DE102018122395B4 - Stirring shaft for a stirred ball mill, stirred ball mill and method for producing a stirring shaft for a stirred ball mill - Google Patents

Abstract

Agitator shaft (1) for an agitator ball mill (50), wherein the agitator shaft (1) has a longitudinal axis (L) and an outer circumferential surface (5) equipped with agitating elements (3), wherein the agitator shaft (1) is formed integrally with the agitating elements (3) and consists of a ceramic material, wherein the agitator shaft (1) has at least one cooling channel (6) which preferably extends at least partially parallel to the longitudinal axis (L) of the agitator shaft (1), wherein the at least one cooling channel (6) extends in at least two regions each parallel to the longitudinal axis (L) of the agitator shaft (1), wherein a deflection region (67) is formed between the two parallel regions (61, 62), in particular wherein a coolant flows through the at least two regions (61, 62) connected to one another via a deflection region (67) in opposite flow directions (SR1, SR2).

Description

The present invention relates to an agitator shaft for an agitator ball mill, an agitator ball mill and a method for producing an agitator shaft for an agitator ball mill according to the features of the independent claims.

State of the art

The invention relates to an agitator ball mill, in particular to an agitator for an agitator ball mill. The agitator ball mill is a device for coarse, fine, and ultrafine comminution or homogenization of material to be ground. An agitator ball mill consists of a vertically or horizontally arranged, usually approximately cylindrical grinding vessel, which is 70% to 90% filled with auxiliary grinding media. In agitator ball mills, the grinding vessel is usually stationary. Many conventional mills are filled through a central opening in one of the end walls. Alternatively, filling can also occur directly via the grinding cylinder. During the grinding process, the product to be ground flows continuously from a product inlet axially through the grinding chamber to a product outlet. The suspended solids are crushed or dispersed between the grinding media by impact and shear forces. The auxiliary grinding media are then separated from the product stream in an outlet area. The discharge depends on the design and takes place, for example, through a sieve at the end of the mill.

The agitator is typically formed by an agitator shaft, which serves to rotate agitating elements in the form of discs or radially projecting pins, particularly to deagglomerate and comminute solids dispersed in the liquid in the milled material. The agitator shaft is usually motor-driven. Suitable agitating elements are, in particular, disc agitators with a plurality of grinding discs arranged on a agitator shaft. The grinding discs are usually circular and can be provided with passage openings. The passage opening ensures, in particular, the product flow.

An annular grinding gap is formed between the inside of the grinding cylinder and the agitator, in which the material to be ground is located during operation of the agitator ball mill. The agitator is driven by rotation and thus exerts pressure on the material to be ground within the grinding gap, thereby comminuting it. This action is supported by the auxiliary grinding media and the agitator's stirring elements. In particular, the material to be ground and the auxiliary grinding media are intensively agitated by means of an agitator shaft. The solid particles of the material to be ground are comminuted through impact, pressure, shear, and friction.

The agitator shafts or agitators are preferably made of an abrasion-resistant material, in particular of a metal or a ceramic material, for example WO 2000/054884 A a stirred ball mill in which the agitator, in particular the disc-shaped stirring elements, is made of a ceramic material.

The utility model specification DE 20 2017 104 764 U1 describes a stirring shaft with cams.

The DE 2626757 A1 discloses a stirring propeller constructed in such a way that only relatively simple and inexpensive parts are subject to wear and tear, and that these parts are easily replaceable. Where economically feasible, these simple parts are made of a particularly abrasion-resistant material, such as ceramic.

Many processes, chemical, mechanical or otherwise, generate process heat, which can negatively impact the process itself or the starting materials used, for example because the substances involved in the process are temperature-sensitive or because temperature changes affect the process speed and thus make orderly process control more difficult. For this reason, it is common practice to stabilize a process by, for example, dissipating the generated process heat using suitable cooling devices or methods. Processes running in containers are usually temperature-controlled via the container wall, for example by means of cooling or hot water pipes running along the wall or by placing another outer container around the first container at a radial distance from the first container, so that a hollow space is formed between the two containers, through which a fluid flow, which can be a hot water flow or a coolant flow, can be guided to transport the process heat.

Heat is also generated during the grinding process. Depending on the product, this heat must be dissipated or heat generation must be prevented. This problem is particularly acute for agitator ball mills with a large grinding volume or when a higher power input is desired. For cooling during the grinding process, for example, the grinding cylinder is designed to be coolable. For example, the published patent application describes DE 3614721 A1 equipping the grinding container with a cooling jacket as known prior art. This document further discloses that the agitator rotor can be provided with at least one cooling channel on its circumference. A grinding container with a cooling jacket is further disclosed in the published application WO 2007/042059 A1. Furthermore, the agitator mill described in this document has an internal stator, which can also be cooled. The agitator is cup-shaped and includes a ring-cylindrical rotor.

As already mentioned in connection with the DE 3614721 A1 As mentioned, cooling can alternatively or additionally be achieved via the agitator rotor. The published patent application DE 3015631 A1 describes an agitator comprising an inner and an outer cylinder, between which an annular cooling chamber is formed, wherein for cooling purposes a coolant supplying pipe is arranged axially parallel within the cooling chamber and is connected to a supply pipe for coolant.

Another coolable agitator shaft is described in the patent DE 10241924 B3 discloses, wherein tubular material in various cross-sectional shapes is used for cooling, within which an inner tube is arranged which extends over almost the entire length, wherein the interior of the tube is connected to the coolant inlet and the exterior space is connected to the coolant outlet.

The patent specification DE 41 09 332 C2 also describes a stirrer shaft with rod-shaped stirring bars attached to the stirrer shaft, which can be cooled via channels.

The utility model specification DE 20 2015 101 859 U1 describes a fluid guide mat with lamellar structures to guide the fluid flow through a cavity. The fluid guide mat is arranged between the jacketed container and the grinding container.

The disclosure document WO 2007/042059 describes an agitator mill with an internal stator and a cylindrical rotor. The internal stator has an outer wall and a cylindrical inner shell, between which a cooling chamber is formed.

Above a certain size, ceramic agitator shafts or stirrers must be constructed from multiple components. Manufacture of the individual parts requires extensive grinding work, which results in very high costs due to the labor required. Furthermore, assembling the agitator shaft from multiple parts creates so-called dead spaces in which grinding material and/or auxiliary grinding media can become trapped and thus contaminate the machine room. Such multi-part ceramic agitator shafts are also very fragile, especially during assembly, disassembly, cleaning, and maintenance. Furthermore, it has not yet been possible to manufacture ceramic rotors with cooling.

Description

The object of the invention is to produce a stirrer shaft for a stirred ball mill simply and cost-effectively, in particular a coolable stirrer shaft for use in high-performance stirred ball mills.

The above object is achieved by an agitator shaft for a stirred ball mill, a stirred ball mill, and a method for producing an agitator shaft for a stirred ball mill, which comprise the features in the independent patent claims. Further advantageous embodiments are described in the subclaims.

The agitator ball mill is used for processing and in particular comminuting material to be ground with the aid of auxiliary grinding bodies and has a grinding container with a material to be ground inlet and a product outlet, to which an agitator is assigned, which is arranged at least partially within the grinding container.

The agitator comprises a drive, an agitator shaft arranged on the drive and rotating in one direction of rotation, and at least one agitator element arranged on the agitator shaft. The agitator shaft has a preferably cylindrical base body with a longitudinal axis, wherein at least one agitator element, preferably a plurality of agitator elements, is/are arranged on the base body. In particular, the agitator shaft has an outer surface equipped with agitator elements. The longitudinal axis of the agitator shaft generally coincides with the longitudinal axis of the grinding container. The drive is generally arranged outside the grinding container and is connected to the agitator shaft arranged inside the grinding container via a drive shaft penetrating the container wall.

