Abstract: The invention relates to a process for producing a spherical grain shape in fine grain toners. The toners are of the type used in electrophotography for developing latent charge images. The treatment of the toner takes place in a material bed which is fluidized by gas streams which are directed against one another. In this manner the grains are subjected to a multitude of reciprocal collisions and friction stress. The intensity of the collisions and frictional stress are adjusted through selection of the operating pressure, velocity, direction and temperature of the gas streams. Thus the grains undergo permanent deformation. A classifier to separate out the super-fine portion resulting from abrasion.

Abstract: A particle classifier comprising a casing, at least two separating wheels, a guide baffle, and a discharge conduit. The casing has a classification chamber and one or more openings that are provided to conduct air and particulate material into the classification chamber and to discharge course particles therefrom. The separating wheels are mounted in the classification chamber, and each wheel includes a multitude of blades forming openings for conducting fine particles into the interiors of the separating wheels. The guide baffle conducts air and particulate material entrained therewith upward to the separating wheels. The discharge conduit conducts from the separation chamber fine particles passing between the blade of the separating wheels.