Patent Publication Number: US-7717424-B2

Title: Sheet conveying device and image scanning apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority from Japanese Patent Application No. 2006-061925, filed on Mar. 7, 2006, the entire subject matter of which is incorporated herein by reference. 
   TECHNICAL FIELD 
   Aspects of the present invention relate to a sheet conveying device that conveys a sheet along a sheet conveying path to discharge the sheet to a discharge position, and an image scanning apparatus having the sheet conveying device. More particularly, the present invention relates to a sheet conveying device and an image scanning apparatus having a mechanism for stacking a plurality of sheets in layers by allowing a next sheet to be placed beneath a preceding discharged sheet. 
   BACKGROUND 
   Conventionally, in an apparatus such as a copying machine, a scanner, a printer, and a multi-function device having a plurality of functions for serving as such apparatuses, there is known a configuration being provided with an ADF (Auto Document Feeder) that conveys a sheet (an original document) from a feed tray to a discharge tray along a sheet conveying path. Examples of such configuration are proposed in JP-A-2005-247575 (counterpart U.S. patent application is published as US 2005/0212195 A1) and JP-A-2005-253013 (counterpart U.S. patent application is published as US 2005/0194731 A1). The ADF disclosed in JP-A-2005-247575 and JP-A-2005-253013 is schematically shown as ADF  130  in  FIG. 23 . A simple overview of the mechanism and operation of the ADF  130  will be described below. 
   The conventional ADF  130  shown in  FIG. 23  has a sheet feeding mechanism  131  that separates a plurality of sheets (hereinafter, referred to as a “stack of sheets”) placed on a feed tray  132  and sequentially feeds the stack of sheets to a sheet conveying path  138 . The sheet feeding mechanism  131  is configured such that a feed chute portion  133  is formed monolithically from the feed tray  132 , and a feed roller  134 , a feed nip piece  135 , a separation roller  136 , and a separation nip piece  137  are arranged in the feed chute portion  133 . 
   The feed roller  134  is rotatably arranged on a lower guide surface of the feed chute portion  133 . The feed nip piece  135  is arranged on a portion of an upper guide surface of the feed chute portion  133  in a position facing the feed roller  134 , such that the feed nip piece  135  is contactable with the teed roller  134 . The feed nip piece  135  is urged toward the feed roller  134  to be in Contact with the feed roller  134  by an urging member that is not shown. 
   The stack of sheets placed on the feed tray  132  are urged toward the feed roller  134  by the feed nip piece  135  and a bottommost sheet of the stack of sheets that contacts the feed roller  134  is fed in a sheet feeding direction due to the rotation of the feed roller  134 . In the configuration shown in  FIG. 23 , the sheets are placed on the feed tray  132  with its right face (face to be scanned) facing downward. 
   The separation roller  136  is rotatably arranged on the lower guide surface of the feed chute portion  133  to be spaced from the feed roller  134  in the sheet feeding direction. The separation nip piece  137  is arranged on the upper guide surface of the feed chute portion  133  that is a position facing the separation roller  136 , such that the separation nip piece  137  contacts the separation roller  136 . The separation nip piece  137  is urged toward the separation roller  136  to be in contact with the separation roller  136  by an urging member that is not shown. A sheet fed by the feed roller  134  is nipped between the separation roller  136  and the separation nip piece  137  and conveyed in the sheet feeding direction by the rotation of the separation roller  136 . 
   The sheet conveying path  138  is configured to have a substantially U-lettered shape when viewed from a side of the ADF  130  and is provided at a position downstream with respect to the feed chute portion  133  in the sheet feeding direction. A conveying roller  139  is arranged on the sheet conveying path  138  and three pinch rollers  140  ( 140   a ,  140   b , and  140   c ) are arranged on an outer circumference of the conveying roller  139 . Each of the pinch rollers  140  are urged toward the conveying roller  139  by an urging member, which is not shown, to be in contact with the conveying roller  139 . 
   A sheet fed to the sheet conveying path  138  by the sheet feeding mechanism  131  is conveyed along the sheet conveying path  138  while being nipped between the pinch roller  140   a , which is disposed immediately upstream of a platen glass  142 , and the conveying roller  139 . The sheet is guided by a guide member  141  and conveyed onto the platen glass  142 . At this time, an image formed on the sheet that is conveyed above the platen glass  142  is scanned by an image sensor  143  arranged below the platen glass  142 . 
   The sheet having been scanned is conveyed upward while being nipped between the pinch roller  140   b , which is disposed immediately downstream of the platen glass  142 , and the conveying roller  139 . At this time, the sheet is guided by a curved guide surface, which is not shown, and conveyed to perform a U-turn along an outer circumferential surface of the conveying roller  139 . 
   The pinch roller  140   c  is arranged on the sheet conveying path  138  at a position most downstream. As shown in  FIGS. 24A-24C , the pinch roller  140   c  is disposed vertically above the conveying roller  139  and supported by an outer guide  147  with the pinch roller  140   c  being urged toward the conveying roller  139  by a coil spring  146 . A sheet is conveyed while being nipped between the pinch roller  140   c  and the conveying roller  139 , to thereby be discharged to a discharge tray  144  from the sheet conveying path  138  through a discharge chute portion  145 . 
   In the ADF  130  configured as described above, sheets are fed one by one from the stack of sheets placed faced down on the feed tray  132 . The fed sheets are sequentially conveyed to the discharge tray  144  disposed above the feed tray  132 . Accordingly, the sheets are stacked on the discharge tray  144  in an order (hereinafter, referred to as “reverse order”) reverse to an original order initially being stacked. In order to prevent the sheets from being thus discharged in reverse order, the conventional ADF disclosed in JP-A-2005-247575 and JP-A-2005-253013 is provided with, as shown in  FIG. 24 , a plate spring piece  148  that lifts up the discharged sheet from a nip position that is configured between the pinch roller  140   c  and the conveying roller  139 . 
   According to this configuration, the sheet S 2  (hereinafter, referred to as a “subsequent sheet”) that is discharged by the pinch roller  140   c  and the conveying roller  139  subsequent to the discharged sheet is guided such that a leading edge of the subsequent sheet S 2  is placed, by the plate spring piece  148 , beneath a trailing edge of the preceding discharged sheet S 1  (hereinafter, referred to as a “preceding sheet”) . Then, the subsequent sheet S 2  is further conveyed, to thereby be discharged to slide beneath the preceding sheet S 1 . Accordingly, the sheets discharged onto the discharge tray  144  will be stacked in the original order. 
   According to the ADF  130  having the plate spring piece  148 , the order of the discharged sheets is not reversed as described above. However, in the conventional ADF  130 , concerns arise about the possible occurrence of an event that due to an amount of the preceding sheets stacked on the discharge tray  144 , or an aged deterioration of the roller surface of the pinch roller  140   c , the subsequent sheet may not be placed beneath the preceding sheets stacked on the discharge tray  144  and may be discharged between the stacked sheets or on the top of the stacked sheets. 
   For example, when the amount of sheets discharged on the discharge tray  144  increases, as shown in  FIG. 25 , a subsequent sheet S 3  is prevented from advancing by the preceding sheets S 1  and S 2  that are already being discharged, and thus, the subsequent sheet S 3  is immediately stopped after a conveying force applied by the nip roller  140   c  and the conveying roller  139  is lost. At this time, a trailing edge of the sheet S 3  remains near the nip position. The trailing edge remaining near the nip position may be scraped upward by the pinch roller  140   c , however, when the roller surface of the pinch roller  140   c  is in a slippery condition due to an aged deterioration, the trailing edge of the sheet S 3  may not be scraped upward. When another subsequent sheet S 4  is discharged with the trailing edge of the sheet S 3  remaining near the nip position, the subsequent sheet S 4  is discharged at a higher position than the preceding sheet S 3 , causing a problem that the order of the discharged sheets may not be the original order. In addition, the subsequent sheet S 4  may collide with the trailing edge of the preceding sheets, thereby causing a jam of the sheets (paper jam). 
   SUMMARY 
   According to a first aspect of the present invention, there is provided a sheet conveying device including: a sheet conveying path that is defined by guide surfaces that face each other with a predetermined gap therebetween and through which a sheet is conveyed; a pair of discharge rollers that is provided at a position most downstream in a conveying direction of the sheet conveying path and discharges the sheet from the sheet conveying path, the discharge rollers including: a drive roller that rotates by a torque applied thereto; and a follower roller that contacts the drive roller and rotates in accordance with the rotation of the drive roller; a discharge chute portion that guides the sheet discharged by the discharge rollers toward downstream in the conveying direction, the discharge chute portion including an upper discharge guide and a lower discharge guide that face each other with a predetermined gap therebetween; an elastic support piece that is provided in the discharge chute portion and supports a trailing edge of the sheet discharged to the discharge chute portion while elastically urging the trailing edge toward the upper discharge guide; and a discharge tray that is provided continuously from the discharge chute portion and retains the sheet guided by the discharge chute portion. The pair of discharge rollers is arranged such that a direction in which the drive roller contacts the follower roller is inclined toward upstream in the conveying direction with respect to a direction of a normal line of a lower one of the guide surfaces that is located in the sheet conveying path at a position the most downstream in the conveying direction. 
