Abstract:
A sheet processor has a sheet transportation path, a punching unit for performing a punching operation on the sheets, the punching unit including a punch slide having a punch mechanism thereon, a moving device for moving the punch slide between a sheet punching operation position and a punch slide home position, the movement occurring in a direction transverse to the sheet transportation direction, and a detector for detecting completion of the punching operation by the punching unit. When the detector detects the completion of the punching operation, the moving device moves the punching unit to the punch slide home position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet processor for the sorting, binding, and loading of sheets discharged from an image forming apparatus after formation of an image thereon, and, more particularly, to a sheet processor with a punching means for punching out a hole in a sheet. The present invention also relates to an image forming apparatus including such a sheet processor. 
     2. Description of the Related Art 
     A conventional sheet processor performs post-processing operations (such as sorting, binding, loading, and punching operations) on sheets to be discharged from an image forming apparatus after formation of an image thereon. 
     In such a sheet processor, a known punching method for punching out a hole in a sheet is used. In this punching method, holes are punched in a batch of sheets on a processing tray. However, because holes are formed in a batch of sheets, the next sheet cannot be transported during a punching operation. In addition, depending on the capacity of the punching means, it may be necessary to temporarily stop the sheets from being transported from an image forming apparatus and perform punching operations separately a number of times, making it difficult to increase processing speed. 
     To overcome the above-described problems, two known methods have been used. In the first method, a hole is formed in the sheets one sheet at a time, as the sheets are continuously discharged at predetermined intervals from an image forming apparatus. In the second method, a punching means comprising a punch and a die is disposed in a sheet transporting path. The transportation of sheets and punching operations are synchronized, so that punching operations can be performed without temporarily stopping sheet transportation. Therefore, sheet processing time is not increased by punching operations. 
     In the above-described conventional example, two methods of adjusting punching positions are used. In the first method, the front edge or the back edge of a sheet being transported in a sheet transporting direction is detected, and, based on the detection results, the timing of punching a hole is changed to adjust the punching position. In the second method, in a direction transverse to the sheet transporting direction (i.e., the sheet width direction), an edge of a sheet being transported is detected, and, based on the detection results, the punching means is moved in the transverse direction to adjust the punching position. 
     In such a sheet processor in which sheets are transported and punching operations are performed in synchronism without temporarily stopping sheet transportation, when the punching position is adjusted with respect to the sheet width (transverse) direction, the edge portion of the next sheet is detected after the driving of the punch motor is completed. In order to detect the edge of the next sheet, the sheet edge detecting means starts to move to a sheet edge detection standby position. Therefore, time is required to perform operations on the next sheet being transported. Consequently, compared to sheet processors in which the punching position is not adjusted in the sheet width direction, this method has lower sheet processing capacity. 
     SUMMARY OF THE INVENTION 
     Accordingly, in view of the above-described problems, it is an object of the present invention to provide a sheet processor which allows a punching means to be set at the punching position more precisely, and which can perform a larger number of punching operations. 
     To this end, according to a first aspect of the invention, there is provided a sheet processor comprising: 
     a sheet transportation path for transporting sheets in a sheet transportation direction; 
     punching means provided in the sheet transportation path for performing a punching operation on the sheets, the punching means comprising a punch slide having a punch mechanism thereon; 
     moving means for moving the punch slide from a sheet punching operation position to a punch slide home position in a direction transverse to the sheet transportation direction; and 
     detecting means for detecting completion of the punching operation by the punching means; 
     wherein when the detecting means detects the completion of the punching operation, the moving means moves the punch slide to the punch slide home position. 
     According to a second aspect of the present invention, there is provided a sheet processor comprising: 
     a sheet transportation path for transporting sheets in a sheet transportation direction; 
     punching means provided in the sheet transportation path for performing a punching operation on the sheets, as a result of rotation of the punching mechanism; 
     moving means for moving the punch slide from a sheet punching operation position to a punch slide home position in a direction transverse to the sheet transportation direction; 
     detecting means for detecting completion of the punching operation, before the punch mechanism rotates back to a punching operation home position; and 
     movement controlling means for starting movement of the punch slide by the moving means when the detecting means detects completion of the punching operation. 
