Patent Publication Number: US-8967618-B2

Title: Sheet transport device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2012-273466, filed on Dec. 14, 2012, the entire subject matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     Aspects of the present invention relate to a sheet transport device which reads an image on a sheet while transporting the sheet along a predetermined transport path. 
     BACKGROUND 
     There has been known a sheet transport device configured to read an image on a sheet using a reading unit while transporting the sheet along a predetermined transport path (for example, refer to JP-A-2011-211480). 
     The sheet transport device disclosed in JP-A-2011-211480 includes a U-turn transport path disposed in a middle portion of the transport path from a sheet feed side to a sheet discharge side. The sheet transport device includes, in the U-turn transport path, a main roller which transports and guides the sheet to U-turn the sheet, and a pinch roller which is arranged to face an upper portion of the main roller during the transport of the sheet and transports the sheet together with the main roller. 
     The sheet transport device further includes a cover member which covers the main roller from above and opens at least a portion of the transport path from above when maintenance is performed or jamming occurs. The pinch roller is supported by a rear surface of the cover member. Also, a shaft of the pinch roller does not necessarily have to receive driving since only the pinch roller is rotated by the driving of the main roller. Therefore, the shaft of the pinch roller is fixed to the rear surface of the cover member by, for example, fitting using the elastic deformation of a rib formed on the rear surface of the cover member. 
     This kind of sheet transport device is demanded to be made thinner and the cover member is demanded to be made thinner. Accordingly, the height of the rib which supports the shaft of the pinch roller is required to be reduced. 
     However, this type of rib is integrally formed on the rear surface of the cover member by resin forming, and thus it is difficult to reduce the height of the rib without limitation to make the cover member thin. In other words, as described above, the shaft of the pinch roller is fixed by using the elastic deformation of the rib, and the amount of elastic deformation becomes insufficient when the height of the rib is excessively reduced and the operation becomes difficult when the shaft is attached. Also, in some cases, there is a possibility that the rib wound be damaged. 
     SUMMARY 
     Accordingly, an aspect of the present invention provides a sheet transport device in which a cover can be made thinner while a shaft of a pinch roller can be easily attached to the cover. 
     According to an illustrative embodiment of the present invention, there is provided a sheet transport device including a transport roller configured to transport a sheet, a cover configured to cover the transport roller, a pinch roller attached to the cover via a shaft facing the transport roller, and configured to transport the sheet in cooperation with the transport roller, and a regulation member projecting from a facing surface, facing the transport roller, of the cover in a first direction which points toward the transport roller, and configured to regulate a movement of the shaft in a direction along an extending direction of the shaft. The regulation member includes a surface which extends along a second direction which is the extending direction of the shaft, a first end portion which is fixed to the facing surface, and a second end portion which faces an end face of the shaft and is located closer to the end face of the shaft than the first end portion in the second direction. 
     According to the above sheet transport device, the height of the regulation member can be reduced while making the cover thinner, and the amount of elastic deformation (amount of deflection) of the regulation member can be easily ensured and the attachment operation can be easily performed when the pinch roller is attached to the cover. After the attachment of the pinch roller, the movement of the pinch roller along the axial direction with respect to the cover can be regulated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects of the present invention will become more apparent and more readily appreciated from the following description of illustrative embodiments of the present invention taken in conjunction with the attached drawings, in which: 
         FIG. 1  is a perspective view of a multifunction printer mounted with a sheet transport device according to an illustrative embodiment of the present invention; 
         FIG. 2  is a perspective view showing a state where a sheet transport unit of the multifunction printer is opened; 
         FIG. 3  is a cross-sectional view showing a state where a sheet holding cover of the sheet transport device is closed; 
         FIG. 4  is a cross-sectional view showing a state where the sheet holding cover of the sheet transport device is opened; 
         FIG. 5  is a plan view showing a state where the sheet holding cover and an extension tray of the sheet transport device are opened; 
         FIG. 6  is a perspective view showing a state where the sheet holding cover, an ADF cover, and the extension tray of the sheet transport device are opened; 
         FIG. 7  is a cross-sectional view of a main part of the sheet transport portion of the sheet transport device; 
         FIG. 8  is a perspective view of a rear surface side of the ADF cover mounted on the sheet transport device; 
         FIG. 9  is a perspective view of a main part of the ADF cover mounted on the sheet transport device; 
         FIG. 10  is a perspective view of the main part of the ADF cover mounted on the sheet transport device; 
         FIG. 11  is a cross-sectional view in the front direction of the main part of the ADF cover mounted on the sheet transport device; 
         FIG. 12  is a cross-sectional view in a lateral direction of the main part of the ADF cover mounted on the sheet transport device; and 
         FIGS. 13A to 13F  are explanatory views showing modified examples of the shapes of ribs of a regulation member formed in the ADF cover mounted on the sheet transport device. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a sheet transport device according to an illustrative embodiment of the present invention, which is applied to a multifunction printer, will be described while referring to the accompanying drawings. The sheet transport device exemplified in the illustrative embodiment is configured as a part of the multifunction printer which has not only an image reading function (scanning function) but also other functions (for example, printing function, copying function, and facsimile transmission/reception function). Also, the illustrative embodiment shown hereinbelow is a preferred specific example of the sheet transport device of the present invention and there are cases in which various technically preferable limitations are given thereto, but the scope of the present invention is not limited to these aspects unless stated to limit the present invention. Further, components of the illustrative embodiment shown hereinbelow can be appropriately replaced by existing components, and various variations, including a combination with other existing components, can be made. 
