Patent Publication Number: US-2010120338-A1

Title: Paper feeding apparatus and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/112,636, filed Nov. 7, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates to, for example, a paper feeding apparatus that feeds a sheet as a recording medium, on which an image is formed, to an image forming apparatus such as a copying machine or a printer. 
     BACKGROUND 
     In recent years, in order to reduce environmental load or reduce an amount of emission of carbon dioxide, image forming apparatuses such as a printer, a copying machine, and a digital multi function peripheral often reuse sheets. Some image forming apparatus in the past receives sheets to be reused from a paper feeding apparatus. The paper feeding apparatus sequentially feeds sheets set by a user to the image forming apparatus. For example, some image forming apparatus reuses sheets on which images are printed with color-fadable inks or toners. The user sets sheets on which images are printed with color-fadable inks or toners in the paper feeding apparatus. The image forming apparatus erases the images on the sheets received from the paper feeding apparatus and reuses the sheets. 
     In the paper feeding apparatus in the past, the user visually checks the state of a sheet to be reused. In other words, the user sets, in the paper feeding apparatus, a sheet that the user considers reusable in the user&#39;s own judgment. However, the user is likely to set a non-reusable sheet in the paper feeding apparatus. For example, the user is likely to set a sheet in the paper feeding apparatus without noticing that remaining dust (e.g., waste of an eraser) adheres to the surface of the sheet. The user is likely to set a sheet in the paper feeding apparatus without noticing that staples enter the paper feeding apparatus together with the sheet. Foreign matters that enter the paper feeding apparatus together with the sheet cause damage to the paper feeding apparatus or the image forming apparatus. A sheet having wrinkles, curls, or the like is highly likely to induce various deficiencies in the paper feeding apparatus or the image forming apparatus. For example, when the paper feeding apparatus feeds the sheet having wrinkles, curls, or the like to the image forming apparatus, a corner of the sheet is folded, a part of an image printed on the sheet is lost, or the wrinkles in the sheet increase. 
     SUMMARY 
     A paper feeding apparatus according to an aspect of the present invention includes: a rack that stores sheets in a vertically placed state; a first conveying roller that conveys a sheet extracted from the rack in a first direction in an erected state; a scraper that scrapes the surface of the sheet conveyed in the erected state by the first conveying roller; and a second conveying roller that conveys the sheet, the surface of which is scraped by the scraper, in a second direction different from the first direction. 
     An image forming apparatus according to another aspect of the present invention includes: a rack that stores sheets in a vertically placed state; a first conveying roller that conveys a sheet extracted from the rack in a first direction in an erected state; a scraper that scrapes the surface of the sheet conveyed in the erected state by the first conveying roller; a second conveying roller that conveys the sheet, the surface of which is scraped by the scraper, in a second direction different from the first direction; and a printer that forms an image on the sheet conveyed by the second conveying roller. 
     An image forming method according to still another aspect of the present invention includes: storing sheets in a rack in a vertically placed state; conveying a sheet extracted from the rack in a first direction in an erected state; scraping the surface of the sheet conveyed in the erected state; conveying the sheet, the surface of which is scraped, in a second direction different from the first direction; and forming an image on the sheet conveyed in the second direction. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a diagram of a configuration example of a digital multi function peripheral; 
         FIG. 2  is a diagram of a configuration example of a collection rack of a paper feeding apparatus; 
         FIG. 3  is a diagram of a configuration example of the collection rack of the paper feeding apparatus; 
         FIG. 4  is a diagram of a paper feeding apparatus according to a first configuration example; 
         FIG. 5  is a diagram of the state of blades until the leading end of a sheet reaches a carry-out roller; 
         FIG. 6  is a diagram of the state of the blades during conveyance of the sheet by the carry-out roller; 
         FIG. 7  is a diagram of a paper feeding apparatus according to a second configuration example;  FIG. 8  is a diagram of a paper feeding apparatus according to a third configuration example; and 
         FIG. 9  is a diagram of a paper feeding apparatus according to a fourth configuration example. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention is explained in detail below with reference to the accompanying drawings. 