     According to a third aspect of the present invention, there is provided a sheet processor comprising: 
     a sheet transportation path for transporting sheets in a sheet transportation direction; 
     punching means for performing a punching operation on the sheets; 
     moving means for moving the punch slide between a sheet punching operation position and a punch slide home position in a direction transverse to the sheet transportation direction; 
     edge detecting means for detecting an edge, in the sheet transporting direction, of each of the sheets; and 
     punching operation completion detecting means for detecting that the punching means has completed the punching operation; 
     wherein when the edge of each of the sheets is detected by the edge detecting means, the moving means causes the punch slide to move to the sheet punching operation position; and 
     wherein when the punching operation completion detecting means detects the completion of the punching operation, the moving means causes the punch slide to move to the punch slide home position. 
     According to a fourth aspect of the present invention, there is provided a sheet processor comprising: 
     a sheet transportation path for transporting sheets in a sheet transportation direction; 
     punching means for performing a punching operation on the sheets, as a result of rotation of the punch mechanism; 
     punch moving means for moving the punch slide between a sheet punching operation position and a punch slide home position in a direction transverse to the sheet transportation direction; 
     edge detecting means for detecting an edge, in the sheet transporting direction, of each of the sheets; 
     punching operation completion detecting means for detecting completion of the punching operation, before the punch mechanism rotates back to the punching operation home position; and 
     movement controlling means which causes the punch moving means to move the punch slide to the sheet punching operation position when the edge of each of the sheets is detected by the edge detecting means, the movement controlling means causing the punch moving means to move the punch slide to the punch slide home position when the completion detecting means detects completion of the punching operation performed on each of the sheets. 
     According to a fifth aspect of the present invention, there is provided an image forming apparatus including any one of the above-described sheet processors. 
     By virtue of the above-described structures, the punch moving means causes the punch slide to move from home position HP, in a direction transverse to the sheet transporting direction, to a predetermined position in order to punch a hole in the back end portion of the sheet. When a detecting means detects that the punch mechanism has completed a punching operation on the sheet, the punch mechanism rotates back to a punching operation home position HP, while simultaneously moving the punch slide to the punch slide home position HP in a direction transverse to the sheet transporting direction, that is, to a standby position. This shortens the time required to punch a hole in a sheet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional front view of an embodiment of the sheet processor and the body of the image forming apparatus. 
     FIG. 2 is a plan view illustrating the structure of a punching unit provided in the sheet processor. 
     FIG. 3 is a side view illustrating a punch section and a dice section at home position (HP). 
     FIG. 4 is a side view illustrating the punch section and the dice section during a punching operation. 
     FIG. 5 is a side view of the punch section and the dice section after a punching operation. 
     FIG. 6 is a timing chart of drive signals for a sheet edge detecting sensor, a punching position detecting sensor, a punch drive motor, and a punch slide motor. 
     FIG. 7 is a block diagram illustrating the sections used for controlling the sheet processor and the body of the image forming apparatus. 
     FIGS. 8A and 8B are a flowchart illustrating the operations of the sheet processor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will now be given of embodiments of the present invention with reference to the drawings. 
     FIG. 1 is a plan view illustrating the entire image forming apparatus  100  comprising a reading position sheet feed device  101 , an image forming apparatus body  102 , and a sheet processor  103 . FIG. 2 is a plan view of a punching unit  50  provided in the sheet processor  103 . 
     The reading position sheet feed device  101  (FIG. 1) comprises an automatic original feed section  51 ; a lamp  179 ; reflective mirrors  172 ,  173 , and  174 ; and a lens  175 . The automatic original feed section  51  is provided to feed an original P, set on an original-placing tray  41 , to an original reading position L 1 , and then to transport the original P to a sheet discharging position L 2 . The lamp  179  is provided to illuminate the original P transported to the reading position so as to be placed on an original table glass  178 . The reflective mirrors  172 ,  173 , and  174  are provided to guide light from the original P to a charge-coupled device (CCD)  176 . The lens  175  is provided to form an image of the original P on a CCD line sensor. 
     The image forming apparatus body  102  includes sheet storage sections  53  and  54 , in which are loaded recording sheets S of different sizes; and sheet feed sections  55  and  56  for feeding the sheets S. Fed sheets S are transported to a sheet transporting path  160  through sheet transporting paths  57 . A laser scanner  161  is provided to perform scanning operations with laser beams based on the image information read by an optical system  52  in order to form a latent image on a photosensitive member of an image forming section  162 . The image forming section (which is an example of an image forming means)  162  is provided to form a toner image on the photosensitive member in order to transfer it onto a sheet S. 
