EP3573762B1 - Stirring mill - Google Patents

Description

• wobei aus einem dem ersten Ende des Mahlbehälters entgegengesetzten zweiten Ende des Mahlbehälters ein Mahlgut-Auslass ausmündet,
• wobei die Rührwelle einen dem Mahlgut-Einlass benachbarten, einen ersten Mahlraum-Bereich begrenzenden ersten Rührwellen-Abschnitt geringeren Durchmessers D24 und einer Länge und einen dem Mahlgut-Auslass benachbarten, einen zweiten Mahlraum-Bereich begrenzenden zweiten Rührwellen-Abschnitt größeren Durchmessers D25 und einer Länge aufweist, wobei gilt: D25 > D24, und wobei zwischen dem ersten Rührwellen-Abschnitt und dem zweiten Rührwellen-Abschnitt ein dem ersten Rührwellen-Abschnitt zugerechneter Übergangs-Abschnitt ausgebildet ist,
• wobei der zweite Rührwellen-Abschnitt einen Hohlraum aufweist, der durch einen Boden gegenüber dem ersten Rührwellen-Abschnitt abgeschlossen ist und eine Länge zum ersten Rührwellen-Abschnitt hin aufweist, und in dem ein mit dem Mahlgut-Auslass verbundenes, im Abstand vor dem Boden endendes Sieb angeordnet ist,
• wobei der zweite Rührwellen-Abschnitt den Hohlraum mit dem zweiten Mahlraum-Bereich verbindende Schlitze aufweist, und wobei die Länge L27 des Hohlraums in Richtung zum ersten Rührwellen-Abschnitt hin geringer ist als die Länge L25 des zweiten Rührwellen-Abschnitts.

The invention relates to an agitator mill with a horizontally arranged grinding container which has a cylindrical inner wall, with an agitator shaft arranged in the grinding container and drivable about a common central longitudinal axis in a driving direction of rotation, with a grinding chamber delimited by the inner wall and the agitator shaft, whereby a ground material inlet opens into the grinding chamber at a first end,

• wherein a ground material outlet opens out from a second end of the grinding container opposite the first end of the grinding container,
• wherein the agitator shaft has a first agitator shaft section of smaller diameter D24 and a length, adjacent to the regrind inlet and delimiting a first grinding chamber area, and a second agitator shaft section of larger diameter D25 and a length, adjacent to the regrind outlet and delimiting a second grinding chamber area has, whereby the following applies: D25 > D24, and a transition section assigned to the first stirring shaft section is formed between the first stirring shaft section and the second stirring shaft section,
• wherein the second agitator shaft section has a cavity which is closed by a floor opposite the first agitator shaft section and has a length towards the first agitator shaft section, and in which a cavity connected to the ground material outlet ends at a distance in front of the floor sieve is arranged,
• wherein the second agitator shaft section has slots connecting the cavity with the second grinding chamber region, and wherein the length L27 of the cavity towards the first agitator shaft section is less than the length L25 of the second agitator shaft section.

In such a case from the DE 100 64 828 B4 In the known agitator mill, the longitudinal slots forming part of a separating device extend in the second agitator shaft section slightly into the first agitator shaft section of smaller diameter. They end approximately in a radial plane with the sieve forming part of the separating device. The ground material flows through the grinding container from the ground material inlet to the opposite end of the grinding chamber and then enters the cavity within the second agitator shaft section together with the grinding auxiliary bodies carried along by the flow of the ground material. Since the cavity is essentially cylindrical, the webs delimited by the slots are larger in the end area of the agitator shaft than in the area of the cover of the sieve. In the entry area of the cavity there is therefore an increased ejection of grinding auxiliary bodies and coarse grinding material particles. This is intended to increase the radial flow of auxiliary grinding bodies from the separating device back into the grinding chamber.

From the DE 10 2013 111 762 A1 an agitator mill similar to the known agitator mill described above is known, in which the agitator shaft has a constant profile over its full length. In the area between the ground material inlet and the separating device, recesses running in the longitudinal direction of the agitator shaft are formed, which open into the slots that surround the cavity with the sieve in the second agitator shaft section. The purpose of the recesses, which are symmetrical to a respective radius, is to convey the grinding auxiliary bodies directly into the slots of the separating device, so that there is increased return to the grinding chamber. A sufficiently uniform and compression-free distribution of the grinding auxiliary bodies in the grinding chamber is not yet achieved by these known measures.

