Patent Publication Number: US-9428351-B2

Title: Feeding device, feeding cassette, and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a feeding device, a feeding cassette, and an image forming apparatus. 
     2. Description of the Related Art 
     Recently, an image forming apparatus such as a copier, a printer, and a facsimile machine includes a feeding device for feeding a sheet and an image forming unit for forming an image on the sheet fed from the feeding device. Such a feeding device may include a feeding cassette that is detachable from the main body of the apparatus. 
       FIG. 11  is a diagram illustrating a configuration of a conventional feeding cassette  150 . The feeding cassette  150  includes a sheet stacking tray  153 . The sheet stacking tray  153  can be raised and lowered so that sheets S stacked on the sheet stacking tray  153  are pressed onto a feeding roller. The feeding cassette  150  further includes a trailing edge regulating plate (not illustrated). The trailing edge regulating plate can slide and regulate a position of an edge (hereinafter referred to as a trailing edge) of the sheets S stacked on the sheet stacking tray  153 , on an upstream side in the feeding direction thereof. Thus, the feeding cassette  150  can accommodate the sheets S of different sizes. The feeding cassette  150  further includes a pair of side regulating portions  151  and  152 . The side regulating portions  151  and  152  regulate positions of the side edges of the sheets S in a direction (hereinafter referred to as a width direction) perpendicular to the feeding direction. The pair of side regulating portions  151  and  152  is coupled with each other via a rack gear and a pinion gear (not illustrated). Thus, when the user moves one side regulating portion  151 , the other side regulating portion  152  moves in conjunction with the side regulating portion  151 . 
     Even the sheets S of a standard size such as A4 or B5 vary in outer dimensions. For example, when a dimensional tolerance in the width direction of the sheet S is ±2 mm, the side regulating portions  151  and  152  need to follow the size of the sheet S in the range of ±2 mm. Thus, conventionally, one side regulating portion  152  serves as a reference surface  152   a , and a sheet pressing portion  154  of the other side regulating portion  151  presses the sheet S against the reference surface  152   a . A distance y between the sheets S and the side regulating portion  152  is zeroed by appropriately setting the stroke of the sheet pressing portion  154  and the spring pressure of a spring  155 . Thus, the variations in the outer dimensions of the sheets S can be accommodated to maintain the print accuracy on the side of the reference surface  152   a.    
     When the feeding cassette  150  is installed in the main body of the apparatus, the sheets S are likely to be pushed by inertia in the direction in which the feeding cassette  150  is installed. Thus, if the installing direction of the feeding cassette  150  is the same as the width direction (the direction indicated by an arrow  150   a ) of the sheets S, and the side regulating portion  152  on the rear side in the installing direction serves as the reference surface  152   a  in the width direction, the sheets S naturally come closer to the side of the reference surface  152   a  during the installation of the feeding cassette  150 , thereby reducing the distance y. Thus, the spring pressure of the sheet pressing portion  154  can be lower in a case where the side regulating portion  152  on the rear side is set as the reference surface side than in a case where the side regulating portion  151  on the front side is set as the reference surface side. Such a configuration can minimize the resistance applied by the sheet pressing portion  154  to the sheets S, whereby the sheets S can be stably fed. 
     When changing the positions of the side regulating portions  151  and  152 , the side regulating portion  151  on the front side can be operated easier than the side regulating portion  152  on the rear side. Thus, in many image forming apparatuses, the side regulating portion  151  on the front side is used as an operation portion for the user. 
     Japanese Patent Application Laid-Open No. 2003-160239 discusses a feeding device having a configuration where, in a pair of side regulating members for regulating the edge portions of sheets stacked on a stacking tray, the one on the rear side is fixed (locked). In the feeding device discussed in Japanese Patent Application Laid-Open No. 2003-160239, the side regulating member on the rear side is fixed, and thus the side regulating member can be prevented from falling down due to the inertia produced when the feeding cassette is inserted in the main body of the apparatus. Japanese Patent Application Laid-Open No. 2003-160239 discusses a configuration where the side regulating member on the rear side is locked or unlocked by a user directly operating a lever used for locking and unlocking the member (first and second exemplary embodiments in Japanese Patent Application Laid-Open No. 2003-160239). Japanese Patent Application Laid-Open No. 2003-160239 further discusses a configuration where the user operates a knob of the side regulating member on the front side so that the side regulating member on the rear side is locked or unlocked (third and fourth exemplary embodiments in Japanese Patent Application Laid-Open No. 2003-160239). 
