Patent Publication Number: US-8528894-B2

Title: Method of detecting sheet in transport device, transport device, image reading device, and image forming apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a method of detecting a sheet in a transport device that transports, for example, a sheet, an image reading device that reads an image recorded on a sheet transported by a transport device, and an image forming apparatus that records an image read by the image reading device. 
     2. Related Art 
     In general, there is known a complex machine as an image forming apparatus that has a transport function for transporting a sheet used as base paper, a reading function for reading an image of the transported sheet, and a recording function for recording the read image on a recording sheet or the like. In the complex machine, a plurality of sheets is set to be stacked in a set section and the sheets are sequentially transported one by one. Further, the set section is provided with a sheet sensor that can detect whether a sheet exists or not. Accordingly, when all the sheets set in the set section are transported and do not exist, the nonexistence of the sheet is detected by the sheet sensor. 
     In the past, a sensor (hereinafter, referred to as a “sensor in the related art”) disclosed in, for example, JP-UM-A-5-32347, has been widely employed as the sheet sensor. The sensor includes a detection lever of which the end freely extends back and forth to the sheet set face of the set section, and the detection lever is pushed so that the end of the detection lever always protrudes upward from the set face. Further, the sensor in the related art detects whether a sheet exists or not by whether a sheet stacked on the set face of the set section presses the end of the detection lever in a retracting direction. 
     However, in the above-mentioned sensor in the related art, if there is warping or a wrinkle on the sheet set in the set section and the sheet is thus deformed, when the position of a portion having warped or the wrinkle corresponds to the detection lever, the end of the detection lever is not pressed by the sheet or a pressing force of the sheet becomes insufficient. For this reason, in that case, there is a problem as follows: there is a false detection that the sheet set in the set section does not exist even though there are sheets remaining in the set section. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a method of detecting a sheet in a transport device that can reliably detect whether a sheet set in a set section exists or not, a transport device, an image reading device, and an image forming apparatus. 
     According to an aspect of the invention, there is provided a method of detecting a sheet in a transport device. The transport device includes a set section, a sheet sensor, and a feeding member. The set section includes a set face on which a sheet can be set. When a detection member, which is provided on the set face of the set section so as to freely extend back and from the lower side, receives pressure from the sheet set in the set section and retracts, the sheet sensor outputs an ON-detection signal. When the detection member does not retract, the sheet sensor outputs an OFF-detection signal. The feeding member is displaced between a feed position and a non-feed position on the basis of the detection signal output from the sheet sensor. At the feed position, the feeding member comes in contact with the sheet set in the set section from above and feeds the sheet toward the downstream side on a transport path. At the non-feed position, the feeding member is separated upward from the feed position. The method includes displacing the feeding member from the non-feed position to the feed position, and detecting that the sheet does not exist in the set section when an OFF-detection signal is output from the sheet sensor while the feeding member is positioned at the feed position. 
     In general, if there is warping or a wrinkle on the sheet set in the set section and the sheet is thus deformed, the detection member does not receive pressure from the sheet and the detection member does not retract despite the existence of the sheet in the set section. In this case, since an OFF-detection signal is output from the sheet sensor, there is a false detection that the sheet does not exist in the set section. In this regard, according to this structure, if an OFF-detection signal is output from the sheet sensor when the feeding member is displaced to the feed position where the feeding member comes in contact with the sheet from above and the feeding member is positioned at the feed position, it is detected that a sheet does not exist in the set section. That is, when the feeding member is positioned at the feed position, the sheet set in the set section is pressed by the feeding member. Accordingly, even though the sheet is deformed, the detection member reliably receives pressure from the sheet. If an OFF-detection signal is output from the sheet sensor in this state, it is detected that a sheet does not exist in the set section. Accordingly, it may be possible to reliably avoid that an OFF-detection signal is output from the sheet sensor despite the existence of the sheet in the set section. As a result, it may be possible to reliably detect whether the sheet set in the set section exists or not. 
     According to another aspect of the invention, there is provided a transport device that includes a set section, a sheet sensor, a feeding member, and a controller. The set section includes a set face on which a sheet can be set. When a detection member receives pressure from the sheet set in the set section and retracts, the sheet sensor outputs an ON-detection signal. When the detection member does not retract, the sheet sensor outputs an OFF-detection signal. The detection member is provided on the set face of the set section so as to freely extend back and forth from the lower side. The feeding member is displaced between a feed position and a non-feed position. At the feed position, the feeding member comes in contact with the sheet set in the set section from above and feeds the sheet toward the downstream side on a transport path. At the non-feed position, the feeding member is separated upward from the feed position. The controller controls a displacing operation of the feeding member on the basis of the detection signal output from the sheet sensor. The controller displaces the feeding member from the non-feed position to the feed position, and displaces the feeding member from the feed position to the non-feed position when an OFF-detection signal is output from the sheet sensor while the feeding member is positioned at the feed position. 
     In general, if there is warping or a wrinkle on the sheet set in the set section and the sheet is thus deformed, the detection member does not receive pressure from the sheet and the detection member does not retract despite the existence of the sheet in the set section. In this case, since an OFF-detection signal is output from the sheet sensor, there is a false detection that the sheet does not exist in the set section. In this regard, according to this structure, if an OFF-detection signal is output from the sheet sensor when the controller displaces the feeding member from the non-feed position to the feed position and the feeding member is positioned at the feed position, the controller displaces the feeding member from the feed position to the non-feed position. That is, when the feeding member is positioned at the feed position, the sheet set in the set section is pressed by the feeding member. Accordingly, even though the sheet is deformed, the detection member reliably receives pressure from the sheet. If an OFF-detection signal is output from the sheet sensor in this state, the controller displaces the feeding member from the feed position to the non-feed position. Accordingly, it may be possible to reliably avoid that an OFF-detection signal is output from the sheet sensor despite the existence of the sheet in the set section. As a result, it may be possible to reliably detect whether the sheet set in the set section exists or not. 