     A sheet S on which an image has been formed by the image forming section  162  is transported to a sheet transporting path TP in the sheet processor  103  by fixing rollers  164  and transporting rollers  165  (which are an example of a sheet discharging means) in the image forming apparatus body  102 . The fixing rollers  164  are provided to soften and melt a toner image and to it fix onto the sheet S. The image forming apparatus also comprises an operation section  40  provided to confirm operation settings and setting contents of the image forming apparatus body  102  and the sheet processor  103 . 
     The operation section  40  includes an indicator section for confirming setting contents (not shown); a touch panel key disposed on the indicator section in order to set detailed image forming operations, operation of the sheet processor, or the like; a keypad for setting the number of sheets to be subjected to image formation; a stop key for stopping image forming operations; a reset key for returning a setting to an initial setting; and a start key for starting image forming operations. 
     The sheet processor  103  is called a “finisher.” Reference numeral  1  denotes entrance rollers of the finisher  103  for transporting sheets S discharged from the image forming device apparatus  102 . Reference numerals  2  and  3  denote pairs of transporting rollers for transporting sheets S or insert sheets I supplied from an insert device  30 . Reference numeral  31  denotes a sheet detecting sensor disposed at the entrance side of the finisher  103  for detecting passage of sheets S or insert sheets I being transported. Reference numeral  50  denotes a punching unit for punching a hole near the back end of sheets S or insert sheets I being transported. 
     Reference numeral  5  denotes a relatively large diameter roller (hereinafter referred to as “buffer roller”) disposed at the sheet transporting path TP. A sheet S is pushed against the peripheral surface of the buffer roller  5  by pusher rollers  12 ,  13 , and  14 , which are disposed along the circumference of the buffer roller  5 , in order to transport the sheet S. 
     Reference numeral  11  denotes a first switching flapper for selectively switching between a nonsorting path  4  and a sorting path  8 . Reference numeral  10  denotes a second switching flapper for switching between the sorting path  8  and a buffer path  29  provided for temporarily holding a sheet S or an insert sheet I. Reference numeral  33  denotes a sheet detecting sensor for detecting any sheet S in the nonsorting path  4 . Reference numeral  32  denotes a sheet detecting sensor for detecting any sheet S in the sorting path  8 . 
     Reference numeral  6  denotes transporting rollers provided at the sorting path  8 . Reference numeral  94  denotes a processing tray unit for temporarily accumulating sheets S thereon and aligning the sheets S or the insert sheets I loaded thereon. It includes an intermediate tray (hereinafter referred to as “processing tray”)  92 , and an alignment plate  98 . The processing tray  92  is provided for allowing stapling of sheets S by a stapling unit  90 . The alignment plate  98  aligns the sheets S or the insert sheets I loaded on the processing tray  92 . A sheet discharging roller  93   b  is disposed at the fixed side of the processing tray  92 . 
     Reference numeral  7  denotes first sheet discharging rollers for discharging any sheet S or any insert sheet I in the sorting path  8  onto the processing tray (or first loading tray)  92 . Reference numeral  9  denotes second sheet discharge rollers for discharging any sheet S or any insert sheet I disposed in the nonsorting path onto a sample tray  95 . 
     Reference numeral  93   a  denotes an upper sheet discharging roller supported by a swinging guide  91 . When the swinging guide  91  is in its closed position, the sheets S or the insert sheets I loaded on the processing tray  92  are pressed against a lower sheet discharging roller  93   b  and discharged in batches onto a stack tray (second sheet loading tray)  96 . Reference numeral  97  denotes a sheet batch loading guide for abutting and supporting the back edge (with respect to a direction in which a sheet batch is discharged) of a sheet batch loaded on the stack tray  96  and the sample tray  95 . Here, the sheet batch loading guide  97  forms an outer portion of the sheet processor  103 . 
