheet is aligned in the width direction by the side guide


11


, thereby improving the alignment property for the sheets.




Lock of the Downstream Delivery Roller while the Rocking Guide is Held




If the downstream delivery roller


17




a


is stopped in a free state (rotatable state) when the subsequent sheets are stacked on the staple tray


12


and aligned, the lowermost sheet may be shifted on the staple tray


12


while the sheets are aligned.




To solve this problem, in this embodiment, the drive mechanism


39


as described below locks the downstream delivery roller


17




a


to render the roller not rotatable while the sheets are stacked on the staple tray


12


and aligned. This structure can reduce shifts of the sheets due to collisions or the like during the paddle operation while the sheets are stacked on the staple tray


12


and aligned.




Reverse Operation of the Downstream Delivery Roller when the Rocking Guide is Closed




When the sheets of a bundle is stacked and aligned on the staple tray


12


, the sheet bundle is sandwiched and fixed where the rocking guide


20


is closed, and then the stapler


13


makes the stapling operation.




In such a situation, the lowermost sheet of the sheet bundle may be shifted more or less on the staple tray


12


while the sheets are aligned by the paddle


31


, the side guide


11


, and the like.




With this embodiment, while the sheet bundle is sandwiched and fixed upon closing the rocking guide


20


, the downstream delivery roller


17




a


is reversed in a prescribed amount (or more or less) by the drive mechanism


38


as described below, thereby providing conveyance force in a direction opposite to the delivery direction to the lowermost sheet of the sheet bundle on the staple tray


12


.




This structure makes possible the alignment in correcting shifts even where the lowermost sheet of the sheet bundle is shifted more or less while the sheets are aligned by the paddle


31


, the side guide


11


, and the like.




Drive Mechanism for the Rocking Guide and the Downstream Delivery Roller




Referring to

FIGS. 25

,


26


, and


27


, the drive mechanism


39


for the rocking guide


20


and the downstream delivery roller


17




a


are described In the drawings, the numeral


39


represents the drive mechanism and performs to open and close the rocking guide


20


and to drive in normal and reverse directions the downstream delivery roller


17




a


. This drive mechanism


39


is constituted of a drive motor


40


as a drive source and a gear series transmitting the drive force from the motor


40


.




The drive motor


40


is formed with an encoder


56


for detecting the rotation number and a drive motor rotation detecting sensor


55


, which detect the rotation speed of respective rollers and traveling amount of the rocking guide.




This drive mechanism


39


performs to rotate the downstream delivery roller


17




a


in the normal direction (rotation in the sheet delivery direction) while the drive motor


40


rotates normally, to open the rocking guide


20


as well as to rotate in the reverse direction (rotate in a direction opposite to the sheet delivery direction) the downstream delivery roller


17




a


while the rocking guide


20


is made open where the drive motor


40


rotates in the reverse direction, to close the rocking guide


20


as well as to rotate in the reverse direction the downstream delivery roller


17




a


while the rocking guide


20


is made closed, and to hold the rocking guide


20


while the drive motor


40


stops temporarily well as to lock the downstream delivery roller


17




a


when the rocking guide


20


is held. Hereinafter, the structure of the drive mechanism is described in detail along the stream of operation.




As shown in

FIG. 25

, when the drive motor


40


is rotated in the normal direction, drive force is transmitted to a fixed gear


42




a


of a pendulum gear unit


42


of the meshing a pinion gear


41


on the motor


40


to rotate the gear. A rocking gear


42




b


is swung to a shown position to mesh a delivery gear


43


of the downstream delivery roller


17




a


, and the sheets S are delivered and conveyed where the downstream delivery roller


17




a


rotates in the sheet delivery direction (normal direction: in the arrow direction in the drawing).




As shown in

FIG. 26

, when the drive motor


40


is rotated in the reverse direction, drive force is transmitted to the fixed gear


42




a


of the pendulum gear unit


42


of the meshing the pinion gear


41


on the motor


40


to rotate the gear. The rocking gear


42




b


meshes an intermediate gear


44


upon swung to the shown position, and an operational gear


46


rotates in the arrow direction via an intermediate gear


45


meshing the intermediate gear


44


. The operational gear


46


includes a gear portion


46




a


meshing the intermediate gear


45


, a projection


46




b


to open and close the rocking guide


20


in contact with an opening and closing arm


47


attached to the rocking guide


20


as a united body, a partially toothless gear portion


46


capable of meshing the intermediate gear


48


in mesh with the delivery gear


43


.




Therefore, when the operational gear


46


rotates in the arrow direction, the partially toothless gear portion


46




c


meshes the intermediate gear


48


to rotate the delivery gear


43


meshing the intermediate gear


48


in the arrow direction in the drawing, and while the downstream delivery roller


17




a


rotates in the direction (the arrow direction in the drawing) opposite to the sheet delivery direction to start pulling back the sheets P, the rocking guide


20


is pushed up in the arrow direction in the drawing where the projection


46




b


pushes up the opening and closing arm


47


in contacting with the arm


47


.




Where the rocking guide


20


reaches the position shown in

FIG. 27

, the drive of the drive motor


40


is stopped temporarily, and the rocking guide


20


is held as in the closed state. At that time, since the partially toothless portion


46




c


of the operational gear


46


is stopped in mesh with the delivery gear


46


via an intermediate gear


48


, the downstream delivery roller


17




a


is locked and not rotatable.




It is to be noted that the holding position of the rocking guide


20


is changeable as described above according to the height (level) of the sheets, to keep constant the contact area of the paddle


31


to the sheet delivered on the staple tray


12


.




Then, stacking and aligning operation for the sheets on the staple tray finishes, and the drive motor


40


is rotated again in the reverse direction. The delivery gear


43


rotates only for a portion meshing the partially toothless gear


46




c


of the operational gear


46


, and the sheets P are pulled back by rotation of the downstream delivery roller


17




a


in the direction opposite to the sheet delivery direction in a prescribed amount (meshed portion as described above). The rocking guide


20


is made closed at the same time, and after closed, the guide prepares for the subsequent processing.




With such a structure, the drive mechanism for driving the rocking guide


20


and the downstream delivery roller


17




a


is not required to be installed individually, so that this apparatus can reduce the costs and be simplified.




Closing Operation of the Rocking Guide




As described above, the rocking guide


20


is pivotable around the rocking shaft


20




a


, and as shown in

FIG. 27

, when the operational gear


46


rotates in the arrow direction, the projection


46




b


formed on the operational gear


46


pushes up the opening and closing arm


47


attached to one end of the rocking guide


20


to open the rocking guide


20


. When the operational gear


46


further rotates in the arrow direction in

FIG. 27

, the rocking guide


20


begins closing, and when the operational gear


46


more rotates, the rocking guide


20


is closed upon falling by its weight where the projection


46




b


is disengaged with the opening and closing arm


47


.




If the operational gear


46


is rotated with a high speed when the rocking guide


20


is closed, and if the initial speed of the closing operation is made faster, the rocking guide


20


falls by its weight with large impacts, and the aligned sheets may be disturbed. Such impacts also adversely affect the durability of the apparatus.




In this embodiment, to solve such problems, as shown in a flowchart of

FIG. 28

, during motor control for closing the rocking guide


20


, after the motor starts, the rocking guide


20


is made closed with a high speed until the prescribed position No. 1 (S


21


), but when the rocking guide


20


is closed up to the prescribed position No. 1 (S


22


, S


23


), the motor output is changed (S


24


), and it is structured that the closing operation of the rocking guide


20


becomes slower. When the rocking guide


20


is further closed up to the prescribed position No. 2 (S


28


, S


26


), the motor output is changed again (S


27


), and the motor drive is stopped after the closing of the rocking guide


20


is detected (S


28


, S


29


).




This makes the rocking guide


20


rotate slowly right before falling by its weight and makes the initial speed for falling by its weight slow. Therefore, the impacts of the rocking guide


20


falling by its weight become smaller, thereby not disturbing the aligned sheets, making the impact sound smaller, and preserving the durability of the apparatus without affected adversely.




It is to be noted that, when the rocking guide


20


is made closed, the rocking guide


20


completes the closing operation after a prescribed time passes after the motor starts, and as shown in

FIG. 26

, the opening and closing arm


47


moves pivotally a sensor flag


49


to turn on the closing sensor not shown. The apparatus recognizes, by this operation, that the rocking guide


20


is closed.




Therefore, if the closing sensor is not turned on even after the prescribed time passes, an error presumably occurs. However, such a situation may be brought by, as a matter of facts, stopping of rotation of the drive motor due to impact resistance between the projection


46




b


of the operational gear


46


and the opening and closing arm


47


and deviations of loads to the coupled gears. In such a case, the operational gear


46


is rotated by transmitting the large rotational force, thereby continuously and smoothly performing the work.




That is, in this embodiment, as shown in the flowchart in

FIG. 29

, where the rocking guide


20


is made closed (S


31


to S


37


), if the closing sensor is not turned on even where the prescribed time passes after the motor states (S


32


), the motor output is changed to transmit a further larger rotational force (S


33


). Then, where the closing sensor is not turned on even if the prescribed time passes, the apparatus displays an error indication of the rocking guide


20


and stops the operation.




Where the closing state of the rocking guide


20


cannot be detected in the first closing operation as described above, the apparatus can reduce occurrences of stop due to errors by performing the closing operation again by enlarging the motor output and can do the sheet post processing continuously and smoothly.




Switching Control of the Rotational Direction




To switch the pendulum gear unit


42


upon driving the drive motor


40


in the reverse direction, since the rocking gear


42




b


is rotatively driven in accordance with the rotation of the fixed gear


42




a


, the rocking gear


42




b


does not easily mesh the delivery gear


43


and the intermediate gear


44


when rotated rapidly and may skip the teeth to be meshed. This may cause noises and reduce the durability and the reliance of the apparatus upon unnecessarily abrading the gears.




