Patent Publication Number: US-11377314-B2

Title: Sheet container, sheet feeder, and image forming system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-159438 filed Sep. 2, 2019. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a sheet container, a sheet feeder, and an image forming system. 
     (ii) Related Art 
     Japanese Unexamined Patent Application Publication No. 2016-000653 describes a sheet feeder and an image forming apparatus in which damage to an extension part may be prevented. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to a sheet container in which a connection member for long sheets may be connected while keeping an attached state of a contact part for non-long sheets. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, there is provided a sheet container comprising a housing, a stacking part provided in the housing so that recording sheets are stacked on the stacking part, a contact part to be brought into contact with edges of the recording sheets in a length direction on the stacking part in an attached state in which the contact part is attached into the housing, a connection member connected to the stacking part or the housing and having an extension part longer than the stacking part in the length direction, and a retreater that retreats the contact part in the attached state from the extension part with the connection member connected to the stacking part or the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a front view illustrating an image forming system including a sheet feeder and a sheet container according to an exemplary embodiment; 
         FIG. 2  is a front sectional view illustrating the sheet feeder in which long sheets are stacked on a first extension member according to the exemplary embodiment; 
         FIG. 3  is a front sectional view illustrating the sheet feeder in which non-long sheets are stacked on the first extension member according to the exemplary embodiment; 
         FIG. 4  is a front sectional view illustrating the sheet feeder in which a long-sheet option is not connected and non-long sheets are stacked on a stacking plate according to the exemplary embodiment; 
         FIG. 5  is a perspective view illustrating the first extension member according to the exemplary embodiment; 
         FIG. 6  is a perspective view illustrating the first extension member and a first shutter according to the exemplary embodiment; 
         FIG. 7  is a perspective view illustrating the first extension member and an end guide extending in a vertical direction according to the exemplary embodiment; 
         FIG. 8  is a perspective view illustrating a posture of the end guide that extends in the vertical direction according to the exemplary embodiment; 
         FIG. 9  is a perspective view illustrating a retreated state of the end guide according to the exemplary embodiment; 
         FIG. 10A  is a perspective view illustrating a posture of an end guide that extends in a vertical direction according to a comparative example compared with the exemplary embodiment; 
         FIG. 10B  is a perspective view illustrating a retreated state of the end guide according to the comparative example; 
         FIG. 11  is a front sectional view illustrating Modified Example 1 of the sheet feeder according to the exemplary embodiment; and 
         FIG. 12  is a front sectional view illustrating Modified Example 2 of the sheet feeder according to the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of the present disclosure is described below. In the following description, a direction indicated by an arrow X in the drawings is a width direction and a direction indicated by an arrow Y in the drawings is a height direction. A direction orthogonal to the width direction and the height direction (direction indicated by an arrow Z) is a depth direction. 
     &lt;Structure of Image Forming System&gt; 
     An image forming system  10  according to the exemplary embodiment forms images on sheets P that are examples of a recording sheet. As illustrated in  FIG. 1 , the image forming system  10  includes an image forming apparatus  12 , a sheet feeder  100 , and a sheet container  200 . The image forming apparatus  12  forms images on the sheets P. The sheet feeder  100  transports the sheets P to the image forming apparatus  12 . The sheet container  200  contains the sheets P having images formed by the image forming apparatus  12  and output from the image forming apparatus  12 . The image forming apparatus  12  is an electrophotographic image forming apparatus including an image former that forms images on recording media, and a transporter that transports the sheets P to the image former. The sheet feeder  100  adjoins the image forming apparatus  12 . The sheet container  200  adjoins the image forming apparatus  12  opposite the sheet feeder  100 . The sheet feeder  100  and the sheet container  200  are attached to the image forming apparatus  12  as its options and are put into market individually. The image former of the image forming apparatus  12  is not limited to the one employing the electrophotographic system. The image former may employ various other systems such as an ink jet system, a relief printing system, a planographic printing system, or an intaglio printing system. 
     [Structure of Sheet Feeder] 
     As illustrated in  FIG. 4 , the sheet feeder  100  includes a sheet container  102  that contains the sheets P to be transported to the image forming apparatus  12 , and transporters  104  that transport the sheets P to the image forming apparatus  12 . In this exemplary embodiment, the transporter  104  includes a transport roller pair  104   a  and a separator  104   b  and is arranged in a housing  106  described later. The transporter  104  transports each sheet P to the image forming apparatus  12  in such a manner that the separator  104   b  separates one sheet P from the stacked sheets P and the transport roller pair  104   a  nips and transports the separated sheet P toward the image forming apparatus  12 . The structure of the transporter  104  of the sheet feeder  100  is not limited to the structure described above. 
     [Structure of Sheet Container  102 ] 
     Next, the structure of the sheet container  102  is described. As illustrated in  FIG. 4 , the sheet container  102  includes the housing  106 , an upper tray  106   a , and a lower tray  106   b . The housing  106  has a rectangular parallelepiped shape and extends in the height direction. The upper tray  106   a  and the lower tray  106   b  are provided in the housing  106  and are drawable toward a user. The upper tray  106   a  and the lower tray  106   b  contain non-long sheets PS. The non-long sheet PS is one type of sheet P having a length of 488 [mm] or smaller. 