The stirring shaft with the stirring elements is made in one piece and is made of a ceramic material.

Furthermore, the agitator shaft has at least one cooling channel, which preferably extends at least partially parallel to the longitudinal axis of the agitator shaft. The at least one cooling channel extends in at least two areas. each parallel to the longitudinal axis of the agitator shaft, wherein a deflection region is formed between the two parallel regions, in particular wherein a coolant flows through the at least two regions connected to one another via a deflection region in opposite flow directions.

One embodiment provides that the at least one cooling channel is formed in a meandering shape.

The grinding container is preferably cylindrical and arranged horizontally or vertically, so that the agitator shaft is arranged horizontally or vertically accordingly. The grinding container can also have a different shape, for example, a truncated cone. In this case, the agitator shaft is preferably also correspondingly truncated conically.

The at least one stirring element is designed, for example, as a cam, which preferably extends approximately radially away from the stirring shaft in the direction of an inner side of the grinding container of the agitator ball mill.

An annular grinding gap is formed between the outer surface of the agitator shaft and the inner surface of the grinding container, containing a mixture of grinding material and auxiliary grinding media. Due to the rotation of the agitator shaft, the grinding material within the grinding gap is comminuted due to stresses such as particle collisions, shear forces, etc. The agitator elements support this process by providing additional energy, particularly to the auxiliary grinding media.

The agitator shaft with the agitator elements is designed and manufactured in one piece and is preferably made of a ceramic material. The agitator shaft is particularly preferably made of silicon carbide (SiC), silicon carbide with free silicon (SiSiC), silicon nitride, zirconium oxide, or mixed ceramics. Silicon carbide ceramics exhibit high wear resistance, low thermal shock sensitivity, low thermal expansion, high thermal conductivity, and good resistance to acids and alkalis. Furthermore, they are lightweight and retain their positive properties up to temperatures above 1400°C. Furthermore, silicon carbide is toxicologically safe and can therefore also be used in the food industry. Although silicon nitride has a reduced hardness compared to silicon carbide, a sintering process can induce columnar recrystallization of the β-silicon nitride crystals, which leads to increased fracture toughness of the material. The high fracture toughness combined with small defect sizes gives silicon nitride one of the highest strengths among engineering ceramic materials. The combination of high strength, low thermal expansion coefficient, and relatively low elastic modulus makes silicon nitride ceramic particularly suitable for components subject to thermal shock. Unlike other ceramic materials, zirconium oxide exhibits very high resistance to crack propagation. Zirconium oxide ceramic also exhibits very high thermal expansion and is therefore a popular choice for creating joints between ceramic and steel.

Particularly preferably, the agitator shaft with the agitator elements is manufactured using a 3D printing process. This makes it possible to produce a component with internal cavities that would not be possible in a single process step using conventional methods such as injection molding or similar without further post-processing, for example, without the subsequent insertion of holes or similar. However, it is now possible to easily and cost-effectively create at least one integrated cooling channel within the agitator shaft.

According to one embodiment of the invention, two parallel regions, through which coolant flows in opposite directions, are located on a common radial of the agitator shaft. This achieves countercurrent cooling of the agitator shaft. In particular, the coolant is guided close to the longitudinal axis of the agitator shaft from the material inlet side to the product outlet side. The coolant is returned from the product outlet side to the material inlet side within the agitator shaft in a region adjacent to the outer surface of the agitator shaft. This ensures that the freshest and therefore coolest coolant is first guided to the region of the agitator ball mill where the material to be ground is warmest. This is particularly the region near the product outlet, after the material to be ground has flowed through the agitator ball mill in the conveying direction from the material inlet side. In particular, the coolant flows through the agitator shaft on the surface of the agitator shaft in the opposite direction to the conveying direction of the material to be ground through the agitator ball mill. This countercurrent cooling allows the cooling process to be further optimized.

One embodiment of the agitator shaft provides that it comprises at least two sub-sections, in particular a first terminal sub-section at which the agitator shaft is connected to the Drive shaft of the agitator. For example, the first terminal sub-section has a receiving area, in particular a shaft receptacle, in which the free end of the drive shaft can be arranged and connected to the agitator shaft in a rotationally fixed manner. Furthermore, at least one second sub-section is provided. The second sub-section is preferably hollow on the inside. In addition, passage openings are formed in the second sub-section, preferably between the outer circumferential surface and the hollow interior or interior region. In particular, a plurality of passage openings are provided which extend parallel to the longitudinal axis of the agitator shaft. A separating device can preferably be formed within the second sub-section. The grinding material/aid grinding body mixture flowing through the grinding gap is deflected at the open end of the second sub-section and flows via the separating device into the hollow interior of the second sub-section. The separation device, which can be designed, for example, as a separating screen or classifying rotor, retains the auxiliary grinding media and transports them, along with any insufficiently ground material, through the passage openings back into the grinding gap. The sufficiently ground material, in turn, is conveyed through the hollow interior to a product outlet of the agitator ball mill, where it can be removed.

Due to the small grinding gap between the agitator shaft and the inner wall of the grinding vessel, the auxiliary grinding media are preferably concentrated in this so-called grinding chamber. Only a small portion of the auxiliary grinding media is redirected along with the material to be ground and flows via the separating device into the hollow interior of the second subsection.

According to one embodiment, the second sub-section is a middle sub-section, to which a further third terminal sub-section adjoins. This third sub-section also has a hollow interior. In the case of a cylindrical base body of the agitator shaft, the interiors of the second and optionally third sub-section are preferably also cylindrical and have a circular cross-section, wherein the radius of the cross-section of the interior in the third sub-section is greater than or equal to the radius of the cross-section of the interior in the second sub-section. In addition, the cylindrically shaped inner cavities each have a longitudinal axis that is congruent with the longitudinal axis of the agitator shaft.

In the third sub-section, preferably no through-openings are provided between the interior and the outer circumferential surface of the agitator shaft. Instead, a wear protection sleeve, which is preferably also cylindrical, can be arranged in the interior of the third sub-section. In particular, the wear protection sleeve is arranged between a container bottom of the grinding container and the separating device in the second interior region. In this embodiment, the grinding material/grinding aid mixture flowing through the grinding gap is deflected at the open end of the third sub-section within the annular gap formed between the wear protection sleeve and the agitator shaft in the direction of the second sub-section, whereby the grinding material is separated from the grinding aids, as already described above.

Preferably, the at least one cooling channel extends within the first terminal sub-section and at least partially within the second, middle sub-section. In one embodiment of an agitator shaft comprising three sub-sections, the at least one cooling channel can extend through all three sub-sections. A meandering cooling channel can, for example, comprise parallel sections which are each formed between passage openings within the second sub-section of the agitator shaft. The parallel sections can extend at least partially into the first and/or third sub-section of the agitator shaft. In particular, at the terminal regions of the first and third sub-sections of the agitator shaft, corresponding deflection regions are formed which deflect the coolant from one parallel section to the next parallel section, so that the coolant preferably flows in opposite directions through parallel sections arranged directly adjacent to one another.

In particular, it is provided that such a cooling channel comprises an even number of parallel sections, so that the coolant inlet and the coolant outlet are each located at the same end of the agitator shaft. In this case, the coolant flows, for example, through the first, third and fifth parallel sections, etc., in a first flow direction and the second, fourth and sixth parallel sections, etc., in an opposite second flow direction. The grinding material/grinding aid mixture flows through the grinding gap in a first conveying direction, which, for example, corresponds to the first flow direction, and is diverted within the second and/or third partial sections of the agitator shaft, in particular into a second conveying direction, which corresponds to the second flow direction. The cooling water guide, in particular the cooling water supply and discharge lines, can be formed by an insert part that For example, it can be arranged and fastened together with the drive shaft on the first sub-section of the agitator shaft; For example, the insert part can be placed on the end of the drive shaft and arranged and fastened together with it in the shaft passage, wherein the cooling water supply and discharge lines are connected to the at least one cooling channel of the agitator shaft.

