Patent Publication Number: US-2021171301-A1

Title: Document feeeder

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/JP2018/034698, filed on Sep. 19, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The embodiments discussed herein are related to a document feeder. 
     BACKGROUND 
     A document feeder that automatically unfolds and conveys a Z-folded document folded in a Z shape is known (refer to Japanese Laid-open Patent Publication No. 2008-174372, Japanese Laid-open Patent Publication No. 09-258496, and Japanese Laid-open Patent Publication No. 09-304977). 
     Unfortunately, such a document feeder may significantly deform a portion other than a crease and buckle a Z-folded document when unfolding and conveying the Z-folded document. 
     SUMMARY 
     According to an aspect of an embodiment, a document feeder includes a document placement member that has a placement surface, a sucker that has a suction surface on which a part of a document placed on the placement surface is sucked and sucks air from a space formed between the document placement member and the suction surface, a blower that blows air into the space, and a paper feeder that conveys the document in a conveyance direction along the placement surface, wherein the suction surface is inclined relative to the placement surface such that the space is narrower toward the upstream side in the conveyance direction. 
     The object and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an image reading apparatus provided with a document feeder in a first embodiment; 
         FIG. 2  is a side view schematically illustrating the image reading apparatus provided with the document feeder in the first embodiment; 
         FIG. 3  is a cross-sectional view illustrating an unfolding unit of the document feeder in the first embodiment; 
         FIG. 4  is a plan view illustrating a Z-folded document placed on a platen of the document feeder in the first embodiment; 
         FIG. 5  is a flowchart illustrating the operation of the image reading apparatus provided with the document feeder in the first embodiment; 
         FIG. 6  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when air is blown in between a front end portion and a first folded portion of the Z-folded document; 
         FIG. 7  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when a second folded portion of the Z-folded document is held by a suction blower; 
         FIG. 8  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the second folded portion of the Z-folded document separates from a suction surface; 
         FIG. 9  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when air is blown in between a front end portion and a folded portion of a double-folded document; 
         FIG. 10  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the folded portion of the double-folded document separates from the suction surface; 
         FIG. 11  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the double-folded document is unfolded; 
         FIG. 12  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when air is blown in between a front end portion and a plurality of folded portions of an accordion-folded document; 
         FIG. 13  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when a back-end folded portion of the accordion-folded document is held by the suction blower; 
         FIG. 14  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the folded portions of the accordion-folded document are unfolded; 
         FIG. 15  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the portions excluding the back-end folded portion among the folded portions are unfolded; 
         FIG. 16  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the back-end folded portion of the accordion-folded document separates from the suction surface; 
         FIG. 17  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when air is blown in between a front end portion and a plurality of folded portions of an inside-folded document; 
         FIG. 18  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the folded portions of the inside-folded document are held by the suction blower; 
         FIG. 19  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when one folded portion among the folded portions of the inside-folded document separates from the suction blower; 
         FIG. 20  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when a back-end folded portion of the inside-folded document separates from the suction blower; 
         FIG. 21  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when a plurality of sheets of Z-folded documents are placed on the platen; 
         FIG. 22  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when air is blown in between the front end portion and the first folded portion of the sheets of Z-folded documents; 
         FIG. 23  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the second folded portion of the sheets of Z-folded documents is held by the suction blower; 
         FIG. 24  is a side view schematically illustrating the unfolding unit of the document feeder in the first embodiment when the second folded portion of the sheets of Z-folded documents separates from the suction blower; 
         FIG. 25  is a side view schematically illustrating the image reading apparatus provided with the document feeder in a second embodiment; 
         FIG. 26  is a plan view illustrating an open/closed guide of the document feeder in the second embodiment; 
         FIG. 27  is a perspective view illustrating the unfolding unit of the document feeder in the second embodiment when the open/closed guide is disposed in an open position; 
         FIG. 28  is another perspective view illustrating the unfolding unit of the document feeder in the second embodiment when the open/closed guide is disposed in the open position; 
         FIG. 29  is a perspective view illustrating the unfolding unit of the document feeder in the second embodiment when the open/closed guide is disposed in a closed position; 
         FIG. 30  is a flowchart illustrating the operation of the image reading apparatus provided with the document feeder in the second embodiment; 
         FIG. 31  is a side view schematically illustrating the image reading apparatus provided with the document feeder in a third embodiment; 
         FIG. 32  is a flowchart illustrating the operation of the image reading apparatus provided with the document feeder in the third embodiment; 
         FIG. 33  is a top view illustrating a part of the unfolding unit of the document feeder in a fourth embodiment; and 
         FIG. 34  is a top view illustrating a part of the unfolding unit of the document feeder in a fifth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the disclosure will be explained with reference to accompanying drawings. A document feeder according to embodiments disclosed by the subject application will be described below with reference to the drawings. It should be noted that the present disclosure is not limited by the following description. In the following description, the same constituent elements are denoted by the same reference signs and an overlapping description will be omitted. 
     First Embodiment 
     A document feeder in a first embodiment is used in an image reading apparatus  10  as illustrated in  FIG. 1 .  FIG. 1  is a perspective view illustrating the image reading apparatus  10  provided with the document feeder in the first embodiment. The image reading apparatus  10  includes an image reading apparatus body  1 , a platen  2 , and an exit tray  3 . The platen  2  has a placement surface  4 , on which a document is placed. The placement surface  4  is substantially flat and substantially parallel to a plane along an installation surface on which the image reading apparatus  10  is installed. 
       FIG. 2  is a side view schematically illustrating the image reading apparatus  10  provided with the document feeder in the first embodiment. The image reading apparatus body  1  has a feed path  5 . The feed path  5  is disposed between the platen  2  and the exit tray  3  to form a path connecting the platen  2  to the exit tray  3 . The exit tray  3  is disposed on the downstream side in a conveyance direction  6  from the platen  2 . The conveyance direction  6  is substantially parallel to a plane along the installation surface on which the image reading apparatus  10  is installed. The feed path  5  guides a document released onto the feed path  5  such that the document released onto the feed path  5  is conveyed to the downstream side in the conveyance direction  6  along the path. 
     The image reading apparatus  10  further includes an unfolding unit  11 , a paper feeding unit  12 , a paper ejecting unit  14 , and a reading unit  15 . The unfolding unit  11  is disposed above the platen  2 . When a document placed on the platen  2  is folded, the unfolding unit  11  unfolds the document substantially flat. The paper feeding unit  12  is disposed at an end on the platen  2  side of the feed path  5 . The paper feeding unit  12  includes a pick roller  21 , a separation roller  22 , and a brake roller  23 . 
     The pick roller  21  is formed in a cylindrical shape and disposed above the platen  2 . The pick roller  21  is switched between a load mode and a distant mode. When switched to the load mode, the pick roller  21  comes closer to the feed path  5  so as to come into contact with a document placed on the platen  2  and rotates forward (counterclockwise in  FIG. 2 ) to release the document in contact with the pick roller  21 , among a plurality of documents placed on the platen  2 , to the feed path  5  and bring the document released onto the feed path  5  into contact with the separation roller  22 . When switched to the distant mode, the pick roller  21  retracts from the platen  2  so as not to come into contact with the document placed on the platen  2 . The separation roller  22  is formed in a cylindrical shape and disposed on the downstream side in the conveyance direction  6  of the pick roller  21  above the feed path  5 . The separation roller  22  rotates forward (counterclockwise in  FIG. 2 ) to convey the document in contact with the separation roller  22  to the downstream side in the conveyance direction  6 . 
