Abstract:
An apparatus for feeding a both-sided document having images on both sides thereof is provided with a document stand; a reading section; a feeder having a feeding passage and to feed the both-sided document from the document stand to the reading section along the feeding passage; a pair of reversing rollers provided on a reversing passage to reverse the both-sided document after an image of the both-sided document is read at the reading section and to reefed the reversed both-sided document from the reversing passage to the feeding passage so that an image on another side of the both-sided document is read at the reading section; a pair of ejecting rollers provided on an ejecting passage and to eject the both-sided document to a delivery section after the images on both sides of the both-sided document are read at the reading section; and a switching mechanism to connect an outlet passage of the reading section to one of the reversing passage and the ejecting passage; wherein one of the pair of reversing rollers and one of the ejecting rollers are mounted coaxially on a shaft.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a document feeding apparatus which enables image reading by feeding an original document in order to form an image by an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, a compound machine having these plural functions, or a printing machine, and to an image forming apparatus.  
           [0002]    Some of document feeding apparatus provided in such an image forming apparatus of a digital type separate to feed a single sheet from the other document sheets stacked on the sheet feeding tray, and are capable of reading the both sides of the document by switching over the pathway between the ejecting passage and the reversing passage.  
           [0003]    In such a document feeding apparatus, the reversing rollers and the ejecting rollers are arranged separately in the up-and-down direction, therefore, the document feeding apparatus is made large-sized in the height direction. Further, because the switching gate for switching over the pathway between the ejecting passage and the reversing passage is disposed at the upstream side of the reversing rollers and the ejecting rollers, the document feeding apparatus is made large-sized in the width direction.  
           [0004]    In the reversing passage, a document sheet is conveyed in direct contact with the guide ribs forming the reversing passage, therefore, the resistance to conveyance is large, and the document sheet skews, often to cause a paper jam to occur.  
           [0005]    Further, a pair of ejecting rollers for ejecting a document sheet after being read and an ejected sheet guide member for guiding the document sheet to be ejected are provided, but the ejecting rollers and the ejection guide members are mounted separately; therefore, the document feeding apparatus is made large-sized.  
         SUMMARY OF THE INVENTION  
         [0006]    This invention has been made in view of the above-mentioned points; it is an object of the invention to provide a document feeding apparatus and an image forming apparatus, which make it possible to make its size smaller by employing a part for common use to plural members and reducing the number of parts, and also make it possible to raise the document conveying ability.  
           [0007]    In order to solve the above-mentioned problems and to accomplish the object, this invention is made to have any one of the following structures.  
           [0008]    An apparatus for feeding a both-sided document having images on both sides thereof, comprises:  
           [0009]    a document stand on which the both-sided document is placed;  
           [0010]    a reading section at which an image of the both-sided document is read by an image reader;  
           [0011]    a feeder having a feeding passage and to feed the both-sided document from the document stand to the reading section along the feeding passage;  
           [0012]    a pair of reversing rollers provided on a reversing passage to reverse the both-sided document after an image of the both-sided document is read at the reading section and to reefed the reversed both-sided document from the reversing passage to the feeding passage so that an image on another side of the both-sided document is read at the reading section;  
           [0013]    a pair of ejecting rollers provided on an ejecting passage and to eject the both-sided document to a delivery section after the images on both sides of the both-sided document are read at the reading section; and  
           [0014]    a switching mechanism to connect an outlet passage of the reading section to one of the reversing passage and the ejecting passage;  
           [0015]    wherein one of the pair of reversing rollers and one of the ejecting rollers are mounted coaxially on a shaft.  
           [0016]    An image forming apparatus, comprises:  
           [0017]    an image reader to read an image on a document;  
           [0018]    a recording device to record an image on a recording sheet based on the image read by the image reader; and  
           [0019]    a document conveying device to convey a both-sided document to the image reader in such a way that images on the both-sided document are read by the image reader,  
           [0020]    the document conveying device comprising  
           [0021]    a document stand on which the both-sided document is placed;  
           [0022]    a reading section at which an image of the both-sided document is read by the image reader;  
           [0023]    a feeder having a feeding passage and to feed the both-sided document from the document stand to the reading section along the feeding passage;  
           [0024]    a pair of reversing rollers provided on a reversing passage to reverse the both-sided document after an image of the both-sided document is read at the reading section and to reefed the reversed both-sided document from the reversing passage to the feeding passage so that an image on another side of the both-sided document is read at the reading section;  
           [0025]    a pair of ejecting rollers provided on an ejecting passage and to eject the both-sided document to a delivery section after the images on both sides of the both-sided document are read at the reading section; and  
           [0026]    a switching mechanism to connect an outlet passage of the reading section to one of the reversing passage and the ejecting passage;  
           [0027]    wherein one of the pair of reversing rollers and one of the ejecting rollers are mounted coaxially on a shaft.  
