Grinding unit, agitator bead mill, method, and use

Abstract

A grinding unit (12) for an agitator bead mill is provided, having a cylindrical stator (18) that forms a container with a container height (h1) for receiving grinding media, and a rotor (20) with a rotor height (h2) that is arranged in the stator (18) such that a grinding gap (22) is formed between the stator (18) and the rotor (20), wherein radially inwardly projecting stator cams (34) are arranged on an inner wall (32) of the stator (18) and radially outwardly projecting rotor cams (38) are arranged on a circumferential wall (36) of the rotor (20), wherein the stator cams (34) and the rotor cams (38) are arranged alternately to each other along the container height (h1) and the rotor height (h2) and partially overlap each other when there is a rotation of the rotor (20), wherein the surfaces of the stator cams (34) and of the rotor cams (38) together occupy 40% to 60% of the total cross-sectional area of the grinding gap (22). Furthermore, an agitator bead mill (10), a method for operating an agitator bead mill, and the use of a grinding unit (12) are indicated.

Description

GRINDING UNIT, AGITATOR BEAD MILL, METHOD, AND USE

[0001] The invention relates to a grinding unit for an agitator bead mill, an agitator bead mill having a grinding unit, a method for operating an agitator bead mill, and the use of a grinding unit for the production of a battery paste.

[0002] Agitator bead mills are used to process suspensions; solids are finely comminuted in the process. Typical applications include varnishes, printing inks, pigment preparations and battery pastes.

[0003] Such agitator bead mills have a grinding unit comprising a cylindrical stator, which forms a container for receiving grinding media, and a rotor, which is arranged in the stator in such a way that a grinding gap is formed between the stator and the rotor. Cylindrical agitating elements, in particular pins, are attached to the rotor and / or the stator, so that rotation of the rotor causes a suspension of material to be ground to be circulated with the grinding media in the grinding mechanism, whereby the product to be ground is comminuted, in particular by the impact and shear forces between the grinding media.

[0004] According to one application example, such agitator bead mills are used to grind materials for the electronics industry or the battery industry, where the required particle sizes are in the nanometer range.

[0005] One challenge here is that when the agitator bead mill stops, the grinding media and the ground product sink down past the pins and "cake" together due to gravity, because of the small particle sizes of the ground product and the correspondingly small size of the grinding media. For one thing, this has the disadvantage that a rotor blockage can occur and the agitator bead mill can no longer be started regularly. A further disadvantage is that the ground product can then only be separated from the grinding media with great effort, wherein it is necessary to remove the grinding media together with the ground product from the agitator bead mill. This is undesirablebecause it involves a very high level of effort and, moreover, the handling of the grinding media is difficult due to their small size.

[0006] This problem is further exacerbated by high grinding media filling levels, which result in high power input.

[0007] This issue is particularly relevant for the materials used to manufacture battery pastes, due to the particle sizes and material properties.

[0008] It is therefore an object of the present invention to provide a grinding unit for an agitator bead mill and a corresponding agitator bead mill which is optimized for grinding material with a target particle size in the nanometer range, which is present, among other things, in the production of battery pastes. Furthermore, it is an object of the invention to provide an optimized method for operating an agitator bead mill.

[0009] The object is solved according to the invention by a grinding unit for an agitator bead mill, with a cylindrical stator which forms a container with a container height for receiving grinding media, and a rotor with a rotor height which is arranged in the stator such that a grinding gap is formed between the stator and the rotor. Stator cams that project radially inward are arranged on an inner wall of the stator. Rotor cams that project radially outward are arranged on a circumferential wall of the rotor. The stator cams and the rotor cams are arranged alternating with one another along the container height and the rotor height. When the rotor rotates, the stator cams and the rotor cams partially overlap. The surfaces of the stator cams and the rotor cams together occupy 40% to 60% of the total cross-sectional area of the grinding gap, in particular in a top view of the grinding unit. This refers in particular to a position of the rotor in which the rotor cams and the stator cams are arranged without overlapping. Such a position can be described as a maintenance position.

[0010] The alternating arrangement of the stator cams and the rotor cams relates to a direction along a longitudinal axis of the grinding unit which is parallel to the axis of rotation of the rotor. This means that the rotor cams and the stator cams are located at different heights relative to the longitudinal axis of the grinding unit, or the rotor cams and the stator cams are arranged in different planes along the longitudinal axis of the grinding unit.

[0011] The overlap of the rotor cams and the stator cams refers to a top view along the longitudinal axis of the grinding unit; that is, the surfaces of the rotor cams and the stator cams overlap, viewed from above along the longitudinal axis of the grinding unit. In other words, during operation when the rotor is rotating, a movement envelope of the rotor cams overlaps with the stator cams in a top view along the longitudinal axis of the grinding unit.

[0012] The grinding unit according to the invention has on the one hand the advantage that the rotor cams and the stator cams are more stable and therefore less prone to breakage compared to the pins usually provided. More precisely, due to their larger size, the cams have more room for wear and therefore a longer service life. Furthermore, the cams are easier to position due to their larger contact surface compared to pins.

[0013] The overlapping surfaces of the rotor cams and the stator cams result in higher power consumption, which has a positive effect on the dispersion result of a product to be ground. In other words, an increase in performance is achieved.

