Abstract:
An image forming apparatus includes a main body having an opening, an image forming unit, storage portions, each to store a sheet inside the main body, and a moving unit. The image forming unit forms an image on a sheet. The moving unit moves the sheet stored in each of the storage portions, and stop the sheet in an exposure state where a trailing edge of the sheet is inside the main body and a leading edge of the sheet is exposed outside the main body through the opening. The moving unit moves a first sheet stored in a first storage portion and a second sheet stored in a second storage portion, and stops the first sheet and the second sheet in the exposure state, wherein the leading edge of the first sheet and the leading edge of the second sheet are exposed outside the main body through the opening.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/394,640, filed Oct. 15, 2014, which is a national stage Entry of PCT/JP2013/001648, filed Mar. 13, 2013, which claims the benefit of Japanese Patent Application No. 2012-094054, filed Apr. 17, 2012, all of which is hereby incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an image forming apparatus, in particular to an image forming apparatus including a sheet storage portion that stores a sheet on which an image is formed. 
     BACKGROUND ART 
     Conventionally, there are image forming apparatuses such as a copying machine, which are provided with a sheet storage portion such as a mail box that stores a sheet on which an image is formed by an image forming unit. 
     As an image forming apparatus provided with such a sheet storage portion, PTL 1 describes an image forming apparatus including a plurality of sheet storage portions, which are provided below the image forming unit and are assigned to each user, separately from a normal stacker portion, which is provided on the upper surface of the main body of the apparatus and is shared by a plurality of users. In the image forming apparatus described in PTL 1, it is possible to selectively receive only sheets stored in any one of the sheet storage portions by an operation of a user. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Patent Laid-Open No. 7-125909 
     However, in the image forming apparatus described in PTL 1, there is a problem that it is difficult for a user to take the sheets out because the stacker portion on the upper surface of the main body of the apparatus and the sheet storage portions below the image forming unit are located at positions largely away from each other. 
     SUMMARY OF INVENTION 
     The present invention provides an image forming apparatus including sheet storage portions and a stacker portion in which it is easy for a user to take sheets out. 
     According to an aspect of the present invention, an image forming apparatus includes a main body formed with an opening, an image forming unit configured to form an image on a sheet, a plurality of storage portions, each configured to store, inside the main body, the sheet on which the image has been formed by the image forming unit, and a sheet moving unit configured to move the sheet stored in each of the plurality of storage portions, and stop the sheet in an exposure state where a trailing edge of the sheet in a movement direction is inside the main body and a leading edge of the sheet in the movement direction is exposed outside the main body through the opening, wherein the sheet moving unit moves a first sheet stored in a first storage portion and a second sheet stored in a second storage portion, and stops the first sheet and the second sheet in the exposure state, wherein the leading edge of the first sheet and the leading edge of the second sheet are exposed outside the main body through the same opening. 
     Advantageous Effects of Invention 
     According to the present invention, the sheet storage portions that store sheets are provided between the image forming unit and the stacker portion on the upper surface of the main body of the apparatus. Therefore, the stacker portion and the sheet storage portions can be arranged near each other, so that a user can easily take any sheets. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing a first embodiment of an image forming apparatus to which the present invention is applied. 
         FIG. 2  is a diagram showing a configuration of sheet storage portions of the first embodiment of the present invention. 
         FIG. 3A  is a diagram showing a configuration of a sheet storage portion of the first embodiment of the present invention. 
         FIG. 3B  is a diagram showing a configuration of the sheet storage portion of the first embodiment of the present invention. 
         FIG. 4  is a block diagram of an image forming apparatus to which the present invention is applied. 
         FIG. 5  is a diagram showing a configuration of the sheet storage portions of the first embodiment of the present invention. 
         FIG. 6  is an external perspective view of the first embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 7A  is a diagram showing the first embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 7B  is a diagram showing the first embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 8  is an external perspective view of a second embodiment of an image forming apparatus to which the present invention is applied. 
         FIG. 9  is a diagram showing a third embodiment of an image forming apparatus to which the present invention is applied. 
         FIG. 10  is a diagram showing the third embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 11A  is a diagram showing a fourth embodiment of an image forming apparatus to which the present invention is applied. 
