Patent ID: 7175710

Claim:
In a coating system where a web to be coated travels in a web-travel direction at a web-travel speed v in an arc over a deflecting roll and underneath a slot nozzle from which a curtain of a coating material falls on the traveling web, an apparatus for stripping a boundary-air layer from the web, the apparatus comprising: a suction box juxtaposed with and open toward the roll and web at the arc and having upstream and downstream sides and ends, the box extending a full axial length of the roll; an upstream seal on the upstream side of the box juxtaposed with the web at the arc, extending the full axial length of the roll, and having upstream and downstream edges extending transverse to the web-travel direction; a downstream seal on the downstream side of the box juxtaposed with the web at the arc, extending the full axial length of the roll, and having upstream and downstream edges extending transverse to the web-travel direction, the downstream-seal down-stream edge being spaced upstream in the direction from where the curtain falls on the web, the downstream seal having an inner face directed radially at the roll and spaced substantially uniformly over its entire surface area from the roll; and end seals on the box between the upstream and downstream seals and closely axially juxtaposed with axially directed end faces of the roll; means for withdrawing air from the box between the seals and thereby suctionally stripping a boundary layer of air from the web between the seals; a corona-charge electrode in the box having a row of points with tips equispaced from the web; and a high-voltage source connected to the points.