     In the transport device according to the aspect of the invention, the detection member of the sheet sensor may be disposed near a position where the feeding member comes in contact with the set face when the feeding member is displaced to the feed position. 
     According to this structure, even though the sheet set in the set section is deformed, the feeding member presses the sheet when the feeding member is displaced to the feed position. Accordingly, since the detection member further reliably receives pressure from the sheet, it may be possible to further reliably detect by using the sheet sensor whether the sheet set in the set section exists or not. 
     According to another aspect of the invention, there is provided an image reading device that includes the transport device that has the above-mentioned structure and a reading unit that reads an image recorded on the sheet transported by the transport device. 
     According to this structure, it may be possible to obtain the same advantages as the transport device. 
     According to another aspect of the invention, there is provided an image forming apparatus that includes the image reading device that has the above-mentioned structure and a recording unit that records an image read by the image reading device. 
     According to this structure, it may be possible to obtain the same advantages as the transport device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a perspective view of a complex machine according to an embodiment of the invention. 
         FIG. 2  is a schematic cross-sectional view of main parts of the complex machine. 
         FIG. 3  is an enlarged perspective view of the main parts when a reverse cover of a transport unit is opened. 
         FIG. 4  is an enlarged perspective view of the main parts of the transport unit when the reverse cover is omitted and a feed roller unit is positioned at a non-feed position. 
         FIG. 5  is an enlarged perspective view of the main parts of the transport unit when the reverse cover is omitted and the feed roller unit is positioned at a feed position. 
         FIG. 6  is a block diagram showing the electrical configuration of the complex machine. 
         FIG. 7  is a flowchart illustrating a routine for transporting a paper sheet. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An image forming apparatus according to an embodiment of the invention, which is applied to a complex machine, will be described below with reference to drawings. Meanwhile, in the following description, a “longitudinal direction”, a “width direction”, and a “vertical direction” respectively represent the longitudinal direction, the width direction, and the vertical direction, which are indicated by arrows in  FIG. 1 . 
     As shown in  FIG. 1 , a complex machine  11  used as an image forming apparatus includes a printer unit  12  that functions as a recording unit, and a scanner device  13  that functions as an image reading device and is disposed on the printer unit  12 . The complex machine has a substantially rectangular parallelepiped shape. The scanner device  13  includes a scanner unit  14  that functions as a reading unit, and a transport unit  15  that functions as a transport device and is disposed on the scanner unit  14 . 
     The transport unit  15  includes a paper feed tray  16  that functions as a set section in which a plurality of paper sheets P used as sheets can be set in a stacked state, and a paper discharge tray  17  that is positioned below the paper feed tray  16 . The paper feed tray  16  is inclined downward toward the rear side, and the upper surface of the paper feed tray functions as a set face  16   a  on which paper sheets P are set. A reverse cover  18 , which covers the rear portion of the paper feed tray  16 , is provided at the upper rear end of the transport unit  15  so as to be freely opened and closed. 
     When a user operates a start switch  19  provided on the right surface of the scanner unit  14 , the paper sheets P set on the set face  16   a  of the paper feed tray  16  positioned one by one upstream on a transport path of the paper sheet P are transported to the paper discharge tray  17 , which is positioned downstream on the transport path. 
     In this case, an image (character “P” in this embodiment) is recorded on the upper surface of each of the paper sheets P that are set on the set face  16   a  of the paper feed tray  16 . The paper sheet is reversed while being transported, and the image is read by the scanner unit  14 . Then, the paper sheet is discharged onto the paper discharge tray  17  so that the surface of the sheet paper on which the image is printed faces the lower side. Further, the image read by the scanner unit  14  is printed on an unused paper sheet (not shown) by the printer unit  12 . 
     As shown in  FIG. 2 , a first detection lever  20 , which is used as a detection member having the shape of a right triangle of which the front side (as seen in the width direction) is an oblique side, is provided on the set face  16   a  near the rear portion of the paper feed tray  16  so as to freely extend back and forth from the lower side. The first detection lever  20  is pushed by a spring (not shown), which is provided in the paper feed tray  16 , so as to always protrude upward from the set face  16   a . Accordingly, if a paper sheet P is set on the set face  16   a , the first detection lever retracts into the paper feed tray  16  against the pushing force of the spring (not shown) due to the weight of the paper sheet P (due to the pressure applied from the paper sheet P). 
     Further, a first detection part  21  (see  FIG. 6 ), which detects whether the first detection lever  20  retracts into the paper feed tray  16 , is provided in the paper feed tray  16 . If the first detection lever  20  retracts into the paper feed tray  16 , the first detection part  21  (see  FIG. 6 ) outputs an ON-detection signal. If the first detection lever  20  does not retract into the paper feed tray  16 , the first detection part outputs an OFF-detection signal. 
     That is, in general, the first detection part  21  (see  FIG. 6 ) outputs an ON-detection signal when the paper sheet P is set on the set face  16   a , and outputs an OFF-detection signal when there is no paper sheet P on the set face  16   a . Meanwhile, in this embodiment, a paper sheet detecting sensor  22  (see  FIG. 6 ) used as a sheet sensor is formed of the first detection lever  20  and the first detection part  21  (see  FIG. 6 ). 
     As shown in  FIGS. 2 and 3 , a stepped portion  23  including a slope  23   a  is formed at the rear end of the paper feed tray  16 . When the paper sheet P is set on the set face  16   a , the end (rear end) of the paper sheet P comes in contact with the slope so that the paper sheet P is set into position. The stepped portion  23  extends over the entire width of the paper feed tray  16  in the width direction of the paper feed tray, and the slope  23   a  inclined upward toward the rear side. A position, where the front end of the paper sheet P is positioned in the longitudinal direction when the paper sheet P is set on the set face  16   a , is referred to as a set position  24 , and the stepped portion  23  is positioned at the set position  24 . 