[0014] The product to be ground is sheared by the overlap of the surfaces of the rotor cams and the stator cams.

[0015] In addition, an agitator bead mill with the grinding unit according to the invention runs more smoothly, meaning that the vibrations occurring during a grinding process are reduced. This is due to the geometry of the rotor and thestator, in particular the distances between the rotor cams and the stator cams, which according to the invention can be larger than in known agitator bead mills with pin-shaped agitating elements. Due to the larger volume and cross section of the stator cams and rotor cams compared to the known pins, the flow surface of the agitating elements remains substantially the same, so that the same grinding performance can be achieved with fewer agitating elements.

[0016] The most significant advantage, however, is that the rotor cams and the stator cams, regarded together, provide a significantly larger contact surface than the pins normally used as agitating elements, due to the ratio according to the invention of the surfaces of the stator cams and the rotor cams relative to the grinding gap. This largely prevents or at least significantly delays the settling of the grinding media and the ground product. This prevents the ground product from sinking completely to the bottom of the container along with the grinding media and caking. This could cause the grinding unit to become blocked after a stop or standstill. In other words, the use of rotor cams and stator cams results in higher machine reliability, or machine availability. This effect is further supported by the alternating arrangement of the rotor cams and the stator cams.

[0017] By preventing the ground product from settling too quickly, the grinding unit can be dimensioned for larger grinding chamber volumes than has previously been the case. For example, the grinding chamber volume can be more than 60 liters, in particular up to 80 liters or more.

[0018] In a top view of the grinding unit, the surfaces of the stator cams and the rotor cams together occupy 40% to 60% of the total cross-sectional area of the grinding gap when the rotor is in a position in which the rotor cams and the stator cams are not overlapping, i.e. in a maintenance position. In other words, a cross section can be made through the grinding unit in this position. The grinding gap, which is formed between the rotor and the stator, has anarea in the sectional plane that is referred to as the cross-sectional area. This area is in particular ring-shaped.

[0019] Furthermore, in a top view of the cross section, the corresponding surfaces of the stator cams and the rotor cams are visible, as these protrude into the grinding gap, even if the stator cams and / or the rotor cams are not in the plane of the cross section. The sum of the stator cams and the rotor cams, i.e. their visible surfaces, results in a total area in the corresponding position of the rotor that corresponds to 40% to 60% of the cross-sectional area of the grinding gap.

[0020] The rotor cams can form a rotor contact surface and / or the stator cams can form a stator contact surface. The rotor contact surface and the stator contact surface are for example flat. The larger the grinding chamber volume of the grinding unit, the larger the contact surface in each case for example. Due to the flat contact surface, a larger proportion of the grinding media remains above the rotor cams or the stator cams, which also prevents the grinding media from settling when the agitator bead mill is stopped. With a pin, in particular a pin with a round profile, the grinding media would fall downwards on both sides of the pin.

[0021] According to one exemplary embodiment, the rotor cams and / or the stator cams are trapezoidal when viewed from above along the longitudinal axis of the grinding unit. This means that the rotor cams and / or the stator cams taper towards their free end. This further prevents the grinding media from sinking, in particular when both the rotor cams and the stator cams taper accordingly and are thus geometrically matched to each other. The taper of the rotor cams and / or the stator cams may also begin in the overlap region of the stator cams and the rotor cams or be particularly pronounced there, i.e. have 50% or less of the maximum width.

[0022] Instead of trapezoidal rotor cams and / or stator cams, cuboidal, oval or otherwise shaped rotor cams and / or stator cams are also conceivable.

[0023] When the rotor rotates, the overlap length of the rotor cams and the stator cams can be from 4 mm to 30 mm, in particular from 10 mm to 15 mm. Such an overlap length contributes to an improvement in the efficiency of the grinding process.

[0024] For example, the ratio of the overlap length of the rotor cams and the stator cams to the axial distance of the rotor cams to the stator cams is 0.25 to 3. Such a ratio ensures sufficient space for a continuous material flow and can help to avoid blockages in the grinding gap.

[0025] Both the rotor cams and the stator cams can each be designed symmetrically with respect to a central axis. In particular, the rotor cams and / or the stator cams extend perpendicular to a longitudinal axis of the grinding unit. The symmetrical arrangement ensures that the rotor cams and / or stator cams are subjected to even loads, resulting in uniform wear and minimizing mechanical stresses.

[0026] Specifically, both the stator cams and the rotor cams can be symmetrical when viewed from above along the longitudinal axis of the grinding unit. This means that a plane of symmetry of each rotor cam or stator cam runs along the longitudinal axis of the grinding unit.

[0027] The symmetrical cam shape helps to avoid assembly errors caused by incorrect cam alignment.

[0028] According to one embodiment, the stator cams are arranged in different positions with respect to the container height, in particular wherein the stator cams are arranged in rows that run along the longitudinal axis of the grinding unit, wherein the stator cams of two adjacent rows are offset from each otherwith respect to the longitudinal axis. In other words, the stator cams are arranged in a checkerboard pattern. With such an arrangement of the stator cams, the barrier described above is realized, while a lower power consumption of the grinding unit is ensured. More precisely, a constant power consumption is possible at higher rotational speeds. This allows higher centrifugal forces to be achieved in order to effectively spin the grinding media away from the sieve.

