Abstract:
An image forming system includes: an image forming apparatus capable of conveying a recording sheet at a predetermined speed; at least one finisher capable of conveying the sheet eject from the image forming apparatus at a prescribed speed to process the sheet; and a controller for changing a conveyance speed of the recording sheet in the finisher to be higher than that of the sheet in the image forming apparatus.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an image forming system composed of an image forming apparatus connected with a finisher for conducting such processing as punching, folding, stapling and shifting.  
         [0002]     An image forming system connected with a finisher for conducting such processing as punching, folding, stapling and shifting to sheet with an image formed thereon is widely used as a system configured on the basis of a high speed image forming apparatus such as an image forming apparatus based on electrophotographic technology.  
         [0003]     In the finisher, processing such as folding and stapling is carried out to sheet, which is temporarily stopped. Accordingly, to prevent collision of the sheets of paper conveyed one after another, the conveyance speed is increased immediately before and after a processing station, thereby ensuring a wide space between sheets of paper (Official Gazette of Japanese Patent Tokkaihei 5-16569). When such control is used, a sensor is installed at the sheet inlet of the finisher, the conveyance speed is increased based on the signal for detecting the trailing edge of the traveling sheet.  
         [0004]     To ensure multiple types of finishing, an image forming system equipped with a plurality of finishers is proposed (Official Gazette of Japanese Patent Tokkai 2002-59496 and 2002-137503). In such an image forming system equipped with the plurality of finishers, not much consideration is given to the operation stability and efficiency in the management of the sheet conveyance speed as the overall image forming system.  
         [0005]     When designing an image forming system equipped with a plurality of finishers, control will become complicated if each finisher is provided with the conveyance speed control function as in Official Gazette of Japanese Patent Tokkaihei 5-16569, and sheet conveyance control is separately carried out. Such a trouble as jamming is likely to occur and finishing efficiency is reduced, with the result that the efficiency of the overall image forming system will be deteriorated.  
         [0006]     Official Gazette of Japanese Patent Tokkaihei 11-301920 discloses an image forming system provided with a finisher where finishing designation information and the information on the sheet attributes are sent from the image forming apparatus to the finisher where finishing is performed. However, such information is not sufficient for effective sheet conveyance control in the finisher and high speed processing in the finisher. For this purpose, it is necessary to capture information on the sheet conveyance speed and sheet ejection timing at the sheet ejection port of the finisher in the preceding step, namely, the finisher of the preceding step in an image forming apparatus and a plurality of finishers. Such information must be obtained in the finisher of the succeeding stage.  
         [0007]     In the prior art, this type of information has been created in the finisher of the succeeding stage by allowing the model of the preceding apparatus to be identified by the succeeding model.  
         [0008]     The control of this conveyance will be explained with reference to  FIG. 1 .  
         [0009]     Timing of ejecting of sheet P and ejection conveyance speed H from the finisher Ml of the preceding stage are obtained from the rotation speed of the ejection roller R and distance D between the ejection sensor S and ejection port. Based on the aforementioned information, the finisher M 2  of the succeeding stage performs various conveyance control.  
         [0010]     In the prior art, the aforementioned information has been created in the finisher of the succeeding stage by allowing the model of the preceding apparatus to be identified by the succeeding model, as described above. To put it another way, if the model of the apparatus in the preceding stage is identified, the sensor distance D in the apparatus of the preceding stage and sheet ejection conveyance speed H in various operation modes of the model can be obtained. Thus, the finisher of the succeeding stage is provided with a table showing the correspondence between the model of the finisher of the preceding stage, sensor distance D and ejection conveyance speed H in various operation modes.  
         [0011]     However, when there is an addition of a new function resulting from improvement of the finisher or modification of the ejection conveyance speed, or when a new model is connected as the finisher of the preceding stage, this table must be rewritten. For this purpose, the model must be changed due to the relationship with other finisher although there is no change in the function of the finisher. Even if there is no change of the model, table rewriting service is required. This raises the problem of increased servicing loads.  
       SUMMARY OF THE INVENTION  
       [0012]     The object of the present invention is to solve the aforementioned problems in an image forming system equipped with a finisher.  
