stirred mill

Abstract

The invention relates to a stirred mill (1), in particular a stirred ball mill with a grinding chamber (2), wherein a stirring shaft (3) carrying stirring elements (8) is rotated, such that a grinding chamber (7) is formed between the stirring shaft (3) and the grinding chamber (2), in which grinding chamber a grinding stock conveyed by a flowable carrier medium, usually in the form of a suspension, is fed in, wherein the grinding chamber (7) is partially filled with grinding bodies, which are moved by the rotating stirring shaft (3), and as a result of which the grinding stock carried by the flowable carrier medium through the grinding chamber (7) is comminuted, wherein the grinding stock conveyed by the flowable carrier medium is discharged together with the carrier medium through a screen (4), which screens off the grinding bodies reaching the region of the screen (4), characterized in that the screen (4) consists of a plurality of screen elements (12) arranged one behind the other along the longitudinal axis of the stirred ball mill (1), which flow parallel, the large surface of the screen elements (12) flowing out of the grinding chamber (7) extending obliquely or radially with respect to an axis about which the stirring shaft (3) rotates.

Description

TECHNICAL FIELD

[0001] The invention relates to a stirred mill having a grinding vessel into which a grinding stock is fed and a screen through which the grinding stock can be discharged from the grinding vessel. BACKGROUND

[0002] The basic principle of a stirred mill is first explained in accordance with Figure 1

[0003] A schematic view of a stirred mill 1 having a horizontal stirring shaft 3 is shown in Figure 1 In this view, the grinding bodies located in the grinding vessel 2 are not shown, which are usually realized as steel or ceramic balls.

[0004] In the operation of the stirred mill 1, the material to be ground is pumped through the inlet 5 of the stirred mill 1 into or through a grinding chamber 7, which is surrounded by the grinding vessel 1. In the case of wet grinding, this relates to a suspension or a dispersion consisting of a liquid, usually in the form of water, and solids for the material to be ground. In other cases, such stirred mills can also be used for dry grinding. It is possible for them to be designed as stirred mills with a vertical shaft, through which the grinding stock is usually entrained downstream by a fluid in the form of a gas.

[0005] The invention relates, in its broadest aspect, to two types of stirred mills. The use is particularly advantageous for stirred mills having a stirring shaft. Through the rotational movement of the stirring shaft 3, the stirring elements 8, which are also usually referred to as grinding discs, which are connected to the stirring shaft 3 in a torsionally rigid manner, are rotated. It is likewise possible for the design of the stirring elements 8 to be in the form of individual pins in the context of the invention, which will be described below. In order to generate the rotational movement, the stirring shaft 3 can be driven by an electric motor 9, for example, via a belt drive 10. Here, the drive of the stirred mill 1 is usually located in a housing 11 adjacent to the grinding vessel 2.

[0006] Through the rotation of the stirring elements 8, the grinding bodies located in the grinding chamber 7, which are located in the vicinity of the stirring elements 8, are entrained in the circumferential direction of the grinding vessel 2. In the intermediate region between each two stirring elements 8, the moving grinding bodies flow back in the direction of the stirring shaft 3 as soon as they reach the apex region. A circulating movement of the grinding bodies thus takes place between each two stirring elements 8.

[0007] ​By the movement of the grinding bodies, collisions between the solids in the grinding stock suspension pumped through the grinding chamber 7 and the grinding bodies take place. This collision leads to the fragmentation of the fine particles of the solids in the grinding stock suspension, so that the solids which reach the outlet 6 of the stirred mill 1 are significantly smaller than the solids fed in at the inlet 5.

[0008] In order to ensure that the grinding bodies do not exit the grinding chamber, a separation system 4, for example in the form of a screen or filter (in the following always only referred to as "screen") is also provided before the outlet 6 through which the grinding stock exits.

[0009] In order to prevent the grinding bodies from leaving the grinding vessel, a trommel sieve is usually used. Such a trommel sieve exerts its sieving action by means of a perforated circumferential side surface and provides a relatively large filter surface while at the same time requiring relatively little space, i.e. causing a relatively small pressure drop.

[0010] By the rotational movement achieved by the stirring shaft, the grinding bodies located in the region of the trommel sieve are also moved in the circumferential direction of the rotational shaft. At the same time, the grinding bodies are accelerated in the direction of the side surface of the screen under the suction effect of the screen.

[0011] This causes the grinding bodies to be ground at the side surface of the trommel sieve under the action of the force in the direction of the normal to the side surface of the screen. This leads to a severe abrasive wear on the side surface of the trommel sieve which is not desired.

[0012] Since only the use of wear-resistant materials can ensure that the screen has a sufficient service life, the possibilities in the selection of the screen material are greatly limited. Usually a ceramic screen or a screen with a ceramic coating is used. Forms in which ceramic bodies are formed, each of which has a circumferential side surface forming the screen and which are stacked one behind the other and screwed to one another, so that a screen sleeve is finally obtained, are not uncommon to date. This ensures a high wear resistance, but at the same time increases the manufacturing costs of the screen. Furthermore, this sets limits precisely for those cases in which a further increase in the screen area is desired. SUMMARY

[0013] In view of the above, the object of the present application is to propose a stirred mill having a separation system which is subjected to less wear caused by the grinding bodies.

