Arrangement in connection with curtain coating of a fibrous web

Abstract

An arrangement in a curtain coater for starting and stopping coating of a web, having a reservoir and a connected surface extending over the web toward the curtain to collect the coating as the coater moves over the web to start coating the web. A cover plate that swing around a cross-direction shaft connected to the cover plate. In one embodiment the shaft also moves in the machine direction. The cover plate is used to protect an leading edge of the collecting surface from being covered with coating and pivots to be cleaned with fluid which may be supply from the shaft. The cover plate is arranged so the fluid drain off the cover plate onto the collecting surface or reservoir. When clean, the cover plate is repositioned to protect an leading edge of the collecting surface during the next start or stop operation of coating the web.

Claims

1. A curtain coater, comprising: a movable nozzle beam forming a coating material curtain for coating a fibrous web; a return reservoir forming an upwardly opening reservoir, and a collecting surface which drains into the upwardly opening reservoir so as to receive coating material and cleaning fluid from above, the collecting surface extending to a tip in a direction which extends over the web toward the nozzle beam when the nozzle beam is positioned for coating the fibrous web, the collecting surface arranged to collect the coating material at least before or after the coating of the fibrous web; a source of cleaning fluid positioned above the return reservoir; a mechanism for moving the nozzle beam from a position over the return reservoir and the collecting surface to a position over the web for coating the web; at least one support member for guiding the fibrous web below the coating material curtain when the nozzle beam is in the position over the web; a cover plate movably mounted to swing around a pivoted shaft connected to the cover plate, the pivoted shaft extending in a cross-direction with respect to a direction of travel of the fibrous web; wherein the cover plate is movable between at least two positions, a front position where the cover plate extends beyond the collecting surface tip and toward the coating material curtain positioned for coating the fibrous web and a cleaning position where the cover plate is located to extend above the collecting surface of the return reservoir and positioned with respect to the source of cleaning fluid such that cleaning fluids applied to the cover plate are conveyed to the return reservoir; and wherein the cover plate is mounted for movement between the cleaning position and the front position.

2. The curtain coater of claim 1 wherein when the cover plate is located in the front position the coating material curtain is spaced a distance of 20-150 mm from the cover plate.

3. The curtain coater of claim 2 wherein when the cover plate is located in the front position the coating material curtain is spaced a distance of 50-100 mm from the cover plate.

4. The curtain coater of claim 1 wherein the cover plate is mounted for movement between the cleaning position and the front position by a swinging motion, and wherein the cover plate is connected to be driven by a speed limiting mechanism from the front position to the cleaning position; wherein the speed limiting mechanism is arranged to have a speed which takes at least 10 seconds for a 90-degree swing.

5. The curtain coater of claim 4 wherein the speed limiting mechanism is arranged to have a speed which takes more than 15 seconds for a 90-degree swing.

6. The curtain coater of claim 1 wherein the cover plate has at least three positions, the front position, a back position and the cleaning position, and that the pivoted shaft and the swingably mounted cover plate are mounted for movement in a linear direction from the front position to the back position and away from the coating material curtain and, when in the back position, the cover plate is mounted to swing about the pivoted shaft into the cleaning position.

7. The curtain coater of claim 6 wherein the cover plate is connected to be driven by a speed limiting drive mechanism controlling the linear motion of the cover plate from the front position to back position; wherein the speed limiting mechanism is arranged to have a speed of no more than 55 mm/s.

8. The curtain coater of claim 1 wherein the cover plate in the front position forms a guide plate for air flows passing in the vicinity of the coating material curtain.

9. The curtain coater of claim 1 wherein the pivoted shaft is connected to the source of cleaning fluid so that the cleaning fluid is conveyed via the pivoted shaft to clean the cover plate.

10. An arrangement for use in connection with curtain coating, having a movable nozzle beam forming a coating material curtain, the beam mounted for movement from a first position not over a moving supported fibrous web to a second position over the moving supported fibrous web, for coating a fibrous web, comprising: a return reservoir forming an upwardly opening reservoir, and a collecting surface connected thereto which drains into the upwardly opening reservoir so as to receive coating material and cleaning fluid from above, the collecting surface extending in a first direction over the web toward the coating material curtain when the nozzle beam is positioned for coating the fibrous web in the second position, the collecting surface arranged to collect the coating material as the beam is moved from the first position to the second position; a source of cleaning fluid positioned above the return reservoir; a cover plate movably mounted to swing around a pivoted shaft connected to the cover plate, the pivoted shaft extending in a cross-direction with respect to a direction in which the fibrous web travels; wherein the cover plate is mounted for movement between at least two positions, a front position where the cover plate extends beyond the collecting surface in the first direction and a cleaning position where the cover plate extends above the return reservoir such that cleaning liquid applied to the cover plate from the source of cleaning fluid will be conveyed to the return reservoir; and wherein the cover plate is mounted for movement between the cleaning position and the front position.