From the EP 0 376 001 A1 an agitator mill with a horizontally arranged grinding container is known, which has a cylindrical inner wall. A stirring shaft that can be driven in a drive direction of rotation about a common central longitudinal axis is arranged in the grinding container. The agitator mill has a grinding chamber delimited by the inner wall and the agitator shaft, into the first end of which a ground material inlet opens. The agitator shaft is either continuously cylindrical with a constant diameter or has areas with different diameters. The agitator shaft has a cavity adjacent to the outlet in which a separating device is arranged. In the area of this cavity, the agitator shaft is provided with longitudinal slots which open from the grinding chamber into the cavity. Based on the longitudinal direction of the grinding chamber, this area is viewed as a separation zone, the length of which in the direction of the axis of the agitator shaft accounts for 40 to 80% of the total length of the grinding chamber. The purpose of these measures is to significantly increase the shredding performance per unit of time and to achieve particularly uniform shredding of the ground material. A sufficiently uniform and compression-free distribution of the grinding auxiliary bodies in the grinding chamber is not achieved by these known measures.

From the DE 44 19 919 C1 an agitator mill with a pot-shaped agitator is known, which is arranged in a likewise pot-shaped grinding container. Both the pot-shaped inner agitator and the outer agitator can be rotated. They are arranged in a vessel. The grinding material is fed from the inside through a separating device that allows the grinding material to pass through but retains the auxiliary grinding particles. The outer, rotatable grinding container has separating devices that allow the grinding material to pass through. The ground material is fed from the inside. It flows through the grinding chambers to the outside and is discharged from an external grinding chamber.

From the DE 102 41 924 B3 an agitator mill with a coolable agitator shaft is known, which has a grinding container in which an agitator is arranged. The agitator has coolable elements with gaps between them. The grinding space between the agitator and the grinding container wall is filled with grinding auxiliary bodies and the material to be ground flows through from an inlet to an outlet. The ground material is guided to the open end of the agitator and enters there into a cavity of the agitator in which a sieve is arranged. Auxiliary grinding bodies are thrown radially outwards through the spaces between the cooled elements of the agitator.

The invention is therefore based on the object of developing an agitator mill according to the preamble of claim 1 in such a way that a largely uniform distribution of the grinding auxiliary bodies in the grinding chamber is achieved while avoiding compression.

This object is achieved according to the invention in that the first agitator shaft section has at least one short-circuit channel which penetrates the bottom of the cavity and connects the first grinding space area to the cavity, which is at least partially formed in the transition section, and that the at least a short-circuit channel is positioned radially outwards against the drive direction of rotation. The measures according to the invention ensure that a material to be ground that is largely free of auxiliary grinding bodies is conveyed directly in the short circuit into the separating device, i.e. directly in front of the sieve. There will be fine regrind particles are discharged directly through the regrind outlet. A portion of the already sufficiently fine ground material is therefore only subjected to a grinding process in the first grinding chamber area. The design of the at least one short-circuit channel increases the centrifugal effect, which has a correspondingly strong effect on grinding auxiliary bodies and coarse grinding material particles.

If, according to an advantageous development of the invention, the at least one short-circuit channel formed in the first agitator shaft section extends in the direction of the central longitudinal axis over 10 to 100%, or at least 70%, or at least 80%, or at least 90% of the length L24 of the first agitator shaft section extends, then it can be achieved that the ground material supplied to the separating device in the short circuit is already freed of grinding auxiliary bodies and coarse ground material particles to the desired extent. This effect is achieved in a particularly pronounced manner if the at least one short-circuit channel has an inner diameter D39 that is smaller than the inner diameter D27 of the cavity.

Further advantageous developments result from further subclaims.