[0014] According to the application, the problem is solved by means of the application.

[0015] The problem is therefore solved by a stirred mill having a grinding chamber, in which a stirring shaft, preferably carrying a stirring element, is rotated, so that a grinding space is formed between the stirring shaft and the grinding chamber. Into this grinding space, grinding material conveyed by a flowable carrier medium is fed. In the usual case, the flowable carrier medium takes the form of a suspension. The grinding space is partially or mostly filled with grinding bodies. Preferably, the degree of filling is between 75 and 90%. These grinding bodies are moved in rotational motion by the rotating stirring shaft. The grinding material carried by the flowable carrier medium through the grinding space is thereby comminuted. The grinding material conveyed by the flowable carrier medium is carried through the sieve with the carrier medium. The sieve, in turn, stops the grinding bodies.

[0016] The stirred mill according to the invention is characterized in that the sieve consists of a plurality of sieve elements which are arranged one behind the other along the longitudinal axis of the stirred mill and which flow parallel to one another. Preferably, at least two, better still at least eight, such sieve elements are arranged one behind the other. The large surface of the sieve elements which flows out of the grinding space, i.e. the generally perforated surface which actually performs the sieving, extends substantially obliquely or radially with respect to the axis about which the stirring shaft rotates.

[0017] The flowable carrier medium and the grinding material carried thereby, as well as the grinding bodies which come into contact with the grinding material and the carrier medium, are carried by the stirring shaft and are thereby moved in the circumferential direction of the stirring shaft. Since the grinding bodies in the region of the sieve elements are significantly larger and heavier than the individual components of the grinding material, the grinding bodies are held away from the region of the sieve elements by centrifugal force, at least substantially so.

[0018] Thus, in the region of the sieve elements, the grinding bodies do not or hardly experience abrasive wear along the sieve surface, even though the sieve is stationary in operation.

[0019] Even during the start-up of the stirred mill, there is hardly any abrasive wear of the sieve elements caused by contact with the grinding bodies. That is to say, the grinding bodies do not immediately tend to move outwards, but first move in a helical path between the sieve elements. Here, the direction of movement of the grinding bodies is also parallel to the surface of the sieve elements. Since the grinding bodies grind along the sieve surface without being pressed significantly against the sieve surface, there is no or only negligible abrasive wear.

[0020] According to the invention, the sieve consists of a plurality of sieve elements. Each sieve element forms at least one sieve surface through which the grinding material can flow out of the grinding chamber together with the carrier medium. The sieve surfaces of all the sieve elements thus together form a total sieve surface which is many times larger than in the known solutions, i.e. in the usual case.

[0021] The term "screen element" refers in each case to a screen portion which forms a screen surface.

[0022] The term "screen surface" refers to a planar portion which is perforated or provided with apertures, slits or pores and which can be used to block grinding bodies when the carrier medium flows through the apertures or slits, etc. together with the grinding material.

[0023] The term "large surface" refers here to one of the two parallel surfaces of the screen element, which is at least four times larger than the remaining surfaces of the screen element in each case. If the term "large surface" is used here with reference to a normal sheet of paper, this refers to the two surfaces of the sheet of paper which can be conventionally described. According to the application, one of these large surfaces is located inside the grinding chamber and forms the inflow surface of the screen element, while the other is located outside the grinding chamber and forms the outflow surface.

[0024] The term "parallel throughflow" corresponds here to a hydraulic or fluid connection which is equivalent in principle to an electrical parallel circuit, preferably even to an overall equivalent of an electrical parallel circuit of a plurality of identically large (at least substantially identically large) resistors. In any case, the screen element is equivalent in meaning to a resistor.

[0025] The grinding bodies are preferably spherical or substantially spherical, but irregular, jagged or uneven grinding bodies of different or not precisely defined geometry can also be used.

[0026] There is a range of possibilities for designing the application in order to further improve its effectiveness or practicability.

[0027] It should generally be noted that it is particularly advantageous if the screen elements and the associated screen supports are designed in such a way that the screen elements can be replaced (ideally manually, without having to detach the material first). This greatly accelerates any maintenance work which can be necessary, since it is not necessary to replace the screen supports each time. It is therefore particularly advantageous if each screen element forms an end face of the screen support which is substantially closed on the circumferential side. Here, each screen element is preferably made of steel and, ideally, of stainless steel.

[0028] Here, each screen support has the shape of a substantially hollow cylinder which has an opening in at least one end face. In the installed state, this at least one opening is covered by a screen element. In the radial direction, each screen support is substantially closed. Ideally, each screen support is arranged coaxially to the stirring shaft.

[0029] As already mentioned above, abrasive wear on the screen elements according to the application due to contact with the grinding bodies is negligible. Thus, the screen elements do not have to be made of or coated with a particularly wear-resistant material. Instead, steel can be used. This facilitates the manufacture of the screen elements. For example, a steel screen manufactured by means of a laser is simpler and more precise than a screen structure made of wear-resistant ceramic.

