WO1994003675A1

WO1994003675A1 - Assembly with a suction roller

Info

Publication number: WO1994003675A1
Application number: PCT/EP1992/001743
Authority: WO
Inventors: Wolfgang Mayer; Karl GRÖNER
Original assignee: J.M. Voith Gmbh
Priority date: 1992-07-31
Filing date: 1992-07-31
Publication date: 1994-02-17

Abstract

The suction roller (13) described has a perforated shell (14) down the inside of which a fixed air-supply pipe (15) extends. The wall (15') of this pipe is curved is such a way that the radial thickness (d) of the gap (17) between the pipe wall and roller shell increases round the inside wall of the roller shell (14), beginning at the air-outflow side (16a) of a longitudinal sealing strip (16) and finishing at the air-inflow side (16b) of the strip (16). The longitudinal sealing strip (16) is disposed a short distance from a point (A) at which a support belt (10) carrying a web of paper runs on to the shell (14) of the suction roller (13).

Description

Arrangement with a suction roller

The invention relates to an arrangement with a suction roll, which is perforated inside

Roll jacket has a stationary air guide body, which in cooperation with the rotation of the perforated roll jacket automatically generates a vacuum and an overpressure zone, in detail according to the preamble of claim 1. Such an arrangement is known from DE-GM 91 06 451 (file P 4585 ).

This known arrangement thus differs from other known arrangements in which the vacuum inside the suction roll is generated by means of a separate suction device connected via a suction line.

The present invention is concerned with the problem of making an arrangement with an automatically generating vacuum roll as simple as possible, so that it can be produced inexpensively. At the same time, the arrangement should work as reliably as possible, so that it is applicable in a single-tier dryer section of a paper making machine. It is important to transport the paper web to be dried at extremely high working speeds (of the order of 1000 to 2000 m / min) by means of a porous support belt from the contact zone with a heatable drying cylinder, for example to a subsequent drying cylinder. This must be done with high reliability, i.e. without the risk of the paper web tearing off.

According to the invention, the above-mentioned problem is essentially solved in that the curved guide wall (in cooperation with the rotation of the perforated roll shell) which produces the depression is in the extends substantially along the entire inner circumference of the roll shell. In other words: there is only one continuous guide wall along the entire inner circumference of the roll shell. In addition, according to the invention, only a single sealing arrangement, which extends over the entire length of the intermediate space, is provided in the annular intermediate space present between the roll shell and the air guide body. This is preferably a simple sealing strip fastened to the stationary air guide body, which forms a sealing gap with the inner surface of the rotatable roller shell.

With regard to the direction of rotation of the roll shell, the sealing arrangement has an outlet side and an inlet side. On the outlet side, the radial distance of the curved guide wall from the inner surface of the roll shell is relatively small. From here, this radial distance (or in other words the "radial thickness of the gap") along the inner circumference of the

Roll shell with its direction of rotation more and more until the curved guide wall approaches the inlet side of the sealing arrangement. Thus, when the roller shell rotates, it is possible to create a suction zone which, starting from the outlet side of the sealing arrangement, extends over a very large part of the inner circumference of the roller shell. In the area of this suction zone, air is sucked in from the outside in through the perforation of the roll shell and is transported in the circumferential direction in the annular space. This creates a pressure zone in the area of the inlet side of the sealing arrangement, in which the incoming air is transported outwards again through the holes in the roller shell. In other words: somewhere at a certain distance in front of the inlet side of the sealing arrangement there is a transition zone in which there is atmospheric pressure and in which the suction zone passes into the pressure zone. In any case, the end of the pressure zone is clearly delimited from the beginning of the suction zone with the aid of the sealing arrangement mentioned.

The curvature of the guide wall is dependent on

The inner diameter of the roll shell is dimensioned such that the width of the pressure zone, measured in the circumferential direction, becomes as small as possible and that the suction zone therefore extends in the circumferential direction over as large a part of the inner circumference of the roll shell as possible. Thanks to the invention, it is entirely possible that the suction zone, starting from the outlet side of the sealing arrangement, extends over 2/3 to 3/4 (or even more) of the inner circumference of the roller shell.

Further refinements of the invention, in particular when used in a single-tier dryer section of a paper production machine, are explained below with reference to the exemplary embodiment shown in the drawing.

Fig. 1 shows an arrangement with a suction roller, in a schematic cross section.

FIG. 2 is a partial longitudinal section along the line II-II of FIG. 1.

FIG. 3 shows an arrangement in cross section that differs from FIG. 1.

Fig. 4 shows schematically a further arrangement with a suction roller.

