Stirred ball mill with a support system for cooling the grinding container

Abstract

A stirred ball mill with a grinding chamber predominantly designed as a grinding chamber tube, in which a stirring shaft and the grinding media circulated by it rotate, and with a system for dissipating heat from the grinding chamber tube, which is formed by the grinding chamber tube and a sleeve circumferentially encompassing the grinding chamber tube, which carry a coolant between them, wherein the sleeve is pressed onto the grinding chamber tube and the grinding chamber tube and / or the sleeve has / have grooves, wherein the grooves alone or together form coolant channels through which a coolant can be passed between the sleeve and the grinding chamber tube.

Description

[0001] The invention relates to a stirred ball mill with a support system for cooling the grinding container according to the preamble of claim 1 and a corresponding system according to the preamble of claim 12. TECHNICAL BACKGROUND

[0002] Conventional stirred ball mills have a vertically or horizontally arranged grinding chamber as their essential component. This grinding chamber is filled with grinding media, which are usually made of hard, wear-resistant materials such as steel, glass, or ceramic. An agitator within the grinding chamber ensures intensive movement of the grinding media. The material to be ground, usually as a suspension, is continuously pumped through the grinding chamber, causing the solid material in the suspension to collide with the grinding media. The impact and shear forces then break down the material.

[0003] Grinding containers typically consist primarily of a tube, the so-called grinding container tube, which is held and preferably sealed by two flange rings. Due to the movement of the grinding media and the aforementioned impact and shear forces, both the material being ground and the grinding media collide with the inner surface of the grinding container tube. The grinding container tube is therefore subject to significant wear, primarily from the grinding media. For this reason, a silicon ceramic is usually used as the material for the grinding container tube, as it meets the necessary requirements for appropriate wear resistance. This silicon ceramic—unlike most conventional ceramics—is highly thermally conductive. It is therefore advantageous to cool the grinding container via the outer surface of its grinding container tube in order to maintain the desired temperature.

[0004] A clear example of a stirred ball mill, which also forms the basis for the invention presented here, is the one described as Fig. 5The applicant's stirred ball mill 5 is shown. The grinding chamber 2 and the rotating agitator shaft within it, which circulates the grinding media, are clearly visible. Also clearly visible is the jacketed chamber provided in this stirred ball mill, which extends beyond the grinding chamber 2 at a distance. In the resulting annular space, radially connected to the outer circumferential surface of the grinding chamber tube, a coolant, preferably cooling water, can be brought into direct contact with the outer circumferential surface of the grinding chamber tube. In the prior art, cooling mats with rubber lips are often used for this purpose, through which coolant is guided in a spiral pattern. These cooling mats are usually made of a plastic such as PVC and are placed on the outer circumference of the grinding chamber tube to dissipate heat. However, in grinding processes that generate a significant amount of heat, for example, when grinding cocoa, the existing plastic cooling mats reach their thermal limits.

[0005] In addition to adequate heat dissipation, another important aspect must be considered in the design of the grinding chamber tube. It is essential to prevent the grinding chamber tube from breaking, and if it does break, to prevent the often very small grinding media from entering the coolant circuit. Many factors can influence the breaking of the grinding chamber tube, such as the weight and dimensions of the tube itself, the grinding material suspension, the grinding chamber pressure, the distribution of the grinding media, and / or pressure surges. To prevent breakage, it is a known practice to press a sleeve, usually made of aluminum, onto the outer circumference of the grinding chamber tube. This sleeve prevents direct contact between the coolant and the grinding chamber tube and also increases the tube's strength by providing support.Since the grinding chamber tubes are ground on the outside, this does not represent a higher manufacturing effort for the grinding chamber tube. The sleeve is usually pressed onto the grinding chamber tube. The cooling mat mentioned above can then be attached to the outer circumference of the sleeve.

[0006] However, the previously considered option of pressing on a sleeve has the disadvantage that it noticeably reduces the effectiveness with which heat can be dissipated via the grinding container tube.

[0007] Even highly thermally conductive metals, such as aluminum, still conduct heat significantly less efficiently than the special ceramic typically used for the grinding container. Furthermore, pressing on a sleeve as a support tube increases the wall thickness, through which the heat must first be conducted. TASK

[0008] The object of the invention is therefore to achieve more efficient heat dissipation from the grinding container without having to do without a sleeve to support the grinding container tube. INVENTIVE SOLUTION

[0009] According to the invention, this problem is solved as follows.

