UNIT AND METHOD FOR CORONA TREATMENT

Abstract

Method for corona treatment using an apparatus having a corona treatment unit with an inlet side and an outlet side, one or more sets of transverse electrodes, at least one electrode in each set being connected to a high voltage source and at least one second electrode connected electrically to ground, wherein the second electrode connected to ground includes a rotatable roller. The method involving through-flow corona treatment of sheet material, the material being conveyed via a mechanical conveyor means. By such a solution sheets of material can be conveyed and corona-treated without holding the material and pulling it through the apparatus.

Claims

1. A process for corona treatment with an apparatus for corona treatment including a corona treatment unit with an inlet side and an outlet side, wherein the unit includes at least one set of transverse electrodes, at least one first electrode in each set being connected to a high voltage source and at least one second electrode connected electrically to ground, wherein the second electrode connected to ground comprising a transversely extending rotatable roller, where the process comprises performing corona treatment on sheet material, the sheet material being conveyed mechanically from the inlet side towards the outlet side of the corona treatment unit between the at least one electrode connected to high voltage and the at least one second electrode, and the sheet material being passed over the transversely extending rotatable roller of the at least one second electrode.

2. The process for corona treatment according to claim 1, wherein air is sucked in via a gap formed between the transversely extending rotatable roller of the at least one of said transverse electrodes and a supporting surface arranged at at least one side of the rotatable roller.

3. The process for corona treatment according to claim 1, where the at least one first electrode comprises at least two transverse electrodes, each of the transvers electrodes being connected to a high voltage.

4. The process for corona treatment according to claim 2, wherein at least one suction box connected to a suction device is used for the sucking in of air via said gap.

5. The process for corona treatment according to claim 4, wherein said air is sucked in through a screen.

6. The process for corona treatment according to claim 1, comprising the further steps of detecting passage of sheets with at least one sensor that is connected to control means, and interrupting said high voltage for the first electrodes when no sheets are detected.

7. The process for corona treatment according to claim 1, comprising the additional step of applying at least one of ink and lacquer to the sheets preliminary to the corona treatment.

8. The process for corona treatment according to claim 1, comprising the additional step of applying at least one of ink and lacquer to the sheets after the corona treatment.

9. The process for corona treatment according to claim 1, wherein the sheet material being treated comprises a plurality of separate sheets.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 shows a corona treatment unit.

[0031] FIG. 2 shows a cross-section of a corona treatment unit.

[0032] FIG. 3 shows details of electrodes and conveying means in a corona treatment unit.

DETAILED DESCRIPTION OF THE INVENTION

[0033] In the explanation of the figures, identical or corresponding elements will be provided with the same designations in different figures. Therefore, an explanation of all details will not necessarily be given in connection with each single figure/embodiment. In FIG. 1 is seen a corona treatment unit 1 which includes an inlet side 2 and an outlet side 3. The material to be corona treated is conveyed from the inlet side 2 via a conveyor table 4 into the central part of the corona treatment unit 1 and exits at the outlet side 3. The central part of the corona treatment unit 1 here appears with a screen 5 in which is arranged two cassettes 6, each with a handle 7 and further including a suction box 8. These parts will be described in more detail below. The corona treatment unit 1 is thus in the shown variant an assembled unit which readily can be arranged in continuation of or in front of machines and other equipment, for, e.g., printing, lacquering, drying and the like.

[0034] FIG. 2 shows a corona treatment unit 1 which, as also shown in FIG. 1, but here in longitudinal section, thus showing a cross-section of the corona treatment unit 1. In this figure, is also seen the inlet side 2 and the outlet side 3 at opposite sides of the central part of the corona treatment unit 1 with the screen 5 over the conveying table 4 and with the suction box 8 under the conveying table 4. On the mentioned conveying table 4, are shown two sheets of material 9 which are passed under six transverse first electrodes 10 via the conveying table 4 and thereby over the six transverse second electrodes 11 which are here in the form of rollers. These rollers are connected to drive means (not shown) such that the material 9 is also advanced irrespectively of the material not having any direct contact with the inlet side 2 and/or the outlet side 3 of the conveying table. Between a set of a transverse first electrode 10 and a transverse second electrode 11 a zigzag line is shown that symbolizes a corona discharge 12.

[0035] The screen 5 has internally a partitioning 13 dividing the screen 5 into two transverse chambers 14, each provided with an aperture 15 for intake of air. These apertures 15 are adjustable in size/area as regulating means that can be adjusted according to specific need. The transverse first electrodes 10 are arranged in groups with three electrodes 10, wherein such group of electrodes 10 is arranged in a cassette 6, as shown in FIG. 1. By means of a handle 7, such a cassette 6 can be pulled out of its seat in the screen 5 for servicing, maintenance or replacement. At the same time, a cassette 6 and the screen 5 may be arranged such that a cassette 6 can be arranged at different heights above the underlying electrodes/rollers 11. The partitioning 13 serves the purpose of facilitating the checking and controlling of the airflow 16 through the screen and around respective electrodes 10, and further down into the suction box 8 that encloses the lower part of the corona treatment unit 1. The six rollers 11 appear in the suction box 8, each roller 11 interacting with a respective electrode 10. Furthermore, in the suction box 8 is seen connecting means 17 for connection to an exhaust device (not shown). By sucking at the bottom of the suction box 8, a uniform flow of air 16 between electrodes 10 and rollers 11 is achieved, whereby uniform cooling of these parts is attained.

[0036] Finally, FIG. 3 shows a detail of a corona treatment unit 11 wherein four sets of first and second transverse electrodes 10, 11 and a sheet of material 9 on the way to the outlet side 3 are seen fully or partially. Between respective electrodes 10, 11 appears a corona discharge 12, and the airflow 16 between the electrodes 10, 11 is represented by arrows. Between two adjacent electrodes/rollers 11 is seen a support surface 18 adapted such that a material sheet 9 can pass over the rollers 11 without being sucked down between two rollers 11. Between a support surface 18 and a roller 11 there is a very small gap 19. This gap 19 ensures that the air is sucked out close to the roller, thereby achieving optimal removal of heat as the rollers 11, so to say, are swept by an optimized amount of air mixed with the ozone which is formed by the corona discharge 12 between the electrodes 10, 11 and thereby on the material 9. Under the support surfaces 18 there are arranged a type of separating and carrying surfaces 20 which assist in controlling the airflow 16 and also assist in propping up the mentioned support surfaces 18.