Patent Publication Number: US-8967619-B2

Title: Image reading apparatus

Description:
Cross-Reference to Related Application 
     This application claims priority under 35 U.S.C. §119 from Japanese Patent Applications No. 2012-251880 filed on Nov. 16, 2012. The entire subject matter of the application is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     An aspect of the present invention relates to an image reading apparatus. 
     Related Art 
     A sheet conveying device is provided, for example, to an image reading apparatus. Typically, in the image reading apparatus, a sheet is picked up from an original sheet placing tray and conveyed along a sheet convey path in a predetermined conveying direction. The sheet convey path is passing an image reading section. When the sheet passes through the image reading section, an image formed on the sheet is read by an image reading unit. 
     Generally, the sheet conveying device has a roller unit for conveying the sheet on an upstream side, in the sheet conveying direction, with respect to the image reading section. Such a roller unit typically has three rollers, which are arranged to be rotatable about a rotation axis extending in a sheet-width direction, which is perpendicular to the sheet convey direction. The three rollers are arranged in the sheet-width direction in a spaced manner. When a sheet of which the width extends over the three rollers (hereinafter, such a sheet will be referred to as a normal size sheet) is conveyed, the normal sheet contacts circumferential surfaces of the three rollers. Thus, the normal size sheet receives a conveying force from the three rollers. 
     If a sheet of which width is smaller than a distance between two rollers respectively arranged at both sides, among the three rollers (hereinafter, such a sheet will also be referred to as a small size sheet) is conveyed such that the center of the sheet in its width direction is aligned to the center of the conveyance path, the small size sheet only contacts a circumferential surface of one roller arranged at a central portion. Therefore, a conveying force applied by the central roller to the small size sheet is less than the conveying force the normal size sheet receives from three rollers. As a result, when the small size sheet is conveyed, in comparison with a case where the normal size sheet is conveyed, a speed of the sheet when passing through the image reading section might be lowered. In such a case, an image of the small size sheet read by the image reader unit may be expanded in the sheet conveying direction. 
     According to aspects of the invention, there is provided an image reading apparatus, which has a separation section configured to supply a sheet one by one, at least three driving rollers arranged on a downstream, in a sheet conveying direction, of the separation section and configured to convey the sheet, at least three driven rollers configured to be urged by the driving rollers and driven to rotate by rotation of the driving rollers, respectively, and an image reader unit configured to read an image of the sheet conveyed in the conveying direction. The at least three driven rollers are arranged at a central portion and both side portions in a sheet width direction, and sheet conveying forces by one of the at least three driven rollers and one of the at least three driving rollers arranged at the central portions in the sheet width direction is greater than sheet conveying forces by others of the at least three driven rollers and others of the at least three driving rollers arranged at both side portions in the sheet width direction. 
     According to aspects of the invention, it is possible to suppress a situation that the conveying force applied to the small size sheet becomes insufficient. As a result, even the small size sheet can be conveyed at an appropriate conveying speed. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a perspective view of an image reading apparatus according to an embodiment of the invention, viewed from an upper-left front side thereof, and a tray is located at a tray position. 
         FIG. 2  is a cross-sectional side view of the image reading apparatus depicted in  FIG. 1 . 
         FIG. 3  is a perspective view of the image reading apparatus according to the embodiment of the invention, viewed from an upper-left front side thereof, and a outlet cover is located at the tray position. 
         FIG. 4  is a cross-sectional side view of the image reading apparatus depicted in  FIG. 3 . 
         FIG. 5  is a perspective view of the image reading apparatus viewed from an upper-right front direction thereof, when the tray is located at the tray position and a maintenance cover is removed. 
         FIG. 6  is a perspective view of the image reading apparatus viewed from an upper-right front direction thereof, when the tray is located at the tray position and the maintenance cover and a first LF roller are removed. 
         FIG. 7  is a cross-sectional view of the image reading apparatus taken along an A-A line indicated in  FIG. 6 . 
         FIG. 8  is a cross-sectional view of one of driven rollers arranged at both sides in a front-and-rear direction. 
         FIG. 9  is a cross-sectional view of a driven roller arranged at a central portion in a front-and-rear direction. 
         FIG. 10  is a cross-sectional view of a driven roller arranged at a central portion in a front-and-rear direction. 
         FIG. 11  is a cross-sectional view of a driven roller arranged at a central portion in a front-and-rear direction. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of the invention will be described referring to the accompanying drawings. 
     &lt;Outer Configuration&gt; 
     An image reading apparatus  1  according to an embodiment of the invention has a housing  2 , a tray  3 , a maintenance cover  4  and an outlet cover  5 . The tray  3 , the maintenance cover  4  and the outlet cover  5  are attached to the housing  2 . The housing  2  includes a front side plate  6 , a rear side plate  7 , a left side plate  8  and a right side plate  9 . 
     As depicted in  FIGS. 1-3 , orientations of the image reading apparatus  1  will be referred to such that a side where the tray  3  and the maintenance cover  4  are arranged is an upside, a side where the outlet cover  5  is provided is a left side, and a side where the front side plate  6  is provided is a front side. With this definition, an up-and-down direction, a right/left direction and a front/rear direction of the image reading apparatus  1  are defined. In each drawing, directions thus defined are indicated in association with arrows. 
     According to the embodiment, another housing of a printer (not shown) is connected to the housing  2  of the image reading apparatus  1  from the above. As described above, the housing  2  has the front side plate  6 , the rear side plate  7 , the left side plate  8  and the right side plate  9 . The front and the rear side plates  6  and  7  are arranged along the front-and-rear direction with a space therebetween. The left side plate  8  is arranged between left ends of the front side plate  6  and the rear side plate  7 . The left side plate  8  is divided into a front-left side plate  10  and a rear-left side plate  11 . The front-left side plate  10  and the rear-left side plate  11  are arranged to be spaced in the front-and-rear direction. The right side plate  9  is arranged between right ends of the front side plate  6  and the rear side plate  7 . 