     Specifically, there is no limitation in combining the various functions of the multifunction printer with each other and in providing additional functions by using options or the like (for example, a sheet feed cassette). Also, the maximum size (for example, A4 or A3) and the minimum size (for example, postcard size or business card size) of sheets (documents) which is allowed for the sheet transport function can be arbitrarily set. Therefore, the illustrative embodiment shown hereinbelow does not limit the contents of the invention described in the claims. The description hereinbelow will be based on the upper-lower, left-right, and front-rear directions shown in the drawings so as to facilitate the understanding of the relative positional relationship between parts of the multifunction printer. Also, each of the directions is defined on the assumption that the standing position of a user is the front side of the device. 
     [External Configuration of Multifunction Printer] 
     Referring to  FIG. 1  and  FIG. 2 , a multifunction printer  1  includes a main body unit  10 , a reading unit  20  which is arranged on an upper part of the main body unit  10 , and a sheet transport unit  30  (example of a sheet transport device) which is arranged on an upper part of the reading unit  20 . An image forming unit (not shown) is accommodated by the main body unit  10 . 
     [Configuration of Main Body Unit  10 ] 
     The main body unit  10  includes drawer-type recording sheet accommodating cassettes  11  and  12  which are arranged in two in the upper-lower direction, and an outlet  13  which is opened at an upper part of the recording sheet accommodating cassettes  11  and  12  and used to discharge recording sheet after an image forming process by the image forming unit. Also, over the outlet  13  and on a front surface side of the main body unit  10 , there is provided an operation unit  16  including a switch  14  which is used for a user to input various instructions to the multifunction printer  1 , and a touch panel-type liquid crystal display panel  15 . 
     The recording sheet accommodating cassettes  11  and  12  can accommodate recording sheet of different sizes (for example, A4 size and A3 size, and the like). Also, the lower recording sheet accommodating cassette  11  is expandable by an option or the like, and also there is a case in which the lower recording sheet accommodating cassette is not provided. The outlet  13  is an opening which is used to discharge the recording sheet after the image forming process, and, for example, may be a known sheet feed and discharge port which allows the manual feed of postcards and the like. The operation unit  16  may be arranged with, for example, known numeric keys and button-type switches such as mode selection switches for various functional modes (scanning function, printing function, copying function, facsimile transmission and reception function, and the like) of the multifunction printer  1  in combination with the liquid crystal display panel  15 . Further, in the illustrative embodiment, the operation unit  16  is arranged on a front cover  17  which is the upper part of the main body unit  10 . The front cover  17  is also used as a front cover of the reading unit  20 . Therefore, the front cover  17  may be integrally configured with a circumferential wall  21  of the reading unit  20  and the operation unit  16  may be arranged in the reading unit  20 . 
     The main body unit  10  includes driving mechanisms which are necessary to perform the various functional modes of the multifunction printer  1 , and a control unit (not shown) which controls the driving mechanism. The control unit controls not only the driving mechanisms arranged in the operation unit  16  and the main body unit  10  but also the various driving mechanisms disposed in the reading unit  20  and the sheet transport unit  30 . The driving mechanisms of the reading unit  20  and the sheet transport unit  30  may be subject to another control unit which can be interface-connected with the control unit of the main body unit  10  to ensure the convenience of option installation, unit exchange, and the like. 
     Within the main body unit  10 , a drive motor which drives a recording sheet transport mechanism portion which is used to discharge and transport the recording sheet accommodated in the recording sheet accommodating cassettes  11  and  12  through a sheet feed and discharge path reaching a sheet discharge port  13 , the image forming unit which is arranged in the transport path, various sensors which detect the transport timing and jamming of the recording sheet in the sheet feed and discharge path, and the like are arranged to be controlled by the control unit. Known techniques can be employed in the specific configurations and control examples thereof, and thus the description will be omitted herein. 
     [Configuration of Reading Unit  20 ] 
     The reading unit  20  has a structure openable and closable with respect to the main body unit  10 , and the pivot center thereof is the axis (not shown) extending in the left-right direction on a rear surface side (rear side shown in  FIG. 1 ) of the main body unit  10  and the reading unit  20 . 
     When the reading unit  20  is displaced to an open position, an upper surface side of the main body unit  10  is opened, and maintenance works can be performed on each part, such as the image forming unit, built into the main body unit  10  although not shown in detail. 
     The reading unit  20  is surrounded at four sides by the circumferential wall  21 , and. As shown in  FIG. 2 , the reading unit  20  includes a first platen  22  formed of a transparent glass or the like, an abutting member  23  along one edge of the first platen  22 , and a second platen  24  formed of transparent glass or the like and arranged on the opposite side from the first platen  22  with respect to the abutting member  23  on an upper surface thereof. 
     The first platen  22  is used as a supporting surface which supports a still document, and the abutting member  23  is used in the positioning of the document when the user supports the fixed document with the first platen  22 . Also, the second platen  24  is used to read the sheets by using the sheet transport unit  30 . The first platen  22  has a rectangular shape extending in the front-rear and left-right directions, and the size thereof is larger than the size at which a document having the maximum document size (for example, A3 size) which is readable by the device can be supported. The first platen  22  and the second platen  24  may be integrally formed, and the abutting member  23  may be arranged on upper surfaces thereof by adhesion or the like. 