   According to a second aspect of the present invention, there is provided an image scanning apparatus including: a sheet conveying device that conveys a sheet; and an image scanning device that scans an image formed on the sheet. The sheet conveying device includes: a sheet conveying path that is defined by guide surfaces that face each other with a predetermined gap therebetween and through which the sheet is conveyed; a pair of discharge rollers that is provided at a position most downstream in a conveying direction of the sheet conveying path and discharges the sheet from the sheet conveying path, the discharge rollers including: a drive roller that rotates by a torque applied thereto; and a follower roller that contacts the drive roller and rotates in accordance with the rotation of the drive roller; a discharge chute portion that guides the sheet discharged by the discharge rollers toward downstream in the conveying direction, the discharge chute portion including an upper discharge guide and a lower discharge guide that face each other with a predetermined gap therebetween; an elastic support piece that is provided in the discharge chute portion and supports a trailing edge of the sheet discharged to the discharge chute portion while elastically urging the trailing edge toward the upper discharge guide; and a discharge tray that is provided continuously from the discharge chute portion and retains the sheet guided by the discharge chute portion. The pair of discharge rollers is arranged such that a direction in which the drive roller contacts the follower roller is inclined toward upstream in the conveying direction with respect to a direction of a normal line of a lower one of the guide surfaces that is located in the sheet conveying path at a position the most downstream in the conveying direction. The image scanning device is disposed below a sheet scanning position along the sheet conveying path. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG. 1  is an external perspective view showing an external configuration of a multi-function device being provided with an ADF according to one example of the present invention; 
       FIG. 2  is an external perspective view of the multi-function device showing a state in which a feed tray and a discharge tray is removed and a door for ink cartridges is opened; 
       FIG. 3  is a vertical cross-sectional view showing an internal configuration of the multi-function device; 
       FIG. 4  is a partial enlarged cross-sectional view showing a main configuration of a printer unit; 
       FIG. 5  is a partial enlarged cross-sectional view showing the main configuration of the printer unit; 
       FIG. 6  is a perspective view showing an external configuration of a scanner unit; 
       FIG. 7  is a front view of the scanner unit; 
       FIG. 8  is a plan view of the scanner unit; 
       FIG. 9  is a plan view of the scanner unit showing a state in which part of an internal configuration of the ADF is perspectively shown; 
       FIG. 10  is a plan view showing a main configuration of the scanner unit; 
       FIG. 11  is a vertical cross-sectional view showing a cross section taken along a line XI-XI shown in  FIG. 8 ; 
       FIG. 12  is a block diagram showing a configuration of a control unit and peripheral devices provided in the multi-function device; 
       FIG. 13  is a cross-sectional view showing the internal configuration of the ADF; 
       FIG. 14  is a perspective view of the scanner unit showing an open state of a discharge chute portion; 
       FIG. 15  is a plan view of the scanner unit showing an open state of the discharge chute portion; 
       FIG. 16  is an enlarged cross-sectional view of a main portion showing a cross section taken along a line XVI-XVI shown in  FIG. 9 ; 
       FIG. 17  is an enlarged cross-sectional view of a main portion showing a cross section taken along a line XVII-XVII shown in  FIG. 9 ; 
       FIG. 18  is an enlarged detailed view of a first conveying roller and a spring piece; 
       FIG. 19  is a partial enlarged view showing a state in which a pinch roller is mounted on guide ribs; 
       FIG. 20  is an enlarged detailed view of the pinch roller; 
       FIG. 21A  is a cross-sectional view showing a cross section taken along a line XXI-XXI shown in  FIG. 20 ; 
       FIG. 21B  is a front view of the pinch roller; 
       FIG. 22  is a cross-sectional view showing a retraction state of projections of the pinch roller; 
       FIG. 23  is a schematic diagram showing a schematic configuration of a conventional ADF; 
       FIGS. 24A-24C  are diagrams for describing a conveyance of a sheet in the conventional ADF; and 
       FIG. 25  is a diagram for describing a conveyance of a sheet in the conventional ADF. 
   

   DESCRIPTION 
   An example of the present invention will be described below by referring to the accompanying drawings. It is to be understood that the following example is merely an example in which the present invention is embodied and, as a matter of course, the example can be appropriately modified without changing the spirit and scope of the present invention. 
   As shown in  FIGS. 1-3 , a multi-function device  1  according to an example of the present invention is a multi-function device (MFD) that is integrally provided with an ink-jet printing type printer unit  2  arranged at the bottom and a scanner unit  3  arranged above the printer unit  2 . The multi-function device  1  has a plurality of functions including a printer function, a scanner function, a copy function, and a facsimile function. The scanner unit  3  of the multi-function device  1  serves as an image scanning apparatus according to the present invention, and an ADF (Auto Document Feeder)  5  provided in the scanner unit  3  serves as a sheet conveying device according to the present invention. 
   Note that functions other than the scanner function are arbitrary and the present invention may be implemented as a scanner that exclusively performs the scanner function. The ADF  5  may be taken as an independent device (i.e., a sheet conveying device). Thus, in this case, a scanner function is also arbitrary. In short, the present invention relates to an apparatus that conveys a sheet and thus can also be applied as an apparatus that conveys a recording sheet to a predetermined scanning position not only in a scanner but also in a printer or a copying machine, for example. 
   When performing the printer function, the multi-function device  1  is connected to a computer, which is not shown, and the printer unit  2  forms an image on a recording sheet based on image data or text data transmitted from the computer. When the multi-function device  1  is connected to an external device, such as a digital camera, the printer unit  2  forms an image on the sheet based on image data input from the external device. When a storage device, such as a memory card and a USB (Universal Serial Bus) memory, is attached to the multi-function device  1 , the printer unit  2  forms an image on the recording sheet based on image data stored in the storage device. 
   When performing the scanner function, image on the sheet is scanned by the scanner unit  3  as image data, and the image data is transferred to a computer connected to the multi-function device  1  by wire or wirelessly. The scanned image data can also be transferred to and stored in various storage media such as a memory card and a USB memory. 
   When performing the copy function, image data scanned by the scanner unit  3  is formed on the recording sheet by the printer unit  2 . When performing the facsimile function, image data read by the scanner unit  3  is transmitted as facsimile signal through a communication network such as a telephone line. Received facsimile signal is formed on the recording sheet by the printer unit  2 . 
   As shown in  FIGS. 1 and 2 , an external appearance of the multi-function device  1  is substantially formed in a box shape having width and depth being larger than height. The printer unit  2  provided at a lower part of the multi-function device  1  has a housing  10  that serves as a frame of the printer unit  2 . A front panel  11  faced to a front side of the housing  10  has an opening  4  formed thereon. 
   A feed tray  20  and a discharge tray  21  are provided in the opening  4  in a state where the discharge tray  21  is stacked above on the feed tray  20 . A connector panel  13  is arranged above the opening  4 . An opening  73  (see  FIG. 2 ) is provided at a rightmost side, in a widthwise direction, on the front panel  11 . A door  72  that opens and closes the opening  73  is pivotably provided to be forwardly openable around an axis provided near a lower end of the door  72 . As shown in  FIG. 2 , a refill unit  70  that retains ink cartridges that stores inks is mounted in the opening  73 . 
   An operation panel  6  that allows a user to operate the printer unit  2  and the scanner unit  3  is provided at a top front portion of the multi-function device  1 . The operation panel  6  is provided with various operation buttons  35  and a liquid crystal display  36  that are appropriately arranged. The multi-function device  1  is operated based on an instruction (instruction signal) inputted by an operation input by the user through the operation panel  6 . When the multi-function device  1  is connected to a computer, the multi-function device  1  is also operated based on an instruction (instruction signal) transmitted from the computer via a printer driver or a scanner driver. 
   As shown in  FIGS. 1 and 2 , the connector panel  13  where various connectors are disposed is provided at the front of the multi-function device  1 . The connector panel  13  is arranged above the opening  4  formed in the front panel  11 . The connector panel  13  is formed in a shape that is elongated in a widthwise direction (a direction perpendicular to the sheet in  FIG. 3 ) of the multi-function device  1 . 
   Note that, the operation buttons  35 , the liquid crystal display  36 , the feed tray  20 , and the discharge tray  21  are omitted in  FIG. 2 . 
   A slot portion  7  is disposed at a rightmost portion of the connector panel  13 . The slot portion  7  allows various types of memory cards to be attached therein to establish an electrical connection between a control unit  100  (see  FIG. 12 ) of the multi-function device  1  and the memory cards. In the present example, the memory cards are card-type storage device having a flash memory as a storage medium. In the slot portion  7 , to allow different types of memory cards to be attached, a first card slot  8  and a second card slot  9  being configured as different types of slots are horizontally arranged. 
   The first and second card slots  8  and  9  allow the memory cards to be inserted therein and removed therefrom in a direction perpendicular to the front panel  11 , i.e., a depth direction of the multi-function apparatus  1  (a direction indicated by an arrow P 1  in  FIG. 1 ). As shown in  FIGS. 1 and 2 , the first and second card slots  8  and  9  are arranged laterally so that insertion and removal of the memory cards is performed with the front and back faces of the memory cards to be horizontal. 
   In the multi-function device  1 , when a memory card is inserted into the slot portion  7 , the control unit  100  (see  FIG. 12 ) of the multi-function device  1  accesses the memory card, whereby image data stored in the memory card is read. When the image data is read, information about the image data, e.g., data names or preview images, is displayed on the liquid crystal display  36  of the operation panel  6 . When the user arbitrarily selects image data based on the information displayed on the liquid crystal display  36 , the selected image data is transferred to the printer unit  3  and the image data is formed on a recording sheet. Operations by the user to select image data is input through the operation panel  6 . 
   A USB connector  14  is disposed at a leftmost portion of the connector panel  13 . The USB connector  14  is a connector for establishing a USB connection between the multi-function device  1  and a USB device such as a USB memory and a USB cable having a USB terminal. The USB connector  14  is provided to allow the user to insert and remove the USB device in the direction perpendicular to the front panel  11  of the multi-function device  1 , i.e., the depth direction of the apparatus (the direction indicated by the arrow P 1  in  FIG. 1 ). A number of USB connectors  14  provided in the connector panel  13  may be appropriately designed, and the number of USB connectors  14  is not limited to one. 
   The printer unit  2  is provided at the lower portion of the multi-function device  1 . As shown in  FIG. 2 , the housing  10  of the printer unit  2  has the door  72  on the front panel  11 . The door  72  opens and closes the opening  73  provided at one of side portions (the far right portion in the present example) in the widthwise direction of the front panel  11 . 
   The refill unit  70  is installed in the printer unit  2 . The refill unit  70  is, as shown in the drawing, installed at a portion near to the front side of the housing  10  of the printer unit  2 , the portion being near to the front panel  11 . More specifically, the refill unit  70  is installed inside the opening  73 . The door  72  is disposed to be pivotable between a posture (opened posture) in which the refill unit  70  is exposed from the opening  73  by opening the opening  73  by pulling down the door  72  forward, and a posture (closed posture) in which the refill unit  70  is covered and accommodated by closing the opening  73 . The door  72  is provided with an axis at a lower end thereof and being pivotably supported by the axis. 
   Four accommodating chambers  78  are formed to be arranged horizontally in the refill unit  70 . Each of the accommodating chambers  78  allows an ink cartridge to be inserted into or removed from the opening  77  provided at the front of the accommodating chambers  78 . The opening  77  is opened and closed by doors  76  provided in front of the accommodating chambers  78 . Ink cartridges of different colors are inserted into the different accommodating chambers  78  and by closing the doors  76 , the ink cartridges are accommodated and retained in the refill unit  70 . 
   Each of the ink cartridges stores one of four color inks, respectively, including black (Bk), yellow (Y), magenta (M), and cyan (C). The color inks stored in the ink cartridges are supplied to a print head  39  (see  FIG. 4 ) through ink tubes  41  (see  FIG. 5 ). 
   As shown in  FIGS. 1 and 2 , the opening  4  is formed on the front panel  11  of the housing  10  of the printer unit  2 . The opening  4  is provided at a central portion, in the widthwise direction, of the front panel  11  and at a position slightly lower than the center in a height direction of the front panel  11 . A lower end of the opening  4  reaches a bottom surface of the multi-function device  1 . Inside the opening  4  of the multi-function device  1 , the feed tray  20  and the discharge tray  21  are provided. 
