Abstract:
A sheet feeder includes; a sheet feed roller that abuts against a topmost sheet of stacked sheets and rotates to convey the topmost sheet in a conveyance direction; an arm spanning across a drive shaft and the sheet feed roller; a rotating transmission member that transmits rotation of the drive shaft to the sheet feed roller, wherein the arm is provided with a cantilever shaft that supports the rotating transmission member, and an elastic member that faces an end face of the rotating transmission member to retain the rotating transmission member in the cantilever shaft.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a sheet feeder in an image forming apparatus, such as a printer, a copying machine, or a facsimile machine.  
         [0003]     2. Description of the Related Art  
         [0004]     The image forming apparatus, such as a printer, has a sheet feeder for feeding a single sheet of cut sheets at a time to a recording section. The sheet feeder is configured as follows. A sheet feed roller is rotated by means of power supplied from a power source, and brought into contact with the cut sheets on a sheet feed cassette having been set in the image forming apparatus, thereby feeding to the recording section a topmost sheet of the cut sheets (see, e.g., U.S. Patent Publication No. U.S. 2002/0054381A1 corresponding to JP-A-2002-060068).  
       SUMMARY OF THE INVENTION  
       [0005]     A sheet feeder is configured to transmit power supplied from the power source to the sheet feed roller by means of a gear system, and the like. However, a rotating member, such as a gear, has conventionally been attached to the inside of a gear box by means of a fastener; e.g., a screw, pin, and the like. Accordingly, there arises a problem that a variety of fasteners, such as a screw, must be prepared, along with a problem that operations for assembling the sheet feeder become complicated.  
         [0006]     It is therefore one of objects of the present invention to provide a sheet feeder which solves the above problems.  
         [0007]     According to a first aspect of the invention, there is provided a sheet feeder including: a sheet feed roller that abuts against a topmost sheet of stacked sheets and rotates to convey the topmost sheet in a conveyance direction; an arm spanning across a drive shaft and the sheet feed roller; a rotating transmission member that transmits rotation of the drive shaft to the sheet feed roller, wherein the arm is provided with a cantilever shaft that supports the rotating transmission member, and an elastic member that faces an end face of the rotating transmission member to retain the rotating transmission member in the cantilever shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     These and other objects and advantages of the present invention will become more fully apparent from the following detailed description taken with the accompanying drawings, in which.  
         [0009]      FIG. 1  is a perspective view of a printer using a sheet feeder according to the present invention;  
         [0010]      FIG. 2  is a vertical cross-sectional view of the printer shown in  FIG. 1 ;  
         [0011]      FIG. 3  is a perspective view of a sheet feed cassette to be attached to the printer shown in  FIG. 1 ;  
         [0012]      FIG. 4  is a perspective view showing the sheet feed cassette together with the sheet feeder;  
         [0013]      FIGS. 5A and 5B  are perspective views of the sheet feeder as viewed from different directions;  
         [0014]      FIG. 6A  is a vertical cross-sectional view of the sheet feeder showing a state where the sheet feeder does not feed paper, and  FIG. 6B  is the same showing a state where the sheet feeder feeds paper;  
         [0015]      FIG. 7  is a perspective view of an arm of the sheet feeder;  
         [0016]      FIG. 8A  is a partially cutaway view showing a process where a gear is attached to the arm of the sheet feeder, and  FIG. 8B  is a partially cutaway view showing a process where a gear is attached to an arm according to a modification of the invention;  
         [0017]      FIGS. 9A through 9B  are views for explaining motions of the sheet feeder when the sheet feed cassette is removed or inserted;  
         [0018]      FIG. 10  is a perspective view of an arm according to a second embodiment;  
         [0019]      FIG. 11  is an enlarged view of a shaft;  
         [0020]      FIG. 12  is a plan view of the arm;  
         [0021]      FIG. 13  is a sectional view of the arm taken in XIII-XIII line shown in  FIG. 12 ;  
         [0022]      FIG. 14  is a sectional view of the arm taken in XIV-XIV line shown in  FIG. 13 ;  
         [0023]      FIG. 15  is a sectional view of the arm taken in XV-XV line shown in  FIG. 13 ;  
         [0024]      FIG. 16  is a perspective view of the arm where intermediate gears are attached in the shafts;  
         [0025]      FIG. 17  is a plan view of the arm where intermediate gears are attached in the shafts;  
         [0026]      FIG. 18  is a sectional view of the arm taken in XVIII-XVIII line shown in  FIG. 17 ; and  
         [0027]      FIG. 19  is a sectional view of the arm taken in XIX-XIX line shown in  FIG. 17 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Hereinafter, preferred embodiments of the present invention will be described by reference to the drawings.  
