Coating apparatus – Solid applicator contacting work – With work-handling or work-supporting
Reexamination Certificate
1999-04-09
2001-04-10
Edwards, Laura (Department: 1734)
Coating apparatus
Solid applicator contacting work
With work-handling or work-supporting
C118S255000, C118S257000, C118S259000, C118S304000, C118S410000, C118S413000
Reexamination Certificate
active
06214112
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for direct or indirect single or double sided application of a liquid or viscous coating medium onto a moving surface.
2. Description of the Related Art
An applicator unit of this type, referred to as a roll applicator, is known from German patent document no. 3,605,409. Such an applicator unit is typically categorized as a Long Dwell Time Applicator.
The scoop roll of an applicator unit typically applies a relatively large amount of coating medium to the moving surface, which is generally an applicator roll or a material web. The volume of coating medium applied onto the moving surface is proportional to the diameter and circumferential speed of the scoop roll. However, there are limits imposed due to splashing of the coating medium as the circumferential speed of the scoop roll increases.
If, due to space constraints or design considerations, a relatively small scoop roll is utilized, the scooping effect is often not sufficient to produce uniform coating on the material web.
Therefore, what is needed in the art is an apparatus which utilizes a relatively small scoop roll and yet produces a uniform coating on the moving surface, or material web.
SUMMARY OF THE INVENTION
The present invention spreads a coating medium evenly and uniformly across the machine width by use of a nozzle applicator device which is installed prior to the scoop roll of the applicator unit relative to the direction of travel of the material web or, equivalently, the rotational direction of the applicator roll. The scoop roll and the nozzle applicator device are assigned or positioned adjacent to the same applicator roll in the case of indirect application, or adjacent to the same backing roll in the case of direct application. In the case of direct application the backing roll is partially wrapped by the material web. This configuration results in a compact arrangement which requires little space.
The nozzle applicator device may be configured as an impulse coater which is equipped with a machine-wide metering nip, as described in WO 95/12031. The nozzle applicator device, however, may also be an applicator whereby the coating medium is directly applied onto the moving surface by individual nozzles which are arranged uniformly across the width of the machine. An individual nozzle applicator device of this type is described in the German patent application 197 22 159.9, which is assigned to the assignee of the present invention. In an applicator of the individual nozzle type, the nozzle arrangement is such that the jets of coating medium exiting from the nozzles overlap on the moving surface thereby ensuring complete coverage of the moving surface with the coating medium.
The present invention applies only a pre-coating to the moving surface with the nozzle applicator device. The main coating is accomplished by the scoop roll. Any excessively applied medium is subsequently removed with a doctoring device, thereby ensuring a uniform coating application both in the transverse and longitudinal direction of the material web relative to the direction of travel thereof. The uniform coating results from the thin layer of applied pre-coating and relatively low volume main coating application. The pre-coating compensates for, or supplements, the reduced scooping effect at relatively small, for example, 350 mm, scoop roll diameters.
This embodiment is particularly suitable for applications where there is already a roll applicator device of this type in the paper machine or the converting machine. In such an instance, the coating machine can easily be retrofitted with the nozzle applicator device, specifically the impulse coating device. In instances where application of coating medium by use of individual nozzles is preferred, the entire coating application is performed with this device. Sufficient coverage of the material web is accomplished by the overlapping areas of the individual nozzle jets.
Where there are already roll applicator units in the paper or converting machine, the scoop roll is not required to fulfill its actual purpose of scooping and applying the coating medium. In the embodiment having individual applicator nozzles, the scoop roll is utilized for leveling and/or averaging out of the applied coating medium, thereby providing an advantageous method of smoothing the overlapping end sections of the individual jets in the nip between the scoop roll and the moving surface by evenly distributing any applied excess of coating medium.
In the embodiment in which the scoop roll is utilized for scooping the main volume of the coating medium, the roll runs in the opposite direction of, and at a lower circumferential speed than, the moving surface or material web.
In the embodiment in which the scoop roll is used for spreading out or evenly distributing the layer of coating medium which was applied with the nozzle applicator device, rather than for scooping, then the scoop roll may run in the same direction as the moving surface or material web. When the scoop roll is used for spreading out or leveling the applied coating medium, it may or may not be driven. On new coating lines, a metering rod, particularly one having a large diameter and smooth surface, may be used for leveling the applied layer of coating medium rather than the scoop roll.
REFERENCES:
patent: 5516365 (1996-05-01), Sandberg et al.
patent: 5626676 (1997-05-01), Voswinckel
patent: 5735953 (1998-04-01), Paulsen
patent: 5789022 (1998-08-01), Kustermann et al.
patent: 5795357 (1998-08-01), Kim
patent: 2238846 (1998-11-01), None
patent: 36 05 409 C2 (1986-02-01), None
patent: 197 22 159A1 (1997-05-01), None
patent: 0 617 167 A1 (1994-09-01), None
patent: 0 812 957 A1 (1997-04-01), None
patent: 0 781 608 A2 (1997-07-01), None
patent: 0 794 287 A1 (1997-09-01), None
patent: WO 93/17182 (1993-09-01), None
patent: WO 95/12031 (1995-05-01), None
patent: 95/17264 (1995-06-01), None
patent: WO 96/19617 (1996-06-01), None
patent: WO 97/13035 (1997-04-01), None
Edward D. Cohen et al, Modern Coating and Drying Technology, p. 8, 1992.
Edwards Laura
Taylor & Aust P.C.
Voith Sulzer Papiertechnik Patent GmbH
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