Abstract:
A sheet feeding device to feed a sheet in a sheet stack into a sheet feeding path is provided. the sheet feeding device includes a feed roller configured to contact the sheet stack and feed the sheet in a feeding direction, a guide member, having a guide surface, which is configured to contact a side of the sheet fed by the feeding roller, to guide the sheet being fed along a guiding direction, and a shifting unit to shift the feed roller in a direction toward the guide surface before the feed roller is rotated.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2008-080625 filed on Mar. 26, 2008, the entire subject matter of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    An aspect of the present invention relates to a sheet feeding device having a roller to pick up a sheet from a sheet stack to feed in a sheet feeding path and an image forming apparatus having the sheet feeding device. 
         [0004]    2. Related Art 
         [0005]    Conventionally, a sheet feeding device having a roller to pick up a topmost sheet from a stack of sheets in, for example, an image forming apparatus has been known. In the sheet feeding device, a feed roller is provided in a position to become in contact with the sheet stack, and as the roller rotates, the topmost sheet in the stack is separated from the rest of the stack and fed in the sheet feeding path. Further, the sheet feeding device may be provided with a side guide, with which a side of the recording sheet becomes in contact so that the picked up sheet is guided in the sheet feeding path. In a sheet feeding device disclosed in Japanese Patent Publication No. 3864936, for example, a feed roller is angled toward the side guide with respect to a direction of the sheet to be carried so that the sheet is urged to the side guide and steadily let in the sheet feeding path in a correct posture. 
       SUMMARY 
       [0006]    When the recording sheet is picked up from the sheet stack and fed in the sheet feeding path, more than one recording sheets may be picked up by the feed roller due to friction and static clings caused in between the sheets. Therefore, in the above-referenced sheet feeding device, a lower side of the recording sheet picked up by the feed roller is rubbed onto a frictional member so that the following sheets can be seized by the frictional member and separated from the topmost sheet. 
         [0007]    In the above sheet feeding device, however, the sheets may not always be separated steadily depending on materials, qualities, and conditions of the cuts. 
         [0008]    In view of the above drawbacks, the present invention is advantageous in that a sheet feeding device with a side guide capable of preventing a plurality of overlaid sheets from being fed and an image forming apparatus having the sheet feeding device are provided. 
         [0009]    According to an aspect of the present invention, a sheet feeding device to feed a sheet in a sheet stack into a sheet feeding path is provided. The sheet feeding device includes a feed roller configured to contact the sheet stack and feed the sheet in a feeding direction, a guide member, having a guide surface, which is configured to contact a side of the sheet fed by the feeding roller, to guide the sheet being fed along a guiding direction, and a shifting unit to shift the feed roller in a direction toward the guide surface before the feed roller is rotated. 
         [0010]    According to the above configuration, the side of the sheet being fed by the feed roller is urged to the guide surface of the guide member, and the feed roller is shifted toward the guide surface before the feed roller starts being rotated. In this regard, a topmost sheet can be urged toward the guide surface by the feed roller, distinctly separated from the sheet stack, and fed in the sheet feeding path. 
         [0011]    According to another aspect of the present invention, an image forming apparatus is provided. The image forming apparatus includes a sheet feeding device to feed a sheet in a sheet stack into a sheet feeding path, and an image forming unit to form the image on the sheet being fed by the sheet feeding device, The sheet feeding device includes a feed roller configured to contact the sheet stack and feed the sheet in a feeding direction, a guide member, having a guide surface, which is configured to contact a side of the sheet fed by the feeding roller, to guide the sheet being fed along a guiding direction, and a shifting unit to shift the feed roller in a direction toward the guide surface before the feed roller is rotated. 
         [0012]    According to the above configuration, a topmost sheet can be urged toward the guide surface by the feed roller and distinctly separated from the sheet stack so that the topmost sheet can be fed in the sheet feeding path and the image can be formed thereon. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0013]      FIG. 1  is a cross-sectional side view of a laser printer according to an embodiment of the present invention. 
           [0014]      FIG. 2  is a perspective view of a sheet feeder assembly in a feeder unit according to the embodiment of the present invention. 
           [0015]      FIG. 3  is a plane view of a sheet tray of the laser printer with a sheet feeder assembly according to the embodiment of the present invention. 
           [0016]      FIGS. 4A and 4B  are exploded view of a universal joint in the sheet feeder assembly according to the embodiment of the present invention. 