     First, the configuration of a digital multi function peripheral  1  as an image forming apparatus is explained. 
       FIG. 1  is a diagram of a configuration example of the digital multi function peripheral  1 . The digital multi function peripheral  1  shown in  FIG. 1  includes a printer  2 , a scanner  3 , and a finisher  4 . The printer  2  forms an image on a sheet. The scanner  3  converts an image of a document into image data. The finisher  4  processes a sheet subjected to image formation. 
     The digital multi function peripheral  1  realizes various functions according to cooperation of the printer  2 , the scanner  3 , and the finisher  4 . For example, the digital multi function peripheral  1  has a copy function for printing, with the printer  2 , an image read by the scanner  3  on a sheet and a finishing function for processing, with the finisher  4 , a sheet on which an image is printed by the printer  2 . 
     In the digital multi function peripheral  1  shown in  FIG. 1 , the printer  2  includes an accumulating unit  10 , an image forming unit  12 , and an erasing unit  18 . In the digital multi function peripheral  1  shown in  FIG. 1 , the finisher  4  includes a paper discharge tray  14  and a paper feeding apparatus  16 . 
     The accumulating unit  10  stores sheets on which images are formed. The accumulating unit  10  includes plural sheet cassettes. The sheet cassettes respectively store sheets classified according to sizes, types, or the like. The sheet cassettes store sheets fed by the paper feeding apparatus  16 . The sheet cassettes pick up plural sheets stored therein one by one and carry out the sheet. The accumulating unit  10  feeds one sheet picked up from a selected sheet cassette to the image forming unit  12 . 
     The image forming unit  12  forms an image on the sheet fed from the accumulating unit  10 . The image forming unit  12  forms an erasable image on the sheet. The image forming unit  12  can be realized by printers of various systems as long as the printers can form images with erasable image forming materials. For example, the image forming unit  12  can be realized by an ink jet printer, a laser printer, or a thermal transfer printer. 
     In  FIG. 1 , a configuration example of a color ink jet printer as the image forming unit  12  is shown. In the configuration example shown in  FIG. 1 , the image forming unit  12  includes a conveying roller pair  21 , a registration roller pair  22 , a driven roller  23 , a driving roller  24 , a conveyor belt  25 , and an ink jet head group  26  ( 26 Y,  26 M,  26 C, and  26 Bk). 
     The conveying roller pair  21  conveys a sheet, which is fed from the accumulating unit  10 , to the registration roller pair  22 . The registration roller pair  22  conveys the sheet onto the conveyor belt  25  at predetermined timing. Tension is applied to the conveyor belt  25  by the driving roller  24  and the driven roller  23 . The conveyor belt  25  is driven according to the rotation of the driving roller  24 . The conveyor belt  25  conveys the sheet while attracting the sheet to the belt with a roller, a fan, or the like. The conveyor belt  25  conveys the sheet on which an image is formed by the ink jet head group  26  to the paper discharge tray  14 . 
     The ink jet head group  26  includes an ink jet head  26 Y, an ink jet head  26 M, an ink jet head  26 C, and an ink jet head  26 Bk. The ink jet heads  26 Y,  26 M,  26 C, and  26 Bk are set in order along the conveyor belt  25 . The ink jet head  26 Y ejects a color-fadable yellow (Y) ink. The ink jet head  26 M ejects a color-fadable magenta (M) ink. The ink jet head  26 C ejects a color-fadable cyan (C) ink. The ink jet head  26 Bk ejects a color-fadable black (Bk) ink. The ink jet heads  26 Y,  26 M,  26 C, and  26 Bk respectively form images of the colors on the sheet. The ink jet heads  26 Y,  26 M, and  26 C respectively eject inks corresponding to a yellow component, a magenta component, and a cyan component in a color image. The ink jet head group  26  prints the images of the colors on the sheets one on top of another to thereby form a color image on the sheet. 
