Patent Publication Number: US-2015069697-A1

Title: Sheet stacking apparatus, sheet storage apparatus and image forming apparatus equipped with the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet storage apparatus storing sheets, and to an image forming apparatus equipped with the sheet storage apparatus. 
     2. Description of the Related Art 
     Conventionally, in connection with an image forming apparatus such as a copying machine, there has been discussed a sheet post-processing apparatus which temporarily stores sheets in a sheet storage unit, and then discharges sheets in bundles or stapled sheet bundles. In Japanese Patent Application Laid-Open No. 2008-156089, in order to reliably discharge the sheet bundles by a discharge member configured to push out the sheet bundle, this pushing-out configuration has a claw shape, and on the upper surface of the claw, there is provided an eaves-shaped protrusion so that the sheet bundles do not slip from the discharge member. 
     However, in the case of the configuration discussed in Japanese Patent Application Laid-Open No. 2008-156089, it has been necessary for the sheets to be dropped to a pressing member by their own weight so that the sheets are reliably stacked between a stacking surface and the eaves-shaped portion of the pressing member. For this purpose, it has been necessary to increase the angle of a stacking portion to a nearly right angle (i.e., erect it), resulting in an increase in the height of the discharge sheet post-processing apparatus. On the other hand, recently, there has been a demand for a reduction in the size of image forming apparatuses. In particular, in the case of an image forming apparatus functioning as a multifunction peripheral, since a document reading device needs to be installed at a relatively lower position, there has been a strong demand for a reduction in the height of the image forming apparatus. Thus, there has been a requirement for the sheet post-processing apparatus to be also reduced in height. 
     SUMMARY OF THE INVENTION 
     Thus, the present invention is directed to a sheet storage apparatus capable of reliably discharging sheets while being reduced in height, and to an image forming apparatus equipped with the same. 
     According to an aspect of the present invention, a sheet stacking apparatus includes a sheet stacking unit having: a stacking member on which a sheet conveyed by a conveyance unit is stacked, a contact member configured to contact an end portion of the sheet stacked on the stacking member, a moving unit configured to move the contact member from a standby position to a movement position in order to move the sheet stacked on the stacking member, and a regulating member configured to regulate, at a regulation position, a position of the sheet stacked on the stacking member from above, and to move from the regulation position by being pushed by the sheet conveyed by the conveyance unit, wherein, in a sheet width direction orthogonal to a direction in which the conveyance unit conveys the sheet, the contact member and the regulating member are arranged at different positions, and in a thickness direction of the sheet stacked on the stacking member, an upper surface of the contact member located at the standby position is located above a lower surface of the regulating member located at the regulation position. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a configuration of a sheet storage unit according to a first exemplary embodiment. 
         FIGS. 2A and 2B  are perspective views illustrating a configuration of the sheet storage unit according to the first exemplary embodiment. 
         FIG. 3  is a diagram illustrating a configuration of a discharge unit according to the first exemplary embodiment. 
         FIGS. 4A ,  4 B, and  4 C are enlarged sectional views each illustrating a portion near a conveyance roller pair according to the first exemplary embodiment. 
         FIG. 5  is a diagram illustrating a configuration of an image forming apparatus according to the first exemplary embodiment. 
         FIG. 6  is an external perspective view illustrating the image forming apparatus according to the first exemplary embodiment. 
         FIG. 7  is a sectional view illustrating a configuration of a sheet storage unit according to a second exemplary embodiment. 
         FIG. 8  is a perspective view illustrating a configuration of the sheet storage unit according to the second exemplary embodiment. 
         FIGS. 9A ,  9 B, and  9 C are enlarged sectional views each illustrating a portion near a conveyance roller pair according to the second exemplary embodiment. 
         FIG. 10  is a perspective view illustrating a discharge unit according to a third exemplary embodiment. 
         FIG. 11A ,  11 B, and  11 C are enlarged sectional views each illustrating a portion near a conveyance roller pair according to the third exemplary embodiment. 
         FIGS. 12A ,  12 B, and  12 C are enlarged sectional views each illustrating a portion near a conveyance roller pair according to a fourth exemplary embodiment. 