     The brake roller  23  is disposed on the underside of the feed path  5  and disposed on the underside of the separation roller  22  so as to be in contact with the separation roller  22 . The brake roller  23  follows the separation roller  22  to rotate forward (clockwise in  FIG. 2 ) when the separation roller  22  is rotating forward and a document is not sandwiched between the separation roller  22  and the brake roller  23 . When the documents are sandwiched between the separation roller  22  and the brake roller  23 , the brake roller  23  rotates backward (counterclockwise in  FIG. 2 ) to convey a document not in contact with the separation roller  22 , among the documents, to the upstream side in the conveyance direction  6 . When being in contact with a document conveyed by the separation roller  22 , the brake roller  23  follows the document conveyed by the separation roller  22  to rotate forward. 
     The paper ejecting unit  14  is disposed at an end on the exit tray  3  side of the feed path  5 , that is, disposed on the downstream side of the paper feeding unit  12  on the feed path  5 . The paper ejecting unit  14  places a document supplied from the paper feeding unit  12  onto the exit tray  3 . The reading unit  15  is disposed between the paper feeding unit  12  and the paper ejecting unit  14  on the feed path  5 . The reading unit  15  reads images on both surfaces of a document conveyed between the paper feeding unit  12  and the paper ejecting unit  14  on the feed path  5 . 
       FIG. 3  is a cross-sectional view illustrating the unfolding unit  11  of the document feeder in the first embodiment. The unfolding unit  11  includes a lifting blower  31 , a suction blower  32 , and a pair of side blowers  33 . The lifting blower  31  has a downstream air-flow opening  38  on the downstream side in the conveyance direction  6  of an unfolding space  34  between the lifting blower  31  and the suction blower  32  above the platen  2  and blows the air into the unfolding space  34  through the downstream air-flow opening. The suction blower  32  has a plurality of air intakes  35  formed along a flat suction surface  36 . The suction surface  36  is oriented obliquely downward and inclined relative to the conveyance direction  6  so as to go further away from the feed path  5  toward the downstream side in the conveyance direction  6 . That is, the unfolding space  34  is formed such that it is narrower toward the upstream side in the conveyance direction  6 . The suction surface  36  is parallel to the width direction. The width direction is parallel to a plane along the installation surface on which the image reading apparatus  10  is installed, and is normal to the conveyance direction  6 . The angle between the plane along the placement surface  4  and the suction surface  36  is equal to a predetermined angle included in a range of 60 degrees or more to less than 90 degrees. The suction blower  32  sucks the air from the unfolding space  34  through the air intakes  35 . A pair of side blowers  33  are disposed on both sides in the width direction of the unfolding space  34  and blows the air into the unfolding space  34  from both sides in the width direction of the unfolding space  34 . 
     The unfolding unit  11  further includes a not-illustrated document detection sensor. The document detection sensor detects whether a document is placed on the platen  2 . 
     A Z-folded document  41  placed on the platen  2  of the document feeder in the first embodiment is formed from a sheet of paper and has a first crease  42  and a second crease  43 , as illustrated in  FIG. 4 .  FIG. 4  is a plan view illustrating the Z-folded document  41  placed on the platen  2  of the document feeder in the first embodiment. The first crease  42  is formed along another straight line substantially parallel to a straight line along a front end  44 , substantially at the center between the front end  44  and a back end  45  of the Z-folded document  41 . The second crease  43  is formed along another straight line substantially parallel to a straight line along the first crease  42 , substantially at the center between the first crease  42  and the back end  45 . The second crease  43  is folded in the opposite direction to the first crease  42  and, for example, is a valley fold when the first crease  42  is a mountain fold. 
     The Z-folded document  41  includes a front end portion  46  and a folded portion  47 . The front end portion  46  is a portion between the front end  44  and the first crease  42  of the Z-folded document  41 . The folded portion  47  is a portion between the first crease  42  and the back end  45  of the Z-folded document  41 . The folded portion  47  includes a first folded portion  48  and a second folded portion  49 . The first folded portion  48  is a portion between the first crease  42  and the second crease  43  of the Z-folded document  41 . The second folded portion  49  is a portion between the second crease  43  and the back end  45  of the Z-folded document  41 . 
     When the Z-folded document  41  is folded in this way, a part of the Z-folded document  41  is not exposed to the outside. The part includes a portion of the front end portion  46  that is covered by the first folded portion  48 , a portion of the first folded portion  48  that is covered by the front end portion  46 , a portion of the first folded portion  48  that is covered by the second folded portion  49 , and a portion of the second folded portion  49  that is covered by the first folded portion  48 . 
     The Z-folded document  41  is placed on the platen  2  such that the folded portion  47  is disposed above the front end portion  46 , that is, such that the front end portion  46  is disposed between the platen  2  and the folded portion  47 . The folded portion  47  is disposed in the unfolding space  34  when the Z-folded document  41  is placed on the platen  2 . 
     A pair of side blowers  33  includes a first side blower  33 - 1  and a second side blower  33 - 2 . The first side blower  33 - 1  includes a first side air-flow opening  37 - 1  disposed on one side in a width direction  50  of the unfolding space  34  and blows the air toward the unfolding space  34  through this first side air-flow opening  37 - 1 . The second side blower  33 - 2  includes a second side air-flow opening  37 - 2  disposed on the other side opposite to the one side in the width direction  50  of the unfolding space  34  and blows the air toward the unfolding space  34  through this second side air-flow opening  37 - 2 . 
     When the Z-folded document  41  is placed on the platen  2 , the Z-folded document  41  is disposed such that an end surface on one side in the width direction  50  of the folded portion  47  faces the first side blower  33 - 1 , an end surface on the other side in the width direction  50  of the folded portion  47  faces the second side blower  33 - 2 , and the second crease  43  faces the lifting blower  31 . 
     The image reading apparatus  10  further includes a not-illustrated control unit. The control unit is a computer and includes a central processing unit (CPU), a storage device, an input/output device, a communication interface, and a media interface. The CPU executes a computer program installed in the control unit to perform information processing and controls the storage device, the input/output device, the communication interface, and the media interface. The CPU executes a computer program installed in the control unit to further control each element provided in the image reading apparatus  10 . Examples of the storage device include a memory such as RAM and ROM, a fixed disk device such as hard disk, and a solid state drive (SSD). The storage device stores a computer program installed in the control unit and stores information used by the CPU. The input/output device outputs information generated through operation by the user to the CPU and outputs information generated by the CPU so that the user can recognize the information. 
     The communication interface is controlled by the CPU to download information to the control unit from another computer connected through a communication line and transmit information from the control unit to another computer. The media interface is formed such that a non-transitory tangible recording medium can be loaded thereto. Examples of the recording medium include a semiconductor memory, a magnetic disk, a magneto-optical disk, and an optical disk. When a recording medium is loaded, the media interface is controlled by the CPU to read information from the recording medium and record information on the recording medium. The computer program installed in the control unit may be the one downloaded from another computer through the communication interface or the one read from a recording medium through the media interface. 
     Operation of Image Reading Apparatus  10   
       FIG. 5  is a flowchart illustrating the operation of the image reading apparatus  10  provided with the document feeder in the first embodiment. To read an image from a plurality of documents using the image reading apparatus  10 , the user places the documents on the platen  2  and operates the input/output device of the control unit to start the image reading apparatus  10 . The documents placed on the platen  2  include the Z-folded document  41 . Upon starting of the image reading apparatus  10 , the control unit controls the lifting blower  31  to blow the air into the unfolding space  34 , controls the suction blower  32  to suck the air from the unfolding space  34 , and controls a pair of side blowers  33  to blow the air into the unfolding space  34  from both sides in the width direction  50  (step S 1 ). 