Figur 1

eine horizontale Rührwerksmühle in vertikalem Längsschnitt,

Figur 2

den Mahlbehälter der Rührwerksmühle im vertikalen Längsschnitt in gegenüber Figur 1 vergrößertem Maßstab,

Figur 3

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie III-III in Figur 2,

Figur 4

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie IV-IV in Figur 2,

Figur 5

eine gegenüber Figur 2 abgewandelte Ausführungsform eines Mahlbehälters in vertikalem Längsschnitt,

Figur 6

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie VI-VI in Figur 5,

Figur 7

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie VII-VII in Figur 5,

Figur 8

eine gegenüber Figur 5 abgewandelte Ausführungsform eines Mahlbehälters in vertikalem Längsschnitt,

Figur 9

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie IX-IX in Figur 8 und

Figur 10

einen Querschnitt durch den Mahlbehälter gemäß der Schnittlinie X-X in Figur 8.

Further features, details and advantages of the invention result from the following description of exemplary embodiments of the invention based on the drawings. It shows

Figure 1

a horizontal agitator mill in a vertical longitudinal section,

Figure 2

the grinding container of the agitator mill in a vertical longitudinal section opposite Figure 1 enlarged scale,

Figure 3

a cross section through the grinding container according to section line III-III in Figure 2 ,

Figure 4

a cross section through the grinding container according to section line IV-IV in Figure 2 ,

Figure 5

one opposite Figure 2 modified embodiment of a grinding container in a vertical longitudinal section,

Figure 6

a cross section through the grinding container according to section line VI-VI in Figure 5 ,

Figure 7

a cross section through the grinding container according to section line VII-VII in Figure 5 ,

Figure 8

one opposite Figure 5 modified embodiment of a grinding container in a vertical longitudinal section,

Figure 9

a cross section through the grinding container according to section line IX-IX in Figure 8 and

Figure 10

a cross section through the grinding container according to the section line XX in Figure 8 .

How Fig. 1 can be removed, a horizontal agitator mill has a machine frame 1 which is supported on the floor 2. In the lower area of the machine frame 1, a drive motor 3 is arranged, which is coupled to a drive shaft 5 by means of a belt drive 4.

In the upper area of the machine frame 1, a horizontal grinding container 6 is attached to it. This has a first grinding container lid 7, which is attached to the machine frame 1 and in which the drive shaft 5 is rotatably mounted by means of roller bearings 8. The grinding container 6 also has a cylindrical inner wall 9, which is surrounded by a temperature control jacket 10, into which temperature control medium, usually coolant, is introduced through an inlet 11 and discharged through an outlet 12. At the end opposite the first grinding container lid 7, i.e. at a distance from the upper region of the machine frame 1, the grinding container 6 is closed by a second grinding container lid 13. The connection between the inner wall 9 and the temperature control jacket 10 with the first cover 7 and the second cover 13 takes place by means of flanges 14, 15 and associated screw connections 16. A grinding chamber 17 is delimited by the cylindrical inner wall 9 and the first cover 7 and the second cover 13, into which a grinding material inlet 18 formed in the first cover 7 opens and from which one in the second The ground material outlet 19 arranged on the cover 13 opens out. A grinding auxiliary body filler connection 20 and an auxiliary grinding body outlet connection 21 also open into the grinding chamber 17, both of which are also formed on the second cover 13.

An agitator shaft 22 is arranged in the grinding chamber 17, which is connected in a rotationally fixed manner to the drive shaft 5 and can be driven by the latter about a common horizontal central longitudinal axis 23 of the drive shaft 5, grinding chamber 17 and agitator shaft 22. The agitator shaft 22 is not mounted in the grinding chamber 17; It is therefore freely mounted via its coupling to the drive shaft 5. The agitator shaft 22 has two sections, namely a first agitator shaft section 24 with an outer diameter D24 following the ground material inlet 18 and then a second agitator shaft section 25 with an outer diameter D25. The following applies:
D25 > D24. A transition section 26 between the first stirring shaft section 24 of smaller diameter D24 and the second stirring shaft section 25 of larger diameter D25 is assigned to the first stirring shaft section 24.