         FIGS. 13A ,  13 B,  13 C, and  13 D are enlarged sectional views each illustrating a portion near a conveyance roller pair according to a fifth exemplary embodiment. 
         FIGS. 14A and 14B  are diagrams illustrating a modification. 
         FIG. 15  is a block diagram. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following, a first exemplary embodiment to which the present invention is applied will be described in detail with reference to the drawings.  FIG. 5  is a diagram illustrating the configuration of an image forming apparatus  100  equipped with a sheet storage apparatus (stacking apparatus)  200  according to the first exemplary embodiment. As illustrated in  FIG. 5 , the image forming apparatus main body (hereinafter referred to as the apparatus main body) includes an image forming unit  101 , a feeding unit  102  configured to feed sheets S to the image forming unit  101 , a fixing unit  103 , and a sheet discharge unit  104 . Further, mounted to the apparatus main body  100  is the sheet storage apparatus  200  configured to temporarily store sheets S on which images have been formed. 
     The image forming unit  101  includes a photosensitive drum  111  configured to rotate clockwise in  FIG. 5 , an exposure device  113 , and a charging roller  112 , a developing device  114 , and a transfer roller  115 , which are arranged substantially in order in the rotational direction of the photosensitive drum  111 . The image forming unit  101  forms toner images on the sheets S by an electrophotographic image forming process by using these processing devices. 
     Further, the feeding unit  102  feeding the sheets S includes a feeding cassette  105  storing sheets S on which image formation is to be performed, a feeding roller pair  107 , a conveyance guide  109 , and a regulation roller pair  110 . 
     The fixing unit  103  includes a fixing roller  116 , a pressing roller  117  held in contact with the fixing roller  116  from below, and a fixing/discharge roller pair  118 , and is configured to fix the toner images formed on the sheets S by the image forming unit  101 . 
     The sheet discharge unit  104  includes a first switching member  120 , a conveyance roller pair  121 , a discharge guide  122 , a discharge roller pair  123 , and a discharge/stacking portion  124  formed on the upper surface of the apparatus main body  100 . 
     The switching member  120  is switched, by a central processing unit (CPU)  50  ( FIG. 15 ), between a storage position indicated by the solid lines in  FIG. 5  and a discharge position indicated by the broken lines in  FIG. 5 . At the storage position, the sheet S on which image formation is performed is caused to head for the sheet storage apparatus  200 , whereas at the discharge position, the sheet S on which image formation is performed is discharged to the discharge/stacking portion  124 . 
       FIG. 15  is a block diagram illustrating the configuration according to the first exemplary embodiment. As illustrated in  FIG. 15 , the CPU  50  is connected to a read-only memory (ROM) and a random-access memory (RAM). The CPU  50  uses the RAM as work memory, thereby executing a program stored in the ROM. 
     Next, the image forming operation of the apparatus main body  100  will be described. First, when image information is sent to the apparatus main body  100  from an external apparatus (personal computer (PC)) or a network such as a local-area network (LAN), the exposure device  113  emits laser light L according to the image information. This laser light L is emitted to the surface of the photosensitive drum  111 , the surface of which is uniformly charged to a predetermined polarity and electrical potential by the charging roller  112 , and the surface is thus exposed to the laser light L. 
     As a result, the electric charge is removed from the exposed portion of the surface of the photosensitive drum  111 , and an electrostatic latent image is formed on the surface of the photosensitive drum  111 . Then, toner is adhered to the photosensitive drum  111  by the developing device  114 , whereby the electrostatic latent image is visualized as a toner image. The toner image on the photosensitive drum  111  is transferred to a sheet S at a transfer nip portion formed between the photosensitive drum  111  rotating clockwise and the transfer roller  115 . 
     On the other hand, the sheets S supplied to the image forming unit  101  are separated and fed one by one from the feeding cassette  105  by the feeding roller pair  107 , and are conveyed to the registration roller pair  110  along the conveyance guide  109 . At this time, the registration roller pair  110  is at rest, so that the sheet S is temporarily stopped by the registration roller pair  110 . Next, the sheet S temporarily stopped is conveyed to the transfer nip portion by the registration roller pair  110  which starts to rotate in synchronization with the formation of the toner image performed by the image forming unit  101 . 