       First Embodiment  
       [0029]     A printer according to a first embodiment is configured as a multifunction machine as shown in  FIGS. 1 and 2 , and has a scanner  2  on the top of a case  1  thereof.  
         [0030]     As shown in  FIGS. 1 and 2 , the printer has a sheet feed cassette  3  at a lower section in the case  1 . The sheet feed cassette  3  has an appearance as shown in  FIG. 3 , and is inserted in the case  1  through an opening  4  in such a manner as to allow insertion and removal in the front-rear direction. A recessed section  3   a  for storing stacked sheets A is provided in the sheet feed cassette  3 . When the sheet feed cassette  3  is inserted in the case  1 , a sheet feed roller, which will be described later, is located on a topmost one of the sheets A in the recessed section  3   a . A tray  3   b  for receiving the sheet A, on which an image has been recorded as will be described later, is formed in the front portion of the sheet feed cassette  3 .  
         [0031]     As shown in  FIG. 2 , a metal frame  5  of a box-like shape is disposed at the rear inside the case  1  and above the paper cassette  3 . The frame  5  is of a rectangular solid shape elongated in the lateral direction (see  FIG. 1 ), and fixed to the inside is of the case  1 .  
         [0032]     A sheet feeder  6  is disposed at the lower section in the frame  5 , and a recording section  7  is disposed at the upper section in the same. In addition, in the rear of the frame  5 , there is formed a guide path  5   a  for guiding the sheet A from the rear of the sheet feed cassette  3  to the recording section  7 . The recording section  7  is specifically a recording device of an inkjet type. The recording section  7  has guide rollers  7   a  at positions adjacent to an exit of the guide path  5   a , and discharge rollers  7   b  at positions for discharging the sheet A, on which an image has been recorded. A recording device of an inkjet type of such a configuration is conventionally known, and detailed description thereof is omitted.  
         [0033]     A discharge section to which the sheet A is discharged from the recording section  7  is disposed in front of the frame  5  in the case  1 . The sheet A discharged in the discharge section is stacked on the tray  3   b  in the sheet feed cassette  3 .  
         [0034]     As shown in  FIGS. 2 , and  4  to  6 B, the sheet feeder  6  has a sheet feed roller  8  for feeding the sheet A in the sheet feed cassette  3  to the recording section  7 . The sheet feed roller  8  is rotatably held at a tip end of an arm  10  which is supported by a drive shaft  9 . The sheet feed roller rotates by means of power transmitted by way of a gear, which will be described later and which serves as a rotating transmission member, from the drive shaft  9 .  
         [0035]     The drive shaft  9  is rotatably supported in the frame  5  so as to extend laterally. A gear  11  is fixed on one end of the drive shaft  9 . An output shaft of a drive source, such as a motor (not shown), is connected to the gear  11  to form a power line. When the drive source is activated and the drive shaft  9  rotates, the rotation is transmitted to the sheet feed roller  8  by way of the gear  11 , which will be described later and which serves as the rotating transmission member. The sheet feed roller  8  is brought into contact with a topmost one of the sheets A in the sheet feed cassette  3 , to thus feed the topmost one of the sheets A to the recording section  7 .  
         [0036]     The rotating transmission member for transmitting the rotation of the drive shaft  9  to the sheet feed roller  8  is specifically constituted as a gear train. The gear train includes a leading gear  12  formed on the other end of the drive shaft  9 , a terminal gear  13  fixed on one end of the sheet feed roller  8 , and first to fourth intermediate gears  14   a ,  14   b ,  14   c , and  14   d  disposed between the leading gear  12  and the terminal gear  13 . The first to fourth intermediate gears  14   a ,  14   b ,  14 , and  14   d  are held by the arm  10  together with the sheet feed roller  8 . In the embodiment, four intermediate gears have been provided; however, as a matter of course, less than or more than four intermediate gears may be provided.  