[0029] According to one aspect, the stator cams can be detachably attached to the stator, in particular wherein at least one fastening means engages in the corresponding stator cam through a stator wall. The fastening means can be screws.

[0030] For example, the stator comprises an inner casing, also known as an inliner, and an outer casing, wherein the stator cams are fastened to the inner casing, in particular wherein the fastening means engage through the inner casing into the stator cams.

[0031] Because the stator cams are detachably attached, they can be replaced when worn. The stator cams are geometrically simple wear parts that can be manufactured at low cost compared to the entire stator. In addition, the stator cams can be turned due to the detachable fastening, which further increases the service life. Furthermore, this makes the grinding unit particularly sustainable, as only the stator cams need to be disposed of when they wear out, and the rest of the stator can be reused.

[0032] Another advantage of the detachable fastening is that the stator cams and a base body of the stator can be made of different materials. For example, the stator cams can be made of steel, hard metal, tungsten carbide, ceramic or plastic. The base body of the stator, for example, is made of ceramic. This allows the materials of the stator components to be selected according to their load-bearing capacity and / or costs to be reduced.

[0033] Alternatively, the stator cams can also be formed as a single unit on the stator. For example, the stator cams are encased in silicon within the stator.

[0034] In addition to at least one fastening means, there can be an adhesive bond between each stator cam and the corresponding fastening means and / or the stator inner wall or the inner casing. The additional adhesive bond achieves a seal of the stator cams to the outside. Specifically, the seal ensures that the product to be ground does not come into contact with the cooling liquid.

[0035] At least one cooling channel can be provided between the inner casing and the outer casing.

[0036] The rotor can comprise a plurality of rotor disks, each rotor disk having a row of rotor cams. This makes the production of the rotor particularly cost-effective. More precisely, a furnace required for sintering individual rotor disks can be significantly smaller than a furnace for sintering a complete rotor. In addition, a tool mold for forming a rotor disk can also be made smaller. The cost-effective production of a rotor formed from rotor discs is a result, therefore, of the lower tooling investment costs. If the rotor is formed from identical rotor discs, only a single tool mold is required. Furthermore, the rotor can be repaired by replacing a rotor disk instead of replacing the entire rotor.

[0037] According to one aspect, the ratio of the cam height of the stator cams to the cam height of the rotor cams is at least 0.5. The cam heights run radially to a longitudinal axis of the grinding unit. The stator cams, for example, are shorter than the rotor cams. In one specific exemplary embodiment, the stator cams have a height of 30 mm and the rotor cams have a height of 45 mm, measured in the radial direction. Higher rotor cams allow more energy to be transferred to the material, increasing the comminution efficiency and speed. The lower stator cams ensure reduced resistance, which in turn optimizes the system's energy absorption and can lower overall energy consumption.

[0038] Overall, the ratio of at least 0.5 between the heights of the stator and rotor cams, for example, ensures that the grinding unit has a balanced performance in terms of comminution, energy consumption and wear, resulting in higher efficiency and a longer service life.

[0039] The minimum distance between the rotor cams and the stator cams in one direction along the longitudinal axis of the grinding unit is at least 4 mm and at most 15 mm. Such a distance ensures sufficient mixing of the ground material, thereby improving the homogeneity of the ground product. Furthermore, such a distance prevents the rotor from jamming against the stator.

[0040] For example, the ratio of the height of the stator cams to the inner diameter of the stator is greater than 0.05. The greater the height of the stator cams in relation to the inner diameter of the stator, the larger the surface area that the stator cams offer for interaction with the material being ground. This allows more energy to be transferred to the material, resulting in more efficient comminution. This can shorten the processing time and improve the quality of the final product. Furthermore, this makes it possible to operate the grinding unit at a lower rotational speed, which has a beneficial effect on wear and thus on the service life of the grinding unit.

[0041] For example, the ratio of the height of the stator cams to the grinding gap width is greater than 0.35 and / or the ratio of the overlap of the stator cams and the rotor cams to the grinding gap width is greater than or equal to 0.1.

[0042] A ratio of the overlap of the stator cams and the rotor cams to the grinding gap width in the range greater than or equal to 0.1 results in a sufficiently intensive interaction between the rotor cams and the stator cams. This results in better and finer comminution of the product, as the particles arecontinuously transported and processed between the rotor cams and the stator cams.

[0043] A ratio of the height of the stator cams to the grinding gap width in the range greater than 0.35 is also advantageous with regard to the efficiency and performance of the grinding unit.

[0044] For example, a point of application for a lifting mechanism is provided at an upper end of the rotor, via which the rotor can be lifted in a vertical direction. This allows the rotor to be removed from the grinding unit, in particular for maintenance purposes. Since the rotor is lifted vertically, the stator can remain in its position, so that the grinding media can also remain in the stator. This makes handling significantly easier. The subsequent emptying of the stator can be carried out separately, away from the agitator bead mill. It is also conceivable to use a second stator, which can reduce maintenance time and increase machine availability.

[0045] The object is further achieved according to the invention by an agitator bead mill with a grinding unit according to the invention, wherein a longitudinal axis of the grinding unit is oriented vertically. The agitator bead mill has a rotor drive and a lifting mechanism for lifting the rotor from an operating position, in which the rotor is located inside the stator, to a maintenance position, in which the rotor is located outside the stator. The rotor can only be lifted out of the stator if the rotor is in a position in which, viewed from above, the rotor cams do not overlap with the stator cams along the longitudinal axis of the grinding unit. This position is also referred to as the maintenance position. A position in which the rotor cams overlap with the stator cams is also referred to as the operating position.

