Abstract:
An image forming device includes: a tray; an image fanning unit; a drive source; a feeding roller; a support portion; a support shaft; and a drive shaft. The tray is configured to support a recording sheet. The image forming unit is configured to form an image on the recording sheet. The drive source is configured to generate a driving force The feeding roller is configured to rotate upon receipt of the driving force to feed the recording sheet supported by the tray toward the image forming unit. The support portion is configured to rotatably support the feeding roller. The support shaft is disposed above the tray and configured to pivotally movably support the support portion. The drive shaft is independent of the support shaft and configured to rotate upon receipt of the driving three from the drive source.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/628,270, filed Sep. 27, 2012, which claims priority from Japanese Patent Application No. 2011-265003 filed Dec. 2, 2011. The entire contents of the above-noted applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an image forming device provided with an image forming unit for forming an image on a recording sheet. More specifically, the present invention relates to an image forming device configured to feed recording sheets stacked on a stacked surface of a sheet supply tray toward the image forming unit by means of a feeding roller supported to one end portion of a pivotally movable support portion. 
       BACKGROUND 
       [0003]    Conventionally, for example, it has been proposed that an image forming device, such as an ink-jet printer, feeds recording sheets, such as recording paper sheets, stacked on a stacked surface of a sheet supply tray toward an image forming unit by means of a feeding roller supported to one end portion of a pivotally movable support portion. In this case, it has also been proposed that the support portion has another end portion supported to and pivotally movable about a drive shaft to which a driving force is transmitted from a motor, and the driving force transmitted to the drive shaft is transmitted to the feeding roller through a gear mechanism described below. That is, a planetary gear mechanism including a sun gear and a planetary gear is provided for transmitting the drive force to the feeding roller. The sun gear is adapted to rotate integrally with the drive shaft. The planetary gear is adapted to be swingably moved about the sun gear while maintaining engagement with the sun gear. Upon swinging movement of the planetary gear in one direction, the planetary gear comes into engagement with a gear train coupling with the feeding roller. In this case, the planetary gear is engaged with the gear train only when the drive shaft rotates in one direction. Even when the drive shaft rotates both in forward and reverse directions, the above configuration can prevent the feeding roller from rotating in a direction opposite to a feeding direction. 
       SUMMARY 
       [0004]    However, in case the gear train is provided at the support portion such as a swing arm, and the sun gear provided at the drive shaft about which the support portion is pivotally moved is rotated to provide engagement of a planetary gear with the gear train, a complex force is applied to a route for transmitting the driving three to the feeding roller. That is, in this case, when the planetary gear is engaged with the gear train, a self-weight of the support portion, and a reaction force applied to the support portion from a recording sheet exert an influence on the driving force transmission route, and hence, a transmission state of the driving force to the feeding roller becomes unstable. As a result, oblique (skew) feeding of the recording sheets by the feeding roller may occur. 
         [0005]    In view of the foregoing, it is an object of the present invention to provide an image forming device configured to transmit a driving force to a feeding roller supported to one end portion of a pivotally movable support portion through a planetary gear mechanism and to feed a recording sheet placed on a sheet supply tray, the image forming device being capable of stably feeding the recording sheet. 
         [0006]    In order to attain the above and other objects, the present invention provides an image forming device that may include: a tray; an image forming unit; a drive source; a feeding roller; a support portion; a support shaft; and a drive shaft The tray may be configured to support a recording sheet. The image forming unit may be configured to form an image on the recording sheet. The drive source may be configured to generate a driving force. The feeding roller may be configured to rotate upon receipt of the driving force to feed the recording sheet supported by the tray toward the image forming unit. The support portion may be configured to rotatably support the feeding roller. The support shaft may be disposed above the tray and configured to pivotally movably support the support portion. The drive shaft may be independent of the support shaft and configured to rotate upon receipt of the driving force from the drive source. 
         [0007]    According to another aspect, the present invention provides a feeding device that may include: a tray; a feeding roller; a support portion; a support shaft; and a drive shaft. The tray may be configured to support a recording sheet. The feeding roller may be configured to feed the recording sheet. The support portion may be configured to rotatably support the feeding roller. The support shaft may be configured to pivotally movably support the support portion. The drive shaft may be independent of the support shaft and connected to a drive source. The drive shaft may be configured to rotate upon receipt of a driving force from the drive source. 