     The toner image on the photosensitive drum  111  is transferred to the sheet S by the transfer roller  115 . After that, the sheet S to which the toner image has been transferred is conveyed to the fixing unit  103 , and is nipped and conveyed by a fixing nip portion formed between the fixing roller  116  and the pressing roller  117 . Then, the sheet S is heated and pressed, whereby the toner image is fixed to the surface of the sheet S. 
     When discharging and stacking the sheet S onto the discharge/stacking portion  124 , the CPU  50  sets the first switching member  120  to the discharge position (the position indicated by the broken lines) where the sheet S is conveyed toward the discharge roller pair  123 . As a result, the sheet S to which the toner image has been fixed is conveyed along the discharge guide  122  by the conveyance roller pair  121 , and is discharged onto the discharge/stacking portion  124  by the discharge roller pair  123 . 
     On the other hand, when conveying the sheet S to the sheet storage apparatus  200 , the CPU  50  previously switches the first switching member  120  to the storage position indicated by the solid lines in  FIG. 5 . As a result, the sheet S is conveyed from the apparatus main body  100  toward the sheet storage apparatus  200  via a conveyance path  128 . 
     The sheet storage apparatus  200  includes sheet storage units  201  through  203  stacked one upon another. Conveyance roller pairs (conveyance units)  204  through  206  convey the sheets S to the respective sheet storage units  201  through  203 . 
     Further, the sheet storage units  201  through  203  respectively include leading edge regulating members  244  through  246  configured to regulate the downstream ends of the sheets S in the sheet conveyance direction, and discharge ports  234  through  236  for discharging the sheets S stored in the respective sheet storage units  201  through  203  to the exterior. The sheet storage units  201  through  203  further include regulating portions  241  through  243 , respectively, which will be described below. 
     The conveyance destinations of the sheets S are switched by a second switching member  211  and a third switching member  212 , and the sheets S are guided by conveyance guides  207  through  210 , so that the sheets S are conveyed to the respective sheet storage units  201  through  203 . 
     The CPU  50  switches each position of the second switching member  211  and the third switching member  212  between a position indicated by the solid lines and a position indicated by the broken lines in  FIG. 5 , by using an actuator  30  (not illustrated). For example, when conveying the sheet S to the sheet storage unit  201 , the CPU  50  switches the first through third switching members  120 ,  211 , and  212  to their respective positions indicated by the solid lines in  FIG. 5 , and retains them at these positions. As a result, the sheet S passes from the conveyance guide  128 , and subsequently passes through the conveyance guides  207  and  208  in this order, and then, the sheet S is conveyed to the sheet storage unit  201 . 
     Alternatively, when conveying the sheet S to the sheet storage unit  202 , the CPU  50  switches only the third switching member  212  to the position indicated by the broken lines and retains it at that position. As a result, the sheet S passes through the conveyance guides  128 ,  207 , and  209  in this order, and then, the sheet S is conveyed to the sheet storage unit  202 . 
     Next, the configuration of the sheet storage apparatus  200  will be described in more detail. The sheet storage units  202  and  203  have similar configurations to that of the sheet storage unit  201 . Thus, only the sheet storage unit  201  will be described, and the descriptions of the sheet storage units  202  and  203  will be omitted. 
       FIG. 1  is a sectional view illustrating the configuration of the sheet storage apparatus  200 . The sheet storage unit  201  includes a stacking portion  231  where the sheets S conveyed by the conveyance roller pair  204  are stacked. The sheet storage unit  201  further includes a discharge unit  233  for discharging sheets S from the discharge port  234  so that a user can receive the leading edge portions of the sheets S stacked on the stacking portion  231 . The discharge unit  233  has a stacking surface on which sheets S are stacked and two contact portions  233   a  provided in the width direction of the sheets S and configured to contact the upstream edges of the sheets S in the conveyance direction. The width direction of the sheets S means a direction orthogonal to the direction in which the conveyance roller pair  204  conveys the sheets S. 
     The sheet storage unit  201  further includes the regulating portion  241  for pressing the sheets S (regulating the position of the sheets S) stacked on the stacking portion  231  from above. The regulating portion  241  is bent at a bending point, and includes a regulating surface substantially parallel to the stacking portion  231 . 
