Patent Publication Number: US-10315868-B2

Title: Sheet feeding apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet feeding apparatus applicable to an image forming apparatus such as a printer and to an image forming apparatus including the same. 
     Description of the Related Art 
     Hitherto, there is known a sheet feeding apparatus comprising a first storage portion in which a sheet is stacked, a feed roller feeding the sheet from the first storage portion, a second storage portion arrayed horizontally with the first storage portion, and a sheet bundle shifting plate shifting sheets within the second storage portion collectively to the first storage portion as disclosed in Japanese Patent No. 3411135 for example. The sheet feeding apparatus also includes a shift home sensor. A state of the shift home sensor is determined when a sheet feed cassette is set after turning the power ON. The shift home sensor is turned ON when a back fence (sheet shift portion) is located at a home position and is turned OFF when the back fence is not located at the home position. Then, in a case when the sheet feed cassette is drawn out of an apparatus body while shifting the sheets during which the sensor is turned OFF, the back fence is moved when the sheet feed cassette is set again to continue the operation of shifting the sheet bundle from the second storage portion to the first storage portion. 
     However, in a case when the sheet feed cassette is erroneously drawn out of the apparatus body while shifting the sheets, there is a possibility of causing the following problem in resetting the sheet feed cassette by noticing that the sheet is left in the first storage portion in the sheet feeding apparatus described above. That is, it is conceivable to erroneously end up setting a sheet bundle to a back side of the back fence (on the second storage portion side of the back fence) stopping on the first storage portion side in setting the sheet bundle to the sheet feed cassette drawn out of the apparatus body. In this case, the back fence cannot return to its home position on the second storage portion side because the sheet bundle stacked on the back of the back fence obstructs. Thereby, such problems that the apparatus body stops to operate and an alarm is indicated occur, and recovery is not made until when an user removes the sheet bundle erroneously stacked as described above, thus inviting a cumbersome resetting work. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the invention, a sheet feeding apparatus comprises an apparatus body, a feed member feeding a sheet, a sheet storage member configured to be movable to an attachment position where the sheet storage member is attached to the apparatus body and to a draw-out position where the sheet storage member is drawn out of the attachment position, and comprising a first sheet storage portion in which the sheet to be fed by the feed member is stored and a second sheet storage portion being provided adjacent horizontally to the first sheet storage portion and storing a sheet, a sheet shifting portion configured to shift the sheet in the second sheet storage portion to the first sheet storage portion, the sheet shifting portion being capable of positioning at a first position and a second position farther than the first position from the first sheet storage portion, a driving unit moving the sheet shifting portion by linking with the sheet shifting portion in a state in which the sheet storage member is located at the attachment position, and a moving portion configured to move the sheet shifting portion from the first position to the second position in a state in which the link of the sheet shifting portion with the driving unit is disconnected in response to a drawing operation of the sheet storage member from the apparatus body in a state in which the sheet shifting portion has moved to the first position by the driving unit. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view schematically illustrating a configuration of a laser beam printer, i.e., an image forming apparatus, including a sheet feeding apparatus of an embodiment. 
         FIG. 2A  is a section view schematically illustrating a feeding state of the sheet feeding apparatus of the present embodiment. 
         FIG. 2B  is a section view schematically illustrating a feed finished state of the sheet feeding apparatus of the present embodiment. 
         FIG. 3A  is a section view schematically illustrating a sheet bundle shifting state of the sheet feeding apparatus of the present embodiment. 
         FIG. 3B  is a section view schematically illustrating a sheet bundle shifting completion state of the sheet feeding apparatus of the present embodiment. 
         FIG. 3C  is a section view schematically illustrating a feed restarting state of the sheet feeding apparatus of the present embodiment. 
         FIG. 4A  is a section view schematically illustrating a state corresponding to the state in  FIG. 2B  of a forced moving mechanism of the sheet feeding apparatus of the present embodiment. 
         FIG. 4B  is a section view schematically illustrating a state corresponding to the state in  FIG. 3B  of the forced moving mechanism of the sheet feeding apparatus of the present embodiment. 
         FIG. 4C  is a section view schematically illustrating a state in which a sheet bundle moving member is forcibly moved to a second sheet storage portion by the forced moving mechanism of the sheet feeding apparatus of the present embodiment. 
         FIG. 5A  is a plan view schematically illustrating a state corresponding to the state in  FIG. 4A  of the forced moving mechanism of the sheet feeding apparatus of the present embodiment. 
         FIG. 5B  is a plan view schematically illustrating a state corresponding to the state in  FIG. 4B  of the forced moving mechanism of the sheet feeding apparatus of the present embodiment. 
         FIG. 6  is a plan view schematically illustrating a state in which a sheet feed cassette of the sheet feeding apparatus of the present embodiment is drawn out of an apparatus body. 
         FIG. 7  is a section view schematically illustrating a forced moving mechanism of a sheet feeding apparatus of a first modified example. 
         FIG. 8  is a section view schematically illustrating a forced moving mechanism of a sheet feeding apparatus of a second modified example. 
         FIG. 9  is a plan view specifically illustrating the sheet feeding apparatus of the present embodiment. 
         FIG. 10  is a section view schematically illustrating the sheet feeding apparatus taken along a line A-A in  FIG. 9 . 
         FIG. 11  is a block diagram illustrating a control system of the image forming apparatus of the present embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described in detail below with reference to the drawings. At first, an image forming apparatus comprising a sheet feeding apparatus of the embodiment of the present invention will be described with reference to  FIG. 1 .  FIG. 1  is a section view schematically illustrating a laser beam printer, i.e., the image forming apparatus of the embodiments, seen from a front side of the apparatus. 
     Image Forming Apparatus 
     As illustrated in  FIG. 1 , the full-color laser beam printer (referred to simply as a ‘printer’ hereinafter)  201 , i.e., an image forming apparatus, includes an image forming apparatus body (referred to simply as an ‘apparatus body’ hereinafter)  201   a . The apparatus body  201   a  includes a control portion  67  controlling each part of the apparatus, an image forming portion  201   b , a fixing portion  220 , and an image reading apparatus  202  disposed substantially horizontally above the apparatus body  201   a.    
     The apparatus body  201   a  is provided with a discharge space S for discharging a sheet below the image reading apparatus  202 . Toner cartridges  215  are disposed under the discharge space S, and a plurality (three in the present embodiment) of sheet feeding apparatuses  51 ,  52 , and  53  is disposed at a lower part of the apparatus body  201   a . The apparatus body  201   a  is provided with attachment spaces, not illustrated, into/out of which sheet feed cassettes  91  and  92  described later in sheet feeding apparatuses  51  and  52  can be attached/drawn. The apparatus body  201   a  is also provided with an attachment space  15  (see  FIG. 6 ) into/out of which a sheet feed cassette  93  described later in the sheet feeding apparatus  53  can be attached/drawn. The attachment space  15  makes it possible for the sheet feeding apparatus  53  to attach/draw the sheet feed cassette  93  into/out of the apparatus body  201   a . The sheet feed cassette  93  is configured to be able to take an attachment position in which the sheet feed cassette  93  is attached to the apparatus body  201   a  and a draw-out position in which the sheet feed cassette  93  is drawn out of the apparatus body  201   a.    