     A recess  25 , which has opened upper and front sides, is formed at a portion of the stepped portion  23  that is slightly closer to the right side than the middle of the stepped portion in the width direction. A transport path forming member  26 , which forms the transport path of the paper sheet P, is integrally connected to the stepped portion  23  on the rear side of the stepped portion  23 . The transport path forming member  26  includes a paper feeding guide section  27 , an opposite section  28 , and a paper discharging guide section  29 . The paper feeding guide section is curved in a U shape so as to rise rearward from the stepped portion  23 , extends toward the lower end of the transport unit  15 , and then extends forward along the upper surface of the scanner unit  14 . The opposite section faces an upper surface  33   a  of a glass  33  that is horizontally disposed at the upper end of the scanner unit  14  and horizontally extends forward. The paper discharging guide section extends substantially in a straight line so as to be inclined upward toward the front side from the opposite section  28 . 
     That is, bent portions  27   a  and  29   a , which are formed by bending upward the lower ends of the paper feeding guide section  27  and the paper discharging guide section  29  in a vertical direction, are respectively formed at the lower ends of the paper feeding guide section  27  and the paper discharging guide section  29 . The upper ends of the bent portions  27   a  and  29   a  are connected to each other by the opposite section  28 . Accordingly, an opposite recess  30 , which includes the opposite section  28  as a bottom and is opened at the lower portion thereof, is formed by the opposite section  28  and the bent portions  27   a  and  29   a . A paper sheet pressing member  32  is provided in the opposite recess  30 , that is, on the lower surface of the opposite section  28  with a spring  31  interposed therebetween so as to extend in the width direction. The paper sheet pressing member  32  has a substantially U shape in cross-sectional view, and the lower end surface  32   a  of the paper sheet pressing member forms a horizontal surface. Further, the lower end surface  32   a  of the paper sheet pressing member  32  is always pressed against the upper surface  33   a  of the glass  33  by the pushing force of the spring  31 . 
     A paper feed guide  34 , which extends along the paper feeding guide section  27 , is provided on the rear side of the paper feeding guide section  27  of the transport path forming member  26  in the transport unit  15 . A gap formed between the paper feed guide  34  and the paper feeding guide section  27  serves as a paper feed passage  35  that forms a part of the transport path of the paper sheet P. A pair of paper feed rollers  38 , which pinches the paper sheet P passing through the paper feed passage  35  and feeds the paper sheet toward the downstream side, is provided at a position, which is close to the downstream side on the paper feed passage  35 , so as to each rotate about rotating shafts  39  that extend in the width direction. Each of the rotating shafts  39  is rotationally driven by a paper feed motor  40  (see  FIG. 6 ) that is provided in the transport unit  15 . Accordingly, if the paper feed motor  40  (see  FIG. 6 ) is driven, each of the paper feed rollers  38  is rotationally driven together with each of the rotating shafts  39 . 
     Meanwhile, a paper discharge guide  36 , which extends along the discharging guide section  29 , is provided below the paper discharging guide section  29  of the transport path forming member  26  in the transport unit  15 . A gap formed between the paper discharge guide  36  and the paper discharging guide section  29  serves as a paper discharge passage  37  that forms a part of the transport path of the paper sheet P. A pair of paper discharge rollers  41 , which pinches the paper sheet P passing through the paper discharge passage  37  and feeds the paper sheet toward the paper discharge tray  17 , is provided at the downstream end of the paper discharge passage  37  so as to each rotate about rotating shafts  42  that extend in the width direction. Each of the rotating shafts  42  is rotationally driven by a paper discharge motor  43  (see  FIG. 6 ) that is provided in the transport unit  15 . Accordingly, if the paper discharge motor  43  (see  FIG. 6 ) is driven, each of the paper discharge rollers  41  is rotationally driven together with each of the rotating shafts  42 . 
     Further, a second detection lever  44 , which has the shape of a right triangle of which the rear side (herein, a side corresponding to the upstream side of the paper sheet P) (as seen in the width direction) is an oblique side, is provided on the transport path of the paper sheet P at the lower end of the paper feeding guide section  27  of the transport path forming member  26  so as to freely extend back and forth from the upper side. The second detection lever  44  is pushed by a spring (not shown), which is provided in the paper feeding guide section  27 , so as to always protrude upward from the transport path of the paper sheet P. Accordingly, if being pressed forward (toward the downstream side of the paper sheet P) by the front end of the paper sheet P transported on the transport path, the second detection lever retracts into the paper feeding guide section  27  against the pushing force of the spring (not shown). 
     Further, a second detection part  45  (see  FIG. 6 ) which detects whether the second detection lever  44  retracts into the paper feeding guide section  27 , is provided in the paper feeding guide section  27 . If the second detection lever  44  retracts into the paper feeding guide section  27 , the second detection part  45  (see  FIG. 6 ) outputs an ON-detection signal. If the second detection lever  44  does not retract into the paper feeding guide section  27 , the second detection part outputs an OFF-detection signal. Meanwhile, in this embodiment, a paper sheet-end sensor  46  (see  FIG. 6 ) is formed of the second detection lever  44  and the second detection part  45  (see  FIG. 6 ). 
     As shown in  FIGS. 2 and 3 , a separation pad  79  is provided in the middle of the stepped portion  23  in the width direction, and the separation pad  79  is pushed upward by a spring (not shown). Further, a feed roller unit  50  functioning as a feeding member, which can feed the paper sheet P set on the set face  16   a  toward the downstream side, is swingably supported on the inner surface of the reverse cover  18  at a position facing the stepped portion  23 . 
