Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Reexamination Certificate
2000-05-15
2002-06-25
Parker, Fred J. (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
C427S471000, C427S479000, C427S482000, C427S483000, C427S485000, C427S424000, C427S358000
Reexamination Certificate
active
06410100
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for directly or indirectly applying a liquid or pasty application medium to one or both sides of a continuous surface.
Methods according to the class and apparatus according to the class are usually used as part of paper-making machines or coating plants in order to provide a continuous surface, for Instance a material web composed e.g. of paper, cardboard or a textile material, with one or more layers of application medium, e.g. dye, starch, impregnating fluid or the like, on one or both sides. So-called direct application involves the application of liquid or pasty application medium from an applicator directly onto the surface of the continuous material web which during application is supported on a revolving support surface, e.g. a continuous belt or a counter-roll. Indirect application of the medium, on the other hand, first involves the application of liquid or pasty application medium onto an opposite surface which acts as a carrier face, e.g. the surface of a counter-roll designed as an application roll from where it is transferred in a roll gap, through which the material web passes, from the application roll onto the material web.
To perform the direct or indirect application techniques described above, use is normally made of application devices which either have an application chamber or are fitted with a single nozzle or free-jet nozzle extending in the form of a narrow, long gap across substantially the entire web width.
A method and an apparatus used to apply a single trace—which is as far as possible narrow—of liquid or pasty medium, preferably glue, onto a continuous material web are known from DE 195 04 652 A1. For this purpose, the apparatus has a nozzle head with a single nozzle from which the medium is sprayed directly and without contact onto a narrow partial region of the material web.
A method, comparable with the technical solution according to DE 195 04 652 A1, and its associated apparatus are also known from DE 295 06 334 U1. The method according to DE 295 06 334 U1 also involves the application of just one strip-like trace of application medium.
SUMMARY OF THE INVENTION
The present invention is based upon the object of providing an innovative, simple and effective method of directly or indirectly applying a liquid or pasty application medium onto one or both sides of a continuous surface essentially over the entire surface area. Another object is to make available a suitable apparatus for performing this method.
According to this method of directly or indirectly applying a liquid or pasty application medium onto one or both sides of a continuous surface, the application medium is applied onto the surface in a plurality of single application regions by means of a plurality of single application nozzles spaced apart from one another side by side and/or in succession in the direction of width and/or longitudinal direction of the surface and clearly distanced from the surface; the application medium emerges from each of these nozzles, whereby adjacent single application regions respectively intersect in their respective edge regions at least to an extent, thus producing a layer of application medium across essentially the entire width of the surface to be coated.
In accordance with the invention, the continuous surface may be a material web, particularly one made of paper or cardboard, (e.g. in the case of direction application) or it may also be the surface of an application roll (e.g. in the indirect technique) or another revolving support or carrier face. The application medium is applied without contact from the respective single application nozzles onto the continuous surface, i.e. there is no direct contact between the nozzles and the surface. In the method according to the invention, the single application nozzles form a nozzle array which extends substantially in the direction of width of the continuous surface or at an angle thereto. The nozzles can be evenly or unevenly arranged in a row and can also be staggered in relation to the continuous surface's longitudinal direction. In this way, arrays with curved sections, such as a wavelike array etc., are possible in addition to a straight array. In a specific configurational pattern, the single application nozzles can also be distributed across substantially the entire width of the continuous surface to be coated, whereby apparent overlaps of individual sections of the course of the array are also possible. As compared with the known prior art, the entire application covering substantially the entire surface area is therefore made up—in the method according to the invention—of a plurality of small single application regions which are primarily obtained from the ejection geometry and ejection characteristic of the respective single application nozzles. A number of nozzle types is in principle conceivable as suitable application nozzles. The following are feasible examples: nozzles which generate a free jet, i.e. a “continuous curtain”—running through the ambient atmosphere—of the ejected application medium, spray nozzles which atomize the application medium, including sprayers with electrostatic and/or mechanical atomizers, e.g. high-rotation bell-type spray systems, and the like.
The respective edge regions of the coated surface's adjacent single application regions can be intersected either in that the application medium ejected by two adjacent single application nozzles respectively in a single operating cycle is intersected before or during application onto the surface, i.e. by overlapping the spray cones or jets of these nozzles, or in that single application regions only overlap in consecutive operating cycles, e.g. by two successive and “staggered” nozzle arrays.
The intersection or overlapping of the respective edge regions of the single application regions produced by the single application nozzles is preferably adapted to one another with such precision that an even layer thickness is obtained over substantially the entire width of the coated continuous surface. This is not, however, absolutely necessary. Particularly in the case of indirect application, it is possible for the application produced by the single application nozzles initially to be still somewhat striped and for it not to be evened out until afterward in the subsequent roll gap or by using metering and/or evening-out means downstream of the nozzles.
The method according to the invention can be performed using particularly simple and inexpensive structural design means, making it possible to produce an even and top-quality application over the entire surface area in a simple and effective manner both in a direct and in an indirect application process,. Since the entire application is, as explained above, composed of a number of small single application regions formed by the single application nozzles, not only a longitudinal profile but also a transverse profile of the application that is generated or is to be generated can—if necessary—in a way be set, manipulated or at least pre-regulated to a considerable extent in a common procedural step. Since the single application nozzles can also in principle be individually controlled, an effective control and/or regulating concept can be implemented in a particularly simple way in the method according to the invention.
The application medium is preferably applied to the surface essentially without excess; for this purpose, only as much application medium is ejected from the single application nozzles as is needed to build up the predetermined layer thickness.
As concerns specific applications, however, it has also proved advantageous to apply an excess of application medium according to another possible embodiment version of the invention, with the amount of application medium preferably corresponding to 2 to 5 times the final application to be achieved. The invention is not, however, exclusively restricted to the aforementioned quantitative data. If necessary, it is by all means possib
Bernert Richard
Dörflinger Hans-Dieter
Kohl Bernhard
Kurtz Rüdiger
Kustermann Martin
Parker Fred J.
Taylor & Aust P.C.
Voith Sulzer Papiermaschinen GmbH
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