           [0028]    Further, the above object may be attained by the following preferable structures.  
           [0029]    (1) A document feeding apparatus, which separates to feed a single sheet from the other document sheets stacked on a sheet feeding tray (document stand) and are capable of reading the both sides of a document sheet, comprising  
           [0030]    a document reading section arranged in the lower part and a reversing passage and a pair of reversing rollers for reading the both sides of the document sheet arranged in the upper part,  
           [0031]    an ejecting passage and a pair of ejecting rollers arranged at the downstream side of said document reading section, and  
           [0032]    a switching gate for switching over the pathway from said document reading section between said reversing passage and said ejecting passage, wherein  
           [0033]    the driven one of said pair of reversing rollers and the driving one of said pair of ejecting rollers are arranged on the same shaft.  
           [0034]    According to the invention described in the structure (1), the driven one of the pair of reversing rollers and the driving one of the pair of ejecting rollers are disposed on the same shaft; therefore, the number of parts is made smaller, and it is possible to make the size in the height direction smaller.  
           [0035]    (2) A document feeding apparatus as set forth in the structure (1), wherein the supporting point (fulcrum) of the aforesaid switching gate is provided on the aforesaid shaft.  
           [0036]    According to the invention described in the structure (2), the supporting point of the switching gate is provided on the shaft on which the driven one of the pair of reversing rollers and the driving one of the pair of ejecting rollers are provided; therefore, the number of parts is made smaller, and it is possible to make smaller the size in the width direction, on top of the height direction.  
           [0037]    (3) A document feeding apparatus, which separates to feed a single sheet from the other document sheets stacked on a sheet feeding tray, is provided with a reversing passage for reading the both sides of a document sheet, and are capable of reading the both sides of the document sheet, wherein  
           [0038]    a conveyance-resistance reducing rolling bar for reducing the resistance to conveyance of a document sheet is attached in said reversing passage.  
           [0039]    According to the invention described in the structure (3), the resistance to conveyance of a document sheet in the reversing passage can be reduced by the conveyance-resistance reducing rolling bar; therefore, the conveying ability for a document is improved, and it becomes possible to reduce the frequency of the occurrence of a paper jam.  
           [0040]    (4) A document feeding apparatus as set forth in the structure (3), wherein the aforesaid reversing passage bends in the shape of S, and at least in a part of the bending portions (curved bent portions), the aforesaid conveyance-resistance reducing rolling bar is disposed.  
           [0041]    According to the invention described in the structure (4), the reversing passage is s-shaped, and the conveyance-resistance reducing rolling bar is disposed in the bending portion; therefore, the apparatus is made compact, and the document conveying ability in the bending portion is improved, to make it possible to reduce the frequency of the occurrence of a paper jam.  
           [0042]    (5) A document feeding apparatus as set forth in the structure (3) or (4), wherein a plurality of the aforesaid conveyance-resistance reducing rolling bars are provided between the guide ribs forming the aforesaid reversing passage.  
           [0043]    According to the invention described in the structure (5), a plurality of the aforesaid conveyance-resistance reducing rolling bars are provided between the guide ribs forming the aforesaid reversing passage; therefore, the apparatus is made compact, and the document conveying ability is improved, to make it possible to reduce the frequency of the occurrence of a paper jam.  
           [0044]    (6) A document feeding apparatus as set forth in any one of the structures (3) to (5), wherein the aforesaid conveyance-resistance reducing rolling bar is provided in such a way that only a part of it is projected out of the aforesaid guide ribs toward the reversing passage in order that a document sheet may hit a portion of the rolling bar deviated to the sheet passing side from the central line.  
           [0045]    According to the invention described in the structure (6), the conveyance-resistance reducing rolling bar is provided in such a way that only a part of it is projected out of the guide ribs toward the reversing passage side and a document sheet hits a portion of the rolling bar deviated to the sheet passing side from the central line; therefore, the apparatus is made compact, and the document conveying ability is improved.  