     The image forming portion  201   b  is what adopts a four drum full-color system and includes a laser scanner  210  and four process cartridges  211  of forming four color toner images of yellow (Y), magenta (M), cyan (C), and black (K). 
     Here, each process cartridge  211  includes a photosensitive drum  212 , i.e., a photosensitive body, a charger  213 , a developer  214 , and a cleaner not illustrated. The image forming portion  201   b  also includes an intermediate transfer unit  201   c  above the process cartridge  211 . 
     The intermediate transfer unit  201   c  includes an intermediate transfer belt  216  wrapped around a driving roller  216   a  and a tension roller  216   b . The intermediate transfer unit  201   c  also includes primary transfer rollers  219  disposed inside of the intermediate transfer belt  216  and being in contact with an inner surface of the intermediate transfer belt  216  at positions facing the photosensitive drums  212 . The intermediate transfer belt  216  is composed of a film-like member, is in contact with the respective photosensitive drums  212  and is rotated in a direction of an arrow in  FIG. 1  by the driving roller  216   a  driven by a driving portion not illustrated. 
     The respective color toner images having negative polarity on the photosensitive drums  212  are sequentially superimposed and transferred onto the intermediate transfer belt  216  by positive transfer bias applied from the primary transfer rollers  219  to the intermediate transfer belt  216 . Thereby, a color image is formed on the intermediate transfer belt  216 . Disposed at a position facing the driving roller  216   a  is a secondary transfer roller  217  transferring the color image formed on the intermediate transfer belt  216  onto a sheet P. It is noted that a secondary transfer portion is constructed by a secondary transfer nip portion N formed by the driving roller  216   a  and the secondary transfer roller  217  being in pressure contact with the driving roller  216   a.    
     A fixing portion  220  is disposed downstream in a sheet conveyance direction of the secondary transfer roller  217 , and a first discharge roller pair  225   a , a second discharge roller pair  225   b , and a double-side inverting portion  201   d  are disposed above the fixing portion  220 . The double-side inverting portion  201   d  includes an inverse roller pair  222  configured to rotate normally and reversely, a re-conveyance passage R conveying a sheet of which an image has been formed on a first surface thereof again to the image forming portion  201   b , and others. It is noted that an image forming unit  27  forming the image on the sheet P delivered from the sheet feeding apparatuses  51 ,  52 , and  53  is constructed by the image forming portion  201   b , the secondary transfer nip portion N, and the fixing portion  220 . 
     The image forming apparatus constructed as described above operates as follows. Image information read by the image reading apparatus  202  or inputted from an outside device such as a personal computer (PC) not illustrated is converted into electrical signals after undergoing image processing and is transmitted to a laser scanner  210  of the image forming portion  201   b.    
     Then, in the image forming portion  201   b , surfaces of the photosensitive drums  212  of the respective process cartridges  211  are scanned by laser beams corresponding to image information of yellow, magenta, cyan, and black component colors emitted from the laser scanner  210 . Thereby, the surfaces of the photosensitive drums  212  charged homogeneously with a predetermined polarity and potential by the charger  213  are sequentially exposed, and electrostatic latent images of yellow, magenta, cyan, and black are sequentially formed on the photosensitive drums  212  of the respective process cartridges  211 . 
     Then, the electrostatic latent images are developed and visualized by toners of the respective colors of yellow, magenta, cyan, and black, and the respective color toner images on the respective photosensitive drums  212  are sequentially superimposed and transferred onto the intermediate transfer belt  216  by the primary transfer bias applied to the primary transfer rollers  219 . Thereby, a color toner image is formed on the intermediate transfer belt  216 . 
     Meanwhile, the sheet P delivered from either one of the sheet feeding apparatuses  51 ,  52 , and  53  passes through a registration roller pair  240  and is sent to the secondary transfer nip portion N. Here, the registration roller pair  240  corrects a skew of the sheet P by making a front end of the sheet P follow a nip portion of the registration roller pair  240  such that the sheet P abutting against the nip portion forms a loop. The toner images formed in the image forming portion  201   b  are secondarily and collectively transferred onto the sheet P at the secondary transfer nip portion N. 
     In succession, the sheet P onto which the toner images have been secondarily transferred as described above is conveyed to the fixing portion  220  to be heated and pressed to fix the toner images on the sheet P as a color image. After that, the sheet P on which the color image has been fixed is discharged to the discharge space S by the first discharge roller pair  225   a  and is stacked on a stacking portion  26  provided within the discharge space S. 
     The sheet feeding apparatuses  51  and  52  are provided respectively with sheet feed cassettes  91  and  92  storing the sheet P. The sheet feeding apparatus  51  is also provided with a sheet feed portion  24  delivering the sheet P stored in the sheet feed cassette  91  toward a sheet drawing roller pair  14 . The sheet feeding apparatus  52  is provided with the sheet feed portion  24  delivering the sheet P stored in the sheet feed cassette  92  toward a drawing roller pair  25 . 
     The sheet feed portion  24  corresponding to the sheet feed cassette  91  includes a pickup roller  11 , a feed roller  12 , and a retard roller  13  disposed above and downstream in a sheet feed direction of the sheet feed cassette  91 . The sheet feed portion  24  corresponding to the sheet feed cassette  92  includes a pickup roller  21 , a feed roller  22 , and a retard roller  23  disposed above and downstream in the sheet feed direction of the sheet feed cassette  92 . 
     The sheet feeding apparatus  53  is provided with a sheet feed cassette  93  storing the sheet P and a sheet feed portion  24  delivering the sheet P stored in a sheet feed cassette  93  toward a pull-out roller pair  34  located downstream of the sheet feed portion  24 . The sheet feed portion  24  corresponding to the sheet feed cassette  93  includes a pickup roller  31 , a feed roller  32 , and a retard roller  33  disposed above and downstream in the sheet feed direction of the sheet feed cassette  93 . 
     The pickup rollers  11  and  21  are turnably supported by arms not illustrated respectively turnable centering on the feed rollers  12  and  22  and deliver the sheet P by rotating while being in pressure contact with the sheet P stored respectively in the sheet feed cassettes  91  and  92 . The sheet feed cassettes  91  and  92  are supported such that they can be attached to/drawn out of the apparatus body  201   a  in a front-back direction of  FIG. 1 . 
     The pickup roller  31  is turnably supported by an arm not illustrated turnable centering on the feed roller  32  and delivers the sheet P stored in the sheet feed cassette  93  by rotating while being in pressure contact with the sheet P stored in the sheet feed cassette  93 . It is noted that the sheet feed cassette  93  is supported such that the sheet feed cassette  93  can be attached to/drawn out of the apparatus body  201   a  along drawing rails  61  and  62  in the front-back direction of  FIG. 1 . 
     Then, in response to a start of an image forming operation, the sheet P is separated and fed one by one from either one of the sheet feed cassettes  91 ,  92 , and  93  by the sheet feed portion  24 . The sheet P sent out by either one of the pickup rollers  11 ,  21 , and  31  is conveyed by either corresponding one of the feed rollers  12 ,  22 , and  32 . If the sheets are doubly fed at this time, the sheet P of the second one and thereafter are returned to a side of the sheet feed cassettes  91 ,  92 , and  93  by either corresponding one of the retard rollers  13 ,  23 , and  33 . The sheet P separated and conveyed by either corresponding one of the feed rollers  12 ,  22 , and  32  and the retard rollers  13 ,  23 , and  33  is sent downstream farther by either one of the pull-out roller pairs  14 ,  25 , and  34  and is conveyed to the registration roller pair  240 . 