     The sheet container  102  may contain long sheets PL by attaching an extension option  110  to the upper tray  106   a . The long sheet PL is one type of sheet P longer than the non-long sheet PS. Description is made first about the sheet container  102  without the extension option  110 , and then about the sheet container  102  with the extension option  110 . 
     (Sheet Container without Extension Option) 
     Referring to  FIG. 4 , description is made about the sheet container  102  without the extension option  110 . 
     As illustrated in  FIG. 4 , the upper tray  106   a  includes a stacking plate  108 , an end guide  170 , slide mechanisms  107 , a shutter  140 , and side shutters  150  (not illustrated). 
     (Stacking Plate  108 ) 
     The stacking plate  108  is an example of a stacking part where the non-long sheets PS are stacked, and is a rectangular plate arranged at the bottom of the upper tray  106   a . The stacking plate  108  may ascend or descend relative to the bottom of the upper tray  106   a  by using a lift (not illustrated). Examples of the lift include a wire lift that raises the stacking plate  108  by being coupled to a hoisting mechanism to hoist four wires fixed to four corners of the stacking plate  108 , and lowers the stacking plate  108  by gravity by being decoupled from the hoisting mechanism. 
     The stacking plate  108  has rectangular side cavities (not illustrated) formed on both sides in the depth direction and extending in the height direction. The stacking plate  108  has a rectangular cavity  108   a  formed between the two side cavities and extending in the height direction. As illustrated in  FIG. 4 , the stacking plate  108  has a plurality of threaded holes  108   c  at the top. A first extension member  120  described later is connected to the stacking plate  108  with screws driven into the threaded holes  108   c . In the exemplary embodiment of the present disclosure, the threaded hole  108   c  is an example of a connector to which a connection member is connected in a removable manner, and is also an example of a receptacle to which a raising member is attached in a removable manner. 
     The stacking plate  108  has an opening  108   e  at the top of the cavity  108   a . The cavity  108   a  allows the end guide  170  to move in the width direction by the slide mechanisms  107  described later. 
     The stacking plate  108  has placement parts  108   d  (not illustrated) in the cavity  108   a  so that the shutter  140  described later may be placed. The stacking plate  108  also has placement parts (not illustrated) at the top of each side cavity on both sides in the depth direction so that the side shutter  150  described later may be placed over the side cavity. 
     (End Guide) 
     As illustrated in  FIG. 4 , the end guide  170  is a rectangular parallelepiped member provided in the cavity  108   a  of the stacking plate  108  at the bottom of the upper tray  106   a  and extending in the height direction. The end guide  170  is an example of a contact part to be brought into contact with the edges of the sheets P on the stacking plate  108  opposite the image forming apparatus  12 . The end guide  170  suppresses movement of the sheets P away from the image forming apparatus  12 . The height of the end guide  170  is set so that its upper end is located above the uppermost non-long sheet PS on the stacking plate  108 . 
     (Slide Mechanism) 
     As illustrated in  FIG. 4 , the slide mechanisms  107  are provided at the bottom of the upper tray  106   a  and support the end guide  170  so that the end guide  170  is movable in the width direction. Each slide mechanism  107  includes a rail  107   a  (not illustrated) and a slider  107   b . The rail  107   a  is fixed to the bottom of the upper tray  106   a  and extends in the width direction. The slider  107   b  is fixed to the lower end of the end guide  170  and attached to the rail  107   a  in a slidable manner. The slide mechanism  107  is an example of a keeper that keeps an attached state in which the end guide  170  is attached to the housing  106 . 
     (Shutter) 
     As illustrated in  FIG. 4 , the shutter  140  is arranged in a removable manner on the placement parts  108   d  (not illustrated) over the cavity  108   a  of the stacking plate  108 . The shutter  140  extends or contracts in the width direction when the end guide  170  extending in the height direction is moved in the width direction by the slide mechanism  107 , thereby closing a part of the opening  108   e  near the image forming apparatus  12  with respect to the end guide  170 . 
     (Side Shutter) 
     Each side shutter  150  is arranged in a removable manner on the placement parts over the side cavity of the stacking plate  108  and closes the side cavity. 
     When the shutter  140  and the side shutters  150  are arranged on the stacking plate  108 , the sheets P on the stacking plate  108  are supported by the stacking plate  108 , the shutter  140 , and the side shutters  150  as illustrated in  FIG. 4 . 
     (Lower Tray) 
     The lower tray  106   b  is arranged below the upper tray  106   a  and has a structure similar to that of the upper tray  106   a.    
     The transporters  104  are arranged near the image forming apparatus  12  above the upper tray  106   a  and the lower tray  106   b  in the housing  106 , respectively. A panel  106   e  is provided in a removable manner on a side of the upper tray  106   a  in the housing  106  opposite the image forming apparatus  12 . When the extension option  110  is attached to the sheet container  102 , the panel  106   e  is removed to form an opening  106   c  on the side of the upper tray  106   a . The housing  106  has an openable cover  106   f  that covers the upper tray  106   a  from the top. The panel  106   e  is removed and the cover  106   f  is opened to form a space through which the long sheets PL are stacked on an extended stacking surface  121  described later from the top. 
     As described above, the sheet container  102  has at least the housing  106 , the stacking plate  108 , the threaded holes  108   c , the end guide  170 , and the shutter  140 . 
     (Sheet Container with Extension Option) 
     Next, description is made about the sheet container  102  with the extension option  110 . 
