Flotation coating device for traveling webs

摘要

A coating applicator for application of coating material to the surface of a web or a flexible substrate. The coating device contains a walled application chamber where a flowing stream of the coating liquid first comes into contact with the substrate. The coating liquid enters a channel of the application chamber at the upstream side and wets the substrate as it flows in the same direction as the substrate. A doctor element is positioned at the downstream side of the channel where the excess coating in the channel follows the contour of the boundary formed by the doctor element and leaves the channel. One of the applicator walls is designed to be a floating or moving wall or belt. The floating applicator wall and geometry of the streamlined boundaries of the coating device eliminates the formation of recirculating eddies or vortices. The elimination of vortices eliminates flow instability due to centrifugal forces and removes harmful pressure fluctuations which could result in coat-weight nonuniformities.