Method and apparatus for forming and refining toner images in an electrostatic printing machine
 A method and apparatus for producing high quality toner images in an electrostatic printing machine. The method using the apparatus includes (a) (a) forming an initial developed toner image on a photoreceptor using a first toner image forming assembly including a charging device for uniformly charging the photoreceptor, and a development assembly, including charged toner solids having a single polarity, for image-wise applying a layer of the toner solids to the latent image to form an initial developed toner image; (b) refining the initial developed toner image using an air breakdown charging assembly, including a relatively large magnitude voltage biasing source and a nip forming roll coupled thereto, for image-wise recharging of the single polarity toner solids layer forming the initial developed toner image. The air breakdown charging assembly induces an air breakdown electrical discharge wherein free mobile ions are introduced into a vicinity of the initial developed toner image, and the latent image underlying the initial developed toner image cooperates with the large magnitude voltage biasing source to cause free mobile ions to flow to toner solids of the initial developed toner image in an image-wise manner, thereby image-wise recharging toner solids of the initial developed toner image such that image area toner solids then have a first polarity, and background toner solids then have a second and relatively opposite polarity; and (c) separating the image area toner solids from the background area toner solids, so as to refine the initial developed toner image, thereby resulting in a high resolution, high quality refined final toner image consisting of the image area toner solids having highly clean background areas. 
Xerox Corporation
G G
G03G G03G
inventional inventional
Weizhong Chu-Heng
Zhao Liu