         FIG. 11B  is a diagram showing the fourth embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 12A  is a diagram showing the fourth embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 12B  is a diagram showing the fourth embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 12C  is a diagram showing the fourth embodiment of the image forming apparatus to which the present invention is applied. 
         FIG. 13  is a diagram showing a modified example of a push-out unit. 
         FIG. 14  is a diagram showing a modified example of a discharge port. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     [First Embodiment] 
       FIG. 1  shows a schematic cross-sectional view of a monochrome digital printer as an example of an image forming apparatus to which the embodiment is applied. 
     In  FIG. 1 , reference numeral  100  denotes an image forming apparatus main body (hereinafter referred to as an “apparatus main body”). An image forming unit  101  is included in the apparatus main body  100 . Reference numeral  102  denotes a sheet feeding and conveying unit that feeds and conveys a sheet to the image forming unit  101 . Reference numeral  103  denotes a fixing unit that fixes an image onto the sheet. Reference numeral  124  denotes a stacker portion which is provided on the upper surface of the apparatus main body and on which sheets on which an image is formed by the image forming unit are stacked. Reference numerals  201 ,  202 , and  203  denote sheet storage portions which store the sheets on which images are formed by the image forming unit  101  and which is provided between the image forming unit  101  and the stacker portion  124 . 
     Here, the image forming unit  101  includes a photosensitive drum  111  that rotates in a clockwise direction in  FIG. 1 , an exposure apparatus  113 , and a charging roller  112 , a developing roller  114 , and a transfer roller  115  which are sequentially arranged along a rotation direction of the photosensitive drum  111 . The image forming unit  101  forms a toner image on a sheet S by an image forming process. 
     The sheet feeding and conveying unit  102  includes a sheet feed cassette  105  in which a plurality of sheets S used to form an image are stored in a stacked state, a feed roller  107 , a conveying guide  109 , and a registration roller  110 . The fixing unit  103  includes a fixing roller  116 , a pressure roller  117  upward in contact with the fixing roller  116 , and a conveying roller  118 . 
     A sheet S re-conveying path  126  used to form images on both sides of the sheet S is provided between a set of the image forming unit  101  and the fixing unit  103  and the sheet feed cassette  105 . 
     In the image forming apparatus of the present embodiment, a plurality of sheet storage portions are vertically stacked. A first sheet storage portion  201 , a second sheet storage portion  202 , and a third sheet storage portion  203  are stacked in order from the above. 
     Reference numeral  204  denotes a conveying roller functioning as a conveying unit that conveys a sheet on which an image is formed to the first storage unit  201 . Similarly, reference numeral  205  denotes a conveying roller that conveys a sheet to the second storage unit  202  and reference numeral  206  denotes a conveying roller that conveys a sheet to the third storage unit  203 . 
     Reference numeral  120  denotes a conveying path switching member whose position can be switched between a first position which is indicated by solid lines in  FIG. 1  and in which the sheet on which an image is formed is moved toward the sheet storage portions and a second position which is indicated by dashed lines and in which the sheet on which an image is formed is discharged to the stacker portion  124 . The position of the conveying path switching member  120  can be switched between the position indicated by solid lines in  FIG. 1  and the position indicated by dashed lines in  FIG. 1  by an actuator not shown in  FIG. 1 . Reference numerals  121  and  123  denote reverse rotation rollers which can rotate in a normal direction and a reverse direction and which conveys the sheet to the stacker portion  124  by rotating in the normal direction and conveys the sheet to the image forming unit  101  again by rotating in the reverse direction. 
     When the sheet is discharged to the stacker portion  124 , the position of the conveying path switching member  120  is switched to the position indicated by the dashed lines and the sheet is conveyed along a discharge guide  122  by the reverse rotation roller  121  and discharged to the stacker portion  124  by the reverse rotation roller  123 . As shown in  FIG. 1 , the stacker portion  124  is disposed on the upper surface of the apparatus main body and can be used commonly by a plurality of users. 
