EP3057710B1 - Pre-comminuting device for a ball mill or an agitator mill and ball mill with pre-comminuting device - Google Patents

Description

The present invention relates to a Vorzerkleinerungsvorrichtung for a ball mill or a stirred ball mill and a ball mill with Vorzerkleinerungseinrichtung according to the features of the preamble of claims 1 and 11.

State of the art

The invention relates to a Vorzerkleinerungsvorrichtung for a ball mill or a stirred ball mill or a ball mill with Vorzerkleinerungsvorrichtung. The ball mill is a device for coarse, fine and fine crushing or homogenization of regrind. It consists of a rotating grinding chamber in which ground material is comminuted by grinding media. Ball mills are usually constructed of a horizontally rotatably mounted, approximately circular cylindrical grinding container. The mills are filled by a central opening in one of the end walls, the so-called Mahlguteinlass. The discharge depends on the design and takes place, for example, through slots in the grinding chamber wall at the end of the mill, the grinding bodies being retained by means of a separating device.

A special form of the ball mill is the agitator ball mill. Agitator ball mills consist of a vertically or horizontally arranged, usually approximately cylindrical grinding container, which is filled to 70 - 90% with grinding media. The grinding container is usually stationary in stirred ball mills, not rotatably mounted. An agitator with suitable stirring elements ensures the intensive movement of the grinding media. The millbase suspension is pumped continuously through the grinding chamber. The suspended solids are crushed or dispersed by impact and shear forces between the grinding media. At the discharge of the mill, the separation of ground material and grinding media by means of a suitable separator.

The document DD217434 B1 describes a vertically arranged agitator ball mill comprising in the upper inlet area a pre-crushing device connected to the stirring shaft. This consists of a crushing cone which is non-rotatably mounted on the agitator shaft and a crushing ring attached to the grinding container. The ground material is introduced into the crushing gap between crushing cone and crushing ring and pre-crushed before it falls into the grinding container, where it is further processed by the stirring shaft and the grinding media.

The document DE 102008058585 A1 discloses an agitator ball mill with a horizontally arranged grinding container and a stirring shaft, wherein between the Mahlguteinlass and the grinding chamber, a pre-shredding device is provided, which has a gap protection to the grinding chamber. This prevents that grinding media can flow back and get into the Vorzerkleinerungsvorrichtung.

EP 1980323 B1 describes a cutting system with a cutting rotor comprising rotor lugs, on the outwardly facing surfaces rotor cutting plates are fixed with cutting edge. Around the cutting rotor is a stator ring with an annular base and stator lugs. The Statorstollen each have an inwardly facing Statorausnehmung with Statorschneidplatte. The Statorschneidplatten are each arranged and fixed so that they are opposite to the rotor cutting plates.

The invention has for its object to improve the pre-crushing of solid constituents of regrind, in particular to provide a pre-crushing device in which the problem of setting coarse particles and / or impurities is reduced or minimized.

The above objects are achieved by a pre-crushing device for ball mills and / or agitating ball mills and a ball mill with pre-crushing device comprising the features in claims 1 and 11. Further advantageous embodiments are described by the subclaims.

description

The invention relates to a pre-crushing device for a ball mill or agitator ball mill. The pre-comminution device is arranged in the grinding container between a grinding material inlet of the ball mill or agitator ball mill and a grinding chamber and serves in particular to pre-comminute the material to be ground, so that the grinding material entering the grinding space preferably has only components with a predefined maximum size. The pre-crushing device consists of a first stationary crushing means and a second rotationally movable crushing means, between which a crushing gap is formed. The first stationarily formed comminution means is in particular a comminution ring arranged in the grinding container.

According to the invention, the first stationarily formed comminuting means has an internal toothing. The second shredding means comprises a first portion and a second portion. The comminution gap is formed, in particular, between the first stationarily formed comminution means and the first subarea of the second comminution means. The second subregion of the second comminuting means has conductive structures for the ground material. The guide structures serve, in particular, to supply the grinding material entering via the grinding material inlet to the grinding chamber in the direction of the first subregion of the second comminuting means and thus in the direction of the comminuting gap formed between comminuting ring and first subregion.

The first portion of the second crushing means comprises a first outer toothing. The first comminuting means and the second comminuting means are arranged so that the external toothing of the first subregion of the second comminuting means largely engages with the formation of the comminution gap into the internal toothing of the first comminuting means, in particular of the comminution ring. The comminution gap forms a minimum distance between the internal toothing and the external toothing. The inner and outer teeth can for example be largely formed positively to one another. However, the teeth are separated from each other by the minimum distance of the comminution gap, that is, the teeth of the two comminution means do not touch each other.