         [0037]     The arm  10  is configured so as to act as a pivotal link having the drive shaft  9  as a pivot. More specifically, a base section of the arm  10  is loosely fitted on the drive shaft  9 , and enters and exits from the frame  5  by way of an opening formed in a bottom plate of the frame  5 . When, as will be described later, when the drive shaft  9  rotates in one direction, the arm  10  rotationally exits the opening as shown in  FIG. 2 , thereby causing the sheet feed roller  8  to descend onto the sheet feed cassette  3 ; and when the drive shaft  9  rotates in the opposite direction, the arm  10  moves rotationally upward, thereby being stored in the frame  5  together with the sheet feed roller  8  through the opening.  
         [0038]     The arm  10  also functions as a gear box. More specifically, the arm  10  is formed into a substantially box-shape whose top is open. The gear train ranging from the leading gear  12  to the terminal gear  13  is stored in the box.  
         [0039]     The first intermediate gear  14   a , which comes into engagement with the leading gear  12 , functions as a clutch. One end of a shaft  16   a  of the first intermediate gear  14   a  is supported by a carrier  15 , which is attached to the drive shaft  9  in a rotationally movable manner; and the other end is restricted, in terms of a rotationally-movable range, by a pressing plate  17  disposed in the arm  10 . The carrier  15  is formed into a plate-shape, and is sandwiched between an end face of the leading gear  12  and a side wall  10   a  of the arm  10  with an appropriate pressure. In addition, interlocking means is disposed between the carrier  15  and the end face of the leading gear  12  for increasing a frictional coefficient therebetween. The interlocking means can be provided by means of, for instance, sandwiching a rubber sheet between the carrier  15  and the leading gear  12 . According to the above configuration, when the drive shaft  9  rotates counterclockwise as shown in  FIG. 6A , the carrier  15  is caused to rotate in the same direction with the drive shaft  9  by means of a frictional force, whereby the first intermediate gear  14   a  is separated from the second intermediate gear  14   b , to thus cut-off transmission of power. When the drive shaft  9  rotates clockwise as shown in  FIG. 6B , the carrier  15  is caused to rotate in the same direction with the drive shaft  9  by means of a frictional force, whereby the first intermediate gear  14   a  comes into engagement with the second intermediate gear  14   b , thereby enabling transmission of power.  
         [0040]     Furthermore, as shown in  FIGS. 5A and 6S , protrusions  15   a  protruding toward the side wall  10   a  of the arm  10  are disposed on the carrier  15 . As shown in  FIG. 5B , each of the protrusions  15   a  fits in one of arc grooves  18  which are formed in the side wall  30   a  of the arm  10  and which are curved about the drive shaft  9 . By virtue of the above configuration, when the drive shaft  9  rotates counterclockwise as shown in  FIG. 6B , the carrier  15  is caused to rotate in the same direction with the drive shaft  9  by means of a frictional force. Accordingly, the first intermediate gear  14   a  is separated from the second intermediate gear  14   b , as shown in  FIG. 6G ; and each of the protrusions  15   a  on the carrier  15  hits one end of the corresponding arc groove  18 , thereby raising the arm  10  to its uppermost position as shown in  FIG. 6A .  
         [0041]     The second, third, and fourth intermediate gears  14   b ,  14   c , and  14   d  are rotatably fitted on shafts  16   b ,  16   c , and  1   d  respectively protruding from an inner face of the side wall  10   a  of the arm  10  in such a manner that one end of each of the respective shafts is supported by the inner wall; i.e., in cantilever fashion. Preferably, the arm  10  is molded of a synthetic resin, and at the time of molding, the shafts  16   b ,  16   c , and  16   d  are molded simultaneously and integrally with the arm  10 .  