The first stirring shaft section 24 is essentially designed as a solid material section, while the second stirring shaft section 25 has a cavity 27 which is open towards the second cover 13. The length L27 of the cavity 27 in the direction of the first stirring shaft section 24 is less than the length L25 of the second stirring shaft section 25. The following therefore applies: L27 <L25. The second stirring shaft section 25 faces outwards open longitudinal slots 28 running parallel to the axis 23, which - like Figure 4 can be removed - based on the drive rotation direction 29 of the agitator shaft 22 are set radially outwards against the direction of rotation 29. The second stirring shaft section 25 is closed at its end adjacent to the second cover 13 by means of an end ring 30, which also closes the longitudinal slots 28 in the direction parallel to the axis 23.

In the second agitator shaft section 25, a separating device 31 is formed concentrically to the axis 23, which consists of the longitudinal slots 28 and a cylindrical sieve 32, which is closed at the end to the first agitator shaft section 24 by means of a cover 33 and that on its other side End is held in a base 34, which is attached to the second lid 13 and has the regrind outlet 19. Like in particular Figure 2 can be removed, the sieve 32 extends into the vicinity of the end of the cavity 27 adjacent to the first agitator shaft section 24.

The stirring shaft 22 is equipped with stirring elements 35, 36 in the form of stirring pins, each of which is mounted at a circumferential distance of 90 degrees from one another on the circumference of the stirring shaft 22 and radially to the axis 23. There are four stirring elements 35, 36 arranged in a plane perpendicular to the axis 23. The stirring elements 35 in the first grinding chamber region 37 surrounding the first stirring shaft section 24 are longer than the stirring elements 36 in the second grinding chamber region 38 surrounding the second stirring shaft section 25. This results from the fact that the inner diameter D24 of the first grinding chamber area 37 is smaller than the inner diameter D25 of the second grinding chamber area 38 and that all stirring elements 35, 36 end at the same distance from the inner wall 9 of the grinding container 6. In the second stirring shaft section 25 are each two longitudinal slots 28 are formed between two stirring elements 35 offset from one another by 90 degrees. Depending on the size of the agitator mill, the circumferential distance between the stirring elements 35 can be less than 90°. In such a case, no longer two but only one longitudinal slot 28 may be formed between two stirring elements 35 adjacent in a circumferential plane.

With the one in the Figures 1 to 4 In the exemplary embodiment shown, short-circuit channels 39 are formed in the transition section 26 from the first stirring shaft section 24 of smaller diameter D24 to the second stirring shaft section 25 of larger diameter D25, which surround the first grinding chamber area 37 with the cavity 27 surrounding the first stirring shaft section 24 connect. These short-circuit channels 39 open - like Figure 2 and Figure 4 can be removed - into the longitudinal slots 28 and are - based on the flow direction 40 from the regrind inlet 18 to the regrind outlet 19 - in front of the cavity 27, i.e. in the solid material area of the agitator shaft 22. They therefore open through the bottom 41 of the cavity 27 into the latter. These short-circuit channels 39 can - like Figure 2 can be removed - be relatively short. Its axial length L39 is at least 10% of the length L24 of the first stirring shaft section 24. The following therefore applies: L39 >= 0.1 L24.

Like the embodiment modified with regard to the design of the short-circuit channels Figures 5 to 7 can be removed, the short-circuit channels 39 'can extend over a significant part of the length L24 of the first agitator shaft section 24, in the limit case over its full length, in which the short-circuit channels 39' are then axial to the first grinding container lid 7 are open. Then the following applies:
L24 >= L39'>= 0.1 L24. In other words, this means that the axial Length L39 'is in the range of 10% to 100% of the length L24 of the first stirring shaft section 24. The short-circuit channels 39' are preferably relatively long. The preferred values for them are L39'>= 0.7 L24 or L39'>= 0.8 L24 and L39'>= 0.9 L24.

As can be seen from the drawing, the short-circuit channels 39, 39 'are positioned against the direction of rotation 29 in the same way as the longitudinal slots 28 - viewed from the central longitudinal axis 23 outwards. They therefore open axially into the longitudinal slots 28. Furthermore, the short-circuit channels 39, 39' - at least in the transition region 26 - have an inner diameter D39, D39' which is smaller than the inner diameter D27 of the cavity 27, so that the short-circuit channels 39, 39' pass directly through the base 41 of the cavity 27 open into this. The inner diameter D39, D39 'is slightly larger than the outer diameter D33 of the cover 33 of the sieve 32.