         [0013]     The aforementioned object of the present invention can be achieved by any one of the following Structures (1) through (17).  
         [0014]     (1) An image forming system comprising: an image forming apparatus capable of conveying a recording sheet at a predetermined speed; at least one finisher capable of conveying the sheet ejected from the image forming apparatus at a prescribed speed to process the sheet; and a controller for changing a conveyance speed of the recording sheet in the finisher to be higher than that of the sheet in the image forming apparatus.  
         [0015]     (2) The image forming system of Structure (1), wherein the controller changes the conveyance speed of the recording sheet in the finisher after the sheet has been delivered from the image forming apparatus to the finisher.  
         [0016]     (3) The image forming system of Structure (2), wherein the image forming apparatus comprises a sheet detection sensor provided in the vicinity of a sheet ejection position thereof, and an information transmitter for transmitting information on a sheet conveyance speed in the image forming apparatus and a distance between the sheet detection sensor and the sheet ejection position, to the finisher.  
         [0017]     (4) The image forming system of Structure (2), wherein the image forming apparatus has a plurality of sheet conveyance modes including different sheet conveyance speeds, and the finisher conveys the sheet at a sheet conveyance speed higher than that in the plurality of sheet conveyance modes.  
         [0018]     (5) The image forming system of Structure (1), comprising a first finisher connected with the image forming apparatus and a second finisher connected with the first finisher.  
         [0019]     (6) The image forming system of Structure (5), wherein the first finisher comprises a sheet detection sensor provided in the vicinity of a sheet ejection position thereof, and an information transmitter for transmitting information on the sheet conveyance speed in the first finisher and a distance between the sheet detection sensor and the sheet ejection position, to the second finisher.  
         [0020]     (7) An image forming system comprising: an image forming apparatus capable of ejecting a recording sheet to a next processing station at a predetermined speed; at least one finisher capable of conveying at a prescribed speed the sheet ejected from the image forming apparatus to process the sheet; and a controller for changing a conveyance speed of the recording sheet in the finisher to be higher than an ejection speed of the sheet ejected from the image forming apparatus.  
         [0021]     (8) The image forming system of Structure (7), wherein the controller changes the conveyance speed of the sheet in the finisher after the sheet has been delivered from the image forming apparatus to the finisher.  
         [0022]     (9) The image forming system of Structure (7), wherein the image forming apparatus has a plurality of sheet conveyance modes including different sheet conveyance speeds, and the finisher conveys the sheet at a sheet conveyance speed higher than that in the plurality of sheet conveyance modes.  
         [0023]     (10) An image forming system comprising: an image forming apparatus capable of conveying a recording sheet at a predetermined speed; at least one finisher capable of changing a conveyance speed of the sheet therein for processing the sheet ejected from the image forming apparatus; an information transmitter for transmitting information on a sheet conveyance speed in the image forming apparatus to the finisher; and a controller for controlling the conveyance speed in the finisher according to the information from the information transmitter.  
         [0024]     (11) The image forming system of Structure (10), wherein the image forming apparatus comprises a sheet detection sensor provided in the vicinity of a sheet ejection position of the image forming apparatus, and the information transmitter transmits information on a distance between the sheet detection sensor and the sheet ejection position and the sheet conveyance speed in the image forming apparatus, to the finisher.  
         [0025]     (12) The image forming system of Structure (11), wherein the controller controls the conveyance speed in the finisher to be higher than a conveyance speed at the sheet ejection position of the image forming apparatus. (13) An image forming system comprising: a first processing apparatus for conveying a recording sheet to a next processing station at a first conveyance speed, having a sheet detection sensor in the vicinity of a sheet ejection position; a second processing apparatus for receiving the sheet ejected from the first processing apparatus, conveying at a second conveyance speed and conducting a desired processing to the sheet; an information transmitter for transmitting information on a distance between the sheet detection sensor and the sheet ejection position and the first conveyance speed, to the second processing apparatus; and a controller for controlling the second conveyance speed according to the information from the information transmitter.  
         [0026]     (14) The image forming system of Structure (13), wherein when the sheet is delivered from the first processing apparatus to the second processing apparatus, the controller controls so that first conveyance speed is equal to the second conveyance speed.  
