Curtain applicator and method for applying an application medium

Abstract

A curtain applicator for applying a liquid or pasty application medium to at least one surface of a running material web, in particular a fibrous web. The curtain applicator has an applicator nozzle, in particular a slotted nozzle, which under the effect of gravity, and optionally with further forces, is suitable for dispensing a single-tier or multi-tier curtain onto the surface of the material web. The curtain applicator further has a wiping device which is suitable for keeping entrained air carried by the material web away from the curtain. Moreover, there is provided at least one further blocking device which is suitable for keeping air movements of the ambient air away from the curtain.

Claims

1. A curtain applicator for applying a liquid or pasty application medium to a surface of a running material web, the curtain applicator comprising: an applicator nozzle which under the effect of gravity is configured for dispensing a single-tier or multi-tier curtain onto the surface of the material web; a wiping device disposed in a vicinity of the running material web upstream of a location at which the curtain dispensed by said applicator nozzle impinges on the running material web, said wiping device being configured for keeping entrained air carried by the running material web away from the curtain; and at least one blocking device that is structurally different from said wiping device and is configured for keeping air movements of ambient air away from the curtain, said at least one blocking device being disposed at a location in front of the curtain, behind the curtain, or in front of and behind the curtain in a running direction of the material web; said at least one blocking device comprising one or a plurality of air nozzles for generating an air shield upstream of said wiping device and reaching upwardly beyond a height of said wiping device, with an upward flow direction of air in the air shield having a component that points away from the material web.

2. The curtain applicator according to claim 1, wherein said applicator nozzle is a slotted nozzle.

3. The curtain applicator according to claim 1, wherein a spacing distance between an opening of said applicator nozzle from the material web is at least 100 mm.

4. The curtain applicator according to claim 3, wherein the spacing distance between the opening of said applicator nozzle from the material web is at least 300 mm.

5. The curtain applicator according to claim 1, wherein a spacing distance of said blocking device from said applicator nozzle is less than 150 cm.

6. The curtain applicator according to claim 5, wherein the spacing distance of said blocking device from said applicator nozzle is between 80 cm and 50 cm.

7. The curtain applicator according to claim 1, wherein said at least one blocking device comprises a plate which is fastened to, or in an immediate proximity of, said applicator nozzle.

8. The curtain applicator according to claim 7, wherein said plate is a first plate and said blocking device comprises a second plate which is fastened to, or in the immediate proximity of, said applicator nozzle, wherein said first plate is attached ahead of the curtain in the running direction of the material web, and said second plate is attached behind the curtain in the running direction of the material web.

9. The curtain applicator according to claim 8, wherein a spacing distance of said first plate and/or of said second plate from the curtain is less than 100 mm.

10. The curtain applicator according to claim 1, wherein said at least one blocking device comprises at least two air nozzles, each for generating a respective air shield, wherein one of said two air nozzles is provided ahead of the curtain and one air nozzle is provided behind the curtain, and wherein a flow direction of the air of said at least two air shields has in each case a component which points toward the material web.

11. A method for applying a liquid or pasty application medium to a surface of a running material web, the method comprising: providing a curtain applicator with an applicator nozzle and dispensing, under the effect of gravity a single-tier or multi-tier curtain from the applicator nozzle onto the surface of the material web; keeping entrained air that is carried by the running material web away from the curtain by way of a wiping device in a vicinity of the running material web upstream of a location at which the curtain dispensed by the applicator nozzle impinges on the running material web; providing at least one blocking device that is structurally different from the wiping device and that is disposed ahead of and/or behind the curtain in a running direction of the material web, the at least one blocking device having one or a plurality of nozzles for generating an air shield; and keeping air flows of ambient air away from the curtain by way of the at least one blocking device by generating at least one air shield with the one or plurality of air nozzles with a flow direction of air in the air shield having a component that points away from the material web and the air shield being formed upstream of the wiping device and reaching upwardly beyond a height of the wiping device.

12. The method according to claim 11, which comprises applying the application medium with the applicator nozzle at a flow rate of less than 10 l/min*m.

13. The method according to claim 12, which comprises applying the application medium with the applicator nozzle at a flow rate between 2 l/min*m and 5 l/min*m.

14. The method according to claim 13, which comprises moving the material web at a speed between 100 m/min and 800 m/min.

15. The method according to claim 14, which comprises moving the material web at a speed between 200 m/min and 600 m/min.

16. The method according to claim 11, wherein the application medium has a solids content between 55% and 75%.

17. The method according to claim 11, wherein a Brookfield viscosity of the application medium at 100 rpm is between 100 mPas and 800 mPas.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention will be explained in more detail hereunder by means of schematic, not-to-scale figures.

(2) FIG. 1 shows a curtain applicator according to one aspect of the invention;

(3) FIGS. 2 and 2b show in each case a curtain applicator according to a further aspect of the invention; and

(4) FIG. 3 shows a curtain applicator according to a further aspect of the invention.

