Sheet feeding apparatus, sheet feeding method and control program

Abstract

A sheet feeding apparatus provided with a fan for blowing air against sheets stacked on a sheet tray, a position detecting sensor for detecting the position of the sheets floated up by the fan, and a tray lifting and lowering mechanism for lifting and lowering the sheet tray. The tray lifting and lowering mechanism is controlled on the basis of a result of detection by the position detecting sensor.

1 - 13 . (canceled) 
   
   
       14 . A sheet feeding apparatus, comprising:
 a tray on which sheets are stacked;   an air discharging portion configured to blow air against the sheets on said tray to float up a sheet;   a sheet feeder configured to feed the sheet floated up by said air discharging portion;   a tray lifting and lowering portion configured to lift and lower said tray in a horizontal attitude;   a position detecting unit configured to detect a position of an uppermost sheet which is being floated up by said air discharging portion; and   a controlling portion adapted to let said tray lifting and lowering portion lower said tray when the uppermost sheet being floated up is above an upper limit of a predetermined range, and let said tray lifting and lowering portion lift said tray when the uppermost sheet being floated up is below a lower limit of said predetermined range, so that a floating position of the uppermost sheet falls within said predetermined range based on a detection result of said position detecting unit.   
   
   
       15 . A sheet feeding apparatus according to  claim 14 , wherein said position detecting unit comprises:
 a first sensor configured to detect a position of the uppermost sheet being floated up above the upper limit of said predetermined range; and   a second sensor configured to detect a position of the uppermost sheet being floated up above the lower limit of said predetermined range.   
   
   
       16 . A sheet feeding apparatus according to  claim 14 , wherein said sheet feeder comprises a belt which sucks the sheet by a lower surface of said belt to convey the sheet. 
   
   
       17 . A sheet feeding apparatus according to  claim 16 , wherein said position detecting unit comprises a distance measuring sensor configured to measure a distance from said lower surface of said belt to the uppermost sheet which is being floated up by said air discharging portion. 
   
   
       18 . A sheet feeding apparatus according to  claim 14 , wherein said controlling portion does not let said tray lifting and lowering portion lift and lower said tray when the uppermost sheet is within said predetermined range. 
   
   
       19 . An image forming apparatus, comprising:
 a tray on which sheets are stacked;   an air discharging portion configured to blow air against the sheets on said tray to float up a sheet;   a sheet feeder configured to feed the sheet floated up by said air discharging portion;   an image forming portion configured to form an image on the sheet fed by said sheet feeder;   a tray lifting and lowering portion configured to lift and lower said tray in a horizontal attitude;   a position detecting unit configured to detect a position of an uppermost sheet which is being floated up by said air discharging portion; and   a controlling portion adapted to let said tray lifting and lowering portion lower said tray when the uppermost sheet being floated up is above an upper limit of a predetermined range, and let said tray lifting and lowering portion lift said tray when the uppermost sheet being floated up is below a lower limit of said predetermined range, so that a floating position of the uppermost sheet falls within said predetermined range based on a detection result of said position detecting unit.   
   
   
       20 . An image forming apparatus according to  claim 19 , wherein said position detecting unit comprises:
 a first sensor configured to detect a position of the uppermost sheet being floated up above the upper limit of said predetermined range; and   a second sensor configured to detect a position of the uppermost sheet being floated up above the lower limit of said predetermined range.   
   
   
       21 . An image forming apparatus according to  claim 19 , wherein said sheet feeder comprises a belt which sucks the sheet by a lower surface of said belt to convey the sheet. 
   
   
       22 . An image forming apparatus according to  claim 21 , wherein said position detecting unit comprises a distance measuring sensor configured to measure a distance from said lower surface of said belt to the uppermost sheet which is being floated up by said air discharging portion. 
   
   
       23 . An image forming apparatus according to  claim 19 , wherein said controlling portion does not let said tray lifting and lowering portion lift and lower said tray when the uppermost sheet is within said predetermined range.