     The tray  3  is arranged between central portions of the front side plate  6  and the rear side plate  7 . The tray  3  is configured to be rotatable about a rotation axis which extends in the front-and-rear direction along a right-side end of the tray  3  itself, between a cover position and a tray position. The cover position of the tray  3  is defined as a position at which an upper surface of the tray  3  is substantially in parallel with the maintenance cover  4  and/or an upper surface  12  to form a substantially same plane therewith, and covers an outlet section  37 . The tray position of the tray  3  is defined as a position where a right side of the tray  3  is lifted as depicted in  FIG. 1  so that an original sheet can be placed on the tray  3 . 
     The maintenance cover  4  is arranged between the front side plate  6  and the rear side plate  7 . The maintenance cover  4  is arranged to be rotatable about a rotation axis which extends in the front-and-rear direction along a right side of the maintenance cover  4  between a closed position and an opened position. The closed position of the maintenance cover  4  is defined as a position where the maintenance cover is substantially in the same plane with the upper surface of the tray  3  located at the cover position and the upper surface  12 , and the maintenance cover  4  covers a first LF roller  27 , a second LF roller  31  and an upper reader unit  30 . The opened position of the maintenance cover  4  is defined as a position where the left side of the maintenance cover  4  is lifted with respect to the housing  2  so that a jammed original sheet inside the image reading apparatus  1  can be removed. 
     The outlet cover  5  is arranged, on the left side surface of the housing  2 , between the front-left side plate  10  and the rear-left side plate  11 . The outlet cover  5  is arranged to be rotatable about a rotation axis  13  which extends in the front-and-rear direction along a lower end of the outlet cover  5  between a cover position and a tray position. The cover position of the outlet cover  5  is defined as a position where the outlet cover  5  is oriented upright along the up-and-down direction, i.e., in the vertical direction, as depicted in  FIGS. 1 and 2 . When the outlet cover  5  is located at the cover position, an outer surface of the outlet cover  5  extends substantially in the same plane including outer surfaces of the front-left side plate  10  and the rear-left side plate  11 . The tray position of the outlet cover  5  is defined as a position where a left side of the outlet cover  5  is lifted as depicted in  FIGS. 3 and 4 . 
     &lt;Inner Configuration&gt; 
     The image reading apparatus  1  has, as depicted in  FIGS. 2 ,  4  and  5 , a supplying section  21 , a pair of sheet width guide  22 , a supplying roller  23 , a separation roller  24 , a separation piece  25 , a common path formation section  26 , three first LF rollers  27  (i.e., two first LF rollers  27 A and one first LF roller  27 B), three driven rollers  28  (i.e., two driven rollers  28 A and one driven roller  28 ), a lower reader unit  29 , the upper reader unit  30 , three second LF rollers  31 , three driven rollers  32 , a driven roller  33 , a first path formation unit  35 , three driven rollers  36 , an outlet  37  and a second path formation section  38 . 
     The supplying section  21  is provided at substantially the central part, in the right-and-left direction, of the housing  2 . A sheet S subject to image reading is placed on an upper surface  14  of the supplying section  21 . 
     The pair of sheet width guides  22  is provided to the supplying section  21 . The sheet width guides  22  are configured to face each other in the front-and-rear direction. The sheet width guides  22  are configured to move closer to each other and to separate from each other by the same amounts with respect to a center therebetween. A distance between the sheet width guides  22  is adjusted in accordance with a width of the sheet S, in the front-and-rear direction, which is placed on the upper surface  41  of the supplying section  21 . The sheet S is to be inserted between the sheet width guides  22  from the right side, thereby the sheet S being placed on the upper surface  41  of the supplying section  21 , with the center of the sheet S is aligned with the center of the pair of sheet width guides  22 . 
     The supply roller  23  is arranged on the left side of the supplying section  21  and substantially at the central portion of the housing  2  in the front-and-rear direction. The supply roller  23  is provided to the housing  2  such that it is rotatable about an axis extending in the front-and-rear direction. 
     The separation roller  24  is arranged on the left side of the supplying roller  23  and substantially at the central portion in the front-and-rear direction of the housing  2 . The separation roller  24  is provided to the housing  2  such that it is rotatable about an axis extending in the front-and-rear direction. 
     The separation piece  25  is arranged above the separation roller  24 . The separation piece  25  is elastically biased to contact the circumferential surface of the separation roller  24  from the above. 
     The common path forming section  26  is provided to the housing  2  on the left side of the separation roller  24  and below the maintenance cover  4 . The common path forming section  26  has an upper formation section  51  and a lower formation section  52 . A lower surface  53  of the upper formation section  51  is inclined such that a left portion thereof is lower than a right portion. An upper surface  54  of the lower formation section  52  extends substantially parallelly with the lower surface  53  of the upper formation section  51  with a space therebetween. A space defined between the lower surface  53  of the upper formation section  51  and the upper surface  54  of the lower formation section  52  defines the common path  55  through which the sheet S is conveyed. 
     The first LF rollers  27  are provided on the downstream, in a conveying direction of the sheet S, of the separation roller  24  and the separation piece  25 . A rotation shaft  56  is rotatably supported by the housing  2  with its rotation axis extending in the front-and-rear direction. Therefore, the rotation shaft  56  extends in the front-and-rear direction in a state where the rotation shaft  56  is supported by the housing  2 . In a following description, directions concerning the rotation shaft  56 , three first LF rollers  27 , a spring shaft  57 , three driven rollers  28 , and the like are explained as directions when these elements are secured to or supported by the housing  2 . The three first LF rollers  27  are secured to the rotation shaft  56 , which extends in the front-and-rear direction, with evenly spaced from each other. The rotation shaft  56  is arranged such that it is on an upper side with respect to the lower surface  53  of the upper formation section  51  at substantially a central part of the upper formation section  51 , in the right-and-left direction. A part of the circumferential surface of each of the first LF roller  27  protrudes through an opening (not shown) formed on the upper formation section  51  toward the common path  55 . 
