Abstract
A stirred ball mill may include a milling jar, at least three agitator shafts, and a drive. The milling jar may be arranged in a main direction and may have a milling chamber that is adapted to receive milling material and milling aid elements. Each of the at least three agitator shafts has a center axis that is arranged parallel to the main direction of the milling jar and is configured as a screw that is mounted fixedly to a frame in the milling jar such that each agitator shaft is rotatable about its center axis. The drive is configured to rotate the agitator shafts about their respective center axes without any contact between the agitator shafts. The center axes of the agitator shafts may be arranged as side edges of a prism.
Claims
1.-14. (canceled)
15. A stirred ball mill comprising: a milling jar arranged in a main direction and having a milling chamber that is configured to receive milling material and milling aid elements; at least three agitator shafts, each agitator shaft having a center axis that is parallel to the main direction of the milling jar, wherein the center axes of the agitator shafts are arranged as side edges of a prism, wherein each agitator shaft is configured as a screw that is mounted fixedly to a frame in the milling jar such that the agitator shaft is rotatable about the center axis; and a drive configured to rotate the agitator shafts about their respective center axes without any contact between the agitator shafts.
16. The stirred ball mill of claim 15 wherein the drive comprises a dedicated drive unit for each of the agitator shafts.
17. The stirred ball mill of claim 15 wherein the drive comprises a common drive unit for at least two of the agitator shafts.
18. The stirred ball mill of claim 15 wherein the drive is configured to drive at least one of the agitator shafts at a rotational speed that is regulatable independently of rotational speeds of the other agitator shafts.
19. The stirred ball mill of claim 15 comprising an inner agitator shaft that has a center axis that is parallel to the main direction of the milling jar, wherein the inner agitator shaft is configured as a screw that is mounted fixedly in the milling jar and is configured to rotate about its center axis without contacting any one of the at least three agitator shafts, wherein the center axis of the inner agitator shaft is arranged within the prism that is formed by the center axes of the at least three agitator shafts.
20. The stirred ball mill of claim 19 comprising a braking device that is configured to decrease a rotational speed or prevent rotational movement of the inner agitator shaft.
21. The stirred ball mill of claim 19 wherein the inner agitator shaft is not connected to the drive.
22. The stirred ball mill of claim 19 wherein the drive includes a drive unit that is configured to rotate the inner agitator shaft about its center axis.
23. The stirred ball mill of claim 19 wherein the at least three agitator shafts are configured for rotational movement in a same rotational direction, wherein the inner agitator shaft is configured for rotational movement in a rotational direction that is different than the same rotational direction of the at least three agitator shafts.
24. The stirred ball mill of claim 15 wherein the agitator shafts are configured to rotate in a same rotational direction.
25. The stirred ball mill of claim 15 wherein a first of the agitator shafts is a right-handed screw, wherein a second of the agitator shafts is a left-handed screw.
26. The stirred ball mill of claim 15 wherein an external diameter of each of the agitator shafts is at most half of a maximum internal width of the milling chamber.
27. A stirred ball mill stirring unit for a stirred ball mill, the stirred ball mill stirring unit comprising: at least three agitator shafts, each of the at least three agitator shafts having a center axis, being configured as a screw that is rotatable about the center axis, and being configured to be fixedly mounted to a frame in a milling jar, wherein the center axes of the at least three agitator shafts are parallel to one another and are arranged as side edges of a prism; and a drive that is configured to rotate the at least three agitator shafts about their respective center axes without causing any contact between the at least three agitator shafts, wherein either: the drive comprises a dedicated drive unit for each of the at least three agitator shafts, or the drive comprises a common drive unit for at least two of the at least three agitator shafts, wherein the drive is configured to drive at least one of the at least three agitator shafts at a rotational speed that is regulatable independently of rotational speeds of the other of the at least three agitator shafts, the stirred ball mil stirring unit further comprising an inner agitator shaft that has a center axis that is parallel to a main direction of the milling jar, is configured as a screw that is rotatable about its center axis, and is configured to be fixedly mounted to the frame in a milling jar, wherein the inner agitator shaft is configured so as not to contact any one of the at least three agitator shafts, wherein the center axis of the inner agitator shaft is disposed within the prism formed by the center axes of the at least three agitator shafts, wherein either the drive is not connected to the inner agitator shaft or the drive includes a drive unit for rotating the inner agitator shaft about its center axis.