According to a preferred embodiment, the guide structures of the second subregion of the second comminuting means are formed by a coarse external toothing of this subregion. In particular, the second subregion comprises a second subregion External teeth with second external teeth, which have a second tooth height and width. This second tooth height and width is greater than a first tooth height and width of the first outer teeth described above in the first portion of the second grinding means.

In particular, the coarse external toothing has a tooth width of the individual teeth, which increases in the direction of the adjacent first subregion from a free end of the second subregion. Alternatively and / or additionally, the tooth height of the second external teeth may also decrease in the direction of the adjacent first partial area. The description of the tooth shape relates in particular to the outer surfaces of the second external teeth.

According to one embodiment of the invention, the sides defining the outer surface of the second outer teeth have a curved course. In particular, one of the two sides has a greater curvature, whereby the broadening of the outer surfaces of the second outer teeth is formed in the direction of the adjacent first portion.

According to one embodiment, the first outer toothing of the first portion of the second comminution means extends over the outer surfaces of the second outer toothing of the second portion, i. the second portion has a so-called double teeth, wherein the outer surfaces of the coarse outer teeth show an attached fine toothing. The fine toothing essentially corresponds to the first outer toothing of the first subregion of the second comminuting means.

According to a particularly preferred embodiment, the second portion of the second rotatably movable comminuting means is formed as a truncated cone-like region with a truncated cone base surface and a truncated cone top surface. The first portion may be formed as a largely cylindrical area with a cylinder base. Alternatively, the first portion could also be formed as a truncated cone-like area. The truncated cone base area of the second subarea and the cylinder base area of the first subarea are largely identical. The largely cylindrical area adjoins the truncated cone base area of the truncated cone-like area with a cylinder base area. In this embodiment, the first outer toothing with first outer teeth of a first tooth height and width is assigned to the largely cylindrical portion. The first external teeth are formed corresponding to the internal teeth of the internal teeth of the first crushing means, in particular to the internal teeth of the internal teeth of the crushing ring. The first crushing means and the second crushing means are arranged so that the external teeth of the cylindrical portion engages with formation of the crushing gap largely in the internal toothing of the first crushing means, wherein the crushing gap forms a minimum distance between the internal teeth and the external teeth.

In the region of the outer circumferential surface between the truncated cone top surface and the truncated cone base surface, the truncated cone-like region of the second shredding medium has a second external toothing with second external teeth. The second outer teeth have a second tooth height and width that is greater than the first tooth height and width of the first outer teeth in the cylindrical portion of the second comminution medium. Furthermore, it can be provided that the tooth width of the second outer teeth increases from the truncated cone cover surface in the direction of the cylindrical area and / or that the tooth height of the second outer teeth decreases in the direction of the cylindrical area. In particular, the sides or edges, which respectively bound the outer surface of the outer teeth, have a curvature. In particular, one of the sides is more curved, which causes the widening of the second external teeth in the direction of the cylindrical area. Preferably, the first outer toothing of the cylindrical portion of the second comminuting means is continued beyond the second outer toothing of the truncated cone-like portion of the second comminuting means.

The present invention is a device for pre-shredding coarse constituents, for example nuts, in the inlet region of a ball mill or agitator ball mill, in particular in a region between the ground material inlet and the grinding chamber. The ball mill or agitator ball mill is used in particular for grinding wet regrind, but can also be used for dry grinding. The pre-shredding device is particularly constructed in two parts and consists of a stationary crushing ring and a movably arranged, in particular rotatable, crushing means. The crushing ring comprises an internal toothing in the region of the inner circumferential surface. The comminuting means comprises a first region having first teeth of a first material thickness and / or material height and a second region having first and second teeth having a first material thickness and / or material height the first teeth and a second material thickness and / or material height of the second teeth. Preferably, the first material thickness and / or material height is smaller than the second material thickness and / or material height. In particular, the first material thickness and / or material height of the teeth of the comminution means correspond to the material thickness and / or material height of the inner teeth of the comminuting ring. The second teeth of the comminuting agent are formed significantly stronger in the feed region of the pre-comminution device than the first teeth of the comminution means in the region of a comminution or crushing ring.