[0030] The term "substantially closed on the circumferential side" means that the carrier medium or the grinding stock which has flowed through the screen elements into the interior of the screen support cannot escape uncontrolled from the screen support in radial direction away from the longitudinal axis of the screen support. This does not exclude that individual openings can be provided on the circumferential side of the screen support. In other preferred embodiments, the stirred mill has screen supports whose two end faces are formed by screen elements.

[0031] The grinding stock can flow into each screen support from both sides and from there out of the grinding housing. Thus, the greatest total screen area can be achieved. Thereby, the throughput of the mill can be maximized with a comparatively small suction effect on the individual screen elements. Thus, a small suction effect on the screen elements is advantageous because the centrifugal force which moves the grinding bodies away from the screen elements is not thereby overcome by the suction effect. This in turn reduces the risk of an increased wear at the screen elements.

[0032] In other preferred embodiments, the stirred mill has screen supports whose outer ring has a substantially closed circumferential side surface.

[0033] Thus, for the sake of ease of installation, it is advantageous to design the screen supports as multipart. In this case, each screen support has an outer ring which has a substantially closed circumferential side surface which, in the installed state, surrounds the remaining screen supports as well as at least one screen element.

[0034] Here, the circumferential surface of the outer ring is preferably made of or coated with a material which has a high wear resistance. In particular, this contributes to an increased service life for stationary screen supports. It should be noted in this connection that it is a particularly preferred option for the respective screen support to be made entirely of ceramic. The term "substantially closed circumferential side surface" corresponds to the already defined term "closed on the circumferential side".

[0035] In the ideal case, the outer ring consists of ceramic. Alternatively, it has a wear-reducing coating, in particular a ceramic coating, on its circumferential side surface.

[0036] Due to the rotational movement around the screen support, the grinding bodies located in the grinding chamber are rotated. As already mentioned, the centrifugal forces resulting therefrom keep the grinding bodies at a distance from the screen elements. However, the same wear effects as in the case of the previously described drum filters also occur on the side surface of the outer ring. Thereby, the service life of the screen support can be increased by using wear-resistant materials.

[0037] In other preferred embodiments, the outer ring of the screen support is connected to the hub sleeve of the screen support by spokes.

[0038] Thereby, a large free flow cross section is provided inside the screen support. This in turn contributes to an improved throughput of the stirred mill.

[0039] The hub sleeve is ideally coaxial to the longitudinal axis of the screen support and serves for mounting the screen support on a shaft.

[0040] The term "spoke" is to be understood in a broader sense and only describes that the region of the screen support close to the longitudinal axis is connected to the region close to the side surface by webs (Stege) and that free spaces exist between the webs. Ideally, the hub of the screen support has at least one discharge opening (Abzugsöffnung) for the fluid carrier and the grinding material carried thereby. Preferably, the hub has a plurality of discharge openings (Austragsöffnung).

[0041] Through the discharge openings of the hub, the flowable carrier flowing through the screen elements into the interior of the screen support can be caused to flow together with the grinding material into the respective outlet channel.

[0042] In other preferred embodiments, the screen support is carried by a discharge pipe. The flowable carrier medium and the grinding material transported thereby can be discharged from the screen support into the discharge pipe.

[0043] To this end, the screen support with its hub sleeve is pushed onto the discharge pipe and is connected thereto in a torsion-proof manner. The discharge openings of the hub of the screen support coincide completely or almost completely with the respective discharge openings in the discharge pipe. However, the flowable carrier entering the screen support can flow together with the grinding material carried thereby through the discharge openings of the hub sleeve and the respective openings of the discharge pipe into the discharge pipe. From there, the flowable carrier as well as the grinding material can be guided out of the grinding vessel.

[0044] It is particularly preferred that in one embodiment at least 5, more preferably at least 10 and most ideally at least 15 preferably mutually independent individual components are arranged one behind the other along the longitudinal axis, which components are usually manufactured in the form of a screen support of identical components. Thereby a very large total screen area is provided. At the same time, the gas flow is spatially distributed, so that the gas flow generated in the radial inward discharge direction or the suction driving it is not strong enough at any location to significantly drag the grinding bodies in the radial inward direction. Thereby the grinding bodies can be better kept away from the screen.

[0045] In another preferred embodiment, the screen or the screen support forming the screen is spatially separated from the grinding chamber and is usually arranged further inward in the radial direction in a screening chamber, which is usually formed in the stirring shaft, which also means an increase in the usable grinding chamber in the ideal case. At the same time, this "further inward arrangement" in the radial direction means that any grinding body reaching the screen support has only a slight wear effect there, because the closer it gets to the rotation axis of the stirring shaft, the smaller its peripheral speed is.

