Laboratory mill, grinding bowl for a laboratory mill and arrangement with a laboratory mill and with a grinding bowl

Abstract

What is illustrated and described is a laboratory mill, in particular centrifugal ball mill and / or planetary ball mill, with at least one grinding bowl holder for at least one grinding bowl (2) and with at least one rotation-lock means for holding the grinding bowl (2) in a defined predetermined position relative to the grinding bowl holder and / or as a positioning aid. According to the invention, it is provided that the grinding bowl holder has at least one surface relief as the rotation-lock means, on an axial surface (4) facing a grinding bowl base during the grinding operation, the surface relief being connectable with a form fit to a mating relief, which is complementary to the surface relief, on an axial surface (10) of the grinding bowl base in order to provide a rotation lock.

Description

[0001] The invention relates to a laboratory mill, in particular a centrifugal ball mill and / or planetary ball mill according to the preamble of claim 1.

[0002] Furthermore, the present invention relates to a grinding bowl for a laboratory mill of the aforementioned type according to the preamble of claim 2 and to an arrangement with a laboratory mill and at least one grinding bowl according to claim 10.

[0003] In centrifugal mills, the grinding bowls are arranged eccentrically to a drive axis within the mill and thus move in a circular path around the drive axis. In centrifugal ball mills, the rotation of a grinding bowl around its own axis is prevented. In contrast, in planetary ball mills, the grinding bowl also rotates around its own axis, forming a planetary gear system with a sun gear rotating around the center axis of the mill housing and at least one driven planet gear mounted thereon, supporting the grinding bowl and rotating around the sun gear axis.

[0004] In such mills, the grinding bowls are filled outside the mill before each grinding process, then sealed with a lid, and then inserted, for example, into a grinding bowl receptacle of a grinding bowl holder. Before the mill is started by switching on the drive, the grinding bowls are secured to the grinding bowl holder by a pre-tensioning device that is attached after the grinding bowl has been inserted into the grinding bowl receptacle. This ensures that they are securely fastened even under the influence of the considerable centrifugal forces that occur and do not pose a danger to the operator.

[0005] Generic laboratory mills in the design of a planetary ball mill are known from DE 42 37 055 C1, wherein a housing with a housing base is provided for holding and receiving a grinding bowl. The housing is placed and fixed on a rotating clamping plate, which is a component of a rotating sun gear. Each housing has webs projecting upwards laterally towards the grinding bowl and containing openings for receiving a multi-armed spider that spans the grinding bowl. A locking screw, which can be rotated via handles and clamps the grinding bowl against the housing base, extends through the spider. As a securing measure and positioning aid for inserting the grinding bowl, the housing base can be provided with a pin engaging in the base of the grinding bowl, wherein the pin is eccentric to the receiving axis in the base of the housing and a blind hole is provided at a corresponding point on the grinding bowl.The pin acts as an anti-rotation device. This secures the grinding bowl to the base of the housing, thereby counteracting any wandering movements of the grinding bowl.

[0006] The pin that engages the base of the grinding bowl as an anti-twist device is subject to high surface pressure due to the high forces resulting from rotational movements during operation of the planetary ball mill, and thus to significant wear. Wear can cause the anti-twist pin to bend or even break, so that the grinding bowl is no longer securely held in place against the base of the housing. Furthermore, with increasing wear, precise positioning of the grinding bowl when inserting it into the housing becomes more difficult.

[0007] CN 208839700 U shows a multi-part grinding bowl lid and a multi-part grinding bowl of a laboratory mill with a lid holder and a lid insert.

[0008] US 2016 / 0107164 A1 discloses a closing system for ball mills and a method for opening and closing ball mills.

[0009] The object of the present invention is to provide a laboratory mill, a grinding bowl and an arrangement of the type mentioned at the outset, which ensure a secure, positive-locking fixing of a grinding bowl to, in and / or on a grinding bowl holder with low surface pressure and reduced wear of at least one anti-rotation device provided for fixing the grinding bowl and enable an exact positioning of the grinding bowl relative to the grinding bowl holder in a simple manner.

[0010] The above-mentioned object is achieved according to the invention by a laboratory mill having the features of claim 1 and by a grinding bowl having the features of claim 2. Advantageous developments of the invention are the subject of the dependent claims.