     The driven rollers  28 A and  28 B are, as depicted in  FIGS. 6 and 7 , arranged in the front-and-rear direction with evenly spaced from each other. Hereinafter, when the driven rollers are described without any specific indication of distinguishing one of the driven rollers from the others, the driven rollers will be indicated as the driven roller(s)  28 , while the driven rollers should be distinguished from each other, the driven rollers are referred to as the driven roller  28 A or  28 B. Each driven roller  28  is supported by the spring shaft  57  extending in the front-and-rear direction. Each driven roller  28  is accommodated n a roller accommodation section  58 . The roller accommodation section  58  is formed on the lower formation section  52 . The roller accommodation section  58  is downwardly concave from the upper surface  54 . Both end portions of the spring shaft  57  are supported by spring accommodation sections  59 , respectively. The spring accommodation sections  59  are formed to be downwardly concave from the upper surface  54  of the lower formation section  52 . 
     A part of the circumferential surface of each driven roller  28  protrudes upward from the roller accommodation section  58 . The part of the driven roller  28  protruded from the roller accommodation section  58  contacts the circumferential surface of the first LF roller  27 . That is, in the common path  55  defined by the upper formation section  51  and the lower formation section  52 , a part of the circumferential surface of each driven roller  28  contacts the circumferential surface of the first LF roller  27 . Each driven roller  28  is driven by the first LF roller  27 . When the leading end of the sheet S is nipped between the circumferential surface of the first LF roller  27  and the circumferential surface of each of the driven rollers  28 , a conveying force is applied to the sheet S as the first LF roller  27  is rotated. 
     Each driven roller  28  is configured to be rotationally symmetrical with respect to an axis of the spring shaft  57  extending in the front-and-rear direction. The driven rollers  28  have the same length in the front-and-rear direction. 
     Each of the driven rollers  28 A which are arranged at both sides in the front-and-rear direction has a protrusion  101  as depicted in  FIG. 8 . The protrusion  101  is formed at a central portion, in the front-and-rear direction, of the driven roller  28 A. The protrusion  101  protrudes from an inner surface  102  of the driven roller  28 A toward the rotation axis of the driven roller  28 A. A top surface  103  of the protrusion  101  is formed to have a cylindrical shape of which diameter is substantially the same as an outer diameter of the spring shaft  57 . The spring shaft  57  is inserted in a space defined (i.e., surrounded) by the top surface  103 . It is preferable that the spring shaft  57  is inserted in the space surround by the top surface  103  with contacting the same. 
     The driven roller  28 B at the center of the three driven rollers  28  is configured to have an inner circumferential surface  104  as depicted in  FIG. 9 . A diameter of the inner circumferential surface  104  is substantially the same as a diameter of a space surrounded by the top surface  103  of the protrusion  101  formed to each of the driven rollers  28 A at both side portions in the front-and-rear direction. In other words, the central driven roller  28 B arranged at the central portion in the front-and-rear direction has a protrusion  105  which extends to bridge between one end surface, in the front-and-rear direction, and the other end surface. In the front-and-rear direction, the protrusion  105  is larger than the protrusion  101  of the driven roller  29 A at each end portion in the front-and-rear direction. The inner circumferential surface  104  which is the top surface of the protrusion  105  is formed to have a cylindrical shape having substantially the same diameter as an outer diameter of the spring shaft  57 . The spring shaft  57  is inserted in the space surrounded by the inner circumferential surface  104 . It is preferable that the spring shaft  57  is inserted in the space surrounded by the inner circumferential surface  104  with contacting the inner circumferential surface  104 . 
     According to the above configuration, a distance L 1  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  101  and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), and a distance L 1  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  101  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) are longer than a distance L 2  which is a distance between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  105  and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), or a distance L 2  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  105  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ). 
     The spring shaft  57  is a kind of a coil spring which is formed by winding a metallic wire member. The spring shafts  57  inserted in the respective driven rollers  28  are made of the same metallic wires, and have the same outer diameter and the same length in the front-and-rear direction. 
     Each driven roller  28  is urged toward the first LF roller  27  due to elastic characteristic of the spring shafts  57 . In the following description, when the first LF rollers are described without discrimination therebetween, the roller will be referred to as the first LF roller  27 , while when discrimination is necessary, the rollers are referred to as the first LF roller  27 A and the second LF roller  28 B. Specifically, when the driven roller  28  is attached to the housing  2 , the driven roller  28  is accommodated in the roller accommodating section  58 . 
     Further, both end portions of the spring shaft  57  are accommodated in the spring accommodation section  59 . With this configuration, the driven roller  28  is supported by the housing  2  via the spring shaft  57 . Then, the first LF rollers  27  are attached to the housing  2 . The three first LF rollers  27  contact the driven rollers  28  from above respectively. As the first LF rollers  27  urge the drive rollers  28 , respectively, each driven roller  28  is displaced downward against the elastic force of the spring shaft  57 . Under such a state, both ends of the rotational shaft  56  of the first LF roller  27  are rotatably secured to the housing  2 . As a result, each driven roller  28  is pressed by the first LF roller  27  due to the elastic characteristic of the spring shaft  57 . 
