Automatic document feeder having a center drive mechanism for loading and unloading a document without skew

摘要

An automatic document feeder mounted removably to a computer input device having a medium receiving and supporting surface includes a plurality of interconnectable modular assemblies for defining a medium path that extends from a medium input tray to a medium output tray via the medium receiving and supporting surface of the computer input device. One of the modular assemblies is a main chassis assembly includes an integrally formed main chassis shell having a substantially planar base. The input tray has a document receiving surface with a concave shape in both the vertical and horizontal planes to help facilitate proper sheet stiffening and alignment for sheet loading purposes onto the receiving and supporting surface of the computer input device. A pair of spaced apart drive rollers mounted to a spring loaded drive axle engage in seriatim individual sheets for loading and unloading them onto the supporting surface of the computer input device. A motor driven transmission system is mounted to a central portion of the drive axle to balance the drive force applied by the drive rollers so that the individual medium sheets are loaded and unloaded without any substantial sheet skewing.