Patent Publication Number: US-10322598-B2

Title: Bundle discharge control for sheet binding device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2016/082660, filed Nov. 2, 2016, which claims the benefit of Japanese Patent Application No. 2015-253601, filed Dec. 25, 2015, both of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet binding processing apparatus, an image forming system, and a sheet binding processing method and, more particularly, to, for example, a method of stacking sheets that have undergone binding processing. 
     Background Art 
     There is a case in which a sheet processing apparatus for performing various types of post-processing on a sheet-like printing medium on which an image has been formed by an image forming apparatus is provided in a conventional image forming system. As such a sheet processing apparatus, there is known, for example, a sheet binding processing apparatus (to be referred to as a needle stapler hereinafter) with a stapler that binds a bundle made of a plurality of printing media by using binding members such as metal staples. Binding processing by the needle stapler will be referred to as needle stapling processing hereinafter. 
     The sheet binding processing apparatus performs the above-described sheet binding processing and discharges/stacks printing media to/on a predetermined tray. It is necessary to set the height of the printing media stacked on that tray to a height that does not inhibit discharge of the printing media. For this reason, an operation is suspended when the number of printing media stacked on that tray reaches a predetermined number. In such a sheet binding processing apparatus, a bundle of printing media that has undergone needle stapling processing becomes higher by portions of staples. If such a bundle is stacked on the tray, a sheet height cannot be determined correctly, the bundle may block a printing medium discharge port, and discharge of the printing media may be left undone. Moreover, the bundle unpiles as the portions of the staples become thicker, making it impossible to align and stack the bundle. 
     In order to solve such problems, patent literature 1 proposes control capable of suspending an operation not only by the number of sheets but also by the number of stapled bundles. Patent literature 2 proposes an arrangement in which the number of sheets discharged to and stacked on a tray is converted into a stacking point and counted, the stacking point is counted in correspondence with a paper size or a non-binding mode/binding mode, and the total is controlled so as not to exceed the predetermined value of the tray. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Laid-Open No. 4-173192 
     Patent Literature 2: Japanese Patent Laid-Open No. 2007-70011 
     Staplers that perform binding processing without using any binding member such as a staple are sold in large numbers because of recent rising awareness of ecological problems. In response to such a trend, a sheet binding processing apparatus that binds a bundle of printing media without using any binding member (to be referred to as an eco-stapler) has also been proposed as a sheet processing apparatus of an image forming system. Binding processing by the eco-stapler will be referred to as eco-stapling processing hereinafter. 
       FIG. 8  is a view showing the state of a bundle of printing media that has undergone needle stapling processing by a conventional sheet binding processing apparatus, and is discharged to and stacked on a tray.  FIG. 9  is a view showing the state of a bundle of printing media that has undergone eco-stapling processing using a press-bonding method by the conventional sheet binding processing apparatus, and is discharged to and stacked on the tray. 
     Both  FIGS. 8 and 9  are the views when a sheet binding processing apparatus  500  is viewed from the side of two discharge ports  700   a  and  701   a  that discharge the printing media outside the apparatus. The sheet binding processing apparatus  500  includes, in correspondence with these two discharge ports, respectively, trays  700  and  701  that stack the discharged printing media. 
     As seen by comparing  FIG. 8  with  FIG. 9 , the bundle of printing media bound by eco-stapling processing ( FIG. 9 ) is different from the bundle of printing media bound by needle stapling processing ( FIG. 8 ) by the thickness corresponding to the amount of used staples. In the case of the bundle bound by eco-stapling processing using the press-bonding method as shown in  FIG. 9 , in particular, unevenness in height of the bundle is small. Therefore, if a discharge operation is suspended with the same upper limit number as needle stapling processing, the tray still has room capable of stacking another bundle in many cases. 
     As described above, in the conventional sheet binding processing apparatus, the discharge operation may be suspended in spite of the fact that there is still room for stacking, keeping a user waiting more than necessary. 