     The control unit waits until a timing after a predetermined period has passed since the timing when the lifting blower  31 , the suction blower  32 , and a pair of side blowers  33  start operation (step S 2 ). The predetermined period is, for example, one second. With passage of a predetermined period, the lifting blower  31  can stably blow the air into the unfolding space  34 . With passage of a predetermined period, the suction blower  32  can stably suck the air from the unfolding space  34 . With passage of a predetermined period, a pair of side blowers  33  can stably blow the air into the unfolding space  34 . 
     After a predetermined period has passed, the control unit starts separate conveyance (step S 3 ). When separate conveyance is started, the control unit switches the pick roller  21  from a retraction mode to a load mode. The pick roller  21 , switched from the retraction mode to the load mode, comes into contact with a document disposed on the top among the documents placed on the platen  2 . The control unit allows the pick roller  21  to rotate forward to bring a document in contact with the pick roller  21 , among the documents placed on the platen  2 , into contact with the separation roller  22 . The control unit allows the separation roller  22  to rotate forward to supply the document in contact with the separation roller  22  to the paper ejecting unit  14 . The control unit allows the brake roller  23  to rotate backward to convey a document not in contact with the separation roller  22 , among the documents sandwiched between the separation roller  22  and the brake roller  23 , to the upstream side in the conveyance direction  6 . 
     The unfolding unit  11  unfolds the Z-folded document  41  when the Z-folded document  41  is conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 . That is, the Z-folded document  41  is conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , whereby the folded portion  47  of the Z-folded document  41  is disposed in the unfolding space  34 . When the folded portion  47  of the Z-folded document  41  is disposed in the unfolding space  34 , as illustrated in  FIG. 6 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  46  and the first folded portion  48 .  FIG. 6  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when air is blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 . The air blown in between the front end portion  46  and the first folded portion  48  lifts the folded portion  47  of the Z-folded document  41  from the front end portion  46  (step S 4 ). 
     Since the suction blower  32  sucks the air from the unfolding space  34 , as illustrated in  FIG. 7 , the second folded portion  49  is pulled to the suction surface  36  when the folded portion  47  of the Z-folded document  41  lifts from the front end portion  46 . After being pulled to the suction surface  36 , the second folded portion  49  of the Z-folded document  41  is held by the suction blower  32  along the suction surface  36  (step S 5 ).  FIG. 7  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the second folded portion  49  of the Z-folded document  41  is held by the suction blower  32 . 
     After being held by the suction blower  32 , the second folded portion  49  of the Z-folded document  41  separates from the suction surface  36  as the Z-folded document  41  is further conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6  (step S 6 ).  FIG. 8  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the second folded portion  49  of the Z-folded document  41  separates from the suction surface  36 . The second folded portion  49  of the Z-folded document  41  separates from the suction surface  36 , whereby the Z-folded document  41  is unfolded substantially flat. At this moment, the Z-folded document  41  is unfolded such that a portion other than the first crease  42  and the second crease  43  is not heavily deformed since the suction surface  36  is inclined at a predetermined angle relative to a plane along the placement surface  4 . Buckling of the Z-folded document  41  is prevented since a portion other than the first crease  42  and the second crease  43  is not heavily deformed during unfolding. The unfolded Z-folded document  41  is supplied to the paper ejecting unit  14  by the paper feeding unit  12 . 
     When a document is supplied from the paper feeding unit  12  to the paper ejecting unit  14 , the control unit controls the reading unit  15  to read images on both surfaces of the document conveyed from the paper feeding unit  12  to the paper ejecting unit  14  and records the read images (step S 7 ). At this moment, since the Z-folded document  41  is unfolded, the reading unit  15  can read an image of a portion not exposed to the outside when the Z-folded document  41  is folded and can read images on both surfaces of the unfolded Z-folded document  41 . The control unit controls the paper ejecting unit  14  to place the document supplied from the brake roller  23  to the paper ejecting unit  14  onto the exit tray  3  (step S 8 ). 
     The control unit controls the document detection sensor of the unfolding unit  11  to detect whether a document is placed on the platen  2  (step S 9 ). The control unit repeatedly performs the process from step S 3  to step S 9  until the document detection sensor detects that no document is placed on the platen  2  (No at step S 9 ). The image reading apparatus  10  performs such an operation to read each of images of the documents placed on the platen  2 . 
     The image reading apparatus  10  unfolds and conveys the Z-folded document  41  but also can unfold and convey a folded document other than a Z-folded document. Examples of the folded document include a double-folded document, an accordion-folded document, and an inside-folded document. 
     As illustrated in  FIG. 9 , a double-folded document  51  has a crease  52  and includes a front end portion  53  and a folded portion  54 .  FIG. 9  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when air is blown in between the front end portion  53  and the folded portion  54  of the double-folded document  51 . When the folded portion  54  of the double-folded document  51  is disposed in the unfolding space  34 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  53  and the folded portion  54 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  53  and the folded portion  54  of the double-folded document  51 . The air blown in between the front end portion  53  and the folded portion  54  lifts the folded portion  54  of the double-folded document  51  from the front end portion  53 . 
     Since the suction blower  32  sucks the air from the unfolding space  34 , the folded portion  54  of the double-folded document  51  is held along the suction surface  36  by the suction blower  32  when being lifted from the front end portion  53 . After being held by the suction blower  32 , the folded portion  54  of the double-folded document  51  separates from the suction surface  36  as the double-folded document  51  is further conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , as illustrated in  FIG. 10 .  FIG. 10  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the folded portion  54  of the double-folded document  51  separates from the suction surface  36 . The folded portion  54  of the double-folded document  51  separates from the suction surface  36 , whereby the double-folded document  51  is unfolded substantially flat, as illustrated in  FIG. 11 .  FIG. 11  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the double-folded document  51  is unfolded. The image reading apparatus  10  can prevent buckling of the double-folded document  51  by appropriately unfolding the double-folded document  51  without heavily deforming a portion other than the crease  52 , in the same manner as the Z-folded document  41 . 
     As illustrated in  FIG. 12 , an accordion-folded document  55  has a plurality of creases  56  and includes a front end portion  57  and a plurality of folded portions  58 .  FIG. 12  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when air is blown in between the front end portion  57  and the folded portions  58  of the accordion-folded document  55 . The creases  56  include a plurality of valley folds and mountain folds alternately formed. That is, when the creases  56  include two valley folds, a mountain fold is formed between the two valley folds, and when the creases  56  include two mountain folds, a valley fold is formed between the two mountain folds. 
     When the folded portions  58  of the accordion-folded document  55  are disposed in the unfolding space  34 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  57  and the folded portions  58 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  57  and the folded portion  58  of the accordion-folded document  55 . The air blown in between the front end portion  57  and the folded portions  58  lifts the folded portions  58  of the accordion-folded document  55  from the front end portion  57 . 
     Since the suction blower  32  sucks the air from the unfolding space  34 , a back-end folded portion  59  of the accordion-folded document  55  is held by the suction blower  32  when the folded portions  58  are lifted from the front end portion  57 , as illustrated in  FIG. 13 .  FIG. 13  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the back-end folded portion  59  of the accordion-folded document  55  is held by the suction blower  32 . The back-end folded portion  59  is one folded portion that forms the back end among the folded portions  58 . 
