Patent Publication Number: US-2005133991-A1

Title: Sheet conveying apparatus, sheet treating apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a sheet conveying apparatus, a sheet treating apparatus and an image forming apparatus provided with the same, and particularly to a sheet treating apparatus which realizes sheet treatment of large capacity with a saved space and at a low cost and by saved electric power, and an image forming apparatus provided with the same.  
      2. Description of Related Art  
      Heretofore, some of image forming apparatuses such as copying machines, printers and facsimile apparatuses have been provided with sheet treating apparatuses adapted to successively introduce sheets having images formed thereon into the apparatus, and subject these sheets to a binding process, in order to mitigate the time and labor required to bind sheets such as sheets for copying machines on which images have been formed.  
      As such sheet treating apparatuses, there are known ones of a type which are provided near the sheet discharging port of an image forming apparatus main body, align the sheets printed on the image forming apparatus main body side, and then successively supplied from the discharging port, and thereafter subject those sheets to a binding process and discharge them.  
      Among such conventional sheet treating apparatuses, there are known ones in which conveying rollers become spaced apart from each other during the binding process to thereby form on a conveying path an intermediate stacking portion for carrying out sheet treatment, alignment is effected and the binding process is carried out, and the conveying rollers again nip the bundle of sheets therebetween and convey the sheets.  
      In the apparatus wherein as described above, the rollers are spaced apart from each other for the alignment, an actuator for performing the roller spacing operation becomes necessary discretely from an actuator used for the aligning operation, whereby the apparatus has become bulky and costly.  
      Also, in view of the problem as noted above, there has been developed an apparatus in which the drive of a motor rotatable in forward and reverse directions is selectively transmitted to aligning means and spacing means by a drive transmitting portion, and the aligning operation of the aligning means, the spacing operation of the pair of rollers and the drive control of the pair of rollers are selectively performed to thereby achieve space saving, lower costs and electric power saving.  
      However, what is used in the conventional apparatus is of a construction in which a roller holding member is raised by the use of a cam alone to thereby space the pair of rollers apart from each other (cf. Japanese Patent Application Laid-open No. H11-130326) and to obtain a large space for stacking a large volume of paper, it is necessary to give a great difference between the maximum radius and minimum radius of the cam, and as a result, a large cam must be used, and this has led to the problem that the apparatus becomes bulky. Also, torque must be set in accordance with the maximum radius portion of the cam, and great torque becomes necessary for spacing the pair of rollers apart from each other, whereby a large motor becomes necessary, and this has also led to the problem that the apparatus becomes bulky and costly.  
     SUMMARY OF THE INVENTION  
      So, the present invention has been made in view of such a situation, and has as its object to provide a sheet conveying apparatus and a sheet treating apparatus which realize the treatment of a large volume of paper with a saved space and at a low cost and by saved electric power, and an image forming apparatus provided with the same.  
      The present invention is provided with a pair of conveying rollers having a first roller and a second roller disposed in opposed relationship with the first roller, a roller supporting member which rotatably supports the first roller, and is movable between a first position in which the first roller can cooperate with the second roller to convey a sheet and a second position in which the first roller is spaced apart from the second roller, a driving member which pivotally moves the roller supporting member, a drive transmitting portion which transmits drive to the driving member, and a drive source which transmits the drive to the drive transmitting portion, and is characterized in that the roller supporting member has a gear portion, and the driving member has a gear meshing with the gear portion of the roller supporting member, and effects the movement of the roller supporting member from the first position to the second position by the meshing engagement between the gear portion and the gear.  
      Also, the present invention is characterized in that the roller supporting member is provided with a cam stopper portion, and the driving member has a cam corresponding to the cam stopper portion of the roller supporting member, effects the holding of the roller supporting member in the first position by the engagement between the cam and the cam stopper portion, and effects the movement of the roller supporting member from the second position to the first position by the release of the engagement between the cam and the cam stopper portion.  
      Also, the present invention is characterized in that the movement of the roller supporting member from the first position to the second position and the movement thereof from the second position to the first position are effected by the driving of the drive source transmitted from the drive transmitting portion to the driving member in only one direction.  