     As illustrated in  FIG. 2 , the extension option  110  includes an extension cover  112 , the first extension member  120 , a second extension member  130 , and an option guide  160 . 
     (Extension Cover) 
     As illustrated in  FIG. 2 , the extension cover  112  is a box-shaped member attached to an outer part of the housing  106  to cover the opening  106   c  of the housing  106 . The extension cover  112  houses a part of a projecting plate  120   b  of the first extension member  120 , which projects outward from the housing  106  through the opening  106   c . The extension cover  112  has an opening  112   a  continuous with the opening  106   c  of the housing  106 , and an opening  112   b  on a side opposite the housing  106 . The extension cover  112  has an openable cover  112   c  that covers the housing part of the extension cover  112  from the top. The cover  112   c  is opened to form a space through which the long sheets PL are stacked on the extended stacking surface  121  from the top. 
     (First Extension Member) 
     As illustrated in  FIG. 5 , the first extension member  120  includes a frame  120   a  and the projecting plate  120   b . The frame  120   a  is rectangular when viewed in the height direction. The projecting plate  120   b  projects from the frame  120   a  and extends away from the image forming apparatus  12 . The projecting plate  120   b  is a flat plate extending along the upper surface of the frame  120   a.    
     The lower end of the frame  120   a  of the first extension member  120  is positioned on the stacking plate  108  of the upper tray  106   a . The frame  120   a  is connected to the stacking plate  108  with screws (not illustrated) driven into the threaded holes  108   c  of the stacking plate  108 . The projecting plate  120   b  projects from the housing  106  through the opening  106   c . Therefore, the upper tray  106   a  is not drawable while the first extension member  120  is connected. In  FIG. 2  and  FIG. 3 , illustration is omitted for the screws and the threaded holes  108   c  that connect the first extension member  120  to the stacking plate  108 . 
     The first extension member  120  has the extended stacking surface  121  defined by the upper end of the frame  120   a  and the projecting plate  120   b . The extended stacking surface  121  is an example of an extension part longer than the stacking plate  108  in the width direction. The first extension member  120  is an example of the connection member having the extended stacking surface  121 . 
     As illustrated in  FIG. 5 , the frame  120   a  has rectangular cavities  120   c  formed on both sides in the depth direction and extending in the height direction. The frame  120   a  has a rectangular cavity  120   d  formed between the two cavities  120   c  and extending in the height direction. The cavities  120   c  are continuous with the side cavities of the stacking plate  108 . The cavity  120   d  is continuous with the cavity  108   a  of the stacking plate  108 . 
     The cavity  120   d  is longer than an upper part  172  of the end guide  170  described later in the width direction. The frame  120   a  has an opening  120   e  at the top of the cavity  120   d . The size of the opening  120   e  is substantially equal to that of the opening  108   e  of the stacking plate  108 . The opening  120   e  allows the end guide  170  to move in the width direction by the slide mechanism  107 . The frame  120   a  has placement parts  120   f  at the top of the cavity  120   d  on both sides in the depth direction so that the shutter  140  may be placed over the cavity  120   d . The frame  120   a  also has placement parts  120   g  at the top of each cavity  120   c  on both sides in the depth direction so that the side shutter  150  may be placed over the cavity  120   c.    
     As illustrated in  FIG. 2 , the projecting plate  120   b  has recesses  120   h  at the top of its end opposite the image forming apparatus  12 . The recesses  120   h  receive two distal ends  136   a  of the second extension member  130  described later. 
     The sheets P are stacked on the extended stacking surface  121  at a position higher than the upper surface of the stacking plate  108  in the height direction. In other words, the first extension member  120  raises the stacking position of the sheets P from the upper surface of the stacking plate  108  to limit the stacking amount of the sheets P in the height direction on the upper tray  106   a  to a smaller amount than in a case where the first extension member  120  is not connected. The first extension member  120  is an example of the raising member that raises the stacking position of the sheets P and is also an example of the connection member described above. The cavity  120   d  is an example of a raising space defined by the raising member. The end guide  170  extending in the height direction projects through the opening  120   e  of the first extension member  120  beyond the extended stacking surface  121  (see  FIG. 3  and  FIG. 7 ). 
     When the stacking plate  108  of the upper tray  106   a  is moved in the height direction by the lift (not illustrated), the first extension member  120  moves together with the stacking plate  108 . 
     (Second Extension Member) 
     As illustrated in  FIG. 2 , the second extension member  130  includes a support  132  and a rectangular plate  134 . The support  132  is attached into the extension cover  112 . The plate  134  is fixed to the support  132  and projects in the width direction through the opening  112   b  of the extension cover  112 . The second extension member  130  further includes a hinge  138  and a rectangular plate  136 . The hinge  138  is provided at an edge of the plate  134  that faces the image forming apparatus  12 . One end of the plate  136  is supported so that the plate  136  turns about the hinge  138 . The height of the upper surface of the plate  134  is set equal to the height of the uppermost non-long sheet PS on the stacking plate  108 . The plate  136  has the two distal ends  136   a  at an end opposite the hinge  138 . The distal ends  136   a  project along the surface of the plate  136 . The two distal ends  136   a  are brought into contact with the bottom surfaces of the recesses  120   h  of the first extension member  120 . The second extension member  130  is removable from the extension cover  112 . 