     After the back-end folded portion  59  of the accordion-folded document  55  is held by the suction blower  32 , the accordion-folded document  55  is conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , whereby the folded portions  58  are unfolded, as illustrated in  FIG. 14 .  FIG. 14  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the folded portions  58  of the accordion-folded document  55  are unfolded. 
     The accordion-folded document  55  is further conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , whereby the portions excluding the back-end folded portion  59  among the folded portions  58  of the accordion-folded document  55  are unfolded, as illustrated in  FIG. 15 .  FIG. 15  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the portions excluding the back-end folded portion  59  among the folded portions  58  are unfolded. 
     After the portions excluding the back-end folded portion  59  among the folded portions  58  are unfolded, the back-end folded portion  59  of the accordion-folded document  55  separates from the suction surface  36  as the accordion-folded document  55  is further conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , as illustrated in  FIG. 16 .  FIG. 16  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the back-end folded portion  59  of the accordion-folded document  55  separates from the suction surface  36 . The back-end folded portion  59  separates from the suction surface  36 , whereby the accordion-folded document  55  is unfolded substantially flat. The image reading apparatus  10  can prevent buckling of the accordion-folded document  55  by appropriately unfolding the accordion-folded document  55  without heavily deforming a portion other than the creases  56 , in the same manner as the Z-folded document  41 . 
     As illustrated in  FIG. 17 , an inside-folded document  61  has a plurality of creases  62  and includes a front end portion  63  and a plurality of folded portions  64 .  FIG. 17  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when air is blown in between the front end portion  63  and the folded portions  64  of the inside-folded document  61 . The creases  56  are formed starting from a valley fold. When the folded portions  64  of the inside-folded document  61  are disposed in the unfolding space  34 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  63  and the folded portions  64 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  63  and the folded portions  64  of the inside-folded document  61 . The air blown in between the front end portion  63  and the folded portions  64  lifts the folded portions  64  of the inside-folded document  61  from the front end portion  63 . 
     Since the suction blower  32  sucks the air from the unfolding space  34 , the folded portions  64  of the inside-folded document  61  are held by the suction blower  32  when being lifted from the front end portion  63 , as illustrated in  FIG. 18 .  FIG. 18  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the folded portions  64  of the inside-folded document  61  are held by the suction blower  32 . 
     After being held by the suction blower  32 , one folded portion among the folded portions  64  of the inside-folded document  61  separates from the suction surface  36  as the inside-folded document  61  is conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 , as illustrated in  FIG. 19 .  FIG. 19  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when one folded portion among the folded portions  64  of the inside-folded document  61  separates from the suction blower  32 . 
     The air is blown into the unfolding space  34  when one folded portion of the inside-folded document  61  separates from the suction blower  32 , whereby a folded portion on the back end side of one folded portion among the folded portions  64  is lifted from the one folded portion. Since the suction blower  32  sucks the air from the unfolding space  34 , the folded portion on the back end side of the inside-folded document  61  is held by the suction blower  32  when it is lifted. In this way, each of the folded portions  64  is held by the suction blower  32  and separates from the suction blower  32 , whereby the folded portions  64  of the inside-folded document  61  are unfolded. 
     A folded portion  65  forming the back end among the folded portions  64  of the inside-folded document  61  is held by the suction blower  32  and thereafter separates from the suction blower  32  as the inside-folded document  61  is conveyed by the paper feeding unit  12  to the downstream side in the conveyance direction  6 .  FIG. 20  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the back-end folded portion  65  of the inside-folded document  61  separates from the suction blower  32 . The back-end folded portion  65  separates from the suction surface  36 , whereby the inside-folded document  61  is unfolded substantially flat. The image reading apparatus  10  can prevent buckling of the inside-folded document  61  by appropriately unfolding the inside-folded document  61  without heavily deforming a portion other than the creases  62 , in the same manner as the Z-folded document  41 . 
     The image reading apparatus  10  unfolds a sheet of a folded document having crease(s) but can also unfold a plurality of sheets of folded documents in which a plurality of sheets of paper are folded in an overlapping state. An example of the folded documents is a plurality of sheets of Z-folded documents. 
     As illustrated in  FIG. 21 , among a plurality of sheets of Z-folded documents  71 , a Z-folded document  72  on the top has two creases and includes a front end portion  73 , a first folded portion  74 , and a second folded portion  75 , in the same manner as the Z-folded document  41 . FIG.  21  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the sheets of Z-folded documents  71  are placed on the platen  2 . Among the sheets of Z-folded documents  71 , a plurality of Z-folded documents  76  different from the Z-folded document  72  each have two creases and include a front end portion  77 , a first folded portion  78 , and a second folded portion  79 , in the same manner as the Z-folded document  72 . The front end portion  77  overlaps the front end portion  73 , the first folded portion  78  overlaps the first folded portion  74 , and the second folded portion  79  overlaps the second folded portion  75 . 
     The air is blown from the lifting blower  31  into the unfolding space  34 , whereby the air is blown in between the front end portion  73  and the first folded portion  74  of the sheets of Z-folded documents  71 , and the second folded portion  75  is lifted from the front end portion  73 , as illustrated in  FIG. 22 .  FIG. 22  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when air is blown in between the front end portion  73  and the first folded portion  74  of the sheets of Z-folded documents  71 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the Z-folded document  72  and the Z-folded documents  76  of the sheets of Z-folded documents  71 . Since the air is blown in between the Z-folded document  72  and the Z-folded documents  76  of the sheets of Z-folded documents  71 , the Z-folded document  72  is easily separated from the Z-folded documents  76 . 
     Since the suction blower  32  sucks the air from the unfolding space  34 , the second folded portion  75  of the sheets of Z-folded documents  71  is held by the suction blower  32 , as illustrated in  FIG. 23 .  FIG. 23  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the second folded portion  75  of the sheets of Z-folded documents  71  is held by the suction blower  32 . The Z-folded document  72  is separated from the Z-folded documents  76  by the separation roller  22  and the brake roller  23  and conveyed to the downstream side in the conveyance direction  6 . 
     The second folded portion  75  separates from the suction blower  32  as the Z-folded document  72  is conveyed to the downstream side in the conveyance direction  6 , as illustrated in  FIG. 24 .  FIG. 24  is a side view schematically illustrating the unfolding unit  11  of the document feeder in the first embodiment when the second folded portion  75  of the sheets of Z-folded documents  71  separates from the suction blower  32 . The second folded portion  75  separates from the suction blower  32 , whereby the Z-folded document  72  is unfolded substantially flat and supplied by the paper feeding unit  12  to the paper ejecting unit  14 . 
     Among the sheets of Z-folded documents  76 , the Z-folded document on the top is unfolded and supplied by the paper feeding unit  12  to the paper ejecting unit  14 , in the same manner as the Z-folded document  72 . That is, each of the sheets of Z-folded documents  71  is unfolded and conveyed in the same manner as the Z-folded document  72 , whereby the sheets of Z-folded documents  71  are supplied one by one to the paper ejecting unit  14  by the paper feeding unit  12 . The image reading apparatus  10  can prevent buckling of the Z-folded document  72  by appropriately unfolding and conveying the Z-folded document  72  without heavily deforming a portion other than the creases, in the same manner as the Z-folded document  41 . The image reading apparatus  10  thus can prevent buckling of each of the sheets of Z-folded documents  71  when the sheets of Z-folded documents  71  are unfolded and conveyed one by one. 