         [0042]     As shown in  FIGS. 5A, 5B , and  FIG. 7A  to  FIG. 8A , plate springs  19   a ,  19   b , which are elastic members, are attached to inside the arm  10  so as to face the end faces of the gears  14   b  and  14   c  on the shafts  16   b  and  16   c . Each of the plate springs  19   a ,  19   b  has an upright section  20  which extends upward from a bottom wall of the arm  10 , and a bent section  21  which extends in a downwardly-oblique direction from an upper end of the upright section toward a front end of the shaft  16   b ,  16   c . A tip end of the bent section  21  of each of the plate springs  198 ,  19   b  faces the end face of the corresponding gear  14   b ,  14   c  on the corresponding shaft  16   b ,  16   c , and preferably faces the center of the end face. In the illustrated example, the tip end of the bent section  21  of each of the plate springs  19   a ,  19   b  is slightly separated from the end face of the gear  14   b ,  14   c  or from the tip end of the shaft; however, the tip end of the bent section  21  may be brought into contact therewith. As in the case of the shafts  16   b ,  16   c , and  16   d , the plate springs  19   a ,  19   b  are preferably molded simultaneously and integrally with the arm  10 . Assembly of the second intermediate gear  14   b  and the third intermediate gear  14   c  is performed as follows. The intermediate gears  14   b ,  14   c  are inserted between the tip ends of the shafts  16   b ,  16   c  and the plate springs  19   a ,  19   b . Accordingly, the intermediate gears  14   b ,  14   c  reach the shafts  16   b ,  16   c  while causing the plate springs  19   a ,  19   b  to deform, and fit on the shafts  16   b ,  16   c . The intermediate gears  14   b ,  14   c  are smoothly guided to the shafts  16   b ,  16   c  by the bent sections  21  of the plate springs  19   a ,  19   b , thereby immediately fitting on the shafts  16   b ,  16   c . When the intermediate gears  14   b ,  14   c  fit on the shafts  16   b ,  16   c , the plate springs  19   a ,  19   b  are restored to their original shapes, and face the end faces of the intermediate gears  14   b ,  14   c , thereby preventing the intermediate gears  14   b ,  14   c  from coming off the shafts  16   b ,  16   c . The plate springs  19   a ,  19   b  are not employed for the first and fourth intermediate gears  14   a ,  14   d , however, the intermediate gears  14   a ,  14   d  also may be configured so as to be retained by a plate spring as in the case of the other intermediate gears  14   b ,  14   c.    
         [0043]     The shafts  16   b ,  16   e  may be formed alternatively. As shown in  FIG. 8B , an oblique surface  22   a , which is slanted in the direction opposite to that of the bent section  21  of the plate spring  19   b , may be formed on the tip end of a shaft  22 . The oblique surface  22   a  and the bent section  21  of the plate spring  19   b  form a V-shaped guide face. Accordingly, when the intermediate gears  14   b ,  14   c  are attached to the shafts  22 , the intermediate gears  14   b ,  14   d  are smoothly guided to the shafts  22 , thereby being fitted on the shafts immediately.  
         [0044]     As shown in  FIG. 4 , a cam  23  is formed on the side wall  3   c  of the sheet feed cassette  3 , and a cam follower  10   b  is attached to the arm  10 . When the sheet feed cassette  3  is removed from the case  1  after driving of the sheet feeder is stopped, and the like, as shown in  FIGS. 9A  to  9 D, the cam  23  raises the sheet feed roller  8  to a position above the sheet feed cassette  3  by way of the cam follower  10   b . According to the above configuration, collision between the sheet feed roller  8  and the sheet feed cassette  3  at the time of insertion or removal of the sheet feed cassette  3  is prevented.  
         [0045]     Next, the operations of the sheet feeder configured as above will be described.  
         [0046]     In the course of assembly of the sheet feeder  6 , the intermediate gears  14   b ,  14   c  are pressed between the plate springs  19   a ,  19   b  and the shafts  16   b ,  16   c  as shown in  FIG. 8A , to thus attach the intermediate gears  14   b ,  14   d  to the arm  10 . The intermediate gears  14   b ,  14   c  deform the plate springs  19   a ,  19   b  while sliding along the slantingly bent sections  21  of the plate springs  19   a ,  19   b , thereby fitting on the shafts  16   b ,  16   c . After the intermediate gears  14   b ,  14   c  fit on the shafts  16   b ,  16   c , the plate springs  19   a ,  19   b  are restored to their original shapes, and face the end faces of the intermediate gears  14   b ,  14   c  so that the intermediate gears  14   b ,  14   c  will not come off the shaft  16   b ,  16   c.    