     Since all the spring shafts  57  have the same structure, the shorter the distances L 1  and L 2  are, the greater the elastic forces generated on the spring shafts  57  as reactive forces against the pressing force by the driven rollers  28  are. As described above, the distance L 2  is shorter than the distance L 1 . Therefore, the elastic force generated on the spring shaft  57  inserted in the central driven roller  28 B, arranged at the central portion in the front-and-rear direction, is greater than that of the driven rollers  28 A arranged at both sides in the front-and-rear direction. Therefore, the conveying forces applied to the sheet S from the first LF roller  27 B at the central portion in the front-and-rear direction and the driven roller  28 B at the central portion in the front-and-rear direction are greater than the conveying forces applied to the sheet S by the first LF rollers  27 A at the side portions in the front-and-rear direction and the driven rollers  28 A at the side portions in the front-and-rear direction. 
     The lower reader unit  29  has a lower contact glass  61  and a contact image sensor module  62  as depicted in  FIGS. 2 and 4 . 
     The lower contact glass  61  is held by the housing  2  below the supplying section  21 , the supply roller  23 , the separation roller  24  and the driven rollers  28 . The lower contact glass  61  is a flat plate having a rectangular shape and arranged substantially parallel with the upper surface  12  of the housing  2 . Longer sides of the lower contact glass  61  extend in the right-and-left direction, and the shorter sides extend in the front-and-rear direction. A light-side end portion of the lower contact glass  61  is arranged on the left of the common path forming section  26 . A common path  55  extends a portion between a lower surface  53  of upper part forming section  51  and an upper surface  54  of a lower part forming section  52  leftward, via a portion above the lower contact glass  61 . 
     The contact image sensor (CIS) module  62  is arranged below the lower contact glass  61  such that the contact image sensor module  62  is movable in the right-and-left direction. Inside the CIS module  62 , an LED (light emitting diode) light source, a lens and an image sensor are provided. The CIS module  62  is located at a position lower left below the lower contact glass  61  when the ADF reading is performed or when the image reading apparatus  1  is not used. 
     The upper reader unit  30  has an upper contact glass  63  and a CIS module  64 . 
     The upper contact glass  63  is held by the housing  2  at a position above the lower contact glass  61  and on the left of the lower contact glass  61 . The upper contact glass  63  is also a rectangular plate member and longer sides thereof extend in the front-and-rear direction. Shorter sides of the upper contact glass  63  are slightly inclined with respect to the right-and-left direction but extend substantially in the right-and-left direction. 
     The CIS module  64  is arranged above the upper contact glass  63 . Inside the CIS module  64 , an LED light source, a lens and an image sensor are provided. 
     The three second LF rollers  31  are arranged on the left of the upper reader unit  30 . The three second LF rollers  31  are attached to a rotation shaft  65  extending in the front-and-rear direction with spaced evenly. The rotation shaft  65  is rotatably held by the housing  2 . 
     Three drive rollers  32  are arranged below the second LF rollers  31 . The three driven rollers  32  are attached to a rotation shaft  66  extending in the front-and-rear direction with spaced evenly. The rotation shaft  66  is rotatably held by the housing  2 . A part of a circumferential surface of each drive roller  32  contacts a circumferential surface of the second LF roller  31 . The drive rollers  32  are driven to rotate as the second LF rollers  31  rotate. 
     The driven rollers  33  are arranged below the central second LF roller  31 , and on the left of the driven rollers  32 . In the driven roller  33 , a rotation shaft  67  extending in the front-and-rear direction is inserted. The rotation shaft  67  is held by the housing  2 . A part of the drive roller  33  contacts the central second LF roller  31 . The driven roller  33  rotates as driven by rotation of the second LF roller  31 . The common path  55  extends from a position where the separation roller  24  contacts the separation piece to a position where the second LF rollers  31  contact the drive roller  33 . 
     A first path forming section  35  has an upper forming section  71  and a lower forming section  72 . The upper forming section  71  is formed on an inner surface of the maintenance cover  4 . A lower surface of the left side section  73  of the upper forming section  71  is formed to curve along the circumferential surface of the second LF roller  31  from a position spaced from the left side of the second LF roller  31 . A lower surface of the right side section  74  of the upper forming section  71  is substantially parallel with the upper surface  12  of the housing  2 , and extends in the front-and-rear and right-and-left directions. The lower forming section  72  is spaced below the right side section  74  of the upper forming section  71  and extends in the front-and-rear and right-and-left directions. A space is defined between the second LF roller  31  and the upper forming section  71 , and between the upper forming section  71  and the lower forming section  72 , which space is a first path  75  through which the sheet S passes. That is, the second LF roller  31  and the upper forming section  71  define a part of the first path  75  while the upper forming section  71  and the lower forming section  72  define another part of the first path  75 . 
     Three driven rollers  36  are arranged above the second LF roller  31 . The three driven rollers  36  are attached to a rotation shaft extending in the front-and-rear direction with spaced evenly. The rotation shaft  76  is rotatably held by the maintenance cover  4 . A part of the circumferential surface of each of the drive roller  36  contacts, in the first path  75 , the circumferential surface of the second LF roller  31 . The driven rollers  32  are driven to rotate in accordance with rotation of the second LF roller  31 . 
     The outlet  37  is formed on the right of the lower forming section  72  and above and spaced from the supplying section  21 . An upper surface  77  of the outlet  37  is formed to have a substantially planar surface extending in the front-and-rear and right-and-left directions. 
     The second path forming section  38  is formed on the housing  2  on the left of the driven roller  33 . The second path forming section  38  extends leftward slightly from a position on the left of the driven roller  33 , spaced therefrom, bent to upper left to a position on the right and spaced for the right side of the lower side section of the outlet cover  5 . A space above the second path forming section  38  is a second path  78  through which the sheet S passes. 
     The image reading apparatus  1  has a flapper  81  and a link mechanism  82 . 