     The sheet storage unit  201  further includes the leading edge regulating member  244  configured to regulate the leading edges of the sheets S stored in the sheet storage unit  201 . The leading edge regulating member  244  is arranged such that the distance between the conveyance roller pair  204  and the sheet leading edge regulating member  244  is larger than the length of the sheets that are possibly stored. The leading edge regulating member  244  rotates around a rotation fulcrum  244   a  and is reciprocated between a position indicated by the solid lines and a position indicated by the broken lines in  FIG. 1  by the actuator  30  (not illustrated). 
       FIG. 3  is a top view illustrating the sheet storage unit  201  as seen from the perpendicular direction of the stacking portion  231 .  FIG. 3  illustrates only the components necessary for description such as the regulating portions  241 , the discharge unit  233 , and the contact portions  233   a,  with the other components being omitted. For each contact portion  233   a,  there is provided one regulating portion  241  on the outer side in the width direction of the sheets S (the direction orthogonal to the direction in which the contact portion  233   a  moves) and in the vicinity thereof. 
     The discharge unit  233  can be moved in a discharge direction of the sheets S (the direction indicated by an arrow X in  FIGS. 1 and 3 ) from a standby position to a discharge position (movement position) by a moving unit. Next, the moving unit for moving the discharge unit  233  between the standby position and the discharge position will be described with reference to  FIG. 2 . 
       FIGS. 2A and 2B  are perspective views illustrating the upstream side portion of the sheet storage unit  201 .  FIGS. 2A and 2B  each illustrate the conveyance roller pair  204 , a part of the upstream side portion of the stacking portion  231 , the discharge unit  233 , the contact portions  233   a,  and the regulating portions  241 . 
     Referring to  FIG. 2A , the discharge unit  233  is illustrated to be at the standby position where it does not hinder the conveyance and stacking of the sheets S in the sheet storage unit  201 . On the other hand, referring to  FIG. 2B , the discharge unit  233  is illustrated to be at the discharge position where it discharges the stored sheets S. 
     On one side in the width direction of the discharge unit  233 , there is provided a rack  237 . The rack  237  engages with a pinion  238 , and the pinion  238  is connected with a motor (drive source) M 1  ( FIG. 15 ). The CPU  50  causes the motor M 1  to perform normal and reverse rotation drive, whereby the pinion  238  is rotated by the drive force generated by the motor M 1 . As a result, the discharge unit  233  reciprocates between the standby position and the discharge position. When discharging the sheets S, the contact portions  233   a  press the upstream side end portions of the sheets S to discharge the sheets S. 
     Next, the sheet discharge operational sequence and the positional relationship between the components will be described with reference to  FIGS. 4A ,  4 B,  4 C, and  6 .  FIGS. 4A ,  4 B, and  4 C are enlarged views each illustrating a portion of the sheet storage unit  201  near the conveyance roller pair  204 .  FIG. 6  is an external perspective view illustrating the image forming apparatus  100 . 
     First, the arrangement and configuration of the regulating portion  241  will be described. The regulating portion  241  has a flag shape so as to be pushed up by the leading edges of the sheets to be conveyed, and the rotation center (rotation fulcrum)  241   b  thereof is arranged on the upstream side of the conveyance roller pair  204  in the conveyance direction. The above arrangement of the rotation center  241   b  of the regulating portion  241  makes the contact angle between the sheets and the regulating portion  241  when the sheets S raise the regulating portion  241  small (shallow), thereby mitigating the damage to the leading edges of the sheets S. Further, the rotational path of a lowermost surface  241   a  of the regulating portion  241  can be caused to approximate the sheet stacking direction (the vertical direction in  FIGS. 4A ,  4 B, and  4 C), so that, even when the trailing edges of the stacked sheets S are raised, it is possible to easily press them. 
     In  FIG. 4A , the regulating portion  241  is located at a regulating position where it regulates the trailing edges of the sheets S such that they are not raised. At this time, the discharge unit  233  is in a state in which the sheets can be conveyed to the sheet storage unit  201 , that is, at the standby position where it does not hinder the conveyance and stacking of the sheets S. 
