Agitator mill with a basket having slits

Abstract

To provide a split pipe which achieves further improvement of separation performance.SOLUTION: An agitator mill includes: a grinding chamber containing grinding bodies; and an agitator shaft supporting several grinding members, preferably grinding discs, which revolve about a horizontal agitator shaft axis in the grinding chamber, are connected to the agitator shaft in a manner which prohibits relative rotation, and move the grinding bodies, spaced apart from one another in a direction of a horizontal axis. The agitator shaft has, on the outlet side, a basket. The basket preferably has grinding members on its outer circumference. Further, the basket encloses an outlet supporting a split pipe to form a separation chamber between an inner surface of the basket and the outlet supporting the split pipe. The basket has slits for returning the grinding bodies from the separation chamber to the grinding chamber. These slits lead to a free front surface of the basket which faces the crushing chamber so as to separate from the crushing chamber.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an agitator mill with a basket having slits according to the preamble of claim 1 and to a corresponding basket according to the preamble of claim 6. [Background technology]

[0002] First, the basic principle of the agitation mill will be explained based on FIG.

[0003] 1 shows diagrammatically an agitator mill 1 with a horizontal agitator shaft 3. The grinding bodies arranged in a grinding vessel 16 and generally configured as steel or ceramic balls have been omitted.

[0004] During operation of the agitator mill 1, the material to be ground is pumped via the inlet 17 of the agitator mill 1 into or through the grinding chamber 2, which is surrounded by a grinding vessel 16. In the case of wet grinding, the material to be ground is a suspension or dispersion of liquid (mainly in the form of water) and solids. Alternatively, such an agitator mill 1 can also be used for dry grinding. In this case, it can be designed, for example, as an agitator mill with a vertical shaft, through which the material to be ground is conveyed mainly in a downward flow by a gaseous fluid.

[0005] In its broadest aspect, the present invention relates to both types of agitator mills. The use of the present invention is particularly suitable in the case of agitator mills with a horizontal agitator shaft 3.

[0006] The grinding elements 5, which are non-rotatably connected to the agitator shaft 3 and are also configured and often referred to as grinding discs, are rotated by the rotational movement of the agitator shaft 3. It is also possible for the grinding elements 5 to be configured in the form of individual pins, as part of the invention, and this will be explained below. To produce the rotational movement, the agitator shaft 3 can be driven by an electric motor 101, for example, via a belt drive 102. The drive of the agitator mill 1 is often arranged in a housing 103 adjacent to the grinding vessel 16.

[0007] As the crushing members 5 rotate, the crushing bodies located in the crushing chamber 2 and in the vicinity of the crushing members 5 are entrained in the circumferential direction of the crushing container 16. As soon as the crushing bodies reach the apex region, they flow back again in the direction of the stirring shaft 3 in the central region between the two crushing members 5. This causes a circulating movement of the crushing bodies between the two crushing members 5.

[0008] Collisions and rollovers between the solids in the grinding material suspension pumped through the grinding chamber 2 and the grinding bodies are caused by the movement of the grinding bodies. These collisions and rollovers cause fine particles to separate from the solids in the grinding material suspension, so that the solids arriving at the outlet of the agitator mill 1 are significantly smaller than the solids fed to the inlet 17.

[0009] To ensure that the grinding bodies are not released from the grinding chamber, a screen, preferably in the form of a split tube 8 (hereinafter typically referred to as the "split tube"), is typically attached before and / or supported by the outlet 7. Around this split tube 8 is arranged a basket 6 which surrounds the split tube 8. The basket serves to prevent damaging grinding body pressure from being exerted on the split tube by the grinding bodies which tend to be pushed towards the split tube by the pressure of the feed pump.

[0010] In most cases, the basket 6 is mounted non-rotatably on the free end of the stirring shaft 7 facing the outlet 7. In this case, the basket rotates together with the stirring shaft 3.

[0011] The area between the basket 6 and the split tube 8 in the circumferential direction forms a separation chamber 9, since the material to be ground or the grinding material suspension is separated from the grinding bodies here and is finally discharged again from the agitator mill 1 via the split tube 8 and the outlet 7.