         [0027]     (15) The image forming system of Structure (13), wherein after the sheet has been delivered from the first processing apparatus to the second processing apparatus, the controller makes the second conveyance speed to be higher than the first conveyance speed.  
         [0028]     (16) The image forming system of Structure (14), wherein the first processing apparatus is an image forming apparatus for printing image information onto a recording sheet.  
         [0029]     (17) The image forming system of Structure (14), wherein the second processing apparatus is a finisher for conducting at least one of punching, folding and stapling processing to the recording sheet.  
         [0030]     Further, the more preferable structures (18) to (23) to achieve the object are as follows.  
         [0031]     (18) An image forming system comprising an image forming apparatus connected with a plurality of finishers and containing the processing mode wherein: the first finisher connected immediately after the image forming apparatus receives the sheet from the image forming apparatus, conveys it at the first conveyance speed at the ejection port of the image forming apparatus, changes the speed to the second conveyance speed higher than the first conveyance speed thereafter, and conveys the sheet in the sheet conveyance path between processing sections at the second conveyance speed and ejects it; and the second finisher connected with the first finisher conveys the sheet in the sheet conveyance path between processing sections at the second conveyance speed and ejects it.  
         [0032]     (19) The aforementioned image forming system described in (18) wherein the image forming apparatus has a sheet ejection sensor, and sends the information on the first conveyance speed and the information on the distance between the sheet ejection sensor and the ejection port of the image forming apparatus, to the first finisher.  
         [0033]     (20) The aforementioned image forming system described in (19) wherein the aforementioned image forming apparatus has a mode of ejecting sheet at various ejection speeds, and the aforementioned first finisher conveys the sheet at a standardized second conveyance speed equal to or higher than the maximum conveyance speed at the ejection port of the image forming apparatus, in all modes, and ejects the sheet.  
         [0034]     (21) The aforementioned image forming system described in any one of (18) through (20) wherein the aforementioned finisher receives the information on the distance between the sheet ejection sensor provided on the first finisher and the ejection port of the finisher, and the information on the second conveyance speed, from the first finisher.  
         [0035]     (22) An image forming system comprising an image forming apparatus connection with a plurality of finishers wherein the aforementioned finisher has a finisher control section for receiving information on the distance between the sheet ejection sensor installed on the image forming apparatus and the ejection port, and the ejection port and the information on the sheet conveyance speed at the ejection port, thereby performing conveyance control.  
         [0036]     (23) The image forming system described in (21) wherein the aforementioned finisher conveys and ejects the sheet at a conveyance speed higher than that at the ejection port.  
         [0037]     In an image forming system composed of an image forming apparatus connected with a plurality of finishers, standardized implementation of sheet conveyance control as the entire system is enabled according to any one of (18) through (21) and (23). This arrangement ensures simplified control, reduces the rate of occurrence of such a trouble as jamming and allows high speed processing in the finisher.  
         [0038]     In the finisher of the preceding stage of the image forming system connected with a plurality of finishers, the structure according to any one of (19), (21) and (22) allows the finisher of the succeeding stage to perform smooth conveyance of sheet, even when sheet is ejected at various ejection speeds in conformity with processing modes.  
         [0039]     Even when the function or model has been changed in the finisher of the preceding stage, this arrangement eliminates the need of changing the control section of the finisher of the succeeding stage; hence it removes the necessity of developing a new model devoid of improved performances and minimizes the maintenance loads. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]      FIG. 1  is a conveyance control diagram;  
         [0041]      FIG. 2  is an overall diagram representing an image forming system as an embodiment of the present invention;  
         [0042]      FIG. 3  is a block diagram representing the control system of the image forming system shown in  FIG. 2 ;  
         [0043]      FIG. 4  is a diagram representing the sheet conveyance control in the processing of folding;  
         [0044]      FIG. 5  is a diagram representing the sheet conveyance control in the processing of stapling; and  
         [0045]      FIG. 6  is a flowchart showing the conveyance speed switching control.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0046]      FIG. 2  is an overall diagram representing an image forming system as an embodiment of the present invention. This image forming system is composed of an image forming apparatus  1 , first finisher  2  and second finisher  3 .  