         [0008]    According to still another aspect, the present invention provides a sheet feeding mechanism that may include: a feeding roller; a support portion; a support shaft; and a drive shaft. The support portion may be configured to rotatably support the feeding roller. The support shaft may be configured to pivotally movably support the support portion. The drive shaft may be independent of the support shaft and connected to a drive source. The drive shaft may be configured to rotate upon receipt of a driving force from the drive source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the drawings; 
           [0010]      FIG. 1  is a perspective view of an outer appearance of an image forming device according to one embodiment of the present invention; 
           [0011]      FIG. 2  is a cross-sectional view schematically illustrating a structure of an essential portion of the image forming device; 
           [0012]      FIG. 3  is a perspective view of a part of the essential portion of  FIG. 2  in a state where a sheet supply tray is at an accommodated position; 
           [0013]      FIG. 4  is a perspective view illustrating a structure of a sheet supply arm in the part of the essential portion of  FIG. 2 ; 
           [0014]      FIG. 5  is a perspective view of the part of the essential portion of  FIG. 2  in a state where the sheet supply tray is pulled outward from a casing of the image forming device; 
           [0015]      FIG. 6  is a plan view illustrating a structure of a main support portion in the part of the essential portion of  FIG. 2 , together with one of follow rollers shown in  FIG. 2 ; 
           [0016]      FIGS. 7A and 7B  are each a cross-sectional view illustrating the structure and movement of the main support portion taken along a line A-B-C-D of  FIG. 6 ; and 
           [0017]      FIG. 8  is a perspective view illustrating the structure of the main support portion, but a cover thereof is omitted. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    An image forming device (feeding device) according to one embodiment of the present invention will be described with reference to  FIGS. 1 through 8 . Throughout the specification, the terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the image forming device I is disposed in an orientation in which it is intended to be used. More specifically, in  FIG. 1 , an upper side will be referred to as an upper side, a side where a display unit  13  (described later) is provided will be referred to as a front side, and a right side of the image forming device as viewed from the front side will be referred to as a right side. 
         [0019]    [Overall Structure of Image Forming Device] 
         [0020]    The image forming device  10  according to the embodiment has a generally rectangular parallelepiped shape. The image forming device  10  has an upper portion at which a printer unit  11  is provided and a lower portion at which a scanner unit  12  is provided. The display unit  13  is provided at a front portion of the image forming device  10 . The image forming device  10  is a multifunction device, including a printing function, a scanning function, and a copying function. The scanner unit  12  may be dispensed with. The image forming device  10  is further provided with a control unit (not shown). The printer unit  11  is controlled by the control unit. 
         [0021]    The printer unit  11  is provided with a sheet supply tray  15 , and a discharge tray  18  positioned above the sheet supply tray  15 . The printer unit  11  is adapted to form an image on a recording sheet  50  ( FIG. 2 ) placed on the sheet supply tray  15 . The recording sheet  50  may be recording paper, glossy paper, a postcard, or letter paper. As shown in  FIG. 1 , the printer unit  11  is formed with an opening  19  at a front wail of the printer unit  11 . The sheet supply tray  15  is accommodated in a lower portion of the printer unit  11 , and can be pulled outward (frontward) from the printer unit  11  through the opening  19 . More specifically, the sheet supply tray  15  is movable in the frontward/rearward direction between an accommodated position inside the printer unit  11  and a pulled-out position outside the printer unit  11 . The sheet supply tray  15  has a flat rectangular parallelepiped shape having an open top. 
         [0022]    As shown in  FIG. 2 , the sheet supply tray  15  has a bottom portion  16  provided with an upper surface (hereinafter referred to as a stacked surface  16 A) on which the recording sheets  50  are stacked. The sheet supply tray  15  has a rear wall  17  extending diagonally upward and rearward from a rear end portion of the bottom portion  16 . The recording sheet  50  to be fed by a sheet feeding unit  20  (described later) is guided to the rear wall  17  to be directed to a position diagonally upward and rearward. 
         [0023]    The printer unit  11  is provided with the sheet feeding unit  20 , an ink-jet type recording unit  24 , and a path switching unit  41  (described later), those positioned above the sheet supply tray  15 . The sheet feeding unit  20  is adapted to feed the recording sheet  50  from the sheet supply tray  15  toward the recording unit  24 . The recording unit  24  is adapted to eject ink droplets on the recording sheet  50  fed by the sheet feeding unit  20  to form an image on the recording sheet  50 . Incidentally, not only the ink-jet type but also various recording types including an electro-photographic type are available for the recording unit  24 . 