28. The stirred ball mill stirring unit of claim 27 comprising a braking device that is configured to decrease a rotational speed or to prevent rotational movement of the inner agitator shaft.
29. The stirred ball mill stirring unit of claim 27 wherein an external diameter of each of the at least three agitator shafts is at most half a maximum internal width of a milling chamber.
30. A method for comminuting milling material, the method comprising: suspending the milling material to be comminuted in a milling aid liquid, thereby obtaining a milling material dispersion; continuously introducing the milling material dispersion into a lower section of a milling chamber, filled with milling aid elements, of a stirred ball mill, continuously vertically conveying a part of the milling material dispersion from the lower section of the milling chamber into an upper section of the milling chamber via at least three rotating, vertical agitator shafts that are mounted fixedly to a frame, wherein the agitator shafts do not make contact with one another, are oriented at least substantially vertically parallel to one another, and have center axes that are arranged as side edges of a prism, wherein a processed milling material dispersion is obtained, wherein at least one part of the milling material dispersed in the milling aid liquid is comminuted; continuously discharging a part of the processed milling material dispersion from the upper section of the milling chamber; and concluding separating of the comminuted milling material from the discharged processed milling material dispersion.
Description
[0047] The invention is to be described in greater detail in the following text with reference to the appended drawings of particularly advantageous examples, without restriction of the general inventive concept which forms the basis of said examples, further advantages and possible uses also additionally arising therefrom. In the drawings, in each case diagrammatically:
[0048] FIG. 1 shows different diagrammatic illustrations of a conventional stirred ball mill, namely a lateral sectional view of a conventional stirred ball mill in FIG. 1a, a simplified symbolic side view of a conventional stirred ball mill in FIG. 1 b, a lateral detailed view of the agitator shaft of a conventional stirred ball mill in FIG. 1c, and a simplified horizontal section through a conventional stirred ball mill in FIG. 1d,
[0049] FIG. 2 shows diagrammatic illustrations of stirred ball mills with three agitator shafts, namely a simplified symbolic side view of a stirred ball mill with three agitator shafts in FIG. 2a, and a simplified horizontal section through a stirred ball mill with three agitator shafts in FIG. 2b,
[0050] FIG. 3 shows diagrammatic simplified horizontal sections through stirred ball mills with four agitator shafts which differ with regard to the rotational directions of the four agitator shafts, namely for a first embodiment in FIG. 3a, for a second embodiment in FIG. 3b, for a third embodiment in FIG. 3c, and for a fourth embodiment in FIG. 3d, and
[0051] FIG. 4 shows diagrammatic simplified horizontal sections through stirred ball mills with five outer agitator shafts, namely FIG. 4a, FIG. 4b and FIG. 4c, FIG. 4c additionally having an inner agitator shaft.