     However, the configurations discussed in Japanese Patent Application Laid-Open No. 2003-160239 needs to be further improved in the following points. First, the first and the second embodiments in Japanese Patent Application Laid-Open No. 2003-160239 need to be improved in usability because the user needs to directly operate the lever to lock or unlock the side regulating portion on the rear side. Next, the third and the fourth exemplary embodiments in Japanese Patent Application Laid-Open No. 2003-160239 require a plurality of dedicated parts for coupling the side regulating portion on the front side with the side regulating portion on the rear side. Thus, an increase in the number of parts may cause a cost increase. Furthermore, the added dedicated parts are disposed in a space below the side regulating members, whereby the size of the feeding cassette might increase in the height direction. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a feeding device and an image forming apparatus in which the movement of a positioning portion for regulating the position of a sheet can be regulated and the regulation can be released without impairing usability. 
     According to an aspect of the present invention, a feeding device for feeding a sheet includes a stacking portion on which the sheet is to be stacked, a first positioning portion, which is disposed movably in a first direction and a second direction opposite to the first direction and is in contact with an edge of the sheet stacked on the stacking portion, configured to regulate a position of the sheet, a second positioning portion, which is disposed movably in the first direction and the second direction and is in contact with an edge of the sheet stacked on the stacking portion, configured to regulate the position of the sheet, an interlocking portion configured to move the first positioning portion and the second positioning portion in conjunction with each other, a first regulating portion configured to regulate a movement of the first positioning portion, and a first release portion configured to release, when the second positioning portion is moved in the first direction or the second direction, the regulation of the movement of the first positioning portion performed by the first regulating portion. 
     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 
         FIGS. 1A and 1B  are diagrams illustrating configurations of first and second positioning portions according to a first exemplary embodiment. 
         FIGS. 2A to 2E  are diagrams illustrating operations according to the first exemplary embodiment. 
         FIG. 3  is a diagram illustrating an operation according to the first exemplary embodiment. 
         FIGS. 4A and 4B  are diagrams illustrating operations according to the first exemplary embodiment. 
         FIGS. 5A to 5C  are diagrams illustrating operations for setting a sheet of a non-standard size in a feeding cassette. 
         FIG. 6  is a perspective view of the feeding cassette according to the first exemplary embodiment. 
         FIG. 7  is a cross-sectional view of a printer according to the first exemplary embodiment. 
         FIG. 8  is a perspective view of a feeding cassette according to a second exemplary embodiment. 
         FIG. 9  is a diagram illustrating configurations of first and second positioning portions according to the second exemplary embodiment. 
         FIGS. 10A to 10D  are diagrams illustrating operations according to the second exemplary embodiment. 
         FIG. 11  is a diagram illustrating a configuration of a conventional feeding cassette. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. The same components are denoted by the same reference numerals in each figure. 
       FIG. 7  is a cross-sectional view of an image forming apparatus including a feeding device according to a first exemplary embodiment of the present invention. A monochrome laser beam printer (hereinafter referred to as a printer)  90  serving as the image forming apparatus includes, in a cartridge  7 , a photosensitive drum  1  serving as an image bearing member. An exposure unit  2  is disposed in the vicinity of the photosensitive drum  1 . The exposure unit  2  irradiates the photosensitive drum  1  with a laser beam based on image information to form an image on the photosensitive drum  1 . A transfer roller  5  for transferring a toner image on the photosensitive drum  1  onto a sheet constitutes a transfer unit together with the photosensitive drum  1 . 
     In the first exemplary embodiment, the feeding device includes a feeding cassette  100  and a feeding roller unit (feeding unit)  18 . The sheets S stored in the feeding cassette  100  are fed by a feeding roller  15  of the feeding roller unit  18 . Then, the sheets S are conveyed one by one by a conveyance roller  16  and a separation roller  17 . 
     The conveyed sheets S are further conveyed to the transfer unit by a pair of registration rollers  3  and  4 . The transfer unit transfers the toner image onto a surface of the sheet S. The sheet S, onto which the toner image has been transferred, is conveyed to a fixing unit  10 . The toner image on the sheet S is fixed on the sheet S by heat and pressure in the fixing unit  10 . The sheet S, on which the toner image has been fixed, is discharged to a discharge portion by a pair of discharging rollers  11  and  12 . 
     Next, the configuration of the feeding cassette  100  according to the first exemplary embodiment will be described.  FIG. 6  is a perspective view of the feeding cassette  100 . The feeding cassette  100  can be pulled out from the printer  90  (see  FIG. 7 ) in the width direction (in the direction indicated by an arrow  100   a ) perpendicular to the feeding direction. 
