Patent Publication Number: US-11021342-B2

Title: Binding apparatus and image forming system including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-008779, filed on Jan. 22, 2019, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     This disclosure relates to a binding apparatus and an image forming system including the binding apparatus. 
     Description of the Related Art 
     A binding apparatus is known that forms images on recording media, stacks the recording media, and binds the recording media with a stapler. 
     In such a binding apparatus, some configurations are known that include a counter to count the number of times of binding (stapling) to detect the remaining quantity of staples. 
     For example, in a method of counting the number of times of stapling, first, the remaining number of staples is stored in a non-volatile memory. The number of times of stapling is subtracted from the remaining number of staples, and an alert is issued when a predetermined number of times of stapling is performed. 
     However, since staples are consumables and replenished, the remaining number of staples may not be updated (for example, when the power is off). As a result, the replenishment of staples may not be detected, and stapling may be continued while the remaining number of staples is erroneously recorded. 
     In such a case, although a sufficient number of staples is actually stored in the binding apparatus, an alert may remain displayed undesirably. 
     SUMMARY 
     An embodiment of this disclosure provides a binding apparatus that bind sheets. The binding apparatus includes a binding device to bind a plurality of stacked sheets with a binding member, a non-volatile memory to store a quantity of binding members in the binding device and control circuitry to control operation of the binding device. The control circuitry outputs an alert when the quantity of binding members stored in the non-volatile memory is equal to or less than a first predetermined value and cancels the alert when the quantity of binding members is equal to or less than a second predetermined value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a schematic view illustrating a configuration of an image forming system as a whole according to an embodiment of this disclosure; 
         FIG. 2  is a block diagram illustrating an example of a configuration of a control unit of the image forming system illustrated in  FIG. 1 ; 
         FIG. 3  is an illustration of a configuration of a post-processing apparatus illustrated in  FIG. 1 ; 
         FIG. 4  is a diagram illustrating an example of increase and decrease of the number of staples and corresponding message display statuses when a binding process is performed; 
         FIG. 5  is a flowchart illustrating an example of a subroutine to determine a near-empty status of the staples in a binding process; 
         FIG. 6  is a flowchart illustrating an example of a process to determine the presence or absence of the staples with a staple sensor, 
         FIG. 7  is a flowchart illustrating an example of a subroutine with a cartridge sensor; and 
         FIG. 8  is a flowchart illustrating an example of a subroutine in a configuration in which the cartridge sensor is not provided. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result. 
     As an example of an embodiment of the present disclosure,  FIG. 1  illustrates a schematic configuration of an image forming system  100 . The image forming system  100  includes an image forming apparatus  101  to form an image on a sheet as a recording medium and a post-processing apparatus  201  as a binding apparatus. 
     The image forming apparatus  101  includes an operation-and-display device  105 , an image reading device  103  and an auto document feeder (ADF)  104 . The operation-and-display device  105  gives instructions to the image forming apparatus  101  in response to user operation. The image reading device  103  reads an original document Q. The ADF  104  feeds and transfers the original document Q into the image reading device  103 . 
     The image forming apparatus  101  further includes an image forming device  102 . The image forming device  102  forms an image onto a surface of a sheet P according to image data of the original document Q read by the image reading device  103 . 
     In the description of the present embodiment, the case is described where the image forming apparatus  101  operates as a so-called copying machine that reads image information from an image formed on a surface of the original document Q and copies the image onto the sheet P. However, embodiments of the present disclosure are not limited to the above-described configuration. For example, a configuration in which an image sent from an external terminal is formed on a surface of the sheet P may be employed, and embodiments of the present disclosure are not limited to a specific image forming method. 
     The image forming device  102 , the image reading device  103 , the ADF  104 , the operation-and-display device  105 , and the like have a general configuration as an image forming apparatus. 
     The image forming apparatus  101 , as illustrated in  FIG. 2 , includes an image formation controller  110  that controls various functions related to image formation. 
