Abstract:
Image forming apparatus connected to a sheet processing apparatus which applies sheet processing such as stapling to a sheet formed image by the image forming apparatus. The image forming apparatus includes an input terminal for inputting image forming job, an image forming unit for forming an image on a sheet in accordance with the image forming job inputted by the input terminal, a discriminator for discriminating if a first image forming job does not include sheet processing whereas a second and subsequent image forming job includes sheet processing, and a controller for instructing the sheet processing apparatus to perform a preparatory operation for he second image forming job during the first image forming job in accordance with a discrimination result, such as by moving a staple unit to designated position for the second image forming job.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to control for an image forming apparatus which conducts a preparing operation for sheet processing. 
     2. Description of the Related Art 
     A conventional image forming apparatus inputs a plurality of image forming jobs and forms an image on a sheet in accordance with the image forming jobs sequentially. The conventional image forming apparatus has sheet processing functions such as sheet stapling, sheet punching, and sheet folding. These functions need preparing operations before each image forming job being processed. In the preparing operation, the image forming apparatus moves a movable unit, which is a part of a sheet processing unit, to a position according to a sheet size and a user designation. The conventional image forming apparatus conducts a first image forming job and then begins a second job, which follows the first image forming job, after the first image forming job is finished. A preparing operation of a processing unit for the second image forming job commences when the first image forming job is finished, even though the processing unit is not used in the first image forming job at all. In a case where there are many image forming jobs, a time loss caused by the preparing operation is an obstacle to an improvement of a productivity of the image forming apparatus. This will be explained with reference to FIGS. 18A and 18B. 
     FIGS. 18A and 18B show job schedules of a conventional image forming apparatus in a case where two image forming jobs are processed sequentially by the image forming apparatus. JOB_A and JOB_B are image forming jobs to be processed sequentially. JOB_A is processed first and JOB_B is processed second. As shown in FIG. 18A, JOB_A is processed first, and then a preparing operation for JOB_B is done after JOB_A. JOB_B is started after the preparing operation. As shown in FIG. 18B, in a case where JOB_B interrupts JOB_A, JOB_A is interrupted, and then a preparing operation for JOB_B is done. JOB_B is processed after the preparing operation. Then, JOB_A is re-started after JOB_B is finished. 
     As described above, when JOB_B is processed, a time for conducting a preparing operation is needed in addition to a time for processing an image forming job and prevents improvement of a productivity of the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide image forming apparatus which a productivity thereof is improved. 
     In order to achieve the above object, the present invention provides an image forming apparatus comprising an input terminal for inputting image forming jobs including a first image forming job and a second image forming job subsequent to the first, an image forming unit for forming an image on a sheet in accordance with an image forming job inputted by said input terminal, a sheet processor for applying a sheet processing to a sheet in accordance with an image forming job inputted by said input terminal, a discriminator for discriminating if the first image forming job does not include sheet processing by said sheet processor and if the second image forming job includes the sheet processing, and a controller for instructing said sheet processor to conduct a preparing operation for the sheet processing of the second image forming job during the first image forming job in accordance with a discrimination results by said discriminator. 
     Specifically, in the image forming apparatus, said sheet processor includes a stapler for stapling a sheet, and the preparing operation includes moving said stapler to a position according to a user designation. 
     Also, in the image forming apparatus, said sheet processor includes a stapler for stapling a sheet, and the preparing operation includes moving said stapler to a position according to a way of stapling. 
     Also, in the image forming apparatus, said sheet processor includes a stapler for stapling a sheet, and the preparing operation includes moving said stapler to a position according to a sheet size. 
     Also, in the image forming apparatus, said sheet processor includes a puncher for punching a sheet, and said puncher includes a sensor for detecting a side edge of the sheet, and the preparing operation includes moving said sensor to a position according to a sheet width, and said discriminator discriminates if said a sheet width of the second image forming job is equal to or larger than a sheet width of the first image forming job. 
     Also, in the image forming apparatus, said sheet processor includes a feeder for an insert sheet, and the preparing operation includes feeding an insert sheet to a predetermined position. 
     Also, in the image forming apparatus, said sheet processor includes a booklet maker for making a booklet, and said booklet maker includes a stopper for stopping a sheet in order to bind sheets and fold sheets, and the preparing operation includes moving said stopper to a position according to a sheet size. 
     Also, in the image forming apparatus, said sheet processor includes a booklet maker for making a booklet, and said booklet maker includes an aligner for aligning sheets, and the preparing operation includes moving said aligner to a position according to a sheet size. 
     Also, in the image forming apparatus, said sheet processor includes a sheet folder for folding a sheet, and said sheet folder includes a stopper for stopping a sheet in order to fold the sheet, and the preparing operation includes moving said stopper to a position according to a sheet size. 
     In another aspect of the invention, the present invention provides an image forming apparatus connectable to a sheet processing apparatus which applies sheet processing to a sheet, said image forming apparatus comprising an input terminal for inputting image forming jobs including a first image forming job and a second image forming job subsequent to the first, an image forming unit for forming an image on a sheet in accordance with an image forming job inputted by said input terminal, a discriminator for discriminating if the first image forming job does not include the sheet processing and if the second image forming job includes the sheet processing, and a controller for instructing said sheet processing apparatus to conduct a preparing operation for the sheet processing of the second image forming job during the first image forming job in accordance with a discrimination results by said discriminator. 