[0046] Here, the screening chamber is formed in such a way that the movement direction of the grinding bodies is diverted before reaching the screening chamber. Thus, the grinding bodies can only or essentially only reach the screening chamber as a result of the suction effect occurring at the screen elements. In the ideal case, the screening chamber is formed by a part of the stirring shaft, which is realized as a hollow shaft, the diameter of which is preferably at least 1.5 times larger than the rest of the stirring shaft.

[0047] In other preferred embodiments, the grinding chamber is connected to the screening chamber in the part forming the screening chamber by a rotor opening. Preferably, the rotor opening is realized in the form of a slit, the main extension axis of which is parallel to the longitudinal axis.

[0048] The part dividing the screening chamber is ideally driven by the stirring shaft, so that the screening chamber rotates. The slit serves to rotate the carrier medium, the grinding material and the grinding bodies. Thus, if possible, the grinding bodies already located in the screening chamber also keep a distance from the screen elements under the action of centrifugal force.

[0049] In a particularly preferred embodiment, the screen support is rotated in operation. The rotational movement of the screen support is ideally caused because it is carried by the rotating discharge pipe. The screen support can be rotated separately by a second drive / motor, or the screen support is mounted on the same shaft as the stirring element.

[0050] The screen support is also connected to the discharge pipe in a rotationally fixed manner, and the discharge pipe is in rotational movement. As a result, there is less wear at the outer circumference of the screen support, since there is less differential speed in the circumferential direction relative to the grinding bodies that are carried in the circumferential direction.

[0051] The flowable carrier medium is fed together with the grinding stock, which helps to flush the area between each two screen supports. In this way, it is possible to remove any grinding stock that adheres to the screen elements from the screen elements. This is particularly important when the screen supports are no longer rotating with the mill but are stationary.

[0052] In another preferred embodiment, the discharge pipe has at least one balancing channel. Through the at least one balancing channel, flowable carrier medium and grinding stock are guided in order to be discharged into at least one intermediate space. Here, each balancing channel is preferably formed by a pipe that is arranged between the discharge pipe and the hub sleeve and is generally held by it. Preferably, the discharge pipe has a plurality of such feed channels.

[0053] By means of the at least one balancing channel with openings, it is ensured that the pressure deficiency caused by the rotation in the intermediate space between adjacent screen surfaces can be balanced. Through the openings and the channels, the intermediate space is connected to the region of the grinding chamber close to the shaft, whereby material loaded with a small number of grinding bodies can subsequently flow into the intermediate space through this connection.

[0054] In another preferred embodiment, the individual screen holes of the screen elements, which preferably rotate with the stirring shaft, have a larger diameter on the side from which the grinding bodies flow out of the grinding chamber than the grinding bodies.

[0055] The advantage of the conical design is that, when the machine is switched off, no grinding bodies can pass through the screen to the feed inlet, since the gravitational force acting at this time causes the grinding bodies that have already entered the screen hole to fall back into the grinding chamber through the slope.

[0056] In another preferred embodiment, the screen holes each taper inwardly funnel-like.

[0057] The diameter of the screen hole thus continuously decreases from the side of the screen hole that faces away from the respective screen support.

[0058] The advantage of this is, on the one hand, that the already described face contact of the grinding bodies with the screen hole can be better ensured. On the other hand, it can be ensured that grinding bodies that have entered the screen hole completely or partially do not remain in the screen hole. Rather, the grinding bodies slide or roll on the slope of the screen hole and fall out of the screen hole again. In particular for rotating screen elements, the grinding bodies that have entered the screen hole are also carried out of the screen hole by the resulting centrifugal force in combination with the slope of the screen hole.

[0059] In other preferred embodiments, the region of the screen hole which narrows in funnel form transitions at its narrowest point into a channel. Preferably, this transition is abrupt. The (minimum) diameter of the channel is smaller than the minimum diameter of the grinding bodies.

[0060] The diameter of the screen hole which is smaller than the average diameter of the grinding bodies is located at a point inside the screen hole such that the grinding bodies must leave their regular path of movement in order to reach this point. Thus, the grinding bodies can only reach this point with reduced kinetic energy and will then no longer cause any significant damage to the screen hole.

[0061] In another preferred embodiment, on the outflow side of the screen hole, a separator plate is arranged at a distance from the large surface of the interior of the screen element here. The separator plate is preferably realized as a metal plate. It is arranged on the screen element such that a gap is formed between the large surface of the interior of the screen element and the separator plate. The flowable carrier medium and the ground material transported thereby must then pass through this gap at the narrowest point of the screen hole. The gap preferably has a gap height which is generally smaller than the diameter of the grinding bodies, in some applications at least 30%.

[0062] The actual separation of the flowable carrier medium and the ground material transported thereby from the grinding bodies takes place in the region in which the grinding bodies, once they reach this region, no longer produce a grinding effect on the material.

[0063] The "outflow side" of the screen hole refers to the side of the screen hole which, in the installed state of the screen element, faces into the interior of the screen support.

[0064] The "interior" large surface of the screen element refers to the large surface which, in the installed state of the screen element, faces into the interior of the screen support.