     When the stacking plate  108  is located at the bottom of the upper tray  106   a  as illustrated in  FIG. 2 , the plate  136  having the distal ends  136   a  in contact with the bottom surfaces of the recesses  120   h  of the first extension member  120  is inclined with respect to the width direction. When the first extension member  120  connected to the stacking plate  108  is moved in the height direction by the lift (not illustrated), the plate  136  in contact with the recesses  120   h  slides along the recesses  120   h  of the moving first extension member  120  to turn about the hinge  138 . When the upper surface of the first extension member  120  is moved by the lift (not illustrated) to a height equal to that of the uppermost non-long sheet PS on the stacking plate  108 , the upper surface of the plate  136  is located at the same height as that of the non-long sheet PS. 
     (Option Guide) 
     As illustrated in  FIG. 2 , the option guide  160  has an L-shape when viewed in the depth direction and is arranged in a removable manner on the first extension member  120  or the second extension member  130 . The option guide  160  is arranged with its side surface including a corner oriented toward the image forming apparatus  12 . The option guide  160  is brought into contact with the edges of the sheets on the first extension member  120  or the second extension member  130  opposite the image forming apparatus  12  to suppress movement of the sheets away from the image forming apparatus  12 . The option guide  160  may be arranged in a removable manner at an arbitrary position on the first extension member  120  or the second extension member  130  by, for example, a magnet plate provided at the bottom of the option guide  160 . 
     (Folding Structure) 
     As illustrated in  FIG. 8 , the end guide  170  is divided into the upper part  172  and a lower part  174  to define a folding structure  190 . The folding structure  190  includes a shaft  192 , a lock mechanism  194 , and a stopper  196 . 
     The lower part  174  has a rectangular parallelepiped body  174   c  extending in the height direction. The height of the body  174   c  is set smaller than the height of the bottom surface of the placement part  120   f  of the first extension member  120  connected to the stacking plate  108 . The body  174   c  has steps  174   a  at its upper end on both sides in the depth direction. The steps  174   a  have stepped surfaces  174   b  relative to the upper surface of the body  174   c . In the exemplary embodiment, the height of the body  174   c  is set larger than the height of the middle part of the end guide  170  in the height direction. 
     As illustrated in  FIG. 8 , the upper part  172  has a rectangular parallelepiped body  172   e  and two projecting plates  172   a . The body  172   e  is arranged above the lower part  174  of the end guide  170  and extends in the height direction. The projecting plates  172   a  projects from both sides of the lower surface of the body  172   e  in the depth direction. The body  172   e  has a rectangular recess  172   c  at the center of a side surface  172   d  opposite the image forming apparatus  12 . Each projecting plate  172   a  is a flat plate extending along the side surface of the body  172   e  and is arranged above the step  174   a  of the lower part  174 . As illustrated in  FIG. 8 , the projecting plate  172   a  has a lower end surface  172   b  and a side surface  172   f  that faces the image forming apparatus  12 . 
     The shaft  192  is arranged through the projecting plates  172   a  of the upper part  172  and the body  174   c  of the lower part  174  in the depth direction and supports the upper part  172  in a turnable manner. 
     The lock mechanism  194  has a known structure inside the end guide  170  to restrain a turn of the upper part  172  about the shaft  192 . The lock mechanism  194  includes a lever  194   a . The lever  194   a  is an example of a manipulator for the folding structure  190  and may be pulled up toward the distal end of the end guide  170  in the recess  172   c . The restraint of the turn of the upper part  172  about the shaft  192  by the lock mechanism  194  is terminated by raising the lever  194   a.    
     The stopper  196  is an example of a regulator that regulates a turnable range of the upper part  172  about the shaft  192 . The stopper  196  includes the projecting plates  172   a  of the upper part  172  and the steps  174   a  of the lower part  174 . 
     When the upper part  172  is in a posture in which the upper part  172  extends in the height direction as illustrated in  FIG. 8  (hereinafter referred to as “upright posture”), the end surfaces  172   b  of the projecting plates  172   a  interfere with the stepped surfaces  174   b  of the steps  174   a . That is, the stopper  196  prevents the upper part  172  in the upright posture from tilting away from the image forming apparatus  12  about the shaft  192 . 
     When the upper part  172  is in a posture in which the upper part  172  turns about the shaft  192  to tilt toward the image forming apparatus  12  and therefore extends in the width direction as illustrated in  FIG. 9  (hereinafter referred to as “horizontal posture”), the stepped surfaces  174   b  of the steps  174   a  interfere with the side surfaces  172   f  of the projecting plates  172   a . Thus, the upper part  172  in the horizontal posture is prevented from tilting toward the lower part  174  about the shaft  192 . In the exemplary embodiment, the stopper  196  regulates the upper part  172  so that the upper part  172  in the upright posture tilts at an angle of 80° or larger and 100° or smaller. 
     The structure of the stopper  196  is not limited to the structure described above. For example, when the upper part  172  is in the upright posture, a thin plate projecting from the side surface  172   d  of the upper part  172  toward the projecting plates  172   a  may interfere with a side surface of the lower part  174  opposite the image forming apparatus  12 . 