         [0024]    As shown in  FIG. 2 , the sheet feeding unit  20  is positioned above the sheet supply tray  15  and below the recording unit  24 . The sheet feeding unit  20  is provided with a sheet supply roller  25 , a sheet supply arm  26 , and a shaft  28 . The shaft  28  has an axis extending in the rightward/leftward direction. The sheet supply roller  25  is rotatably supported to a leading end portion (rear end portion) of the sheet supply arm  26  and adapted to feed the recording sheets  50  stacked on the stacked surface  16 A of the sheet supply tray  15  toward the recording unit  24 . The sheet supply arm  26  is supported to the shaft  28  provided at a base end portion (front end portion) of the sheet supply arm  26  and pivotally movable about the shaft  28  in a direction indicated by an arrow A. With this configuration, the sheet supply roller  25  is movable so as to contact the stacked surface  16 A and to be spaced away from the stacked surface  16 A. Hence, the sheet supply arm  26  is pivotally moved according to the number of the recording sheets  50  stacked on the stacked surface  16 A, so that the sheet supply roller  25  is normally in contact with an uppermost sheet of the recording sheets  50  stacked on the stacked surface  16 A. A driving mechanism of the sheet supply roller  25  will be described later in detail. 
         [0025]    Here, as shown in  FIG. 2 , within the printer unit  11 , a conveying path  65  is formed. The conveying path  65  extends from a leading end portion (rear end portion) of the sheet supply tray  15  toward the discharge tray  18  via the recording unit  24 . The conveying path  65  includes a curved path  65 A and a discharge path  65 B. The curved path  65 A, is defined from the rear end portion of the sheet supply tray  15  to a first conveying roller  60 . The discharge path  65 B is defined from the first conveying roller  60  to the discharge tray  18 . 
         [0026]    The sheet supply roller  25  separates the uppermost recording sheet  50  from the remaining recording sheets  50  stacked on the stacked surface  16 A to supply the uppermost recording sheet  50  to the curved path  65 A, while the uppermost recording sheet  50  is in contact with the sheet supply roller  25 . 
         [0027]    The curved path  65 A is a curved passage extending from a position adjacent to an upper end portion of the rear wall  17  of the sheet supply tray  15  to a position adjacent to the recording unit  24 . The curved path  65 A has a generally arcuate shape with a center thereof positioned inside the printer unit  11 . The recording sheet  50  fed by the sheet supply roller  25  from the sheet supply tray  15  is curved along the curved path  65 A in a conveying direction (i.e. a direction indicated by a chain line in  FIG. 2 ), and guided to a pinching position where the recording sheet  50  is pinched between the first conveying roller  60  and a pinch roller  61 . The curved path  65 A is further defined between an outer guide member  33  and an inner guide member  34 . The outer guide member  33  and the inner guide member  34  are arranged in confrontation with each other at a predetermined interval therebetween in a generally frontward/rearward direction. 
         [0028]    Incidentally, the outer guide member  33 , the inner guide member  34 , and each guide member  31 ,  32 ,  83 ,  84  (described later) extend in a direction perpendicular to a sheet surface of  FIG. 2  (i.e. rightward/leftward direction). 
         [0029]    The discharge path  65 B is a linear passage extending from the pinching position where the recording sheet  50  is pinched between the first conveying roller  60  and the pinch roller  61  to the discharge tray  18 . The recording sheet  50  is guided in the discharge path  65 B in the conveying direction (i.e. the direction indicated by the chain line in  FIG. 2 ). 
         [0030]    The discharge path  65 B is further defined between the recording unit  24  and a platen  42  at a position where the recording unit  24  is provided. The recording unit  24  and the platen  42  are arranged in confrontation with each other at a predetermined interval therebetween in a vertical direction, The discharge path  65 B is still further defined between an upper guide member  84  and a lower guide member  83  at a position where the recording unit  24  is not provided. The upper guide member  84  and the lower guide member  83  are arranged in confrontation, with each other at a predetermined interval therebetween in the vertical direction. 
         [0031]    In the printer unit  11 , a divergence position  36  is provided at a downstream side of the recording unit  24  and also at a downstream side of a second conveying roller  62  (described later) in the conveying direction. The recording sheet  50  conveyed in the discharge path  65 B switchbacks (moves backward) at a position. downstream of the divergence position  36  in the conveying direction to be conveyed toward a reverse conveying path  67  (described later) when images are formed on respective sides of the recording sheet  50 . 
         [0032]    The recording unit  24  is positioned above the sheet supply tray  15 . The recording unit  24  has a recording head reciprocatingly movable in the rightward/leftward direction (i.e. the direction perpendicular to the sheet surface in  FIG. 2 ). The platen  42  is positioned below the recording unit  24 . The platen  42  is adapted to support the recording sheet  50  horizontally. The recording head of the recording unit  24  ejects ink supplied from an ink cartridge (not shown) as a form of ink droplets through nozzles  39  on the recording sheet  50  conveyed on the platen  42  during the reciprocating movement of the recording head in the rightward/leftward direction. As a result, an image is formed on the recording sheet  50 . 