[0010] A stirred ball mill is proposed, featuring a grinding chamber primarily designed as a grinding tube, in which a stirring shaft and the grinding media it circulates. This stirred ball mill includes a system for dissipating heat from the grinding chamber.

[0011] In its broadest sense, the invention is characterized in that the system is formed by a sleeve (3) which encompasses the outer circumference of the grinding container tube and serves to guide the coolant, wherein the sleeve (3) is pressed onto the grinding container tube (2) and has grooves or channels which are involved in guiding the coolant.

[0012] In its preferred, narrower sense, the invention is characterized in that the system is formed by the grinding container tube and a sleeve that circumferentially surrounds the grinding container tube, the sleeves being designed such that the coolant is guided between the sleeve and the grinding container tube. The invention is further characterized in that the sleeve is pressed onto the grinding container tube and the grinding container tube and / or the sleeve has / have grooves, wherein the grooves, either alone or in combination, form coolant channels through which a coolant can be guided between the sleeve and the grinding container tube.

[0013] A crimp connection between the sleeve and the grinding chamber tube refers to a press fit between the sleeve and the grinding chamber tube. This is achieved because the inner diameter of the sleeve, in its unassembled state, is smaller than the outer diameter of the grinding chamber tube. As a result, after assembly, the sleeve and the grinding chamber tube are pressed together over their majority or essentially their entire contact surface. This press fit allows for the transmission of more than negligible forces from the grinding chamber tube to the sleeve and vice versa, even in the longitudinal direction of the tube. Whether the crimp is achieved by pressing the sleeve onto the grinding chamber tube using a press or, preferably, by thermal shrinking, is initially irrelevant.

[0014] The invention, in its narrower sense, thus opens up the possibility for the highly efficient thermally conductive special ceramic of the grinding chamber tube, if such a material is used, to come into direct contact with the coolant and thereby transfer heat to the coolant particularly effectively. In any case, it is no longer necessary for the heat to be transferred to pass through the supporting sleeve before it can be transferred to the coolant. Both of these factors significantly reduce the thermal load on the grinding chamber tube and its contents. The latter is of great importance, for example, when grinding materials that generate high friction and are therefore heat-sensitive – such as chocolate or cocoa beans, which require high drive power.

[0015] In general, the existing grinding chamber tube and / or the existing sleeve for internal coolant routing can be used without having to add any additional parts to the system. This contributes to the simplicity of the overall system, reduces assembly effort, and can save radial installation space in many situations.

[0016] As already mentioned, it is preferable for the coolant to be routed between the grinding chamber tube and the sleeve. One way to achieve this is for the grinding chamber tube and the sleeve to have interacting grooves that together form coolant channels. This design is particularly suitable when the grinding chamber tube is not subjected to extremely high mechanical stress, and therefore the notch effect of grooves on the grinding chamber tube is not a concern. Instead, the focus is on creating the largest possible direct contact area between the highly thermally conductive special ceramic and the coolant. Another possibility is for the sleeve to have grooves on its inner circumferential surface—the surface facing the grinding chamber tube—which are complemented by the smooth, ungrooved surface of the grinding chamber tube to form closed cooling channels.This allows cooling channels to be formed without weakening the grinding container tube in any way.

[0017] In both cases, the sleeve, which is pressed onto the grinding chamber tube via webs between the grooves, provides additional support for the grinding chamber tube, resulting in greater strength and stability of the grinding chamber tube with a reduced material thickness. This further improves cooling performance and reduces the risk of the grinding chamber tube breaking. OPTIONAL OPPORTUNITIES FOR FURTHER EDUCATION OF THE INVENTION

[0018] A preferred embodiment consists in the grooves of the grinding container tube and / or the sleeve having a concave and preferably semicircular clear cross-section. Preferably, the groove depth is thus uniform across the entire surface. This contributes to the ease of manufacturing the components and, on the other hand, ensures good coolant flow in the resulting coolant channels without the formation of areas with reduced or no flow.

[0019] Furthermore, it is particularly advantageous if the aforementioned grooves spiral around the circumferential surface. This allows for easier, continuous coolant circulation across the entire surface – without "dead zones" where the coolant barely circulates and which are therefore subject to higher heat loads.

