Coating apparatus – Immersion or work-confined pool type – Work-confined pool
Patent
1997-01-13
1998-08-18
Lamb, Brenda A.
Coating apparatus
Immersion or work-confined pool type
Work-confined pool
118410, B05C 302
Patent
active
057953937
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a coating edge limiter for a coating arrangement with a short dwell time.
BACKGROUND OF THE INVENTION
A short dwell coater is disclosed in U.S. Pat. No. 4,250,211. Coating edge limiters of the aforementioned type are known and used mainly as sealing elements at both roll ends in order to prevent coating color from flowing laterally out of a coating chamber.
An end seal for a coating arrangement with a short dwell time is described in German Patent publication 38 15 764 A1. An upper outer surface of the end seal facing the paper web has openings through which water is introduced between the outer surface and the paper web for the purpose of improving tightness and reducing wear on the end seal. A disadvantage of this design is that the coating color diluted by the introduced water leaves behind less coating on the edges of the paper web thereby creating a transitional area in which the coating weight declines. A trimming edge of corresponding width must then be cut off because the machine operator cannot determine visually the exact point up to which the paper web has the required coating weight. Furthermore, the water supply causes the dry web edges to become moist. This leads to waviness at the web edges, particularly in the case of lightweight paper webs. The running qualities of the web deteriorate to the point that the web tears. Using this known end seal, it is not possible to obtain a clean edge free of coating color.
SUMMARY OF THE INVENTION
The object of the present invention is to create coating edge limiters capable of attaining sharply delineated web edges completely free of coating color while avoiding contamination with encrusted color.
This object is attained with the present inventive coating edge limiter for a coating arrangement with a short dwell time, including a mating roll with a circumferential surface that carries a material web, especially a paper web. A doctor blade element extends over the entire width of the material web and is used to apply the coating. An application zone is formed between the doctor blade element and a barrier wall oriented parallel to the doctor blade element. Two coating edge limiters, each with a sealing block and a sliding element, are arranged in an edge region movable at a right angle to the web direction. A formatting plate holder is connected permanently to the sealing block and extends outwardly over the barrier wall. On the formatting plate holder a thin formatting plate is arranged in such a way as to extend from the outside over the barrier wall into the space between the barrier wall and the doctor blade element in order to completely cover the application zone in the edge region of the material web. The sealing block, on the side facing the formatting plate, has at least one depression, that extends parallel to the direction of web movement and is connected to a water supply by a channel. A narrow sealing gap, from 1 to 3 mm wide, is formed between the formatting plate and the sealing block. Water introduced into the sealing gap through the depression produces a pressure cushion and presses the formatting plate flatly against the material web. The formatting plate holder, preferably formed of spring steel, has a thickness greater than or equal to 0.4 mm and is attached to the formatting plate holder by some type of clamping means. Furthermore, the formatting plate, at a right angle to the direction of web movement, is of a width that overlaps the width of the sealing block by approximately 5% to 20%. Preferably, the sealing block is formed of a metal material. A water spraying device is located at the free end of the formatting plate holder. The water spraying device has a needle nozzle through which a fine jet of water is sprayed onto the formatting plate.
The formatting plate permanently connected to the coating edge limiter completely covers the application zone in the edge area of the web. The continuous supply of water in the sealing nip between the formatting plate and the sealing block
REFERENCES:
patent: 4250211 (1981-02-01), Damrau et al.
patent: 4434194 (1984-02-01), Gebert et al.
Lamb Brenda A.
Stora Feldmuhle AG
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