     The flapper  81  is arranged below the left side part of the upper forming section  71  of the first path forming section  35 . The flapper  81  is supported by the housing  2  such that the flapper  81  movable to be oriented between an orientation depicted in  FIG. 2  and an orientation depicted in  FIG. 4 . When oriented as depicted in  FIG. 2 , the flapper  81  allows the sheet S to enter the first path  75 , while when oriented as depicted in  FIG. 4 , the flapper  81  extends along the second path  78 . That is, when oriented as depicted in  FIG. 4 , the flapper  81  allows the sheet S to enter the second path  78 . 
     The link mechanism  82  causes the flapper  81  to be displaced to have the orientation depicted in  FIG. 2  and the orientation depicted in  FIG. 4  in association with displacement of the outlet cover  5 . Specifically, when the outlet cover  5  is displaced from the cover position to the tray position, the link mechanism  82  causes the flapper  81  having the orientation depicted in  FIG. 2  to have the orientation depicted in  FIG. 4 . When the outlet over  5  is displaced from the tray position to the cover position, the link mechanism causes the flapper  81  having the orientation depicted in  FIG. 4  to have the orientation depicted in  FIG. 2 . 
     The image reading apparatus has a first receiving member  91  and a second receiving member  93 . 
     The first receiving member  91  is provided to the outlet cover  5  with spaced from an inner surface  94  of the outlet cover  5 . With this configuration, between the first receiving member  91  and the inner surface  94  of the outlet cover  5 , a space  95  capable of accommodating the second receiving member  93  is formed. 
     The second receiving member  93  is provided to be rotatable between an accommodation position at which the second receiving member  93  is accommodated in the space  95  and an extended position at which the second receiving member  93  is extended out of the space  95 . The second receiving member  93  extends along the inner surface  94  of the outlet cover  5  from the space  95  when located at the extended position. The second receiving member  93  has an extending section  97  and the protruded section  98 . The protruded section  8  is formed on the left of the extended section  97  when the second receiving member  93  is located at the extended position. 
     &lt;Image Reading Operation 1&gt; 
     When the sheet S subject to image reading is a sheet of which rigidity is relatively small, the outlet cover  5  is closed as depicted in  FIGS. 1 and 2 . That is, as the outlet path (i.e., an ejection path) of the sheet S, the first path  75  is selected. It is noted that opening/closing of the outlet cover  5  is done by a user manually. As described above, the sheet S is placed on the supplying section  21  and on the tray  3  with the centers thereof being aligned to each other. 
     In such a state, the leading end portion of the sheet S is arranged on the circumferential surface of the supplying roller  23 . When an image reading operation is started in accordance with a user&#39;s instruction, the supplying roller  23  rotates counterclockwise in  FIG. 2 . Then, with a friction between the lowermost sheet S on the supplying section  21  and the circumferential surface of the supplying roller  23 , the sheet S is fed between the separation roller  24  and the separation piece  25 . 
     At this stage the separation roller  24  also rates counterclockwise in  FIG. 2 . As the leading end of the sheet S is nipped between the separation roller  24  and the separation piece  25 , sheets S are separated one by one, each passing through the nip between the separation roller  24  and the separation piece  25  and sent to the common path  55 . 
     At this stage, the first LF roller  27  is rotating clockwise in  FIG. 2 . Therefore, the driven roller  28  is being rotated counterclockwise in  FIG. 2  in association with the rotation of the first LF roller  27 . When the leading end of the sheet S fed into the common path  55  reaches a position where the circumferential surfaces of the first LF roller  27  and the driven roller  28  contact, the leading end of the sheet S is introduced in the nip between the circumferential surfaces of the first LF roller  27  and the driven roller  28 . Then, a conveying force is applied from the first LF roller  27  and the driven roller  28  to the sheet S. When a length of the width of the sheet S in the front-and-rear direction is equal to or greater than a distance between the side drive rollers  28 A, the driving force is applied to the sheet S from the three pairs of the first LF roller  27  and the driven roller  28 . That is, the driving force is applied to the sheet S from a pair of the first LF roller  27 B and the driven roller  28 B arranged at the central portion in the front-and-rear direction. The driving force is also applied to the sheet S from the first LF rollers  27 A and the drive rollers  28 A which are arranged at both side portions in the front-and-rear direction. 
     Thereafter, the sheet S passes above the upper surface of the lower contact glass  61  and below the lower surface of the upper contact glass  63  in this order. To the sheet S above the upper surface of the lower contact glass  61 , and to the sheet S below the lower surface of the upper contact glass  33 , light is emitted from the LED light sources of the CIS modules  62  and  64 , respectively. The light reflected by the sheet S is received by the image sensors of the CIS modules  62  and  64 , respectively. As a result, images on both sides of the sheet S can be read. 
     At this stage, the second LF roller  31  is rotating clockwise in  FIG. 2 . Therefore, the driven rollers  32  and  33  are rotating counterclockwise in  FIG. 2 . When the leading end of the sheet S reaches a position where the circumferential surfaces of the second LF roller  31  and the driven roller  32  contact, conveying forces are applied from the second LF roller  31  and the driven roller  32  to the sheet S. Thereafter, when the leading end of the sheet reaches a position when the circumferential surfaces of the second LF roller  31  and the drive roller  33  contact, conveying forces are applied to the sheet S from the second LF roller  31  and the driven roller  33 . 
     In this case, since the outlet cover  5  is closed, the flapper  81  has the orientation depicted in  FIG. 2 . That is, the flapper  81  closes a pathway to the second path  78  and opens a pathway to the first path  75 . It is noted that an expression “to close a pathway to the second path  78 ” does not always mean that the pathway to the second path  78  is completely closed, but include a situation that the pathway is partially closed and only suppresses entrance of the sheet S to the second path  78 . Similarly, an expression “to open the pathway to the first path  75 ” is not used to always mean that the pathway is completely opened. Therefore, the sheet S fed out from the nip between the second LF roller  31  and the driven roller  32  proceeds such that the leading end moves along the inner surface of the flapper  81 , thereby the sheet S being conveyed along the first path  75 . 