[0012] However, the basket 6 can in principle only perform its function if the grinding bodies that have entered the separation chamber 9 can leave the separation chamber and return to the grinding chamber 2, because otherwise the separation chamber 9 would quickly fill with grinding bodies, which would clog the split tube and possibly cause it to wear out prematurely.

[0013] To prevent this, the basket 6 is provided with various openings 104. These openings 104 allow the grinding bodies to pass more easily from the separation chamber 9 back into the grinding chamber 2. FIG. 2 shows the basket 6 of an agitator mill designed in this way, which served as a test or comparison object until the present invention was developed. FIG. 2 also shows the grinding bodies and / or grinding material flow in the grinding vessel 16 described above. As shown in FIG. 2, the basket 6 preferably supports, also on its outer jacket surface, grinding elements 5 that cause the grinding bodies to move or swirl in the area between the basket and the inner wall of the grinding vessel 16. This swirl of the grinding bodies makes it easier for the grinding bodies located in the separation chamber 9 to escape through the openings 104 back into the grinding chamber 2.

[0014] However, the inventors have found that even with the basket configuration shown in Figure 2, there is still a tendency for ground bodies that enter the separation chamber 9 to adhere firmly to the split tube 8, blocking the split tube 8 or causing unnecessary wear, both of which have a negative effect on the separation efficiency of the split tube 8. This tendency is indicated diagrammatically by the arrow pointing towards the split tube 8 in Figure 2. Although the ground bodies could be released from the separation chamber 9 through the opening 104, they tend instead to migrate towards the split tube 8.

[0015] German Patent No. 4412408 describes an agitator mill which comprises a grinding vessel enclosing a grinding chamber which can be partially filled with auxiliary grinding bodies and through which the grinding material can flow mainly axially, a stirring shaft supporting stirring elements arranged axially one behind the other, an outlet body connected upstream of the grinding material outlet (48) of the grinding vessel, and a pre-classifying means arranged immediately before the outlet body, which has an axial passage and a pre-classifying disc which conveys the auxiliary grinding bodies which have reached its effective area preferably radially outward, characterized in that in this agitator mill the pre-classifying disc is at the same time part of a rotating cage which substantially surrounds the outlet body, so that the grinding material can reach the outlet body through the pre-classifying disc. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] German Patent No. 4412408 Summary of the Invention [Problem to be solved by the invention]

[0017] In view of the above background circumstances, an object of the present invention is to further improve the separation performance of a split tube. [Means for solving the problem]

[0018] According to the invention, this problem is solved by the features of the first main claim.

[0019] For this purpose, an agitator mill is envisaged, which comprises a grinding chamber containing grinding bodies and an agitator shaft which rotates in the grinding chamber about a horizontal agitator shaft axis. The agitator shaft supports several grinding elements which are connected in a non-rotatable manner and spaced apart from one another in the direction of the horizontal axis, preferably in the form of grinding discs. During operation of the agitator mill, the grinding elements move the grinding bodies described above.

[0020] On the outlet side, the agitator shaft has a basket. This means that the basket preferably follows the agitator shaft directly and is directly or indirectly connected to it. However, the agitator shaft and the basket are preferably not formed integrally with each other, and are therefore two separate parts, and the agitator shaft does not directly assume the function of the basket. Furthermore, the length of the basket is preferably at most one-third, particularly preferably at most one-quarter, of the length of the agitator shaft.

[0021] The outer periphery of the basket is preferably studded with additional grinding elements. As mentioned above, this not only allows for an additional grinding effect in the radial circumferential area between the outer periphery of the basket and the inner wall of the grinding container, but also, in particular, causes a swirling movement of the grinding bodies, which facilitates their re-exit from the separation chamber. These grinding elements on the basket are preferably not configured like the grinding elements on the agitator shaft. While the grinding elements on the agitator shaft are preferably in the form of grinding discs, the grinding elements on the basket are preferably in the form of pins.