     A cassette frame member  20  forms a frame that allows the feeding cassette  100  to serve as a unit that can be pulled out from the printer  90 . In the illustration in  FIG. 6 , a stacking plate  21  serving as a stacking portion, on which the sheets S are to be stacked, is partially cut out for the convenience of description. The stacking plate  21  is attached to the frame member  20 , and is able to swing about supporting portions  20   a  and  20   b . An urging member (not illustrated) causes the downstream side of the stacking plate  21  in the feeding direction to swing upward. 
     The trailing edge regulating plate  22  serving as a feeding direction positioning portion, which regulates a position of the sheets S in the feeding direction, comes into contact with the trailing edge of the sheets S stacked on the stacking plate  21 , and thus regulates the position of the sheets S in the feeding direction. The trailing edge regulating plate  22  can slide in and opposite to the feeding direction (the direction indicated by an arrow  22   a ), so that sheets of different sizes can be accommodated. 
     The first side regulating portion  102  serving as the first positioning portion and the second side regulating portion  101  serving as the second positioning portion come into contact with the edge portions of the sheets S stacked on the stacking plate  21  to regulate the side edge positions of the sheets S in the width direction perpendicular to the feeding direction. The first side regulating portion  102  is disposed more on the rear side than the second side regulating portion  101  in the insertion direction of the feeding cassette  100 . Conversely, the second side regulating portion  101  is disposed more on the front side than the first side regulating portion  102 . The first and the second side regulating portions  102  and  101  can slide in an insertion direction (first direction) and a pullout direction (second direction) of the feeding cassette  100 . The frame member  20  movably holds the first and the second side regulating portions  102  and  101 . 
     The first and the second side regulating portions  102  and  101  are coupled with each other via a rack gear  23   a , a pinion gear  36 , and a rack gear  35   a . When the user operates and moves the second side regulating portion  101  on the front side in the width direction  101   a , the first side regulating portion  102  on the rear side moves in the direction  102   a  in conjunction with the second side regulating portion  101 . When the user operates and moves the second side regulating portion  101  in the direction  102   a , the first side regulating portion  102  moves in the direction  101   a  in conjunction with the second side regulating portion  101 . More specifically, in the first exemplary embodiment, the rack gear  23   a  disposed in the second side regulating portion  101 , the rack gear  35   a  disposed in the first side regulating portion  102 , and the pinion gear  36  disposed in the cassette frame portion  20  constitute an interlocking portion for moving the first and the second side regulating portions  102  and  101  in conjunction with each other. 
     Sheet pressing members  25  and  26  disposed in the second side regulating portion  101  are pressured by a compression spring  38  (see  FIGS. 5A to 5C ). Thus, the sheet pressing members  25  and  26  press the edge portion of the sheets S so that the sheets S are pressed against a reference surface (contact portion)  32   a  of the first side regulating portion  102 . In other words, the reference surface  32   a , which the sheets S come into contact with, is disposed in the first side regulating portion  102 . 
       FIGS. 1A and 1B  are each an exploded perspective view illustrating inner components of the pair of side regulating portions  101  and  102 .  FIGS. 1A and 1B  respectively illustrate the second and the first side regulating portions  101  and  102 . 
     First, the configuration of the second side regulating portion  101  will be described. In  FIG. 1A , a second side regulating plate  23  is a component that forms the second side regulating portion  101  together with a second side regulating plate holder  24  (see  FIG. 6 ). Inner components of the second side regulating portion  101  are held between the second side regulating plate  23  and the second side regulating plate holder  24 . The rack gear  23   a  is formed in the second side regulating plate  23 , and engages with the pinion gear  36  (see  FIG. 6 ). 
     By operating (holding) a knob  27 , the user can move the second side regulating portion  101 . The knob  27  is held by the second side regulating plate holder  24 , and is able to swing about a fulcrum  27   a . A lever  28  is held by the second side regulating plate holder  24 , and slides upward in conjunction with the operation of the knob  27 . The lever  28  is pressured downward by a compression spring  29 , and thus is in a lower position when the knob  27  is not operated. 
     A return gear  30  is held by the second side regulating plate holder  24 , and is able to swing about a fulcrum  30   a . The return gear  30  only has a single gear  30   b  engaging with the rack gear  20   c  (see  FIGS. 6 and 2A to 2E ) formed in the cassette frame member  20 . When the lever  28  is in a lower position, a rib  28   a  of the lever  28  is in a groove  30   c  of the return gear  30 . 