Fig. 1 shows a section of a single-tier dryer section of a paper making machine, with a first drying cylinder 11, a second drying cylinder 12 and a suction roller designated overall by 13. On endless porous support belt 10 (preferably a so-called dryer fabric) runs from the first drying cylinder 11 via the suction roll 13 to the second drying cylinder 12. A paper web to be dried, which is omitted in the drawing, runs together with the support belt 10 through the entire arrangement; it is located in the area of the suction roll 13 on the outside of the support belt 10, that is to say it is pressed against the drying cylinders 11 and 12 by the support belt.

The suction roller 13 has a rotatable and perforated roller jacket 14 and a stationary air guide body 15 extending through the interior of the roller jacket. In cross section according to FIG. 1, the air guide body has a convexly curved guide wall 15 'which extends in the circumferential direction at least approximately along the whole Inner circumference of the roll shell extends. The radius of curvature K1, K2 of the guide wall 15 'is smaller than the radius R of the inner surface area of the roll shell 14.

A seal arrangement 16 is provided on the air guide body 15, preferably in the form of a single sealing strip, which extends over the entire length of the suction roll and forms a sealing gap with the inner lateral surface of the rotating roll casing 14. With regard to the direction of rotation of the suction roll 13, the sealing arrangement 16 has an outlet side 16a and an inlet side 16b. The radius of curvature Kl, K2 of the convexly curved guide wall 15 • is along the circumference of the

Air guide body 15, starting from the outlet side 16a of the seal 16, gradually or continuously smaller, until the curved guide wall 15 reaches the inlet side 16b of the seal 16.

In the example shown, the air guide body 15 is composed of two semi-cylindrical parts, the the first part has the radius of curvature Kl, which (as already mentioned) is smaller than the radius R of the inner lateral surface of the roll shell 14, and the second part has the even smaller radius of curvature K2. This is between the roll shell and the

Air guide body has an intermediate space 17, the radial "thickness" d of which, starting from the outlet side 16a of the seal 16, increases substantially along the entire circumference of the air guide body 15. The radial thickness is greatest on the inlet side 16b; there it is generally about 20 to 50 mm or in exceptional cases less than 20 mm.

The seal 16 is arranged at a small distance from the point A with respect to the circumferential direction, where the support belt 10 runs onto the roller jacket 14. The point where the support belt 10 runs again from the suction roller 13 is designated by B. In the example shown, the support belt 10 wraps around the suction roll 14 in a wrapping zone running from A to B, the angle U of which is generally greater than 180 °.

Due to the described shape of the air guide body 15, this forms - in cooperation with the rotation of the perforated roller jacket 14 - a suction zone in the intermediate space 17, which begins at the seal 16 (i.e. before the contact point A) and ends only after the contact point B, namely approximately at point C. This ensures that negative pressure is generated not only in the area of the wrap zone U, but also in the inlet and outlet branches in Za and Zb. In the central region of the zone of the roll shell circumference not wrapped by the support belt 10 (the so-called pressure zone), on the other hand, a relatively high pressure is established in the intermediate space 17, so that the air sucked inward in the suction zone is removed to the outside. The pressure which arises in the pressure zone is approximately equal to that Atmospheric pressure or slightly less than or greater than this.

In the so-called pocket (this is the space between the cylinders 11 and 12, the support belt 10 and the suction roll 13) there is a stationary exhaust air collecting box 18 which is open towards the roll jacket 14. This has two longitudinal sealing strips 19 and 20 which form sealing gaps with the outside of the roll shell 14 and thus seal the interior of the exhaust air collecting box 18 from the outside. One longitudinal sealing strip 19 is arranged in the vicinity of the seal 16 already mentioned, the other longitudinal sealing strip 20, however, in the vicinity of point C, in the area of which the suction zone merges into the pressure zone. The drain collecting box 18 has an exhaust air opening 22 on an end wall 21 (or on both end walls), to which a suction line 23 can be connected.

The exhaust air collecting box 18 has in the area of the outlet point of the support band 10 from the first

Drying cylinder 11 has a suction chamber 24 which is delimited by sealing strips 24a and 24b and is delimited from the remaining part by an intermediate wall 25. Suction line 26 and suction fan 27 are only indicated schematically. Both side walls 28 and 29 of the exhaust air collecting box 18 diverge - with respect to the tape running direction - from the path of the support belt 10, so that negative pressure is also generated along the straight paths of the support belt 10 in order to keep the paper web in safe contact with the support belt 10.