     In another aspect of the invention, the present invention provides a method for controlling an image forming apparatus connected to a sheet processing apparatus which applies one or more sheet processing to a sheet having an image formed by said image forming apparatus, said method comprising inputting a first image forming job, inputting a second image forming job, conducting the first image forming job, discriminating if the first image forming job does not include sheet processing and second image forming job includes sheet processing, instructing said sheet processing apparatus to conduct a preparing operation for the sheet processing of the second image forming job during said conducting step of the first image forming job in accordance with the discrimination, and conducting the second image forming job. 
     In another aspect of the invention, the present invention provides a recording medium, which includes code for process steps that can be read by a controller of an image forming apparatus connected to a sheet processing apparatus which applies one or more sheet processing to a sheet having an image formed by said image forming apparatus, said code comprising code for inputting a first image forming job, code for inputting a second image forming job, code for conducting the first image forming job, code for discriminating if the first image forming job does not include sheet processing and second image forming job includes sheet processing, code for instructing said sheet processing apparatus to conduct a preparing operation for the sheet processing of the second image forming job during said conducting step of the first image forming job in accordance with the discrimination, and code for conducting the second image forming job. 
     In another aspect of the invention, the present invention provides a computer program, which includes code for process steps that can be conducted by a controller of an image forming apparatus connected to a sheet processing apparatus which applies one or more sheet processing to a sheet having an image formed by said image forming apparatus, said code comprising code for inputting a first image forming job, code for inputting a second image forming job, code for conducting the first image forming job, code for discriminating if the first image forming job does not include sheet processing and second image forming job includes sheet processing, code for instructing said sheet processing apparatus to conduct a preparing operation for the sheet processing of the second image forming job during said conducting step of the first image forming job in accordance with the discrimination, and code for conducting the second image forming job. 
     Other objects and features of the invention will be apparent from the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an image forming system which includes an image forming apparatus and a sheet processing apparatus. 
     FIG. 2 is a block diagram for explaining control over the image forming system. 
     FIG. 3 is a flowchart showing a preparing operation for a stapling operation of a reserved image forming job. 
     FIG. 4 is a flowchart showing a preparing operation regarding sheet stapling operation. 
     FIGS. 5A and 5B are timing diagrams showing timing to conduct the preparing operation. 
     FIG. 6 shows a side view of punch unit. 
     FIG. 7 shows a front view of punch unit. 
     FIGS. 8A through 8G show movement of the rollers and the sensor. 
     FIG. 9 is a flowchart showing a preparing operation regarding sheet punching operation. 
     FIG. 10 is a flowchart showing the image forming operation shown in FIG.  9 . 
     FIG. 11 is a flowchart showing a preparing operation regarding insert feeding operation. 
     FIG. 12 is a flowchart showing the image forming operation shown in FIG.  11 . 
     FIG. 13 shows a sheet processing apparatus. 
     FIG. 14 is a flowchart showing a preparing operation regarding booklet making operation. 
     FIG. 15 is a flowchart showing the image forming operation shown in FIG.  14 . 
     FIG. 16 is a flowchart showing a preparing operation regarding sheet folding operation. 
     FIG. 17 is a flowchart showing the image forming operation shown in FIG.  16 . 
     FIGS. 18A and 18B are diagrams of the preparing operation in the prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an image forming system which comprises document reading apparatus  101 , image forming apparatus  102  and sheet processing apparatus  103 . 
     Document reading apparatus  101  includes document feeder  51 . Document feeder  51  feeds an original document D 1  onto a reading position of document glass  78  and transports the document to a discharging position  40 . Document reading apparatus  101  includes lump  79 , mirrors  72 ,  73  and  74  and lens  75 . Lamp  79  exposes document D 1  fed onto the reading position of document reading apparatus  101 . Mirrors  72 ,  73  and  74  lead light reflected from document D 1  to lens  75 . Lens  75  focuses the reflected lights onto CCD line sensor (CCD)  76 . CCD  76  converts the focused image into an electrical signal. The electrical signal is converted into a digital signal by an A/D converter (not shown). The digital signal is outputted to laser scanner  61  which is described later. 
     Image forming apparatus  102  has sheet cassettes  53  and  54  which hold sheets P 1  and P 2  respectively. The size of sheets P 1  and P 2  are different. Sheets P 1  and P 2  are fed by pick-up belts  55  and  56  respectively. The sheet is transported to sheet path  60  via sheet path  57 . Image forming apparatus  102  has laser scanner  61 . Laser scanner  61  emits a laser beam toward photosensitive drum  62   a  of image forming unit  62  in accordance with the digital signal converted from CCD  76  to form an electrostatic latent image on photosensitive drum  62   a . Image forming unit  62  develops the electrostatic latent image by toner to visualize the electrostatic latent image and transfers the toner image onto a sheet transported to sheet path  60 . 
     The sheet having the toner image is transported to fixing roller  64  by transporting belt  63 . Fixing roller  64  fixes the toner image on the sheet by heat and pressure. Roller  65  transports the sheet to sheet processing apparatus  103 . Image forming unit  62  may be an ink jet printer which forms an image on a sheet by an ink jet process. 