      According to the present invention, there can be provided a sheet conveying apparatus and a sheet treating apparatus which can achieve space saving and low costs and electric power saving, and an image forming apparatus provided with the same. Particularly, the construction of the driving system of the sheet treating apparatus which can form an intermediate stacking portion capable of stapling a large volume of paper can be inexpensively realized by a compact and simple construction. Also, torque used becomes smaller than in the conventional construction comprising only a cam, and electric power saving is realized and therefore, the electric power supply capacity of the apparatus can also be made small. Thus, the post-treatment of a large volume of paper in the sheet conveying apparatus, the sheet treating apparatus and a laser beam printer (image forming apparatus) provided with the same can be realized a construction of saved space, low cost and saved electric power. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic cross-sectional view showing the general construction of a laser beam printer which is an example of an image forming apparatus provided with a sheet treating apparatus according to a first embodiment of the present invention.  
       FIG. 2  is a perspective view of a pair of discharging rollers provided in the sheet treating apparatus.  
       FIG. 3A  is a plan view of the essential portions of the sheet treating apparatus,  FIG. 3B  is a side view of the essential portions of the sheet treating apparatus, and  FIGS. 3C and 3D  show stamp means as it is seen from a direction indicated by the arrow A of  FIG. 3A .  
       FIGS. 4A and 4B  show a state in which a slide guide provided in the sheet treating apparatus is located at a home position and a bundle of sheets falls.  
       FIGS. 5A and 5B  illustrate the movement of each portion in the binding operation of the sheet treating apparatus.  
       FIGS. 6A and 6B  show a state in which sheets are aligned by the slide guide.  
       FIG. 7  illustrates the drive transmitting portion of the sheet treating apparatus.  
       FIGS. 8A and 8B  illustrate the drive transmission during the spacing operation and the drive interrupting operation of the pair of discharging rollers of the sheet treating apparatus.  
       FIG. 9  illustrates the mechanical construction of the discharging roller supporting member and spacing gear of the sheet treating apparatus.  
       FIGS. 10A and 10B  illustrates the cut-away gear shapes of the discharging roller supporting member and the spacing gear of the sheet treating apparatus.  
       FIGS. 11A and 11B  illustrate the spacing operation of the pair of discharging rollers.  
       FIGS. 12A and 12B  illustrate the drive transmission during the approaching operation of the pair of discharging rollers of the sheet treating apparatus.  
       FIGS. 13A and 13B  illustrate the drive transmission during the paddle rotating operation of the sheet treating apparatus.  
       FIG. 14  is a side view of the drive transmitting portion of a sheet treating apparatus according to a second embodiment of the present invention.  
       FIG. 15A  is a plan view of the vicinity of the pair of discharging rollers of a sheet treating apparatus according to a third embodiment of the present invention, and  FIG. 15B  is a cross-sectional view taken along the line XVB-XVB of  FIG. 15A .  
       FIGS. 16A and 16B  are cross-sectional views of the vicinity of the pair of discharging rollers of the sheet treating apparatus shown in  FIG. 15A  taken along line XVI-XVI. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Some embodiments of the present invention will hereinafter be described in detail with reference to the drawings.  
     First Embodiment  
       FIG. 1  is a cross-sectional view of an image forming process system constituted by an image forming apparatus provided with a sheet treating apparatus and an image reading apparatus according to the present invention.  
      In  FIG. 1 , the reference numeral  100  designates a printer provided with an image reading portion  200 , and after an image is formed on a sheet supplied from a sheet supplying cassette  101 , two discharging routes are set. They are an A conveying path  105  which U-turn-conveys a sheet to the upper portion of a writing scanner  104  by fixed sheet discharging rollers  102  and a pair of runners  103 , and effects reversal conveyance, and a B conveying path  106  which effects direct conveyance.  
      Also, a sheet treating apparatus  300  is adapted to stack on a stacking portion  301  the sheets discharged out of the printer main body  100 , and thereafter effect the alignment of the sheets by aligning means  302 , bundle the sheets in each predetermined job and staple the sheets at one or more portions thereof and discharge and stack them on a second stacking portion  303 , or simple discharge and stack the sheets on a second stacking portion  303  in a face-down or face-up posture.  
      Description will now be made of the construction of the sheet treating apparatus  300  and the movement of each portion when the sheet S conveyed from the printer main body  100  travels toward the sheet treating apparatus  300 .  
      In  FIG. 1 , the sheet treating apparatus  300  is provided with a discharging upper roller  330   a,  a discharging lower roller  330   b,  a resilient paddle  321  for moving the sheet in an aligning direction, and a reference wall  322  against which the trailing edge of the sheet is rammed.  