     As shown in  FIGS. 3 and 4 , the feed roller unit  50  includes a frame  51  that has a substantially rectangular shape in plan view. First and second feed rollers  52  and  53  are rotatably supported in the frame  51  so as to make a pair, and are positioned parallel to each other in the longitudinal direction. That is, the first feed roller  52  is disposed on the rear side of the second feed roller  53  in the frame  51 , and the first and second feed rollers are each rotatable about axes extending in the width direction. In this case, the first feed roller  52  is positioned so as to always come in contact with the upper surface of the separation pad  79 . 
     In the frame  51 , first and second gears  54  and  55  are rotatably supported on the left side of the first and second feed rollers  52  and  53 . The first gear  54  and the first feed roller  52  are rotatable about the same axis, and the second gear  55  and the second feed roller  53  are rotatable about the same axis. Further, a transmission gear  56  is rotatably supported between the first and second gears  54  and  55  in the frame  51 , and the transmission gear  56  meshes with the first and second gears  54  and  55 . 
     A first one-way clutch  57   a  is provided between the first feed roller  52  and the first gear  54 . When the first gear  54  is rotated in a normal direction (rotated clockwise in this embodiment as seen from the right side), the first one-way clutch  57   a  transmits the torque of the first gear  54  to the first feed roller  52 . When the first gear  54  is rotated in a reverse direction (rotated counterclockwise in this embodiment as seen from the right side), the first one-way clutch does not transmit the torque of the first gear  54  to the first feed roller  52 . 
     Likewise, a second one-way clutch  57   b , which has exactly the same structure as the first one-way clutch  57   a , is provided between the second feed roller  53  and the second gear  55 . Accordingly, when the second gear  55  is rotated in the normal direction, the torque of the second gear  55  is transmitted to the second feed roller  53  by the second one-way clutch  57   b . When the second gear  55  is rotated in the reverse direction, the torque of the second gear  55  is not transmitted to the second feed roller  53  by the second one-way clutch. 
     A main shaft  58 , which extends in the width direction and is rotated about the axis of the first feed roller  52 , is rotatably supported on the inner surface of the reverse cover  18 . A right end of the main shaft  58  passes through the left wall of the frame  51  and is connected to the first gear  54 . A main shaft gear  58   a  is fixed to the left end of the main shaft. The main shaft  58  and the first gear  54  are rotated about the same axis as a single body. The main shaft supports the left wall of the frame  51  while not interfering with the rotation thereof. 
     Further, the main shaft gear  58   a  of the main shaft  58  meshes with a motor gear (not shown) fixed to an output shaft (not shown) of the feeding motor  59  (see  FIG. 6 ), which is provided in the transport unit  15 , through a motor transmission gear (not shown). Accordingly, the feeding motor  59  is driven in the normal direction when the main shaft  58  is rotated in the normal direction, and is rotated in the reverse direction when the feeding motor  59  is driven in the reverse direction. 
     A sub-shaft  60  is connected to the second gear  55  from the left side, and the sub-shaft  60  and the second gear  55  are rotated about the same axis as a single body. The sub-shaft  60  passes through the left wall of the frame  51  and protrudes from the left side of the frame  51  toward the outside of the frame  51 . A sub-shaft gear  61  is fixed to the end (left end) of the sub-shaft  60 , and the left wall of the frame  51  does not interfere with the rotation of the sub-shaft gear. Further, the sub-shaft gear  61  is interposed in the longitudinal direction between front and rear support plates  62  and  63 , which are provided on the inner surface of the reverse cover  18 . 
     The surface of the front support plate  62 , which faces the sub-shaft gear  61 , comes in contact with and slides across the sub-shaft gear  61 . Meanwhile, a rack (not shown), which extends in the vertical direction, is formed on the surface of the rear support plate  63  that faces the sub-shaft gear  61 . The rack meshes with the sub-shaft gear  61 . Accordingly, when the sub-shaft gear  61  (sub-shaft  60 ) is rotated in the normal direction, the sub-shaft gear  61  is moved down along the rack (not shown) of the rear support plate  63  while being rotated. When the sub-shaft gear  61  (sub-shaft  60 ) is rotated in the reverse direction, the sub-shaft gear  61  is moved up along the rack (not shown) of the rear support plate  63  while being rotated. 
     A covered cylindrical support  64  protrudes toward the right side from the outer surface of the right wall of the frame  51  at a position corresponding to the first feed roller  52 . A step is formed at the support  64  so that the outer diameter of the end portion of the support is smaller than that of the base portion thereof. Accordingly, the end portion of the support is rotatably supported by the support member  65  that is provided on the inner surface of the reverse cover  18 . In addition, an engagement arm  66 , which extends toward the right side, is formed at the upper front end on the outer surface of the right wall of the frame  51 . 
     Further, when the first and second feed rollers  52  and  53  are parallel to each other in a horizontal direction (see  FIGS. 2 and 4 ), the position of the feed roller unit  50  is referred to as a non-feed position. When being positioned at the non-feed position, the feed roller unit does not feed the paper sheet P set on the set face  16   a  toward the downstream side of the transport path. That is, when the feed roller unit  50  is positioned at the non-feed position, the second feed roller  53  is separated upward from the set face  16   a  or the paper sheet P that is set on the set face  16   a . Meanwhile, when the transport unit  15  is in a standby state, the feed roller unit  50  is generally positioned at the non-feed position. 
     Further, if the main shaft  58  is rotated in the normal direction when the feed roller unit  50  is positioned at the non-feed position, the first gear  54  is rotated in the normal direction. Accordingly, the transmission gear  56  is rotated in the reverse direction and the second gear  55  is rotated in the normal direction. In this case, the torque of the first and second gears  54  and  55  is respectively transmitted to the first and second feed rollers  52  and  53  by the first and second one-way clutches  57   a  and  57   b  so that the first and second feed rollers  52  and  53  are rotated in the normal direction, 
     In this case, if the sub-shaft  60  is rotated in the normal direction as the second gear  55  is rotated in the normal direction, the sub-shaft gear  61  meshes with the rack (not shown) of the rear support plate  63  and is moved down along the rack while being rotated. Accordingly, the feed roller unit  50  is swung about the main shaft  58  so that the front portion of the feed roller unit is lower then the rear portion thereof. The feed roller unit is inclined so that the front portion of the feed roller unit is lower than the rear portion thereof, that is, the feed roller unit is in a state where the second feed roller  53  comes in contact with the set face  16   a  or the paper sheet P that is set on the set face  16   a  (see  FIG. 5 ). 