     Operation panel  40  is provided on the top of document reading apparatus  101  for setting modes and for showing the modes of image forming apparatus  102  and sheet processing apparatus  103 . Operation panel  40  has a display, a touch panel, a keypad, a stop key, a reset key and a start key. The display displays settings such as image forming modes and a number of image formation set by the touch panel and the keypad. The touch panel is provided on the display and enables a user to set various settings easily. The keypad is provided for setting a number of image formation. The stop key is provided for interrupting the image formation of image forming apparatus  102 . The start key is provided for starting the image formation of image forming apparatus  102 . 
     Operation panel  40  and document reading apparatus  101  function as an input terminal for inputting an image forming job. The input terminal is not limited to be an operation panel and a document reading apparatus. An input terminal can be a printer board which receives an image forming job from a computer and is connected to image forming apparatus  102 . An input terminal can be a network board which receives image forming jobs from a plurality of computers through a network. An input terminal can be a facsimile board which receives an image forming job from a facsimile machine and is connected to image forming apparatus  102 . Other equivalent forms of an input terminal are possible. 
     Sheet processing apparatus  103  has sheet feeder  104  which feeds insert sheet I 1 . Insert sheet I 1  fed by sheet feeder  104  is transported to either stack tray  85  or stack tray  86  without going through image forming apparatus  102 . Insert sheet I 1  can be a color blank sheet or a sheet formed image by another image forming apparatus such as a color printer. Since sheet feeder  104  can feed insert sheet I 1  between timings that image forming apparatus  102  discharges sheets to sheet processing apparatus  103 , sheet feeder  104  is called an inserter. 
     Insert sheet I 1  set on tray  20  is fed by rollers  21  and  22 . Roller  21  rotates a feeding direction to feed insert sheet I 1 . Roller  22  rotates an opposite direction to the feeding direction to separate the rest of sheets from insert sheet I 1 . Sheet feeder  104  feeds the top insert sheet I 1  on tray  20 . Sensor  29  detects if rollers  21  and  22  feeds insert sheet I 1 . Insert sheet I 1  is transported by roller  23 ,  24 ,  25  and  26 . Sensor  27  is provided on tray  20  for detecting if there is insert sheet I 1  on tray  20 . 
     Sheet P 1 , P 2  or I 1  is transported by roller  2  and  3 . When punching processing is designated by operation panel  40 , punching unit  50  punches the sheet transported by roller  3 . The sheet is looped to buffer roller  5  after the sheet is processed by punching unit  50  or after it passes punching unit  50 . Rollers  12 ,  13  and  14  and flapper  10  and  11  are provided around buffer roller  5 . Flapper  11  leads the sheet to either non-sort path  4  or sort path  8  by switching the position of flapper  11 . Flapper  10  leads the sheet to either buffer path  23  or sort path  8  by switching the position of flapper  10 . Buffer path  23  stores the sheet temporarily. Sensor  32  is provided on sort path  8  for detecting sheet P 1 , P 2  or I 1 . 
     Sensor  33  is provided on non-sort path  4  for detecting sheet P 1 , P 2  or I 1 . Sheet P 1 , P 2  or I 1  transported to non-sort path  4  is discharged to stack tray  85  by discharge roller  9 . 
     The sheet led to sort path  8  is transported to processing unit  84  by roller  6 . Processing unit  84  has processing tray  82  which stacks sheets temporarily. The sheets on processing tray  82  are aligned by aligning plate  88  and stapled by staple unit  80  if designated by operation panel  40 . Staple unit  80  is movable in a sheet width direction which is perpendicular to a sheet transportation direction. Stapling position can be selected from among several positions such as corner stapling and 2-position stapling by operation panel  40 . Staple unit  80  is moved in accordance with the designation of operation panel  40  and a sheet width. The bundle of sheets on processing tray  82  is discharged to stack tray  86  by roller  83   a  and  83   b . Roller  83   a  touches the bundle of sheets on processing tray  82  and discharges the bundle of sheets when stay  81  swings down. 
     Stack tray  85  and stack tray  86  incline toward housing  87  of sheet processing apparatus  103 . The sheet discharged onto stack tray  85  or stack tray  86  slides toward housing  87  and hits housing  87 . Thereby, the sheets are aligned on stack tray  85  and stack tray  86 . 
     FIG. 2 shows block diagram for controlling the image forming system shown in FIG.  1 . Main controller  200  has CPU  2002 , memory  2001  and I/O controller  2003 . CPU  2002  controls and administrates the whole of the image forming system in accordance with a program code which is stored in memory  2001 . Memory  2001  includes ROM, RAM, IC card, hard disk and floppy disk. Although a program code described hereinafter is stored in ROM of memory  2001 , the program code can be stored in CD-ROM, floppy disk or Internet server and can be installed into RAM or hard disk of memory  2001 . I/O controller  2003  controls inputting and outputting of signals. I/O controller  2003  and memory  2001  are controlled by CPU  2002 . 