           [0046]    (7) A document feeding apparatus, which separates to feed a single sheet from the other document sheets stacked on a sheet feeding tray and are capable of reading the both sides of a document sheet, comprising  
           [0047]    a pair of outlet rollers for ejecting said document sheet after said document sheet is read and an outlet guide member for guiding a document sheet to be ejected, wherein  
           [0048]    the shaft of one of said pair of outlet rollers is used also as the mounting portion for said outlet guide member.  
           [0049]    According to the invention described in the structure (7), the shaft of one of the pair of outlet rollers is used also as the mounting portion for the outlet guide member; therefore, the number of parts is made smaller, and it is possible to make the size smaller.  
           [0050]    (8) A document feeding apparatus as set forth in the structure (7), wherein the driving one and the driven one of the aforesaid pair of outlet rollers are pressed to each other by a ring-shaped spring.  
           [0051]    According to the invention described in the structure (8), the driving one and the driven one of the aforesaid pair of outlet rollers are pressed to each other by a ring-shaped spring; therefore, the pair of ejecting rollers are made to form a compact unit.  
           [0052]    (9) An image forming apparatus provided with a document feeding apparatus as set forth in any one of the structures (1) to (8).  
           [0053]    According to the invention described in the structure (9), the image forming apparatus can be provided with a document feeding apparatus, which makes it possible to make its size smaller by employing a part for common use to plural members and reducing the number of parts, and also make it possible to raise the document conveying ability.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0054]    [0054]FIG. 1 is a drawing showing the overall structure of an image forming apparatus provided with an print sheet finishing apparatus, a document feeding apparatus, and an image reading apparatus;  
         [0055]    [0055]FIG. 2 is a cross-sectional view of a document feeding apparatus;  
         [0056]    [0056]FIG. 3 is the plan of a document feeding apparatus;  
         [0057]    [0057]FIG. 4 is the front view of the reversing-ejecting unit;  
         [0058]    [0058]FIG. 5 is an enlarged cross-sectional view of the conveyance section;  
         [0059]    [0059]FIG. 6 is the rear view of the paper feed driving motor section;  
         [0060]    [0060]FIG. 7 is the rear view of the reversible driving motor section;  
         [0061]    [0061]FIG. 8 is an enlarged drawing of the reversing passage; and  
         [0062]    [0062]FIG. 9 is the front view of the conveyance-resistance reducing rolling bars.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0063]    In the following, an embodiment of an image forming apparatus provided with a document feeding apparatus of this invention will be explained on the basis of the drawings; however, this invention is not to be limited to this embodiment.  
         [0064]    [0064]FIG. 1 is a drawing showing the overall structure of the image forming apparatus  1  equipped with the print sheet finishing apparatus FS, the document feeding apparatus DF, and the image reading apparatus (scanner) SC.  
         [0065]    The image forming apparatus mainframe  1 A shown in the drawing is provided with the image processing section  2 , the image writing section  3 , the image forming section  4 , the high-voltage power source section  5 , the cassette sheet feeding section  6 , the fixing section  7 , the sheet ejection section  8 , and the re-conveyance means (ADU)  9  for automatic duplex copying.  
         [0066]    On the upper side of the image forming apparatus mainframe  1 A, the image reading apparatus SC and the document feeding apparatus DF are installed. To the upper left side, the side of the sheet ejection section  8 , of the image forming apparatus mainframe  1 A, the print sheet finishing apparatus FS is connected.  
         [0067]    The document sheet d, which is set on the document base of the document feeding apparatus DF with the first side made to face up, is conveyed to the direction of the arrow mark, and the image of the one or both sides of the document is read by the CCD image sensor C 1  through the optical system of the image reading apparatus SC.  
         [0068]    The analogue signal obtained by the photoelectric conversion by the CCD image sensor C 1  is subjected to analogue processing, A/D conversion, shading correction, image compression processing, etc., and then it is transmitted to the image writing section  3 .  