     The image forming unit  12  conveys the sheet on which the image is formed to the paper discharge tray  14  of the finisher  4 . The paper discharge tray  14  of the finisher  4  stores the sheet on which the image is formed by the printer  2 . A user receives, as a print result, the sheet stored in the paper discharge tray  14 . 
     The finisher  4  includes the paper feeding apparatus (a reuse paper collecting apparatus)  16  besides the paper discharge tray  14 . The paper feeding apparatus  16  feeds sheets to be reused to the printer  2 . The paper feeding apparatus  16  includes a collection rack  31  and a conveying mechanism  32 . The collection rack  31  stores the sheets to be reused. The collection rack  31  stores the sheets in an erected state on the bottom surface of the finisher  4 . The conveying mechanism  32  conveys the sheets in the collection rack  31  one by one. The conveying mechanism  32  extracts the sheets in order from one stored in the collection rack  31  earliest. The conveying mechanism  32  conveys the sheet while rectifying the sheet. The conveying mechanism  32  conveys the sheet while removing dust adhering to the sheet. The conveying mechanism  32  feeds the sheet to the printer  2 . 
     The erasing unit  18  of the printer  2  captures the sheet fed by the paper feeding apparatus  16 . The erasing unit  18  includes an erasing mechanism  18   a.  The erasing mechanism  18   a  erases an image formed of an erasable image forming material on the sheet. The erasing mechanism  18   a  has a configuration corresponding to characteristics of image forming materials that should be erased. For example, when the erasing mechanism  18   a  erases an image formed with an ink to be erased by heating, the erasing mechanism  18   a  includes a heating head that heats the sheet. 
     The erasing unit  18  only has to be an erasing unit that erases the image on the sheet fed from the paper feeding apparatus  16  until the sheet reaches the image forming unit  12 . For example, the erasing mechanism  18   a  only has to be set in a place along a path through which the sheet reaches the registration roller pair  22  of the image forming unit  12  in the printer  2 . As an example, the erasing mechanism  18   a  may be set to erase an image on a sheet immediately after the sheet is extracted from the sheet cassette in the accumulating unit  10 . 
     The configuration of the paper feeding apparatus  16  is explained below. 
       FIGS. 2 and 3  are diagrams of configuration examples of the collection rack  31  of the paper feeding apparatus  16 . 
     In the configuration example shown in  FIG. 2 , the finisher  4  includes a hatch  41  on the front surface thereof. The hatch  41  is openable and closable on the front side. When the hatch  41  is opened, the collection rack  31  of the paper feeding apparatus  16  appears. The collection rack  31  includes a moving mechanism  42  that moves from the inside of the finisher  4  to the front side. The user can set sheets to be reused in the collection rack  31  in a state in which the collection rack  31  is drawn out from the inside of the finisher  4  to the front side. 
     In the configuration shown in  FIG. 2 , the user sets reuse sheets in a procedure explained below. 
     The user opens the hatch  41 . In a state in which the hatch  41  is opened, the user draws out the collection rack  31  from the inside of the finisher  4  to the front side. The user sets, in an erected state, sheets to be reused in the collection rack  31  drawn out to the front side. The user pushes the collection rack  31 , in which the reuse sheets are set, into the finisher  4 . The user closes the hatch  41 . 
     In the configuration example shown in  FIG. 3 , the finisher  4  includes a hatch  43  on the left surface. The hatch  43  is openable and closable on the left side. When the hatch  43  is opened, the collection rack  31  of the paper feeding apparatus  16  appears. The collection rack  31  includes a moving mechanism  44  that moves from the inside of the finisher  4  to the left side. The user can set sheets to be reused in the collection rack  31  in a state in which the collection rack  31  is drawn out from the inside of the finisher  4  to the left side. 
     In the configuration shown in  FIG. 3 , the user sets the reuse sheets in a procedure explained below. 