     The present invention has been made in consideration of the above-described related art, and has as its objective to provide a sheet binding processing apparatus, image forming system, and sheet binding processing method capable of setting the volume of sheets stacked on a stacking unit to an appropriate volume according to the type of binding processing. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above-described objective, a sheet binding processing apparatus of the present invention has a following configuration. 
     That is, there is provided a sheet binding processing apparatus comprising: a sheet binding unit configured to be capable of performing a plurality of sheet binding processing; and a control unit configured to change, in accordance with sheet binding processing executed by the sheet binding unit, a stackable amount of sheets, that have undergone sheet binding processing, on a stacking unit. 
     According to another aspect of the present invention, there is provided an image forming system comprising: a sheet binding processing apparatus having the above construction; and an image forming apparatus that forms an image on a sheet and outputs the sheet on which the image has been formed to the sheet binding processing apparatus. 
     According to still another aspect of the present invention, there is provided a sheet binding processing method comprising: performing a plurality of sheet binding processing; and changing, in accordance with sheet binding processing performed in the performing, a stackable amount of sheets, that have undergone sheet binding processing, on a stacking unit. 
     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 
       The accompanying drawings are included in this specification and are used to form a part thereof, show embodiments of the present invention, and describe the principle of the present invention together with its description. 
         FIG. 1  is a front view showing the overview of a copying machine; 
         FIG. 2  is a sectional view showing the arrangement of a sheet binding processing apparatus shown in  FIG. 1 ; 
         FIG. 3  is a block diagram showing the control arrangement of the copying machine shown in  FIG. 1 ; 
         FIG. 4  is a view showing an example of a display screen of an operation panel of the copying machine shown in  FIG. 1 ; 
         FIG. 5  is a flowchart showing binding processing according to the first embodiment; 
         FIG. 6  is a view showing an example of a display screen of an operation panel of a copying machine shown in  FIG. 1 ; 
         FIG. 7  is a flowchart showing binding processing according to the second embodiment; 
         FIG. 8  is a view showing the state of printing media stacked on a conventional sheet binding processing apparatus; and 
         FIG. 9  is a view showing the state of printing media stacked on the conventional sheet binding processing apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In this specification, the term “printing” (to be also referred to as “print”) not only includes the formation of significant information such as characters and graphics, but also broadly includes the formation of images, figures, patterns, and the like on a printing medium, or the processing of the medium, regardless of whether they are significant or insignificant and whether they are so visualized as to be visually perceivable by humans. 
     Also, the term “printing medium” not only includes paper used in common printing apparatuses, but also broadly includes materials, such as cloth, a plastic film, a metal plate, glass, ceramics, wood, and leather, capable of accepting ink. 
     In embodiments below, a description will be given by taking an image forming unit of a copying machine equipped with an image reading unit (scanner) as an example of an image forming apparatus. However, the present invention is not limited to this. For example, an image forming apparatus (printing apparatus) independent as a single function apparatus or a multi-function peripheral obtained by adding a facsimile function to the copying machine may be used as the above-described image forming unit. Further, an apparatus of an arrangement that includes not only a printer engine according to an electrophotographic method but also a printer engine adopting an inkjet printing method may be used as the image forming unit. 
     An example will be described in which a sheet binding processing apparatus is externally attached to the main body of the copying machine. However, a configuration may be adopted in which the apparatus is incorporated into the main body. 
     &lt;Description of Copying Machine ( FIG. 1 )&gt; 
       FIG. 1  is an exemplary example of the present invention, and is a front view showing the schematic arrangement of the image forming system (copying machine) that is equipped with the image reading unit (scanner) and the image forming unit (image forming apparatus) which forms an image on a printing medium such as printing paper according to the electrophotographic method and includes the sheet binding processing apparatus. 
     As shown in  FIG. 1 , the image forming system includes an image forming apparatus  200  that forms an image according to the electrophotographic method, an image reading apparatus  300 , an operation unit  600  with a ten-key pad  601 , and a sheet binding processing apparatus  500 . 