         [0069]    In the image writing section  3 , the output light beam from a semiconductor laser is applied to the photoreceptor drum  4 A of the image forming section  4 , to form a latent image. In the image forming section  4 , the processes such as charging, exposure, development, transfer, detachment, and cleaning are carried out, and the image is transferred to the paper sheet S, which has been conveyed from the cassette sheet feeding section  6 . The paper sheet S carrying an image is subjected to fixing in the fixing apparatus  7 , and is conveyed from the sheet ejection section  8  to the print sheet finishing apparatus FS. In other way, the paper sheet S having an image on one side processed, which has been fed to the re-conveyance means  9  by the ejecting passage switching plate  8 A, is subjected to duplex image processing in the image forming section  4  again, and then, it is fed to the print sheet finishing apparatus FS by the ejecting rollers  8 B of the sheet ejection section  8 .  
         [0070]    The print sheet finishing apparatus FS is mounted to the upper left portion of the image forming apparatus mainframe  1 A in a manner capable of being mounted and dismounted. The print sheet finishing apparatus SF is composed of the sheet conveyance means  10 , the sheet ejection means  20 , the after-print processing means  30 , and the up-and-down moving ejection means  40 , which are arranged in the print sheet finishing apparatus mainframe  100 .  
         [0071]    In FIG. 1, in the right side inside the image forming apparatus mainframe  1 A, with respect to the image forming section  4  positioned at the center, in the lower part of the image forming apparatus mainframe  1 A in the height direction, there is provided the cassette sheet feeding section  6 , and in the upper part of it, there are provided the fixing apparatus  7  and the sheet ejection section  8 . By this structure of vertical arrangement, the sheet conveying passage (1) in the almost vertical direction is formed. The paper sheet S, which has been conveyed out from the cassette sheet feeding section  6 , is conveyed along this upward-directing sheet conveying passage and ejected to the outside of the image forming apparatus mainframe  1 A.  
         [0072]    Approximately parallel to this sheet conveying passage (1) in the vertical direction, the sheet conveying passage (2) by the re-conveyance means  9  is formed.  
         [0073]    By forming the above-mentioned sheet conveying passages (1) and (2) in the vertical direction, a sheet conveying passage having the shortest length from the cassette sheet feeding section  6  to the sheet ejection section  8  is made up.  
         [0074]    The sheet conveyance means  10  of the print sheet finishing apparatus SF is contained in the space portion above the image forming apparatus mainframe  1 A as shown in the drawing. The sheet entrance portion  11  of the sheet conveyance means  10  is adjacent to the ejecting rollers  8 B of the sheet ejection section  8  of the image forming apparatus mainframe  1 A. Further, in this state of mounting, in the space portion at the upper left part of the image forming apparatus mainframe  1 A shown in the drawing, the sheet ejection means  20  and the after-print processing means  30  of the print sheet finishing apparatus SF are contained. The up-and-down moving ejection means  40  composed of the plural trays for ejected sheets (also called bins)  41  and the up-and-down movement driving means  42  is located at the left side of the after-print processing means  30  shown in the drawing.  
         [0075]    In the following, the document feeding apparatus will be explained on the basis of FIG. 2 to FIG. 8. FIG. 2 is a cross-sectional view of the document feeding apparatus, FIG. 3 is the plan of the document feeding apparatus, FIG. 4 is the front view of the reversing-ejection unit, FIG. 5 is an enlarged cross-sectional view of the conveyance section, FIG. 6 is the rear view of the sheet feed driving motor section, FIG. 7 is the rear view of the reversible driving motor section, FIG. 8 is an enlarged drawing of the reversing passage, and FIG. 9 is the front view of the conveyance-resistance reducing rolling bars.  
         [0076]    In the document feeding apparatus DF, the document feeding section  200 , the ejection section  300 , and the conveyance section  400  are arranged.  
         [0077]    The document feeding section  200  comprises the sheet feeding tray  201 , on which a plurality of sheets of a document can be set, and in this sheet feeding tray  201 , a pair of regulation plates  202  for positioning document sheets in the width direction are provided in such a manner as to be able to move in the width direction. Further, in the sheet feeding tray  201 , a plurality of rib-shaped projections  201   a,    201   b,    201   c,  and  201   d  are provided respectively at the positions with a short distance from the positions where the trailing edges of the document sheets of the pertinent sizes come, to prevent that a document sheet is made to move back to the upstream direction by stopping the sheet at the time of feeding.  
         [0078]    The ejection section  300  comprises the output tray  301 , and this output tray  301  is disposed at the position under the document feeding section  200 . Onto the output tray  301 , it is ejected the document sheet having been conveyed by the conveyance section  400  in such a way that the one side or the both sides are read.  