In this embodiment, as shown in

FIG. 30

, the apparatus judges as to whether the rotational direction of the drive motor


40


is switched according to the control of the apparatus (S


41


), and if the rotational direction is not identical (S


42


), the drive motor


40


is controlled to drive with a low speed (S


43


). When an adequate prescribed time passes for switching the direction (S


44


), the drive motor is driven with a speed of the normal control (S


45


).




With such a structure, the rocking gear


42




b


can be meshed surely with the delivery gear


43


and the intermediate gear


44


, thereby preventing the gear tooth skipping or noises, and the apparatus can have a good durability.




Staple Operation




As described above, the bundle of the sheets P staked on the stack tray


12


are nipped by the downstream delivery roller pair


17


secured by the delivery gear


43


and are stapled in this state. The stapled position, though various combinations are conceivable, can be selected as shown in

FIG. 31

in this embodiment from a mode that a corner is stapled at a single location or mode that an edge is stapled at two locations.




When the stapler


13


is not located at a prescribed staple position, the stapler


13


is required to move, but this may cause the sheet bundle stacked on the staple tray


12


to move. Therefore, when the stapler


13


is made to travel, the side guide


11


presses the end of the sheet bundle. This operation prevents the alignment of the stacked sheets P from becoming disordered.




However, if the staple operation is performed while the sheets are pressed by the side guide


11


, failure of the staple operation may occur because the sheet bundle may be bent in the width direction due to pressing of the side guide


11


.




When the sheets are stapled, pressing of the side guide


11


is released as shown by a solid line in

FIG. 31

to separate the side guide


11


from the bundle of the sheets P, and the staple operation is performed in a state that the sheets are nipped by the downstream delivery roller pair


17


. This can release bending of the sheet bundle caused by the pressure of the side guide


11


, thereby preventing possible staple failures.




Replacement of the Staples




As shown in

FIG. 32

, the stapler


13


is structured to attach a staple cartridge


50


, and to exchange the staple cartridge


50


is replaced when the staples are supplemented. In the staple cartridge


50


, plural staple plates


50




a


constituted in connecting plural staples with each other can be loaded.




Inside the stapler


13


, formed are a staple cartridge sensor


13




a


for detecting the frame of the staple cartridge


50


, a staple detection sensor


13




b


for directly detecting the staple exposed at a lower surface of the staple cartridge


50


, and a starting staple detection sensor


13




c


formed at the tip of the stapler


13


.




Control for replacing the staple cartridge


50


is shown in a flowchart in FIG.


33


. When a job accompanied with the staple processing (S


51


), or when no staple state is detected during continuation (S


52


), the apparatus informs the user of no staple state and ask replacement of the staple cartridge


50


(S


53


). The user opens a stapler door


51


(see,

FIG. 1

) on a front surface of the finisher unit C, and loads the staple cartridge


50


in which staple plates


50




a


are filled to the stapler


13


.




Though the stapler


13


detects by the sensor that the staple cartridge


50


has been attached, the staple detection sensor


13




b


judges, at a time when staples are inserted to some extent, that there are staples by detecting the lower surface of the staple cartridge


50


. At this time, the cartridge is not attached or secured to a prescribed position yet, so that the staples may not be able to be fed or hit.




Therefore, in this embodiment, the apparatus judges whether both of the staple cartridge sensor


13




a


and the staple detection sensor


13




b


are turned on (S


54


), and if so, the apparatus recognizes that there are staples. This makes the apparatus capable of not only detecting the existence of the staples but also recognizing a state ready for striking the staples, thereby performing surely the staple replacement work.




Initializing Processing for Staples




When the apparatus detects that there are staples (S


54


) and that the staple door


51


is closed (S


55


), an initializing processing for staples begins (S


56


). Conventionally, for making staples ready, it was done by empty shots for certain times. However, such a system cannot recognize the staples even if the staple plates


50




a


already reaches the front end of the staple cartridge


50


, and those were wasteful shots.




In this embodiment, the stapler


13


has a staple head detection sensor


13




c


, which is arranged at a position opposing to the front end of the staple cartridge


50


. This staple head detection sensor


13




c


detects the end of the initializing processing, and consequently, the apparatus is not required to blindly make wasteful shots of staples any more. On the other hand, with control that empty shots are made until the staple head sensor detection sensor


13




c


detects the staples, such empty shots may be continued endlessly even where staple jamming occurs in the staple cartridge


50


because there is no limitation to the number of the empty shots.




To solve such a problem, as shown in

FIG. 34

, when the initializing processing (S


56


) starts, a counter n is first reset (S


61


). The staple plate


50




a


is fed by a single staple upon doing an empty shot (S


62


). If the staple bead detection sensor


13




c


detects the staple (S


63


), the processing ends, and if the sensor does not detect, the counter n is counted up by one (S


64


). It is then judged as to whether the counter n reaches the prescribed number (S


65


). If it is within the prescribed number, further empty shots are repeated, and if it exceeds the prescribed number, the apparatus informs the user of occurrence of staple jamming (S


66


).




By thus imposing a limitation on the empty shot number with the staple head detection sensor


13




c


when staples are detected, the apparatus can avoid the endless loop of the initializing processing. If staple jamming occurs (S


66


) during the initializing processing (S


56


), it is recognized as no staple state in the cartridge replacement processing.




Staple Jamming Processing




In some case, staple jamming occurs while the staple operation is going on When the finisher unit C detects staple jamming, in a conventional apparatus, as shown in

FIG. 35

, it is judged as to whether staple jamming occurs (S


72


) after the staple processing (S


71


) is performed. If no staple jamming occurs, the sheet bundle is delivered (S


73


) to continue the processing, and if the staple jamming occurs, the apparatus informs the user of this occurrence (S


74


) and interrupts the processing. However, this operation makes the stapler


13


stay at a position where the staple operation is executed, and even if the user wants to clear up the jamming by opening the stapler door


51


, the user's hand may not reach there.




In this embodiment, as shown in

FIG. 36

, the sheet bundle is first delivered (S


83


) after the staple processing (S


81


) is executed, and it is judged as to whether the staple jamming occurs (S


83


). If no staple jamming occurs, the processing is going on as it is, and if the staple jamming occurs, the apparatus informs the user of the jamming after the stapler


13


is moved to an initial position near the stapler door


51


(S


84


) and then stops the processing. The initial position is the vicinity of the stapler door


51


and the easiest position for clearing the jamming by the user when the user opens the door. The reason that the sheet bundle is delivered is that a remaining bundle may receive damages upon contacting with the stapler


13


while the stapler


13


is moved to the initial position.




Moving of the stapler to the initial position, even where stapler jamming occurs, can avoid a situation that the user may not reach the stapler easily, thereby making the maintenance of the apparatus easy.




Stapler Initializing Operation During Stapler Jamming




The stapler door


51


of the finisher unit C is made open and closed at a time that the staples are replaced as described above, but if the sheet under carried causes jamming, there is no need for opening and closing the door. However, the user may open and close the door, and at that time, it is foreseeable that the user may inadvertently move the stapler.




The position control of the stapler is controlled by a travelling amount from the initial position, and the present position is not confirmed by means such as a sensor or the like. Therefore, the position of the stapler is moved during recovery from paper jamming, the apparatus cannot recognize this, and the stapler may make stapling at a wrong place if the staple operation starts as it is.




In this embodiment, as shown in

FIG. 37

, where opening and closing of the stapler door


51


is detected (S


91


) and where the stapling processing is performed (S


92


), the stapler


13


is returned once to the initial position before the staple operation is executed (S


93


), and is then moved again to the stapling position to execute the staple operation (S


95


). Because the apparatus is structured to execute the staple operation after the position of the stapler


13


is thus confirmed, staples may not be placed at wrong locations even where the user moves the stapler


13


.




Delivery of Sheet Bundle




As described above, when the staple operation ends, the drive motor


40


rotates in the normal direction to render the pendulum gear unit


42


in mesh with the delivery gear


43


, and the bundle of the sheets P is delivered on the stack tray


18


upon rotation of the upstream delivery roller pair


17


in the conveyance direction.




Where a sheet bundle whose one corner is subjecting to the staple operation is delivered, an edge surface on the side opposite to the side where the staple operation is made is easily disordered. This phenomenon occurs with influences according to the size and number of the sheets, and such disorder becomes more remarkable, since the friction between sheets becomes smaller as the sheet size is smaller.




In the conventional apparatus, the control in which the downstream delivery roller pair


17


delivers the sheet bundle is unchanged, and as shown in FIG.


38


(


a


), the control of the drive motor


40


is done by the output of 100%. For example, where the delivery speed is set again in reference to the sheet bundle of sheets of a medium number under this circumstance, excessive conveyance force may be given to the sheet bundle having a small number and easily cause such disorders, and on the other hand, the delivery speed may be reduced because the mass of the sheet bundle may be larger where the number of the stacked sheets becomes larger.




In this embodiment, to solve this problem, the stack tray


18


is moved up where the sheet bundle whose one location is subject to the staple operation is delivered, and the apparatus delivers the sheets where the stacking surface of the stack tray


18


is made closer to the downstream delivery roller pair


17


. This makes resistance between the sheet bundle and the stacked surface of the stack tray


18


smaller and suppresses occurrences of such disorders.




Furthermore, the stack tray


18


located closer to the downstream delivery roller pair


17


is dissented for a fixed amount right before the rear end of the sheet bundle passes by the downstream delivery roller pair


17


. This prevents the sheets from proceeding in the reverse way due to contacts or the like of the rear end of the sheet bundle with the downstream delivery roller pair


17


.




