Patent Publication Number: US-2007108696-A1

Title: Sheet feeder capable of reducing multi feed

Description:
BACKGROUND  
      1. Field  
      Example embodiments generally relate to a sheet feeder that may include a feed roller, a sole plate, and/or a separation pad member, and for example to a sheet feeder capable of reducing a multi feed.  
      2. Discussion of the Background  
      A background image forming apparatus such as a printer, a copying machine, and/or a facsimile may use a sheet feeder for feeding sheet in a predetermined or desired direction one by one. A friction pad separation type sheet feeder is well known because of its low cost. Most conventional sheet feeders are capable of feeding a wide variation of sheets and are low cost.  
      There are at least two types of friction pad separation type sheet feeders in general. One has a feed roller and a friction pad to form a nip press region with a predetermined or given nip pressure and also has a sole plate to constantly push sheets against the feed roller. The other has a sole plate that moves between an evacuation position and a pressing feed roller position for the feeding of every sheet, and when operating is stopped, the sole plate is in the evacuation position.  
       FIG. 1  illustrates a configuration of a background sheet feeder.  FIG. 2  also illustrates a configuration of the background sheet feeder when a multi feed occurs in the sheet feeder in  FIG. 1 . As shown in  FIG. 1 , the background sheet feeder may include a feed roller  101 , a separation pad member  102 , a spindle  103 , a friction pad  104 , and a sole plate  105 . The feed roller  101  may feed a sheet P by rotating clockwise. The separation pad member  102  may move the spindle  103  as a fulcrum to form a nip press region N between the friction pad  104  and the feed roller  101  by pushing member that is not shown. The sole plate  105  pushes a stacked sheet P against the feed roller  101  by moving up and down by a driving member that is not shown.  
      At the time of feeding, the sole plate  105  may be moved to a pressing position shown as a chain double-dashed line from an evacuation position shown as a solid line in  FIG. 1 , so that a stacked sheet P is pressed against an undersurface of the feed roller  101 . Holding this position, rotating the feed roller  101  feeds a top sheet into the nip press region N between the friction pad  104  and the feed roller  101 . When only one sheet P is fed, the sheet P passes through the nip press region N downstream correctly. But, when a multi feed occurs, the friction pad  104  stops under sheet P, only a top sheet P is fed downstream with a rotation force of the feed roller  101 .  
      The sole plate  105  moves between an evacuation position and a pressing feed roller position for the feeding at every sheet for feeding, and when operating is stopped, the sole plate  105  is located at the evacuation position. When the sole plate  105  is located at the evacuation position, an operator may easily set the sheets P on the sole plate  105 .  
      As shown in  FIG. 2 , when the sheet P, which may include a thick sheet on top of it, is multi fed, the separation pad member  102  may move down, because a first thick sheet P 1  has a stiffness or a weight to generate a down force.  
      If, a first thick sheet P 1  and a second thick sheet P 2  are multi fed, a tip part A of the separation pad member  102  is pushed down by the first thick sheet P 1  and the second thick sheet P 2 , so that the nip press region N may be open.  
      Therefore, a necessary nip pressure may not be generated at the nip press region N, so that a multi feed may occur, in which the second thick sheet P 2  is fed with the first thick sheet P 1 .  