     Accordingly, in this state, the feed roller unit  50  can feed the paper sheet P, which is set on the set face  16   a , toward the downstream side of the transport path. In this case, the position of the feed roller unit  50  is referred to as a feed position. Meanwhile, the first detection lever  20  is disposed near a position where the second feed roller  53  of the feed roller unit  50  can come in contact with the set face  16   a  when the feed roller unit  50  is positioned at the feed position. 
     Meanwhile, if the main shaft  58  is rotated in the reverse direction when the feed roller unit  50  is positioned at the feed position, the first gear  54  is rotated in the reverse direction. Accordingly, the transmission gear  56  is rotated in the normal direction and the second gear  55  is rotated in the reverse direction. In this case, the torque of the first and second gears  54  and  55  is not respectively transmitted to the first and second feed rollers  52  and  53  by the first and second one-way clutches  57   a  and  57   b . Further, in this case, if the sub-shaft  60  is rotated in the reverse direction as the second gear  55  is rotated in the reverse direction, the sub-shaft gear  61  meshes with the rack (not shown) of the rear support plate  63  and is moved up along the rack while being rotated. Accordingly, the feed roller unit  50  is displaced to the feed position. 
     Therefore, the feed roller unit  50  is displaced between the feed position and the non-feed position. That is, the feed roller unit  50  may be swung about the main shaft  58  between the feed position and the non-feed position. 
     As shown in  FIGS. 2 to 4 , a restricting member  70  made of a hard synthetic resin is disposed on the right side of the feed roller unit  50 . The restricting member  70  is supported by a support arm  71  that is provided on the inner surface of the reverse cover  18 . That is, the restricting member  70  includes a shaft  72  extending in the longitudinal direction that is the transport direction of the paper sheet P at the set position  24  and the shaft  72  is rotatably supported by the support arm  71 . 
     A front connection portion  73 , which extends straight upward so as to be slightly inclined toward the left side from the vertical direction, is integrally formed with the front end of the shaft  72 . A columnar engagement portion  74 , which extends in a straight line toward the front side, is integrally formed with the upper end of the front connection portion  73 . Further, the engagement portion  74  comes in contact with the lower surface of the engagement arm  66  of the feed roller unit  50  that is positioned at the non-feed position. 
     Meanwhile, a rear connection portion  75 , which extends straight toward the right side, is integrally formed with the rear end of the shaft  72 . A plate-like restricting section  76 , which extends straight toward the lower side, is integrally formed with the right end of the rear connection portion  75 . The end (lower end) of the restricting section  76  is inserted into the recess  25 . That is, when the feed roller unit  50  is positioned at the non-feed position, the end of the restricting section  76  is inserted into the recess  25  (see  FIGS. 2 and 4 ). In this state, the restricting section  76  crosses the transport path of the paper sheet P in the vertical direction that is the thickness direction of the paper sheet P. For this reason, the restricting section  76  protrudes on the transport path of the paper sheet P, and blocks the transport path in the vertical direction without leaving a gap. Further, the position of the restricting member  70  in this case is referred to as a first position. 
     Furthermore, a locking portion  77 , which extends straight upward in the vertical direction, is integrally formed with the shaft  72  at a position that is slightly closer to the rear side than the middle of the shaft  72  in the longitudinal direction. A hook  77   a , which has a U shape in plan view, is formed at the upper end of the locking portion  77 . One end of a coil spring  78 , which functions as a pusher extending in the width direction, is caught by the hook  77   a . The other end of the coil spring  78  is caught by a hook piece (not shown) that is formed on the inner surface of the reverse cover  18 . 
     Further, if the feed roller unit  50  is displaced from the non-feed position to the feed position, the engagement portion  74  of the restricting member  70  is pressed down by the engagement arm  66  of the feed roller unit  50 . In this case, the shaft  72  is rotated clockwise (as seen from the front side) against the pushing force of the coil spring  78  by the front connection portion  73 , and the restricting section  76  is rotated clockwise (as seen from the front side) about the shaft  72  by the rear connection portion  75  with the rotation of the shaft  72 . Accordingly, the restricting member  70  is in a state where the restricting section  76  is separated from the recess  25  and moved up (see  FIG. 5 ), that is, the restricting section  76  retracts upward from the transport path of the paper sheet P. Further, the position of the restricting member  70  in this case is referred to as a second position. 
     Meanwhile, if the feed roller unit  50  is displaced from the feed position to the non-feed position, the shaft  72  of the restricting member  70  is rotated counterclockwise (as seen from the front side) by the pushing force of the coil spring  78 . Accordingly, the shaft  72  is rotated counterclockwise (as seen from the front side) with the rotation of the shaft  72  so that the engagement portion  74  follows the engagement arm  66  of the feed roller unit  50 . As a result, the restricting member  70  is again in a state where the restricting section  76  is inserted into the recess  25 , that is, the restricting section  76  protrudes from the transport path of the paper sheet P from above. 
     The electrical configuration of the complex machine  11  will be described below. 