     As shown in  FIG. 3  and  FIG. 4 , a movable reading sensor  25  is arranged in a movable manner below the first platen  22  and the second platen  24 . The movable reading sensor  25  reciprocates by the driving of a moving motor, which is not shown, along a guide shaft  26  spanning in the left-right direction in an inner space surrounded by the circumferential wall  21  of the reading unit  20 . When the image on the sill document is read, the movable reading sensor  25  moves in the left-right direction (sub-scanning direction) within the reading unit  20  along a lower surface side of the first platen  22  as shown in  FIG. 3  to read the image on the still document. Also, when the image on the sheet transported by the sheet transport unit  30  is read, the movable reading sensor  25  moves to a position facing the second platen  24  as shown in  FIG. 4 , and reads the image on the sheet transported by the transport unit  30  at that position. The movable reading sensor  25  reads the image upward while the first platen  22  and the second platen  24  are arranged over the movable reading sensor  25 . 
     [Configuration of Sheet Transport Unit  30 ] 
     As shown in  FIG. 2 , the sheet transport unit  30  has a structure openable and closable with respect to the reading unit  20 , and the pivot center thereof is an axis P extending in the left-right direction on a back surface side of the reading unit  20  and the sheet transport unit  30 . Therefore, the sheet transport unit  30  can be displaced to a closed position as shown in  FIG. 1 , that is, a state where the upper surface of the reading unit  20  having the first platen  22  is covered (closed state) and to the open position as shown in  FIG. 2 , that is, a state where the upper surface of the reading unit  20  having the first platen  22  is exposed (open state). When the sheet transport unit is at the closed position, the sheet transport unit  30  functions as a document cover which covers the first platen  22  and a sheet which is a reading object supported by the first platen  22 . 
     As shown in  FIG. 1 , the sheet transport unit  30  is arranged with a sheet holding cover  31  to the left from around the center of the upper surface, a sheet discharge tray  32  to the right from around the center of the upper surface, and an extension tray  33  near a right end of the upper surface. The sheet transport unit  30  is surrounded at four sides by the circumferential wall  34 , and the circumferential wall  34  is formed by assembling a plurality of divided panels. In the illustrative embodiment, a left side surface portion is further divided vertically into a lower panel portion  34 A and an upper panel portion  35 A. Also, a driving unit cover portion  34 B is mounted on a rear surface of the sheet transport unit  30 . 
     The sheet holding cover  31  can be displaced to the closed state shown in  FIG. 3  in which a left side from the center in the left-right direction of the sheet transport unit  30  is covered and the open state shown in  FIG. 4  and  FIG. 5  in which the transport sheet holding surface  31 A is exposed. The sheet holding cover  31  is pivotably attached to the sheet transport unit  30  using a pivot shaft  31 B which is engaged in the front-rear direction with a cover (not shown) placed inside the circumferential wall  34  near the center in the left-right direction of the sheet transport unit  30  as a fulcrum. When the sheet holding cover  31  is in the opened state, the sheet transport function can be used as an automatic document feeder (ADF). Therefore, when the sheets are held by the transport sheet holding surface  31 A, the sheet holding cover  31  is in the opened state with an inclination in which the pivot shaft  31 B side is down forward and the free end side is up rearward. Also, when the sheet holding cover  31  is in the opened state, an ADF cover  35  integrally having the upper panel portion  35 A and a sheet guide surface  36  are exposed. On the sheet guide surface  36 , a pair of sheet guide members  37  which support both side edges along the transport direction of the sheets held by the transport sheet holding surface  31 A are arranged. The pair of sheet guide members  37  suppress skew transport by guiding both side edges of the sheets held by the transport sheet holding surface  31 A. For example, relative approach and separation can be made between a position corresponding to the width of the maximum allowable size (for example, A3 vertical) set in advance using the main body unit  10  or the sheet transport unit  30  as shown with the solid line in  FIG. 5  and a position corresponding to the width of the minimum allowable size (for example, postcard horizontal) shown with the chain line in  FIG. 5 . 
     Between the transport sheet holding surface  31 A and the ADF cover  35 , a sheet feed inlet  38  for the sheet is formed. Between the transport sheet holding surface  31 A and the sheet discharge tray  32 , a sheet discharge port  39  for the sheet is formed. 
     In a normal state, the ADF cover  35  covers the sheet transport portion  40  from the sheet feed inlet  38  to the sheet discharge port  39  from above. When maintenance is performed or sheet jamming or the like occurs, the sheet transport portion  40  is opened upward as shown in  FIG. 6 . The ADF cover  35  may be an attachable and detachable type instead of a pivoting type as long as the sheet transport portion  40  placed therebelow can be opened. 
     [Overall Configuration of Sheet Transport Portion  40 ] 
     Next, the specific configuration of the sheet transport portion  40  will be described while referring to  FIG. 7 . In the description below, the sheet transport direction is referred to as a downstream side based on the sheet transport direction (refer to the thick two-dot chain line) and the opposite side is referred to as an upstream side. 
     The sheet transport portion  40  includes a sheet feed unit  41  which is arranged on the downstream side of the sheet feed inlet  38 , a fixed reading unit  42  which is arranged at the downstream side of the sheet feed unit  41 , a U-turn transport unit  43  which is arranged at the downstream side of the fixed reading unit  42 , and a discharge unit  44  which is arranged at the downstream side of the U-turn transport unit  43  to reach the sheet discharge port  39 . 