   The feed tray  20  and the discharge tray  21  are arranged such that the discharge tray  21  is stacked above the feed tray  20 . Recording sheets as recording medium are accommodated in the feed tray  20 . The feed tray  20  accommodates the recording sheets of various sizes not larger than A4 size, such as B5 size and a postcard size. The feed tray  20  is provided with a slide tray (not shown). The slide tray is pulled out where necessary to extend a tray surface of the feed tray  20 . Accordingly, recording sheets hating legal-size can be accommodated in the feed tray  20 . 
   As shown in  FIG. 3 , the feed tray  20  is disposed at a lower portion of the multi-function device  1 . The feed tray  20  can be inserted into and removed from the opening  4  in the direction indicated by the arrow P 1  shown in  FIG. 1  (a left-right direction in  FIG. 3 ). 
   When the feed tray  20  is inserted into the opening  4  and mounted inside the multi-function device  1 , a recording sheet is pulled out in a right direction (sheet feeding direction) in  FIG. 3  by a sheet feed roller  25 , as will be described later, and conveyed to an image forming unit  24  along a sheet conveying path  23  that is configured to have a substantially U-lettered shape when viewed from a side of the multi-function device  1 . The user can supply the recording sheets to the feed tray  20  by drawing out the feed tray  20  from the front side of the multi-function device  1 . In the present example, the bottom surface of the feed tray  20  serves as the bottom surface of the multi-function device  1  in a state where the feed tray  20  is inserted into the opening  4 . 
   As shown in  FIG. 3 , the discharge tray  21  is arranged above the feed tray  20 . A recording sheet having an image recorded thereon by the image forming unit  24  is discharged into the discharge tray  21  with a recording surface of the recording sheet being in a horizontal direction. In the present example, the feed tray  20  and the discharge tray  21  are monolithically formed. As shown in  FIG. 3 , the feed tray  20  and the discharge tray  21  are disposed in the opening  4  with placement surfaces of recording sheets, being kept horizontal. Thus, recording sheets, accommodated in the feed tray  20  and recording sheets, discharged into the discharge tray  21  are retained with recording surfaces thereof being kept horizontal. 
   Although the feed tray  20  and the discharge tray  21  are monolithically formed in the present example, the feed tray  20  and the discharge tray  21  may be formed by separate members. Instead of employing a configuration in which the feed tray  20  and the discharge tray  21  are removable from the multi-function device  1  as in the present example, each of the feed tray  20  and the discharge tray  21  may be configured in the housing  10  to be unremovable therefrom. 
   As shown in  FIG. 3 , a inclined separation plate  22  that is inclined to lean toward a backside of the multi-function device  1  is provided upright on a leading edge side, in an insertion direction, of the feed tray  20 . The inclined separation plate  22  separates and guides the recording sheet, which is fed from the feed tray  20 , upward. The sheet conveying path  23  is configured above the inclined separation plate  22 . The sheet conveying path  23  is configured upward from the inclined separation plate  22  and to turn toward the front side of the multi-function device  1 , to extend toward the front side from the backside of the multifunction device  1 , to pass through the image forming unit  24 , and then to the discharge tray  21 . The recording sheet fed from the feed tray  20  is conveyed along the sheet conveying path  23  to perform a U-turn upward toward the image forming unit  24 . The recording sheet being formed with an image by the image forming unit  24  is further conveyed and discharged to the discharge tray  21 . 
     FIG. 4  is an enlarged partial cross-sectional view showing a main configuration of the printer unit  2 . As shown in  FIG. 4 , the sheet feed roller  25  is provided above the feed tray  20 . The sheet feed roller  25  pressure contacts recording sheets stacked on the feed tray  20  to feed the topmost one of the recording sheets toward the inclined separation plate  22 . The sheet feed roller  25  is rotatably supported at a leading end of a sheet feeding arm  26 . The sheet feed roller  25  is rotated by a torque supplied by a motor, which is not shown, and transmitted by a torque transmission mechanism  27  having a plurality of gears engaging with one another. 
   The sheet feeding arm  26  swings up and down with respect to the feed tray  20  while a base shaft  28  serving as a pivotal axis. As shown in  FIG. 4 , the sheet feeding arm  26  swings downward by its own weight to allow the sheet feed roller  25  to be contactable with the teed tray  20 . When the feed tray  20  and the discharge tray  21  are inserted into or removed from the opening  4 , the sheet feeding arm  26  is retracted upward. When the sheet feed roller  25  is rotated while being in pressure contact with a recording sheet on the feed tray  20 , by a frictional force between a roller surface of the sheet feed roller  25  and the recording sheet, the topmost recording sheet is fed toward the inclined separation plate  22 . The recording sheet thus fed is guided upward to the sheet conveying path  23  by a leading edge of the recording sheet abutting against the inclined separation plate  22 . 
   When the topmost recording sheet is fed by the sheet feed roller  25 , a recording sheet immediately beneath the topmost recording sheet may be fed together toward the inclined separation plate  22  by the action of friction or static electricity. However, the recording sheet immediately beneath is prevented from being fed upward to the sheet conveying path  23  by abutting against the inclined separation plate  22 . 
   The sheet conveying path  23  is configured by an outer guide surface and an inner guide surface which face each other with a predetermined interval therebetween, except at a portion where the image forming unit  24  is arranged. For example, a portion of the sheet conveying path  23  that is located at the backside of the multi-function device  1  is configured by an outer guide member  18  and an inner guide member  19  that are fixed in the frame. The outer guide member  1  is provided with a plurality of conveying rollers  17 . A roller surface of the conveying rollers  17  is exposed from a guide surface of the outer guide member  18 . The conveying roller  17  is rotatably supported by the outer guide member  18  such that an axis of the conveying rollers  17  is configured to be in parallel with a widthwise direction of the sheet conveying path  23 . The conveying rollers  17  allow the recording sheet to be conveyed smoothly at a position where the sheet conveying path  23  curves in a U-shaped manner. 
   As shown in  FIG. 4 , the image forming unit  24  is provided on the sheet conveying path  23 . The image forming unit  24  includes a carriage  38  that is provided with the print head  39  and reciprocating in a main scanning direction (a direction parallel to the widthwise direction of the multi-function device  1 ). Color inks, including black (Bk), yellow (Y), magenta (M), and cyan (C), are supplied through the ink tubes  41  (see  FIG. 5 ) to the print head  39  from the ink cartridges in the refill unit  70  (see  FIG. 2 ) provided at the rightmost side of the front panel  11  in the multi-function device  1 . Then, the print head  39  selectively ejects the inks as ultra-small ink drops. By ink drops being selectively ejected from the print head  39  during reciprocation of the carriage  38 , an image forming is performed on the recording sheet conveyed on a platen  42 . 
     FIG. 5  is a plan view showing a main configuration of the printer unit  2 . As shown in  FIG. 5 , a pair of guide rails  43  and  44  is provided on the upper side of the sheet conveying path  23  with a predetermined interval therebetween in a conveying direction (an up-down direction in  FIG. 5 ) of the recording sheets, to extend in a direction (a left-right direction in  FIG. 5 ) orthogonal to the conveying direction of the recording sheets. The carriage  38  is placed across the guide rails  43  and  44  to be reciprocable in a horizontal direction orthogonal to the conveying direction of the recording sheets. The guide rail  43  arranged on the upstream side in the conveying direction of the recording sheets has a flat shape such that a length of the guide rail  43  in the widthwise direction of the sheet conveying path  23  is longer than a reciprocating range of the carriage  38 . A top surface of the guide rail  43  on the downstream side in the conveying direction is a guide surface  43 A. The guide surface  43 A slidably supports an end of the carriage  38  on the upstream side. 
   The guide rail  44  arranged on the downstream side in the conveying direction of the recording sheets has a flat shape such that a length of the guide rail  44  in the widthwise direction of the sheet conveying path  23  is substantially the same as that of the guide rail  43 . In the guide rail  44 , an end  45  on the upstream side is bent upward at a substantially right angle. A top surface of the guide rail  44  on the downstream side in the conveying direction is a guide surface  44 A. The guide surface  44 A slidably supports an end of the carriage  38  on the downstream side. The carriage  38  nips the edge  45  with rollers, which are not shown, or the like. Accordingly, the carriage  38  is slidably supported on the guide surfaces  43 A and  44 A of the guide rails  43  and  44  and reciprocates relative to the edge  45  of the guide rail  44  in the horizontal direction orthogonal to the conveying direction of the recording sheets. 
   A belt drive mechanism  46  is provided along the guide rail  44  on the top surface of the guide rail  44 . The belt drive mechanism  46  is such that an endless ring-shaped timing belt  49  having teeth provided on an inner side thereof is stretched between a drive pulley  47  and a follower pulley  48  which are respectively provided near both ends, in the widthwise direction of the sheet conveying path  23 , of the belt drive mechanism  46 . Due to the timing belt  49  being coupled to the carriage  38 , the carriage  38  reciprocates in accordance with an operation of the belt drive mechanism  46 . 
   The drive pulley  47  is rotatably provided at one end (a right end in  FIG. 5 ) of the top surface of the guide rail  44  with a direction orthogonal to the guide surface  44 A of the guide rail  44  as an axis. That is, the axis of the drive pulley  47  is in a vertical direction. Although not shown in  FIG. 5 , a motor is provided below the guide rail  44 . Due to a torque that is applied to the axis of the drive pulley  47  from the motor, the drive pulley  47  is rotated. 
   The timing belt  49  is stretched between the drive pulley  47  and the follower pulley  48 . Although not shown in  FIG. 5 , spur teeth that engage with the inner teeth of the timing belt  49  are formed on an outer circumference of the drive pulley  47 . Accordingly, rotation of the drive pulley  47  is reliably transmitted to the timing belt  49  and thereby the timing belt  49  performs a circular motion. Note that although in the present example the endless (looped) timing belt  49  is used, a timing belt having ends (non-looped timing belt) may be used instead. In such a case, both of the ends of the timing belt are coupled to the carriage  38 . 
   The carriage  38  is coupled to the timing belt  49 . When the timing belt  49  performs a circular motion, the carriage  38  reciprocates relative to the edge  45  on the guide rails  43  and  44 . The print head  39  is installed on the carriage  38 , whereby the print head  39  reciprocates in the widthwise direction of the sheet conveying path  23  as the main scanning direction. 
   An encoder strip  54  of a linear encoder (not shown) is arranged along the edge  45  of the guide rail  44 . The linear encoder detects the encoder strip  54  by a photo-interrupter  55  installed on the carriage  38 . The reciprocation of the carriage  38  is controlled based on a detection signal of the linear encoder. 