     A sliding gear  31  is held rotatably about the fulcrum  30   a . The sliding gear  31  is pressured towards the return gear  30  (in the direction indicated by an arrow  31   b ) by a compression spring  37 , and has a sliding surface  31   a  in contact with a surface (not illustrated) of the return gear  30 . The sliding gear  31  engages with the rack gear  20   c  formed in the cassette frame member  20  (see  FIGS. 6 and 2A to 2E ). 
     Next, the configuration of the first side regulating portion  102  will be described. In  FIG. 1B , the surface  32   a  of the first side regulating plate  32  serves as a reference surface of the sheets S in the width direction. A click member  33  is held by the first side regulating plate  32  and can slide in the vertical direction. The click member  33  is pressured downward by a spring (not illustrated). A click feeling is obtained when a distal end of the click member  33  sinks in (engages with) a click groove  20   e  formed in the cassette frame member  20  (see  FIG. 6 ). The groove  20   e  (see  FIG. 6 ) is formed at a position corresponding to a standard size of the sheet S such as A4 or B5. 
     The first side regulating plate  32  is provided with a locking member  34 . The locking member  34  locks the first side regulating portion  102  to the cassette frame member  20 . The locking member  34  is able to swing about a fulcrum  34   a , and is pressured downward by a compression spring  39 . A protrusion  34   b  is formed in the locking member  34 . A protrusion  20   d  (engagement portion) is formed in the frame member  20 . The protrusions  34   b  and  20   d  (see  FIGS. 6 and 2A to 2E ) engage with each other, whereby the first side regulating plate  32  is locked to the cassette frame member  20 . In other words, the protrusion  34   b  of the locking member  34  and the protrusion  20   d  of the frame member  20  form a first regulating portion for regulating the movement of the first side regulating portion  102 . 
     When the first side regulating plate  32  is locked, the first side regulating portion  102  is fixed. Thus, even when the user strongly inserts the feeding cassette  100  into the main body of the apparatus, the first side regulating portion  102  does not move. Thus, the first side regulating portion  102  can be accurately positioned, and misalignment of the sheets S can be prevented. 
     The locking by the locking member  34  is released by a lock release plate  35  that is connected to the first side regulating plate  32  and moves along with the movement of the second side regulating portion  101 . Two oblong holes  35   b  and  35   c  are formed in the lock release plate  35 . Bosses  32   b  and  32   c  of the first side regulating plate  32  are inserted in the oblong holes  35   b  and  35   c , respectively. A distance t is set between the oblong hole  35   b  and the boss  32   b , and a distance w longer than the distance t is set between the oblong hole  35   c  and the boss  32   c . In such a configuration, when the lock release plate  35  moves in the width direction, the first side regulating plate  32  starts moving with a delay corresponding to the distance t. While the lock release plate  35  moves toward the first side regulating plate  32  to zero the distance t, an edge  35   d  or an edge  35   e  lifts an inclined surface (release surface)  34   c  or  34   d  of the locking member  34 . Thus, the locking of the first side regulating portion  102  is released. In other words, the edges  35   d  and  35   e  form a first release portion for releasing the locking of the first side regulating portion  102 . 
     The rack gear  35   a  is formed in the lock release plate  35 , and engages with the pinion gear  36  (see  FIG. 6 ). 
     Next, the operations of the first and the second side regulating portions  102  and  101  will be described. First, an operation of narrowing the distance between the first and the second side regulating plates  32  and  23  will be described.  FIGS. 2A to 2E  are cross-sectional views illustrating operations of the first and the second side regulating portions  102  and  101 , in a case where the user moves the second side regulating portion  101  in the insertion direction of the feeding cassette  100  (the direction  101   a  in  FIG. 6 ). In  FIGS. 2A to 2E , only the portions necessary for the description are illustrated. 
       FIG. 2A  illustrates the state of the first and the second side regulating portions  102  and  101  before the user starts the operation. The lever  28  is lowered by the compression spring  29  (see  FIGS. 1A and 1B ). Thus, the rib  28   a  of the lever  28  is in the groove  30   c . The gear  30   b  of the return gear  30  engages with the rack gear  20   c  of the cassette frame member  20 . In this positional relationship, the second side regulating portion  101  is locked to the cassette frame member  20 , and thus cannot slide. The protrusion  34   b  of the locking member  34  engages with the protrusion  20   d  formed in the cassette frame member  20 . Thus, the first side regulating portion  102  is locked to the cassette frame member  20 , and thus cannot slide. In other words, before the user performs the operation, the first and the second side regulating portions  102  and  101  are locked to the cassette frame member  20  and thus cannot slide. There is clearance corresponding to the distance t between the boss  32   b  of the first side regulating plate  32  and each end of the oblong hole  35   b  of the lock release plate  35 . 