[0046] By lifting the rotor out of the stator, the center of gravity of the entire agitator bead mill can be kept low. This makes the agitator bead mill lesssusceptible to vibrations during operation. Furthermore, this makes the agitator bead mill easier to transport and position.

[0047] The lifting mechanism is, for example, a hydraulic mechanism, in particular a hydraulic column.

[0048] Because the lifting mechanism is integrated into the agitator bead mill, no external lifting equipment is required.

[0049] The vertical orientation is also advantageous in that less space is required when lifting out the rotor or opening the grinding unit than with a horizontal design. Furthermore, as mentioned previously, the grinding media can remain in the stator, thus avoiding a loss of grinding media. The grinding media are, in particular, loosely filled into the grinding unit of the agitator bead mill.

[0050] The grinding media are, for example, ceramic grinding media.

[0051] The rotor and the rotor drive can be arranged on different sides with respect to the lifting mechanism, in particular diametrically opposite each other with respect to the lifting mechanism. The rotor drive thus forms a counterweight to the rotor, which also contributes to a stable construction.

[0052] The rotor drive, for example, is coupled to the rotor via a belt drive so as to transmit torque.

[0053] According to one aspect, the agitator bead mill has a control unit which controls the rotor drive to control a rotation of the rotor, wherein the agitator bead mill includes a sensor which detects a rotary movement and / or an angular position of the rotor, wherein the control unit is configured to control the rotor drive such that the rotor is stopped in a position in which the rotor cams and the stator cams are arranged in non-overlapping fashion such thatthe rotor is axially movable relative to the stator. This position is also referred to as the maintenance position.

[0054] The sensor and the control unit thus form a rotor positioning device in combination with each other. The sensor is for example a rotary encoder.

[0055] By stopping the rotor in the position in which the rotor cams and the stator cams are not overlapping, it is ensured that the rotor can be lifted upwards out of the stator.

[0056] Another significant advantage is that such an arrangement of the rotor and stator cams, in which the rotor and stator cams are arranged with gaps to each other, represents a barrier which prevents the grinding media from sinking directly downwards when the agitator bead mill stops and accumulating and compressing there, as has already been described in connection with the grinding unit according to the invention. In other words, the rotor cams and the stator cams together form a labyrinth for the grinding media, which means it takes significantly longer for the grinding media to sink to the bottom when there is a standstill. Below each cam, a region with a lower concentration of grinding media is formed. This means it is possible to prevent compression of the grinding media or a pressure increase in a lower region of the grinding gap due to rapidly downward-flowing grinding media.

[0057] Another advantage of such a positioning is that when refilling grinding media, an uncontrolled flow of the grinding media from the upper area of the process zone, i.e. the grinding gap, is avoided, so that in a lower area of the process zone a pressure due to gravity is reduced. The displacement of the ground product in the lower part of the process zone is also reduced. Overall, a more uniform distribution of the grinding media in the process zone or grinding gap is achieved.

[0058] The object is further achieved according to the invention by a method for operating an agitator bead mill according to the invention, wherein the agitator bead mill has a control unit which controls the rotor drive to drive the rotor and a sensor which detects a rotational movement and / or an angular position of the rotor.

[0059] In a first process step, the rotor drive powers the rotor, so that the rotor rotates and a product to be ground in the agitator bead mill is comminuted between the rotor and stator.

[0060] The control unit detects, for example continuously, a position signal from the sensor and uses it to determine the angular position of the rotor.

[0061] In a further process step, the control unit controls the rotor drive of the rotor, taking into account the angular position of the rotor, in such a way that the rotor reaches a speed of 0, in particular comes to a stop, in a position in which the stator cams and the rotor cams are arranged offset from each other when viewed from above, in particular when viewed from above along a longitudinal axis of the grinding unit. In other words, the stator cams and the rotor cams do not overlap at the end of the grinding process.

[0062] The method according to the invention thus ensures that the rotor can be lifted out of the stator and that the stator cams or the rotor cams do not block or collide with each other during lifting. Furthermore, by stopping the rotor in a defined position in which the stator cams and the rotor cams are offset from each other, the labyrinth effect already described in connection with the agitator bead mill is achieved.

[0063] The object is further solved according to the invention by using the grinding unit according to the invention for the production of a battery paste, wherein silicon is ground in the grinding unit in such a way that at least 50% of the silicon particles achieve a particle size of less than 100 nanometers.

[0064] In order to achieve such a particle size, the silicon is ground in the agitator bead mill for multiple days or even weeks.

[0065] The grinding media used for grinding silicon have a size of for example 100 pm.

[0066] Due to the small particle size of the ground silicon and the grinding media, it is essential to prevent the ground product and the grinding media from settling when the machine stops, as they would otherwise compact within a very short time, blocking the grinding unit and preventing it from being started again. The rotor would then have to be lifted out of the stator. This can be prevented by means of the grinding unit according to the invention.

[0067] The silicon is ground e.g. in a liquid, for example in ethanol.