     The image formation controller  110  is a computer that includes a central processing unit (CPU)  111 , a read only memory (ROM)  112 , a random access memory (RAM)  113 , a serial interface (I/F)  114 , and the like. A controlling program is stored in the ROM  112 . The CPU  111  reads the program stored in the ROM  112 , loads the program into the RAM  113 , stores data necessary for the control in the RAM  113 , and performs the control defined by the program using the RAM  113  as a work area. 
     The image formation controller  110  is connected with the image forming device  102 , the image reading device  103 , and the operation-and-display device  105 . The image forming device  102 , the image reading device  103 , and the operation-and-display device  105  are controlled via the image formation controller  110 . 
     Similarly, the post-processing apparatus  201 , as illustrated in  FIG. 2 , includes a post-processing controller  210  that controls various functions related to a sheet binding process, a non-volatile memory  220 , and various sensors  222 . The post-processing apparatus  201  further includes various components such as rollers, motors and a stapler, which are collectively illustrated as various loads  221  in a block diagram of  FIG. 2 . 
     The post-processing controller  210  is a computer that includes a CPU  211 , a ROM  212 , a RAM  213 , a serial I/F  214 , and the like. A controlling program is stored in the ROM  212 . The CPU  211  reads the program stored in the ROM  212 , loads the program onto the RAM  213 , stores data necessary for the control in the RAM  213 , and performs the control defined by the program using the RAM  213  as a work area to control the loads  221 . 
     The non-volatile memory  220  has a function as a non-volatile memory that stores various types of data including a state of the post-processing apparatus  201  such as the remaining number of staples stored in the post-processing apparatus  201 , adjustment data, and the like. 
     The image forming apparatus  101  and the post-processing apparatus  201  are connected via the serial I/Fs  114  and  214 , and perform communication such as exchange of commands necessary for sheet conveyance control. 
     The post-processing apparatus  201 , as illustrated in  FIG. 3 , includes a sheet receiving unit  230 , a proof ejection unit  231 , a shift ejection unit  232 , an edge binding unit  233 , a saddle-stitching and folding unit  234 , and a punching unit  235 . The sheet receiving unit  230  receives the sheet P from the image forming apparatus  101 . The proof ejection unit  231  conveys the sheet P. The shift ejection unit  232  adjusts collating positions of the sheet P. The edge binding unit  233  as a binding device binds an edge portion of the sheet P. The saddle-stitching and folding unit  234  performs saddle stitching and folding of the sheet P, and the punching unit  235  makes holes on the sheet P. 
     The sheet receiving unit  230  includes an introduction path  1 . The introduction path  1  receives the sheet P, on which an image has been formed, discharged from the image forming apparatus  101 . The sheet receiving unit  230  further includes an upper conveyance path  2 , a straight conveyance path  3 , and a lower conveyance path  4  that are three branch paths branched from the introduction path  1 . 
     The sheet receiving unit  230  includes an entrance sensor  13 , an entrance roller  10 , a horizontal conveyance roller  11 , and separators  7  and  8 . The entrance sensor  13  detects the sheet P entering the introduction path  1 . The horizontal conveyance roller  11  is disposed downstream from the entrance roller  10  in a direction of conveyance of the sheet P. The separators  7  and  8  switch the direction of conveyance path of the sheet P from the introduction path  1  to the upper conveyance path  2 , the straight conveyance path  3 , and the lower conveyance path  4 . 
     When the sheet P enters the sheet receiving unit  230 , the post-processing controller  210  (See  FIG. 2 ) determines a post-processing necessary for the sheet P based on an instruction from the image formation controller  110 . Also, based on an instruction from the post-processing controller  210 , the entrance roller  10 , the horizontal conveyance roller  11 , and the separators  7  and  8  operate to change conveyance path of the sheet P. 
     The proof ejection unit  231  is connected with the upper conveyance path  2  of the sheet receiving unit  230  and includes a proof tray  6 . 