     Sheet Feeding Apparatus 
     Next, the sheet feeding apparatus  53  of the present embodiment will be described in detail below with reference to  FIGS. 2A through 3C . It is noted that  FIGS. 2A through 3C  are section views describing the sheet feeding apparatus  53  of the present embodiment in different states. 
     As illustrated in  FIGS. 2A through 3C , the sheet feeding apparatus  53  is configured such that the sheet P can be fed one by one in a state in which a bundle of sheets of small size such as A4 size and letter size is stacked respectively in first and second sheet storage portions  28   b  and  28   a . The sheet feeding apparatus  53  is configured to feed in order from the sheet P within the first sheet storage portion  28   b  on a right side in the drawings. The sheet feeding apparatus  53  adopts a tandem cassette feeding structure in which a bundle of sheets P within the second sheet storage portion  28   a  on a left side of the drawings is collectively shifted to the first sheet storage portion  28   b  when the sheet within the first sheet storage portion  28   b  runs out. 
     The sheet feeding apparatus  53  is provided with a lifter plate  35  supported so as to lift the stacked sheet P within the first sheet storage portion  28   b . The pickup roller  31 , disposed above the lifter plate  35 , of the apparatus body  201   a  (see  FIG. 1 ) is supported turnably by the arm not illustrated turnable centering on the feed roller  32  and feeds the sheet P stacked on the lifter plate  35 . Then, the sheet P thus fed is conveyed by the feed roller  32 . However, in a case when two or more sheets are fed, the second sheet and thereafter are returned to a side of the sheet feed cassette  93  by a separation action effected by the feed roller  32  and the retard roller  33 . It is noted that the pickup roller  31  composes a feed member feeding the sheet P. 
     As illustrated in  FIGS. 2A and 2B , a lifter HP (home position) sensor  84  is disposed at a lower part of a front end portion of the sheet feed cassette  93 , i.e., a sheet storage member. The control portion  67  (see  FIG. 1 ) controls and drives a lifter motor  86  (see  FIG. 11 ) such that the lifter plate  35  is lifted corresponding to a level in a vertical direction of the pickup roller  31  so that the pickup roller  31  can be always stably in contact with an uppermost sheet of the sheets P on the lifter plate  35 . 
     The sheet feed cassette  93  includes the first sheet storage portion  28   b  on the right side of the drawings and the second sheet storage portion  28   a  on the left side of the drawings, and is supported so as to be attachable to/drawable out of an attachment space  15  (see  FIG. 6 ) within the apparatus body  201   a . The first sheet storage portion  28   b  stores the sheet P to be fed by the pickup roller  31 . The second sheet storage portion  28   a  adjoins the first sheet storage portion  28   b  in a horizontal direction and stores sheets P to be replenished to the first sheet storage portion  28   b.    
     The sheet feeding apparatus  53  also comprises a fixed set tray  88  formed such a part thereof extends from a bottom of the second sheet storage portion  28   a  to a side of the first sheet storage portion  28   b . The sheet bundle moving member  37  supported so as to slidably move from the second sheet storage portion  28   a  to the first sheet storage portion  28   b  side along the set tray  88  is disposed in the sheet feed cassette  93 . The sheet bundle moving member  37  is provided so as to be able to be in contact with the sheet bundle Sb set in the second sheet storage portion  28   a . That is, the sheet bundle moving member  37  is supported so as to be able to slidably move in the horizontal direction in  FIGS. 2A and 2B  by the driving motor  50  controlled by the control portion  67  and slidably moves the whole sheet bundle Sb set in the second sheet storage portion  28   a  to the first sheet storage portion  28   b . It is noted that the sheet bundle moving member  37  composes a sheet shift portion movable so as to shift the sheet bundle Sb collectively from the second sheet storage portion  28   a  to the first sheet storage portion  28   b.    
     As illustrated in  FIGS. 2A through 3C , the sheet feed cassette  93  of the sheet feeding apparatus  53  is provided with an arm member  36  partitioning the left sheet bundle Sb from the right sheet bundle Sb in setting the sheet bundle Sb at a center part thereof. 
     The arm member  36  is constructed so as to be able to move between a partitioning position and an opening position by being driven by a partitioning solenoid  20  (see  FIG. 11 ). The partitioning position is a position partitioning the first sheet storage portion  28   b  from the second sheet storage portion  28   a  by projecting between the first and second sheet storage portions  28   b  and  28   a , and the opening position is a position for opening between the first and second sheet storage portions  28   b  and  28   a  by receding from the partitioning position. 
     A home position of the arm member  36  is normally the partitioning position where the arm member  36  projects as a partition between the sheet bundles Sb of the first and second sheet storage portions  28   b  and  28   a . Then, the arm member  36  recedes from the partitioning position to the opening position in shifting the sheet bundle Sb stacked in the second sheet storage portion  28   a  on the left side to the first sheet storage portion  28   b  on the right side in  FIGS. 2A and 2B . 
     Still further, as illustrated in  FIGS. 2A and 2B , the apparatus body  201   a  is provided with a sheet sensor  78  (see  FIG. 11 ) disposed above the lifter plate  35  of the first sheet storage portion  28   b . The control portion  67  (see  FIGS. 1 and 11 ) of the apparatus body  201   a  controls the partitioning solenoid  20  so as to move the arm member  36  to the opening position before operating and shifting the sheet bundle moving member  37  based on a sheet detection result of the sheet sensor  78 . This arrangement makes it possible to operate and shift the sheet bundle moving member  37  after moving the arm member  36  quickly to the opening position and to smoothly replenish the sheet bundle Sb to the first sheet storage portion  28   b  when the sheet P within the first sheet storage portion  28   b  runs out. 
     Next, the sheet feeding apparatus  53  of the present embodiment will be described in detail with reference to  FIGS. 4A through 4C, 9, and 10 . It is noted that  FIG. 4A  is a section view illustrating a state of the sheet feeding apparatus  53  of the present embodiment in which the sheet bundle Sb is stacked in the second sheet storage portion  28   a .  FIG. 4B  is a section view illustrating a state of the sheet feeding apparatus  53  of the present embodiment in which the sheet bundle Sb is shifted collectively from the second sheet storage portion  28   a  to the first sheet storage portion  28   b .  FIG. 4C  is a section view illustrating a state in which the sheet bundle moving member  37  which has completed to shift the sheet bundle Sb is returned to the second sheet storage portion  28   a . It is noted that  FIG. 4C  is also a section view illustrating an operation of returning the sheet bundle moving member  37  to the second sheet storage portion  28   a  when the sheet feed cassette  93  is drawn out of the apparatus body  201   a .  FIG. 9  is a plan view specifically illustrating the sheet feeding apparatus  53  in  FIGS. 5A and 5B .  FIG. 10  is a section view taken along a line A-A in  FIG. 9 . 