     Effects of Document Feeder in First Embodiment 
     The document feeder in the first embodiment includes the platen  2 , the suction blower  32 , the lifting blower  31 , a pair of side blowers  33 , and the paper feeding unit  12 . The platen  2  has the placement surface  4 . The suction blower  32  sucks the air from the unfolding space  34  formed between the platen  2  and the suction surface  36  and holds a part of a document placed on the placement surface  4  on the suction surface  36 . The lifting blower  31  and a pair of side blowers  33  blow the air into the unfolding space  34 . The paper feeding unit  12  conveys a document to the downstream side in the conveyance direction  6  along the placement surface  4 . The suction surface  36  is inclined relative to the placement surface  4  such that the unfolding space  34  is narrower toward the upstream side of the conveyance direction  6 . 
     Such a document feeder can unfold the Z-folded document  41  by conveying the front end portion  46  of the Z-folded document  41  to the downstream side in the conveyance direction  6  such that the second folded portion  49  of the Z-folded document  41  separates from the suction surface  36  after the second folded portion  49  is held by the suction surface  36 . Since the suction surface  36  is inclined relative to the placement surface  4 , the document feeder can reduce the degree of deformation of a portion other than the creases of the Z-folded document  41  when unfolding the Z-folded document  41 . By reducing the degree of deformation of the Z-folded document  41 , the document feeder can prevent buckling of the Z-folded document  41  and appropriately unfold and convey the Z-folded document  41 . 
     The document feeder in the first embodiment has the downstream air-flow opening  38  that blows the air toward the unfolding space  34  from the downstream side in the conveyance direction  6 . Such a document feeder can blow the air in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41  with high efficiency and can bring the second folded portion  49  closer to the suction surface  36  and appropriately hold the second folded portion  49  along the suction surface  36 . 
     When a plurality of documents are placed on the platen  2 , the paper feeding unit  12  of the document feeder in the first embodiment conveys one document separated from the documents to the downstream side. Such a document feeder can unfold the Z-folded documents  71  one by one and convey the unfolded document to the downstream side in the conveyance direction  6 . 
     The document feeder in the first embodiment further includes the first side air-flow opening  37 - 1  and the second side air-flow opening  37 - 2  that blow the air into the unfolding space  34  from both sides in the width direction  50  normal to the conveyance direction  6 . Such a document feeder can blow the air in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41  with high efficiency. Such a document feeder can further blow the air in between the Z-folded document  72  of the Z-folded documents  71  and the Z-folded documents  76  with high efficiency and can appropriately unfold the Z-folded documents  71  one by one and convey the unfolded document to the downstream side in the conveyance direction  6 . 
     Second Embodiment 
       FIG. 25  is a side view schematically illustrating the image reading apparatus provided with the document feeder in a second embodiment. The document feeder in the second embodiment is used in an image reading apparatus and includes the platen  2 , the exit tray  3 , and the feed path  5  as illustrated in  FIG. 25 , in the same manner as the document feeder in the foregoing first embodiment. The document feeder in the second embodiment includes a first paper feeding unit  81 , a processing unit  82 , a conveyance mechanism  84 , a second paper feeding unit  85 , an unfolding unit  86 , a paper ejecting unit  87 , and a reading unit  88 . The first paper feeding unit  81  is disposed at an end on the platen  2  side on the feed path  5 . The first paper feeding unit  81  detects whether a document is placed on the platen  2 . When a plurality of documents are placed on the platen  2 , the first paper feeding unit  81  releases one document disposed on the top of the documents placed on the platen  2 , to the feed path  5 , and supplies the document released from the platen  2  to the feed path  5  to the processing unit  82 . When one document is placed on the platen  2 , the first paper feeding unit  81  releases the document to the feed path  5  and supplies the document released from the platen  2  to the feed path  5  to the processing unit  82 . 
     The processing unit  82  is disposed on the downstream side of the first paper feeding unit  81  on the feed path  5 , that is, disposed between the first paper feeding unit  81  and the exit tray  3  on the feed path  5 . The processing unit  82  detects whether the document supplied from the first paper feeding unit  81  is a one-sheet document or a bound document. The one-sheet document is formed of one sheet of paper. The bound document is formed by binding a plurality of sheets with a binder member. An example of the binder member is a staple. 
     When it is detected that the document supplied from the first paper feeding unit  81  is a one-sheet document, the processing unit  82  supplies the one-sheet document as it is to the conveyance mechanism  84 . When it is detected that the document is a bound document, the processing unit  82  removes the binder member from the bound document to generate a plurality of one-sheet documents and supplies the generated one-sheet documents to the conveyance mechanism  84 . The processing unit  82  may be unable to remove the binder member from the bound document in some cases. The processing unit  82  detects whether the binder member has been removed appropriately from the bound document and, when it is detected that the binder member has not been removed from the bound document, supplies the bound document as it is to the conveyance mechanism  84 . 
     The conveyance mechanism  84  is disposed in a region on the downstream side of the processing unit  82  on the feed path  5 , that is, disposed between the processing unit  82  and the exit tray  3  on the feed path  5 . The conveyance mechanism  84  supplies the document supplied from the processing unit  82  to the second paper feeding unit  85 . 
     The second paper feeding unit  85  is disposed on the downstream side of the conveyance mechanism  84  on the feed path  5 , that is, disposed between the conveyance mechanism  84  and the exit tray  3  on the feed path  5 . In the second paper feeding unit  85 , the brake roller  23  of the paper feeding unit  12  previously described is replaced by another brake roller  91  and a document detection sensor  92  is added, and the other part is the same as the paper feeding unit  12  previously described. The pick roller  21  of the second paper feeding unit  85  is switched to the load mode or the distant mode. When switched to the load mode, the pick roller  21  rotates to bring a document in contact with the pick roller  21 , among a plurality of documents supplied from the conveyance mechanism  84 , into contact with the separation roller  22 . When switched to the distant mode, the pick roller  21  retracts from the platen  2  so as not to come into contact with the document supplied from the conveyance mechanism  84 . The separation roller  22  of the second paper feeding unit  85  rotates to convey the document in contact with the separation roller  22  to the downstream side in the conveyance direction  6 . 
     The brake roller  91  is disposed on the downstream side of the pick roller  21  on the feed path  5 , that is, disposed between the pick roller  21  and the exit tray  3  on the feed path  5 . The brake roller  91  is switched to a separation force mode or a no separation force mode. In a case where the brake roller  91  is switched to the separation force mode, when one sheet of document is sandwiched between the separation roller  22  and the brake roller  23 , the brake roller  91  follows one sheet of document conveyed by the separation roller  22  to rotate forward. In a case where the brake roller  91  is switched to the separation force mode, when a plurality of sheets of documents are sandwiched between the separation roller  22  and the brake roller  23 , the brake roller  91  rotates backward. In a case where the brake roller  91  is switched to the no separation force mode, when a document is sandwiched between the separation roller  22  and the brake roller  23 , the brake roller  91  follows the document conveyed by the separation roller  22  to rotate forward. 
     The document detection sensor  92  is disposed between the pick roller  21  and the separation roller  22  on the feed path  5 . The document detection sensor  92  detects whether a document is disposed at a predetermined position between the pick roller  21  and the separation roller  22  on the feed path  5 . 
     In the unfolding unit  86 , an open/closed guide  93  and an open/closed guide driver  94  are added to the unfolding unit  11  of the document feeder in the foregoing first embodiment, and the other part is the same as the unfolding unit  11  of the document feeder in the foregoing first embodiment. The open/closed guide  93  is rotatably supported about a rotation axis  99  so as to be disposed in an open position or a closed position. The rotation axis  99  is parallel to the width direction  50 . The open/closed guide driver  94  rotates the open/closed guide  93  about the rotation axis  99 . 