     The image reading apparatus  300  includes an original feeding apparatus, conveys, to a reading position, a plurality of sheet-like originals placed on an original tray of the original feeding apparatus one by one, generates image data by reading an image of each original, and transfers this to the image forming apparatus  200 . The image forming apparatus  200  forms an image based on the image data transferred from the image reading apparatus  300  and forms an image on a sheet-like printing medium such as printing paper. The printing medium on which the image has been formed is conveyed from the image forming apparatus  200  to the sheet binding processing apparatus  500 . 
     The sheet binding processing apparatus  500  performs binding processing on the printing medium conveyed from the image forming apparatus  200 . In this embodiment, binding processing is performed on a bundle obtained by binding a plurality of printing media. With respect to the image forming apparatus  200 , the image reading apparatus  300 , and the sheet binding processing apparatus  500 , the operation unit  600  is an interface for a user to input an instruction to the image forming system or for informing the user of information from the image forming system. By the instruction from the user, a series of processes such as original reading, image formation, binding processing, and the like is performed. The operation unit  600  also includes a display and notifies the user of various kinds of information via the display. The operation unit  600  may be configured as, for example, a touch panel capable of performing an input instruction and display output. 
     The image forming apparatus  200  includes a photosensitive drum on which an electrostatic latent image is formed and a developer configured to develop the electrostatic latent image. A toner image is formed on the photosensitive drum by developing the electrostatic latent image. The electrostatic latent image is formed by a laser scanner that exposes the photosensitive drum with beam light in accordance with image data. The laser scanner can obtain image data not only from the image reading apparatus  300  but also from a host computer (to be referred to as a host hereinafter) to be described later. 
     Toner images formed on the photosensitive drum are sequentially transferred, by a transfer belt and a transfer roller, to printing media conveyed from a paper feed cassette. A fixing unit performs thermo-pressure bonding on the toner images, fixing images to the printing media to which the toner images have been transferred. The printing media to which the images are fixed are conveyed from the image forming apparatus  200  to the sheet binding processing apparatus  500 . 
     Note that the arrangement of the image forming apparatus described above is merely illustrative. The present invention is not limited to the above-described arrangement as long as an arrangement is adopted in which an image is formed on a sheet-like printing medium and conveyed to the sheet binding processing apparatus  500 . 
     The sheet binding processing apparatus  500  may be of a type incorporated in the image forming apparatus  200 . 
     &lt;Description of Sheet Binding Processing Apparatus ( FIG. 2 )&gt; 
       FIG. 2  is a sectional view showing the detailed arrangement of the sheet binding processing apparatus. The sheet binding processing apparatus  500  sequentially takes in the printing media conveyed from the image forming apparatus  200  and performs various kinds of sheet processing. The sheet processing includes processing for obtaining a bundle by binding a plurality of printing media, needle stapling processing for binding the bundle with a binding member (for example, a staple), eco-stapling processing for binding the bundle without using any binding member, sorting processing for aligning the printing media without binding and discharging it, non-sorting processing for discharging the printing media without aligning them, and the like. 
     As shown in  FIG. 2 , the sheet binding processing apparatus  500  includes, as the first binding processing mechanism that performs binding processing on a bundle of printing media, a needle stapler  602  that performs binding processing on the bundle of printing media by using a binding member such as a staple. The sheet binding processing apparatus  500  also includes, as the second binding processing mechanism, a staple free stapler (eco-stapler)  630  that performs binding processing on the bundle of printing media without using any binding member. Because the needle stapler uses the binding member, it has a higher binding ability and the larger number of printing media that can be bound in one binding processing operation than the eco-stapler. 
     The printing medium conveyed from the image forming apparatus  200  is sandwiched by an inlet roller pair  502  and further conveyed by conveyance roller pairs  503  and  504 , reaching a buffer roller  505 . Note that a conveyance sensor  531  that detects the printing medium is provided between the inlet roller pair  502  and the conveyance roller pair  503 . 