       FIG. 4A  corresponds to  FIG. 2B ,  FIG. 4B  corresponds to  FIG. 3B , and  FIG. 4C  corresponds to a state in which the sheet bundle moving member  37  is on a way of returning from the state in  FIG. 3B  to the position of  FIG. 3C . In  FIGS. 4A through 4C , the arm member  36 , the pickup roller  31 , the feed roller  32 , the retard roller  33 , the drawing rails  61  and  62 , and others illustrated in  FIGS. 2A through 3C  are not illustrated. An inner part of the set tray  88  in  FIGS. 2A through 3C  is illustrated in section also in  FIGS. 4A  though  4 C, though their sizes are different more or less. 
     As illustrated in  FIG. 4A , the sheet bundle Sb is stacked and set on the set tray in a state in which a rear end part of the sheet bundle is in contact with the sheet bundle moving member  37  located at the home position within the second sheet storage portion  28   a.    
     Then, as illustrated in  FIG. 4B , the sheet bundle moving member  37  is moved in a first direction D 1  which is a direction in which the sheet bundle moving member  37  is moved from the second sheet storage portion  28   a  to the first sheet storage portion  28   b  by a driving unit  10  described later. Thereby, the sheet bundle Sb is shifted collectively onto the lifter plate  35  of the first sheet storage portion  28   b.    
       FIG. 4C  illustrates a case when the sheet feed cassette  93  is drawn out of the apparatus body  201   a  when the sheet bundle moving member  37  is located at the position between the first and second sheet storage portions  28   b  and  28   a , i.e., a first position, as illustrated in  FIG. 4B .  FIG. 4C  illustrates the operation of returning the sheet bundle moving member  37  to the second sheet storage portion  28   a . As illustrated in  FIG. 4C , the sheet bundle moving member  37  moves in a second direction D 2  from the state illustrated in  FIG. 4B  to the second sheet storage portion  28   a  side by a spring force of the charged tensile spring  44  and approaches to its home position. The position of the sheet bundle moving member  37  illustrated in  FIG. 4A  is the home position of the sheet bundle moving member  37 . The home position is located outside of the second sheet storage portion  28   a  farther than the first sheet storage portion  28   b  in the moving direction of the sheet bundle moving member  37 . When the sheet bundle moving member  37  is located at the home position, the user can stack the sheet bundles Sb in the first and second sheet storage portions  28   b  and  28   a . Then, when the sheet P stored in the first sheet storage portion  28   b  runs out, the sheet bundle moving member  37  located at the home position shifts the sheet bundle Sb stored in the second sheet storage portion  28   a  collectively to the first sheet storage portion  28   b . The pair of tensile springs  44  is provided widthwise (in a direction of an arrow B in  FIG. 5A ) orthogonal to the sheet feeding direction (in a direction of an arrow A in  FIG. 5A ). One ends upstream in the sheet feed direction of the pair of tensile springs  44  are attached to fixing portions  89  and  90  provided on a bottom of the sheet feed cassette  93 , and other ends thereof are attached to both end portions in the width direction of the charge member  43 . 
     According to the present embodiment, the tensile spring  44  and the charge member  43  compose the forced moving mechanism, i.e., moving portion,  19  forcibly moving the sheet bundle moving member (sheet shifting portion)  37  from the first sheet storage portion  28   b  side to the second sheet storage portion  28   a  side. Here, in describing a relationship between two positions of the sheet bundle moving member  37 , a position close to the first sheet storage portion  28   b  will be expressed as ‘the first sheet storage portion  28   b  side’ and a position far from the first sheet storage portion  28   b  will be expressed as ‘the second sheet storage portion  28   a  side’. It is noted that the pair of tensile springs  44  may be one tensile spring  44  or three or more tensile springs  44  may be used depending on their disposition. 
     Disposed under the sheet bundle moving member  37  are driving shafts  46   a  and  40   a  extending in the width direction orthogonal to the sheet feed direction and rotatably supported upstream and downstream in the sheet feed direction (in the direction of the arrow A in  FIG. 2A ). A driving pulley  40  and a driven pulley  46  are respectively supported by the driving shafts  46   a  and  40   a . An endless timing belt  41  is wound around and stretched between the driving pulley  40  and the driven pulley  46 . 
     A bent portion  37   a  formed at a lower part of the sheet bundle moving member  37  is fixed such that the sheet bundle moving member  37  erects by fixing members  45  on a lower side of an inner circumferential surface of the timing belt  41 . The bent portion  37   a  is configured so as to project in the width direction from the set tray  88  as illustrated in  FIG. 9  so that the sheet bundle moving member  37  can reciprocate in the sheet feed direction by using the lengthy set tray  88  extended in the sheet feed direction as a rail. 
     Next, the driving mechanism and others moving the sheet bundle moving member  37  of the present embodiment will be described with reference to  FIGS. 5A, 5B, and 6 . It is noted that  FIG. 5A  is a plan view illustrating a state of the forced moving mechanism  19  which corresponds to the state in  FIG. 4A ,  FIG. 5B  is a plan view illustrating a state of the forced moving mechanism  19  which corresponds to the state in  FIG. 4B , and  FIG. 6  is a plan view illustrating the state in which the sheet feed cassette  93  is drawn out of the apparatus body  201   a.    
     As illustrated  FIGS. 5A, 5B, and 6 , the apparatus body  201   a  is provided therein with an opening/closing sensor  16  detecting whether the sheet feed cassette  93  is opened or closed, i.e., drawn out of or attached to the apparatus body  201   a.    
     The sheet feed cassette  93  is provided also with side restricting plates  38  and  39  restricting and aligning the sheet P within the sheet feed cassette  93  in the width direction (in a direction of an arrow B in  FIG. 5A ) orthogonal to the sheet feed direction (in the direction of the arrow A in  FIG. 5A ). These side restricting plates  38  and  39  are supported at a bottom of the sheet feed cassette  93  so as to be able move corresponding to a widthwise size of a sheet to be set in the sheet feed cassette  93 . 
     In response to a drive of the timing belt  41  driven by the driving pulley  40  as illustrated in  FIG. 5A , the sheet bundle moving member  37  moves along with the rotation of the timing belt  41 . At this time, the sheet bundle moving member  37  moves from the second sheet storage portion  28   a  side as illustrated in  FIG. 5A  to the first sheet storage portion  28   b , so that the sheet bundle Sb is shifted collectively to the first sheet storage portion  28   b  and is stacked on the lifter plate  35  within the first sheet storage portion  28   b.    
     The charge member  43  is supported so as to slidably move within a guide portion  42  illustrated in  FIG. 4A . The guide portion  42  extends widthwise so as to be able to support the charge member  43  extending in the width direction within the set tray  88 . The charge member  43  engages with the sheet bundle moving member  37  at a predetermined position, moves together with the sheet bundle moving member  37 , and drags the tensile spring  44 . When the shift of the sheet bundle Sb is completed as illustrated in  FIG. 4B , the sheet bundle moving member  37  presses the charge member  43  together with the sheet bundle Sb to the first sheet storage portion  28   b  side. Because a spring force acts on the charge member  43  from the predetermined position in the sheet feed direction, the charge member  43  drags the tensile spring  44  and charges the spring force (moving force) by being pressed by the sheet bundle moving member  37 . 
