Paper feeding method and paper feeder

Abstract

An image-forming apparatus has a limitation pad 31 c and a retard roller 34 , which separately feed recording paper P on an elevation tray 31 in an MPT cover 30 by bringing the recording paper P against an outer peripheral surface 33 a of the feeding roller 33 . In this image-forming apparatus (paper feeder), when the feeding roller is stopped by passing recording paper to be separately fed to a pair of relay transport rollers, the elevation tray is lowered before stoppage of the feeding roller, thereby separating an extremity of the recording paper from the outer peripheral surface of the feeding roller.

1 . A paper feeder for separately feeding a sheet of paper from plural sheets of paper along a transfer path, said paper feeder comprising: 
 a feed roller;    a retard roller in pressed contact with the feed roller and forming a first nip between the feed roller and the retard roller, wherein an axis-to-axis distance between the feed roller and the retard roller is fixed;    a lift plate on which plural sheets of paper can be set, the lift plate being located in an upstream side of the transfer path with respect to the feed roller and being movable between a first position where a front end of the plural sheets of paper set on the lift plate is brought into contact with the feed roller and a second position where the front end of the plural sheets of paper set on the lift plate is separated from the feed roller;    a pair of transport rollers in contact with each other to form a second nip, and being located in a downstream side of the transfer path with respect to the feed roller; and    a controller which moves the lift plate from the first position to the second position in a state in which the sheet of paper is held between the feed roller and the retard roller at the first nip and is also held between the transport rollers at the second nip.    
   
   
       2 . The paper feeder according to  claim 1 , wherein when the controller moves the lift plate from the first position to the second position, the controller stops rotation of the feed roller.  
   
   
       3 . The paper feeder according to  claim 2 , wherein controller moves the lift plate from the second position to the first position when the controller restarts the rotation of the feed roller.  
   
   
       4 . The paper feeder according to  claim 1 , wherein the plural sheets of paper set on the lift plate is of cardboard.  
   
   
       5 . The paper feeder according to  claim 1 , wherein the controller is communicatable with an interface by which a user can selectively enter cardboard and plan paper as information of the plural sheets of paper set on the lift plate to set a first mode and a second mode, respectively, 
 in the first mode, a controller moves the lift plate at the first position to the second position before the sheet of paper completely passes through the first nip.    
   
   
       6 . The paper feeder according to  claim 5 , wherein in the second mode, the controller maintains the lift plate at the first position until the sheet of paper completely passes through the first nip.  
   
   
       7 . The paper feeder according to  claim 5 , wherein in the second mode, the controller moves the lift plate at the first position to the second position when the controller stops rotation of the feed roller and before the sheet of paper completely passes through the first nip.  
   
   
       8 . The paper feeder according to  claim 5 , wherein in the first mode, the controller moves the lift plate from the second position to the first position after the sheet of paper completely passes through the first nip, to thereby feed a subsequent sheet of paper to the first nip.  
   
   
       9 . The paper feeder according to  claim 7 , wherein in the second mode, the controller moves the lift plate from the second position to the first position after the sheet of paper completely passes through the first nip and when the controller restarts the rotation of the feed roller, to thereby feed a subsequent sheet of paper to the first nip.  
   
   
       10 . A paper feeder comprising: 
 a separation-and-feeding section for separating a sheet of paper from plural sheets of paper set in a load position and feeding said sheet of paper downstream;    a transport section which transports said sheet of paper sent from said separation-and-feeding section further downstream to feed said sheet of paper to a processing position on an apparatus main body;    a transfer path for guiding said sheet of paper to be sent from said load position to said processing position using said separation-and-feeding section and said transport section; and    a control section for controlling driving action of individual sections of said apparatus so that said sheet of paper is fed from said load position to said processing position in synchronism with processing timing of said apparatus main body, wherein    said separation-and-feeding section includes 
 a feeding roller for feeding, to a downstream transfer path, said sheet of paper brought into pressed contact therewith,  
 a separation roller which is rotationally driven or subjected to limited rotation according to frictional force developing between said separation roller and said sheet of paper while bringing said sheet of paper into pressed contact with said feeding roller, thereby separating, from said plural sheets of paper, said sheet of paper to be fed by said feeding roller, and  
 a movement mechanism which is configured so as to be able to carry said plural sheets of paper and which moves an extremity of said plural sheets of paper in a direction in which said extremity is brought into contact with or separated from a portion of an outer peripheral surface of said feeding roller, said portion of said outer peripheral surface being located upstream of said separation roller;  
   said separation-and-feeding section is designed to such a configuration that said separation roller remains in pressed contact with said feeding roller at all times; and    said control section drives and controls said movement mechanism such that said extremity of said plural sheets of paper is separated from said feeding roller at a timing at which said feeding roller comes to a stop.    
   