     The traveling direction of the sheet P is changed by the separator  7  from the introduction path  1  and the sheet P is ejected to the proof tray  6 . 
     The shift ejection unit  232  is connected with the straight conveyance path  3 , and includes an intermediate conveyance roller  12 , an output tray  5 , a sheet ejection roller  26  and a driven roller  27  as a pair of rollers facing each other and a sheet ejection sensor  28 . The intermediate conveyance roller  12  includes a shift mechanism to change the position of the intermediate conveyance roller  12 . 
     The sheet P ejected from the straight conveyance path  3  is shifted in a direction perpendicular to the direction of conveyance by a certain distance when the shift mechanism moves the intermediate conveyance roller  12  in the direction perpendicular to the direction of conveyance by a certain amount. As a result, the sheet P is sandwiched between the sheet ejection roller  26  and the driven roller  27  and sequentially ejected and overlaid onto the output tray  5 . 
     As described above, when the sheet P is sandwiched between the sheet ejection roller  26  and the driven roller  27 , the driven roller  27  or a sheet ejection guide plate equipped with the driven roller  27  approaches and separates from the sheet ejection roller  26 . Owing to this mechanism, a closed state in which the sheet P can be ejected and an open state in which the sheet P is not sandwiched can be selected. After the position shift of the sheet P is completed, the shift ejection unit  232  controls to set the distance between the sheet ejection roller  26  and the driven roller  27  to the closed state and eject sheets P or a bundle of the sheet P of which the position is shifted. 
     The shift ejection unit  232  also includes a feeler  40  near an upper portion of an ejection port. 
     The feeler  40  is rotatably disposed near the center of the sheet P discharged to the output tray  5 , and a projecting edge  40   a  of the feeler  40  contacts an upper surface of the sheet P. 
     The feeler  40  is provided with an upper surface detection sensor  40   b  that detects the height of the projecting edge  40   a  of the feeler  40 . When the upper surface detection sensor  40   b  detects that the height of the projecting edge  40   a  of the feeler  40  is equal to or greater than a predetermined value, the output tray  5  is lowered via the post-processing controller  210 . 
     Thus, by lowering and raising the position of the output tray  5 , even when a large number of the sheet P is discharged, the sheet ejection operation from a sheet outlet can be stably performed. Further, when the output tray  5  reaches a lower limit position, that is, a position where the output tray  5  becomes full, the post-processing controller  210  may issue a stop signal to the image formation controller  110  to stop an image forming operation of the image forming system  100 . 
     The edge binding unit  233  includes a staple tray  21 , a return roller  41 , joggers  22  and  23  that align the position of the sheet P in a width direction of the sheet P, rear end fences  24  and  25  that align the position of the sheet P in a length direction, and a stapler  50  as a binder. 
     The edge binding unit  233  includes a staple sensor  52  to detect the presence or absence of staples loaded in the stapler  50 . 
     The edge binding unit  233  aligns and stacks sheets P conveyed to the staple tray  21 , using the joggers  22  and  23 , and the rear end fences  24  and  25 . The stapler  50  moves in a direction perpendicular to a sheet surface of the bundle of the sheet P to bind a bundle of sheets P, which is aligned and stacked, at a lower edge portion of the bundle of the sheets P at an appropriate position. 
     The operation described above is a binding operation. The bundle of sheets P to which the binding operation is applied, is conveyed to an ejection direction by an ejection claw  29 , sandwiched between the sheet ejection roller  26  and the driven roller  27 , and ejected to the output tray  5 . 
     The saddle-stitching and folding unit  234  is connected to an end of the lower conveyance path  4 . In performing a saddle stitching and folding of sheets P, the post-processing controller  210  switches the separator  8  when the sheet P passes through the straight conveyance path  3  and a leading-edge sensor  14  detects the passage of the sheet P. When the separator  8  is switched, the intermediate conveyance roller  12  rotates in reverse to switch back the sheet P and convey the sheet P toward the lower conveyance path  4 . 