[0011] According to the invention, the grinding bowl holder has at least one surface relief or a surface topography as an anti-rotation means on an axial surface facing a grinding bowl bottom during grinding operation, which can be positively connected to a counter-relief complementary to the surface relief or a corresponding complementary surface topography on an axial surface of the grinding bowl bottom to form an anti-rotation means.

[0012] Accordingly, in a grinding bowl according to the invention, a surface relief is provided on an axial surface of a grinding bowl base facing a grinding bowl holder of the laboratory mill during grinding operation as an anti-rotation means, which can be positively connected to a counter-relief complementary to the surface relief on an axial surface of the grinding bowl holder to form an anti-rotation means.

[0013] According to the invention, the rotational security of the grinding bowl is achieved by means of complementary reliefs or profiles on the underside of the grinding bowl base and the facing upper side of the grinding bowl holder.

[0014] The terms "surface relief" and "counter-relief" are to be interpreted as having the same meaning within the meaning of the invention.

[0015] According to the invention, a specific surface profiling or anti-twist geometry is provided on an axially upwardly directed surface of the grinding bowl holder facing the grinding bowl, and a complementary surface profiling is provided on an axially downwardly directed surface of the grinding bowl base facing the grinding bowl holder, in order to prevent a relative rotation of the grinding bowl about its central axis in the coupled state, i.e. after at least partially positive connection of the surface profilings or anti-twist geometries on the mutually facing surfaces of the grinding bowl holder and the grinding bowl base.When inserting the grinding bowl into the grinding bowl holder, the relief-like surface areas of the grinding bowl base and the grinding bowl holder engage with each other at least in some areas and / or come into contact with each other in the circumferential direction and thereby form a positive connection in the circumferential direction in order to prevent a rotational movement of the grinding bowl relative to the grinding bowl holder about the axial center axis of the grinding bowl.

[0016] In order to ensure that the grinding bowl is secured against rotation relative to the grinding bowl holder, the surface relief and the counter-relief each have a suitable complementary relief pattern in the circumferential direction of the grinding bowl, i.e., a relief pattern that interacts in the sense of securing against rotation and is related to the outer edges of the reliefs.

[0017] The effective anti-rotation surfaces of the surface reliefs or surface topographies on the grinding bowl holder and the grinding bowl are formed by axial surface sections extending in the axial direction, i.e. in the direction of the center axis of the grinding bowl, on the surfaces of the grinding bowl holder and grinding bowl facing each other during grinding operation, which prevent a rotational movement of the grinding bowl relative to the grinding bowl holder or cause a positive connection in the circumferential direction when the grinding bowl is inserted or placed in or on the grinding bowl holder.

[0018] An anti-rotation pin, provided in the prior art as the sole anti-rotation device, is subject to significant wear during operation of a laboratory mill due to its small anti-rotation surface. The anti-rotation surface of the pin is formed by its cylindrical outer surface. The surface reliefs or surface topographies of the surfaces of the grinding bowl holder and grinding bowl that face each other during grinding operation, provided according to the invention, allow the effective anti-rotation surface to be significantly increased compared to the effective anti-rotation surface or outer surface of an anti-rotation pin, which leads to a reduction in surface pressure and thus to less wear on the effective anti-rotation surfaces.Due to the axial surface sections which cooperate according to the invention for a positive connection in the circumferential direction on the surfaces of the grinding bowl holder and the grinding bowl which face each other during grinding operation, the grinding bowl is fixed in a positive connection with the base of the grinding bowl holder over a long service life, even under high centrifugal forces, and wandering movements of the grinding bowl are counteracted with a high degree of reliability.

[0019] A surface relief within the meaning of the invention is formed by at least one surface region that is recessed or projected in the axial direction relative to an adjacent surface region of the surface, wherein, when the grinding bowl is placed on or into a base of the grinding bowl holder, at least one recessed or projected surface region on an axial surface of the grinding bowl base engages with at least one projected or recessed surface region on an axial surface of the grinding bowl holder. The complementary geometries of the reliefs or the complementary contours of the outer edges of the reliefs are selected such that a rotational movement of the grinding bowl relative to the grinding bowl holder is excluded after the recessed and projected surface regions on the grinding bowl base and the holding device have been joined together.

[0020] Particularly preferably, the relief surface merges integrally into the adjacent surface of the grinding bowl base or the grinding bowl holder, or the surface relief is formed in the surface of the grinding bowl base or the grinding bowl holder.