         [0033]    The recording sheet  50  is conveyed to the platen  42  by the first conveying roller  60  and the pinch roller  61 , where an image is formed by the recording unit  24 . Then, the recording sheet  50  is further conveyed by the second conveying roller  62  and a spur roller  63 . As shown in  FIG. 2 , a third conveying roller  45  and a spur roller  46  are provided at a downstream side of the second conveying roller  62  and the spur roller  63  in the conveying direction. Further, the third conveying roller  45  and the spur roller  46  are positioned downstream of the divergence position  36  in the conveying direction. 
         [0034]    The third conveying roller  45  is driven to rotate in a forward rotation direction and a reverse rotation direction as described below. 
         [0035]    For example, on the one hand, at the time of forming an image on one surface of the recording sheet  50 , the third conveying roller  45  rotates in the forward rotation direction. As a result, the recording sheet  50  is pinched between the third conveying roller  45  and the spur roller  46  to be conveyed downstream in the conveying direction, and discharged to the discharge tray  18 . 
         [0036]    On the other hand, at the time of forming images on both surfaces of the recording sheet  50 , when a rear end portion of the recording sheet  50  is pinched between the third conveying roller  45  and the spur roller  46 , the third conveying roller  45  stops rotating in the forward rotation direction to start rotating in the reverse rotation direction. As a result, the recording sheet  50  is conveyed in a direction opposite to the conveying direction, that is, a direction opposite to the direction in which the recording sheet  50  is directed toward the third conveying roller  45  from the first conveying roller  60 . Hence, the recording sheet  50  is conveyed toward the reverse conveying path  67  (described later) by the path switching unit  41 . 
         [0037]    [Structure of Path Switching Unit] 
         [0038]    As shown in  FIG. 2 , the path switching unit  41  is positioned at the discharge path  65 B between the second conveying roller  62  and the divergence position  36 . The path switching unit  41  is provided with supplemental rollers  47 ,  48 , a flap portion  49 , and a shaft  87 . The shaft  87  extends in the rightward/leftward direction and is supported to a frame of the printer unit  11 . The flap portion  49  is supported to the shaft  87  and pivotally movable about the shaft  87 . The flap portion  49  has a rear end portion supported to the shaft  87 , and a front end portion  49 A positioned closer to the discharge tray  18  than the rear end portion. The supplemental rollers  47 ,  48  are rotatably supported to the flap portion  49 . The supplemental rollers  47 ,  48  are contactable with a recording surface of the recording sheet  50 , and thus formed in a spur like shape similar to the shape of the spur rollers  63 ,  46 . 
         [0039]    The flap portion  49  is pivotally movable about the shaft  87  between a discharge position (indicated by a broken line in  FIG. 2 ) and a reverse position (indicated by a solid line in  FIG. 2 ). In the discharge position, the flap portion  49  is positioned above the lower guide member  83 . In the reverse position, the front end portion  49 A is advanced downward of the divergence position  36 . 
         [0040]    When the flap portion  49  is at the discharge position, the recording sheet  50  conveyed past the recording unit  24  is further conveyed downstream in the conveying direction, When the flap portion  49  is at the reverse position, the third conveying roller  45  is rotated in the reverse rotation direction, so that the recording sheet  50  whose rear end portion is pinched between the third conveying roller  45  and the spur roller  46  is moved backward and conveyed to the reverse conveying path  67 . 
         [0041]    The flap portion  49  is normally at the reverse position due to its self-weight. However, the flap portion  49  is lifted up by the recording sheet  50  conveyed in the discharge path  65 B, so that the flap portion  49  is pivotally moved to the discharge position. Further, when the rear end portion of the recording sheet  50  is conveyed past the supplemental roller  47 , the flap portion  49  is pivotally moved from the discharge position to the reverse position due to its self-weight. Incidentally, the flap portion  49  may be pivotally moved by a motor. 
         [0042]    The reverse conveying path  67  diverges from the discharge path  65 B at the divergence position  36 . The reverse conveying path  67  is positioned below the recording unit  24  and above the sheet feeding unit  20 . The reverse conveying path  67  joins the curved path  65 A at a convergence position  37  positioned upstream of the recording unit  24  in the conveying direction. 
         [0043]    After the rear end portion of the recording sheet  50  is conveyed past the supplemental roller  47  and the flap portion  49  is pivotally moved to the reverse position, the third conveying roller  45  is rotated in the reverse rotation direction. As a result, the recording sheet  50  is conveyed toward the convergence position  37  in the reverse conveying path  67 , as indicated by a two-dot chain line in  FIG. 2 . Further, the reverse conveying path  67  is defined between a first guide member  31  and a second guide member  32  positioned above the first guide member  31 . 