     SUMMARY  
      Example embodiments are directed to a sheet feeder that may more effectively reduce multi feed. In example embodiments, a sheet feeder may include a feed roller to feed a plurality of sheets, a sole plate to press stacked sheets against the feed roller moving between an evacuation position and a pressing feed roller position, a separation pad member provided downstream from the sole plate in a feeding sheet direction switching between in contact and out of contact with the feed roller to separate each of the plurality of sheets one by one, and a protruding guide member provided near the separation pad member in a feeding sheet path to guide each of the plurality of sheets by contacting an under side of each sheet and controlling a downward movement of each sheet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
       FIG. 1  illustrates a configuration of a background sheet feeder;  
       FIG. 2  also illustrates a configuration of the background sheet feeder when a multi feed occurs in the sheet feeder in  FIG. 1 ;  
       FIG. 3  illustrates a configuration of an electrophotographic apparatus according to example embodiments;  
       FIG. 4A  is an example perspective diagram of a sheet feeder in a manual bypass tray of the electrophotographic apparatus of  FIG. 3 ;  
       FIG. 4B  is an example perspective diagram of a guide plate of the sheet feeder of  FIG. 4A ;  
       FIG. 5  is an example perspective diagram of a part of the sheet feeder of  FIG. 4A ;  
       FIG. 6  is an example perspective diagram of a pressing plate of the sheet feeder of  FIG. 4A ;  
       FIG. 7  is an example perspective diagram of a back of the pressing plate of the sheet feeder of  FIG. 4A ;  
       FIG. 8  is an example cross-sectional diagram of a part of the sheet feeder of  FIG. 4A ;  
       FIG. 9  is an example cross-sectional diagram of a part of the sheet feeder of  FIG. 4A ;  
       FIG. 10  is an example cross-sectional diagram illustrating part of the sheet feeder of  FIG. 4A ;  
       FIG. 11  is another example cross-sectional diagram of part of the sheet feeder of  FIG. 4A ;  
       FIG. 12  is another example cross-sectional diagram of part of the sheet feeder of  FIG. 4A ;  
       FIG. 13  is another example cross-sectional diagram of part of the sheet feeder of  FIG. 4A ;  
       FIG. 14  is another example cross-sectional diagram of part of the sheet feeder of  FIG. 4A ; and  
       FIG. 15  is another example cross-sectional diagram of part of the sheet feeder of  FIG. 4A . 
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS  
      In describing example embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to  FIG. 3 , an electrophotographic apparatus  1  according to example embodiments is explained.  
       FIG. 3  illustrates an electrophotographic apparatus according to example embodiments. A main body  1  may include an image forming section  2  in the center and a feed section  3  under the image forming section  2 . The feed section  3  may include sheet cassettes  4   a ,  4   b ,  4   c , and  4   d . The sheet cassettes  4   a ,  4   b ,  4   c , and  4   d  may be provided like a drawer and may slide in the cross direction in  FIG. 3 .  
      A scanner  5  may be provided on the topside of the image forming section  2 , which scans an original image and converts the original image to an electric signal. A catch tray  7  may be provided on the left side (downstream) of the image forming section  2 , on which an ejected sheet P is stacked. A manual bypass tray  8  may be provided on the right side (upstream) of the image forming section  2  capable of opening and closing as a cover of the main body  1 , which feeds a sheet P by a manual bypass.  
      An image forming unit  10  for each color, such as for example, a yellow (Y), a magenta (M), a cyan (C), and a black (K) is provided above a middle transfer belt  9  that is an endless belt. In the image forming unit  10 , a charging unit  12 , a developing unit  13 , a cleaner  14 , and/or an exposing unit  15   a  that may be a part of a light beam device  15  may be provided around a photo conductor drum  11  for each color to form an electrophotographic process.  
      The charging unit  12  may charge the surface of the photo conductor drum  11 . The exposing unit  15   a  may expose the surface of the photo conductor drum  11  with laser light to form an electrostatic latent image on the surface of the photo conductor drum  11 . The developing unit  13  may develop the electrostatic latent image into a visible toner image. After transferring on the surface of the photo conductor drum  11 , waste toner may be removed by the cleaner  14 .  
      A toner of each color on the photo conductor drum  11  may be transferred onto the middle transfer belt  9  to form a full color image. The full color image on the middle transfer belt  9  may be transferred onto the sheet P with a transferring device  16 . The sheet P may be conveyed from the sheet cassettes  4   a ,  4   b ,  4   c , and  4   d  or the manual bypass tray  8 . The full color image on the sheet P may be fixed on the sheet P in a fixing unit  17 . A sheet ejecting roller  18  may eject the sheet P onto the catch tray  7 .  
      A conveyance path  20  may connect each of the sheet cassettes  4   a ,  4   b ,  4   c , and  4   d , the manual bypass tray  8 , and a resist roller  19 , so that the sheet P is conveyed to the resist roller  19  through the conveyance path  20 . The resist roller may hold the sheet P, and send the sheet P so that the paper sheet P may have a predetermined or desired position against the toner image on the middle transfer belt  9 .  
      A sheet feeder in example embodiments, may be applied to both the sheet cassettes  4   a ,  4   b ,  4   c , and  4   d , and the manual bypass tray  8 . Below is an example of the manual bypass tray  8 .  