     The buffer roller  505  includes press rollers  512 ,  513 , and  514  around its circumference, and can stack and wind the predetermined number of conveyed printing media. By rotating the buffer roller  505 , the press rollers  512 ,  513 , and  514  wind the printing medium around the buffer roller  505 . The buffer roller  505  rotates counterclockwise as shown in this figure, and the printing medium wound around the buffer roller  505  is conveyed in the rotation direction of the buffer roller  505 . 
     A switching flapper  511  is provided between the press roller  513  and the press roller  514 . A switching flapper  510  is provided on the downstream side of the press roller  514 . By the operations of the switching flapper  511  and switching flapper  510 , the printing medium wound around the buffer roller  505  is conveyed to one of a non-sorting path  521 , a buffer path  523 , and a sorting path  522 . When the printing media are conveyed to the non-sorting path  521  and the sorting path  522 , the predetermined number of printing media are stacked in the buffer roller  505 , and thus the printing media are conveyed as a bundle. 
     When the bundle of printing media wound around the buffer roller  505  is guided to the non-sorting path  521 , the switching flapper  511  operates. The switching flapper  511  moves its tip to the side of the buffer roller  505 , separates the bundle of printing media wound around the buffer roller  505 , and guides it to the non-sorting path  521 . The bundle of printing media guided to the non-sorting path  521  is discharged, via a conveyance roller pair  509 , to a tray  701  serving as a stacking unit. A conveyance sensor  533  that detects passage of the bundle of printing media is provided on the path of the non-sorting path  521 . 
     When the bundle of printing media wound around the buffer roller  505  is guided to the buffer path  523 , neither switching flapper  510  nor switching flapper  511  operates, and each of their tips is positioned apart from the buffer roller  505 . The bundle of printing media is conveyed to the buffer path  523  while being wound around the buffer roller  505 . A conveyance sensor  532  that detects passage of the bundle of printing media is provided on the path of the buffer path  523 . 
     When the bundle of printing media wound around the buffer roller  505  is guided to the sorting path  522 , the switching flapper  511  does not operate, and only the switching flapper  510  operates. The switching flapper  510  moves its tip to the side of the buffer roller  505 , separates the bundle of printing media wound around the buffer roller  505 , and guides it to the sorting path  522 . The bundle of printing media guided to the sorting path  522  is conveyed to the processing tray  630  via conveyance roller pairs  506  and  507 . A conveyance sensor  534  that detects passage of the bundle of printing media is provided on the path of the sorting path  522 . 
     The bundle of printing media conveyed to the processing tray  630  undergoes eco-stapling processing or needle stapling processing. A knurling belt  661  and paddle  660  driven in synchronism with the conveyance roller pair  507  pull the bundle of printing media conveyed to the processing tray  630  back to a trailing-end side in a conveyance direction. When an eco-stapler  550  is used, the bundle of printing media is pulled back until it abuts against an eco-stapling alignment plate  690  and undergoes alignment processing in the conveyance direction. The eco-stapler  550  is an eco-stapling processing mechanism that performs binding processing, without using any binding member such as a staple, on the bundle of printing media stacked at this position. 
     At the time of needle stapling processing, the bundle of printing media is pulled back by the knurling belt  661  and the paddle  660  until it abuts against a staple alignment plate  691 , and undergoes alignment processing in the conveyance direction. The needle stapler  602  is a needle stapling processing mechanism that performs, by using the binding member such as the staple, on the bundle of printing media stacked at this position. As described above, the stacking position (binding position) of the bundle of printing media is different between the times of eco-stapling processing and needle stapling processing. Note that the needle stapler  602  can move in a direction perpendicular to the conveyance direction along the circumference of the processing tray  630  and can perform binding processing at a position set by the user. 
     An alignment member  641  is provided in the processing tray  630  so as to hold the side end portions of the bundle of printing media. The alignment member  641  is configured to be movable in a direction (widthwise direction) perpendicular to the conveyance direction of the bundle of printing media and performs alignment processing on the bundle of printing media conveyed onto the processing tray  630  in the widthwise direction (direction perpendicular to drawing paper). Thus, the sheet binding processing apparatus  500  can provide, by performing alignment processing in the conveyance direction and the widthwise direction each time the printing media are stacked on the processing tray  630 , a bundle of printing media with less misalignment even if it performs binding processing on the large number of printing media. 
