Metering coatings

Details Metering coatings Metering coatings

1996-08-20

2001-11-13

Pianalto, Bernard (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Pretreatment of coating supply or source outside of primary...

C427S428010, C427S600000, C427S601000

Reexamination Certificate

active

06316060

ABSTRACT:

FIELD OF INVENTION
The present invention relates to metering rod type coaters and in particular, to a coater having improved control of the coat weight of the coating formulation being applied.
BACKGROUND OF THE INVENTION
The use of metering rod type applicators for applying coating to a surface such as the surface of a roll of a size press coater for application to a web passing through the nip of the size press coater are well known and have been in commercial use for some time. Examples of such equipment are shown in Canadian published patent applications 2,078,320 published Feb. 17, 1993 to Rantanen, 2,078,735 published Mar. 20, 1993 to Beisswanger, 2,082,121 published May 7, 1993 to Rantanen et al. or 2,040,845 published Oct. 20, 1991 to Rantanen.
In these devices, generally, the pressure applied in the nip formed between the metering rod and the backing surface (generally the surface of an application roll) is used to meter the amount of coating that passes through the nip and is available for application to the web in the size press coater. Generally, the amount of coating passing through the nip is also significantly affected by the diameter of the metering rod and hardness of the backing surface. The rheology of the coating also influences the passage of the coating through the nip. Generally, as the solids content of the coating increases, the film thickness on the supporting surface leading to the size press application nip must be reduced to apply the same coating solids to the web.
When operating at the pressure limit for the nip, the coat weight passing through the nip and available for application to the web may be too large and must be accommodated for by reducing coating solids, however, this affects the application and take up of the coating by the web as well as the quality of the coated sheet.
Redesign of the equipment to permit increase in the pressure applicable in the metering nip formed by the rod and the backing surface may further extend the range of control of coat weight. However, this, in many cases, is simply not practical.
It has been found, at least for some coating formulations, increasing nip pressure above a threshold in a given nip configuration does not significantly influences the amount of coating passing through the nip.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to improve the metering ability of a metering rod type applicator to control the amount of coating metered onto the transfer surface.
Broadly, the present invention relates to a metering rod coating applicator and method for applying a coating to a transfer surface comprising a coating head, passage means for delivering coating from said coating head toward said surface, a metering rod, means for pressing said metering rod toward said surface to form a metering nip between said rod and said surface to meter the amount of coating passing through said nip, means to vibrate said rod, said means to vibrate said metering rod to reduce the amount of coating passing through said nip at a given pressure applied in said nip.
Preferably, said surface is a peripheral surface of a transfer roll of a size press coater.
Preferably, said means to vibrate applies vibrating forces substantially axially of said rod.
Preferably, said means to vibrate said rod by applying vibrations having a frequency in the range of 10 to 1000 Hz, more preferably 20 to 200 Hz and an amplitude in the range of 1 to 10 mils RMS, preferably 2 to 5 mils RMS to said rod.
Preferably, said amplitude will be in the range of 2.8 to 28 mils peak to peak.


REFERENCES:
patent: 4088074 (1978-05-01), Dahlgren et al.
patent: 2031705 (1990-12-01), None
patent: 2040845 (1991-10-01), None
patent: 2078320 (1993-02-01), None
patent: 2078735 (1993-03-01), None
patent: 2082121 (1993-05-01), None

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