       FIG. 4A  is an example perspective diagram of a sheet feeder in a manual bypass tray of the electrophotographic apparatus of  FIG. 3 .  FIG. 4B  is an example perspective diagram of a guide plate of the sheet feeder of  FIG. 4A .  FIG. 5  is an example perspective diagram of a part of the sheet feeder of  FIG. 4A .  FIG. 6  is an example perspective diagram of a pressing plate of the sheet feeder of  FIG. 4A .  FIG. 7  is an example perspective diagram of a back of the pressing plate of the sheet feeder of  FIG. 4A .  
      A sheet feeder  30  may be a friction pad separation type sheet feeder for a manual bypass tray. The sheet feeder  30  may include a feed roller  31 , a sole plate  32 , a friction pad  33   a  (shown in  FIG. 5 ), and/or a separation pad member  33 . The feed roller  31  may feed a sheet P from a stacked sheets P on the manual bypass tray  8 . The sole plate  32  may be located near the feed roller  32  and may push the stacked sheets P against the feed roller  32 , and may move between an evacuation position and a pressing feed roller position. The friction pad  33   a  may be located downstream from the sole plate  32 , may be separate the fed sheet P one by one using friction force. The friction pad  33   a  may be provided on the separation pad member  33  that may be a plate like member.  
      The friction pad  33   a  may be made of a material with a relatively high friction coefficient, for example, a rubber, a rubber cork, a foaming urethane, a thermoplastic elastomer, etc. The separation pad member  33  may move a spindle  33   b  as a fulcrum. The spindle  33   b  may be located downstream of the separation pad member  33 .  
      A plastic structure  34  may be provided as a lower part of the sheet feeder  30 . The plastic structure  34  may include a guide plate  34   a  and a side guide plate  34   b  formed, for example, by integral moulding. The guide plate  34   a  and the side guide plate  34   b  may guide the fed sheet P.  
      The feed roller  31  and the separation pad member  33  may be positioned in the center of the sheet width direction that intersects perpendicularly with the feed direction of the sheet, and the feed roller  31  may be provided on a feed roller shaft  35  that has a longitudinal direction the same as the sheet width direction. Both ends of the feed roller shaft  35  may be provided on the side guide plate  34   b  through a roller bearing  36  that may rotate freely.  
      As shown in  FIG. 5 , the feed roller  31  has a form that a part of a cylinder is cut by a plane parallel to a center line. The feed roller  31  may have a feed roller  31   a  that forms a cylinder, and a cutout part  31   b . A guide roller  37 , which may have a disk shape and may have a smaller diameter than the feed roller  31   a , may be provided on each end of the feed roller  31 . The guide roller  37  is omitted on one side in  FIG. 5 .  
      A cam  38  may be provided on each end of the feed roller shaft  35 . A missing tooth gear  39  for transmitting driving force to the feed roller shaft  35  may be provided on one end of the feed roller shaft  35 . The missing tooth gear  39  may have a form lacking a portion of a circle, and when the missing tooth gear  39  and an input gear (not shown) mesh with each other, the feed roller shaft  35  and the feed roller  31  may be rotated. When the input gear rotates to reach a cutout part of the missing tooth gear  39 , a driving force from the input gear to the missing tooth gear  39  is cut off, and rotation of the feed roller shaft  35  and the feed roller  31  may be stopped.  
      A feed roller position control member  40  may be fixed to the other end side of the feed roller shaft  35 . A first projection  41  may be formed on the feed roller position control member  40 . When a flapper  44  of a solenoid  43  catches the first projection  41 , rotation of the feed roller shaft  35  and the feed roller  31  may be controlled. Further, a second projection  45  may be formed on the feed roller position control member  40 . A tension spring  46  may be provided on the second projection  45 , which pulls the feed roller shaft  35  and the feed roller  31  in a rotating direction of feeding a sheet P.  
      Rotation of the feed roller shaft  35  and the feed roller  31  may be intermittently performed as follows.  
      When the missing tooth gear  39  and the input gear do not mesh with each other, the solenoid  43  turns off and the flapper  44  is caught by the first projection  41 . Therefore, rotation of the feed roller shaft  35  and the feed roller  31  are stopped. After that, the solenoid  43  may turn on at a certain or desired timing, the catch between the flapper  44  and the first projection  41  is not present. Then, the feed roller shaft  35  and the feed roller  31  may rotate in the feed direction by pulling force of the tension spring  46 , and the rotation causes a mesh between the missing tooth gear  39  and the input gear.  