         [0047]     An automatic document conveyance apparatus  101  and an image read apparatus  102  are mounted on the top of the image forming apparatus  1 , and a printer is located on the lower portion of the image forming apparatus  1 .  
         [0048]     In the printer, numerals  103  and  104  denote sheet store sections for sheet P. It contains a photoconductor  106 . An image is formed on sheet P in an image forming section  105  for forming an image on the sheet P by the electrophotographic process, and the formed image is fixed on sheet P by the fixing apparatus  107 .  
         [0049]     An image is formed on the sheet P supplied by a sheet store section  103  or  104 . The sheet P with an image formed thereon is ejected from the ejection port  113  by an ejection roller  110 .  
         [0050]     Sheet conveyance paths include a sheet conveyance path  108  from the sheet store sections  103  and  104  to the image forming section  105 ; a sheet conveyance path  109  from image forming section  105  to ejection port  113  through the fixing apparatus  107  and ejection roller  110 ; and a back conveyance path  112  for reversing and conveyance.  
         [0051]     The image forming modes includes a single side face down ejection mode, a single side face up ejection mode and a double-side mode. In the single side face down ejection mode, the sheet P with an image formed on the one side is reversed by the processing of reversing, and is conveyed and ejected by the ejection roller  110 .  
         [0052]     In the single side face up ejection mode, the sheet P with an image formed on the one side and conveyed to the sheet conveyance path  109  is directly conveyed and ejected by the ejection roller  110 .  
         [0053]     In the double-side mode, sheet P, with an image formed on one side, having passed the fixing apparatus  107  is conveyed downward to go through the back conveyance path  112 . After having been reversed, the sheet is conveyed to the sheet conveyance path  108  again.  
         [0054]     A back face image is formed on the back face of the sheet P conveyed again by the image forming section  106 . The sheet P with back face image formed thereon passes through the fixing apparatus  107 , and is conveyed and ejected by the ejection roller  110 . Numeral  130  denotes an operation section. Various modes of the image forming apparatus  1  and output modes using the first and second finisher are set by the operation of the operation section  130 .  
         [0055]     The first finisher  2  is a finisher for performing at least one of punching, stapling, stacking and shifting. In the illustrated example, it contains a punching processing section  204  and folding sections  205 ,  206  and  207 .  
         [0056]     The first finisher  2  is provided with a sheet conveyance section  212  for the additional sheet such as inter-sheet, which is added to the sheet, carrying an image, discharged from the image forming apparatus  1 . The sheet P discharged from the image forming apparatus  1  and introduced from a sheet inlet  201  provided with an inlet sensor  214  passes through a horizontal linear sheet conveyance path  202 , and is ejected from the ejection port  216  by the ejection roller  203  or travels along the sheet conveyance path  208  extending downward. The sheet P having traveled downward is punched by the punching processing section  204  or is folded by passing through the folding sections  205 ,  206  and  207 . Then the sheet P is ejected from the ejection port  216  by the ejection roller  203 . Use of three folding sections  205 ,  206  and  207  allows the sheet to be folded in various forms; in two folding, three folding in the shape of letter Z or in three folding inward.  
         [0057]     The second finisher  3  is a finisher for performing at least one of punching, folding, stacking and stapling. In the illustrated example, it has a stapling section  302  and a stacker  303  to apply stapling or shifting to the sheet and to eject it into an elevating ejection tray  310 .  
         [0058]     The second finisher  3  has a stationary ejection tray  311 . In a low-volume image forming jobs, sheet P is ejected into a stationary ejection tray  311 .  
         [0059]     After a predetermined number of sheets have been accumulated in the stacker  303 , stapling is carried out to sheet by the stapling section  302 . The bundle of processed sheet P goes up the stacker  303  and is ejected into the elevating ejection tray  310 .  
         [0060]     In a low-volume image forming jobs, the sheet conveyance path  305  is selected and sheet P is ejected into the stationary ejection tray  311 .  
