Abstract:
A sheet processing apparatus for processing sheets from an image forming apparatus includes a first processing unit for processing a sheet, the first processing unit including a processing station for processing a sheet, a first path for transporting a sheet therethrough, and a second path for transporting a sheet to the processing station, a second processing unit for processing the sheet transported from the first processing unit, a power supply for supplying power independently to the first processing unit and the second processing unit. The first processing unit selects the first path when the first processing unit is not supplied with power by the power supply.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet processing apparatus having a plurality of processing unit. 
     2. Description of the Related Art 
     A conventional sheet processing apparatus is connected to an image forming apparatus which forms an image onto a sheet. The sheet processing apparatus has plural sheet processing units such as a sheet folding unit, a sheet punching unit, an insert sheet feeder unit, a booklet making unit and sheet stapling unit, by which the sheet processing apparatus can vary sheet processing. All such sheet processing units are supplied with power simultaneously, and if one unit malfunctions, all sheet processing units are not supplied with a power until the malfunctioning sheet processing unit is fixed. That is, even though sheet processing units other than the broken sheet processing unit can process a sheet, all sheet processing units do not work. 
     In view of this problem, Japan patent application publication 10-265121 shows that a broken sheet processing unit is not supplied with power and sheet processing units other than the broken sheet processing unit are supplied with power. This permits the normal sheet processing units to work while the broken sheet processing unit is waiting for fixing. 
     However, in a case where a broken sheet processing unit has a sheet feed path which selects between transport of a sheet to another sheet processing unit and transport of a sheet to a sheet processing station within the broken sheet processing unit, if the broken sheet processing unit has selected the path to the sheet processing station when the broken sheet processing unit is not supplied with power, the sheet cannot be transported to the normal sheet processing units which remain supplied with power. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide sheet processing apparatus which can transport a sheet to an operative sheet processing unit through a malfunctioning sheet processing unit which is not supplied with power. 
     In one aspect, the present invention provides a sheet processing apparatus for processing sheets from an image forming apparatus comprising a first processing unit for processing a sheet, said first processing unit including a processing station for processing a sheet, a first path for transporting a sheet therethrough, and a second path for transporting a sheet to said processing station, a second processing unit for processing the sheet transported from said first processing unit, a power supply for supplying power independently to said first processing unit and said second processing unit, wherein said first processing unit selects said first path when said first processing unit is not supplied with power by said power supply. 
     Preferably, in the sheet processing apparatus, said first processing unit includes leading means for leading a sheet to one of said first and second paths alternatively, and said leading means leads a sheet to said first path when said first processing unit is not supplied with the power by said power supplier. 
     More preferably, in the above sheet processing apparatus, said processing unit includes driving means for driving said leading means to select said second path, wherein said driving means is not supplied with the power when said first processing unit is not supplied with the power by said power supplier. 
     Also, in the above sheet processing apparatus, said leading means is driven by said driving means so that said leading means selects said second path, wherein said leading means is pulled by elastic means so that said leading means selects said first path. 
     Also, in the above sheet processing apparatus, said leading means is a flapper, and said driving means is a solenoid, and said elastic means is a spring. 
     Specifically, the sheet processing apparatus further comprises an invalidation terminal for designating which unit is not supplied with power, wherein said power supply supplies power in accordance with a designation at said invalidation terminal. 
     More specifically, in the above sheet processing apparatus, said invalidation terminal includes first and second switches corresponding to said first and second processing units respectively, said first and second switches are grounded and are connected to first and second resistors respectively which are connected to a power source, said power supply includes a first voltage detector for detecting a voltage between said first or second switch and its respective resistor, and said power supply supplies power when a voltage detected by said first voltage detector is a predetermined voltage. 
     Also, the above sheet processing apparatus further comprises a unit attachment detector for detecting an attachment state of said first and second processing units which are detachable from said sheet processing apparatus, wherein said first or second switches is connected to its respective resistor through a connector when said first or second unit is attached, and is disconnected from its respective resistor when said first or second unit is detached, wherein said unit attachment detector includes a second voltage detector for detecting a voltage between said first or second resistor and said connector, wherein said unit attachment detector includes a third switch which is grounded and connected to a third resistor which is connected to a point between said first or second switches and said connector, and wherein said unit attachment detector turns said third switch on and detects the attachment state based on a voltage by detected said second voltage detector. 
     Also, in the sheet processing apparatus, said first processing unit is comprised by a sheet folder for folding a sheet. 
     Also, the sheet processing apparatus further comprises a display for displaying an indication when at least one of said first and second processing unit is not supplied with a power. 
     Also, the sheet processing apparatus further comprises a transmitter for transmitting a notification to a service center when at least one of said first and second processing unit is not supplied with a power. 
     In another aspect of the invention, the present invention provides a controlling method of a sheet processing apparatus for processing sheets from an image forming apparatus, said sheet processing apparatus including a first processing unit for processing a sheet, said first processing unit including a processing station for processing a sheet, a first path for transporting a sheet therethrough, and a second path for transporting a sheet to said processing station, and a second processing unit for processing the sheet transported from said first processing unit, said controlling method comprising a step for supplying power independently to said first processing unit and said second processing unit, and a step for selecting said first path when said first processing unit is not supplied with power by said power supply. 