[0065] In other preferred embodiments, the separator plate has openings on one side thereof, the longitudinal axes of which are parallel to the longitudinal axis of the stirred mill. In this case, the openings of the separator plate are arranged offset to one another in the radial direction and / or in the circumferential direction from the corresponding openings of the screen element. The offset is formed such that the flowable carrier medium and the ground material transported thereby must pass through the gap between the large surface of the interior of the screen element and the separator plate in order to flow away from the screen hole through the openings of the separator plate.

[0066] In addition, in this embodiment, the actual separation of the flowable carrier medium and the ground material transported thereby from the grinding bodies takes place in the region in which the grinding bodies, once they reach this region, no longer produce a grinding effect on the material.

[0067] Basically, it can be said that the screen openings - for dynamic designs of its screen support that rotate along - can be larger than the grinding body diameter. For static designs of its screen support that do not rotate along but are completely fixed in position, the screen openings must be smaller than the grinding body diameter. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 A schematic diagram of a stirred mill is shown.

[0069] Figure 2 A longitudinal sectional view of a screen of a stirred mill according to the invention is shown.

[0070] Figure 2a An enlarged sectional view of Figure 2 is shown.

[0071] Figure 2b A perspective view of the assembly shown by Figure 2 is shown.

[0072] Figure 3 An isometric exploded view of a screen support with mounted screen elements and discharge duct is shown.

[0073] Figure 4 A longitudinal sectional view of a screen of a stirred mill according to the invention (with balancing channel), i.e. a second particularly preferred embodiment, is shown.

[0074] Figure 4a A perspective view of the assembly shown by Figure 4 is shown.

[0075] Figure 5 A sectional view of a screen shown in Figure 4 is shown, with curved sections.

[0076] Figure 6 A sectional view of a screen support is shown, with screen elements equipped with specially designed screen openings, preferably in the form of funnels.

[0077] Figure 6a An enlarged sectional view of Figure 6 the screen support on the left is shown.

[0078] Figure 6b An enlarged sectional view of Figure 6 the screen support on the right is shown.

[0079] Figure 7 A variant of the assembly shown in Figure 6 is shown, which is now equipped with pump vanes.

[0080] Figure 8 A sectional view of a screen support is shown, for screen elements with additional separator plates. Detailed Implementation

[0081] according to Figures 2 to 8 The working method of this application will be illustrated by examples.

[0082] exist Figure 2 The figure shows a longitudinal cross-sectional view of a first embodiment of a stirred mill 1 with a screen 4 according to the present invention.

[0083] Screen 4 is located in screening chamber 21. Screening chamber 21 is formed by a portion of agitator shaft 3, which is implemented as a hollow shaft. Therefore, it is conceivable that, instead, the rotor cage forming screening chamber 21 could be fixed to agitator shaft 3. Preferably, agitator elements 8 are also located on the side of agitator shaft 3 forming screening chamber 21, away from screen 4. These agitator elements 8 cause the grinding media to move. As a result, the grinding material conveyed by the carrier medium in the direction of screen 4 is pulverized by the grinding media as it passes through the agitator elements 8.

[0084] Because the grinding media are driven by the stirring shaft 3 and the stirring element 8 to move in the circumferential direction of the stirring shaft, these grinding media are, in principle, kept at a certain distance from the screen 4 by the centrifugal force generated. Furthermore, the portion of the stirring shaft 3 that forms the screening chamber 21, together with the grinding container 2, forms a channel through which the carrier medium, the grinding material, and the grinding media must pass when flowing in the direction of the screen 4. Moreover, when the stirring shaft 3 is stationary, the grinding media do not easily reach the screen 4.

[0085] The screen 4 is composed of multiple screen support members 15 (see in particular) Figure 2a (Enlarged cross-sectional view in the image) Each screen support is equipped with one or two screen elements 12. Here, the screen support 15 is mounted on the discharge pipe 20 in parallel front and rear by means of a hub 17.

[0086] To ensure that the screen support 15 does not slide axially, one of the screen support 15 rests against the grinding container 2 in the installed state. A partition sleeve 26 is also provided between the individual screen supports 15. The screen support 15 installed on the free end of the discharge pipe 20 is also secured by an axial lock 29.

[0087] Preferably, the first and last screen supports 15 each carry only a single screen element 12 on their free end faces. The screen support 15 located between the first and last screen supports 15 carries a screen element 12 on each of its two free end faces.

[0088] This is a special reference. Figure 2bThe screen element 12 has screen openings 13. The diameter of the screen openings 13 is determined in such a way that only the carrier medium from the grinding chamber 7 can pass through the screen openings together with the ground grinding stock. In contrast, the grinding bodies cannot pass through the screen openings 13.

[0089] After the carrier medium together with the grinding stock has passed through the screen element 12 into the interior of the screen support 15, it can flow into the discharge pipe 20 through the corresponding discharge openings 19 of the hub 17 of the screen support 15 and through the discharge opening 27 of the discharge pipe 20. It finally flows out of the discharge pipe from the grinding container 2.