The exemplary embodiment according to the Figures 8 to 10 differs from the one according to the Figures 5 to 7 only in that the inner diameter D39" of the short-circuit channels 39" is smaller than the outer diameter D33 of the cover 33 of the sieve 32. This can of course also be the case in the exemplary embodiment according to Figures 1 to 4 be the case.

The operation method is as follows:
The grinding chamber 17, i.e. the free space between the inner wall 9 and the agitator shaft 22, is filled to approximately 90% with only indicated grinding auxiliary bodies 42. The diameter D42 of the grinding auxiliary bodies 42 is in the range from 0.03 mm to 0.8 mm and preferably in the range from 0.03 mm to 0.4 mm. The ground material to be ground or dispersed is pumped through the ground material inlet 18 into the grinding container 6 and flows through the grinding chamber 17 in the flow direction 40 under intensive stress caused by the stirring elements 35, 36 and the grinding auxiliary bodies 42, the average flow rate in the first grinding chamber area 37 being lower than in the second grinding chamber area 38, because of the different large free cross sections of these grinding chamber areas 37, 38.

How Figure 2 can be removed, according to the flow arrow 43, part of the ground material flows through the short-circuit channels 39 directly into the cavity 27 and leaves the grinding chamber 17 through the sieve 32, as long as this ground material has a fineness that allows it to pass through the sieve 32. The ground material that is not removed through the sieve 32 is centrifuged through the longitudinal slots 28 into the second grinding chamber area 38. A further part of the material to be ground is conveyed through the second grinding chamber region 38 under further intensive action by the auxiliary grinding bodies 42 and flows around the end ring 30 into the cavity 27 between the sieve 32 and the second agitator shaft section 25, where the auxiliary grinding bodies 42 and Coarse ground material particles are thrown off more pronouncedly than fine ground material particles according to the outwardly directed flow arrows 45 through the longitudinal slots 28 into the second grinding chamber area 38.

Due to the relatively lower flow speed of the material to be ground in the first grinding chamber area 37 compared to the second grinding chamber area 38, the risk of compaction and compression of auxiliary grinding bodies 42 in the first grinding chamber area 37 is lower than in the second grinding chamber area 38 If part of the ground material is already fed directly from the first grinding chamber area 37 to the separation device 31 in the short-circuit channels 39, the flow rate of the ground material becomes also reduced in the second grinding chamber area 38, so that the risk of pressing of the grinding auxiliary bodies 42 is reduced there too.

If - as in the exemplary embodiments according to Figures 5 to 7 and 8 to 10 - the short-circuit channels 39', 39" extend over a greater length L39', L39" in the direction of the regrind inlet 18, then the stream of regrind, which is fed directly to the separating device 31 in the short circuit, is in Comparison to the exemplary embodiment according to Figures 1 to 4 enlarged because, due to the described design of the short-circuit channels 39 ', 39", grinding auxiliary bodies 42 and coarse regrind particles are thrown out radially into the first grinding chamber area 37 from the short-circuit channels 39" in accordance with the directional arrows 46 shown become. This applies in particular to the exemplary embodiment according to Fig. 8 to 10 .

The measures described greatly reduce the risk of grinding auxiliary bodies 42 being pressed, so that a significant increase in throughput is possible. This brings significant advantages, particularly in so-called passage operations; Here, ground material is conveyed several times in the circuit through the grinding container 6.