[0068] In the battery industry, such finely ground silicon is added to graphite anodes, for example, to increase the anode's capacity. In the long term, a replacement of graphite with silicon is planned. The addition of silicon increases the energy storage capacity of the anode.

[0069] In terms of mass used, silicon can store many times more lithium than graphite, for example ten times more.

[0070] Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. In the drawings:- Figure 1 shows an agitator bead mill according to the invention,- Figure 2 shows a grinding unit according to the invention of the agitator bead mill from Figure 1 in a sectional view with a detail view,- Figure 3 shows another section through a grinding unit of the agitator bead mill from Figure 1 ,- Figure 4 shows a partial section through a grinding unit in a perspective view, - Figure 5 shows a top view of the grinding unit from Figure 2 in an operating position,- Figure 6 is a detail view of the top view of Figure 5,- Figure 7 shows a top view of the grinding unit from Figure 2 in a maintenance position,- Figure 8 is a detail view of the top view of Figure 7,- Figure 9 shows a stator of the grinding unit from Figures 2 to 8,- Figure 10 shows a cross section through the stator at the level of a row of stator cams,- Figure 11 shows a detailed view of the stator in the region of a stator cam, - Figure 12 shows a detailed view of the stator in the region of an alternative stator cam,- Figure 13 shows a rotor of the grinding unit from Figures 2 to 8,- Figure 14 shows an alternative stator for the agitator bead mill according to Figures 1 to 8,- Figure 15 shows the stator from Figure 14 and a rotor held in the stator in an overlapping position of the stator cams and the rotor cams, wherein the wall of the stator is shown partially transparent,- Figure 16 shows the arrangement from Figure 15 in a cross section,- Figure 17 shows the stator and rotor from Figure 15 in a disassembled position, and- Figure 18 shows the arrangement from Figure 17 in a cross section.

[0071] Figure 1 shows an agitator bead mill 10 with a grinding unit 12, a lifting mechanism 14 and a rotor drive 16, which in the exemplary embodiment is an electric motor.

[0072] The grinding unit 12 comprises a cylindrical stator 18 and a rotor 20.

[0073] The stator 18 forms a container for holding grinding media. The container or stator 18 has a container height hi , which can also be referred toas stator height. In contrast, rotor 20 has a rotor height h2. The corresponding heights hi, h2 can be seen in particular in Figure 2.

[0074] The rotor 20 is arranged in the stator 18 of the agitator bead mill 10 in such a way that a grinding gap 22 is formed between the stator 18 and the rotor 20, as can be seen in Figures 2 and 3, which show the mill 12 from Figure 1 in a sectional view.

[0075] The longitudinal axis LS of the grinding unit 12 is accordingly vertically oriented.

[0076] The lifting mechanism 14 serves to lift or extend the rotor 20 from an operating position, in which the rotor 20 is arranged in the stator 18 as shown in Figure 2, to the maintenance position illustrated in Figure 1, in which the rotor 20 is arranged outside the stator 18. A point of application 24 for the lifting mechanism 14, via which the rotor 20 can be lifted out in a vertical direction, is provided at an upper end of the rotor 20 (see also Figure 13)

[0077] When the rotor 20 is in the maintenance position shown in Figure 1 , the stator 18 can be removed from the agitator bead mill 10. For this purpose, the stator 18 can be mounted on rollers 26 (see Figures 2 and 3) in order to be moved accordingly.

[0078] The rotor 20 and the rotor drive 16 are arranged on different sides with respect to the lifting mechanism 14, as can be clearly seen in Figure 1. More precisely, the rotor 20 and the rotor drive 16 are diametrically opposed to each other with respect to the lifting mechanism 14. The weight of the rotor 20 and the weight of the rotor drive 16 thus (substantially) balance each other out.

[0079] The agitator bead mill 10 also comprises a control unit 28 and a sensor 30 that detects a rotary movement and / or an angular position of the rotor 20.The control unit 28 and the sensor 30 are shown schematically in Figure 1. The sensor 30 is for example a rotary encoder.

[0080] The control unit 28 is configured to control the rotor drive 16 and thereby to control a rotation of the rotor 20, i.e. a rotational speed of the rotor 20 as well as a stop position of the rotor 20, in particular to obtain a maintenance position of the rotor 20. This is described in more detail below.

[0081] As can be seen particularly clearly from the top views of Figures 5 to 8, stator cams 34 projecting radially inwards are arranged on an inner wall 32 of the stator 18 and rotor cams 38 projecting radially outwards are arranged on a circumferential wall 36 of the rotor 20. The rotor cams 38 and the stator cams 34 are arranged alternately to each other along the container or stator height hi or the rotor height h2, as can also be seen from Figures 2 and 3. This means that the stator cams 34 and the rotor cams 38 are arranged in different planes along the longitudinal axis LS of the grinding unit 12, i.e. along the vertical direction.

[0082] In the illustrated exemplary embodiment, both the stator cams 34 and the rotor cams 38 are trapezoidal when viewed from a top view along a longitudinal axis LS of the grinding unit 12 and taper towards their free ends, as can be clearly seen from Figures 5 to 8. This means that the contact area of the stator cams 34 with the stator 18 is larger than the end face of the stator cams 34 facing the rotor 20.