   As shown in  FIG. 5 , the platen  42  is arranged on the lower side of the sheet conveying path  23  to face the print head  39 . The platen  42  is composed of a plurality of ribs  42 A placed vertically and upwardly from a bottom surface of the platen  42 . The ribs  42 A are a thin-width plate-like member extending in the conveying direction of recording sheets (the up-down direction in  FIG. 5 ). The plurality of ribs  42 A are provided in the widthwise direction of the apparatus with a predetermined interval therebetween. A recording sheet is supported on the top of the plurality of ribs  42 A thus provided. The platen  42  is arranged at a central portion of the reciprocating range of the carriage  38 , through which a recording sheet passes. The width of the platen  42  is sufficiently greater than the maximum width of the conveyable recording sheets. Both edges of a recording sheet always pass above the platen  42 . 
   Maintenance units such as a purge mechanism  56  and a waste ink tray  57  are arranged in an area where a recording sheet does not pass through, i.e., an area other than an area where image recording is performed by the print head  39 . The purge mechanism  56  suctions and removes air bubbles or foreign matter from a nozzle (not shown) of the print head  39 . The purge mechanism  56  is provided with a cap  58  that covers the nozzle of the print head  39 , a pump mechanism connected to the print head  39  via the cap  58 , and a movement mechanism for allowing the cap  58  to contact the nozzle of the print head  39 . Note that in  FIG. 5 , the pump mechanism and the movement mechanism are located below the guide rails  43  and  44  and the cap  58  and thus are not shown in  FIG. 5 . When air bubbles or the like of the print head  39  are suctioned and removed, the carriage  38  is moved such that the print head  39  is located on the cap  58 . Under such a state, the cap  58  is moved upward and thereby makes intimate contact to hermetically seal the nozzle underneath the print head  39  and ink is sucked from the nozzle of the print head  39  by a pump coupled to the cap  58 . 
   The waste ink tray  57  receives idle ejection of ink from the print head  39 , called flushing. The waste ink tray  57  is integrally provided with the platen  42  in an area within the reciprocating range of the carriage  38  and outside the image recording area. Due to the maintenance units, maintenance such as removing air bubbles or mixed color ink within the print head  39  is performed. 
   Inks are supplied to the print head  39  through the ink tubes  41  coupled to ink cartridges (not shown) held in the refill unit  70  (see  FIG. 2 ). The ink cartridges are provided for different ink colors, respectively, and different color inks are supplied to the print head  39  by the ink tubes  41  independently provided for each color. Each of the ink tubes  41  are a synthetic resin tube and have flexibility to bend according to the reciprocation of the carriage  38 . 
   The ink tubes  41  coupled to the respective ink cartridges are pulled out to approximately the center of the apparatus along the widthwise direction of the apparatus and fixed to a fixing clip  59  of an apparatus frame. Note that in  FIG. 5 , the ink tubes  41  extending outward toward the ink cartridge side from the fixing clip  59  are omitted. The ink tubes  41  are not fixed to the frame at portions between the fixing clip  59  and the carriage  38 , and its posture changes along with the reciprocation of the carriage  38 . Specifically, along with the movement of the carriage  38  to one end in a reciprocating direction (left side in  FIG. 5 ), each of the ink tubes  41  moves in the moving direction of the carriage  38  while being bent such that the bending radius of a U-shaped curve portion becomes smaller. On the other hand, along with the movement of the carriage  38  to the other end in the reciprocating direction (right side in  FIG. 5 ), each ink tube  41  moves in the moving direction of the carriage  38  while being bent such that the bending radius of the curve portion becomes larger. 
   As shown in  FIG. 4 , a conveying roller  67  is provided on the upstream side of the image forming unit  24 . A pinch roller  71  is provided at a position facing the conveying roller  67 . The pinch roller  71  is urged by an urging member, such as a coil spring, to be contactable with the conveying roller  67 . When a recording sheet enters between the conveying roller  67  and the pinch roller  71 , the pinch roller  71  is retracted by an amount equal to the thickness of the recording sheet and nips the recording sheet with the conveying roller  67 . Accordingly, a torque of the conveying roller  67  is reliably transmitted to the recording sheet. Then, the recording sheet is conveyed onto the platen  42 . 
   A sheet discharge roller  68  is provided on the downstream side of the image forming unit  24 . A spur roller  69  is provided at a position facing the sheet discharge roller  68 . The spur roller  69  is in contact with the sheet discharge roller  68 . The recording sheet on which an image is formed is nipped and conveyed by the sheet discharge roller  68  and the spur roller  69 . The spur roller  69  is also urged to be contactable with the sheet discharge roller  68 , as with the pinch roller. However, since the spur roller  69  contacts a recorded recording sheet, a roller surface is made rough in a spur-like fashion so that an image recorded on the recording sheet is not degraded. 
   The conveying roller  67  and the sheet discharge roller  68  are intermittently driven at a predetermined linefeed width by a drive force being transmitted to the conveying roller  67  and the sheet discharge roller  68  from a motor which is not shown. Rotation of the conveying roller  67  is synchronized with rotation of the sheet discharge roller  68 . A rotary encoder (not shown) provided to the conveying roller  67  detects, by a photo-interrupter, an encoder disk  51  that rotates with the conveying roller  67 , whereby the rotation of each of the conveying roller  67  and the sheet discharge roller  68  is controlled. 
   A top portion of the multi-function device  1  is configured as the scanner unit  3 . Referring to  FIGS. 6-11 , a schematic configuration of the scanner unit  3  will be described below. 
   The scanner unit  3  is configured such that a cover  30  is mounted on a scanning platform  15  that serves as an FBS (Flatbed Scanner), via a hinge on the backside to be freely openable and closable in a direction indicated by an arrow P 2  in  FIG. 6 . The cover  30  is provided with the ADF  5  and thus the ADF  5  is also opened and closed along with the opening/closing of the cover  30 . 
   A platen glass  80  ( FIG. 11 ) is disposed on a top surface of the scanning platform  15 . As shown in  FIG. 6 , when the cover  30  is closed over the scanning platform  15 , the platen glass  80  is covered by the cover  30 . A pressing member  82  is provided below the cover  30 , i.e., a surface facing the platen glass  80 . The pressing member  82  presses a sheet (document) to be scanned placed on the platen glass  80  and is composed of a sponge, a plate member, and the like. The pressing member  82  has a single color, such as white, over the entire area to obtain stable reflected light from the sheet to be scanned. 
   An opening  31  (see  FIG. 13 ) is provided at one end of the underside of the cover  30 . The opening  31  is communicated with a sheet conveying path  151 , as will be described later. The opening  31  is used, when an image on the sheet is scanned using the ADF  5 , to temporarily expose the sheet to a scanning area  80 A of the platen glass  80  from the sheet conveying path  151 . 
   The platen glass  80  is a transparent plate made of glass or acrylic resin. A positioning member  83  that partitions between the scanning area  80 A used when scanning an image on the sheet using the ADF  5  and a scanning area  80 B used when the scanner unit  3  is used as an FBS is provided at a leftmost portion of the platen glass  80 . The positioning member  83  serves as a positioning reference used when the sheets to be scanned are placed on the platen glass  80 . Marks indicating placement positions according to the size of the sheet, such as A4 size and B5 size, are marked on a top surface of the positioning member  83 . When the ADF  5  is used, the positioning member  83  serves as a guide that guides to return the sheet passed above the scanning area  80 A to the sheet conveying path  151  (see  FIG. 13 ) provided in the ADF  5 . 
   As shown in  FIG. 10 , the scanning platform  15  is provided with an image scanning unit  32 . When the scanner unit  3  is used as an FBS, the cover  30  is opened and the sheet (document) is placed on the platen glass  80 . Then, the cover  30  is closed and the sheet is fixed onto the platen glass  80 . The image on the sheet is scanned by the image scanning unit  32  performs scanning while moving along the platen glass  80 . 
   The scanning platform  15  has a thin box shaped casing  84 . The image scanning unit  32  is disposed in the inner space of the casing  84  to be reciprocable in a horizontal direction. The casing  84  is made of a synthetic resin. The casing  84  has a base portion  90  including a bottom plate, a sidewall  91  rising from a periphery of the base portion  90 , and a partition plate  92 , which are monolithically formed. The partition plate  92  partitions between a region where the image scanning unit  32  is arranged and a region where a board of the operation panel  6  are arranged. The casing  84  is formed with various parts such as support ribs for supporting the platen glass  80 , a boss portion for screwing various members, and through-holes for electrical wiring. The parts formed on the casing  84  may be appropriately designed according to the employment and design of the scanning platform  15 , and thus a detailed description thereof will be omitted. 
   The image scanning unit  32  is provided with a contact image sensor (hereinafter, referred to as the “CIS”)  85  which is an example of an image scanning element, and an elongated box-shaped carriage  86 . The CIS  85  is installed in the carriage  86  to be supported from below. The CIS  85  faces a bottom surface of the platen glass  80 . The CIS  85  is a so-called intimate-contact-type line image sensor that allows a light source such as an LED to emit light to irradiate the light on the sheet, guides light reflected from the sheet to a photoelectric conversion element by a lens, and outputs, by the photoelectric conversion element, an electrical signal according to the intensity of the reflected light. The CIS  85  is installed on the carriage  86  and reciprocates below the platen glass  80 . 
   As shown in  FIG. 10 , a guide shaft  87  is disposed over a widthwise direction of the casing  84  (a left-right direction in  FIG. 10 ). The carriage  86  is fitted in the guide shaft  87 , and the image scanning unit  32  is supported to be smoothly movable below the platen glass  80  in a direction (the left-right direction in  FIG. 10 ) orthogonal to a longitudinal direction of the carriage  86 . A belt drive mechanism  88  is provided along the guide shaft  87 . As with the above-described belt drive mechanism  46 , the belt drive mechanism  88  includes a timing belt  89  installed between pulleys. The carriage  86  is fixed to the timing belt  89  of the belt drive mechanism  88  and reciprocates by a circular motion of the timing belt  89 . Accordingly, when the scanner unit  3  is used as an FBS, the CIS  85  scans an image on the sheet placed on the platen glass  80  while the carriage  86  is moved along the bottom surface of the platen glass  80 . 
   As shown in  FIGS. 6-9 , on the cover  30  at the top of the scanner unit  3 , a feed tray (supply sheet retaining portion)  33  and a discharge tray (discharged sheet retaining portion)  34  are arranged such that the discharge tray  34  is stacked above the feed tray  33 . In the feed tray  33 , a pair of sheet guides  93  is provided in a depth direction of the multi-function device  1  with a space therebetween, to be slidably movable in the depth direction. The sheet guides  93  rise from the feed tray  33  and regulate the position, in a widthwise direction of the sheet placed on the feed tray  33 . 
   The sheet guides  93  is provided with a known coupling mechanism such as a rack and a pinion so that when one of the sheet guides  93  is slid and moved, the other of the sheet guide  93  is also slid and moved in conjunction with the opposing sheet guide  93  in a contrary direction. When the sheet width is small, by sliding and moving one of the sheet guides  93  positioned on the front side of the multi-function device  1  to the backside, the other of the sheet guides  93  positioned on the backside is slid and moved toward the front side in conjunction with the opposing sheet guide  93 . According to this configuration, the sheet width to be regulated by the pair of sheet guides  93  can be narrowed with substantially the center in the depth direction as the center. 
