EP1337344B1 - Solid bowl screw centrifuge comprising a distributor - Google Patents

Abstract

The invention relates to a solid bowl screw centrifuge comprising a centrifuging chamber (19) having a rotating screw (1) and a likewise rotating drum (21) surrounding the centrifuging chamber (19), in addition to a distributor (15) which is preferably embodied as a tube and is used to introduce the material to be centrifuged (S) into the centrifuging chamber (19). Said distributor is oriented in a angular manner, especially perpendicularly, in relation to the central axis (A) of the screw (1). The material to be centrifuged is guided through an axially extending inflow tube (13) into the distributor (15). At least one wall (15a) of the distributor is provided with a surface structure consisting of projections (27) in such a way that the main part of the material to be centrifuged (S) which passes through the distributor must flow around at least one of the projections (27) on the at least one wall (15a) on the radial path from the inflow tube (13) to the centrifuging chamber (19).

Description

The invention relates to a solid bowl screw centrifuge according to the preamble of claim 1.

The prior art is known from DE 1 272 231. The Protrusions serve to grind the solids.

For solid bowl centrifuges, the product to be centrifuged should be at the peripheral speed the screw at the diameter of the liquid level (surface) be accelerated in the screw channel. Here is the relative speed to be as low as possible when entering the centrifugal space (liquid surface).

In the distributor caused by the acceleration to the peripheral speed the screw on the liquid level diameter at the Mitnehmerwänden (the Distributor) a surface flow whose velocity with the radius strong increases, to a value which is approximately equal to the peripheral speed the worm is at the liquid level diameter.

From US 5,403,486 ist.es known, the range of Schleudergutzufuhr - ie in broad sense the distributor - a Vollmazitel-centrifuge with a larger number of outlet openings to be provided, which at different angles aligned with each other. However, this solution is relatively expensive, In addition, no lowering of the relative speed is achieved.

From DE 1 293 089 it is also known, nozzle-like distribution openings in the Cover centrifugal space with a baffle plate, which deflects the centrifugal material, to reduce currents. This measure is enough for an effective reduction but not from turbulences.

It is therefore the object of the invention, the generic solid bowl screw centrifuge in such a way that the relative speed of the Spinning material when entering into the liquid surface on structurally simple Way is reduced.

The invention solves this problem by the subjects of claims 1 and 19th

Advantageous embodiments are specified in the subclaims.

Thereafter, at least one wall of the distributor with a Surface structure of at least two or more radially offset from each other Provided rows of projections, wherein the projections of the rows to each other in such a way axially offset, that substantially no radial free flow channels are formed on the wall.

Thus, at least one wall of the distributor is so with a surface structure of projections provided that the essential part dea the splitter flowing through centrifugally good at this at least one wall on the substantially radial and / or substantially in the direction of Centrifugal extending distance from the inlet pipe into the centrifugal space at least must flow around one of the projections.

It will be effective and yet simple and relative cheap way ensured that at least the essential part, preferably but the entire centrifugal material no longer on a direct radial path from the inlet pipe can flow into the spin room. Under "radial" here is the direction to understand the Verteilerwandung in which the centrifuged by turning the Distributor by the centrifugal force substantially flow into the centrifugal space wants, i. The term "radial" may also include an axial component of motion and / or a peripheral component. It is important that at least the essential Part of the centrifugal material not directly "in the direction of centrifugal force" in the Centrifugal space flows.

Although it is already known from DE PS 1 272 231, some of the distributor wall to form grinding (smashing) bodies. Between these bodies exist however, still direct paths radially into the centrifugal space, so that the liquid essentially not braked but with unchanged high radial velocity enters the centrifugal space. The possibility of using protrusions to reduce the relative velocity of the material to be centrifuged Entry into the liquid surface in a structurally simple way was here not recognized.

After a structurally particularly simple and yet particularly effective Variant are the projections as circular in cross-section, diamond-shaped or other n-shaped pimples trained.

In other variants, however, the projections have a meander shape. Here as well as for further embodiments, it is advantageous if the projections are formed as sheets.

After a further, independently considered variant is at least one Wall of the distributor with a circumferentially extending, staircase-like Surface structure provided, which also a braking, u.a. by Turbulence, causes.