[0083] The stator cams 34 each have a stator contact surface 40 and the rotor cams 38 each have a rotor contact surface 39, wherein the stator contact surfaces 40 and the rotor contact surfaces 39 have, for example, an area of at least three square centimeters.

[0084] In the exemplary embodiment, the stator support surfaces 40 and the rotor support surfaces 39 are flat, in particular parallel to each other.

[0085] In a top view of the grinding unit 12, the surfaces of the rotor cams 38 and the stator cams 34 together occupy up to 40% to 60% of the total cross-sectional area of the grinding gap 22. This value is achieved when the stator cams 34 and the rotor cams 38 do not overlap, i.e. in the maintenance position shown. Due to their flat design, the surfaces correspond to the sum of the stator support surfaces 40 and the rotor support surfaces 39.

[0086] The grinding gap 22 is accordingly provided between the stator 18 and the rotor 20. Therefore, the stator cams 34 and the rotor cams 38 protrude into the grinding gap 22.

[0087] Instead of the trapezoidal shape, other shapes are also conceivable, as long as a flat or almost flat support surface 39, 40 is realized.

[0088] During rotation of the rotor 20, the stator cams 34 and the rotor cams 38 partially overlap with each other, i.e. during operation or in operating positions present during rotation, as shown in Figures 5 and 6. More precisely, the movement envelope of the rotor cams 38 overlaps with the stator cams 34 during rotation.

[0089] Both the stator cams 34 and the rotor cams 38 are symmetrical with respect to a central axis M of the stator cams 34 and rotor cams 38 in the view shown in Figures 5 to 8. This allows the stator cams 34 and the rotor cams 38 in particular to be turned if desired, to enable homogeneous wear during the service life of the stator cams 34 and the rotor cams 38.

[0090] In the exemplary embodiment, the ratio of the cam heights hr, hs of the stator cams 34 and the rotor cams 38 is at least 0.5, wherein the cam height hs of the stator cams 34 is less than the cam heights hr of the rotor cams 38, as can be seen in Figures 5 to 8.

[0091] In the specific exemplary embodiment shown in the figures, the stator cams 34 have a height hs of 30 mm, whereas the rotor cams 38 have a height hr of 45 mm, each measured in the radial direction.

[0092] The ratio of the height hs of the stator cams 34 to the inner diameter of the stator 18 is greater than 0.05.

[0093] The ratio of the height hs of the stator cams 34 to the grinding gap width MS is greater than 0.35.

[0094] The overlap length u (see Figures 4 and 6) of the rotor cams 38 and the stator cams 34 is 4 mm to 30 mm, in particular 10 mm to 15 mm.

[0095] The ratio of the overlap length u to the axial distance a of the rotor cams 38 from the stator cams 34 is 0.25 to 3.

[0096] The ratio of the overlap length u of the stator cams 34 and the rotor cams 38 to the grinding gap width MS is greater than or equal to 0.1.

[0097] A minimum distance a between the rotor cams 38 and the stator cams 34 in one direction along the longitudinal axis LS of the grinding unit 12 is at least 4 mm and at most 15 mm, as illustrated in the detailed view shown in Figure 2.

[0098] An axial extension ar of the rotor cam 38 and an axial extension as of the stator cam 34 as well as the minimum distance a of the rotor cam 38 and the stator cam 34 are illustrated in Figure 4.

[0099] Figure 3 also illustrates a core diameter d of the rotor 20 and an inner diameter D of the stator 18. A difference between the inner diameter D of the stator 18 and the core diameter d of the rotor 20 gives the grinding gap MS (see also Figure 8).

[0100] For clarity, the bottom of the container is not shown.

[0101] In the illustrated exemplary embodiment, the rotor 20 has eleven cam planes in the vertical direction and sixteen rotor cams 38 per plane along the circumference, for a total of 176 rotor cams 38. This is also evident from Figures 2 to 4.

[0102] In the illustrated exemplary embodiment, the stator 18 has twelve cam planes in the vertical direction and eight stator cams 34 per plane along its inner wall, for a total of 96 stator cams 34. This can be seen from Figures 9 to 10.

[0103] In Figures 7 and 8, the rotor cams 38 and the stator cams 34 are arranged offset from each other, so that, viewed from above, the rotor cams 38 are each arranged between the stator cams 34. This position corresponds to a maintenance position of the rotor 20 in which the rotor 20 can be lifted upwards to assume the maintenance position shown in Figure 1.

[0104] To stop the rotor 20 in the maintenance position, the control unit 28 is configured to control the rotor drive 16 accordingly. Specifically, the control unit 28 is configured to control the rotor drive 16 in such a way that the rotor 20 is stopped in a position that can also be referred to as the disassembly position. In this position, i.e. the maintenance position or disassembly position, the rotor cams 38 and the stator cams 34 are arranged in non-overlapping fashion, as illustrated in Figures 7 and 8. This makes it possible to move the rotor 20 axially relative to the stator 18, in particular to lift it out of the stator 18 using the lifting mechanism 14.

[0105] According to a method for operating the agitator bead mill 10, the rotor drive 16 is controlled by the control unit 28 and drives the rotor 20, so that therotor 20 rotates and a product to be ground is comminuted in the agitator bead mill 10.

[0106] The control unit 28 detects a position signal from the sensor 30 and determines the angular position of the rotor 20.