     [Configuration of Sheet Feed Unit  41 ] 
     The sheet feed unit  41  performs sheet feed toward the downstream side while separating the sheets held in a face-up state by the transport sheet holding surface  31 A (sheet guide surface  36 ) sheet by sheet from the uppermost one. The sheet feed unit  41  includes a sheet feed roller  45 , a separation roller  46 , a separation pad  47 , a swinging holder  48 , and a relay roller pair  49 . 
     The sheet feed roller  45  is rotation-driven at a position along the sheet guide surface  36  on the transport direction upstream side of the sheet feed unit  41 . The sheet feed roller  45  is rotation-driven in a predetermined direction (clockwise direction in  FIG. 7 ), that is, a direction in which the sheets are drawn to the separation roller  46  by transmitting the driving force of a sheet feed motor (not shown) of a known driving transmission mechanism. In this manner, the sheet feed roller  45  feeds the sheets set on the transport sheet holding surface  31 A toward the separation roller  46 . 
     The separation roller  46  is rotatably supported to a frame, which is not shown, at the transport direction downstream side from the sheet feed roller  45 . The separation roller  46  is rotated in the same direction as the sheet feed roller  45  by the power transmission caused by the driving of the sheet feed motor. 
     The separation pad  47  is arranged at a position facing the separation roller  46 . The separation pad  47  is biased by a biasing spring  50  toward an outer circumferential surface of the separation roller  46 . In this manner, the separation roller  46  operates together with the separation pad  47  and separates only the uppermost sheet in contact with the separation roller  46  from the other sheets to transport the uppermost sheet toward the downstream side. 
     The swinging holder  48  is supported by a rotating shaft  46 A of the separation roller  46  via a bearing, which is not shown. The swinging holder  48  extends from the rotating shaft  46 A of the separation roller  46  toward the transport direction upstream side, and rotatably supports the sheet feed roller  45 . The swinging holder  48  is swung about the rotating shaft of the separation roller  46  by the power transmission from the sheet feed motor. 
     At the transport direction downstream side of the sheet feed unit  41 , the relay roller pair  49  transports the sheet after the separation toward the fixed reading unit  42 . The number of the relay roller pair  49  can be increased or decreased depending on the length of the transport path corresponding to the allowable size set in advance, for example, in the main body unit  10  and the sheet transport unit  30 . 
     [Configuration of Fixed Reading Unit  42 ] 
     If necessary, the fixed reading unit  42  reads the image on the sheet that is transported from the sheet feed unit  41 . The fixed reading unit  42  is arranged in a portion of the linear-shaped path at the transport direction downstream side than the relay roller pair  49  and at the upstream side than the U-turn transport unit  43 . The fixed reading unit  42  includes a fixed reading sensor  51 , a third platen  52 , a sheet pressing member  53  which faces the fixed reading sensor  51  across the third platen  52 , and a biasing spring  54  which biases the sheet pressing member  53  toward the third platen  52 . 
     A contact image sensor (CIS) is used in the fixed reading sensor  51 , and the fixed reading sensor  51  is arranged with a reading surface of the image directed upward. The reading range of the fixed reading sensor  51  in a main scanning direction (front-rear direction) is the length corresponding to a short side of the A3 size. Herein, the sheet which is transported by the relay roller pair  49  passes between the third platen  52  which faces the reading surface of the fixed reading sensor  51  and the sheet pressing member  53 , and the sheet is transported while being pressed to the third platen  52  side by the sheet pressing member  53 . The fixed reading sensor  51  reads the image on a back surface of the passing sheet when the sheet has images on both sides. 
     [Configuration of U-Turn Transport Unit  43 ] 
     The U-turn transport unit  43  includes a main transport roller  55 , a pinch roller  56 , and a pinch roller  57  so as to form a U-turn transport path  58 . 
     The main transport roller  55  is rotatably supported by a frame, which is not shown, placed inside the lower panel portion  34 A, and is rotation-driven by the sheet feed motor or an additional drive motor (not shown). In the illustrative embodiment, the range of approximately one-half to the left of an outer circumferential surface of the main transport roller  55  is used as the U-turn transport path  58 . The pinch roller  56  is arranged near an upper end of the main transport roller  55  to be in contact with the main transport roller  55 . The pinch roller  57  is arranged to be in contact with the main transport roller  55  from the lower left of the main transport roller  55 . Also, at a position which faces the main transport roller  55 , a plurality of guide ribs (guide members)  35 C which project from an inner surface  35 B of the ADF cover  35  toward the main transport roller  55  side and extend in a direction along the transport direction and a guide surface  34 D which bends and extends inside from the lower panel portion  34 A and is shaped along the outer circumferential surface of the main transport roller  55  are arranged. Therefore, the guide ribs  35 C and the guide surface  34 D form the U-turn transport path  58  so as to face the main transport roller  55  with a gap. Also, the guide ribs  35 C fix a shaft  59  of the pinch roller  56 . 
     [Configuration of Discharge Unit  44 ] 
     The discharge unit  44  includes a guide panel  60  which spans in a range reaching the vicinity of the sheet discharge port  39  from a position which faces near a lower end of the main transport roller  55  at the transport direction downstream side than the pinch roller  57 , a lower guide panel portion  32 A which extends so as to face the guide panel  60  with a gap to form a sheet discharge path  61 , a sheet discharge roller  62 , and a pinch roller  63  which faces the sheet discharge roller  62 . The lower guide panel portion  32 A integrally has the sheet discharge tray  32  which is placed at the downstream side. 