The second coarse teeth in the second region of the comminution means also have a tapered tooth shape. In particular, the tooth form tapers in the direction of the free end region of the cone-like comminution means facing away from the comminution ring or in the direction of the top surface of the comminution means embodied as a truncated cone.

By the larger second teeth of the comminution coarse particles can be better detected and pre-shredded. The entire pre-shredding device is designed and arranged between Mahlguteinlass and grinding chamber that as possible no dead space is formed in order to avoid the setting of coarse particles and / or impurities. The invention finds particular use in ball mills or stirred ball mills for the production of chocolate masses, fillings for chocolate and other foods. However, the invention is also suitable for other products to be crushed and can also be used for millbase suspensions or with appropriate dimensioning for the pre-crushing of regrind in mining etcetera.

The innovation in the invention thus consists in a combination of a fine toothing and a coarse toothing, in particular in combination with a tapered tooth shape of the coarse toothing, which leads to a better intake behavior with coarse product components, especially if the ground material comprises product components of different sizes. Due to the coarse toothing, a larger tooth depth is formed on the inlet side. As a result, a better pumping action and / or turbulence is achieved with the pre-shredding device according to the invention, which prevents the ground material or product from adhering to the inlet region.

The finished first comminution means, in particular the comminution ring equipped with an internal toothing, is arranged and fastened in a grinding container of a ball mill or agitator ball mill. The crushing ring is arranged so that it divides the interior of the ball mill or agitator ball mill in a grinding room and an anteroom. The second crushing means is arranged and fixed to a rotatable shaft along a longitudinal axis of the grinding container, so that the first portion of the second crushing means is arranged with the first outer teeth so that they largely engage in the internal teeth of the crushing ring to form the forming a minimum gap forming crushing gap. The second portion of the second comminuting agent is then arranged in the antechamber between Mahlguteinlass the ball mill or agitator ball mill and the first crushing or grinding chamber.

The first stationarily formed comminuting means generally has an outer diameter which corresponds approximately to the inner diameter of the grinding container and is arranged and fixed in the grinding container. According to one embodiment of the invention, the second crushing means is arranged and fixed to the agitator shaft of a stirred ball mill. When using a Vorzerkleinerungsvorrichtung in a ball mill own drive for the second crushing means is provided.

Advantageously, with the device according to the invention, the millbase for large mills, in particular of wet-grinding mills, can be pre-comminuted before it is further processed in the milling space by the grinding aids. The coarse toothing of the rotating comminuting agent also improves the introduction of the millbase into the grinding chamber and at least largely prevents residues of millbase in the antechamber between the millbase inlet and the grinding chamber.

The pre-shredding device according to the invention can be integrated directly in the assembly of mills in this. But it is also possible to retrofit mills with a Vorzerkleinerungseinrichtung invention, if necessary, an existing Vorzerkleinerungseinrichtung must be dismantled before.

figure description

• Figur 1 zeigt eine schematische Ansicht einer Rührwerkskugelmühle mit vertikal angeordnetem Mahlbehälter und Rührwerkzeug gemäß dem Stand der Technik.
• Figur 2 zeigt eine schematische Ansicht einer Rührwerkskugelmühle mit horizontal angeordnetem Mahlbehälter und Rührwerkzeug gemäß dem Stand der Technik.
• Figuren 3 zeigen verschiedene Ansichten eines ersten Zerkleinerungsmittels einer erfindungsgemäßen Vorzerkleinerungsvorrichtung.
• Figuren 4 zeigen verschiedene Ansichten eines zweiten Zerkleinerungsmittels einer erfindungsgemäßen Vorzerkleinerungsvorrichtung.
• Figur 5 zeigt einen Detailausschnitt der Verzahnung zwischen erstem Zerkleinerungsmittel und zweiten Zerkleinerungsmittel.
• Figur 6 zeigt einen Querschnitt durch eine erfindungsgemäße Vorzerkleinerungsvorrichtung.

In the following, embodiments of the invention and their advantages with reference to the accompanying figures will be explained in more detail. The proportions of the individual elements to one another in the figures do not always correspond to the actual size ratios, since some shapes are simplified and other shapes are shown enlarged in relation to other elements for better illustration.

• FIG. 1 shows a schematic view of a stirred ball mill with vertically arranged grinding container and stirring tool according to the prior art.
• FIG. 2 shows a schematic view of a stirred ball mill with horizontally arranged grinding container and stirring tool according to the prior art.
• Figures 3 show various views of a first crushing means of a pre-crushing device according to the invention.
• FIGS. 4 show various views of a second crushing means of a pre-crushing device according to the invention.
• FIG. 5 shows a detail of the gearing between the first crushing means and second crushing means.
• FIG. 6 shows a cross section through a Vorzerkleinerungsvorrichtung invention.