         [0061]     In the shifting and ejection, sheet P is conveyed along the sheet conveyance path  306  to the stacker  303  where it is stopped. Then sheet P is subjected to processing of shifting at the stacker  303  and is ejected to the elevating ejection tray  310 . In the stapling apparatus, sheet P travels along the sheet conveyance path  306 . The sheets are stacked in the number preset on the stacker  303 . The stacked sheets of sheet P are stapled by the stapling section  302 , and are conveyed to the upper left over the stacker  303 . Then they are ejected into the elevating ejection tray  310 .  
         [0062]     Even in the mode where stapling or shifting is not carried out, sheet P is ejected to the elevating ejection tray  310  through the sheet conveyance path  306  if high-volume image formation is performed. To put it another way, in the process of forming a large amount of images, sheet P travels along the sheet conveyance path  306  and is ejected into the elevating ejection tray  310  after traveling straight without passing through the stacker  303 .  
         [0063]      FIG. 3  is a block diagram representing the control system of the image forming system shown in  FIG. 2 .  
         [0064]     Numeral  120  denotes an image forming apparatus control section for overall control of the image forming system such as processing of the system as a whole, including image reading, image formation, sheet conveyance and processing by the finisher.  
         [0065]     Numeral  121  denotes a sheet store section as a control unit. It controls start of the sheet conveyance in the sheet store sections  103  and  104 .  
         [0066]     Numeral  122  denotes a sheet presence detection section composed of various sensors such as a sheet sensor. It contains sensors mounted on the recording sheet storage section and sheet conveyance path. The ejection sheet sensor  111  is a component of the sheet presence detection section  122 .  
         [0067]     Numeral  123  denotes a sheet size detection section and is composed of the sensors provided on the sheet store sections  13  and  104  in  FIG. 2 . It should be noted that one sensor serves as both the sheet presence detection section  122  and sheet size detection section  123  in some cases.  
         [0068]     The sheet conveyance section  124  provides conveyance control on the sheet conveyance path  108  in  FIG. 2 .  
         [0069]     The conveyance section  125  provides conveyance control on the double-side conveyance section  109  in  FIG. 2 .  
         [0070]     The sheet ejection section  126  controls the ejection roller  110 .  
         [0071]     The image data storing section  128  stores the image data generated by the image read apparatus  102  in  FIG. 2  and the image data received from outside via the network. It is composed of a large capacity memory such as a semiconductor memory and hard disk memory.  
         [0072]     An image forming section  129  controls the image forming section  105  and fixing apparatus  107  of  FIG. 2 .  
         [0073]     An operation section  130  comprises an input section  131  including operation keys or the like and a display section  132  having a LCD panel or CRT.  
         [0074]     Numeral  220  denotes a finisher control section for overall control in the first finisher  2 .  
         [0075]     An ejection path selection section  221  is used to select whether the sheet having been received from the image forming apparatus  1  and sheet supplied from the sheet conveyance section  212  are to be rejected through the sheet conveyance path  202  or though the sheet conveyance path  208 . The ejection path selection section selects the sheet conveyance path for the folding sections  205 ,  206  and  207  to carry out various types of folding.  
         [0076]     A punching section  222  controls the punching processing section  204 .  
         [0077]     A folding section  223  controls the folding sections  205 ,  206  and  207  in  FIG. 2 .  
         [0078]     A first conveyance section  224  controls the conveyance along the sheet conveyance path  202  in  FIG. 2 .  
         [0079]     A second conveyance section  225  controls the conveyance along the sheet conveyance path  208  in  FIG. 2 .  
         [0080]     A third conveyance section  226  controls the conveyance between folding sections along sheet conveyance paths  209 ,  210  and  211  in  FIG. 2 .  
         [0081]     A detection section  228  includes a sensor for detecting sheet. The inlet sensor  201  and ejection sensor  215  in  FIG. 2  constitute the detection section  228 .  
         [0082]     Numeral  320  is a finisher control section for overall control of the second finisher.  
         [0083]     An ejection path selection section  321  controls the selection to determine if the sheet received from the first finisher  2  should be ejected to the stationary ejection tray  311  through the sheet conveyance path  305  in  FIG. 2 , or to the elevating ejection tray  310  through the sheet conveyance path  306  and stacker  303 .  
