Method For Coating A Drying Cylinder

Abstract

A method for coating a drying cylinder of a drying apparatus for drying and/or smoothing a fibrous web includes carrying out the coating within the drying apparatus. A system including a coating unit for coating the circumferential surface of a drying cylinder and a drying apparatus, as well as a method for converting or producing a drying apparatus, are also provided.

Claims

1-16. (canceled)

17. A method for coating a drying cylinder of a drying apparatus for at least one of drying or smoothing a fibrous web, the method comprising the following step: carrying out the coating step within the drying apparatus.

18. The method according to claim 17, which further comprises: supplying a spray additive in a direction of a circumferential surface of the drying cylinder to be coated; using a beam from a radiation source to melt at least the supplied spray additive and produce a layer; and carrying out the melting step, in an operating state of the drying apparatus, to cause the beam to impinge along an extension of an application direction of the beam at a point on the circumferential surface located outside a wrap area on the circumferential surface being wrapped with the fibrous web or a clothing carrying the fibrous web.

19. The method according to claim 18, which further comprises using a laser or an electron radiation source to produce the layer.

20. The method according to claim 18, wherein the application direction of the beam extends substantially counter to the direction of gravity.

21. The method according to claim 17, which further comprises applying the coating gradually and layer by layer to provide the coating in a plurality of layers disposed above one another in a radial direction of the drying cylinder.

22. The method according to claim 17, which further comprises applying the coating in at least one layer being: an adhesive layer, or a functional layer, or at least one adhesive layer and at least one functional layer applied to the at least one adhesive layer in a radial direction, or a functional layer applied to a circumferential surface of the drying cylinder being free of an adhesive layer lying underneath the functional layer.

23. The method according to claim 17, which further comprises applying the coating in at least one layer produced by using laser cladding or an equivalent method in which a circumferential surface of the drying cylinder to be coated with the at least one layer is partly melted.

24. The method according to claim 17, which further comprises surface-treating a circumferential surface of the drying cylinder at least one of before or after the coating step.

25. The method according to claim 24, which further comprises carrying out the surface-treating step by machining with material removal, grinding or blasting.

26. The method according to claim 24, which further comprises carrying out the surface-treating step before the coating step to remove a possibly already existing coating from the circumferential surface of the drying cylinder.

27. The method according to claim 24, which further comprises carrying out at least one of the coating or surface treatment steps in a non-operating state of the drying apparatus.

28. A system, comprising: a drying apparatus including at least one drying cylinder having a circumferential surface; and a coating unit for coating said circumferential surface of said drying cylinder, said coating unit including a material supply for a spray additive, an application device for bringing the spray additive to said circumferential surface of said drying cylinder in an application direction, and a radiation source emitting a beam for melting at least the supplied spray additive; said coating unit being configured to cause the beam for melting at least the spray additive, during an intended operation of said drying apparatus, to impinge at a point on said circumferential surface in an extension of said application direction, said point lying outside a wrap area of said circumferential surface of said drying cylinder being wrapped with a fibrous web or a clothing carrying the fibrous web.

29. The system according to claim 28, wherein said coating unit is configured to determine a main application direction of the spray additive substantially counter to gravity in an installed position for operation of said coating unit.

30. The system according to claim 28, wherein said radiation source is configured to determine an application direction of the beam emitted by said radiation source parallel to or at an angle to a main application direction of the spray additive or to coincide with said main application direction of the spray additive.

31. The system according to claim 28, wherein said radiation source is a laser radiation source, the beam is a laser beam and said laser radiation source is configured for laser cladding.

32. The system according to claim 28, wherein the spray additive fed to said material supply is a strip or a wire or a cord or a powder.

33. The system according to claim 28, wherein said coating unit is nondestructively detachably connectable to said drying apparatus.

34. A method for converting or producing a drying apparatus including at least one drying cylinder for at least one of drying or smoothing a fibrous web, the method comprising the following steps: providing a coating unit for coating a circumferential surface of the drying cylinder, the coating unit including a material supply for a spray additive, an application device for bringing the spray additive to the circumferential surface of the drying cylinder in an application direction, and a radiation source emitting a beam for melting at least the supplied spray additive; placing the coating unit, in an operating state of the drying apparatus, in an installation position located outside a wrap area of the circumferential surface of the drying cylinder being wrapped with the fibrous web or a clothing carrying the fibrous web; and using the beam to impinge at a point lying outside the wrap area on the circumferential surface in an extension of the application direction, to melt at least the spray additive during an intended operation of the drying apparatus.

35. The method according to claim 34, which further comprises removing the coating unit following the application of the coating to the circumferential surface of the drying cylinder or after a subsequent surface treatment of the coating by the drying apparatus.

Description

[0042] The invention will be described in more detail below with reference to the drawings, without restricting generality. In the drawings:

[0043] FIGS. 1a and 1b show a highly schematic illustration in side view of two drying apparatuses suitable for the invention, the drying cylinders of which can be coated;

[0044] FIGS. 2a and 2b show a development of the embodiment of the subject of FIG. 1a;

[0045] FIG. 3 shows a highly schematic plan view of a system comprising drying apparatus and coating unit;

[0046] FIG. 4 shows an embodiment in a highly schematic sectioned view through a coating according to the invention.