     The user opens the hatch  43  and draws out the collection rack  31  from the inside of the finisher  4  to the left side. The user sets, in an erected state, sheets to be reused in the collection rack  31  drawn out to the left side. The user pushes the collection rack  31 , in which the reuse sheets are set, into the finisher  4  and closes the hatch  43 . 
     The collection rack  31  may be a collection rack that moves to the back or to the right side. For example, in the configuration of the digital multi function peripheral  1  shown in  FIG. 1 , the finisher  4  including the paper feeding apparatus  16  is connected to the left side of the printer  2 . As shown in  FIG. 1 , in the configuration in which the finisher  4  is set on the left side of the printer  2 , it is considered reasonable to move the collection rack  31  to the front side or the left side of the finisher  4  as shown in  FIG. 2  or  3 . 
     A first configuration example of the paper feeding apparatus  16  is explained in detail below. 
       FIG. 4  is a diagram of a paper feeding apparatus  16 A according to the first configuration example. 
     In the first configuration example shown in  FIG. 4 , the paper feeding apparatus  16 A includes the collection rack  31 , a conveying roller pair (a pickup roller)  51 , a conveying roller pair (a carry-out roller)  52 , a blade  53   a,  a blade  53   b,  a conveyance guide plate  54   a,  a conveyance guide plate  54   b,  a conveying roller pair (a stop roller)  55 , a conveying roller pair (a bottom roller)  56 , a guide rib  57 , and a tray  58 . 
     The collection rack  31  has a mechanism (not shown) for pressing sheets stored in an erected state to the pickup roller  51  side. The pickup roller  51  captures one sheet moved to the endmost part of the collection rack  31 . The pickup roller  51  conveys the captured sheet to the carry-out roller  52 . In the configuration example shown in  FIG. 4 , the pickup roller  51  conveys the sheet in an arrow “a” direction. 
     The blades  53   a  and  53   b  function as a scraper that scrapes the surfaces of the sheet. The blades  53   a  and  53   b  function as a cleaning member that cleans the surfaces of the sheet and a rectifying member that rectifies the sheet to a flat state. In the configuration of this embodiment, the blades  53   a  and  53   b  hold a sheet being conveyed between the pickup roller  51  and the carry-out roller  52  to thereby respectively scrape both the surfaces of the sheet. As a result, the blades  53   a  and  53   b  scrape off foreign matters (dust) adhering to the surfaces of the sheet and rectify the state of the sheet. 
     When only one surface of the sheet has to be scraped, any one of the blades  53   a  and  53   b  may be set. As the cleaning member that cleans the surfaces of the sheet, members other than the blades may be used. For example, as the cleaning member, brushes that scrape off foreign matters adhering to the surfaces or sponges that scrape off foreign matters adhering to the surfaces can be applied. As the rectifying member that rectifies the sheet to a flat state, members other than the blades may be used. For example, as the rectifying member, rollers that apply stretching force to the sheet can be applied. 
     The foreign matters scraped off by the blades  53   a  and  53   b  drop with the own weight thereof. The tray  58  functions as a dust box that stores the foreign matters scraped off by the blades  53   a  and  53   b.  The tray  58  only has to store at least the foreign matters scraped off by the blades  53   a  and  53   b.    
     The carry-out roller  52  conveys a part of the sheet that finishes passing through the blades  53   a  and  53   b  to the conveyance guide plates  54   a  and  54   b  side. The conveyance guide plats  54   a  and  54   b  guide the leading end of the sheet conveyed by the carry-out roller  52  to the stop roller  55 . The sheet conveyed by the carry-out roller  52  passes between the conveyance guide plate  54   a  and the conveyance guide plate  54   b.  In the configuration example shown in  FIG. 4 , the carry-out roller  52  and the conveyance guide plates  54   a  and  54   b  convey the sheet in the arrow “a” direction. The stop roller  55  catches the leading end of the sheet guided by the conveyance guide plates  54   a  and  54   b.  When the stop roller  55  catches the leading end of the sheet conveyed by the carry-out roller  52 , the carry-out roller  52  stops the conveyance of the sheet. 