     The bundle of printing media that has undergone alignment processing and binding processing is discharged to a tray  700  by a discharge roller pair  680  formed by discharge rollers  680   a  and  680   b . A swing guide  650  supports the discharge roller  680   b . The swing guide  650  swings so as to bring the discharge roller  680   b  in contact with the uppermost portion of the bundle of printing media stacked on the processing tray  630 . When the discharge roller  680   b  is in contact with the uppermost portion of the bundle of printing media stacked on the processing tray  630 , the discharge roller pair  680  can discharge the bundle of printing media stacked on the processing tray  630  toward the tray  700  via a discharge port. Therefore, the tray  700  is also referred to as a discharge tray. 
     A tray  670  protrudes upward when the bundle of printing media is stacked on the processing tray  630 . This prevents the bundle of printing media conveyed by the conveyance roller pair  507  from sagging or being unable to return to straight, aligning the bundle of printing media on the processing tray  630 . 
     The tray  700  can lift and moves downward as the number of bundles of printing media discharged from the discharge port increases, preventing the discharge port from being blocked by the bundles of discharged printing media. Therefore, a paper surface detection sensor  540  detects the tray  700  or the uppermost surface of the bundle of printing media on the tray  700 . In accordance with a detection result by the paper surface detection sensor  540 , the tray  700  is controlled to lift such that the uppermost surface of the bundle of printing media has a predetermined position. If the tray  700  cannot move downward anymore, discharge of the printing media is stopped regardless of the presence/absence of binding processing in order to prevent the discharge port from being blocked by the bundle of discharged printing media. A paper presence detection sensor  541  detects the presence/absence of the printing medium on the tray  700 . When the user takes out the bundle of printing media, the tray  700  moves upward and is adjusted such that a distance between the tray  700  and the discharge port becomes constant. Note that the tray  701  cannot lift as the tray  700  and is fixed at a position shown in  FIG. 2 . 
     &lt;Description of Control Arrangement ( FIG. 3 )&gt; 
       FIG. 3  is a block diagram schematically showing a control arrangement for controlling driving of the copying machine. 
     An image forming control unit  210  mainly controls the image forming apparatus  200 , the image reading apparatus  300 , and the operation unit  600 . The image forming control unit  210  includes a CPU  211 , a ROM  212 , and a RAM  213 . The CPU  211  uses the RAM  213  as a work area, and controls the image forming apparatus  200 , the image reading apparatus  300 , and the operation unit  600  by reading and executing control programs from the ROM  212  as needed. 
     A communication controller  220  receives an instruction for image formation or the like from a host computer (to be referred to as a host hereinafter). The host is, for example, a personal computer connected in order to transmit/receive data to/from the image forming system via a network such as a LAN. The communication controller  220  sends the received instruction to the image forming control unit  210 . Based on the instruction sent from the communication controller  220 , the CPU  211  controls the operations of a drum motor  230 , laser scanner  240 , fixing unit  250 , and fixing motor  260  in the image forming apparatus  200 . Consequently, an image is formed on a sheet-like printing medium (for example, cut paper). Note that such an instruction can also be input from the operation unit  600  to the image forming control unit  210  directly, in addition to the host. The CPU  211  can transmit/receive data to/from the sheet binding processing apparatus  500  via a communication interface  270 . 
     A sheet binding processing control unit  560  mainly controls the sheet binding processing apparatus  500 . The sheet binding processing control unit  560  includes a CPU  561 , a ROM  562 , and a RAM  563 . Based on data received from the image forming apparatus  200  via a communication interface  570 , the CPU  561  uses the RAM  563  as a work area, and controls the sheet binding processing apparatus  500  by reading and executing control programs from the ROM  562  as needed. 