A plurality of stirring elements are preferably arranged on the stirring shaft. In particular, a regular arrangement of stirring elements arranged in rows parallel to the longitudinal axis of the stirring shaft and/or in a series of successive rows along a circumferential line of the main body of the stirring shaft is provided. All stirring elements can be identical or have different shapes. Furthermore, areas on the stirring shaft can be provided in which more cams are formed than in other areas, etc.

Preferably, the stirring elements are designed as cams projecting from the base body of the stirring shaft, wherein the connecting surface of the cams formed on the base body is relatively large, in particular in comparison to the height of the cams with which they project radially beyond the base body.

The cam has a connecting surface formed on the base body of the agitator shaft, an upper surface facing the inside of the grinding container, a leading side in the direction of rotation of the agitator shaft, a trailing side in the direction of rotation of the agitator shaft, and two sides arranged between the leading side and the trailing side. The leading side is also referred to as the upstream side, and the trailing side is also referred to as the downstream side. The distance between the connecting surface and the upper surface is referred to as the height of the cam.

The relatively large connecting surface of the cams advantageously allows heat to be dissipated from the grinding material/grinding aid mixture into the agitator shaft and in particular into the coolant within the at least one cooling channel of the agitator shaft. The shape of the cams, described in more detail below, reduces the susceptibility of the ceramic material to chipping or breaking off. The base body and cams are manufactured together as a monolithic component from a ceramic material, in particular using a 3D printing process, so that there is a direct material connection between the base body of the agitator shaft and the cams. The one-piece design of the agitator shaft promotes both stability and heat conduction, as potential fracture points and heat conduction barriers are eliminated.

For good stability of the cams and to achieve a consistently good grinding result, it is advantageous if each cam has a connecting surface to the base body of the agitator shaft and a leading side, wherein a ratio of the projection of the leading side onto a plane normal to the base body of the agitator shaft and the size of the connecting surface is less than one.

The leading side is hereinafter referred to as the frontal inflow surface. The angle of inclination of the frontal inflow surface relative to the plane perpendicular to the base body can preferably be in a range of -45° to 85°. An angle of 0° corresponds to an inflow surface arranged perpendicular to the base body, whereas an angle with a negative sign denotes an undercut inflow surface, i.e., an inflow surface inclined so that it virtually covers a certain area of the connecting surface. Angles of inclination with a positive sign therefore indicate a frontal inflow surface that is inversely inclined, i.e., where the end of the inflow surface closest to the base body receives the airflow first.

Furthermore, it has proven advantageous if each cam has a connection surface to the agitator shaft with a maximum width, and the ratio of the height of each cam normal to the agitator shaft to the maximum width is greater than 0.2. The connection surface just mentioned corresponds in particular to a base surface of each cam and refers to the surface with which each cam is in contact with the agitator shaft. It has also proven advantageous if each cam has a connection surface to the agitator shaft with a maximum length, and the ratio of the height of each cam to the maximum length is less than one.

It is also advantageous if each cam has a connecting surface to the agitator shaft with a greatest length and a greatest width, the ratio of the greatest width and the greatest length being less than one.

If several cams are arranged consecutively in a row along a circumferential line of the agitator shaft base body in the circumferential direction of the agitator shaft base body, then it may be advantageous, for example, to select a distance between the circumferentially successive cams of a row that is equal to or greater than the greatest length of a cam in the circumferential direction. If a plurality of cams If the cams are arranged in a row along several circumferential lines spaced apart from one another in the axial direction, then an axial distance between each two axially adjacent cam rows can advantageously be selected to be greater than or equal to 1.1 times the maximum width of a cam. When arranging cams spaced apart from one another in the axial direction on the base body of the agitator shaft, it can be provided that the cams are arranged axially aligned or offset from one another.

As already described above, a wear protection sleeve can be arranged in the third terminal section of the agitator shaft, in particular in the third interior area, and installed within the agitator ball mill in such a way that it can be easily replaced.

The wear protection sleeve is cylindrical, at least in some areas, in particular as a hollow cylinder. The hollow cylinder has an outer diameter that is smaller than the inner diameter of the third interior region. A fastening area, for example a flange, can be provided at one end region of the wear protection sleeve to position and fasten the wear protection sleeve in or on the agitator ball mill.

In particular, a grinding gap is formed between the inner surface of the agitator shaft in the third interior space or interior region and the outer surface of the preferably cylindrical wear protection sleeve, through which the grinding material/grinding aid mixture is guided toward the second interior region of the second subsection. The wear protection sleeve is preferably also made of one piece and, in particular, of a ceramic material. It can be manufactured analogously to the agitator shaft, for example, using a 3D printing process.

Furthermore, it can be provided that the wear protection sleeve comprises at least one cooling channel, which is also designed in a meandering shape, for example, and thus forms a large cooling surface. The outer surface of the wear protection sleeve can also be designed with cam-shaped elevations. The shape of the elevations can, for example, correspond to the shape of the cams described above arranged on the agitator shaft. The elevations reduce the gap between the inner surface of the agitator shaft in the third interior region and the outer surface of the wear protection sleeve. The elevations serve in particular as scrapers to prevent grinding material and/or auxiliary grinding bodies from adhering to the inner surface of the agitator shaft. Instead, the elevations ensure that the grinding material/auxiliary grinding body mixture flows in the direction of the passage openings for returning the auxiliary grinding bodies towards the grinding chamber formed between the outer surface of the agitator shaft and the inner wall of the grinding container.

The wear protection sleeve can preferably be used in a stirred ball mill in conjunction with the agitator shaft described above. However, the wear protection sleeve can also be used in conjunction with an agitator shaft manufactured using conventional methods. In this respect, it should be emphasized that the monolithic design of the wear protection sleeve, with or without raised portions on the outer surface and/or with or without at least one cooling channel, represents an independent invention.

A stirrer shaft as described above, monolithically designed with cams or similar features and at least one cooling channel, combines the advantages of optimal cooling with maximum wear resistance and is therefore particularly suitable for use in high-performance mills.

The application also encompasses, in particular, agitator shafts formed in one piece, in particular made of a ceramic material, which are designed without a cooling channel. These agitator shafts preferably also have at least two differently designed subsections, in particular at least one first terminal subsection for fastening the agitator shaft to a drive shaft and at least one second subsection with a hollow interior region and passage openings between the interior region and the outer surface of the agitator shaft in the second subsection.

It should be expressly mentioned at this point that all aspects and embodiments explained in connection with the device according to the invention equally relate to or can be partial aspects of the method according to the invention. Therefore, if at any point in the description or in the claim definitions for the device according to the invention certain aspects and/or relationships and/or effects are mentioned, this equally applies to the method according to the invention. The same applies conversely, so that all aspects and embodiments explained in connection with the method according to the invention equally relate to or can be partial aspects of the device according to the invention. Therefore, if at any point in the description or in the claim definitions for the method according to the invention certain aspects and/or relationships and/or effects, this applies equally to the device according to the invention.

