Electrostatic printing apparatus

Abstract

An electrostatic printing apparatus of the ion-flow type for printing an image on record paper in response to an information signal includes a corona generator for generating ions; a back electrode over which the paper travels for producing a bias potential to cause the generated ions to flow from the corona generator toward the back electrode onto the recording paper; a control electrode interposed between the corona generator and the back electrode for controlling the flow of ions therebetween and including a plurality of apertures through which the ions are adapted to flow; and a control signal generator for supplying a control signal to the control electrode to cause the latter to control the amount of ion flow through each aperture, in response to the level of the information signal, to a first amount corresponding to an area on the paper which is black, a second amount corresponding to an area on the paper which is white, or at least one other amount corresponding to at least one area on the paper which is gray, with different shadings available. In one embodiment, the control signal generator supplies the control signal to the control electrode to cause the latter to control the area of ion flow through each aperture and, in another embodiment, the control signal generator supplies the control signal to the control electrode to cause the latter to control the time within which ions flow through each aperture.