     In this state, the regulating portion  241  has a regulation region (a section A-B in  FIG. 4A ) located below an uppermost surface  233   b  of the contact portion  233   a  in the thickness direction (stacking direction) of the sheets S. Further, the standby position of the contact portion  233   a  is located within the regulation region in the conveyance direction of the sheets S. In other words, the contact portion  233   a  and the regulating portion  241  overlap each other in the thickness direction of the sheets S (the vertical direction) (a section OL in  FIG. 4A ). 
     The conveyance roller pair  204  rotates in the direction indicated by an arrow in  FIG. 4B , whereby the sheet S having passed a conveyance guide  261  is conveyed to the sheet storage unit  201 . At this time, as illustrated in  FIG. 4B , the regulating portion  241  is pressed by the sheets S, and retreats upwards as seen in the drawing using the rotation center  241   b  as an axis. On the downstream side of the sheet storage unit  201 , there is provided the leading edge regulating member  244  illustrated in  FIG. 1 . Thus, it is possible to prevent the sheets S conveyed by the conveyance roller pair  204  from protruding, and to prevent the already stored sheets S from being pushed out, so that the sheets S do not protrude from the discharge port  234 . 
     When the user gives a discharge command through an operation display unit  292  ( FIG. 6 ) provided on the apparatus main body, the discharge of the sheets S is started. When discharging the sheets S, the leading edge regulating member  244  is first opened by the actuator (not illustrated) to the position indicated by the broken lines in  FIG. 1 , thereby forming a conveyance path leading to the discharge port  234 . After that, the discharge unit  233  moves from the standby position to the discharge position along the discharge direction. 
     In the present exemplary embodiment, even when the discharge unit  233  is at the discharge position, as illustrated in  FIG. 4C , which is the position where the discharge unit  233  has completed the discharge of the sheets S, the contact portion  233   a  is located within the regulation region of the regulating portion  241  illustrated in  FIG. 4A . 
     When the discharge operation is completed, and the user receives the sheets discharged from the discharge port  234 , a reception detection unit  70  ( FIG. 15 ) recognizes that the user has received the sheets S, and the discharge portion  233  returns to the standby position illustrated in  FIG. 4A . As a result, it is possible to accept the next sheet S. 
     According to the first exemplary embodiment described above, while reducing the height of the apparatus main body, the trailing edges of the sheets S can be prevented from slipping from the discharge unit  233   a  during the discharge operation, causing defective discharge. As a result, the stored sheets S can be reliably discharged. 
     While in the first exemplary embodiment described above, the sheet storage apparatus  200  includes three sheet storage units  201  through  203 , the configuration of the present invention is not limited thereto. For example, the sheet storage unit may be only one. 
     Further, while in the first exemplary embodiment described above, the sheet storage units  201  through  203  are arranged inside the image forming apparatus, the configuration of the present invention is not limited thereto. For example, the sheet storage units may be arranged outside the image forming apparatus. 
     Further, while in the first exemplary embodiment described above, the contact portions  233   a  are moved by the rack  237  and the pinion  238 , the configuration of the present invention is not limited thereto. For example, a member to be engaged with the contact portions  233   a  may be provided on a belt configured to rotate by the drive force generated by a drive source. 
     Next, a second exemplary embodiment will be described with reference to  FIGS. 7 ,  8 ,  9 A,  9 B, and  9 C. In the following description of the second exemplary embodiment, the description of the configuration and operations that are common to the first exemplary embodiment will be omitted as appropriate. The second exemplary embodiment differs from the first exemplary embodiment in that there is provided a sheet guide member  371 . 
       FIG. 7  is a sectional view illustrating a sheet storage unit  201  according to the second exemplary embodiment. The sheet guide member  371  has a guide configuration extending in a discharge direction X of the sheets S in  FIG. 7 . 