[0022] During intended operation, the basket at least partially surrounds the outlet, and the outlet supports the split tube. The basket preferably surrounds the split tube along its entire length. As part of these embodiments, the narrow definition of "split tube" preferably refers to a tube with various slits and / or other shaped openings, while the broad definition of the term "split tube" includes any type of screen body.

[0023] As already mentioned in the previous paragraph, the surrounding arrangement of the basket creates a free area between the inner surface of the basket and the outer surface of the outlet or the split tube supported by the outlet, this area being referred to as the "separation chamber".

[0024] The agitator shaft according to the invention is characterized in that the aforementioned basket has slits for returning the grinding bodies from the separation chamber to the grinding chamber, the slits being designed to lead to the free front face of the basket facing away from the grinding chamber.

[0025] This is based on the following insight of the inventors: in Fig. 2, in the inlet region immediately behind the free front face of the basket, the flow is mainly horizontal to enter the separation chamber, but an excessively pronounced constriction is formed, because the basket shown in Fig. 2 forms a circumferentially closed annular structure in that region.

[0026] Although the grinding bodies theoretically achieve a higher flow velocity when flowing through the constriction, which is actually desirable, they are entrained, especially in the axial direction, and have limited options for exiting the basket. Therefore, the grinding bodies often collide with the basket and / or split tube, which causes them to be significantly slowed down. Furthermore, the constriction is often so narrow that some grinding bodies collide with each other and with the basket and / or split tube at the entrance to the separation chamber, thus already initially losing kinetic energy.

[0027] Even if the crushed bodies eventually reach the outer surface of the split tube below the opening, they often do not have enough kinetic energy to avoid the suction of the split tube and return to the grinding chamber using the opening. Therefore, some of the crushed bodies stop and accumulate on the outer surface of the split tube, which further reduces the dynamics of the crushed bodies. Under unfavorable conditions, the split tube may become blocked after a certain operating time.

[0028] The "grinding chamber" as mentioned above refers to the chamber inside the grinding vessel between the inlet and the outlet, filled with grinding bodies and / or grinding material or grinding material suspension, and not surrounded by a basket. In other words, the grinding chamber is the interior of the grinding vessel excluding the internal components and the separation chamber that pass through it.

[0029] The slits according to the invention thus significantly increase, at least locally, the radial gap between the inner surface of the basket and the outer surface of the outlet or split tube, through which the crushed bodies pass during the flow into the separation chamber. This reduces the "accumulation" of crushed bodies and / or the material to be crushed or the crushed material suspension at the basket inlet and / or prevents the crushed bodies from being guided towards the screen, allowing the crushed bodies to enter the separation chamber at least partially much more easily and with greater dynamics. This creates a favorable flow at this point, so that the crushed bodies are instead directed away from the split tube and are transported back from the separation chamber through the slits into the crushing chamber more quickly and / or more easily.

[0030] This allows the grinding bodies to be guided back into the grinding chamber more quickly and / or more favorably for the split tube, thereby reducing blockage and / or wear of the split tube.In the area where the grinding bodies enter directly from the slits (especially in the area between the outer periphery of the basket and the inner wall of the grinding vessel), additional turbulence is inherently created, activating the surrounding grinding body bed.

[0031] This generally results in a higher grinding efficiency of the agitator mill, reduced wear on the split tube during operation, and reduced settling of grinding bodies in or on the split tube, thus allowing the agitator mill to operate at a higher throughput with longer basket life and reduced maintenance.

[0032] A "slit" is an aperture and / or opening and / or notch having a generally elongated shape, which is provided in or on the basket. In this case, the slit according to the invention provides an opening in the outer surface of the basket to the grinding chamber in at least one region, but preferably not along the entire length of the slit. Material can therefore be locally adjacent to the slit, so that the slit is, so to speak, "covered," "lined," and / or surrounded by the material of the basket.

[0033] Furthermore, the slit according to the invention preferably does not have the same cross section over its entire length, but rather varies locally in extent and / or shape.

[0034] In connection with the above-mentioned "covering" of the slits in the basket, it should additionally be mentioned that each slit of the basket according to the invention is preferably configured so that, on the side facing away from the grinding chamber, it has material radially outwardly and thus directly and locally adjacent to the slit, thus forming an "end ring" in that area, which preferably forms a continuous circumferential surface.