For identical or equivalent elements of the invention, identical reference numerals are used. Furthermore, for the sake of clarity, only reference symbols are shown in the individual figures, which are required for the description of the respective figure. The illustrated embodiments are merely examples of how the device or method of the invention may be configured and are not an exhaustive limitation.

FIG. 1 shows a schematic view of a stirred ball mill 1a with vertically arranged grinding container 2 and stirring tool 3 according to the prior art. The agitator ball mill 1a has an upper Mahlguteinlass 4 and a lower Mahlgutauslass 5, which is associated with a separator 6. The separator 6 holds the grinding media (not shown) in the grinding container 2 back. The agitator ball mill 1a further comprises one with the agitator shaft 3 * of the agitating tool This consists of a crushing cone 8, which is rotatably mounted on the agitator shaft 3 * and attached to the grinding container 2 crushing ring 9. The ground material is introduced into the crushing gap S between crushing cone 8 and crushing ring 9 and is pre-crushed before it falls into the grinding container 2, where it is further processed by the stirring tool 3 and the grinding media. The ground product is then removed via the Mahlgutauslass 5 from the stirred ball mill 1a.

FIG. 2 shows a schematic view of another agitator ball mill 1b with horizontally arranged grinding container 2 and stirring tool 3 according to the prior art. The agitator ball mill 1b has an upper Mahlguteinlass 4 and on the opposite side of the grinding container 2 centrally arranged Mahlgutauslass 5, which is associated with a separator 6. The separator 6 holds the grinding media M in the grinding container 2 back. The agitating ball mill 1b further comprises a pre-shredding device 7 connected to the agitator shaft 3 *. This consists of a crushing cone 8, which is arranged fixed against rotation on the agitator shaft 3 * of the agitating tool 3 and a crushing ring 9 fastened to the grinding container 2. The ground material is introduced into the crushing gap S introduced between crushing cone 8 and crushing ring 9 and is pre-crushed before it enters the grinding container 2, where it is further processed by the stirring tool 3 and the grinding media M. The ground product is then removed via the Mahlgutauslass 5 from the agitator ball mill 1b. The pre-shredding device 7 has a gap protection for the grinding space 2R, which prevents the grinding bodies M from flowing back and from entering the pre-shredding device 7.

A pre-shredding device 7 according to the invention (compare in particular FIG. 6 ) consists of a first stationary crushing means 20 (see Figures 3 ) and a second rotatably movable comminuting means 30 (cf. FIGS. 4 ), between which a crushing gap S is formed. In particular, the first comminuting means 20 is designed as a so-called comminution ring 21 and the second comminution means 30 is designed as a so-called extended truncated cone 31. The pre-comminuting device is arranged inside the mill between the grinding stock inlet 4 and the grinding space 2R (see also FIG FIGS. 1, 2 and 6 ) that the second crushing means 30 engages on the grinding chamber 2R side facing at least partially into the first crushing means 20 to form the crushing gap S, so that the material to be ground when entering the Grinding chamber 2R must pass through the crushing gap S, where it is pre-crushed.

Figures 3 show various views of a first crushing means 20 a Vorzerkleinerungsvorrichtung invention, in particular FIG. 3B a section along the section line AA according to FIG. 3A The first comminuting means 20 is designed in particular as a comminuting ring 21. The inner circumferential surface 24 of the comminution ring 21 has a so-called internal toothing of internal teeth 26.

FIG. 3C shows a perspective view of the comminution ring 21 formed as the first crushing means 20 and Figure 3D shows a detail FIG. 3A , Here, in particular, the internal toothing of the inner peripheral surface 24 by means of fine inner teeth 26 can be clearly seen.

FIGS. 4 show different views of a second crushing means 30 of a pre-crushing device according to the invention, in particular FIG. 4C a section along the section line AA according to FIG. 4B represents. Figure 4D shows a detail of FIG. 4C , Figure 4E shows a plan view of the second crushing means 30 on a top surface DF.

The second comminuting means 30 comprises a region designed as a truncated cone 35 and a cylindrical region 34. The region formed as a truncated cone 35 has a base area GF, a top surface DF and an outside circumferential surface AF ₃₅ . The cylindrical region 34 has a cylinder base area ZF with the same cross section or the same diameter as the base area GF of the truncated cone 35 and an outer lateral surface AF ₃₄ .

