Suction or Ventilation Roll

Abstract

The invention relates to a suction or ventilation roll of a machine for producing and/or finishing a paper, cardboard, tissue or other fibrous material web (2). Said roll comprises a rotatable, perforated roll jacket (1) and at least one pressure zone (9), which only extends over part of the roll circumference and is formed by a fixed pressure compartment (6) located in the interior of the roll and open towards the roll jacket (1). The pressure compartment (6) is connected to a negative- or excess-pressure source and is sealed in relation to the roll jacket (1) by means of at least one sealing element (7). One aim of the invention is to reduce the noise emissions. To achieve this, a substantially air-tight cover (5), which runs in the direction of the circumference and is located outside the pressure compartment (6), adjoins a sealing element (7), said cover making contact with the roll jacket (1), or being placed at a distance of less than 100 mm to the latter.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a suction or blow roll for a machine for producing and/or finishing a paper, board, tissue or another fibrous web, having a rotatable perforated roll shell and at least one pressure region which extends over only part of the roll circumference and is formed by a stationary pressure box in the interior of the roll which is open toward the roll shell, the pressure box being connected to a negative or positive pressure source and being sealed off with respect to the roll shell by at least one sealing element.

2. Discussion of Background Information

When, in these rolls, the perforation leaves the pressure region, equalization takes place between the air pressure in the perforation and that of the surroundings. The result is that in blow rolls, the air flows out of the perforation and, in the case of suction rolls, into the perforation. This air flow causes considerable noise.

Irrespective of this, air leakage in the region of the sealing elements can also lead to the development of noise.

In order to counteract this, special sealing arrangements in the region of the pressure box have been developed but are not sufficiently effective and/or are too complicated.

SUMMARY OF THE INVENTION

Accordingly, one object of the invention to reduce the noise emission considerably with simple means in rolls of this type.

According to the present invention, the object has been achieved in that, at least on one sealing element, an at least substantially air-impermeable cover running in the circumferential direction and arranged outside the pressure box and/or the roll shell adjoins or is arranged in the vicinity of a side wall of the at least one pressure box on the outer side of the roll shell, the cover either being in contact with the roll shell or having a spacing of less than 100 mm from the latter.

The cover is thus either totally air-impermeable or allows air through only to a low extent.

The cover is either arranged on the inner side of the roll shell, where it preferably adjoins a wall of the pressure box directly or, alternatively, the cover is fitted at a short distance from the wall of the pressure box. In a further alternative or additional arrangement of the cover, provision is made for the latter to extend outside the perforated roll shell. In this case, it projects as far as possible into the pocket between the roll shell and the belt which carries the fibrous web with it, in order to keep pressure losses as low as possible, or provision is made for the cover to reach the contact region between the belt and the roll shell, apart from a defined distance, in particular also a variable distance according to the invention. Combinations of covers located on the inside and/or outside can be produced in accordance with this invention.

In addition, it can also be advantageous to seal off the cover with respect to the roll shell, preferably at the axial ends.

This cover prevents the pressure equalization between the perforation and the interior of the roll considerably or even completely. As a result, pressure equalization is possible substantially only with the outer region of the roll or, depending on the embodiment, substantially only with the inner region of the roll.

The water mist which is often present in the region of these rolls increases the flow resistance, so that pressure equalization takes place more gradually and therefore also with less noise. In addition, a negative pressure forms in the opening gap between the fibrous web or a belt supporting the latter and the roll at the end of the pressure region located in the direction of rotation and, in the case of suction rolls, counteracts ventilation of the perforation after the pressure region.

In order to reduce the air flow in the interior of the roll considerably, the distance between the cover and the roll shell should be less than 20 mm, preferably less than 10 mm.

Depending on the application and the requirements, the distance between roll shell and cover can be substantially the same everywhere or increase or decrease away from the pressure box or even fluctuate in the longitudinal and/or transverse direction of the machine.

It is particularly efficient if the cover adjoins a sealing element running approximately transversely with respect to the web running direction.

In this case, the air flow in the perforation can be reduced particularly considerably if a cover adjoins the end of the pressure box located in the direction of rotation.

With regard to the reduction of air leakage, however, it is also advantageous if a cover adjoins the end of the pressure box located counter to the direction of rotation.

In order to be able to achieve the highest possible effectiveness of the cover, the cover should extend over a circumferential region of at least 10 mm, preferably at least over a circumferential region of at least 100 mm and in particular more than 200 mm.

It is particularly advantageous in this case if the cover extends in the circumferential direction over the entire region located outside the pressure box.

The greatest possible reduction in noise is of course achieved if the cover extends axially at least over the entire perforated region of the roll shell.

However, in order to minimize the expense, it may also already be sufficient if the cover extends axially over only part of the perforated region of the roll shell. This applies in particular to rolls having a plurality of pressure regions arranged axially beside one another. Here, the arrangement of the cover in the region of the pressure region with the highest negative or positive pressure may be sufficient.