Fig. 1

eine Schnittdarstellung einer Vollmantel-Schneckenzentrifuge;

Fig. 2

den Einlaufbereich eines Verteilers in einen Schleuderraum einer Vollmantel-Schneckenzentrifuge;

Fig. 3

eine schematische Darstellung eines Schnittes durch die Trommel der Fig. 1;

Fig. 4a-e

verschiedene zylindrische Noppenanordnungen;

Fig. 5-11

verschiedene Strukturen von Vorsprüngen an Wandungen von Verteilern;

Fig. 12

ein Diagramm zur Veranschaulichung der Geschwindigkeiten des Schleudergutes.

Embodiments will be described in more detail with reference to the drawing. It shows:

Fig. 1

a sectional view of a solid bowl screw centrifuge;

Fig. 2

the inlet area of a distributor into a centrifugal space of a solid bowl centrifuge;

Fig. 3

a schematic representation of a section through the drum of Fig. 1;

Fig. 4a-e

various cylindrical knob arrangements;

Fig. 5-11

various structures of protrusions on walls of manifolds;

Fig. 12

a diagram illustrating the velocities of the spinning material.

Fig. 1 shows a solid bowl screw centrifuge with a screw 1, a Screw body 3 and here a worm-like surrounding the screw body 3 Schneckenblatt 5 has. Between the worm threads x, x + 1, ... is a Screw channel 7 for conveying / transporting a centrifugal material to be processed educated.

The screw body 3 has in its rear in Fig. 1 area a cylindrical Section 9 and in his in Fig. 1 adjoining the front area a stepwise (alternatively conical) tapered section 11.

Centrifugal S is through the centrally arranged inlet pipe 13 into a manifold 15 and from there through radial openings 17 in the manifold 15 in the centrifugal space 19 with the screw 1 and the screw 1 surrounding drum 21 passed.

When passing through the distributor 15 and when entering the centrifugal chamber 19 the centrifugal material S accelerates. Set by the action of centrifugal force The solid particles in a short time on the drum wall.

The screw 1 rotates at a speed slightly lower or higher than the drum 21 and conveys the ejected solid F to the tapered portion 11 out of the drum 21 for solids 23.

On the other hand, the liquid L flows toward the larger drum diameter at the rear End of the drum 21 and is derived there (overflow 25).

Below is the structural design of Schleudergutzufuhr from the inlet pipe 13 in the centrifugal space 19 - ie in particular the structure of the distributor 15 - be considered closer.

Reference is first made to Fig. 2.

Fig. 2 again shows the inlet pipe 13, which projects into the manifold 15, the here has a substantially rectangular cross-section (perpendicular to the image plane 2) or is formed substantially as a rectangular tube. Alternative training are of course conceivable, so a training of the distributor as Pipe construction of two intersecting rectangular pipes or pipes, which not perpendicular to the drum axis but at any angle to this aligned are. Furthermore, deviating cross-sectional geometries are also of a rectangular cross-section realizable.

The entering into the manifold 15 centrifugal S moves at the moment of Outlet from the inlet pipe 13 with the axial flow velocity in the inlet pipe 13. When entering the distributor 15, it is then taken from the distributor 15. The centrifuged material S thus rotates with the distributor 15 and moves This is due to the centrifugal force in the manifold 15 substantially radially outward.

In the area of the openings 17 at the outer radial edge of the distributor 15 has the Spun the absolute velocity x (see Fig. 3), with which it the distributor 15 leaves (see also Fig. 3). The velocity vector x has both a Component u in the circumferential direction of the drum 21 as well as a component v - Called relative speed. The relative velocity v can be both a Component in the radial direction as well as other components in others Directions (e.g., axially).

For many products to be spun, the relative velocity component should be v when entering the sling in the centrifugal chamber 19 as small as be possible, for example, in products which are relatively strong for foaming tend or have sensitive structures, just not as in the state of Technology may be destroyed or damaged (e.g., flocculants that are not to be destroyed). The S should therefore ideally only with the Circumferential rotational speed of the screw body 3 and without relative speed v (see also Fig. 12) enter the centrifugal space.

In order to reduce the relative velocity v or in particular a too large To prevent acceleration in the radial direction is provided, at least the walls 15a, d of the distributor, which in the opposite Ends of the distributor 15, the centrifuged material substantially during the rotation of the Take distributor 15 - or in addition the vertical side walls 15b (or alternatively also all walls) of the distributor with a surface structure to be provided, which in particular formed directly on the wall 15a, d or on at least one separate, attachable to the wall Sheet 29 formed projections 27 may consist. Also a multilayer arrangement of several superimposed sheets 29 with projections 27 is feasible (Fig. 3).