[0021] Further preferably, the surface relief has a flat relief surface.

[0022] The recessed or projecting surface area forming the relief can have a height or depth that is constant over the entire relief extension compared to an adjacent (flat) surface area of ​​the grinding bowl holder or the grinding bowl, in particular wherein the height or depth can be between 1 and 5 mm, for example 2 mm.

[0023] In order to provide sufficiently large anti-twist surfaces and to reduce wear on the surface relief during grinding operation, the surface relief can extend, relative to an outer edge of the relief, in the circumferential direction at least over a rotation angle around the center axis of the grinding bowl of at least 30°, preferably over a rotation angle of at least 60°, in particular over a rotation angle of 180° or more. However, the surface relief is particularly preferably formed by a continuously circumferential or self-contained depression or elevation over the entire circumference of the grinding bowl. However, a plurality of separate depressions or elevations can also be provided in order to form a relief or anti-twist profile on the grinding bowl base and / or on the grinding bowl holder.

[0024] In a plan view of the relief surface or in a cross-sectional view through the surface relief based on a section transverse to the central axis of the grinding bowl (based on the arrangement of the grinding bowl in the holding device during operation of the laboratory mill), the surface relief can have any contour of a radially inner or radially outer longitudinal or outer edge of the relief, provided that in the interaction with the counter-relief, an anti-twist protection of the grinding bowl is ensured by a positive fit of the reliefs achieved in the circumferential direction.For this purpose, the surface relief has, in a plan view of the relief surface, a contour profile of at least one outer edge of the surface relief which deviates from the exact circular shape and / or from the exact ring shape, in particular wherein the outer edge has at least one section-wise change in the curvature behavior in the circumferential direction, in particular wherein the outer edge forms an undercut for a positive connection with the counter-relief acting in the circumferential direction.

[0025] In principle, the surface relief can have any desired relief geometry, defined by the circumferential extension of a longitudinal or outer edge of the surface relief. Particularly preferably, the relief geometry can approximate the geometry of a multi-tooth tooth, with the contour line of a longitudinal or outer edge of the surface relief forming several teeth or points that can interact with complementary teeth or points of the counter-relief to form a positive coupling acting in the circumferential direction. This design of the relief promotes force distribution and ensures a broad application of the forces arising as a result of the rotary movement of the components of the laboratory mill during grinding operation. Flower-shaped geometries can also be realized.

[0026] A particularly favorable wear behavior and an advantageous effect of the surface relief as a positioning aid when inserting or placing the grinding vessel in or on the base of the grinding bowl holder can be achieved if the surface relief shows a circumferentially, preferably at least in sections, wave-shaped course of a radially inner and / or a radially outer longitudinal or outer edge of the surface relief.

[0027] Tests carried out in connection with the invention have shown that particularly favorable wear behavior of the surface relief can be achieved if the surface relief, in a plan view of the relief surface and based on the course of a radially inner and / or a radially outer longitudinal or outer edge of the surface relief, is flower-shaped or star-shaped in the circumferential direction with a plurality of radial bulges and radial indentations following in the circumferential direction, in particular wherein at least 3 radial bulges, more particularly between 4 and 6 radial bulges, can be provided. The bulges and indentations form relief cams which make it possible to insert or place the grinding bowl in and / or onto the grinding bowl holder only in a defined position relative to the grinding bowl holder.This results in a handling advantage, particularly in conjunction with a pre-tensioning device that features a spider that can be attached to the grinding bowl holder as a counterbearing for a spindle that pre-tensions the grinding bowl against the grinding bowl holder, as the spider can be easily and precisely pre-positioned. The relief cams of the flower- or star-shaped surface relief, like a multi-tooth profile, promote force distribution with a wide force application.

[0028] The surface relief can have rounded edges and peripheral surfaces to facilitate the formation of a positive connection with the counter-relief. If the surface relief is flower- or star-shaped and features a plurality of relief cams and relief valleys arranged between them, the relief can have a flattened peripheral contour in the area of ​​the relief cams and / or in the area of ​​the relief valleys. This results in a high wear resistance of the profile.