         [0044]    A fourth conveying roller  68 , a re-conveying drive shaft  68 A (described later,  FIGS. 7A ,  7 B), a gear  68 B (described later,  FIGS. 7A ,  7 B), and a follow roller  69  are provided at the reverse conveying path  67 . That is, the reverse conveying path  67  and various components provided at the reverse conveying path  67 , such as the fourth conveying roller  68 , the re-conveying drive shaft  68 A, the gear  68 B, and the follow roller  69 , constitute a re-conveying unit. 
         [0045]    The fourth conveying roller  68  is positioned below the follow roller  69  and in confrontation with the follow roller  69  at the reverse conveying path  67 . The fourth conveying roller  68  is adapted to convey the recording sheet  50  with one surface on which an image has been. formed toward the recording unit  24  for forming an image on another surface of the recording sheet  50 . More specifically, the recording sheet  50  which has been conveyed to the reverse conveying path  67  by the third conveying roller  45  is pinched between the fourth conveying roller  68  and the follow roller  69 , and conveyed along the reverse conveying path  67  by the fourth conveying roller  68  toward the convergence position  37 . Then, the recording sheet  50  is again conveyed to the discharge path  65 B, passing through the convergence position  37 . As a result, images can be formed on both surfaces of the recording sheet  50 . 
         [0046]    [Support Structure of Sheet Feeding Unit] 
         [0047]    The image forming device  10  has a main frame  14  to which a main support portion  70  is assembled (fixed). Here, the main frame  14  implies a portion assembled to the image forming device  10  integrally with the platen  42 , the first guide member  31 , the second guide member  32 , the lower guide member  83 , the upper guide member  84 , and the like. The main support portion  70  is formed of resin. As shown in  FIG. 3 , the sheet supply arm  26  is pivotally movably supported to the main support portion  70 . The main support portion  70  is provided independently from the sheet supply arm  26 . The main support portion  70  is generally rectangular shaped in a plan view and elongated in the rightward/leftward direction. The main support portion  70  has a length in the rightward/leftward direction substantially the same as a length in the rightward/leftward direction of the sheet supply tray  15 . Incidentally, the main support portion  70  has an upper wall. constituting a part of the first guide member  31 . Further, the fourth conveying roller  68  including a pair of right end left roller segments is rotatably supported to the upper wall of the main support portion  70 . 
         [0048]    The sheet supply tray  15  has a left side wall at which a cam surface  15 A is provided. The cam surface  15 A has heights different at positions in a direction in which the sheet supply tray  15  is inserted into and pulled outward from the printer unit  11  (i.e. in the frontward/rearward direction). 
         [0049]    As shown in  FIG. 4 , the sheet supply arm  26  is provided with an arm portion  26 D, an extending portion  26 A, a lever portion  26 B, and a protruding portion  26 E. The arm portion  26 D, the extending portion  26 A, the lever portion  26 B, and the protruding portion  26 E are integral with each other and formed of resin. 
         [0050]    The arm portion  26 D extends in the frontward/rearward direction. The arm portion  26 D has a rear end portion to which the sheet supply roller  25  including a pair of right and left roller segments is rotatably supported, and a front end portion formed with shaft holes  26 C through which the shaft  28  extends, The shaft hole  26 C serves as a center of pivotal movement of the sheet supply arm  26 . 
         [0051]    The extending portion  26 A extends leftward from the front end portion of the arm portion  26 D toward a left end portion of the sheet supply tray  15 . The extending portion  26 A has a left end portion from which the lever portion  26 B extends parallel to the arm portion  26 D (i.e., in the frontward/rearward direction). 
         [0052]    The lever portion  26 B is pivotally movable integrally with the arm portion  26 D. The lever portion  26 B has a rear end portion with which a cap  27  is fitted. The rear end portion of the lever portion  26 B is abuttable on the cam surface  15 A through the cap  27 . The cap  27  is provided to facilitate smooth sliding movement of the lever portion  26 B with the cam surface  15 A. 
         [0053]    The protruding portion  26 E protrudes leftward from a front end portion of the lever portion  26 B and is coaxial with the shaft hole  26 C. The protruding portion  26 E is rotatably supported to a U-shaped notch formed in a left side wall of the main support portion  70 . The protruding portion  26 E is positioned spaced apart from the shaft  28  in the rightward/leftward direction. 
         [0054]    When the sheet supply tray  15  is at the accommodated position, the recording sheet  50  accommodated in the sheet supply tray  15  can be fed toward the recording unit  24  as described above while referring to  FIG. 2 . At this time, the cap  27  is not in contact with the cam surface  15 A, as shown in  FIG. 3 . Hence, as described above, the sheet supply roller  25  is normally contactable with the uppermost recording sheet  50  stacked on the stacked surface  16 A. 