       FIG. 26  is a plan view illustrating the open/closed guide  93  of the document feeder in the second embodiment. The open/closed guide  93  is formed in a substantially flat plate shape. The open/closed guide  93  has a plurality of notches  96 . 
     As illustrated in  FIG. 27 , the feed path  5  includes a document placement member  97 .  FIG. 27  is a perspective view illustrating the unfolding unit  86  of the document feeder in the second embodiment when the open/closed guide  93  is disposed in the open position. The document placement member  97  has a substantially flat placement surface  95 . The document placement member  97  is disposed below the unfolding unit  86  such that the feed path  5  is formed between the document placement member  97  and the unfolding unit  86 . Further, the document placement member  97  is disposed such that a plane along the placement surface  95  is parallel to the conveyance direction  6  and the width direction  50  and such that the placement surface  95  faces the unfolding space  34  of the unfolding unit  86 . 
     When disposed in the open position, the open/closed guide  93  is disposed in the vicinity of the suction blower  32 .  FIG. 28  is another perspective view illustrating the unfolding unit  86  of the document feeder in the second embodiment when the open/closed guide  93  is disposed in the open position. When the open/closed guide  93  is disposed in the open position, the notches  96  are fitted in a plurality of air intakes  35  of the suction blower  32 . Since the notches  96  are fitted in the air intakes  35 , the open/closed guide  93  can be disposed on the upstream side in the conveyance direction  6  of the air intakes  35  of the suction blower  32 , that is, can be disposed on the upstream side in the conveyance direction  6  from the suction surface  36 . When the open/closed guide  93  is disposed on the upstream side in the conveyance direction  6  from the suction surface  36 , the folded document conveyed on the feed path  5  can be unfolded in the unfolding space  34  of the unfolding unit  86  without coming into contact with the open/closed guide  93 . 
       FIG. 29  is a perspective view illustrating the unfolding unit  86  of the document feeder in the second embodiment when the open/closed guide  93  is disposed in the closed position. When disposed in the closed position, the open/closed guide  93  is disposed in the vicinity of the placement surface  95  of the document placement member  97  such that a plane along the open/closed guide  93  is parallel to the conveyance direction  6  and the width direction  50 . That is, when disposed in the closed position, the open/closed guide  93  isolates the unfolding space  34  from the path of a document formed by the feed path  5 . 
       FIG. 30  is a flowchart illustrating the operation of the image reading apparatus provided with the document feeder in the second embodiment. To read an image from a plurality of documents using the image reading apparatus, the user places the documents on the platen  2  and operates the input/output device of the control unit of the image reading apparatus to start the image reading apparatus. The documents placed on the platen  2  include a one-sheet document or a bound document. The one-sheet document may be a Z-folded document that is Z-folded. Upon starting of the image reading apparatus, the control unit starts an initial operation (step S 11 ). Upon starting of the initial operation, the control unit stops the operation of the lifting blower  31 , the suction blower  32 , and a pair of side blowers  33  and further controls the open/closed guide driver  94  to dispose the open/closed guide  93  into the closed position. 
     After the initial operation is performed, the control unit controls the first paper feeding unit  81  to detect whether a document is placed on the platen  2 . When it is detected that a document is placed on the platen  2 , the control unit controls the first paper feeding unit  81  to release one document disposed on the top of the documents placed on the platen  2 , to the feed path  5 , and supplies the released document to the processing unit  82  (step S 12 ). 
     The control unit further controls the processing unit  82  to detect whether the document supplied from the first paper feeding unit  81  is a bound document or a one-sheet document. When it is detected that the document supplied from the first paper feeding unit  81  is a bound document, the control unit controls the processing unit  82  to remove a binder member from the bound document. The control unit further controls the processing unit  82  to detect whether the binder member has been removed appropriately from the bound document. When the binder member has been removed appropriately from the bound document, the control unit controls the processing unit  82  to supply a plurality of one-sheet documents from which the binder member has been removed appropriately, to the conveyance mechanism  84 . When the binder member is not removed appropriately from the bound document, the control unit controls the processing unit  82  to supply the bound document as it is to the conveyance mechanism  84 . When it is detected that the document supplied from the first paper feeding unit  81  is a one-sheet document, the control unit controls the processing unit  82  to supply the one-sheet document as it is to the conveyance mechanism  84 . 
     The control unit switches to the separation mode or the non-separation mode in accordance with the operation of the processing unit  82  (step S 13 ). That is, the control unit switches to the separation mode when the processing unit  82  has removed a binder member appropriately from the bound document or when the one-sheet document has been supplied from the first paper feeding unit  81  to the processing unit  82 . The control unit switches to the non-separation mode when the processing unit  82  has not removed a binder member appropriately from the bound document. 
     When switching to the separation mode (separation at step S 13 ), the control unit controls the document detection sensor  92  to detect whether the document is disposed at a predetermined position between the pick roller  21  and the brake roller  91 . When it is detected that the document is disposed at a predetermined position between the pick roller  21  and the brake roller  91 , the control unit controls the conveyance mechanism  84  to stop conveyance of the document (step S 14 ). After conveyance of the document is stopped, the control unit controls the open/closed guide driver  94  to dispose the open/closed guide  93  into the open position (step S 15 ). After conveyance of the document is stopped, the control unit further controls the lifting blower  31  to blow the air into the unfolding space  34 , controls a pair of side blowers  33  to blow the air into the unfolding space  34  from both sides in the width direction  50 , and controls the suction blower  32  to suck the air from the unfolding space  34  (step S 16 ). 
     The control unit waits until a timing when a predetermined period has passed since the timing when the lifting blower  31 , the suction blower  32 , a pair of side blowers  33 , and the open/closed guide driver  94  start operation (step S 17 ). The predetermined period is, for example, one second. With passage of a predetermined period, the lifting blower  31  can stably blow the air into the unfolding space  34 . With passage of a predetermined period, the suction blower  32  can stably suck the air from the unfolding space  34 . With passage of a predetermined period, a pair of side blowers  33  can stably blow the air into the unfolding space  34 . With passage of a predetermined period, the open/closed guide driver  94  can reliably dispose the open/closed guide  93  into the open position. 
     After a predetermined period has passed, the control unit starts separate conveyance (step S 18 ). Upon starting of separate conveyance, the control unit switches the conveyance mechanism  84  to the distant mode, switches the pick roller  21  to the load mode, and switches the brake roller  91  to the separation force mode. The control unit allows the pick roller  21  to rotate forward so that the document in contact with the pick roller  21  is conveyed to the downstream side in the conveyance direction  6  so as to be sandwiched between the separation roller  22  and the brake roller  91 . The control unit allows the separation roller  22  to rotate forward so that the document disposed on the top of a plurality of documents sandwiched between the separation roller  22  and the brake roller  91  is supplied to the paper ejecting unit  87 . 
     In a case where the brake roller  91  is switched to the separation force mode, when one sheet of document is sandwiched between the separation roller  22  and the brake roller  91 , the brake roller  91  follows the one sheet of document conveyed to rotate forward and conveys the one sheet of document as it is to the paper ejecting unit  87 , and when a plurality of sheets of documents are sandwiched between the separation roller  22  and the brake roller  91 , the brake roller  91  rotates backward to convey the document not in contact with the separation roller  22  to the upstream side in the conveyance direction  6 . That is, upon starting of separation conveyance, the second paper feeding unit  85  supplies the documents supplied from the conveyance mechanism  84  one by one to the paper ejecting unit  87 . 