     When the carry-out roller  52  stops the conveyance of the sheet, the bottom roller  56  catches the lower end of the sheet. When the bottom roller  56  catches the lower end of the sheet, the stop roller  55  releases the caught sheet. The bottom roller  56  may catch the lower end of the sheet released by the stop roller  55 . When the stop roller  55  releases the sheet, the bottom roller  56  rotates to convey the sheet in a downward direction. In the configuration example shown in  FIG. 4 , the bottom roller  56  conveys the sheet in an arrow “b” direction. 
     The guide rib  57  guides a conveying direction of the sheet conveyed by the bottom roller  56 . The guide rib  57  is formed by erecting plural tabular members. In the guide rib  57 , the plural tabular members change a conveying direction of a falling sheet. For example, the guide rib  57  guides the sheet to a conveying mechanism in the finisher  4  for feeding the sheet to the printer  2 . 
     The configuration of the blades  53   a  and  53   b  is explained in detail. 
       FIGS. 5 and 6  are diagrams of states of the blades  53   a  and  53   b  corresponding to conveying states of the sheet. In  FIG. 5 , the state of the blades  53   a  and  53   b  until the leading end of the sheet reaches the carry-out roller  52  is shown. In  FIG. 6 , the state of the blades  53   a  and  53   b  during conveyance of the sheet by the carry-out roller  52  is shown. 
     The blades  53   a  and  53   b  have a mechanism (not shown in the figure) for holding the sheet present between the pickup roller  51  and the carry-out roller  52  and releasing the sheet. The state shown in  FIG. 5  is a release state in which the blades  53   a  and  53   b  release the sheet not to prevent the conveyance of the sheet. The state shown in  FIG. 6  is a state in which the blades  53   a  and  53   b  hold the sheet present between the pickup roller  51  and the carry-out roller  52 . The pickup roller  51  and the carry-out roller  52  convey the sheet even if the state in which the blades  53   a  and  53   b  hold the sheet as shown in  FIG. 6  is maintained. 
     Specifically, until the leading end of the sheet conveyed by the pickup roller  51  reaches the carry-out roller  52 , the blades  53   a  and  53   b  are in the release state shown in  FIG. 5  not to prevent the conveyance of the sheet. When the leading end of the sheet conveyed by the pickup roller  51  reaches the carry-out roller  52 , the carry-out roller  52  catches the sheet. When the carry-out roller  52  catches the sheet, as shown in  FIG. 6 , the blades  53   a  and  53   b  hold the sheet present between the pickup roller  51  and the carry-out roller  52 . The pickup roller  51  and the carry-out roller  52  convey the sheet while the blades  53   a  and  53   b  keep holding the sheet. 
     Between the pickup roller  51  and the carry-out roller  52 , the blades  53   a  and  53   b  hold the sheet conveyed thereto to thereby respectively strongly scrape both the surfaces of the sheet. For example, when the blade  53   a  scrapes the front surface of the sheet, the blade  53   b  scrapes the rear surface of the sheet. The blades  53   a  and  53   b  scrape both the surfaces of the sheet being conveyed to thereby scrape off foreign matters adhering to the surfaces of the sheet and rectify wrinkles, curls, or the like of the sheet. 
     In other words, the blades  53   a  and  53   b  have a function as blades that remove foreign matters and a function as levelers that rectify the state of the sheet to a flat state. Specifically, the blades  53   a  and  53   b  refresh the sheet (the reuse sheet) extracted from the collection rack  31 . The sheet refreshed by the blades  53   a  and  53   b  can be expected to prevent deficiencies in the printer  2  and improve the quality of an image to be printed. 
     A second configuration example of the paper feeding apparatus  16  is explained below. 
       FIG. 7  is a diagram of a paper feeding apparatus  16 B according to the second configuration example. 
