Patent Publication Number: US-9409738-B2

Title: Printing apparatus and control method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing apparatus that can discharge sheets to a stacking apparatus and a control method. 
     2. Description of the Related Art 
     A configuration is known in which while a preceding job is performing post-processing such as book binding, sheets of a succeeding job are discharged to a sheet discharging apparatus different from the sheet discharging apparatus that performs post-processing such as book binding (Japanese Patent Laid-Open No. 2009-160849). Also, there is a high-capacity stacking apparatus such as a stacker that includes a stacking tray for stacking sheets in the stacker, and a discharge tray that discharges bundles of sheets to the outside of the device. This stacking apparatus configuration is known to perform continuous stacking of sheets to the stacking tray by automatically discharging the discharge tray to the outside of the apparatus when fully stacked with sheets. 
     In Japanese Patent Laid-Open No. 2009-160849, when print processing for one set in the preceding job is complete, processing of the preceding job is interrupted, and processing of the succeeding job is started. Also, when a notification of book binding processing completion for one set in the preceding job is received, processing of the succeeding job is interrupted, and remaining processing of the preceding job is resumed. 
     Normally, the sheet discharging apparatus needs to prepare for sheet discharge processing in order for the sheet discharging apparatus to begin sheet discharge processing. For this reason, sheet discharge processing cannot be immediately started when the sheet discharging apparatus is switched from the preceding job to the succeeding job, or from the succeeding job to the preceding job. On the other hand, in a high-capacity stacking apparatus such as a stacker, there is a need to interrupt the discharge of sheets to the stacker during a switch from the stacking tray to the discharge tray and the period it takes for the stacking of sheets to the stacking tray to resume. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to eliminate the above-mentioned problems with the conventional technology. The present invention provides a printing apparatus and a control method that improves processing efficiency in the case in which multiple jobs are processed in a printing apparatus that can discharge sheets to a stacking apparatus. 
     The present invention in one aspect provides a printing apparatus that can discharge sheets to a stacking apparatus that includes a first stacking unit onto which discharged sheets are stacked, and a second stacking unit onto which the sheets stacked onto the first stacking unit can be caused to slide from the first stacking unit to a position for user retrieval, the printing apparatus comprising: a first control unit configured to control execution of a first job of discharging sheets to the stacking apparatus, and a second job of discharging sheets to a finisher that is different from the stacking apparatus; and a second control unit configured to perform sheet discharge preparation in the finisher before the discharge of sheets to the stacking apparatus is interrupted by an operation for sliding the stacked sheets to the position for the user retrieval, wherein the first control unit executes the second job when sheet discharge preparation is performed in the finisher by the second control unit. 
     According to the present invention, processing efficiency can be improved in the case of processing multiple jobs in a printing apparatus that can discharge sheets to a stacker. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an overall configuration of a printing system. 
         FIG. 2  is a diagram showing a configuration of a printing apparatus. 
         FIGS. 3A to 3I  are diagrams for describing operations of a stacker unit. 
         FIG. 4  is a block diagram showing a hardware configuration of the printing apparatus. 
         FIG. 5  is a block diagram showing a software configuration of the printing apparatus. 
         FIG. 6  is a diagram for describing job output processing. 
         FIGS. 7A and 7B  are flowcharts showing job output processing. 
         FIG. 8  is a diagram showing a job management table. 
         FIG. 9  is a diagram showing a job status display screen. 
         FIG. 10  is a flowchart showing processing for determining a job priority ranking (a job priority order). 
         FIG. 11  is a diagram showing a job management table that manages job priority rankings. 
         FIG. 12  is a flowchart showing processing for determining a processing target job. 
         FIGS. 13A to 13C  are other diagrams showing a job status display screen. 
         FIGS. 14A and 14B  are other diagrams for describing job output processing. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Preferred embodiments of the present invention will now be described hereinafter in detail, with reference to the accompanying drawings. It is to be understood that the following embodiments are not intended to limit the claims of the present invention, and that not all of the combinations of the aspects that are described according to the following embodiments are necessarily required with respect to the means to solve the problems according to the present invention. Note that the same configuration elements have the same reference numbers, and redundant descriptions have been omitted. 
     First Embodiment 
       FIG. 1  is a diagram showing the overall configuration of a printing system. As shown in  FIG. 1 , a printing apparatus  100  is connected to an information processing apparatus  101  via a network  102  such as a LAN so that mutual communication is possible. The network  102  may be a wired network, or it may be a wireless network. The printing apparatus  100  performs printing on printing mediums such as printing sheets by an ink jet printing method, electrophotographic printing method, or the like. The printing apparatus  100  may be a multi-functional printer (MFP) in which a function that optically reads an original, a copy function, a FAX function and the like are integrated. The printing apparatus  100  is described below as an MFP. The information processing apparatus  101  is, for example, a generic PC that has a CPU, a display, a keyboard, a pointing device, a hard disk drive (HDD), a memory, a network communication interface, and the like. The information processing apparatus  101  transmits job data to the printing apparatus  100  in a data format that the printing apparatus  100  can print, such as job data that has been converted into PDL data. The printing apparatus  100  performs printing based on job data transmitted from the information processing apparatus  101 . 