       FIG. 2B  illustrates the state of the first and the second side regulating portions  102  and  101 , in a case where the user holds the knob  27  (see  FIGS. 1A and 1B ). The lever  28  is raised by the knob  27 , and thus the rib  28   a  of the lever  28  is pulled out of the groove  30   c  of the return gear  30 . The knob operation releases the locking of the second side regulating plate portion  101 . Meanwhile, the first side regulating portion  102  is in the same state as in  FIG. 1A , that is, locked to the cassette frame member  20 . 
       FIG. 2C  illustrates the state of the first and the second side regulating portions  102  and  101 , in a case where the user holding the knob  27  (see  FIGS. 1A and 1B ) moves the second side regulating portion  101  in the right direction in  FIG. 2C  (in the direction  101   a  in  FIG. 6 ) by the distance t. In this state, the return gear  30  swings in the clockwise direction, and thus the gear  30   b  of the return gear  30  does not engage with the rack gear  20   c . At the same time, the lock release plate  35  coupled to the second side regulating portion  101  via the pinion gear  36  (see  FIG. 6 ) moves in the left direction in  FIG. 2C  (in the direction  102   a  in  FIG. 6 ) by the distance t. The edge  35   e  of the lock release plate  35  raises the cam surface  34   d  of the locking member  34 , and thus the protrusion  34   b  of the locking member  34  is disengaged from the protrusion  20   d  of the cassette frame member  20 . Thus, the locking of the first side regulating portion  102  is released. The lock release plate  35  moves by the distance t, whereby the edge  35   f  of the oblong hole  35   b  of the lock release member  35  comes into contact with the boss  32   b  of the reference plate  32  on the rear side. As a result, the distance t between the oblong hole  35   b  and the boss  32   b  is zeroed. 
       FIG. 2D  illustrates the state of the first and the second side regulating portions  102  and  101 , in a case where the user further moves the second side regulating portion  101  in the right direction from the state in  FIG. 2C , by a distance u. The edge  35   f  of the oblong hole  35   b  of the lock release member  35  is in contact with the boss  32   b  of the first side regulating plate  32 , and thus the lock release plate  35  and the first side regulating plate  32  move to the left side by the distance u. 
       FIG. 2E  illustrates the state of the first and the second side regulating portions  102  and  101 , in a case where the user releases the knob  27  in the state in  FIG. 2D . When the user releases the knob  27 , the lever  28  is lowered by the spring force of the compression spring  29  (see  FIGS. 1A and 1B ). Then, the rib  28   a  of the lever  28  pushes the cam surface  30   d  of the return gear  30 . The return gear  30  swings in the anticlockwise direction until the rib  28   a  enters into the groove  30   c . When the return gear  30  swings in the anticlockwise direction, the gear  30   b  of the return gear  30  engages with the rack gear  20   c  of the cassette frame member  20 , and the second side regulating portion  101  moves to the left side by the distance t. At the same time, the lock release plate  35  moves in the right direction by the distance t. Thus, the edge  35   e  of the lock release plate  35  moves away from the cam surface  34   d  of the locking member  34 , and the protrusion  34   b  of the locking member  34  engages with the protrusion  20   d  of the cassette frame member  20 . Thus, the first and the second side regulating portions  102  and  101  are locked to the cassette frame member  20 , whereby the operation performed by the user to narrow the first and second side regulating plates  32  and  23  is completed. 
     As described above, in the first exemplary embodiment, when the user operates the knob  27  to move the second side regulating portion  101  in a direction that narrows the distance to the first side regulating portion  102 , and then releases the knob  27 , the second side regulating portion  101  moves in a direction that widens the distance to the first side regulating portion  102  (a direction opposite to the direction in which the user has moved the second side regulating portion  101 ). In other words, the return gear  30  and the rib  28   a  form a movement portion for moving the second side regulating portion  101 , which has been moved in the installing direction of the feeding cassette  100 , in the pullout direction of the feeding cassette  100 . On the other hand, the first side regulating portion  102  disposed on the rear side in the insertion direction of the feeding cassette  100  does not move. Thus, even when the user strongly inserts the feeding cassette  100  into the main body of the apparatus, the sheets S can be prevented from being misaligned. 
     Next, the operation performed by the user to widen the distance between the first and the second side regulating plates  32  and  23  will be described with reference to  FIG. 3 .  FIG. 3  is a cross-sectional view illustrating operations of the first and the second side regulating portions  102  and  101  in a case where the user moves the second side regulating portion  101  in the pullout direction of the cassette  100  (the direction  102   a  in  FIG. 6 ). In  FIG. 3 , only the portions necessary for the description are illustrated. 