[0020] Another conceivable embodiment consists of several enclosing tubes within the grinding chamber. Preferably, at least two tubes are pressed together, namely, typically, the grinding chamber tube made of special ceramic and a smooth support tube made of aluminum. The sleeve is pressed onto the outer surface of the support tube. While this design is less effective at cooling, it guarantees that even if a crack should develop in the grinding chamber tube, no cooling water will enter the grinding chamber and no grinding media will enter the cooling water circuit.

[0021] Another conceivable embodiment involves the sleeve having grooves on its outer circumferential surface, while the grinding chamber tube has no grooves. In this configuration, the cooling channels are located on the side facing away from the grinding chamber tube; however, in some cases, the cooling capacity is sufficient to dissipate heat adequately due to the high thermal conductivity of the materials in that area. The decisive advantage of such a variation is that even in the event of a crack or break in the grinding chamber tube, no coolant can escape into the grinding chamber, thus preventing costly cleaning operations. Conversely, and preferably, no grinding media can escape into the coolant branch or circuit.

[0022] It is particularly advantageous if the sleeve is made at least mostly of aluminum or an aluminum alloy. Aluminum is corrosion-resistant, durable, and, most importantly, has a sufficiently high thermal conductivity to dissipate heat from the inner tube.

[0023] Furthermore, it is particularly advantageous if the grinding chamber tube is made at least largely of ceramic, preferably silicon carbide ceramic. It is very light, yet also the hardest ceramic material, exhibits very good thermal conductivity with low thermal expansion, and very good resistance to acids and alkalis.

[0024] Another preferred embodiment consists in the sleeve being shrunk onto the grinding chamber tube. For this purpose, the sleeve is preferably first heated – e.g., in an oven – until it expands sufficiently to be slid onto the grinding chamber tube. Upon cooling, the sleeve then achieves an interference fit. The inner diameter of the sleeve is selected such that, at temperatures that the sleeve material can withstand without structural damage, it is larger than the outer diameter of the grinding chamber tube, and at room temperature, it is smaller than the outer diameter of the grinding chamber tube.

[0025] Further modes of operation, advantages and design possibilities result from the figure-based description of the exemplary embodiment. LIST OF FIGURES

[0026] The Figure 1shows a preferred embodiment of the heat dissipation system in a sectional three-dimensional view.

[0027] The Figure 2 shows the preferred embodiment from Fig. 1 in a cutaway side view.

[0028] The Figure 3 shows a grinding container tube with grooves of the preferred embodiment in side view.

[0029] The Figure 4 shows a sleeve with grooves of the preferred embodiment in a cutaway side view.

[0030] The Fig. 5 illustrates a stirred ball mill known in the prior art, which also forms the basis of today's invention. PREFERRED EXAMPLE OF EXECUTION

[0031] The stirred ball mill 5, presented here as an example, can be constructed in the same way as the Fig. 5As illustrated, only the periphery of the outer circumference of the grinding container tube 2 is designed differently in each case according to the invention, namely as shown in the Figures 1 to 4 show when one applies their teachings to the Fig. 5 applies.

[0032] The Figs. 1 to 4 For better illustration, we show a preferred embodiment of system 1 for heat dissipation from the grinding container tube 2, wherein both the grinding container tube 2 and the sleeve 3 pressed onto the grinding container tube 2 have grooves.

[0033] The grinding container tube 2 has grooves 2a on its outer circumferential surface, which run spirally around it (see Fig. 3 The sleeve 3 has grooves 3a on its inner circumferential surface, which run spirally around it (see Fig. 4The grooves 2a and 3a are also designed and arranged in such a way that, when the grinding container tube 2 and the sleeve 3 are pressed together as intended, they jointly form coolant channels 4 that run spirally around (see Fig. 1 and Fig. 2 The grooves 2a and 3a preferably have a substantially semicircular cross-section. After pressing the sleeve 3 and the grinding container tube 2 together, the grooves 3a of the sleeve 3 and the grooves 2a of the grinding container tube 2 preferably complement each other in such a way that spirally circumferential coolant channels 4 with a substantially round cross-section are formed, through which the coolant can then flow. For this purpose, the grooves 3a of the sleeve 3 and the grooves 2a of the grinding container tube 2 must be coordinated with each other in their positioning, diameter, and spiral shape so that they can complement each other to form a circumferential, hollow spiral with a round cross-section.