     An upstream end side of the guide panel  60  is arranged with a sheet pressing member  64  which faces an upper surface of the second platen  24 , and a biasing spring  65  which biases the sheet pressing member  64  toward the second platen  24 . Also, the abutting member  23  (refer to  FIG. 2 ) is placed at a position of the guide panel  60  and specifically, at an upstream end of the downstream side lower guide panel portion  32 A. Further, a sheet pad  67  which has a white sheet  66  is attached to a surface of the lower guide panel portion  32 A of the sheet discharge tray  32  at an area facing the first platen  22 . The sheet pad  67  presses the sheet which is supported by the first platen  22  from above. 
     [Sheet Transport Operation] 
     In this configuration, when the sheet is set such that a lower edge of the sheet is directed to the sheet feed inlet  38  while spanning from the transport sheet holding surface  31 A to the sheet guide surface  36 , the sheet transport portion  40  detects the sheet by using a sheet sensor SW 1  (refer to  FIG. 6 ) whose tip end projects from an upper surface of the sheet guide surface  36  at a position close to the swinging holder  48 . When the sheet which is set on the transport sheet holding surface  31 A is the maximum sheet, the sheet is detected by a maximum sheet sensor SW 2  (refer to  FIG. 6 ) whose tip end projects from the upper surface of the sheet guide surface  36  near a rear end of the opposite side to the sheet sensor SW 1  across the swinging holder  48 . Based on the detection results of the sensors SW 1  and SW 2 , the size of the sheet which is set on the transport sheet holding surface  31  is determined. 
     When a reading start operation (scanning function or copying function) is made in a state where the sheet sensor SW 1  detects the setting of the sheet, the sheets which are set on the transport sheet holding surface  31 A are drawn in by the sheet feed roller  45 , and the uppermost sheet is separated from the other sheets as the separation roller  46  and the separation pad  47  operate together with each other and is transported toward the relay roller pair  49 . 
     The relay roller pair  49  transports the transported sheet toward the downstream side, and, in a case of a double-sided reading, the image on the back surface side of the sheet is read by the fixed reading sensor  51  when the sheet passes between the third platen  52  and the sheet pressing member  53  during the transport. Also, in a case of a single-sided rearing, the fixed reading sensor  51  does not perform the reading while transporting toward the U-turn transport path  58 . 
     In the U-turn transport path  58 , the sheet is transported so as to be U-turned toward the downstream side by the driving of the main transport roller  55  as the pinch roller  56 , the guide ribs  35 C, the guide surface  34 D, and the pinch roller  57  operate together with each other. 
     When the sheet passes between the sheet pressing member  64  and the second platen  24  through the U-turn transport path  58 , the image on a front surface side of the sheet is read by the movable reading sensor  25  at the fixed position. Further, in the discharge unit  44  after the reading of the image, the sheet is discharged from the sheet discharge port  39  toward the sheet discharge tray  32  through the sheet discharge path  61  between the guide panel  60  and the lower guide panel portion  32 A by the nip transport by the sheet discharge roller  62  and the pinch roller  63 . A height different is formed between the sheet discharge port  39  and the sheet discharge tray  32 . 
     [Configuration of ADF Cover  35 ] 
     As described above, the ADF cover  35  is integrally formed with the guide ribs  35 C which extend along the sheet transport direction from the inner surface  35 B. As shown in  FIG. 8 , the multiple guide ribs  35 C are formed in the front-rear direction crossing the sheet transport direction with a gap. Also, between the guide ribs  35 C, multiple reinforcing ribs  35 D that extend in a direction orthogonal to the extending direction of the guide ribs  35 C are formed. The ADF cover  35  holds the shaft  59  of the pinch roller  56  and the sheet pressing member  53 . In the illustrative embodiment, the pinch roller  56  is arranged in a plural number (three positions) in the front-rear direction, and is supported in a rotatable manner by the one shaft  59 . It is noted that the number of the pinch rollers  65  is not limited to three positions. 
     The ADF cover  35  includes a fixed side rib  35 E which projects from the inner surface  35 B and covers a portion of one end  59 A of the shaft  59 . By covering a portion facing an end face of the one end  59 A of the shaft  59  and an upper section of the one end  59 A in the drawing (lower section in the state of use in  FIG. 7 ), the fixed side rib  35 E prevents the one end  59 A from moving and falling out in the axial direction and toward the upper section in the drawing, respectively. Also, the ADF cover  35  supports the other end  59 B of the shaft  59  by a mounting unit  35 F which allows attachment and detachment operations. 
     In the illustrative embodiment, the mounting unit  35 F includes a stop portion F 1  which stops the other end  59 B from falling out downward, a regulation member F 2  which regulates the position of the other end  59 B along the axial direction, and a stopper portion F 3  which regulates the amount of deflection of the regulation member F 2  as shown in  FIGS. 9 to 12 . The guide rib  35 C is formed in plural positions as described above, and the extension strength in the direction along the transport direction and the height from the inner surface  35 B are different from each other in the portion of formation. Therefore, in the description and drawings hereinbelow, the guide rib  35 C in which a portion is recessed to install the pinch roller  56  is referred to as the guide rib  35 C (A), the guide rib  35 C in which a portion is recessed such that the other end  59 B passes is referred to as the guide rib  35 C (B), the guide rib  35 C at the more front side thereof is referred to as the guide rib  35 C (C), and the guide rib  35 C at the further front thereof is referred to as the guide rib  35 C (D). 