      A pair of discharging rollers  330  constituted by the discharging upper roller  330   a  and the discharging lower roller  330   b,  as shown in  FIG. 1 , is rotatively driven by a driving motor M 1  which will be described later. Also, the discharging upper roller  330   a  is supported on a discharging roller supporting member  331  as a pivotally movable roller supporting member.  
      Further, in the present embodiment, the pair of discharging rollers  330 , as shown in  FIG. 2 , is such that the roller main bodies  330   a   1 ,  330   a   2  of the discharging upper roller  330   a  as a first roller and the roller main bodies  330   b   1 ,  330   b   2  of the discharging lower roller  330   b  as a second roller are disposed in a so-called staggered fashion so as to come into between the respective roller main bodies. Thus, there is provided a so-called comb-tooth construction in which the discharging upper roller  330   a  and the discharging lower roller  330   b  do not contact with each other. Also, the discharging upper roller  330   a  and the discharging lower roller  330   b  are adapted to overlap each other in the axial direction thereof.  
      The discharging upper roller  330   a  and the discharging lower roller  330   b  overlap each other as described above, whereby when the sheet (bundle) is discharged by the pair of discharging rollers  330 , the sheet (bundle) becomes wavy and the rigidity of the sheet (bundle) becomes strong. As a result, the sheet (bundle) comes to be discharged straight without being downwardly flexed even after it has passed the pair of discharging rollers  330 . Further, this rigidity becomes stronger as the amount of overlap of the discharging upper roller  330   a  and the discharging lower roller  330   b  becomes greater, and as the rigidity thus becomes stronger, the distance by which the sheet (bundle) is discharged straight becomes longer.  
      As shown in  FIG. 2 , the roller main bodies  330   b   1  contacting with the opposite end portions of the discharging lower roller  330   b  are formed so as to be larger in diameter toward the outer portions thereof, thereby raising the opposite end portions of the sheet (bundle).  
      The sheet (bundle) is thus given rigidity to thereby lengthen the distance by which the sheet (bundle) is discharged straight, and raise the opposite end portions of the sheet (bundle), whereby even when the amount of curl and the discharging direction of the sheet discharged from the printer main body  100  differ greatly due to the difference in the kind of paper or a fixing mode or a printer mode, and irrespective of whether the stapling process has been carried out or not, the leading edge of a sheet (bundle), when it is discharged, can be prevented from contacting with an already discharged sheet (bundle), and the stackability of the sheet (bundle) can be improved.  
      On the other hand, slide guides  302   a  and  302   b  which will be described later are driven by a jogger motor M, which in the present embodiment is a stepping motor. Also, the paddle  321  as aligning means is formed of a flexible material such as rubber, and a plurality of such paddles are fixed to a paddle shaft  350  in a direction orthogonal to a sheet conveying direction. When the sheet is discharged from the printer main body  100 , the paddles are rotated counter-clockwisely by the driving of the paddle shaft  350 , whereby the sheet S is moved in a direction opposite to the sheet conveying direction which is an aligning direction, and contacts with the reference wall  322  and is aligned.  
      Also, as shown in  FIG. 3A , in the sheet treating apparatus  300  according to the present embodiment, the slide guides  302   a  and  302   b  which will be described in detail later are provided as aligning members which effect the widthwise alignment of the sheet. The letter M designates a jogger motor as a drive source, and in  FIG. 3A , the letter H denotes a stapler as binding means for stapling the sheet bundle to thereby carry out a binding process to the sheet bundle, and this stapler H is fixedly disposed on the slide guide  302   a  side to carry out stapling on the left upper corner portions of the image bearing surfaces of the sheets on which images are formed to thereby bind the sheets.  
      Now, in the present embodiment, this sheet treating apparatus  300  is designed to be capable of stacking, aligning and stapling the sheets on a first stacking portion  301 , discharging and stacking the sheets onto a second stacking portion  303 , and discharging and stacking the sheets onto the second stacking portion  303  simply in a face-down or face-up posture.  
      Description will now be made of the simple stacking operation of discharging and stacking the sheets onto the second stacking portion  303  in the face-down posture. In this case, as shown in  FIG. 4A , the bottom surfaces of the right slide guide  302   a  and the left slide guide  302   b  with respect to a sheet carrying-in direction are retracted to a position in which they do not contact with the sheet S carried in, i.e., a position outer by a predetermined amount from the widthwise direction of the sheet in which the sheet S is not supported.  
      Accordingly, the sheet S conveyed by a pair of inlet rollers  362  passes the front of the stapler H, and then is conveyed by the pair of discharging rollers  330  constituted by the discharging upper roller  330   a  and the discharging lower roller  330   b,  and falls toward a second sheet discharging portion  303 , as indicated by the arrow in  FIG. 4B .  
