Patent ID: 7186445

Claim:
A method for coating a paper or board web in a dry surface treatment process, wherein motion of the paper or board web defines an upstream and a downstream direction, comprising the steps of: pre-charging particles of a dry powder within a charging unit by causing the dry powder to move between an electrode producing corona charging within the unit and an electrode at a lower or opposite potential within the charging unit to form pre-charged particles; supplying the pre-charged particles from the charging unit to a feeding nozzle which forms an electrode and blowing the pre-charged particles from the feeding nozzle toward the paper or board web, the feeding nozzle being positioned between an upstream electrode producing a corona discharge, the upstream electrode positioned outside of the charging unit and laterally spaced in the upstream direction from the feeding nozzle, and a downstream electrode producing a corona discharge, the downstream electrode positioned outside of the charging unit and laterally spaced in the downstream direction from the feeding nozzle, wherein the feeding nozzle is spaced further from the paper or board web than the upstream electrode and the downstream electrode; wherein the paper or board web is backed by a grounding electrode at a potential which is lower than or opposite to the potentials of the feeding nozzle, the upstream electrode and the downstream electrode.