     By virtue of the above invention, even if said first processing unit is not supplied with power by said power supply, a sheet is transported to said second processing unit through said first processing unit. This permits said sheet processing apparatus to use said second processing unit when said first processing unit is not supplied with power even if a sheet must go through said first processing unit. 
     Other objects and features of the invention will be apparent from the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an image forming apparatus. 
     FIG. 2 shows a block diagram of the image forming apparatus of FIG.  1 . 
     FIG. 3 shows a sheet folder and finisher. 
     FIG. 4 shows a block diagram for controlling the sheet folder and the finisher. 
     FIG. 5 shows a detailed diagram with respect to an invalidation unit and a unit detection switch unit. 
     FIG. 6 shows a detailed circuit diagram with respect to the sheet folder of FIG.  4 . 
     FIG. 7 shows an interface circuit between a finisher controller and a sheet punching unit. 
     FIG. 8 shows a function discrimination table. 
     FIGS. 9A and 9B show a flapper for selecting a sheet transportation path in the sheet folder and a flapper for selecting a sheet transport path in the finisher. 
     FIG. 10 shows a detailed diagram with respect the to invalidation unit and the unit detection switch unit in another embodiment. 
     FIG. 11 shows a flowchart for controlling the finisher and the sheet folder. 
     FIG. 12 shows a block diagram of an image forming apparatus in a third embodiment. 
     FIG. 13 shows a display screen when no function is invalidated. 
     FIG. 14 shows a display screen when some functions are invalidated. 
     FIGS. 15 to  17  show display screens for selecting sheet processing. 
     FIGS. 18 and 19 show a flowchart for detecting if each unit is attached to the finisher. 
     FIGS. 20 and 21 show a flowchart for detecting if each unit of the finisher is validated. 
     FIGS. 22 and 23 show a flowchart for deciding if a warning screen is displayed. 
     FIG. 24 shows a flowchart for controlling the display screen of the operation panel. 
     FIGS. 25 and 26 show a flowchart for displaying an invalidated function message. 
     FIG. 27 shows a flowchart for displaying a message to call a service center. 
     FIG. 28 shows a flowchart for notifying the service center of an invalidated function. 
     FIGS. 29 and 30 show display screens for selecting sheet processing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows image forming apparatus  1000  which includes document feeder  100 , image reader  200 , printer  300 , sheet folder  400  and finisher  500 . Document feeder  100  feeds original documents set on document tray  130  to plate glass  102  one by one in a page order and discharges the originals to discharge tray  112 . Scanner unit  104  scans a document at a predetermined position while the document is transported from left side to right side on plate glass  102  in order to read the document. When a document passes by scanner unit  104 , the document is exposed by lamp  103  of scanner unit  104  and the reflected light from the document is led to image sensor  109  through mirrors  105 ,  106  and  107  and lens  108 . Document scanning can also be done by stopping a document on plate glass  102  and moving scanner unit  104  from left to right. 
     A document image read by image sensor  109  is image processed into an image signal and is sent to exposure controller  110 . Exposure controller  110  emits a laser beam in accordance with the image signal. The laser beam is led to photosensitive drum  111 . An electrostatic latent image is formed on photosensitive drum  111  in accordance with the laser beam. The electrostatic latent image is visualized by developing unit  113  as a toner image. Meanwhile, a sheet is fed from one of cassettes  114  and  115 , manual feed unit  125  and re-feed path  124 , in synchronization with the time the laser beam is emitted. The sheet is fed to transfer unit  116 . The toner image on photosensitive drum  111  is transferred to the fed sheet by transfer unit  116 . 
     The sheet with the transferred toner image is transported to fixing unit  117 . Fixing unit  117  fixes the toner image to the sheet by heat and pressure. The fixed sheet is led to path  122  by flapper  121  and is transported in the opposite direction after the trailing edge of the sheet goes through flapper  121 . Then the sheet is discharged out of printer  300  by discharge roller  118  in a face-down state in which the toner image faces downward. This discharge manner is referred to as an inversion discharge. 
     When sheets are fed from manual feeding unit  125 , the inversion discharge is not done, that is, the fixed sheet is discharged in a face-up state. When a two sided copy is done, the fixed sheet is transported to path  122  by flapper  121  after the trailing edge passes by flapper  121  and transported to path  124 . 
     A sheet discharged from discharge roller  118  is transported to sheet folder  400 . Sheet folder  400  folds a sheet into a Z shape. When sheet folding is designated by an user and a sheet is A 3  size or B 4  size, sheet folder  400  conducts sheet folding. Otherwise, sheet folder  400  transports a sheet to finisher  500  without conducting sheet folding. Finisher  500  conducts booklet making, sheet stapling and sheet punching. Insert sheet feeder  900  is provided to finisher  500  and feeds an insert sheet such as a cover sheet to finisher  500 . 
     FIG. 2 shows a block diagram of image forming apparatus  1000 . Image forming apparatus  1000  includes operation panel  1 , document feeder controller  101 , CPU circuit unit  150 , image reader controller  201 , image signal controller  202 , external I/F  209  connecting an external user&#39;s computer  210 , printer controller  301  and finisher controller  2000 , all controlled in accordance with a program stored in ROM  151  and a designation through operation panel  1 . CPU circuit unit  150  includes ROM  151 , RAM  152  and CPU  153 . 