As shown in the drawing, the setting up speed of the drive motor


40


during delivery is controlled to be slow according to the sheet size and sheet number, and thereby the apparatus corresponds to the sheet bundles having different sheet sizes and sheet numbers. That is, the apparatus starts with drive force of about 80% to the sheets of a large size and with drive force of about 60% to the sheets of a small size.




More specifically, as shown in FIG.


38


(


b


), when the sheet size is the small size, the setting up speed is made slower than that of the large size, thereby preventing disorders which otherwise occurs due to quick acceleration. When the stacked number is large, the drive torque at the setting up time is made lower than the time when the number is smaller, and the torque from the drive roller is controlled as to transmit to the lowermost sheet of the sheet bundle adequately and evenly. The drive shifts to have gradually the normal conveyance speed and the normal drive torque, and finally, any sheet bundles even having the different size and number are delivered with substantially the equal speed.




From those operations, this apparatus can improve the stacking property on the stack tray


18


in preventing the disorder in the edge surface on a side where no staple is made even when the sheet bundle whose one location is subjecting to the staple operation is delivered, and can deliver the sheets with the same speed regardless the size and number of the bundle. The drive motor


40


is not drive with the 100% output, so that this apparatus has an effect to reduce the operating sounds generated from the apparatus.




By making closer the stack tray


18


to the downstream delivery roller pair


17


, the sheet bundle to be delivered is prevented from being bent, so that the lowermost sheet of the sheet bundle is prevented from bending.




Detection of Stacking Mixed Sheets




Where the stacked sheets on the stacking tray


18


are delivered with control for sheet size or sheet processing mode, which is different from the stacked sheets, the apparatus is required to impose some limitation on the sheet number to be stacked as a special handling for mixed sheets because the stacking property becomes impaired in comparison with the sheet stacking in the same size or sheet stacking for the same processing.




A stack sensor


53


is therefore provided at about a center of the stacking tray


18


for detecting whether the sheet is stacked on the tray, and if the sheet P is stacked on the stacking tray


18


, the apparatus executes the handling program for mixed sheets with the following conditions.




(1) Where the sheet P stacked on the tray is not a sheet delivered and stacked on the finisher unit C.




(2) Where a sheet P having the different sheet size is delivered and stacked on the stack tray


18


by the finisher unit C.




(3) Where a sheet is delivered and stacked with the different processing mode by the finisher unit C.




In the finisher C according to this embodiment, a detection signal from stack sensor


53


is monitored when image formation starts, and the signal is not monitored after the image formation has already started. This is because the first delivered sheet may be misidentified as a sheet of mixed sheets if the detection signal from the stack sensor


53


is monitored even after the sheet is delivered after the image formation has already started.




Detection of the Stacked Amount




A measuring sensor


54


arranged on a top of the rocking guide


20


detects the level of the sheets stacked on the stack tray


18


or the topmost surface of the sheet bundle. The measuring sensor


54


includes a light emitting portion radiating light such as infrared ray to sheet bundles and a photo receiving portion for receiving light reflected irregularly at the sheet bundle. The sensor


54


detects the level by measuring the angle of the reflected light.




When the sheets are delivered on the stack tray


18


, as shown in FIG.


39


(


a


), the sheet P may not fall because the rear end of the sheet P is trapped at the finisher unit C. If the level detection is implemented in such a circumstance, the level may not be detected accurately. Therefore, this apparatus has a structure that when the sheet P is delivered the stack tray


18


moves down once and up again to render the sheet P settled on the stack tray


18


.




It is desirable that the measuring sensor


54


detects the level when the stack tray


18


moves up where the level of the sheets P stacked on the stack tray


18


is detected. However, because the subsequent sheet P is in fact already delivered when the stack tray


18


moves up, the sensor cannot detect the sheet on the stack tray


18


due to interference from the delivered sheet.




This apparatus is structured to get the detected result if data within the permissive error range are brought successively where the level is detected twice or more with a prescribed time interval, because the sheets may not be settled yet at a moment where a level detection is performed during dissenting of the stack tray


18


. The apparatus can detect the established actual level and maximizes the productivity of the apparatus.




The position of the stack tray


18


after moved up is controlled so that the stacked surface becomes always constant based on the data obtained by the level detection (paper surface level control).




Here, a structure for recognizing the sheet stacking amount (the level of the stacked sheets) on the stack tray


18


is briefly described using FIG.


39


(


b


). It is to be noted that the detailed structure is disclosed in Japanese Unexamined Patent Publication (KOKAI) Heisei No. 9-48549. FIG.


39


(


b


) is a perspective view showing a schematic structure, as the essential portion, of the tray unit, a driver for the tray unit, and a position detecting portion of the tray unit.




In this embodiment, a tray unit


58


is structured by securing three stack trays


18


to respective tray frames


57


, and the three stack trays


18


can move up and down as a united body with respect to the finisher frame


59


of the finisher unit C. Moving up and down of the tray unit


58


, or namely, the stack trays


18


, is structured by moving up and down of the tray unit itself with respect to the finisher frame


59


where the normal and reverse rotational drive of a stacker motor


209


is transmitted to a rack portion


58




a


formed at a portion of the tray unit


58


via a pinion gear


225


.




An encoder


226


is mounted on an output shaft of the stacker motor


209


. Where the pulse amount from the encoder


226


is detected with a stacker motor clock sensor


227


, the apparatus can detect how far pulses the tray unit


58


moves from a home position as the initial position, or the traveling amount of the tray unit


58


. It is to be noted that the detection whether the stack tray


18


is in the home position is made by detection of a tray unit flag


57




a


provided at a lower portion of the tray frarne


57


by a tray home position sensor


228


.




After the tray unit


58


is detected as in the home position from a copy operation signal or the like (or the tray home position sensor


228


detects the tray unit flag


57




a


), the stack trays


18


are set at the predetermined positions with respect to the downstream delivery roller pair


17


based on the detection signal of the measuring sensor


54


, and the stack trays


18


receive the sheets delivered from the downstream delivery roller pair


17


.




This apparatus also has a structure that the stack tray


18


is moved down by a prescribed amount at each stack of the sheet or sheet bundle to maintain the topmost level of the sheet on the stack tray


18


at a position of the prescribed amount from the downstream delivery roller pair


17


.




In this apparatus, an MPU


200


(see,

FIG. 42

) in the finisher unit C as described below can recognize what amount of clocks the tray unit


58


travels from the home position or namely, the traveling amount of the stack tray


18


.




The apparatus thus structured, can determine the positions of the stack tray


18


and the topmost surface of the sheets on the stack tray


18


and can recognize the stacked amount of the stacked sheets on the stack tray


18


(the height of the stacked sheets).




As described above, the apparatus recognizes that sheets are fully stacked if it is over the predetermined amount based on the processing mode and the sheet size upon detecting the position of the stack tray


18


and the stacked amount of the sheets P stacked on the stack tray


18


through the level detection in a manner.




However, even if the fully stacked state is detected, the sheets P, in some case, may be not settled yet due to curling or a state of the trapped rear end of the sheets P on the stack tray


18


. Therefore, the apparatus may stop the operation in judging as it is the full stacked state though in fact not fully stacked, thereby possibly reducing the productivity.




In this embodiment, the apparatus stops the operation upon judging that the sheets are fully stacked only when detecting that the topmost sheet on the stacked tray


18


is at a prescribed level or higher, or when detecting plural times that the stacked amount of the sheets on the stack tray


18


exceeds the prescribed amount. More specifically, the apparatus stops the operation upon moving up and down the stack tray


18


and judging that the sheets are fully stacked only when detecting plural times (three times in this embodiment) that the stacked amount of the sheets on the stack tray


18


exceeds the prescribed amount upon detecting the sheet stacked amount on the stack tray


18


at every operation (or after completion of the operation).




Moreover, in this embodiment, the apparatus performs detection of the fully stacked state as described above at every sheet delivery of a prescribed number (e.g., five sheets) onto the stack tray


18


.




This apparatus thus can detect as to whether the sheet stacked amount exceeds the prescribed amount after solving curling or a state of the trapped rear end of the sheets P occurred on the stack tray


18


, can prevent erroneous recognition in the detection of the fully stacked sheets because the apparatus judges that the sheets are fully stacked only when detecting successively that the sheet stacked amount exceeds the prescribed amount and stops the operation, and can provide adequate productivity.




It is to be noted that the apparatus has a structure for suggesting to the user that the stacked sheet (or sheet bundle) should be removed from the stack tray


18


when the apparatus detects the fully stacking of the sheets and stops its operation.




System Stop Timing During Detection of Fully Stacked Sheets




However, if image formation is stopped upon detection that the sheets are fully stacked as described above even while the sorting operation is going on, the sheet bundle in a midway of the sorting operation is stacked on the stack tray


18


, and removal of this may make complicated handling of the stacked sheets because the sorting operation ends. On the other hand, a margin to some extent may usually be set for detection of the fully stacked sheets on the stack tray


18


, and even where the sheets are detected as full, further sheets can be stacked thereon.




In this embodiment, as shown in

FIG. 40

, if the fully stacked state is detected (S


102


) in a midway of the image formation and stacking operation (S


101


), the apparatus judges whether a single bundle is completed (S


103


), and if image formation of the single bundle is not yet completed, the image formation is continued as it is without stopping the formation. This structure avoids a sheet bundle in a midway of the sorting operation even where the sheet bundle is removed from the stack tray


18


and makes easier the handling.