Reference symbol list

1

Machine frame

2

Floor

3

Drive motor

4

Belt drive

5

Drive shaft

6

grinding container

7

first grinding container lid

8th

roller bearing

9

Interior wall

10

Tempering jacket

11

Intake

12

Sequence

13

second grinding container lid

14

flange

15

flange

16

screw connection

17

grinding room

18

Ground material inlet

19

Ground material outlet

20

Grinding auxiliary body filler neck

21

Grinding auxiliary body outlet connection

22

Stirring shaft

23

Mid-longitudinal axis

24

first stirring shaft section

25

second agitator shaft section

26

Transition section (24-25)

27

cavity

28

Longitudinal slits

29

Direction of rotation

30

End ring

31

Separation device

32

Sieve

33, 33'

cover

34

base

35

Stirring elements

36

Stirring elements

37

first grinding room area

38

second grinding room area

39, 39', 39"

Short circuit channel

40

Flow direction

41

floor (27)

42

grinding auxiliary body

43

Flow arrow

44

Directional arrow

45

Flow arrow

46

Directional arrow

Claims (8)

1. A stirring mill

   comprising a horizontally arranged milling vessel (6), which has a cylindrical inner wall (9),

   comprising a stirring shaft (22), which is arranged in the milling vessel (6) and which can be driven about a common central longitudinal axis (23) in a drive direction of rotation (29),

   comprising a milling chamber (17), which is limited by the inner wall (9) and the stirring shaft (22), wherein, at a first end of the milling chamber (17), a milling material inlet (18) discharges into said milling chamber,

   wherein a milling material outlet (19) opens out from a second end of the milling vessel (6) opposite the first end of the milling vessel (6),

   wherein the stirring shaft (22) has a first stirring shaft section (24) of a smaller diameter D24 and of a length L24, which is adjacent to the milling material inlet (18) and which limits a first milling chamber region (37), and a second stirring shaft section (25) of a larger diameter D25 and of a length L25, which is adjacent to the milling material outlet (19) and which limits a second milling chamber region (38), wherein the following applies: D25 > D24, and wherein a transition section (26), which is assigned to the first stirring shaft section (24), is formed between the first stirring shaft section (24) and the second stirring shaft section (25),

   wherein the second stirring shaft section (25) has a hollow space (27), which is closed by a bottom (41) with respect to the first stirring shaft section (24) and which has a length L27 towards the first stirring shaft section (24), and in which a screen (32) is arranged, which is connected to the milling material outlet (19) and which ends at a distance upstream of the bottom (41), and

   wherein the second stirring shaft section (25) has the hollow space (27) comprising slits (28), which connect the hollow space (27) to the second milling chamber region (38),

   wherein the length L27 of the hollow space (27) is smaller in the direction towards the first stirring shaft section (24) than the length L25 of the second stirring shaft section (25), characterized in

   that the first stirring shaft section (24) has at least one bypass channel (39, 39', 39"), which penetrates the bottom (41) of the hollow space (27) and which connects the first milling chamber region (37) to the hollow space (27) and which is at least partially formed in the transition section (26), and

   that the at least one bypass channel (39, 39', 39") is inclined radially to the outside opposite to the drive direction of rotation (29).
2. The stirring mill according to claim 1, characterized in
   that the at least one bypass channel (39, 39', 39") has an inner diameter D39, D39', D39", which is smaller than the inner diameter D27 of the hollow space (7).
3. The stirring mill according to claim 1 or 2,
   characterized in
   that the at least one bypass channel (39, 39', 39") formed in the first stirring shaft section (24) extends in the direction of the central longitudinal axis (23) over 10 to 100% of the length L24 of the first stirring shaft section (24).
4. The stirring mill according to one of claims 1 to 3,
   characterized in
   that the at least one bypass channel (39, 39', 39") runs parallel to the central longitudinal axis (23).
5. The stirring mill according to one of claims 1 to 4,
   characterized in
   that the at least one bypass channel (39, 39', 39") partially transitions into a slit (28) of the second stirring shaft section (25).
6. The stirring mill according to claim 3, characterized in that the at least one bypass channel (39', 39") formed in the first stirring shaft section (24) extends in the direction of the central longitudinal axis (23) over at least 70% of the length L24 of the first stirring shaft section (24).
7. The stirring mill according to claim 3, characterized in that the at least one bypass channel (39', 39") formed in the first stirring shaft section (24) extends in the direction of the central longitudinal axis (23) over at least 80% of the length L24 of the first stirring shaft section (24).
8. The stirring mill according to claim 3, characterized in that the at least one bypass channel (39', 39") formed in the first stirring shaft section (24) extends in the direction of the central longitudinal axis (23) over at least 90% of the length L24 of the first stirring shaft section (24).

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