Character description

• 1 zeigt eine perspektivische Darstellung einer Ausführungsform einer erfindungsgemäß einstückig ausgebildeten Rührwelle.
• 2 zeigt eine technische Darstellung einer Seitenansicht der Rührwelle gemäß 1.
• 3 zeigt eine Schnittdarstellung der Rührwelle entlang der Schnittlinie A-A gemäß 2.
• 4 zeigt eine weitere Schnittdarstellung der Rührwelle entlang der Schnittlinie B-B gemäß 3.
• 5 zeigt eine technische Darstellung einer perspektivischen Ansicht der Rührwelle.
• 6 zeigt eine aufgeschnittene Rührwelle mit freigelegten mäanderförmigen Kühlkanälen.
• 7 zeigt eine seitliche Darstellung einer Verschleißschutzhülse.
• 8 zeigt eine perspektivische Darstellung der Verschleißschutzhülse.
• 9 zeigt eine Vorderansicht einer Rührwerkskugelmühle.
• 10 zeigt eine Schnittdarstellung der Rührwerkskugelmühle entlang der Schnittlinie A-A gemäß 9.
• 11 zeigt eine Schnittdarstellung der Rührwerkskugelmühle entlang der Schnittlinie B-B gemäß 10.
• 12 zeigt eine Schnittdarstellung der Rührwerkskugelmühle entlang der Schnittlinie C-C gemäß 11.
• 13 zeigt eine Schnittdarstellung der Rührwerkskugelmühle entlang der Schnittlinie D-D gemäß 12.
• 14 zeigt eine Schnittdarstellung der Rührwerkskugelmühle gemäß den Schnittlinien E-E gemäß 9.
• 15 zeigt eine perspektivische Darstellung einer weiteren Ausführungsform einer erfindungsgemäß einstückig ausgebildeten Rührwelle mit Gegenstromkühlung.
• 16 zeigt einen Längsschnitt einer Rührwerkskugelmühle mit einem als Gegenstromkühlung ausgebildeten Kühlkanal.
• 17 zeigt einen Querschnitt einer Rührwerkskugelmühle mit Rührwelle gemäß 16 entlang einer Schnittlinie A-A.
• 18A bis 18E zeigen jeweils weitere Ausführungsformen von Rührwellen.

In the following, exemplary embodiments will explain the invention and its advantages in more detail with reference to the accompanying figures. The relative sizes of the individual elements in the figures do not always correspond to the actual sizes, as some shapes are simplified and others are shown enlarged relative to other elements for better illustration.

• 1 shows a perspective view of an embodiment of a stirrer shaft formed in one piece according to the invention.
• 2 shows a technical representation of a side view of the agitator shaft according to 1 .
• 3 shows a sectional view of the agitator shaft along the section line AA according to 2 .
• 4 shows a further sectional view of the agitator shaft along the section line BB according to 3 .
• 5 shows a technical representation of a perspective view of the agitator shaft.
• 6 shows a cut-open stirrer shaft with exposed meander-shaped cooling channels.
• 7 shows a side view of a wear protection sleeve.
• 8 shows a perspective view of the wear protection sleeve.
• 9 shows a front view of an agitator ball mill.
• 10 shows a sectional view of the agitator ball mill along the section line AA according to 9 .
• 11 shows a sectional view of the agitator ball mill along the section line BB according to 10 .
• 12 shows a sectional view of the agitator ball mill along the section line CC according to 11 .
• 13 shows a sectional view of the agitator ball mill along the section line DD according to 12 .
• 14 shows a sectional view of the agitator ball mill according to the section lines EE according to 9 .
• 15 shows a perspective view of a further embodiment of an agitator shaft constructed in one piece according to the invention with countercurrent cooling.
• 16 shows a longitudinal section of a stirred ball mill with a cooling channel designed as countercurrent cooling.
• 17 shows a cross section of a stirred ball mill with agitator shaft according to 16 along a section line AA.
• 18A to 18E each show further embodiments of agitator shafts.

Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only reference numerals necessary for the description of the respective figure are shown in the individual figures. The illustrated embodiments merely represent examples of how the device or method according to the invention can be configured and do not represent a definitive limitation.

1 to 6 show different views and sectional representations of a stirrer shaft 1 formed in one piece according to the invention. Such a stirrer shaft 1 is preferably used in a stirred ball mill 50, as will be described below with reference to the 9 to 14 will be explained in more detail. The agitator shaft 1 has a cylindrical base body 2 with a longitudinal axis L, wherein agitator elements 3, in particular cams 4, are formed on the outer surface of the cylindrical base body 2. The outer surfaces of the cams 4 and the outer surfaces of the cylindrical base body 2 not covered by cams 4 together form the outer jacket surface 5 of the agitator shaft 1. The agitator elements 3 are formed in several rows, in particular in an aligned arrangement, on the outside of the cylindrical base body 2, wherein the rows are arranged and/or formed parallel to the longitudinal axis L of the agitator shaft 1.

According to the invention, the agitator shaft 1 is formed in one piece and, in particular, consists of a ceramic material. Particularly preferably, the agitator shaft 1 is manufactured from the ceramic material in a single process step. A 3D printing process is particularly preferably used for this purpose, since this process also allows cavities to be created within the agitator shaft 1 in a single process step.

The ceramic material can be, for example, silicon carbide (SiC), especially sintered silicon carbide (SSiC), silicon carbide with free silicon (SiSiC), silicon nitride, zirconium oxide, or mixed ceramics. Silicon carbide ceramics exhibit high wear resistance, low thermal shock sensitivity, low thermal expansion, high thermal conductivity, and good resistance to acids and alkalis. They are also lightweight and retain their positive properties up to temperatures above 1400°C. Furthermore, silicon carbide is toxicologically safe and can therefore also be used in the food industry. Although silicon nitride has a reduced hardness compared to silicon carbide, a sintering process can induce columnar recrystallization of the β-silicon nitride crystals, which leads to increased fracture toughness of the material. The high fracture toughness combined with small defect sizes gives silicon nitride one of the highest strengths among engineering ceramic materials. The combination of high strength, low thermal expansion coefficient, and relatively low elastic modulus makes silicon nitride ceramic particularly suitable for components subject to thermal shock. Unlike other ceramic materials, zirconium oxide has a very high resistance to crack propagation. Zirconium oxide ceramic also has a very high thermal expansion and is therefore often chosen for the creation of joints between ceramic and steel.

In the technical representation of a side view of the agitator shaft 1 according to 2 and in the cutaway view according to 6 a cooling channel 6 can be seen, which is formed within the one-piece agitator shaft 1. Preferably, this extends at least partially parallel to the longitudinal axis L of the agitator shaft 1. It is particularly preferred that the cooling channel 6 extends meanderingly between the end regions of the agitator shaft 1 and, in particular, is deflected at each end region, wherein the regions between the deflections can each be arranged substantially parallel to one another. 2 For example, three parallel sections 61, 62, 63 of the cooling channel 6 can be seen, which are parallel to one another and also arranged parallel to the longitudinal axis L of the agitator shaft. Between the three parallel sections 61, 62, 63, two deflection regions 67, 68 are formed in the end regions of the agitator shaft 1.

A coolant flowing through the first parallel section 61 in a first flow direction SR1 is diverted in the first diversion region 67 into the second parallel section 62 and flows through it in a second flow direction SR2, which is opposite to the first flow direction SR1. The coolant is then diverted in the second diversion region 68 into the third parallel section 63 and flows through it again in the first flow direction SR1.

The 3 shown sectional view of the agitator shaft 1 along the section line AA according to 2 shows that the cooling channel 6 formed within the agitator shaft 1 has six parallel sections 61, 62, 63, 64, 65 and 66, each of which, the first parallel section 61 and the second parallel section 62 are connected via a first deflection region 67, the second parallel section 62 and the third parallel section 63 are connected via a second deflection region 68, the third parallel section 63 and the fourth parallel section 64 are connected via a third deflection region (not shown), the fourth parallel section 64 and the fifth parallel section 65 are connected via a fourth deflection region (not shown), and the fifth parallel section 65 and the sixth parallel section 66 are connected via a fifth deflection region 69 (cf. 6 ). In particular, it can be provided that the coolant is introduced into the agitator shaft 1 via the first parallel section 61 of the cooling channel 6 and is discharged from the agitator shaft 1 via the sixth parallel section 66 of the cooling channel 6.