Subsequently, the measuring sensor


54


detects the fully stacked state, and the apparatus stops the image recording as in the fully stacked state while it is not in the sorting operation (S


104


).




Special Sheets




If sheets delivered and stacked on the stack tray


18


are special sheets, particularly, OHP sheets, because the light emitted from the measuring sensor


54


does not reflect irregularly so much on the OHP sheet surface but reflect mostly in a mirror fashion, errors of distances of 20 to 30 mm (experimental values) may occur in comparison with measurements to the ordinary sheets. If the ordinary control is made, the stack tray


18


is moved up since the apparatus recognizes that the stacked top surface is far (low) that the actual one where detecting the fully stacked state or controlling the stacked height, and in some case, the stacked sheet may be trapped at the delivery opening, so that failures in stacking such that sheets are damaged by collisions of the delivered sheets to the stacked sheets may occur.




In this embodiment, as shown in

FIG. 41

, the apparatus judges whether the stacked sheets containing the sheets fed from the apparatus multi-tray (manual feeding tray) are removed from the sheets on the stack tray


18


(S


111


), and if such sheets are removed, an approximate detection flag is cleared (S


112


), or namely, it is detected as not the approximate detection.




If the approximate detection flag is off (S


113


), the normal tray control is performed (S


114


) as presuming that no sheet is stacked or sheets having no error in detection of the measuring sensor are stacked. If the approximate detection flag is on (S


113


), the apparatus does the approximate detection control (S


115


).




The approximate detection control herein presumes errors in advance and amend them where the surface level of the delivered stacked sheets on the stack tray


18


, which is measured by the measuring sensor


54


, is not trustful due to special sheets or the like. In this embodiment, it indicates a possibility that the sheets fed from the apparatus multi-tray (manual feeding tray) are stacked on the stack tray


18


.




The approximate detection control also indicates that based on the errors in the sensor, it is controlled to be lower than the predetermined stacked surface level, more specifically, about 30 mm lower.




After the delivered sheets are stacked on the stack tray


18


(S


116


), the apparatus judges whether the stacked sheets are the subject matter of the approximate detection (S


117


). This judgment is made in the same way depending on whether the stacked sheets are fed from the apparatus multi-tray (manual feeding tray).




According to this judgment, when the sheets are of the subject matter of the approximate, detection, the approximate detection flag is set (S


118


), and in the subsequent tray control, the approximate detection control enters (S


115


).




If the sheets are not of the subject matter of the approximate detection, the apparatus implements the stacked amount detection and the sheet height control (S


121


), but if they are of the subject matter of the approximate detection, the apparatus implements only the stacked amount detection (S


119


).




In the above embodiment the control is described in which all the sheets fed from the apparatus manual feeding opening are processed entirely as special sheets. Herein, a control for turning on and off the approximate detection flag in judging whether the stacked sheets are special.




This judgment is made by a calculation of a distance by the measuring sensor


54


at two points where the stack tray


18


is moved at the two points having the different heights at which a traveling amount is known in advance. On the other hand, the distance that the stack tray


18


is moved is measured by a traveling amount detecting means not shown. If the differential between the measured value and the difference of the distances measured by the measuring sensor is equal to or more than a prescribed amount (in general, the measure value by the sensor is larger), the apparatus judges that the stacked sheets are the subject matter of the approximate detection.




By this operation, even if the sheets to he conveyed are special sheets such as the OHP sheets that the measuring sensor


54


cannot measure easily, or even if the sheets are changed to special sheets in a midway, the apparatus can do the sheet processing substantially the same as the normal sheets.




The measurement of the OHP sheets done by the measuring sensor creates a shift of a certain amount (20 to 30 mm) in comparison with plain paper as described above, but the deviations in the measure values according the sheet number are in the same way as the plain paper. Therefore, if the delivered sheets are recognized as the OHP sheets, the apparatus can do the detection of the fully stacked state and control for stacked height in use of the measuring sensor


54


in the same manner as the normal cases by shifting in a certain amount the stack tray


18


downward.




Structure of the Control System for the Finisher Unit




Referring to

FIG. 42

, the structure of the control system for the finisher unit C of the sheet processing apparatus B is briefly described.




In

FIG. 42

, numeral


200


represents the MPU as a control means. The MPU


200


receives input signals from the loading sensor


28


, the entry sensor


27


, the buffer sensor


26


, the delivery sensor


29


, the measuring sensor


54


, the stack sensor


53


, the drive motor rotation detecting sensor


55


, the staple cartridge sensor


13




a


, the staple detection sensor


13




b


, the starting staple detection sensor


13




c


, the stacker motor clock sensor


227


for detecting the pulse amount of the encoder


226


provided on the output shaft of the stacker motor


209


, the tray home position sensor


228


detecting the home position of the tray unit


58


(or its stack tray


18


), and the like.




Based on the above signals, the apparatus drives, through respective drivers D


1


to D


11


, a first flapper solenoid


201


switching the first flapper


21


, a second flapper solenoid


202


switching the second flapper


22


, a third flapper solenoid


203


switching the third flapper


23


, the buffer roller


23


, the downstream delivery roller pair


16


, and the knurled belt


32


, and moves up and down the shutter portion


34


by the reverse rotation. The apparatus also controls a paddle solenoid


206


for engagement and disengagement of the drive force from the buffer conveyance motor


204


to rotate the paddle


31


, a side guide motor


207


for moving the side guide


11


in sliding the side guide


11


, a reference guide solenoid


208


for escaping the reference guide


37


from the staple tray


12


during the sheet shift, the drive motor


40


for rocking the rocking guide


20


and driving rotatively the downstream delivery roller


17




a


in the normal and reversc directions, the stacker motor


209


for moving up and down the stack tray


18


, a stapler motor


210


for staple operation of the stapler


13


and feeding of the staples, a stapler traveling motor


211


for moving the position of the stapler


13


, and so on.




The respective motors control the traveling amount, speed, and so on according to the control input pulse and the input from the encoder detecting the rotation amount.




Stitcher Unit




Respective structures of portions in the stitcher unit D in the sheet processing apparatus B is described in detail next. As described above, the stitcher unit D as shown in

FIG. 3

delivers sheets in providing the folding operation after the sheets delivered from the image forming apparatus body A are conveyed in the vertical path


60


composed of path guides


60




a


,


60




b


and are stapled at the center of the sheets by means of the stapler unit


61


.




The sheets P delivered from the image forming apparatus body A are fed to the vertical path


60


of the stitcher unit D in cooperation with the first flapper


21


, and are stacked and aligned while the lower end of the sheets is in contact with the stopper


62


. An upper roller pair


63


is provided as a conveying means at an upper portion of the vertical path


60


, and plural flappers


64


are formed on the downstream side of the pair. In this embodiment, the flappers


64


are constituted of a first flapper


64




a


and a second flapper


64




b


, which allow to change selectively the conveyance route according to the size of the sheets P.




A movable guide


65


is provided around the flappers


64


. The guide


65


is urged toward the flapper


64


by an urging means


65




a


to constitute a part of the conveyance route of the vertical path


60


. This movable guide


65


can expose the inside of the vertical path


60


near the flappers


64


by pivotally movement by gripping a handle


65




b


, thereby allowing recovery for sheets when jamming occurs.




Plural sheet sensors


66


are arranged at positions opposing to the flapper


64


with respect to the vertical path


60


. A first upper sensor


66




a


is placed between the upper roller pair


63


and the first flapper


64




a


; a second upper sensor


66




b


is placed at a position opposing to the first flapper


64


; and a third upper sensor


66




c


is placed at a position opposing to the second flapper


64




b


. Those sheet sensors


66


can detect existence of the passing sheet and the front end or rear end of the sheet.




Lower Roller Pair




The stapler unit


61


as describe below is arranged around the center of the vertical path


60


, and an anvil


61




d


is placed at a position opposing to the stapler unit


61


with respect to the vertical path


60


. A lower roller pair


67


is formed as a conveying means on a downstream side of the stapler unit


61


, and the pair


67


includes a drive roller


68


as a drive rotary body for transmitting the drive force from the drive source not shown, and a pickup roller


69


as a movable rotary body driven to rotate in pushing the sheet to the drive roller


68


.




As shown in

FIG. 43

, the pickup roller


69


is mounted at one end of a conveyance roller arm


69




a


, and the other end of the conveyance roller arm


69




a


is rotatively supported to the path guide


60




b


of the vertical path


60


through a pivotal shaft


69




b


. An elastic member


69




c


is attached around the center of the conveyance roller arm


69




a


, thereby urging the pickup roller


69


to the drive roller


68


. Meanwhile, a pressing releasing arm


70


driven by a solenoid not shown is formed at the conveyance roller arm


69




a


, and the arm


70


is able to separate the pickup roller


69


from the drive roller


68


. Therefore, the pickup roller


69


can change its position between the pressing position for pushing the sheet to the drive roller


68


and the separation position for separating the roller


69


from the drive roller


68


.




Pressing of the Pickup Roller




When the sheet P is conveyed by the lower roller pair


67


, the roller


69


is pressed as shown in FIG.


44


(


a


) on the sheet after the front end of the sheet passes by the position of the pickup roller


69


, and the sheet P is carried while nipped by the pickup roller


69


and the drive roller


68


. The subsequently fed sheet proceeds at that time toward the drive roller side of the already stacked sheets P, and is conveyed in skidding together with the already stacked sheets.




If the pickup roller


69


is normally in pressed contact with the drive roller


68


, the roller may exert conveyance force to the sheets P that have reach the stopper


62


and been stacked there and may fold the sheets. In this embodiment, the pickup roller


69


comes in pressed contact with the roller


68


only when necessary, so that the sheets are aligned well and can be stacked precisely to the vertical path


60


.




