Patent Publication Number: US-7722034-B2

Title: Sheet discharge tray, as well as sheet conveying apparatus, image forming apparatus, and image reading apparatus having the sheet discharge tray

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a sheet discharge tray, and more particularly to a sheet discharge tray that stacks sheets such as originals, printing paper, or plastic sheets discharged from a sheet conveying apparatus that conveys sheets and is provided in an image forming apparatus, such as a copying machine or a printer, an image reading apparatus, such as a sheet feed scanner, etc., as well as a sheet conveying apparatus, a image forming apparatus, and an image reading apparatus having the sheet discharge tray. 
   2. Description of the Related Art 
   A sheet conveying apparatus that conveys sheets is provided in an image forming apparatus, such as a copying machine or a printer, and an image reading apparatus, such as a sheet feed scanner. This kind of sheet conveying apparatus discharges conveyed sheets onto the stacking surface of a sheet discharge tray provided in the image forming apparatus or the image reading apparatus. Some sheet discharge trays are provided with an extension tray, described later using  FIG. 9 , in order to stack large size sheets that are discharged from the sheet conveying apparatus (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2004-010220 ( FIG. 2 )). 
     FIG. 9  is a side view showing schematic configuration of a conventional sheet discharge tray. 
   In  FIG. 9 , a sheet discharge tray  10  comprises a plate-shaped member  11  on which a stacking surface  11   a  is formed for stacking sheets discharged from sheet discharge section  20  of a sheet conveying apparatus, an extension tray  12  comprising a plate-shaped member, on which an extension stacking surface  12   a  is formed, that is capable of face-to-face superposition with the stacking surface  11   a , and a pivot  13  that is provided between the plate-shaped member  11  and the extension tray  12 . The pivot  13  is provided in proximity to the end of the stacking surface  11   a  in the discharging direction. The plate-shaped member  11  rotatably supports the extension tray  12  via the pivot  13 . 
   The extension tray  12  arrives at a housing position (not shown) by being rotated in the direction of an arrow D shown in  FIG. 9 . At the housing position, the extension stacking surface  12   a  of the extension tray  12  is opposite to the stacking surface  11   a  of the plate-shaped member  11 . When the extension tray  12  is in the housing position, a sheet of a size that is smaller than the length in the discharging direction of the stacking surface  11   a , such as a business card or a postcard, can be stacked on the surface opposite to the extension stacking surface  12   a  of the extension tray  12 , i.e. the rear surface. In contrast, when stacking sheets that are longer than the length in the discharging direction of the stacking surface  11   a , the extension tray  12  is rotated in the opposite direction to the arrow D to reach the extension position shown in  FIG. 9 . 
   According to the sheet discharge tray  10  shown in  FIG. 9 , the length of the stacking surface of the sheet discharge tray  10  can be changed depending on the size of the sheets to be discharged from the sheet discharge section  20  of the sheet conveying apparatus. 
   As described later using  FIG. 10 , a sheet discharge tray that stacks sheets discharged from a sheet conveying apparatus while aligning the sheets has also been proposed (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 10-109807 ( FIG. 1 )). 
     FIG. 10  is a side view showing schematic configuration of another conventional sheet conveying apparatus in which a sheet discharge section is provided. 
   A sheet discharge tray  30  that is connected to a sheet conveying apparatus  300  as shown in  FIG. 10  comprises a base  31  on which are formed a sloping surface  31   a  and a horizontal surface  31   b  for stacking sheets discharged from sheet discharge section  320  of the sheet conveying apparatus  300 , a first end fence  32  provided at the end in the discharging direction of the base  31 , two ribs  35  that are vertically arranged in parallel in the discharging direction on the upper surface of the base  31 , and a second end fence  33  as a abutment plate that is provided between the two ribs  35 . The second end fence  33  may also be configured to be movable in the discharging direction. 