[0090] Since the screen 4 is located in the screening chamber 21, the grinding bodies are in principle kept at a distance from the screen 4. However, the grinding bodies can still enter the screening chamber 21 through the passage between the stirring shaft 3 forming the screening chamber 21 and the grinding container 2. However, due to the rotational movement of the part of the stirring shaft 3 forming the screening chamber 21, the grinding bodies located in the screening chamber 21 perform a rotational movement about the longitudinal axis of the stirring shaft 3. In the part of the stirring shaft 3 forming the screening chamber 21, a slit 22 is provided, so that the grinding bodies are removed from the screening chamber 21 under the action of the centrifugal force generated. Thus, the screen element 12 is almost not in contact with the moving grinding bodies. Thereby, the wear phenomena caused by the grinding bodies on the screen element 12 are avoided to the greatest extent. In contrast, if there are many grinding bodies already in the screening chamber 21, so that these grinding bodies accumulate in the area of the slit 22 before they can leave the screening chamber 21 through the slit 22 under the action of the centrifugal force, there can be more contact with the grinding bodies on the outer ring 16 of the screen support 15. For this reason, the outer ring 16 is preferably made of a wear-resistant material, usually a ceramic material.

[0091] Since the individual components of the grinding stock have a significantly smaller weight than the grinding bodies, the centrifugal force acting on the grinding stock is not sufficient to overcome the suction prevailing at the screen element 12.

[0092] In Figure 3 the individual screen supports 15 are shown together with the screen element 12, in front of which the discharge pipe 20 is shown. Here, the screen element 12 is shown in a partial cross-sectional view, in order to be able to illustrate the interior of the screen support 15. It can be seen that the screen element is configured to be preferably essentially flat or completely flat. Preferably, the screen element has the form of a circular disc, the large surface of which extends completely or at least essentially in the radial direction.

[0093] The outer ring 16 of the screen support 15 is connected with the hub 17 by means of spokes 18. Thereby, the interior of the screen support 15 provides a large space for the carrier medium and the milled material which flows in through the screen elements 12. Through the discharge opening 19 of the hub 17, which coincides with the discharge opening 27 of the discharge pipe 20 in the installed state, the carrier medium can flow out together with the milled material into the discharge pipe 20.

[0094] In Figure 4 , Figure 4a and Figure 5 a further embodiment is shown. Therein, one or usually a plurality of balancing channels 23 are additionally provided. The balancing channels 23 are formed by a pipe which, in the installed state, extends between the discharge pipe 20 and the hub 17 of the screen support 15. Through the balancing channels 23 the above-mentioned pressure balancing can be carried out. For this purpose, the balancing channels 23 have openings 30. In the installed state, these openings coincide with the openings 28 in the partition sleeve 26 between the screen supports 15.

[0095] In Figures 6 to 8 different embodiments of the screen holes 13 in the screen elements 12 are shown.

[0096] In Figure 6 and Figure 6a at least some of the screen holes 13 on the side of the screen elements 12 through which the carrier medium and the milled material flow together into the screen support 15 have a larger diameter than the screen holes on the side of the screen elements 12 which is inside the screen support 15. Here, the transition from the larger diameter to the smaller diameter is preferably funnel-shaped or conical. With such a design of the screen holes 13, in addition to the milled material, the milling bodies can also flow at least partially into the screen holes 13. Thus, the largest diameter A of the screen holes 13 is larger than the diameter of the milling bodies. The advantage of this is that the milling bodies cannot come into a stressful collision with the edge of the screen hole 13 which is relevant for the screen function, since they first enter the respective screen hole 13. The milling bodies do not come into contact with the edge, but rather tend to come into contact with the screen hole 13 over a larger surface, which further reduces the wear.

[0097] Here, the smallest diameter B and the smallest cross section of the screen holes 13 can be smaller than the milling bodies, so that the milling bodies cannot pass through the respective screen hole 13. Alternatively, it is also possible for the smallest diameter to be larger than the milling bodies, depending on whether it relates to a dynamic embodiment or a static embodiment in the above-mentioned sense, according to Figure 6 and Figure 6a .

[0098] The design shown here helps to prevent the grinding media from passing through, especially when stationary, because after entering the screen openings, the grinding media falls back outwards from the ramp under the influence of its own gravity, i.e., back into the screening chamber.

[0099] exist Figure 6 and Figure 6a The wear protection layer VSS, which surrounds or binds the circumferential side surface of the screen support 15, can be clearly seen in the middle.

[0100] For in Figure 6 The illustrated embodiment (see) Figure 6b At least some or all of the screen openings 13 of the screen element 12 have a diameter that initially decreases in a funnel-like or conical shape from the side of the screen element 12—on which the carrier medium flows into the screen support 15—and then abruptly decreases in diameter. From the point where the diameter abruptly decreases, a channel 14 with a substantially constant diameter is eventually formed. Here, the diameter of the channel 14 is smaller than the average diameter of the grinding media. Therefore, the grinding media can enter the screen openings 13 until it reaches the channel 14. The channel 14 extends into the screen openings 13 at a position that the entering grinding media must deviate from its normal path of movement to reach. Therefore, the grinding media has less kinetic energy when it reaches the channel 14 and thus does not cause significant damage to the channel 14.

