Paper feeding device for image forming apparatus

Abstract

A paper feeding device for an image forming apparatus includes a pick-up roller for picking up paper from a paper feeding cassette and for feeding the paper to a registration roller. The registration roller registers a leading end of a sheet of paper and compensates for skew of the paper by stopping to allow the leading end of the paper to contact the registration roller to form a paper curl and maintaining the paper curl. The paper feeding device does not require a feeding roller but instead controls the rotation of the pick-up roller to form the paper curl. Therefore, the paper feeding device is compact and can be used with a compact image forming apparatus.

1 . A paper feeding device for an image forming apparatus, comprising: 
 a pick-up roller with a paper contact portion;    a registration roller for registering a leading end of a paper fed by the pick-up roller and compensating for skew of the paper; and    a driving unit to drive the pick-up roller between a first position for preparing to pick up a sheet of paper and a second position for forming a paper curl.    
   
   
       2 . The device as claimed in  claim 1 , the driving unit comprising: 
 a pick-up gear engaged with a pick-up roller shaft; and    a solenoid engaging the pickup gear, the solenoid stopping the pick-up gear from rotating at each of the first and the second positions.    
   
   
       3 . The device as claimed in  claim 2 , wherein 
 the pick-up gear comprises first and second locking portions corresponding to each of the first and the second positions; and    the solenoid comprises a movable body which may be locked in the first and the second locking portions so that the pick-up gear is stopped at the first and the second positions, respectively.    
   
   
       4 . The device as claimed in  claim 3 , wherein 
 each of the first and the second locking portions comprises a locking protrusion at one side, and a guide contour at the other side.    
   
   
       5 . The device as claimed in  claim 1 , wherein 
 a rotational distance of the pick-up roller is set to meet the following equation:     1+α≦ <L<LE     in which, L is the distance the pick-up roller rotates from a reference position (S 1 ) where the paper contact portion of the pick-up roller starts to contact the paper to the second position (S 2 ), 1 is a distance between the reference position (S 1 ) and the registration roller, α is an amount of paper curl, and LE is a distance between the reference position (S 1 ) and the first position (S 3 ).    
   
   
       6 . The device as claimed in  claim 1 , further comprising: 
 a bottom tray for pressing the paper into contact with the pick-up roller; and    means for preventing a reverse moment which is generated at the pick-up roller by the bottom tray.    
   
   
       7 . The device as claimed in  claim 6 , wherein the means for preventing the reverse moment comprises: 
 a pick-up cam rotating coaxially with the pick-up roller to move the bottom tray upwardly and downwardly; and    a cam stopper pressing the pick-up cam to prevent the reverse moment generated by the bottom tray.    
   
   
       8 . The device as claimed in  claim 7 , wherein 
 the pick-up cam comprises a locking recess in which a leading end of the cam stopper is locked.    
   
   
       9 . A paper feeding device for an image forming apparatus comprising: 
 a registration roller for registering a leading end of a sheet of paper and compensating for skew of the paper; and    a pick-up roller for picking up a sheet of paper to feed to the registration roller and, as the leading end of the sheet of paper contacts the registration roller to form a certain paper curl, stopping to maintain the paper curl.    
   
   
       10 . The device as claimed in  claim 9 , further comprising: 
 a solenoid controlling the rotation of the pick-up roller to stop the pick-up roller at a first position for preparing to pick-up a sheet of paper and at a second position for forming a paper curl.    
   
   
       11 . The device as claimed in  claim 10 , further comprising: 
 a pick-up roller shaft rotatably supporting the pick-up roller;    a pick-up gear engaged with the pick-up roller shaft to rotate the pick-up roller,    wherein the pick-up gear comprises a first and a second locking portions corresponding to the first and the second positions, and    wherein the solenoid comprises a movable body which may be locked in the first and the second locking portions so that the pick-up gear is stopped at the first and the second positions, respectively.    
   
   
       12 . The device as claimed in  claim 11 , wherein 
 each of the first and the second locking portions comprises a locking protrusion at one side, and a guide contour at the other side.    
   
   
       13 . The device as claimed in  claim 10 , wherein 
 a rotational distance of the pick-up roller is set to meet the following equation:     1+α≦ L<LE     in which, L is the distance the pick-up roller rotates from a reference position (S 1 ) where the paper contact portion of the pick-up roller starts to contact the paper to the second position (S 2 ), 1 is a distance between the reference position (S 1 ) and the registration roller, α is an amount of paper curl, and LE is a distance between the reference position (S 1 ) and the first position (S 3 ).    
   
   
       14 . The device as claimed in  claim 9 , further comprising: 
 a bottom tray for pressing the paper into contact with the pick-up roller; and    means for preventing a reverse moment which is generated at the pick-up roller by the bottom tray.    
   
   
       15 . The device as claimed in  claim 14 , wherein the means for preventing the reverse moment comprises: 
 a pick-up cam rotating coaxially with the pick-up roller to move the bottom tray upwardly and downwardly; and    a cam stopper pressing the pick-up cam to prevent the reverse moment generated by the bottom tray.    
   
   
       16 . The device as claimed in  claim 15 , wherein 
 the pick-up cam comprises a locking recess in which a leading end of the cam stopper is locked.    
   
   
       17 . A paper feeding device for an image forming apparatus, comprising: 
 a registration roller for registering a leading end of a sheet of paper;    a rotatable pick-up roller for picking up a sheet of paper from a stack of paper and feeding the sheet of paper to the registration roller, the pick-up roller having a paper contact portion;    means for rotating the pick-up roller and stopping the pick-up roller at a first stop position and a second stop position, wherein the first stop position and the second stop position are arranged to meet the following equation:     1+α≦ L<LE     in which, L is the distance the pick-up roller rotates from a reference position (S 1 ) where the paper contact portion of the pick-up roller starts to contact the paper to the second stop position (S 2 ), 1 is a distance between the reference position (S 1 ) and the registration roller, α is an amount of paper curl, and LE is a distance between the reference position (S 1 ) and the first stop position (S 3 ).    
   
   
       18 . The device as claimed in  claim 17 , wherein the means for rotating and stopping the pick-up roller comprises: 
 a rotatable pick-up roller gear engaging the pick-up roller, the pick-up roller gear being driven to rotate the pick-up roller, the pick-up roller gear having first and second locking portions; and    means for engaging the first and second locking portions of the pick-up roller gear to prevent the pick-up roller gear from rotating.    
   
   
       19 . The device as claimed in  claim 18 , wherein the means for engaging the first and second locking portions of the pick-up roller gear comprises: 
 a solenoid engaging the pickup gear.    
   
   
       20 . The device as claimed in  claim 18 , wherein 
 the pick-up roller gear is driven by an input gear, and the pick-up roller gear has a toothed portion where the pick-up roller gear is engaged with the input gear, and has first and second cut-off portions where the pick-up roller gear is not engaged with the input gear, the first and second cut-off portions corresponding to the first and second stop positions.