     In order to convey the sheet-like printing medium, the sheet binding processing apparatus  500  includes an inlet motor M 1 , a buffer motor M 2 , a discharge motor M 3 , solenoids S 1  and S 2 , and the conveyance sensors  531  to  534 . The inlet motor M 1  drives the inlet roller pair  502 , and the conveyance roller pairs  503  and  504 . The buffer motor M 2  drives the buffer roller  505 . The discharge motor M 3  drives the conveyance roller pairs  507  and  509 . The solenoid S 1  drives the switching flapper  511 . The solenoid S 2  drives the switching flapper  510 . 
     The sheet binding processing apparatus  500  also includes a bundle discharge motor M 4 , a swing motor M 8 , a retractable tray motor M 11 , a tray lifting motor M 12 , the paper surface detection sensor  540 , and the paper presence detection sensor  541  for performing processing such as sorting processing on the printing media. The bundle discharge motor M 4  drives the discharge roller pair  680 . The swing motor M 8  drives the swing guide  650 . The retractable tray motor M 11  drives the tray  670  to retract it outside the apparatus. The tray lifting motor M 12  lifts up and moves down the tray  700 . 
     In order to perform binding processing, the sheet binding processing apparatus  500  also includes a front alignment motor M 5 , a rear alignment motor M 6 , a paddle motor M 7 , a needle stapling motor M 9 , a needle stapling moving motor M 10 , an eco-stapling motor M 13 , and an eco-stapling alignment plate driving motor M 14 . The front alignment motor M 5  and the rear alignment motor M 6  drive the alignment member  641 . The paddle motor M 7  drives the paddle  660 . The needle stapling motor M 9  drives the needle stapler  602 . The needle stapling moving motor M 10  moves the needle stapler  602 . 
     As described with reference to  FIG. 2 , the eco-stapling motor M 13  drives the eco-stapler  550 . The eco-stapling alignment plate driving motor M 14  lifts up and moves down the eco-stapling alignment plate  690 . The sheet binding processing apparatus  500  further includes a needle presence detection unit  580  and detects the presence/absence of the needle stapler  602  by using this. 
     The sheet binding processing apparatus  500  receives, from the image forming apparatus  200 , an instruction for sheet processing performed by the host or the operation unit  600  via the communication interface  570 . The sheet processing control unit  560  performs sheet processing based on the received instruction. 
     In this embodiment, an example will specifically be described in which binding processing is instructed as sheet processing. In accordance with the instruction for binding processing, the sheet processing control unit  560  controls the respective units of the apparatus such as the needle stapling motor M 9 , the needle stapling moving motor M 10 , the eco-stapling motor M 13 , and the like used for binding processing. 
     The user can select, by the operation unit  600 , one of needle stapling processing, eco-stapling processing, and automatic stapling processing as binding processing. In “automatic stapling processing”, the image forming system determines, in accordance with the number of printing media of a bundle, whether to perform binding processing by one of eco-stapling processing and needle stapling processing. 
       FIG. 4  is a view showing an example of a display screen on which such selection of the processing mode of binding processing (to be referred to as a binding processing mode hereinafter) is made. This selection screen is displayed on the display of the operation unit  600 . Selection icons of eco-stapling  611 , needle stapling  612 , and automatic stapling  613  are displayed on this selection screen, and the user can select one of these. 
     The user selects, from the displayed selection screen, the binding processing mode by a touch operation on the display or the operation of the ten-key pad  601 . The sheet binding processing apparatus  500  receives that selection result via the image forming apparatus  200 . The sheet binding processing apparatus  500  performs binding processing by the needle stapler  602  if the selection result gives an instruction to perform needle stapling processing or performs binding processing by the eco-stapler  550  if the result gives an instruction to perform eco-stapling processing. Alternatively, if the selection result gives an instruction to perform automatic stapling processing, the sheet binding processing apparatus  500  performs binding processing by the eco-stapler  550  or the needle stapler  602  in accordance with the number of printing media of a bundle. 