     CPU  153  controls document feeder controller  101 , image reader controller  201 , image signal controller  202 , printer controller  301 , finisher controller  2000  and external I/F  203 . Document feeder controller  101  controls document feeder  100 . Image reader controller  201  controls image reader  200 . Printer controller  301  controls printer  300 . Finisher controller  2000  controls finisher  500  and sheet folder  400 . 
     ROM  151  stores a program and parameters. RAM  152  is used to store control data temporarily and as working area for computing. External I/F  209  is an interface to external computer  210  and converts print data from computer  210  into image data and outputs the image data to image signal controller  202 . Image reader controller  201  outputs image data read by image sensor  109  to image signal controller  202 . Image signal controller  202  outputs image data to printer controller  301 . Printer controller  301  outputs image data to exposure controller  110 . 
     FIG. 3 shows sheet folder  400  and finisher  500 . Path  402  receives a sheet from printer  300  and leads the sheet to finisher  500 . Flapper  410  leads a sheet to either finisher  500  or path  420 . When sheet folding is conducted, flapper  410  leads a sheet to path  420 . A sheet led to path  420  is folded in a Z shape by fold roller  421 . When sheet folding is not conducted, flapper  410  leads a sheet to finisher  500  through path  402 . 
     In finisher  500 , when booklet making is designated, flapper  551  leads a sheet to path  553 . Booklet making is conducted to the sheet led to path  553  by booklet making unit  800 . Otherwise, flapper  551  leads a sheet to path  552 . When sheet punching is designated, sheet punching is conducted by sheet punching unit  550 . When sheet punching is not designated, a sheet goes through sheet punching unit  550 . 
     When sheet stapling is designated, flappers  510  and  511  lead a sheet to path  522 . The sheet is transported to processing tray  630 . Sheets on processing tray are stapled by sheet stapling unit  601  and discharged to stack tray  700 . When flapper  510  leads a sheet to path  521 , the sheet is discharged to stack tray unit  701 . When insert sheet feeding is designated, insert sheet feeder  900  feeds an insert sheet to path  908 . The sheet is transported to path  552 . 
     FIG. 4 shows a block diagram for controlling sheet folder  400  and finisher  500 . Finisher controller  2000  includes CPU, ROM, RAM and communication IC. Finisher controller  2000  discriminates if stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800  are connected by checking signals from lines  2090 . 
     Invalidation unit  2010  includes dip switches corresponding to stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800  in order to invalidate them electrically even though those are connected to finisher  500  mechanically. The dip switches are operated by a user or a service technician. Finisher controller  2000  can check for mechanical connection of each unit to finisher  500  by control over signal  2021  connected to unit detection switch unit  2020 , independently of the status of the dip switches of invalidation unit  2010 . 
     FIG. 5 shows a detailed diagram with respect to invalidation unit  2010  and unit detection switch unit  2020 . Invalidation unit  2010  includes dip switches  2011  (SW 1 -SW 5 ). One terminal of each of the dip switches  2011  is grounded. The other terminal of dip switch SW 1  is connected to line  2091  through line  2081  and loop-back line  2031  of stack tray unit  701 . Line  2091  is connected to input port Pina of CPU  2009  of finisher controller  2000 . Line  2023  is connected to line  2081  in unit detection switch unit  2020 . Line  2023  is connected to the collector of transistor  2022 . The emitter of transistor  2022  is grounded. The base of transistor  2022  is connected to output port Pout of CPU  2009  of finisher controller  2000 . 
     Likewise, other terminals of the dip switches SW 2 -SW 5  are connected to lines  2092 - 2095  through lines  2082 - 2085  and loop-back lines  2032 - 2035  respectively. Loop-back line  2032  is in sheet punching unit  550 . Loop-back line  2033  is in insert sheet feeder  900 . Loop-back line  2034  is in sheet folder  400 . Loop-back line  2035  is in booklet making unit  800 . 
     Lines  2092 - 2095  are connected to input ports Pinb-Pine of CPU  2009  of finisher controller  2000  respectively. Lines  2024 - 2027  are connected to lines  2082 - 2085  in unit detection switch unit  2020  respectively. Lines  2024 - 2027  are connected to the collector of transistor  2022 . 
     FIG. 6 shows a detailed circuit diagram with respect to sheet folder  400 . Voltage monitor  2062  monitors voltage V 1  of loop-back line  2061  by comparing voltage V 1  with reference voltage ES 2 . Voltage monitor  2062  outputs a signal to power switch  2064  in accordance with the comparison result in order to control whether power is supplied to solenoid driver  2065  and motor driver  2069 . Solenoid driver  2065  drives solenoid  2066  which moves flapper  410 . Motor driver  2069  drives motor  2070  which rotates rollers  421 . When voltage monitor  2062  outputs an ON signal, power switch  2064  supplies power to solenoid driver  2065  and motor driver  2069 . When voltage monitor  2062  outputs an OFF signal, power switch  2064  does not supply power to solenoid driver  2065  and motor driver  2069 . Power is supplied to motor driver  2067  regardless of power switch  2064 . Motor driver  2067  drives motor  2068  which rotates rollers  422 . 
