Method of operating a document feeding mechanism to detect and recover from a multi-feed condition and an apparatus therefor

Abstract

A method is provided of operating a document feeding mechanism having a document feed path which extends through a nip defined between an advance roller disposed on one side of a document feed path and a retard roller disposed on an opposite side of the document feed path. The method comprises detecting a multi-feed condition in which a first document and a second document overlapping the first document have been fed through the nip from an upstream end of the document feed path to a downstream end of the document feed path, and controlling operation of the advance roller and the retard roller such that the second document is driven backwards through the nip to allow the first document to be fed through the nip by itself in a non-overlapping manner without any human intervention.

1 . A method of operating a document feeding mechanism having a document feed path which extends through a nip defined between an advance roller disposed on one side of a document feed path and a retard roller disposed on an opposite side of the document feed path, the method comprising:
 detecting a multi-feed condition in which a first document and a second document overlapping the first document have been fed through the nip from an upstream end of the document feed path to a downstream end of the document feed path; and   controlling operation of the advance roller and the retard roller such that the second document is driven backwards through the nip to allow the first document to be fed through the nip by itself in a non-overlapping manner without any human intervention.   
     
     
         2 . A method according to  claim 1 , further comprising:
 after the first document has been fed through the nip by itself, controlling operation of the advance roller and the retard roller such that the second document is fed through the nip by itself in a non-overlapping manner without any human intervention.   
     
     
         3 . A method of operating a document feeding mechanism having a document feed path which extends through a nip defined between an advance roller disposed on one side of a document feed path and a retard roller disposed on an opposite side of the document feed path, the method comprising:
 detecting a multi-feed condition in which a first document and a second document overlapping the first document have been fed through the nip from an upstream end of the document feed path to a downstream end of the document feed path;   halting operation of the advance roller when the multi-feed condition is detected; and   reversing direction of rotation of the retard roller when the multi-feed condition is detected such that the second document which is adjacent to the retard roller is driven backwards through the nip from the downstream end of the document feed path to the upstream end of the document feed path while the first document which is adjacent to the halted advance roller is maintained in the nip between the advance roller and the retard roller.   
     
     
         4 . A method according to  claim 3 , further comprising:
 after the second document has been driven backwards completely through the nip, continuing operation of the advance roller such that the first document continues to be fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path.   
     
     
         5 . A method according to  claim 4 , further comprising:
 after the first document has been fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path, continuing operation of the advance roller such that the second document is fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path.   
     
     
         6 . A document feeding apparatus comprising:
 an advance roller disposed on one side of a document feed path;   a retard roller disposed on an opposite side of the document feed path and facing the advance roller to form a nip therebetween;   a sensor for (i) detecting a multi-feed condition in which a first document and a second document overlapping the first document have been fed through the nip from an upstream end of the document feed path to a downstream end of the document feed path, and (ii) providing a sensor signal indicative of the multi-feed condition;   a controller for (i) providing a first control signal to halt operation of the advance roller when the sensor signal indicative of the multi-feed condition is detected, and (ii) providing a second control signal to reverse direction of rotation of the retard roller when the sensor signal indicative of the multi-feed condition is detected such that the second document which is adjacent to the retard roller is driven backwards through the nip from the downstream end of the document feed path to the upstream end of the document feed path while the first document which is adjacent to the halted advance roller is maintained in the nip between the advance roller and the retard roller.   
     
     
         7 . A document feeding apparatus according to  claim 6 , wherein after the second document has been driven backwards completely through the nip, the controller provides a third control signal to continue operation of the advance roller such that the first document continues to be fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path. 
     
     
         8 . A document feeding apparatus according to  claim 7 , wherein after the first document has been fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path, the controller provides a fourth control signal to continue operation of the advance roller such that the second document is fed through the nip from the upstream end of the document feed path to the downstream end of the document feed path. 
     
     
         9 . A document feeding apparatus according to  claim 8 , wherein the third control signal and the fourth control signal are substantially the same. 
     
     
         10 . A document feeding apparatus according to  claim 6 , wherein the sensor comprises an ultrasonic-type of sensor.