     Reference numeral  125  denotes a stacker full detection lever which detects that the stacker portion  124  is filled with sheets stacked thereon. When the stacker full detection lever  125  detects that the stacker portion  124  is filled with sheets, a control unit not shown in  FIG. 1  controls so that no image is formed on a sheet until the sheets on the stacker portion  124  are removed. 
     When images are formed on both sides of the sheet, a sheet where a toner image is fixed onto one side (front side) thereof is conveyed toward the reverse rotation roller  123 . After the rear end of the sheet passes through a branch portion  127 , the reverse rotation rollers  121  and  123  are rotated in the reverse direction, so that the sheet is switched back and conveyed to the image forming unit  101  through the re-conveying path  126 . 
     When the sheet is conveyed to the sheet storage portions, the position of the conveying path switching member  120  is switched to the position indicated by the solid lines and the sheet is conveyed to the sheet storage portion  200  through a conveying path  128 . 
     Reference numerals  211  and  212  denote respectively a first switching member and a second switching member for switching a path through which the sheet is conveyed. The positions of the first switching member  211  and the second switching member  212  can be switched between the position indicated by solid lines in  FIG. 1  and the position indicated by dashed lines in  FIG. 1  by an actuator not shown in  FIG. 1 . 
     When the sheet S is conveyed to the first sheet storage portion  201 , the positions of the first switching member  211  and the second switching member  212  are switched to the positions indicated by the solid lines in  FIG. 1  and held. The sheet on which an image is formed passes through the conveying path  128 , a conveying guide  207 , and a conveying guide  208  in this order, and the sheet is further conveyed to the first sheet storage portion  201  by a conveying roller  204  in a face down state, that is, in a state in which the side on which the toner image is formed faces down. 
     When the sheet S is conveyed to the second sheet storage portion  202 , the position of the first switching member  211  is switched to the position indicated by the solid lines in  FIG. 1  and held and the position of the second switching member  212  is switched to the position indicated by the dashed lines in  FIG. 1  and held. The sheet on which an image is formed passes through the conveying path  128 , the conveying guide  207 , and a conveying guide  209  in this order, and the sheet is further conveyed to the second sheet storage portion  202  by a conveying roller  205  in the face down state, that is, in the state in which the side on which the toner image is formed faces down. 
     When the sheet S is conveyed to the third sheet storage portion  203 , the position of the first switching member  211  is switched to the position indicated by the dashed lines in  FIG. 1  and held. The sheet on which an image is formed passes through the conveying path  128  and a conveying guide  210  in this order, and the sheet is further conveyed to the third sheet storage portion  203  by a conveying roller  206  in the face down state, that is, in the state in which the side on which the toner image is formed faces down. 
     Next, a detailed configuration of the sheet storage portions will be described with reference to  FIG. 2 . In the image forming apparatus of the present embodiment, a plurality of sheet storage portions are vertically stacked. Each sheet storage portion has the same configuration, so that here, the configuration of the first sheet storage portion  201  will be described. 
     The sheet conveyed to the first sheet storage portion by the conveying roller  204  is temporarily stacked on a stacking surface  231  and stored. Whether or not sheets are placed on the stacking surface  231  is detected by a sheet presence/absence detection unit not shown in the drawings. Reference numeral  233  denotes a push-out unit that pushes a conveying direction upstream end (rear end) of the stored sheets and pushes out apart of the sheets on the downstream side (front end) from a discharge port  234  to the outside of the apparatus main body  100 . The sheets are pushed out from the discharge port  234  by the push-out unit  233 , so that the user can receive the sheets. In the present embodiment, the length of the stacking surface  231  is set to a length in which the front end of a sheet does not protrude from the discharge port  234  even when a longest sheet that can be stored in the sheet storage portion is stacked. 
     When a sheet is conveyed to the first storage unit  201 , the push-out unit  233  is positioned at a stacking position indicated by solid lines in  FIG. 2  at which the push-out unit  233  does not prevent the sheet from being conveyed and stacked. On the other hand, when push-out unit  233  pushes out the stored sheets, the push-out unit  233  moves toward the discharge port  234  along a sheet discharge direction and moves to a push-out position (sheet discharge position) indicated by dashed lines. 