     As illustrated in  FIGS. 5A, 5B, and 6 , a driving motor  50  is fixed at a position adjacent the attachment space  15  within the apparatus body  201   a . A pinion  74  is secured to a rotating shaft  50   a  of the driving motor  50 . The apparatus body  201   a  also includes a drive transmitting coupling  49  receiving a driving force from the driving motor  50  is rotatably supported through a support mechanism not illustrated at a position facing a driven coupling  48  operative when the sheet feed cassette  93  is inserted into the attachment space  15 . The driven coupling  48  engages with the drive transmitting coupling  49  when the sheet feed cassette  93  is attached to the attachment space  15  and is decoupled from the drive transmitting coupling  49  when the sheet feed cassette  93  is drawn out of the attachment space  15 . 
     A driving gear  76  is secured to a rotating shaft  77  rotatably supporting the drive transmitting coupling  49  to the apparatus body  201   a , and a transmission gear  75  rotatably supported by the apparatus body  201   a  is engaged with the driving gear  76 . A driving shaft  40   a  supported in this state is supported in a condition in which the driving shaft  40   a  penetrates through a penetration portion  39   a  formed through the side restricting plate  39 . It is noted that a driving mechanism  29  is composed of the driving motor  50 , the pinion  74 , the transmission gear  75 , and the driving gear  76 . 
     The rotation of the driving motor  50  is transmitted to the driven coupling  48  through the pinion  74 , the transmission gear  75 , the driving gear  76 , the rotating shaft  77 , and the drive transmitting coupling  49 . Still further, because this rotation is also transmitted to the driving pulley  40  through the driving shaft  40   a , the sheet bundle moving member  37  is moved in the direction of the arrow A illustrated in  FIG. 5A  while rotating the driven pulley  46  through the timing belt  41  by the rotation of the driving pulley  40 . 
     Still further, according to the present embodiment, the driving mechanism  29  also includes the timing belt  41  rotated by the output of the driving motor  50  transmitted from the drive transmitting coupling  49  to the driven coupling  48 . Then, the sheet bundle moving member  37  is linked with the timing belt  41  so as to move between the first and second sheet storage portions  28   b  and  28   a  during when the timing belt  41  rotates. This arrangement makes it possibly to steadily move the sheet bundle moving member  37  by transmitting the driving force of the driving motor  50  to the timing belt  41  through the driving shaft  40   a  and the driving pulley  40 . 
     As illustrated in  FIG. 6 , the drive transmitting coupling  49  on the apparatus body  201   a  side is decoupled from the driven coupling  48  on the sheet feed cassette  93  side in the state in which the sheet feed cassette  93  is drawn out of the apparatus body  201   a . The drive transmitting coupling  49  and the driven coupling  48  are known members transmitting driving torque of the driving motor  50 . By decoupling them from each other, the transmission route of the driving motor  50  is disconnected. Then, by being released from an influence of holding torque of the driving motor  50  itself, the charge member  43  moves the sheet bundle moving member  37  quickly to the predetermined position by the charged spring force of the tensile spring  44 . In the present embodiment, the charge member  43  is moved substantially around to a center position, i.e., a second position, where the sheet bundle is set in the second sheet storage portion  28   a.    
     Because the sheet bundle moving member  37  returns to a position as indicated in  FIG. 6 , the user will not set a sheet bundle Sb because the sheet bundle moving member  37  itself is located at an obstructive position even if the user tries to set the sheet bundle Sb in the second sheet storage portion  28   a . It becomes possible to set the sheet bundle Sb to the position of the second sheet storage portion  28   a  after moving the sheet bundle moving member  37  to the left side in  FIG. 6 . Because the driven coupling  48  is decoupled from the drive transmitting coupling  49  by this time, the user can readily move and position the sheet bundle moving member  37  to the left to a position (the home position illustrated in  FIG. 5A ) adequate for setting the sheet bundle Sb. This arrangement of moving the sheet bundle moving member  37  substantially around to the center of the second sheet storage portion  28   a  makes it possible to appeal to the user and to induce the user to reset the sheet bundle moving member  37  at the adequate position. 
     In the present embodiment, the home position of the sheet bundle moving member  37  is the leftmost position as indicated in  FIG. 5A . In replenishing the sheet bundle Sb to the first sheet storage portion  28   b  in the state in which the sheet feed cassette  93  is attached to the apparatus body  201   a , the sheet bundle moving member  37  which has moved to the first sheet storage portion  28   b  side and replenished the sheet bundle Sb can be returned by automatically moving to the home position by the driving force of the driving motor  50 . This operation ends in several seconds, e.g., 10 seconds, though it depends on an output of the driving motor  50 . Still further, basically the sheet bundle moving member  37  stands still always at the left home position. 
     However, if the sheet feed cassette  93  is drawn out of the apparatus body  201   a , the transmission route of the driving force of the driving motor  50  is disconnected, so that the sheet bundle moving member  37  cannot return to the home position by the driving force of the driving motor  50 . According to the present embodiment, however, the sheet bundle moving member  37  can be moved instantly in the left direction by the operation of the charge member  43  and the tensile spring  44 . 
     Here, ‘instantly’ means a time, e.g., within one second, less than a time required for the user to draw the sheet feed cassette  93  out of the apparatus body  201   a . Because the sheet bundle moving member  37  moves instantly in the left direction as described above, there is no space for setting the sheet bundle Sb on the left set tray  88 , and the user will not erroneously set the sheet bundle Sb at this position. Because this arrangement makes is possible to avoid the user from erroneously setting the sheet bundle Sb, it is possible to avoid a stoppage of the printer  201  or the occurrence of a cumbersome resetting work. 
     Control System 
     Next, a control system involved in the shift of the sheet bundle of the present embodiment will be described with reference to  FIG. 11 .  FIG. 11  is a block diagram illustrating the control system involved in the shift of the sheet bundle. 
     As illustrated in  FIG. 11 , the control system of the present embodiment comprises a control portion (controller)  67  comprising a CPU, a RAM, and a ROM. An opening/closing sensor  16 , a bundle pressing HP sensor  81 , a bundle pressing sensor  82 , a partitioning sensor  83 , a lifter HP sensor  84 , and a sheet sensor  78  are connected to an input port of the control portion  67 . The partitioning solenoid  20 , the driving motor  50 , and a lifter motor  86  are connected to an output port of the control portion  67 . 
     The opening/closing sensor  16  is composed of a photo interrupter and detects a state of the sheet feed cassette  93  attached to the apparatus body  201   a  in response to a light blocking plate  17  (see  FIGS. 5A through 6 ) fixed on a back surface side of the sheet feed cassette  93  and entering and receding between light emitting and receiving portions not illustrated. That is, when the light blocking plate  17  on the back surface side of the sheet feed cassette  93  moves and advances/recedes with respect to the opening/closing sensor  16 , an output signal of the light receiving portion turns to Low level when the light blocking plate  17  interrupts an optical path between the light emitting and receiving portions of the photo interrupter and turns to High level when the light blocking plate  17  does not interrupt the optical path. Accordingly, it is possible to detect the state of the sheet feed cassette  93  whether or not the sheet feed cassette  93  is attached by setting a position where the output signal of the light receiving portion changes as a reference position and by detecting whether or not the sheet feed cassette  93  is located at the reference position. 