     As described above, the end guide  170  may switch the two postures of the upper part  172 , that is, the upright posture (see  FIG. 8 ) and the horizontal posture (see  FIG. 9 ), by using the folding structure  190 . The operation of switching the upper part  172  of the end guide  170  from the upright posture to the horizontal posture is referred to as an operation of “folding the end guide  170 ”. When the end guide  170  switches the two postures, the upper part  172  passes through the opening  120   e.    
     When the upper part  172  is in the folded posture as illustrated in  FIG. 9 , the height of the end guide  170  attached to the bottom of the upper tray  106   a  by the slide mechanism  107  is equal to the height of the lower part  174 . As illustrated in  FIG. 2 , the end guide  170  in this state does not project beyond the extended stacking surface  121  but retracts into the cavity  120   d  of the first extension member  120 . Therefore, the end guide  170  does not interfere with the long sheets PL stacked on the extended stacking surface  121 . In other words, the end guide  170  attached into the housing  106  by the slide mechanism  107  is folded by the folding structure  190  to retreat from the extended stacking surface  121 . The “retreat from the extended stacking surface  121 ” means that the end guide  170  does not interfere with the uppermost long sheet PL on the extended stacking surface  121 . The folding structure  190  may be regarded as an example of a retreater that retreats the end guide  170  in the attached state from the extended stacking surface  121 . When the end guide  170  is retreated from the extended stacking surface  121  by the folding structure  190 , the long sheets PL may be stacked on the extended stacking surface  121  (see  FIG. 2 ). The long sheets PL stacked on the extended stacking surface  121  are brought into contact with the option guide  160  and movement of the long sheets PL away from the image forming apparatus  12  is suppressed. 
     When the first extension member  120  is connected to the stacking plate  108  as illustrated in  FIG. 7 , the end guide  170  extending in the height direction projects through the opening  120   e  of the first extension member  120  beyond the extended stacking surface  121 . At this time, the non-long sheets PS may be stacked on the extended stacking surface  121  (see  FIG. 3 ). The non-long sheets PS stacked on the extended stacking surface  121  are brought into contact with the end guide  170  extending in the height direction and movement of the non-long sheets PS away from the image forming apparatus  12  is suppressed. 
     (Others) 
     When the first extension member  120  is connected to the stacking plate  108 , the shutter  140  and the side shutters  150  are arranged in a removable manner on the placement parts  120   f  and  120   g  of the first extension member  120  as illustrated in  FIG. 6 , respectively. When the shutter  140  and the side shutters  150  are arranged on the first extension member  120 , the sheets P on the extended stacking surface  121  are supported by the first extension member  120 , the shutter  140 , and the side shutters  150  (see  FIG. 2 ). Thus, the sheets P on the extended stacking surface  121  are placed along the width direction. The shutter  140  extends or contracts when the end guide  170  extending in the height direction and projecting beyond the extended stacking surface  121  moves in the width direction, thereby closing a part of the opening  120   e  near the image forming apparatus  12  with respect to the end guide  170 . The shutter  140  is an example of an opening/closing member that opens or closes the opening  120   e.    
     [Structure of Sheet Container  200 ] 
     Next, the structure of the sheet container  200  is described. The structure of the sheet container  200  is similar to that of the sheet container  102  except that the top of the housing  106  and the top of the extension cover  112  in the sheet container  102  are open. The sheet container  200  adjoins the image forming apparatus  12  opposite the sheet feeder  100  while being oriented opposite the sheet container  102  in the width direction. 
     In the following description, comparative examples and comparative apparatuses may be provided in comparison with the exemplary embodiment of the present disclosure. When the components of the image forming system  10  according to the exemplary embodiment of the present disclosure are described, the reference symbols and names of the components are used as they are. 
     The first extension member  120  serves as the connection member having the extended stacking surface  121  and as the raising member that raises the stacking position of the sheets P. In other words, the first extension member  120  has the connection member and the raising member integrated together. 
     The sheet container  102  has the structure in which a part of the projecting plate  120   b  of the first extension member  120  projects outward from the housing  106  through the opening  106   c  of the housing  106  (first structure). That is, the size of the housing  106  of the sheet container  102  depends on the size of the frame  120   a  of the first extension member  120 . The size of a housing of a sheet container having the projecting plate  120   b  inside the housing (first comparative apparatus) depends on the size of the first extension member  120  including the projecting plate  120   b . The first comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the folding structure  190  retreats the end guide  170  to a space below the extended stacking surface  121  (second structure). The sheet container  102  having the second structure is compared with a sheet container in which the end guide retreats to a space above the extended stacking surface  121  (second comparative apparatus). The structure of the second comparative apparatus is similar to that of the sheet container  102  except that the end guide of the upper tray  106   a  is attached to a ceiling of the upper tray  106   a  while being inverted compared with the end guide  170  of the exemplary embodiment. In the second comparative apparatus, the maximum stacking amount of the sheets P in the height direction on the extended stacking surface  121  is limited by a space from the extended stacking surface  121  to the end guide because the end guide retreats to the space above the extended stacking surface  121 . In the sheet container  102  having the second structure, the maximum stacking amount of the sheets P in the height direction on the extended stacking surface  121  is not limited by the space from the extended stacking surface  121  to the end guide. The second comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the end guide  170  retreats from the extended stacking surface  121  to the cavity  120   d  of the first extension member  120  (third structure). The sheet container  102  having the third structure is compared with a sheet container in which the end guide  170  retreats to a space provided on a side of the first extension member  120  (third