The agitator shaft 1 has three sub-sections, in particular a first terminal sub-section I, a second middle sub-section II and a third terminal sub-section III. The agitator shaft 1 can be connected at its first terminal sub-section I to a drive shaft 70 of the agitator ball mill (not shown). For this purpose, a shaft receptacle 7 is formed, for example, in the first terminal sub-section I. The agitator shaft 1 is designed as a hollow shaft at least in some regions; in particular, the second sub-section II and the third sub-section III and, if appropriate, the first sub-section I each have interior regions. In particular, the second middle sub-section II has a first hollow interior space or interior region 12 and the third sub-section III has a second hollow interior space or interior region 13. These preferably also have a cylindrical shape, the longitudinal axis of which is congruent with the longitudinal axis L of the agitator shaft 1. Furthermore, it is intended that the third part - Section III - is open at the end and, in particular, in this open area shows a further enlarged hollow interior. As will be explained below in connection with the 9 to 14 As explained, a wear element or similar can be arranged in this hollow interior.

Furthermore, it can be provided that in the second middle section II between the hollow interior area 12 and the outer surface 5 of the agitator shaft 1, passage openings 15 are formed, the function of which will also be explained below in connection with the 9 to 14 The second middle section - Section II is therefore also called the open section, while the first section - Section I and the third section - Section III are each closed sections The passage openings 15 extend in particular parallel to the longitudinal axis L of the agitator shaft, preferably between the rows of agitator elements 3, as they are used in particular in connection with 1 have been described.

For example, based on the 6 As can be clearly seen, the at least one cooling channel 6 preferably extends through all three subsections I, II, and III of the agitator shaft 1, with the deflection regions 67, 68, 69 being formed in the terminal subsections I and III, respectively. In particular, the cooling channel 6 can be designed in a meandering shape—this will be described in more detail below.

4 shows a longitudinal section of the agitator shaft 1, in particular a sectional view of the agitator shaft 1 along the section line BB according to 3 . At 3 This is in particular a cross-section of the agitator shaft 1 in the second part section II, which in particular passes through the agitator elements 3. Here, the passage openings 15 between the first hollow interior area 12 and the outer surface 5 of the agitator shaft 1 are clearly visible. 4 It can be seen that the cooling channel 6 is designed in particular parallel to the longitudinal axis L and to the parallel-axially extending passage openings 15, wherein a parallel section 61, 62, 63, 64, 65, 66 of the cooling channel 6 extends adjacent to a row of stirring elements 3.

7 shows a side view of a wear protection sleeve 30 and 8 shows a perspective view of the wear protection sleeve 30. The arrangement of the wear protection sleeve 30 within a stirred ball mill 50 and its function is described in particular in connection with the 10 , 12 and 13 described below.

The wear protection sleeve 30 is cylindrical in shape at least in some areas. In particular, the wear protection sleeve 30 comprises a hollow cylinder 33 as the base body 32, on the outside of which elevations 34 are preferably formed, in particular in the form of cams 35 described in more detail below. The hollow cylinder has an outer diameter d30 that is smaller than the smallest inner diameter dIII of the third interior region in the third part section III of the agitator shaft 1 (see 2 ). At one end region of the wear protection sleeve 30, a fastening area, for example a flange 36, can be provided in order to position and fasten the wear protection sleeve 30 in or on the agitator ball mill 50, in particular in order to fix the wear protection sleeve 30 on the grinding container bottom 59, in particular in a suitable receptacle on the grinding container bottom 59 - see 10 and 12 .

The wear protection sleeve 30 is preferably also made in one piece and in particular from a ceramic material and can be produced analogously to the agitator shaft 1, for example by 3D printing from one of the ceramic materials described above.

Furthermore, it can be provided that the wear protection sleeve 30 comprises at least one cooling channel, which is also designed in a meandering shape, for example, and thus forms a large cooling surface (not shown). The design of the at least one cooling channel of the wear protection sleeve can correspond to the design of a cooling channel 6 of the agitator shaft 1. The supply lines for the coolant supply and coolant discharge can, for example, lead through the grinding container bottom (59, see 10 , 12 ) must be trained.

The wear protection sleeve 30 can preferably be arranged in a 9 to 14 shown agitator ball mill 50 with a stirring shaft 1 according to the 1 to 6 However, the wear protection sleeve 30 can also be used in conjunction with a stirrer shaft manufactured using conventional methods.

9 to 14 show different views and representations of an agitator ball mill 50 with agitator shaft 1 according to the invention, in particular 9 a front view of a stirred ball mill 50, 10 shows a sectional view of the agitator ball mill along the section line AA according to 9 and 11 shows a sectional view of the agitator ball mill 50 along the section line BB according to 10 .

The agitator ball mill 50 comprises a cylindrical grinding container 51 extending along a horizontal axis L50 and having an inner surface 52. The grinding container 51 can be made of a metal or, analogous to the agitator shaft 1, of a ceramic material. Furthermore, it can be provided that the grinding container is designed to be coolable and, for example, comprises an outer cylinder 53 and an inner cylinder 54, between which a cooling chamber 55 is formed, into which coolant K can be introduced via a suitable coolant inlet 56 and a coolant outlet 57. The grinding container 51 further comprises a grinding container lid 58 and a grinding container base 59.

Within the grinding container 51, a stirring shaft 1 with a longitudinal axis L is arranged horizontally. The longitudinal axis L of the stirring shaft 1 simultaneously represents its axis of rotation and is also arranged congruent with the horizontal axis L50 of the grinding container 51. The stirring shaft 1 corresponds to the 1 to 6 described a stirring shaft 1, so that reference is made thereto for the description of its features.

A drive shaft 70 is arranged through the grinding container lid 58 and is connected to a drive, for example, an electric motor or similar (not shown). The drive shaft 70 is connected in a rotationally fixed manner to the agitator shaft 1; in particular, the end of the drive shaft 70 projecting into the grinding container 51 engages in the shaft receptacle 7 in the first subsection I of the agitator shaft 1. Furthermore, the grinding container lid 58 comprises the grinding material inlet 71, through which the grinding material M is poured into the agitator ball mill 50. A product outlet 72 is provided in the grinding container base 59, through which the ground product P leaves the agitator ball mill 50.

An annular grinding gap MS is formed between the inner surface 52 of the grinding container 51 and the outer surface 5 of the agitator shaft, particularly in the area of the agitator elements 3. During operation of the agitator ball mill 50, the grinding material/grinding aid mixture is located therein. By rotating the agitator shaft 1 in combination with the auxiliary grinding bodies (not shown), the material to be ground M is moved in the grinding gap MS from the material inlet side to the product outlet side and is subjected to such stress that it is comminuted, for example by the material particles colliding with one another, by the material particles colliding with auxiliary grinding bodies, by shear forces, etc. To enhance the comminution effect, it can be provided that projections such as cams, rods or the like can also be arranged on the inner circumferential surface 52 of the grinding container 51, which on the one hand bring about additional mixing of the material to be ground/auxiliary grinding body mixture and on the other hand, for example, increase the number of collision processes taking place in the grinding gap MS and thus increase the comminution effect of the agitator ball mill 50.

Furthermore, it is provided that the product outlet 72 is formed within a so-called receiving part 75, which extends through a central opening in the grinding container base 59. This receiving part 75 can also have cooling channels 76, through which coolant K is passed to cool the product P. The receiving part 75 extends in particular axially in the inner cavity of the agitator shaft 1 in the direction of the grinding material inlet 71 and is partially surrounded by the wear protection sleeve 30 in the region of the product outlet 72. At the end region of the receiving part 75, which is arranged axially opposite the product outlet 72, a separating sieve 40, described in more detail below, is preferably arranged, which serves to retain the auxiliary grinding bodies in the interior of the agitator ball mill while the product P is removed.