   In contrast, when the sheet width is wide, by sliding and moving one of the sheet guides  93  positioned on the front side of the multi-function device  1  to the front side, the other of the sheet guides  93  positioned on the backside is slid and moved toward the backside in conjunction with the one sheet guide  93 , whereby the sheet width to be regulated by the pair of sheet guides  93  can be widened. 
   The discharge tray  34  is monolithically formed with the pair of sheet guides  93  with a gap provided therebetween in an upward direction of the feed tray  33 . Specifically, the discharge tray  34  is provided as canopy-like flat plates provided to extend from the tops of the sheet guides  93  to the inner side. The discharge tray  34  is arranged at a position lower than a top surface of an upper flat portion  179  (see  FIGS. 13 and 14 ) constituting a lower discharge guide of a discharge chute portion  158 , as will be described later. Thus, although a trailing edge of the sheet discharged to the discharge tray  34  remains in the discharge chute portion  158 , a leading edge side is supported by the discharge tray  34  arranged at a position lower than the upper flat portion  179 . Hence, the load applied to the leading edge side of the sheet increases and the load applied to the trailing edge side decreases, and thus, the trailing edge is easily lifted up. 
   The sheet discharged from the ADF  5  is supported on the discharge tray  34  at its both sides and held to be separated from the sheet on the feed tray  33 . Since the length, in a sheet discharge direction, of the discharge tray  34  is shorter than the length of the sheet, a leading edge side, in the sheet discharge direction, of the sheet is held on the feed tray  33  to hang from the discharge tray  34 . Thus, a leading edge portion, in the sheet discharge direction, of the sheet on the discharge tray  34  overlaps the trailing edge portion, in a sheet feeding direction, of the sheet on the feed tray  33 . However, since the leading edge portion, in the sheet feeding direction, of the sheet on the feed tray  33  and the trailing edge portion, in the sheet discharge direction, of the sheet on the discharge tray  34  are held in two tiers above and below the discharge tray  34 , the sheets are not mixed. By shortening the discharge tray  34 , space necessary on the cover  30  is reduced, the multi-function device  1  may be made to be thinner and smaller. 
   Sheets are placed on the feed tray  33  with their faces to be scanned facing down. A plurality of sheets (a stack of sheets) placed on the feed tray  33  are fed one by one in order from a bottommost sheet of the stack and conveyed by the ADF  5 . The sheets fed are continuously conveyed, by the ADF  5 , from the feed tray  33 , via a feed chute portion  154 , the sheet conveying path  151 , and the discharge chute portion  158 , to the discharge tray  34  disposed above the feed tray  33 . In the sheet conveying process, the sheet is conveyed onto the scanning area  80 A and an image on the sheet is scanned by the image scanning unit  32  disposed below the scanning area  80 A. Details of the ADF  5  will be described later. 
     FIG. 12  shows a configuration of a control unit  100  of the multi-function device  1  and peripheral devices connected to the control unit  100 . The control unit  100  performs overall control of the whole operation of the multi-function device  1  including the scanner unit  3  and the printer unit  2 . However, in the description of the present example, components of the printer unit  2  are omitted in  FIG. 12 . As shown in  FIG. 12 , the control unit  100  is provided with a microcomputer that includes a CPU (Central Processing Unit)  101 , a ROM (Read Only Memory)  102 , a RAM (Random Access Memory)  103 , and an EEPROM (Electrically Erasable and Programmable ROM)  104 . The control unit  100  is connected to an ASIC (Application Specific Integrated Circuit)  106  via a bus  105 . 
   The ROM  102  stores therein a program for controlling various operations of the multi-function device  1 . The EEPROM  104  stores therein various data to be used for processing to be performed according to the program. The RAM  103  is used as a storage area where various data to be used when the CPU  101  executes the program is temporarily stored, or as a data or program expansion area. 
   The CPU  101  performs overall control of devices provided in the control unit  100  or controlled devices that is to be controlled by the control unit  100 . The CPU  101  reads, a program stored in the ROM  102  or data stored in the RAM  103  or the EEPROM  104  and performs computation according to the program. 
   The ASIC  106  generates, according to an instruction from the CPU  101 , a phase excitation signals that are applied to each of a carriage motor (CR motor)  108  of the scanner unit  3  and a conveying motor (LF motor)  110  of the ADF  5 , and provides the signal to drive circuits  107  and  109  of the carriage motor  108  and the conveying motor  110 . The ASIC  106  generates a drive signal to be applied to the carriage motor  108  and the conveying motor  110  via the drive circuits  107  and  109 , and controls the rotation of the carriage motor  108  and the conveying motor  110 . 
   The drive circuit  107  drives the carriage motor  108  connected to the carriage  86  of the scanner unit  3 . The drive circuit  107  receives the signal output from the ASIC  106  and generates an electrical signal for rotating the carriage motor  108 . The carriage motor  108  having received the electrical signal is rotated and a torque of the carriage motor  108  is transmitted to the carriage  86  via a scanning mechanism, whereby the carriage  86  is scanned (moved back and forth). 
   The drive circuit  109  drives the conveying motor  110  connected to a separation roller  166 , a first conveying roller  168  (which serves as a drive roller), and a second conveying roller  171  of the ADF  5 . The drive circuit  109  receives the signal output from the ASIC  106  and generates an electrical signal for rotating the conveying motor  110 . The conveying motor  110  having received the electrical signal is rotated and a torque of the conveying motor  110  is transmitted to the separation roller  166 , the first conveying roller  168 , and the second conveying roller  171  via a drive mechanism that is provided with gears and a drive shaft. The torque is transmitted to a feed roller  164  from the separation roller  166  via a torque transmission mechanism. 
   The CIS  85  that scans an image on the sheet in the scanner unit  3  is connected to the ASIC  106 . The ASIC  106  provides, based on an instruction from the CPU  101 , an electrical signal for irradiating light from a light source and a timing signal for outputting image data from a photoelectric conversion element, to the CIS  85 . The CIS  85  receives these signals and thereby irradiates light on the sheet at predetermined timing and outputs image data converted by the photoelectric conversion element. 
   A panel gate array (panel G/A)  111  that controls the operation buttons  35  from which a desired instruction is inputted to the multi-function device  1  is connected to the ASIC  106 . The panel gate array  111  detects any of the operation buttons  35  of the operation panel  6  that is pressed by the user and outputs a predetermined code signal. Each of the operation buttons  35  is associated with unique key codes, respectively. When the CPU  101  receives a key code indicated by the code signal from the panel gate array  111 , the CPU  101  performs a control process that should be performed, according to a predetermined key processing table. The key processing table is a table in which the key codes are associated with control processes, and stored in the ROM  102 . 
   An LCD controller  112  that controls screen display of the liquid crystal display (LCD)  36  is connected to the ASIC  106 . The LCD controller  112  allows the liquid crystal display  36  to display information on an operation of the printer unit  2  or the scanner unit  3  on a screen, based on an instruction from the CPU  101 . 
   The slot portion  7  into which various small memory cards are inserted, and a parallel interface  113  and the USB connector  14  that perform data transmission and reception with a computer via a parallel cable or a USB cable are connected to the ASIC  106 . Furthermore, an NCU (Network Control Unit)  114  and a MODEM  115  for implementing a facsimile function are connected to the ASIC  106 . 
   A sheet sensor  116  for detecting a sheet in the sheet conveying path  151  (see  FIG. 13 ) in the ADS and a cover sensor  117  for detecting opening and closing of an ADS cover  153  (which serves as a cover member) are connected to the ASIC  106 . 
   With reference to  FIGS. 13-22 , the configuration and operation of the ADF  5  will be described in detail below. 
   As shown in  FIG. 13 , a housing of the ADF  5  is configured by an ADF main body  152  (which serves as an apparatus main body) formed monolithically with the cover  30 , and the ADS cover  153  provided to be pivotable relative to the ADF main body  152 . The ADF cover  153  forms a top surface of the housing of the ADF  5 . The ADF cover  153  pivots relative to the ADF main body  152  about a pivot shaft, which is not shown, provided at one side (left side in  FIG. 13 ) of the ADF main body  152 , in a direction indicated by an arrow P 3  in  FIG. 13 . When the ADF cover  153  is opened, inner components of the ADF  5  are exposed. A pivot free end of the ADF cover  153  extends to cover the entire area of a partition plate  156 , as will be described later. 
   The guide ribs  177  are protrudingly provided on an inner side of the ADS cover  153 . The plurality of guide ribs  177  are formed in a widthwise direction of the sheet conveying path  151  with a predetermined interval therebetween. The guide ribs  177  form outer guide surfaces of a curving path  157  and an upper sheet conveying path  160  of the sheet conveying path  151 , and the discharge chute portion  158 . 
   The posture of the ADF cover  153  changes between a closed posture shown in  FIG. 6  and an opened posture shown in  FIG. 14 , by pivoting the ADF cover  153  relative to the ADF main body  152 . When using the ADF  5 , the ADF cover  153  is brought into a closed posture. The ADF cover  153  is locked to the ADF main body  152  to maintain the closed posture. Specifically, as shown in  FIG. 14 , locking pieces  198  are formed at both ends, in the widthwise direction, of the pivot free end of the ADF cover  153 . When the ADF cover  153  is closed over the ADF main body  152 , the locking pieces  198  enter slots  200  formed in the ADF main body  152 , whereby the ADF cover  153  is locked to the ADF main body  152 . 
   For a locking mechanism of the ADF cover  153 , as shown in  FIG. 14  and  FIG. 15 , hook  199  is provided to each slot  200  and when the locking pieces  198  enter the slots  200 , the hooks  199  fit in slots  198 A (see  FIG. 14 ) of the locking pieces  198 . As a matter of course, it is also possible to use other known locking mechanisms such as a lock lever. Due to the locking mechanism being disengaged and thereby the ADF cover  153  being brought into an opened posture, the guide ribs  177  also pivot with the ADF cover  153 , whereby the curving path  157  and the upper sheet conveying path  160  of the sheet conveying path  151  and the discharge chute portion  158  are opened. 
   The sheet conveying path  151  that couples the feed tray  33  to the discharge tray  34  is formed inside the ADF  5 . The sheet conveying path  151  is configured to have a substantially U-lettered shape when viewed from the front side of the multi-function device  1 . The sheet conveying path  151  is divided into a lower sheet conveying path  159 , the curving path  157 , and the upper sheet conveying path  160 . The sheet conveying path  151  is configured by the ADF main body  152  and the guide ribs  177  formed on the ADF cover  153 . 