[0035] This is essential to stabilize the basket and avoid vibrations. Each slit therefore forms a tunnel below the end ring.

[0036] There are many options for designing the present invention to further enhance its effectiveness or usability.

[0037] In a preferred embodiment of the present invention, the slits also pass through the wheel discs connecting the basket to the stirring shaft, so that each slit is also connected to the grinding chamber via the wheel disc itself, allowing the grinding bodies to reach the separation chamber even through the wheel disc, assisted by the movement of the grinding bodies in the grinding chamber on the opposite side of the wheel disc, thus making the release of the grinding bodies from the separation chamber even easier.

[0038] Furthermore, particularly preferably, the slits form tunnels below a stabilizing ring formed on the side or in the region of the free end of the basket facing away from the grinding chamber, which stabilizing ring is preferably configured to project radially outward into the grinding chamber further than the remaining diameter of the basket, which on the one hand increases the stability of the basket and on the other hand further improves the flow guidance or dynamics.

[0039] In a further preferred embodiment, the main axes of the slits extend completely or at least essentially parallel to the axis of the stirring shaft. This is achieved if they deviate from the axis of the stirring shaft by a maximum of 10°, preferably by a maximum of 5°. In this case, the main axes run along the entire length of the slits, and thus along the entire extension of the slits, and are preferably also parallel to the longitudinal axis of the basket, and are located in the center of the slits, and therefore halfway across the width of the slits.

[0040] Furthermore, it is particularly preferred that the sides of the slots running in the direction of rotation have an angle of attack of 0° to 45° relative to the imaginary radius of the main axis passing through the slot, which creates a surface on the basket with a "scooping effect", so to speak, which results in a deflection of the comminution bodies and a better release. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a side cross-sectional view showing a conventional agitation mill. [Figure 2] 1 is a side cross-sectional view of a grinding vessel in an agitator mill having a basket with openings, contemplated by the applicant; [Figure 3] 1 is a side view of a basket according to a first exemplary embodiment of the present invention; [Figure 4] 4 is a three-dimensional view of the basket of the first exemplary embodiment of the present invention in FIG. 3. [Figure 5] 4 is a front view of the basket of the first exemplary embodiment of the present invention shown in FIG. 3. FIG. [Figure 6]10 is a three-dimensional view of a second exemplary embodiment of a basket according to the present invention with a stabilization ring. FIG. [Figure 7] 7 is a side view of an exemplary embodiment of a basket according to the present invention with the stabilization ring of FIG. 6. [Figure 8] 7 is a cross-sectional side view of an exemplary embodiment of a basket according to the present invention with a stabilization ring as in FIG. 6, surrounding an outlet supporting a split tube. [Figure 9] 10 is a cross-sectional side view of a third exemplary embodiment of a basket according to the present invention, with an alternative stabilization ring shape, together with a grinding vessel of an agitator mill. FIG. [Figure 10] FIG. 10 is a side view of a basket according to a fourth exemplary embodiment of the present invention. [Figure 11] 11 is a three-dimensional view of the exemplary embodiment basket of FIG. 10 according to the present invention. [Figure 12] FIG. 10 is a front view of a basket according to a fifth exemplary embodiment of the present invention. [Figure 13] 13 is a three-dimensional view of the exemplary embodiment basket of FIG. 12 according to the present invention. [Figure 14] FIG. 10 is a front view of a basket according to a sixth exemplary embodiment of the present invention. [Figure 15] 15 is a three-dimensional view of the exemplary embodiment basket of FIG. 14 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] 3 to 5 show a first preferred exemplary embodiment of the basket 6 according to the present invention in different views. In this case, the basket 6 is provided (sprinkled) with additional grinding elements 18, which are arranged in horizontal rows in the form of pins regularly distributed over the circumference of the basket 6 and extend parallel to the agitator shaft axis 4. Similarly, the slits 10 are regularly distributed over the circumference of the basket 6 and, as mentioned above, intersect with the wheel discs 12 facing the grinding chamber 2 and the front face 11 facing away from the grinding chamber 2. It may be advantageous if a single row is not assigned to each individual slit 10, but rather there are directly adjacent slits whose connecting areas do not support any of the rows. On the side facing the front face 11, the slits 10 also form a tunnel below the end ring 19, which is circumferentially closed.