     The bundle pressing HP sensor  81  (see  FIG. 2A ) detects that the sheet bundle moving member  37  is located at the home position. The bundle pressing sensor  82  (see  FIG. 2A ) detects a position where the sheet bundle moving member  37  completes to press the bundle. 
     The partitioning sensor  83  has substantially the same structure with the opening/closing sensor  16  described above. The partitioning sensor  83  detects whether the arm member  36  is located at the partitioning position or the opening position based on the relationship of the advancing/receding move of the a light blocking plate fixed on the arm member  36  side with a photo interrupter fixed on the sheet feed cassette  93  side. 
     The lifter HP sensor  84  (see  FIG. 2A ) is disposed at a lower part of the front end of the sheet feed cassette  93  and detects a lowermost position of the lifter plate  35 . The sheet sensor  78  (see  FIGS. 2A and 2   b ) is disposed above the lifter plate  35  of the first sheet storage portion  28   b  and detects whether or not the sheet P exists within the first sheet storage portion  28   b.    
     The driving motor  50  rotationally drives to move the sheet bundle moving member  37  from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side and to return the sheet bundle moving member  37  from the first sheet storage portion  28   b  side to the second sheet storage portion  28   a  side in accordance to the controls made by the control portion  67 . 
     The partitioning solenoid  20  advances/sets back a plunger not illustrated so as to turn the arm member  36  to the partitioning position/opening position in accordance to the controls made by the control portion  67 . The driving motor  50  rotates in accordance to the controls of the control portion  67 , and the rotation thereof is transmitted to the drive transmitting coupling  49  through the gear train including the pinion  74 . The lifter motor  86  operates so as to lift the lifter plate  35  such that the uppermost sheet P on the lifter plate  35  is always and stably in contact with the pickup roller  31  corresponding to a level of the pickup roller  31  in accordance to the controls of the control portion  67 . 
     Corresponding to the detection signals from the various sensors described above, the control portion  67  controls and drives the partitioning solenoid  20 , the driving motor  50 , and the lifter motor  86 . The control portion  67  also controls a display on of an user&#39;s operating screen not illustrated. 
     Here, a series of states in which the sheet bundle Sb within the second sheet storage portion  28   a  is shifted to the first sheet storage portion  28   b  when the sheet P within the first sheet storage portion  28   b  runs out will be described with reference to  FIGS. 2A through 3C . 
     That is,  FIG. 2A  illustrates a state in which the sheet P is fed by the pickup roller  31  from the first sheet storage portion  28   b  and the sheet bundle Sb within the second sheet storage portion  28   a  is kept in a standby state. Then,  FIG. 2B  illustrates a state in which the sheet P within the first sheet storage portion  28   b  runs out and the lifter plate  35  is lowered to its lowest position. Then,  FIG. 3A  illustrates a state in which the sheet bundle Sb is shifted collectively from the second sheet storage portion  28   a  to the first sheet storage portion  28   b.    
       FIG. 3B  illustrates a state in which the shift of the sheet bundle Sb to the first sheet storage portion  28   b  is completed. Then,  FIG. 3C  illustrates a state in which the sheet bundle moving member  37  is returned to its home position on the second sheet storage portion  28   a  side and the lifter plate  35  is lifted to deliver an uppermost sheet P on the lifter plate  35  by the pickup roller  31 . 
     Thus, it is possible to continue an image forming process even if the sheet P within the first sheet storage portion  28   b  runs out by repeatedly replenishing the sheet bundle Sb by automatically and continuously performing the steps in  FIGS. 2A through 3C . That is, it is possible to continue the image forming operation (printing operation) by swiftly shifting the sheet bundle Sb already set within the second sheet storage portion  28   a  to the first sheet storage portion  28   b.    
     As illustrated in  FIG. 4C , the sheet bundle moving member  37  is pulled back to the predetermined position by the charged spring force if the user draws the sheet feed cassette  93  out of the apparatus body  201   a  right after when the shift of the sheet bundle Sb is finished. Then, when the sheet feed cassette  93  is drawn out of the apparatus body  201   a , the driven coupling  48  is decoupled from the drive transmitting coupling  49  supported by the apparatus body  201   a  side. Then, because the driving force from the driving motor  50  to the driving shaft  40   a  of the driving pulley  40  is disconnected, a load is suddenly lightened. Thereby, the sheet bundle moving member  37  is instantly pulled back to the second sheet storage portion  28   a  side in drawing the sheet feed cassette  93  out of the apparatus body  201   a.    
     It is noted that the driving unit  10  is composed of the driving mechanism  29  comprising the driving motor  50  as a driving source outputting the driving force, the drive transmitting coupling  49 , the driven coupling  48 , and the timing belt  41  as the endless belt. The driving unit  10  is linked with the sheet shifting portion through a transmission portion  18  described later to transmit the driving force of the driving unit  10  to the sheet shifting portion and to drive the sheet shifting portion. The present embodiment is configured to be able to move the sheet bundle moving member  37  in an inverse direction toward the second sheet storage portion  28   a  by the forced moving mechanism (the moving portion)  19  when the transmission of the driving force of the driving unit  10  is disconnected. 
     This arrangement makes it possible to move the sheet bundle moving member  37  automatically to the home position side when the sheet feed cassette  93  is drawn out at the moment when the shift of the sheet bundle by the move of the sheet bundle moving member  37  is finished (when the sheet feed cassette  93  is drawn out at the moment of finishing to shift the sheet bundle). Thus, it is possible to move the sheet bundle moving member  37  automatically to the home position side of the second sheet storage portion  28   a.    
     That is, if the sheet feed cassette  93  is drawn out of the attachment space  15  and the link with the driving unit  10  is disconnected in the state in which the sheet bundle moving member  37  has moved to the first sheet storage portion  28   b  side, the forced moving mechanism  19  forcibly moves the sheet bundle moving member  37  to the second sheet storage portion  28   a  side. That is, in the case when the sheet feed cassette  93  is drawn out during when the sheet bundle is being shifted, the sheet bundle moving member  37  can be moved to the second sheet storage portion  28   a  side instantly by the action of the forced moving mechanism  19 . Due to that, even if the sheet feed cassette  93  is erroneously drawn out during the shift of the sheet bundle Sb, it is possible to avoid such problem that the sheet bundle Sb is erroneously stacked from occurring because the sheet bundle moving member  37  can be forcibly moved to the second sheet storage portion  28   a  side. 
     That is, no such problem that the user erroneously sets the sheet bundle Sb on the left side of the sheet bundle moving member  37  (the second sheet storage portion  28   a  side) occurs in a state in which the sheet bundle moving member  37  cannot return to the second sheet storage portion  28   a  side. Due to that, it is possible to avoid the user from erroneously setting the sheet bundle Sb to the sheet feed cassette  93  drawn out of the apparatus body  201   a  on the back side of the sheet bundle moving member  37  stopping after having moved to the first sheet storage portion  28   b  side. Accordingly, it is possible to reliably avoid such situations that the sheet bundle moving member  37  cannot return to the home position and the printer  201  has to be stopped or an alarm is indicated from otherwise occurring by erroneously setting the sheet bundle Sb. Thus, it is possible to steadily prevent such problem requiring the cumbersome work that the printer  201  is not recovered until when the user removes the sheet bundle Sb from occurring. 
