WO2015180955A1

WO2015180955A1 - Filter

Info

Publication number: WO2015180955A1
Application number: PCT/EP2015/060425
Authority: WO
Inventors: Ralf Burger; Melanie Schädler
Original assignee: Voith Patent Gmbh
Priority date: 2014-05-28
Filing date: 2015-05-12
Publication date: 2015-12-03
Also published as: EP3149239A1

Abstract

The invention relates to a filter (8) for fiber suspensions (5), having a shape which is rotationally symmetrical with respect to a filter axis (3) and consisting of a plurality of profiled rods (1) which are arranged in an axially parallel manner relative to one another and between which filter slots (4) are located, said rods being inserted in a clamped manner into open-edge recesses (7) of strip-shaped rod holders (2) which are curved into rings, wherein the two abutting ends of the rod holders are rigidly connected to each other. The strength of the filter (8) and the assembly is improved in that the profiled rod (1) foot (9) located in the rod holders (2) is connected to the rod holders (2) in a formfitting manner, and more than at least 40% of the radial extension of the rod foot (9) is delimited by lateral surfaces (10) which run in a parallel and radial manner.

Description

scree

The invention relates to a sieve for pulp suspensions and its production with respect to a Siebachse rotationally symmetrical shape, consisting of a plurality of mutually axially parallel profiled bars with intervening screen slots, which are clamped in open-edge recesses of bent to rings, strip-like rod holders are used, the two butt ends are firmly connected.

Such screens are used for example for wet screening of pulp suspensions to remove impurities present therein. As a rule, they are rigid and differ from flexible endless screens used in screen presses and paper machines.

The characteristic of such a sieve results essentially from the size, shape and number of sieve openings therein. These are usually kept smaller than the auszusiebenden substances.

A well-known example of the use of cylindrical screening devices is the sorting of pulp suspensions, as is done in pressure sorters of the paper producing industry.

In this case, the fibers contained in the suspension should pass through the sieve, while the unwanted solid constituents are rejected at the gap and are led out of the sieve device again.

The fact that the openings have a substantially elongated shape, that is slots or gaps, allows fibrous particles to pass through more easily than the cubic ones, even though both species should be of similar size. With such a sorting technology, therefore, a very good precipitation effect of non-fibrous contaminants from pulp suspensions is possible.

It is also conceivable use for the separation of different fiber components, the so-called fiber fractionation. Prerequisite, however, is a high precision of the slot shape on the whole screen surface.

A possible method for producing such baskets is shown in DE 10 2006 007 660 A1, in which the profiled bars are clamped by plastic deformation of the bar holders provided with recesses for the bars.

It is important that the dimensions of the screen openings are kept to very tight tolerances. In order to keep them free of blockages, scrapers are usually required, which are moved at a smaller distance past the screen surface and generate the hydraulic impulses. Screening devices for use in pressure sorters must therefore be manufactured very precisely and withstand high loads. Another requirement is a relatively high resistance to hydraulic pressure. Such sieve elements are used in a production plant in which it even comes to disruptions, which leads to different and considerable pressure load of the sieve elements. Since a blockage can not always be ruled out, high pressures and, in the case of correspondingly large areas, even high forces can act on the surface of such screening elements. These increased forces must be able to be absorbed by the sieve without damaging it.

The object of the invention is therefore to simplify its assembly while ensuring a high accuracy and strength of the screen.

According to the invention, this object is achieved in that the rod foot of the profile bars located exclusively in the bar holders is positively connected to the bar holders and the bar base is delimited over at least 40% of its radial extent by parallel and radially extending side surfaces. The positive connection ensures an accurate and stable arrangement of the profile bars in the rod holders. In addition, the opposite, parallel and radially extending side surfaces of the profile bars facilitate insertion into the recesses, especially at low clearance. The small clearance, in conjunction with the parallel side surfaces, in turn prevents tilting of the profiled bars when these are inserted into the recesses.

To improve the flow through the sieve, the slits should expand in the direction of flow, which is why the width of the profiled bars, preferably starting from the parallel side surfaces, increases towards the rod head.

In conjunction with a sieve scraper, beneficial flows can also be generated when the outer surface of the rod heads forms an angle with the radials that is between 60 and 85 degrees. Since the profile bars are pressed radially into the recesses with a tool acting on the rod head, the conical rod head and the inclined outer surface of the rod head increase the risk of tipping the profile bar. This makes a safe guide through the small game and the parallel side surfaces even more important.

In order to make full use of this advantage, the rod foot should be delimited over at least 50%, preferably at least 60% and / or over at least 3 mm, preferably at least 4 mm, of its radial extension of parallel side surfaces.

A positive connection between the profiled bar and bar holder can be produced in a particularly simple and secure manner by virtue of the fact that the bar holders and the profiled bars each have at least one axially extending recess or a corresponding projection. This allows a click connection between the profile bar and rod holder, so that the profile bars after their insertion already without Clamping are sufficiently fixed.

In the interest of a simple solution, the profile bars should each have an axially extending recess and the rod holder has a corresponding axially extending projection for realizing a positive connection between the two.