   According to the sheet discharge tray  30  shown in  FIG. 10 , since the sloping surface  31   a  is formed to become lower as it proceeds towards the end side in the discharging direction, through the force of gravity, the sheets can be stacked so as to collide against either the end fence  32  or the end fence  33  depending on the sheet size. It is therefore possible to reduce misalignment among the discharged sheets in the discharging direction. 
   Further, in a case where the size of the discharged sheets is small, since the inside faces of the ribs  35  contact the sheets before the sheets collide against the end fence  33 , the ribs  35  can function as widthwise regulating plates that reduce misalignment among sheets with regard to the width direction that is orthogonal to the discharging direction. 
   According to the sheet discharge tray  10  shown in  FIG. 9 , an improvement in the discharging direction alignment of sheets can be expected by forming a sloping surface in which the stacking surface  11   a  and the extension stacking surface  12   a  become lower as they approach the sheet discharge section  20 . However, an improvement in the alignment of sheets in the width direction that is orthogonal to the discharging direction can not be expected. It is thus necessary for the user to remove a bundle of sheets that is stacked on the sheet discharge tray  10  and correct the misalignment in the width direction. 
   Further, according to the sheet discharge tray  30  shown in  FIG. 10 , an improvement in the discharging direction alignment of discharged sheets can be expected when the user adjust the position in the discharging direction of the second end fence  33  to match the size of discharged sheets. However it is necessary for the user to consume time to adjust the position of the second end fence  33 . Furthermore, according to the sheet discharge tray  30  shown in  FIG. 10 , since a sheet whose width exceeds the space between the two ribs  35  is stacked on the upper surface of the ribs  35 , an improvement in the width direction alignment of such sheets can not be expected. Therefore, when large size sheets are discharged, the user must perform the time consuming work of removing a bundle of sheets that are stacked in a disorderly manner on the sheet discharge tray  30  and then aligning the bundle of sheets. 
   SUMMARY OF THE INVENTION 
   The present invention provides a sheet discharge tray that can improve width direction alignment of discharged sheets of various sizes with a simple structure, and another sheet discharge tray that can improve discharging direction alignment and width direction alignment of discharged sheets of various sizes with a simple structure, as well as a sheet conveying apparatus, a image forming apparatus, and an image reading apparatus having the sheet discharge tray. 
   According to a first aspect of the present invention, there is provided a sheet discharge tray having a stacking surface adapted to stack sheets that are discharged in a discharging direction from a sheet discharge section of a sheet conveying apparatus adapted to convey sheets, comprising at least two ribs which are disposed on the stacking surface and are elongate substantially in the discharging direction, wherein, the at least two ribs are arranged respectively such that a space with respect to a width direction that is orthogonal to the discharging direction between at least a pair of adjacent ribs among the at least two ribs at a discharging direction upstream end portion is narrower than a space with respect to the width direction between the at least a pair of adjacent ribs at a discharging direction downstream end portion. 
   According to a first aspect of the present invention, ribs are disposed on a sheet discharge tray. And a space between at least a pair of adjacent ribs among the ribs at a discharging direction upstream end portion is narrower than a space between the at least two adjacent ribs at a discharging direction downstream end portion. It is thereby possible to improve width direction alignment of discharged sheets with a simple structure. As a result, the time and labor required of a user to align a bundle of sheets that is stacked on the sheet discharge tray can be reduced. 
   According to a second aspect of the present invention, there is provided a sheet discharge tray having a stacking surface adapted to stack sheets that are discharged in a discharging direction from a sheet discharge section of a sheet conveying apparatus adapted to convey sheets, comprising an extension tray comprising a plate-shaped member on which is formed an extension stacking surface for extending the stacking surface in the discharging direction, a pivot adapted to make the extension tray rotatable between a first position at which the extension stacking surface is opposite to the stacking surface and a second position for extending the stacking surface, at least two first ribs which are disposed on the extension stacking surface and are elongate substantially in the discharging direction, and at least two second ribs which are disposed on a surface of the extension tray opposite to the extension stacking surface and are elongate substantially in the discharging direction, wherein, when the extension tray is at the second position, the first ribs are arranged respectively such that an upper end of a discharging direction downstream end portion thereof is higher than an upper end of a discharging direction upstream end portion thereof, whereas, when the extension tray is at the first position, the second ribs are arranged respectively such that an upper end of a discharging direction downstream end portion thereof is higher than an upper end of a discharging direction upstream end portion thereof. 