   The feed chute portion  154  is formed to continue to the sheet conveying path  151  from the feed tray  33 . The feed chute portion  154  of the ADF  5  is formed to extend from the feed tray  33 . The feed chute portion  154  is configured as a passage with a predetermined width defined in a vertical direction, by a guide plate  155  integrally formed with the ADF main body  152  and the partition plate  156  arranged on the inner side of the ADF cover  153  as guide surfaces. The sheet that is to be scanned is placed on the feed tray  33  with its face to be scanned facing down, such that a leading edge, in a sheet feeding direction, of the sheet is inserted in the feed chute portion  154 . 
   A sheet feeding mechanism having a plurality of rollers is provided in the feed chute portion  154 . Specifically, the sheet supply unit includes the feed roller  164 , a feed nip piece  165  that pressure contacts the feed roller  164 , the separation roller  166 , and a separation nip piece  167  that pressure contacts the separation roller  166 . Note that the configuration of the rollers and the nip pieces is merely an example and it is, as a matter of course, possible to change it to other known mechanisms, by changing the number or disposition of the rollers or using a pinch roller instead of each nip piece. 
   The feed roller  164  is rotatably provided near a center in a sheet widthwise direction of the feed chute portion  154  such that part of a roller surface of the feed roller  164  is exposed from atop surface of the guide plate  155 . The separation roller  166  is rotatably provided at a position spaced from the feed roller  164  toward the downstream side in a sheet feeding direction of the sheets, such that part of a roller surface of the separation roller  166  is exposed from the top surface of the guide plate  155 . The feed roller  164  and the separation roller  166  are driven to rotate by a torque being transmitted thereto from the conveying motor  110  (see  FIG. 12 ). 
   The feed nip piece  165  is provided at a position where the partition plate  156  faces the feed roller  164 , to be movable up and down in a direction in which the feed nip piece  165  contacts the feed roller  164 . The feed nip piece  165  is a pad-like piece with a width slightly narrower than a roller width, in an axial direction, of the feed roller  164  and contacts the roller surface of the feed roller  164 . The feed nip piece  165  is elastically urged downward by an urging member, which is not shown, and contacts the feed roller  164  while not nipping the sheet. 
   The separation nip piece  167  is provided at a position where the partition plate  156  faces the separation roller  166 , to be movable up and down in a direction in which the separation nip piece  167  contacts the separation roller  166 . The separation nip piece  167  is a pad-like piece with a width slightly narrower than a roller width, in an axial direction, of the separation roller  166  and contacts the roller surface of the separation roller  166 . The separation nip piece  167  is elastically urged downward by a spring member which is not shown, and contacts the roller surface of the separation roller  166  while not nipping the sheet. 
   As shown in  FIG. 13 , the sheet conveying path  151  has the lower sheet conveying path  159 , the curving path  157 , and the upper sheet conveying path  160 . The sheet conveying path  151  is configured to have a substantially U-lettered shape that continues from the feed chute portion  154  to the discharge chute portion  158  via the lower sheet conveying path  159 , the curving path  157 , and the upper sheet conveying path  160 . 
   The lower sheet conveying path  159  of the sheet conveying path  151  is continuously formed, as a passage with a predetermined vertical dimension, by a guide end  161  on the downstream side in a conveying direction of the guide plate  155  and a sheet guide  173  that presses the sheet exposed to the scanning area BOA from the opening  31 . As shown in  FIG. 16 , the guide end  161  has a slope  162  inclined gently downwardly from near an exit of the feed chute portion  154  toward the downstream side in the conveying direction. The slope  162  continues to the opening  31 . 
   The sheet guide  173  has a horizontal portion  173 A having a horizontal surface facing the scanning area  80 A and a sloped portion  173 B continuing from the horizontal portion  173 A to the upstream side in the conveying direction. The sloped portion  173 B is provided to extend along the slope  162  of the guide end  161  and has a sloping surface facing the slope  162 . A passage with a predetermined vertical dimension is formed by the sloped portion  173 B and the slope  162 . The passage serves as the lower sheet conveying path  159 . As such, since the lower sheet conveying path  159  is gently inclined and formed to the opening  31 , the sheet conveyed from the feed chute portion  154  is smoothly guided to the opening  31  without being strongly bent. 
   As shown in  FIGS. 13 and 16 , a pinch roller  169  is arranged in the lower sheet conveying path  159 . The pinch roller  169  is arranged such that its axial direction matches a widthwise direction (a direction perpendicular to the paper in  FIG. 13 ) of the lower sheet conveying path  159 . The pinch roller  169  is rotatably provided such that part of a roller surface of the pinch roller  169  is exposed to the lower sheet conveying path  159  from the slope  162  of the guide end  161 . 
   The first conveying roller  168  is arranged at a position facing the pinch roller  169  with the lower sheet conveying path  159  being interposed therebetween. The first conveying roller  168  is also arranged such that its axial direction matches the widthwise direction (the direction perpendicular to the paper in  FIG. 13 ) of the lower sheet conveying path  159 . The first conveying roller  168  is rotatably supported on the ADF main body  152  and part of a roller surface of the first conveying roller  168  is exposed to the lower sheet conveying path  159 . 
   The pinch roller  169  is supported to be urged to the side of the first conveying roller  168  by an elastic member such as a coil spring, which is not shown. In the lower sheet conveying path  159 , the roller surface of the pinch roller  169  is in pressure contact with the roller surface of the first conveying roller  168 . The first conveying roller  168  is coupled to the conveying motor  110  (see  FIG. 12 ) via a torque transmission mechanism, which is not shown, and driven to rotate by a torque transmitted from the conveying motor  110 . The pinch roller  169  also rotates according to the rotation of the first conveying roller  168 . The pinch roller  169  conveys the sheet to the lower sheet conveying path  159  from the feed chute portion  154  pressure contacts the first conveying roller  168 . The torque of the first conveying roller  168  is transmitted to the sheet, whereby the sheet is conveyed. 
   The first conveying roller  168  is formed to have an outer diameter sufficiently larger than the outer diameter of the pinch roller  169 . Thus, a contact surface between the first conveying roller  168  and the sheet increases and accordingly the torque of the first conveying roller  168  is reliably transmitted to the sheet, to thereby prevent an occurrence of a slip of the sheet. 
   The sheet conveyed through the lower sheet conveying path  159  is exposed to the scanning area  80 A from the opening  31  with its face to be scanned facing down. At this time, an image on the face of the sheet is scanned by the image scanning unit  32  provided below the scanning area  80 A. The sheet being scanned is returned to the curving path  157  of the ADF  5  such that a leading edge of the sheet is guided upward by a scoop-up member  175  provided at an end of the platen glass  80 . 
   The curving path  157  of the sheet conveying path  151  is formed such that the curving path  157  starts near the opening  31 , bent upward and then curves to greatly bend toward the rear (a right direction in  FIG. 13 ) and then continues to the upper sheet conveying path  160 . As shown in  FIG. 13 , at an end of the partition plate  156  on the side of the curving path  157 , a curve end  176  curving to trail down along the Curving path  157  is formed continuously from the partition plate  156 . The curving path  157  is defined by the curve end  176  as an inner conveying guide surface and a curve portion  177 A of the guide ribs  177  (which serves as an upper conveying guide) formed on the backside of the ADF cover  153  and guide ribs  178  integrally formed with the ADF main body  152  as an outer conveying guide surface. 
   The second conveying roller  171  and a pinch roller  172  that contacts the second conveying roller  171  are arranged at a portion most upstream in the conveying direction of the curving path  157 . The second conveying roller  171  is arranged on an inner side of the curving path  157  and the pinch roller  172  is arranged on an outer side of the curving path  157 . Part of a roller surface of each of the second conveying roller  171  and the pinch roller  172  is exposed to the curving path  157 . 
   The pinch roller  172  is, as with the pinch roller  169 , supported to be urged toward the second conveying roller  171  by an elastic member such as a coil spring, which is not shown. Accordingly, in the curving path  157 , the roller surface of the pinch roller  172  contacts the roller surface of the second conveying roller  171 . As with the first conveying roller  168 , the second conveying roller  171  is also coupled to the conveying motor  110  (see  FIG. 12 ) via a torque transmission mechanism, which is not shown, and driven to rotate by a torque transmitted from the conveying motor  110 . The pinch roller  169  rotates in accordance with the second conveying roller  171 . According to the pinch roller  172 , the sheet contacts the second conveying roller  171  and the torque of the second conveying roller  171  is transmitted to the sheet. Accordingly, the sheet is conveyed through the curving path  157  and sent to the upper sheet conveying path  160  on the downstream side. 
   The upper sheet conveying path  160  of the sheet conveying path  151  is formed continuously from the curving path  157 . The upper sheet conveying path  160  is configured as a passage with a predetermined dimension provided in a vertical direction, using the guide ribs  177  (corresponding to an upper conveying guide in the present invention) formed on the backside of the ADF cover  153  and a lower flat portion  181  of the partition plate  156  as a pair of conveying guide surfaces. The lower flat portion  181  has a top surface horizontally extending toward the downstream in the conveying direction from the curving path  157 . The lower flat portion  181  defines a part of the partition plate  156  continuing to the curve end  176 . As shown in  FIGS. 13 and 16 , the upper sheet conveying path  160  is formed in a substantially straight manner and guides the sheet conveyed from the curving path  157  to the downstream side in the conveying direction with the sheet being kept horizontal. 
   As shown in  FIGS. 13-16  and  18 , a through-hole  182 , which penetrates through the partition plate  156 , is provided in a leading end portion of the upper sheet conveying path  160 , i.e., a portion of the partition plate  156  corresponding to a position most downstream in the conveying direction of the sheet conveying path  151 . As shown in the drawings, a part of a topside of the first conveying roller  168  is exposed to the upper sheet conveying path  160  via the through-hole  182 . 
   The pinch roller  170  is arranged at the terminal of the upper sheet conveying path  160 . The pinch roller  170  is arranged such that its axial direction matches a widthwise direction (a direction perpendicular to the paper in  FIG. 13 ) of the upper sheet conveying path  160 . The pinch roller  170  is formed to have an outer diameter sufficiently smaller than the outer diameter of the first conveying roller  168 . The pinch roller  170  is rotatably supported by the guide ribs  177  formed on the backside of the ADF cover  153 . The support structure of the pinch roller  170  will be described later. The pinch roller  170  is rotatably supported on the guide ribs  177  with a rotary shaft  185  of the pinch roller  170  being elastically urged. Thus, in a state in which the ADF cover  153  is closed over the ADF main body  152 , the roller surface of the pinch roller  170  contacts the roller surface of the first conveying roller  168  exposed from the through-hole  182 . 