     The insert device  30  includes an insert sheet storage section  20 , a sheet feed roller  21 , and a separation roller  22 . The insert sheet storage section  20  is provided to set an insert sheet I for insertion into the sheet processor  103 . The sheet feed roller  21  is provided to feed insert sheets I. The separation roller  22  is provided to separate fed insert sheets I. Reference numeral  27  denotes an insert sheet setting detection sensor for detecting whether or not an insert sheet I is set on the insert sheet storage section  20 . Fed insert sheets I are transported to transporting rollers  2  through transporting rollers  23 ,  24 ,  25 , and  26 . 
     An original P is set on the reading position sheet feed device  101 . When the original P is set, the user performs the desired setting operations at the operation section  40  and directs the image forming apparatus to start image forming operations on a sheet S. At the same time that the original P is read at the reading position sheet feed device  101 , the feeding of sheets S from the set sheet storage sections  53  and  54  is started in order to transport them to the image forming section  162  through the sheet transporting paths  57 . A toner image, formed based on the image information read at the reading position sheet feed section  101 , is transferred onto a sheet S. This sheet S with the toner image formed thereon passes through a fixing section  164 , which fixes the toner image onto the sheet S. After fixing of the toner image, the sheet processor  103  causes insert sheets to be transported, punched, sorted, and stapled, whereby final output sheets are obtained. 
     (Punching unit) 
     A description will now be given of the punching unit  50  with reference to FIG.  2 . 
     The punching unit  50  includes a punching means  60  and a horizontal regist detecting means  80 . The punching means  60  includes a punch  61  and a die  62 , each of which is supported by respective supporting shafts  61   b  and  62   b . A gear (not shown) is affixed to each of the supporting shafts  61   b  and  62   b . These gears engage each other. When the punch drive motor  66  is driven, the punch  61  and the die  62  rotate in the direction of arrow B and in the direction of arrow C (in FIG.  3 ), respectively, in synchronism with each other. 
     Ordinarily, the punch  61  and the die  62  are at home position (HP)i, as shown in FIG.  3 . After detection of the back end of a sheet S by the sheet detecting sensor (which is an example of a sheet detecting means)  31 , when the punch drive motor M 67  is driven at a predetermined timing, the punch  61  and the die  62  rotate in the direction of arrow B and in the direction of arrow C, respectively. Then, as shown in FIG. 4, the punch  61  engages a die hole  62   a  formed in the die  62  in order to punch a hole in the sheet S being transported. 
     Since the rotational speeds of the punch  61  and the die  62  are the same as the rotational speeds of the pair of transporting rollers  3 , a hole can be punched in the sheet S being transported. 
     In FIG. 2, reference numeral  63   a  denotes a rack gear formed on a portion of a casing  63 . It engages a pinion gear (punch moving means)  70  provided at the punch slide motor M 66 . Reference numeral  71  denotes a punching means initial position detecting sensor with a light-receiving portion  71   a  provided parallel to a sheet transporting direction A. It is mounted to the casing  63 . 
     By virtue of the above-described structure, when the punch slide motor  66  is driven, the punching means  60  moves in the direction of arrow D or in the direction of arrow E, both directions being at right angles, i.e., transverse to, to the sheet S transporting direction A. By moving the punching means initial position detecting sensor  71  in the direction of arrow E, a punch slide HP member  72  provided in the body of the sheet processor  103  can be detected by the light-receiving member  71   a . The initial position of the punching means  60  corresponds to a position a few millimeters in front of a sheet standard position. It is set in correspondence with the amount of oblique movement of a sheet S or the amount of displacement of the horizontal regist. 
     The horizontal regist detecting means  80  is mounted to the punching means  60 . In the horizontal regist detecting means  80 , a light-receiving portion  85   a  is provided parallel to the sheet S transporting direction A, and a sheet end portion detecting sensor  85  is mounted to an end of a sensor arm  82  in order to detect a side edge of a sheet S. 
     A rack gear  82   a  is formed on a portion of the sensor arm  82  so as to engage a pinion gear  83  of a sensor slide motor M 68  mounted to the casing  63 . At the back end of the sensor arm  82  is mounted a horizontal regist initial position detecting sensor  84  with a light-receiving portion  84   a . The sheet edge-detecting sensor  85  is disposed on one side of the sensor arm  82 , while the light-receiving portion  84   a  is disposed on the opposite side of the sensor arm  82 . 