[0029] For simplified centering of the grinding bowl when inserting or placing the grinding bowl in or on the base of the grinding bowl holder, at least one centering relief can be formed in and / or on the surface of the grinding bowl holder and / or in and / or on the surface of the grinding bowl base, which cooperates with a complementary centering relief on the grinding bowl base or the holding device for centering the grinding bowl relative to the holding device when the positive connection between the surface relief and the counter-relief is formed.

[0030] For example, a centrally arranged recessed surface area (centering recess) can be provided on the axial surface of the grinding bowl holder facing the grinding bowl base during grinding operation. This recess is positively connected to a complementary, centrally arranged projecting surface area (centering projection) on the surface of the grinding bowl base when the grinding bowl is inserted or placed into or onto the base of the grinding bowl holder. In particular, the centering recess or the centering projection can be formed by a central, in particular circular, flat surface section of the axial surface.

[0031] Particularly preferably, a central, in particular circular, flat surface section of the axial surface can be provided as a centering projection or as a centering recess, which is delimited and / or surrounded, preferably completely, by a surface relief, in particular annular in shape, wherein the surface relief acts as an anti-twist means in the manner described above.

[0032] In addition to the anti-rotation device implemented according to the invention via complementary surface reliefs on the grinding bowl holder and grinding bowl base, wherein the reliefs are designed to hold the grinding bowl in a defined, predetermined position relative to the rotation axis and / or as a positioning aid, an additional anti-rotation device can be provided via at least one anti-rotation element, in particular an anti-rotation pin. In particular, the anti-rotation element can be provided to form a positive connection between the grinding bowl holder and a grinding bowl in the surface region of the surface relief. At least one anti-rotation pin can be provided, which engages axially parallel to the central axis of the grinding bowl into a bore provided in a surface section of the surface relief.If the surface relief is, for example, flower-shaped or star-shaped and has a plurality of relief cams and relief valleys arranged between them, holes can be provided in the area of ​​the relief cams to accommodate a locking pin.

[0033] Although the larger effective anti-rotation surface of the surface relief provided as an anti-rotation means according to the invention, compared to the circular shape, results in increased wear resistance, signs of wear can occur on the surface relief over a long period of use. In a preferred embodiment of the invention, the surface relief can therefore be formed on a relief shaped piece detachably connected to the holding device or the grinding bowl, which allows the relief shaped piece to be replaced as needed depending on the state of wear.

[0034] Further advantages, features, properties, and aspects of the present invention emerge from the claims and the following description of preferred embodiments with reference to the drawings, wherein the features of the embodiments can be combined with one another. They show: Fig. 1 shows an arrangement of a grinding bowl according to the invention mounted on and / or inserted into a disc-like base of a grinding bowl holder (not shown in detail) of a laboratory mill according to the invention, in particular a planetary ball mill, in a perspective view obliquely from above; Fig. 2 shows a view of the grinding bowl base of the grinding bowl from Fig. 1 from below; Fig. 3 a top view of the bottom of the grinding bowl holder from Fig. 1 ; Fig. 4 a perspective view of the bottom and the grinding bowl of the Fig. 1shown arrangement obliquely from below before placing or inserting the grinding bowl onto or into the base, Fig. 5 a perspective view of the base and the grinding bowl of the Fig. 1 shown arrangement obliquely from above before placing or inserting the grinding bowl onto or into the base, Fig. 6 a second embodiment of a grinding bowl according to the invention in a perspective view obliquely from below and Fig. 7 a third embodiment of a grinding bowl according to the invention in a perspective view obliquely from below.

[0035] In Fig. 1An arrangement of a disc-like base 1 of a grinding bowl holder (not shown in detail) of a laboratory mill, in particular a planetary ball mill, for at least one grinding bowl 2 of the laboratory mill is shown. The grinding bowl holder can provide a holding and / or receiving device as described in DE 20 2008 008 473 U1, wherein the grinding bowl 2 can be placed on the base 1 and secured by means of a pretensioning device comprising a spider that can be secured against a grinding bowl receptacle connected to the base 1 of the grinding bowl holder and serves as an abutment for a spindle that braces the grinding bowl 2 against the base 1.

[0036] The grinding bowl holder can also have a spatial-geometric design that differs from the holding and / or receiving device shown and described in DE 20 2008 008 473 U1. It is essential that the grinding bowl holder is intended and designed to hold or secure at least one grinding bowl 2 of the laboratory mill.