     Note that when the needle stapler  602  and a constituent element related to it are used as binding processing, constituent elements related to that binding processing will collectively be referred to as the first binding processing mechanism. On the other hand, when the eco-stapler  550  and a constituent element related to it are used as binding processing, constituent elements related to that binding processing will collectively be referred to as the second binding processing mechanism. 
     Two embodiments of binding processing executed by the copying machine of the above-described arrangement will now be described with reference to flowcharts. 
     First Embodiment 
       FIG. 5  is a flowchart showing binding processing according to the first embodiment. 
     First, an image forming apparatus  200  forms images in accordance with various print instructions of an input print job in step S 101 , and printing media on which the images have been formed are conveyed to a sheet binding processing apparatus  500 . Then, in step S 102 , it is determined whether binding processing is executed, as sheet processing, on the printing media conveyed to the sheet binding processing apparatus  500 . If it is determined that binding processing is not executed, the printing media are counted, and the process advances to processing step S 108 . In contrast, if it is determined that binding processing is executed, the process advances to step S 103 . 
     In step S 103 , it is determined whether the processing is needle stapling processing by a needle stapler  602  or eco-stapling processing by an eco-stapler  550 . If it is determined here that eco-stapling processing is performed (if the second binding processing mechanism is used), the process advances to step S 104  in which an upper limit value Xa of the number of stacked copies for eco-stapling processing is set. In contrast, if it is determined that needle stapling processing is performed (if the first binding processing mechanism is used), the process advances to step S 105  in which an upper limit value Xb of the number of stacked copies for needle stapling processing is set. Binding processing is executed after the setting in step S 104  or step S 105 , and then a bundle of printing media is discharged to and stacked on a tray  700  in step S 106 . Then, in step S 107 , bundles Y of printing media discharged to the tray  700  are counted. 
     After that, it is determined in step S 108  whether the input print job is completed. If it is determined here that the print job is completed, the process ends. However, if it is determined that the print job is not completed, the process advances to step S 109 . 
     In step S 109 , a set upper limit value X of the number of stacked copies, or the upper limit value Xa or Xb of the number of stacked copies is compared with the count value Y of the number of bundles of printing media discharged to the tray  700 . Note that the upper limit value X of the number of stacked copies is a value set when the sheet binding processing apparatus does not execute binding processing, and this value is set as a default value when the sheet binding processing apparatus  500  is activated. 
     If it is determined here that the count value Y of the number of bundles of printing media exceeds the upper limit value of the number of stacked copies (X, Xa, or Xb) (Y&gt;X, Y&gt;Xa, or Y&gt;Xb), the process advances to step S 110  in which a discharge operation is stopped. Further, in step S 111 , the sheet binding processing apparatus  500  notifies the image forming apparatus  200  of the full load state of the tray  700  and displays a warning message on the display of an operation unit  600 . Subsequently, the process ends. 
       FIG. 6  is a view showing a display example of the warning message. 
     Here, the tray becomes full, urging a user to remove output bundles. 
     Note that if it is determined in step S 109  that the count value of the number of bundles of printing media is equal to or smaller than the upper limit value of the number of stacked copies (Y≤X, Y≤Xa, or Y≤Xb), the process returns to step S 101 , and operations of image formation and sheet processing are continued. 
     Therefore, as described above, according to this embodiment, the upper limit value of the number of bundles of printing media stacked on the tray is set according to the type of stapling processing, and the number of bundles of stacked printing media is changed in accordance with the upper limit value. This makes it possible to set the volume of printing media stacked on the tray to an appropriate volume in accordance with the type of stapling processing. 
     Second Embodiment 
       FIG. 7  is a flowchart showing binding processing according to the second embodiment. In the second embodiment, a process in a case in which a bundle that has undergone eco-stapling processing, a bundle that has undergone needle stapling processing, and a bundle that has not undergone binding processing are mixed on a tray  700  will be described. Note that in  FIG. 7 , the same processing steps as already described in the first embodiment are denoted by the same step reference numbers, and a description thereof will be omitted. Only characteristic processing steps of the second embodiment will be described here. 