The projections 27 are so on the at least one wall 15 a of the manifold 15 distributes that at least the majority of entering the distributor 15 Spun material S on the radial path to the outside at least one, but preferably several - the projections 27 must flow around.

The at least one wall 15a is to ensure a sufficient "Braking effect" also preferably substantially in such a way with the projections 27 provided that substantially no radial (or perpendicular outward facing) remain free flow paths 33 for the centrifuged.

Preferably, on an area of 30 to 70% of the at least one wall 15a of the distributor 15, the projections 27 distributed.

Preferably, the projections 27 are further at least in the radially outer region the distributor wall 15a, d formed. This has the following advantage.

Since the centrifugal force proportional to the square of the angular velocity and proportional to the radius r behaves (F _z = mω ² r), it is immediately clear that the acceleration of the centrifuged material in the outer radial region of the manifold 15 is greater than in the inner region, so that in outer radial region of the manifold 15a, the braking effect of the projections 27 of this acceleration particularly advantageous counteracts. For this reason, the projections 27 are preferably also formed to the outer radial edge of the manifold 15 and to the discharge opening 17 on the wall 15 a of the manifold 27. The radially inner part of the distributor (eg the inner 30 or 50% of the wall surface of the wall 15a), however, can be smooth, ie formed vorsprungsfrei without the "braking effect" is substantially reduced.

Since the centrifugal acceleration also increases with increasing radius, Also, a variant of the invention has proved to be particularly advantageous in which at least one or more wall (s) 15a, d of the distributor or the on the wall 15 a patch plate 29 with the projections 27 radially over the Edge of the opening 17 projects into the centrifugal space.

According to Fig. 2, the projections 27 as cylindrical nubs 27 a, b - preferably different diameter - formed, which in holes 31 of the wall 15a attached, e.g. are welded.

Alternative geometries are conceivable, such as triangular cross sections, rectangular cross sections, Diamonds etc.

The projections 27 may also widen away from the wall 15 a or also rejuvenate. Also ball-like shapes are conceivable.

The extent of the projections 27 perpendicular to the distribution wall 15a is such in each preferred application (e.g., fruit juice recovery etc.) and at maximum throughput of centrifugal the projections 27 at least are as high as the liquid level on the wall 15a. Preferably the protrusions are about twice as high as the average liquid level.

The projections may alternatively be formed as rods, which the Distributor 15 from the wall 15a to the opposite wall 15d push through.

The knobs 27 can also be formed as forms or in others Way directly integrally formed with the wall 15 a, d or the sheet 29 be. This one-piece forming can be done in the casting or by milling the nub structure out of a correspondingly thick wall plate.

2 is an inner radial region of the wall 15 a vorsprungs- or designed noppenfrei. At this inner radial area, a middle closes radial region with four parallel to the drum axis A aligned rows Nubs 27a, which each have a first diameter a. At the middle The area is followed by an outer area with three rows of nubs 27b, which have a smaller diameter b than the diameter a and also closer to each other, so that between the nubs 27b extending, obliquely to the drum axis A aligned flow channels 33b narrower than the flow channels remaining between the wider knobs 27a 33a.

The nubs 27a, b are each arranged in rows, which are parallel to the drum axis A are aligned. The rows are so half of each other Distance between two adjacent nubs 27 a, b axially offset arranged that the Centrifugal S is denied a direct flow in the radial direction. Of the axial distance d of the knobs 27a, b to each other here is slightly larger than that Diameter of the nubs 27a, b. The distance between the centers of the knobs in radial Direction corresponds approximately to their diameter a, b.

The knobs 27, according to Fig. 2, a radially outwardly gradually smaller Expected diameter. The Durchströmkanäle 33 are also smaller or narrower. This training causes an increasing braking of the Spin good radially from the inside out, that is, it acts the increasing Acceleration due to the increasing centrifugal force. It will the path to be covered for the goods S to spin around the nubs 27a, b longer.

4 to 10 show further variants of nub structures.

According to Fig. 4a, the rows of nubs 27a are each about the diameter of Nubs offset from one another, wherein the distance between the centers or Central axes of the cylindrical knobs 27a in each row each have the diameter d of the nubs 27a corresponds.