           [0017]      FIG. 5  is a perspective view of a gear assembly in a feeder unit according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Hereinafter, an embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings.  FIG. 1  is a cross-sectional side view of a laser printer  1  according to an embodiment of the present invention. In  FIG. 1 , a right-hand side is referred to as front of the laser printer  1 , and a left-hand side is referred to as rear of the laser printer  1 . Further, a near side and a far side are respectively referred to as left and right of the laser printer  1 . 
         [0019]    Overall configuration of the laser printer  1  according to the present embodiment will be described. The laser printer  1  includes a feeder unit  4  to feed a recording sheet  3 , an image forming unit  5  to form an image on the recording sheet  3 , and a casing  2  in which the feeder unit  4 , the image forming unit  5 , and other components are stored. On a front side of the casing  2 , an openable/closable front cover  2   a  is provided. The front cover  2   a  covers an opening in which a process cartridge  30  is removably set. Configuration of the process cartridge  30  will be described later in detail. 
         [0020]    The feeder unit  4  includes a sheet tray  11 , a holder plate  51 , and a lifter plate  52 . The sheet tray  11  is removably attached to a bottom portion of the casing  2 . A stack of recording sheets  3  is placed in the sheet tray  11 . The holder plate  51  is provided to hold the recording sheets  3  in a position to be fed in the sheet tray  11  and is pivotable about a rear end thereof. The lifter plate  52  is provided underneath the holder plate  51  to uplift the holder plate  51 . The lifter plate  52  is pivotably attached to the bottom of the sheet tray  11  at a rear end  53  thereof. The lifter plate  52  can be pivoted about the rear end  53  by driving force provided by a main body of the laser printer  1  from a ready position ( FIG. 1 ). Thus, a front portion of the holder plate  51  is uplifted by the lifter plate  52 , and the front portion of the recording sheets in the sheet tray  11  is uplifted accordingly. The configuration of the lifter plate  52  is known and disclosed in, for example, Japanese Patent Provisional Publication No. 2006-176321. In the present embodiment, the main body refers to the laser printer  1  excluding the sheet tray  11  and components included in the sheet tray  11 . 
         [0021]    The feeder unit  4  further includes a feed roller  61 , which is provided above the front end of the sheet feed tray  11 , and a separator roller  62  in a position nearer to the front with respect to the feed roller  61 . The feed roller  61  is in a position to be in contact with a topmost recording sheet  3  in the uplifted sheet stack in the sheet tray  11 . The separator roller  62  is arranged to mutually abut a separator pad  12 , which is a piece made of a material with resiliency. The separator pad  12  is provided with expanding force by a spring (not shown) and presses the recording sheet  3  being carried by the separator roller  62  on a surface opposite from a surface being in contact with an outer peripheral surface of the separator roller  62 . 
         [0022]    Thus, the recording sheet  3  picked up by the feed roller  61  is nipped between the separator roller  62  and the separator pad  12  to be separated by friction occurring therebetween from a successive recording sheet which may otherwise be carried along with the recording sheet  3 . The feeder unit  4  further includes a dust remover roller  13  and a paired roller  14 , which are arranged to oppose to each other. The recording sheet  3  is carried between the dust remover roller  13  and the paired roller  14  and turned an orientation thereof toward the rear of the laser printer  1  along the sheet feeding path  19 . Further, a pair of register rollers  15  is provided in the sheet feeding path  19  approximately above the feed roller  61 . The recording sheet  3  is thus forwarded to the image forming unit  5 . 
         [0023]    The image forming unit  5  provided approximately above the feeder unit  4  in the casing  2  includes a scanner unit  20 , a process cartridge  30 , and a fixing unit  40  and forms an image on a surface of the recording sheet  3  electrophotgraphically. 
         [0024]    The scanner unit  20  is disposed at an upper portion inside the casing  2 , and includes a laser emitter (not shown), a rotatable polygon mirror  21 , lenses  22  and  23 , and reflecting mirrors  24 ,  25 . Laser beam emitted from the laser emitter according to predetermined image data is reflected by or transmitted through the polygon mirror  21 , the lens  22 , the reflecting mirror  24 , the lens  23 , and the reflecting mirror  25  as shown in a dotted chain line in  FIG. 1 . The transmitted laser beam is thus irradiated to scan a surface of a photosensitive drum  23  in the process unit at a high speed. 