In addition to FIG. 1, the following can be seen in FIG. 2: A machine stand 31 stands on a foundation 30. A longitudinal support 32 rests thereon and a bearing 33 for the drying cylinder 11 rests thereon. A bearing housing also rests on the foundation 30 34 for the suction roll 13. On the perforated roll cover 14 a cover 35 is fastened with a hollow journal 36 which is rotatably mounted in the bearing housing 34. The stationary air guide body 15 has an end wall 37 in the region of the roller end and also a hollow bearing journal 38 therein, which extends through the bearing journal 36 and beyond it to the outside. There, the bearing journal 38 and thus the entire stationary air guide body 15 are fastened to the bearing housing 34 by means of a bell 39. The exhaust air collecting box 18 is fastened to the side member 32 by means of a bracket 40.

FIG. 3 shows some possibilities of how the design according to FIGS. 1 and 2 can be modified. For example, instead of a single longitudinal sealing strip 16 (FIG. 1), two longitudinal sealing strips 16A and 16B can be provided, which are arranged one behind the other with respect to the circumferential direction. A neutral zone is thus created between these two sealing strips, which serves for better sealing between the suction zone and the pressure zone. The radial thickness d of the

Intermediate space 17 in turn increases - starting from the sealing strip 16A - in the circumferential direction, but only according to FIG. 3 as far as point C, which, as in FIG. 1, is located at a certain distance behind drain point B. Here, the thickness d of the space 17 has a maximum value D of approximately 20 to 50 mm. Between the point C and the sealing strip 16B, the thickness of the intermediate space 17 can remain the same or decrease. This area, designated P in FIG. 3, corresponds approximately to the pressure zone of the suction roll 13. The length of this

The pressure zone P in the circumferential direction is at most one third of the inner circumference of the roller shell 14. The area from the longitudinal sealing strip 16A to said point C is approximately equal to the suction zone S, which generally extends over more than 3/4 of the inner circumference of the roller shell 14 . 3 can be made simpler than in accordance with FIG. 1. For example, it suffices to provide a longitudinal sealing strip 19 only in front of the run-up point A, while a corresponding longitudinal sealing strip in the region of the discharge point B can be omitted. Instead of a lateral exhaust air opening (22, FIG. 1), a plurality of exhaust air openings 22 * can be provided at the top in the area of the longitudinal sealing strip 24a. The suction chamber 24 (FIG. 1) can also be omitted in some cases. The side wall 28 is preferably arranged in such a way that it diverges from the path of the support belt 10 in order to thereby suck the paper web onto the support belt. Likewise, it is again expedient that the opposite side wall 29 also diverges from the path of the support band 10.

However, if another suction device is present, then the side walls 28 and 29 (also in FIG. 1) can be arranged parallel to the path of the support belt.

4 schematically shows a section of a two-tier dryer section

Papermaking machine, with several drying cylinders 41 to 44 (and generally with further drying cylinders, not shown. The drying cylinders are arranged in two rows one above the other. The paper web to be dried runs alternately over the upper and lower drying cylinders in a known manner. An upper endless drying screen 51 presses the paper web against the upper drying cylinders 41, 43. A lower endless drying wire 52 presses the paper web 9 against the lower drying cylinders 42, 44. Suction rollers 13 • are provided for guiding the drying fabrics 51, 52 from cylinder to cylinder, each of which is preferably close the outlet of the paper web from the preceding drying cylinder, preferably so that the straight path of the paper web 9 is the suction roll 13 'affects. Each of the suction rolls 13 'in turn has an air guide body 15 with a single sealing arrangement 16. The thickness of the intermediate space 17 (between the roll jacket and the air guide body) again increases with the direction of rotation of the roll jacket. It is also important that the sealing arrangement 16 is arranged in the area of the wrapping zone, that is to say in that part of the circumference of the suction roll which is touched by the drying screen 51 or 52 in question. The sealing arrangement is preferably located at the point where the drying wire runs off the suction roll 13 '. In this way, the following is achieved: the suction roller 13 'can suck in air in the part of its circumference free of the drying wire and in the looping zone (in the area in front of the sealing arrangement 16) through the drying wire into the so-called

Blow pocket 49. This pocket 49 is delimited by the paper web 9 and one of the drying cylinders, e.g. the lower drying cylinder 42 and through the opposite, the upper support belt 41 leading suction roller 13 '. So there is a ventilation of the pocket 49 so that the steam vapors emerging from the paper web 9 are better discharged laterally. Another effect of the suction roller 13 'is that the paper web 9 is first sucked into the drying screen 51 or 52 in question at the outlet point of each drying cylinder.