     As shown in  FIG. 6 , the complex machine  11  includes a control unit  80 , which functions as a controller for controlling the operation of the complex machine  11 . The start switch  19 , the paper sheet detecting sensor  22 , the paper sheet-end sensor  46 , the feeding motor  59 , the paper feed motor  40 , and the paper discharge motor  43  are electrically connected to the control unit  80 . Further, an operation signal output when a user operates the start switch  19 , an ON-detection signal or an OFF-detection signal that is output from the paper sheet detecting sensor  22 , and an ON-detection signal or an OFF-detection signal that is output from the paper sheet-end sensor  46  are input to the control unit, so that the control unit  80  controls the driving of the feeding motor  59 , the paper feed motor  40 , and the paper discharge motor  43 . Meanwhile, the control unit  80  includes a memory (not shown), and a program for transporting a paper sheet is stored in the memory. 
     The operation of the transport unit  15 , when a user sets the paper sheet P on the set face  16   a  of the paper feed tray  16 , will be described below. 
     The setting of the paper sheet P on the set face  16   a  is performed when the transport unit  15  is in a standby state. Accordingly, in this standby state, the feed roller unit  50  is positioned at the non-feed position, that is, the restricting member  70  is positioned at the first position. Further, in this state, a user inserts (pushes) by hand the stacked paper sheets P into the gap between the set face  16   a  and the feed roller unit  50  (toward the rear side) along the set face  16   a . Accordingly, the front end of each paper sheet P comes in contact with the slope  23   a , so that each paper sheet P is set into position. 
     Further, if each paper sheet P is vigorously inserted toward the rear side on the set face  16   a  by a user, the front ends of some paper sheets P among the paper sheets P get over the slope  23   a . However, since the front ends of the paper sheets P getting over the slope  23   a  come in contact with the restricting section  76  of the restricting member  70 , the paper sheets P do not get over the set position  24  toward the downstream side of the transport path. Accordingly, the front end of each paper sheet P is stopped at the set position  24 . 
     Furthermore, if a user inserts each paper sheet P toward the rear side on the set face  16   a  by a very strong force, a strong pressing force is applied rearward to the restricting section  76  of the restricting member  70  from each paper sheet P inserted by the user. However, the restricting member  70  is rotatable about the shaft  72  extending in a direction where the transport path of the paper sheet P extends (herein, the longitudinal direction). Accordingly, the pressing force is not applied to the restricting member  70 , which is positioned at the first position, in a rotational direction. That is, the pressing force is applied to the restricting member  70 , which is positioned at the first position, in a direction substantially orthogonal to the rotational direction. 
     For this reason, the restricting force for restricting the front end of each paper sheet P, which gets over the set position  24  against the pressing force toward the downstream side on the transport path, depends not on the pushing force of the coil spring  78  but the strength of the material of the restricting member  70 . Further, since the restricting member  70  is made of a hard synthetic resin in this embodiment, the strength of the restricting member is significantly higher than that of the paper sheet P. For this reason, a restricting force for restricting the front end of each paper sheet P, which gets over the set position  24  against the pressing force toward the downstream side on the transport path, is significantly secured. 
     Accordingly, when the paper sheet P is set in the paper feed tray  16 , the front end of the paper sheet P, which gets over the set position  24  in the paper feed tray  16  toward the downstream side, is reliably restricted by the rotary restricting member  70 . 
     A routine for transporting the paper sheet, which is performed by a control unit  80  when a user operates the start switch  19 , will be described below with reference to a flowchart of  FIG. 7 . 
     Meanwhile, if an operation signal is input to the control unit from the start switch  19 , the control unit  80  determines whether an ON-detection signal is input from the paper sheet detecting sensor  22  (Step S 1 ). If the determination result of Step S 1  corresponds to a positive determination, the control unit  80  drives the feeding motor  59  in the normal direction on the basis of the ON-detection signal input from the paper sheet detecting sensor  22  and displaces the feed roller unit  50  from the non-feed position to the feed position (Step S 2 ). Then, the restricting member  70  is displaced to the second position from the first position, the second feed roller  53  comes in contact with the uppermost paper sheet P that is set on the set face  16   a  in a stacked state while being rotated in the normal direction, and the paper sheet P is fed toward the paper feed passage  35 . That is, a feeding force is applied to the paper sheet P from the first and second feed rollers  52  and  53 . 
     In this case, if a lower paper sheet P is led and moved by the uppermost paper sheet P, the uppermost paper sheet P and the lower paper sheet P are separated from each other when passing between the first feed roller  52  and the separation pad  79 , so that only the uppermost paper sheet P is fed toward the paper feed passage  35 . Meanwhile, if the determination result of Step S 1  corresponds to a negative determination, the control unit  80  makes the process proceed to Step S 7  to be described below on the basis of the OFF-detection signal input from the paper sheet detecting sensor  22 . 
     Subsequently, the control unit  80  determines whether the paper feed motor  40  and the paper discharge motor  43  are driven (Step S 3 ). If the determination result of Step S 3  corresponds to a positive determination, the control unit  80  determines whether an ON-detection signal is input from the paper sheet-end sensor  46  (Step S 4 ). Meanwhile, if the determination result of Step S 3  corresponds to a negative determination, the control unit  80  drives the paper feed motor  40  and the paper discharge motor  43  (Step S 5 ) and makes the process proceed to Step S 4 . Accordingly, the paper feed roller  38  and the paper discharge roller  41  are rotationally driven. 
     If the determination result of Step S 4  corresponds to a negative determination, the control unit  80  repeatedly performs the process of Step S 4  until the determination result of Step S 4  becomes a positive determination. Meanwhile, if the determination result of Step S 4  corresponds to a positive determination, the control unit  80  drives the feeding motor  59  in the reverse direction and displaces the feed roller unit  50  from the feed position to the non-feed position (Step S 6 ). In this case, a feeding force, which is applied to the paper sheet P from the first and second feed rollers  52  and  53 , is lost, but the transport of the paper sheet P has already left to the paper feed roller  38 . Accordingly, the paper sheet P is transported without delay onto the upper surface  33   a  of the glass  33  by the paper feed roller  38 . Further, when the paper sheet P passes between the upper surface  33   a  of the glass  33  and the paper sheet pressing member  32 , the image is read by the scanner unit  14 . After that, the paper sheet P passes through the paper discharge passage  37  and is discharged onto the paper discharge tray  17  by the paper discharge roller  41 . 