     When a folded document is conveyed between the conveyance mechanism  84  and the second paper feeding unit  85  on the feed path  5 , the unfolding unit  86  unfolds the folded document in the same manner as the unfolding unit  11  of the document feeder in the foregoing first embodiment. For example, when the folded portion  47  of the Z-folded document  41  is disposed in the unfolding space  34 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  46  and the first folded portion  48 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 . The air blown in between the front end portion  46  and the first folded portion  48  lifts the folded portion  47  of the Z-folded document  41  from the front end portion  46  (step S 19 ). 
     Since the suction blower  32  sucks the air from the unfolding space  34 , the second folded portion  49  of the Z-folded document  41  is held along the suction surface  36  by the suction blower  32  when the folded portion  47  is lifted from the front end portion  46  (step S 20 ). After being held by the suction blower  32 , the second folded portion  49  of the Z-folded document  41  separates from the suction surface  36  as the Z-folded document  41  is further conveyed by the second paper feeding unit  85  to the downstream side in the conveyance direction  6  (step S 21 ). The second folded portion  49  separates from the suction surface  36 , whereby the Z-folded document  41  is unfolded substantially flat. The unfolding unit  86  can prevent buckling of the Z-folded document  41  in the same manner as the unfolding unit  11  of the document feeder in the foregoing first embodiment. 
     When the document is supplied from the second paper feeding unit  85  to the paper ejecting unit  87 , the control unit controls the reading unit  88  to read images on both surfaces of the document conveyed from the second paper feeding unit  85  to the paper ejecting unit  87  and record the read images (step S 22 ). The control unit controls the paper ejecting unit  87  to place the document supplied from the brake roller  91  to the paper ejecting unit  87  onto the exit tray  3  (step S 23 ). 
     The control unit controls the document detection sensor  92  to detect whether a document is disposed at a predetermined position between the pick roller  21  and the brake roller  91  (step S 24 ). When it is detected that a document is disposed at a predetermined position between the pick roller  21  and the brake roller  91  (Yes at step S 24 ), the control unit repeatedly performs the process from step S 18  to step S 24 . The process from step S 18  to step S 24  is repeatedly performed, whereby a plurality of one-sheet documents generated by the processing unit  82  removing a binder member from the bound document are unfolded one by one, have images read therefrom, and are placed onto the exit tray  3 . 
     When switched to the non-separation mode (non-separation at step S 13 ), the control unit starts non-separate conveyance (step S 25 ). Upon starting of non-separate conveyance, the control unit switches the pick roller  21  to the distant mode and switches the brake roller  91  to the no separation force mode while the conveyance mechanism  84  is kept switched to the load mode and the open/closed guide  93  is kept disposed in the closed position. The control unit controls the conveyance mechanism  84  to supply the bound document supplied from the processing unit  82  to the conveyance mechanism  84  to the second paper feeding unit  85 . 
     When the open/closed guide  93  is disposed in the closed position, the front end of the bound document does not enter the unfolding space  34 , and the bound document is supplied appropriately to the second paper feeding unit  85 . In the document feeder, in a case where the bound document is supplied to the second paper feeding unit  85 , when the front end of the bound document enters the unfolding space  34 , the front end may be caught, for example, by a member of the unfolding unit  86  to cause breakage of the bound document or cause occurrence of inconvenience such as a jam. The document feeder, provided with the open/closed guide  93 , can guide the bound document appropriately to the second paper feeding unit  85  and prevent occurrence of such inconvenience. 
     When the open/closed guide  93  is disposed in the closed position and the lifting blower  31 , the suction blower  32 , and a pair of side blowers  33  are not in operation, the bound document, even folded, is supplied to the second paper feeding unit  85  without being unfolded by the unfolding unit  86 . The bound document is guided by the open/closed guide  93  and supplied to the second paper feeding unit  85 , and then sandwiched between the separation roller  22  and the brake roller  91 . With the brake roller  91  being switched to the no separation force mode, the bound document sandwiched between the separation roller  22  and the brake roller  91  is supplied to the paper ejecting unit  87  without being separated when the separation roller  22  rotates forward. 
     When the bound document is supplied from the second paper feeding unit  85  to the paper ejecting unit  87 , the control unit controls the reading unit  88  to read images on both surfaces of the bound document and record the read images (step S 26 ). The control unit controls the paper ejecting unit  87  to place the bound document onto the exit tray  3  (step S 27 ). 
     After the bound document is placed onto the exit tray  3 , the control unit controls the first paper feeding unit  81  to detect whether a document is placed on the platen  2  (step S 28 ). Even when it is detected that no document is disposed at a predetermined position between the pick roller  21  and the brake roller  91  (No at step S 24 ), the control unit detects whether a document is placed on the platen  2 , similarly. When it is detected that a document is placed on the platen  2  (Yes at step S 28 ), the control unit repeatedly performs the process from step S 11  to step S 28 . The process from step S 11  to step S 28  is repeatedly performed, whereby the documents placed on the platen  2  have images read therefrom and are placed onto the exit tray  3 . 
     Effects of Document Feeder in Second Embodiment 
     The document feeder in the second embodiment includes the open/closed guide  93  movable between the closed position and the open position. When disposed in the closed position, the open/closed guide  93  guides a document to the second paper feeding unit  85 , and when disposed in the open position, the open/closed guide  93  retracts such that a part of the document is movable toward the suction surface  36 . Such a document feeder can prevent breakage of a bound document or occurrence of inconvenience such as a jam since the open/closed guide  93  is disposed in the closed position when the bound document passes through the unfolding unit  86 . 
     The document feeder in the second embodiment further includes the open/closed guide driver  94  to move the open/closed guide  93  to the closed position or the open position. Such a document feeder can automatically dispose the open/closed guide  93  into the closed position or automatically dispose the open/closed guide  93  into the open position. 
     Although the document feeder in the second embodiment includes the open/closed guide driver  94 , the open/closed guide driver  94  may be omitted. In this case, when a document is unfolded by the unfolding unit  86 , the open/closed guide  93  is disposed into the open position by the user, and when a document is not unfolded by the unfolding unit  86 , the open/closed guide  93  is disposed into the closed position by the user. Such a document feeder also can unfold and convey a folded document appropriately when the open/closed guide  93  is disposed in the open position, in the same manner as the document feeder in the foregoing embodiment. 
     Third Embodiment 
     The document feeder in the foregoing first embodiment separates the documents placed on the platen  2  from each other in the paper feeding unit  12 . However, the documents are not necessarily separated. As illustrated in  FIG. 31 , in the document feeder in a third embodiment, the paper feeding unit  12  of the document feeder in the foregoing first embodiment is replaced by another paper feeding unit  101 , and the other part is the same as the document feeder in the foregoing first embodiment.  FIG. 31  is a side view schematically illustrating the image reading apparatus provided with the document feeder in the third embodiment. The paper feeding unit  101  includes a pair of conveyance rollers  102  and a document detection sensor  103 . A pair of conveyance rollers  102  are proximate to each other such that a document is sandwiched between a pair of conveyance rollers  102 . When a document is sandwiched between a pair of conveyance rollers  102 , a pair of conveyance rollers  102  rotate to supply the document to the paper ejecting unit  14 . The document detection sensor  103  detects whether a document is disposed between a pair of conveyance rollers  102 . 