         [0079]    In the conveyance section  400 , there are provided the feeding passage P 1 , the ejecting passage P 2 , and the reversing passage P 3 ; the switching-over between the ejecting passage P 2  and the reversing passage P 3  is carried out by the switching gate  401 , and the switching-over between the feeding passage P 1  and the reversing passage P 3  is carried out by the switching gate  402 . Here, the switching gate  401  can swing as indicated with an arrow mark around the shaft  431  so that the switching gate  401  can lead the document from a document reading section  409  to one of the reversing passage P 3  and the ejecting passage P 2 . In the case where only one side of an original document is read, the document sheet fed from the document feeding section  200  passes the feeding passage P 1  and is ejected to the ejection section  300  through the ejecting passage P 2  which is switched over by the switching gate  401 .  
         [0080]    Further, in the case where both sides of an original document are read, the document sheet fed from the document feeding section  200  is conveyed once from the feeding passage P 1  to the reversing passage P 3  to reverse the document sheet, wherein the pathway is switched over to the reversing passage P 3  by the switching gate  402 , and the reversed document sheet is conveyed again to the feeding passage P 1  to which the pathway is switched over by the switching gate  402 ; then the first side of the document sheet is read at the document reading section  409 . After the first side of the document sheet is read, the document sheet is led to the reversing passage P 3  to which the pathway is switched over by the switching gate  401 . When the document sheet is fed again from the reversing passage P 3  to the feeding passage P 1 , the document sheet is reversed. Then, the second side of the document is read at the document reading section  409 . Thereafter, the document sheet is ejected to the ejection section  300  by the switching gate  402  through the ejecting passage P 2 .  
         [0081]    In the feeding section, the movable pressing plate  403 , the pickup roller  499 , the feeding roller  404 , the double-feed preventing roller  406 , the driving registration roller  405   a,  and the driven registration roller  405   b  are arranged. The movable pressing plate  403  is moved upward to press the document sheets to the pickup roller  499  when the document is fed, and the pickup roller  499  leads the top sheet to the feeding roller  404 ; thus, the document sheets are fed one by one by the feeding roller  404  and the double-feed preventing roller  406 . This document sheet is conveyed by the driving of the feeding roller  404  to the driving registration roller  405   a  and the driven registration roller  405   b,  the skew of the fed sheet is corrected by the driving registration roller  405   a  and the driven registration roller  405   b,  the timing is adjusted by the retard roller  407 , and the document sheet is fed to the document reading section  409 .  
         [0082]    As shown in FIG. 6, the movable pressing plate  403 , the feeding roller  404 , and the driving registration roller  405   a  are driven by the sheet feed driving motor M 1 , and by the rotation of this motor M 1 , the torque limiter  411  is driven through the belt  410 ; the up-and-down movement driving shaft  412  of this torque limiter  411  is rotated to make the movable pressing plate  403  move upward, and the up-and-down movement driving shaft  412  acts as the supporting point for the movable pressing plate  403  to move up and down. By the rotation of this sheet feed driving motor M 1 , the pulleys  414  and  415  of the feeding roller  404  and the driving registration roller  405   a  are rotated through the belt  413 ; however, because the one-way clutches  418  and  419  are provided at the roller shafts  416  and  417  of the feeding roller  404  and the driving registration roller  405   a  respectively, when the sheet feed motor M 1  rotates in the direction to make the movable pressing plate  403  move upward, it is prevented the reverse rotation to the feeding direction of the feeding roller  404  and the driving registration roller  405   a.  By the reverse rotation of the sheet feed driving motor M 1 , the pulleys  414  and  415  of the feeding roller  404  and the driving registration roller  405   a  are rotated through the belt  413 , to rotate the feeding roller  404  and the driving registration roller  405   a.    
         [0083]    The document reading section  409  is located at the lower side, and the reversing passage P 3  and the pair of reversing rollers  420  for reading both sides of a document, and the pair of ejecting rollers  430  are arranged in the middle part of the conveyance section  400 . Further, at the downstream side of the document reading section  409 , the ejecting passage P 2  and the outlet roller unit  421  are disposed, in which the switching gate  401  for switching over the pathway from the document reading section  409  between the ejecting passage P 2  and the reversing passage P 3  is disposed.  