   According to a second aspect of the present invention, first ribs and second ribs are disposed on an extension tray. It is thereby possible to improve discharging direction alignment and width direction alignment of discharged sheets with a simple structure. As a result, the time and labor required of a user to align a bundle of sheets that is stacked on the sheet discharge tray can be reduced. 
   According to a third aspect of the present invention, there is provided a sheet discharge tray having a stacking surface adapted to stack sheets that are discharged in a discharging direction from a sheet discharge section of a sheet conveying apparatus adapted to convey sheets, comprising an extension tray comprising a plate-shaped member on which is formed an extension stacking surface for extending the stacking surface in the discharging direction, a pivot adapted to make the extension tray rotatable between a first position at which the extension stacking surface is opposite to the stacking surface and a second position for extending the stacking surface, and at least two ribs which are disposed on a surface of the extension tray opposite to the extension stacking surface and are elongate substantially in the discharging direction, wherein, when the extension tray is at the first position, the at least two ribs are arranged respectively such that an upper end of a discharging direction downstream end portion thereof is higher than an upper end of a discharging direction upstream end portion thereof. 
   According to a fourth aspect of the present invention, there is provided a sheet conveying apparatus comprising the sheet discharge tray. 
   According to a fifth aspect of the present invention, there is provided an image reading apparatus comprising the sheet discharge tray. 
   According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising the sheet discharge tray. 
   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 perspective view showing schematic configuration of a sheet discharge section and a stacking section of a scanner comprising a sheet discharge tray according to an embodiment of the present invention. 
       FIG. 2  is a cross-sectional view of the scanner taken on line II-II of  FIG. 1 . 
       FIG. 3A  is a top view of the stacking section of the scanner, and  FIG. 3B  is a top view of its variation. 
       FIG. 4  is a cross-sectional view taken on line IV-IV of  FIG. 1 , showing the state of a sheet that is stacked on the extension tray shown in  FIG. 1  when the extension tray is in a housing position. 
       FIG. 5  is a perspective view showing the state of the stacking section of the scanner when the extension tray shown in  FIG. 1  is extended to the extension position. 
       FIG. 6  is a cross-sectional view of the scanner taken on line VI-VI of  FIG. 5 . 
       FIG. 7  is a top view of the stacking section of the scanner in the state shown in  FIG. 6 . 
       FIG. 8  is a cross-sectional view taken on line VIII-VIII of  FIG. 7 , showing the state of a sheet stacked on the extension tray when the extension tray is extended to the extension position. 
       FIG. 9  is a side view showing schematic configuration of a conventional sheet discharge tray. 
       FIG. 10  is a side view showing schematic configuration of another conventional sheet conveying apparatus in which a sheet discharge section is provided. 
   

   DESCRIPTION OF THE EMBODIMENTS 
   The present invention will now be described in detail with reference to the drawings showing preferred embodiments thereof. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. 
   Hereunder, an embodiment of the present invention is described in detail while referring to the drawings. 
     FIG. 1  is a perspective view showing schematic configuration of a sheet discharge section and a stacking section of a scanner comprising a sheet discharge tray according to an embodiment of the present invention.  FIG. 2  is a cross-sectional view of the scanner taken on line II-II of  FIG. 1 .  FIG. 3A  is a top view of the stacking section of the scanner. 