Separation of the Pickup Roller




As shown in FIG.


44


(


b


), the pickup roller


69


is separated at a position where the front end of the sheet P come close to a prescribed position from the stopper


62


. In this embodiment, the prescribed position from the stopper


62


is set for 10 mm in this embodiment, and after the pickup roller


69


is separated, the sheet P is conveyed to the stopper


62


from the inertial moment prior to this moment and the weight of the sheet itself. It is to be noted that the position of the front end of the sheet P is recognized by a conveyance distance after the front end of the sheet passes by the sheet sensor


66


.




If the sheet is conveyed while the pickup roller


69


is in pressed contact with the drive roller


68


until the sheet P reaches the stopper


62


, the sheet may be bent or may impair proper alignment due to occurrences of rebounding when the pickup roller


69


is separated. In this embodiment, the pickup roller


69


is separated at an early stage, thereby preventing the sheets from overly conveyed and avoiding the above problem.




Drive Roller when the Pickup Roller is Separated




As described above, if the pickup roller


69


is separated before the sheet P is stacked on the stopper


62


, the sheet P may proceed with great force in the vertical path


60


where the stacked number is not so large, and rebounding of the sheet may create disorder in alignment. If the stacked number is large, the friction opposing to smooth passage may increase due to narrower space in the vertical path


60


, so that the sheet may not reach the stopper


62


.




This embodiment is structured that the drive roller


68


keeps drive rotation even after the pickup roller


69


is separated. The sheet P conveyed at that time receives only weak conveyance force from contact force because the sheet is not in pressed contact with the drive roller


68


. Accordingly, the sheet P is surely conveyed to the stopper


62


, and can be aligned certainly because pushed.




Vertical Path Shape




The sheet P stacked upon hitting the stopper


62


is aligned in the width direction by an alignment member


71


. At that time, the sheet P is in an upright state, and if the sheet is flexible, the sheet is folded. In this embodiment, to solve such a problem, a projection


60




c


projecting in the conveyance route of the vertical path


60


is formed at the path guide


60




a


, thereby bending the stacked sheets horizontally, or namely creating rigidity in the vertical direction. Accordingly, the sheets P can be stacked without folding of the sheets.




On the other hand, if the sheets remain bent in the horizontal direction, it is not favorable when the stapler unit


61


makes the stapling operation. In this embodiment, as shown in

FIG. 45

, the vertical path


60


is bent between the upper portion and the lower portion of the stapler unit


61


, thereby making the sheets P bent around the center to the vertical direction. That is, the sheets P are stacked where the lower portion is bent in the horizontal direction and where the center portion is bent in the vertical direction. This structure can stack the sheets without folding the sheets and can make the position for executing the staple operation flat.




Stopper Mechanism




Referring to

FIG. 47

, a drive mechanism for the stopper


62


is described. Sliding members


62




a


are mounted on both ends of the stopper


62


and supported slidably along a stopper frame


72


. The stopper


62


is securely coupled to a stopper drive belt


73


wound around a drive pulley


73




a


and idler pulley


73




b


. A drive gear


73




d


is fixed to a rotary shaft


73




c


of the drive pulley


73




a


and is connected to a stopper drive motor


74


. That is, if the stopper drive motor


74


rotates, the stopper drive belt


73


rotates upon receiving the drive force and can drive the stopper


62


up and down.




A stopper sensor


75


is provided on a sheet stacking surface of the stopper


62


and can detect the sheet P where the front end of the sheet P hits the stopper


62


. A flag


62




b


is formed at the lower portion of the stopper


62


, and a stopper home sensor


76


detects the stopper


62


when the stopper


62


reaches the home position.




Stapler Unit




A mechanism of the stapler unit as a sheet stapling means for rendering the staple operation of the sheet bundle is described next.




As shown in

FIG. 48

, the stapler unit


61


is mounted at two locations symmetrically in the horizontal direction with respect to the center in the sheet width direction by a support plate


77


secured to the frame at a center position in the conveyance direction of the sheet bundle aligned by the vertical path


60


.




In

FIG. 48

, the stapler unit


61


is constituted of a forming portion


61




b


serving as a staple shooting means located on an upper side and supported pivotally around a rotary shaft


61




a


, a drive unit


61




c


, and a anvil


61




d


.




The vertical path


60


extends below the stapler unit


61


to guide the sheet bundle by the path guides


60




a


,


60




b


and the anvil


61




d


. The vertical guide


60


is structured so that a guide surface


60




b




1


of the path guide


60




b


for guiding the sheet bundle and a stapling surface


61




d




1


of the anvil


61




d


for stapling the guided sheet bundle are angled with alpha to each other. The path guide


60




a


with the angle alpha on the upper surface side for forming the vertical path has a cutoff hole


60




a




1


of a size not interfering with the forming portion


61




b


when the forming portion


61




b


of the stapler unit


61


is moved pivotally.




A staple cartridge


61




e


is detachably attached to the forming portion


61




b


, and in the staple cartridge


61




e


, the staples


61




f


connected as a plate form are filled in a number of about 2000 to 5000. The staples


61




f


in the plate form filled in the staple cartridge


61




e


are urged downward by a spring


61




g


provided at a topmost end of the staple cartridge


61




e


, and the spring


61




g


gives the conveyance force to a staple feeding roller


61




h


disposed on a lowermost side.




The staples


61




f


fed by the staple feeding roller


61




h


are formed individually into a rectangular letter-U shape by rocking the forming portion


61




b


around the rotary shaft


61




a


as the center in the arrow direction (the counterclockwise direction in FIG.


48


). That is, when a stapler motor


61




i


starts moving, an eccentric cam gear


61




k


rotates through a gear series


61




j


. By operation of an eccentric cam mounted to the eccentric cam gear


61




k


as a united body, the forming portion


61




b


performs the stapling operation (clinching operation) by its rocking movement in the arrow direction in

FIG. 48

(toward the anvil


61




d


), thereby stapling the sheet bundle by folding the hit staple


61




f


at the anvil


61




d


located at the lower surface of the sheet bundle.




A flag not shown is disposed coaxially with the eccentric cam gear


61




k


, and the apparatus detects the flag with a stapler sensor not shown to monitor whether the stapler unit


61


is in a clinching state, ends the clinching operation (or it is before clinching start).




Filling of the Staples




In the staple operation as described above, if no staple exists in the staple cartridge


61




e


as a staple filling member, the cartridge


61




e


has to be replaced. Now, filling of staples for the stapler unit


61


is described.




To the stapler unit


61


according to the embodiment, two staple cartridges


61




e


are to be attached for stapling two positions in the sheet width direction as shown in

FIG. 49

, and if all staple has gone from either staple cartridges


61




e


, the stapler unit can detect the no staple status.




When the no staple status is detected, the stapler unit


61


as shown in

FIG. 49

is pulled in the arrow direction, and staples are newly filled in the staple cartridge


61




e


. If only one staple cartridge


61




e


becomes the no staple status where the other staple cartridge


61




e


still has some staples, the staples in the other staple cartridge


61




e


may be used up soon even where the staples are filled in the one staple cartridge


61




e


, and it is unproductive to pull the stapler unit


61


upon stopping the operation of the apparatus to fill the staples.




In this embodiment, when the no staple status is detected, the control panel as a display indicates to prompt to fill staples at the same time in the two staple cartridges


61




e


by pulling the stapler unit


61


to fill the staples in the one staple cartridge


61




c


in the no staple status and by replacing the remaining staples in the other staple cartridge


61




e


with new staples even where some staples are remaining the other staple cartridge


61




e.






According to this display, where the staples are filled simultaneously in the two staple cartridges


61




e


, the two staple cartridges generally enter in the no staple status at the same time, so that when the one staple cartridge


61




e


holds no staple, the other staple cartridge


61




e


holds only few remaining staples even where both do not enter in the no staple status at the same time. Filling the staples in both cartridges at the same time makes this operation more productive than filling the staples individually in each staple cartridge


61




e


when each runs out the staples.




It is to be noted that although in this embodiment the two staple cartridges


61




e


are placed, staples in the all cartridges can be replaced at the same time even in a case that three or more staple cartridges


61


e are installed in the stapler unit


61


.




The apparatus is required to detect as to whether the staple initialization is made where the stapler motor


61




i


(see,

FIG. 48

) is drive to initialize the staple state after the staples are filled as described above. Although such a staple initialization can be detected by a sensor or the like, the initialization in this embodiment is detected by checking the drive current value of the stapler motor


61




i.






That is, where staples are set to the initialized position by drive of the stapler motor


61




i


, the stapler motor


61




i


is subject to a small load prior to the staple initialization (the empty shot state), and therefore, the current driving the stapler motor


61




i


is small as shown in FIG.


50


(


a


). On the other hand, when the staples are set to the initial position (the staple shot state), the stapler motor


61




i


is subject to a large load, and therefore, the current driving the motor becomes larger than that in the empty shot state as shown in FIG.


50


(


b


). Accordingly, when the value of the current driving the stapler motor


61




i


is detected, the apparatus detects that it is before the staple initialization if the detected current value is smaller than the prescribed value and that the staple initialization is done if the detected current value is larger than the prescribed value.




Such detection of the staple initialization in use of the drive current of the stapler motor


61




i


eliminates necessity for installing a special sensor for the staple initialization and can reduce the number of parts and costs.




Post-Processing of the Staple Operation)




After the sheet bundle P, which is conveyed and aligned at the vertical path


60


as described above, is stapled at the center in the sheet conveyance direction by drive of the stapler unit


61


, the stopper


62


is moved down to convey the sheet bundle to the folding position. As shown in

FIG. 51

, at that time, if the staple


61




f


after the staple operation is fitted in a groove


61




d




2


on the anvil


61




d


, the staple


61




f


is trapped at the groove


61




d




2


even if the stopper


62


moves downward, thereby possibly causing conveyance failures of the sheet bundle P.