comparative apparatus). The structure of the third comparative apparatus is similar to that of the sheet container  102  except that the end guide  170  retreats to that space. In the third comparative apparatus, the size of the housing of the third comparative apparatus depends on the sizes of the first extension member  120  and the space because the space is provided on the side of the first extension member  120 . In the sheet container  102 , the space corresponds to the cavity  120   d  of the first extension member  120  and the size of the housing  106  is smaller than that of the housing of the third comparative apparatus by an amount corresponding to the space. The third comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the upper part  172  extending in the height direction (see  FIG. 8 ) is tilted into the horizontal posture (see  FIG. 9 ) by the folding structure  190  to retreat from the extended stacking surface  121  (fourth structure). The sheet container  102  having the fourth structure is compared with a sheet container including an end guide  570  illustrated in  FIGS. 10A and 10B  (fourth comparative apparatus). The structure of the fourth comparative apparatus is similar to that of the sheet container  102  except that the end guide  570  has a nesting structure as illustrated in  FIGS. 10A and 10B  and retreats from the extended stacking surface  121  by retracting an upper part  572  into a lower part  574 . In the fourth comparative apparatus, the upper part  572  is thinner than the lower part  574  in the width direction and the strength of the upper part  572  is lower than that of the lower part  574  because of the nesting structure of the end guide  570 . In the sheet container  102  having the fourth structure, the upper part  172  is not thinner than the lower part  174  in the width direction and the decrease in the strength is suppressed. The fourth comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The height of the lower part  174  is set larger than the height of the middle part of the end guide  170  in the height direction. That is, the sheet container  102  has the structure in which the upper part  172  positioned above the middle part of the end guide  170  in the height direction tilts in the width direction (fifth structure). The sheet container  102  having the fifth structure is compared with a sheet container including an end guide  170  that retreats from the extended stacking surface  121  by tilting at the root of the lower part  174  (fifth comparative apparatus). The structure of the fifth comparative apparatus is similar to that of the sheet container  102  except that the end guide  170  retreats from the extended stacking surface  121  by tilting at the root of the lower part  174 . In the fifth comparative apparatus, the end guide  170  retreats from the extended stacking surface  121  by tilting at the root of the lower part  174 , that is, tilting in a range from the upper part  172  to the lower part  174 . In the sheet container  102  having the fifth structure, the end guide  170  retreats from the extended stacking surface  121  by tilting the upper part  172  alone. Thus, the movement range of the retreating end guide  170  is narrower in the sheet container  102  than in the fifth comparative apparatus. The fifth comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the upper part  172  of the end guide  170  tilts in the direction in which the upper part  172  is brought into contact with the sheets P (sixth structure). The sheet container  102  having the sixth structure is compared with a sheet container including an end guide  170  that retreats from the extended stacking surface  121  by tilting the upper part  172  in a direction opposite the direction in which the upper part  172  is brought into contact with the sheets P (sixth comparative apparatus). The structure of the sixth comparative apparatus is similar to that of the sheet container  102  except that the end guide  170  retreats from the extended stacking surface  121  by tilting the upper part  172  in the direction opposite the direction in which the upper part  172  is brought into contact with the sheets P, that is, tilting the upper part  172  away from the image forming apparatus  12 . Since the upper part  172  of the sixth comparative apparatus tilts away from the image forming apparatus  12 , the upper part  172  may interfere with the housing  106  when the end guide  170  farthest from the image forming apparatus  12  in the cavity  120   d  retreats. In the sheet container  102  having the sixth structure, the end guide  170  farthest from the image forming apparatus  12  in the cavity  120   d  retreats by tilting the upper part  172  in the direction in which the upper part  172  is brought into contact with the sheets P, that is, in a direction in which the upper part  172  does not interfere with the housing  106 . The sixth comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the end guide  170  retreats by tilting the upper part  172  in the upright posture at the angle of 100° or smaller (seventh structure). The sheet container  102  having the seventh structure is compared with a sheet container in which the upper part  172  of the end guide  170  in the upright posture tilts at an angle larger than 100° (seventh comparative apparatus). The structure of the seventh comparative apparatus is similar to that of the sheet container  102  except that the upper part  172  of the end guide  170  in the upright posture tilts at the angle larger than 100°. In the sheet container  102  having the seventh structure, the tilting motion of the upper part  172  when the end guide  170  retreats is smaller than that in the seventh comparative apparatus. The seventh comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the end guide  170  retreats by tilting the upper part  172  in the upright posture at the angle of 80° or larger (eighth structure). The sheet container  102  having the eighth structure is compared with a sheet container in which the upper part  172  of the end guide  170  in the upright posture tilts at an angle smaller than 80° (eighth comparative apparatus). The structure of the eighth comparative apparatus is similar to that of the sheet container  102  except that the upper part  172  of the end guide  170  in the upright posture tilts at the angle smaller than 80°. The height of the first extension member having the extended stacking surface depends on the height of the retreated end guide  170 . The height of the end guide  170  in which the upper part  172  in the upright posture tilts at the angle of 80° or larger is smaller than the height of the end guide  170  in which the upper part  172  tilts from the lower part  174  at the angle smaller than 80°. In the sheet container  102  having the eighth structure, the height of the first extension member  120  having the extended stacking surface  121  is smaller than the height of the first extension member of the eighth comparative apparatus. The eighth comparative apparatus is encompassed in the technical thought of the exemplary embodiment of the present disclosure as its modified example. 
