Sheet feeding apparatus with buffer function and method thereof

Abstract

Disclosed is a sheet feeding apparatus having a sheet buffer function (temporal storage function), which has a simple structure without a buffer drum and feeds a present sheet and a subsequent sheet by stacking the present sheet and the subsequent sheet. The sheet feeding apparatus includes a pair of discharge rollers including a driving roller and an idle roller, a first feeding path connected to the discharge rollers, a second feeding path located at a rear of the first feeding path, branch flaps installed at a branch part of the first and second feeding paths, a sheet detecting sensor installed on the first feeding path, a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller, and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller.

What is claimed is: 
     
         1 . A sheet feeding apparatus having a buffer function, the sheet feeding apparatus comprising:
 a pair of discharge rollers including a driving roller and an idle roller;   a first feeding path connected to the discharge rollers;   a second feeding path located at a rear of the first feeding path while being branched from the first feeding path;   a branch flap installed at a branch part of the first and second feeding paths;   a sheet detecting sensor installed on the first feeding path between the branch flap and the discharge rollers;   a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller; and   a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller.   
     
     
         2 . The sheet feeding apparatus of  claim 1 , wherein the rotating shaft of the driving roller is connected to a reversible motor. 
     
     
         3 . The sheet feeding apparatus of  claim 2 , wherein the cam holder has a substantially rectangular ring shape having a stepped top surface, the cam is installed in an internal cavity of the cam holder, and the cam selectively makes contact with a stepped inner surface of the cam holder. 
     
     
         4 . A method for feeding sheets in a sheet feeding apparatus having a buffer function, the sheet feeding apparatus including a pair of discharge rollers including a driving roller and an idle roller, a first feeding path connected to the discharge rollers, a second feeding path located at a rear of the first feeding path while being branched from the first feeding path, a branch flap installed at a branch part of the first and second feeding paths, a sheet detecting sensor installed on the first feeding path between the branch flap and the discharge rollers, a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller, and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller, the method comprising:
 discharging a first sheet outward through the pair of discharge rollers until a rear end of the first sheet is detected by the sheet detecting sensor as the first sheet is fed along the first feeding path;   reversely driving the pair of discharge rollers as the sheet detecting sensor detects the rear end of the first sheet and moving back the first sheet by guiding the rear end of the first sheet to the second feeding path using the branch flap;   driving the cam such that the driving roller and the idle roller of the discharge rollers are spaced part from each other, and returning the branch flap to an initial position thereof to allow a second sheet to be fed along the first feeding path; and   allowing the driving roller and the idle roller of the discharge rollers to make contact with each other when a predetermined time has elapsed after a front end of the second sheet has passed through the sheet detecting sensor and rotating the driving roller and the idle roller of the discharge rollers in a forward direction such that the first and second sheets are simultaneously discharged out of the pair of the discharge rollers.