To solve such a problem, in this embodiment, as shown in

FIG. 51

, the pickup roller


69


of the lower roller pair


67


is structured to be rocked once in the arrow direction in

FIG. 51

before the stapled sheet bundle P is conveyed downward. This rocking movement of the pickup roller


69


as the position changing means pushes the sheet bundle P toward the path guide


60




a


, and therefore, the staple


61




f


fitted in the groove


61




d




2


on the anvil


61




d


is surely taken out of the groove


61




d




2


. Accordingly, the stopper


62


does not move down while the staple


61




f


is fitted in the groove


61




d




2


, and the apparatus can surely prevent failures in sheet conveyance from occurring.




Although in this embodiment, exemplified is an example that the pickup roller


69


is rocked to shift the position of the sheets to render the staple


61




f


escape from the groove


61




d




2


, a special member as shifting means for shifting the sheets so as to take the staple


61




f


out of the groove


61




d




2


may be provided instead of the pickup roller


69


and be executed so.




It is to be noted that when the sheet bundle is conveyed down by moving the stopper


62


downward, the pickup roller


69


is spaced from the drive roller


68


, and the drive roller


68


is driven to rotate in a direction to move the sheet P down.




This structure does not create any frictional load during moving down of the sheet when the sheet bundle falls by its weight even where the sheet is in contact with the drive roller


68


formed of a material having a high frictional co-efficient. The sheet surely follows the dissenting stopper


62




b


, thereby guaranteeing the accuracy in the folding position.




Fine Adjustments of the Staple Position and the Folding Position




To perform the staple operation and the folding operation as described below accurately with respect to the center in the conveyance direction of the sheet bundle, the stopper


62


is required to move so that the center of the sheet bundle is positioned precisely at the staple position as well as the folding position. However, the length of the sheets may be not constant due to deviations when the sheets are cut or extensions or contractions due to humidity, and in some case, the staple position and the folding position may be out of the center of the sheet bundle P. In such a case, the position of the stopper


62


as a supporting means for supporting the lower end of the sheets is required to be finely adjusted.




In a conventional apparatus, the stopper is structured to be screwed in a long hole bored in a frame supporting the stopper, and the position of the stopper is finely adjusted in the range of the long hole, thereby finely adjusting the staple position and the folding position of the sheet bundle as described above.




However, such an apparatus is required to loosen the screw to finely adjust the position as described above and to fasten the screw after a fine adjustment is made, so that it requires laborious work for adjustment as well as makes tough to do a fine adjustment precisely. Such adjustment work is also done only by service persons.




In this embodiment, to solve such a problem, the shift amount of the stopper


62


is finely adjustable by a drive mechanism (see

FIG. 47

) as described above according to designations from an input means such as a control panel formed on the image forming apparatus body A or the sheet processing apparatus B.




More specifically, the apparatus is structured so that the shift amount (moving up amount) when the stopper


62


is moved from the home position to a lower end stopping position (stapling stopping position) as a stopping position for the staple operation according to the sheet size is finely adjustable according to the designation from a control panel (not shown) formed on the image forming apparatus body A. For example, the shift amount from the home position to the lower end position of the sheet of the respective sizes is normally constant for every sheet size, but the shift amount is increased or decreased by an amount according to the designation from the control panel as an input means to finely adjust the shift amount when the stopper


62


is moved up, thereby changing the stopping position by the portion of the fine adjustment.




Alternatively, the apparatus is structured so that the shift amount (moving down amount) when the stopper


62


is moved, after the sheets are stapled, from the lower end stopping position (stapling stopping position) according to the sheet size to a lower end stopping position (folding stopping position) during the folding operation is finely adjustable according to a dip switch (not shown) or a control panel on an electrical circuit substrate formed on the sheet processing apparatus B. The shift amount of the stopper


62


from the lower end stopping position during the staple operation to a lower end stopping position during the folding operation is constant (e.g., 70 mm in this embodiment) regardless the sheet size, but the shift amount is increased or decreased by an amount according to the dip switch on the electrical circuit substrate to finely adjust the shift amount when the stopper


62


is moved down, thereby changing the stopping position by the portion of the fine adjustment.




With such a constitution, the stopper for receiving the lower end of the sheet is finely adjustable precisely and easily.




The sheet may extend longitudinally due to roller pressure, temperature, humidity, and the like during the conveyance of the sheet. Therefore, where the sheet length is detected by a sheet length detecting means during conveyance of the sheet, the stopping position of the stopper


62


can be automatically adjusted according to the detected results.




For example, as shown in a flowchart of

FIG. 52

, when the sheet is conveyed to the vertical path


60


, any one of the upper sensors


66




a


to


66




c


detects this according to the sheet size. When this sensor detects the front end of the sheet (S


131


), the pulse counter, not shown, for conveyance motor is turned on (S


132


) to count the pulse number up to a time from passing of the rear end of the sheet at the sensor position until the sensor is turned off (S


133


, S


134


). From this operation, the length of the sheet fed in the vertical path


60


can be detected precisely. The shift amount of the stopper


62


from the home position to the staple stopping position and the shift amount from the staple stopping position to the folding stopping position are finely adjusted upon automatic calculation by the control means according to the length of the conveyed sheet (slightly extended sheet) (S


135


), and the stopper


62


is moved according to the shift amount after the fine adjustment.




Where the stopper shift amount is automatically adjusted finely according to the sheet length detected during the conveyance, the user does not have to set for fine adjustment, and the sheet can be stopped at the staple position and the folding position precisely and easily.




Folding of the Sheet Bundle




Thus, the staple position is conveyed until reaching the position of the folding roller


78


disposed below the stapler unit


61


by the down movement of the stopper


62


, and the sheets are hit by a striking plate


79




a


at the staple position and folded in folio on conveyed through nipping the sheets by the folding roller


78


while the sheets are in folio. Referring to

FIG. 53

to

FIG. 57

, the sheet folding structure is described next




As shown in

FIG. 53

, the folding roller


78


is constituted of a stable roller


78




a


pivotally movable around a secured rotary shaft


78




c


, and a movable roller


78




b


attached pivotally to a support arm


80


which can be pivotally moved around a pendulum


80




a


with respect to the apparatus frame. The folding roller


78


is constituted in which a spring


81


engaged at one end of the support arm


80


renders both rollers


78




a


,


78




b


in pressed contact with each other. This structure allows the pitch between the folding rollers


78


to be corrected according to the thickness of the sheet bundle P to be nipped.




The structure for driving the folding roller


78


is as shown in FIG.


54


and

FIG. 55

with a motor pulley


83


secured to an output shaft


82




a


of a folding motor


82


. The drive force of the motor pulley


83


is transmitted to a pulley of an idler gear pulley


85


via a timing belt


84


. The idler gear pulley


85


is formed coaxially with the pulley and the gear portion.




Respective folding gears


86


,


87


are secured to the shaft of the folding roller


78


described above, and both gears


86


,


87


are in mesh with each other. One end of the folding gear


86


is in mesh with the gear portion of the idler gear pulley


85


. The folding gear


86


is also meshing an idler gear


88


.




The rotary force of the folding motor


82


is transmitted to the idler gear pulley


85


from the motor pulley


83


through the timing belt


84


. The rotation of the idler gear pulley


85


is transmitted to the folding gear


87


from the folding gear


86


, thereby driving the folding roller


78


. The rotation force is also transmitted at the same time to the idler gear


88


in meshing with the folding gear


86


. The idler gear


88


also transmits the rotation force to the delivery roller as described below.




In

FIG. 54

, the numeral


79


is a projecting unit as a projecting means, and is constituted of a projecting plate


79




a


, holders


79




b


,


79




d


, axes


79




c


,


79




e


, and so on. The projecting plate


79




a


is supported by the holders


79




b


,


79




d


, and the axes


79




c


,


79




e


are secured to the holder


79




b


. A roller not shown is rotatively mounted on outer peripheral surfaces of the axes


79




c


,


79




e


, and the roller slides in a groove


89


formed in the housing frame.




The numeral


90


is a projecting motor, and a motor pulley


90




a


is secured to the output shaft of the motor. The numeral


91


is an idler pulley, in which a pulley portion and a gear portion are formed coaxially. A timing belt


92


is wound around the pulley portion of the idler gear pulley


91


and the motor pulley


90




a


. The gear portion of the idler gear pulley


91


is in mesh with a gear


126


having an axis


93


as a part. As shown in

FIG. 55

, flags


95




a


,


95




b


are fixed to a rotary shaft


94




a


of a gear


94


. The flags


95




a


,


95




b


have cutoffs as a part. A projecting home sensor


96




a


and a projecting position sensor


96




b


are provided at positions where the cutoffs of the flags


95




a


,


95




b


are detected. The projecting home sensor


96




a


is arranged to detect the projecting plate


79




a


at a position deeper than the sheet conveyance surface constituted by the path guides


60




a


,


60




b


, and the projecting position sensor


96




b


is arranged to detect the projecting plate


79




a


at a position where the projecting plate


79


is inserted.




As shown in

FIG. 55

, a rotational plate


97


having a shaft


97




a


in substantially the same way as the gear


94


is secured to the other end of the gear


94


On the rotary shaft


94




a


, and is structured to rotate in synchrony with the gear


94


.