       FIG. 8  is a top view illustrating the sheet storage unit  201  as seen from the perpendicular direction of the stacking portion  231 .  FIG. 8  illustrates the regulating portions  241 , the discharge unit  233 , the contact portions  233   a,  and the sheet guide members  371 , which are necessary for the description. The descriptions of the other components are omitted. Each sheet guide member  371  is arranged between the contact portion  233   a  and the regulating portion  241  in the width direction of the sheets S. Further, each sheet guide member  371  extends in the X-direction (the moving direction of the contact portion  233   a ), and the sheet guide member  371  and the regulating portion  241  overlap each other in the X-direction as seen from the direction of  FIG. 7  (the thickness direction of the sheets S). 
     Next, the sheet discharge operational sequence and the positional relationship between the components will be described with reference to  FIGS. 9A ,  9 B, and  9 C. The configurations and operations illustrated in  FIGS. 9A and 9B  are similar to those of the first exemplary embodiment, so the descriptions thereof will be omitted. 
     In the second exemplary embodiment, the moving amount of the contact portion  233   a  in the X-direction can be made larger than that in the first exemplary embodiment. This is because, if the contact portion  233   a  moves to the discharge position, the contact portion  233   a  can overlap the sheet guide member  371 , as illustrated in  FIG. 9C . In this state, the uppermost surface  233   b  of the contact portion  233   a  is above a lowermost surface  371   a  of the sheet guide member  371 . 
     In other words, according to the second exemplary embodiment, the contact portion  233   a  overlaps either the regulating portion  241  or the sheet guide member  371  without fail. 
     Thus, according to the second exemplary embodiment, in addition to the effects described in the first exemplary embodiment, defective discharge can be prevented even if the moving amount of the discharge unit  233  is increased. 
     Next, a third exemplary embodiment will be described with reference to  FIGS. 10 ,  11 A,  11 B, and  11 C. In the following description of the third exemplary embodiment, the description of the configuration and operations that are common to those of the first exemplary embodiment will be omitted as appropriate. The third exemplary embodiment differs from the first exemplary embodiment in that a discharge unit  433  includes an eaves-shaped portion  433   b.    
       FIG. 10  is a perspective view illustrating the upstream side portion of a sheet storage unit  201  according to the third exemplary embodiment. In  FIG. 10 , the sheet stacking portion  231  is omitted.  FIGS. 11A ,  11 B, and  11 C are enlarged views each illustrating a portion near the conveyance roller pair  204  according to the third exemplary embodiment. 
     In the third exemplary embodiment, the eaves-shaped portion  433   b  is formed on the top surface of the discharge unit  433 . 
     Next, the sheet discharge operational sequence and the positional relationship between the components will be described with reference to  FIGS. 11A ,  11 B, and  11 C. The configurations and operations illustrated in  FIGS. 11A and 11B  are similar to those of the first exemplary embodiment, so the descriptions thereof will be omitted. 
     In the third exemplary embodiment, while the discharge unit  433  is discharging the sheets S, a contact portion  433   a  leaves the downstream side end (a portion B in  FIG. 11A ) of the regulating portion  241 . At this time, the trailing edges of the sheets S have got under the eaves-shaped portion  433   b.  Even when the discharge unit  433  is at the position (discharge position) where it has completed the discharge of the sheets S, as illustrated in  FIG. 11C , a similar state continues to be maintained. 
     Thus, according to the third exemplary embodiment, in addition to the effects described in the first exemplary embodiment, the moving amount of the discharge unit  433  can be increased without increasing the number of components, so that defective discharge can be prevented. 
     Next, a fourth exemplary embodiment will be described with reference to  FIGS. 12A ,  12 B, and  12 C. In the following description of the fourth exemplary embodiment, the description of the configuration and operations that are common to those of the first exemplary embodiment will be omitted as appropriate. The fourth exemplary embodiment differs from the first exemplary embodiment in the configuration of a regulating portion  541 . 
       FIGS. 12A ,  12 B, and  12 C are enlarged views each illustrating a portion near the conveyance roller pair  204  according to the fourth exemplary embodiment. 
     In the fourth exemplary embodiment, a rotation center  541   b  of the regulating portion  541  is located on the downstream side of the conveyance roller pair  204 . The above arrangement of the rotation center  541   b  causes the rotational path of a lowermost surface  541   a  of the regulating portion  541  to approximate the thickness direction of the sheets S (the vertical direction in  FIGS. 12A ,  12 B, and  12 C), so that even when the trailing edges of the stacked sheets S are raised, it is possible to easily press them. 