     The stop portion F 1  is integrally formed with the inner surface  35 B, and includes a first stop portion F 11 , a second stop portion F 12 , and a third stop portion F 13  formed integrally with each other. The first stop portion F 11  has a surface facing the other end  59 B from a left side along the extending direction of the shaft  59  from a front surface side of the guide rib  35 C (B). The first stop portion F 11  regulates the movement of the other end  59 B of the shaft  59  in the left direction. The second stop portion F 12  is formed in a shape which is curved from the first stop portion F 11  toward the upper panel portion  35 A. The third stop portion F 13  is continuous from a portion of each of the stop portions F 11  and F 12 , and faces the other end  59 B of the shaft  59  from below. The third stop portion F 13  regulates a downward movement of the other end  59 B of the shaft  59 . 
     The regulation member F 2  is a plate-shaped regulation rib which projects from the inner surface  35 B toward the main transport roller  55 . 
     Herein, it may be preferable that the regulation member F 2  be a plate-shaped regulation rib projecting from the inner surface  35 B toward the rotation center Q 1  of the main transport roller  55  on an imaginary line L which connects the center Q 2  of the shaft  59  of the pinch roller  56  with the rotation center Q 1  of the main transport roller  55 . The extending direction of the imaginary line L is an example of a first direction. Also, the extending direction of the shaft  59 , that is, the extending direction of the center Q 2  is an example of a second direction. 
     In the illustrative embodiment, the pinch roller  56  is arranged so as to be in contact with the top of the main transport roller  55 , and thus the regulation member F 2  projects in the vertical direction (upper-lower direction) toward the rotation center Q 1  of the main transport roller  55  by forming the inner surface  35 B facing the pinch roller  56  to be orthogonal to the imaginary line L. Also, the regulation member F 2  is a plate-shaped regulation rib which has a surface extending along the extending direction of the shaft  59  and has a thickness in a direction orthogonal to the extending direction of the shaft  59 , that is, a direction along the extending direction of the guide rib  35 C which is the sheet transport direction. 
     As shown in  FIG. 12 , the regulation member F 2  includes the three portions of a base F 21  (example of a first surface) which is placed farthest away from an end face  59 C of the shaft  59 , a middle portion F 22  (example of a second surface) which gradually approaches the end face  59 C, and a tip end portion F 23  (example of a third surface) which approaches closest to the end face  59 C. In this manner, the regulation member F 2  is shifted in a direction in which a projecting end F 25  (example of a second end portion) which is the other side end portion approaches the end face  59 C of the shaft  59  with respect to a fixed end F 24  (example of a first end portion) with a width W1 which is a connection end connected to the inner surface  35 B and extends along the axial direction of the shaft  59 , and a curved shape (example of a curved portion) is formed between the fixed end F 24  and the projecting end F 25 . In other words, the projecting end F 25  is located closer to the end face  59 C of the shaft  59  than the fixed end F 24  in the extending direction of the shaft  59 . 
     Focusing on an end edge of the regulation member F 2  at the side of the shaft  59 , the base F 21  has a first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , the middle portion F 22  has a second end edge F 27  which is continuous to the first end edge F 26  and extends in a diagonal direction so as to approach the end face  59 C of the shaft  59 , and the tip end portion F 23  has a third end edge F 28  which is continuous to the second end edge F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . It may be preferable that an end edge of the regulation member F 2  which is placed on the opposite side from the shaft  59  have the same direction (parallel) as each of the surfaces F 26 , F 27 , and F 28  with an extension length allowing for the surface width of the base F 21 , the middle portion F 22 , and the tip end portion F 24 . 
     When the extension height of the first end edge F 26  is H1, the extension height of the second end face F 27  is H2, the extension height of the third end edge F 28  is H3, and the total height of the regulation F 2  is H4 as shown in  FIG. 12 , it may be preferable that the extension height increase toward the tip end side (H1&lt;H2&lt;H3) so as to facilitate the elastic deformation (hereinafter referred to as ‘deflection’) in the direction of tilt of the regulation member F 2 , that is, the left-right direction. Similarly, it may be preferable that the width W2 of the projecting end F 25  be narrower than the width W1 of the fixed end F 24  (W1&gt;W2), and it may be preferable that the range of W1 and the range of W2 have a positional relationship in which the ranges do not overlap with each other in the upper-lower direction. In other words, it may be preferable that the fixed end F 24  and the projecting end F 25  be shifted from each other so as not to overlap with each other when viewed from the upper-lower direction. Further, the third end edge F 28  of the tip end portion F 23  has a linear shape so as to face the end face  59 C of the shaft  59  in parallel. The third end edge F 28  may have a linear shape in which a portion in contact with the end face  59 C of the shaft  59  is along the end face  59 C. 
     Further, for the shape of the ADF cover  35 , the regulation member F 2  can be formed even though the line L connecting the center Q 2  of the shaft  59  with the rotation center Q 1  of the main transport roller  55  is not orthogonal to the inner surface  35 B in the inner surface  35 B. Also, the regulation member F 2  can ensure the functions even though the direction in which the regulation member projects from the inner surface  35 B is shifted from the rotation center Q 1  of the main transport roller  55  and the center Q 2  of the shaft  59  if the regulation member is a plate-shaped regulation rib which has no curve or the like in the facing direction to the end face  59 C with respect to the movement along the axial direction of the shaft  59 . 