       FIG. 2  is a diagram showing the configuration of the printing apparatus  100 . The printing apparatus  100  includes an MFP body  200 , a stacker (a stacking apparatus)  205 , and a finisher  209 . As shown in  FIG. 2 , the stacker  205  is connected to the downstream side of the MFP body  200 , the finisher  209  is connected further downstream, and the MFP body  200  can discharge sheets to the stacker  205  and the finisher  209 . 
     An automatic document feeder (ADF) provided in the upper portion of the MFP body  200  provides originals one sheet at a time to a reading unit. Sheet feeding cassettes  202 ,  203  and  204  provided in the MFP body  200  store sheets for printing by a printing unit (a printer engine) of the MFP body  200 . The stored sheets are conveyed to the printing unit of the MFP body  200  by sheet feeding conveyer rollers, or the like. 
     The stacker  205  discharges sheets printed by the MFP body  200  to a stacker unit  206 . The stacker unit  206  is generally used when discharging a large amount of sheets in one go. The stacker unit  206  has a lift tray  207  and a discharge tray  208 . The lift tray  207  stacks sheets that have been discharged to the stacker unit  206 . The discharge tray  208  discharges a sheet bundle having a predetermined amount of stacked sheets on the lift tray  207  to the outside of the stacker  205 . The configuration of the lift tray  207  and the discharge tray  208  will be described later. A sample tray  212  discharges sheets printed by the MFP  200 . The sample tray  212  is used in the case in which the user wants to confirm an image on a sheet that is being discharged in a large volume to the stacker unit  206  by checking a sample print, for example. 
     The finisher  209  executes various types of finishing processes such as saddle stitch book binding and staple processing on sheets printed by the MFP body  200 , and discharges the sheets to sheet discharge trays  210  or  211 . The finisher  209  is also called a sheet processing apparatus or a saddle stitch book binding apparatus. 
     As described above, in the printing apparatus  100 , sheets printed by the MFP body  200  can be discharged to the stacker  205 , and can also be discharged to the finisher  209 . A sheet conveyer path switch unit  213  provided in the stacker  205  can switch the output destination of a sheet conveyed by the stacker  205  to the stacker unit  206 , the sample tray  212 , or the downstream side of the stacker  205  (in other words, the finisher  209 ). 
       FIGS. 3A to 3I  are diagrams for describing operations of the stacker unit  206 .  FIG. 3A  is a diagram of the lift tray  207  and the discharge tray  208  when viewed from above the stacker unit  206 .  FIGS. 3B to 3I  are diagrams of the lift tray  207  and the discharge tray  208  when viewed from the left of the stacker unit  206 . 
     As shown in  FIG. 3A , the lift tray  207  (a first stacking unit) and the discharge tray  208  (a second stacking unit) are configured so as to intersect with each other in a grid-like manner. Furthermore, the discharge tray  208  is configured to be able to slide to a position for a discharged item to be user retrievable. Sheets stacked to the lift tray  207  slide to the discharge tray  208  and are automatically restacked. As shown in  FIG. 3B , when the stacking of sheets starts, the lift tray  207  is at the stack start position (the uppermost position) of the stacker unit  206 , and the discharge tray  208  is inside the stacker unit  206 . 
     As shown in  FIG. 3C , when the stacking of sheets  300  starts, the lift tray  207  gradually descends in accordance with the stacking amount. The distance and time of descent is different depending on the weight of the sheets. As shown in  FIG. 3D , when the lift tray  207  is fully stacked and has descended to the lowermost portion, sheets  300  are automatically restacked onto the discharge tray  208 . This is because the lift tray  207  and the discharge tray  208 , as shown in  FIG. 3A , are configured so as to intersect with each other in a grid-like manner. 
     As shown in  FIG. 3E , when the sheets  300  have been restacked onto the discharge tray  208 , the discharge tray  208  has slid to the outside of the stacker unit  206 . As shown in  FIG. 3F , when the discharge tray  208  has slid to the outside of the stacker unit  206 , the lift tray  207  has ascended to the stack start position. As shown in  FIG. 3G , when the lift tray  207  has ascended to the stack start position, the stacking of sheets resumes. 