To support a tilt-free insertion of the profile bar while the width of the profile bars before and after the recess should be about the same size.

For the same reason, it is advantageous regardless of the number of recesses and projections, when recess and projection are arranged in the bar head opposite half of the rod foot.

The sieve according to the invention can be produced particularly advantageously from C-shaped rod holders. These should be produced by means of a cutting process, preferably by means of laser cutting. In this way, the strength can be significantly increased by the lack of stress due to the deformation of straight rod holder.

After fitting the C-shaped rod holder with the profile bars, the two butt ends of the rod holder are brought together and connected by bending the rod holder.

As a result, the rod holder are brought into a circular ring shape and the recesses slightly compressed, resulting in the clamping of the profile bars.

Since this only leads to a predominantly, preferably completely elastic deformation of the rod holder, this hardly affects the strength of the rod holder.

Depending on the direction of flow of the sieve, their structure differs and thus also their manufacture. In a centrifugally flowed sieve, the recesses should be on the inside the rod holder be present and the C-shaped rod holder for clamping the profile bars in the recesses are compressed to the ring shape.

In contrast, in a centripetal through-flow sieve the recesses should be present on the outside of the rod holder and the C-shaped rod holder for clamping the profile bars in the recesses are expanded to the ring shape.

The invention will be explained in more detail with reference to an exemplary embodiment. In the attached drawing shows:

Figure 1: a pressure sorter for pulp treatment;

Figure 2: a cylindrical sieve 8 of the pressure sorter;

Figure 3: the insertion of a profile bar 1 in a rod holder 2 and

Figure 4: a partial section through a rod holder 2 with profiled bars. 1 FIG. 1 shows a pressure sorter with a cylindrical sieve 8, here with a vertical sieve 3, which divides the interior of the pressure sorter into an inlet space 16 and an accepts space 17.

Into the inlet space 16, via a suspension inlet 18, the medium 5 to be treated, i. fed to the pulp suspension.

In the pressure sorter used here, the pulp suspension 5 receives an angular momentum which causes it to move circumferentially. In addition to this, a transport flow is generated as a result of the applied pressure gradient between the above-drawn suspension inlet 18 and the underlying Rejektauslauf 19 of the inlet chamber 16.

On the way of this transport flow, a large part of the pulp suspension 5 is intended derived by the sieve surface of the screen 8 as accepts 20 in the accepts space 17 and discharged from there via the accepts 21. At the same time, at least a large part of the fibers contained in the pulp suspension 5 also passes into the accept chamber 17. The rejected from the sieve 8 part of the pulp suspension 5 is conveyed as a reject 22 via the Rejektauslauf 19 from the feed chamber 16.

In order to prevent the screen openings are blocked, a known Siebräumer is used, which moves relative to the screen surface.

By way of example, this sieve scraper is formed by a rotor 23 rotating in the cylindrical sieve 8 with rotor blades 24 fastened thereto. In this case, the rotor 23 has the shape of a cylindrical drum, wherein the axis of rotation 6 coincides with the Siebachse 3.

All rotor blades 24 in this case have the same shape, which leads to a uniform effect on the pulp suspension 5 and the screen cylinder. In addition, the rotor blades 24 are arranged distributed over a plurality of perpendicular to the axis of rotation 6 extending circumferential planes of the rotor 23.

In FIG. 1, the rotor vanes 24 are designed, for example, as elevations on the rotor 23. According to FIG. 2, the cylindrical sieve 8 consists of a multiplicity of profile bars 1 extending parallel to the cylinder axis or sieve line 3, which are held over a plurality of bar holders 2, which are spaced apart axially from one another and extend perpendicular to the cylinder axis.

The screen openings of the screen 8 are formed by the slots 4 adjacent profiled bars 1. In practice, such slots 4 often have a width between 0.05 and 2 mm.

The C-shaped, strip-like rod holder 2 are produced as one-piece rings, for example by means of laser cutting, wherein the diameter is slightly larger or smaller than the final screen cylinder. This is the basis for a high dimensional accuracy of the screen 8.

In the example shown in Figures 1 and 2, the pulp suspension 5 flows centrifugally, i. from inside to outside through the sieve 8. Accordingly, the profile bars 1 are supported on the inside of the rod holder 2 from.

For this purpose, have the rod holder 2 on the inside a plurality of evenly distributed, open-edged recesses 7 for the profile bars. 1

After the introduction of the profile bars 1 shown in Figures 3 and 4 in the recesses 7, the two butt ends of the rod holder 2 are brought together and welded.

This deformation leads to a narrowing of the recesses 7, which leads to the clamping of the profile bars 1 because of the complementary shape. In a centripetal flow through the screen 8, the open-edged recesses 7 are arranged on the outside of the rod holder 2 and the diameter of the C-shaped rod holder 2 during assembly with the profile bars 1 slightly smaller than the screen cylinder.

After placement, it also comes as a result of the expansion of the rod holder 2 for clamping the profile bars 1 in the recesses. 7

In both cases, the only small diameter change also leads

only for elastic and therefore gentle and uniform deformation of the rod holder 2, which has a positive effect on their strength.