   Since the first conveying roller  168  is driven to rotate by a torque transmitted from the conveying motor  110  (see  FIG. 12 ), the pinch roller  170  contacts the first conveying roller  168  and rotates in accordance with the rotation of the first conveying roller  168 . The first conveying roller  168  and the pinch roller  170  serve as a pair of discharge rollers. 
   In the present example, as shown in  FIG. 16 , the first conveying roller  168  and the pinch roller  170  are arranged such that a direction in which the first conveying roller  168  contacts the pinch roller  170 , i.e., a direction (hereinafter, referred to as a “line segment direction”)  183  indicated by a line segment connecting a shaft center of the first conveying roller  168  and a shaft center of the pinch roller  170 , as viewed in a cross section, is inclined at an angle φ toward upstream in the conveying direction with respect to a normal direction  184  to the lower flat portion  181  at the end of the upper sheet conveying path  160 . 
   That is, a pair of discharge rollers (conveying roller  168  and the pinch roller  170 ) is arranged such that a direction in which the drive roller (conveying roller  168 ) contacts the follower roller (pinch roller  170 ) is inclined at an angle φ toward upstream in the conveying direction with respect to a direction of a normal line (normal direction  184 ) of the guide surface of the sheet conveying path  160  at a position the most downstream in the conveying direction. 
   Note that the angle φ is appropriately set to an optimal value, which is determined by the outer diameters of the first conveying roller  168  and the pinch roller  170 , and the shape of the sheet conveying path. 
   As described above, the upper sheet conveying path  160  is configured as a flat linear sheet conveying path. Thus, in the present example, as a means of inclining the line segment direction  183  toward upstream in the conveying direction with respect to the normal direction  184 , a means of arranging the pinch roller  170  at a position shifted by a distance AD to the upstream side in the conveying direction from a position vertically above the first conveying roller  168  is adopted. Since the first conveying roller  168  and the pinch roller  170  are thus arranged, the sheet discharged by the rollers  168  and  170  is conveyed upward at the angle φ or an angle corresponding to the distance ΔD. 
   The configuration in which the first conveying roller  168  and the pinch roller  170  are arranged, as in the present example, is particularly effective when the sheet is discharged in the following manner. Specifically, the sheet discharged from the first conveying roller  168  and the pinch roller  170  may be prevented from advancing by a preceding discharged sheet (preceding sheet) and be stopped immediately. In such a case, the trailing edge of the preceding sheet remains near the nip position; however, when the stacking amount of sheets discharged to the discharge chute portion  158  or the discharge tray  34  is small, the trailing edge of the preceding sheet is scraped upward by the pinch roller  170 , and thus, a problem that a subsequent sheet rises above the preceding sheet is not likely to occur. 
   However, when the stacking amount of sheets discharged to the discharge chute portion  158  or the discharge tray  34  is large or when the roller surface of the pinch roller  170  is changed to be slippery due to its aged deterioration, the trailing edge of a preceding sheet may not be scraped upward, as described earlier by referring to  FIG. 25 . Even in such a case, since in the present example the rollers are arranged such that the line segment direction  183  is inclined more toward the upstream side in the conveying direction than the normal direction  184 , the trailing edge of a preceding sheet is easily scraped upward by the pinch roller  170 . Thus, a subsequent sheet is not discharged above a preceding sheet. 
   In the present example, as shown in  FIGS. 14 and 15 , a plurality of first conveying rollers  168  and a plurality of pinch rollers  170  are arranged in a widthwise direction of the sheet conveying path  151  with a predetermined interval therebetween. Specifically, three first conveying rollers  168  and three pinch rollers  170  are arranged at the center in the widthwise direction and at both ends. The first conveying rollers  168  and the pinch rollers  170  on both sides in the widthwise direction are disposed to support a maximum size sheet that is conveyable through the sheet conveying path  151 . For example, when the maximum size of a conveyable sheet is A4-size, the rollers are disposed at positions where both edges of the sheet can be nipped. Since a plurality of rollers are thus disposed, the sheet is conveyed using a uniform force over the entire area in the widthwise direction of the sheet. Though not shown in the drawings, a plurality of pinch rollers  169  which contact the corresponding first conveying rollers  168  below the first conveying rollers  168 , a plurality of second conveying rollers  171 , and a plurality of pinch rollers  172  may be arranged in the widthwise direction of the sheet conveying path  151 . Note that the arrangement position of each roller and the number of rollers to be disposed are not limited to the above-described positions and numbers. They can be appropriately changed according to the configuration of the multi-function device  1  such as the maximum size of the conveyable sheet, and the shape of the sheet conveying path. 
   The discharge chute portion  158  is formed continuously from the leading end of the upper sheet conveying path  160 . The discharge chute portion  158  is configured as a passage with a predetermined dimension defined in a vertical direction by an upper guide surface including the guide ribs  177  (which serves as an upper discharge guide) formed on the backside of the ADF cover  153  and a lower guide surface including a sloped portion  180  and the upper flat portion  179  of the partition plate  156  (which serves as a lower discharge guide, see  FIG. 14 ). When the sheet is discharged to the discharge chute portion  158 , the sheet is guided to the discharge tray  34  by the upper and lower guide surfaces of the discharge chute portion  158 . 
   The sloped portion  180  of the partition plate  156  is formed continuously from the lower flat portion  181  and includes part of the partition plate  156 . The sloped portion  180  continues to the upper flat portion  179  located at a higher position on the downstream side in the conveying direction than the lower flat portion  181 . The upper flat portion  179  also includes part of the partition plate  156  and has a top surface horizontally extending toward the downstream in the conveying direction from the sloped portion  180 . In the present example, the upper flat portion  179  is set at a position higher than the nip position between the first conveying rollers  168  and the pinch rollers  170 . 
   Since the discharge chute portion  158  is thus formed, the sheet discharged to the discharge chute portion  158  is smoothly guided to the upper flat portion  179  along the sloped portion  180 . When a plurality of sheets are discharged, even if trailing edges of the sheets are not elastically supported by the spring pieces  190 , as will be described later, the sheets climb up on the upper flat portion  179  disposed at a position higher than a nip position H (a nip height, see  FIG. 17 ) between the first conveying rollers  168  and the pinch rollers  170  and the trailing edges of the sheets are supported extending to the sloped portion  180 , and thus, the trailing edges of the sheets are easily lifted up. Accordingly, a subsequent sheet is easily placed beneath a preceding sheet and the stacking order of sheets is kept to be the original ascending order. Note that the top surface of the upper flat portion  179  disposed in the above-described manner serves as an upper guide surface. 
   In the present example, as shown in  FIG. 17 , the sloped portion  180  is disposed at a position near to the pinch rollers  170  at a downstream side in the conveying direction with respect to the pinch rollers  170 . In other words, the sloped portion  180  is provided at an immediately down stream portion of the pinch rollers  170 . The sloped portion  180  is, as described above, inclined to the upper flat portion  179 . As shown in the drawings, a sloping surface of the sloped portion  180  is provided to be higher at an immediately downstream portion of the spring pieces  190  than the nip position H between the first conveying rollers  168  and the pinch rollers  170 . Thus, even in a state in which the trailing edge of a sheet is not lifted up by the spring pieces  190 , since the trailing edge of the sheet is lifted at a position higher than the nip position H on the downstream side of the spring pieces  190 , a leading edge of the sheet can be easily guided beneath the preceding sheet. 
   The sheet guided to the upper flat portion  179  is guided to the discharge tray  34  provided on the downstream side in the conveying direction of the sheet. As described above, the discharge tray  34  is arranged at a lower position than the top surface of the upper flat portion  179  (see  FIGS. 13 and 14 ). Thus, although the trailing edge of the sheet discharged to the discharge tray  34  remains in the discharge chute portion  158 , the leading edge of the sheet is supported by the discharge tray  34  arranged at a lower position than the upper flat portion  179 . Hence, the load applied to the leading edge of the sheet increases and the load applied to the trailing edge of the sheet decreases, and thus, the trailing edge is easily lifted up. 
   Although the present example describes an example in which the top surface of the upper flat portion  179  horizontally extends to the downstream in the conveying direction, a sloping surface inclined downwardly toward the downstream in the conveying direction may be provided on a topside of the upper flat portion  179 . The sloping surface may be inclined at a certain inclination angle or may be inclined such that the degree of inclination gradually increases toward the downstream in the conveying direction, for example. 
   With the configuration in which a sloping surface is thus provided to the upper flat portion  179 , the load of a portion supported by the discharge chute portion  158  transfers to the leading edge of the sheet, and thus, the load applied to the trailing edge decreases and the trailing edge of the sheet is easily lifted up. Accordingly, the subsequent sheet is easily placed beneath the preceding sheet. In this case, a boundary portion between the sloped portion  180  and the upper flat portion  179  is the highest position on the partition plate  156 . Thus, the trailing edge of the sheet is easily lifted up with the apex serving as a fulcrum. Note that the boundary portion described above serves as the apex. 
   Although not particularly described in the drawings, when the top surface of the upper flat portion  179  is configured to be horizontal, as in the present example, a projection composing the highest position on the partition plate  156  may be provided near the boundary portion between the sloped portion  180  and the upper flat portion  179 . By providing such a projection, the trailing edge of the sheet is more easily lifted up with the projection serving as a fulcrum. Such projection also serves as the apex. Note that a configuration for providing the apex is not limited to the above-described configuration. 
   As shown in each of the accompanying drawings, the spring pieces  190  (which serve as elastic support pieces) are arranged in the discharge chute portion  158 . The spring pieces  190  support the sheet discharged to the discharge chute portion  158  while elastically urging the sheet to the side of the guide ribs  177 , and are formed to be bent in a substantially L-lettered shape when viewed in a cross section. The spring pieces  190  are formed of an elastic plate member made of a synthetic resin with high elasticity, such as PET (polyethylene terephthalate), with a thickness on the order of 0.2 millimeters to 1.0 millimeter. 
   As shown in  FIGS. 14 and 15 , four spring pieces  190  are arranged in the widthwise direction (an up-down direction in  FIG. 15 ) of the discharge chute portion  158  with a predetermined interval therebetween. In the present example, to prevent interference between the spring pieces  190 , and the first conveying rollers  168  and the pinch rollers  170 , as shown in the drawings, one spring piece  190  is arranged between the first conveying rollers  168 , and one spring piece  190  is arranged at the outer side of each of the first conveying rollers  168  that are disposed on both sides in the widthwise direction. 
   A recess  194  for fixing a spring piece  190  is provided for each spring piece  190  in the lower flat portion  181  of the partition plate  156 . As shown in  FIG. 18 , a wall surface  195  of a recess  194  on the downstream side in the conveying direction is inclined to the downstream side in the conveying direction. A fitting groove is formed on the wall surface  195 . By a base  191  of a spring piece  190  being inserted in the fitting groove, the spring piece  190  is fixed to the partition plate  156 . Note that the base  191  is part of the spring piece  190  which is fixed to be elastically deformable and the position of the base  191  is not particularly limited. 