      Description will now be made of the operations of stacking, aligning and stapling the sheets on the first stacking portion  301 , and discharging and stacking the sheets onto the second stacking portion  303 . In this case, the slide guides  302   a  and  302   b,  as shown in  FIG. 3A , wait at a waiting position in which they can place the sheets carried thereto and do not interfere with the side edge portions of the sheets. In the present embodiment, when the size (width) of the sheet S is a maximum size which can be passed, the waiting position of the slide guides  302   a  and  302   b  is set so that as shown in  FIG. 3B , the gaps on the opposite sides may be of a predetermined amount “d”.  
      Also, at this time, the interval between the end surfaces of the bottom surfaces of the two slide guides  302   a  and  302   b  is smaller than the width of the sheet S. Design is made such that the two slide guides  302   a  and  302   b  are at such positions, whereby they can constitute the first stacking portion  301  for supporting the sheet S coming in, together with a sheet guide portion between the reference wall  322  and the pair of discharging rollers  330 . Accordingly, the sheet conveyed by the pair of inlet rollers  362  passes the front of the stapler H, and then is conveyed by the pair of discharging rollers  330 , and is further conveyed onto the guide surface of the first sheet stacking portion  301  constituted by the slide guides  302   a  and  302   b.    
      On the other hand, immediately after as shown in  FIG. 5A , the first sheet has been conveyed onto a surface formed by the slide guides  302   a  and  302   b,  the discharging roller supporting member  331  is clockwisely pivotally moves as shown in  FIG. 5A , whereby the discharging upper roller  330   a  supported by the discharging roller supporting member  331  is upwardly retracted, and the pair of discharging rollers are spaced apart from each other.  
      Also, at the same time, the drive connected to the pair of discharging rollers  330  is cut off to thereby stop the rotation of the discharging upper roller  330   a  and the discharging lower roller  330   b.  When the trailing edge of the sheet S completely passes between the pair of inlet rollers  362 , the paddles  321  make one bull rotation counter-clockwisely about the paddle shaft  350  while contacting with the upper surface of the sheet S. Thereby the sheet S is rammed against the reference wall  322 , thus completing the aligning operation in the conveying direction.  
      Next, only the left slide guide  302   b  operates, and the width wise aligning operation of the sheet S stacked on the first sheet stacking portion  301 . Specifically, the slide guide  302   b  is driven by the jogger motor M and is moved to the right side in  FIG. 4A , whereby the slide guide  302   b  contacts with the left side edge of the sheet S and pushes the sheet S toward the slide guide  302   a  side.  
      The right side edge of the sheet S then strikes against the slide guide  302   a,  whereby the widthwise alignment of the sheet is effected. Setting is done so that the sheet S may be moved to a stapling position set in the position wherein the sheet contacts with the slide guide  302   a  and has been aligned. After the aligning operation, the slide guide  302   b  is moved in a direction to widen more than the width of the sheet S so as to be capable of coping with the conveyance of the next sheet again at the waiting position.  
      In order to keep the thus aligned state, near the right end portion of the sheet in its aligned state, there is provided stamp means  380  as holding means of which the lever  380   b  provided with a frictional member  380   a  as shown in  FIG. 3C  is moved in a vertical direction and presses the aligned sheet to thereby hold it at a predetermined position.  
      This stamp means  380  is provided with a lever  380   b  pivotally movable in a vertical direction. After the aligning operation has been completed and before the sheet coming in next contacts with the aligned sheet, the lever  380   b  upwardly pivotally moved as shown in  FIG. 3D  is downwardly pivotally moved by a solenoid (not shown), and presses the upper surface of the sheet as shown in  FIG. 3C , whereby the sheet in its aligned state is moved by the coming-in of the next sheet so as to prevent the alignment from being disturbed.  
      After the alignment of the first sheet has been completed in this manner, the second sheet is conveyed, but during the conveyance of the second and succeeding sheets, the pair of discharging rollers  330  are spaced apart from each other and therefore, after the trailing edge of the sheet S has completely passed through the pair of inlet rollers  362  and before the aligning operation is started, the stamp means is upwardly moved, thus terminating the holding operation. The aligning operation thereafter is entirely similar to that of the first sheet and therefore need not be described.  