     The saddle-stitching and folding unit  234  includes saddle-stitch conveyance rollers  61 ,  62 , and  63 , a saddle-stitching stapler  51  serving as a binder, a folding stopper  64  for adjusting a folding position, a folding blade  71  and a folding plate  72 . The folding blade  71  contacts the sheet P and presses the sheet P in a direction perpendicular to the sheet surface to perform folding. 
     The saddle-stitching and folding unit  234  also includes a saddle-stitching ejection roller  73  provided downstream from the folding plate  72  in the direction of conveyance of the sheet P and a saddle-stitching tray  9 . When folding is performed by the folding blade  71  and the folding plate  72 , the sheet P is ejected to the saddle-stitching tray  9  by the saddle-stitching ejection roller  73 . 
     The punching unit  235  is disposed on a route of the introduction path  1 . The punching unit  235  includes a registration detector and a puncher to perform punching at a desired position on the sheet P in consideration of a misregistration detected by the registration detector. 
     When the post-processing controller  210  determines that such punching is necessary, the post-processing controller  210  performs punching with the punching unit  235  at an appropriate position of the sheet P received. 
     In the present embodiment, the post-processing apparatus  201  is illustrated in  FIG. 1  as a configuration including both the saddle-stitching and folding unit  234  and the punching unit  235 . However, in such a configuration, the saddle-stitching and folding unit  234  and the punching unit  235  are removably attached and may be detached from the post-processing apparatus  201 . With such a configuration in which components are removably attached, a post-processing apparatus meeting the needs of a user can be provided. 
     Of the post-processing apparatus  201 , when in particular the edge binding unit  233  continuously performs binding with the stapler  50 , the remaining number of staples as stapler consumables is checked. 
     As a method of checking the remaining number of staples with the stapler  50 , near-empty display is employed. In such a method, after staples are replenished, the number of times of binding performed using the stapler  50  is recorded on the non-volatile memory  220 . When the remaining number of staples is equal to or less than a given threshold, an alert is displayed as the near-empty display indicating that the number of the staples is in a near-empty status. The near-empty display of the present embodiment is an alert display to recommend replenishment of staples when the remaining number of staples is small, although a certain number of staples still remains. However, the configuration of checking the remaining number of staples is not limited to such near-empty display. 
     However, in such a mechanism, staples may be replenished while the non-volatile memory  220  is not operating, such as during the power-off. In such a case, although there is a sufficient number of the staples remaining after replenishment, as illustrated in  FIG. 4 , the remaining number of staples remains recorded and the post-processing controller  210  may continue to display the alert. 
     Therefore, in the present embodiment, the post-processing controller  210  outputs an alert when the number n of staples stored in the non-volatile memory  220  is equal to or less than a first predetermined value n1 that is a first threshold value. When the number n of staples becomes equal to or less than a second predetermined value n2 that is a second threshold value, the post-processing controller  210  cancels the alert. In the present embodiment, the number n of staples stored in the non-volatile memory  220  is equal to or less than the first or the second threshold value. However, in some embodiments, the number n may be lower than the first or the second threshold value, and what actions occur at the threshold values can be suitably changed according to design values. 
     A configuration of the above-described mechanism is described with reference to  FIG. 4 . 
     First, the initial value of the number n of staples stored in the non-volatile memory  220  is set to 5,000 staples, the first predetermined value n is set to 500 staples, and the second predetermined value n2 is set to −500 (at time point A). 
     The second predetermined value n2 may be any integer less than the first predetermined value n1, but more preferably zero or a negative integer less than zero. 
     This is because, as described below, the second predetermined value n2 is preferably a value at which binding is not performed if the number n of staples is correct. 
     Next, for example, when an edge binding operation is performed with the edge binding unit  233  and 4,000 staples are consumed, the number n of staples stored in the non-volatile memory  220  becomes 1,000 staples, and no alert is displayed yet. 
