RU2842064C1 - Mill with mixing of grinding medium - Google Patents

Abstract

FIELD: crushing or grinding of various materials.

SUBSTANCE: invention relates to a mill with mixing of the grinding medium, in particular to a bead mill. Mill comprises a grinding container in which a mixing shaft is mounted with possibility of rotation, forming a grinding chamber between the mixing shaft and the grinding container wall, into which the material to be ground is introduced, transported by a fluid carrier, the latter is partially filled with grinding bodies driven by rotary mixing shaft to grind material carried by fluid carrier through grinding chamber. Grinding material transported by the fluid carrier substance together with the carrier substance itself is discharged through a sieve, which holds grinding bodies that fall into the sieve area, wherein said screen comprises several sieve elements arranged one after another along mill lengthwise axis to allow parallel passage of material discharged therefrom. Working surfaces of sieves facing grinding chamber extend inclined or radially relative to mixing shaft rotational axis. Screen elements are mounted on several screen frames arranged one after another at a distance from each other along axis of rotation of mixing shaft, wherein screen-forming screen frames are arranged in screen chamber arranged in mixing shaft.

EFFECT: mill provides the least susceptibility to wear by grinding bodies.

20 cl, 8 dwg

Description

The invention relates to a mill with a stirred grinding medium, comprising a grinding container into which the material to be ground is introduced, and a sieve through which the material to be ground is removed from the grinding container, in accordance with the generic concept of paragraph 1 of the formula.

Field of technology

First, the operating principle of the mill with mixing of the grinding medium is explained with reference to Fig. 1.

Fig. 1 schematically shows a mill 1 with mixing of the grinding medium, containing a horizontal mixing shaft 3. The grinding bodies located in the grinding container 2, forming the grinding medium and usually made in the form of steel or ceramic balls, are not shown for clarity.

During operation of the mill 1 with agitation of the grinding medium, the material to be ground is admitted through its inlet 5, pumped into the grinding chamber 7 enclosed in the grinding vessel 1 and pumped through it. In the case of wet grinding, the material to be ground is a suspension or dispersion consisting of a liquid, most often water, and solids. In other cases, such a mill with agitation of the grinding medium can also be used for dry grinding. Then it can be designed, for example, as a mill with a vertical mixing shaft, in which the material to be ground is transported through the mill by a gaseous medium, most often moving in a downward flow.

The present invention in its broadest sense relates to both of the above-mentioned types of mills with agitation of the grinding medium. However, its application is most preferable in mills with agitation of the grinding medium containing a horizontal mixing shaft. Due to the rotational movement of the mixing shaft 3, the mixing elements 8 are set in rotation, which are connected to the mixing shaft 3 with a fixation against rotation relative to it and are often called grinding disks. In addition, when implementing the present invention, mixing elements 8 made in the form of separate rods can be used. To impart rotational movement to the mixing shaft 3, it can be set in rotation, for example, by an electric motor 9 via a belt transmission 10. In this case, the drive of the mill 1 with agitation of the grinding medium is most often located in the housing 11 adjacent to the grinding container 2.

Due to the rotation of the mixing elements 8, the grinding bodies contained in the grinding chamber 7, which are located near the mixing elements 8, are carried by these mixing elements in the circumferential direction of the grinding container 2. In the zone located in the middle between each two mixing elements 8, the grinding bodies moved in this way, having reached the peripheral region, flow back in the direction of the mixing shaft 3. Thus, a circulation movement of the grinding bodies is created between any two mixing elements 8.

Such movement of the grinding bodies causes collisions between the solid phase of the suspension of the material being ground, pumped through the grinding chamber 7, and the grinding bodies. These collisions lead to the splitting of the solid phase in the suspension of the material being ground into small particles, as a result of which the solids that ultimately enter the outlet 6 of the mill 1 with the mixing of the grinding medium have a noticeably smaller size than the solids fed to the inlet 5.

In order to prevent the grinding media from escaping from the grinding chamber, a separation system 4 is installed in front of the outlet 6, through which the material being ground is discharged, for example, in the form of a sieve or filter (hereinafter the term "sieve" is used in the text).

State of the art

Drum sieves are usually used to prevent the grinding media from escaping from the grinding container. They retain the grinding medium on a side surface that is permeable to the material being ground, running along the circumference of the sieves, and have a relatively large filter partition surface with a relatively small occupied volume, i.e. they cause a comparatively small pressure drop.