   In  FIG. 1  and  FIG. 2 , a scanner  100  that reads an image on a sheet being conveyed comprises a sheet feed tray  110  that stacks a sheet bundle consisting of a plurality of sheets, feeding section  120  that feeds sheets while separating the sheets, one by one, from the sheet bundle, conveying section  130  that conveys sheets that are fed from the feeding section  120  along a conveying path, image reading section (not shown) that reads images of sheets being conveyed in the conveying path, sheet discharge section  140  that discharges sheets conveyed by the conveying section  130 , and a sheet discharge tray  150  including a base  151  on which is formed a stacking surface  150   a  that stacks discharged sheets. 
   Next, an image reading operation that is executed by the scanner  100  shown in  FIG. 1  to  FIG. 3A  is described. 
   The feeding section  120  separates sheets, one by one, from a bundle of sheets that is stacked on the sheet feed tray  110  and feeds the separated sheets to the image reading section via the conveying path of the conveying section  130 . At the image reading section, a light source irradiates a light on a sheet that is being conveyed and an image sensor receives light that is reflected from the sheet in question to read an image on the sheet. The image information that is read is conveyed to unshown image processing section. In this connection, a sheet from which the image reading section reads an image may be any kind of original, such as a recording sheet made with an OA sheet, a receipt, or a check. Even in a case where multiple kinds of originals are mixed, as long as the sizes of the originals are substantially the same the alignment of originals according to the present invention is favorable. 
   After the above described image reading operation is performed, the sheets pass through the conveying path of the conveying section  130  and are discharged onto the stacking surface  150   a  by the sheet discharge section  140 . 
   Next, the sheet discharge tray  150  shown in  FIG. 1  to  FIG. 3A  is described in detail. 
   As shown in  FIG. 1  and  FIG. 2 , the stacking surface  150   a  of the sheet discharge tray  150  is a sloping surface which forms a predetermined angle with the horizontal plane so as to one side of the stacking surface  150   a  is lower in the discharging direction than the other side. A discharged bundle of small size sheets are stacked on sloping ribs  162 , described later, and the sloping stacking surface  150   a , such that the trailing ends of the sheets in the discharging direction collide with a wall surface  151   a  that is arranged in a substantially perpendicular direction at an end portion of the base  151  near the sheet discharge section  140  to thereby align the discharged bundle of sheets. As shown in  FIG. 3A , the length in the discharging direction of the sloping surface of the stacking surface  150   a  is set to a length that can stack small size sheets such as a business card size sheet S 1  or a postcard size sheet S 2 . It is thus possible to stack small size sheets on the stacking surface  150   a  and the ribs  162  even without extending the extension tray  160  to the extension position. 
   The sheet discharge tray  150  includes an extension tray  160  on which an extension stacking surface  160   a  is formed for extending the stacking surface  150   a , and a pivot  155  that is provided between the stacking surface  150   a  and the extension stacking surface  160   a . The pivot  155  is provided near the end of the stacking surface  150   a  in the discharging direction. The base  151  of the sheet discharge tray  150  rotatably supports the extension tray  160  via the pivot  155 . 
     FIG. 1  to  FIG. 3A  show the sheet discharge tray  150  in a stored state in which the extension tray  160  is rotated to reach a housing position at which the stacking surface  150   a  is opposite to the extension stacking surface  160   a . At this time, a stacking surface  160   b  that is the rear side of the extension stacking surface  160   a  of the extension tray  160  forms a substantially complementary shape to the stacking surface  150   a  and serves as a substitute for at least one portion of the stacking surface  150   a  (see  FIG. 1  and  FIG. 3A ). Further, the length in the discharging direction of the extension stacking surface  160   a  and the stacking surface  160   b  is substantially equal to the length in the discharging direction of the stacking surface  150   a.    
   The extension tray  160  comprises a base  161  and two ribs  162  that are disposed on the stacking surface  160   b  of the base  161 . 
