Energy storing sheet feeder

Abstract

A sheet feeder includes a separation roller, a friction roller, a shaft and an energy storing element. The energy storing element stores energy when the friction roller is driven by the separation roller to rotate in the sheet-feeding direction and releases energy to make the friction roller rotate in a direction opposite to the sheet-feeding direction.

1 . An energy storing sheet feeder for feeding and separating a first sheet and a second sheet, which are stacked together, the sheet feeder comprising:
 a separation roller rotating in a sheet-feeding direction and driven by a driving device;   a friction roller, which may be rotated by the separation roller;   a shaft, which passes through the friction roller; and   an energy storing element for storing energy when the friction roller is driven by the separation roller to rotate in the sheet-feeding direction and for releasing energy to make the friction roller rotate in a direction opposite to the sheet-feeding direction.   
     
     
         2 . The sheet feeder according to  claim 1 , wherein the friction roller has a first forwarding state, a reversing state and a second forwarding state, wherein:
 in the first forwarding state, the separation roller rotates the friction roller to feed the first sheet alone or to feed the first sheet and the second sheet simultaneously, and the friction roller drives the energy storing element to make the energy storing element store the energy;   in the reversing state, the energy storing element releases the energy to reverse the friction roller to push the second sheet away from a nip between the friction roller and the separation roller; and   in the second forwarding state, the separation roller drives the second/first sheet to make the second/first sheet rotate the friction roller and thus make the energy storing element store the energy.   
     
     
         3 . The sheet feeder according to  claim 1 , wherein the shaft moves relative to the rotating friction roller and the energy storing element is disposed between the shaft and the friction roller. 
     
     
         4 . The sheet feeder according to  claim 1 , wherein the shaft is stationary relative to the rotating friction roller and the energy storing element is connected to the shaft. 
     
     
         5 . The sheet feeder according to  claim 1 , wherein the energy storing element is a worm spring or a torsional spring. 
     
     
         6 . The sheet feeder according to  claim 5 , wherein the energy storing element is preloaded to store predetermined energy in advance. 
     
     
         7 . The sheet feeder according to  claim 1 , further comprising:
 a force-applying mechanism for pushing the separation roller against the friction roller.   
     
     
         8 . The sheet feeder according to  claim 7 , wherein the energy storing element is a worm spring or a torsional spring. 
     
     
         9 . The sheet feeder according to  claim 8 , wherein the energy storing element is preloaded to store predetermined energy in advance.