As a result of the rotational motion of the mixing shaft, the motion in the circumferential direction of the shaft is also communicated to the grinding bodies located in the area of the drum sieve. At the same time, the suction force acting on the sieve tends to press the grinding bodies against the side surface of the sieve.

This results in the grinding bodies, being under the action of a force directed normally to the side surface of the drum screen, sliding along this surface. This is undesirable, as it leads to strong abrasive wear of the side surface of the drum screen.

Since sufficient durability of such a sieve can only be ensured by using wear-resistant materials, the possibilities for choosing the sieve material are very limited. Ceramic sieves or sieves with a ceramic coating are usually used. Until now, sieves have often been manufactured as ceramic elements with a filter partition running along the circumference and forming a sieve, assembled one after another into a package and then screwed together to ultimately obtain a filter bushing. Although this guarantees high wear resistance, it simultaneously increases production costs when manufacturing sieves. In addition, such technology limits the designer's capabilities in cases where it is necessary to additionally increase the sieve surface, i.e. the working surface of the sieve.

The problem underlying the invention

Taking this into account, the invention was based on the task of creating a mill with mixing of the grinding medium, having a separation system that is less susceptible to wear by the grinding bodies.

The solution proposed in the invention

In accordance with the invention, this problem is solved by the features of an independent claim of the invention.

Accordingly, the above-mentioned problem is solved in a mill with agitation of the grinding medium, comprising a grinding vessel, in which a stirring shaft is mounted with the possibility of rotation, preferably carrying stirring elements, with the formation of a grinding chamber between the stirring shaft and the wall of the grinding vessel. The material to be ground, transported by a fluid carrier substance, is introduced into the grinding chamber. As a rule, the fluid carrier substance is a suspension. The grinding chamber is partially or predominantly filled with grinding bodies. The degree of filling of the grinding chamber with grinding bodies is preferably from 75% to 90%. The grinding bodies are set in rotational motion by a rotating stirring shaft. Due to this, the material to be ground, transported by the fluid carrier substance through the grinding chamber, is crushed, or ground. The material to be ground, transported by the fluid carrier substance, together with the carrier substance is drawn through a sieve. In this case, the sieve retains the grinding bodies.

In the mill proposed in the invention, the sieve comprises several sieve elements arranged one behind the other along the longitudinal axis of the mill with the possibility of parallel passage of the material discharged from the mill through them. The sieve preferably comprises at least two such sieve elements arranged one behind the other, more preferably at least eight such sieve elements. The working surfaces of the sieve elements facing the flow of the discharged material to the grinding chamber, i.e. receiving the flow of material from the grinding chamber and in a broad sense representing permeable surfaces that ensure the actual effect of filtering the grinding bodies, extend obliquely or radially with respect to the axis of rotation of the mixing shaft.

The flowing carrier substance together with the material to be ground which it carries, as well as the grinding bodies which are in contact with the material to be ground and the carrier substance, are carried along by the mixing shaft and accordingly move in the circumferential direction of the mixing shaft. Since the grinding bodies which are in the area of the screen elements are noticeably larger and heavier than the individual components of the material to be ground, these grinding bodies are at least mainly thrown away from the area of the screen elements by centrifugal forces and are held at a distance from it.

Due to this, even if the sieves are stationary during operation, there is no or almost no abrasive sliding of the grinding bodies along the sieve surfaces in the area of the sieve elements.

Abrasive wear on the sieve elements due to contact with the grinding media is also practically absent during the start-up of the mill with mixing of the grinding medium. The grinding media do not rush out immediately, but first move between the sieve elements along a spiral trajectory. In this case, the direction of movement of the grinding media also runs parallel to the surface of the sieve elements. However, since the grinding media slide along the sieve surfaces without significant pressure on them, wear does not occur or occurs only to a small extent.

According to the invention, the sieve is assembled from several sieve elements. Each of the sieve elements forms at least one sieve surface capable of passing through itself the material to be ground, coming together with the carrier substance from the grinding chamber. Then the sieve surfaces of all the sieve elements together give, in comparison with known solutions, as a rule, a many times increased total sieve surface.

The term "sieve element" means the corresponding part of the sieve which forms the sieve surface.