      After the mesh between the missing tooth gear  39  and the input gear, the missing tooth gear  39  rotates by almost 360 degrees until a non-mesh-position, and the feed roller  31  also rotates by almost 360 degrees. When the missing tooth gear  39  and the input gear do not mesh with each other, the solenoid  43  turns off and the flapper  44  is caught by the first projection  41 . Therefore, the rotation of the feed roller shaft  35  and the feed roller  31  are stopped.  
      The guide plate  34   a  may be opened at a feed roller  31  position, and the separation pad member  33  may be located at the opening position. The separation pad member  33  may move a spindle  33   b  as a fulcrum. The friction pad  33   a  may be attached by, for example, a double-stick tape on the separation pad member  33 , which faces the feed roller  31 . A compression spring  47  may be provided under the separation pad member  33 , and the friction pad  33   a  may press the surface of the feed roller  31  by a pressing force of the compression spring  47 .  
      The sole plate  32  may be formed with resin. An arc projection  32   a  may be provided on each side of the sole plate  32  to face the cam  38 , which may be located outside of a sheet P stack area. A guide roller  48  may be provided at the arc projection  32   a , which contacts a surface of the cam  38 . The guide roller  48  may be formed with resin, for example, polyacetal. A U-type slot may be provided on the arc projection  32   a  for attaching the guide roller  48 , an entrance of which may be slightly narrower than a guide roller shaft. Therefore, the guide roller  48  may not easily escape. When attaching the guide roller  48 , the slot may be extended by the elasticity of the resin.  
      A concave area  32   b  may be formed on the sole plate  32  center in the width direction, which may face the feed roller  31 . A friction pad  49  may be attached on the concave area  32   b.    
      A guide pin  50  may be provided near a side plate  34   b  on the plastic structure  34 . When the sole plate  32  moves between an evacuation position and a pressing feed roller position, two pins  50  may serve as a guide. A guide hole  51  (shown in  FIG. 6 ) may be is formed in each side of the sole plate  32  so that the guide pin  51  may pass through the guide hole  51 . The guide hole  51  is located outside of a sheet P stack area so that it may not prevent feeding sheet P.  
      A conic compression spring  52  may be provided between the sole plate  32  and the plastic structure  34 , which presses the sole plate  32  against the feed roller  31 . The conic compression spring  52  may be formed around the guide pin  50 , and a pressing direction by the conic compression spring  52  may be the same as an axis of the guide hole  51 .  
      The feed roller shaft  35  and the feed roller  31  may be driven to rotate intermittently by an on-and-off of the solenoid  43  and a transfer from the input gear to the missing tooth gear  39 . The cam  38  may also rotate at the time of this intermittent rotation. When the cam  38  rotates, it contacts the arc projection  32   a  and the guide roller  48 , or it releases that contact. Then the sole plate  32  moves toward a separating direction from the feed roller  31 , which may be pressed with the conic compression spring  52  against the feed roller  31 .  
      When the feed roller  31   a  faces the sole plate  32 , the cam  38  separates from the arc projection  32   a  and the guide roller  48 , and the sole plate  32  is located in the pressing feed roller position pressing the stacked sheet P against the feed roller  31   a . When the cam  38  contacts with the arc projection  32   a  and the guide roller  48 , the sole plate  32  moves to the evacuation position and pressing the stacked sheet P against the feed roller  31   a  is released.  
      A pressing direction of the sole plate  52  by the conic compression spring  52  may be the same as an axis of the guide hole  51 , and the cam  38  may contact the arc projection  32   a  and the guide roller  48  near the guide hole  51 . Therefore, a bending stress of the sole plate  32  may be reduced during its movement between the evacuation position and the pressing feed roller position. Even if the sole plate  32  is made of resin, a deformation which may cause a feed performance decrease may not occur, and durability of the sole plate  32  may increase.  
      Further, if the sole plate  32  is made of resin, a charge of a static electricity by friction with the sheet P may be smaller, so that it may be unnecessary to connect to ground to reduce or eliminate static electricity.  
       FIG. 8  is an example cross-sectional diagram of a part of the sheet feeder  30  of  FIG. 4A . The sheet feeder  30  may be a friction pad separation type sheet feeder for a manual bypass tray. The sheet feeder  30  may include the manual bypass tray  8 , the feed roller  31 , the sole plate  32 , the friction pad  33   a , and/or the separation pad member  33 . The friction pad  33   a  may be provided on the separation pad member  33  that may be a board-like or plate-like member. The compression spring  47  may be provided under the separation pad member  33 . The conic compression spring  52  may be provided between the sole plate  32  and the plastic structure  34 .  