       FIG. 32  is a flowchart illustrating the operation of the image reading apparatus provided with the document feeder in the third embodiment. To read an image from the Z-folded document  41  using the image reading apparatus, first, the user operates the input/output device of the control unit of the image reading apparatus to start the image reading apparatus. Upon starting of the image reading apparatus, the control unit of the document feeder in the third embodiment starts an initial operation (step S 31 ). Upon starting of the initial operation, the control unit brings the lifting blower  31 , the suction blower  32 , and a pair of side blowers  33  into operation and allows a pair of conveyance rollers  102  to rotate. After the initial operation is performed, the user places the Z-folded document  41  onto the platen  2  such that the folded portion  47  of the Z-folded document  41  is disposed in the unfolding space  34  and such that the front end of the Z-folded document  41  is sandwiched between a pair of conveyance rollers  102  of the paper feeding unit  101  (step S 32 ). 
     When the folded portion  47  of the Z-folded document  41  is disposed in the unfolding space  34 , the air is blown into the unfolding space  34  from the lifting blower  31 , whereby the air is blown in between the front end portion  46  and the first folded portion  48 . The air is blown into the unfolding space  34  from a pair of side blowers  33 , whereby the air is further blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 . The air blown in between the front end portion  46  and the first folded portion  48  lifts the folded portion  47  of the Z-folded document  41  from the front end portion  46  (step S 33 ). 
     Since the suction blower  32  sucks the air from the unfolding space  34 , the second folded portion  49  of the Z-folded document  41  is held along the suction surface  36  by the suction blower  32  when the folded portion  47  is lifted from the front end portion  46  (step S 34 ). After the second folded portion  49  of the Z-folded document  41  is held by the suction blower  32 , the Z-folded document  41  is further conveyed by the paper feeding unit  101  to the downstream side in the conveyance direction  6 , whereby the second folded portion  49  separates from the suction surface  36  (step S 35 ). The second folded portion  49  separates from the suction surface  36 , whereby the Z-folded document  41  is unfolded substantially flat. 
     When the document is supplied from the paper feeding unit  101  to the paper ejecting unit  14 , the control unit controls the reading unit  15  to read images on both surfaces of the document conveyed from the paper feeding unit  101  to the paper ejecting unit  14  and record the read images (step S 36 ). The control unit controls the paper ejecting unit  14  to place the document supplied from the paper feeding unit  101  to the paper ejecting unit  14  onto the exit tray  3  (step S 37 ). 
     To read an image from another Z-folded document different from the Z-folded document  41 , the user places the Z-folded document onto the platen  2  within a certain period of time from the timing when the Z-folded document  41  exits from between a pair of side blowers  33 . The control unit controls the document detection sensor  103  to detect whether a document is disposed between a pair of conveyance rollers  102  within a period of time from the timing when the Z-folded document  41  exits from between a pair of side blowers  33  (step S 38 ). When it is detected that a document is disposed between a pair of conveyance rollers  102  within a certain period of time (Yes at step S 38 ), the control unit repeatedly performs the process from step S 32  to step S 38 . 
     The document feeder in the third embodiment can prevent buckling of the Z-folded document  41  when unfolding and conveying the Z-folded document  41 , in the same manner as the document feeder in the foregoing first embodiment. The document feeder in the third embodiment can unfold and convey a folded document other than the Z-folded document  41  and can prevent buckling of the folded document when unfolding and conveying the folded document, in the same manner as the document feeder in the foregoing first embodiment. 
     Fourth Embodiment 
       FIG. 33  is a top view illustrating a part of the unfolding unit of the document feeder in a fourth embodiment. In the unfolding unit of the document feeder in the fourth embodiment, a pair of side blowers  33  of the unfolding unit  11  of the document feeder in the foregoing first embodiment are omitted, and the other part is the same as the unfolding unit  11  of the document feeder in the foregoing first embodiment. The document feeder in the fourth embodiment can operate similarly to the document feeder in the foregoing first embodiment to prevent buckling of a folded document when unfolding and conveying the folded document, in the same manner as the document feeder in the foregoing first embodiment. Since a pair of side blowers  33  are omitted, the production cost of the document feeder in the fourth embodiment can be reduced compared with the document feeder in the foregoing first embodiment. 
     Since a pair of side blowers  33  are omitted in the document feeder in the fourth embodiment, much of the air blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41  by the lifting blower  31  is ejected from the ends in the width direction  50 . In the document feeder in the foregoing first embodiment, compared with the document feeder in the fourth embodiment, the air blown in between the front end portion  46  and the first folded portion  48  of the Z-folded document  41  is less ejected, so that the folded portion  47  can be lifted with high efficiency, and the Z-folded document  41  can be unfolded with high efficiency. 
     Fifth Embodiment 
       FIG. 34  is a top view illustrating a part of the unfolding unit of the document feeder in a fifth embodiment. In the document feeder in the fifth embodiment, the lifting blower  31  of the document feeder in the foregoing fourth embodiment is replaced by a first lifting blower  111 - 1  and a second lifting blower  111 - 2 , and the other part is the same as the document feeder in the foregoing fourth embodiment. The first lifting blower  111 - 1  includes a first downstream air-flow opening  112 - 1  disposed on one side in the width direction  50  of the downstream side of the unfolding space  34  and blows the air toward the center in the width direction  50  of the unfolding space  34  through this first downstream air-flow opening  112 - 1 . The second lifting blower  111 - 2  includes a second downstream air-flow opening  112 - 2  disposed on the other side in the width direction  50  of the downstream side of the unfolding space  34  and blows the air toward the center in the width direction  50  of the unfolding space  34  through this second downstream air-flow opening  112 - 2 . 
     The document feeder in the fifth embodiment operates similarly to the document feeder in the foregoing fourth embodiment. At this time, the air blown out from the first downstream air-flow opening  112 - 1  and the air blown out from the second downstream air-flow opening  112 - 2  collide against each other at the center in the width direction  50  between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 . The air blown in between the front end portion  46  and the first folded portion  48  is therefore less ejected from between the front end portion  46  and the first folded portion  48 . Since the air is less ejected from between the front end portion  46  and the first folded portion  48  of the Z-folded document  41 , the document feeder in the fifth embodiment can lift the folded portion  47  with high efficiency and can unfold the Z-folded document  41  with high efficiency, compared with the document feeder in the foregoing fourth embodiment. 
     The unfolding units  11  and  86  of the document feeder in the foregoing embodiments are provided with a plurality of blowers, which may be replaced by one blower. For example, the document feeder has a plurality of shutters that open/close the downstream air-flow opening, the first side air-flow opening  37 - 1 , the second side air-flow opening  37 - 2 , and the air intakes  35 . The downstream air-flow opening, the first side air-flow opening  37 - 1 , the second side air-flow opening  37 - 2 , and the air intakes  35  are connected to the one blower. Such a document feeder can operate similarly to the document feeder in the foregoing embodiments by opening and closing the shutters and can prevent buckling of a folded document when unfolding and conveying the folded document. The production cost of the document feeder can be reduced compared with the document feeder in the foregoing embodiments. 
     The document feeder in the foregoing embodiments is used for an image reading apparatus but may be used for other devices. An example of other devices is a printer. For example, when the document feeder is used for a printer, the reading unit  15  is replaced by a printing device. Even when the document feeder is used for other devices different from the image reading apparatus, a folded document can be unfolded and conveyed appropriately. 
     The document feeder of the disclosure can unfold and convey a folded document appropriately. 
     All examples and conditional language recited herein are intended for pedagogical purposes of aiding the reader in understanding the disclosure and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the disclosure. Although the embodiments of the disclosure have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.