[0101] according to Figure 7 The embodiments generally correspond to Figure 6 The illustrated embodiment differs only in that a web or pump blade PF is provided between directly adjacent screen supports. This is designed to produce a pumping effect, either conveying the grinding media outwards or supporting its outward conveyance.

[0102] According to Figure 8 In the embodiment (left side), the screen opening 13 may optionally have a gradually tapering cross-section that is funnel-shaped, conical, or trapezoidal. Here, its minimum diameter or net cross-section C is greater than the minimum diameter or net cross-section of the grinding material. On the side of the screen element 12 located inside the screen support 15, a separator plate 24 is also connected to the screen element 12, thereby covering the screen opening 13. However, a distance retainer is provided between the separator plate 24 and the screen element 12. Therefore, a small "air" gap exists between the separator plate 24 and the screen element 12. The size of this air gap is determined so that the grinding material entering the screen opening 13 cannot pass through. Conversely, the carrier medium and the grinding material can pass through this air gap to reach the interior of the screen support 15. In this embodiment, once the grinding material enters the screen opening 13 and reaches the separator plate 24, the grinding material will no longer produce an abrasive grinding effect.

[0103] exist Figure 8In the embodiment shown on the right-hand side, the screen holes 13 have a conical cross-section. However, the screen holes can also have a constant cross-section. In any case, a separator plate 24 can be provided on the side of the screen element 12 which is inside the screen support 15. This rests directly on the screen element 12 and covers the screen holes 13. However, the (preferably peripherally sealed) separator plate 24 also has at least one opening 25 which is arranged offset to the screen holes 13. The width of the screen element 12 is reduced in the region of the offset between the screen holes 13 and the opening 25 of the separator plate 24, so that a gap exists between the separator plate 24 and the screen element 12. The carrier medium, together with the grinding stock, can flow through this gap into the interior of the screen support 15. In contrast, the grinding bodies cannot pass through this gap. However, here, once a grinding body has entered a screen hole 13 to the separator plate 24, the grinding body can no longer produce a grinding effect on the grinding stock.

[0104] At the appropriate time, it can also be chosen to claim protection for the pure form or for the form extended by additional technical features from the description and / or the drawings and / or by individual features or all features of the description:

[0105] A stirred mill, in particular a stirred ball mill with a grinding vessel, wherein a stirring shaft, preferably carrying stirring elements, is rotated, so that a grinding chamber is formed between the stirring shaft and the grinding vessel, in which grinding chamber a grinding stock can be fed which is conveyed by a flowable carrier medium, usually in the form of a suspension, wherein the grinding chamber is partially filled with grinding bodies, wherein the grinding stock conveyed by the flowable carrier medium is discharged together with the carrier medium through a screen 4, which screen bars the grinding bodies, wherein the screen 4 consists of only individual screen elements, which are ideally substantially radially extending or in individual cases also obliquely extending, which are exempt from forming a circumferential side surface; or substantially of a plurality of, preferably at least ten, screen elements which are arranged one behind the other along the longitudinal axis of the stirred ball mill 1, which flow parallel.

[0106] List of reference signs

[0107] 1 stirred mill / stirred ball mill

[0108] 2 grinding vessel

[0109] 3 stirring shaft

[0110] 4 separation system / screen

[0111] 5 inlet

[0112] 6 outlet

[0113] 7 grinding chamber

[0114] 8 stirring element

[0115] 9 electric motor

[0116] 10 belt drive

[0117] 11 housing

[0118] 12 screen element

[0119] 13 screen hole

[0120] 14 passage of screen hole

[0121] 15 screen support

[0122] 16 outer ring of screen support

[0123] 17 hub

[0124] 18 spoke

[0125] 19 discharge outlet of hub sleeve

[0126] 20 discharge duct

[0127] 21 screening chamber

[0128] 22 gap

[0129] 23 balancing passage

[0130] 24 separator plate

[0131] 25 opening of separator plate

[0132] 26 baffle sleeve

[0133] 27 discharge outlet of discharge duct

[0134] 28 feed opening in baffle sleeve

[0135] 29 axial lock

[0136] 30 opening in balancing passage

[0137] VSS wear protection layer

[0138] A maximum clear cross section / diameter of screen hole 13

[0139] B minimum clear cross section / diameter of screen hole 13

[0140] C clear cross section / diameter of screen hole 13

[0141] PF pump blade

[0142] L longitudinal axis of mill, axis of rotation

Claims

1. A stirred mill (1) with a grinding chamber (2) in which a stirring shaft (3) carrying a stirring element (8) is rotated so that a grinding space (7) is formed between the stirring shaft (3) and the grinding chamber (2) in which a grinding stock conveyed by a flowable carrier medium in the form of a suspension is fed in, wherein The grinding chamber (7) is partially filled with grinding bodies which are moved by a rotating stirrer shaft (3) and by which grinding material carried through the grinding chamber (7) by the flowable carrier medium is comminuted, wherein the grinding material transported by the flowable carrier medium is discharged together with the carrier medium through a screen (4) which screens the grinding bodies from the area reaching the screen (4), characterized in that the screen (4) consists of a plurality of screen elements (12) which are arranged one behind the other along the longitudinal axis of the stirred mill (1) and which flow through parallel to one another, the screen surface of the screen elements (12) which flows out of the grinding chamber (7) extending obliquely or radially with respect to an axis about which the stirrer shaft (3) rotates, the stirred mill (1) having screen supports (15) of which at least two are arranged one behind the other along the longitudinal axis, each screen element (12) forming an end face of a screen support (15) which is closed on the circumferential side.