On the suction or blow roll there is advantageously an adjusting device, by means of which a cover can be varied axially over its entire width or over part of its width with respect to its distance or its angle of attack in relation to the roll shell. The adjusting device can be adjusted hydraulically, pneumatically or mechanically, for example.

In another embodiment of the present invention, the position may be adjusted by a control device which comprises a controller. Depending on a controlled variable measured by a measuring device, said controller acts via a signal variable on the adjusting device, which changes the position of a cover in accordance with the signal variable. The controlled variable measured by the measuring device is, for example, the pressure in the pressure box or the moisture of the fibrous web or of the fabric or of the felt by which the fibrous web is carried.

In a further advantageous embodiment, a cover has a straight, curved, undulating, zigzag or irregularly broken terminating edge on only one transverse or longitudinal side or a plurality of sides. Under particular circumstances, the cover also has openings, for example in the form of drilled holes or apertures.

In a further embodiment of the present invention, between the roll shell and a cover there are arranged spacers, in particular in the form of rods, wedges or strips, which can in particular be adjusted by the adjusting device.

A cover consists either of a single material or of a plurality of materials, in particular of a metal, a plastic and/or a composite material.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

FIG. 1 shows a cross section of a roll with a plurality of covers,

FIG. 2 shows a cross section of a roll with a continuous cover,

FIG. 3 shows a cross section of a roll with two covers arranged on the inside and outside after the pressure box in the direction of rotation, and

FIG. 4 shows a cross section of a roll with the two covers according to FIG. 3, which can be adjusted via spacers and an adjusting device.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

The rolls shown in FIGS. 1-4 are suction rolls having a perforated, rotatable roll shell 1, such as are used in paper machines, in particular in the former during sheet formation, in the press section and in the drying section.

These suction rolls are wrapped around here by an air-permeable belt 3, that is to say for example a fabric or a felt or a belt consisting of another material, and the fibrous web 2 located on the outside, the negative pressure region 9 being located in the wrap region. This negative pressure region 9 is formed by a stationary pressure box 6 in the roll interior which is open toward the roll shell 1. The interior of the pressure box 6 is connected to a negative pressure source. In order to minimize the air leakage, the pressure box 6 is sealed off completely with respect to the roll shell 1 by sealing elements 5 in the form of sealing strips.

In this way, the negative pressure of the pressure box 6 through the holes of the perforation of the roll shell 1 effects attraction of the fibrous web 2 by suction onto the air-permeable belt 3 in the pressure region 9.

In FIG. 1, the axial sealing elements 7 are adjoined by air-impermeable covers 5 running in the circumferential direction. These covers 5 have only a small spacing of less than 10 mm from the roll shell 1, the distance increasing away from the pressure box 6. In another design, the distance between the roll shell 1 and one of the covers 5 or both covers 5 remains constant.

At the inlet to the pressure box 6, these covers 5 reduce air leakage and, at the outlet, the ventilation of the perforation from the interior of the roll. As a result, there is a considerable reduction in the emission of noise.

As can be seen in FIG. 1, the ventilation of the perforation, in which a negative pressure prevails at the exit from the pressure region 9, can take place substantially only by means of an air flow 8 from outside. This air flow 8 is already hindered by the water mist present in the region of the suction roll. Furthermore, a negative pressure forms in the pocket opening between the belt 3 and the suction roll, which counteracts ventilation of the perforation to a considerable extent.

As a result, the ventilation takes place substantially more gradually and therefore without noise. At the inlet, the cover 5 covers approximately a region of 25° and, at the outlet, of 50°.

In FIG. 2, a design is shown in which the cover 5 extends in the circumferential direction over the entire region located outside the pressure box 6. This entirely prevents ventilation from the inside, in particular when the distance between the cover 5 and the roll shell 1 lies in the range of a few millimeters or the cover 5 is even in contact with the roll shell 1.

Axially, the covers 5 here extend over the entire perforated region of the roll shell 1.

In another embodiment shown in FIG. 3, in addition to the cover 5, there is a further cover 10 on the outside of the roll shell 1, in the pocket formed by the latter with the belt 3. The two covers 5, 10 can preferably be adjusted via joints 11 and 12.

In another of the suction or blow roll shown in FIG. 4, spacers 13, 14 are fitted to the cover 5 and spacers 15, 16 to the cover 10. The spacers 13 to 16 consist either of plastic or metal; they may be configured in the shape of wedges; for example, they are wearing plastic parts which can easily be replaced.

The spacers 13 to 16 are formed either as rods or as sealing strips, in particular from sheet metal. The sealing strips can also be present in addition to the spacers 13 to 16. In particular in the case of the cover 10 fitted to the outside of the roll shell 1, the spacers 15, 16 ensure the maintenance of the desired spacing between the roll shell 1 and the cover 10, since the latter is attracted by the roll shell 1 on account of the low component section modulus. The component section modulus characterizes the intensity of the deformation under external loading. In this case, a lower deformation signifies a high section modulus and vice versa.