         [0025]    The process cartridge  30 , which can be detached from the casing  2 , is disposed approximately below the scanner unit  20  and includes a drum cartridge  30 A, which holds a photosensitive drum  32  therein, and a toner cartridge  30 B, which is removably attached to the photosensitive drum cartridge  30 A and contains toner T therein. 
         [0026]    The drum cartridge  30 A is provided with a case  31 , in which the photosensitive drum  32 , a scorotoron charger  33 , and a transfer roller  34  are housed. The toner cartridge  30 B is provided with a toner case  35 , in which a developing agent (i.e., toner T) is contained, a developing roller  36 , a toner supplier roller  38 , and an agitator  39 . 
         [0027]    The toner T in the toner case  35  is agitated by the agitator  39  and supplied to the developing roller  36  as the toner supplier roller  38  rotates in a direction indicated by an arrow in  FIG. 1  (i.e., the counterclockwise direction). Between the toner supplier roller  38  and the developing roller  36 , the toner T being transferred is frictionally charged positively and carried according to rotation of the developing roller in a direction indicated by an arrow (i.e., the clockwise direction) to a portion between a toner thickness adjusting blade B and the developing roller  36  in which the toner is further and substantially charged. Thus, the toner is evenly applied over the surface of the developing roller  36  to form a thin layer. 
         [0028]    The photosensitive drum  32  is provided to be rotatable in the counterclockwise direction and arranged in parallel with and to be in contact with the developing roller  36 . The photosensitive drum  32  includes a drum body (not shown), which is grounded, and a positively chargeable photosensitive layer (not shown) to cover the drum body. 
         [0029]    The scorotoron charger  33  is arranged approximately above the photosensitive drum  32  in a position to be substantially apart from the photosensitive drum  32 . The scorotoron charger  33  is a corona charger which electrically discharges through electrically charging wires (not shown). The surface of the photosensitive drum  32  is uniformly charged with positive polarity to a predetermined level by the scorotoron charger  33 . 
         [0030]    The transfer roller  34  is arranged immediately below the photosensitive drum  32  to be in parallel with the rotation axis of the photoconductive drum  32  and is supported by the drum case  31  rotatably to rotate in the counterclockwise direction. The transfer roller  34  includes a rotation shaft (not shown) made of a metal and a roller layer (not shown) made of conductive rubber to cover the rotation shaft. On the surface of the transfer roller  34 , a predetermined level of transfer bias of a reverse polarity to the photosensitive drum  32  is applied so that the toner image developed on the surface of the photosensitive drum  32  is transferred to the surface of the recording sheet  3  to form the normal image when the recording sheet  3  is carried in between the photosensitive drum  32  and the transfer roller  34 . 
         [0031]    The surface of the photosensitive drum  32  is exposed to laser beam that scans the surface of the photosensitive drum  32  in parallel with the rotation axis according to image data, and a latent image is formed on the surface of the photosensitive drum  32 , as regions where the latent image is formed gains a lower potential due to an effect of the laser beam. As the photoconductive drum  32  with the latent image on the surface thereof is rotated, the toner positively charged on the surface of the developing roller  34  is transferred and adhered to the lower-potential region, which corresponds to the latent image on the surface of the photosensitive drum  32 . Thus, the latent image is developed to be a reverse image. 
         [0032]    The fixing unit  40  is disposed on a downstream side of the sheet feeding path  19  with respect to the process cartridge  30 . The fixing unit  40  includes a heat roller  41  with a heat source (not shown) and a pressure roller  42 , which is pressed to be in contact with the heat roller  41 . The toner image transferred onto the recording sheet  3  in the process cartridge  30  is thermally fixed thereto when the recording sheet  3  is fed between the heat roller  41  and the pressure roller  42 . The recording sheet  3  fed along a discharging path  44  is passed to a pair of discharge rollers  45  to be discharged out of the laser printer  1 . The discharged recording sheet  3  is received by a discharge tray  46 . 
         [0033]    Next, configuration of the feeder unit  4  will be described in detail. The feed roller  61  and the separator roller  62  are respectively provided with a feed roller gear  61   a  and a separator roller gear  62   a , which are respectively rotatable integrally with the feed roller  61  and the separator roller  62 . The feed roller gear  61   a  and the separator roller gear  62   a  are engaged via an idle gear  63   a  and rotate substantially synchronously in a same direction. 