[0052] FIG. 1 shows different diagrammatic illustrations of a conventional stirred ball mill from the prior art and details in this respect. Here, FIG. 1 a shows a conventional stirred ball mill 1′ in a lateral sectional view. The stirred ball mill 1′ is a stirred ball mill with a vertically oriented screw. The stirred ball mill 1′ has a milling jar 2′ which is arranged vertically, with an interior space which is configured as a milling chamber 5′. A single agitator shaft 3′, the center axis of which is likewise oriented vertically as a rotational axis, is arranged in the milling chamber 5′. The milling chamber 5′ is covered toward the top by a covering, on which the drive 4′ for the single agitator shaft 3′ is situated. For this purpose, the drive 4′ has a drive unit 6′ which is configured as an electric motor and is the uppermost termination of the stirred ball mill 1′. Moreover, the drive has a vertical axle, by which the drive unit 6′ is operatively connected to the single agitator shaft 3′. The upper end of the single agitator shaft 3′ is fastened by means of a flange connection to the lower end of the axle in such a way that the torque which is provided by the drive unit 6′ is transmitted to the single agitator shaft 3′. The individual agitator shaft 3′ is configured as a screw, namely as a screw of cylindrical basic shape with a filled center region. This screw has two thread turns 8′, with the result that it is a two-start screw. The drive 4′ and the agitator shaft 3′ together form the stirred ball mill stirring unit. An opening which forms the intake 9′ of the milling chamber 5′ is provided in the side wall of the milling jar 2′ close to the bottom, configured as a base surface, of the milling jar 2′. During operation, a mixture of milling material dispersion and milling aid elements (not shown) is fed continuously to the milling chamber 5′ through said opening. As a consequence of the rotational movement of the agitator shaft 3′, the mixture of milling material dispersion and milling aid elements in the milling chamber 5′ is conveyed from bottom to top in the vertical direction and is subjected in the process to pronounced impact stress and shear stress, the milling material being comminuted. In order to reduce the wear of the stirred ball mill 1′, the wall of the milling chamber 5′ is lined with a milling chamber lining 11′ made from a high-strength material. In its upper region, the milling jar 2′ has a further opening which forms the discharge 10′ of the milling chamber 5′. Said opening is arranged outside the milling volume. A screen is situated in front of said opening, with the result that the milling aid elements are retained in the milling chamber 5′, and merely the milling material dispersion with the at least partially comminuted milling material is discharged from the milling chamber via the discharge 10′.
[0053] FIG. 1b shows a simplified symbolic side view of the conventional stirred ball mill 1′ (shown in FIG. 1a). In FIG. 1b, many structural elements are omitted for the sake of improved clarity, and what is shown is merely the stirred ball mill 1′ with the milling jar 2′, in the interior space 5′ of which the single agitator shaft 3′ with the thread turn 8′ is situated, which agitator shaft 3′ is set in a rotational movement via the drive 4′ which is arranged on the milling jar 2′. The drive 4′ and the agitator shaft 3′ together also form the stirred ball mill stirring unit here.
[0054] FIG. 1c shows a lateral detailed view of the agitator shaft 3′ of the conventional stirred ball mill (shown in FIG. 1a). The agitator shaft 3′ is configured as a two-start screw of cylindrical basic shape with a filled central region. Two thread turns 8′ which are provided with an abrasion-resistant coating are arranged on the shell side of the central center region which includes the center axis of the agitator shaft 3′. The flange connection, via which the agitator shaft 3′ is connected directly to the axle of the drive, is indicated at the upper end of the agitator shaft 3′.
[0055] FIG. 1d shows a simplified horizontal section through the conventional stirred ball mill 1′ (shown in FIG. 1a). As in FIG. 1b, a simplified illustration has likewise been selected here, in which most of the structural elements are not shown for reasons of clarity, as a result of which substantial differences from the present invention can be seen more clearly. FIG. 1d is a horizontal section through the stirred ball mill 1′ at the level of the agitator shaft 3′. The agitator jar 2′, the interior space of which is configured as a milling chamber 5′, has a square cross section (outline). In FIG. 1d, the thread turn is not shown separately for the single agitator shaft 3′, but merely the maximum cross-sectional area which is claimed by the agitator shaft 3′ is shown, that is to say the outer border of the screw of the agitator shaft 3′ (this is therefore not the crossover sectional area of the agitator shaft 3′ itself, but rather the projection of the agitator shaft 3′ onto the plane of the illustration). Furthermore, the effective diameter of the agitator shaft 3′ is illustrated as a double arrow, and the center axis, running perpendicularly with respect to the plane of the illustration, of the agitator shaft 3′ is illustrated as a cross, the agitator shaft 3′ rotating about said center axis in the rotational direction which is represented by way of a single arrow (here, in the clockwise direction).