       FIGS. 3A and 3B  are perspective views of the push-out unit  233 .  FIG. 3A  shows a case in which the push-out unit  233  is located at the stacking position and  FIG. 3B  shows a case in which the push-out unit  233  is located at the push-out position. The push-out unit  233  includes two sheet rear end pressure hooks  233   a  and  233   b  along the sheet width direction in order to prevent the sheets S from being rotated when the sheets S are discharged. The push-out unit  233  pushes out the sheets, the sheet rear end pressure hooks  233   a  and  233   b  push the upstream end of the sheets S to discharge the sheets. The push-out unit  233  is connected to an actuator  239  and the push-out unit  233  reciprocates between the stacking position and the push-out position along the sheet discharge direction when the actuator  239  is driven in a normal direction and a reverse direction. 
       FIG. 4  is a block diagram showing a control unit and a functional configuration of the image forming apparatus shown in  FIGS. 1, 2, 3A, and 3B . 
     The image forming apparatus  100  includes an image forming apparatus control unit  501  as a control unit. The image forming apparatus control unit  501  includes a video controller  502  and an image forming apparatus control CPU  503 . 
     The video controller  502  communicates with an external device  500  such as a host computer and receives print data (including control information such as code data based on a predetermined program language, image data, and the like). Also, the video controller  502  specifies a print condition (paper discharge port and the like) created from the print data to the image forming apparatus control CPU  503  through a serial I/F and issues a print instruction to the image forming apparatus control CPU  503 . Also, the video controller  502  instructs the image forming apparatus control CPU  503  to discharge sheets from the sheet storage portions  200  on the basis of user information inputted from an operation display unit  240  and user information obtained from an ID card by an ID card authentication unit  241 . 
     The image forming apparatus control CPU  503  controls printing according to the print condition received from the video controller  502  as well as detects an error such as a jam of the image forming apparatus  100  on the basis of information from the jam detection sensor  504  and notifies the video controller  502  of the error. The image forming apparatus control CPU  503  controls a sheet conveying mechanism  506  and performs feed conveyance and discharge conveyance of a sheet as well as controls the image forming unit  101  and the fusing unit  103  and performs an image forming operation and a fusing operation on the sheet. The image forming apparatus control CPU  503  controls a sheet storage portion control mechanism  507  including conveying rollers  204  to  206  and conveys the sheet on which an image is formed to a sheet storage portion. The image forming apparatus control CPU  503  controls the sheet push-out unit  233  by an instruction from the video controller  502  and performs control to discharge sheets stored in a sheet storage portion by using information of a connected sheet discharge sensor  505 . 
     Next, an operation of the sheet storage portions will be described with reference to  FIG. 5 . When a user performs a print operation from the external device  500  to the apparatus main body  100 , the user can select whether the sheet is discharged to the stacker portion  124  or the sheet is temporarily stored in a sheet storage portion from the external device. 
     If the user selects that the sheet is stored in a sheet storage portion, the control unit detects a sheet storage portion in which no sheet is stored on the basis of detection results of the sheet presence/absence detection units provided for each sheet storage portion and determines a conveyance destination of the sheet. 
     For example, when the conveyance destination of the sheet is determined to be the first sheet storage portion  201 , the switching member is switched and the sheet is conveyed onto the stacking surface  231  of the first sheet storage portion  201 . 
     Since the control unit has information indicating who&#39;s job is stored in what sheet storage portion, it is possible to select a sheet storage portion in which sheets have been already stored as a storage destination if the job is performed by the same user. The user need not select a sheet storage portion to which a job of the user is stored and a sheet is automatically stored in a sheet storage portion to which the sheet can be stored. 
     In the present embodiment, sheets stored in each sheet storage portion are stored so that the sheets cannot be taken out from the outside of the apparatus main body. The sheets stored in a sheet storage portion are pushed out by the push-out unit by a discharge instruction from a user, so that a discharge operation is started. Examples of the discharge instruction include pressing a discharge operation start button on the operation display unit provided on the apparatus main body, ID card authentication, and issuing a discharge operation start command from an external device connected to the image forming apparatus. Specific methods for issuing the discharge operation start command on an operation unit are as follows: For example, names and personal ID numbers of users who store a job in a sheet storage portion are shown on the operation display unit  240  provided on the apparatus main body  100  shown in  FIG. 6  and a user operates a portion corresponding to the user, so that the user can issue the discharge instruction. Or, when a user is authenticated by using an ID card, an ID card authentication unit  241  is attached to the apparatus main body and ID information is acquired from the ID card authentication unit  241 , so that the sheet discharge instruction can be issued. 