      Such an operation is then repetitively performed and the operation of aligning the last (nth) sheet (Sn) in one job is performed, and the left side edge portion of the sheet is rammed against the slide guide  302   b,  and in the state of  FIG. 6A  in which the movement of the slide guide  302   b  has been stopped, the right position of the trailing edge of the sheet bundle is stapled by the stapler H.  
      On the other hand, when the stapling operation is terminated in this manner, the discharging roller supporting member  331  is counter-clockwisely rotated as shown in  FIG. 5B , whereby the discharging upper roller  330   a  supported by the discharging roller supporting member  331  is downwardly moved, and the pair of discharging rollers  330  are formed. Thereafter, the drive is connected to both of the rollers of the pair of discharging rollers  330  to thereby start the rotation of the discharging upper roller  330   a  and the discharging lower roller  330   b.    
      Simultaneously with this operation, the jogger motor M is rotatively driven, whereby the slide guides  302   a  and  302   b  are moved from the state shown in  FIGS. 6A and 6B  in a direction in which the spacing therebetween widens. When thereafter, the spacing between the two slide guides  302   a  and  302   b  becomes approximate to or widen than the width of the sheet, the stapled sheet bundle supported by the slide guides  302   a  and  302   b  downwardly falls as shown in  FIGS. 4B and 5B , and is stacked on the second stacking portion  303 .  
      Reference is not had to FIGS.  7  to  12 A and  12 B to describe a construction for rotating the paddle shaft  350  and a construction for upwardly retracting the discharging roller  330   a  supported by the discharging roller supporting member  331 .  
       FIG. 7  shows a gear train for transmitting the drive to the discharging upper roller  330   a,  and a gear train for transmitting the drive to the discharging lower roller  330   b.  In  FIG. 7 , the reference numeral  505  designates a discharging upper roller gear fixed to the shaft  505   a  of the discharging upper roller  330   a,  and the reference numeral  506  denotes a discharging lower roller gear fixed to the discharging lower roller  330   b.  Also, the discharging upper roller gear  505  receives the drive from an idler gear  503  through a belt  504 , and the discharging lower roller gear  506  receives the drive from a discharging lower roller idler gear  508  (disposed coaxially with the spacing gear  404 ) belt-driven from the idler gear  503 . Also, during the initial state shown in  FIG. 7 , the discharging roller supporting member  331  is designed to be biased by a spring P in a direction in which the rollers are moved toward each other, and strike against stopper means (not shown), and the position of the discharging upper roller  330   a  is determined by this stopper means, and the amount of nip between the pair of discharging rollers  330  is prescribed.  
      Also, the present driving train includes the paddles  321  and a roller spacing drive system, besides a conveying drive system for driving the discharging upper roller  330   a  and the discharging lower roller  330   b.  The conveying drive system is for receiving rotation from a motor gear  501  fixed to the shaft of the driving motor M 1 , and driving two pairs of rollers, i.e., the pair of discharging rollers  330  and the pair of inlet rollers  362  mounted on a gear  513  to thereby convey the sheet.  
      Also, the paddle  321  and the roller spacing drive system are rotated by a driving force form a motor gear  401  driven by a driving motor M 2  which is a single forwardly and reversely rotatable drive source. A rocking holder  450  which is a rocking member which rotatably supports a changeover gear  403  for selectively transmitting the driving of the driving motor M 2  to the paddles  321  or the discharging roller supporting member  331  and a step gear  402  meshing with the motor gear  401 , and rocks with the center of rocking movement  450   a  as a fulcrum is rocked. Thereby, the changeover gear  403  is selectively connected to a spacing gear  404  having a cut-away tooth gear  404   a  (which will be described later) and a cam gear  404   b  (which will be described later) for spacing the pair of-discharging rollers  330  apart from each other by the driving of the driving motor M 2 , or a paddle idler gear  406  for transmitting the drive of the driving motor M 2  to the paddle  321 .  
      A predetermined frictional force acts between the step gear  402  and the rocking holder  450  so that when the step gear  402  is rotated with the rotation of the motor gear  401 , the rocking holder  450  may be rocked by the rotation of this step gear  402 . In the present embodiments, design is made such that when the rocking holder  450  is counter-clockwisely rocked, the changeover gear  403  is connected to the spacing gear  404 , and when the rocking holder  450  is clockwisely rocked, the changeover gear  403  is connected to the paddle idler gear  406 , so as to transmit the drive.  
