Assembly for Varying Pick Normal Force in an Automatic Document Feeder

Abstract

An assembly for varying pick normal force in an imaging device includes a spring mounted above a pick mechanism having a pick arm mounted at a first end thereof on a shaft and a pick roller mounted at a second end of the pick arm. A rib projects from the first end of the pick arm towards the spring such that the spring is in contact with the rib to impart a rotational force to the pick arm. The rib on the pick arm changes an amount of deflection of the spring as the angular position of the pick arm changes such that an amount of the rotational force imparted by the spring to the pick arm changes thereby changing an amount of a normal force applied by the pick roller to a media stack.

We claim: 
     
         1 . An assembly for varying a normal force exerted by a pick mechanism on a media stack in an imaging device, comprising:
 a spring mounted above the pick mechanism with the pick mechanism having a pick arm mounted at a first end thereof on a shaft and a pick roller mounted at a second end of the pick arm, the pick roller for contacting and applying the normal force on the media stack; and   a rib projecting from the first end of the pick arm towards the spring such that the spring engages the rib to impart a rotational force to the pick arm at a point of contact between the spring and the rib, wherein the point of contact changes along the spring as the angular position of the pick arm changes such that an amount of the rotational force imparted by the spring to the pick arm changes thereby changing an amount of the normal force applied by the pick roller to the media stack.   
     
     
         2 . The assembly of  claim 1 , wherein the spring includes a cantilevered spring. 
     
     
         3 . The assembly of  claim 1 , wherein the spring includes a leaf spring. 
     
     
         4 . The assembly of  claim 1 , wherein the spring includes a first segment attached to the imaging device and a second segment extending at an angle from the first segment, the point of contact between the spring and the rib changes along the second segment of the spring as the angular position of the pick arm changes. 
     
     
         5 . The assembly of  claim 1 , wherein the spring imparts the rotational force to the pick arm that causes more normal force to be applied by the pick roller at a top page of the media stack than at a bottom page of the media stack. 
     
     
         6 . The assembly of  claim 1 , wherein the spring causes the pick roller to apply a decreasing normal force on the media stack as a height of the media stack decreases. 
     
     
         7 . An assembly for varying a normal force exerted by a pick mechanism on a media stack in an imaging device, comprising:
 a spring mounted above the pick mechanism with the pick mechanism having a pick arm mounted at a first end thereof on a shaft and a pick roller mounted at a second end of the pick arm, the pick roller for contacting and applying the normal force on the media stack; and a rib projecting from the first end of the pick arm towards the spring such that the spring engages the rib to impart a rotational force to the pick arm at a point of contact between the spring and the rib, wherein the point of contact changes along the rib as the angular position of the pick arm changes such that an amount of the rotational force imparted by the spring to the pick arm changes thereby changing an amount of the normal force applied by the pick roller to the media stack.   
     
     
         8 . The assembly of  claim 7 , wherein the spring includes a cantilevered spring. 
     
     
         9 . The assembly of  claim 7 , wherein the spring includes a leaf spring. 
     
     
         10 . The assembly of  claim 7 , wherein the spring includes a first segment attached to the imaging device and a second segment extending at an angle from the first segment, the point of contact between the spring and the rib changes along the rib and along the second segment of the spring as the angular position of the pick arm changes. 
     
     
         11 . The assembly of  claim 7 , wherein the spring imparts the rotational force to the pick arm that causes more normal force to be applied by the pick roller at a top page of the media stack than at a bottom page of the media stack. 
     
     
         12 . The assembly of  claim 7 , wherein the spring causes the pick roller to apply a decreasing normal force on the media stack as a height of the media stack decreases. 
     
     
         13 . An assembly for varying a normal force exerted by a pick mechanism on a media stack in an imaging device, comprising:
 a spring mounted above the pick mechanism with the pick mechanism having a pick arm mounted at a first end thereof on a shaft and a pick roller mounted at a second end of the pick arm, the pick roller for contacting and applying the normal force on the media stack; and   a rib projecting from the first end of the pick arm towards the spring such that the spring is in contact with the rib to impart a rotational force to the pick arm, wherein the rib on the pick arm changes an amount of deflection of the spring as the angular position of the pick arm changes such that an amount of the rotational force imparted by the spring to the pick arm changes thereby changing an amount of the normal force applied by the pick roller to the media stack.   
     
     
         14 . The assembly of  claim 13 , wherein the spring includes a cantilevered spring. 
     
     
         15 . The assembly of  claim 13 , wherein the spring includes a leaf spring. 
     
     
         16 . The assembly of  claim 13 , wherein the spring engages the rib to impart the rotational force to the pick arm at a point of contact between the spring and the rib, wherein the point of contact changes along the rib as the angular position of the pick arm changes. 
     
     
         17 . The assembly of  claim 13 , wherein the spring engages the rib to impart the rotational force to the pick arm at a point of contact between the spring and the rib, wherein the point of contact changes along the spring as the angular position of the pick arm changes. 
     
     
         18 . The assembly of  claim 17 , wherein the spring includes a first segment attached to the imaging device and a second segment extending at an angle from the first segment, the point of contact between the spring and the rib changes along the second segment of the spring as the angular position of the pick arm changes. 
     
     
         19 . The assembly of  claim 13 , wherein the spring imparts the rotational force to the pick arm that causes more normal force to be applied by the pick roller at a top page of the media stack than at a bottom page of the media stack. 
     
     
         20 . The assembly of  claim 13 , wherein the spring causes the pick roller to apply a decreasing normal force on the media stack as a height of the media stack decreases.