From FIGS. 4a to 4d, the axial offset of the rows of knobs is in each case relative to one another reduced. In a direction oblique to the drum axis A arise here obliquely outwardly pointing, narrowing flow channels 33. Also These can be completely avoided if the diameter of the nubs 27a, b as in Fig. 2 or the offset of the rows of nubs from row to row varies or even is further reduced (see Fig. 4e). By a suitable design of the rows of nubs can be achieved a variety of flow characteristics.

It is conceivable to make the nubs using pot cutters. For the pimples are various materials such as steel, cast iron or even plastics conceivable. plastic has the advantage that the knobs are slightly flexible or movable, which is the Can increase braking effect.

Fig. 4e shows a variant in which the nubs of a row such a small Distance from each other, that at an axial offset of the rows of knobs by half the distance between two adjacent knobs no perpendicular to the central axis A centrifuge extending linear flow channels 33 remain.

According to Fig. 5, the projections are diamond-shaped. The connecting lines the peaks of the diamonds 227 are perpendicular and parallel to the central axis A of Centrifuge. The peaks of the diamonds 227 also show in the various diamond rows to each other, wherein between the diamonds 227 flow channels 33 in oblique or inclined direction to the central axis remain. The flow channels 33 or diamonds 227 can be e.g. produce by a milling process.

Fig. 6a shows a variant of the invention in which instead of rows of nubs at least two rows of sheet metal strips 127 on the wall 15 a of the distributor are attached.

These metal strips 127 are each aligned at an angle to the central axis A of the centrifuge and are so close to each other in opposite angularly offset In turn, that no flow channels in the radial direction at the Verteilerwandung remain but a strong deflection and deceleration occurs. The angle here is about 30 °. The smaller the angle to the central axis, the better the speed must be higher, so that no deposits on the sheet metal strip form. The angle could also be reduced to the outside, possibly to to the value 0.

The metal strips 127 could not be perpendicular to the screw body but any angle (see Fig. 6b) and / or L- or U or T-shaped design and / or arranged (see, by way of example, FIGS. 6c and 6d). In places at high speed, the angle to the central axis should be greater than Set at lower speed.

A variant shows Fig. 7. A first very flat plate 127 leads to strong deceleration into a labyrinth arrangement 128 of further bent sheets 127, which is designed so that again no radial flow is possible.

According to Fig. 8, the projections have a kind of meandering shape. The zigzag-like Meander 327 engage each other in such a way that again no flow channels radially remain outside in the distributor 15.

According to Fig. 9 to 11 is a kind of stair-like surface structure (step construction 427) realized in the manifold 15 and on the walls 15a of the distribution shaft Service. Both in Fig. 9 and in Fig. 10, the liquid flow over Flow "steps" in the circumferential direction. Optimal is the effect here again, though the step construction extends into the liquid level.

According to Fig. 9, the step contour is made of a plurality of sheets 428, alternatively For example, the contour can also be shaped (for example milled) out of a workpiece.

The sheets 428 have an angular cross-section, i. they each consist of one substantially parallel to the distribution wall extending portion 428a and an angled section 428b, which here exemplifies an inclination of about 30 ° to the vertical on the distributor wall has.

The section 428a extending substantially parallel to the distributor wall of the first sheet 428 is placed directly on the distributor wall. The parallel to the distribution wall 428 a extending portions of the following plates 428 are respectively at the backsides of the angled portions 428b of the preceding panels attached so that between the successive sheets 428 a kind Verwirbelungsraum arises.

This arrangement has the following advantages.

The liquid jet hits from one step or sheet 428 to the next Step or the next sheet 428, he (in Fig. 9 to the left and right) in the flow direction and directed and swirled against it in different directions, which in turn causes a braking effect.

Since the plates 428 are offset from each other, the liquid jet moves slightly opposite to the direction of rotation (in Fig. 9 and 10 to the right, arrow P3) along the dashed line.

When hitting the liquid is split in the direction of rotation and opposite the direction of rotation (arrows P1, P2). This division and the turbulence of the Strahles ensures a particularly advantageous braking effect. The braking effect is here almost from the effect of the oblique sections of the sheets 428 and the shadow effect of the turbulences (arrow P2).