[0107] At the end of a grinding process, the control unit 28 controls the rotor drive 16 to stop the rotor 20, taking into account the angular position of the rotor 20, such that the rotor 20 remains in the position shown in Figures 7 and 8, in which the stator cams 34 and the rotor cams 38 are arranged offset from each other. As explained above, this position can be described as the maintenance position or disassembly position.

[0108] Figure 9 shows the stator 18 of the agitator bead mill 10 separately. In the exemplary embodiment, the stator 18 is composed of two stator cylinders 41 which are connected to each other along a flange 42, in particular by screws.

[0109] At the interface of the two stator cylinders 41 there is a seal, which is located for example in the flange 42, for which reason the seal is not visible in Figure 9.

[0110] Manufacturing the stator 18 from two stator cylinders 41 has the advantage that the individual cylinders have a lower height than the overall height of the stator 18, which simplifies handling during manufacturing and transport of the stator 18. In particular, the furnaces required for sintering the stator cylinders 41 can be made smaller.

[0111] In the embodiment shown in Figure 9, the stator cams 34 are arranged in rows extending along the longitudinal axis LS of the grinding unit 12, with the stator cams 34 of adjacent rows being arranged at the same height.

[0112] In the exemplary embodiment, the stator cams 34 are detachably attached to the stator 18, as illustrated in Figures 10 and 11.

[0113] Figure 10 shows a cross section through the stator 18 at the level of a row of stator cams 34, i.e. the row of stator cams 34 which is assigned to the cross-sectional plane. This illustration also makes it clear that eight stator cams 34 are provided per plane.

[0114] Figure 10 also shows, particularly taking into account Figure 9, that the stator cams 34 of different planes are each arranged in a column-like manner in a vertical direction, making it possible for the rotor 20 to be moved in an axial direction relative to the stator 18 in its maintenance position. In other words, continuous free spaces are formed on the inside of the stator 18 between adjacent stator cams 34, in which spaces the rotor cams 38 lie when the rotor 20 is in the maintenance position.

[0115] Figure 11 shows a detailed view of a section through a fastening point of the stator cam 34.

[0116] To fasten the stator cams 34 to the stator 18, at least one fastening element 44, for example a screw, projects from an outside of the stator 18 through a stator wall 46 into the corresponding stator cam 34.

[0117] The stator 18 typically has an inner casing formed by the stator wall 46 and an outer casing 47. This can be seen in Figure 2. Coolant channels 49 are formed between the inner casing or stator wall 46 and the outer casing 47.

[0118] In the exemplary embodiment, two fastening means 44 are provided for each stator cam 34.

[0119] In addition to the mechanical fastening means 44, an adhesive bond between each stator cam 34 and the corresponding fastening means 44 and / orthe stator inner wall 32 can also be provided. The adhesive bond simultaneously ensures a seal of the grinding gap 22 to the outside.

[0120] Figure 12 illustrates an alternative attachment of the stator cams 34 to the stator 18. Specifically, the stator cam 34 illustrated in Figure 12 is siliconized into the stator wall 46.

[0121] Figure 13 shows a rotor 20 in a perspective view.

[0122] The rotor 20 comprises a plurality of rotor disks 48, each rotor disk 48 having a row of rotor cams 38.

[0123] The described agitator bead mill 10 is used for example to grind silicon to achieve a particle size of 100 to 150 nanometers. Silicon ground to such a fine consistency is used in battery manufacturing, in particular for the production of battery paste.

[0124] Figure 14 shows an alternative stator for use in an agitator bead mill 10 as described above, in particular with a checkerboard arrangement of the stator cams 34.

[0125] The stator 18 differs from the previously described stator 18 by the arrangement of the stator cams 34 on the stator wall 46. Specifically, the stator cams are arranged in rows that run along the longitudinal axis LS of the grinding unit, with the stator cams of two adjacent rows being offset from each other with respect to the longitudinal axis LS.

[0126] Figure 15 shows the stator 18 with the stator wall 46 from Figure 14 in combination with a rotor 20, wherein the stator 18 is shown (partially) transparently. This clearly shows the interaction of the cams of the stator 18 and of the rotor 20.

[0127] Figure 16 shows the corresponding arrangement of Figure 15 in a cross section, in which the overlap of the rotor cams 38 and the stator cams 34 in the corresponding position is particularly clearly visible.

[0128] Figures 17 and 18 show the arrangement from Figures 15 and 16 in the disassembly position, in which the rotor cams 38 and the stator cams 34 do not overlap, so that the rotor 20 can be lifted out upwards.

[0129] In particular, Figure 18 shows that the surfaces of the stator cams 34 and the rotor cams 38 together occupy 40% to 60% of the total cross-sectional area of the grinding gap 22 formed between the stator 18 and the rotor 20, in a top view of the grinding unit 12. In other words, the stator cams 34 and the rotor cams 38 cover 40% to 60% of the annular cross-sectional area of the grinding gap 22 in a view from above of the grinding unit 12, as shown in Figure 18. The stator cams 34 and the rotor cams 38 protrude into the grinding gap 22, as can be seen in Figure 18.