[0047] FIGS. 1a and 1b show two embodiments of the invention in a schematic side view of an operating state of the drying apparatus. In both figures, a part of a drying apparatus of a machine for producing and/or finishing a fibrous web F, such as a paper, board or tissue web, is respectively illustrated. In both cases, the fibrous web F is formed in the machine, dewatered and then transferred to the drying apparatus for the drying and/or smoothing thereof.

[0048] In FIG. 1a, the drying cylinder 1 is embodied as a Yankee cylinder. The fibrous web F formed in the machine is transferred here to the drying apparatus at a first removal point by a transport belt by means of a press roll 10. The first removal point is formed here by a press nip, which the press roll 10 and the drying cylinder 1 form with each other. The drying cylinder 1 is of heated design. Also assigned thereto is a dryer hood 11, in order to additionally dry the fibrous web F. After the fibrous web F has left the dryer hood 11, it is removed from the drying cylinder 1 at a second removal point. This is carried out in this case by a crping doctor 12, which is pressed against the circumferential surface of the drying cylinder. As seen in the running direction of the fibrous web F through the drying apparatus (and in the direction of rotation of the drying cylinder 1), the crping doctor 12 is arranged after the press roll 10. In the further sequence, the crped fibrous web F is wound up. In the direction of view in FIG. 1a, the fibrous web is thus always in direct contact with the rotating drying cylinder and its circumferential surface only within the wrap area illustrated dashed. Expressed in another way, the wrap area is thus bounded in the direction of rotation of the drying cylinder by the first removal point and the second removal point.

[0049] According to FIG. 1b, the fibrous web F is led over a plurality of drying cylinders 1 arranged one after another in the running direction of the fibrous web F. Said drying cylinders are arranged parallel to and at a distance from one another with regard to their longitudinal axes. In the present case, the drying cylinders directly adjacent to one another are spaced apart from one another horizontally and also vertically. As a rule, the fibrous web F does not come directly into contact with the drying cylinders 1 but is carried by a clothing (not illustrated). In this case, the clothing rests directly on the respective drying cylinder 1. Here, the fibrous web F also wraps partly around the respective drying cylinder 1 in a respective wrap area (illustrated dashed).

[0050] The invention will now be explained in more detail by using the embodiment of FIG. 1a. In principle, the explanations made also apply in a corresponding way to the embodiment of FIG. 1b. To this end, the operating state is illustrated in FIG. 2a and the non-operating state of the drying apparatus in FIG. 2b. In the last-named case, the fibrous web F does not run through the drying cylinder 1, as is shown in FIG. 2a. Instead, only the path traced by the fibrous web F in the operating state of the drying apparatus is indicated dashed.

[0051] In order to coat the drying cylinder 1, without removing the latter from the drying apparatus, it is coated in the drying apparatus itself. To this end, the drying apparatus is set into the non-operating state according to FIG. 2b and possibly converted appropriately for the first time for the coating. For the conversion, the drying apparatus is provided with a coating unit 13. The latter is arranged in an installed position in the drying apparatus, which is located outside the wrap area of the fibrous web F that is present in the operating state of the drying apparatusthus close to the coating application areahere, therefore, underneath the drying cylinder 1, between the two first removal positions, namely the crping doctor 12 and the press roll 10. If the coating unit 13 is installed at the aforementioned point in the drying apparatus, then the system according to the invention comprising the two is achieved. The coating unit 13 can thus be installed retrospectively in existing drying apparatuses. It can remain there permanently or else only temporarily for the duration of the coating or a surface treatment of the drying cylinder 1, carried out previously or following thereafter. In the last-named case, it is then advantageous if the coating unit 13 can be connected detachably to the drying apparatus via means. These means include, for example, the cross-member 14 on which the coating unit 13 is supported. The cross-member 14 can be supported indirectly on the drying apparatus, for example via the floor on which the latter stands. However, the cross-member 14 could also be connected firmly, that is non-detachably, to the floor or the drying apparatus, therefore being part of the drying apparatus.

[0052] In order at the same time to remove a possibly already existing coating from the drying cylinder 1 within the drying apparatus or to re-machine the finished coating once more, the coating unit 13 can also be assigned a device for surface treatment 6. This is likewise provided in the area of the aforementioned installation position of the coating unit 13. The former can be embodied as a grinding machine and/or for blasting, such as shot-blasting of the drying cylinder 1. In addition, the device 6 can be detachably supported on the drying apparatus via appropriate means, such as the cross-member 14 or via a dedicated cross-member (not shown).

[0053] Because the coating unit 13 is installed in the drying apparatus at the aforementioned point, neither the dryer hood 11 nor the crping doctor 12 nor the press roll 10 has to be removed for the coating. In other words, the space which is normally free and which results outside the wrap area is provided for the installation of the coating unit 13. The latter can therefore also remain at the point in operation of the drying apparatus, since it does not influence treatment of the fibrous web F by the drying apparatus.