     As shown in  FIG. 3H , when the discharge tray  208  has slid to the outside of the stacker unit  206  and the sheet bundle on it has been retrieved by the user, the discharge tray  208  returns to the inside of the stacker unit  206 . As shown in  FIG. 3I , the stacking of sheets to the lift tray  207  can be continuously performed by the discharge tray  208  returning to a home position inside the stacker unit  206  while the lift tray  207  is stacking and descending. 
       FIG. 4  is a block diagram showing the hardware configuration of the printing apparatus  100 . The printing apparatus  100  includes a CPU  401 , a ROM  402 , a RAM  403 , an HDD  404 , a network interface (I/F)  405 , and a user interface (UI)  406 . These components are mutually connected via an internal bus  400 . 
     The CPU  401  reads (loads) various types of programs stored in the ROM  402  or the HDD  404  to the RAM  403 , and executes operations of the present embodiment, for example. The RAM  403  is used as a work memory that is necessary for the CPU  401  to operate, and temporarily stores data and variables, for example. The HDD  404  stores programs and various types of data before they are loaded to the RAM  403 . The network I/F  405  is a communication interface for executing communication with the information processing apparatus  101  on the network  102 . The UI  406  includes various types of buttons and a touch panel, etc. that are not shown in the diagrams, and receives instruction operations from the user, and displays a status of the printing apparatus  100 , such as the operation mode. 
     A printer  407  is a printing unit that prints print target image data onto a sheet. The members from the CPU  401  to the printer  407  in  FIG. 4  correspond to the MFP body  200  of  FIG. 2 . When the stacker  205  and the finisher  209  are successively connected to the downstream side of the MFP body  200 , they are electrically connected to the printer  407  by a dedicated bus  408 , and communication can be performed therebetween. 
       FIG. 5  is a block diagram showing the software configuration of the printing apparatus  100 . The blocks shown in  FIG. 5  are realized by the CPU  401  executing the programs stored in the ROM  402 . A communication unit  501 , an operation unit  502 , a control unit  503 , a printing unit  504 , a print data management unit  505 , a stacker control unit  506 , and a finisher control unit  507  are realized by the CPU  401 . 
     The communication unit  501  performs communication with other devices via the network I/F  405 . The operation unit  502  receives various types of user instructions and operations from the UI  406  and displays the status of the printing apparatus  100  (the operation mode, the job execution status, etc.) on the UI  406 . The control unit  503  performs various types of control based on job data that has been input to the printing apparatus  100 . The printing unit  504  controls the printer  407  and performs printing. The print data management unit  505  stores image data that has been converted from job data into a bitmap by the control unit  503  to the HDD  404 . The stacker control unit  506  performs control so that sheets printed by the printing unit  504  are discharged to the stacker  205 . The finisher control unit  507  performs control so that sheets printed by the printing unit  504  are discharged to the finisher  209 . 
     The control unit  503  has a job information analysis unit  508 , a PDL data analysis unit  509 , a data rendering unit  510 , a job information management unit  511 , an intermediate data management unit  512 , and an output control unit  513 . The job information analysis unit  508  performs analysis processing on job information from job data. The PDL data analysis unit  509  analyzes page data for each page from job data, and performs conversion processing into intermediate data such as a display list. Also, the PDL data analysis unit  509  accumulates and stores converted intermediate data to the intermediate data management unit  512  in the RAM  103 . 
     The data rendering unit  510  performs processing for converting the intermediate data accumulated and stored in the intermediate data management unit  512  into bitmap data in units of pages, and accumulates and stores the resulting data to the print data management unit  505 . The job information management unit  511  performs management of job information that has been analyzed by the job information analysis unit  508  and various types of statuses of printing jobs that are processed by the printing apparatus  100 . The intermediate data management unit  512  stores the intermediate date that has been converted by the PDL data analysis unit  509 . The output control unit  513  performs processing for converting the bitmap data in units of pages into a video signal, and performs image transfer processing in synchronization with image formation in the printing unit  504  and paper feed processing. 
       FIG. 6  is a diagram for describing job output processing in the printing apparatus  100 .  FIG. 6  shows an example in which a preceding job 1 is output to the stacker unit  206 , and a succeeding job 2 is output to the sheet discharge tray  211  of the finisher  209  while output to the stacker unit  206  is interrupted. 
     In step S 601  in which the preceding job 1 is being output to the stacker unit  206 , the control unit  503  monitors a pre-set timing for making an interruption announcement. The timing for the interruption announcement will be explained later, but it is determined based on the capability information of the stacker unit  206  with regards to the sheets to be output (the number of pages that can be stacked, etc.). 
