Xerographic developer unit having multiple magnetic brush rolls rotating with the photoreceptor

A method for developing developer having semiconductive carrier particles in an electrostatographic printing machine, comprising:

• retaining a quantity of developer having semiconductive carrier particles and toner particles;
• driving a first sleeve about a first magnetic core at a first velocity to present developer to a photoreceptor surface before any other sleeve rotating about a magnetic core presents developer to the photoreceptor;
• and
• driving a second sleeve about a second magnetic core at a second velocity that is less than the first velocity, the second sleeve receiving developer from the first sleeve for development of a latent image on a photoreceptor, the first sleeve and the second sleeve rotating in a direction that is with the photoreceptor surface as the photoreceptor surface passes by the first sleeve and the second sleeve.

A printing unit for an electrostatographic printing machine comprising:

• a photoreceptor that continuously moves about a circuit;
• a raster output scanner (ROS) that generates a latent image on a portion of the photoreceptor as the photoreceptor moves past the ROS;
• a development station for developing toner on the latent image;
• a transfer station for transferring the developed toner to a substrate;
• a fusing station for fixing the transferred toner to the substrate;
• and the development station further comprising:
• a developer housing, for retaining a quantity of developer having semiconductive carrier particles and toner particles;
• a first magnetic roll having a stationary core with at least one magnet and a sleeve that rotates about the stationary core of the first magnetic roll at a first velocity;
• a second magnetic roll having a stationary core with at least one magnet and a sleeve that rotates about the stationary core of the second magnetic roll at a second velocity, the second velocity being slower than the first velocity and the first and the second magnetic rolls being arranged in the developer housing to form a development zone in which the first magnetic roll presents developer to the latent image on the photoreceptor before any other magnetic roll in the developer housing presents developer to the latent image on the photoreceptor as the photoreceptor passes in a direction through the development zone;
• a motor coupled to the first and the second magnetic rolls to drive the sleeves of the first and the second magnetic rolls in a direction that is with the direction of the photoreceptor as the photoreceptor passes through the development zone and the first and the second magnetic rolls carry semiconductive carrier particles and toner particles through the development zone formed by the first and the second magnetic rolls.