Patent ID: 7636534

Claim:
An electrophotographic printing device, comprising: a guideway which transports individual pages of a print medium; a printing unit opposite the guideway which prints a side of the respective individual pages facing it; a fixing station immediately downstream from the printing unit which fixes an applied toner image; an inverter that inverts the individual pages with the fixed toner image after a first printing event and re-supplies them to the printing unit for printing on another side; the printing unit comprising at least first and second printing groups that each respectively comprise first and second exposure units, first and second charge corona devices and first and second developer stations arranged along an extent of a respective toner carrier, the individual pages being immediately supplied in succession to both printing groups, and the first and second printing groups each respectively printing two varicolored print images on the same side of the same individual page for a total of four of said print images on said same individual page; the first printing group first exposure unit generating a first latent charge image which is inked with a first color toner at said first developer station, and said first printing group second exposure unit generating a second latent charge image which is inked with a second color toner at said second developer station given circulation of the toner carrier, the second exposure unit generating said second latent charge image via superimposition on the developed first latent charge image so that a second color toner image is thus superimposed on a first color toner image on the toner carrier; the second printing group first exposure unit generating a third latent charge image which is inked with a third color toner at said first developer station, and said second printing group second exposure unit generating a fourth latent charge image which is inked with a fourth color toner at said second developer station given circulation of the toner carrier, the second exposure unit generating said fourth latent charge image via superimposition on the developed third latent charge image so that a fourth color toner image is thus superimposed on a third color toner image on the toner carrier; and said first through fourth different respective color toners being used in the respective first and second developer stations of the first printing group and the respective first and second developer stations of the second printing group to perform four color printing of the print images with each of the colors being different to achieve full color printing of the print images.