Valmet Corporation

Valmet Paper Machinery Inc.

Jukka Koskinen

Vilho Nissinen

Petri Paloviita

Jorma Kinnunen

Seppo Luomi

Erkki Kirveskari

Rauno Verner Rantanen

Aaron Mannio

Markku Lummila

Hannu Korhonen

Jukka Linnonmaa

A method and assembly for coating a moving web of paper or paperboard by means of a coating mix jet which is directed to the surface of the web without mechanical support. The present invention is based on applying a desired amount of the coating mix to the web via a narrow-gap slit orifice, and by measuring the coat weight on the web, adjusting the position of at least one lip of the slit orifice to achieve the desired weight and cross-machine profile of the applied coat.

Method and apparatus for coating a moving web of paper or paperboard using a controlled coating jet

An apparatus for coating a paper web in which a coating mix is applied onto a paper web using an applicator unit which forms a linear mechanical force on the web against a first backing surface situated on the back side of the web. The coating mix applied onto the web is doctored using a doctor unit acting against a second backing surface. The speed of at least one of the backing surfaces is independently controlled relative to the speed of the first backing surface and the web speed in order to attain control of the tensile stress of the web.

Apparatus for coating a paper web

Method and apparatus for coating a moving paper or cardboard web

An apparatus and method for preventing plugging of a narrow, slot-orifice-type jet nozzle 6 used in a paper and board coater in which the jet nozzle extends over the entire cross-machine width of the web being coated. The coater has an application chamber 11, a coating mix infeed channel 5 connected thereto and a clot orifice 6 as well as at least one inlet port 13 for feeding the coating mix into the application chamber 11. An easily cleanable strainer element 12 is placed close to the applicator apparatus to separate aggregates of the coating mix that otherwise could plug the slot orifice 6.

Coater nozzle having means for preventing the plugging thereof, and

Method of calendering a paper web or equivalent

A method and apparatus for applying a coat mix to a high-speed running board or paper web by accurately premetering and pre-smoothing the applied coat with an applicator apparatus and then minimally doctoring the applied coat with an air knife. The applicator apparatus has a narrow slot-orifice extending in a cross-machine direction for facilitating high-speed laminar flow of coating mix into a gap region defined by confronting surfaces of the applicator apparatus and the web. The applicator apparatus has a member for directing the ejected coating mix in the gap region in a direction reverse to a travel direction of the web so that only a predetermined portion of the ejected coating mix is allowed to form an applied coat on the web. This accurate premetering of the coating mix by the applicator apparatus permits an operator to readily optimize the subsequent process of doctoring the applied coating with an air knife.

Blade metering unit and method for blade-coating a material web

An assembly, for preventing striping in an applicator used for coating a paper or paperboard web, comprising a doctor blade suitable for metering and smoothing a coat to be applied, a cross-machine elongated application chamber adapted immediately in front of the doctor blade, one of the sides of the chamber being formed by the web being coated. A flexible leading blade forming a front sealing edge of the chamber has a perforated stem with openings to allow coating mix from the application chamber to travel in front of the leading blade. A homogenizing chamber is formed in front of the openings in the leading blade using a dam lip or similar flow barrier. The flow exiting the openings of the leading blade is homogenized in the homogenizing chamber as the flow impinges against the flow barrier.

Assembly for preventing striping in a short dwell time applicator

A method and apparatus for applying a coat mix to a high-speed running board or paper web by accurately premetering and pre-smoothing the applied coal with an applicator apparatus and then minimally doctoring the applied coat with an air knife. The applicator apparatus has a narrow slot-orifice extending in a cross-machine direction for facilitating high-speed laminar flow of coating mix into a gap region defined by confronting surfaces of the applicator apparatus and the web. The applicator apparatus has a member for directing the ejected coating mix in tho gap region in a direction reverse to a travel direction of the web so that only a predetermined portion of the ejected coating mix is allowed to form an applied coat on the web. This accurate premetering of the coating mix by the applicator apparatus permits an operator to readily optimize the subsequent process of doctoring the applied coating with an air knife.

A method and apparatus for coating a moving paper or cardboard web, in which the moving web is brought to a first backing roll and coating mix is metered onto the web by means of a pre-doctoring blade in the form of a high-velocity laminar flow in front of the pre-doctoring blade. The applied coating mix is smoothed evenly onto the web with the pre-doctoring blade and the coated web is brought to a second backing roll, where the applied coating mix is smoothed using a doctor blade working on the web supported by the second backing roll. The tension of the web is measured upstream from the first backing roll and the rotational speed of the second backing roll is set so that the tension of the web is set at a desired value. The rotational speed of the first backing roll is set so that a speed difference between the first and the second backing roll compensates for elongation of the web caused by wetting between the first and second backing rolls.

Method and apparatus for coating a moving paper web

In air-knife coating, the coating mix is applied to the paper or board web by a coating applicator, and the coating mix is doctored to the desired coating thickness by blowing a sharp air jet discharged from an air knife. The air knife doctoring separates coating mix that has not been absorbed by the web forming a filter-cake layer. The air knife is directed at the upper boundary between the filter-cake layer and the un-absorbed coating mix. The coat weight is controlled by adjusting the distance between the point of initial application of the coating mix to the web and the point of doctoring where coating mix is removed.

Method and apparatus for controlling the thickness of a coating applied

A jet coating apparatus and method for applying coating mix onto a moving web in a noncontacting manner in ambient pressure. The apparatus includes an upper lip placed close to the web, a lower lip situated in the vicinity of the upper lip and arranged essentially on the trailing side relative to the moving direction of the web. The slot orifice bounding surface of the upper lip and the slot orifice bounding surface of the lower lip form a slot orifice suited for feeding the coating mix onto the web. In the slot orifice, at least the directional vector along the slot orifice surface of the lower lip has a vector component opposite to the tangential velocity vector of the web.

Jet coating apparatus

This invention relates to a method and assembly for loading the doctor blade of a doctoring unit used, e.g., in coating a paper web, characterized in that the blade can be loaded close to the edge of the blade without compromising the accuracy of blade profile control. The blade is loaded by backing member (8) having a Z-shaped cross section in which one side of the section forms a base (13), while the middle part forms a waist (18) which turns toward the base (13), and the other side of the shape forms a tip (12) pointing to an opposite direction relative to the base (13) and has at its end a tapering edge suited for pressing against the doctor blade (7). This approach is capable of eliminating the sliding movement of the backing member (8) relative to the blade which tends to impair the accuracy of blade pressure control.

Assembly for loading a doctor blade

A jet coating method for applying coating mix onto a moving web in a noncontacting manner in ambient pressure which includes the step of directing a jet of the coating mix counter to an approach direction of the web at a velocity sufficiently high to attain a splitting of the jet into a return flow and a coating mix application flow.

Jet coating method

A method and device for keeping a coating rod and a rod cradle in a bar coater clean and for preventing leakage of the lubrication and/or cooling water used in the bar coater is disclosed. The invention is intended for a bar coater in which the coating rod is, supported revolvingly in a rod cradle substantially over its entire length. The rod cradle is attached to the frame constructions of the coater. The rod cradle is also provided with at least one groove substantially parallel to the coating rod and open towards said coating rod, in which grooves(s) water is circulated to lubricate, cleanse and/or cool the coating rod and the rod cradle. The coating rod is loaded towards the base to be coated by loading the rod cradle. The rod cradle and the sealing lips of the rod cradle are loaded so that the loading seals the glide faces between the coating rod and the rod cradle substantially over the entire length of the rod cradle and prevents leakage, or at least substantially reduces leakage, from the water grooves.

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Helsinki, Finland

Jukka Koskinen