11. The arrangement of claim 10 wherein when the cover plate is located in the front position the coating material curtain is spaced a distance of 20-150 mm from the cover plate.

12. The arrangement of claim 10 wherein when the cover plate is located in the front position the coating material curtain is spaced a distance of 50-100 mm from the cover plate.

13. The arrangement of claim 10 wherein the swinging motion of the cover plate is connected to be driven by a speed limiting mechanism from the front position to the cleaning position; and wherein the speed limiting mechanism is arranged to have a speed which takes more than 10 seconds for a 90-degree swing.

14. The arrangement of claim 10 wherein the pivoted shaft is connected to a supply of cleaning fluid and the pivoted shaft comprises a source of cleaning fluid to clean the cover plate.

15. An arrangement for use in connection with curtain coating, having a movable nozzle beam forming a coating material curtain, the beam mounted for movement from a first position not over a moving supported fibrous web to a second position over the moving supported fibrous web, for coating a fibrous web, comprising: a return reservoir forming an upwardly opening reservoir, and a collecting surface connected thereto which drains into the upwardly opening reservoir so as to receive coating material and cleaning fluid from above, the collecting surface extending in a first direction over the web toward the coating material curtain when the nozzle beam is positioned for coating the fibrous web in the second position, the collecting surface arranged to collect the coating material as the beam is moved from the first position to the second position; a source of cleaning fluid positioned above the return reservoir; a cover plate movably mounted to swing around a pivot shaft connected to the cover plate, the pivot shaft extending in a cross-direction with respect to a direction in which the fibrous web travels; wherein the cover plate and the pivot shaft are mounted for linear movement to move in a second direction opposite the first direction; wherein the cover plate is movable in the second direction between a front position where the cover plate extends over and beyond the collecting surface in the first direction, and a back position where the cover plate does not extend beyond the collecting surface in the first direction, and in the back position the cover plate is swingable around the pivot shaft to a cleaning position in which the cover plate extends above the return reservoir such that cleaning liquids applied to the cover plate from the source of cleaning fluid will be conveyed to the return reservoir; and wherein the cover plate is mounted for movement between the cleaning position and the front position.

16. The curtain coater of claim 15 wherein the cover plate is connected to be driven by a speed limiting drive mechanism controlling the linear motion of the cover plate from the front position to back position; wherein the speed limiting mechanism is arranged to have a speed of no more than 55 mm/s.

17. The arrangement of claim 16 wherein the pivoted shaft is connected to a supply of cleaning fluid and the pivoted shaft comprises a source of cleaning fluid to clean the cover plate.

18. The arrangement of claim 15 wherein the cover plate in the front position is a guide plate of air flows passing in the vicinity of the coating material curtain.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows an example of an arrangement according to the invention at the start of coating when using a slide nozzle beam as a curtain coater.

(2) FIG. 2 schematically shows an example according to FIG. 1 in the cleaning step of a cover plate.

(3) FIG. 3 schematically shows another example of an arrangement according to the invention in the cleaning step of the cover plate when using the slide nozzle beam as a curtain coater.

(4) FIG. 4 schematically shows an example according to FIG. 1 of an arrangement according to the invention at the start of coating when using a slot nozzle beam as a curtain coater.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIGS. 1-4 and the following description employ the same designations of parts and subassemblies corresponding each other, if not otherwise stated.

(6) In FIGS. 1-4, a fibrous web W to be curtain-coated is guided via a support member/support members of the fibrous web W, which in the examples of the figures consist of two rolls 11, 12, to curtain coating by a coating material curtain C via the roll 11 and then, after the coating, to further processing via the roll 12. Close to the roll 12 after the coating, after the roll 12, is located a return reservoir 25, a collecting plate 24 connected to which substantially extends above the fibrous web W in the main travel direction of the fibrous web W such that a tip of the collecting surface 24 of the return reservoir 25 is at a substantial distance from the curtain C. The distance between the fibrous web W and the collecting surface 24/cover plate 20 is advantageously 5-25 mm. The coating material curtain C is formed by a nozzle beam 15 which is a slide nozzle beam 15 in the examples of FIGS. 1-3 and a slot nozzle beam 15 in the example of FIG. 4. The arrangement comprises a mechanism, e.g., a rail and piston, drive motor or linkage, for moving the nozzle beam 15. Coating material can be e.g. coating color, sizing agent, barrier material or other equivalent coating material which is applied on the fibrous web W.