     When the timing for the interruption announcement is reached, in step S 602  the control unit  503  causes the finisher control unit  507  to perform finisher output preparation (discharge preparation). Then, when the output of the preceding job 1 to the stacker unit  206  is interrupted, in step S 603  the control unit  503  outputs the succeeding job 2 to the sheet discharge tray  211  of the finisher  209 . 
     Also, while the output to the stacker unit  206  is interrupted in step S 604 , if the number of sheets output to the sheet discharge tray  211  of the finisher  209  has reached a predetermined number of sheets, in step S 605  the control unit  503  resumes output of the preceding job 1 to the stacker unit  206 . This will be described later, but the number of sheets output to the sheet discharge tray  211  of the finisher  209  while output to the stacker unit  206  is interrupted, is determined based on the sheet conveying performance values of the MFP body  200 , the stacker  205 , and/or the finisher  209  with respect to output target sheets, and capability information of the stacker unit  206 . 
     Thereafter, steps S 606  to S 609  are performed similarly to steps S 602  to S 605 . As described above, in the present embodiment, due to performing the finisher output preparation when the stacker interruption announcement is made, finisher output can be started immediately when the stacker is interrupted, the total output time of the job 1 and the job 2 can be reduced, and processing efficiency can be improved. 
       FIGS. 7A and 7B  are flowcharts showing job output processing in the printing apparatus  100 . The processes in  FIGS. 7A and 7B  are realized by the CPU  401  reading out a program stored in the ROM  402  to the RAM  403  and executing it, for example. 
     In step S 701 , the control unit  503  reads out the job information stored in the job information management unit  511 . In the case of the execution order of a job 1 and then a job 2, the job that is to be output to the stacker unit  206  is read out as the job 1, and a job that is to be output to a unit other than the stacker unit  206  (e.g., the finisher  209 ) is output as the job 2. 
     In step S 702 , the control unit  503  determines the processing target job in  FIGS. 7A and 7B  based on the job information read out from the job information management unit  511 . At this time, the control unit  503  determines the job 2 as the processing target job if it is the case that the processing of the job 1 was executed in step S 713 . Also, the job 1 is determined as the processing target job again if it is the case that the processing of the job 2 was executed in step S 716 . 
     In step S 703 , the control unit  503  determines whether or not the output of all of the pages that are to be processed is complete in the job that was determined in step S 702  (hereinafter referred to as the “processing target job”). Here, in the case in which it was determined that the output of all of the pages is complete, the processing in  FIGS. 7A and 7B  ends. On the other hand, in the case in which it was determined that the output of all of the pages is not complete, the procedure moves to step S 704 . 
     In step S 704 , the control unit  503  determines the number of pages on which output processing is to be performed based on the job information of the processing target job. For example, all pages are to be processed in the case in which output processing has not been performed. In step S 705 , the control unit  503  determines the start page that is to undergo output processing based on the job information of the processing target job. For example, the first page is determined as the start page in the case in which output processing has not been performed. 
     In step S 706 , the control unit  503  determines whether or not the output destination of the processing target job is the stacker unit  206  based on the job information of the processing target job. Here, in the case in which it is determined that the output destination is the stacker unit  206 , then the procedure moves to step S 707 , and in the case in which it is determined that the output destination is not the stacker unit  206 , the procedure moves to step S 714 . 
     In step S 707 , the control unit  503  determines the page at which interruption of output of the processing target job is to be performed and the page at which the output interruption announcement is to be made, and stores the pages to the job information management unit  511 . The page at which the output interruption is to be performed and the page at which the output interruption announcement is to be made are determined based on the following information, for example. The page at which the output interruption announcement is to be made may be determined by deducting a predetermined number of pages from the page at which output interruption is to be performed.
         The remaining number of output sheets of the processing target job (number of original pages×number of units−number of sheets output)   Capability information of the stacker unit  206 , which is managed by the stacker control unit  506  (number of stackable sheets for each sheet type (sheet weight))   The designated number of sets or the sheet discharge setting value for each designated number of sheets, which are input from the operation unit  502  (for example, output by the discharged tray  208  every 100 units)       

     For example, if the remaining number of output pages of the processing target job is 3000 sheets, and the number of sheets that can be stacked onto the stacker unit  206  is 1000 sheets, page  1000  and page  2000  are determined as the pages at which output interruption is to be performed. Also, for example, in the case in which the remaining number of output sheets of the processing target job is 1000 sheets, and the discharge of 100-page sets by the discharge tray  208  every three sets has been set, page  300 , page  600  and page  900  are determined as the pages at which output interruption is to be performed. 
     In step S 708 , the control unit  503  determines the number of pages of the succeeding job that are to undergo output processing (number of discharge sheets) while output of the processing target job is interrupted, and stores this information to the job information management unit  511 . The number of pages at which output of the succeeding job is to be performed is determined based on the following information, for example.