     In the second configuration example shown in  FIG. 7 , the paper feeding apparatus  16 B includes the collection rack  31 , the conveying roller pair (the pickup roller)  51 , the conveying roller pair (the carry-out roller)  52 , the blade  53   a,  the blade  53   b,  a conveyance guide lattice  64   a,  a conveyance guide lattice  64   b,  the conveying roller pair (the stop roller)  55 , the conveying roller pair (the bottom roller)  56 , and the guide rib  57 . In the paper feeding apparatus  16 B shown in  FIG. 7 , the conveyance guide plates  54   a  and  54   b  in the paper feeding apparatus  16 A shown in  FIG. 4  are replaced with the conveyance guide lattices  64   a  and  64   b.    
     In the paper feeding apparatus  16 B shown in  FIG. 7 , the pickup roller  51  extracts one sheet from the collection rack  31 . The sheet extracted by the pickup roller  51  is conveyed to the carry-out roller  52 . Between the pickup roller  51  and the carry-out roller  52 , the blades  53   a  and  53   b  scrape off foreign matters (dust) adhering to the surfaces of the sheet and rectify the state of the sheet. 
     The carry-out roller  52  conveys the sheet refreshed by the blades  53   a  and  53   b  to the conveyance guide lattices  64   a  and  64   b.  The conveyance guide lattices  64   a  and  64   b  guide the leading end of the sheet conveyed by the carry-out roller  52  to the stop roller  55 . The sheet conveyed by the carry-out roller  52  passes between the conveyance guide lattice  64   a  and the conveyance guide lattice  64   b.  In the configuration example shown in  FIG. 7 , the carry-out roller  52  and the conveyance guide lattices  64   a  and  64   b  convey the sheet in the arrow “a” direction. 
     The conveyance guide lattices  64   a  and  64   b  are formed by lattice cells in which a sheet conveyed by the carry-out roller  52  and a sheet conveyed by the bottom roller  56  are not caught. For example, the conveyance guide lattices  64   a  and  64   b  may be formed by wires extending in the direction of conveyance by the carry-out roller  52  to prevent the sheet conveyed by the carry-out roller  52  from being caught. The lower ends of the conveyance guide lattices  64   a  and  64   b  may be provided above the lower end of the sheet conveyed by the carry-out roller  52  to prevent the falling sheet (the lower end of the sheet) from being caught. Any one of the conveyance guide lattices  64   a  and  64   b  may be replaced with the conveyance guide plate  54   a  or  54   b.    
     When the stop roller  55  catches the leading end of the sheet guided by the conveyance guide lattices  64   a  and  64   b,  the carry-out roller  52  stops the conveyance of the sheet. When the carry-out roller  52  stops the conveyance of the sheet, the bottom roller  56  catches the lower end of the sheet supported by the conveyance guide lattices  64   a  and  64   b  and conveys the sheet in the downward direction. In the configuration example shown in  FIG. 7 , the bottom roller  56  conveys the sheet in the arrow “b” direction. 
     The guide rib  57  guides a conveying direction of the sheet conveyed by the bottom roller  56 . The guide rib  57  changes the conveying direction of the falling sheet with the plural tabular members. Walls do not have to be formed on the sides of the guide rib  57  to smoothly remove dust. 
     A third configuration example of the paper feeding apparatus  16  is explained. 
       FIG. 8  is a diagram of a paper feeding apparatus  16 C according to the third configuration example. 
     In the third configuration example shown in  FIG. 8 , the paper feeding apparatus  16 C includes the collection rack  31 , the conveying roller pair (the pickup roller)  51 , the conveying roller pair (the carry-out roller)  52 , the blade  53   a,  the blade  53   b,  the conveyance guide lattice  64   a,  the conveyance guide plate  54   b,  the conveying roller pair (the stop roller)  55 , an assist roller  71 , the conveying roller pair (the bottom roller)  56 , and the guide rib  57 . In the paper feeding apparatus  16 C shown in  FIG. 8 , the conveyance guide plate  54   a  in the paper feeding apparatus  16 A shown in  FIG. 4  is replaced with the conveyance guide lattice  64   a  and the assist roller  71  is added. 