         [0047]     The sheet feeder  6  is assembled in the case  1  as shown in  FIG. 2 , thereby performing paper feeding to the recording section  7 .  
         [0048]     In a case where the printer performs recording the drive shaft  9  rotates clockwise in  FIGS. 2 and 6 B and the leading gear  12  also starts clockwise rotation integrally with the drive shaft  9 . By virtue of the above configuration, the arm  10  and the carrier  15  rotate clockwise in a linked manner. Accordingly, as shown in  FIG. 6B , the first intermediate gear  14   a  comes into engagement with the second intermediate  14   b ; and the arm  10  rotates downward about the drive shaft  9  serving ea a pivot. The sheet feed roller  8  on the tip end of the arm  10  is brought into contact with the sheets A in the sheet feed cassette  3  as shown in  FIG. 2  and rotates upon transmission of power from the drive shaft  9 , thereby feeding a single sheet of the sheets A at a time out of the sheet feed cassette  3 . The protrusions  15   a  on the carrier  15  side are engaged in the arc grooves  18  on the arm  10  side. Accordingly, the sheet feed roller  8  is vertically displaced together with the arm  10  in accordance with a height of a stack of the sheets A in the sheet feed cassette  3 .  
         [0049]     A leading edge of the sheet of the sheet A having been fed from the sheet feed roller  8  is pinched by the guide rollers  7   a  of the recording section  7 , pulled into the recording section  7 , and a predetermined image is recorded on its surface. The sheet A on which the image has been recorded is discharged onto the tray  3   b  in the sheet feed cassette  3  by means of the discharge rollers  7   b.    
         [0050]     When the sheet feed cassette  3  is taken out of the case  1  in a case where the sheet A in the sheet feed cassette  3  has been consumed or the like, as shown in  FIGS. 9A  to  9 D, the cam  23  on the side wall  3   c  of the sheet feed cassette  3  pulls up the arm  10  by way of the cam follower  10   b . By virtue of the above configuration, the sheet feed cassette  3  can be pulled out of the case  1  without colliding with the sheet feed roller  8 . In addition, similarly, the sheet feed cassette  3 , which has been refilled with the sheets A, is inserted into the case  1  without colliding with the sheet feed roller  8 .  
         [0051]     In a case where the printer stops, the drive shaft  9  rotates counterclockwise in  FIGS. 2 and 6 B, and the leading gear  12  also starts to rotate counterclockwise integrally with the drive shaft  9 . By virtue of the above configuration, the carrier  15  is caused to rotate counterclockwise in a linked manner, whereby, as shown in  FIG. 6A , the first intermediate gear  14   a  is separated from the second intermediate gear  14   b , to thus interrupt transmission of power to the sheet feed roller  8 . Furthermore, each of the protrusions  15   a  on the carrier  15  side hits one end of the corresponding arc groove  18 , thereby raising the arm  10  to its uppermost position as shown in  FIG. 6A . As a result, the arm  10  is stored in the frame  5  together with the sheet feed roller  8  through the opening in the frame  5 .  
         [0052]     As described above, according to the first embodiment, there is provided a printer including a sheet feeder ( 6 ) in which rotating transmission members ( 14   b ,  14   c ) for transmitting rotation of a drive shaft ( 9 ) to a sheet feed roller ( 8 ) are supported by means of cantilever shafts ( 16   b ,  16   c ) on an arm ( 10 ) spanning between the drive shaft ( 9 ) and the sheet feed roller ( 8 ). The elastic members ( 19   a ,  19   b ) are attached to the arm ( 10 ) so as to face end faces of the rotating transmission members ( 14   b ,  14   c ) on the shafts ( 16   b ,  1   c ).  
         [0053]     The elastic members are plate springs ( 19   a ,  19   b ) protruding toward the end faces of the rotating transmission members ( 14   b ,  14   c ).  
         [0054]     The elastic members ( 19   a ,  19   b ) are molded integrally with the arm ( 10 ), from &amp; synthetic resin.  
