Dual-speed drive mechanism

Abstract

A dual-speed printer drive mechanism is disclosed. The drive mechanism includes a drive motor, a drive roller for feeding a media sheet toward and through a printing area and a drive transmission for coupling the drive roller to the drive motor for turning the drive roller with different gear reduction ratios. The drive mechanism further includes a gear reduction ratio selector disposed in the drive transmission for selectively turning the drive roller at a first gear reduction ratio for feeding the media sheet to the printing area, and for selectively turning the drive roller at a second gear reduction ratio for feeding the media sheet with precision for image printing while in the printing area.

1 . A printer drive mechanism, comprising: 
 a drive motor;    a drive roller for feeding a media sheet towards and through an image printing area;    a drive transmission for coupling the drive roller to the drive motor for turning the drive roller at different speeds; and    a speed selector disposed in the drive transmission for selecting turning speeds of the drive roller at a first speed for feeding the media sheet to the printing area and at a second speed for feeding the media sheet with precision for image printing while in the printing area, wherein the speed selector comprises a clutch gear coupled to the motor wherein the clutch gear is movable between a first and a second position, wherein the first and second positions respectively correspond to the first and second speeds.    
   
   
       2 . (canceled)  
   
   
       3 . The drive mechanism of  claim 1 , wherein the first speed is faster than the second speed.  
   
   
       4 . The drive mechanism of  claim 1 , wherein the first speed is characterized by rapid media sheet feeding and the second speed is characterized by media sheet feeding-at a speed slower than the first speed.  
   
   
       5 . The drive mechanism of  claim 1 , wherein the drive transmission comprises a low-reduction and a high-reduction mechanism, and the speed selector selectively engages the drive roller with the drive motor through one of the low-reduction and high-reduction transmission mechanisms such that the drive roller feeds the media sheet at the first or second speed respectively.  
   
   
       6 . The drive mechanism of  claim 5 , wherein the high-reduction transmission mechanism is a harmonic drive for providing a precise line feed characteristic to the drive roller.  
   
   
       7 . The drive mechanism of  claim 6 , further comprising an encoder disk coupled to the drive motor for detecting rotational positions of the drive roller through rotational positions of the drive motor.  
   
   
       8 . A printer drive mechanism, comprising: 
 a drive motor;    a drive roller for feeding a media sheet towards and through an image printing area;    a low-reduction gear train coupled to the drive roller and selectively engagable with the drive motor for selectively coupling the drive roller to the drive motor and for turning the drive roller at a first speed;    a harmonic drive coupled to the drive roller and selectively engagable with the drive motor for selectively coupling the drive roller to the motor and for turning the drive roller at a second speed; and    a clutch gear movable between a first and a second position for selectively engaging one of the low-reduction gear train and the harmonic drive with the drive motor.    
   
   
       9 . The drive mechanism of  claim 8 , wherein the first speed is faster than the second speed.  
   
   
       10 . A process for feeding a media sheet in a printer, comprising the steps of: 
 coupling a low-reduction gear train to a drive roller and a drive motor to feed the media sheet at a first speed towards a print zone in the printer before the media sheet reaches the print zone;    decoupling the low-reduction gear train from the driver moto when the media sheet reaches the print zone; and    coupling a harmonic drive to the drive motor and the drive roller to feed the media sheet at a second speed through the print zone where images are printed onto the media sheet.    
   
   
       11 . The process of  claim 10 , wherein the first speed is higher than the second speed.  
   
   
       12 . The process of  claim 10 , further comprising the step of feeding the media sheet out of the print zone to an output area at a third speed.  
   
   
       13 . The process of  claim 12 , wherein the first and third speeds are equal.  
   
   
       14 . A printer having a drive mechanism for handling a media sheet, the drive mechanism comprising: 
 a drive motor;    a drive roller for feeding a media sheet towards and through an image printing area;    a low-reduction gear train coupled to the drive roller and selectively engagable with the drive motor for selectively coupling the drive roller to the drive motor and for turning the drive roller at a first speed;    a harmonic drive coupled to the drive roller and selectively engagable with the drive motor for selectively coupling the drive roller to the motor and for turning the drive roller at a second speed; and    a clutch gear movable between a first and a second position for selectively engaging one of the low-reduction gear train and the harmonic drive with the drive motor.