         [0034]    The feed roller  61 , the feed roller gear  61   a , the separator roller  62 , the separator roller gear  62   a , and the idle gear  63   a , and a roller holder  65  are included in a feed roller assembly  60 , and the roller holder  65  rotatably supports the feed roller  61 , the separator roller  62 , and the idle gear  63   a .  FIG. 2  is a perspective view of the feed roller assembly  60  in the feeder unit  4  according to the embodiment of the present invention. It is to be noted that a right-hand side in  FIG. 2  corresponds to a right end of the laser printer  1 , and a left-hand side in  FIG. 2  corresponds to a left end of the laser printer  1 , as indicated by arrows in  FIG. 2 . The roller holder  65  is rotatable about a rotation shaft  62   b  of the separator roller  62 , and one end of the roller holder  65  close to the feeder roller  61  is connected with the right end of a lifting arm  71 , which will be described later in detail. The separator roller  62  is coupled to a separator roller driving shaft  73  through a universal joint  72 . The separator roller driving shaft  73  is rotated by a gear assembly  90 , which is arranged on the left end of the sheet tray  11 . 
         [0035]    The lifting arm  71  is swingably supported by the main body of the laser printer  1  at a fulcrum point  71   a , which is at an approximate center of the lifting arm  71 . The lifting arm  71  is formed to have an opening  71   b , in which a projection  65   a  of the roller holder  65  is inserted, on the right end thereof. The lifting arm  71  is further provided with a tension coil spring  74  in the vicinity of the left end thereof, which pulls the lifting arm  71  upward. By effects of the tensile force by the tension coil spring  74  and a weight of the feed roller assembly  60 , the lifting arm  71  is biased to rotate about the fulcrum point  71   a  in the counterclockwise direction in  FIG. 2  (i.e., the right end being downward). According to the biasing force, the feed roller  61  is pressed onto the topmost recording sheet in the sheet stack held by the holder plate  51 . 
         [0036]    The separator roller  62  and the separator roller driving shaft  73  are held by bearing holders  76 ,  77 , and  78 , which are attached to a frame (not shown) of the main body to support the image forming unit  5 . While being held by the bearing holders  76 ,  77 , and  78 , the separator roller  62  and the separator roller driving shaft  73  are rotatable about an axis and slidable in a longitudinal direction in the bearing holders  76 ,  77 , and  78 .  FIG. 3  is a plane view of the sheet tray  11  with the feed roller assembly  60  according to the embodiment of the present invention. As shown in  FIG. 3 , the separator roller driving shaft  73  is arranged in the right-left direction (i.e., a widthwise direction of the recording sheet). Meanwhile, the feed roller  61  and the separator roller  62  are oriented to have the left ends thereof being angled toward the front. The bearing holder  76  is provided in an angled position toward the front with respect to the bearing holders  77 ,  78  and holds a bearing  65   b , which rotatably supports the rotation shaft  62   b  of the separator roller  62 . The bearing holder  78  rotatably and slidably supports the separator roller driving shaft  73  at an approximately center thereof. The bearing holder  77  rotatably and slidably supports the separator roller driving shaft  73  at an approximate right end thereof. The bearing holder  77  further rotatably and slidably supports the rotation shaft  62   b  of the separator roller  62  at an engageable portion  72   d.    
         [0037]    Configuration of the universal joint  72  will be described with reference to  FIGS. 4A and 4B .  FIGS. 4A and 4B  are exploded view of the universal joint  72  in the feed roller assembly  60  according to the embodiment of the present invention. The universal joint  72  includes a pair of projections  72   a , which are provided on an outer periphery of a right-end portion  73   a  of the separator roller driving shaft  73  to be apart from each other approximately at 180 degrees, and the engageable portion  72   d , which is formed integrally on the left end of the rotation shaft  62   b . The engageable portion  72   d  includes a pair of grooves  72   b , to which the projections  72   a  are respectively inserted, and a recess  72   c  to receive a tip end of the right-end portion  73   a.    