         [0055]    When the sheet supply tray  15  is pulled outward from the accommodated position, for example, to replenish the sheet supply tray  15  with the recording sheets  50 , the cap  27  rides up over the cam surface  15 A. As a result, the lever portion  26 B is pivotally moved about the protruding portion  26 E so that the rear end portion of the lever portion  26 B is moved upward. In conjunction with pivotal movement of the lever portion  26 B, the arm portion  26 D is pivotally moved about the shaft  28  so that the rear end portion of the arm portion  26 D is moved upward. Hence, the sheet supply roller  25  is spaced apart from the stacked surface  16 A or the uppermost recording sheet  50  stacked on the stacked surface  16 A. Accordingly, the sheet supply tray  15  can be easily pulled outward from the printer unit  11 . 
         [0056]    [Drive Mechanism of Sheet Feeding Unit] 
         [0057]    As shown in  FIG. 7 , a planetary gear mechanism  80  (pendulum gear mechanism) and a drive shaft  81 A ( FIG. 6 ) are provided at the main support portion  70 . The drive shaft  81 A is rotatably supported to the main. support portion  70 . The planetary gear mechanism  80  includes a sun gear  81 , a planetary gear  82 , and a lever  85 . The sun gear  81  is rotatable integrally with the drive shaft  81 A. The lever  85  is pivotally movable about the drive shaft  81 A. The planetary gear  82  is rotatably assembled to the lever  85  and meshingly engageable with the sun gear  81 . Since the planetary gear  82  is rotatably assembled to the lever  85 , the planetary gear  82  is swingably moved about the sun gear  81  while maintaining meshing engagement with the sun gear  81 . In other words, the planetary gear  82  is partially orbitally movable around the sun gear  81 , while maintaining meshingly engagement with the sun gear  81 . 
         [0058]    Further, the planetary gear mechanism  80  is covered by a cover  71  provided at an upper end face of the main support portion  70 . Hence, the planetary gear mechanism  80  does not exert an influence on conveyance of the recording sheet  50 . 
         [0059]    A driving force transmission mechanism is provided at the sheet supply arm  26 , more specifically, at the arm portion  26 D. The driving force transmission mechanism is adapted to transmit a driving force to the sheet supply roller  25 , and includes an input gear  89 , a toothed timing pulley  91 , a toothed timing pulley  92 , and a toothed timing belt  93 . 
         [0060]    The input gear  89  is rotatably supported to the shaft  28  and rotatable about an axis of the shaft  28 . That is, the input gear  89  is rotatably mounted on the shaft  28 . The input gear  89  is provided at the front end portion of the arm portion  26 D of the sheet supply arm  26 . The input gear  89  is meshingly engageable with the planetary gear  82 . Further, the input gear  89  is meshingly engaged with a gear (not shown) rotatable integrally with the toothed timing pulley  91 . The toothed timing pulley  92  is rotatable integrally with the sheet supply roller  25 , and positioned between the pair of right and left roller segments of the sheet supply roller  25 . Incidentally, the toothed timing pulley  92  and the pair of right and left roller segments of the sheet supply roller  25  are coaxial with each other. The toothed timing belt  93  is stretched around the toothed timing pulley  91  and the toothed timing pulley  92 . That is, the toothed timing belt  93  is stretched in a direction from the input gear  89  to the sheet supply roller  25 . 
         [0061]    When the sun gear  81  is rotated in a counterclockwise direction in  FIG. 7A , the planetary gear  82  is swingingly moved about the sun gear  81  in a direction the same as a direction in which the sun gear  81  is rotated, that is, in the counterclockwise direction. As a result, as shown in  FIG. 7A , the planetary gear  82  is moved toward the input gear  89  and brought into meshing engagement with the input gear  89 . In association with counterclockwise rotation of the sun gear  81 , the sheet supply roller  25  can be rotated in a clockwise direction in  FIG. 7A , that is, in a feeding direction of the recording sheet  50 , through the planetary gear  82 , the input gear  89 , the toothed timing pulley  91 , the toothed timing belt  93 , and the toothed timing pulley  92 . 