     When dip switch SW 4  in invalidation unit  2010  is OFF and transistor  2022  is OFF, voltage V 1  on loop-back line  2061  is equal to voltage VH of a power source Vcc. When dip switch SW 4  is OFF and transistor  2022  is ON, voltage V 1  on loop-back line  2061  is voltage VM. Voltage VM depends on a forward voltage of diode D 2026  and a partial voltage between resistor R 2004  and resistor R 2026 . When dip switch SW 4  is ON, voltage V 1  on loop-back line  2061  is almost equal to ground voltage VL. 
     Reference voltage ES 2  is lower than voltage VM and is higher than voltage VL. 
     
       
         VM&gt;ES 2 &gt;VL 
       
     
     When dip switch SW 4  is ON, voltage V 1  on loop-back line  2061  is lower than reference voltage ES 2  and voltage monitor  2062  outputs an ON signal to power switch  2064  no matter whether transistor  2022  is ON or OFF in order to power on sheet folder  400 . When dip switch SW 4  is OFF, voltage V 1  on loop-back line  2061  is higher than reference voltage ES 2  and voltage monitor  2062  outputs OFF signal to power switch  2064  no matter when transistor  2022  is ON or OFF in order to power off sheet folder  400 . 
     Reference voltage ES 1  for unit connection detector C 2004  is higher than voltage VM and is lower than voltage VH of the power source. 
     
       
         VH&gt;ES 1 &gt;VM&gt;VL 
       
     
     When sheet folder  400  is detached from finisher  500  and transistor  2022  is ON, voltage V 1  of line  2061  is voltage VH. When sheet folder  400  is connected to finisher  500  and dip switch SW 4  is ON and transistor  2022  is ON, voltage V 1  of line  2061  is almost ground voltage VL. When sheet folder  400  is connected to finisher  500  and dip switch SW 4  is OFF and transistor  2022  is ON, voltage V 1  of line  2061  is voltage VM. That is, voltage V 1  is lower than reference ES 1  when sheet folder  400  is connected to finisher  500 . Voltage V 1  is higher than reference ES 1  when sheet folder  400  is detached from finisher  500 . Therefore, regardless of whether dip switch SW 4  is ON or OFF, CPU  2009  of finisher controller  2000  can detect whether sheet folder  400  is connected to finisher  500  by setting transistor  2022  to a high level signal through line  2021 . 
     Basic circuits of stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900  and booklet making unit  800  are similar Lo the circuits of sheet folder  400  shown in FIGS.  6 . 
     FIG. 7 shows an interface circuit between finisher controller  2000  and sheet punching unit  550 . Motor M 2041  rotates a puncher of sheet punching unit  550  in order to punch a sheet. Driver D 2041  drives motor M 2041 . A motor ON signal is outputted from output driver T 2001  of finisher controller  2000 . Motor M 2042  moves the puncher of sheet punching unit  550  in a sheet width direction in order to adjust a punching position to a center of sheet. Driver D 2042  drives motor M 2042 . A motor ON signal is outputted from output driver T 2002  of finisher controller  2000 . 
     Sensor SE 2041  detects if the puncher, which is rotated by motor M 2041 , is in a home position. Sensor SE 2041  outputs a detection result to finisher controller  2000  through output driver T 2041 . Sensor SF 2042  detects if the puncher, which is moved by motor M 2042 , is in a home position. Sensor SE 2042  outputs a detection result to finisher controller  2000  through output driver T 2042 . 
     A valid logic between finisher controller  2000  and sheet punching unit  550  is a low level. Thereby, a signal voltage of an output side is not transferred to an input side. Therefore, there is no problem regarding differences of voltages between units regardless of whether a unit is powered on or off. 
     FIG. 8 shows function discrimination table  801  for discriminating if each unit is attached and if each function is validated with respect to stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800 . Function discrimination table  801  includes areas  2301 - 2304 . 
     “Yes” on mechanical connection of function discrimination table  801  means that an unit is connected to finisher  500  mechanically. “No” on the mechanical connection means that an unit is not connected to finisher  500  mechanically. When dip switch  2011  is ON, a function of a unit is validated. When dip switch  2011  is OFF, a function of a unit is invalidated. When line  2021  is a high level, transistor  2022  is ON. When line  2021  is a low level, transistor  2022  is OFF. 
     CPU  2009  sets output Pout to a low level and reads a logic level of each port Pina-Pine. Referring to the position of the dip switches in FIG. 5, since SW 1  of dip switch  2011  is ON and stack tray unit  701  is attached, a low level appears on Pina of CPU  2009 . Since SW 2  of dip switch  2011  is ON and sheet punching unit  550  is detached, a high level appears on Pinb of CPU  2009 . Since SW 3  of dip switch  2011  is OFF and insert sheet feeder  900  is attached, a high level appears on Pinc of CPU  2009 . Since SW 4  of dip switch  2011  is OFF and sheet folder  400  is detached, a high level appears on Pind of CPU  2009 . Since SW 5  of dip switch  2011  is ON and booklet making unit  800  is attached, a low level appears on Pine of CPU  2009 . 