The 11 The cross section of the agitator ball mill 50 shown in particular shows a cross section in the area of the second middle part section II of the agitator shaft 1, comparable to 3 . The detailed enlargement shows in particular an alternative embodiment of a cooling channel 6*, which does not have a circular cross-section, but is designed with an optimized, enlarged cross-section.

In this context, the shape of the cams 4 will be discussed in more detail. As already described, the agitator shaft 1 is manufactured in one piece; in particular, the agitator elements 3 are formed directly during the manufacture of the agitator shaft 1 and are not subsequently attached. The agitator elements 3 are designed in particular as cams 4 protruding from the cylindrical base body 2 of the agitator shaft 1. The connecting surface 20 of the cams 4 formed on the base body 2 of the agitator shaft 1 is relatively large, in particular in relation to the radial height h of the cams 4. The shape of the cams 4 can take on any geometric form, both in axial section and in radial view, for example trapezoidal, with rounded corners, with chamfered edges, etc. The connecting surface 20 corresponds in particular to a base surface of each cam 4 and refers to the surface with which each cam 4 is in contact with the outer circumferential surface of the agitator shaft 1.

Since, in the illustrated embodiment, the cooling channel 6, 6* is formed adjacent to the cams 4, heat can advantageously be dissipated from the grinding material/grinding aid mixture into the coolant within the cooling channel 6, 6* via the large connecting surface 20 of the cams 4, as the large connecting surface 20 dissipates the heat more effectively. Furthermore, the shape significantly reduces the susceptibility of the cams 4 to breaking off or breaking off, which is particularly common with ceramic material. The one-piece design of the agitator shaft 1 promotes both stability and heat conduction, as potential fracture points and heat conduction barriers are eliminated.

For good stability of the cams 4 and to achieve a uniformly good grinding result, it is advantageous if each cam 4 has a connecting surface 20 to the base body 2 of the agitator shaft 1 and a frontal inflow surface 21 (see also 1 ), wherein a ratio of a projection of the frontal inflow surface 21 onto a plane perpendicular to the base body 2 of the agitator shaft 1 and the size of the connecting surface 20 is less than 1.

It is advantageous, for example, if each cam 4 has a connection surface 20 to the agitator shaft 1 with a greatest width and the ratio of the height of each cam 4 normal to the agitator shaft 1 and the greatest width is greater than 0.2. Furthermore, each cam 4 can have a connection surface 20 to the agitator shaft 1 with a greatest length, wherein the ratio of the height of each cam 4 and the greatest length is preferably less than one. According to a further embodiment, it is advantageous if each cam 4 has a connection surface 20 to the agitator shaft 1 with a greatest length and a greatest, wherein the ratio of the greatest width and the greatest length is less than one.

In this context, reference is also made to the 18A to 18E referred to. 18A to 18E show further embodiments of agitator shafts 1. These each show a cross section of the outer surface 5, the representation of the passage openings, cooling channels etc. analogous to 3 was omitted here. In particular, the arrangement and design of the stirring elements 3 or cams 4 on the outer surface 5 are different in the various embodiments. For example, the inclination of the side leading in the direction of rotation D or the inflow surface 21 and the inclination of the side trailing in the direction of rotation D are designed to different degrees.

In this case, an angle of inclination of the frontal inflow surface 21 with respect to a plane perpendicular to the inside of the grinding container 59 and/or a plane perpendicular to the cylindrical outer surface of the agitator shaft 1 can be in a range of -45° to 85°. An angle of 0° corresponds to an inflow surface 21 that is located within a plane perpendicular to the inside of the grinding container 51 (cf. 18C ), whereas an angle with a negative sign indicates an undercut inflow surface 21, ie an inflow surface 21 which is inclined in such a way that it virtually covers a certain area of the connecting surface 20 (compare in particular 18D , 18E) . Inclination angles with a positive sign therefore indicate a frontal inflow surface 21 which is inversely inclined, ie in which the end of the inflow surface 21 located on the base body 2 is first subjected to flow (compare in particular 18A , 18B , 18E) .

In principle, it is advantageous to provide a plurality of cams 4 on the agitator shaft 1 to promote the desired interaction with the grinding material/grinding aid mixture. The agitator shaft 1 may also have cam-free areas, or may have more cams 4 in some areas and fewer cams 4 in others. Furthermore, not all cams 4 need to be of the same design, but can be arranged in different shapes and sizes in different areas.

As can be seen in particular from the 1 As can be seen, it may be advantageous to arrange several cams 4 in a row along a circumferential line of the base body 2 of the agitator shaft 1 in the circumferential direction of the base body 2 of the agitator shaft 1. For example, a distance between cams 4 of a row that follow one another in the circumferential direction can be equal to or greater than the greatest length of a cam 4 in the circumferential direction.

If a plurality of cams 4 are arranged successively in a row along a plurality of circumferential lines spaced apart from one another in the axial direction, then an axial distance between each two axially adjacent rows of cams is advantageously greater than or equal to 1.1 times the greatest width of a cam 4. If cams 4 are formed on the base body 2 of the agitator shaft 1 spaced apart from one another in the axial direction, then these cams 4 can either be axially aligned or offset from one another.

Based on the sectional view 12 , which the agitator ball mill 50 along the section line CC according to 11 shows, the path of the grinding material/aid grinding media mixture G within the agitator ball mill 50 is described in particular. Grinding material M is filled into the interior of the grinding container 51 via the grinding material inlet 71. This is already partially filled with auxiliary grinding media; for example, the interior of the grinding container is already approximately 80% filled with auxiliary grinding media. Due to the rotation of the agitator shaft 1, the grinding material M and the auxiliary grinding media (not shown) are mixed to form a grinding material/aid grinding media mixture G, which flows along the agitator shaft 1 between the inner circumferential surface 52 of the grinding container 51 and the outer circumferential surface 5 of the agitator shaft 1 in a first conveying direction FR1 towards the grinding container bottom 59. A distance is formed between the open end region of the third sub-section III of the agitator shaft 1 and the grinding container bottom 59, in which distance the flow of the grinding material/grinding aid mixture G is deflected, so that it now flows through the second hollow interior region 13 of the third sub-section III of the agitator shaft 1 in a second conveying direction FR2 opposite to the first conveying direction FR1.

Within the second interior area 13, a wear protection sleeve 30 (see also 10 ). Such a wear protection sleeve 30 has already been used in connection with the 7 and 8 described, to the description of which reference is hereby made. Between the inner surface of the agitator shaft 1 in the third interior region 13 and the outer surface of the wear protection sleeve 30, a type of grinding gap is formed, in which the grinding material/grinding aid mixture G is guided in the conveying direction FR2 in the direction of the first hollow interior region 12 of the second middle sub-section II. Between the cams 35 of the wear protection sleeve 30 and the inner surface of the agitator shaft 1 in the third interior region 13, this grinding gap is particularly small. The cams 35 serve in particular as scrapers to prevent grinding material and/or grinding aids from adhering to the inner surface of the agitator shaft 1. Instead, the cams 35 ensure that the grinding material/grinding aid mixture G is kept in flow and is fed in the conveying direction FR2 to the passage openings 15 in the second sub-section, where a return of the grinding aids takes place in the direction of the grinding chamber or grinding gap MS formed between the outer surface of the agitator shaft 1 and the inner surface 52 of the grinding container 51.

Arranged within the first hollow interior region 12 is a separating screen 40, a classifying rotor 41, or another suitable device that retains the auxiliary grinding media of the grinding material/auxiliary grinding media mixture G, while sufficiently ground grinding material passes through as finished product P and can be removed from the agitator ball mill 50 via the product outlet 72. The auxiliary grinding media retained by the separating screen 40, the classifying rotor 41, or the like, and any insufficiently ground grinding material M, pass through the passage openings 15 in the second central subsection II of the agitator shaft 1 back into the grinding gap MS between the grinding container 51 and the agitator shaft 1 and are again moved in the conveying direction FR1.