     The operations of the components for widening the distance between the first and the second side regulating plates  32  and  23  are different from the operations of the components for narrowing the distance between the first and the second side regulating plates  32  and  23 , only in the operation direction. Thus,  FIG. 3  illustrates only a diagram corresponding to  FIG. 2D . 
     When the user  27  holds the knob  27  (see  FIGS. 1A and 1B ) to move the second side regulating portion  101  in the left direction in  FIG. 3 , the return gear  30  swings in the anticlockwise direction. At the same time, the lock release plate  35  moves in the right direction so that the edge  35   d  of the lock release plate  35  raises the cam surface  34   c  of the locking member  34 . Thus, the locking of the first side regulating plate  32  is released. Then, the edge  35   g  of the oblong hole  35   b  comes into contact with the boss  32   b  of the reference plate  32  on the rear side, causing the first side regulating plate  32  to move in the right direction. When the user releases the knob  27  (see  FIGS. 1A and 1B ) after moving the first side regulating plate  32  to a desired position, the rib  28   a  of the lever  28  pushes a cam surface  30   e  of the return gear  30 . Thus, the return gear  30  swings in the clockwise direction, whereby the second side regulating portion  101  moves to the right side by the distance t. At the same time, the lock release plate  35  moves in the left direction by the distance t. Thus, the movement operation of widening the distance between the first and the second side regulating plates  32  and  23  is completed. 
     As described above, the distance between the first and the second side regulating plates  32  and  23  can be changed according to the size of the sheets S to be used. 
     Next, an operation of moving the second side regulating plate  23  back and forth, performed by the user holding the operation knob  27  (see  FIGS. 1A and 1B ), will be described with reference to  FIGS. 4A and 4B .  FIGS. 4A and 4B  are cross-sectional views illustrating the inner components of the second side regulating portion  101 . Only the portions necessary for the description are illustrated in  FIGS. 4A and 4B . 
       FIG. 4B  illustrates the state of the second side regulating portion  101  in a case where the user holding the knob  27  moves the second side regulating portion  101  in the right direction and stops the movement. At this time, the return gear  30  swings in the clockwise direction. 
     Next, when the user holding the knob  27  moves the second side regulating portion  101  in the left direction, the sliding gear  31  engaging with the rack gear  23   a  rotates in the anticlockwise direction. As described above, the sliding gear  31  has the sliding surface  31   a  (see  FIGS. 1A and 1B ) pushed against a surface (not illustrated) of the return gear  30 . Thus, when the sliding gear  31  rotates in the anticlockwise direction, the return gear  30  swings in the anticlockwise direction due to the sliding resistance of the slide surface  31   a . Thus, the gear  30   b  of the return gear  30  can engage with the rack gear  20   c  of the cassette frame member  20 . Then, when the second side regulating portion  101  is further moved in the left direction, the state of the second side regulating portion  101  illustrated in  FIG. 4A  is achieved. 
     If the sliding gear  31  is not provided, when the user holding the knob  27  changes the direction of the second side regulating portion  101 , the gear  30   b  of the return gear  30  cannot engage with the rack gear  20   c , thereby causing a malfunction to occur. The sliding gear  31  is provided to prevent such a malfunction from occurring. 
     Next, a procedure for the user to set the sheets S in the feeding cassette  100  will be described. Here, a procedure of setting the sheets S of the A4 size in the feeding cassette  100  will be described with reference to  FIG. 6 . A procedure recommended to the user is that the first and the second side regulating portions  102  and  101  and the trailing edge regulating plate  22  area set at positions corresponding to the A4 size, and then the sheets S are set in the feeding cassette  100 . 
     First, the user moves the second side regulating portion  101  so that the reference surface  32   a  of the first side regulating plate  32  is set at the position corresponding to the A4 size, engraved in the stacking plate  21 . When the reference surface  32   a  is moved to the position corresponding to the A4 size, the user can recognize that the first side regulating plate  32  is precisely set at the position corresponding to the A4 size, from the click feeling produced by the click member  33  (see  FIGS. 1A and 1B ). When the user stops the second side regulating portion  101  at the position, the second side regulating portion  101  is also set at the position corresponding to the A4 size. 
     Similarly, the user sets the trailing edge regulating plate  22  at the position corresponding to the A4 size. Then, the user stacks the sheets S of the A4 size on the stacking plate  21 . By the user setting the sheets S in the feeding cassette  100  through the procedure described above, an edge portion of the sheets S on the rear side can be set at the proper position, regardless of the variations in the outer dimensions of the sheets S in the width direction. 