The term "sieve surface" means a flat area that is perforated or permeable, i.e. provided with holes, slits or pores, and serves to retain the grinding bodies while allowing the carrier substance together with the material being ground to pass through the holes, slits, etc.

The term "working surface" herein means one of the two parallel surfaces of the corresponding sieve element, which is at least four times larger than the other surface(s) of the sieve element. In relation to a conventional sheet of writing paper, the term "working surface" used in this description means two surfaces of the sheet suitable for writing. In accordance with the invention, one of these working surfaces is located in the grinding chamber and forms the input surface of the sieve element, i.e. facing the flow of the material being discharged to the grinding chamber, and the other is located outside the grinding chamber and forms the output surface, i.e. facing the flow of the material being discharged from the grinding chamber.

The term "parallel passage" (of the material to be discharged through the screen elements) in the context of the invention corresponds to a circuit of hydraulic or hydrodynamic connection of the screen elements, which is in principle equivalent to a parallel electrical circuit - preferably also in the sense that such a circuit is generally equivalent to an electrical circuit of several resistances connected in parallel and at least essentially identical. In this case, the screen elements correspond in their operating principle to the electrical resistances.

The grinding bodies are preferably balls or are essentially spherical, but at the same time grinding bodies of other geometric shapes or grinding bodies whose shape is not precisely defined in geometric terms, with unevenly distributed teeth (protrusions) or crevices (depressions) can also be used.

The above-mentioned problem is solved in the mill proposed in the invention due to the fact that the sieve elements are installed on several sieve frames located one after the other at a distance from each other along the axis of rotation of the mixing shaft, i.e. the longitudinal axis of the mill, and the sieve frames forming the sieve are located in a sieve chamber located in the mixing shaft.

In this way, the sieve frames forming the sieve are spatially separated from the grinding chamber, located in the sieve chamber formed in the mixing shaft and located radially inside the grinding chamber, which in the ideal case simultaneously means an increase in the available volume of the grinding chamber. At the same time, due to such a "radially internal" arrangement of the sieve, the grinding bodies that manage to reach the sieve frames are capable of creating only a small wearing effect, simply because their peripheral speed is the lower, the closer they are to the axis of rotation of the mixing shaft.

In this case, the sieve chamber is designed so as to deflect the direction of movement of the grinding bodies before they enter the sieve chamber. Accordingly, the grinding bodies can enter the sieve chamber only or mainly due to the suction effect acting on the sieve elements. Ideally, the sieve chamber is formed due to the fact that the corresponding section of the mixing shaft is designed as a hollow shaft, the diameter of which is preferably at least one and a half times greater than the diameter of the remaining part of the mixing shaft.

Preferred embodiments of the invention

There are a number of possibilities for implementing the invention that provide further improvement in the efficiency of the mill or its suitability.

First of all, it should be noted that in general it is particularly advisable to design the screen elements and the corresponding screen frames in such a way that it would ensure the possibility of non-destructive, ideally manual, replacement of the screen elements. This significantly speeds up any necessary restoration, since replacement of the screen frame itself is not required every time.

It is particularly preferable that each screen element forms the end surface of a screen frame closed in the circumferential direction. In this case, each screen element preferably consists of steel, ideally of stainless steel.

In this case, each sieve frame has essentially the form of a hollow cylinder having an opening on at least one end face. This at least one opening is closed by a sieve element in the mounted state. In the radial direction, each sieve frame is essentially closed. Ideally, each sieve frame is located coaxially with the mixing shaft.

As stated above, the screen elements proposed in the invention are subject to only minor abrasive wear due to contact with the grinding bodies. Therefore, the screen elements do not need to be made of particularly wear-resistant materials or provided with a coating of such materials. Steel can be used instead. This simplifies the manufacture of the screen elements. Thus, for example, steel screens can be manufactured with lasers much more simply and accurately than screen structures made of wear-resistant ceramics.

The expression "essentially closed in the circumferential direction" means that the carrier substance and the crushed material, having already passed through the sieve element into the interior of the sieve frame, cannot uncontrollably exit the sieve frame in a radial direction facing away from the longitudinal axis of the sieve frame. This does not exclude the possibility that single openings may be provided in the circumferential side surface of the sieve frames.

In another preferred embodiment of the invention, the mill with agitated grinding medium comprises sieve frames, both end surfaces of which are formed by sieve elements.