13 shows a sectional view of the agitator ball mill 50 along the section line DD according to 12 , in which the arrangement of the wear protection sleeve 30 within the second hollow interior area 13 of the third sub-section III of the agitator shaft 1 can be seen

14 shows a sectional view of the agitator ball mill 50 with a meandering cooling channel 6 according to the section lines EE according to 9 . In particular, the course of the first parallel section 61 of the cooling channel 6 and the course of the sixth parallel section 66 of the cooling channel 6 are visible. The coolant K is supplied via the coolant inlet 56 and flows through the first parallel section 61 of the cooling channel 6 in a first flow direction SR1. As in connection with 6 As described, the coolant 6 is deflected several times and finally flows through the sixth parallel section 66 of the cooling channel 6 in a second flow direction SR2, opposite to the first flow direction SR1, before it is discharged from the agitator shaft 1 via the coolant outlet 57.

15 shows a perspective view of a further embodiment of a stirrer shaft 1 formed in one piece according to the invention. In this embodiment, the representation of the stirring elements 3, in particular cams 4, as well as the more precise design of the features of the three sub-sections I, II and III has been partially omitted. The information provided in connection with 1 However, the features described also apply to this embodiment, since the design of the at least one cooling channel 6 will be discussed in more detail below.

The cooling channel 6 shown here represents a so-called countercurrent cooling. On the one hand, the cooling channel 6 has two parallel sections 81, 82 on a first radial R1 extending between the longitudinal axis L and the outer surface 5 of the agitator shaft 1. In particular, it is provided that the coolant is introduced into the first parallel section 81 and flows through it in a first flow direction SR1 from the first partial section I towards the third partial section III, wherein the first flow direction SR1 preferably corresponds to the first conveying direction FR1 for the grinding material/grinding aid mixture G according to the 9 to 14 corresponds. In countercurrent cooling, it is particularly provided that the coolant K flows successively through two parallel sections 81 and 82, 83 and 84, 85 and 86, 87 and 88, which are each located on a common radial R, R1, R2, R3, R4 of the agitator shaft 1. In particular, the coolant K first flows through the parallel section 81, 83, 85, 87 which is closer to the longitudinal axis L. Subsequently, the coolant K is deflected in the end region of the third sub-section III in a deflection region 95 into the parallel section 82, 84, 86 or 88 which are each arranged on the same radial R1, R2 or R3 and flows through this in a second flow direction SR2 which is opposite to the first flow direction SR1. In the free end region of the first partial section I, a deflection region 91 is formed, which deflects the coolant K from the second parallel section 82 on the first radial R2 into the third parallel section 83 on the second radial R2, which is formed closer to the longitudinal axis L of the agitator shaft. The coolant now flows through the third parallel section 83 again in the first flow direction SR1 and can subsequently be directed via a further deflection region 95 in the third partial section III into the third parallel section 83 formed on the same second radial R2, further from the longitudinal axis L, etc. Finally, the coolant flows in the second flow direction SR2 through the last parallel section 88 formed on the fourth radial R4 and is discharged from the agitator shaft 1. In the countercurrent cooling described here, two parallel sections 81 and 82, 83 and 84 etc. of the cooling channel 6, through which coolant K flows in opposite flow directions SR1, SR2, are located on a common radial R of the agitator shaft 1. In particular, the coolant K is guided close to the longitudinal axis L of the agitator shaft 1 from the grinding material inlet side to the product outlet side. The return of the coolant K from the product outlet side to the grinding material inlet side takes place within the agitator shaft 1 in a region adjacent to the outer circumferential surface of the agitator shaft 1.

Preferably, it can be provided that the coolant K does not flow through the parallel sections 81 to 88 one after the other, but that fresh coolant K flows into each of the parallel sections 81, 83, 85, 87 formed closer to the longitudinal axis L and is discharged from the parallel sections 82, 84, 86, 88 formed closer to the outer circumferential surface of the agitator shaft 1. The deflection region 91 is designed in particular as an annular gap 92. This ensures that the freshest and therefore coolest coolant K is first guided into the area of the agitator ball mill in which the material to be ground is the warmest. This is in particular the area near the product outlet, after the material to be ground has flowed through the agitator ball mill from the material inlet side. With the help of this countercurrent cooling, the cooling process can be further optimized.

16 shows a longitudinal section of a stirred ball mill with a further embodiment of a stirrer shaft 1 with a cooling channel 6 designed as a countercurrent cooling and 17 shows a cross section of the agitator ball mill with agitator shaft according to 16 along a section line AA. Here, it is provided that the coolant is supplied in a first flow direction SR1 via a coolant supply line 93 within the drive shaft 70 of the agitator shaft 1 and flows through the first parallel sections 81 of the cooling channel 6 in the flow direction SR1. This first flow direction SR1 preferably corresponds to the first conveying direction FR1 for the grinding material/grinding aid mixture G according to the 9 to 14 . The first parallel sections 81 are each also referred to as inner flow channel 94.

In the end region of the third sub-section III, a deflection region 95 is formed, each connecting an inner flow channel 94 to a second parallel section 82 of the cooling channel 6. The second parallel section 82 is also referred to as an outer flow channel 96. In particular, the coolant K is deflected in the deflection region 95 and now flows through an outer flow channel 96 in a second flow direction SR2 opposite to the first flow direction SR1, and then leaves the agitator shaft 1 via coolant discharge lines 97 within the drive shaft 70. An inner flow channel 94 and an outer flow channel 96 are each arranged on a radial R of the agitator shaft 1, with the inner flow channel 94 being arranged closer to the longitudinal axis L of the agitator shaft 1 than the outer flow channel 96.

With this type of countercurrent cooling, two parallel sections 81 and 82 of the cooling channel 6 are located on a common radial R of the agitator shaft 1 and are flowed through by the coolant K in opposite flow directions SR1, SR2. It is particularly advantageous that the coolant K is discharged again after it has flowed through the agitator shaft 1 once in the first flow direction SR1 and once in the second flow direction SR2. Thus, all parallel sections 82 are cooled to the same extent, whereas in the exemplary embodiment according to 15 the cooling in the last parallel section 88 is significantly reduced compared to the cooling in the second parallel section 82. Thus, the cooling is a stirrer shaft 1 according to 16 compared to the cooling of a first embodiment of the agitator shaft 1 according to 15 further optimized.

In 16 Furthermore, the supply of grinding material M, the flow of the grinding material/grinding aid mixture G within the agitator ball mill 50 and the removal of product P are shown - compare also the description of 12 .

Furthermore, embodiments are conceivable in which an annular gap is formed in the first subsection I of the agitator shaft 1 for the coolant supply. Starting from this annular gap, a plurality of cooling channels run in a first flow direction SR1 towards the third subsection III. Here, a plurality of deflection channels are then formed, which then return the cooling medium in counterflow to the first flow direction SR1 and in counterflow to the conveying direction FR of the grinding material/grinding aid mixture G in a second flow direction SR2, in particular to a further annular gap which removes the "used" cooling medium in a collected manner. This ensures that each shaft section is cooled with fresh coolant.

The embodiments, examples, and variants of the preceding paragraphs, the claims or the following description and the figures, including their various views or respective individual features, may be used independently of one another or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless the features are incompatible.

Although the figures are generally referred to as "schematic" representations and views, this by no means means that the figures and their descriptions are of secondary importance with regard to the disclosure of the invention. A person skilled in the art will be perfectly capable of deriving sufficient information from the schematic and abstractly drawn representations to facilitate their understanding of the invention, without their understanding being impaired in any way by the drawn, and possibly not exactly true-to-scale, size relationships of the piece goods and/or parts of the device or other drawn elements. The figures thus enable the skilled reader, on the basis of the more concretely explained implementations of the method according to the invention and the more concretely explained mode of operation of the device according to the invention, to derive a better understanding of the inventive concept formulated more generally and/or abstractly in the claims and in the general part of the description.