     When the video controller  502  receives the sheet discharge instruction, the video controller  502  issues the sheet discharge instruction to the image forming apparatus control CPU  503  and the image forming apparatus control CPU  503  controls the actuator to move the push-out unit from the stacking position to the push-out position. 
     At this time, information related to users who issued a print instruction of the sheets stored in the sheet storage portions is stored by a storage unit. Since the storage unit stores information indicating who&#39;s job is stored in what sheet storage portion, a user need not recognize the sheet storage portion in which the job of the user is stored and the user can receive his or her job when issuing the sheet discharge instruction. 
     In the first embodiment, each sheet storage portion is provided with an individual actuator that drives the push-out unit of the sheet storage portion. Therefore, even when jobs of the same user are stored in a plurality of sheet storage portions, it is possible to discharge sheets so that the user can receive sheets at the same time by driving each actuator. Hence, even when jobs of the same user are stored in a plurality of sheet storage portions, it is possible to receive sheets from a plurality of sheet storage portions at the same time by displaying one portion that indicates the user on the operation display unit and by only operating the one portion. Similarly, in the method of the ID card authentication, it is possible to receive sheets at the same time from a plurality of sheet storage portions in which sheets corresponding to user information of the ID card are stored. 
     The third sheet storage portion  203  in  FIG. 5  shows a state in which sheets are pushed out and discharged. An upstream end B 1  of a sheet bundle B stacked on the stacking surface  231  is pushed out by the push-out unit  233 . Thereby, the sheet bundle B moves in the downstream direction and passes through the discharge port  236 , and the conveying direction downstream end B 2  of the sheet bundle B is exposed to the outside of the apparatus main body. 
       FIG. 6  shows a perspective view of the apparatus main body  100  at this time. A printed job J of a plurality of users is stacked on the stacker portion  124  and the downstream end B 2  of the sheet bundle B discharged from the third sheet storage portion  203  is exposed from the discharge port  236 . A user can receive the sheet bundle of the user by catching the downstream end B 2  exposed to the outside of the apparatus and pulling out the sheet bundle B. 
     At this time, it is desired that the amount of exposure of the sheet bundle B is set so that the center of gravity of the sheet bundle B does not go beyond the discharge port  236 . This is because if the center of gravity of the sheet bundle B is pushed out to a position beyond the discharge port  236 , the sheet bundle B slips out of the discharge port  236  before the user receives the sheet bundle B. 
     A discharge sensor, which is not shown in the drawings and which functions as a detection unit to detect that a user pulls out the sheet bundle B, is provided near the discharge ports  234  to  236 . When the discharge sensor not shown in the drawings detects that a user pulls out the sheet bundle B, the push-out unit  233  moves from the push-out position to the stacking position. Further, the sheet presence/absence detection unit detects that no sheet is stacked on the sheet storage portion, so that the control unit deletes sheet storage information and the sheet storage portion becomes in a state in which the sheet storage portion can store new sheets. 
     As shown in  FIG. 7A , the sheet storage portions  201  to  203  can integrally rotate around a fulcrum of rotation X. Further, as shown in  FIG. 7B , it is possible to take out a process cartridge  150  after rotating the sheet storage portions. The fulcrum of rotation X is provided on a downstream side of the conveying rollers that conveys a sheet to the sheet storage portions in the sheet conveying direction. 
     In this way, the sheet storage portions  201  to  203  can be integrally opened, so that even when a jam occurs in any one of the sheet storage portions  201  to  203 , the jam can be removed by the same operation. Further, it is not necessary to provide a mechanism for individually opening each of the sheet storage portions  201  to  203 , so that the jam can be removed by a simple configuration. 
