Patent ID: 7146125

Claim:
An electrophotographic machine for printing toner-based images comprising: a charging station for applying an electrostatic charge to a photoconductor; a discharge station for selectively discharging the photoconductor to create a charged, latent electrostatic image; a toner station for applying toner particles to the latent electrostatic image to develop a toner image of said electrostatic image; and a transfer station for transferring the toner image to a receiver sheet traveling at a speed of at least 15 inches per second, said transfer station comprising a constant current source, a transfer roller coupled to the constant current source, said transfer roller comprising a metal core and sleeve with a selected resistivity, said selected resistivity being high enough to generate a sufficient transfer voltage but low enough to prevent a breakdown of the dielectric material comprising the transfer roller, receiver sheet, toner, air and the photoreceptor.