[0056] FIG. 2 shows diagrammatic illustrations of stirred ball mills in accordance with one embodiment of the present invention, the stirred ball mills having three agitator shafts. FIG. 2a shows a simplified symbolic side view of a stirred ball mill of this type with three agitator shafts, the illustration having been selected and analogously with respect to the illustration in FIG. 1b, with the result that many structural elements are not shown for the sake of improved clarity. The stirred ball mill 1 with a vertically oriented milling jar 2 can be seen in FIG. 2a, in the interior space 5 of which milling jar 2 three agitator shafts 3 with in each case one thread turn 8 are situated. The agitator shafts 3 are arranged in the form of a triangle, two agitator shafts 3 being positioned on the same plane parallel to the plane of the illustration, and a further agitator shaft 3 being positioned centrally in front of them in the viewing direction. A drive 4 is arranged on the milling jar 2, by means of which drive for the three agitator shafts 3 are set in rotation about the center axes. Here, the drive 4 comprises three separate drive units; instead, however, a common drive unit can also be provided which is connected via gear mechanisms to the three agitator shafts 3, or else two drive units, of which one drive unit drives two of the three agitator shafts 3 and the third drive unit drives the third agitator shaft 3. Each drive unit can have a dedicated controller, but a common controller can also be provided, which likewise comprises control of the rotational speeds of the three agitator shafts. The center axes of the three agitator shafts 3 are oriented parallel to one another and do not make contact with one another.
[0057] FIG. 2b shows a simplified horizontal section through a stirred ball mill in accordance with the above-described embodiment of the present invention. As in FIG. 1d, this is likewise a simplified illustration, in which most structural elements are not reproduced for reasons of improved clarity, as a result of which substantial differences from the conventional stirred ball mill (shown in FIG. 1d) come to light considerably more clearly. Accordingly, FIG. 2b is also a horizontal section through a stirred ball mill 1 at the level of the three agitator shafts 3. The agitator jar 2, the interior space of which is configured as a milling chamber 5, has a square cross section for improved distinguishability, but all other suitable forms are fundamentally also possible, for example a circular or oval cross section, a regular or irregular polygonal cross section, for example a triangle, a rhombus, a pentagon, hexagon, heptagon, octagon and the like. FIG. 2b does not show the thread turns for the three agitator shafts 3 separately, but merely the maximum crossover sectional areas which are claimed by the agitator shafts 3, that is to say the outer borders of the screws (that is to say, a projection of the outer edges of the thread turns onto the plane of the illustration). Furthermore, the center axes, running perpendicularly with respect to the plane of the illustration, of the agitator shafts 3 are shown as crosses, about which the agitator shafts 3 rotate in the rotational directions which are represented in each case by way of single arrows. In FIG. 2b, all three agitator shafts 3 have the same rotational direction in the clockwise direction, but all three agitator shafts 3 can also have the same rotational direction counter to the clockwise direction, or in each case two of the three agitator shafts can have a common rotational direction and the third can have an opposite rotational direction. The center axes of the three agitator shafts 3 are arranged as side edges of a trigonal prism.
[0058] Apart from the configuration of the steering unit with three agitator shafts, the remaining elements of a stirred ball mill 1 according to the invention can be fundamentally selected to be similar to the elements of conventional stirred ball mills; possible embodiments have already been mentioned in conjunction with the general description of the invention and with the description of FIG. 1.
[0059] For instance, the stirred ball mill can have, in particular, a horizontally arranged milling jar or a vertically arranged milling jar, and can be configured for a discontinuous, continuous or quasi-continuous procedure in wet operation or in dry operation. The milling jar which is arranged (vertically or horizontally) in the main direction can be formed, for example, from individual segments or can be configured in one piece. The milling chamber typically has a shape which is derived from that of a cylinder or polygonal prism, it being possible for its inner wall to have high-strength linings or coatings made from low-abrasion and wear-resistant materials. A vertically arranged milling jar which is configured for continuous operation as a rule has one or more intakes, for example on the base face or in the vicinity of the base face, wherein a discharge can be provided above the intake, for instance in the upper region of the milling jar. Moreover, the milling jar can have further elements, for example a separate feed opening for fresh milling aid elements, screen units for retaining the milling aid elements, maintenance openings and the like.
[0060] The stirred ball mill staring unit comprises the three agitator shafts 3 and the drive 4. Here, the drive has at least one suitable drive unit, for instance a motor, and further components, such as, for instance, units for changing the rotational speed, for example frequency converters, or other control units, for instance those with control electronics or logic circuits, or else machine elements for changing motion variables, for example gear mechanisms. For instance, a separate drive unit can be provided for each agitator axle, but a plurality of agitator shafts or even all agitator shafts can have a common drive unit, it being possible for the actuation of the different drive units to take place via a common controller or via separate controllers.