[0037] In the Figs. 1 to 5 In the embodiment shown, the base 1 is disk-shaped and has bores 3 on the shell side with an internal thread for fixing vertical tabs (not shown) which form a grinding bowl receptacle, as shown and described in DE 20 2008 008 473 U1.

[0038] The soil 1 has according to Fig. 3 and Fig. 5On its surface 4 facing a grinding bowl base of the grinding bowl 2 during grinding operation, it has a flat surface area 5 that is recessed relative to the adjacent surface 4 and forms a surface relief of the base 1. The surface relief is delimited radially inwardly by an outer edge with a wavy contour line 6. Axial surfaces 7 of the outer edge form anti-twist surfaces. The recessed flat surface area 5 is continuously circumferential and self-contained.

[0039] In the embodiment shown, the contour line 6 is wave-shaped with radial indentations 8 and radial bulges 9 or contour cams.

[0040] The grinding bowl bottom of the grinding bowl 2 has Fig. 2 and Fig. 4On its surface 10 facing the base 1 of the grinding bowl holder during grinding operation, the grinding bowl holder has a flat surface area 11 that projects beyond the adjacent surface 10 and forms a surface relief of the grinding bowl base. The surface relief is bounded radially outward by an outer edge with a wavy contour line 12 and radially inward by an outer edge with a circular contour line 13. Axial surfaces 14 of the outer edge form anti-rotation surfaces. The projecting flat surface area 11 is continuously circumferential and self-contained.

[0041] In the embodiment shown, the contour line 12 is wave-shaped with radial indentations 15 and radial bulges 16 or contour cams.

[0042] When the grinding bowl is placed on the base 1 of the grinding bowl holder, the projecting surface area 11 on the grinding bowl base engages in a form-fitting manner in the recessed surface area 5 of the base 1, so that a form-fitting coupling of the grinding bowl 2 with the base 1 is achieved in the circumferential direction of the grinding bowl 2 or along a lateral surface of the grinding bowl 2, which prevents a rotational movement of the grinding bowl 2 about its central axis Z. In this case, the axial surfaces 7, 14 on the base 1 or the grinding bowl base, which come into contact with one another, prevent a rotational movement of the grinding bowl 2 about its central axis Z when coupled to the grinding bowl holder due to the selected complementary contour geometries of the outer edges of the surface relief.In this case, the radially outwardly extending bulges 16 on the grinding bowl base come to rest in a form-fitting manner in the circumferential direction against the radially inwardly extending bulges 9 on the base 1 of the grinding bowl holder.

[0043] As can be seen from Fig. 5 The base 1 of the grinding bowl holder can have a central, recessed surface area 15 with a circular base area, which is recessed compared to an adjacent surface area 16 of the base 1, which in turn is delimited by the contour line 6 of the surface relief on the base 1, and can have a depth of, for example, 1 to 5 mm.

[0044] As can be seen from Fig. 7The grinding bowl base can have a central, projecting surface area 17 with a circular base area, which is raised compared to the adjacent surface area 11 of the grinding bowl base, which forms the relief surface of the surface relief on the grinding bowl base, and can have a height of, for example, 1 to 2 mm.

[0045] When the grinding bowl 2 is placed on the base 1, the projecting surface area 17 on the grinding bowl base engages the recessed surface area 15 on the base 1, so that the grinding bowl 2 is centered. As a result, complementary centering reliefs are formed on the grinding bowl base and on the base 1 of the grinding bowl holder, which cooperate to center the grinding bowl and can be connected to one another in a form-fitting manner.

[0046] As can be seen from the Figures 2 , 6 and 7holes 18 can be provided in the surface area 11 of the surface relief formed on the grinding bowl base to accommodate at least one anti-twist pin (not shown) fixed to the base 1 as a further anti-twist means.

[0047] The surface relief on the grinding bowl base and on the base 1 of the grinding bowl holder each features rounded edges and a flattened profile in the area of ​​the indentations 8, 16 and the protrusions 9, 15. This results in a high level of wear resistance of the profile. Furthermore, the meshing of the reliefs is simplified.

[0048] The surface relief on the base 1 of the grinding bowl holder can be formed on a particularly disc-shaped or annular relief piece that is detachably connected to the base 1. In particular, a replaceable ring part can be provided on which the surface relief is formed and which can be screwed to a base body 19 of the base 1 via screws 20. This allows the ring part to be easily replaced when the surface relief becomes increasingly worn. It is understood that, in principle, the surface relief can also be provided for the grinding bowl base on a particularly disc-shaped or annular relief piece that is detachably connected to the grinding bowl 2.