     Then, CPU  2009  sets output Pout to a high level and reads the logic level of each port Pina-Pine. Since SW 1  of dip switch  2011  is ON and stack tray unit  701  is attached, a low level appears on Pina of CPU  2009 . Since SW 2  of dip switch  2011  is ON and sheet punching unit  550  is detached, a high level appears on Pinb of CPU  2009 . Since SW 3  of dip switch  2011  is OFF and insert sheet feeder  900  is attached, a low level appears on Pinc of CPU  2009 . Since SW 4  of dip switch  2011  is OFF and sheet folder  400  is detached, a high level appears on Pind of CPU  2009 . Since SW 5  of dip switch  2011  is ON and booklet making unit  800  is attached, a low level appears on Pine of CPU  2009 . 
     Then, CPU  2009  discriminates which unit is attached and which function is validated with respect to stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800  by reference to function discrimination table  801 . 
     With regard to stack tray unit  701 , CPU  2009  discriminates that the unit is attached and the function is validated. With regard to sheet punching unit  550 , CPU  2009  discriminates that the unit is detached. With regard to insert sheet feeder  900 , CPU  2009  discriminates that the unit is attached and the function is invalidated. With regard to sheet folder  400 , CPU  2009  discriminates that the unit is detached. With regard to booklet making unit  800 , CPU  2009  discriminates that the unit is attached and the function is validated. 
     FIGS. 9A and 9B show flapper  410  of sheet folder  400  and flapper  551  of finisher  500 . Flapper  410  of sheet folder  400  is described hereinafter. When flapper  410  is in the state shown in FIG. 9A, a sheet is transported along path  402 . When flapper  410  is in the state shown in FIG. 9B, a sheet is transported to path  420 . Flapper  410  is moved by solenoid  2066  which is driven by solenoid driver  2065  shown in FIG.  6 . 
     Flapper  410  has arm  2502  and rotates on axis  2503 . Shaft  2066   a  of solenoid  2066  is linked by shaft  2501 . Flapper  410  is rotated by back-and-forth motion of shaft  2066   a . Flapper  410  is pulled by spring  2504 . When solenoid  2066  is activated, shaft  2066   a  is pulled by solenoid  2066  and flapper  410  is in the state shown in FIG.  9 B. When solenoid  2066  is not activated, shaft  2066   a  is pulled by spring  2504  and flapper  410  is in the state shown in FIG.  9 A. When power is not supplied to solenoid driver  2065 , flapper  410  is in the state shown in FIG. 9A and a sheet is transported to finisher  500  along path  402 . When dip switch SW 4  is OFF, power is not supplied to solenoid  2066  and motor  2070 , and flapper  410  leads a sheet to finisher  500 . When sheet folder  400  is out of order, dip switch SW 4  is set OFF. Thereby, a power is not supplied to sheet folder  400  except for motor driver  2067 , and flapper  410  is in a state where a sheet is led to finisher  500 . 
     Instead of solenoid  2066 , a motor may be provided for driving flapper  410 . Instead of flapper  410 , a short path, which is connected to the upperstream part of path  402  and is movable between path  420  and the downstream part of path  402 , may be provided for leading a sheet to either path  420  or the downstream part of path  402 . The short path may be driven by either a solenoid or a motor. Instead of spring  2504  which is an extension spring, other elastic means such as a compression spring, a blade spring and a rubber band may be provided. 
     Flapper  551  of finisher  500  has the same structure as flapper  410 . Reference numbers regarding flapper  551  are enclosed within parentheses. 
     FIG. 10 shows a detailed diagram with respect to invalidation unit  2010  and unit detection switch unit  2020  in another embodiment. One difference between FIG.  10  and FIG. 5 is that switches  2012  are controlled by CPU  2009  and are included instead of dip switches  2011 . 
     FIG. 11 shows a flowchart for controlling finisher  500  and sheet folder  400 . A program for executing this flowchart is stored in ROM of finisher controller  2000  and executed by CPU  2009 . 
     CPU  2009  discriminates if a start key of operation panel  1  is pressed (S 201 ). If the start key is pressed, CPU  2009  instructs sheet folder  400  to rotate rollers  422  and instructs finisher  500  to rotate roller  502  (S 202 ). 
     CPU  2009  discriminates if insert sheet feeding is designated by operation panel  1  (S 203 ). If insert sheet feeding is designated, CPU  2009  sets SW 3  of switches  2012  ON in order to supply power to insert sheet feeder  900  (S 204 ). Then, CPU  2009  instructs insert sheet feeder  900  to feed an insert sheet to a predetermined position which is located just before roller  502  (S 205 ). 
     After step S 205  or if insert sheet feeding is not designated at step S 203 , CPU  2009  requests CPU circuit unit  150  to feed a sheet on which an image is to be printed (S 206 ). Then, CPU  2009  discriminates if sheet folding is designated by operation panel  1  (S 207 ). If sheet folding is designated, CPU  2009  sets SW 4  of switches  2012  ON in order to supply a power to sheet folder  400  (S 208 ). Then, CPU  2009  instructs sheet folder  400  to conduct sheet folding (S 209 ). 
     After step S 209  or if sheet folding is not designated at step S 207 , CPU  2009  discriminates if booklet making is designated by operation panel  1  (S 210 ). If booklet making is designated, CPU  2009  sets SW 5  ON in order to supply power to booklet making unit  800  (S 211 ). Then, CPU  2009  instructs booklet making unit  800  to conduct booklet making (S 212 ) and returns to step S 201 . 