[0043] For clarity, not all slits and all grinding members in each figure are labeled with reference numerals, but only one slit and one or two grinding members are labeled with reference numerals for illustrative purposes.

[0044] FIG. 5 shows a front view of the basket 6, in this case showing the front face 11 facing away from the grinding chamber. Due to the angle of attack A of the illustrated slits, the side faces 15 of the slits 10 running in the direction of working rotation or their imaginary extension are not radially perpendicular to the outer contour of the basket 6. This angle of attack A is preferably between 0° and 45°. For clarity, an imaginary upper slit radially perpendicular to the outer contour of the basket 6 is additionally shown in dashed lines. From the main axis of such an imaginary upper slit, an angle corresponding to the angle of attack A is plotted to the main axis 14 of the inventive slit 10.

[0045] 6-8 show a second preferred embodiment of the basket 6, which supports a stabilizing ring 13 with an increased outer diameter. The illustrated slits 10 also form a tunnel below the end ring 19 on the side facing the front face 11, which in this case is part of the stabilizing ring 13. The slits 10 in the illustrated embodiment also preferably extend through the wheel disc 12 and the front face 11 facing the grinding chamber. The illustrated basket 6 is also provided with additional grinding elements 18, and the above also applies. The stabilizing ring itself can also be provided with additional grinding elements 18, in particular protruding pins or other agitators that circumferentially entrain the grinding bodies. The pins of the stabilizing ring are preferably arranged primarily parallel to the agitator shaft axis 4, so as to be aligned with the other pins of the basket described above (see FIGS. 6 and 7).

[0046] 8 shows, for the sake of clarity, the basket 6 thus formed in its preferred installation position, in which it surrounds (overlaps) the outlet 7 supporting the split tube 8. It may be advantageous if the outlet 7 has a constriction (designed "spool-like" as shown and optionally including run-in and run-off slopes), which is arranged to widen the slit through which the inflow into the separation chamber 9 occurs. Even if such a constriction does not produce any "scooping" effect in the circumferential direction, in contrast to the slits or openings according to the invention, and therefore leads to different dynamics, the constriction may serve to reinforce the effect to be achieved according to the invention, especially in synergistic cooperation with the slits or openings according to the invention.

[0047] Finally, FIG. 9 shows a further preferred embodiment of the basket 6, which also supports the stabilizing ring 13, but in the form of a completely cylindrical section. The slits 10 shown form a tunnel under the entire stabilizing ring 13, so that the stabilizing ring almost simultaneously functions as an end ring. FIG. 9 also shows a schematic diagram of the flow behavior in the grinding vessel 16 of the agitator mill 1. Reference is now made to the general operating mode of the agitator mill described in the "Background Art" section with reference to FIGS. 1 and 2. The basic function and flow behavior up to the basket 6 area are the same or similar, and therefore will not be described further. However, the basket 6 shown in FIG. 9 has a slit 10 that intersects the wheel disc 12 and the front surface 11 facing away from the grinding chamber. This allows the grinding bodies and / or grinding material suspension to enter the separation chamber 9 more easily, and in particular the grinding bodies are ejected from the separation chamber 9 through the slit again into the grinding chamber 2 by the flow formed thereby, which is also facilitated by the additional connection to the grinding chamber via the partially slit wheel disc 12. In this way, the grinding bodies are directed away from the split tube 8 or the outlet 7 supporting the split tube, resulting in an increased grinding effect in the grinding chamber 2 after being released from the separation chamber 9 .

[0048] 10 and 11 show a further preferred embodiment of the basket 6 with the slits 10 and additional crushing elements 18, in which the outer contour of the basket 6 is formed in the shape of a truncated cone. This design (in contrast to the embodiment of FIG. 9) avoids flow disturbances when flowing over the conical structure and achieves a continuously increasing dynamics during flow over the basket. At the same time, the conical structure forms, in its free end region, approximately an integral stabilizing ring, and no abrupt narrowing occurs in this region. The illustrated slits 10 also form a tunnel below the circumferentially closed end ring 19.