Claims

Claims1. Agrinding unit(12)foran agitator bead mill (10), comprising a cylindrical stator (18) that forms a container with a container height (hi) for receiving grinding media, and a rotor (20) with a rotor height (h2) that is arranged in the stator (18) such that a grinding gap (22) is formed between the stator (18) and the rotor (20), wherein radially inwardly projecting stator cams (34) are arranged on an inner wall (32) of the stator (18) and radially outwardly projecting rotor cams (38) are arranged on a circumferential wall (36) of the rotor (20), wherein the stator cams (34) and the rotor cams (38) are arranged alternately to each other along the first container height (hi) and the rotor height (h2) and partially overlap each other when there is a rotation of the rotor (20), wherein the surfaces of the stator cams (34) and of the rotor cams (38) together occupy 40% to 60% of the total cross-sectional area of the grinding gap (22).

2. The grinding unit (12) according to claim 1 , characterized in that during a rotation of the rotor (20) the overlap length (u) of the rotor cams (38) and the stator cams (34) is 4 mm to 30 mm, in particular 10 mm to 15 mm.

3. The grinding unit according to claim 2, characterized in that the ratio of the overlap length (u) of the rotor cams (38) and the stator cams (34) to an axial distance (a) of the rotor cams (38) to the stator cams (34) is 0.25 to 3.

4. The grinding unit (12) according to claim 1 or 2, characterized in that both the rotor cams (38) and the stator cams (34) are each designed symmetrically with respect to a central axis (M).

5. The grinding unit (12) according to one of the preceding claims, characterized in that the stator cams (34) are arranged in different positions with respect to the container height (hi ), in particular wherein the stator cams are arranged in rows which run along the longitudinal axis (LS) of the grinding25unit (12), wherein the stator cams (34) of two adjacent rows are offset from each other with respect to the longitudinal axis (LS).

6. The grinding unit (12) according to one of the preceding claims, characterized in that the stator cams (34) are detachably attached to the stator (18), in particular wherein at least one fastening means (44) engages through a stator wall (46) into each stator cam (34) and / or wherein an adhesive bond is present between each stator cam (34) and the corresponding fastening means (44) and / or the stator inner wall (32).

7. The grinding unit (12) according to one of the preceding claims, characterized in that the rotor comprises a plurality of rotor disks (48), each rotor disk (48) having a row of rotor cams (38).

8. The grinding unit (12) according to one of the preceding claims, characterized in that the ratio of the cam height (hs) of the stator cams (34) to the cam height (hr) of the rotor cams (38) is at least 0.5.

9. The grinding unit (12) according to one of the preceding claims, characterized in that the distance (a) between the rotor cams (38) and the stator cams (34) in a direction along the longitudinal axis (LS) of the grinding unit (12) is at least 4 mm and at most 15 mm.

10. The grinding unit (12) according to one of the preceding claims, characterized in that the ratio of the height (hs) of the stator cams (34) to the inner diameter of the stator (18) is greater than 0.05, and / or that the ratio of the height (hs) of the stator cams to the grinding gap width is greater than 0.35, and / or that the ratio of an overlap of the stator cams and the rotor cams to the grinding gap width is greater than or equal to 0.1.

11. The grinding unit (12) according to one of the preceding claims, characterized in that an engagement point (24) for a lifting mechanism (14) isprovided at an upper end of the rotor (20), via which the rotor (20) can be lifted in the vertical direction.

12. An agitator bead mill (10) comprising a grinding unit (12) according to one of the preceding claims, wherein a longitudinal axis (LS) of the grinding unit (12) is vertically oriented, wherein the agitator bead mill (10) has a rotor drive (16) and a lifting mechanism (14) for lifting the rotor (20) from an operating position in which the rotor (20) is arranged inside the stator (18) to a maintenance position in which the rotor (20) is arranged outside the stator (18).

13. The agitator bead mill (10) according to claim 12, characterized in that the agitator bead mill (10) has a control unit (28) which controls the rotor drive (16) in order to control a rotation of the rotor (20), wherein the agitator bead mill (10) comprises a sensor (30) which detects a rotary movement and / or an angular position of the rotor (20), wherein the control unit (28) is configured to control the rotor drive (16) such that the rotor (20) is stopped in a position in which the rotor cams (38) and the stator cams (34) are arranged in nonoverlapping fashion such that the rotor (20) is axially movable relative to the stator (18).

14. A method for operating an agitator bead mill (10) according to one of claims 12 and 13, wherein the agitator bead mill (10) has a control unit (28) which controls the rotor drive (16) to drive the rotor (20) and a sensor (30) which detects a rotational movement and / or an angular position of the rotor (20), comprising the following steps:- the rotor drive (16) drives the rotor (20) so that the rotor (20) rotates and a product to be ground is comminuted in the agitator bead mill (10) between the rotor (20) and stator (18),- the control unit (28) detects a position signal from the sensor (30) and determines the angular position of the rotor (20) from it,- the control unit (28) controls the rotor drive (16) of the rotor (20), taking into account the angular position of the rotor (20), in such a way that the rotor(20) reaches the speed 0, in particular comes to a stop, in a position in which the stator cams (34) and the rotor cams (38) are offset relative to one another when viewed from above.

15. A use of the grinding unit (12) according to one of claims 1 to 11 for the production of a battery paste, wherein silicon is ground in the grinding unit (12) such that at least 50% of the silicon particles achieve a particle size smaller than 100 nanometers.

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