         The amount of time that the discharge tray  208  in the stacker unit  206  takes to shift from the home position to the sheet bundle user retrieval position, which is managed by the stacker control unit  506     The amount of time that the lift tray  207  takes to shift from the lowermost position to the stack start position, which is managed by the stacker control unit  506     The sheet conveying performance value of the MFP body  200 , which is managed by the output control unit  513     The sheet conveying performance value of the stacker  205 , which is managed by the stacker control unit  506     The sheet conveying performance value of the finisher  209 , which is managed by the finisher control unit  507         

     The paper conveying performance value of the MFP body  200  is, for example, the sheet conveyance time per sheet in the MFP body  200 , which is the time required for a sheet to be fed to the stacker  205 . Also, the sheet conveying performance value of the stacker  205  is, for example, the sheet conveyance time per sheet in the stacker  205 , which is the time required for a sheet to be fed to the finisher  209 . Also, the sheet conveying performance value of the finisher  209  is, for example, the sheet conveyance time required for a sheet to be discharged from the finisher  209  to the sheet discharge tray  210  or  211 . 
     In step S 709 , the control unit  503  reads out image data that corresponds to one page from the print data management unit  505 , and outputs the image data to the stacker unit  206  via the output control unit  513  and the stacker control unit  506 . 
     In step S 710 , the control unit  503  determines whether or not the output target page is the output interruption announcement page calculated in step S 707 . Here, in the case in which it is determined that the page to be output is the output interruption announcement page, the procedure moves to step S 711 . In step S 711 , the control unit  503  instructs the finisher control unit  507  to perform output preparation in the finisher  209 . Then, the finisher control unit  507  instructs the finisher  209  to perform wakeup, warm-up, and other output preparation. Following the processing in step S 711 , the procedure returns to step S 709 . 
     In the case in which it is determined that the page is not the output interruption announcement page in step S 710 , the procedure moves to step S 712 . The case in which it is determined that the page is not the output interruption announcement page in step S 710 , includes the case in which the output interruption announcement page has not yet been reached, and the case in which the output interruption announcement page has already been reached but the output interruption page has not been reached. 
     In step S 712 , the control unit  503  determines whether or not the output target page is the output interruption page. Here, the procedure moves to step S 713  in the case in which it is determined that the output target page is the output interruption page, and the procedure returns to step S 709  in the case in which it determined that the output target page is not the output interruption page. 
     In step S 713 , the control unit  503  instructs the stacker control unit  506  to perform discharge of a sheet bundle. Then, the stacker control unit  506  instructs the stacker  205  so that the discharge tray  207  performs a discharge operation. Following the processing in step S 713 , the number of completed output sheets of the processing target job is stored to the job information management unit  511 . Thereafter, processing is repeated from step S 701  with the succeeding job (job 2) as the new processing target job. 
     In the case in which it is determined that the output destination of the processing target job is not the stacker unit  206  in step S 706 , for example if the output destination was the finisher  209 , the control unit  503  performs output to the finisher  209  via the finisher control unit  507  in step S 714 . 
     In step S 715 , the control unit  503  determines whether or not the number of output pages has reached the number of pages determined in step S 708  (the number of pages to be output during interruption). Here, in the case in which it is determined that the number of pages output has not reached the number of pages to be output during interruption, the processing in step S 714  is repeated. On the other hand, in the case in which it is determined that the number of output pages has reached the number of pages to be output during interruption, the control unit  503  stores the number of completed output pages of the processing target job to the job information management unit  511  in step S 716 . In step S 715 , if the remaining number of pages to be output to the finisher  209  is less than or equal to a predetermined threshold value, it may be deemed that the output of all pages to the finisher  209  is complete. Following the processing in step S 716 , the procedure returns to step S 701 . 
       FIG. 8  is a diagram showing an example of a job management table for managing job information. As shown in  FIG. 8 , a job ID  801 , a status  802 , input information  803 , output information  804 , and a data storage destination  805  of corresponding job data is managed in a job management table  800 . Information indicating a link to the print data management unit  505  is described in the data storage destination  805 . Also, a sheet output destination  806 , a number of pages  807 , and a number of sets  808  are managed in the input information  803 . Information obtained from the job information analysis unit  508  and the PDL data analysis unit  509  is stored in the sheet output destination  806 , the number of pages  807 , and the number of sets  808 . Also, a sheet output destination  809 , a number of processed pages  810 , a number of processed sets  811 , and a number of processed output sheets  812 , which are information obtained from the output control unit  513 , are stored in the output information  804 . Also, the interruption announcement page  813  determined in step S 707  of  FIG. 7A  and the number of pages output during interruption  814  calculated in step S 708  are stored in the job management table. 
