Paper feeding device and paper feeding method applied thereto

Abstract

A paper feeding device includes a motor, a pickup roller assembly, a velocity sensor and a feeding roller assembly. The pickup roller assembly is driven by the motor for picking up the papers. The velocity sensor is mounted to the pickup roller assembly for detecting rotating speeds of the pickup roller assembly so as to detect speeds of feeding forward the papers. The feeding roller assembly is driven by the motor for continuing feeding forward the papers. A speed discrepancy will be generated between the rotating speed of the pickup roller assembly after the one of the papers is fed to the feeding roller assembly and the rotating speed of the pickup roller assembly which just picks up the one of the papers, when the speed discrepancy reaches a preset value set by the scanner, the scanner is triggered to start scanning.

1 . A paper feeding device mounted in a scanner for feeding papers, the paper feeding device comprising:
 a motor;   a pickup roller assembly connected with and driven by the motor for picking up the papers and transmitting the papers to the feeding roller assembly;   a velocity sensor mounted to the pickup roller assembly for detecting rotating speeds of the pickup roller assembly so as to detect speeds of feeding forward the papers, the rotating speed of the pickup roller assembly being detected by virtue of counting pulses outputted by the velocity sensor; and   a feeding roller assembly connected with and driven by the motor, and located in front of the pickup roller assembly for continuing feeding forward the papers;   wherein a rotating speed of the feeding roller assembly is faster than the rotating speed of the pickup roller assembly, after one of the papers is fed to the feeding roller assembly, the feeding roller assembly drives the one of the papers to be fed acceleratedly, at the moment, the pickup roller assembly rotates acceleratedly on account of being dragged by the one of the papers, a speed discrepancy will be generated between the rotating speed of the pickup roller assembly after the one of the papers is fed to the feeding roller assembly and the rotating speed of the pickup roller assembly which just picks up the one of the papers, and when the speed discrepancy reaches a preset value set by the scanner, the scanner is triggered to start scanning.   
     
     
         2 . The paper feeding device as claimed in  claim 1 , wherein the pickup roller assembly includes a pickup shaft, a pickup roller pivotally mounted around one end of the pickup shaft, and the velocity sensor is mounted to the pickup shaft. 
     
     
         3 . The paper feeding device as claimed in  claim 2 , wherein the velocity sensor is an optical rotary encoder. 
     
     
         4 . The paper feeding device as claimed in  claim 3 , wherein the optical rotary encoder includes a light source, a coded disc and a light receiver, the coded disc is fastened to the pickup shaft, the coded disc is disposed between the light source and the light receiver, and when the motor drives the pickup roller assembly to rotate to pick up the papers, the pickup shaft and the coded disc rotate together at the same speed, but the light source and the light receiver do not rotate with the pickup shaft. 
     
     
         5 . The paper feeding device as claimed in  claim 4 , wherein the light source is turned on, the coded disc opens a plurality of equidistant openings arranged as a ring shape, and the light receiver receives light beams penetrating through the openings at the time of the pickup shaft and the coded disc rotating together. 
     
     
         6 . A paper feeding method applied to a paper feeding device which is mounted in a scanner for feeding papers, the paper feeding device including a motor, a pickup roller assembly connected with the motor, a velocity sensor mounted to the pickup roller assembly, and a feeding roller assembly connected with the motor, the paper feeding method comprising steps of:
 the motor driving the pickup roller assembly to rotate to pick up the papers and transmit the papers to the feeding roller assembly;   the velocity sensor detecting rotating speeds of the pickup roller assembly by virtue of counting pulses outputted by the velocity sensor so as to detect speeds of feeding forward the papers;   the motor driving the feeding roller assembly to rotate for continuing feeding forward the papers transmitted by the pickup roller assembly to a scan passageway of the scanner; and   getting a speed discrepancy between the rotating speed of the pickup roller assembly after the one of the papers is fed to the feeding roller assembly and the rotating speed of the pickup roller assembly which just picks up the one of the papers;   wherein the rotating speed of the feeding roller assembly is faster than the rotating speed of the pickup roller assembly, after one of the papers is fed to the feeding roller assembly, the feeding roller assembly drives the one of the papers to be fed acceleratedly, at the moment, the pickup roller assembly rotates acceleratedly on account of being dragged by the one of the papers, and when the speed discrepancy reaches a preset value set by the scanner, the scanner is triggered to start scanning.   
     
     
         7 . The paper feeding method as claimed in  claim 6 , further comprising a step of modulating a scan scaling of the scanner according to the speeds of feeding forward the papers. 
     
     
         8 . The paper feeding method as claimed in  claim 6 , further comprising a step of detecting whether paper jam problems are caused in the process of feeding the papers by virtue of getting pulse frequency variations of the velocity sensor. 
     
     
         9 . The paper feeding method as claimed in  claim 8 , further comprising a step of sending instructions at the time of the paper jam problems being detected, and the motor being stopped rotating. 
     
     
         10 . The paper feeding method as claimed in  claim 6 , wherein the pickup roller assembly includes a pickup shaft, a pickup roller pivotally mounted around one end of the pickup shaft, and the velocity sensor is mounted to the pickup shaft. 
     
     
         11 . The paper feeding method as claimed in  claim 10 , wherein the velocity sensor is an optical rotary encoder. 
     
     
         12 . The paper feeding method as claimed in  claim 11 , wherein the optical rotary encoder includes a light source, a coded disc and a light receiver, the coded disc is fastened to the pickup shaft, the coded disc is disposed between the light source and the light receiver, and when the motor drives the pickup roller assembly to rotate to pick up the papers, the pickup shaft and the coded disc rotate together at the same speed, but the light source and the light receiver do not rotate with the pickup shaft. 
     
     
         13 . The paper feeding method as claimed in  claim 12 , wherein the light source is turned on, the coded disc opens a plurality of equidistant openings arranged as a ring shape, and the light receiver receives light beams penetrating through the openings at the time of the pickup shaft and the coded disc rotating together.