         [0055]     The elastic members ( 19   a ,  19   b ) are molded integrally with the shafts ( 16   b ,  16   c ) and the arm ( 10 ), from a synthetic resin.  
         [0056]     The oblique surface ( 22   a ) for guiding the rotating transmission members ( 14   b ,  14   c ) at the time of attachment of the rotating transmission members ( 14   b ,  14   c ) is formed at a tip end of a shaft ( 22 ).  
         [0057]     According to the first embodiment, rotating transmission member rotating transmission member when the rotating transmission members ( 14   b ,  14   c ) are inserted between the tip ends of the shafts ( 16   b ,  16   c ) and the elastic members ( 19   a ,  19   b ), the rotating transmission members ( 14   b ,  14   c ) reach the shaft ( 16   b ,  16   c ) while causing the elastic members ( 19   a ,  19   b ) to deform, and fit on the shafts ( 816   b ,  16   c ). When the rotating transmission members ( 14   b ,  14   c ) fit on the shafts ( 16   b ,  16   c ), the elastic members ( 19   a ,  19   b ) are restored to their original shapes, and face the end faces of the rotating transmission members ( 14   b ,  1   c ), thereby preventing the rotating transmission members ( 14   b ,  14   c ) from coming off the shafts ( 16   b ,  16   c ). Therefore, the rotating transmission members ( 14   b ,  14   c ) can be attached to the arm ( 10 ) easily, and, in addition, the structure of the sheet feeder ( 6 ) can be simplified.  
         [0058]     In the first embodiment, the elastic members are plate springs ( 19   a ,  19   b ) protruding toward the end faces of the rotating transmission members ( 14   b ,  14   c ). Accordingly, when the rotating transmission members ( 14   b ,  14   c ) are inserted between the tip ends of the shafts ( 16   b ,  16   c ) and the elastic members ( 19   a ,  19   b ), the rotating transmission members ( 14   b ,  14   c ) are smoothly guided by the plate springs ( 19   a ,  19   b ) to the shafts ( 16   b ,  16   c ), thereby fitting on the shafts ( 16   b ,  16   c ) immediately.  
         [0059]     In the first embodiment, the elastic members ( 19   a ,  19   b ) are molded integrally with the arm ( 10 ), from a synthetic resin. Accordingly, the structure of the sheet feeder ( 6 ) is simplified, thereby reducing the number of components.  
         [0060]     In the first embodiment, the elastic members ( 19   a ,  19   b ) are molded integrally with the shafts ( 16   b ,  16   c ) and the arm ( 10 ), from a synthetic resin. Accordingly, the structure of the sheet feeder ( 6 ) is further simplified, thereby further reducing the number of the components.  
         [0061]     In the first embodiment, an oblique surface ( 22   a ) is formed at a tip end of a shaft ( 22 ) for guiding the rotating transmission members ( 14   b ,  24   c ) at a time of attachment of the rotating transmission members ( 14   b ,  14   c ). Accordingly, when the rotating transmission members ( 14   b ,  14   c ) are inserted between the tip ends of the shafts ( 16   b ,  16   c ) and the elastic members ( 19   a ,  19   b ), the rotating transmission members ( 14   b ,  14   c ) are smoothly guided by the oblique surface ( 22   a ) to the shaft ( 22 ), thereby fitting on the shaft ( 22 ) immediately.  
       Second Embodiment  
       [0062]     Hereinbelow, a printer according to a second embodiment will be described in detail. In the following description of the second embodiment, parts the same as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description of the parts will be omitted.  
         [0063]     The printer according to the second embodiment has the arm  110  as shown in  FIGS. 10-19 .  
         [0064]     As shown in  FIGS. 16 and 18 , each of the rotating transmission members (intermediate gears  14   a - 14   c ) are formed with a shaft hole in which a corresponding cantilever shaft (shafts  116   a - 116   c ) are inserted.  
         [0065]     As shown in  FIGS. 10-19 , a plurality of elastic members  50  are provided on the arm  10  to protrude in a direction parallel to a direction that the shafts  116   a - 116   c  extend to be inserted into the shaft hole.  