DESCRIPTION OF THE INVENTION

(5) The curtain applicator shown in FIG. 1 comprises an applicator nozzle 1 from which a curtain 2 under the influence of gravity is applied to material web 4, for example a paper web or a cardboard web. The material web 4 herein is deflected by means of a deflection roller 3 such that the profile of said material web 4 runs so as to be largely horizontal below the curtain 2. The impact point of the curtain here, when viewed in the running direction of the material web 4, is somewhat behind the deflection roller 3. The entrained air carried by the material web 4 here is kept away from the curtain 2 by a wiping device 5. So-called air blades are known as suitable wiping devices 5 in the industry, for example. The wiping device 5 often reaches up to just before the impact point of the curtain. The at least one further blocking device 9, 9a, 9b according to the invention in FIG. 1 is implemented in the form of two plates 9a and 9b. The two plates 9a, 9b here are fastened directly to the applicator nozzle. While it is in principle also possible for the plates to be fastened otherwise, the fastening directly to the applicator nozzle 1 offers the advantage that the spacing of the plates 9a, 9b from the curtain 2 is extremely minor. Spacings of less than 100 mm, and even less than 50 mm, can be implemented here. This leads to a very compact construction mode. Moreover, the environment around the applicator nozzle, for example the deflection roller 3 or the wiping device 5, is freely accessible for maintenance works and similar during the operation without the curtain 2 being disturbed by a movement of the ambient air arising herein,

(6) A curtain applicator according to a further aspect of the invention is illustrated in FIG. 2. The at least one further blocking device 9, 9a, 9b herein is implemented by an air shield 9. The air for generating the air shield 9 exits an air nozzle 6 or a series of nozzles 6. The flow direction of the air, and thus the alignment of the air shield 9, herein can be perpendicularly upward or else also be slightly inclined toward said direction. Said inclination will advantageously be aligned away from the applicator nozzle 1 and thus also away from the curtain 2, so as to avoid the curtain 2 being influenced by the air shield 9. The air shield 9 can advantageously extend at least across the entire width of the curtain 2 in the machine cross direction.

(7) In the case of the embodiment shown in FIG. 2, the air nozzle 6, or the series of nozzles 6, respectively, is fastened directly to the wiping device 5. This can be advantageous; however other possibilities for fastening can be possible and expedient, depending on the situation. The spacing of the air shield from the applicator nozzle can advantageously be less than 150 cm, in particular less than 100 cm, particularly preferably less than 50 cm. In the case of spacings of 80 cm and less, for example, it is possible for the operating personnel of the machine to be able to reach through the air shield 9 and to be able to perform jobs such as the retrieval of specimens on the nozzle or the curtain, respectively. As is shown in FIG. 2, a further deflection device such as, for example, a deflection roller 3a will usually also be provided behind the curtain 2. The spacing of said deflection device 3a from the curtain 3 can vary in different installations.

(8) The applicator illustrated in FIG. 2b differs from that from FIG. 2 in that said applicator in FIG. 2b comprises a second blocking device 9 which is provided behind the curtain 2, or the applicator nozzle 1, respectively. This second blocking device 9 is likewise implemented by an air shield 9. The air for generating the air shield 9 exits an air nozzle 6 or a series of air nozzles 6. The flow direction of the air, and thus the alignment of the air shield 9, herein can be perpendicularly upward, as in the first blocking device, or else be slightly inclined toward said direction. Said inclination will advantageously be aligned away from the applicator nozzle 1 and thus also away from the curtain 2 so as to avoid the curtain 2 being influenced by the air shield 9. The air shield 9 can advantageously extend at least across the entire width of the curtain 2 in the machine cross direction. The same applies to the spacing of said second blocking device 9 from the curtain as to the first blocking device. Here too, spacings between 80 cm and 50 cm are very advantageous. However, larger or smaller spacings can also be chosen by virtue of the respective situation in terms of construction such as, for example, the disposal of the rollers 3a or the routing of the material web 4.

(9) An embodiment in which the at least one further blocking device comprises at least two air nozzles for generating in each case one air shield is shown in FIG. 3. Herein, one of the air nozzles is provided ahead of the curtain, and one further air nozzle is provided behind the curtain. (When viewed in the running direction of the material web). The flow direction of the air of the two air shields has in each case a component which points toward the material web.

(10) The two air nozzles herein are advantageously attached close to the curtain. The spacing from the curtain can be less than 100 mm, preferably less than 50 mm. In the embodiment of FIG. 3, the nozzles are fastened directly to the applicator nozzle. An extremely compact construction mode of the curtain applicator is thus possible. Furthermore, the two air shields, or the air nozzles, respectively, are provided at an identical spacing from the curtain. Nozzles of identical construction can be used therefor.

(11) Moreover, the two air shields are symmetrical which means that the direction and/or the air velocity and/or the air quantity thereof are/is in particular identical. On account thereof it can be prevented that the curtain is disturbed by the air shield per se even in the case of a minor spacing of the air nozzles from the curtain. Advantageous air velocities for such an embodiment can be between 5 m/s and 50 m/s, in particular between 10 m/s and 15 m/s.

(12) While a curtain applicator which applies a single-tier curtain is illustrated in an exemplary manner in each of the figures, the invention is not limited thereto. The known applicator nozzles 1 can likewise be used for two-tier or multi-tier curtains 2 in a curtain applicator according to the invention. While the applicator nozzle 1 is in an exemplary manner illustrated in the schematic form of a so-called “slot die” in the figures, illustrated embodiments can in each case also be implemented using other types of nozzles, for example so-called “slot dies.”