     The job ID “1” is job data in which the number of pages  807  indicates 20 pages, the sheet output destination  809  indicates output to the “stacker”, the processed number of units  811  indicates “150” sets, the processed number of output sheets  812  indicates “3000” sheets, and the status  802  indicates “interrupted”. Also, the job ID “2” is job data in which the sheet output destination  809  indicates output to “Tray 1”, the processed number of output sheets  812  indicates “90” sheets, and the status  802  indicates “printing”. 
     Also, the job ID “4” and the job ID “5” are interrupted processing target jobs after output of the job ID “2” is complete. In the case in which output sheets of the job ID “2” remain in the tray 1 at the point at which processing starts, output is performed to “tray 2”, and in the case in which no output sheets remain, output to “tray 1” is performed, but at the current point the sheet output destination  809  is “undetermined”. 
     The control unit  503  determines the processing target job in step S 702  with reference to the job management table in  FIG. 8 .  FIG. 8  shows a state in which after the control unit  503  has performed processing of the job with the job ID=1 through to step S 713 , the process returns to step S 701 , and the state of the case in which processing of the job with the job ID=2 in step S 714 . 
     As described above, the preceding job 1 is output to the stacker  205 , the stacker interruption announcement is made, finisher output preparation is performed, and the succeeding job 2 is output to the sheet discharge tray  211  of the finisher  209  while output to the stacker  205  is interrupted. 
       FIG. 9  is a diagram showing an example of a job status display screen displayed on the UI  406 . As shown in  FIG. 9 , a job ID  902 , a job name  903 , a status  904 , an output destination  905 , and a status of deliverables at the output destination  906  in corresponding job data is displayed as a print data list  901  in the job status display screen  900 . For example, concerning the job ID “1”, the status  904  indicates “interrupted”, but the state of deliverables at the output destination  906  indicates “retrievable”. In other words, the user can retrieve a deliverable (a sheet bundle) of the job 1 from the stacker  205  and confirm that offline processing is executable. 
     According to the above description, in the case in which output to the finisher is to be performed during stacker processing interruption while sheets are being continuously output to the stacker, finisher output preparation is performed when a stacker interruption announcement is made, thus making it possible to immediately start the finisher output during stacker interruption. As a result, the total output time of the job 1 and the job 2 can be reduced, and processing efficiency can be improved. 
     Second Embodiment 
     In the present embodiment, degrees of priority (priority rankings) are set for multiple jobs that succeed a stacker output job, and the processing target job that can be processed while processing of the stacker output job is interrupted is determined based on the set degrees of priority. 
       FIG. 10  is a flowchart showing processing for determining a job priority ranking in the present embodiment. The processes in  FIG. 10  are realized by the CPU  401  reading out a program stored in the ROM  402  to the RAM  403  and executing it. 
     In step S 1001 , when the intermediate data of each job has been stored and accumulated in the intermediate data management unit  512 , the control unit  503  reads out a piece of job information from the job information management unit  511 . In step S 1002 , the control unit  503  determines whether or not the output destination of the corresponding job is the stacker  205  based on the read out job information (the output destination  806 ). Here, the processing in  FIG. 10  ends in the case in which it is determined that the output destination is the stacker  205 . On the other hand, the procedure moves to step S 1003  in the case in which it is determined that the output destination is not the stacker  205 . 
     In step S 1003 , in the case in which the job preceding the corresponding job is a stacker output job (a job output to the stacker unit  206 ) the control unit  503  determines whether or not interruption due to discharge processing will occur during stacker output processing of the preceding job. This determination is performed based on, for example, capability information of the stacker unit  206  (the stackable number of sheets for every sheet type (sheet weight)), sheet information of the preceding job, and the number of output sheets calculated from the number of pages/number of sets. For example, it is determined that an interruption will occur in the case in which the number of output sheets is greater than the stackable number of sheets. 
     Here, in the case in which it is determined that an interruption due to a discharge operation will occur during stacker output processing, the procedure moves to step S 1004 . In step S 1004 , the control unit  503  determines whether or not the output of the entire corresponding job in finisher output can be completed while the stacker output processing is interrupted, based on the information described in step S 708 , job sheet information, and the number of output sheets calculated from the number of pages and number of sets. Here, in step S 1006 , in the case in which it was determined that the output of the entire corresponding job can completed, the control unit  503  determines that the degree of output priority of the corresponding job is [ 1 ], and stores this in the job information management unit  511 . On the other hand, the procedure moves to step S 1005  in the case in which it was determined that the output of the entire corresponding job cannot be completed. 