The invention has been described with reference to a preferred embodiment. However, it is conceivable to a person skilled in the art that modifications or variations of the invention can be made without departing from the scope of the following claims.

List of reference symbols

1

agitator shaft

2

cylindrical base body

3

stirring element

4

cam

5

Outer surface

6.6*

cooling channel

7

Wave recording

12

first interior area

13

second interior area

15

Passage opening

20

connecting surface

21

frontal inflow surface

30

Wear protection sleeve

32

cylindrical base body

33

hollow cylinder

34

Survey

35

cam

36

flange

40

Separating sieve

41

Classifying rotor

50

agitator ball mill

51

Grinding container

52

inner surface

53

outer cylinder

54

inner cylinder

55

cold room

56

Coolant inlet

57

Coolant outlet

58

Grinding container lid

59

Grinding container bottom

61

(first) parallel section of the cooling channel

62

(second) parallel section of the cooling channel

63

(third) parallel section of the cooling channel

64

(fourth) parallel section of the cooling channel

65

(fifth) parallel section of the cooling channel

66

(sixth) parallel section of the cooling channel

67

(first) deflection area of the cooling channel

68

(second) deflection area of the cooling channel

69

(fifth) deflection area of the cooling channel

70

drive shaft

71

Grinding material inlet

72

Product outlet

75

Recording part

76

cooling channel

81

(first) parallel section

82

(second) parallel section

83

(third) parallel section

84

(fourth) parallel section

85

(fifth) parallel section

86

(sixth) parallel section

87

(seventh) parallel section

88

(eighth / last) parallel section

91

Deflection area

92

Annular gap

93

Coolant supply line

94

inner flow channel

95

Deflection area

96

outer flow channel

97

Coolant discharge line

d30

Outer diameter wear protection sleeve

dIII

Inner diameter of third section

D

Direction of rotation

FR1

first conveying direction

FR2

second conveying direction

G

Grinding material/grinding aid mixture

h

Height of the cams

I

first terminal sub-section

II

second middle section

III

third terminal sub-section

K

coolant

L

Longitudinal axis of the agitator shaft

L50

horizontal axis of the grinding container of the agitator ball mill

M

Ground material

MS

Grinding gap

P

product

R

Radial

R1

first radial

R2

second radial

R3

third radial

R4

fourth radial

SR1

first flow direction

SR2

second flow direction

Claims (15)

Agitator shaft (1) for an agitator ball mill (50), wherein the agitator shaft (1) has a longitudinal axis (L) and an outer circumferential surface (5) equipped with agitating elements (3), wherein the agitator shaft (1) is formed integrally with the agitating elements (3) and consists of a ceramic material, wherein the agitator shaft (1) has at least one cooling channel (6) which preferably extends at least partially parallel to the longitudinal axis (L) of the agitator shaft (1), wherein the at least one cooling channel (6) extends in at least two regions each parallel to the longitudinal axis (L) of the agitator shaft (1), wherein a deflection region (67) is formed between the two parallel regions (61, 62), in particular wherein a coolant flows through the at least two regions (61, 62) connected to one another via a deflection region (67) in opposite flow directions (SR1, SR2). Stirring shaft (1) after Claim 1 , wherein the at least one cooling channel (6) is meander-shaped. Stirring shaft (1) after Claim 1 or 2 , wherein two parallel regions (61, 62) through which coolant flows in opposite flow directions (SR1, SR2) are arranged on a common radial (R1, R2 or R3) of the agitator shaft (1). Stirring shaft (1) according to one of the preceding claims, wherein the stirring shaft (1) has a first terminal partial section (I) at which the stirring shaft (1) can be arranged on a drive shaft (70), wherein the stirring shaft (1) further has a second middle partial section (II) and a third terminal partial section (III). Stirring shaft (1) after Claim 3 , wherein the at least one cooling channel (6) extends within the first terminal sub-section (I) and at least partially within the second, middle sub-section (II), in particular wherein the at least one cooling channel (6) extends through all three sub-sections (I, II, III). Stirring shaft (1) after Claim 4 or 5 , wherein the second, middle part section (II) has a first hollow interior space (12), in particular a cylindrically shaped first hollow interior space (12) with a longitudinal axis which is congruent with the longitudinal axis (L) of the agitator shaft (1). Stirring shaft (1) after Claim 4 or 5 , wherein the third terminal subsection (III) has a second hollow interior (13), in particular a cylindrically shaped second hollow interior (13) with a longitudinal axis which is congruent with the longitudinal axis (L) of the agitator shaft (1). Stirring shaft (1) after Claim 6 , wherein passage openings (15) are formed between the first hollow interior (12) of the second, middle sub-section (II) and the outer circumferential surface (5) of the agitator shaft (1) in the region of the second, middle sub-section (II). Agitator shaft (1) according to one of the preceding claims, wherein the agitator elements (3) are designed as cams (4) projecting from a base body (2) of the agitator shaft (1), wherein the connecting surface (20) of the cams (4) formed on the base body (2) is relatively large, in particular wherein each cam (4) has a connecting surface (20) to a base body (2) of the agitator shaft (1) and a leading side, wherein a ratio of the projection of the leading side onto a plane normal to the base body (2) of the agitator shaft (1) and the size of the connecting surface (20) is less than 1. Stirring shaft (1) according to one of the preceding claims, wherein the stirring shaft (1) with the stirring elements (3) can be produced using a 3D printing process. Agitator ball mill (50) with a grinding container (51) extending along a horizontal or vertical axis (L50) and having an inner circumferential surface (52), with an agitator shaft (1) rotatable within the grinding container (51) about the horizontal or vertical axis (L50) and having an outer circumferential surface (5), wherein agitator elements (3) are formed on the outer circumferential surface (5), wherein a grinding gap (MS) is formed between the agitator elements (3) of the agitator shaft (1) and the inner circumferential surface (52) of the grinding container (51), wherein the agitator shaft (1) is formed integrally with the agitator elements (3) and consists of a ceramic material, wherein the agitator shaft (1) has at least one cooling channel (6), which preferably extends at least partially parallel to the longitudinal axis (L) of the agitator shaft (1), wherein the at least one cooling channel (6) extends in at least two regions (61, 62) each parallel to the longitudinal axis (L) of the agitator shaft (1), wherein a deflection region (67) is formed between the two parallel regions (61, 62), in particular wherein a coolant flows through the at least two regions (61, 61) connected to one another via a deflection region (67) in opposite flow directions (SR1, SR2). Agitator ball mill (50) according to Claim 1 with a stirring shaft (1) according to one of the Claims 2 until 10 . Agitator ball mill (50) according to Claim 11 or 12 , comprising a wear protection sleeve (30) which can be arranged in an interior of the agitator shaft (1), which consists of a ceramic material and is formed in one piece. Method for producing an agitator shaft (1) for an agitator ball mill (50), wherein the agitator shaft (1) is manufactured in one piece from a ceramic material, wherein the agitator shaft (1) has at least one cooling channel (6) which preferably extends at least partially parallel to the longitudinal axis (L) of the agitator shaft (1), wherein the at least one cooling channel (6) extends in at least two regions (61, 62) each parallel to the longitudinal axis (L) of the agitator shaft (1), wherein a deflection region (67) is formed between the two parallel regions (61, 62), in particular wherein a coolant flows through the at least two regions (61, 62) connected to one another via a deflection region (67) in opposite flow directions (SR1, SR2). Procedure according to Claim 14 for producing a stirrer shaft (1) according to one of the Claims 2 until 10 , in particular wherein the stirring shaft (1) with the stirring elements (3) is produced by means of 3D printing.

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