Document transport for raster scanners

Claim 1

In a raster input scanner having at least one array for scanning documents line by line, the combination of; (a) means forming a surface for supporting a document to be scanned, said surface forming means having a slit-like scanning aperture therein through which said array scans said document, the longitudinal axis of said aperture being substantially parallel to the direction of scan by said array; (b) transport means for moving a document to be scanned along said surface forming means and across said scanning aperture in a direction substantially perpendicular to the direction of scan by said array; (c) means forming a transparent viewing window in said scanning aperture; (d) said transport means including a document feed roll, the periphery of said feed roll cooperating with said viewing window to form a nip through which a document to be scanned passes; (e) bias means for releasably biasing said viewing window and said document feed roll periphery into contact; and (f) drive means for rotating said document feed roll to transport the document to be scanned along said surface forming means and across said viewing window for scanning by said array, tangential contact of said document feed roll with said viewing window imparting constant velocity to said document while said bias means permits said nip to expand to accommodate passage of said document therethrough while minimizing velocity variations of said document as said document enters and leaves said nip.