   Although according to the present embodiment the ribs  162  are formed in a shape that is substantially triangular when viewed from the side, the shape of the ribs is not limited thereto. A feature of the present invention is that the height of the upper end of the ribs  162  is arranged to be lower at the end portion near the sheet discharge section  140  (upstream side in the discharging direction) than the height at the discharging direction downstream end portion. Thus, discharged sheets are moved towards the sheet discharge section  140  on the base  151  along the sloping surface of the upper end of the ribs  162  by the force of gravity. Then the trailing ends of the sheets stacked on the ribs  162  collide with the wall surface  151   a  to thereby align the discharged sheets. As a result, in comparison to a case of extending the extension tray  160  to stack discharged sheets on the stacking surface  150   a , particularly for small size sheets it is possible to more surely prevent discharged sheets from being scattered in the discharging direction on the stacking surface  150   a . Thus, the discharging direction alignment of discharged sheets can be improved. 
   Further, as shown in  FIG. 1  and  FIG. 3A , the two ribs  162  are arranged in a substantially divergent layout on the stacking surface  160   b . More specifically, the space between the two ribs  162  at the end portion near the sheet discharge section  140  is narrower than the space at the discharging direction downstream end portion with respect to the width direction that is orthogonal to the discharging direction. As a result, as shown by the region A in  FIG. 4 , when the extension tray  160  is in the housing position, depending on the space between the two ribs  162 , a deflection occurs at the center part in the width direction of a sheet S that is stacked on the top of the stacking surface  150   a  and also on the top surface of the ribs  162 . The deflection deformation volume differs with regard to the discharging direction. More specifically, the deflection is noticeably larger at the leading end in the discharging direction of the sheet S than at the trailing end thereof. Such difference in the deflection deformation volume is assured by the fact that the angle formed between the upper end of the ribs  162  and the horizontal plane is greater than the angle formed between the stacking surface  150   a  and the horizontal plane. Because of this deflection, scattering of sheets in the width direction is controlled by the upper end of the ribs  162  at the leading ends of the sheets in the discharging direction in particular. Further, the two side edges of the sheets move toward the center of the sheets because of the deflection. As a result, the width direction alignment of discharged sheets can be improved. It is therefore possible to reduce the time and labor required of a user to align the sides of a bundle of sheets that are stacked on the sheet discharge tray. Further, since the aforementioned deflection reduces the area of contact portion of a discharging sheet at which a discharging sheet contacts with a sheet that is already stacked on the sheet discharge tray  150 , the friction force that acts between these sheets decreases. Consequently, it is also possible to prevent deterioration in alignment caused by push-out of a sheet that is already stacked. 
   As described above, the discharging direction alignment of sheets is ensured by the sheets colliding with the wall surface  151   a  of the base  151 . 
   It is therefore possible to omit the installation of the end fence  33  as an abutment plate and the ribs  35  as widthwise regulating plates shown in  FIG. 10 . 
   Next, the stacking of sheets when the extension tray  160  is in the extension position is described. 
   When a sheet to be discharged from the sheet discharge section  140  has a larger size than the aforementioned sheets S 1 , and S 2 , for example, a B4 size or A3 size sheet S 3 , is to be stacked on the stacking surface  150   a , the extension tray  160  is rotated in the direction indicated by the arrow B shown in  FIG. 6 , described later, to place the extension tray  160  in the extension position. As a result, an extended stacking surface is formed that includes the stacking surface  150   a  and the extension stacking surface  160   a.    
     FIG. 5  is a perspective view showing the state of the stacking section of the scanner  100  when the extension tray  160  is extended to the extension position.  FIG. 6  is a cross-sectional view of the scanner  100  taken on line VI-VI of  FIG. 5 .  FIG. 7  is a top view of the stacking section of the scanner  100  in the state shown in  FIG. 6 . 
   As shown in  FIG. 5  to  FIG. 7 , two ribs  163  that are disposed on the extension stacking surface  160   a  of the base  161  are also provided on the extension tray  160 . These ribs  163  can be stored in slits  153  that are formed in the stacking surface  150   a  of the base  151 . 