      The friction pad  33   a  may be made of a material with a relatively high friction coefficient, for example, a rubber, a rubber cork, a foaming urethane, a thermoplastic elastomer, etc. The separation pad member  33  may move the spindle  33   b  as a fulcrum. The spindle  33   b  may be located downstream of the separation pad member  33 .  
      As shown in  FIG. 4B , a protruding guide portion  55  may protrude from the guide plate  34   a  near both sides of the separation pad member  33 , which guides an under side of the sheet P. A tip part  55   a  of the protruding guide portion  55  may be formed higher than a sheet approaching guide part  33   c  of the separation pad member  33  when the feed roller  31  and the friction pad  33   a  contacts.  
       FIG. 9  is an example cross-sectional diagram of a part of the sheet feeder  30  of  FIG. 4A . At the time of feeding, the sole plate  32  with stacked paper P may move from the evacuation position shown as a solid line to the pressing feed roller position shown as a chain double-dashed line. Then, the sheet P is pressed against an undersurface of the feed roller  31 . Holding this position and driving the feed roller  31  to rotate may cause feeding of top sheet P into the nip N between the feed roller  31  and the friction pad  33   a . When only one sheet P is fed, the sheet P passes through the nip press region N downstream correctly by a rotation of the feed roller  31 . But, when a multi feed occurs, the friction pad  33   a  stops an under sheet P, only a top sheet P is fed downstream with a rotation force of the feed roller  31 . Thus, a proper feed with a separation is performed.  
      The sole plate  32  that moves between the evacuation position and the pressing feed roller position for feeding every sheet, and when operating is stopped, the sole plate  32  is located at the evacuation position. When the sole plate  32  is located at the evacuation position, an operator may easily set the sheets P on the sole plate  32 .  
       FIG. 10  is an example cross-sectional diagram illustrating a multi feed in a part of the sheet feeder  30  of  FIG. 4A . As shown in  FIGS. 1 and 2 , when the sheet P, which includes a thick sheet on top, is multi fed, the separation pad member  102  may move down, because a first thick sheet P 1  may have sufficient stiffness or weight to generate a down force. As shown in  FIG. 10 , the down force caused by the thick sheet P 1  may be reduced because the tip part  55   a  of the protruding guide portion  55 , which protrudes higher than the sheet approaching guide part  33   c , pushes the under side of the sheet P 2  up and reduces or eliminates a part of the down force.  
      Therefore, the sheet approaching guide part  33   c  may not depressed by the sheet P and the nip press region N between the feed roller  31  and the separation pad member  33  may not open. As a result, a chance of a multi feed is reduced because a proper nip pressure is constantly applied. Because the down force from the thick sheet is reduced or eliminated, various types of sheets may be used easily without changing a characteristic value, for example, a nip pressure.  
      When the top sheet P 1  is fed from the sole plate  32 , the sole plate  32  falls to the evacuation position, the sole plate  32  sides of the sheets P 1  and P 2  hang down. Even if the sole plate  32  falls, the tip part  55   a  of the protruding guide portion  55  supports the sheets P 1  and P 2 , so that the nip press region N between the feed roller  31  and the separation pad member  33  may not open. As a result, the proper nip pressure may be constantly applied, and a feed with a good separation is performed.  
      The protruding guide portion  55  may act as a nip press holding member at the nip press region N by contacting the sheet P that is fed into the nip N. The protruding guide portion  55  may also act as a member that prevents the sheet P from hanging down from a feeding path. Therefore, a feed with a good separation is performed constantly.  
      Because a depression of the protruding guide portion  55  is suppressed, conveyance guide members may be provided, for example, a guide plate  56  and a conveyance roller  57  that guide the sheet P steeply as shown in  FIG. 10 . As a result flexibility in the design of feeding or conveyance path may increase. A conveyance load rise due to the thick sheet at the separation pad member  33  may be reduced especially with many stacked thick sheets.  
      In example embodiments, the protruding guide portion  55  is provided upstream of the sheet approaching guide part  33   c . Further, as shown in  FIG. 9 , a gap K between G (the tip part  55   a ) and F (an undersurface of the feed roller  31 ) is provided. Therefore, feeding block formed sheets P into the nip N may be reduced or prevented.  