[0054] As soon as the coating or retrospective surface treatment of the drying cylinder 1 has been completed, the system comprising the drying apparatus and coating unit 13 can be dissolved again. To this end, the coating unit 13 is removed from the drying apparatus again, so that the arrangement shown in FIG. 2a results again.

[0055] In FIG. 3, the coating unit 13 is shown in detail in a highly schematic plan view. The longitudinal axis of the drying cylinder 1 extends in the drawing plane here.

[0056] The drying cylinder 1 rotating about its longitudinal axis is driven suitably. The coating unit 13 comprises an application device 7 supported on the cross-member 14, displaceable to and fro relative to the drying cylinder 1, parallel to the longitudinal axis thereof (see the double arrow). Said application device comprises a material supply 8 that can be optionally connected and disconnected for supplying a spray additive (indicated dotted), a beam 9 which is emitted by a radiation source, not illustrated, into which the spray additive is put, and also a protective gas supply, not shown, for supplying protective gas to the drying cylinder 1. The application device 7 can be embodied as a spray burner. The spray additive in the present case is present in the form of powder. By means of the coating unit 13, the entire surface of the drying cylinder 1 can be coated gradually, for example in a continuous spiral line. However, it is also possible to apply the coating in another way, for example in radial rings or axial stripes. Of course, it would be conceivable that multiple such application devices 7 could be arranged at a distance from one another along the cross-member 14 and the longitudinal axis of the drying cylinder 1. In this way, the coating process could be carried out considerably more quickly.

[0057] The application of protective gas is indicated in the present case by the cone of the beam 9. The protective gas can serve to entrain and/or accelerate the material such as spray additive, which is introduced into the beam path of the radiation source for the melting. The spray additive accelerated by means of protective gas and incipiently melted or melted is thrown onto the drying cylinder 1 to be coated, here for example the naked (that is to say freed of an existing coating) roll core 2 machined by means of the device 6 (see FIG. 4). If the surface of the roll core 2 is also melted, then the melted spray additive also gets into the melt of the roll core 2. The application device 7 can be designed in such a way that protective gas, beam 9 and spray additive emerge together, for example concentrically, from one and the same spray burner. In that case, the beam can be coupled into the spray burner, so that at least the longitudinal axis of the beam and the main application direction of the spray additive coincide.

[0058] According to the illustration in FIG. 2b, the spray additive is thrown out of the application device 7 in the main application direction. Both the main application direction of the spray additive and the application direction of the beam 9 extend counter to the direction of gravity in the view illustrated, the latter extending along a vertical through the longitudinal axis of the drying cylinder 1 here. Expressed in another way, the spray additive is applied to the drying cylinder 1 from belowunderneath the longitudinal axis/axis of rotation of the drying cylinder 1, counter to gravity. It would also be conceivable for both beam 9 and spray additive to arrive from different directions, so that the application direction of the beam 9 is at an angle to the main application direction of the spray additive. Thus, for example, the spray additive can be brought tangentially up to the circumferential surface of the drying cylinder 1, while the beam 9 still extends counter to gravity and therefore at an angle to the main application direction of the spray additive.

[0059] In FIG. 4, one embodiment of the present invention is illustrated in a highly schematic sectional view in a partial cross section at right angles to the longitudinal axis through the drying cylinder 1 from FIG. 1a or 1b. To simplify the illustration, the roll curvature has been disregarded. It should likewise be noted that the thickness, seen in the radial direction of the individual layers of the roll 1, is not illustrated to scale. The intention is merely to symbolize the sequence of the layers. The respectively illustrated drying cylinder 1 usually has a radially inner roll core 2, which can at least partly be produced from a metal such as steel.

[0060] In the present case, the coating 5 according to the invention is applied directly in the radial direction to the roll core 2, to its circumference. It comprises a functional layer 4. This can be applied directly to the roll core 2 or, as illustrated dashed, arranged on at least one adhesive layer 3. The adhesive layer 3 is used for adhesion promotion between the roll core 2 and the layer following next toward the outside in the radial direction, here the functional layer 4. The adhesive layer 3 is advantageously chosen when the coating 5 is intended to have improved adhesion between functional layer 4 and roll core 2. Although this is not illustrated, on the one hand the roll core 2 and the adhesive layer 3 and/or the adhesive layer 3 and the functional layer 4 could together form an alloying region.

[0061] Seen in the radial direction of the drying cylinder 1, the functional layer 4 is applied to the at least one adhesive layer 3. The entire coating 5, in each case produced in accordance with the embodiment illustrated, can be produced by means of the coating unit 6.

LIST OF DESIGNATIONS

[0062] 1 Drying cylinder [0063] 2 Roll core [0064] 3 Adhesive layer [0065] 4 Functional layer [0066] 5 Coating [0067] 6 Device for surface treatment [0068] 7 Application device [0069] 8 Material supply [0070] 9 Beam [0071] 10 Press roll [0072] 11 Dryer hood [0073] 12 Crping doctor [0074] 13 Coating unit [0075] 14 Cross-member [0076] F Fibrous web