     By virtue of this structure, when the sensor slide motor M 68  is driven, the sheet edge detecting sensor  85  and the horizontal regist initial position detecting sensor  84  move in the direction of arrow D or in the direction of arrow E, both directions being transverse to the sheet transporting direction A. When the horizontal regist initial position detecting sensor  84  moves in the direction of arrow E, a horizontal regist initial position defining section  63   b  provided on the casing  63  can be detected by the light-receiving portion  84   a . The sheet edge detecting sensor  85  can move in the direction of arrow D to a location corresponding to a location for a selected sheet size. 
     In detecting a side edge of a sheet S, after detection of the front edge of the sheet S by the sheet detecting sensor  31 , the punch slide motor M 66  is driven at a predetermined timing, causing the punching means  60  and the sheet edge detecting sensor  85  to move in the direction of arrow D or in the direction of arrow E. When the sheet edge detecting sensor  85  is covered by the side edge of the sheet S, the punch slide motor M 66  stops. As a result, the punching position of the sheet S can be set at the detected edge of the sheet S. 
     As shown in FIG. 3, a flag  75  is affixed to the supporting shaft  61   b  mounted to the punch  61  so that the rotation of the punch  61  can be detected by a punching position detecting sensor (punching operation detecting means)  76 . FIG. 3 shows the punch  61  at home position (HP). FIG. 4 shows the punch  61  and the die  62  during a punching operation. FIG. 5 shows the punch  61  and the die  62  after a punching operation. 
     FIG. 6 illustrates a timing chart of drive signals, for punching in a hole in a sheet S, of the sheet side edge detecting sensor  85 , the punching position detecting sensor  76 , the horizontal regist initial position detecting sensor  84 , the punch drive motor M 67  (provided for rotating the punch  61  and the die  62 ), and the punch slide motor  66  (provided for sliding the punch  61  and the die  62 ). t7 represents the timing of starting the driving of the punch slide motor M 66  after the passage of a predetermined timing following the detection of the sheet edge by the sheet detecting sensor  31 . When the driving of the punch slide motor M 66  is started, the punching means  60  and the sheet edge detecting sensor  85  start to move in the direction of arrow D. 
     t11 represents the timing in which the horizontal regist initial position detecting sensor  84  determines that the horizontal regist initial position defining section  63   b  has not been detected by moving in the direction of arrow D. 
     t1 represents the timing in which the sheet edge detecting sensor  85  is covered by the side edge of the sheet being transported. With the timing t1 being defined as the timing in which the side edge of the sheet being transported is detected, t8 is the timing in which the edge of the sheet is reached and the driving of the punch slide motor M 66  is stopped. 
     t5 represents the timing in which the driving of the punch drive motor M 67  is started after the passage of a predetermined timing following the detection of the edge of the sheet by the sheet detecting sensor  31 . When the driving of the punch drive motor M 67  is started, the punch  61  and the die  62  rotate, thereby staring a punching operation on the sheet being transported. 
     t3 represents the timing in which the punching operation on the sheet being transported is completed. In other words, it is the timing in which the punch  61  moves out of the transportation path and stops contacting the sheet being transported. 
     With t3 being defined as the timing in which the punching operation on the sheet being transported is completed, t9 is defined as the timing in which the driving of the punch slide motor M 66  is started. When the driving is started, the punch means  60  and the sheet edge detecting sensor  85  move in the direction of arrow E. 
     t2 represents the timing in which the back edge of the sheet being transported passes by the sheet edge detecting sensor  85 . 
     t12 represents the timing in which the horizontal regist initial position detecting sensor  84  detects the horizontal regist initial position defining section  63   b  by moving in the direction of arrow E. 
     With t12 being defined as the timing in which the the horizontal regist initial position detecting sensor  84  detects the horizontal regist initial position defining section  63   b , t10 represents the timing in which the horizontal regist initial position defining section  63   b  is reached and the driving of the punch slide motor M 66  is stopped. 
     t4 represents the timing in which the home position (HP) of the punch  61  is detected by the punching position detecting sensor  76 . 
     With t4 being defined as the timing in which the punching position detecting sensor  76  detects the home position (HP) of the punch  61 , t6 is the timing in which the driving of the punch drive motor M 67  is stopped. 
     FIG. 7 is a block diagram of the controlling sections, used in the embodiment of the present invention. 