     I/O controller  2003  is connected to operation panel controller  201 , sheet feeding controller  202 , document reading controller  203 , image forming controller  204  and sheet processing controller  205 . Main controller  200  controls operation panel controller  201 , sheet feeding controller  202 , document reading controller  203 , image forming controller  204  and sheet processing controller  205  via I/O controller  2003 . 
     When a user makes copy by using this image forming system, the user sets documents on document feeder  51  and designates settings and number of copies by operation panel  40 . In response to the start key of operation panel  40  being pushed, document feeder  51  feeds documents to document glass  78  one by one and document reading apparatus  101  reads the documents. CCD  76  converts the document image to electric signal and outputs the electric signal as image signal. Image processing, which is designated by the user through operation panel  40 , is applied to the image signal outputted from CCD  76 . Then, the image signal is converted into laser signal for exposing photosensitive drum  62   a . The image according to the image signal is formed on a sheet through an electrophotography process. The sheet on which the image is formed is transported into sheet processing apparatus  103  via roller  65  and  1 . Sheet processing apparatus  103  is controlled by main controller  200  in accordance with a designation from operation panel  40 . 
     When a feed of insert sheet I 1  by sheet feeder  104  is designated by the user through operation panel  40 , main controller  200  instructs sheet processing controller  205  to move roller  21  down until roller  21  touches the top of sheets I 1 . Then, main controller  200  instructs processing controller  205  to drive motors for roller  21 ,  22 ,  23  and  24  at the timing designated by the user through operation panel  40 . 
     When sheet punching is designated by the user through operation panel  40 , main controller  200  instructs sheet processing controller  205  to drive a motor for punching unit  50  in order to punch a sheet. 
     Main controller  200  instructs sheet processing controller  205  to drive flapper  11  in order to switch paths. When a sheet is transported to stack tray  85 , the sheet is discharged by discharge roller  9 . When a sheet is transported to stack tray  86 , the sheet is discharged onto processing tray  82  by discharge roller  7  via roller  6 . 
     When sheet stapling is designated by the user through operation panel  40 , main controller  200  instructs sheet processing controller  205  to move staple unit  80  to a position designated by operation panel  40  and to staple sheets on processing tray  82 . Main controller  200  also instructs sheet processing controller  205  to drive aligning plate  88  in order to align a sheet and to control a stacking position of a sheet on stack tray  86 . Main controller  200  instructs sheet processing controller  205  to drive discharge roller  83   a  and  83   b  in order to discharge a bundle of sheets on processing tray  82  to stack tray  86  after instructing sheet processing controller  205  to move stay  81  down. 
     When a reading operation for first set of documents, which is set on document feeder  51 , is done, main controller  200  permits a reading operation for second set of documents even if an image forming operation for the first set of documents is not done. That is, a mode setting operation and a reading operation for second image forming job or succeeding image forming job is available during a first image forming job. An user can make a reservation for the second or succeeding image forming job during the first image forming job. 
     When the second image forming job includes a stapling operation which is not designated by the first image forming job, main controller  200  instructs sheet processing controller  205  to move staple unit  80  to a position designated for the second image forming job during the first image forming job. After the first image forming job is finished, main controller  200  instructs image forming controller  204  to conduct the second image forming job. 
     When main controller  200  is informed that JOB_B including a stapling operation follows JOB_A not including the stapling operation, main controller  200  instructs sheet processing controller  205  to conduct a preparing operation for the stapling operation of JOB_B during JOB_A as shown in FIG.  5 A. Therefore, JOB_B can be started right after JOB_A is finished. When main controller  200  is informed that JOB_B including a stapling operation which interrupts JOB_A not including the stapling operation, main controller  200  instructs sheet processing controller  205  to conduct the preparing operation for the stapling operation of JOB_B as shown in FIG.  5 B. After the preparing operation is finished, main controller  200  instructs image forming controller  204  to interrupt JOB_A and to conduct JOB_B. Then, after JOB_B is finished, main controller  200  instructs image forming controller  204  to recover JOB_A. As mentioned above, the preparing operation for JOB_B is conducted in parallel with JOB_A. Thereby, the total job time is shortened. 
     FIG. 3 is a flowchart for conducting a preparing operation of a reserved image forming job such as the above second image forming job (JOB_B). A program code of the flowchart of FIG. 3, as well as all flowcharts herein, is stored in ROM of memory  2001  and is conducted by CPU  2002 . CPU  2002  receives designations about sheet stacking, sheet stapling, sheet punching and sheet inserting from operation panel controller  201  which connects to operation panel  40 . CPU  2002  controls sheet feeding controller  202 , document reading controller  203 , image forming controller  204  and sheet processing controller  205  in accordance with the designations from operation panel controller  201 . 
     As shown in FIG. 3, CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  to a home position (S 12 ). Then, CPU  2002  checks if the start key of operation panel  40  is pressed by an user (S 1 ). When the start key is pressed, CPU  2002  instructs the start of an image forming operation (S 2 ). Then, CPU  2002  discriminates if a current job includes a stapling operation (S 3 ). If the current job does not include the stapling operation, CPU  2002  discriminates if there is a next job (S 6 ). If there is a next job, CPU  2002  discriminates if the next job includes a stapling operation (S 7 ). If the next job includes the stapling operation, CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  to a designated position for the next job during the current job (S 8 ). The designated position is determined by a way of stapling, which is designated by the user through operation panel  40 , and a sheet size. Then, CPU  2002  discriminates if the current job is finished (S 4 ). In a case where stapling unit  80  is not in the home position before executing step S 8 , CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  directly to a designated position from a current position without returning stapling unit  80  to the home position. 
