Coating apparatus – Solid member or material acting on coating after application – Rotary member
Patent
1996-06-11
1998-07-21
Bareford, Katherine A.
Coating apparatus
Solid member or material acting on coating after application
Rotary member
118126, 427285, 427286, 427356, 427359, 427361, B05C 1102
Patent
active
057829772
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for the coating of a travelling web, preferably a paper web. The invention also embraces a process for such coating.
BACKGROUND OF THE INVENTION
By blade coating there is meant a coating process, wherein a web engaging a back-up member, for example a roll, in a first step is supplied with a coating liquid in excess. In the next stage removal of the excess of coating liquid and evening of the coating layer by using a so called coating blade take place.
In the coating of a paper web in accordance with conventional techniques the coating does not take place all the way up to the side edges of the web but sections having a width of about 10 mm are left uncoated along the two web edges. The reason for this is that if coating is performed all the way out to the side edges all the side surface of the edge which is more or less uneven will be coated. In view of this uneven side surface coating liquid is entrained in a larger amount than compared to the quantity on the normal coating surface of the paper. The coating liquid applied to the side surface also partly migrates to the other side of the web, and since this side during the transport of the web through the coating machine is in contact with rolls coating liquid will be deposited on said rolls thereby creating operational problems. The manner of avoiding coating of the web all the way out to the side edges thereof thus constitutes a solution to said problem.
However, the conventional techniques described above are associated with an important disadvantage residing in the fact that the coating blade is more rapidly worn out at the edge sections where no coating liquid is applied. Therefore, the coating blade must be replaced before it has been worn out on the section thereof where coating liquid is applied. Frequent blade replacements are expensive, on the one hand by the cost of the blade itself, on the other hand by the interruption of the production caused by the exchange.
The present invention has for an object to seek elimination of the edge wear problem in all blade coating where there is used the techniques of uncoated edge sections.
Another object of the present invention is to provide techniques, whereby the outer extension line for applied coating liquid becomes substantially rectilinear.
For these and other objects which will be clear from the following description there is provided through the present invention a device for the coating of a travelling web, preferably a paper web, comprising a back-up element, a metering means cooperating therewith and intended for the application onto the web across essentially the full width thereof of a coating liquid, a coating blade positioned downstreams of the metering means, and means for feeding the web in the nip between the back-up element and the metering means and between the back-up element and the coating blade. The device according to the invention comprises at least one edge lubricating means which is positioned adjacent to one edge of the web and upstream of the metering means and which is arranged to deposit along said one edge a string of lubricating liquid at least up to a position cross-wise and inwardly of the web adjacent to the margin of the coating liquid then applied. By this lubrication of the edge of the web there is avoided a much too early wear of the coating blade in the area immediately outside of the applied coating liquid.
In a preferred embodiment of the device according to the invention the edge lubrication means is positioned in the cross-wise direction in relation to the outer extreme of the metering means in such a manner that overlap between the coating liquid and the lubricating liquid will be obtained. In this manner there is obtained by the coating blade removal of the overlapping section of the coating liquid so that a rectilinear limit line for the coating liquid will be obtained.
It is particularly preferred to arrange an edge lubricating means at each edge of the web. It is also preferred that the back-up e
REFERENCES:
patent: 4292349 (1981-09-01), Ishiwata et al.
patent: 4738877 (1988-04-01), Krautzberger
patent: 4976992 (1990-12-01), Chino et al.
patent: 5112653 (1992-05-01), Damrau et al.
Eriksson Tore
Karlsson H.ang.kan
Bareford Katherine A.
BTG Kalle Inventing AB
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