     The controller circuit section  200  includes a central processing unit (hereinafter referred to as “CPU”)  2002 , a memory  2001 , and an input/output (I/O) control section  2003 . The CPU  2002  is provided to perform computations based on a predetermined program and to control the controlling sections. The memory  2001  is provided to store a program or data therein or to output a program or data therefrom. The memory  2001  may include a read-only memory (ROM) for storing a program or predetermined data, a random access memory (RAM) for temporarily storing data in accordance with a signal processing operation, an integrated circuit (IC) card, and a floppy disk. The I/O control section  2003  is provided to transmit and control input/output signals. The memory  2001  and the I/O control section  2003  are controlled by control signals from the CPU  2002 . 
     The controller circuit section  200  also controls operation of an operation section control section  201 , a recording sheet feed control section  202 , a reading position sheet feed device control section  203 , an image forming control section  204 , a sheet processor control section  205 , etc. 
     The user places originals in the automatic original feed section  51  (FIG. 1) of the reading position sheet feed device  101 . Using the operation section  40  of the image forming apparatus, the user then sets an operation mode and directs the image forming apparatus to start a copying operation. The automatic original feed section  51  feeds the originals P one at a time, and the fed originals P are read by the optical system  52 . 
     The image of the exposed originals are subjected to photoelectric conversion by a charge-coupled device (CCD) line sensor  176 , and are read as electrical signals. The electrical signals are subjected to image processing in accordance with settings selected by the user at the operation section  40 . Then, the electrical signals are converted into light signals for exposing a photosensitive member. 
     Thereafter, the images are recorded on sheets S after the usual electrophotography process, i.e., charging operation, exposure operation, latent image forming operation, developing operation, transfer operation, separation operation, and fixing operation. The sheets S with an image formed thereon are transported to a send-in roller  1 , provided in the sheet processor  103 , through a conveyor belt  163  and a transporting roller  165 . The sheet processor  103  is controlled by the controller circuit  200  in accordance with the settings selected by the user at the operation section  40 . 
     Sheets S discharged from the image forming apparatus  102  are sent into the sheet processor  103 . When sheet punching operation is selected at the operation section  40 , the controller circuit  200  causes the sheet processor control section  205  to operate. This causes the sensor slide motor M 68  to be driven, causing the sheet edge detecting sensor  85  to move to a predetermined location, depending on the size of the sheets S, before transporting the sheets S. 
     When the front edge of a sheet S has been detected by the sheet detecting sensor  31 , the controller circuit  200  and the sheet processor control section  205  cause the punch slide motor M 66  to be driven, causing the punching means  60  and the sheet edge detecting sensor  85  to move toward the sheet S. When the sheet edge detecting sensor  85  detects an edge of the sheet S, the controller circuit  200  causes the punch slide motor M 66  to stop, that is, causes the punching means  60  and the sheet edge detecting sensor  85  to stop moving. 
     After the passage of a predetermined amount of time from the detection of the back edge of the sheet S by the sheet detecting sensor  31 , the controller circuit  200  causes the punch drive motor M 67  to be driven. This causes the punching means  60  to operate and punch a hole in the sheet S. When a detection is made by the punching position detecting sensor  76  that the punching operation is completed (FIG.  5 ), the controller circuit  200  and the sheet processor control section  205  cause the punch slide motor M 66  to be driven, causing the punching means  60  and the sheet edge detecting sensor  85  to move to punch slide home position (HP) at the opposite side with respect to the sheet S. When the punching position detecting sensor  76  detects the punching operation home position (FIG.  3 ), the controller circuit  200  and the sheet processor control section  205  cause the punch drive motor M 67  to stop, so that the punching means  60  stops moving. 
     The transporting flapper  11  (see FIG. 1) operates to switch transporting paths. When sheets S are to be loaded onto the sample tray  95 , they are discharged via the sheet discharging rollers  9 . When sheets S are to be loaded onto the stack tray  96 , they are discharged onto the processing tray  92  after passing between the transporting rollers  6  and the sheet discharging rollers  7 . 
     When the stapling operation is selected at the operation section  40 , the controller circuit  200  and the sheet processor control section  205  to operate cause the stapling unit  90  to staple the sheets S loaded on the processing tray  92 . 