(7) The examples shown in FIGS. 1-4 are simplified end views. It should be understood that the shown parts and subassemblies extend in the cross-direction of the fibrous web W, i.e. in the crosswise direction of the main travel direction of the fibrous web W substantially over the cross-direction of the fibrous web W at a desired distance.

(8) As shown in FIG. 1 at the start of coating, the nozzle beam 15 is transferred from its position above the return reservoir 25, which is shown by a dashed line, into the coating position, which is shown by a uniform line, in which coating position, the coating material curtain C meets the fibrous web W as a curtain directed from above substantially extending in the cross-direction of the web. Equivalently at the end of coating, the nozzle beam is transferred from the coating position to the position being above the return reservoir.

(9) As shown in FIGS. 1-4, the arrangement comprises a turnable cover plate 20 which is provided with a pivoted shaft 21 to turn the cover plate in fibrous web W around its pivoted shaft 21 extending in the crosswise direction in relation to a fibrous web W from a front position to a cleaning position. The turning motion of the cover plate 20 from the front position to the cleaning position is shown by a swinging direction arrow S in FIGS. 2 and 3. FIG. 2 shows the front position of the cover plate 20 by dashed lines and its cleaning position by uniform lines. The return swinging motion from the cleaning position to the front position is naturally opposite to that of the swinging direction arrow S. In the front position, the cover plate 20 is located such that it covers above at least the tip of the collecting surface 24 of the return reservoir 25. The cover plate 20 is in its front position at least at the start of coating and the end of coating, advantageously also during coating except for the washing of the cover plate 20 after the start, whereby the cover plate 20 is in the cleaning position. In the front position, FIGS. 1 and 4, the cover plate 20 thus covers the tip of the collecting surface 24 of the return reservoir 25. After the start of coating, the cover plate 20 is turnable around its pivoted shaft 21 into the cleaning position for cleaning/washing the cover plate 20. In the cleaning position, FIGS. 2 and 3, the cover plate 20 is located above the return reservoir 25, particularly the collecting surface 24 of the return reservoir 25, such that cleaning liquids are conveyable to the return reservoir 25. When the cover plate 20 has been washed, it is turnable back to its front position to protect the tip of the collecting surface 24 of the return reservoir 25 from dirtying caused by the end of coating. During coating, the cover plate 20 operates in this front position also as a guide plate of air flows passing in the vicinity of the curtain C.

(10) In the example of FIG. 3, the cover plate 20 is transferable by the swinging motion S but also by a linear motion L from the front position, which is designated with dashed lines on the side of the curtain C, into a back position being away from the curtain C, which is designated with dashed lines on the side of the return reservoir. From the back position, the cover plate 20 is turnable around its pivoted shaft 21 into the cleaning position, which is designated with uniform lines. In this embodiment, when the start of coating has occurred and the nozzle beam 15 has been transferred to its operating position i.e. coating position, the cover plate 20 is transferred to the back position by the linear motion away from the coating material curtain C and, from the back position, the cover plate 20 is turnable to the cleaning position and thus the cover plate 20 is washable. When the cover plate 20 has been washed, it is guidable back into its front position to protect the tip of the collecting surface 24 of the return reservoir 25 from dirtying caused by the end of coating and to guide air flows in the vicinity of the curtain C.

(11) The arrangement can comprise a mechanism, e.g., a motor or piston, for providing the swinging motion S of the cover plate 20 around the pivoted shaft 21 and, in the example according to FIG. 3, a mechanism for implementing the linear motion of the cover plate 20. The swinging motion S and the linear motion L can also be implemented for manual performance.

(12) The pivoted shaft 21 of the cover plate 20 is advantageously formed as a cleaning shaft with opening(s) from which cleaning liquids are conveyed onto the cover plate 20 for its cleaning.

(13) The invention was described above referring to its advantageous embodiments to the details of which the invention is not intended to be narrowly limited but many modifications and variations are possible within the inventive idea.