         [0084]     A sheet alignment section  322  controls the alignment of sheet in the stacker  303  of  FIG. 2 . It controls the drive of the regulating plate for regulate the side edge of the stacked sheets of sheet P, thereby aligning the sheets and pushing up and ejecting the stapled sheet P.  
         [0085]     A stapling section  323  controls the stapling section  302  in  FIG. 2 .  
         [0086]     A first sheet conveyance section  324  controls the conveyance along the sheet conveyance path  306  in  FIG. 2 .  
         [0087]     A second sheet conveyance section  325  controls the conveyance along the sheet conveyance path  305  in  FIG. 2 .  
         [0088]     A third sheet conveyance section  326  controls the conveyance from the stacker  303  to the stationary ejection tray. 311  in  FIG. 2 .  
         [0089]     A first sheet ejection section  327  controls ejection of sheet to the elevating ejection tray  310  and elevation of the elevating ejection tray  310 .  
         [0090]     A second sheet ejection section  328  controls ejection of sheet to the stationary ejection tray  311 .  
         [0091]     Communication among the image forming apparatus  1 , first finisher  2  and second finisher  3  is carried out by the serial communication sections  127  and  229 , and between  230  and  329 .  
         [0092]     The sheet conveyance control by the control system shown in  FIG. 3  is carried out as shown in  FIG. 4  representing the sheet conveyance speed in each apparatus.  FIG. 4  shows an example of folding, and  FIG. 5  an example of stapling.  
         [0093]     In the example shown in  FIG. 4 , sheet is conveyed out of the sheet store section  121  and is conveyed along the sheet conveyance path  108  at the conveyance speed Hi by the sheet conveyance section  124 .  
         [0094]     After having been stopped temporarily at the registration station, sheet is conveyed along the sheet conveyance path  109  at the conveyance speed H 2  (first conveyance speed) lower than the conveyance speed H 1  by the conveyance section  125 , and is ejected from the sheet ejection section  126  into the first finisher  2 .  
         [0095]     In the first finisher  2 , sheet is conveyed along the sheet conveyance paths  208  and  209  at the conveyance speed H 3  (second conveyance speed) higher than the conveyance speed H 2  by the first and second conveyance sections  225  and  226 . After having been folded, sheet is ejected from the sheet ejection section  227  at the conveyance speed H 3  into the second finisher  3 . In the second finisher  3 , the sheet is conveyed along the sheet conveyance path  306  at the conveyance speed H 3  by the conveyance section  324 , and is ejected into the elevating ejection tray  310 .  
         [0096]     As described above, the conveyance speed H 3  along the sheet conveyance paths  208  and  202  before and after folding in the first finisher  2  and the conveyance speed H 3  along the sheet conveyance path  306  in the second finisher  3  are set at a value higher than the conveyance speed H 2  at the ejection port  113 .  
         [0097]     In the example shown in  FIG. 5 , the sheet having been processed by the image forming apparatus  1  and ejected at the conveyance speed H 2  (first conveyance speed) similarly to the case of  FIG. 4  is conveyed along the sheet conveyance path  202  by the sheet conveyance section  224  at the conveyance speed H 3  (second conveyance speed) higher than the conveyance speed H 2  in the first finisher  2 , and is ejected into the second finisher  3 .  
         [0098]     In the second finisher  3 , sheet is conveyed along the sheet conveyance path  306  at the conveyance speed H 3  by the second sheet conveyance section  325 , and is stopped by the stacker  303 . After having been stapled, sheet is conveyed at the conveyance speed H 4  lower than the conveyance speed H 3 , and is ejected into the elevating ejection tray  310 .  
         [0099]     Switching of conveyance speed from H 2  to H 3  in  FIGS. 4 and 5  is controlled by the finisher control section  220  based on the signal coming from the sheet detection section  228 .  
         [0100]     To put it another way, the conveyance speed H 2  is switched to H 3  according to the signal from the sheet detection section  228  that detects passage of the trailing edge of the sheet ejected from the image forming apparatus  1  at the conveyance speed H 2 .  
         [0101]      FIG. 6  is a flowchart showing the conveyance speed switching control using the sheet detection section  228 .  
         [0102]     Decision in step F 1  on whether or not ejection information is present is made in conformity to the signal sent from the sheet ejection sensor  111  located in the sheet presence detection section  122  of the image forming apparatus  1 .  