     Here, assume that, as illustrated in  FIG. 5 , a stapler cartridge is replenished during the power-off, and the remaining number n of staplers stored in the non-volatile memory  220  is not updated (at time point B), although the actual number x of staples loaded in the stapler  50  is replenished. 
     Note that, when the post-processing controller  210  is operating and the remaining number n stored in the non-volatile memory  220  is updated, the remaining number n stored and the actual number x of staples loaded in the stapler  50  match, which causes no problem. 
     After the stapler cartridge is replenished, the number n of staples stored in the non-volatile memory  220  remains 1,000. Further, when 500 staples are consumed, the post-processing controller  210  determines that the remaining number n of staples is equal to or less than the first predetermined value n1, and displays an alert as a near-empty display of the remaining number of staples on the operation-and-display device  105  via the serial I/F  214  and the serial I/F  114  (at time point C). 
     However, at the time point C, the actual number x of staples loaded in the stapler  50  is 4,500, and such an alert display is erroneous. 
     That is, in a conventional method, such an erroneous alert display continues until the remaining number n of staples stored in the non-volatile memory  220  is updated to a correct value, that is, until the staple cartridge is replaced again, resulting in inconvenience of a user. 
     Hence, in the present embodiment, the second predetermined value n2 is set to reduce the time during which an erroneous-alert display is generated. 
     For example, assume that, even though an alert is displayed, binding operation is continued. When 1,000 more staples are consumed, the remaining number n of staples becomes −500. As a result, the post-processing controller  210  determines that the remaining number n of staples is equal to or less than the second predetermined value n2, and cancels the near-empty display on the operation-and-display device  105  via the serial I/F  214  and the serial I/F  114  (at time point D). 
     As described above, the second predetermined value n2 is set in advance and the alert display is canceled when the remaining number n of staples is equal to or less than the second predetermined value n2, thus shortening the time during which an erroneous alert is displayed. 
     After the remaining number n of staples is less than the second predetermined value n2, the remaining number n of staples stored in the non-volatile memory  220  also continues to decrease as stapling is performed. When the actual number x of staples loaded in the stapler  50  becomes zero (x=0), the post-processing controller  210  displays an end display and stops the edge binding operation (at time point D). 
       FIG. 5  is a flowchart of a process of the near-empty display operation as described above. 
     In step S 101 , the post-processing controller  210  compares the second predetermined value n2 with the remaining number n of staples stored in the non-volatile memory  220 . 
     In step S 101 , when the second predetermined value n2 is less than the remaining number n of staples, the subroutine proceeds to step S 102 . The post-processing controller  210  compares the first predetermined value n with the remaining number n of staples stored in the non-volatile memory  220  (step S 102 ). 
     Alternatively, in step S 101 , when the second predetermined value n2 is not less than the remaining number n of staples, the post-processing controller  210  cancels the alert as the near-empty display of the staples (step S 105 ). 
     Note that a subroutine for near-empty status determination as illustrated in  FIG. 5  is always in operation when the post-processing controller  210  operates. The remaining number n of staples stored in the non-volatile memory  220  gradually decreases from the initial value, and the second predetermined value n2 is less than the first predetermined value n1 (n2&lt;n1). Therefore, the subroutine needs to go through step S 104  at least once before the subroutine goes to step S 105 . 
     That is, the near-empty alert of staples is already displayed when the subroutine process transitions to step S 105  for the first time. 
     Next, in step S 102 , the post-processing controller  210  compares the first predetermined value n1 with the remaining number n of staples stored in the non-volatile memory  220 . At this time, if n1 is greater than or equal to n (n1≥n), the process proceeds to step S 104  to display the near-empty alert of staples. In step S 104 , near-empty notification is performed to issue an alert of the remaining number of staples with the operation-and-display device  105 . 