     If the current job includes the stapling operation at step S 3 , CPU  2002  proceeds step S 4 . If there is no next job at step S 6  or if the next job does not include the stapling operation at step S 7 , CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  to the home position (S 13 , S 14 ) and proceeds to step S 4 . 
     If the current job is finished at step S 4 , CPU  2002  discriminates if there is a next job (S 5 ). If there is a next job, CPU  2002  returns to step S 2 . If there is no next job at step S 5 , CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  to the home position (S 15 ) and returns to step S 1 . 
     If the current job is not finished at step S 4 , CPU  2002  discriminates if a next job is being inputted, that is, documents of the next job are being read (S 9 ). If a next job is being inputted, CPU  2002  returns to step S 2 . If a next job is not being inputted at step S 9 , CPU  2002  discriminates if the start key of operation panel  40  is pressed for inputting a next job (S 10 ). If the start key is not pressed, CPU  2002  returns to step S 2 . If the start key is pressed at step S 10 , CPU  2002  instructs document reading controller  203  to start inputting documents of the next job (S 11 ) and returns to step S 2 . 
     FIG. 4 shows a flowchart of a subroutine of the image forming operation at step S 2 . CPU  2002  discriminates if a current job includes a stapling operation (S 21 ). If the current job does not include the stapling operation, CPU  2002  instructs image forming controller  204  to conduct an image forming operation (S 22 ) and returns to the flowchart shown in FIG.  3 . If the current job includes the stapling operation at step S 21 , CPU  2002  discriminates if stapling unit  80  has been moved to the designated position for the current job (S 23 ). If stapling unit  80  has been moved to the designated position, CPU  2002  proceeds to step S 22 . If stapling unit  80  has not been moved to the designated position, CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  to the designated position (S 24 ) and proceeds to step S 22 . In a case where stapling unit  80  is not in the home position before executing step S 24 , CPU  2002  instructs sheet processing controller  205  to move stapling unit  80  directly to the designated position from a current position without returning stapling unit  80  to the home position. 
     Conducting the preparing operation for the next job during the current job is applicable to not only sheet stapling but also any other sheet processing, such as sheet punching, insert sheet feeding, booklet making and sheet folding. 
     FIG. 6 shows a side view of punch unit  50 . Punch unit  50  has rollers  40  and  41 . Rollers  40  and  41  are metal rollers and have a protrusion and a depression respectively. When a sheet is punched, rollers  40  and  41  rotate in the direction shown in FIG. 6 in sync with the transportation of the sheet. Thereby, a sheet is punched by the protrusion of roller  40  and the depression of roller  41  while the sheet is being transported. Rollers  40  and  41  start rotating at a predetermined timing that the trailing side of the sheet is punched. There is a gap between roller  40  and roller  41  so that a sheet can be transported without rotating rollers  40  and  41  when the sheet is not punched. 
     FIG. 7 shows a front view of punch unit  50 . Punch unit  50  has three rollers  40  and  41  in order to punch 3-holes to a sheet. Rollers  40  and rollers  41  are fixed to shafts  45  and  46  respectively. The distance B between rollers  40  and the distance B between rollers  41  are constant. Although a sheet is basically transported with reference to a center D whenever a sheet in any size is transported, sometimes the center of the sheet is shifted from the center D in direction A by the time the sheet reaches to punch unit  50 . Shafts  45  and  46  are movable in direction A in order to adjust rollers  40  and  41  to a sheet. Sensor  43  detects a side edge of a sheet and is movable with shafts  45  and  46  dependently in direction A to adjust rollers  40  and  41  to a position of a sheet. Sensor  43  is also movable independently to adapt to a width of a sheet in a preparing operation. 
     FIGS. 8A through 8G show movements of rollers  40  and sensor  43 . First, rollers  40  and sensor  43  are in a home position as shown in FIG.  8 A. At this time, the distance between right most roller  40  and sensor  43  is C 1 . In a preparing operation, sensor  43  is moved to a position according to a sheet width as shown in FIG.  8 B. At this time, the distance between right most roller  40  and sensor  43  is C 2  which is less than C 1 . The distance B+C 2  is equal to a half width of a sheet. When a leading edge of a sheet reaches to punch unit  50  as shown in FIG. 8C, rollers  40  and sensor  43  are started moving in direction A 1 . When sensor  43  detects the side edge of the sheet, rollers  40  and sensor  43  are stopped as shown in FIG.  8 D. Then, the trailing side of the sheet is punched by rotating rollers  40  and  41 . After a sheet punching operation, rollers  40  and sensor  43  are returned as shown in FIG. 8E for a next sheet. When a job finished, sensor  43  is moved to either the home position as shown in FIG. 8F or another position according to a sheet width for another job as shown in FIG.  8 G. 
     FIG. 9 shows a flowchart for conducting a preparing operation regarding a sheet punching operation. A program code of the flowchart is stored in ROM of memory  2001  and is conducted by CPU  2002 . 