   As shown in  FIG. 17 , the spring piece  190  is inclined from the fixed base  191  to the downstream side in the conveying direction. Furthermore, a free end  192  extending downward from a bending portion  196  of the spring piece  190  is inserted downward in a through slot  193  provided in the sloped portion  180  on the downstream side in the conveying direction of the recess  194 . Accordingly, when a load is applied to the spring piece  190 , the spring piece  190  is elastically deformed with respect to the fixed base  191 . Specifically, the postures of the bending portion  196  and the free end  192  of the spring piece  190  are changed in an up-down motion as viewed in a cross section, according to an applied load. 
   As shown in  FIGS. 16 and 17 , the spring piece  190  thus provided is, in a natural posture, held in a posture in which the bending portion  196  enters between guide ribs  177  of the ADF cover  153 . Thus, when no load is applied to the spring piece  190 , the upper sheet conveying path  160  is blocked by the spring piece  190 . 
   When the sheet conveyed through the upper sheet conveying path  160  to the downstream side in the conveying direction while being nipped between the first conveying rollers  168  and the pinch rollers  170 , a leading edge of the sheet climbs up on sloping surfaces of the spring pieces  190  inclined to the downstream side in the conveying direction. At this time, the self-weight of the sheet and a conveying force (a force acting in a direction in which the sheet is pushed out) by each roller are applied to the spring pieces  190 , whereby the postures of the spring pieces  190  are changed downward. Accordingly, the bending portions  196  move downward and the upper sheet conveying path  160  is opened. Accordingly, the sheet is guided within the discharge chute portion  158  to the downstream side in the conveying direction while being elastically supported on the spring pieces  190 . 
   When the sheet is further conveyed and the trailing edge of the sheet comes out of the nip position between the first conveying rollers  168  and the pinch rollers  170 , the conveying force applied to the sheet is lost at that moment. Here, only the self-weight of the trailing edge of the sheet is applied to the spring pieces  190 . The spring constant of the spring pieces  190  is set such that the postures of the spring pieces  190  cannot be changed downward against the urging force of the spring pieces  190  only by the self-weight of the trailing edge of the sheet. Thus, when the trailing edge of the sheet comes out of the nip position, the trailing edge of the sheet is lifted upward by the urging force of the spring pieces  190 . At this time, the trailing edge of the sheet is pressed against the guide ribs  177  by the spring pieces  190 . Accordingly, the trailing edge of the sheet is nipped between the spring pieces  190  and the guide ribs  177 . 
   When, in a state in which the trailing edge of a sheet is nipped between the spring pieces  190  and the guide ribs  177  in the above-described manner, a subsequent sheet is discharged to the discharge chute portion  158 , the subsequent sheet is conveyed while pressing down the spring pieces  190 , as with a preceding discharged sheet. At this time, since the sheet discharged by the rollers is conveyed upward at a predetermined angle, while a leading edge of a subsequent sheet presses the trailing edge of the preceding discharged sheet upward, the subsequent sheet enters to be placed beneath the trailing edge of the preceding discharged sheet along the sloping surfaces of the spring pieces  190 . Hence, even if a large number of sheets have been discharged, the subsequent sheet can easily enter beneath the stack of discharged sheets. 
   Next, the support structure of the pinch rollers  170  and a detailed configuration of the pinch rollers  170  will be described. 
   As shown in  FIG. 14 , the pinch rollers  170  are mounted on the guide ribs  177  formed on the backside of the ADF cover  177 . In the present example, three pinch rollers  170  are arranged to correspond to the number of the first conveying rollers  168  being arranged. The rotary shaft  185  is inserted in a shaft center of each of the pinch rollers  170 . Thus, the rotary shaft  185  serves as a shared shaft of the plurality of pinch rollers  170 . 
   The rotary shaft  185  is made of a metal round bar that is sufficiently long, for example. Both ends of the rotary shaft  185  are freely supported by shaft receiving portions  197  provided on both sides, in the widthwise direction, of the ADF cover  153 , respectively. Accordingly, the rotary shaft  185  is supported to span in the widthwise direction of the ADF cover  153 . Since the pinch rollers  170  are thus rotatably supported on the shared rotary shaft  185 , the number of components can be reduced by omission and assembling of pinch rollers can be facilitated. 
   As shown in  FIGS. 14 and 19 , a groove  205  extending in a direction perpendicular to the backside of the ADF cover  153  is formed in a shaft receiving portion  197 . The rotary shaft  185  is rotatably supported such that ends, in an axial direction, of the rotary shaft  185  are inserted in the grooves  205 . Thus, the rotary shaft  185  can slide and move in the direction perpendicular to the backside of the ADF cover  153  while being rotatably supported on the backside of the ADF cover  153 . 
   As shown in  FIG. 14 , spring receiving portions  187  are formed between the three pinch rollers  170  provided on the guide ribs  177 . That is, two spring receiving portions  187  in total are formed at positions corresponding to the rotary shaft  185  on the guide ribs  177 . 
   As shown in  FIG. 19 , a spring receiving portion  187  is formed by concaving a part of a guide rib  177 . Slits  188  are formed in sidewalls of the spring receiving portion  187  in the axial direction of the pinch rollers  170 . The slits  188  are cut out in the direction perpendicular to the backside of the ADF cover  153 . The groove width of the slits  188  is slightly larger than the diameter of the rotary shaft  185  and the rotary shaft  185  is inserted in the slits  188 . The moving direction of the rotary shaft  185  is regulated by the slits  188  in the direction perpendicular to the backside of the ADF cover  153 , whereby the position of the rotary shaft  185  is prevented from being shifted to the conveying direction of the sheets. 
   A coil spring  186  is accommodated in each spring receiving portion  187 . The coil springs  186  are compressed with the rotary shaft  185  being rotatably supported on the shaft receiving portions  197 . The rotary shaft  185  is supported while being urged by the coil springs  186 . Accordingly, the rotary shaft  185  is urged to a direction substantially perpendicular to the backside of the ADF cover  153 . Thus, when the ADF cover  153  is closed over the ADF main body  152 , the pinch rollers  170  are urged to a direction close to the first conveying rollers  168  and contacts the roller surfaces of the first conveying rollers  168 . 
   Note that the spring constant of the coil springs  186  is set to a value at which when the sheet passes through a position where the first conveying rollers  168  contacts the pinch rollers  170  the coil springs  186  are retractable according to the thickness of the sheet. 
   As described above, the plurality of pinch rollers  170  are supported by the shared rotary shaft  185  and the rotary shaft  185  is urged by the coil springs  186 . Therefore, urging forces against the pinch rollers  170  become uniform. As a result, contact forces against the first conveying rollers  168  are uniformalized. Accordingly, skewing of the sheet caused by non-uniform contact forces can be prevented. 
   As shown in  FIGS. 20 ,  21 A and  21 B, a pinch roller  170  includes an outer roller body  201  and an inner roller body  202 . The inner roller body  202  and the outer roller body  201  are roughly formed in a cylindrical shape that is elongated in an axial direction. 
   The inner roller body  202  is formed by a synthetic resin using a molding die, for example. The diameter of an inner hole of the inner roller body  202  is substantially the same size as the outer diameter of the rotary shaft  185 . Due to the rotary shaft  185  being inserted into the inner hole of the inner roller body  202 , the inner roller body  202  is rotatably supported on the rotary shaft  185 . The outer diameter of the inner roller body  202  is substantially the same size as the diameter of an inner hole of the outer roller body  201 , in a large region including an axial direction central portion  202 A. On the other hand, the outer diameter of the axial direction both ends  202 B of the inner roller body  202  has a smaller diameter than the diameter of the inner hole of the outer roller body  201 . Thus, the axial direction both ends  2023  of the inner roller body  202  have formed therein a step that is recessed in a diameter direction from the axial direction central portion  202 A by a difference E between the radius of the axial direction both ends  202 B of the inner roller body  202  and the radius of the axial direction central portion  202 A, as viewed in a cross section. The step of the difference E is set to substantially match the amount of projection of a projection  203 , as will be described later. The length, in the axial direction, of the axial direction both ends  202 B with a reduced diameter is set to substantially match the length, in the axial direction, of a projection  203 , as will be described later. 
   The outer roller body  201  is formed to be slightly shorter in the axial direction than the inner roller body  202 . The outer roller body  201  is formed of an elastically deformable member like a rubber material such as BR (Butadiene Rubber) and NBR (nitrile rubber, acrylonitrile-butadiene rubber). Hence, the coefficient of friction of a roller surface of the outer roller body  201  is relatively high, and thus it is suitable to convey the sheet. The diameter of the inner hole of the outer roller body  201  is substantially the same size as the outer diameter of the axial direction central portion  202 A of the inner roller body  202 . 
   A pinch roller  170  is formed by the inner roller body  202  being disposed into an inner hole of the outer roller body  201 . A wall surface of the inner hole of the outer roller body  201  is formed to be a uniform surface. Thus, since a step is formed in the axial direction both ends  202 B of the inner roller body  202 , with the inner roller body  202  fitting in the outer roller body  201 , a gap  204  equivalent to the difference E is provided on the inner side of both ends of the pinch roller  170 . 
   On axial direction both ends of the outer roller body  201 , a plurality of paddle-like projections  203  (which serve as paddle portions) which project in the diameter direction of the outer roller body  201  from the roller surface are provided. The projections  203  are radially arranged along an outer circumferential direction of the outer roller body  201  with an appropriate gap therebetween. In the present examples a projection  203  shows a substantially wedge shape when viewed in a cross section, having a sloping surface  203 A inclined outwardly in the axial direction, a parallel surface  203 B parallel to the roller surface, and a surface  203 C which is the same as a side surface of the outer roller body  201 . However, the projection  203  is not particularly limited to such a shape as long as the projection  203  projects from the roller surface. For example, the projection  203  may have a pin-like or bump-like structure. Alternatively, the projection  203  may have a wave-like or spur-like structure that continues along the outer circumference, as viewed in a cross section. 
   Since such projections  203  are provided on the axial direction ends of an outer roller body  201 , the trailing edge of the sheet that came out of the nip position between the first conveying rollers  168  and the pinch rollers  107  is easily scraped upward. As a result, the subsequent sheet is easily placed beneath the preceding sheet. Upon conveying the sheet, the sheet may be damaged by the projections  203  pressing against the sheet. However, the pinch rollers  170  adopted in the present example have, as described above, the gap  204  provided therein, and thus, in a state in which the pinch rollers  170  are in contact with the first conveying rollers  168  by pressure, as shown in  FIG. 22 , the projections  203  are retracted inward. Accordingly, damage to the sheet by the projections  203  does not occur. 
   It is to be understood that the above-described example is merely an example of the present invention and, as a matter of course, the example can be appropriately changed without departing from the spirit and scope of the present invention.