     The sheet container  102  has the structure in which the extended stacking surface  121  has the opening  120   e  through which the upper part  172  may pass. Thus, even though the extension option  110  is attached to the sheet container  102 , the upper part  172  of the retreated end guide  170  may pass through the opening  120   e  into the upright posture to project beyond the extended stacking surface  121 . The end guide  170  projecting beyond the extended stacking surface  121  and extending in the height direction is brought into contact with the non-long sheets PS stacked on the extended stacking surface  121 . 
     In the sheet container  102 , the opening  120   e  is shaped such that the end guide  170  is allowed to move in the width direction by the slide mechanism  107 . 
     In the sheet container  102 , the cavity  120   d  is formed in the frame  120   a  of the first extension member  120 . In other words, the opening  120   e  at the top of the cavity  120   d  is formed within the range of the stacking plate  108 . 
     The sheet container  102  includes the shutter  140  that opens or closes the opening  120   e  in the extended stacking surface  121  or the opening  108   e  in the stacking plate  108 . When the shutter  140  closes the opening  120   e  or the opening  108   e , the sheets P on the extended stacking surface  121  or the stacking plate  108  are placed along the width direction. 
     The shutter  140  of the sheet container  102  closes a part of the opening  120   e  or the opening  108   e  near the image forming apparatus  12  with respect to the end guide  170  in response to the movement of the end guide  170  in the width direction. In other words, the first shutter  140  closes the opening  120   e  or the opening  108   e  on a side where the end guide  170  is brought into contact with the sheets P. 
     The end guide  170  may switch the two postures, that is, the upright posture (see  FIG. 8 ) and the folded posture (see  FIG. 9 ), by using the folding structure  190 . When the long sheets PL are stacked on the extended stacking surface  121  in the sheet container  102 , the end guide  170  is folded to retreat from the extended stacking surface  121 , thereby bringing the option guide  160  into contact with the long sheets PL. When the non-long sheets PS are stacked on the extended stacking surface  121  in the sheet container  102 , the end guide  170  is extended in the height direction to project beyond the extended stacking surface  121 , thereby bringing the end guide  170  into contact with the non-long sheets PS. 
     In the sheet container  200 , the first extension member  120  is connected to define the extended stacking surface  121  where the long sheets may be stacked. 
     Modified Example 1 
     Next, Modified Example 1 of the exemplary embodiment is described. When the components of the image forming system  10  according to the exemplary embodiment are described in Modified Example 1, the reference symbols and names of the components are used as they are. 
     The sheet container  102  of Modified Example 1 may contain the long sheets PL by attaching an extension option  310  to the upper tray  106   a . The extension option  310  of Modified Example 1 includes the extension cover  112 , a raising member  320   a , a first extension member  320   b , the second extension member  130 , and the option guide  160 . 
     In Modified Example 1, the upper tray  106   a  has threaded holes  106   g  at the bottom (see  FIG. 11 ). The threaded hole  106   g  is an example of a receptacle to which the raising member  320   a  described later is attached. 
     In Modified Example 1, the stacking plate  108  has threaded holes  108   g  at its end opposite the image forming apparatus  12  (see  FIG. 11 ). The threaded hole  108   g  is an example of a connector to which the first extension member  320   b  described later is connected. 
     The raising member  320   a  has the same structure as that of the frame  120   a  of the first extension member  120  according to the exemplary embodiment. The raising member  320   a  is attached to the upper tray  106   a  with screws (not illustrated) driven into the threaded holes  106   g  of the upper tray  106   a . The stacking plate  108  is mounted on the raising member  320   a . In other words, the raising member  320   a  raises the stacking plate  108 . That is, the raising member  320   a  raises the stacking position of the sheets P. Thus, the raising member  320   a  limits the stacking amount of the sheets P in the height direction on the upper tray  106   a  to a smaller amount than in a case where the raising member  320   a  is not connected. 
     The first extension member  320   b  has a shape similar to that of the projecting plate  120   b  of the first extension member  120  according to the exemplary embodiment. The first extension member  320   b  is an example of a connection member having an extended stacking surface  321  and is connected to the stacking plate  108  with screws (not illustrated) driven into the threaded holes  108   g  of the stacking plate  108 . When the first extension member  320   b  is connected to the stacking plate  108 , the upper surface of the first extension member  320   b  extends along the upper surface of the stacking plate  108 . Thus, the upper surface of the first extension member  320   b  and the upper surface of the stacking plate  108  raised by the raising member  320   a  define the extended stacking surface  321  that is an example of the extension part longer than the stacking plate  108  in the width direction. 
     In Modified Example 1, the shutter  140  is arranged on the placement parts  108   d  over the opening  108   e  in the stacking plate  108  raised by the raising member  320   a . In Modified Example 1, each side shutter  150  is arranged on the placement parts over the side cavity in the stacking plate  108  raised by the raising member  320   a.    
     When the raising member  320   a  is attached to the upper tray  106   a  as illustrated in  FIG. 11 , the end guide  170  extending in the height direction projects beyond the extended stacking surface  321  through the opening  108   e  of the stacking plate  108  raised by the raising member  320   a . When the end guide  170  switches the upper part  172  between the upright posture (see  FIG. 8 ) and the folded posture (see  FIG. 9 ) by using the folding structure  190 , the upper part  172  passes through the opening  108   e  longer than the upper part  172 . The end guide  170  is folded by the folding structure  190  to retreat from the extended stacking surface  321 . Thus, the long sheets PL may be stacked on the extended stacking surface  321 . 
