Electric heating – Metal heating – By arc
Reexamination Certificate
2000-06-10
2001-11-20
Paschall, Mark (Department: 3742)
Electric heating
Metal heating
By arc
C219S121480, C219S121400, C427S569000, C427S207100, C264S483000
Reexamination Certificate
active
06320157
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
Not applicable.
Statement Regarding Federally Sponsored Research or Development
Not applicable.
BACKGROUND OF THE INVENTION
The invention relates to a corona station for pretreating on both sides a material web.
TECHNICAL FIELD
EP 0 426 880 has disclosed a corona station for treating plastic web materials which have a pattern created in surface portions thereof which is achieved as a direct result of a charge treatment. Therefore the material web is brought into contact with a portion of a circumferential surface of a counter-electrode. The circumferential surface of the counter-electrode has been engraved with a pattern for producing a selectively patterned, surface treated web.
Furthermore, a non-generic device for removing dust particles on material webs has been disclosed by EP 0 524 415 A2, an has two rod-shaped emission electrodes which run parallel to one another and are connected to an opposite potential, and between which the material web runs through. In the process, the dirt particles are charged, with the result that the latter can easily be detached from the material web and sucked off. Although this device has emission electrodes, it cannot be used for pretreating material webs. Even if this device were to be used the following disadvantages would occur. In this device, there is a need upstream and downstream of the emission electrodes for guide rolls which are rotatably mounted and must be coordinated with one another in terms of their circumferential speed in such a way that a certain web tension is maintained as the material web is being guided through the device. On the one hand, this is required in order not to damage the material web by making contact with the emission electrodes, and on the other hand in order to ensure a uniform air gap on the topside and bottom side relative to the emission electrodes so that adequate surface treatment is rendered possible. Moreover, this device also has a design which is complicated in terms of apparatus. The disadvantages arising therefrom with regard to the space requirement, mounting, maintenance etc., are obvious. Moreover, the failure rate by comparison with a single corona station is twice as high.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to create a corona station which renders it possible to treat completely the surface of the material web on both sides in a simple and cost-effective way, without damaging the surface of the material web.
This object is achieved by an air nozzle provided at least upstream of the counter-electrode, seen in the conveying direction of the material web so that the material web does not bear with its whole surface against the counter-electrode.
Owing to the fact that the air nozzle is provided at least upstream to the counter-electrode it is possible by at least partially blowing in air between the material web and the counter-electrode that the material web does not bear with its whole surface against the counter-electrode. It is therefore possible to form a more or less completely constructed air gap between the counter-electrode and the material web to be treated. Consequently, both the surface of the material web pointed towards electrodes and the surface of the material web pointed towards the counter-electrode are completely surface-treated, since an air gap or a quasi air gap is formed on both surfaces. Due to blowing in air between the material web and the circumferential surface of the counter-electrode a plurality of air gaps in the depressions act like one quasi air gap. The corona treatment, rendered possible by the depressions, of the surface is emitted onto the linear or punctiform contacts of the material web on the counter-electrode, so that after leaving the counter-electrode the surface, pointing towards the counter-electrode, of the material web is essentially wholly surface -treated by a spill-over effect. Therefore, by contrast with prior attempts not to carry out any treatment on the counter-electrode, this development has chosen an avenue in the opposite direction, in accordance with which it is now possible to treat completely a material web on both sides with the aid of a corona station. It is ensured thereby that the material web does not bear its whole surface against the counter-electrode, but touches the surface covering the counter-electrode only very slightly in a linear or punctiform fashion. The construction of a grid is a feature of the invention in which the surface of the depressions is constructed into a multiple of the elevations, with the result that, on the one hand, an adequate bearing surface is created for the surface bearing against the counter-electrode and, on the other hand, the grid does not give the surface a structure.
According to a refinement of the invention, a further electrode is provided immediately after the material web lifts off the counter-electrode. The spill-over effect will be additionally strengthened.
According to a further refinement of the invention, it is provided that the grid extends perpendicular to the transport direction of the material web. The result is to enable the material web on the counter-electrode to be uniformly unwound and/or deflected without it being possible for the material web to be warped or deviate from the true course with respect to the conveying direction. Moreover, it is possible to counteract the formation of folds during deflection.
According to a further refinement of the invention, it is provided that the depression are arranged in a plurality of different grid patterns, or are distributed over the circumferential surface into partially identical or different grid patterns. As a result, it is possible to treat only specific surface sections, for example. Consequently, a specific pattern can be rendered possible on the basis of the printing which follows, for example, since without corona treatment the corresponding sections cannot accept coating materials.
The depression are introduced without cutting into the circumferential surface by means of a knurling device. Furthermore, it is advantageously possible to provide for it to be possible by laser machining or spark erosion, or by other alternative machining operations such as, for example, by chemical removal or the application of a coating, to achieve a grid-shaped or structured arrangement of depressions, or else also an irregular arrangement of depressions or a surface roughness which permits the formation of an at least partial air gap between the counter-electrode and that surface of the material web which is to be treated.
According to a further refinement of the invention, it is provided that a suction device is provided on the housing of the corona station or separately therefrom for the corona-treated surface on the counter-electrode. As a result, the ozone gas can be sucked off and disposed of or preprocessed in accordance with the safety rules.
The invention renders it possible for a device, known to date from the prior art, for one-sided web treatment now to be used and also retrofitted for two-sided material web treatment.
REFERENCES:
patent: 4024038 (1977-05-01), Luc
patent: 4999733 (1991-03-01), Kakuda
patent: 5271970 (1993-12-01), Griggin et al.
patent: 2458499 (1974-12-01), None
patent: 9538176 (1995-10-01), None
patent: 0426880 (1991-05-01), None
patent: 0510891 (1992-10-01), None
Bloss Fritz
Dippmann Klaus
LandOfFree
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