Abstract: An improved sheet feeder mechanism includes a D-shaped roller that is mounted on a shaft and is positioned transversely to a direction of sheet feed. A D-roller gear is mounted on the shaft and has both a non-recessed geared region and a recessed non-geared region that extends partially about a circumference of the D-roller gear. A shaft extension extends from and is attached to the shaft, and a spring engages the shaft extension to cause the shaft and the D-roller gear to rotate to a position that enables a gear drive to engage the non-recessed geared region of the D-roller gear. A spiral cam assembly is mounted for rotation with the gear drive and includes a spiral cam that is positioned between and resiliently bears upon inner and outer annuli of the cam assembly.