Claims

1. Laboratory mill, in particular centrifugal ball mill and / or planetary ball mill, having at least one grinding bowl holder for at least one grinding bowl (2) and having at least one anti-rotation means for holding the grinding bowl (2) in a defined, predetermined position relative to the grinding bowl holder and / or as a positioning aid, wherein the grinding bowl holder has, on an axial surface (4) which faces a grinding bowl base during grinding operation, at least one surface relief as an anti-rotation means, which surface relief can be connected in a form-fitting manner to a mating relief, which is complementary to the surface relief, on an axial surface (10) of the grinding bowl base in order to form an anti-rotation means, characterized in that the surface relief is formed by a depression or elevation which runs continuously around or is closed in itself over the entire circumference of the grinding bowl (2), and / or in that the surface relief has, in a plan view of the relief surface, a contour profile of at least one outer edge of the surface relief which deviates from the exact circular shape and / or from the exact annular shape.

2. Grinding bowl (2) for a laboratory mill according to Claim 1, having a surface relief on an axial surface (10), which faces a grinding bowl holder of the laboratory mill during grinding operation, of a grinding bowl base as an anti-rotation means, which surface relief can be connected in a form-fitting manner to a mating relief, which is complementary to the surface relief, on an axial surface (4) of the grinding bowl holder in order to form an anti-rotation means, characterized in that the surface relief is formed by a depression or elevation which runs continuously around or is closed in itself over the entire circumference of the grinding bowl (2), and / or in that the surface relief has, in a plan view of the relief surface, a contour profile of at least one outer edge of the surface relief which deviates from the exact circular shape and / or from the exact annular shape.

3. Laboratory mill according to Claim 1 or grinding bowl (2) according to Claim 2, characterized in that the surface relief is formed by at least one surface region (5, 11) which is recessed or projects in the axial direction and is formed with respect to an adjacent surface region of the surface (4, 10), wherein, when the grinding bowl (2) is placed on or in a base (1) of the grinding bowl holder, at least one recessed or projecting surface region (11) on an axial surface (10) of the grinding bowl base engages in at least one projecting or recessed surface region (5) on an axial surface (4) of the grinding bowl holder.

4. Laboratory mill or grinding bowl according to one of the preceding claims, characterized in that the relief surface merges integrally into the adjacent surface region of the surface (4, 10), and / or in that the surface relief has a planar relief surface.

5. Laboratory mill or grinding bowl (2) according to one of the preceding claims, characterized in that the outer edge has, in the circumferential direction, at least one change in the curvature behavior in sections, in particular wherein the outer edge forms an undercut for a form fit, which acts in the circumferential direction, with the mating relief.

6. Laboratory mill or grinding bowl according to one of the preceding claims, characterized in that the surface relief has, in a plan view of the relief surface, a contour profile, which is undulating in the circumferential direction, preferably at least in sections, of at least one outer edge of the surface relief, and / or in that the surface relief forms an internal or external multi-tooth profile.

7. Laboratory mill or grinding bowl (2) according to one of the preceding claims, characterized in that at least one centring relief is formed in the base (1) of the grinding bowl holder and / or the grinding bowl base, which centring relief can be connected in a form-fitting manner to a complementary centring relief on the grinding bowl base or the grinding bowl holder in order to centre the grinding bowl (2) relative to the holding device when the form-fitting connection is formed between the surface relief and the mating relief.

8. Laboratory mill or grinding bowl (2) according to one of the preceding claims, characterized in that at least one bore (18), which extends in the axial direction, for receiving an anti-rotation pin as a further anti-rotation means is provided in and / or on the surface (4) of the grinding bowl holder and / or on the surface (10) of the grinding bowl base, in particular wherein the bore (18) is arranged in the surface region of the relief surface.

9. Laboratory mill or grinding bowl (2) according to one of the preceding claims, characterized in that the surface relief is formed on an in particular disc-shaped or annular exchangeable part which is connected releasably to the holding device or the grinding bowl (2).

10. Arrangement having a laboratory mill and having a grinding bowl (2) according to one of the preceding claims.

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