     Still further, according to the present embodiment, the charge member  43 , i.e., a pulling member, is linked with the tensile spring  44  so as to pull the tensile spring  44  to the first sheet storage portion  28   b  side through the sheet bundle moving member  37  moving from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side. When the load of the driving motor (driving source)  50  to the forced moving mechanism  19  is cut, the sheet bundle moving member  37  receives the forced moving force of the tensile spring  44  through the charge member  43  and is moved to the second sheet storage portion  28   a  side. This arrangement makes it possible to move the sheet bundle moving member  37  reliably to the second sheet storage portion  28   a  when the load to the forced moving mechanism  19  is cut. 
     Still further, the driving unit  10  can move the sheet bundle moving member  37  from the first sheet storage portion  28   b  to the second sheet storage portion  28   a  side in the state in which the sheet feed cassette  93  is attached to the attachment space  15 . Because the sheet feeding apparatus  53  includes the driving unit  10  as described above, it is possible to move the sheet bundle moving member  37  steadily and smoothly between the first and second sheet storage portions  28   b  and  28   a  by such simple mechanical configuration. 
     Still further, according to the present embodiment, the transmission portion  18  is composed of the drive transmitting coupling  49  supported on the apparatus body  201   a  side, the driven coupling  48  supported on the sheet feed cassette  93  side, and the timing belt  41 . The sheet bundle moving member  37  is firmly linked with the timing belt  41  so as to be able to move between the first and second sheet storage portions  28   b  and  28   a  by the rotation of the timing belt  41 . The driven coupling  48  can be engaged and coupled with the drive transmitting coupling  49  by attaching the sheet feed cassette  93  to the attachment space  15 . Still further, the driven coupling  48  can be decoupled and disconnected from the drive transmitting coupling  49  by drawing the sheet feed cassette  93  out of the attachment space  15 . 
     It is possible to simply and reliably switch the link state and the disconnect state by linking/decoupling the driven coupling  48  on the sheet feed cassette  93  side with/from the drive transmitting coupling  49  on the apparatus body  201   a  side. Still further, in response to the link of the driven coupling  48  with the drive transmitting coupling  49 , the driving force of the driving motor  50  is transmitted from the drive transmitting coupling  49  to the driven coupling  48 , and the timing belt  41  is rotated. It is possible to steadily transmit the driving force of the driving motor  50  to the sheet bundle moving member  37  by the simple mechanical configuration as described above. 
     The forced moving mechanism  19  includes the tensile spring, i.e., a spring member,  44  charging the moving force by being dragged by the sheet bundle moving member  37  moving from the second sheet storage portion  28   a  to the first sheet storage portion  28   b . When the sheet feed cassette  93  is drawn out of the attachment space  15 , the sheet bundle moving member  37  is moved to the second sheet storage portion  28   a  side by the tensile spring  44  in the state in which the load of the transmission portion  18  is cut. At this time, it is possible to steadily make the moving force act on the sheet bundle moving member  37  and move the sheet bundle moving member  37  to the second sheet storage portion  28   a  side just by drawing the sheet feed cassette  93  out of the apparatus body  201   a.    
     The charge member  43  also pulls the tensile spring  44  to the first sheet storage portion  28   b  side by engaging with the sheet bundle moving member  37  moving from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side. Then, when the load of the driving motor  50  on the forced moving mechanism  19  is cut, the sheet bundle moving member  37  receives the moving force of the tensile spring  44  through the charge member  43  and is returned to the second sheet storage portion  28   a  side. Therefore, it is possible to release the load of the driving motor  50  being applied on the forced moving mechanism  19  and to move the sheet bundle moving member  37  to the second sheet storage portion  28   a  side quickly by the moving force of the tensile spring  44  automatically by drawing the sheet feed cassette  93  out of the apparatus body  201   a.    
     The forced moving mechanism  19  also charges the moving force forcibly moving the sheet bundle moving member  37  to the second sheet storage portion  28   a  side when the sheet bundle moving member  37  is moved from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side by the driving unit  10 . This arrangement makes it possible to reliably charge the moving force in the direction of returning the sheet bundle moving member  37  after extending the tensile spring  44  just by moving the sheet bundle moving member  37  to the first sheet storage portion  28   b  side by the driving force of the driving motor  50 . 
     It is noted that while the known tensile spring whose load increases as the spring is dragged more has been exemplified in the present embodiment, another method using a compression type spring in contrary may be adopted as long as the sheet bundle moving member  37  can be moved to the home position side. That is, the spring is not limited to the tensile spring  44  of the present embodiment. 
     Still further, while the charge member  43  slidably moving within the guide portion  42  illustrated in  FIGS. 4A through 4C  has been configured so as to start to move from the middle part of the second sheet storage portion  28   a  in the present embodiment, the present invention is not limited to such configuration. That is, the charge member  43  and the tensile spring  44  may be configured such that the charge member  43  and the tensile spring  44  are disposed farther on the left side of the second sheet storage portion  28   a  and the tensile spring  44  can charge the moving force as soon as the sheet bundle moving member  37  starts to move from its home position. Then, the charge member  43  and the tensile spring  44  may be configured such that the sheet bundle moving member  37  moves to the home position detectable by the bundle pressing HP sensor  81  when the charge member  43  returns to the second sheet storage portion  28   a  side by the moving force. In this case, the user can replenish a sheet bundle Sb to the second sheet storage portion  28   a  as it is in a state in which the sheet bundle moving member  37  has returned to the home position. 
     It is noted that while the sheet bundle moving member  37  has been configured to instantly move in the left direction by the action of the charge member  43  and the tensile spring  44  when the user draws the sheet feed cassette  93  out of the apparatus body  201   a  in the present embodiment, the present invention is not limited to such configuration. For instance, the sheet bundle moving member  37  may be moved by the charge member  43  and the tensile spring  44  also at timing when the user draws the sheet feed cassette  93  out to the draw-out position. The user will notice that the sheet bundle moving member  37  is not located at the home position by watching that the sheet bundle moving member  37  is moving to the home position side. Then, it is also possible to urge the user to move the sheet bundle moving member  37  to the home position. In this case, the sheet bundle moving member  37  may not be returned to the home position by the action of the charge member  43  and the tensile spring  44 . 
     Still further, the case when the sheet feed cassette  93  is drawn out of the apparatus body  201   a  when the sheet bundle moving member  37  is located between the first and second sheet storage portions  28   b  and  28   a  has been described with reference to  FIGS. 4B and 4C , the present invention is not limited to such configuration. For instance, the configuration of the present embodiment is effective even in a case when the sheet bundle moving member  37  is located at an area overlapping with the second sheet storage portion  28   a  in  FIGS. 4A through 4C  if the user can store the sheet P in the left part of the sheet bundle moving member  37 . 
     First Modified Example 
     Next, a first modified example of the embodiment described above will be described with reference to  FIG. 7 .  FIG. 7  is a section view illustrating the forced moving mechanism  19  and others of the sheet feeding apparatus  53  of the first modified example. It is noted that the same or corresponding members with those of the embodiment described above will be denoted by the same reference numerals and descriptions of those having the same configurations and functions will be omitted. 
