Magnetic brush/stationary electrode development system

Abstract

An electrophotographic copying apparatus is disclosed, including a first rotating cylindrical electrode positioned above the lowest point of rotation of the photoconductive surface and closely adjacent that surface. This first electrode is suitably biased to form a brush of toner which, as the brush rotates with the direction of the travel of the image, develops the image. A second rotating cylindrical electrode is positioned at the low point of travel of the latent image surface; the brush formed on the surface of this electrode as the electrode rotates against the direction of travel of the image, develops the trailing edges of the image. A biased electrode plate extends from the upper electrode to a point near to the lowest electrode. As toner material is supplied to the first rotating electrode, it is carried over the surface of this electrode and flows down through the development path defined by the electrode plate and the rotating drum surface to develop the latent image. A gap is formed between the lower point of the plate and the rotating electrode so that unused carrier may fall away from the surface of the rotating drum and into the sump which is defined in the bottom of the housing. A third roller is located further along the development path and above the second roller and rotates against the direction of travel of the photoconductive surface. This roller is used primarily for cleaning. A second plate electrode extends from this third roller substantially down to a point closely adjacent the second rotating electrode. Toner material flows over the surface of the third electrode and down through this gap defined by the second plate electrode and the moving latent image surface. The development in this region supplements the development action of the second roller.