     The driven roller  36  rotates counterclockwise in  FIG. 2  in accordance with the rotation of the second LF roller  31 . When the leading end of the sheet S reaches a position where the circumferential surfaces of the second LF roller  31  and the driven roller  36 , conveying forces are applied to the sheet S from the second LF roller  31  and the driven roller  36 . 
     The sheet S passed through the nip between the second LF roller  31  and the driven roller  36  is discharged, for example, as bridging between the outlet section  37  and the tray  3 . The leading end of the sheet S is, for example, passes the right end part of the outlet section  37  and placed on the tray  3 . The trailing end of the sheet S remains, for example, in the outlet section  37  and placed on the outlet section  37 . With this configuration, it is prevented that the sheet S on the outlet section  37  and the sheet S bridging on the supplying section  21  and the tray  3  are overlaid. 
     &lt;Image Reading Operation 2&gt; 
     When the sheet S subject to image reading is a relatively rigid sheet such as a postcard or name card, the outlet cover  5  is opened as depicted in  FIG. 3  or  FIG. 4 . That is, as an outlet path of the sheet S, the second path  78  is selected. As mentioned above, opening/closing of the outlet cover  5  is done by a user manually. The sheet S is inserted between a pair of sheet width guides  22  from the right side, and arranged on the upper surface  41  of the supplying section with the centers thereof being aligned to each other. 
     At this stage, the leading end of the sheet S is arranged on the circumferential surface of the supplying roller  23 . When the image reading operation is started in accordance with the user instruction, the supplying roller  23  rotates counterclockwise in  FIG. 2 . Then, by the frictional force between the lowermost sheet S and the circumferential surface of the supplying roller  23 , the sheet S is introduced in a position where the separation roller  24  contacts the separation piece  25 . 
     At this stage, the separation roller  24  is rotating counterclockwise in  FIG. 2 . When the leading end of the sheet S is nipped between the separation roller  24  and the separation piece  25 , a plurality of sheets S is separated one by one, and only one sheet S passes through a position between the separation roller  24  and the separation piece  25 , and the sheet S is sent to the common path  55 . 
     At this stage, the first LF rollers  27  are rotating clockwise in  FIG. 2 . Therefore, the driven rollers  28  rotate counterclockwise in association with the rotation of the first LF rollers  27 . When the leading end of the sheet S reaches the position where the circumferential surfaces of the first LF rollers  27  and the driven rollers  28  contact, the leading end of the sheet S is introduced in the nip between the first LF rollers  27  and the driven rollers  28 . Thus, the conveying forces are applied to the sheet S from the first LF rollers  27  and the driven rollers  28 . When the length of the width of the sheet S along the front-and-rear direction is longer than a distance between the driven rollers  28 A at both side portions in the front-and-rear direction, the conveying forces are applied to the sheet S from three pairs of the first LF roller  27  and the driven roller  28 . That is, the conveying force is applied by a pair of the first LF roller  27 B and the driven roller  28 B arranged at the central portion in the front-and-rear direction, and further the conveying forces are applied to the sheet S by two pairs of the first LF roller  27 A and the driven roller  28 A arranged at both side portions in the front-and-rear direction. If the length of the width of the sheet S in the front-and-rear direction is less than the distance between the two driven rollers  28 A arranged at both end portions in the front-and-rear direction, the conveying force is applied to the sheet S only by one pair of the first roller  27 B and the driven roller  28 B arranged at the central portion in the front-and-rear direction. 
     When the leading end of the sheet S is located between the circumferential surfaces of the first LF roller  27 B and the driven roller  28 B, the trailing end portion of the sheet S, that is the upstream side end portion, in the sheet conveying direction, of the sheet S is located between the separation roller  24  and the separation piece  25 . Therefore, to the sheet S, the conveying force directed to downstream side in the conveying direction is applied by the first LF roller  27 B and the driven roller  28 B, while a frictional force directed to the upstream side in the conveying direction is applied by the separation roller  24  and the separation piece  25  as a back tension. 
     Thereafter, the sheet S passes above the upper surface of the lower contact glass  61  and below the lower surface of the upper contact glass  63  in this order. To the sheet S above the upper surface of the lower contact glass  61 , and to the sheet S below the lower surface of the upper contact glass  33 , light is emitted from the LED light sources of the CIS modules  62  and  64 , respectively. The light reflected by the sheet S is received by the image sensors of the CIS modules  62  and  64 , respectively. As a result, images on both sides of the sheet S can be read. 
     At this stage, the second LF roller  31  is rotating clockwise in  FIG. 2 . Therefore, the driven rollers  32  and  33  are rotating counterclockwise in  FIG. 2 . When the leading end of the sheet S reaches a position where the circumferential surfaces of the second LF roller  31  and the driven roller  32  contact, conveying forces are applied from the second LF roller  31  and the driven roller  32  to the sheet S. Thereafter, when the leading end of the sheet reaches a position when the circumferential surfaces of the second LF roller  31  and the drive roller  33  contact, conveying forces are applied to the sheet S from the second LF roller  31  and the driven roller  33 . 
     In this case, since the outlet cover  5  is opened, the flapper  81  has the orientation depicted in  FIG. 4 . That is, the flapper  81  opens a pathway to the second path  78 , while closes a pathway to the first path  75 . It is noted that an expression “to close a pathway to the first path  75 ” does not always mean that the pathway to the first path  75  is completely closed, but include a situation that the pathway is partially closed and only suppresses entrance of the sheet S to the first path  75 . Similarly, an expression “to open the pathway to the second path  78 ” is not used to always mean that the pathway is completely opened. Therefore, the sheet S fed out from the nip between the second LF roller  31  and the driven roller  32  proceeds such that the leading end is conveyed below the flapper  81 . 