   Although according to the present embodiment the ribs  163  are formed in a shape that is substantially triangular when viewed from the side, the shape of the ribs is not limited thereto. A feature of the present invention is that the height of the upper end of the ribs  163  is arranged to be lower at the end portion near the sheet discharge section  140  than the height at the discharging direction downstream end portion. Thus, discharged large size sheets S 3  are moved towards the sheet discharge section  140  on the base  151  along the sloping surface of the upper end of the ribs  163  by the force of gravity. And the trailing ends of the sheets stacked on the stacking surface  150   a , the extension stacking surface  160   a , and the ribs  163  collide against the wall surface  151   a  to thereby align the sheets. It is therefore possible to more surely prevent the sheets S 3  on the stacking surface  150   a  and the extension stacking surface  160   a  from being scattered in the discharging direction. Thus the discharging direction alignment of discharged sheets S 3  can be improved. Further, since an angle formed between the upper end of the ribs  163  and the horizontal plane is greater than an angle formed between the stacking surface  150   a  and the horizontal plane, a returning force applied to the leading end portion of a sheet is greater than a returning force applied to the trailing end portion of the sheet. Consequently, excellent sheet alignment is achieved by colliding the trailing ends of sheets against the wall surface  151   a.    
   In this connection, the larger the angular difference between the extension stacking surface  160   a  and the horizontal plane becomes, the more friction occurs when the leading end of the sheet S 3  contacts the extension stacking surface  160   a . However, with the ribs  163  provided on the extension stacking surface  160   a  the friction acting on the leading end of the sheet S 3  can be reduced by reduction of contact area. Further, because the sheets collide with the ribs  163  and deflect, the rigidity of the leading end portion of the sheets increase, and it is therefore possible to prevent the leading ends from curling up. 
   Preferably, as shown in  FIG. 5  and  FIG. 6 , the extension stacking surface  160   a  can be set to be higher in the vertical direction than at least one portion of the stacking surface  150   a . Further, one portion of the extension stacking surface  160   a  can be set to be higher than the height in the vertical direction of the sheet discharge section  140 . It is thereby possible to surely prevent sheets S 3  from scattering when passing over the top of the extension tray  160 . 
   As shown in  FIG. 5  and  FIG. 7 , the two ribs  163  are disposed to be mutually parallel on the extension stacking surface  160   a . The space between the two ribs  163  is narrower than the width of a large size sheet S 3 , for example the length of the narrow side of an A3 size sheet. It is therefore possible to surely support the sheet S 3  on the top surface of the ribs  163 . As a result, the slits  153  for storing the ribs  163  can be easily formed. 
   Thus, when the extension tray  160  is in the extension position, as shown by a region C in  FIG. 8 , a deflection depending on the space between the two ribs  163  occurs in the center part in the width direction of a sheet S 3  that is stacked on the top surface of the ribs  163  of the extension stacking surface  160   a . The deflection deformation volume differs with respect to the discharging direction. More specifically, the deflection at the leading end in the discharging direction of the sheet S 3  is larger than at the trailing end thereof, because the stacking surface  150   a  where the trailing end of the sheet S 3  is located has no ribs for supporting the sheet S 3 . Thus, scattering of the sheets S 3  in the width direction is controlled by the upper end portions of the ribs  163  at the leading end of the sheets in the discharging direction in particular. Further, the two side edges of the sheets move towards the center of the sheets because of the deflection. As a result, the width direction alignment of the discharged sheets S 3  can be improved. It is therefore possible to reduce the time and labor required of a user to align the sides of a bundle of sheets S 3  stacked on the sheet discharge tray. 
   The discharging direction alignment of the sheets S 3  is also assured by the wall surface  151   a  of the base  151 . 
   It is therefore possible to omit the installation of the end fence  33  as an abutment plate and the ribs  35  as widthwise regulating plates as shown in  FIG. 10 . 
   As described in detail above, according to the present embodiment, respective ribs  162  and  163  are disposed on the sheet stacking surface  160   b  and the extension stacking surface  160   a  of the extension tray  160 . It is thus possible to improve discharging direction alignment and width direction alignment of discharged sheets with a simple configuration. As a result, the time and labor required of a user to align the sides of a bundle of sheets that are stacked on the sheet discharge tray can be reduced. 