     Next, the sheet discharge operational sequence and the positional relationship between the components will be described with reference to  FIGS. 12A ,  12 B, and  12 C. The configurations and operations illustrated in  FIGS. 12A and 12B  are similar to those of the first exemplary embodiment except that the regulating portion  541  rotates around the rotation center  541   b,  so the descriptions thereof will be omitted. 
     Further, in the fourth exemplary embodiment, even when the discharge unit  233  is at the discharge position where it has completed the discharge of the sheets S as illustrated in  FIG. 12C , the contact portion  233   a  is located within the regulation region of the regulating portion  541  illustrated in  FIG. 12A . 
     Thus, according to the fourth exemplary embodiment, in addition to the effects described in the first exemplary embodiment, the moving amount of the sheet discharge unit  233  can be increased without increasing the number of components, so that defective discharge can be prevented. 
     Next, a fifth exemplary embodiment will be described with reference to  FIGS. 13A ,  13 B,  13 C, and  13 D. In the following description of the fifth exemplary embodiment, the description of the configuration and operations that are common to those of the first exemplary embodiment will be omitted as appropriate. The fifth exemplary embodiment differs from the first exemplary embodiment in the arrangement relationship of the regulating portion  241  and the contact portion  233   a  in the conveyance direction (the moving direction of the contact portion  233   a ). 
       FIGS. 13A ,  13 B,  13 C, and  13 D are enlarged views each illustrating a portion near the conveyance roller pair  204  according to the fifth exemplary embodiment. 
     In the fifth exemplary embodiment, when the contact portion  233   a  is at the standby position, the regulating portion  241  and the contact portion  233   a  do not overlap each other. As compared with the arrangement relationship in the first exemplary embodiment, in the fifth exemplary embodiment, the standby position of the contact portion  233   a  is set to be on the upstream side in the conveyance direction. 
     As illustrated in  FIG. 13C , during the movement of the contact portion  233   a  from the standby position to the discharge position, and at a point in time when the contact portion  233   a  comes into contact with the trailing edges of the sheets S, the regulating portion  241  and the contact portion  233   a  overlap each other. In other words, the regulating portion  241  has a regulation region located below the uppermost surface  233   b  of the contact portion  233   a  in the thickness direction of the sheets S. 
     In addition, as illustrated in  FIG. 13D , even when the discharge unit  233  is at the discharge position where it has completed the discharge of the sheets S, the contact portion  233   a  and the regulating portion  241  continue to maintain the overlapped state described above. 
     Thus, according to the fifth exemplary embodiment, in addition to the effects described in the first exemplary embodiment, it is possible to provide a degree of freedom in connection with the standby position of the discharge unit  233 . 
     The first through fifth exemplary embodiments described above may be combined with each other as appropriate. For example, while in the fifth exemplary embodiment, the contact portion  233   a  overlaps the regulating portion  241  even at the discharge position, the configuration of the present invention is not limited thereto. It is also possible to combine the configuration of the fifth exemplary embodiment with the configuration of any of the first through fourth exemplary embodiments. 
     Further, as illustrated in  FIGS. 14A and 14B  as a modification, there may be provided an end portion regulating portion  731  being a stationary member below the conveyance roller pair  204  and on the downstream side of the standby position of the discharge unit  233 . Due to the presence of the end portion regulating portion  731 , it is possible to set the position where the lowermost surface  241   a  of the regulating portion  241  and the contact portion  233   a  overlap each other to be on the upstream side of the end portion regulating portion  731 . Thus, when determining the arrangement (the overlapping position) of the contact portion  233   a  and the regulating portion  241 , there is no need to take into account the variation in the positions of the trailing edges of the sheets S when the sheets S are stored in the sheet storage unit  201 . 
     According to an exemplary embodiment of the present invention, it is possible to provide a sheet storage unit capable of reliably discharging sheets while suppressing an increase in the height of the apparatus main body. 
     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. 
     This application claims the benefit of Japanese Patent Application No. 2013-184932 filed Sep. 6, 2013, which is hereby incorporated by reference herein in its entirety.