     Next, a procedure of setting the sheets S of a non-standard size in the feeding cassette  100  will be described with reference to  FIGS. 5A to 5C . The sheets of non-standard size are sheets of a size different from the standard size such as A4 or B5. A description of the trailing edge regulating plate  22  will be omitted here. 
     First, as illustrated in  FIG. 5A , the user widens the distance between the pressing member  26  of the second side regulating portion  101  and the reference surface  32   a  of the first side regulating plate  32 , to make it larger than the size of the sheets S of the non-standard size. Then, the user places the sheets S of the non-standard size on the stacking plate  21 . 
     Next, as illustrated in  FIG. 5B , the user narrows the distance between the first and the second side regulating plates  101  and  102 , so that the sheets S of the non-standard size are held between the pressing member  26  and the reference surface  32   a . When the user releases the knob  27 , the second side regulating portion  101  returns to the left side by the distance t and then stops as illustrated in  FIG. 5C . 
     In the first exemplary embodiment, a movable distance v of the pressing member  26  is larger than the distance t. Thus, even when the second side regulating portion  101  returns by the distance t, the pressing member  26  can press the sheets S against the reference surface  32   a  of the first side regulating portion  102 . 
     The sheets S of the standard size may be set in the same procedure as that for the sheets S of the non-standard size. However, the position of the edge portion of the sheets S on the rear side may slightly deviate from the proper position due to, for example, variations in outer shape sizes of the sheets S. Thus, the recommended procedure is that the first and the second side regulating portions  102  and  101  and the trailing edge regulating plate  22  are positioned and then, the sheets S of the standard size are set. 
     In the present exemplary embodiment, not only the first side regulating portion  102  on the rear side, but also the second side regulating portion  101  on the front side is locked. This can prevent the first and the second side regulating portions  102  and  101  from being moved during the time between when the pair of side regulating portions  101  and  102  are positioned and when the sheets S are set and the feeding cassette  100  is inserted in the printer  90 . That is, the sheets S can be prevented from being misaligned 
     Further, in the first exemplary embodiment, the user can lock or unlock the first side regulating portion  102  on the rear side by operating the knob  27  of the second side regulating portion  101  on the front side to move the second side regulating portion  101 . Thus, the user does not need to directly operate the first side regulating portion  102  on the rear side, whereby high usability is achieved. 
     Next, a second exemplary embodiment of the present invention will be described. A description of a configuration and an operation in the second exemplary embodiment that are similar to those in the first exemplary embodiment will be omitted as appropriate. 
       FIG. 8  is a perspective view of the feeding cassette  100  according to the second exemplary embodiment. The feeding cassette  100  can be pulled out from the printer (see  FIG. 7 ) in the width direction (the direction indicated by the arrow  100   a ) perpendicular to the feeding direction. 
     First and second side regulating portions  104  and  103  regulate the positions of the side edges of the sheets S in the width direction. The first and second side regulating portions  104  and  103  are coupled with each other via a rack gear  40   a , a pinion gear  50 , and a rack gear  48   a . Thus, when an operation portion  40   b  of the second side regulating portion  103  is moved in the width direction (the direction  103   a ), the first side regulating portion  104  moves in the width direction (the direction  104   a ) in conjunction with the second side regulating portion  103 . The operation portion  40   b  of the second side regulating portion  103  is integrally formed with the second side regulating plate  40 . A boss  20   f , in which grooves of male screw shape are formed, is disposed on a rear-side wall surface of the cassette frame member  20 . 
       FIG. 9  is an exploded perspective view illustrating inner components of the first side regulating portion  104 . A reference surface  41   a  of the first side regulating plate  41  serves as a reference of the position of the sheets S in the width direction. 
     A first return lever  42  is held to be capable of swinging about a fulcrum  42   a . A second return lever  43  is held to be capable of swinging about a fulcrum  43   a . A boss  41   d  disposed below the first side regulating plate  41  is inserted into the first and the second levers  42  and  43 . Tension springs  44  and  45  are respectively hooked on spring hook portions  42   b  and  43   b . Hooks of the tension springs  44  and  45  on the opposite side are hooked on spring hook portions  41   f  and  41   g  of the first side regulating plate  41 . 
     A pair of lock arms  46  and  47  locks the first side regulating plate  41  to the cassette frame member  20 . A boss  41   h  is inserted in the first and the second lock arms  46  and  47 . The first lock arm  46  can swing about a fulcrum  46   a . The second lock arm  47  can swing about a fulcrum  47   a . The pair of lock arms  46  and  47  is respectively pressured in the directions indicated by arrows  46   d  and  47   d  by springs (not illustrated). Grooves  46   c  and  47   c  of female screw shape are respectively formed in the pair of lock arms  46  and  47 . The grooves  46   c  and  47   c  of female screw shape engage with the boss  20   f  (see  FIG. 8 ) of male screw shape on the cassette frame member  20 . Thus, the first side regulating plate  41  is locked to the cassette frame member  20 . 