         [0062]    More specifically, when the drive shaft  81 A is driven to rotate in the counterclockwise direction in  FIG. 7A  so as to rotate the sun gear  81  in the counterclockwise direction, the planetary gear  82  assembled to the lever  85  is swingingly moved about the sun gear  81  in the counterclockwise direction while rotating in the clockwise direction, so that the planetary gear  82  is moved toward the input gear  89  and brought into meshing engagement with the input gear  89 , thereby transmitting a driving force from the drive shaft  81 A to the input gear  89 . The driving force transmitted to the input gear  89  is then transmitted to the sheet supply roller  25  through the toothed timing pulley  91 , the toothed timing belt  93 , and the toothed timing pulley  92 . As a result, the sheet supply roller  25  is rotated in the feeding direction. 
         [0063]    When the sun gear  81  is rotated in a clockwise direction in  FIG. 7B , the planetary gear  82  is swingingly moved about the sun gear  81  in a direction the same as a direction in which the sun gear  81  is rotated, that is, in the clockwise direction. As a result, as shown in  FIG. 7B , the planetary gear  82  is moved away from the input gear  89  to be disengaged from the input gear  89 . Accordingly, rotation of the sheet supply roller  25  is stopped. 
         [0064]    That is, when the drive shaft  81 A is driven to rotate in the clockwise direction in  FIG. 7B  so as to rotate the sun gear  81  in the clockwise direction, the planetary gear  82  assembled to the lever  85  is swingingly moved about the sun gear  81  in the clockwise direction while rotating in the counterclockwise direction, so that the planetary gear  82  is moved away from the input gear  89  and disengaged from the input gear  89 , thereby interrupting transmission of the driving force from the drive shaft  81 A to the input gear  89 . As a result, the driving force is not transmitted to the sheet supply roller  25 , and thus, rotation of the sheet supply roller  25  is interrupted. 
         [0065]    Further, as shown in  FIGS. 7A and 7B , the main support portion  70  rotatably supports the re-conveying drive shaft  68 A. The re-conveying drive shaft  68 A is adapted to drive (rotate) the fourth conveying roller  68  through the gear  68 B rotatable integrally with the re-conveying drive shaft  68 A. 
         [0066]    As shown in  FIG. 8 , the main support portion  70  is provided with a plurality of bearing portions  72 , a plurality of bearing portions  76 , and a plurality of bearing portions  78 . Each bearing portion  72  serves to support the shaft  28 , and the shaft  28  is rotatable relative to the bearing portion  72 , Each bearing portion  76  serves to support the re-conveying drive shaft  68 A, and the re-conveying drive shaft  68 A is rotatable relative to the bearing portion  76 . Each bearing portion  78  serves to support the drive shaft  81 A, and the drive shaft  81 A is rotatable relative to the bearing portion  78 . 
         [0067]    The arm portion  26 D of the sheet supply arm  26  and the shaft  28  are positioned at a center portion of the main support portion  70  in the rightward/leftward direction (i.e. widthwise direction). The drive shaft  81 A and the re-conveying drive shaft  68 A extend rightward from the center portion of the main support portion  70  in the rightward/leftward direction and parallel to each other, and protrude rightward from a right side wall of the main support portion  70 . The drive shall  81 A and the re-conveying drive shaft  68 A. extend parallel to the shaft  28  and are independent of the shaft  28 . 
         [0068]    The drive shaft  81 A has a right end portion at which a gear  81 C is provided. The re-conveying drive shaft  68 A has a right end portion at which a gear  68 C is provided. A motor  95  ( FIG. 6 ) adapted to generate a driving force is provided in the printer unit  11 . The driving force is transmitted from the motor to the gear  81 C and the gear  68 C to rotate the drive shaft  81 A and the re-conveying drive shaft  68 A, respectively, so that the sheet supply roller  25  and the fourth conveying roller  68  are rotated, as described above. More specifically, the motor  95  can rotate in a first direction and in a second direction opposite to the first direction. When the motor  95  rotates in the first direction, the drive shaft  81 A and the sun gear  81  rotate in the counterclockwise direction. When the motor  95  rotates in the second direction, the drive shaft  81 A and the sun gear  81  rotate in the clockwise direction. 
         [0069]    The drive shaft  81 A and the planetary gear mechanism  80  are positioned frontward of the shaft  28 . In other words, the drive shaft  81 A and the planetary gear mechanism  80  are positioned opposite to the sheet supply roller  25  with respect to the shaft  28 . Further, the drive shaft  81 A and the planetary gear mechanism  80  are positioned partly superposed with the shaft  28 , the sheet supply arm  26 , and the fourth conveying roller  68  along the stacked surface  16 A in the frontward/rearward direction ( FIGS. 7A ,  7 B). 