     Subsequently, after driving the feeding motor  59  in the normal direction and displacing the feed roller unit  50  from the non-feed position to the feed position (Step S 7 ), the control unit  80  determines whether an ON-detection signal is input from the paper sheet detecting sensor  22  (Step S 8 ). Accordingly, Step S 8  is performed while the feed roller unit  50  is positioned at the feed position. 
     In this case, if there are deformations, such as a wrinkle or warping, on the following paper sheet P on the set face  16   a  when Step S 8  is performed while the feed roller unit  50  is positioned at the non-feed position, pressure is not sufficiently applied to the first detection lever  20  from the following paper sheet P. For this reason, even though the following paper sheet P exists on the set face  16   a , an OFF-detection signal, not an ON-detection signal, is input to the control unit  80  from the paper sheet detecting sensor  22 . 
     In this regard, in Step S 8  of this embodiment the control unit determines whether an ON-detection signal is input from the paper sheet detecting sensor  22  when the feed roller unit  50  is positioned at the feed position. For this reason, if the following paper sheet P exists on the set face  16   a , a portion of the paper sheet P corresponding to the first detection lever  20  is pressed from above by the second feed roller  53 . Accordingly, even though there are deformations, such as a wrinkle or warping, on the paper sheet P on the set face  16   a , pressure is sufficiently applied to the first detection lever  20  from the paper sheet P. For this reason, it may be possible to reliably avoid that an OFF-detection signal, not an ON-detection signal, is input to the control unit  80  from the paper sheet detecting sensor  22  despite the existence of the following paper sheet P on the set face  16   a.    
     If the determination result of Step S 8  corresponds to a positive determination, the control unit  80  makes the process proceed to Step S 3  on the basis of the ON-detection signal input from the paper sheet detecting sensor  22 . Meanwhile, if the determination result of Step S 8  corresponds to a negative determination, the control unit  80  drives the feeding motor  59  in the reverse direction on the basis of the OFF-detection signal input from the paper sheet detecting sensor  22  and displaces the feed roller unit  50  from the feed position to the non-feed position (Step S 9 ). 
     Subsequently, the control unit  80  determines whether the paper feed motor  40  and the paper discharge motor  43  are being driven (Step S 10 ). If the determination result of Step S 10  corresponds to a positive determination, the control unit  80  stops the paper feed motor  40  and the paper discharge motor  43  (Step S 11 ) and then terminates the routine for transporting the paper sheet. Meanwhile, if the determination result of Step S 10  corresponds to a negative determination, the control unit  80  terminates the routine for transporting the paper sheet. 
     According to the above-mentioned embodiment, it may be possible to obtain the following advantages. 
     (1) The restricting member  70  is rotatable about the shaft  72  extending along the transport path. Accordingly, even if the paper sheet P is strongly pushed toward the downstream side of the set position  24  in the transport direction by a user&#39;s manual operation, a pushing force in the rotational direction is not applied to the restricting member  70 , which is positioned at the first position. For this reason, the restricting force for restricting the front end of the paper sheet P, which gets over the set position  24  against the pushing force toward the downstream side on the transport path, depends on the strength of the material (a hard synthetic resin in this embodiment) of the restricting member  70 . Therefore, when the paper sheet P is set in the paper feed tray  16 , it may be possible to reliably restrict the front end of the paper sheet P, which gets over the set position  24  in the paper feed tray  16  toward the downstream side, by the rotary restricting member  70 . 
     (2) When the restricting member  70  is positioned at the first position, the restricting section  76  blocks the transport path of the paper sheet P in the thickness direction of the paper sheet P, which is set in the paper feed tray  16 , without leaving a gap. Accordingly, it may be possible to further reliably restrict the front end of the paper sheet P, which gets over the set position  24  in the paper feed tray  16  toward the downstream side. 
     (3) The recess  25 , into which the end of the restricting section  76  is inserted when the restricting member  70  is positioned at the first position, is formed at the set position  24  in the paper feed tray  16 . For this reason, even though the restricting section  76  may be pushed to deform by the pushing force that is applied from the front side by the paper sheet P when the restricting member  70  is positioned at the first position, the end of the restricting section  76  is engaged with the rear surface of the recess  25 . Accordingly, it may be possible to suppress the deformation of the restricting section  76 , that is, to reinforce the restricting section  76 . 
     (4) When the feed roller unit  50  is displaced to the feed position in order to feed the paper sheet P, the engagement portion  74  of the restricting member  70  is pressed by the engagement arm  66  of the feed roller unit  50 , so that the restricting member  70  is positioned at the second position. Accordingly, the restricting section  76  reliably retracts from the transport path of the paper sheet P. For this reason, it may be possible to smoothly feed the paper sheet P, which is set in the paper feed tray  16 , toward the downstream side of the set position  24  on the transport path by the feed roller unit  50 . In this case, since an operation for displacing the restricting member  70  from the first position to the second position is performed by an operation for displacing the feed roller unit  50  from the non-feed position to the feed position, an actuator for displacing the restricting member  70  from the first position to the second position is not separately needed. Therefore, the number of components also does not need to be increased. 