     A lock release plate  48  releases the locking of the pair of lock arms  46  and  47 . Bosses  41   b  and  41   c  of the first side regulating plate  41  are respectively inserted in two oblong holes  48   b  and  48   c  formed in the lock release plate  48 . The distance t is set between the oblong hole  48   b  and the boss  41   b . In such a configuration, when the lock release plate  48  moves in the width direction, the first side regulating plate  41  starts moving with a delay corresponding to the distance t. 
     The lock release plate  48  is provided with a cam surface  48   e . The cam surface  48   e  pushes out a surface  46   b  of the first lock arm  46  and a surface  47   b  of the second lock arm  47 , whereby the locking is released. 
     A brake portion  49  provides resistance to the movement of the first side regulating plate  41 . The brake portion  49  is in contact with a surface of the cassette frame member  20 . 
     &lt;Operation of Side Regulating Plate&gt; 
     Next, an operation of the side regulating plates  41  and  40  as a feature of the second exemplary embodiment will be described with reference to  FIGS. 10A to 10D .  FIGS. 10A and 10C  are diagrams viewing from below (the direction indicated by an arrow  104   b  in  FIG. 9 ) the side regulating portion  104  on the rear side.  FIGS. 10B and 10D  are diagrams viewing from the back (the direction indicated by an arrow  104   c  in  FIG. 9 ) the side regulating portion  104  on the rear side. 
       FIGS. 10A and 10B  illustrate the state of the first side regulating portion  104  before the user performs the operation. The grooves  46   c  and  47   c  of female screw shape in the pair of lock arms  46  and  47  engage with the boss  20   f  of male screw shape on the cassette frame member  20 . Thus, the first side regulating portion  104  is locked to the cassette frame member  20 , and thus cannot slide. 
       FIGS. 10C and 10D  illustrate the state of the first side regulating portion  104  in a case where the user operates the operation portion  40   b  (see  FIG. 8 ) to move the second side regulating portion  103  by the distance t in a direction in which the distance to the first side regulating portion  104  becomes narrower. Here, the lock release plate  48  moves in the left direction in  FIG. 10C  by the distance t. 
     When the lock release plate  48  moves, the second return lever  43  is pushed by the rib  48   d  of the lock release plate  48  to swing. The first return lever  42  is in contact with the rib  41   e  of the first side regulating plate  41 , and thus does not swing. At the same time, the cam surface  48   e  of the lock release plate  48  pushes out the surface  46   b  of the first lock arm  46  and the surface  47   b  of the second lock arm  47 . Thus, the grooves  46   c  and  47   c  of female screw shape are disengaged from the boss  20   f  of male screw shape on the cassette frame member  20 . 
     Then, the user moves the first side regulating plate  41  to a predetermined position and releases the operation portion  40   b  (see  FIG. 8 ). Thus, the lock release plate  48  is returned to the right by the distance t, by the spring force of the spring  45 . Then, the states illustrated in  FIGS. 10A and 10B  where the first side regulating portion  104  is locked are achieved, whereby the operation of narrowing the distance between the side regulating plates  41  and  40  is completed. 
     If the resistance applied by the brake portion  49  to the side regulating plate  41  is set to be larger than the force applied by the springs  44  and  45  to return the lock release plate  48 , a smooth operation can be achieved. 
     According to the second exemplary embodiment, the number of parts can be reduced, and cost reduction can be achieved. Since the upper position of the first side regulating portion  104  can be locked, the reference surface  41   a  of the first side regulating plate  41  is less likely to fall down due to the impact produced when the user strongly inserts the cassette. 
     In the above-described exemplary embodiments, as an example of the image forming unit for forming an image on a sheet, an electrophotograpic image forming process is used. The present invention is not limited to the unit using the electrophotograpic image forming process. For example, the image forming unit for forming an image on a sheet may use an inkjet image forming process that forms an image on a sheet by ejecting ink from a nozzle. 
     The configurations where the first and the second exemplary embodiments are applied to a cassette for feeding a sheet have been described above. However, the present invention is not limited thereto. For example, the exemplary embodiments of the present invention may be applied to a document reading device for reading a document, a feeding device, or a manual feeding device. 
     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. 2013-096014 filed Apr. 30, 2013, which is hereby incorporated by reference herein in its entirety.