An additional attachment of the profile bars 1 can be dispensed with as a rule.

The profile bars 1 have outside the recess 7 a rod head 1 1 and a rod holder 9 fixed in the rod holder 9. It is essential here that the rod feet 9 and thus the corresponding recesses 7 in the rod holders 2 over here About 50% or 4 mm of their radial extent of parallel and radially extending side surfaces 10 are limited.

This shape allows a small clearance between profile bar 1 and

Recess 7 and also prevents tilting of the profile bars 1 when inserted into the recesses. 7

In order to achieve a fixation of the profile bars 1 in the recesses 7 of the rod holder 2 before clamping, the profile bars 1 each have an axially extending recess 14 and the rod holder 2 has a corresponding axially extending projection 15 to realize a click connection between the two. This facilitates the assembly considerably, for the projection usually already a height of 0.15 mm is sufficient.

When forming the C-shaped rod holder 2, this positive connection amplified even further. To ensure safe insertion of the profile bars 1 in the recesses 7 according to Figure 3, the width of the profile bars 1 before and after the recess 14 is about the same size.

Again, a tilting of the profile bars 1 during insertion can be avoided by recess 14 and projection 15 in the rod head 1 1

opposite half of the rod foot 9 preferably close to the end of

Profile bar 1 are arranged.

To improve the flow through the screen 8, the width of the profile bars 1 increases starting from the parallel side surfaces 10, starting from the rod head 1 1, so that a conical cross section of the rod head 1 1 results. As a result, this leads to a widening of the screen slots 4 in the flow direction, which prevents clogging of the screen 8.

In order to flow in conjunction with the arranged before the screen 8 rotor 23 better to exploit, the outer surface 12 of the rod heads 1 1 forms with the radial 13 an angle between 60 and 85 °.

Since the forces required for the insertion of the profile bars 1 in the recesses 7 act on this outer surface 12, there is a high risk of tilting. Above all, that the rod feet 9 substantially have a constant width and are inserted radially with little play, is very helpful in avoiding the tilting.

Claims

Claims 1. Sieve (8) for pulp suspensions (5) with respect to a Siebachse (3) rotationally symmetrical shape, consisting of a plurality of mutually axially parallel arranged profile bars (1) with intervening screen slots (4), the clamping in edge-open recesses (7) of Rings bent, strip-like rod holders (2) are used, the two butt ends are firmly connected, characterized in that in the rod holders (2) located bar base (9) of the profile bars (1) is positively connected to the rod holders (2) and the rod base (9) is delimited over at least 40% of its radial extent by parallel and radially extending side surfaces (10).

2. sieve (8) according to claim 1, characterized in that the width of the profile bars (1), preferably from the parallel side surfaces (10) starting from the rod head (1 1) increases.

3. sieve (8) according to claim 1 or 2, characterized in that the

Outer surface (12) of the rod heads (1 1) with the radial (13) forms an angle which is between 60 and 85 °.

4. sieve (8) according to any one of the preceding claims, characterized in that the rod base (9) over at least 50%, preferably at least 60% of its radial extent of parallel side surfaces (10) is limited.

5. sieve (8) according to any one of the preceding claims, characterized in that the rod foot (9) over at least 3 mm, preferably at least 4 mm its radial extent is limited by parallel side surfaces (10).

6. sieve (8) according to any one of the preceding claims, characterized in that the rod holder (2) and the profile bars (1) each have at least one axially extending recess (14) or a corresponding projection (15) for realizing a positive connection between the two have.

7. sieve (8) according to claim 6, characterized in that the profiled bars (1) each have an axially extending recess (14) and the rod holder (2) has a corresponding axially extending projection (15) for realizing a positive connection between the two.

8. sieve (8) according to claim 7, characterized in that the width of the profile bars (1) before and after the recess (14) is approximately equal.

9. sieve (8) according to one of claims 6 to 8, characterized in that

Recess (14) and projection (15) in which the rod head (1 1) opposite half of the rod foot (9) are arranged.

10. A method for producing a sieve (8) according to any one of the preceding claims, characterized in that C-shaped rod holder (2) equipped with the profile bars (1) and the two butt ends of the rod holder (2) by bending the rod holder (2) be merged and connected.

1 1. A method according to claim 10, characterized in that the C-shaped rod holder (2) are produced by means of a cutting process.

12. The method according to claim 10 or 1 1, characterized in that in a centrifugally flowed sieve (8), the recesses (7) on the inside of the Rod holder (2) are present and the C-shaped rod holder (2) for clamping the profile bars (1) in the recesses (7) are compressed to form a ring.

13. The method according to claim 10 or 1 1, characterized in that in a centripetal flowed sieve (8), the recesses (7) on the outside of the rod holder (2) are present and the C-shaped rod holder (2) for clamping the profile bars (1) are widened in the recesses (7) to the ring shape.

14.Verfahren according to claim 12 or 13, characterized in that the

Deformation of the C-shaped rod holder (2) predominantly, preferably completely elastic takes place.