The second shredding means 30 has at least partially outer teeth 36 on. Furthermore, the second shredding means 30 at least partially second external teeth 37. In particular, the second shredding means 30 comprises a first cylindrical portion 34, having first teeth 36 of a first material thickness and / or material height and a second frusto-conical portion 35 having first teeth 36 and second teeth 37 of a second material thickness and / or material height and wherein the first material thickness and / or material height is smaller than the second material thickness and / or material height. In particular, the first material thickness and / or material height of the fine outer teeth 36 of the second correspond Crushing means 30 at least largely with the material thickness and / or material height of the inner teeth 26 of the crushing ring 21 (see also Figures 3 ).

The so-called coarse teeth 37 of the second comminuting means 30 are formed significantly stronger in the intake area of the pre-comminuting device 7 than the fine teeth 36 of the second comminution means 30 and / or the fine inner teeth 26 of the first comminuting means 20 or comminution ring 21. The second coarse outer teeth 37 in the second Region 35 of the second comminution means 30 also have a tapered tooth shape. In particular, the tooth form tapers in the direction of the free end region of the second comminuting means 30 facing away from the comminution ring 21 or in the direction of a cover surface DF of the second region of the second comminution means 30 designed as truncated cone 35.

According to a preferred embodiment, fine teeth 36 extend over the outer circumferential surfaces of the coarse outer teeth 37. By the coarser second outer teeth 37 of the second crushing means 30 coarse particles of the ground material can be better detected and pre-shredded. The entire pre-comminuting device is designed in this way and between grinding stock inlet 4 and grinding space 2R (see also FIG FIG. 2 and 6 ) arranged so that no possible dead space is formed in order to avoid the seizure of coarse particles and / or impurities by the material to be ground.

According to an optional embodiment of the invention, the sides delimiting the outer surface of the coarse outer teeth 37 have a curved course. In particular, one of the two sides has a greater curvature, whereby the widening of the outer teeth 37 in the direction of the adjacent cylindrical portion 34 is formed.

FIG. 5 shows a detail of the toothing between the first crushing means 20 and second crusher 30, in particular the fine inner teeth 26 of the crushing ring 21 and the fine outer teeth 36 of the cylindrical portion 34 of the second crushing means 30. The fine inner teeth 26 and the fine outer teeth 36 engage to form a crushing gap S. largely intertwined. The comminution gap S defines a minimum distance between the fine inner teeth 26 of the comminuting ring 21 and the fine outer teeth 36 of the cylindrical portion 34 of the second comminution means 30, so that through the comminution gap S into the grinding space 2R (cf. FIGS. 1, 2 and 6 ) is pre-crushed entering grind. The combination of a fine toothing 26, 36 and a coarse toothing 37, in particular in combination with a tapering tooth form of the coarse toothing 37, leads to a better intake behavior with coarse product components, in particular if the mill base comprises product components of different sizes. Due to the coarse toothing 37, a larger tooth depth is additionally formed on the inlet side. As a result, a better pumping action and / or turbulence is achieved with the pre-shredding device according to the invention, which prevents the product from adhering to the inlet region 10 (cf. Figures 2 and 6 ).

The invention has been described with reference to a preferred embodiment. However, it will be apparent to those skilled in the art that modifications or changes may be made to the invention without departing from the scope of the following claims.

LIST OF REFERENCE NUMBERS

1

stirred ball mill

2

Cutting container

2R

grinding chamber

3

agitator

3 *

agitator shaft

4

grinding stock

5

grinding stock

6

separator

7

Vorzerkleinerungsvorrichtung

8th

crushing cone

9

break ring

10

inlet area

20

first crusher

21

shredding ring

24

Inner circumferential surface

26

internal teeth

30

second crusher

31

extended truncated cone

34

Cylinder / cylindrical area

35

formed as a truncated cone area

36

fine outer teeth

37

rough outer teeth

AF

Outer casing surface

d

diameter

DF

cover surface

GF

Floor space

M

grinding media

Q

cross-section

S

Crushing gap / crushing gap

ZF

Cylinder base

Claims (11)