     As described above, according to the first embodiment, the sheet storage portions are provided above the image forming unit  101  and below the stacker portion  124 . Therefore, it is possible to arrange the stacker portion  124  and the discharge ports of the sheet storage portions to be near each other. Thus, when a user receives any sheet, the user can receive the sheet without being forced into an unnatural posture. Further, since the stacker portion  124  is disposed on the upper surface of the apparatus, the sheets stacked on the stacker portion can be easily seen and easily taken out. 
     In the first embodiment, a configuration is described in which three sheet storage portions are provided. However, the number of the sheet storage portions is not limited to three. The number of the sheet storage portions and the number of sheets that can be stored in each sheet storage portion may be set according to an environment in which the apparatus main body is used, the number of users who use the apparatus main body, and the specification of the apparatus main body. 
     [Second Embodiment] 
     Next, a second embodiment of the present invention will be described with reference to  FIG. 8 . In the second embodiment, only the direction in which the sheets are discharged from the sheet storage portions is different from that of the first embodiment and the other configuration is the same as that of the first embodiment, so that the description will be appropriately omitted. 
     In the second embodiment, the direction in which the sheet is discharged to the stacker portion  124  by the reverse rotation roller  123  and the direction in which the sheets are discharged from the sheet storage portions by the push-out unit are perpendicular to each other. Accordingly, the direction in which the sheet feed cassette  105  is pulled out and the position of the operation display unit  240  are changed. 
     In the same manner as in the first embodiment, also in the second embodiment, it is possible to arrange the stacker portion  124  and the discharge ports  234  to  236  of the sheet storage portions to be closely near each other. Therefore, when a user receives any sheet, the user can receive the sheet without being forced into an unnatural posture. 
     [Third Embodiment] 
     Next, a third embodiment of the present invention will be described with reference to  FIGS. 9 and 10 . 
     In the third embodiment, there are two sheet storage units  300   a  and  300   b  in each of which three sheet storage portions are piled vertically. The sheet storage units  300   a  and  300   b  have the same configuration. Reference numeral  400  denotes a stacker unit for stacking sheets on the stacker portion  124 . The sheet storage units  300   a  and  300   b  and the stacker unit  400  are removably stacked on a main body unit  130 . 
       FIG. 10  is a diagram showing these units with a vertical gap in between for explaining each connection portion. The upper surface of the main body unit  130  includes positioning holes  131  and  132  to which the sheet storage unit  300   a  or  300   b  or the stacker unit  400  is connected. Also, the upper surface of the main body unit  130  includes a drawer connector  133 . Positioning pins  134  and  135  and a drawer connector  136  are provided on the lower surface of the sheet storage units  300   a  and  300   b.    
     When the positioning pins  134  and  135  are inserted into the positioning holes  131  and  132 , the main body unit  130  and the sheet storage units  300   a  and  300   b  are positioned relative to each other. At this time, the drawer connectors  133  and  136  are connected to each other. The drawer connectors include a signal line, a power line, and a ground line, so that the drawer connectors can transmit signals and supply electric power. 
     Similarly, positioning holes  131  and  132  and a drawer connector  133  are provided on the upper surface of sheet storage units  300   a  and  300   b  and positioning pins  134  and  135  and a drawer connector  136  are provided on the lower surface of the stacker unit  400 . 
     The main body unit  130  includes a sheet conveying path  140  through which a sheet on which an image is formed is conveyed to the sheet storage unit or the stacker unit. The sheet on which an image is formed is conveyed vertically from the upper surface of the main body unit  130 . 
     In this way, the sheet storage units and the stacker unit are removably stacked, so that the number of the sheet storage units attached to the apparatus main body  100  can be changed according to an operating environment. For example, the following change can be made: When the apparatus main body  100  is shared by several users, only one sheet storage unit is mounted, and when the apparatus main body  100  is shared by tens of users, a plurality of sheet storage units are mounted. Further, when the user does not need the sheet storage unit, the stacker unit  400  can be mounted immediately above the apparatus main body  130 . 