     In step S 1005 , the control unit  503  determines whether or not output of a predetermined unit of finishing of the corresponding job can be completed. The predetermined unit of finishing is, for example, a unit of a bundle that is bundled by a staple. Here, in the case in which it was determined that output of a unit bundle of the corresponding job can be completed, in step S 1007  the control unit  503  determines that the output degree of priority of the corresponding job is [ 2 ] and stores this in the job information management unit  511 . On the other hand, in the case in which it was determined that output of a unit of a bundle of the corresponding job cannot be completed, in step S 1008  the control unit  503  determines that the output degree of priority of the corresponding job is [ 3 ] and stores this in the job information management unit  511 . 
     In step S 1004  and S 1005 , whether or not the entire job or output of a unit of finishing can be completed may be further determined based on the remaining quantity of sheets in the sheet feeding cassettes, and execution information regarding regularly implemented calibration, or the like that are managed by the output control unit  513 . 
       FIG. 11  is a diagram showing an example of a job management table that manages the job priority rankings. As shown in  FIG. 11 , a degree of output priority  1101  is managed in addition to the information in  FIG. 8 , in the job management table  800 . 
       FIG. 12  is a flowchart showing processing for determining a processing target job that is based on the job priority ranking. The processes in  FIG. 12  are realized by the CPU  401  reading out a program stored in the ROM  402  to the RAM  403  and executing it. 
     In step S 1201 , when discharge output from the stacker control unit  506  to the stacker unit  206  starts, the control unit  503  reads out a piece of job information from the job information management unit  511 . In step S 1202 , the control unit  503  determines from the read-out job information (output destination  806 ) whether or not a determination has been made for all of the jobs that are in output-standby and do not have the stacker unit  206  as the output destination. Here, the procedure moves to step S 1203  in the case in which the determination is complete, and the procedure moves to step S 1208  in the case in which the determination is not complete. 
     In step S 1203 , the control unit  503  determines whether or not the degree of output priority of the current job in focus is [1]. Here, in the case in which it is determined that the degree of output priority is [1], the procedure moves to step S 1209  and the corresponding job is determined to be the processing target job. On the other hand, the procedure moves to step S 1204  in the case in which it is determined that the degree of output priority is not [1]. 
     In step S 1204 , the control unit  503  determines whether or not the degree of output priority for the corresponding job is [2]. Here, in the case in which it is determined that the degree of output priority is [2], the procedure moves to step S 1206  and the control unit  503  determines whether or not a job that has a degree of output priority [2] or more has been stored to a top priority job temporary storage region. The top priority job temporary storage region is ensured in the RAM  403 , for example. In the case in which it is determined that a job with a degree of output priority [2] or more is stored in the top priority job temporary storage region in step S 1206 , processing from step S 1201  repeated. However, in the case in which it is determined that a job with a degree of output priority [ 2 ] or more is not stored in the top priority job temporary storage region in step S 1206 , the procedure moves to step S 1207 . In step S 1207 , the control unit  503  stores the information of the corresponding job as a top priority job in the top priority job temporary storage region, and thereafter processing from step S 1201  is repeated. At this time, in the case in which it is determined that a top priority job is already stored, the job is updated to a top priority job. 
     In the case in which it is determined that the degree of output priority is not [ 2 ] in step S 1204 , the procedure moves to step S 1205 , and the control unit  503  determines whether or not the degree of output priority of the corresponding job is [ 3 ]. Here, in the case in which it is determined that the degree of output priority is [ 3 ], the procedure moves to step S 1206  and the control unit  503  determines whether or not a job that has a degree of output priority [ 3 ] or more has been stored to the top priority job temporary storage region. Processing from step S 1201  is repeated in the case in which it is determined that a job that has a degree of output priority [ 3 ] or more is stored in the top priority job temporary storage region in step S 1206 . On the other hand, the procedure moves to step S 1207  in the case in which it is determined that a job that has a degree of output priority [ 3 ] or more has not been stored to the top priority job temporary storage region. In step S 1207 , the control unit  503  stores the information of the corresponding job as a top priority job in the top priority job temporary storage region, and thereafter processing is repeated from step S 1201 . At this time, in the case in which it is determined that a top priority job is already stored, the job is updated to a top priority job. 
     Processing is repeated from step S 1201  in the case in which it is determined that the degree of output priority is not [3] in step S 1205 . 
     If it was determined in step S 1202  that a determination has been made for all jobs on output standby, excluding jobs with an output destination that is the stacker unit  206 , in step S 1208  the control unit  503  determines whether or not there are jobs stored in the top priority job temporary storage region. Here, in the case in which it is determined that a job has been stored to the top priority job temporary storage region, in step S 1209  the control unit  503  determines the corresponding job to be the processing target job to be processed while the output of the stacker output job is interrupted. On the other hand, the processing in  FIG. 12  ends in the case in which it is determined in step S 1208  that a job is not stored in the top priority job temporary storage region. 