         [0038]    According to the above configuration, when the projections  72   a  are inserted in the grooves  72   b , rotation of the separator roller driving shaft  73  is conveyed to the separator roller  62 . The engageable portion  72   d  is held by the bearing holder  77  to be rotatable about the rotation shaft  62   b  and slidable in the axial direction of the rotation shaft  62   b . The bearing holders  77 ,  78  are formed to have openings, through which the separator roller driving shaft  73  is penetrated. The openings are formed to have shapes of ovals, with longitudinal sides being parallel with each other, so that the separator roller driving shaft  73  is movable in parallel with the longitudinal sides (see  FIG. 2 ). A position of the right-end portion of the separator roller driving shaft  73  is defined by the universal joint  72 . 
         [0039]    The feed roller assembly  60  is biased toward the universal joint  72  by a compression coil spring  81 , which is provided between a right side of the roller holder  65  and the bearing holder  76  (see  FIGS. 2 and 3 ). Further, the separator roller driving shaft  73  is provided with a separator roller driving gear  73 , which rotates integrally with the separator roller driving shaft  73  at the left end thereof, and the separator roller driving shaft  73  is biased toward the universal joint  72  by a compression coil spring  82  at the left side of the separator roller driving gear  73 . The compression force of the compression coil spring  82  is configured to be greater than the compression force of the compression coil spring  81  so that the separator roller driving shaft  73  and the feed roller assembly  60  are biased overall toward the right. 
         [0040]    Further, the sheet tray  11  is provided with guides  83 ,  84  at the bottom, which protrudes through holes  51   a ,  51   b  respectively formed on the holder plate  51  to project from the holder plate  51  (see  FIG. 3 ). The guide  83  is fixed to the bottom of the sheet tray  11  and includes a guide surface  83   a , with which a left side end of the recording sheet  3  is in contact to guide the recording sheet  3  in the sheet feeding path. The guide  84  is provided to the sheet tray  11  and slidable in the right-left direction. The guide  84  includes a guide surface  84   a , with which a right side end of the recording sheet  3  is in contact to guide the recording sheet  3  in the sheet feeding path. Furthermore, the separator pad  12  is provided with shaft portions  12   a , which extend from the both ends of the separator pad  12  in order to swingably support the separator pad  12 . The shaft portions  12   a  are arranged to be parallel with the rotation shaft  62   b  of the separator roller  62 . Thus, the separator pad  12  can become in line-contact with the surface of the separator roller  62 . 
         [0041]    Next, the gear assembly  90  will be described with reference to  FIG. 5 .  FIG. 5  is a perspective view of the gear assembly  90  to drive the separator roller driving shaft  73  according to the embodiment of the present invention. The gear assembly  90  is provided with a sector gear  91  to be rotated about a shaft hole  91   a , into which a shaft (not shown) extending in the right-left direction is fitted. The sector gear  91  includes a substantially disk-shaped cam  92 , an input gear  93  formed on a right side of the cam  92 , to which driving force from a driving system (not shown) is conveyed, and an output gear  94  formed on a left side of the cam  92 , which conveys the driving force provided through the input gear  93  to the separator roller driving gear  73   c . The output gear  94  is not formed on an entire circumference corresponding to the circumference of the disk-shape of the cam  92 , but is formed to have a teeth-absent portion  94   a , in which no tooth to convey the driving force of the cam  92  is provided. Therefore, when the separator roller driving gear  73   c  is rotated to meet the teeth-absent portion  94   a , the driving force from the input gear  93  is not conveyed to the separator roller driving gear  73   c  so that the feed roller  61  and the separator roller  62  can be rotated without being affected by the separator roller driving shaft  73 . 
         [0042]    The cam  92  is formed to have a stopper projection  92   a  (see  FIG. 2 ) on the circumference thereof so that rotation of the sector gear  91  is stopped thereby when the stopper projection  92   a  is engaged with a solenoid-operable lever  95 , which is provided underneath the sector gear. The solenoid-operable lever  95  is formed to have an engaging portion  95   b , which can be engaged with the stopper projection  92   a  to stop rotation of the sector gear  91  when the solenoid-operable lever  95  is rotated about a shaft hole  95   a  in the counterclockwise direction in  FIG. 2  by a solenoid (not shown) to be in a ready position. When the solenoid-operable lever  95  is rotated in the clockwise direction, the stopper projection  92   a  is released, and the sector gear  91  is allowed to rotate. 
         [0043]    The cam  92  is further formed to have a convex  92   b , which projects leftward, on a portion on the circumference and corresponding to the teeth-absent portion  94   a  of the output gear  94 . When the convex  92   b  becomes in contact with a cam-follower sleeve  99 , which is coupled to the separator roller driving shaft  73 , and presses the separator roller driving gear  73   c  leftward, the separator roller driving shaft  73  along with the feed roller assembly  60  is displaced leftward against the expanding force of the compression coil spring  82 . 