     When n1 is less than n (n1&lt;n), the post-processing controller  210  determines that the remaining number n of staples is sufficient, and sends a notice to the image forming apparatus  101  that the remaining number of staples is sufficient (step S 103 ). When the near-empty alert is displayed, the alert is cancelled (step S 106 ). 
     Note that in step S 105  and step S 106 , the alert is canceled. However, embodiments of the present disclosure are not limited to the above-described configuration. For example, a configuration may be employed in which a user can select with the operation-and-display device  105  whether the alert is canceled or the output of the alert is continued. 
     If such a setting is employed, the near-empty display of staples continues. Accordingly, a case where an empty display is displayed abruptly, such as at a time point D in  FIG. 4 , can be avoided. 
     Further, since cancelling or continuing the alert display on the operation-and-display device  105  is selectable, a user can grasp that the remaining number n of staples stored in the non-volatile memory  220  and the actual number of staples x are different. 
     Further, in addition to the above-described configuration, the second predetermined value n2 may be configured to be changeable. In such a configuration, the timing to display the alert display can be arbitrarily changed according to the frequency to use the binding operation by a user or the stock amount of the staples for replenishment. Therefore, it is possible to prompt the user to replace the staples without impairing the convenience for the user. 
     Next, descriptions are provided of the setting of the second predetermined value n2. 
     As a matter of course, when the non-volatile memory  220  correctly stores the remaining number n of staples, the remaining number n of staples and the actual number x of staples loaded in the stapler  50  match. 
     When the remaining number n of staples stored in the non-volatile memory  220  matches the actual number x of staples as described above, it is not possible that the actual number x of staples becomes a negative value. Whenever the actual number x of staples becomes zero (x=0), the post-processing controller  210  displays the empty display and stops the edge binding operation based on a signal received from the staple sensor  52 . 
     On the other hand, if the remaining number n of staples stored in the non-volatile memory  220  is different from the actual number x of the staples loaded in the stapler  50  due to some reasons (such as replenishment of a staple cartridge during the power-off in the present embodiment), the remaining number n of staples may not easily be counted and it is substantially difficult to correct the remaining number x of staples stored in the non-volatile memory  220 . 
     However, if the second predetermined value n2 is arbitrarily set in a range between zero and a negative integer, the actual number x of staples may not become zero (x=0) while the remaining number n of staples becomes equal to or less than n2. Such a case is none other than a state where the remaining number n of staples stored in the non-volatile memory  220  is largely different from the actual number x of staples loaded in the stapler  50 . 
     In the present embodiment, setting the second predetermined value n2 as described above allows the post-processing controller  210  to detect a difference between the actual number x of staples and the remaining number n of staples stored in the non-volatile memory  220 . 
     Further, on a condition in which such a difference is detected, the alert display as a display of the near-empty status of staples is canceled. Such a configuration allows the alert to be correctly canceled even if an erroneous alert display occurs. 
     Further, the second predetermined value n2 may be arbitrarily determined in a range in which n2 is less than a value obtained by subtracting a maximum loading number of staples from an initial value of the remaining number n. In the setting of the range described above, a case where the remaining number n of staples stored in the non-volatile memory  220  is equal to or less than n2 is none other than a state where the remaining number n of staples stored in the non-volatile memory  220  is largely different from the actual number x of staples loaded in the stapler  50 . 
     In the present embodiment, the initial value and the maximum value are both 5,000 staples, but the initial value and the maximum value may be arbitrarily changed according to the design of the image forming system  100 . 
     Further, although the first predetermined value n1 is equal to 500 (n1=500) and the second predetermined value n2 is equal to −500 (n2=−500) in the present embodiment, the first predetermined value n1 and the second predetermined value n2 may be appropriately determined within the above-described limitations. 
       FIG. 6  is a flowchart of a subroutine of the present embodiment illustrating a process to determine the presence or absence of staples. 
     As illustrated in  FIG. 6 , in step S 201 , the edge binding unit  233  determines whether the actual number x of staples is zero based on a signal from the staple sensor  52  (step S 201 ). 