FIG. 10 differs from FIG. 9 not only in that the step construction 427 was realized in one piece from a cast or milled part, but that the step construction is designed such that the substantially parallel to the distribution wall extending portion 429a of the steps 429 respectively at the ends of Angled portions 429b of the preceding stage connects, so that between the successive stages no turbulence space arises.

An alternative to FIGS. 9 and 10 is shown in FIG. 11. In this figure, a kind of "waterfall brake feed" is shown. realized. Again, a kind of stepped contour 427 is realized however, the individual stages 430 will again be essentially through formed parallel to the drum axis extending rows of protrusions 431 or in a plate grooved rows 432 are milled. The rows of grooves 432 have again an angled cross section, i. they each consist of one substantially parallel to the distributor wall extending portion 432a and an angled section 432b, which here by way of example has an inclination of about 30 ° to the vertical on the distributor wall has. The respectively essentially parallel to the distribution wall extending portions 432a of the rows of grooves are substantially aligned with each other, that is, they lie in one plane, which is the production compared to the variant of FIG. 10 cheaper (less waste during milling or less casting material required). It is advantageous in the case shown here For example, the inclined portion 432b makes an angle of about 30 ° to the vertical on the Verteilerwandung and that the impact of the liquid jet to the next stage also at an angle of e.g. 30 °.

LIST OF REFERENCE NUMBERS

slug

1

screw body

3

screw blade

5

screw channel

7

cylindrical section

9

rejuvenating section

11

inlet pipe

13

distributor

15

walls

15a-d

discharge

17

centrifugal chamber

19

drum

21

solids

23

overflow

25

projections

27

burl

27a, b

sheet

29

drilling

31

flow channels

33

metal strip

127

labyrinth arrangement

128

diamonds

227

Meander

327

stage design

427

sheets

428

sections

428a, b

stages

429

stages

430

projections

431

rows of grooves

432

sections

432a, b

drum axis

A

centrifuged

S

Diameter: pimples

a, b,

Distance: nubs axially

d

screw flights

x, x + 1, ...

centrifuged

S

solid fuel

F

liquid

L

radius

r

tilt angle

α, α1

arrows

P1-P3

Claims (26)

1. Solid-bowl screw centrifuge, which includes:

   a) a rotating drum (21), which surrounds a centrifuging space (19) with a screw (1) which likewise rotates,

   b) a distributor (15) which is preferably designed as a tube, for introducing material (S) which is to be centrifuged into the centrifuging space (19), which distributor is oriented at an angle, in particular perpendicular, to the centre axis (A) of the screw (1), the material to be centrifuged being passed through an axially extending feed tube (13) into the distributor (15),

   c) at least one wall (15a) of the distributor being provided with a surface structure made up of projections (27),
   characterized in that