In this way, the material to be ground can pass into each sieve frame from the grinding container body and exit from there on both sides. Consequently, this ensures the maximum total sieve surface area. This allows the maximum mill productivity to be achieved with a relatively small suction effect created on the individual sieve elements. The creation of a small suction effect on the sieve elements is advantageous from the point of view that the suction force does not interfere with the centrifugal forces that tend to carry away the grinding bodies from the sieve elements. This, in turn, reduces the risk of increased wear on the sieve elements.

In another preferred embodiment of the invention, the mill with agitated grinding media comprises sieve frames with an outer ring having a closed side surface extending around the circumference.

Thus, to facilitate installation, it is advisable to make the sieve frames composite, i.e. consisting of several parts. In this case, each sieve frame has an outer ring, the side surface of which runs along the circumference (in the circumferential direction) and is essentially closed and which surrounds the rest of the sieve frame and at least one sieve element in its state mounted on the frame.

In this case, the lateral (circumferential) surface of the outer rings is preferably made of a material with high wear resistance or provided with a coating of such a material. In particular, in the case of fixed sieve frames, this helps to increase the service life. In this connection, it should be mentioned that a particularly preferred option is the manufacture of the corresponding sieve frames entirely from ceramics.

The expression "a lateral surface extending along a circle and essentially closed" corresponds to the above definition of the expression "closed in the circumferential direction".

Ideally, the outer ring is made of ceramic. Alternatively, its circumferential side surface is provided with a wear-reducing coating, in particular a ceramic coating.

Due to the rotational movement of the mixing shaft, the grinding bodies in the grinding chamber rotate around the sieve frames. As explained above, the resulting centrifugal forces keep the grinding bodies at a distance from the sieve elements. The same wear patterns as in the case of the drum filters described above may occur on the lateral surface of the outer ring. Therefore, the use of wear-resistant materials allows for an increase in the service life of the sieve frames.

In another preferred embodiment of the invention, the outer ring of the sieve frame is connected by spokes to the central sleeve of the sieve frame.

This creates a large free flow area in the internal space of the sieve frame. This, in turn, helps to increase the productivity of the mill with mixing of the grinding medium.

Ideally, the central bushing is positioned with alignment relative to the longitudinal axis of the screen frame and serves to mount the screen frame on the shaft.

The term "spokes" should be understood in a broad sense as indicating only that the part of the sieve frame closest to the longitudinal axis is connected to the part closest to the periphery by crossbars, between which there are gaps.

Ideally, at least one outlet opening is provided in the central sleeve of the sieve frame for the discharge of the flowing carrier substance and the crushed material carried by it. In a preferred embodiment, the central sleeve has several outlet openings.

Through such a discharge or exhaust opening of the central bushing, the flowing carrier substance, which has passed together with the crushed material through the sieve element into the internal space of the sieve frame, can be discharged into the corresponding outlet channel.

In another preferred embodiment of the invention, the sieve frames are mounted on a vent pipe. The vent pipe is designed with the possibility of diverting the flowing carrier substance and the crushed material transported by it from the sieve frame into it.

For this purpose, the sieve frames are put on the exhaust pipe with their central bushings and connected to the exhaust pipe with a fixation against rotation relative to it. In this case, the drain holes in the central bushing of the sieve frame and the corresponding drain holes in the exhaust pipe coincide completely or almost completely. Then the fluid carrier substance that has entered the sieve frame together with the crushed material carried by it can pass into the exhaust pipe through the drain holes in the central bushing and the corresponding holes in the exhaust pipe. Through the exhaust pipe, the fluid carrier substance and the crushed material can be removed from the grinding container.

Particularly preferred is an embodiment of the invention in which at least five sieve frames, preferably at least ten, and ideally at least fifteen, are arranged one after the other along the longitudinal axis, which are preferably manufactured as independent individual components, most often as identical components.

This achieves a significant increase in the total area of the sieve surfaces (filter partitions). At the same time, the flow is distributed in space, due to which the flow of material moving in the direction of its extraction radially inward, i.e. the suction force creating it, is not locally so powerful in any one place as to entrain a significant amount of grinding media in a radially inward direction. This facilitates a better separation of the grinding media from the sieve.

In another preferred embodiment of the invention, the grinding chamber is connected to the sieve chamber via rotor openings formed in the section forming the sieve chamber. Such rotor openings are preferably made in the form of slots, the axes of the main extensions of which run parallel to the longitudinal axis.