     As shown in FIG. 9, CPU  2002  instructs sheet processing controller  205  to move sensor  43  to a home position (S 31 ). Then, CPU  2002  checks if the start key of operation panel  40  is pressed by an user (S 91 ). When the start key is pressed, CPU  2002  instructs the start of an image forming operation (S 32 ). Then, CPU  2002  discriminates if a current job includes a punching operation (S 33 ). If the current job does not include the punching operation, CPU  2002  discriminates if there is a next job (S 92 ). If there is a next job, CPU  2002  discriminates if the next job includes a punching operation (S 34 ). If the next job includes a punching operation, CPU  2002  compares a sheet width of the next job and a sheet width of the current job (S 37 ). If the sheet width of the next job is larger than the sheet width of the current job or is equal to the sheet width of the current job, CPU  2002  instructs sheet processing controller  205  to move sensor  43  to a position according to the sheet width of the next job (S 38 ). Then, CPU  2002  discriminates if the current job is finished (S 93 ). In a case where sensor  43  is not in the home position before executing step S 38 , CPU  2002  instructs sheet processing controller  205  to move sensor  43  directly to a position according to the sheet width of the next job from a current position without returning sensor  43  to the home position. 
     If the current job includes a punching operation at step S 33 , CPU  2002  proceeds to step S 93 . If there is no next job at step S 92  or if the next job does not include the punching operation at step S 34 , CPU  2002  instructs sheet processing controller  205  to move sensor  43  to the home position (S 35 , S 36 ) and proceeds to step S 93 . If the sheet width of the next job is smaller than the sheet width of the current job at step S 37 , CPU  2002  proceeds to step S 93 . 
     If the current job is finished at step S 93 , CPU  2002  discriminates if there is a next job (S 94 ). If there is a next job, CPU  2002  returns to step S 32 . If there is no next job at step S 94 , CPU  2002  instructs processing controller  205  to move sensor  43  to the home position (S 39 ) and returns to step S 91 . 
     If the current job is not finished at step S 93 , CPU  2002  discriminates if a next job is being inputted, that is, documents of the next job are being read (S 95 ). If a next job is being inputted, CPU  2002  returns to step S 32 . If a next job is not being inputted at step S 95 , CPU  2002  discriminates if the start key of operation panel  40  is pressed for inputting a next job (S 96 ). If the start key is not pressed, CPU  2002  returns to step S 32 . If the start key is pressed at step S 96 , CPU  2002  instructs document reading controller  203  to start inputting documents of the next job (S 97 ) and returns to step S 32 . 
     FIG. 10 shows a flowchart of a subroutine of the image forming operation at step S 32 . CPU  2002  discriminates if a current job includes a punching operation (S 41 ). If the current job does not include the punching operation, CPU  2002  instructs image forming controller  204  to conduct an image forming operation (S 45 ) and returns to the flowchart shown in FIG.  9 . If the current job includes the punching operation at step S 41 , CPU  2002  discriminates if sensor  43  has been moved to the position according to the sheet width of the current job (S 43 ). If sensor  43  has been moved to the position, CPU  2002  proceeds to step S 45 . If sensor  43  has not been moved to the position, CPU  2002  instructs sheet processing controller  205  to move sensor  43  to the position (S 44 ) and proceeds to step S 45 . In a case where sensor  43  is not in the home position before executing step S 44 , CPU  2002  instructs sheet processing controller  205  to move sensor  43  directly to a position according to the sheet width of the current job from a current position without returning sensor  43  to the home position. 
     FIG. 11 shows a flowchart for conducting a preparing operation regarding a feed operation for an insert sheet. A program code of the flowchart is stored in ROM of memory  2001  and is conducted by CPU  2002 . 
     As shown in FIG. 11, CPU  2002  checks if the start key of operation panel  40  is pressed by an user (S 111 ). When the start key is pressed, CPU  2002  instructs the start of an image forming operation (S 52 ). Then, CPU  2002  discriminates if a current job includes an insert sheet feeding operation (S 53 ). If the current job does not include an insert sheet feeding operation, CPU  2002  discriminates if there is a next job (S 112 ). If there is a next job, CPU  2002  discriminates if the next job includes an insert sheet feeding operation (S 54 ). If the next job includes an insert sheet feeding operation, CPU  2002  discriminates if insert sheet I 1  is set on tray  20  based on a detection result of sensor  27  (S 55 ). If insert sheet I 1  is set on tray  20 , CPU  2002  instructs sheet processing controller  205  to feed insert sheet I 1  (S 56 ) and to stop insert sheet I 1  at a predetermined position which is right before roller  2  (S 57 ). CPU  2002  monitors a position of a transported insert sheet I 1  by sensor  28  and controls the stopping position of the insert sheet I 1 . After stopping insert sheet I 1 , CPU  2002  discriminates if the current job is finished (S 113 ). 
     If the current job includes the insert sheet feeding operation at step S 53 , CPU  2002  proceeds to step S 113 . If there is no next job at step S 112  or if the next job does not include an insert sheet feeding operation at step S 54 , CPU  2002  proceeds to step S 113 . If insert sheet I 1  is not set on tray  20  at step S 55 , CPU  2002  proceeds to step S 113 . 
