Abstract: A cascade-type developing unit for an electrostatic copying apparatus is disclosed. A mixture of toner and carrier particles circulates in the unit and its particles become electrostatically charged due to electrification. An arrangement is provided for limiting the charge of the particles to user-selectable values.

Abstract: An optical copier has a transparent support on which an imaging area is bounded by a frame having at least one abutment edge for an original to be copied which is placed on the support. To guard against a possibly remaining gap between original and abutment edge being reproduced in the copy as a dark area, the underside of the support facing away from the original is provided with a transparent or semi-transparent strip extending along the abutment edge and projecting beyond the same into the imaging area by about 1-5 mm. A surface of the strip facing towards an optical imaging system is light-scattering.

Abstract: An electrostatic copier has a travelling endless carrier on the photoconductive surface of which an electrostatic image pattern can be formed. Toner particles are electrostatically attracted to this pattern so as to form a visible image on the surface and are thereupon transferred to an image carrier. The photosensitive surface is then cleaned of residual toner particles in preparation for the next image formation. For the cleaning operation a mechanical wiper is in contact with the photosensitive surface and wipes the residual toner particles off the same; most of these particles adhere to the wiper and are then dislodged from their positions on the same and thereupon accelerated through space toward a container by the action of an electric field which is established intermediate the wiper and the container.