Patent ID: 7974559

Claim:
A marking apparatus comprising: a traveling wave grid toner transport circuit structure having in series a feed portion, a marking portion, and a recirculation portion, the traveling wave grid toner transport structure including: a generally continuous transport surface; a plurality of spaced apart electrodes included on the marking portion; and a resistivity layer included on the marking portion; the transport circuit structure being configured to support a powdered toner cloud that adheres to the transport surface by van der Waals adhesion and transport the powdered toner cloud along the transport surface generally along a transport direction; a receiver having a receiver surface adjacent and separated by a gap from the transport surface of the marking portion of the transport circuit structure; a circuit for generating a projection electric field in the gap between the receiver surface and the transport surface; a plurality of electric field concentrating elements located in the marking portion of the transport circuit structure, the electric field concentrating elements adapted to be selectively driven to release patches of toner from a portion of the toner cloud such that the selectively released toner patches overcome the adhesion and are projected across the gap by the projecting electric field; the traveling wave grid toner transport structure being configured to prevent toner from contacting the receiver surface except for the toner patches released by the electric field elements; and the projecting electric field being insufficient to cause transfer of toner to the receiver surface except when released by the electric field concentrating elements.