     If booklet making is not designated at step S 210 , CPU  2009  discriminates if sheet punching is designated by operation panel  1  (S 213 ). If sheet punching is designated, CPU  2009  sets SW 2  ON in order to supply power to sheet punching unit  550  (S 214 ). Then, CPU  2009  instructs sheet punching unit  550  to conduct sheet punching (S 215 ). 
     After step S 215  or if sheet punching is not designated at step S 213 , CPU  2009  discriminates a sort mode (S 216 ). If a nonsort mode is designated at step S 216 , CPU  2009  instructs finisher  500  to conduct nonsort mode (S 217 ). Then, CPU  2009  instructs sheet folder  400  to stop rotating rollers  422  and instructs finisher  500  to stop rotating roller  502  and sets SW 1 -SW 5  OFF in order to stop supplying power to stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800  (S 220 ). 
     If a sort mode is designated at step S 216 , CPU  2009  instructs finisher  500  to conduct sort mode (S 218 ) and proceeds to step S 220 . If staple sort mode is designated at step S 216 , CPU  2009  instructs finisher  500  to conduct staple sort mode (S 219 ) and proceeds to step S 220 . After step S 220 , CPU  2009  returns to step S 201 . 
     Since power is supplied to the unit corresponding to the function only when a function is needed, it can minimize power consumption during a waiting state. 
     FIG. 12 shows a block diagram of image forming apparatus  1000  in third embodiment. The difference between FIGS. 12 and 2 is that service center  250  is connected to computer  210  through modem  211 , or other means such as the Internet. Computer  210  transmits data to service center  250  through modem  211  and receives data from service center  250  through modem  211 . 
     Finisher controller  2000  discriminates which unit is attached and which function is invalidated with respect to stack tray unit  701 , sheet punching unit  550 , insert sheet feeder  900 , sheet folder  400  and booklet making unit  800  as described above. Finisher controller  2000  transmits the discrimination result to CPU circuit unit  150 . CPU circuit unit  150  instructs operation panel  1  to display the discrimination result or the state of finisher  500  in accordance with a program stored in ROM  151 . 
     FIGS. 13 and 14 show display screens of operation panel  1  in a ready state. A display of operation panel  1  is a touch panel display. FIG. 13 shows a display screen when no function is invalidated. FIG. 14 shows a display screen when one function is invalidated. As shown in the display of FIG. 14, “Part of finisher is out of order”, which means finisher  500  is out of order, is displayed at the bottom of the display screen of operation panel  1 . 
     FIG. 15 shows a display screen for selecting sheet processing. The display screen is displayed in a case where the sorter key of the display screen is touched when the display screen shown in FIG. 14 is displayed. The insert sheet feeding select key and sheet punching select key are shaded in order to instruct that the functions for insert sheet feeding and sheet punching are invalidated, that is, the insert sheet feeding function and the sheet punching function are out of order. FIG. 16 shows a display screen in a case where the insert sheet feeding select key is touched when the display screen shown in FIG. 15 is displayed. FIG. 17 shows a display screen in a case where the sheet punching select key is touched when the display screen shown in FIG. 15 is displayed. 
     CPU circuit unit  150  transmits the attachment information and the invalidation information, which are received from finisher controller  2000 , to computer  210  through external I/F  209 . The attachment information and the invalidation information are displayed on a monitor of computer  210 . 
     FIGS. 18 and 19 show a flowchart for detecting if each unit is attached to finisher  500 . In this flowchart, a high level is represented by “1” and a low level is represented by “0”. CPU  2009  sets Pout of CPU  2009  to a high level (S 1001 ). After waiting for  100  ms (S 1002 ), CPU  2009  discriminates Pina (S 1003 ). If Pina is a high level, CPU  2009  discriminates that stack tray unit  701  is detached, and sets variable Al to “1” (S 1004 ). If Pina is a low level, CPU  2009  discriminates that stack tray unit  701  is attached, and sets variable A 1  to “0” (S 1005 ). 
     Then, CPU  2009  discriminates Pinb (S 1006 ). If Pinb is a high level, CPU  2009  discriminates that sheet punching unit  550  is detached, and sets variable B 1  to “1” (S 1007 ). If Pinb is a low level, CPU  2009  discriminates that sheet punching unit  550  is attached, and sets variable B 1  to “0” (S 1008 ). Then, CPU  2009  discriminates Pinc (S 1009 ). If Pinc is a high level, CPU  2009  discriminates that insert sheet feeder  900  is detached, and sets variable C 1  to “1” (S 1010 ). If Pinc is a low level, CPU  2009  discriminates that insert sheet feeder  900  is attached, and sets variable C 1  to “0” (S 1011 ). 
     Then, CPU  2009  discriminates Pind (S 1012 ). If Pind is a high level, CPU  2009  discriminates that sheet folder  400  is detached, and sets variable D 1  to “1” (S 1013 ). If Pind is a low level, CPU  2009  discriminates that sheet folder  400  is attached, and sets variable D 1  to “0” (S 1014 ). Then, CPU  2009  discriminates Pine (S 1015 ). If Pine is a high level, CPU  2009  discriminates that booklet making unit  800  is detached, and sets variable El to “1” (S 1016 ). If Pine is a low level, CPU  2009  discriminates that booklet making unit  800  is attached, and sets variable E 1  to “0” (S 1017 ). 