         [0103]     If there is ejection information, the conveyance speed at the sheet inlet section of the first finisher  2  is set. To set this conveyance speed is to control of adding the conveyance speed at the inlet  201  of the first finisher to the conveyance speed at the ejection port  113  of the image forming apparatus  1 . As shown in the case of F 2  and F 3 , F 6  and F 7 , and R 8  and F 9 , when the conveyance speed at the ejection port  113  is 500 mm/sec., the conveyance speed at the inlet sensor  201  is 500 mm/sec.; when the conveyance speed at the ejection port  113  is 800 mm/sec., the conveyance speed at the inlet sensor  201  is 800 mm/sec.; and when the conveyance speed at the ejection port  113  is 1000 mm/sec., the conveyance speed at the inlet sensor  201  is 1000 mm/sec.  
         [0104]     Upon detection of passing of the trailing edge of sheet through the inlet sensor  214  in the sheet detection section  228  of the first finisher  2  (Yes in F 4 ), the conveyance speed is set to 1000 mm/sec. and sheet is conveyed.  
         [0105]     In the step F 5  and thereafter in  FIG. 6  in the first finisher  2 , sheet is conveyed along the main conveyance path of the first finisher  2  and second finisher  3 , namely, the conveyance path between processing sections at the conveyance speed 1000 mm/sec. (H 3 ), as shown in  FIGS. 4 and 5 .  
         [0106]     As is clear from  FIG. 6 , conveyance at the inlet sensor  201  of the first finisher  2  is controlled under the conveyance conditions of the image forming apparatus  1 , until passing of the trailing edge of sheet is detected by the inlet sensor  214  provided at the sheet inlet  201 .  
         [0107]     The above description also applies to the second finisher  3 . The conveyance is controlled under the conveyance conditions of the second finisher  3 , until passing of the trailing edge of sheet is detected by the sensor  312  that is provided at the sheet inlet  301  of the second finisher  3 .  
         [0108]     In other words, in the finisher, control at the sheet inlet is provided under the conveyance conditions in the finisher of the preceding stage, until the trailing edge of the sheet passes by.  
         [0109]     In the control carried out under the conveyance conditions of the apparatus of the preceding stage, information on the conveyance conditions of the apparatus in the preceding stage must be captured by the apparatus of the succeeding stage. For example, to improve the processing efficiency in the second finisher  3 , two sheets of sheet conveyed in succession are conveyed one on top of the other. To be more specific, to improve productivity, when the sheet is conveyed continuously with the space between sheets minimized, two sheets are conveyed one on top of the other in the second finisher  3 . A bypass gate  313  is provided in the sheet conveyance path  306  close to the sheet inlet, and the preceding sheet and succeeding sheet are conveyed one on top of the other, by switching of this bypass gate. In this case, the setting of the stop time for stopping the preceding sheet temporarily is controlled according to the information on conveyance speed at the sheet ejection port and sensor distance in the finisher of the preceding stage., namely the first finisher  2 .  
         [0110]     According to the present invention, when sheet is sent from the finisher of the preceding stage to the finisher of the succeeding stage, namely, from the image forming apparatus  1  to the first finisher  2 , and from the first finisher  2  to the second finisher  3  in the example of  FIG. 2 , information on the conveyance speed H at the ejection port of the apparatus of the preceding stage and information on the sensor distance D, namely, information between the sheet ejection sensor and the ejection port is conveyed to the finisher of the succeeding stage.  
         [0111]     The conveyance speed H and sensor distance D are as shown in  FIG. 1 .  
         [0112]     As shown above, the first finisher having received sheet from the finisher of the succeeding stage, that is, image forming apparatus  1 , and the second finisher  3  having received sheet from the first finisher  2  control the conveyance of sheet, using the information shown in  FIG. 1 , without identifying the model of the finisher of the preceding stage.  
         [0113]     These items of information are transmitted through the serial communication sections  127 ,  229 ,  230  and  329  shown in  FIG. 3 . To put it more specifically, these items of information are transmitted together with the operation command issued from the image forming control section  120  to the finisher control sections  220  and  320  before execution of the image forming job starts.