     In the paper feeding apparatus  16 C shown in  FIG. 8 , the pickup roller  51  extracts one sheet from the collection rack  31 . The sheet extracted by the pickup roller  51  is conveyed to the carry-out roller  52 . Between the pickup roller  51  and the carry-out roller  52 , the blades  53   a  and  53   b  scrape off foreign matters (dust) adhering to the surfaces of the sheet and rectify the state of the sheet. 
     The carry-out roller  52  conveys the sheet refreshed by the blades  53   a  and  53   b  to the conveyance guide lattice  64   a  and the conveyance guide plate  54   b.  The conveyance guide lattice  64   a  and the conveyance guide plate  54   b  guide the leading end of the sheet conveyed by the carry-out roller  52  to the stop roller  55 . In the configuration example shown in  FIG. 8 , the sheet conveyed by the carry-out roller  52  moves in the arrow “a” direction between the conveyance guide lattice  64   a  and the conveyance guide plate  54   b.    
     The conveyance guide lattice  64   a  is formed by lattice cells in which a sheet conveyed by the carry-out roller  52  and a sheet conveyed by the bottom roller  56  are not caught. For example, the conveyance guide lattice  64   a  may be formed by wires extending in the direction of conveyance by the carry-out roller  52  to prevent the sheet conveyed by the carry-out roller  52  from being caught. The lower end of the conveyance guide lattice  64   a  may be provided above the lower end of the sheet conveyed by the carry-out roller  52  to prevent the falling sheet (the lower end of the sheet) from being caught. 
     When the stop roller  55  catches the leading end of the sheet guided by the conveyance guide lattice  64   a  and the conveyance guide plate  54   b,  the carry-out roller  52  stops the conveyance of the sheet. The assist roller  71  conveys the sheet supported by the conveyance guide lattice  64   a  and the conveyance guide plate  54   b  downward. 
     The assist roller  71  includes a driving mechanism  71   b  that presses a conveying roller  71   a  against the sheet from a space of a lattice cell of the conveyance guide lattice  64   a.  While the carry-out roller  52  conveys the sheet (in the example shown in  FIG. 8 , while the carry-out roller  52  conveys the sheet in the arrow “a” direction), the driving mechanism  71   b  of the assist roller  71  prevents the conveying roller  71   a  from coming into contact with the sheet not to hinder the conveyance of the sheet. When the conveyance of the sheet by the carry-out roller  52  is stopped, the assist roller  71  presses the conveying roller  71   a  against the sheet from the space of the lattice cell of the conveyance guide lattice  64   a.  The conveying roller  71   a  pressed against the sheet rotates to convey the sheet downward. The bottom roller  56  catches the sheet conveyed by the conveying roller  71   a  and conveys the sheet downward. In the configuration example shown in  FIG. 8 , the conveying roller  71   a  and the bottom roller  56  convey the sheet in the arrow “b” direction. 
     The assist roller  71  conveys the sheet by holding the sheet between the conveying roller  71   a  and the conveyance guide plate  54   b.  The assist roller  71  assists the downward conveyance of the sheet. A positional relation between the conveyance guide lattice  64   a  and the conveyance guide plate  54   b  may be reversed. In other words, the conveying direction of the sheet conveyed by the carry-out roller  52  may be guided by the conveyance guide plate  54   a  and the conveyance guide lattice  64   b.  When the paper feeding apparatus  16 C includes the conveyance guide plate  54   a  and the conveyance guide lattice  64   b,  the assist roller  71  only has to press the conveying roller  71   a  against the sheet from a space of a lattice cell of the conveyance guide lattice  64   b.    
     A fourth configuration example of the paper feeding apparatus  16  is explained below. 