         [0044]    Next, movements of the gear assembly  90  and effects caused by the movements will be described in detail. When the engaging portion  95   b  of the solenoid-operable lever  95  is in the ready position to be engaged with the stopper projection  92   a  (see  FIG. 5 ), the teeth-absent portion  94   a  is in a position to confront the separator roller driving gear  73   c , and the convex  92   b  of the cam  92  is not in contact with the cam-follower sleeve  99 . When a sheet feeding operation starts, the sector gear  91  is rotated in the clockwise direction, which is indicated by an arrow in  FIG. 5 . Accordingly, the convex  92   b  comes in contact with the cam-follower sleeve  99  so that the separator roller driving shaft  73  and the feed roller assembly  60  are shifted leftward from the biased positions according to the displacement of the cam-follower sleeve  99 . In this regard, the feed roller  61  and the separator roller  62  are pressed onto the surface of the recording sheet  3  due to the tensile force of the tension coil spring  74 . Therefore, the topmost recording sheet  3  can be distinctly separated from the sheet stack in the sheet tray  11  by the feed roller  61  and the separator roller  62 , which are slid leftward on the topmost recording sheet  3  and urge the topmost recording sheet  3  against the guide surface  83   a.    
         [0045]    When the cam  92  is rotated further and the convex  92   b  passes by the separator roller driving gear  73   c , the separator roller driving shaft  73  and the feed roller assembly  60  return to the biased positions. Further, the output gear  94  is engaged with the separator roller driving gear  73   c . Accordingly, the feed roller  61  and the separator roller  62  are rotated by the driving force conveyed through the separator roller driving shaft  73 . In this regard, it is to be noted that the feed roller  61  and the separator roller  62  are oriented to have the left ends thereof being angled toward the front; thus, a direction in which the feed roller  61  feeds the recording sheet  3  and a direction in which the separator roller  62  transports the recording sheet  3  are identical and angled toward the guide surface  83   a  with respect to a direction parallel with the guide surface  83   a . Therefore, the feed roller  61  and the separator roller  62  can again urge the recording sheet  3  to the guide surface  83   a  to separate from the sheet stack in the sheet tray so that a successive recording sheet in the sheet stack can be prevented from being fed along with the topmost recording sheet  3 . Further, a direction, in which the separator pad  12  provides the resistance to separate the successive recording sheet from the topmost recording sheet  3 , is opposite from the direction in which the separator roller  62  forwards the topmost recording sheet  3 . Thus, the recording sheet  3  can be effectively separated from the successive sheet by the cooperative effect of the movements of the separator roller  62  and the separator pad  12 . 
         [0046]    According to the above embodiment, the recording sheet  3  can be distinctly separated from the sheet stack and fed in the image forming unit  5 . Further, when the feed roller  61  and the separator roller  62  are shifted in the right-left direction, the separator roller driving gear  73   c  confronts the teeth-absent portion  94   a  of the output gear  94  so that the feed roller  61  and the separator roller  62  are released from the rotating force of the separator roller driving shaft  73 . Therefore, the feed roller  61  and the separator roller  62  can travel on the recording sheet  3  easily so that the topmost recording sheet  3  can be separated from the sheet stack even more effectively. 
         [0047]    Although an example of carrying out the invention has been described, those skilled in the art will appreciate that there are numerous variations and permutations of the sheet feeding device and an image reading apparatus that fall within the spirit and scope of the invention as set forth in the appended claims. It is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or act described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. 
         [0048]    For example, in the above embodiment, the separator roller driving shaft  73  is shifted in the direction perpendicularly to the sheet feeding direction by the cam-follower sleeve  99  pressed onto the side of the cam  92 . However, the cam  92 , which is a face cam as shown in  FIG. 2 , can be replaced with a grooved cam. 
         [0049]    For another example, the separator roller driving shaft  73  can be replaced with another configuration that can be embedded in, for example, the lifting arm  71 . Furthermore, the sheet feeding device may not necessarily be installed in the image forming apparatus, but may be configured independently from the image forming apparatus. Moreover, the sheet feeding device may be a device to feed sheets in an apparatus other than an image forming apparatus.