     As described above, in the present embodiment, a degree of priority is set for each job that succeeds a stacker output job, and the processing target job is determined based on the degrees of priority. 
     Third Embodiment 
     In the present embodiment, the total output time of a stacker output job can be reduced by, while the processing of the stacker output job is interrupted by the stacker output, outputting the succeeding pages of the stacker output job to another sheet discharging apparatus, other than the stacker unit  206 . 
       FIGS. 13A to 13C  are diagrams showing an example of the job status display screen that displays the status of a job. Interruption information  1301  that shows whether or not processing interruption due to stacker output will occur when the stacker output job is executed, is displayed on the job status display screen  900  in  FIG. 13A . Here, as shown in  FIG. 13B , a processing mode selection screen  1302  for the corresponding job is displayed by the user selecting the interruption information  1301 . 
     In the case in which the user selects a [No] button  1303  on the processing mode selection screen  1302 , the corresponding job is output to the stacker unit  206  only, and output to another sheet discharging apparatus is not performed. Also, in the case in which the user selects an “output destination: automatic” button  1304 , the corresponding job is output to the stacker unit  206 , and the succeeding pages are output to another sheet discharging apparatus, other than the stacker unit  206 . 
     Also, in the case in which the user selects an “output destination: tray 1” button  1305 , the corresponding job is output to the stacker unit  206 , and succeeding specified pages are output to the tray  211  due to selection by the user. Also, in the case in which the user selects an “output destination: tray 2” button  1306 , the corresponding job is output to the stacker unit  206 , and succeeding specified pages are output to the tray  210  due to selection by the user. 
     When a button other than the [No] button  1303  is selected on the processing mode selection screen  1302  and a determining button  1306  is pressed, the job status display screen  900  is displayed as shown in  FIG. 13C . Specifically, a display  1309  that shows a second output destination (output destination 2) of the corresponding job and a display  1310  that shows the status of deliverables at the output destination 2 are displayed on the job status display screen  900 . 
       FIGS. 14A and 14B  are diagrams for describing job output processing in the present embodiment. Below is a description of an example in which the stacker output job (job 3) is output from the first page to the stacker unit  206 , and while output to the stacker unit  206  is interrupted, the job 3 is in reverse order output from the final page to the sheet discharge tray  211  of the finisher  209 . 
     In step S 1401  shown in  FIG. 14A , the control unit  503  monitors a pre-set timing for making an interruption announcement while the job 3 is being output from the front page to the stacker unit  206 . Here, a description of the timing for making an interruption announcement is the same as the description in the first embodiment. 
     When the timing for making an interruption announcement is reached, in step S 1402  the control unit  503  instructs the finisher control unit  507  to perform a finisher output preparation  1406 . Then when output of the job 3 to the stacker unit  206  is interrupted, in step S 1403  the control unit  503  outputs the job 3 in reverse order from the final page to the sheet discharge tray  211  of the finisher  209 . Also, the status of deliverables at the output destination  906  is displayed as “retrievable” on the job status display screen  900 , and the user is prompted to retrieve a sheet bundle  1410  from the stacker unit  206 . 
     While output to the stacker unit is interrupted in step S 1404 , when the number of sheets discharged to the sheet discharge tray  211  of the finisher  209  has reached a predetermined number of pages, the control unit  503  resumes output of the job 3 to the stacker unit  206  in step S 1405 . 
     Thereafter, in the case in which interruption of output to the stacker unit  206  reoccurs, steps S 1406  to S 1409  are performed similarly to steps S 1402  to S 1405 . At that time, the status of deliverables  1310  at the output destination 2 is displayed as “outputting” on the job status display screen  900 , and the user is prevented from performing retrieval of a sheet bundle  1413  on the sheet discharge tray  211 . If an interruption in output to the stacker unit  206  ceases, the status of deliverables  1310  at the output destination 2 is displayed as “retrievable” on the job status display screen  900 , and the user is prompted to retrieve a sheet bundle  1414  on the sheet discharge tray  211 . 
     As a result of the above processing, by combining the sheet bundle  1414  on the sheet discharge tray  211  and the sheet bundles  1410  to  1412  output to the stacker unit  206  as shown in  FIG. 14B , the user can obtain the output deliverables of the job 3. Also, regarding the stacker output job, the total output time of the stacker output job can be reduced by outputting specified succeeding pages to another sheet discharging apparatus, other than the stacker, while the stacker output processing is interrupted. 
     OTHER EMBODIMENTS 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). he computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. he computer executable instructions may be provided to the computer, for example, from a network or the storage medium. he storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2014-167956, filed Aug. 20, 2014, which is hereby incorporated by reference herein in its entirety.