       FIG. 9  is a diagram of a paper feeding apparatus  16 D according to the fourth configuration example. 
     In the fourth configuration example shown in  FIG. 9 , the paper feeding apparatus  16 D includes an inclined rack  81 , the conveying roller pair (the pickup roller)  51 , the conveying roller pair (the carry-out roller)  52 , the blade  53   a,  the blade  53   b,  the conveyance guide lattice  64   a,  the conveyance guide lattice  64   b,  the conveying roller pair (the stop roller)  55 , the conveying roller pair (the bottom roller)  56 , the guide rib  57 , and the tray  58 . In the paper feeding apparatus  16 D shown in  FIG. 9 , the collection rack  31  of the paper feeding apparatus  16 B shown in  FIG. 7  is replaced with the inclined rack  81 . Detailed explanation of the operation and the like of the components other than the inclined rack  81  in the paper feeding apparatus  16 D shown in  FIG. 9  is omitted. 
     In the paper feeding apparatus  16 D shown in  FIG. 9 , the incline rack  81  stores sheets in the same manner as the collection rack  31  of the paper feeding apparatus  16 A,  16 B, or  16 C. The inclined rack  81  is a modification of the collection rack  31 . The inclined rack  81  stores the sheets in an erected state. The bottom surface (a sheet supporting surface) of the inclined rack  81  is inclined at an angle α to be lower on a sheet extracting side. The user places sheets to be reused from a high side of the inclined rack  81  in the erected state. The sheets stored in the inclined rack  81  move to the lower bottom surface side because of the own weight of the sheets. In the inclined rack  81 , the stored sheets tend to move to the sheet extracting side. 
     As explained above, the paper feeding apparatuses according to this embodiment have the configuration explained below. 
     The blades  53   a  and  53   b  scrape the surface of the sheet conveyed in the erected state. Foreign matters (paper powder, eraser waste, dust, staples, and the like) scraped off by the blades  53   a  and  53   b  drop with the own weight thereof. The tray  58  set below the blades  53   a  and  53   b  catches the foreign matters that drop with the own weight. When the blades  53   a  and  53   b  scrape off the foreign matters, the sheet is in the erected state. Therefore, it is less likely that the foreign matters scraped off by the blades  53   a  and  53   b  adhere to the surfaces of the sheet again. 
     The blades  53   a  and  53   b  scrape off foreign matters adhering to the surfaces of the sheet and apply the stretching force to the sheet. The blades  53   a  and  53   b  also play a role of levelers that apply the stretching force to the sheet to thereby rectify the sheet to flatten wrinkles, curls, or the like. 
     Sheets to be reused are vertically placed in the collection rack  31  or the inclined rack  81  in the paper feeding apparatus  16 . When the sheets are vertically placed in the collection rack  31  or the inclined rack  81 , it is easy to extract the sheets in order from the sheet set earliest (oldest sheet). In other words, first-in and first-out of the reuse sheets can be realized by vertically placing the sheets in the collection rack  31  or the inclined rack  81 . In the configuration for the first-in and first-out of the reuse sheets, it is possible to prevent only specific sheets from being repeatedly used and equalize reuse frequencies of the sheets. 
     The paper feeding apparatus  16  feeds, after refreshing the sheets vertically placed in the collection rack  31  or the inclined rack  81  in the erected state, the sheets to the printer  2  in a laid state by changing a conveying direction. The printer  2  often includes a conveying mechanism that extracts a sheet in the laid state from the cassette and conveys the sheet. Since the paper feeding apparatus  16  feeds the sheet to the printer  2  in the laid state, the paper feeding apparatus  16  can be easily connected to the existing printer  2 . Further, the paper feeding apparatus  16  feeds the refreshed sheet to the printer  2 . Therefore, in the printer  2  connected to the paper feeding apparatus  16 , it can be expected that deficiencies in a conveying system are reduced and a quality of an image printed on the sheet is improved. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiment shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.