     If the current job is finished at step S 113 , CPU  2002  discriminates if there is a next job (S 114 ). If there is a next job, CPU  2002  returns to step S 52 . If there is no next job at step S 114 , CPU  2002  returns to step S 111 . 
     If the current job is not finished at step S 113 , CPU  2002  discriminates if a next job is being inputted, that is, documents of the next job are being read (S 115 ). If a next job is being inputted, CPU  2002  returns to step S 52 . If a next job is not being inputted at step S 115 , CPU  2002  discriminates if the start key of operation panel  40  is pressed for inputting a next job (S 116 ). If the start key is not pressed, CPU  2002  returns to step S 52 . If the start key is pressed at step S 116 , CPU  2002  instructs document reading controller  203  to start inputting documents of the next job (S 117 ) and returns to step S 52 . 
     FIG. 12 shows a flowchart of a subroutine of the image forming operation at step S 52 . CPU  2002  discriminates if a current job includes an insert sheet feeding operation (S 61 ). If the current job does not include an insert sheet feeding operation, CPU  2002  instructs image forming controller  204  to conduct an image forming operation (S 65 ) and returns to the flowchart shown in FIG.  11 . If the current job includes an insert sheet feeding operation at step S 61 , CPU  2002  discriminates if insert sheet I 1  has been transported to the predetermined position (S 63 ). If insert sheet I 1  has been transported to the predetermined position, CPU  2002  proceeds to step S 65 . If insert sheet I 1  has not been transported to the predetermined position (S 63 ), CPU  2002  instructs sheet processing controller  205  to feed insert sheet I 1  to the predetermined position (S 64 ) and proceeds to step S 65 . 
     FIG. 13 shows sheet processing apparatus  105  which conducts booklet making and sheet folding in addition to sheet stapling, sheet punching and insert sheet feeding which are conducted by sheet processing apparatus  103 . Sheet processing apparatus  105  is controlled by CPU  2002  through sheet processing controller  205 . Sheet processing apparatus  105  includes sheet folding apparatus  106  and booklet making unit  107 . 
     When booklet making is selected, a sheet is led to path  91  by flapper  89 . The sheet is stopped by stopper  92  in order to staple at the center of the sheet by staple unit  93 . Sheets at staple unit  93  are aligned by aligning plate  97 . Stopper  92  is movable in a direction shown by arrow A. Aligning plate  97  is movable in a sheet width direction in accordance with a sheet width. At the time of stapling by staple unit  93 , the distance between stopper  92  and staple unit  93  is the half length of the sheet. Staple unit  93  staples two points on the center of the sheet. After stapling by staple unit  93 , stopper  92  moves down until a distance between pushing plate  95  and stopper  92  becomes the half length of the sheet. Then, pushing plate  95  pushes sheets to folding rollers  94  which are rotating. Pushing plate  95  is movable in a direction shown by arrow B. The sheet are folded by folding rollers  94  and discharged onto booklet tray  98 . 
     When sheet folding is selected, a sheet is led to path  111  by flapper  110 . The sheet is stopped by stopper  112  in order to fold the sheet by rollers  113  and  114 . Stopper  112  is movable in a direction shown by arrow C. The distance between stopper  112  and rollers  113  and  114  is controlled in accordance with the length of the sheet and a way of folding. When Z-folding is conducted, the distance between stopper  112  and rollers  113  and  114  is the quarter length of the sheet. The sheet is folded by rollers  113  and  114 . Then, the sheet is stopped by stopper  116  in order to fold the sheet by rollers  114  and  115 . Stopper  116  is movable in direction shown by arrow D. The distance between stopper  116  and rollers  114  and  115  is controlled in accordance with the length of the sheet and the way of folding. When Z-folding is conducted, the distance between stopper  116  and rollers  114  and  115  is the quarter length of the sheet. The sheet is folded by rollers  114  and  115  and then transported to roller  1 . 
     FIG. 14 shows a flowchart for conducting a preparing operation regarding booklet making operation. A program code of the flowchart is stored in ROM of memory  2001  and is conducted by CPU  2002 . 
     As shown in FIG. 14, CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  to a home position (S 71 ). Then, CPU  2002  checks if the start key of operation panel  40  is pressed by an user (S 141 ). When the start key is pressed, CPU  2002  instructs to start an image forming operation (S 72 ). Then, CPU  2002  discriminates if a current job includes a booklet making operation (S 73 ). If the current job does not include the booklet making operation, CPU  2002  discriminates if there is a next job (S 142 ). If there is a next job, CPU  2002  discriminates if the next job includes a booklet making operation (S 74 ). If the next job includes the booklet making operation, CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  to a predetermined position according to a sheet size for the next job during the current job (S 75 ). Then, CPU  2002  discriminates if the current job is finished (S 143 ). In a case where stopper  92  and aligning plate  97  are not in the home position before executing step S 75 , CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  directly to the predetermined position from a current position without returning stopper  92  and aligning plate  97  to the home position. 
     If the current job includes the booklet making operation at step S 73 , CPU  2002  proceeds to step S 143 . If there is no next job at step S 142  or if the next job does not include the booklet making operation at step S 74 , CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  to the home position (S 76 , S 77 ) and proceeds to step S 143 . 