     (5) In general, if there is warping or a wrinkle on the paper sheet P set in the paper feed tray  16  and the paper sheet P is thus deformed, the first detection lever  20  may not sufficiently receive pressure from the paper sheet P and the first detection lever  20  may not retract into the paper feed tray  16  despite the existence of the paper sheet P in the paper feed tray  16 . Further, in this case, an OFF-detection signal is input to the control unit  80  from the paper sheet detecting sensor  22 . Accordingly, there is a false detection that the paper sheet P does not exist in the paper feed tray  16 . In this regard, in this embodiment, if an OFF-detection signal is input to the control unit  80  from the paper sheet detecting sensor  22  when the feed roller unit  50  is displaced from the non-feed position to the feed position and the feed roller unit  50  is positioned at the feed position, the control unit  80  determines that a paper sheet P does not actually exist in the paper feed tray  16  and then displaces the feed roller unit  50  from the feed position to the non-feed position. That is, when the feed roller unit  50  is positioned at the feed position, the paper sheet P set in the paper feed tray  16  is pressed from above by the feed roller unit  50 . Accordingly, even though the paper sheet P is deformed, the first detection lever  20  reliably and sufficiently receives pressure from the paper sheet P. If an OFF-detection signal is input to the control unit  80  from the paper sheet detecting sensor  22  in this state, the control unit  80  determines that a paper sheet P does not actually exist in the paper feed tray  16  and then displaces the feed roller unit  50  from the feed position to the non-feed position. Accordingly, it may be possible to reliably avoid that an OFF-detection signal is input to the control unit  80  from the paper sheet detecting sensor  22  despite the existence of the following paper sheet P in the paper feed tray  16 . As a result, it may be possible to reliably detect whether the paper sheet P set in the paper feed tray  16  exists or not. 
     (6) The first detection lever  20  of the paper sheet detecting sensor  22  is disposed near a position where the feed roller unit  50  can come in contact with the set face  16   a  when being displaced to the feed position. For this reason, even though the paper sheet P set on the set face  16   a  is deformed, the paper sheet P is pressed from above by the feed roller unit  50  when the feed roller unit  50  is displaced to the feed position. Accordingly, the first detection lever  20  reliably and sufficiently receives pressure from the paper sheet P. As a result, it may be possible to reliably and accurately detect by the paper sheet detecting sensor  22  whether the paper sheet P set on the set face  16   a  exists or not. 
     (Modification) 
     Meanwhile, the above-mentioned embodiment may be modified as follows: 
     The first detection lever  20  of the paper sheet detecting sensor  22  does not need to be necessarily disposed near a position where the feed roller unit  50  can come in contact with the set face  16   a  when being displaced to the feed position. That is, as long as the first detection lever  20  can detects the paper sheet P set on the set face  16   a , the first detection lever may be disposed at any position on the set face  16   a . However, in this case, it is necessary to avoid the first detection lever being disposed at a position where engagement with the feed roller unit  50  is caused when the feed roller unit  50  is displaced to the feed position. 
     As for the routine for transporting the paper sheet, the control unit  80  may terminate the routine for transporting the paper sheet if the determination result of Step S 1  corresponds to a negative determination. In addition, Step S 6 - 1  for determining whether an ON-detection signal is input to the control unit  80  from the paper sheet detecting sensor  22  may be interposed between Steps S 6  and S 7 . The control unit  80  may make the process proceed to Step S 2  if the determination result of Step S 6 - 1  corresponds to a positive determination, and makes the process proceed to Step S 7  if the determination result of Step S 6 - 1  corresponds to a negative determination. Steps S 3  and S 10  may be omitted in this case. Accordingly, when Steps S 3  and S 10  are omitted, the control unit  80  performs Step S 5  after performing Step S 2  and then performs Step S 4 , and performs Step S 11  after performing Step S 9 . 
     A plastic film may be used as a sheet instead of a paper sheet P. 
     In addition, the scope, which may be obtained from the above-mentioned embodiment, will be described below. 
     (A) There is a provided a method of detecting a sheet in a transport device. The transport device includes a set section, a sheet sensor, and a feeding member. The set section includes a set face on which sheets can be set in a stacked state. When a detection member, which is provided on the set face of the set section so as to freely extend back and forth from the lower side, receives pressure from the sheet set in the set section and retracts, the sheet sensor outputs an ON-detection signal. When the detection member does not retract, the sheet sensor outputs an OFF-detection signal. The feeding member is transferred between a feed position and a non-feed position on the basis of the detection signal output from the sheet sensor. At the feed position, the feeding member comes in contact with the sheet set in the set section from above and feeds the sheet toward the downstream side on the transport path. At the non-feed position, the feeding member is separated upward from the feed position. The method of detecting a sheet includes displacing the feeding member from the feed position to the non-feed position and then displacing the feeding member to the feed position again when an OFF-detection signal is output from the sheet sensor after the feeding member has been displaced to the feed position on the basis of an ON-detection signal output from the sheet sensor and sheets have begun to be fed, and detecting that the sheet does not exist in the set section when an OFF-detection signal is output from the sheet sensor again while the feeding member is positioned at the feed position. 
     (B) There is a provided a transport device. The transport device includes a set section, a sheet sensor, a feeding member, and a controller. The set section includes a set face on which sheets can be set in a stacked state. The sheet sensor outputs an ON-detection signal when a detection member receives pressure from the sheet set in the set section and retracts, and outputs an OFF-detection signal when the detection member does not retract. The detection member is provided on the set face of the set section so as to freely extend back and forth from the lower side. The feeding member is displaced between a feed position and a non-feed position. At the feed position, the feeding member comes in contact with the sheet set in the set section from above and feeds the sheet toward the downstream side on the transport path. At the non-feed position, the feeding member is separated upward from the feed position. The controller controls a displacing operation of the feeding member on the basis of the detection signal output from the sheet sensor. The controller displaces the feeding member from the feed position to the non-feed position and then displacing the feeding member to the feed position again when an OFF-detection signal is output from the sheet sensor after the feeding member has been displaced to the feed position on the basis of an ON-detection signal output from the sheet sensor and the sheets have begun to be fed, and displaces the feeding member from the feed position to the non-feed position when an OFF-detection signal is output from the sheet sensor again while the feeding member is positioned at the feed position.