The rotary force of the projecting motor


90


is transmitted to the idler gear pulley


91


from the motor pulley


90




a


through the timing belt


92


. The gear


94


rotates because the idler gear pulley


91


, thereby moving the axis


93


circularly. One end of a link


98


is fitted to the axis


93


, and the other end of the link


98


is fitted to the axis


79




c


of the projecting unit


79


. Thus, the circle movement of the axis


93


is transmitted to the axis


79




c


of the projecting unit


79


through the link


98


, and the axis


79




c


moves linearly along the groove


89


on the frame fitting to the axis


79




c


together through a roller, not shown.




The other end of the projecting unit is, in substantially the same manner, converting the circle movement of the rotational plate


97


and the axis


97


on the rotational plate


97


to a linear movement of the projecting unit through the link. The projecting unit


79


thus moves slidably in always parallel to the folding roller


78


in the arrow direction of

FIG. 54

upon receiving drive at the opposing ends.




Moreover, as shown in

FIGS. 55

,


56


, stopper shafts


97




b


,


97




c


are formed on a surface opposite to the axis


97




a


of the rotational plate


97


; a stopper member


99


is provided pivotally around the a shaft


99




a


as a center on the housing frame and is urged toward the rotary shaft


94




a


by a spring


100


. As described above, the projecting unit


79


moves in sliding by rotary movement of the rotational plate


97


; the rotational plate


97


rotates in the arrow direction of FIG.


56


(


b


); the projecting unit


79


projects therein; when the projection position sensor


96




b


reaches the detected position (upper left position in FIG.


54


), the stopper shaft


97




c


and stopper member


99


are fitted to each other, and the rotational plate


97


rotates no more. Therefore, the projecting unit


79


is immobilized at the projecting position. When the projecting unit


79


is returned to the home position, the projecting motor


90


is rotated in a direction opposing to the direction at a time for projecting the unit, thereby disengaging the stopper member


99


and the stopper shaft


97




c


from each other. When the projecting unit returns to the home position, the stopper shaft


97




b


and the stopper member


99


are engaged with each other at a position (upper right position in

FIG. 54

) detected by the home sensor


96




a


, and therefore the rotational plate


97


rotates no more.




As described above, the apparatus is structured so that the projecting unit


79


moves horizontally from the normal and reverse rotations of the projecting motor


90


.




Distance Between Nips of the Folding Roller and Center Adjustment of the Projecting Plate




As described above, in the folding roller


78


, the movable roller


78




b


moves up according to the thickness of the sheet bundle P. That is, the distance between the nips of the folding roller


78


may change. To the contrary, if the projecting position of the projecting plate


79




a


is always constant, the projecting plate


79




a


does not always strikes the center of the space between the nips of the folding roller


78


, so that the sheet bundle P may be not be folded at a stapling position.




In this embodiment, the apparatus is so structured that a cam member allow the projecting plate


79




a


to strike always the center of the space between the nips even if the space between the nips of the folding roller


78


is deviated. This structure is described in reference to

FIG. 57

in detail.




As shown in

FIG. 57

, the pushing unit


79


is structured to be rotatable around a sliding roller


79




g


as a center (the outer diameter of the sliding roller


79




f


is smaller than the width of the groove


89


), and a cam member


101


to attached to both shafts


78




c


,


78




d


of the folding roller


78


. The cam member


101


has a cam groove


101




a


capable of engaging with the movable roller shaft


78




d


and a guide portion


101




b


of the projecting unit


79


, and the projecting unit


79


is slidable on the guide portion


101




b


and is urged downward by a spring


102


.




The cam member


101


is mounted pivotably around a shaft


78




c


as a center of the stable roller


78




a


. When the movable roller


78




b


moves up upon rotation of the movable roller


78




b


around the center


80




a


(see, FIG.


53


), the shaft


78




d


of the movable roller


78




b


pushes up the cam groove


101




a


. By this pressing, the cam member


101


rotates in the counterclockwise direction in

FIG. 57

, and as shown in FIG.


57


(


b


), the guide portion


101




b


pushes up the projecting unit


79


. It is to be noted that the cam groove


101




a


and the guide portion


101


are shaped to always project the projecting plate


79




a


to the center of the space between the nips of the folding roller


78


.




By providing the cam member


101


thus structured, the projecting center of the projecting plate


79


is adjusted to strike always the center of the space between the nips, thereby surely folding the sheet bundle P at the staple position. The center adjustment of the projecting plate


79




a


can be done by replacement of the cam member


101


as described above, so that the structure cannot be complicated.




It is to be noted that although the sheet bundle P is nipped by the folding roller


78


upon folding the sheet bundle P by projection of the projecting plate


79




a


, wrinkles may occur on an inner sheet due to frictional force between the folded sheet and the projecting plate


79




a


if the projecting plate


79




a


is located at a position where the projecting unit


79


is projected even after the folding roller


78


nips the sheet bundle P.




In this embodiment, as shown in

FIG. 58

, the apparatus is structured that after the sheet bundle P is nipped by the folding roller


78


, the projecting plate


79




a


is returned to the home position. If the projecting plate


79




a


is returned too early, the projecting plate


79




a


returns before the folding roller


78


nips the sheet bundle P. Therefore, in this embodiment, the projecting plate


79




a


is pulled back at a time that the folding roller


78


rotates in a prescribed amount to fold the sheet bundle P.




This operation prevent wrinkles from occurring where the folded sheet bundle P proceeds without suffering from friction to the projecting plate


79




a


, because the projecting plate


79




a


escapes to the home position at a time when the sheet bundle P is conveyed upon nipped by the folding roller


78


.




Folding Operation




Folding operation for sheet bundle P is executed by projecting the center of the sheet bundle P already subjecting to the staple operation by the projecting plate


79




a


, and by conveying the sheet bundle P upon nipping the sheet bundle P with the folding roller


78


at the center of the sheet bundle P which is struck by the projecting plate


79




a.






Images are recorded on respectively upstream half and downstream half, with respect to the sheet center, in the conveyance direction of respective sheets constituting the sheet bundle. Similarly, such image formation thus described is made on double sides of the sheet, and such image formation on the sheet bundle subjecting to the staple and folding operations is made according to the page order.




When the sheet bundle is pulled by the folding roller as described above, if an image is formed at the center of the sheet bundle, the image (toners) makes lower the sheet frictional coefficient, thereby causing a failure in pulling of the sheet bundle by the folding roller and possibly creating wrinkles and tears.




Referring to

FIG. 59

, a mechanism of occurrences of tears and wrinkles of the sheet during the folding operation is briefly described. It is to be noted that a sheet bundle made of the two sheets P


11


, P


12


is exemplified herein.




Where the fictional force between the folding roller


503


and the first sheet P


11


is denoted as F


1


, where the frictional force between the first sheet P


11


and the second sheet P


12


is denoted as F


2


, and where the binding force of the staples fastening the sheet bundle is denoted as F


3


, ordinary folding operation is generally made while the forces satisfy the formula F


1


=F


2


+F


3


. However, to satisfy the above formula when the frictional force F


2


between the sheets P


11


, P


12


is made smaller, the binding force F


3


of the staple is required larger. At that time, even where the sheet strength is durable enough against the binding force F


3


of the staple, the second sheet P


12


may be pulled by the staple, thereby inflicting scars as shown in FIG.


59


(


a


), and creating warps as shown in FIG.


59


(


b


). If the sheet bundle passes by the folding roller


503


in this state, wrinkles as shown in FIG.


59


(


c


) may occur. Moreover, if the sheet is broken down due to the binding force F


3


of the staple, tears as shown in FIG.


59


(


d


) may occur.




In this embodiment, as shown in

FIG. 60

, a margin (folding margin t) of a certain size is provided at a center of the sheet (sheet bundle) P as a folded area. More specifically, image formation to the sheet P subjecting to a processing in the stitcher unit D is done during image recording in the image forming apparatus body A by avoiding in advance the folding margin t at the sheet center (in this embodiment, it is set as t=about 5 to 8 mm, margin width 2t=about 10 to 16 mm).




It is to be noted that in the drawing, Ps denotes the center (center in the conveyance direction) on the sheet P and that Pg denotes the image recording areas on the sheet P.




With this structure, the margin (folding margin t) formed on the sheet P in advance makes the frictional force between the sheet P and the folding roller


78


larger where the sheet bundle is pulled by the folding roller


78


, so that wrinkles and tears as described above are suppressed, and so that the sheet bundle P is pulled in surely.




If the width of the margin is narrower than about 10 mm, adequate frictional force may not be obtained when the sheet bundle is pulled, and if the margin width exceeds about 16 mm, the image forming area may become smaller. Therefore, it is desirable to set the margin width between about 10 mm and 16 mm.




It is to be noted that although in this embodiment image formation is made in providing the margin of the prescribed width as described above for the sheet subjecting to the folding operation, the setting of the margin can be reset or cancelled where a larger image formation area is required. Where the sheet number of the sheets to be fold is few, the setting of the margin of the prescribed width can be cancelled to form images with an ordinary margin width (e.g., about 4 mm) because tears. may not be created even where the margin of the folded portion is narrowed. With this operation, the wide image formation area can he obtained.




In a case where the sheet bundle subjecting to the staple and folding operations as described above has a sheet forming a front cover (during a front cover mode), if images are formed on a back side of the sheet forming the front cover (hereinafter, referred to as “front cover sheet” ), silicon oil or the like may adhere when transferred toner images are fixed by a fixing means on the back side of the front cover sheet, thereby making lower the frictional coefficient between the back side of the front cover sheet and the sheet in contact with the front cover sheet. It is to be noted that though a fine quality paper (thick paper, cardboard paper, as well) can be used frequently, if silicon oil adheres on the fine quality paper, the frictional coefficient is further lowered in comparison with other sheets (plain papers). If such a front cover sheet is nipped by the folding roller to fold the sheet and is pulled in, the sheet may be skipped between the sheets because the frictional coefficient is so small between the back side of the front cover sheet and the sheet in contact with the front cover sheet, so that only the front cover sheet may be pulled.