   
       11 . The paper feeder according to  claim 10 , wherein said transfer path is designed to a transfer path length over which feeding of said sheet of paper to said processing position of said apparatus main body by said transport section is commenced before said sheet of paper passes through a nipping position existing between said feeding roller and said separation roller of said separation-and-feeding section; and 
 when transfer of said sheet of paper received from said separation-and-feeding section is temporarily stopped before said sheet of paper passes through said nipping position between said feeding roller and said separation roller so that said transport section feeds said sheet of paper to said processing position in synchronism with a processing timing of said apparatus main body, said control section stops said feeding roller of said separation-and-feeding section.    
   
   
       12 . The paper feeder according to  claim 11 , wherein said control section stops said feeding roller even after said sheet of paper transported by said transport section has passed through said nipping section between said feeding roller and said separation roller.  
   
   
       13 . The paper feeder according to  claim 10 , wherein, when transfer of said sheet of paper received from said separation-and-feeding section is temporarily stopped before said sheet of paper passes through said nipping position between said feeding roller and said separation roller so that said transport section feeds said sheet of paper to said processing position in synchronism with said processing timing of said apparatus main body, said control section controls driving of said movement mechanism such that said extremity of said plural sheets of paper is separated from said feeding roller before occurrence of temporary stoppage of said sheet of paper until said sheet of paper passes through said nipping position.  
   
   
       14 . A paper feeding method for a paper feeder including a paper feeding roller which comes into contact with a topmost sheet of paper in stacked sheets of paper to thereby feed said topmost sheet of paper, a retard roller which comes into contact with said paper feeding roller to separate said topmost sheet of paper from a subsequent sheet of paper in said stacked sheets, and a lift plate which supports said stacked sheets of paper to be fed by said paper feeding roller and presses a front portion of said stacked sheets of paper against said paper feed roller, wherein 
 when said paper is plain paper, said paper is fed while said lift plate remains pressed; and    when said paper is cardboard, said paper is fed while said lift plate is lifted and lowered every time one sheet of cardboard paper is fed.    
   
   
       15 . A paper feeder comprising: 
 a paper feeding roller which comes into contact with a topmost sheet of paper in stacked sheets of paper to thereby feed said topmost sheet of paper;    a retard roller which comes into contact with said paper feeding roller to separate said topmost sheet of paper from a subsequent sheet of paper in said stacked sheets;    a lift plate which supports said stacked sheets of paper to be fed by said paper feeding roller and presses a front portion of said stacked sheets of paper against said paper feed roller;    a lift plate lifting-and-lowering mechanism for lifting or lowering said lift plate; and    a controller which selects either a plain paper mode, where paper is fed while said lift plate remains pressed by said lift plate lifting-and-lowering mechanism when said paper is plain paper, or a cardboard mode, where paper is fed while said lift plate is lifted and lowered by said lift plate lifting-and-lowering mechanism every time one sheet of cardboard is fed when said paper is cardboard.    
   
   
       16 . The paper feeder according to  claim 15 , further comprising: 
 a first tray which has said lift plate and is tilted at a tilt angle with respect to a horizontal plane; and    a second tray which is coupled to a rear portion of said first tray, supports a rear portion of said stacked sheets of paper, and has a smaller tilt angle with respect to said horizontal plane than the tilt angle of said first tray, wherein    a paper support face of said second tray falls within a range of angle made between a paper support face of said lift plate at a lift-up position where said lift plate is lifted when the stacked sheets of paper is maximum in number that can be set on said first tray and a paper support face of said lift plate at another lift-up position where said lift plate is lifted when one sheet of paper is supported by said first tray.    
   
   
       17 . The paper feeding method according to  claim 14 , wherein lifting/lowering of said lift plate performed when said paper is cardboard is effected by: lowering said lift plate after one sheet of cardboard has been fed and before a trailing edge of said cardboard passes through a contact section between said paper feeding roller and said retard roller, and lifting said lift plate before initiation of feeding of a next sheet of cardboard.