         [0084]    The outlet roller unit  421  comprises the pair of outlet rollers  423  and the outlet guide members  424 . The pair of outlet rollers  423  comprise the driving one  423   a  and the driven one  423   b,  and the shafts are used also for the mounting of the outlet guide members  424 , which reduces the number of parts and makes it possible to make the apparatus small-sized. Further, the driving one and the driven one of the pair of outlet rollers  423  are pressed to each other by the ring-shaped spring  425 , which makes it possible to make the pair of outlet rollers  423  a compact unit.  
         [0085]    The pair of reversing rollers  420  comprises the driving one  420   a  and the driven one  420   b,  and the pair of ejecting rollers also comprise the driving one  430   a  and the driven one  430   b.  The driven one  420   b  of the pair of reversing rollers  420  and the driving one  430   a  of the pair of ejecting rollers  430  are arranged on the same shaft  431 , and the driven one  420   b  is mounted rotatably around the common shaft  431 . Further, the supporting point (fulcrum) of the switching gate is also provided on the common shaft  431 , which makes the number of parts small.  
         [0086]    The driven one  430   b  of the pair of ejecting rollers  430  is provided rotatbly around the shaft  432  as shown in FIG. 4 and FIG. 5, this shaft  432  being supported by the ejection guide member  433 , and is disposed in the ribs  433   a  of the ejection guide member  433 . The driving one  420   a  of the pair of reversing rollers  420  is mounted on the shaft  434 .  
         [0087]    As shown in FIG. 3 and FIG. 5, the shaft  434  is supported by the shaft  436  through the supporting members  435 , and the shaft  436  is rotated in the forward and reverse direction by the reversible driving motor M 2  shown in FIG. 7. The shaft  436  and the shaft  434  is connected by the drive belt  437 , and the rotating force of the shaft  436  is transmitted to the shaft  434  through the belt  437  to rotate it in the forward and reverse direction.  
         [0088]    The pair of reversing rollers  420  and the pair of ejecting rollers  430  are arranged in the vertical direction, which makes the apparatus small-sized in the height direction, and the supporting point (fulcrum) of the switching gate  401  is provided on the common shaft  431 , which makes the apparatus small-sized in the width direction.  
         [0089]    Further, by the shaft  436 , the double-feed preventing roller  406 , which is provided to its right, is supported through the stay member  450 , and the supporting point of the driving side is also the supporting point of the double-feed preventing roller  406 , which makes it unnecessary to provide two shafts as the shaft  436  for the supporting point of the two rollers and makes it possible to reduce the size.  
         [0090]    As shown in FIG. 7, regarding the reversing rollers  420  and the switching gate  402 , the normal rotation of the reversible driving motor M 2  rotates the pulley  452  through the belt  451 , and rotates the shaft  436 . Linked to this motion, the cam shaft  453  of the switching gate  402  is rotated, and the switching gate  402  is made to operate by the cam  454 , to switch over the pathway to the reversing passage P 3 . The reverse rotation of the reversible driving motor M 2  rotates the shaft  436  in the reverse direction through the belt  451 , and linked to this motion, the cam shaft  453  of the switching gate  402  is rotated reversely, and the switching gate  402  is made to operate by the cam  454 , to switch over the pathway to the feeding passage P 1 .  
         [0091]    At the time of ejection, by-the driving of the reading motor M 3  shown by the double dot and dash line in FIG. 5, the driving one  430   a  of the pair of ejecting rollers  430  is rotated, and a document sheet is ejected by the rotation of the driving one  430   a  and the driven one  430   b  in the direction of ejection.  
         [0092]    At the time of reversing, the rotation of the shaft  436  is transmitted to the shaft  434  through the belt  437 , and it is further transmitted from the driving one of the pair  420   a  of reversing rollers  420  to its driven one  420   b,  to convey out a document sheet by the driving one  420   a  and the driven one  420   b;  next, the reverse rotation of the shaft  436  is transmitted to the shaft  434  through the belt  437 , and the reverse rotation is further transmitted from the driving one  420   a  of the pair of reversing rollers  420  to the driven one  420   b,  to reverse the document and return the document sheet to the feeding passage P 1  by the driving one  420   a  and the driven one  420   b.    