[0034] It should be mentioned that the system 1 shown is preferably used in stirred ball mills 5, but can also be used in other types of mills and machines that require heat dissipation from an inner container.

[0035] The inner container or the grinding container tube 2 preferably has a cylindrical shape, but other shapes are also conceivable.

[0036] The grooves 2a and 3a preferably have a semicircular cross-section, but other shapes are also conceivable. MISCELLANEOUS

[0037] In general, the spiral grooves for guiding the coolant ensure very uniform cooling without dead water zones.

[0038] In general, it is important that each, or essentially each, of the webs located between two immediately adjacent grooves forms a press fit with its radially corresponding counterpart. This allows for a significant supporting effect between the sleeve and the outer circumferential surface of the grinding chamber tube, despite the design of the coolant-carrying grooves. This stabilizes the grinding chamber tube, particularly due to the helical shape of the grooves – the much stronger webs separated by the grooves stabilize like a helical spring. Generally, strain and / or resistance measurements can be provided on the sleeve to detect any cracking or breakage of the grinding chamber tube before the sleeve also fails due to the overload imposed during such a cracking or breakage. REFERENCE MARK LIST

[0039] 1 System 2 Grinding container tube 2a Groove of the grinding container tube 3 Sleeve 3a Groove of the sleeve 4 Coolant channel 5 Stirred ball mill

Claims

1. Stirred ball mill (5) with a grinding container designed at least predominantly as a grinding container tube (2) in which a stirring shaft and the grinding media circulated by it rotate, and with a system (1) for dissipating heat from the grinding container tube (2), which is formed by or with the participation of a sleeve (3) encompassing the outer circumference of the grinding container tube, which serves for the coolant guidance, characterized by the fact that the sleeve (3) is pressed together with the grinding container tube (2) and has grooves or channels that are involved in the coolant guidance.

2. Stirred ball mill (5,) preferably according to claim 1, with a grinding container designed at least predominantly as a grinding container tube (2) in which a stirring shaft and the grinding media circulated by it rotate, and with a system (1) for dissipating heat from the grinding container tube (2), which is formed by the grinding container tube (2) and a sleeve (3) circumferentially encompassing the grinding container tube (2) on its outer circumference, which carry a coolant between them, characterized by the fact that the sleeve (3) is pressed together with the grinding container tube (2) and the grinding container tube (2) and / or the sleeve (3) has / have grooves (2a, 3a), wherein the grooves (3a) of the sleeve alone or together with the grooves (2a) of the grinding container tube form coolant channels (4) through which a coolant can be passed between the sleeve (3) and the grinding container tube (2).

3. Stirred ball mill (5) according to claim 1, characterized by the fact thatthe grooves (2a, 3a) have a concave and preferably semicircular clear cross-section.

4. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the grooves (2a, 3a) spiral around the circumferential surface.

5. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the grinding container tube (2) has grooves (2a) on its outer circumferential surface which interact with grooves (3a) on the inner circumferential surface of the sleeve (3a) in such a way that spirally circumferential coolant channels (4) are formed which have a preferably round cross-section.

6. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the grinding container tube (2) consists of several enclosing tubes.

7. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact thatthe sleeve (3) has grooves (3a) on its inner circumferential surface, whereas the grinding container tube (2) has no grooves.

8. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the sleeve (3) has grooves (3a) on its outer circumferential surface, whereas the grinding container tube (2) has no grooves.

9. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the sleeve (3) consists at least mostly of aluminium or an aluminium alloy.

10. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the grinding container tube (2) consists at least mostly of ceramic, preferably a silicon carbide ceramic.

11. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact that the sleeve (3) has been shrunk onto the grinding container tube (2).

12. Stirred ball mill (5) according to one of the preceding claims, characterized by the fact thatThe grinding container tube (2) has such a much larger outer diameter compared to the inner diameter of the sleeve (3) that the press connection between the sleeve (3) and the grinding container tube (2) is not yet released even when the maximum permissible grinding container temperature is exceeded by 20 percent.

13. System (1) for a stirred ball mill (5), characterized by the fact that the system (1) consists of a grinding container tube (2) and a sleeve (3) and is designed according to at least one of the claims directed to this system (1).

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