      If the protruding guide portion  55  is formed of a lower friction material, for example, using resin coating, a rise of the conveyance load by frictional resistance with a sheet may be reduced, and a slip ratio rise at the time of feeding may also be reduced.  
      If the protruding guide portion  55  is formed of a wear-proof material, for example, a metal or a plastic containing glass fiber, a wear of the protruding guide portion  55  by contacting with the sheet may be reduced. Therefore, an effect of pressing the sheet may be maintained for a longer period, and an effect of reducing multi feed may also continue for a longer period.  
      An angle of gradient of the tip part  55   a  of the protruding guide portion  55  may be almost the same as the sheet feeding angle to the nip press region N. This may reduce a rise of a feed load, and feeding sheet into the nip press region N may be performed smoothly.  
       FIG. 11  is another example cross-sectional diagram of part of the sheet feeder  30  of  FIG. 4A . A length of a projection of the protruding guide portion  55  may be adjustable according to a type of sheet.  
      As shown in  FIG. 11 , a rack  55   b  may be provided on an under part of the protruding guide portion  55  so that the rack  55   b  meshes with a pinion gear  58 . The pinion gear  58  may be rotated using a control lever  59 , so that the protruding guide portion  55  moves up and down via the rack  55   b.    
      When the protruding guide portion  55  protrudes into a sheet conveyance path, an edge part of a thin sheet P may fold due to a large feeding angle to the friction pad  33   a . But a height adjustable protruding guide portion  55  may reduce or eliminate the folding problem of the thin sheet.  
      When a thin sheet is twisted, a wave of the sheet may occur or an OHP sheet may be scratched. Thus, the thin sheet may generate a smaller down force at the sheet approaching guide part  33   c  of the separation pad member  33 . In example embodiments, lowering the height of the projection of the protruding guide portion  55  may reduce an occurrence of wave and/or scratch.  
       FIG. 12  is another example cross-sectional diagram of part of the sheet feeder  30  of  FIG. 4A . A roller  60  for guiding sheet may be provided at the tip part  55   a  of the protruding guide portion  55 .  
      A thick sheet may generate a larger down force, so that a conveyance load may become larger at the protruding guide portion  55 . The roller  60  may reduce the conveyance load and hold a proper conveyance force, so that various types of sheets may be used. In general, it may be necessary to increase a feed pressure for holding a proper conveyance force. In example embodiments shown in  FIG. 12 , it may be unnecessary to change a characteristic value, and various types of sheets may be used.  
       FIG. 13  is another example cross-sectional diagram of part of the sheet feeder  30  of  FIG. 4A . A relay conveyance roller  61  may be provided downstream from the feed roller  31 .  
      The relay conveyance roller  61  may be located close to the friction pad  33   a  of the separation pad member  33 , and may be arranged as one pair on both sides of the separation pad member  33 . Thus, it is possible to reduce or prevent non-sending at the time of feeding in a last sheet of OHP that tends to have a short conveyance distance due to a high slip tendency by using the relay conveyance roller  61  close to the nip press region N as much as possible.  
       FIG. 14  is another example cross-sectional diagram of part of the sheet feeder  30  of  FIG. 4A . A separation pad member  33  may be almost horizontally oriented. A bent or inclined part  33   d  may be formed on a friction pad  33   a  at the end of the separation pad member  33 , so that an inside corner M, which faces a sheet path, is formed at the bent or inclined part  33   d.    
      When the separation pad member  33  is almost horizontally oriented, a thick sheet may easily pass through the nip press region N. The inside corner M may act to prevent multi feed because the inside corner M may resist a sheet passing.  
       FIG. 15  is another example cross-sectional diagram part of the sheet feeder  30  of  FIG. 4A . An inside corner M on a friction pad  33   a  may be located at the nip press region N.  
      When the inside corner M is separated from the nip press region N, an edge of sheet P may swing away from the nip press region N, so that the multi feed prevents function of the inside where M may be reduced. When the inside corner M is located at the nip press region N, a movement of the edge of the sheet P is reduced, so that the multi feed preventing function the inside corner M is improved.  
      Any construction of example embodiments may be suitably adopted according to an apparatus&#39;s construction.  
      Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.  
      This patent specification is based on Japanese patent applications, No. JPAP2005-331412 filed on Nov. 16, 2005 in the Japan Patent Office, the entire contents of which are incorporated by reference herein.