1. A pre-crushing device (7) for a ball mill or agitator bead mill (1), wherein the pre-crushing device (7) can be arranged between a ground material inlet (4) of the ball mill or agitator bead mill (1) and a milling chamber (2R), and comprises a first stationary crushing means (20) and a second rotatable crushing means(30), between which a crushing gap (S) is formed, and wherein the first stationary crushing means (20) is a crushing ring that can be arranged in the grinding jar (2), characterized in that the first stationary crushing means (20) has an internal gearing, and that the second crushing means (30) comprises first partial area (34) and a second partial area (35), wherein the second partial area (35) has guide structures for the ground material which can guide the ground material in the direction of the first partial area (34), and wherein at least the first partial area (34) of the second crushing means (30) comprises a first external gearing, wherein the first crushing means (20) and the second crushing means (30) can be arranged in such a way that the external gearing of the first partial area (34) of the second crushing means (30) largely engages into the internal gearing of the first crushing means with the formation of the crushing gap (S).
2. The pre-crushing device (7) according to claim 1, wherein the second crushing means (30) in the second partial area (35) has a second external gearing with two external teeth (37), wherein the second external teeth (37) have a second tooth height and width greater than a first tooth height and width of the first external teeth (36) in the first partial area (34) of the second crushing means (30), and wherein the second external gearing comprises the guide structures for the ground material.
3. The pre-crushing device (7) according to claim 2, wherein the tooth width of the second external teeth (37) increases from one free end of the second partial area (35) in the direction of the adjoining first partial area (34), and/or wherein the tooth height of the second external teeth (37) decreases in the direction of the adjoining first partial area (34).
4. The pre-crushing device (7) according to claim 2 or 3, wherein the sides adjoining an outer area (AF₃₅) of the external teeth (37) have a curved progression, in particular wherein one of the sides has more of a curvature.
5. The pre-crushing device (7) according to one of claims 2 to 4, wherein the first external gearing of the first partial area (34) of the second crushing means (30) continues over the outer areas (AF₃₅) of the second external gearing of the second partial area (35) of the second crushing means (30).
6. The pre-crushing device (7) according to one of claims 2 to 5, wherein the second partial area (35) of the second rotatable crushing means (30) is designed as a truncated cone with a truncated cone base area (GF) and a truncated cone deck area (DF), and wherein the first partial area (34) of the second rotatable crushing means (30) is designed as a largely cylindrical area with a cylinder base area (ZF), wherein the truncated cone base area (GF) and cylinder base area (ZF) are largely identical, and wherein a cylinder base area (ZF) of the largely cylindrical area (34) adjoins the truncated cone base area (GF) of the truncated cone area (35).
7. The pre-crushing device (7) according to claim 6, wherein the largely cylindrical area (34) has a first external gearing with first external teeth (36) of a first tooth height and width, whose design largely corresponds to the internal teeth (26) of the internal gearing of the first crushing means (20), and wherein the first crushing means (20) and second crushing means (30) are arranged in such a way that the external gearing of the cylindrical area (34) largely engages into the internal gearing of the first crushing means (20) with the formation of the crushing gap (S).
8. The pre-crushing device (7) according to claim 6 or 7, wherein the second crushing means (30) in the area of an external shell surface (AF₃₅) between the truncated cone deck area (DF) and the truncated cone base area (GF) of the truncated cone area has a second external gearing with second external teeth (37), wherein the second external teeth (37) have a second tooth height and width that is greater than the first tooth height and width of the first external teeth (36) in the cylindrical area (34) of the second crushing means (30) .
9. The pre-crushing device (7) according to claim 8, wherein the tooth width of the second external teeth (37) increases from the truncated cone deck area (DF) of the truncated cone area (35) in the direction of the cylindrical area (34), and/or wherein the tooth height of the second external teeth (37) decreases in the direction of the cylindrical area (34), in particular wherein the sides adjoining the outer area (AF₃₅) of the external teeth (37) have a curvature, in particular wherein one of the sides has more of a curvature.
10. The pre-crushing device (7) according to one of claims 7 to 9, wherein the first external gearing of the cylindrical area (34) of the second crushing means (30) continues over the outer area (AF₃₅) of the second external gearing of the truncated cone area (35) of the second crushing means (30).
11. A ball mill, in particular an agitator bead mill (1), comprising a ground material inlet (4), a grinding jar (2), a milling chamber (2R) and a pre-crushing device (7) according to one of claims 1-10, wherein the pre-crushing device (7) is arranged between the ground material inlet (4) and the milling chamber (2R, and wherein the crushing ring of the pre-crushing device (7) is arranged in grinding jar (2).

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