     In other respects, the structure of the image forming system of Modified Example 1 is similar to that in the exemplary embodiment. 
     Modified Example 2 
     Next, Modified Example 2 of the exemplary embodiment is described. When the components of the image forming system  10  according to the exemplary embodiment and the components in Modified Example 1 are described in Modified Example 2, the reference symbols and names of the components are used as they are. 
     The sheet container  102  of Modified Example 2 may contain the long sheets PL by attaching an extension option  311  to the upper tray  106   a . The extension option  311  of Modified Example 2 includes the raising member  320   a , a first extension member  330 , and the option guide  160 . 
     In Modified Example 2, the stacking plate  108  is raised by the raising member  320   a  similarly to Modified Example 1. The stacking plate  108  has a recess  108   j  at the end of its upper surface opposite the image forming apparatus  12  (see  FIG. 12 ). The recess  108   j  receives the distal end of a plate  336  of the first extension member  330  described later. 
     In Modified Example 2, the housing  106  has threaded holes  106   j  in its side surface opposite the image forming apparatus  12  (see  FIG. 12 ). The threaded hole  106   j  is an example of a connector to which the first extension member  330  described later is connected. 
     The first extension member  330  includes a support  332 , a plate  334 , the plate  336 , and a hinge  338  similarly to the second extension member  130  according to the exemplary embodiment. The support  332  of the first extension member  330  is connected to the housing  106  with screws (not illustrated) driven into the threaded holes  106   j  of the housing  106 . A distal end  336   a  of the plate  336  of the first extension member  330  that faces the image forming apparatus  12  is brought into contact with the bottom surface of the recess  108   j  of the stacking plate  108  (see  FIG. 12 ). Thus, the upper surfaces of the plates  334  and  336  of the first extension member  330  and the upper surface of the stacking plate  108  raised by the raising member  320   a  define an extended stacking surface  331  that is an example of the extension part longer than the stacking plate  108  in the width direction. 
     When the raising member  320   a  is attached to the upper tray  106   a  as illustrated in  FIG. 12 , the end guide  170  extending in the height direction projects beyond the extended stacking surface  331  through the opening  108   e  of the stacking plate  108  raised by the raising member  320   a . When the end guide  170  switches the upper part  172  between the upright posture (see  FIG. 8 ) and the folded posture (see  FIG. 9 ) by using the folding structure  190 , the upper part  172  passes through the opening  108   e  longer than the upper part  172 . The end guide  170  is folded by the folding structure  190  to retreat from the extended stacking surface  331 . Thus, the long sheets PL may be stacked on the extended stacking surface  331 . 
     In other respects, the structure of the image forming system of Modified Example 2 is similar to that in Modified Example 1. 
     In the exemplary embodiment, the threaded hole is the example of the connector to which the connection member is connected. However, the connector is not limited to the threaded hole. For example, the connector may be a recess formed in the upper surface of the stacking plate  108  and a projection formed on the bottom surface of the frame  120   a  of the first extension member  120  may be fitted into the recess. The connection member may be connected to the connector by a clamp mechanism. The same applies to the receptacle to which the raising member is attached. 
     In Modified Example 1 and Modified Example 2, the threaded hole  106   g  of the housing  106  serves as the receptacle to which the raising member  320   a  is attached. However, the receptacle may be provided at the bottom of the stacking plate  108 . 
     In Modified Example 1, the threaded hole  108   g  of the stacking plate  108  serves as the connector to which the first extension member  320   b  is connected. However, the connector is not limited to the one provided to the stacking plate  108 . For example, the connector may be a threaded hole formed in the side surface of a raising member opposite the image forming apparatus  12 . In this case, the raising member is attached to the upper surface of the stacking plate  108 . 
     In the exemplary embodiment, the folding structure  190  of the end guide  170  serves as the retreater. However, the retreater is not limited to the one provided to the end guide  170 . For example, the retreater may be a retractor that is provided at the bottom of the housing  106  and retracts the end guide  170  to a space below the upper tray  106   a  by lowering the end guide  170  in the height direction. 
     In the exemplary embodiment, the lever  194   a  arranged in the recess  172   c  formed in the side surface  172   d  of the upper part  172  of the end guide  170  serves as the manipulator of the lock mechanism  194 . However, the manipulator of the lock mechanism  194  is not limited to the lever or to the one arranged on the side surface  172   d  of the end guide  170 . For example, the manipulator of the lock mechanism  194  may be a button. Further, the manipulator of the lock mechanism  194  may be arranged at the distal end of the upper part  172  of the end guide  170 . 
     In the exemplary embodiment, the wire lift may be used as the example of the lift that moves the stacking plate  108  in the height direction. However, the lift may be provided on the stacking plate  108 . Specifically, the lift may be legs that are provided on the bottom surface of the stacking plate  108  and extend or contract in the height direction. 
     In the exemplary embodiment, the lower tray  106   b  is arranged below the upper tray  106   a  in the housing  106 . However, the housing  106  need not have the lower tray  106   b.    
     The foregoing description of the exemplary embodiment of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.