     The sheet S passed below the flapper  81  is conveyed along the second path  78 . When the sheet S passes through the nip between the second LF roller  31  and the driven roller  32 , discharge of the sheet S from the housing  2  is completed. The sheet S discharged from the housing  2  is received by a first receiving member and a second receiving member  93 , and held thereby. 
     As described above, to the sheet S of which the length of the width in the front-and-rear direction is equal to or greater than a distance between the driven rollers  28 A arranged at both end portions in the front-and-rear direction, the conveying forces are applied to the sheet S by the three pairs of the first LF roller  27  and the driven roller  28 . That is, for the normal sheet S, the conveying force is applied by the pair of the first LF roller  27 B and the driven roller  28 B which is arranged at the central portion in the front-and-rear direction. Further, to such a sheet S, the conveying forces are also applied by two additional pairs of the first LF roller  27 A and the driven roller  28 A, which are arranged at both end portions in the front-and-rear direction. 
     To the sheet S of which the length of the width in the front-and-rear direction is less than the distance between the two driven rollers  28 A arrange at both side portions in the front-and-rear direction, that is, to a small size sheet S, the conveying force is applied only by the first roller  27 B and the driven roller  28 B which are arranged at the central portion in the front-and-rear direction. 
     The image reading apparatus  1  according to the embodiment is configured such that the conveying forces applied by the driven roller  28 B and the first LF roller  27 B, which are arranged at the central portion in the front-and-rear direction are stronger than those applied by each pair of the driven roller  28 A and the first LF roller  27 A arranged at a side portions in the front-and-rear direction. In other words, the conveying force of a pair of the driven roller  28 B and the first LF roller  27 B is stronger than the conveying force of each pair of the driven roller  28 A and the first LF roller  27 A. With this configuration, when a small size sheet S is conveyed, shortage of the conveying force applied to the sheet S can be suppressed. As a result, the small size sheet can be conveyed at appropriate conveying speed. Since the sheet S can be appropriately even if the size is small, expansion of the image read by the lower reader unit  29  and the upper reader unit  30  in the right-and-left direction due to insufficient conveying force for a small sheet S can be suppressed. 
     The image reading apparatus  1  according to the embodiment is configured such that the spring shaft  57  is inserted in each driven roller  28  in the front-and-rear direction, as described above. 
     According to such a configuration, it becomes possible to make the driven roller  28  press-contact the first LF roller  27  by the elastic force of the spring shaft  57 . Further, in comparison with a configuration in which a shaft of the driven roller  28  is urged using a coil spring or the like, a size of the image reading apparatus  1  in a up-and-down direction can be suppressed since the number of components can be reduced and/or a space for the mechanical structure can be reduced. 
     Further, as described above, the driven roller  28 B arranged at the central portion in the front-and-rear direction has the protrusion  105 , while each of the driven rollers  28 A arranged at side portions in the front-and-rear direction has the protrusion  101 . The length of the protrusion  105  in the front-and-rear direction is greater than the length of the protrusion  101  in the front-and-rear direction. 
     According to the above configuration, a distance L 1  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  101  of the driven roller  28 A arranged at each side portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), and a distance L 1  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  101  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) are longer than a distance L 2  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  105  of the driven roller  28 B arranged at the central portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), or a distance L 2  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  105  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ). Since all the spring shafts  57  have the same structure, the shorter the distances L 1  and L 2  are, the greater the elastic forces generated on the spring shafts  57  as reactive forces against the pressing force by the driven rollers  28  are. Therefore, it is possible to make the conveying force of the sheet S by a pair of the driven roller  28 B and the first LF roller  27 B greater than the conveying force by each pair of the driven roller  28 A and the first LF roller  27 A. 
     &lt;Modified Embodiments&gt; 
     A configuration of the driven roller  28 B arranged at the central portion in the front-and-rear direction is not limited to the configuration depicted in  FIG. 9 . For example, a configuration depicted in  FIG. 10  may be employed as the configuration of the driven roller  28 B arranged at the central portion in the front-and-rear direction. In the configuration depicted in  FIG. 10 , a driven roller  28 C arranged at the central portion in the front-and-rear direction has a protrusion  205 . The protrusion  205  is configured to protrude from an inner circumferential surface  204  of the driven roller  28 C toward the spring shaft  57 . An end surface  206  of the protrusion  205  is larger than the end surface  103  of the protrusion  101  of the driven roller  28 B. According to the above configuration, a distance L 2  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  205  of the driven roller  28 C arranged at each side portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), and a distance L 2  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  205  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) are shorter than a distance L 1  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  101  of the driven roller  28 B arranged at the central portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), or a distance L 1  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  101  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) depicted in  FIG. 8 . Therefore, even if the driven roller  28 C depicted in  FIG. 10  is employed with the driven roller arranged at the central portion in the front-and-rear direction, it is possible to make the conveying force of the sheet S by a pair of the driven roller  28 C and the first LF roller  27 Bgreater than the conveying force by each pair of the driven roller  28 A and the first LF roller  27 A. 