   In this connection, in the above described embodiment, the two ribs  162  are arranged in the substantially divergent layout on the stacking surface  160   b  and the two ribs  163  are arranged in a parallel state on the extension stacking surface  160   a . The shape of the ribs  162  and  163  can be changed depending on the size of the extension tray  160  or the size of angles that the stacking surfaces  150   a  and  160   b  and the extension stacking surface  160   a  respectively form with the horizontal plane or the like. For example, when the width of the extension tray  160  is larger than the width of the discharged sheet, the ribs  163  may be arranged in the substantially divergent layout on the extension stacking surface  160   a . Further, the ribs  163  may be arranged in a substantially divergent layout on the extension stacking surface  160   a , and the ribs  162  may be arranged in parallel on the stacking surface  160   b . Both the ribs  162  and the ribs  163  may also include both a substantially parallel portion and a substantially divergent portion. 
   The ribs  162  and  163  may be formed in any shape as long as the shape is one that can be disposed on the base  161 . Further, although the number of ribs is ideally two as in the above described embodiment, the number of ribs may be more than two. In such case, the spaces between the plurality of ribs or an angle that the upper end of each rib forms with the horizontal plane is determined so that the above described effect can be obtained. For example, as shown in  FIG. 3B , a configuration may be adopted in which four ribs  162   a  to  162   d  disposed on stacking surface  160   b  and are elongate substantially in the discharging direction are provided. In this case, the same effect can be obtained by making the space between the two ribs  162   a  and  162   b  near the sheet discharge section  140  narrower than the space between the two ribs  162   c  and  162   d  that are arranged further from the sheet discharge section. The ribs  162   a  and  162   b  need not be parallel, and need not be in the shape of a straight line. Likewise, the ribs  162   c  and  162   d  need not be parallel, and need not be in the shape of a straight line. In such case, the space between the aforementioned ribs is made a space that is determined as an average value. 
   The upper ends of the ribs  162  and  163  are not limited to a flat surface, and may be a curved surface. Although, the upper ends of the ribs  162  and  163  have preferably a linear shape, they need not have a linear shape. In these cases, an angle formed by the upper ends of the ribs  162  and  163  and the horizontal plane is assumed to be an angle that is obtained as an average value. More specifically, the relevant angle is calculated by regarding the upper ends of the ribs  162  and  163  as linear shapes. 
   Although the ribs  162  and  163  can be formed in an integrated condition with respect to the base  161 , the ribs  162  and  163  may be separate members to the base  161 . In this case, the ribs  162  and  163  may be movably disposed on the base  161 . The material comprising the ribs  162  and  163  may be any kind of material, and a material can be preferably used that facilitates sliding of sheets at least on the top surface of the ribs  162  and  163 . 
   Further, the stacking surfaces  150   a  and  160   a  need not be a planar shape. In this case, an angle formed with the horizontal plane is assumed to be an angle that is obtained as an average value in the same manner as described above. 
   Although the sheet discharge tray  150  according to the above described embodiment is provided in an image reading apparatus such as the scanner  100 , it may also be provided in an image forming apparatus such as a copying machine, a printer, or a facsimile machine. Further, the sheet discharge tray  150  according to the present invention may be any kind of device as long as it is capable of stacking sheets that are discharged from the conveying section  130  that conveys sheets. Furthermore, in a case where it is sufficient to make the alignment of small size sheets, only the ribs  162  may be provided, and this configuration is included in the present invention. Furthermore, in a case where extension tray  160  is not provided, ribs  162  may be disposed on stacking surface  150   a , and this configuration is included in the present invention. And when only widthwise alignment is required, the height or the inclination of the upper end of the ribs  162  is not restricted. Those configurations are also included in the present invention. 
   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 modifications, equivalent structures and functions. 
   This application claims priority from Japanese Patent Application No. 2006-249557 filed Sep. 14, 2007, which is hereby incorporated by reference herein in its entirety.