The position of the covers 5, 10 is changed by adjusting devices 17 and 18. These are connected to the spacers 13, 14 and 15, 16 via pressure lines 19, 20, for example, so that the spacing of the covers 5, 10 with respect to the roll shell 1 both at the leading end and the trailing end of the covers 5, 10 can be changed hydraulically or pneumatically by means of a fluid medium (oil, water, air) supplied via the lines 19, 20. Alternatively or additionally, provision is made for the angle of attack of the covers 5, 10 to be adjusted, the joints 11, 12 being influenced by the devices 17, 18 via appropriate lines.

As an alternative, the devices 17, 18 influence the positions as a result of the fact that there are mechanical adjusting means, for example in the form of threaded spindles. The spacings of the devices 17, 18 can be changed by means of appropriate configurations of the devices 17, 18 either over the entire width of the covers 5, 10 exclusively or else at points or in specific sections of the covers 5, 10. By means of the devices 17, 18, distance regulation in the radial and/or axial direction is thus possible.

The devices 17, 18 have signal variables applied to them by measuring devices, for example, it being possible, for example, for the sound level determined outside the roll or the pressure measured in the pressure box 6 to be used as controlled variable.

It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

Claims

1-19. (canceled)

20. A roll for a machine comprising: a rotatable perforated roll shell having at least one pressure region that extends over a first portion of a roll circumference; a stationary pressure box in the interior of the roll which is open toward the roll shell forming the at least one pressure region, the pressure box being connected to one of a negative and a positive pressure source; at least one sealing element, the at least one sealing element sealing off the pressure box is sealed off with respect to the roll shell; and at least one substantially air-impermeable cover; wherein the at least one sealing element and the at least one substantially air-impermeable cover running in the circumferential direction and arranged at least one of outside the pressure box and the roll shell and adjoins or is arranged in the vicinity of a side wall of the pressure box on an outer side of the roll shell, and wherein the cover is one of in contact with the roll shell and having a spacing of less than 100 mm from the outer side of the roll shell.

21. The roll of claim 20, wherein the roll is one of a suction roll and a blow roll.

22. The roll of claim 20, wherein the distance between the cover and the outer side of the roll shell is one of less than 20 mm and less than 10 mm.

23. The roll of claim 20, wherein the distance between the cover and the outer side of the roll shell is substantially the same about the roll.

24. The roll of claim 20, wherein the distance between the outer side of the roll shell and the at least one cover one of increases and decreases away from the pressure box.

25. The roll of claim 20, wherein the distance between the outer side of the roll shell and the at least one cover fluctuates in at least one of a longitudinal and transverse direction of the machine.

26. The roll of claim 20, wherein the at least one cover adjoins the at least one sealing element running approximately transversely with respect to a web running direction.

27. The roll of claim 20, wherein the at least one cover adjoins an end of the pressure box located in the direction of rotation.

28. The roll of claim 20, wherein the at least one cover adjoins an end of the pressure box located counter to the direction of rotation.

29. The roll of claim 20, wherein the at least one cover extends over a circumferential region of one of at least 10 mm, at least 100 mm and more than 200 mm.

30. The roll of claim 20 wherein the cover extends in the circumferential direction over an entire region located outside the pressure box.

31. The roll of claim 20, wherein the at least one cover extends axially at least over the entire perforated region of the roll shell.

32. The roll of claim 20, wherein the at least one cover extends axially over a first portion the perforated region of the roll shell.

33. The roll of claim 20, further comprising an adjusting device, whereby the at least one cover can be varied axially over a first width with respect to one of its distance and angle of attack in relation to the roll shell.

34. The roll of claim 33, wherein the adjusting device is adjusted by one of hydraulically, pneumatically and mechanically.

35. The roll of claim 33, further comprising a measuring device that measures a control variable and outputs the control variable to a controller, wherein, based on the control variable, the controller outputs a signal variable to the adjusting device, whereby the adjusting device which changes the position of the at least one cover in accordance with the signal variable.

36. The roll of claim 20, wherein the at least one cover has one of a straight, curved, undulating, zigzag and irregularly broken terminating edge.

37. The roll of claim 20, wherein the at least one cover has openings.

38. The roll of claim 20, further comprising spacers, the spacers arranged between the roll shell and the at least one cover, wherein the spacers are in the form of at least one of rods, wedges or strips.

39. The roll of claim 38, wherein the spacers are adjustable by an adjusting device.

40. The roll of claim 20, wherein the at least one cover comprises at least one of a single material and a plurality of materials.

41. The roll of claim 40, wherein the at least one of a single material and a plurality of materials is at least one of a metal, a plastic and a composite material.

42. The machine of claim 20, wherein the machine at least one of produces and finishes at least one of a paper, a board, a tissue and a fibrous web.