     Also, the base F 21  extends such that the fixed end F 24  spans orthogonally to the guide rib  35 C (C) closest to the end face  59 C of the shaft  59 . At this time, a cutout-shaped slit  23 E is formed using a mold structure in the guide rib  35 C (C) not integrally with the base F 21  to ensure the large total width W3. At this time, as shown in  FIG. 11 , in the guide rib  35 C (C), an angular portion R formed by an edge portion (end face) extending along the extending direction, that is, the sheet transport direction and an edge portion (end face) which forms the slit  23 E is chamfered. In other words, the guide rib  35 C has a chamfered portion at the angular portion R. Also, the total height H4 of the regulation member F 2  is formed to be lower than the height H5 from the inner surface  35 B to the angular portion R. Also, the height H5 of the guide rib  23 C (C) to the angular portion R is formed to be lower than the height H6 of the guide rib  35 C (C) from the inner surface  35 B at the upstream side than the slit  23 E, that is, lower than the height from the inner surface  35 B of the other guide ribs  35 C (A),  35 C (B), and  35 C (D) which do not form the slit  23 E. 
     The stopper portion F 3  integrally includes a first stopper F 31  which extends along the axial direction of the shaft  59  from the second stop portion F 12  of the stop portion F 1 , and a second stopper F 32  which projects toward the regulation member F 2  from the first stopper F 31 . A tip end of the second stopper F 32  has a predetermined gap from the regulation member F 2 . 
     In this configuration, the one end  59 A of the shaft  59  which holds the pinch roller  56  in a rotatable manner is first engaged with and inserted into the fixed side rib  35 E, and then the other end  59 B is engaged with the stop portion F 1 . Both of the ends  59 A and  59 B are not required to be in contact with the fixed side rib  35 E and the stop portion F 1 . 
     When the other end  59 B is engaged with the stop portion F 1 , the projecting end F 25  of the regulation member F 2  is fully deflected toward the stopper portion F 3 , and the tip end portion F 23  is retracted from on the axis of the shaft  59 . In this manner, the other end  59 B of the shaft  59  can be easily engaged with the stop portion F 1 . The width W1 of the fixed end F 24  is narrower than the total width W3 while the total width W3 of the regulation member F 2  in the direction along the axial direction of the shaft  59  is ensured to be wide, and thus the deflection in the direction of tilt of the tip end portion F 23  can be easily ensured. In other words, the projecting end F 25  has a shape extending in the direction approaching the end face  59 C of the shaft  59  from the fixed end F 24  of the regulation member F 2 , and thus the length with which the deflection can be made can be ensured to be longer with respect to the height of the regulation member F 2 . 
     The shape of the regulation member F 2  is not limited to the above description. If the projecting end F 25  is shifted to the side of the end face  59 C with respect to the fixed end F 24 , the third end face F 28  can be shifted with respect to the end portion of the shaft  59  of the fixed end F 24 , and the ease of the deflection can be ensured even though the height of the regulation member F 2  is formed to be lower than in the related-art technique. Also, the middle portion F 22  may be integrated with the base F 21  or the tip end portion F 23  in appearance. 
     For example, as shown in  FIG. 13A , the base F 21  and the middle portion F 22  may have the first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , and the tip end portion F 23  may have the second end edge F 27  which is continuous to the first end edge F 26  and extends in parallel with the center Q 2  so as to approach the end face  59 C of the shaft  59  and the third end edge F 28  which is continuous to the second end edge F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     Also, as shown in  FIG. 13B , the base F 21  may have the first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , the middle portion F 22  may have the second end edge F 27  which is continuous to the first end face F 26  and extends in parallel with the center Q 2  so as to approach the end face  59 C of the shaft  59 , and the tip end portion F 23  may have the third end edge F 28  which is continuous to the second end face F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     Also, as shown in  FIG. 13C , the base F 21  may have the first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , the middle portion F 22  may have the second end edge F 27  which is continuous to the first end face F 26  and extends in the diagonal direction so as to approach the end face  59 C of the shaft  59 , and the tip end portion F 23  may have the third end edge F 28  which is continuous to the first end edge F 26  and extends in parallel with the center Q 2  so as to approach the end face  59 C of the shaft  59  and a fourth end edge F 29  which is continuous to the third end edge F 28  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     Also, as shown in  FIG. 13D , the base F 21  may have the first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , and the tip end portion F 23  may have the second end edge F 27  which is continuous to the first end face F 26  and extends in the diagonal direction so as to approach the end face  59 C of the shaft  59 , and the third end edge F 28  which is continuous to the second end face F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     Also, as shown in  FIG. 13E , the base F 21  may have the first end edge F 26  which rises in the diagonal direction from the inner surface  35 B so as to approach the end face  59 C, and the tip end portion F 23  may have the second end edge F 27  which is continuous to the first end face F 26  and extends in parallel with the center Q 2  so as to approach the end face  59 C of the shaft  59  and the third end edge F 28  which is continuous to the second end edge F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     Also, as shown in  FIG. 13F , the base F 21  may have the first end edge F 26  which vertically rises from the inner surface  35 B so as to be orthogonal to the center Q 2  of the shaft  59 , and the tip end portion F 23  may have the second end edge F 27  which is continuous to the first end edge F 26  and is curved and extends obliquely so as to approach the end face  59 C of the shaft  59 , and the third end edge F 28  which is continuous to the second end edge F 27  and vertically extends so as to be orthogonal to the center Q 2  of the shaft  59 . 