      Also, in  FIG. 7 , a drive releasing plate  550  supporting the drive transmitting gear  502  and rockable about the center of rocking movement  550   a  is clockwisely biased by a spring  555 . When the discharging roller supporting member  331  spaces the pair of discharging rollers  330  apart from each other, a releasing lever portion  331   a  presses the drive releasing plate  550  to thereby release the drive transmission from the drive transmitting gear  502  to the idler gear  503  disposed on the paddle shaft  350 , thereby releasing the drive to the pair of discharging rollers  330 .  
      A drive transmitting portion  500  is constituted by the changeover gear  403 , the spacing gear  404 , the paddle idler gear  406  and the releasing lever portion  331   a  provided on the discharging roller supporting member  331 .  
      The operation of upwardly retracting the discharging upper roller  330   a  in the drive transmitting portion  500  of such a construction will now be described with reference to  FIGS. 8A and 8B  to  FIGS. 11A and 11B .  FIGS. 8A and 8B  show a state in which the paddle gear  407  and the paddles  321  are not shown.  
       FIG. 8A  shows the drive transmission during the spacing operation of the discharging upper roller  330   a.  When the motor gear  401  is clockwisely rotated, the step gear  402  is rotated while counter-clockwisely rocking the rocking holder  450 . Thereby, the changeover gear  403  comes into meshing engagement with the spacing gear  404 . When the changeover gear  403  thus comes into meshing engagement with the spacing gear  404 , the rocking holder  450  is not rocked any further. Also, when in this state, the changeover gear  403  is not in meshing engagement with the paddle idler gear  406 .  
      Subsequently, the details of the spacing operation by the spacing gear will be described with reference to  FIGS. 8A and 8B  to  FIGS. 12A and 12B .  FIG. 9  shows the construction of the spacing gear  404  and the construction of the discharging roller supporting member  331 . The spacing gear  404  as a driving member is comprised of the cut-away tooth gear.  404   a,  the cam gear  404   b  and a drive transmitting gear  404   c  to which the drive is transmitted from the changeover gear  403 . Also, the discharging roller supporting member  331  has a cut-away tooth gear portion  331   b  and a cam stopper portion  331   c.    
      Also, in the present embodiment, the cut-away tooth gear portion  331   b  of the discharging roller supporting member and the cut-away tooth gear  404   a  of the spacing gear are such that as shown in  FIGS. 10A and 10B , the second gears (indicated by black paint) as counted from the teeth  331   b   1  and  404   a   1  meshing with each other at first are blank. This is because the presence of the second teeth does not mean that the first teeth  331   b   1  and  404   a   1  mesh with each other when the spacing operation is started, but as shown in  FIG. 10B , the tooth  404   a   1  meshes with the tooth  331   b   2  to thereby prevent predetermined meshing engagement from deviating, and effect stable spacing. The cut-away tooth gear portion  331   b  and the cut-away tooth gear  404   a  can obtain a similar effect even if they are ordinary gears, but the precise control of the driving motor becomes necessary. To make complicated motor control unnecessary, one of the gears can be of a cut-away tooth gear construction, and by both gears being cut-away tooth gears, more reliable meshing engagement is realized.  
      The spacing operation will now be described with reference to  FIGS. 8A, 8B ,  11 A and  11 B. As described in connection with  FIG. 8A , when the changeover gear  403  meshes with the spacing gear  404 , the spacing gear  404  is counter-clockwisely rotated by the clockwisely rotated changeover gear  403  and meshes with the cur-away tooth gear portion  331   b  of the discharging roller supporting member  331  to thereby begin to push up the discharging roller supporting member  331 . Then, as shown in  FIG. 11A , the cam gear  404   b  follows the rotation of the cut-away tooth gear  404   a  and is rotated, and abuts against the cam stopper portion  331   c  of the discharging roller supporting member in a position in which the spacing gear  404  has been rotated by  104  degrees. At this time, the meshing engagement between the cur-away tooth gear  404   a  of the spacing gear  404  and the cur-away tooth gear portion  331   b  of the discharging roller supporting member is released.  
      In the present embodiment, when the cut-away tooth gear  404   a  has been rotated by 131 degrees, the driving of the driving motor M 2  is stopped, and the discharging roller supporting member  331  is held by the cam gear  404   b  and the pair of discharging rollers  330  becomes paced apart from each other. Along therewith, as shown in  FIG. 8B , the releasing lever portion  331   a  of the discharging roller supporting member  331  pushes the drive releasing plate  550 , whereby the meshing engagement between the drive transmitting gear  502  and the idler gear  503  is released and the driving of the pair of discharging rollers  330  is stopped. As described above, the driving for spacing is effected by the cut-away tooth gear, whereby reliable driving becomes possible by small torque and also, it becomes possible to cope with an increase in the spacing distance. Also, stable holding becomes possible by the cam. The aforedescribed rotational angle is an angle derived by the construction of the present embodiment, and of course, the rotational angle when the construction has been changed differs.  