     The alignment plate  98  operates to align the loaded batch of sheets. The controller circuit  200  controls the sorting direction of the sheet batch to be loaded onto the stack tray  96 . 
     The sheet batch discharging roller  93   b  is driven after the swinging guide  91  has been closed. This causes the sheet batch on the processing tray  92  to be discharged and loaded onto the stack tray  96 . 
     A description will now be given of the operation of the punching unit with reference to the flowchart of FIG.  8 . 
     The CPU  2002  causes the operation section control section  201  to allow input of any one of loading operation, stapling operation, and punching operation. Based on the input operation performed by the user at the operation section  40 , the CPU  2002  causes the recording sheet feed control section  202 , the reading location sheet feed device control section  203 , the image forming control section  204 , and the sheet processor control section  205  to operate in order to execute the input operation. 
     When the user selects punching operation, and when a copy start operation is executed (Step S- 0 ), the CPU  2002  and the sheet processor control section  205  cause the sensor slide motor M 68  to be driven, causing the sheet edge detecting sensor  85  to move to a predetermined location in accordance with the size of the sheets (Step S- 1 ). Then, the CPU  2002  waits for the sheet detecting sensor  31  to detect the front edge of a sheet S (Step S- 3 ). When the front edge of the sheet S is detected, the CPU  2002  and the sheet processor control section  205  cause the punch slide motor M 66  to be driven (Step S- 4 ), causing the punching means  60  to move in the sheet width (transverse) direction until the sheet edge detecting sensor  85  detects the edge of the sheet S (Step S- 5 ). 
     When the sheet edge detecting sensor  85  detects the edge of the sheet S, the CPU  2002  causes the punch  61  to stop moving in the transverse direction (Step S- 6 ). Then, the CPU  2002  waits for the sheet detecting sensor  31  to detect the back edge of the sheet (Step S- 7 ). When the back edge of the sheet is detected, the CPU  2002  waits for a predetermined length of time until the back edge of the sheet is positioned at a previously set punching position with respect to the sheet transporting direction (Step S- 8 ). Thereafter, the CPU  2002  and the sheet processor control section  205  cause the punch drive motor M 67  to be driven in order to punch a hole in the sheet S being transported (Step S 9 ). 
     When the punching position detecting sensor  76  detects that the punching means  60  has completed a punching operation (Step S- 10 ), the CPU  2002  and the sheet processor control section  205  cause the punch slide motor M 66  to be driven (Step S- 11 ). When the punch slide home position (HP) sensor (punch home position detecting means)  71  detects (Step S- 12 ) the punch slide home position HP (or standby position) of the punching means  60  (punch  61  and die  62 ), the CPU  2002  causes the punch  61  to stop sliding (Step S- 13 ). 
     When the punching position detecting sensor  76  detects the punch operation home position HP (S- 14 ), the CPU  2002  causes the punch  60  to stop rotating (Step S- 15 ). The CPU  2002  determines whether or not the job has been completed (Step S- 16 ). The CPU  2002  then causes the sensor slide motor M 68  to be driven, causing the sheet edge detecting sensor  85  to move to the horizontal regist home position HP (Step S- 17 ) and then to stop moving (Step S- 18 ). If the job has not been completed, the CPU  2002  determines whether the width of the next sheet S is the same width as the present sheet S (Step S- 2 ). If the sheet widths are the same, the CPU  2002  executes Step S- 3  otherwise it executes Step S- 1 . 
     According to the above-described embodiment, when a detection is made by the punching position detecting sensor  76  that the punching means  60  has completed punching a hole in a sheet S (FIG.  5 ), the punching means  60  is made to start moving to the home position HP (or standby position) in a direction transverse to the sheet transporting direction. Therefore, during rotation of the punching means  60  to the punching operation home position HP (FIG.  3 ), the punching means  60  simultaneously can move to the punch slide home position HP in the transverse direction. Consequently, the sheet punching time can be shortened. 
     As can be understood from the foregoing description, according to the present invention, the punching operation detecting means detects that the punching means has completed punching a hole in a sheet. During movement of the punching means to the punching operation home position HP, standby operation is started in order to move the punching means to the home position HP in a direction crossing the sheet transporting means. This reduces the sheet processing time, making it possible to increase the number of sheet processing operations. 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.