     When the staple sensor  52  detects that the actual number x of staples is equal to zero (x=0), the process proceeds to step S 202 , and the post-processing controller  210  notifies the operation-and-display device  105  that the staples run out, and stops the binding operation (step S 202 ). 
     Alternatively, when the staple sensor  52  detects that the actual number of staples x is not zero (x≠0), the process proceeds to step S 203  and continues the subroutine of near-empty status determination as illustrated in  FIG. 5 . 
       FIG. 7  is a flowchart of a subroutine of the present embodiment illustrating a cartridge replacement process when a cartridge sensor  53  of the stapler  50  is provided. 
     The cartridge sensor  53  detects whether a cartridge for replenishing staples is connected to the post-processing apparatus  201 . The cartridge sensor  53  is included in, for example, the stapler  50 . 
     In step S 301 , first, when the cartridge sensor  53  detects that the cartridge is not connected, the process proceeds to step S 302  to perform notification of the absence of staples, and then proceeds to step S 303 . 
     In step S 303 , the cartridge sensor  53  continues a detection loop until the cartridge is detected. When the cartridge sensor  53  detects the cartridge, the process proceeds to step S 304 . 
     In step S 304 , the post-processing controller  210  notifies the image formation controller  110  that the number x of staples is replenished. 
     On a condition in which the number x of staples is replenished, the post-processing controller  210  updates the remaining number n of staples stored in the non-volatile memory  220  (step S 305 ) and terminates the subroutine. 
     As described above, providing the cartridge sensor  53  allows detection of replenishment of staples. Such a configuration can reduce a difference between the actual number x of staples with the remaining number n of staples stored in the non-volatile memory  220 . 
       FIG. 8  is a flowchart of a subroutine of the present embodiment illustrating a cartridge replacement process when the cartridge sensor  53  of the stapler  50  is not provided. 
     In step S 401 , first, when a door of the post-processing apparatus  201  is closed and the staple sensor  52  detects that there is no staple, the process proceeds to step S 402 . 
     The post-processing controller  210  notifies the image formation controller  110  that the staples run out (step S 402 ). 
     The staple sensor  52 , on a condition in which the door of the post-processing apparatus  201  opens or close, repeatedly performs detection of staples (step S 403 ). 
     In step S 403 , when the staple sensor  52  detects the presence of staples after the door of the post-processing apparatus  201  opens and closes, the post-processing controller  210  notifies the image formation controller  110  of the presence of staples (step S 404 ). 
     In step S 404 , when the presence of staples is notified, the post-processing controller  210  updates the remaining number n of staples stored in the non-volatile memory  220  (step S 405 ). 
     If such a subroutine is used, the remaining number n of staples can be updated with the staple sensor  52  even when the cartridge sensor  53  is not provided. 
     The above-described embodiments are illustrative and do not limit this disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure. 
     For example, in the present embodiment, only the post-processing apparatus  201  combined with the image forming apparatus  101  is described as a part of the image forming system  100 . However, the present disclosure may be applied to a post-processing apparatus that performs post processing on a recording medium sent from any other terminals. Alternatively, such a post-processing apparatus may be incorporated in the image forming apparatus  101 . 
     In the present embodiment, the image forming system  100  is described. However, for example, a method of checking the remaining number of staples may be performed by a program that executes each of the above-described actions or by various storage media that store the program. 
     The effects described in the embodiments of this disclosure are listed as examples of most preferable effects derived from this disclosure, and therefore are not limited to the effects described above. In the above descriptions, the term “printing” in the present disclosure may be used synonymously with, e.g. the terms of “image formation”, “recording”, “printing”, and “image printing”. 
     The suffixes Y, M, C, and K attached to each reference numeral indicate only that components indicated thereby are used for forming yellow, magenta, cyan, and black images, respectively, and hereinafter may be omitted when color discrimination is not necessary. 
     The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.