The section separating the sieve chamber (from the grinding chamber) is ideally driven by a mixing shaft, causing the sieve chamber to rotate. The slots in this case also serve to drive the carrier substance, the material to be ground and the grinding media into rotation. Thus, this variant also ensures that the grinding media already in the sieve chamber are kept at a distance from the sieve elements as much as possible by centrifugal forces.

In a particularly preferred embodiment of the invention, the sieve frames rotate during operation. Ideally, the rotational movement is imparted to the sieve frames by means of their being mounted on a suction pipe, which in turn also rotates. The sieve frame can either be driven separately by means of a second drive/motor, or the sieve frame is mounted on the same shaft as the mixing elements.

Thus, the sieve frames are connected to the exhaust pipe with a fixation against rotation relative to it, and the exhaust pipe is set in rotational motion. As a consequence, the sieve frames on the outer circumference (periphery) are less subject to wear due to smaller differences in the circumferential speed of the sieve frames and the grinding bodies carried away in the circumferential direction.

Due to the fact that the crushed material is introduced with a flowing carrier substance, the area between two adjacent screen frames is flushed. In this way, any crushed material that may have accumulated on the screen elements is separated from them. This is of particular importance when the screen frames are not set in rotation but remain stationary.

In another preferred embodiment of the invention, the exhaust pipe is provided with at least one equalizing channel. Through at least one equalizing channel, the carrier fluid with the material to be ground is supplied to at least one gap and discharged into it. In this case, each equalizing channel is preferably formed by a pipe located between the exhaust pipe and the central bushings and, as a rule, fixed by them. The exhaust pipe is preferably provided with several such feed channels.

The use of at least one equalizing channel with corresponding openings makes it possible to equalize the vacuum that occurs due to rotation in the gap between adjacent sieve surfaces. Through the openings and the channel, the above-mentioned gap communicates with the region of the grinding chamber closest to the shaft, as a result of which, due to this communication, material with a small content of grinding bodies can enter the said gap.

In another preferred embodiment of the invention, the individual sieve openings in the sieve element, preferably rotating with a stirring shaft, have a larger transverse dimension on the inlet side facing the flow of the discharged material to the grinding chamber than the grinding bodies.

This conical design of the sieve openings has the advantage that when the machine is switched off, the grinding bodies will not be able to get through the sieve into the discharged (unloaded) material, since in this case the grinding bodies that have penetrated the sieve opening will, under the force of gravity, slide down its inclined surface and fall back into the sieve chamber.

In another preferred embodiment of the invention, the above-mentioned sieve openings taper inward in a funnel-shaped manner.

Thus, the transverse size of the sieve openings continuously decreases, starting from their side opposite the corresponding sieve frames.

This has, firstly, the advantage that it ensures even better the above-described flat contact of the grinding bodies with the sieve openings. Secondly, it ensures that grinding bodies that have completely or partially penetrated the sieve openings cannot be retained in them. On the contrary, such grinding bodies slide or roll down the inclined surface of the sieve opening and fall out of it. In addition, in the particular case of rotating sieve elements, the movement of grinding bodies that have penetrated the sieve openings from the sieve openings is ensured by the action of centrifugal forces in combination with the inclined surfaces of the sieve openings.

In another preferred embodiment of the invention, the funnel-shaped narrowing section of the sieve opening transitions into a channel at its narrowest point. This transition is preferably abrupt. The (smallest) transverse dimension (or diameter) of such a channel is smaller than the smallest transverse dimension of the grinding bodies.

In this case, the section of the sieve opening where its transverse dimension is smaller than the average transverse dimension of the grinding bodies is located so deep inside the sieve opening that the grinding bodies have to leave their normal trajectory of movement to reach this section. Therefore, the grinding bodies reach the section of the sieve opening with this transverse dimension only after their kinetic energy has decreased and therefore do not cause significant damage to the sieve openings.

In another preferred embodiment of the invention, a partition is mounted at a distance from the outlet side of the sieve openings on the corresponding inner working surface of the sieve element. This partition is preferably designed as a shield. It is mounted on the sieve element in such a way that a gap is formed between the inner working surface of the sieve element and the partition. The flowing carrier substance with the material to be ground transported by it must pass through this gap after passing the narrowest point of the sieve opening. The gap preferably has a width that is generally smaller than the transverse dimension of the grinding bodies, in some applications it is smaller by at least 30%.