      On the other hand, thereafter the aligning operation is terminated and further, the driving motor M 2  is clockwisely rotated, whereupon as shown in  FIG. 11B , the spacing gear  404  is further rotated counter-clockwisely, and the holding by the cam gear  404   c  is released. Along therewith, the discharging upper roller  330   a  is lowered together with the discharging roller supporting member  331  and approaches the discharging lower roller  330   b,  thus bringing about a state shown in  FIG. 12B . This discharging roller supporting member  331  is biased by the already described pressure spring P shown in FIG.  7 , and by this pressure spring P, the discharging upper roller  330   a  is biased toward the discharging lower roller  330   b  with predetermined pressure. Also, it is to be understood that at this time, the discharging roller supporting member  331  is rammed against and held by stopper means (not shown).  
      Also, the spacing gear  404  is counter-clockwisely rotated, whereby the drive releasing plate  550  is returned to a home position shown in  FIG. 7 . By these series of operations, the spacing and nearing of the pair of discharging rollers  330  and the release and connection of the drive to the pair of discharging rollers  330  are effected.  
      The rotating operation of the paddles  321  in the drive transmitting portion  500  of such a construction will now be described with reference to  FIGS. 13A and 13B .  FIGS. 13A and 13B  show a state in which the idler gear  503  and the drive transmitting gear  502  are not shown.  
      When the motor gear  401  is counter-clockwisely rotated, the step gear  402  is rotated while clockwisely rocking the rocking holder  450 , whereby as shown in  FIG. 13B , the changeover gear  403  comes into meshing engagement with the paddle idler gear  406 . When the changeover gear  403  thus comes into meshing engagement with the paddle idler gear  406 , the rocking holder  450  is not rocked any further. Also, at this time, the changeover gear  403  and the spacing gear  404  are not connected together.  
      The paddle idler gear  406  is in meshing engagement with the paddle gear  407  fixed to the paddle shaft  350 , whereby the paddle shaft  350  is counter-clockwisely rotated and as a result, the paddle  321  is counter-clockwisely rotated. When the paddles  321  are thus counter-clockwisely rotated, the sheet is moved to the side opposite to the sheet conveying direction and contacts with the reference wall  322 , and is aligned.  
      As described above, the drive of the forwardly and reversely rotatable single driving motor M 2  is selectively transmitted to the paddle  321  and the discharging roller supporting member  331  by the drive transmitting portion  500  so that the aligning operation by the paddle  321 , the spacing operation of the pair of discharging rollers  330  and the drive control of the pair of discharging rollers  330  may be selected performed, and the spacing construction is effected by the use of the cut-away tooth gear and the cam gear in combination, whereby the construction of the driving system of a sheet treating apparatus which can form an intermediate stacking portion capable of stapling a large volume of paper can be inexpensively realized by a compact and simple construction. Also, the torque used becomes smaller than in the conventional construction using only a cam, and electric power saving is realized and therefore, the power supply capacity of the apparatus can also be made small. Thereby, the post-treatment of a large volume of paper in the sheet treating apparatus  300  and the laser beam printer (image forming apparatus)  100  provided with the same can be realized by a construction of saved space, low cost and saved electric power.  
     Second Embodiment  
       FIG. 14  shows a second embodiment of the present invention, and the portions thereof overlapping those of the first embodiment need not be described.  
       FIG. 14  represents a drive transmitting portion  600  in the second embodiment. A gear  401  mounted on the driving motor M 2  for effecting the spacing of the pair of discharging rollers  330  and the driving of the paddles  321  is in meshing engagement with a drive transmitting gear  601  which is in meshing engagement with both of the spacing gear  404  and the paddle idler gear  406 .  
      Also, the spacing gear  404  has incorporated therein a one-away clutch  602  for transmitting only counter-clockwise drive, and the paddle idler gear  406  has incorporated therein a one-way clutch  603  for transmitting only clockwise drive. Thus, the drive transmitting portion  600  effects the spacing and nearing of the pair of discharging rollers  330  when the motor is counter-clockwisely rotated, and effects the driving of the paddle  321  when the motor is clockwisely rotated.  