     FIGS. 20 and 21 show a flowchart for detecting if each unit of finisher  500  is validated. In this flowchart, a high level is represented by “1” and a low level is represented by “0”. CPU  2009  sets Pout of CPU  2009  to a low level (S 1018 ). After waiting for 100 ms (S 1019 ), CPU  2009  discriminates Pina (S 1020 ). If Pina is a high level, CPU  2009  discriminates that stack tray unit  701  is invalidated or detached, and sets variable A 0  to “1” (S 1021 ). if Pina is a low level, CPU  2009  discriminates that stack tray unit  701  is attached and validated, and sets variable A 0  to “0” (S 1022 ). 
     Then, CPU  2009  discriminates Pinb (S 1023 ). If Pinb is a high level, CPU  2009  discriminates that sheet punching unit  550  is invalidated or detached, and sets variable B 0  to “1” (S 1024 ). If Pinb is a low level, CPU  2009  discriminates that sheet punching unit  550  is attached and validated, and sets variable B 0  to “0” (S 1025 ). Then, CPU  2009  discriminates Pinc (S 1026 ). If Pinc is a high level, CPU  2009  discriminates that insert sheet feeder  900  is invalidated or detached, and sets variable C 0  to “1” (S 1027 ). If Pinc is a low level, CPU  2009  discriminates that insert sheet feeder  900  is attached and validated, and sets variable C 0  to “0” (S 1028 ). 
     Then, CPU  2009  discriminates Pind (S 1029 ). If Pind is a high level, CPU  2009  discriminates that sheet folder  400  is invalidated or detached, and sets variable D 0  to “1” (S 1030 ). If Pind is a low level, CPU  2009  discriminates that sheet folder  400  is attached and validated, and sets variable D 0  to “0” (S 1031 ). Then, CPU  2009  discriminates Pine (S 1032 ). If Pine is a high level, CPU  2009  discriminates that booklet making unit  800  is invalidated or detached, and sets variable E 0  to “1” (S 1033 ). If Pine is a low level, CPU  2009  discriminates that booklet making unit  800  is attached and validated, and sets variable E 0  to “0” (S 1034 ). 
     FIGS. 22 and 23 show a flowchart for deciding if warning screen B is displayed. CPU  2009  discriminates if A 1 =0 and A 0 =1 (S 1035 ). If A 1 =0 and A 0 =1, CPU  2009  sets variable AF to “1” (S 1037 ). If not, CPU  2009  sets variable AF to “0” (S 1036 ). 
     CPU  2009  discriminates if B 1 =0 and B 0 =1 (S 1038 ). If B 1 =0 and B 0 =1, CPU  2009  sets variable BF to “1” (S 1040 ). If not, CPU  2009  sets variable BF to “0” (S 1039 ). CPU  2009  discriminates if C 1 =0 and C 0 =1 (S 1041 ). If C 1 =0 and C 0 =1, CPU  2009  sets variable CF to “1” (S 1043 ). If not, CPU  2009  sets variable CF TO “0” (S 1042 ). 
     CPU  2009  discriminates if D 1 =0 and D 0 =1 (S 1044 ) If D 1 =0 and D 0 =1, CPU  2009  sets variable DF to “1” (S 1046 ). If not, CPU  2009  sets variable DF to “0” (S 1045 ). CPU  2009  discriminates if E 1 =0 and E 0 =1 (S 1047 ). If E 1 =0 and F 0 =1, CPU  2009  sets variable EF to “1” (S 1049 ). If not, CPU  2009  sets variable EF to “0” (S 1048 ). 
     Then, CPU  2009  discriminates if at least one of variables AF, BF, CF, DE and EF is  1  (S 1050 -S 1054 ). If at least one of them is 1, CPU  2009  informs CPU  153  that one of the units is invalidated, and transmits variables AF, BF, CF, DF and EF to CPU  153 . CPU  153  of CPU circuit unit  150  instructs operation panel  1  to display a message “Part of finisher is out of order” at the bottom of the display of operation panel  1  as shown in FIG. 14 (S 1055 ). 
     FIG. 24 shows a flowchart for controlling the display screen of operation panel  1 . CPU  153  discriminates if the sorter key on the display of operation panel  1  as shown in FIG. 14 is touched (S 2001 ). If the sorter key is touched, CPU  2009  discriminates if variable BF is 1 (S 2002 ). If BF is 1, CPU  153  instructs operation panel  1  to change the sheet punching select key on the display into a shaded key from a non-shaded key (S 2003 ). After step S 2003  or if BF is not 1 at step S 2002 , CPU  153  discriminates if variable CF is 1 (S 2004 ). If CF is 1, CPU  153  instructs operation panel  1  to change the insert sheet feeding select key on the display into a shaded key from a non-shaded key (S 2005 ). 
     After step S 2005  or if CF is not 1 at step S 2004 , CPU  153  discriminates if variable DF is 1 (S 2006 ). If DF is 1, CPU  153  instructs operation panel  1  to change the sheet folding select key on the display into a shaded key from a nonshaded key (S 2007 ). After step S 2007  or if DF is not 1 at step S 2006 , CPU  153  discriminates if variable EF is 1 (S 2008 ). If EF is 1, CPU  153  instructs operation panel  1  to change the booklet making select key on the display into a shaded key from a nonshaded key (S 2009 ). 
