Unit for and method of registering/feeding paper and image forming apparatus using the same

Abstract

A paper registering/feeding unit that registers a sheet of print paper and feeds it to a printing unit, a method of registering/feeding a sheet of print paper, and an image forming apparatus using the same are provided. A paper registering/feeding unit includes a rotatable pick-up roller including an effective contact surface which contacts a sheet of print paper to pick up the print paper. The paper registering/feeding unit also includes a pair of registration rollers in contact with each other to form a nip along the pathway of the print paper, a sensor sensing the approach of the front end of the print paper picked up by the pick-up roller toward the nip of the registration rollers, and a controller that controls a rotation of the registration rollers based on a time of sensing the end of the print paper by the sensor.

1 . A paper registering/feeding unit comprising: 
 a rotatable pick-up roller including a contact surface which contacts a sheet of print paper to pick up the print paper;    a plurality of registration rollers in contact with each other to form a nip along the pathway of the print paper;    a sensor sensing the approach of the front end of the print paper picked up by the pick-up roller toward the nip of the registration rollers; and    a controller that controls rotation of the registration rollers based on a time of sensing the front end of the print paper by the sensor,    wherein the length of the arc of the contact surface is greater than the distance between the pick-up roller and the nip of the registration rollers along the pathway of the print paper.    
   
   
       2 . The paper registering/feeding unit of  claim 1 , wherein the controller comprises a unit that rotates the registration rollers after a first time-lag from the time of sensing the front end of the print paper so that the front end of the print paper curls, registered and passed through the nip of the registration rollers, and that pauses the registration rollers after a second time-lag from the time of sensing the front end of the registered print paper passing through the nip so that the transportation of the front end of the print paper is discontinued and on standby for printing.  
   
   
       3 . The paper registering/feeding unit of  claim 1 , wherein the paper registering/feeding unit comprises no additional rollers for feeding the print paper between the pick-up roller and the registration rollers.  
   
   
       4 . The paper registering/feeding unit of  claim 1 , wherein the paper registering/feeding unit further comprises a clutch that selectively connects and disconnects the registration rollers to and from a driving source for driving the registration roller according to control signals generated by the controller.  
   
   
       5 . An image forming apparatus having a printing unit that prints an image on print paper and a paper registering/feeding unit that registers and feeds the print paper to the printing unit, wherein the paper registering/feeding unit comprises: 
 a rotatable pick-up roller including a contact surface which contacts a sheet of print paper to pick up the print paper;    a plurality of registration rollers in contact with each other and forming a nip along the pathway of the print paper;    a sensor sensing the approach of the front end of the print paper picked up by the pick-up roller toward the nip of the registration rollers; and    a controller that controls rotation of the registration rollers based on the time of sensing the front end of the print paper by the sensor,    wherein the length of the arc of the contact surface is greater than the distance between the pick-up roller and the nip of the registration rollers along the pathway of the print paper.    
   
   
       6 . The image forming apparatus of  claim 5 , wherein the controller comprises a unit that rotates the registration rollers after a first time-lag from the time of sensing the front end of the print paper so that the front end of the print paper is curled, registered and passed through the nip of the registration rollers, and that pauses the registration rollers after a second time-lag from the time of sensing the front end of the registered print paper passing through the nip so that the transportation of the front end of the print paper is discontinued and on standby for printing.  
   
   
       7 . The image forming apparatus of  claim 5 , wherein the image forming apparatus comprises no additional rollers for feeding print paper between the pick-up roller and the registration rollers.  
   
   
       8 . The image forming apparatus of  claim 5 , wherein the image forming apparatus further comprises a clutch that selectively connects and disconnects the registration rollers to and from the driving source for driving the registration roller according to control signals generated by the controller.  
   
   
       9 . A method of registering/feeding print paper, the method comprising: 
 picking up and transporting the print paper toward a nip of registration rollers by rotating a pick-up roller;    sensing the approach of the front end of the print paper toward the nip;    driving the registration rollers after a first time-lag from a time of sensing the front end of the print paper so that the front end of the print paper is curled, registered and passed through the nip of the registration rollers; and    pausing the registration rollers after a second time-lag from the time of sensing the front end of the print paper toward the nip so that the transportation of the front end of the print paper registered and passed through the nip is discontinued and on standby for printing.    
   
   
       10 . The method of  claim 9 , wherein, in the transporting of the print paper, the print paper is directly transported to the nip of the registration rollers by only the transportation force of the pick-up roller.  
   
   
       11 . A paper registering/feeding unit comprising; 
 a rotatable pick-up roller including an effective contact surface which contacts a sheet of print paper to pick up the print paper;    a pair of registration rollers in contact with each other to form a nip along the pathway of the print paper;    a sensor sensing the approach of the front end of the print paper picked up by the pick-up roller toward the nip of the registration rollers; and    a controller that controls rotation of the registration rollers based on a time of sensing the front end of the print paper by the sensor,    wherein the length of the arc of the effective contact surface is greater than the distance from the position where the pick-up roller initially contacts the print paper to the nip of the registration rollers along the pathway of the print paper.    
   
   
       12 . The paper registering/feeding unit of  claim 11 , wherein the controller comprises a unit that rotates the registration rollers after a first time-lag from the time of sensing the front end of the print paper so that the front end of the print paper is curled, registered and passed through the nip of the registration rollers, and that pauses the registration rollers after a second time-lag from the time of sensing the front end of the registered print paper passing through the nip so that the transportation of the front end of the print paper is discontinued and on standby for printing.  
   
   
       13 . The paper registering/feeding unit of  claim 11 , wherein the paper registering/feeding unit comprises no additional rollers for feeding print paper between the pick-up roller and the registration rollers.  
   
   
       14 . The paper registering/feeding unit of  claim 11 , wherein the image forming apparatus further comprises a clutch that selectively connects and disconnects the registration rollers to and from the driving source for driving the registration roller according to control signals generated by the controller.  
   
   
       15 . An image forming apparatus having a printing unit that prints an image on print paper and a paper registering/feeding unit that registers and feeds the print paper to the printing unit, wherein the paper registering/feeding unit comprises: 
 a rotatable pick-up roller including an effective contact surface which contacts a sheet of print paper to pick up the print paper;    a pair of registration rollers in contact with each other to form a nip along the pathway of the print paper;    a sensor sensing the approach of the front end of the print paper picked up by the pick-up roller toward the nip of the registration rollers; and    a controller that controls rotation of the registration rollers based on a time of sensing the front end of the print paper by the sensor,    wherein the length of the arc of the effective contact surface is greater than the distance from the position where the pick-up roller initially contacts the print paper to the nip of the registration rollers along the pathway of the print paper.    
   
   
       16 . The image forming apparatus of  claim 15 , wherein the controller comprises a unit that rotates the registration rollers after a first time-lag from the time of sensing the front end of the print paper so that the front end of the print paper is curled, registered and passed through the nip of the registration rollers, and that pauses the registration rollers after a second time-lag from the time of sensing the front end of the registered print paper passing through the nip so that the transportation of the front end of the print paper is discontinued and on standby for printing.  
   
   
       17 . The image forming apparatus of  claim 15 , wherein the image forming apparatus comprises no additional rollers for feeding print paper between the pick-up roller and the registration rollers.  
   
   
       18 . The image forming apparatus of  claim 15 , wherein the image forming apparatus further comprises a clutch that selectively connects and disconnects the registration rollers to and from the driving source for driving the registration roller according to control signals generated by the controller.