      By adopting the above-described construction, in the present embodiment, not only an effect similar to that of the first embodiment is obtained, but also it becomes possible to effect the selection of the spacing of the motor driving and the driving of the paddles without using a rocking gear and therefore, the rocking space can be omitted and the apparatus can be further downsized. Also, the rocking time by the rocking gear is unnecessary and by only the changeover of the rotating direction of the motor, the spacing and the driving of the paddles can be changed over and therefore, it also becomes possible to cope with still a higher speed.  
     Third Embodiment  
       FIGS. 15A, 15B ,  16 A and  16 B show a third embodiment of the present invention, and the portions thereof overlapping those of the first embodiment need not be described.  
       FIG. 15A  shows the construction of the vicinity of a pair of discharging rollers in a sheet treating apparatus according to the present embodiment.  FIG. 15A  is a plan view of the vicinity of the pair of discharging rollers, and  FIG. 15B  is a cross-sectional view taken along the line XVB-XVB of  FIG. 15A . In  FIG. 15A , for example, the same reference characters as those in  FIG. 2  designate the same or corresponding portions.  FIGS. 15A and 15B  show a stamp member  700  vertically pivotally movable with a shaft  700   b  as a fulcrum, a pulley  702  provided on a paddle shaft  350 , a stamp cam  703 , and a belt  701  passed over the pulley  702  and the cam shaft  705  of the stamp cam  703 . When the paddle shaft  350  is rotated by the construction shown in the already described first or second embodiment, the rotation of this paddle shaft  350  is transmitted to the cam shaft  705  through the belt  701 , whereby the stamp cam  703  is rotated.  
      On the other hand,  FIGS. 16A and 16B  are cross-sectional views taken along the line XVI-XVI of  FIG. 15A .  FIG. 16A  shows a state in which the stamp cam  703  is in a home position. When the stamp cam  703  is thus in the home position, the stamp member  700  presses the sheet by its underside.  
      When the paddle shaft  350  is rotated counter-clockwisely as viewed in  FIG. 16A , the stamp cam  703  is also rotated counter-clockwisely about the cam shaft  705  to thereby push up a contacting portion  700   a  with the stamp member  700  by an amount corresponding to H, thus assuming the position of FIG.  16 B. By the stamp member  700  being thus pushed up by the amount corresponding to H by the stamp cam  703 , the sheet holding operation by the stamp member  700  is released.  
      In the present embodiment, the positions of the stamp cam  703  and the paddle  321  are set to such a positional relation that the paddles  321  contact with the sheet S when the stamp member  700  is releasing its pressing operation. Thereby, the sheet holding operation by the stamp member  700  can be performed by the driving motor M 2  for performing the sheet aligning operation, etc. by the paddles  321 , even if a discrete actuator such as a solenoid is not provided, and downsizing and electric power saving can be realized more inexpensively.  
      By adopting the construction as described above, according to the first embodiment, the construction of the driving system of the sheet treating apparatus which enables the intermediate stacking portion capable of stapling a large volume of paper to be retractable can be inexpensively realized by a compact and simple construction. Also, the spacing drive using the cut-away tooth gear becomes smaller in the torque used than the conventional construction using only a cam, and can realize electric power saving and can therefore also make the power supply capacity of the apparatus small. Also, without the gear diameter being made large, a large space for spacing can be secured. Thereby, the post treatment of a large volume of paper in the sheet treating apparatus  300  and the laser beam printer (image forming apparatus)  100  provided with the same can be realized by a construction of saved space, low cost and saved electric power.  
      Also, according to the second embodiment, of course, an effect similar to that of the first embodiment is obtained, and the rocking space can be curtailed, whereby a sheet treating apparatus more compact than that according to the first embodiment can be realized. Also, the rocking time by the rocking gear is unnecessary and the spacing and paddle driving can be changed over by only the changeover of the rotating direction of the motor and therefore, still a higher speed can be coped with.  
      Also, according to the third embodiment, not only an effect similar to that of the first and second embodiments is obtained, but also the sheet holding operation by the stamp member can be performed by the driving motor for performing the sheet aligning operation, etc. by the paddles even if a discrete actuator such as a solenoid is not provided, and downsizing and electric power saving can be realized more inexpensively.  
      This application claims priority from Japanese Patent Application Nos. 2003-405141 filed on Dec. 3, 2003 and 2004-302244 filed on Oct. 15, 2004, which are hereby incorporated by reference herein.