Claims

1. Arrangement with a suction roller (13) with the following features:

a) there is a between the inner surface of a rotatable and perforated roller shell (14) and a extending through the interior of the roller shell stationary air guide (15)

Gap (17);

b) the air guide body (15) - seen in cross section - has a curved guide wall (15 ¹ ), the radial thickness (d) of the intermediate space (17) along the inner circumference of the roll shell (14) - to form a suction zone - with the direction of rotation of the roll shell increases and a pressure zone is formed in another area of the intermediate space;

c) characterized in that - seen in cross section - the curved guide wall extends essentially along the entire inner circumference of the roller shell (14), and in that in the intermediate space (17) only a single sealing arrangement extending over the entire length of the intermediate space ( 16) is provided for the purpose of separating the suction zone from the pressure zone.

2. Arrangement according to claim 1, characterized in that the suction zone, starting from the sealing arrangement (16), extends over at least 2/3, preferably over more than 3/4 of the inner circumference of the roller shell (14).

3. Arrangement according to claim 1 or 2, characterized in that the radial thickness (d) of the intermediate space (17), starting from the outlet side (16a) of the sealing arrangement (16), substantially along the entire inner circumference of the roller shell (14) to increases in the area of the inlet side (16b) of the sealing arrangement.

4. Arrangement according to claim 1 or 2, characterized in that the radial thickness (d) of the

Gap (17) on the inlet side (16b) of the sealing arrangement (16), remains the same or decreases over at most a third (preferably over less than a quarter) of the inner circumference of the roller shell (14).

5. Arrangement according to one of claims 1 to 4, characterized in that the radial thickness (d) of the intermediate space (17) has a maximum value of about 20 to 50 mm.

6. Arrangement according to one of claims 1 to 5, characterized in that the sealing arrangement (16), seen in cross section, has only a single longitudinal sealing strip.

7. Arrangement according to one of claims 1 to 5, characterized in that the sealing arrangement has two sealing strips arranged one behind the other in the circumferential direction at a short distance (16A and 16B).

8. Arrangement according to one of claims 1 to 7, characterized by the use in a single-tier dryer section of a papermaking machine, wherein a paper web to be dried together with a porous support band (10) from a drying cylinder (11) which holds the paper web touches, runs to the suction roller (13) that touches the support belt.

Arrangement according to claim 8, characterized in that the sealing arrangement (16) is arranged in the region of the part of the roll shell circumference which is free from the support band, the distance of the sealing arrangement (16) from the run-up point (A) being smaller than from the run-off point (B ).

10. The arrangement according to claim 9, characterized in that in the part of the roll shell circumference free of the support belt (10) outside the roll shell (14) a stationary, to the roll shell open exhaust air collecting box (18) is arranged.

11. The arrangement according to claim 10, characterized in that the exhaust air collecting box (18) in the region of said sealing arrangement (16) has a longitudinal sealing strip (19) which together with the

Outside of the roll shell (14) seals the interior of the exhaust air collecting box to the outside.

12. The arrangement according to claim 10 or 11, characterized in that the exhaust air collecting box (18) on at least one of its two end walls (21) has an exhaust air opening (22).

13. The arrangement according to claim 12, characterized in that a suction line (23) is connected to the exhaust air opening (22).

14. Arrangement according to claim 10 or 11, wherein the paper web runs in the direction from top to bottom from the drying cylinder (11) to the suction roller (13), characterized in that the exhaust air collecting box (18 ') has at least one exhaust air opening (22) in its upper region.

15. Arrangement according to one of claims 10 to 14, characterized in that the exhaust air collecting box (18) in the region of the discharge point of the paper web and the support belt from the drying cylinder has a suction chamber (24) known per se.

16. Arrangement according to one of claims 10 to 15, characterized in that the exhaust air collecting box (18) - along the path of the support belt (10) from the drying cylinder (11) to the suction roller (13) - has a side wall (28) diverges at a small angle with respect to the tape running direction from the mentioned travel path.

17. Arrangement according to one of claims 10 to 16, wherein the support belt (10) and paper web - after wrapping the suction roll (14) - run from the suction roll to a second drying cylinder (12), characterized in that the exhaust air collecting box (18th ) along the path of the support belt (10) to the second drying cylinder (12) has a second side wall (29) which diverges from the support belt at a small angle with respect to the direction of travel.

18. The arrangement according to claim 17, characterized in that the exhaust air collecting box (18) behind the drain point (B) of the support band (10) of the

Suction roller (13) has a second longitudinal sealing strip (20).

19. Arrangement according to one of claims 1 to 7, characterized by the use in a two-tier dryer section of a papermaking machine, wherein a porous Support belt (51; 52) - without the paper web (9) to be dried - runs over the suction roller (13 '), the support belt forming a looping zone on the suction roller.

20. The arrangement according to claim 19, characterized in that the sealing arrangement (16) is in the region of the wrapping zone.

21. The arrangement according to claim 20, characterized in that the sealing arrangement (16) is in the region of the point where the support belt runs from the suction roller (13 ').