     FIGS. 25 and 26 show a flowchart for displaying an invalidated function message. CPU  153  discriminates if the sheet punching select key is touched (S 4001 ). If the sheet punching select key is touched, CPU  153  discriminates if variable BF is 1 (S 4002 ). If BF is 1, CPU  153  instructs operation panel  1  to display a message “sheet punching unit is out of order” at the bottom of the display (S 4003 ). After step S 4003  or if the sheet punching select key is not touched at step S 4001 , CPU  153  discriminates if the insert sheet feeding select key is touched (S 4004 ). If the insert sheet feeding select key is touched, CPU  153  discriminates if variable CF is 1 (S 4005 ). If CF is 1, CPU  153  instructs operation panel  1  to display a message “insert sheet feeder is out of order” at the bottom of the display (S 4006 ). 
     After step S 4006  or if the insert sheet feeding select key is not touched at step S 4004 , CPU  153  discriminates if the sheet folding select key is touched (S 4007 ). If the sheet folding select key is touched, CPU  153  discriminates if variable DF is 1 (S 4008 ). If DF is 1, CPU  153  instructs operation panel  1  to display a message “sheet folder is out of order” at the bottom of the display (S 4009 ). After step S 4009  or if the sheet folding select key is not touched at step S 4007 , CPU  153  discriminates if the booklet making select key is touched (S 4010 ). If the booklet making select key is touched, CPU  153  discriminates if variable EF is 1 (S 4011 ). If EF is 1, CPU  153  instructs operation panel  1  to display a message “booklet making unit is out of order” at the bottom of the display (S 4012 ). 
     After step S 4012  or if the booklet making select key is not touched at step S 4010 , CPU  153  confirms if the invalidated function key is OFF (S 4013 ). 
     CPU  153  transmits variables AF, BF, CF, DF and EF to computer  210  through external I/F  209 . Computer  210  displays the same message as the one displayed on operation panel  1 . Thereby, a user can avoid designating a function which is out of order when print data is transmitted from computer  210  to image forming apparatus  1000 . 
     FIG. 27 shows a flowchart for displaying a message in a case where image forming apparatus  1000  does not connect to computer  210  or computer  210  cannot connect to service center  250 . CPU  153  discriminates if the sheet punching select key is touched (S 5001 ). If the sheet punching select key is touched, CPU  153  discriminates if variable BF is 1 (S 5002 ). Tf BF is 1, CPU  153  instructs operation panel  1  to display a message “call service center 1-800-XXX-XXXX” at the bottom of the display as shown in FIG. 29 (S 5009 ). If BF is not 1 at step S 5002  or if the sheet punching select key is not touched at step S 5001 , CPU  153  discriminates if the insert sheet feeding select key is touched (S 5003 ). If the insert sheet feeding select key is touched, CPU  153  discriminates if variable CF is 1 (S 5004 ). If CF is 1, CPU  153  proceeds to step S 5009 . 
     If CF is not 1 at step S 5004  or if the insert sheet feeding select key is not touched at step S 5003 , CPU  153  discriminates if the sheet folding select key is touched (S 5005 ). If the sheet folding select key is touched, CPU  153  discriminates if variable DF is 1, (S 5006 ). If DF is 1, CPU  153  proceeds to step S 5009 . If DF is not 1 at step S 5006  or if the sheet folding select key is not touched at step S 5005 , CPU  153  discriminates if the booklet making select key is touched (S 5007 ). If the booklet making select key is touched, CPU  153  discriminates if variable EF is 1 (S 5008 ). If EF is 1, CPU  153  proceeds to step S 5009 . 
     After step S 5009  or if the booklet making select key is not touched at step S 5007 , CPU  153  confirms if the invalidated function key is OFF (S 5010 ). 
     CPU  153  controls operation panel  1  to display the message of step S 5009  and the messages shown by FIG. 25 alternately. 
     FIG. 28 shows a flowchart for notifying service center  250  of the invalidated function by computer  210 . A program of this flowchart is installed to a hard disc of computer  210  from a CD-ROM or a floppy disc and executed by computer  210 . 
     Computer  210  monitors variables AF, BF, CF, DF and EF received from CPU  153  and discriminates if there is a change with the variables (S 6001 ). If at least one of variables AF, BF, CF, DF and EF is changed to 1, computer  210  connects to service center  250  through modem  211  and transmits information regarding an invalidated function according to variables AF, BF, CF, DF and EF and an identification number of image forming apparatus  1000  to service center  250  (S 6002 ). Then, computer  210  informs CPU  153  that service center  250  has been notified (S 6003 ). CPU  153  instructs operation panel  1  to display a message “notification to service center has been done on ##/##/##”. Computer  210  monitors a response from service center  250  (S 6004 ). Service center  250  transmits information including when a service technician is coming. If the information is received from service center  250 , computer  210  transmits the received information to CPU  153  (S 6005 ). CPU  153  instructs operation panel  1  to display a message “service technician is coming on ##/##/##” as shown in FIG.  30 . 
     It is to be understood that the phraseology or terminology employed herein in for the purpose of description and not of limitation. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.