     While a basic part of the first modified example is the same with the configuration of the embodiment described above with reference to  FIGS. 4A through 4C , the forced moving mechanism, i.e., the moving portion,  19  is provided with not the tensile spring  44  but a spiral spring member  70 . That is, a transmission gear  71  engaging with a gear portion not illustrated provided on the driving pulley  40  is disposed on the first sheet storage portion  28   b  side of the timing belt  41  stretched between the driving pulley  40  and the driven pulley  46  a gear portion around which the spiral spring member  70  is wound is engaged with the transmission gear  71 . 
     The arrangement described above also makes it possible to move the sheet bundle moving member  37  from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side by the timing belt  41  rotated by the rotating driving pulley  40  by the first modified example in the same manner with the embodiment described above. At this time, it is possible to charge the moving force by rotating the spiral spring member  70  through the transmission gear  71 . 
     According to the forced moving mechanism  19  of the first modified example constructed as described above, it is possible to charge the moving force by rotating the spiral spring member  70  in linkage with the move of the sheet bundle moving member  37  from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side. Then, it is possible to move the sheet bundle moving member  37  to the second sheet storage portion  28   a  side by the spiral spring member  70  in the state in which the load of the transmission portion  18  is cut when the sheet feed cassette  93  is drawn out of the attachment space  15 . 
     According to the first modified example described above, the driven coupling  48  on the sheet feed cassette  93  side is decoupled from the drive transmitting coupling  49  on the apparatus body  201   a  side and the driving force of the driving motor  50  is released when the sheet feed cassette  93  is drawn out of the apparatus body  201   a . Thereby, the spiral spring member  70  thus set free rotates in an inverse direction, so that the driving pulley  40  is driven in a direction of an arrow B, a lower part of the timing belt  41  rotates in a direction of an arrow C, and the sheet bundle moving member  37  is moved in a direction of an arrow D. This arrangement makes it possible to obtain the same effect with the embodiment described above because the sheet bundle moving member  37  instantly moves toward the home position on the second sheet storage portion  28   a  side. 
     It is noted that in the first modified example, it is possible to apply a pre-load by the spiral spring member  70  to the sheet bundle moving member  37  at the home position indicated by a solid line in  FIG. 7 . This arrangement makes it possible to immediately return the sheet bundle moving member  37  to the home position illustrated in  FIG. 7  by the moving force of the spiral spring member  70  when the sheet feed cassette  93  is drawn out of the apparatus body  201   a  after moving the sheet bundle moving member  37  to the first sheet storage portion  28   b  side. 
     In contrary, it is conceivable that the sheet bundle moving member  37  returns only to an intermediate position indicated by a two-dot chain line in  FIG. 7  if the pre-load by the spiral spring member  70  is not applied to the sheet bundle moving member  37 . However, because the sheet bundle moving member  37  can be moved to the middle part of the second sheet storage portion  28   a  side also in this case, no such problem that the user erroneously sets a sheet bundle Sb on the left side of the sheet bundle moving member  37  in  FIG. 7  in a state in which the sheet bundle moving member  37  is unable to return to the second sheet storage portion  28   a  side occurs. 
     Second Modified Example 
     Next, a second modified example of the embodiment described above will be described with reference to  FIG. 8 .  FIG. 8  is a section view illustrating the forced moving mechanism  19  and others of the sheet feeding apparatus  53  of the second modified example. It is noted that the same or corresponding members with those of the embodiment described above will be denoted by the same reference numerals and descriptions of those having the same configurations and functions will be omitted. 
     While a basic part of the second modified example is the same with the configuration of the embodiment described above with reference to  FIGS. 4A through 4C , the forced moving mechanism, i.e., the moving portion,  19  is provided with not the tensile spring  44  but a weight  79 , i.e., a weight member. That is, one end of a wire  80  is fixed windably round an end side of a driving shaft  40   a  of the driving pulley  40  on the first sheet storage portion  28   b  side of the timing belt  41  stretched between the driving pulley  40  and the driven pulley  46 . Then, another end of the wire  80  is attached to the weight (weight member)  79  of a predetermined weight through a pulley  73  rotatably supported to a rotary shaft  73   a . This arrangement makes it possible to rotate the driving shaft  40   a  in a direction of an arrow B when the weight  79  falls by its own weight in a direction of an arrow E and to move the sheet bundle moving member  37  in a direction of an arrow D in which the sheet bundle moving member  37  returns to its home position. 
     The arrangement described above also makes it possible to move the sheet bundle moving member  37  from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side by the timing belt  41  rotated by the rotating driving pulley  40  by the second modified example in the same manner with the embodiment described above. At this time, it is possible to charge the moving force by lifting the weight  79  while winding the wire  80  around the driving shaft  40   a.    
     According to the forced moving mechanism  19  of the second modified example constructed as described above, it is possible to charge the moving force as a potential energy by the weight  79  lifting in linkage with the move of the sheet bundle moving member  37  from the second sheet storage portion  28   a  side to the first sheet storage portion  28   b  side. Then, it is possible to move the sheet bundle moving member  37  to the second sheet storage portion  28   a  side by the moving force of the weight  79  immediately falling in the state in which the load of the transmission portion  18  is reduced when the sheet feed cassette  93  is drawn out of the attachment space  15 . 
     According to the second modified example described above, the driven coupling  48  on the sheet feed cassette  93  side is decoupled from the drive transmitting coupling  49  on the apparatus body  201   a  side and the driving force of the driving motor  50  is released when the sheet feed cassette  93  is drawn out of the apparatus body  201   a . Thereby, because the weight  79  thus set free falls by its own weight, the driving pulley  40  is rotated in the direction of the arrow B, the lower part of the timing belt  41  rotates in the direction of the arrow C, and the sheet bundle moving member  37  is moved in the direction of the arrow D. This arrangement makes it possible to obtain the same effect with the embodiment described above because the sheet bundle moving member  37  instantly moves toward the home position on the second sheet storage portion  28   a  side. 
     It is noted that the configuration in which the sheet bundle moving member  37  is forcibly moved to the second sheet storage portion  28   a  side in response to the decoupling of the driven coupling  48  from the drive transmitting coupling  49  has been described in the embodiment and in the first and second modified examples. However, the present invention is not limited to such configuration and may be configured as follows. For instance, it is possible to configure such that the driving unit such as the motor and the gear train not illustrated driving the charge member  43  is provided on the sheet feed cassette  93  side and power is supplied to the motor from the apparatus body  201   a  side through a connector or the like not illustrated. Then, it is possible to configure such that the sheet bundle moving member  37  moves toward the second sheet storage portion  28   a  when the supply (transmission) of the power through the connector is disconnected. It is noted that in this case, it is preferable to use a normal DC motor not generating cogging torque and others as the motor setting on the sheet feed cassette  93  side. Such arrangement also makes it possible to bring about effects substantially the same with those of the embodiment and the first and second modified examples described above. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-043472, filed Mar. 5, 2015 and Japanese Patent Application No. 2015-241946, filed Dec. 11, 2015 which are hereby incorporated by reference herein in its entirety.