2. A stirred mill (1) according to claim 1, characterized in that, Each screen element (12) is made of steel.

3. A stirred mill (1) according to claim 1, characterized in that, Both end faces of the screen support (15) are formed by screen elements (12).

4. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, The stirred mill (1) has screen supports (15) whose outer ring (16) has a closed circumferential side surface.

5. A stirred mill (1) according to claim 4, characterized in that, The outer ring (16) is made of ceramic and the circumferential side surface of the outer ring (16) is provided with a wear-reducing coating.

6. A stirred mill (1) according to claim 5, characterized in that, The wear-reducing coating is a ceramic coating.

7. A stirred mill (1) according to claim 2 or 3, characterized in that, The outer ring (16) of the screen support (15) is connected to the hub (17) of the screen support (15) by spokes (18).

8. A stirred mill (1) according to claim 2 or 3, characterized in that, The hub (17) of the screen support (15) has at least one discharge opening (19) for the flowable carrier and the grinding material carried by the flowable carrier.

9. A stirred mill (1) according to claim 2 or 3, characterized in that, The screen support (15) is carried by a discharge duct (20) into which the flowable carrier medium and the grinding material transported by the flowable carrier medium is discharged from the screen support (15).

10. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, At least six screen supports (15) are arranged one behind the other along the longitudinal axis.

11. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, At least ten screen supports (15) are arranged one behind the other along the longitudinal axis.

12. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, At least fifteen screen supports (15) are arranged one behind the other along the longitudinal axis.

13. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, The screen (4) or the screen supports (15) forming it are arranged in a screening chamber (21) in the stirrer shaft (3).

14. A stirred mill (1) according to claim 13, characterized in that, The grinding chamber (7) is connected to the screening chamber (21) by a rotor opening in the form of a slit (22) whose main extension axis is parallel to the longitudinal axis.

15. A stirred mill (1) according to claim 2 or 3, characterized in that, The screen support (15) is rotated in operation.

16. A stirred mill (1) according to claim 15, characterized in that, The screen support (15) is carried by a discharge duct (20) and the discharge duct (20) is rotated.

17. A stirred mill (1) according to claim 16, characterized in that, The discharge duct (20) carries at least one balancing channel (23) through which flowable carrier medium with grinding material is fed and discharged into at least one intermediate space.

18. A stirred mill (1) according to claim 17, characterized in that, Each balancing channel (23) is formed by a duct which is arranged between the discharge pipe (20) and the hub (17) of the screen support (15) and is held thereby.

19. A stirred mill (1) according to any one of claims 1 to 3, characterized in that, The individual screen openings (13) of the screen element (12) rotating with the stirrer shaft (3) have a larger diameter on their outflow side from the grinding chamber (7) than the grinding bodies.

20. A stirred mill (1) according to claim 19, characterized in that, The screen openings (13) each taper inwards funnel-shaped.

21. A stirred mill (1) according to claim 20, characterized in that, The funnel-shaped tapering-inwards region of the screen openings (13) transitions at its narrowest point into a channel (14) which can have a diameter which is smaller than the diameter of the grinding bodies.

22. A stirred mill (1) according to claim 20, characterized in that, The funnel-shaped tapering-inwards region of the screen openings (13) transitions at a jump into a channel (14) which can have a diameter which is smaller than the diameter of the grinding bodies.

23. A stirred mill (1) according to claim 19, characterized in that, On the outflow side of the screen openings (13), a spacer plate (24) realized as a metal plate is arranged at a distance therefrom on the screen surface inside the screen element (12) here, so that a gap is formed between the screen surface inside the screen element (12) and the spacer plate (24) through which the flowable carrier medium and the ground material conveyed thereby must then pass at the narrowest point of the screen openings (13).

24. A stirred mill (1) according to claim 23, characterised in that, The spacer plate (24) also has openings (25) whose opening axes are parallel to the longitudinal axis of the stirred mill (1), wherein the openings (25) of the spacer plate (24) and the corresponding openings (13) of the screen element (12) are arranged offset from one another in radial and / or in circumferential direction, so that the flowable carrier medium and the ground material conveyed thereby must pass through the gap between the screen surface inside the screen element (12) and the spacer plate (24) in order to flow out of the screen openings (13) through the openings (25) of the spacer plate (24).

25. A stirred mill (1) according to claim 23 or 24, characterized in that, The gap has a gap height which is at least 30% smaller than the diameter of the smallest grinding body.

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