         [0093]    In the reversing passage P 3 , the conveyance-resistance reducing rolling bars  460  for reducing the resistance to conveyance of a document sheet are mounted; in this embodiment, the reversing passage P 3  bends in S-shape, and in these two bending portions (two curved bent sections), the conveyance-resistance reducing rolling bars  460  are arranged. These plural conveyance-resistance reducing rolling bars  460  are provided rotatably on the shaft  462  between the guide ribs  461  forming the reversing passage P 3  as shown in FIG. 9.  
         [0094]    As shown in FIG. 8, regarding the conveyance-resistance reducing rolling bars  460 , the shaft  461  is disposed in the concave portion  461   a  of the guide ribs  461  in order that the document sheet d may hit the portion of the rolling bars deviated to the sheet passing side from the central line O of the rolling bars, that is, the conveyance-resistance reducing rolling bars  460  are provided in a manner such that only a part of them is projected out of the guide ribs  461  toward the reversing passage.  
         [0095]    As described in the above, only a part of the conveyance-resistance reducing rolling bars  460  is projected out of the guide ribs  461  toward the reversing passage, and a document sheet hits the portion of the rolling bars deviated to the sheet passing side from the central line O of the rolling bars; therefore, the apparatus is made compact, and the document conveying ability is improved, which makes it possible to reduce the frequency of the occurrence of a paper jam. Further, the reversing passage P 3  is S-shaped, and the conveyance-resistance reducing rolling bars  460  are disposed in each of the bending portions; therefore, the apparatus is made compact, and on top of it, the document conveying ability in the bending portions is made higher.  
         [0096]    Further, in the document feeding apparatus DF of this embodiment, as shown in FIG. 3, the hinges  470  are provided at the deep side; the document feeding apparatus DF is of such a type as to be opened from the image forming apparatus mainframe  1 A, by lifting upward the front side of the main body  471  of the document feeding apparatus.  
         [0097]    Near the front side of the document reading section  409 , the bumping member  472 , which bumps against the image forming apparatus mainframe  1 A at a point, is provided, and in order to apply a force in the direction to lift up the main body  471  of the document feeding apparatus, the mechanism  480  for applying a rotational force by torsion acting upward against the weight of the main body  471  itself is provided.  
         [0098]    The up-lifting mechanism  480  is composed of the shaft  481  for applying the rotational force arranged in such a manner as to extend from the deep side of the main body  471  of the document feeding apparatus to the front side, and the resilient member  482  arranged at the deep side of the main body  471  of the document feeding apparatus for giving the shaft  481  a rotational force to lift up the main body  471 . The resilient member  482  is made up of a coil spring, and the one end  482   a  is fixed to the main body  471  of the document feeding apparatus and the other end  482   b  is fixed to the shaft  481  for applying the rotational force by the screw  483 , to give the shaft  481  a force for lifting up the main body  471  by torsion.  
         [0099]    As described in the above, the transmission of force is carried out by the shaft  481  for applying a rotational force, and owing to the simple mechanism for lifting up composed of the shaft  481  for applying a rotational force and the resilient member  482  for giving the shaft  481  a force to lift up the main body by torsion, the falling down by the self-weight of the main body  471  of the document feeding apparatus is prevented.  
         [0100]    As described in the above, when the main body  471  of the document feeding apparatus is closed, only the bumping member  472  bumps the image forming apparatus mainframe  1 A at a point near the front side of the document reading section  409 , and the falling down by the self-weight of the main body  471  of the document feeding apparatus is prevented by the force to lift it up; therefore, [it is possible to make the main body  471  brought into contact with a point near the front side of the document reading section reliably without adjustment], the ease of operation is good, and the document conveying ability of is made higher.  
         [0101]    Further, in this embodiment of the invention, a document feeding apparatus connected to a copying machine is shown, but this invention can be applied to a document feeding apparatus to be used by being connected to an image forming apparatus such as a printer, or a facsimile machine, a compound machine having these plural functions, or a light-duty printing machine.  
         [0102]    As described in the foregoing, according to a document feeding apparatus of this invention, it is achieved to employ a part common to a plurality of members to reduce the number of parts, it is possible to make the apparatus small-sized, and also it is possible to make the document conveying ability higher.  
         [0103]    Further, owing to the above-mentioned document feeding apparatus, for an image forming apparatus, it is achieved to employ a part common to a plurality of members to reduce the number of parts, it is possible to make the apparatus small-sized, and also it is possible to make the document conveying ability higher.