     If the current job is finished at step S 143 , CPU  2002  discriminates if there is a next job (S 144 ). If there is a next job, CPU  2002  returns to step S 72 . If there is no next job at step S 144 , CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  to the home position (S 78 ) and returns to step S 141 . 
     If the current job is not finished at step S 143 , CPU  2002  discriminates if a next job is being inputted, that is, documents of the next job are being read (S 145 ). If a next job is being inputted, CPU  2002  returns to step S 72 . If a next job is not being inputted at step S 145 , CPU  2002  discriminates if the start key of operation panel  40  is pressed for inputting a next job (S 146 ). If the start key is not pressed, CPU  2002  returns to step S 72 . If the start key is pressed at step S 146 , CPU  2002  instructs document reading controller  203  to start inputting documents of the next job (S 147 ) and returns to step S 72 . 
     FIG. 15 shows a flowchart of a subroutine of the image forming operation at step S 72 . CPU  2002  discriminates if a current job includes a booklet making operation (S 81 ). If the current job does not include a booklet making operation, CPU  2002  instructs image forming controller  204  to conduct an image forming operation (S 85 ) and returns to the flowchart shown in FIG.  14 . If the current job includes a booklet making operation at step S 81 , CPU  2002  discriminates if stopper  92  and aligning plate  97  have been moved to the predetermined position according to the sheet size for the current job (S 83 ). If stopper  92  and aligning plate  97  have been moved to the predetermined position, CPU  2002  proceeds to step S 85 . If stopper  92  and aligning plate  97  have not been moved to the predetermined position, CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  to the predetermined position according to the sheet size (S 84 ) and proceeds to step S 85 . In a case where stopper  92  and aligning plate  97  are not in the home position before executing step S 84 , CPU  2002  instructs sheet processing controller  205  to move stopper  92  and aligning plate  97  directly to the predetermined position from a current position without returning stopper  92  and aligning plate  97  to the home position. 
     FIG. 16 shows a flowchart for conducting a preparing operation regarding a sheet folding operation. A program code of the flowchart is stored in ROM of memory  2001  and is conducted by CPU  2002 . 
     As shown in FIG. 16, CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  to a home position (S 91 ). Then, CPU  2002  checks if the start key of operation panel  40  is pressed by a user (S 161 ). When the start key is pressed, CPU  2002  instructs the start of an image forming operation (S 92 ). Then, CPU  2002  discriminates if a current job includes a sheet folding operation (S 93 ). If the current job does not include a sheet folding operation, CPU  2002  discriminates if there is a next job (S 162 ). If there is a next job, CPU  2002  discriminates if the next job includes a sheet folding operation (S 94 ). If the next job includes a sheet folding operation, CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  to a predetermined position according to a sheet size and a way of folding for the next job during the current job (S 95 ). Then, CPU  2002  discriminates if the current job is finished (S 163 ). In a case where stoppers  112  and  116  are not in the home position before executing step S 75 , CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  directly to the predetermined position from a current position without returning stoppers  112  and  116  to the home position. 
     If the current job includes a sheet folding operation at step S 93 , CPU  2002  proceeds to step S 163 . If there is no next job at step S 162  or if the next job does not include a sheet folding operation at step S 94 , CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  to the home position (S 96 , S 97 ) and proceeds to step S 163 . 
     If the current job is finished at step S 163 , CPU  2002  discriminates if there is a next job (S 164 ). If there is a next job, CPU  2002  returns to step S 92 . If there is no next job at step S 164 , CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  to the home position (S 98 ) and returns to step S 161 . 
     If the current job is not finished at step S 163 , CPU  2002  discriminates if a next job is being inputted, that is, documents of the next job are being read (S 165 ). If a next job is being inputted, CPU  2002  returns to step S 92 . If a next job is not being inputted at step S 165 , CPU  2002  discriminates if the start key of operation panel  40  is pressed for inputting a next job (S 166 ). If the start key is not pressed, CPU  2002  returns to step S 92 . If the start key is pressed at step S 166 , CPU  2002  instructs document reading controller  203  to start inputting documents of the next job (S 167 ) and returns to step S 92 . 
     FIG. 17 shows a flowchart of a subroutine of the image forming operation at step S 92 . CPU  2002  discriminates if a current job includes a sheet folding operation (S 101 ). If the current job does not include a sheet folding operation, CPU  2002  instructs image forming controller  204  to conduct an image forming operation (S 105 ) and returns to the flowchart shown in FIG.  16 . If the current job includes a sheet folding operation at step S 101 , CPU  2002  discriminates if stoppers  112  and  116  have been moved to the predetermined position according to the sheet size for the current job (S 103 ). If stoppers  112  and  116  have been moved to the predetermined position, CPU  2002  proceeds to step S 105 . If stoppers  112  and  116  have not been moved to the predetermined position, CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  to the predetermined position according to the sheet size (S 104 ) and proceeds to step S 105 . In a case where stoppers  112  and  116  are not in the home position before executing step S 104 , CPU  2002  instructs sheet processing controller  205  to move stoppers  112  and  116  directly to the predetermined position from a current position without returning stoppers  112  and  116  to the home position. 
     It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. 
     While the invention has been described with reference to the embodiment disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.