         [0070]    Further, the sheet supply roller  25  and the planetary gear mechanism  80 , the driving force transmission mechanism including the input gear  89 , the toothed timing pulley  91 , the toothed timing pulley  92  and the toothed timing belt  93  are aligned in the frontward/rearward direction. Further, a distance between an outer (right) end face (claimed first end face) of the right roller segment of the sheet supply roller  25  and an outer (left) end face (claimed third end face) of the left roller segment of the sheet supply roller  25  is greater than a length (claimed first length) in the axial direction of the driving force transmission mechanism, and also greater than a length (claimed second length) in the axial direction of the planetary gear mechanism  80 . 
         [0071]    [Operational Advantages and Modifications] 
         [0072]    As described above, in the image forming device  10  according to the present embodiment, the planetary gear mechanism  80  and the drive shaft  81 A are provided independently from the shaft  28  about which the sheet supply arm  26  is pivotally moved. Hence, this configuration can suppress unstable transmission of the driving force relative to the sheet supply roller  25 , thereby preventing occurrence of skew feeding when the recording sheet  50  is fed by the sheet supply roller  25 . As a result, the recording sheet  50  can be fed stably. 
         [0073]    Further, according to the present embodiment, the sun gear  81  and the planetary gear  82  are provided not at the pivotally movable sheet supply arm  26  but at the main support portion  70  fixed to the main frame  14  of the image forming device  10 . In case the sun gear  81  and the planetary gear  82  are provided in the sheet supply arm  26 , a space is required for swinging movement of the planetary gear mechanism  80  in conjunction with pivotal movement of the sheet supply arm  26 . Accordingly, the configuration according to the present embodiment can downsize the image forming device  10  in its entirety, compared to the latter configuration. 
         [0074]    Further, the input gear  89  is rotatable about the shaft  28 . A force applied to the input gear  89  when the planetary gear  82  is moved toward and away from the input gear  89  is unlikely to act in a direction to pivotally move the sheet supply arm  26 . Hence, this configuration can avoid change in the contact state between the sheet supply roller  25  and the recording sheet  50  in accordance with the contacting and separating movement of the planetary gear  82  relative to the input gear  89 . 
         [0075]    Further, the shaft  28  and the drive shaft  81 A are supported to the main support portion  70  through the bearing portions  72  and the bearing portions  78 , respectively, and are arranged parallel to each other. Hence, the positional relationship between the shaft  28  and the drive shaft  81 A can be reliably maintained. Thus, unstable transmission of the driving force relative to the sheet supply roller  25  can be suppressed more reliably. Accordingly, the recording sheet  50  can be fed more stably. 
         [0076]    Further, in the image forming device  10  according to the present embodiment, the drive shaft  81 A and the planetary gear mechanism  80  are positioned opposite to the sheet supply roller  25  with respect to the shaft  28 . In other words, the drive shaft  81 A and the planetary gear mechanism  80  are positioned frontward of the shaft  28 . Further, the drive shaft  81 A, and the planetary gear mechanism  80  are provided at a position partially overlapping with the sheet supply arm  26  along the stacked surface  16 A. Further, the drive shaft  81 A and the planetary gear mechanism  80  are provided at a position partly overlapping with the fourth conveying roller  68  along the stacked surface  16 A. Thus, the image forming device  10  can also be downsized in the vertical direction. 
         [0077]    Further, in the image forming device  10  according to the present embodiment, the mechanism for pivotally moving the sheet supply arm  26 , such as the lever portion  26 B, is provided at a left side of the sheet supply arm  26  (the arm portion  26 D), while the mechanism for rotating the sheet supply roller  25  and the fourth conveying roller  68 , such as the drive shaft  81 A and the re-conveying drive shaft  68 A, is provided at a right side of the sheet supply arm  26  (the arm portion  26 D). Thus, these two mechanisms are separately disposed at one and another sides in the widthwise direction, which leads to further downsizing of the image forming device  10 . 
         [0078]    In addition, the drive shaft  81 A and the re-conveying drive shaft  68 A both extend to a right side of the main support portion  70 . Simplification of the driving system for driving the drive shaft  81 A and the re-conveying drive shaft  68 A leads to further downsizing of the image forming device  10 . 
         [0079]    Further, various modifications are conceivable. 
         [0080]    For example, the driving force may be transmitted from the input gear  89  to the sheet supply roller  25  by gears only. However, according to the above-described embodiment, the driving force is transmitted from the input gear  89  to the sheet supply roller  25  through the toothed timing belt  93 . In this case, a thickness of the arm portion  26 D in a direction perpendicular to a direction from the input gear  89  to the sheet supply roller  25  can be made smaller than that in the former configuration. Hence, the image forming device  10  can be further reliably downsized. Further, the input gear  89  is not necessarily rotated about an axis of the shaft  28 . The input gear  89  may be supported to a shaft other than the shaft  28 . 
         [0081]    While the present invention has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the present invention.