     Alternatively, a configuration depicted in  FIG. 11  may be employed as a configuration of the driven roller arranged at the central portion in the front-and-rear direction. According to the configuration depicted in  FIG. 11 , a driven roller  28 D arranged at the central portion in the front-and-rear direction has a protrusion  215  and two protrusions  216 . The protrusion  215  and the two protrusions  216  are formed to protrude from the inner circumferential surface  214  toward the spring shaft  57 . The protrusion  215  is formed at a central portion, in the front-and-rear direction, of the driven roller  28 D. The protrusion  215  is the same size as the protrusion  103  of the driven roller  28  depicted in  FIG. 8 . The protrusions  216  are formed spaced from the protrusion  215  in the front-and-rear direction. The top surface  218  of the protrusion  215  and the top surface  217  of the protrusion  216  are formed to define a cylindrical surface which has substantially the same diameter as the outer diameter of the shaft spring  57 . The spring shaft  57  is inserted in a space surrounded by the top surfaces  217  and  218 . In this case, it is preferable that the spring shaft  57  is inserted in the space surrounded by the top surfaces  217  and  218  contacting the same. 
     According to the above configuration, a distance L 2  between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  216  of the driven roller  28 D arranged at each side portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), and a distance L 2  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  216  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) are shorter than a distance L 1  which is a distance between the front end (i.e., a front end in the front-and-rear direction) of the protrusion  101  of the driven roller  28 B arranged at the central portion in the front-and-rear direction and the rear end of the accommodating section  59  (i.e., a rear end of the front accommodation section  59 ), or a distance L 1  between the rear end (i.e., a rear end in the front-and-rear direction) of the protrusion  101  and the front end of the accommodating section  59  (i.e., a front end of the rear accommodation section  59 ) depicted in  FIG. 8 . Therefore, even if the driven roller  28 D depicted in  FIG. 11  is employed with the central portion in the front-and-rear direction, it is possible to make the conveying force of the sheet S by a pair of the driven roller  28 D and the first LF roller  27 B greater than the conveying force by each pair of the driven roller  28 A and the first LF roller  27 A. 
     The configurations of the three driven rollers  28  may be identical to each other. In such a case, in order to make the conveying force applied by a pair of the driven roller  28  and the first LF roller  27  arranged at the central portion in the front-and-rear direction greater than the conveying force of a pair of the driven roller  28  and the first LF roller  27  arranged at each side portion in the front-and-rear direction, a spring constant of the shaft spring  57  inserted in the driven roller  28  arranged at the central portion in the front-and-rear direction may be set to greater than the spring constant of the shaft spring  57  inserted in the driven roller  28  arranged at each side portion in the front-and-rear direction. 
     In order to make the conveying force applied by a pair of the driven roller  28  and the first LF roller  27  arranged at the central portion in the front-and-rear direction greater than the conveying force of a pair of the driven roller  28  and the first LF roller  27  arranged at each side portion in the front-and-rear direction, a length of the spring shaft  57  inserted in the driven roller  28  arranged at the central portion in the front-and-rear direction may be shorter than that of the spring shaft  57  inserted in the driven roller  28  arranged at each side portion in the front-and-rear direction. In this case, the configurations of the three driven rollers  28  are identical except for the length in the front-and-rear direction. The length of the driven roller  28  arranged at the central portion in the front-and-rear direction may be made shorter in accordance with the length of the spring shaft  57  to be inserted in the driven roller  28  arranged at the central portion in the front-and-rear direction. 
     In order to make the conveying force applied by a pair of the driven roller  28  and the first LF roller  27  arranged at the central portion in the front-and-rear direction greater than the conveying force of a pair of the driven roller  28  and the first LF roller  27  arranged at each side portion in the front-and-rear direction, a displaceable amount of the spring shaft  57  inserted in the driven roller  28  arranged at the central portion in the front-and-rear direction may be set to be larger than the displaceable amount of the spring shaft  57  inserted in the driven roller arranged at each side in the front-and-rear direction. 
     In the above described embodiment and modifications, the spring shaft  57  is inserted in the driven roller  28 . Alternatively, a metal shaft which is a rigid body may be inserted in the driven roller which has the same structure as the driven roller  28 . In this case, in order to make the driven roller  28  press-contacts the first LF roller  27 , an urging member that urges the rotation shaft (i.e., the metal shaft) toward the rotation shaft  56  of the first LF roller  27  may be employed. In this case, the urging force applied by the urging member to urge the metal shaft inserted in the driven roller  28  toward the rotation shaft  56  of the first LF roller  27  may be set to greater than the urging force to urge the metal shaft of the driven roller  28  arranged at each end. For this purpose, the urging force of the urging member (e.g., the spring constant) may be adjusted. Alternatively or optionally, the length from the urging member to the metal shaft may be adjusted to set an appropriate urging force. 
     In order to make the conveying force applied by a pair of the driven roller  28  and the first LF roller  27  arranged at the central portion in the front-and-rear direction greater than the conveying force of a pair of the driven roller  28  and the first LF roller  27  arranged at each side portion in the front-and-rear direction, friction factors of the driven rollers  28  may be differentiated such that the friction factors of the driven roller  28  or the first LF roller  27  contacting the driven roller  28  which are arranged at the central portion in the front-and-rear direction may be made greater than that of the driven roller  28  or the first LF roller  27  arranged at the side portion in the front-and-rear direction. In this case, the friction factor of material or the roller or the friction factor of the material arranged on the surface of the rollers may be adjusted. 
     Further, in order to make the conveying force applied by a pair of the driven roller  28  and the first LF roller  27  arranged at the central portion in the front-and-rear direction greater than the conveying force of a pair of the driven roller  28  and the first LF roller  27  arranged at each side portion in the front-and-rear direction, the outer diameter of the driven roller  28  arranged at the central portion in the front-and-rear direction may be made larger than the outer diameter of each of the driven rollers  28  arranged at the side portions in the front-and-rear directions. 
     More than three driven rollers  28  may be arranged in the front-and-rear direction. In such a case, in comparison with the conveying force of the driven rollers  28  and the first LF roller  27  at the side portions in the front-and-rear direction, the conveying force of the other driven rollers  28  and the first LF rollers  27  may be set stronger. 
     Alternatively or optionally, various modifications can be realized without departing from the scope of the invention.