Cloud suppression in an electrostatic copying apparatus

Abstract

There is provided an electrostatic copying apparatus having means for delivering a toner material consisting of relatively small particles, a portion of which exist in an air suspension, to an image retention surface for developing a latent image on the surface, a housing for forming with the surface an enclosure for the toner material delivery means, said housing and said surface forming an air gap interface therebetween, and means positioned near said air gap interface for electrostatically precipitating and collecting the toner particles existing in air suspension thereby reducing the flow of particles from the housing through the interface. The toner particles cascaded over the surface are charged to a first polarity opposite to that of the image; the unwanted particles in air suspension have charges of both the first polarity and the opposite polarity. To attract the oppositely charged particles in air suspension the precipitating member, in the form of a roller, is held at a potential of the first polarity -- i.e., opposite to the image and the same as the cascading particles. The remaining suspended particles, those of the first polarity, are repelled by the roller and are attracted by the latent image on the surface in the same manner as the cascaded particles.

Dependencies are inferred from the claim text.