     The regulation member F 2  has a surface with a predetermined width in the extending direction of the shaft  59  from each of the first end edge, the second end edge, and the third end edge. 
     As described above, the sheet transport unit  30  according to the illustrative embodiment of the present invention includes the main transport roller  55  which transports a sheet, the ADF cover  35  which covers the main transport roller  55 , the pinch roller  56  which is attached to the ADF cover  35  via the shaft  59  to face the main transport roller  55  to transport the sheet, and the regulation member F 2  provided to face the end face  59 C of the shaft  59  to regulate the movement of the shaft  59  in the direction along the extending direction. The regulation member F 2  is the regulation rib which projects in the first direction from the surface of the ADF cover  35  facing the main transport roller  55  toward the main transport roller  55  and has the surface along the second direction which is the extending direction of the shaft  59 . The regulation member F 2  includes the fixed end F 24  which is fixed to the facing surface, and the projecting end F 25  which is the end portion at an opposite side to the fixed end F 24  and faces the end face  59 C of the shaft  59 . The projecting end F 25  is shifted with respect the fixed end F 24  in the direction approaching the shaft  59  along the second direction. 
     That is, the regulation member F 2  is formed in a non-linear shape in which the projecting end F 25  is shifted with respect to the fixed end F 24  in the direction approaching the end face  59 C of the shaft  59  of the pinch roller  56 . Therefore, even in the case of the regulation member F 2  which has a predetermined height in the first direction, the length from the fixed end F 24  to the projecting end F 25  can be ensured to be longer compared to the regulation member F 2  extending in a linear shape in the first direction, and the amount of deflection in the direction of tilt of the regulation member F 2  can be easily ensured. Therefore, when the pinch roller  56  is attached to the ADF cover  35 , the regulation member F 2  can be deflected in the direction of tilt, so that the shaft  59  of the pinch roller  56  can be easily held by the ADF cover  35 . After the attachment of the shaft  59 , the movement of the shaft  59  of the pinch roller  56  in the extending direction with respect to the ADF cover  35  can be regulated by the projecting end F 25  of the regulation member F 2 . Therefore, even when the ADF cover  35  is made thin and the height of the regulation member F 2  is smaller than in the related-art technique, the shaft  59  of the pinch roller  56  can be easily attached to the ADF cover  35 . Also, the movement of the shaft  59  of the pinch roller  56  can be regulated. 
     Also, the regulation member F 2  has an inclined or curved portion between the fixed end F 24  and the projecting end F 25 , and thus the width of the regulation member F 2  can be ensured to be large while the regulation member F 2  can be formed in an easily deflected shape. 
     Further, the surface of the regulation member F 2  includes the base F 21  which projects in the first direction from the fixed end F 24 , the middle portion F 22  which is continuous to the base F 21  and is inclined or curved in the second direction, and the tip end portion F 23  which is continuous to the middle portion F 22  and projects in the direction along the end face  59 C of the shaft  59 , and thus the length of the regulation member F 2  can be ensured by the middle portion F 22 . Therefore, even when the regulation member F 2  has a limited height, the deflection in the direction of tilt is facilitated during the attachment of the shaft  59 , and the regulation member F 2  can have the shape in which the functions of the regulation member F 2  is reliably achieved after the attachment of the shaft  59 . 
     Also, the part of the projecting end F 25  of the regulation member F 2  facing the end face  59 C of the shaft  59  has a linear shape along the end face  59 C of the shaft  59 , and thus the projecting end F 25  of the regulation member F 2  can be accurately brought into contact with the end face  59 C of the shaft  59 , and the regulation member F 2  can reliably achieve the functions. 
     Also, the inner surface  35 B of the ADF cover  35  which faces the main transport roller  55  includes the plurality of guide ribs  35 C extending along the sheet transport direction, and the guide rib  35 C (C) closest to the end face  59 C of the shaft  59  among the plurality of guide ribs  35 C is formed with a cutout portion, and the regulation member F 2  extends in the direction intersecting the extending direction of the closest guide rib  35 C (C) in the cutout portion, and thus the total width W3 of the regulation member F 2  can be arranged to be wider while the gap between the plurality of guide ribs  35 C (C) is maintained, and a decrease in the accuracy of the transport can be prevented by the guide ribs  35 C. 
     Also, in the closest guide rib  35 C, the angular portion R formed by the edge portion extending in the extending direction of the closest guide rib  35 C and the edge portion of the slit  23 E is chamfered, and thus the hanging of the sheet which is in transport onto the angular portion R of the guide rib  35 C can be prevented by the slit  23 E. 
     Also, the height H4 in the projecting direction of the regulation member F 2  is formed to be lower than the height H6 in the projecting direction of the rib  35 C, and thus the blocking by the regulation member F 2  of the transport of the sheet by the guide rib  35 C can be suppressed. 
     Further, the regulation member F 2  is integrally formed with the ADF cover  35 , and thus the fixed end F 24  of the regulation member F 2  can be solid and the shape in which the deflection in the direction of tilt of the projecting end F 25  side can be properly ensured can be easily formed.