   d) at least one wall (15a) of the distributor is provided with at least two or more rows of the projections (27) which are radially offset with respect to one another, the projections (27) of the rows being axially offset with respect to one another in such a manner that substantially no radial flow passages and/or flow passages extending substantially in the direction of the centrifugal force are formed at the wall (15a).
2. Solid-bowl screw centrifuge according to Claim 1, characterized in that the projections are designed as studs (27) which are circular, diamond shaped or in some other polygonal form in cross section.
3. Solid-bowl screw centrifuge according to Claim 1, characterized in that the projections (227) are meandering in form.
4. Solid-bowl screw centrifuge according to Claim 1, characterized in that the projections (127) are formed as sheet-metal strips and/or are produced by welding, milling or the like.
5. Solid-bowl screw centrifuge according to Claim 4, characterized in that the sheet-metal strips (127) are each oriented at an angle - preferably 30° - to the centre axis A of the centrifuge and are arranged in such tight rows, in particular rows which are angle-offset with respect to one another, that no through-flow passages in the radial direction remain at the distributor wall.
6. Solid-bowl screw centrifuge according to Claim 5, characterized in that the angles (α) preferably between the sheet-metal strips (127) and the centre axis A decrease with an increasing radius of the distributor (15) or at an increasing distance from the drum axis.
7. Solid-bowl screw centrifuge according to one of Claims 4 to 6, characterized in that the sheet-metal strips (127) form a labyrinth with respect to the centrifuging space.
8. Solid-bowl screw centrifuge according to Claim 2, characterized in that the studs (27) have a contour which narrows or widens from the wall of the distributor (15) or is circular or spherical or is constant in diameter.
9. Solid-bowl screw centrifuge according to Claim 2 or 8, characterized in that the studs (27) are formed integrally with the wall (15a) or the metal sheet (29).
10. Solid-bowl screw centrifuge according to Claim 9, characterized in that the studs (27) are welded into bores in the metal sheet (29) or the wall (15a).
11. Solid-bowl screw centrifuge according to one of Claims 2 or 8 to 10, characterized in that the height of the studs (27) substantially perpendicular to the wall (15a) is such that at a maximum throughput of material (S) to be centrifuged, the liquid level at the wall (15a) is lower than the height of the studs.
12. Solid-bowl screw centrifuge according to one of the preceding Claims 2 or 8 to 11, characterized in that the diameter and/or spacing of the studs (27) decreases in the radially outward direction.
13. Solid-bowl screw centrifuge according to one of the preceding Claims 2 or 8 to 12, characterized in that the diameter and/or the spacing of the studs (27) is constant in the radially outward direction.
14. Solid-bowl screw centrifuge according to one of the preceding claims, characterized in that the wall (15a) provided with the projections or the metal sheet (29) on the wall together with projections extend over the circumferential wall of the screw body into the centrifuging space (19).
15. Solid-bowl screw centrifuge according to one of the preceding claims, characterized in that the projections (27) are formed at least in the outer radial region of the distributor (15).
16. Solid-bowl screw centrifuge according to one of the preceding claims, characterized in that the surface structure with the projections (27) covers at least 40% of the area of the wall (15a).
17. Solid-bowl screw centrifuge according to one of the preceding claims, characterized in that a plurality of layers, located above one another, of metal sheets provided with the projections are arranged in the distributor (15) on the at least one wall (15a), so that the flow of material to be centrifuged flowing through the distributor is divided into a number of parts.
18. Solid-bowl screw centrifuge according to one of the preceding claims, characterized in that the projections (27) and/or the metal sheet which receives the projections consist of steel, cast iron or plastic or rubber.
19. Solid-bowl screw centrifuge which includes:

    a rotating drum (21), which surrounds a centrifuging space (19) with a screw (1) which likewise rotates,

    a distributor (15) which is preferably designed as a tube, for introducing material (S) which is to be centrifuged into the centrifuging space (19), which distributor is oriented at an angle, in particular perpendicular, to the centre axis (A) of the screw (1),

    the material to be centrifuged being passed through an axially extending feed tube (13) into the distributor (15), characterized in that

    at least one wall (15a) of the distributor is provided with a staircase-like surface structure - stepped construction (427) - extending in the circumferential direction.
20. Solid-bowl screw centrifuge according to Claim 19, characterized in that the stepped construction (427) comprises a plurality of metal sheets (428) which lie on top of/against one another in the circumferential direction.
21. Solid-bowl screw centrifuge according to Claim 19, characterized in that the stepped construction (427) comprises a single-piece metal or plastic body.
22. Solid-bowl screw centrifuge according to Claim 20, characterized in that the metal sheets (428) have an angular cross section and each comprise a section (428a) running substantially parallel to the distributor wall and a section (428b) at an angle with respect thereto.
23. Solid-bowl screw centrifuge according to one of the preceding Claims 20 or 22, characterized in that the section (428a) of the first metal sheet (428) which runs substantially parallel to the distributor wall has been placed directly onto the distributor wall, and in that the sections of the following metal sheets (428) which run parallel to the distributor wall (428a) are each arranged on the rear sides of the angled sections (428b) of the preceding metal sheets, so that a swirl space is formed between the successive metal sheets (428).
24. Solid-bowl screw centrifuge according to one of the preceding Claims 19-23, characterized in that the stepped construction is designed in such a manner that the section (429a) of each step (429) which runs substantially parallel to the distributor wall in each case adjoins the end of the angled section (429b) of the preceding step.
25. Solid-bowl screw centrifuge according to one of the preceding Claims 19-24, characterized in that the individual steps (430) are formed by rows of grooves (432) which run substantially parallel to the drum axis and preferably have an angled cross section.
26. Solid-bowl screw centrifuge according to one of the preceding Claims 19 to 25, characterized in that the sections (432a) of the rows of grooves (432) which in each case run substantially parallel to the distributor wall lie substantially in one plane.

Images