         [0066]     Each of the elastic members  50  is provided with a protruded portion  51  at a tip end thereof. Each pair of opposed protruded portions  51  face the end face of the corresponding intermediate gear  14   a - 14   c  to retain the corresponding intermediate gear  14   a - 14   c  in the corresponding shaft  116   a - 116   c.    
         [0067]     In the second embodiment, the elastic members  50  are protruded in the direction that the shafts  116   a - 116   c  extend, and the intermediate gears  14   a - 14   c  are retained in the corresponding shafts  116   a - 116   c  by the protruded portions  51 . According to the configuration, the elastic members  50  extend in the direction parallel to the direction of a force that urges the intermediate gears  14   a - 11   c  to come off from the shafts  14   a - 14   c . Therefore, the elastic members  50  can bear the force more efficiently in comparison with the configuration of the first embodiment.  
         [0068]     As shown in  FIG. 10-19 , each of the protruded portions  51  are formed with an oblique surface  51   a  at a tip and thereof. The oblique surfaces  51   a  guide the intermediate gears  14   a - 14   c  to be attached into the shafts  116   a - 116   c . According to this configuration, the intermediate gears  14   a - 14   c  can be snapped onto the corresponding shafts  16   a - 16   c , whereby the assembling workability can be improved.  
         [0069]     As shown in  FIGS. 10-19 , each of a plurality of latches  70  is engaged with an engagement portion  60  formed on the corresponding shaft  116   a - 116   c . The latch  70  prevents the elastic member  50  from being bent in a direction parallel to a radius direction of the intermediate gears  14   a - 14   c . According to this configuration, the elastic members  50  become more bearable to the force that urges the intermediate gears  14   a - 14   c  to come off from the shafts  14   a - 14   c.    
         [0070]     Each of the engagement portions  60  is formed on the corresponding shaft  116   a - 116   c  to extend in a radial direction of the corresponding shaft  116   a - 116   c . Accordingly, the engagement portions  60  improve rigidity of the shafts  116   a - 116   c  and prevent the shafts  116   a - 116   c  from bending in the radial direction at a circumferential peripheral of the shafts  116   a - 116   c.    
         [0071]     In the second embodiment, the elastic members  50  are molded integrally with the arm  110 , from a synthetic resin. Accordingly, the structure of the sheet feeder  6  is simplified, thereby reducing the number of components.  
         [0072]     In the second embodiment, the elastic members  50  are molded integrally with the shafts  116   a - 116   c  and the arm  110 , from a synthetic resin. Accordingly, the structure of the sheet feeder  6  is further simplified, thereby further reducing the number of the components.  
         [0073]     As shown in  FIGS. 10 and 11 , each of the shafts  116   a - 116   c  has a cylindrical base portion  200  connected to an inner surface  110   a  of the arm  110 . The arm  110  is provided with pairs of opposed elastic members  50  that extend from the base portion  200  perpendicularly to the inner surface  110   a  of the arm  110 . Each of the elastic members  50  faces the end face of the corresponding intermediate gear  14   a - 14   c.    
         [0074]     Each of the shafts  116   a - 116   c  has a pair of opposed peripheral portions  201  that extend from the base portion  200  perpendicularly to the inner surface  110   a  of the arm  110 , and the engagement portion (beam)  60  that bridges the opposed peripheral portions  201 . Each of the intermediate gears  14   a - 14   c  is fitted around the corresponding elastic members  50  and the corresponding peripheral members  201 .  
         [0075]     In the second embodiment, each of the latches  70  is attached to the corresponding engagement portion  60 , and prevents the elastic members  50  from being bent in the radial direction (radius direction) of the intermediate gears  14   a - 14   c.    
         [0076]     In the above-described embodiments, an example where the sheet feeder is attached to a printer has been described; however, the sheet feeder can be attached to a copying machine, facsimile machine, or the like. In addition, the embodiments have been described on an assumption that the drive device of the sheet feed roller is a gear system; however, the drive device may be replaced with or used in combination with a belt system, a friction wheel system, or the like. Moreover, the term “cut sheet” has been employed in the description of the embodiment, however, the cut sheet is a concept encompassing a variety of sheets, such as a resin sheet, a laminated sheet of resin, and paper.  
         [0077]     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application program to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.