[0061] The three agitator shafts in each case have a center axis which is arranged parallel to the main direction of the milling jar and about which the agitator shafts are configured rotatably, without the three agitator shafts making contact with one another in the process. The agitator shafts are mounted fixedly to the frame in the milling jar, and have thread turns as agitator elements, with the result that the agitator shaft overall are configured as screws, for example as axially arranged single-start or multiple-start screws, for instance as two-start screws, three-start screws or four-start screws, it being possible, for example, for said screws to be those with a cylindrical basic shape and those with a slightly conical basic shape, for them to have a filled center region or unfilled center region, and for them to be right-handed screws or left-handed screws of a respective suitable screw line, screw surface or coil surface, lead and angle. Furthermore, the screws (above all, their thread turn and tip) can have high-strength linings or coatings made from low-abrasion and wear-resistant materials. As is shown in the following comments, more than three agitator shafts can fundamentally also be provided (for example, for agitator shafts, five agitator shafts or six agitator shafts), the center axes of which can then represent the side edges of prisms which have different base areas, for example of a triangle, a square, a pentagon, hexagon or the like. The agitator shaft can be selected to be identical or different and can therefore also have different diameters and screw geometries.
[0062] In the case of the comminution of milling material in a stirred ball mill of this type with a vertically arranged milling jar in wet operation, the milling material to be comminuted is first of all suspended in a milling aid liquid, a milling material dispersion being obtained. The milling material dispersion is then introduced continuously into a lower section of the milling chamber of the above-described stirred ball mill, which milling chamber is filled with milling aid elements. The mixture obtained here of milling material dispersion and milling aid elements is stirred/thoroughly mixed by way of the rotational movement of the three vertical agitator shafts which are mounted fixedly to the frame, do not make contact with one another, and are oriented at least substantially vertically parallel to one another, the center axes being arranged as side edges of a prism, namely a trigonal prism. During a rotational movement, the milling material is comminuted and at the same time a part of the milling material dispersion is conveyed continuously out of the lower section of the milling chamber vertically into an upper section of the milling chamber. The processed milling material dispersion which is obtained in this way and in which at least part of the milling material which is dispersed in the milling aid liquid has already been comminuted is finally discharged continuously from the upper section of the milling chamber. Here, the milling aid elements can be separated from the milling material dispersion, for instance with the aid of a screen in front of the discharge of the stirred ball mill. Finally, the comminuted milling material is separated from the discharged milling material dispersion. Possible embodiments of a comminution method of this type have already been mentioned in conjunction with the general description of the invention.
[0063] FIG. 3 shows a diagrammatic simplified horizontal sections through stirred ball mills in accordance with further embodiments of the present invention, each stirred ball mill which is shown there having in each case four agitator shafts. The form of simplified illustrations has also been selected here, which form in each case shows horizontal sections through a stirred ball mill 1 at the level of the four agitator shafts 3. FIGS. 3a, 3b, 3c and 3d in each case show agitator jars 2, the interior space of which is configured in each case as a milling chamber 5 which has a square cross section. The thread turns are not shown separately in each case for the four agitator shafts 3, but rather merely the outer boundaries of the screws. The center axes, running perpendicularly with respect to the plane of the illustration, of the agitator shafts are indicated as crosses, about which the agitator shafts 3 rotate in the rotational directions which are represented in each case by way of the singularities. The center axes of the four agitator shafts 3 are arranged in each case as side edges of a prism with a square base area. The four partial illustrations in FIG. 3 differs merely in terms of the rotational direction of the respective four agitator shafts. In FIG. 3a, all four agitator shafts 3 have the same rotational direction (here, in the clockwise direction); in FIG. 3b, three agitator shafts 3 have in each case the same rotational direction (here, counter to the clockwise direction) and one agitator shaft 3 has a rotational direction which is different therefrom (here, in the clockwise direction); in FIGS. 3c and 3d, in each case two agitator shafts 3 have the one rotational direction and the other two agitator shafts 3 have the other rotational direction, the two agitator shafts 3 with the same rotational direction being arranged in each case adjacently with respect to one another in FIG. 3c, whereas adjacent agitator shafts 3 in each case have different rotational directions in FIG. 3d. Apart from the use of four agitator shafts 3 instead of three agitator shafts, the considerations stated in conjunction with FIG. 2 in respect of the structural embodiment and in respect of any design freedoms also apply to the further embodiments shown in FIG. 3; the same applies to the method for comminuting milling material.