[0049] As can be clearly seen in Figure 11, the basket forms a cylindrical inner jacket surface on its inside, so that the separation chamber 9 in particular (starting from the free front face of the basket) is not conically tapered, i.e. a conical separation chamber would be counterproductive due to the fact that, due to the conical inner profile, there is a risk of the comminution bodies getting stuck in the separation chamber after they have entered it.

[0050] 12 and 13 show a further preferred embodiment of the basket 6. In this embodiment, too, a stabilizing ring 13 is provided and the slits 10 form tunnels below the end ring 19. However, the slits 10 shown extend or are designed to pass through the front face 11 only by circular holes.

[0051] 14 and 15 show a further preferred embodiment of the basket 6. In this embodiment, too, a stabilizing ring 13 is provided and the slits 10 form tunnels below the end ring 19. However, the slits 10 shown are extended or designed in such a way that they have areas of material provided directly below them in the area of ​​the front face 11 or on the side facing the front face 11, so that the slits 10 are locally "lined", so to speak. [Explanation of symbols]

[0052] 1. Stirring mill 2 Crushing Chambers 3 stirring shaft 4 Agitator shaft axis 5. Grinding element (grinding disc) on the stirring shaft 6 Basket 7 Exit 8 Split Tube 9. Separation Chamber 10 slits 11 Front face (facing away from the grinding chamber) 12 wheel discs 13 Stabilization Ring 14 Main axis of slit 15 Side of the slit 16 Grinding container 17 Entrance 18 Crushing element on basket 19 End ring 101 Electric Motor 102 Belt drive 103 Housing 104 Aperture A. Angle of attack

Claims

1. a grinding chamber (2) containing grinding bodies; an agitator shaft (3) rotating in the grinding chamber (2) about a horizontal agitator shaft axis (4) and supporting several grinding elements (5) connected to the agitator shaft (3) in a non-rotatable manner and spaced apart from one another in the horizontal axial direction to move the grinding bodies; a splitter pipe (8) that allows the material to be ground or the suspension of the material to be ground to pass through but not the grinding body, and that is attached before the outlet (7) of the grinding chamber (2); An agitation mill (1) comprising: In the agitation mill, the agitation shaft (3) has a basket (6) on the outlet side, the basket (6) has a grinding member (18) on the outer periphery of the basket (6) and surrounds the outlet (7) supporting the split tube, thereby forming a separation chamber (9) between the inner surface of the basket (6) and the outlet (7) supporting the split tube, the basket (6) has a slit (10) for returning the grinding bodies from the separation chamber (9) into the grinding chamber (2), the slit (10) leading to a free front surface (11) of the basket (6) facing away from the grinding chamber (2), the expansion and / or shape of the slit (10) varying at least locally; A stabilizing ring (13) having an outer diameter larger than that of other regions is formed at the free end of the basket (6), and the slit (10) extends from the other regions to the stabilizing ring (13); An agitation mill, characterized in that the solids in the material to be pulverized or the suspension of the material to be pulverized are pulverized by the pulverizing body moved by the pulverizing member.

2. 2. A stirring mill (1) according to claim 1, characterized in that the slits (10) also pass through a wheel disc (12) connecting the basket (6) with the stirring shaft (3), whereby each of the slits (10) is also connected to the grinding chamber (2) via the wheel disc (12) itself.

3. 3. A stirring mill (1) according to claim 1 or 2, characterized in that the slit (10) forms a tunnel below the stabilizing ring (13).

4. 3. A stirring mill (1) according to claim 1 or 2, characterized in that the main axis (14) of the slit (10) extends parallel to the stirring shaft axis (4).

5. 5. A stirring mill (1) according to claim 4, characterized in that the side (15) of the slit running in the direction of working rotation has an angle of attack (A) of 0° to 45° with respect to the imaginary radius of the main axis (14) passing through the slit.

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