     [Fourth Embodiment] 
     Next, a fourth embodiment of the present invention will be described with reference to  FIGS. 11A, 11B, 12A, 12B , and  12 C. In the fourth embodiment, only the configuration of the conveying path through which the sheet on which an image is formed is conveyed and the position at which the switching member is provided are different from those of the first embodiment and the other configuration is the same as that of the first embodiment, so that the description will be appropriately omitted. 
     As shown in  FIGS. 11A and 11B , the conveying path through which the sheet conveyed by the conveying roller  118  passes branches to a first conveying path  40  through which the sheet is conveyed to the reverse rotation roller  123  and to a second conveying path  41  through which the sheet is conveyed to the sheet storage portions. As shown in  FIG. 11A , when the conveying path switching member  42  is located at a first position, the sheet is conveyed to the reverse rotation roller  123 . As shown in  FIG. 11B , when the conveying path switching member  42  is located at a second position, the sheet is conveyed to the sheet storage portions through the second conveying path. The position of the conveying path switching member  42  can be switched between the first position and the second position by an actuator not shown in  FIG. 1 . 
     An operation in which images are formed on both sides of the sheet will be described with reference to  FIGS. 12A, 12B, and 12C . As shown in  FIG. 12A , the position of the conveying path switching member  42  is switched and the preceding sheet S 1  on a first side of which an image is formed is conveyed to the reverse rotation roller  123 . As shown in  FIG. 12B , after the rear end of the sheet S 1  passes through a branch portion R, the reverse rotation rollers  121  and  123  are rotated in the reverse direction, so that the sheet S 1  is switched back and conveyed to the image forming unit  101  through a reverse path  600 . As shown in  FIG. 12C , even when the preceding sheet S 1  is passing through the reverse path  600 , the following sheet S 2  can be conveyed to the sheet storage portions through the second conveying path. 
     Therefore, according to the fourth embodiment, even when the preceding sheet is being conveyed for reverse printing, the following sheet can be conveyed to the sheet storage portions. 
     Although the embodiments of the present invention have been described in detail, the first to the fourth embodiments can be combined with each other and used. 
     [Modified Embodiment] 
     In the first to the fourth embodiments, a configuration is described in which each sheet storage portion has an actuator that drives the push-out unit. However, the number of the actuators can be smaller than that of the sheet storage portions. For example, a drive transmission switching unit that can selectively switch ON/OFF of a drive transmission state of a drive from the actuator may be provided so that a plurality of push-out units can be moved by one actuator. Thereby, the number of the actuators can be reduced. 
     In the first to the fourth embodiments, a configuration is described in which the rear end pressure hooks push out the sheets. However, in the present invention, the configuration of the push-out unit should not be limited to this configuration. For example, a pair of detachable rollers as shown in  FIG. 13  may be used as a push-out unit. When a sheet is conveyed to the sheet storage portion, the rollers are away from each other as shown by a pair of rollers  250 , so that the rollers do not prevent the sheet from being conveyed. When the sheet bundle is discharged, the rollers come into contact with the upper surface and the lower surface of the stored sheets, respectively, and nip the sheet bundle as shown by a pair of rollers  251 . Further, the rollers rotate in directions indicated by arrows shown around a pair of rollers  252 , so that the sheets stored in the sheet storage portion are discharged. 
     In the first to the fourth embodiments, a configuration is described in which each sheet storage portion has one discharge port. However, the present invention should not be limited to this. For example, as shown in  FIG. 14 , the sheet storage portions are merged at a merged portion  260  on the downstream side in the conveying direction and the sheet storage portions may have only one shared discharge port  261 . In this case, even when the jobs of a user are separately stored in a plurality of sheet storage portions, the user can receive the plurality of jobs of the user as one sheet bundle by driving the push-out units of the plurality of sheet storage portions at the same time. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     REFERENCE SIGNS LIST 
       100  Image forming apparatus main body 
       101  Image forming unit 
       124  Stacker unit 
       201  First sheet storage portion 
       202  Second sheet storage portion 
       203  Third sheet storage portion 
       204  Conveying roller 
       205  Conveying roller 
       206  Conveying roller 
       234  Discharge port 
       235  Discharge port 
       236  Discharge port 
       233  Push-out unit 
     B Sheet bundle 
     X Fulcrum of rotation