Sheet feed assembly defining curved and straight feed path

Abstract

A sheet feed assembly for feeding sheets of material having a known bending stiffness through a device with low friction. The sheet feeding assembly has feed path structures for defining a feed path, the feed path having a first point with a first radius of curvature, a second point with a second radius of curvature and a transition section extending between the first point and the second point. The transition section defines conforms to a shape adopted by one of the sheets of material extending from the first point where it has a curvature of the first radius, to the second point where it has a curvature of the second radius.

1 . A sheet feed assembly for feeding sheets of material having a known bending stiffness, the sheet feeding assembly comprising:
 feed path structures for defining a feed path, the feed path having a curved section connected to a straight section such that the straight section is downstream of the curved section with respect to the sheet feed direction; wherein,   the curved section and the straight section meet at a transition point where the straight section is tangential to the curved section and configured such that a sheet partially in the curved section and partially in the straight section has zero bending moment at the transition point and zero bending moment in any part on the straight portion.   
   
   
       2 . A sheet feed assembly according to  claim 1  wherein the feed path structures include a roller pair positioned such that its nip is at the transition point. 
   
   
       3 . A sheet feed assembly according to  claim 1  wherein the feed path structures include a roller partially defining the curved section of the feed path. 
   
   
       4 . A sheet feed assembly according to  claim 1  wherein the curved section has an upstream end where the feed direction is parallel to and opposite the feed direction at the transition point. 
   
   
       5 . A sheet feed assembly according to  claim 4  wherein the feed structures include a chute extending between the upstream end and the transition point, the chute having an inner curved surface nesting within an outer curved surface to define a gap between the inner and outer curved surfaces through which the sheets are fed. 
   
   
       6 . A sheet feed assembly according to  claim 5  wherein the inner and the outer curved surfaces are identical and displaced from each other to form the gap. 
   
   
       7 . A sheet feed assembly according to  claim 6  wherein the inner and outer curves are identical to a bending curve adopted by at least part of a sheet that is bent over and held by co-planar and directly opposing forces such that tangents at both ends of the bending curve are parallel to each other and spaced apart by the spacing between the upstream end and the transition point. 
   
   
       8 . A sheet feed assembly according to  claim 7  wherein the feed path extends through an inkjet printer. 
   
   
       9 . A sheet feed assembly according to  claim 8  wherein the inkjet printer has a printhead positioned adjacent the feed path downstream of the transition point. 
   
   
       10 . A sheet feed assembly according to  claim 9  wherein the upstream end of the chute receives sheets sequentially fed from a stack of the sheets by a picker arm. 
   
   
       11 . A sheet feed assembly for feeding sheets of material having a known bending stiffness, the sheet feeding assembly comprising:
 feed path structures for defining a feed path, the feed path having a first point with a first radius of curvature, a second point with a second radius of curvature and a transition section extending between the first point and the second point; wherein,   the transition section defines conforms to a shape adopted by one of the sheets of material extending from the first point where it has a curvature of the first radius, to the second point where it has a curvature of the second radius.   
   
   
       12 . A sheet feed assembly according to  claim 11  wherein the feed path in the transition section is determined analytically using the first point and the first radius of curvature as a first boundary condition and the second point and the second radius of curvature as a second boundary condition. 
   
   
       13 . A sheet feed assembly according to  claim 11  further comprising a first sheet feed drive roller pair and a second drive roller pair for feeding the sheet along the feed path wherein the first drive roller pair and the second drive roller pair are configured for synchronous operation. 
   
   
       14 . A sheet feed assembly according to  claim 11  wherein the feed path at the first point is normal to the feed path at the second point. 
   
   
       15 . A sheet feed assembly according to  claim 14  wherein the feed structures include a chute extending between the first point and the second point, the chute having an inner curved surface nesting within an outer curved surface to define a gap between the inner and outer curved surfaces through which the sheets are fed. 
   
   
       16 . A sheet feed assembly according to  claim 15  wherein the inner and the outer curved surfaces are identical and displaced from each other to form the gap. 
   
   
       17 . A sheet feed assembly according to  claim 16  wherein the feed path extends through an inkjet printer. 
   
   
       18 . A sheet feed assembly according to  claim 17  wherein the inkjet printer has a printhead positioned adjacent the feed path downstream of the second point.