[0064] FIG. 4 shows diagrammatic simplified horizontal sections through stirred ball mills in accordance with further embodiments of the present invention, each stirred ball mill having in each case five agitator shafts 3, the center axes of which are arranged as side edges of a prism with a regular pentagonal base area. The form of simplified illustrations has also been selected here, which illustrations in each case show horizontal sections through a stirred ball mill 1 at the level of the agitator shafts 3. FIGS. 4a, 4b and 4c in each case show agitator jars 2, the interior space of which is configured in each case as a milling chamber 5 which has a square cross section. FIG. 4a shows a stirred ball mill 1 which has merely five agitator shafts 3 in a pentagonal arrangement; the stirred ball mills 1 which are shown in FIGS. 4b and 4c have, moreover, a sixth agitator shaft which is arranged as an inner agitator shaft 7 in the interior of the pentagon which is defined by the five outer agitator shafts 3. The thread turns are in each case not shown separately for all three agitator shafts 3, 7 in FIG. 4, but rather merely the outer borders of the screws. The center axes, running perpendicularly with respect to the plane of the illustration, of the agitator shafts 3, 7 are indicated as crosses, about which the agitator shafts 3, 7 rotate in the rotational directions which are represented in each case by way of single arrows. In FIGS. 4a, 4b and 4c, the rotational directions are in each case selected to be identical for the five outer agitator shafts 3, but they can fundamentally also be selected to be different. In FIG. 4b, the rotational direction of the inner agitator shaft 7 is different than the rotational directions of the five outer agitator shafts 3, whereas the rotational direction of all six agitator shafts 3, 7 is identical in FIG. 4c. In FIGS. 4b and 4c, the inner agitator shafts 7 have, moreover, diameters which differ from the diameters of the five outer agitator shafts 3 (in FIG. 4b, the inner agitator shaft 7 has a smaller diameter than the five outer agitator shafts 3; in FIG. 4c, in contrast, it has a greater diameter). Instead, the inner agitator shaft can of course also have the same diameter as outer agitator shafts. More than one inner agitator shaft can fundamentally also be provided in the interior space of the prism defined by the center axes of the outer agitator shafts. As an alternative or in addition, the (at least one) inner agitator shaft can be connected to the drive (for instance, to a separate or a common drive unit) or else can have no drive, with the result that it can be set passively in rotation merely via the flow movement of the mixture of milling material dispersion and milling aid elements. Furthermore, the (at least one) inner agitator shaft can also have a braking device, for instance mechanical braking systems, magnetic braking systems, electric braking systems, fluid braking systems or the like. Apart from this, the considerations stated in conjunction with FIG. 2 in respect of the structural embodiment and any design freedoms likewise applied to the further embodiments shown in FIG. 4; the same applies to the method for comminuting milling material.
TABLE-US-00001 List of Designations 1.sup. Stirred ball mill 1′ Conventional stirred ball mill 2.sup. Milling jar 2′ Milling jar of a conventional stirred ball mill 3.sup. (Outer) agitator shaft 3′ (Single) agitator shaft of a conventional stirred ball mill 4.sup. Drive 4′ Drive of a conventional stirred ball mill 5.sup. Milling chamber 5′ Milling chamber of a conventional stirred ball mill 6′ Drive unit of a conventional stirred ball mill 7.sup. Inner agitator shaft 8.sup. Thread turn 8′ Thread turn of a conventional stirred ball mill 9′ Intake 10′ .sup. Discharge 11′ .sup. Milling chamber lining X Center axis