In this embodiment, during the front cover mode, the apparatus does not make recording on the back side of the front cover sheet. More specifically, during the image recording period in the image forming apparatus body A, the front cover sheet is delivered without passing through the re-feeding path


7


(see,

FIG. 1

) after the image is recorded on the surface of the front cover sheet and is sent to the stitcher unit D.




It is to be noted that since in this embodiment the front cover sheets (fine quality sheets or the like) are to be fed from a multi-tray


8


(see, FIG.


1


), the sheet is controlled to be delivered without passing through the re-feeding path


7


if the last sheet fed to the stitcher unit D is fed from the multi-tray


8


.




This structure prevents the back side of the front cover sheet from contacting with the fixing means (namely, a fixing roller provided on a side of the image surface), and therefore, the silicon oil will not adhere on the back side of the front cover sheet, thereby preventing the frictional coefficient from lowering, and preventing the front cover sheet from being pulled solely.




Detection of Tears of the Sheet Bundle




A structure detecting tears by a detecting means such as a sensor may be generally conceivable in the case where the tears occur in the sheet bundle during folding processing as described above, but if such a detecting means is provided separately to detect the tears, the number of parts and costs are increased. Because the subsequent sheet may be already conveyed when the tears are detected, paper jamming of a more serious degree may occur where the proceeding, sheet is remaining.




In this embodiment, as shown in

FIG. 61

, using an intermediate sensor


103


formed near the folding roller


78


(upstream side), the stopper sensor


75


formed at the stopper


62


, and a delivery sensor


105


formed near a delivery roller


104


, when the respective sensors detect the existence of the sheet at the same time, the apparatus is structured to detect that a sheet (or sheet bundle) is torn and stays at the stitcher unit D.




It is to be noted that although in this embodiment the occurrence of tears in sheets is detected when all of the intermediate sensor


103


, the stopper sensor


75


, and the delivery sensor


105


detect the existence of the sheet at the same time, the invented structure is not limited to this, and for example, the apparatus may detect the occurrence of tears in sheets when both of the stopper sensor


75


and the delivery sensor


105


detect the sheet existence.




With this structure, a detecting means for detecting as to whether tears occur in the sheet (or sheet bundle) is not necessarily installed separately, it is possible to prevent the increase of the number of the parts and the costs. Tears of the sheets can be detected early at the folding timing of the sheets, so that jamming of the sheets can be prevented by stopping the conveyance of the sheets early.




Delivery Operation




As described above, the sheet bundle subjecting to the folding operation is delivered on the stack tray


106


by the delivery roller


104


and stacked on the tray. A sheet bundle pressing member


107


for pressing the sheet bundle P is rotatively formed above the delivery roller


104


as shown in

FIG. 63

around the rotary shaft


107




a


as a center. When the sheet bundle P subjecting to the folding operation is delivered on the stack tray


106


by the delivery roller


104


through the delivery opening, the pressing member


107


can press the end of the sheet bundle P, thereby stacking the sheet bundle P even where the bundle P is inadequately folded on the tray without unfolding the sheet bundle on the stack tray


106


.




This pressing member


107


is restricted so that a roller


107




b


formed at a tip of the member does not move below a prescribed height h (height not contacting with the stacking tray


106


), but can freely move in a direction that the roller


107




b


is raised. Accordingly, any delivery failure, otherwise occurring by pressing the front end of a flexible sheet bundle P with the pressing member


107


, would not occur, and therefore, the sheets can be surely stacked on the stack tray


106


.




Where the sheet bundle P thus subjecting to the folding operation is delivered on the stack tray


106


by the delivery roller


104


, since the sheets expand more on the sheet bundle folded side (the downstream side in the delivery direction) in comparison with the sheet bundle open side, if the bundles are stacked as they are, only the sheet bundle side becomes higher, thereby possibly rendering the stacking property of the sheet bundles unstable. To solve such a problem, as shown in

FIG. 62

, a device has been proposed having a structure to deliver and stack the sheet bundles P bundle by bundle in a positionally shifting manner so that the sheet bundles P delivered by the delivery roller


505


are shiftingly stacked on the stack tray


504


.




However, the above structure requires a large stack tray for delivering many sheet bundles, and the apparatus may become larger, so does the installation space.




With this embodiment, as shown in

FIG. 63

, a portion near the delivery roller


104


of the stack tray


106


is made higher than the stacking surface


106




b


(projection


106




a


), the sheets are delivered so that the folded side of the sheet bundle P comes over the stacking surface


106




b


on the front end side (downstream side in the delivery direction) of the stack tray


106


and the open side comes over the projection


106




a


. By this structure, the folded side goes lower than the open side, and the height differential from the open side can be made smaller even where the folded side expands greatly more than the open side.




More specifically, when the sheet bundle P is thick (that is, in the case that the folded side particularly expands), the sheet bundle delivery speed by the delivery roller


104


is made slow, and the sheet bundles are delivered so that the open side of the sheet bundles P comes over the projection


106




a


. When the sheet bundle P is thin (that is, in the case that the folded side relatively does not expand so much), the sheet bundle delivery speed by the delivery roller


104


is made faster, and the sheet bundles are delivered so that the open side of the sheet bundles P does not come over the projection


106




a.






With this operation, the sheet bundles P delivered on the stack tray


106


can avoid a situation that only one side (the folded side) is raised, thereby making the stacking property of the sheet bundle stable. The sheet bundles P are not necessarily stacked in a shifting manner, a large stack tray may not be needed.




Although in this embodiment the projection is formed, the invention is not limited to this structure, and can be structured with a slant portion, the stack tray


106


itself modified in a shape having a slope, or a projection extendable from the bottom of the stack tray


106


or detachable.




Description of the Control System




Referring to

FIG. 64

, the structural elements of the control system for drive controlling the respective members in the stitcher unit as described above is briefly described.




In

FIG. 64

, an MPU


200


as a control means inputs respective sensors such as first to third upper sensors


66




a


to


66




c


detecting the existence, the front end, and the rear end of the sheet conveyed by the stitcher unit, an alignment member home sensor


220


for detecting the home position of the alignment member


71


, the stopper home sensor


76


for detecting the home position of the stopper


62


, the stopper sensor


75


formed at the stopper


62


for detecting the sheet, the delivery sensor


105


formed near the delivery roller


104


, the projecting position sensor


96




b


for detecting the projecting position of the projecting plate


79




a


, the intermediate sensor


103


formed near the folded roller


78


, and so on.




Based on the signals from the respective sensors and the image forming apparatus body A, the MPU


200


controls, through respective drivers D


20


to D


28


, a first flapper solenoid


201


for driving the first flapper


21


to feed the sheets to the vertical path of the stitcher unit, a switching upper solenoid


221


and a switching lower solenoid


222


for switching the first and second flappers


64




a


,


64




b


on the route of the vertical path, a conveyance motor


223


for conveying sheets by driving the upper and lower roller pairs


63


,


67


, the stapler motor


61




i


, a squeezing motor


224


for operating the alignment member


71


, the stopper drive motor


74


for moving the stopper


62


, the folding motor


82


for driving the folding roller


78


, the projecting motor


90


for driving the projecting plate


79




a


, and so on, and renders operations as described above.



Claims
  • 1. An image forming apparatus for folding plural sheets in folio comprising:image forming means for forming images on a recording area on sheets, and forming a margin between the recording area and another forming area; two rollers for folding the sheets in folio; and projecting means for folding the sheets upon nipping the sheets between the two rollers by projecting between the two rollers, so as to nip a part of the sheets where the margin is formed at first, wherein the projecting means projects to the margin of a prescribed width of images formed at an image forming apparatus body to fold the plural sheets.
  • 2. An image forming apparatus for folding plural sheets in folio comprising:an image forming apparatus body having image forming means for forming images on the sheets; a sheet processing apparatus for stapling the plural sheets on which images are formed at the image forming apparatus body and bookbinding the sheets in folio; and margin determination means for determining a margin of a prescribed width wherein the margin of the prescribed width is placed at a folded portion of the sheets when the images are formed at the image forming apparatus body on the sheets to be folded and made into a book in the sheet processing apparatus.
  • 3. The image forming apparatus according to claim 1, wherein the width of the margin is 10 to 16 mm.
  • 4. The image forming apparatus according to claim 1, further comprising means for canceling the operation of the protecting means for placing the margin at the prescribed width.
  • 5. An image forming apparatus for folding plural sheets in folio comprising:an image forming apparatus body having image forming means for forming images on the sheets; image forming means for forming images on a recording area on the sheets, and forming a margin between the recording area and another forming area; and a sheet processing apparatus for stapling the plural sheets on which images are formed at the image forming apparatus body and bookbinding the sheets in folio, wherein the margin is placed at a folded portion of the sheets when the images are formed at the image forming apparatus body on the sheets to be folded and made into a book in the sheet processing apparatus.
Priority Claims (1)
Number Date Country Kind
10-130348 May 1998 JP
US Referenced Citations (7)
Number Name Date Kind
4640611 Ohdake et al. Feb 1987
4891681 Fiske et al. Jan 1990
5461469 Farrell et al. Oct 1995
5993369 Sekita et al. Nov 1999
6003853 Nakazawa et al. Dec 1999
6006065 Seki Dec 1999
6027107 Natsume et al. Feb 2000
Foreign Referenced Citations (1)
Number Date Country
0 757 964 Feb 1997 EP