Arrangement for web coating

Apparatus for non-pressurized coating a vertically travelling web moving in an upward direction open to atmospheric pressure at a given speed comprising, in combination:

• a vertical coating chamber of the mainly closed type defined by said web, a pair of vertically adjustable side walls, a back wall spaced from said web, and a flexible blade applied against the web and forming a top closure of said coating chamber, and said coating chamber being open at all times and free of any seal to atmospheric pressure through portions above said side walls;
• a back-up member at the opposite side of said web and forming a coating nip together with said flexible blade, through which nip said web passes, said vertically adjustable side walls providing means for substantially closing said coating chamber while maintaining the interior of said coating chamber under atmospheric pressure and below said blade;
• said side walls of said coating chamber determining the level of said coating substance;
• a horizontally oriented slot at the bottom of said coating chamber forming a web entrance of said coating chamber such that the web moves in a substantially vertical direction upwardly through said horizontally oriented slot and enters said slot in a substantially vertical direction;
• a collecting tank separate from said coating chamber open against said web and mounted below said slot;
• means for supplying the coating substance to said coating chamber, said coating substance having a given viscosity;
• the coating substance supply to said coating chamber and the width of said slot being so adapted to said speed of said web and said viscosity of said coating substance, that only a small amount or substantially none of said coating substance flows directly downwardly through said slot into said collecting tank during normal operation of said apparatus;
• said width of said slot being independently adjustable while maintaining said coating chamber at a fixed position relative to said backup member;
• and
• means for recycling the coating substance from said collecting tank to said coating chamber.

Apparatus for coating a vertically upwardly travelling web moving at a given speed comprising, in combination:

• a vertical coating chamber at ambient atmospheric pressure forming a coating applicator defined by said web, a pair of side walls, a back wall spaced from said web, and a flexible blade applied against said web and forming a top closure for said coating chamber;
• a back-up member confronting said flexible blade at the opposite side of said web and forming a coating nip, together with said flexible blade, through which nip said web passes;
• level regulating means below said nip in the direction of travel of the web comprising said side walls and an overflow wall at the back of said coating applicator for regulating the level of coating substance in said coating chamber;
• a slot at the bottom of said coating chamber forming a substantially horizontal web entrance to said coating chamber such the the web moves in a substantially vertical direction upwardly through said horizontal slot and enters thereinto in a vertical direction;
• means for supplying a coating substance of a given viscosity to said coating chamber;
• the coating substance supply to said coating chamber and the width of said slot being so adapted to said speed of said web and said viscosity of said coating substance, that only a small amount or substantially none of said coating substance flows vertically downwardly through said slot during normal operation of said apparatus;
• a flow regulating member arranged crosswise to said web and at a distance therefrom between said slot and said nip and forming between itself and said web a slightly converging duct allowing an undirected substance flow and converging in the travelling direction of said web and having an average height perpendicular to said web which is smaller than the thickness of the coating substance layer that would adhere to the travelling web in the absence of said flow regulating member, said flow regulating member reducing the amount of coating substance following said web in the running direction thereof, said coating substance between said flow regulating member and said web being substantially uniform in thickness;
• and
• the height position of said flow regulating member is at the level of the coating substance in said coating chamber and extends above and below the fluid level of the coating substance, said flow regulating member at the height of said coating substance forming said slightly converging duct at the web, and said overflow wall keeps said coating substance in said coating chamber at a constant height at a rear side of said flow regulating member while allowing the undirected substand flow between said web and a front side of said flow regulating member facing said web.

Apparatus for two-sided non-pressurized coating under atmospheric pressure of a vertically upwardly travelling web of paper or the like comprising:

• a pair of vertical coating chambers open to atmospheric pressure and provided with means for substantially closing said chambers for their use as substantially closed cases while being under atmospheric pressure separated by said web and containing coating material for each side of said web, said chambers being open to atmospheric pressure and having the coating materials in each of said chambers isolated from each other;
• said chambers each having in their upper ends a flexible blade forming a coating nip therebetween through which said web passes;
• a horizontally oriented entry slot for said web below said chambers formed by slot limiting members mounted on said chambers such that said web moves in a substantially vertical direction upwardly through said horizontal slot and enters said slot in a substantially vertical direction;
• said slot limiting members comprising movable members forming a slot width regulator for adjustment of the width of said slot on each side of the web;
• overflow members determining the level of said coating substance above said slot;
• at least one collecting tank below said entry slow and open against said web;
• means for supplying a coating substance to said chambers;
• and
• the coating substance supply to said coating chamber and the width of said slot being so adapted to the speed of said web and to the viscosity of said coating substance, that only a small amount or substantially none of said coating substance flows directly downwardly through said slot during normal operation of said apparatus in a direction opposite to the direction of said upwardly moving web to thereby decrease the thickness variations of the coating substance layer adhering to said web.