     If it is determined that binding processing is executed after steps S 101  and S 102 , the process advances to step S 106  directly. If it is determined that binding processing is not executed, the same process as in the first embodiment is performed. After the process in step S 106 , it is determined in step S 106 A whether the processing is needle stapling processing or eco-stapling processing as in step S 103  of the first embodiment. 
     If it is determined here that eco-stapling processing is performed, the process advances to step S 107 A in which a weighted bundle counter Ya of printing media in eco-stapling processing is used to accumulate counts of bundles Y of discharged printing media. In contrast, if it is determined that needle stapling processing is performed, the process advances to step S 107 B in which a weighted bundle counter Yb of printing media in needle stapling processing is used to accumulate counts of the bundles Y of discharged printing media. Note that the height of each bundle of discharged printing media becomes higher in needle stapling processing than in eco-stapling processing, making weighting of the printing media in needle stapling processing larger than that in eco-stapling processing. In a case in which, for example, weighting of the printing media in eco-stapling processing is 1.1, and weighting of the printing media in needle stapling processing is 1.4, Ya=1.1×10=11, Yb=1.433 10=14, and the count value of the number Y of bundles becomes Y=25 if 10 bundles of printing media are discharged for each binding method. 
     After that, step S 108  is executed as in the first embodiment. If it is determined that a print job is not completed, the process compares, in step S 109 A, the count value Y of the number of bundles of printing media discharged to the tray  700  with an upper limit value X of the number of stacked copies preset in the tray  700 . The process advances to step S 110  if the count value Y of the number of bundles of printing media exceeds the upper limit value X of the number of stacked copies (Y&gt;X), and the process returns to step S 101  if the count value Y of the number of bundles of printing media is equal to or smaller than the upper limit value X of the number of stacked copies (Y≤X). 
     Note that in the second embodiment, if it is determined in step S 102  that binding processing is not executed, the printing media is counted to be used as the count value Y, and the process advances to processing step S 108 . In the second embodiment, the count value Y is weighted, and thus the value becomes larger than the actual number of bundles. Therefore, the upper limit value X of the number of stacked copies is also set in accordance with weighting. For example, if the upper limit of the number of stacked copies when a staple is performed on all the discharged printing media is 50, the upper limit value X of the number of stacked copies is 50×1.4=70. 
     Therefore, as described above, according to the second embodiment, even in the case in which the bundle that has undergone eco-stapling processing, the bundle that has undergone needle stapling processing, and the bundle that has not undergone binding processing are mixed on a discharge tray, it is possible to set the volume of the printing media stacked on the discharge tray to the appropriate volume according to the type of stapling processing. 
     Note that in the above-described embodiments, the binding processing mechanism is changed in accordance with whether binding processing uses the eco-stapler or the needle stapler. However, the binding processing mechanism may be changed when a needle stapler different in length of each staple used or upper limit number of binding is used. Moreover, the height of the bundle of printing media that has undergone eco-stapling processing may be about the same as in a case in which binding processing is not performed, and thus the upper limit value of the number of stacked copies in eco-stapling processing may not be set, and discharge of the printing media may be stopped if a volume that does not allow the tray  700  to move downward further is discharged. 
     Note that the above-described embodiments have been described assuming that a system arrangement externally attaches, to the main body of the copying machine, the sheet binding processing apparatus configured as a separate and independent housing. However, the present invention is not limited to this. For example, the present invention is also applicable to, for example, an arrangement in which the sheet binding processing apparatus is incorporated in one housing of the main body as a post processing unit or an arrangement in which the printing media are passed from the copying machine to the sheet binding processing apparatus via a relay path apparatus. Further, the present invention is also applicable to a system of an arrangement in which a plurality of sheet processing apparatuses are connected. 
     Therefore, according to the present invention, it is possible to set the volume of sheets stacked on a stacking unit to an appropriate volume according to the type of binding processing. 
     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.