In this case, the actual separation of the fluid carrier substance and the crushed material transported by it from the grinding bodies occurs in an area in which it is possible to eliminate the abrasive effect of the grinding body that has entered the sieve opening and reached the partition on the elements of the sieve structure.

The "output side" of the sieve opening is the side of the sieve opening that, when the sieve element is mounted, faces the interior space of the sieve frame.

The "inner" working surface of the sieve element is its working surface, which, in the mounted state of the sieve element, faces the inner space of the sieve frame.

In another preferred embodiment of the invention, openings are made in the partition itself, the longitudinal axes of which run parallel to the longitudinal axis of the mill with mixing of the grinding medium. In this case, the openings in the partition and the corresponding openings in the sieve element are arranged with an offset from each other in the radial and/or circumferential direction. This offset is implemented in such a way that in order to exit the sieve opening through the opening in the partition, the fluid carrier substance with the material being ground transported by it must pass through the gap between the inner working surface of the sieve element.

In this embodiment of the invention, the actual separation of the fluid carrier substance and the ground material transported by it from the grinding bodies also occurs in a region in which it is possible to eliminate the abrasive effect of the grinding body that has entered the sieve opening and reached the partition on the structural elements of the sieve.

In principle, it can be said that in the case of a dynamic sieve design, in which its sieve frames rotate (together with the mixing shaft), the sieve openings can be larger than the transverse size of the grinding bodies. In the case of a static sieve design, in which its sieve frames do not rotate (together with the mixing shaft), but are stationary, the sieve openings must be smaller than the transverse size of the grinding bodies.

List of drawings

Fig. 1 shows a schematic representation of a mill with mixing of the grinding medium.

Fig. 2 shows a longitudinal section of the sieve of the mill with mixing of the grinding medium proposed in the invention.

Fig. 2a shows an enlarged fragment shown in Fig. 2.

Fig. 2b shows a perspective view of the unit shown in Fig. 2.

Fig. 3 shows an isometric view of the sieve frame with a sieve element mounted on it and the exhaust pipe in a disassembled state.

Fig. 4 shows a longitudinal section of the sieve of the mill with mixing of the grinding medium according to the invention, provided with a leveling channel, i.e. the sieve in the second, particularly preferred embodiment of the invention.

Fig. 4a shows a perspective view of the unit shown in Fig. 4.

Fig. 5 shows a stepped section of the sieve shown in Fig. 4.

Fig. 6 shows a fragment with sieve frames, the sieve elements of which are made with sieve openings of a special, preferably funnel-shaped, shape.

Fig. 6a shows a fragment of the left sieve frame in Fig. 6 on an enlarged scale.

Fig. 6b shows a fragment of the right sieve frame in Fig. 6 on an enlarged scale.

Fig. 7 shows a variant of the unit shown in Fig. 6, equipped with blades.

Fig. 8 shows a fragment with sieve frames having sieve 10 elements with additional partitions.

Examples of implementation of the invention

The principle of operation of the invention in various examples of its implementation is considered with reference to Fig. 2-8.

Fig. 2 shows a longitudinal section of a fragment of the mill 1 proposed in the invention with mixing of the grinding medium in the first example of its implementation, illustrating the sieve 4.

The sieve 4 is located in the sieve chamber 21. The sieve chamber 21 is formed by a section of the mixing shaft 3, which is hollow (in the form of a hollow shaft). In addition, instead of such an embodiment of the sieve chamber, a rotor cage can be fixed on the mixing shaft 3, forming the sieve chamber 21. In addition, on the side of the section of the mixing shaft 3, which forms the sieve chamber 21, facing away from the sieve 4, mixing elements 8 are preferably located. They set the grinding bodies in motion. As a result, the material to be ground, transported by the carrier substance in the direction of the sieve 4, is ground by the grinding bodies when passing the mixing elements 8.

Since the grinding bodies are set in motion by the mixing shaft 3 and the mixing elements 8 in the circumferential direction of the mixing shaft, they are in principle held at a distance from the sieve 4 by the centrifugal forces that arise in this case. In addition, the section of the mixing shaft 3 that forms the sieve chamber 21 and the grinding container 2 together form a channel through which the carrier substance and the material to be ground, as well as the grinding bodies, must pass as they move in the direction of the sieve 4. Accordingly, the supply of the grinding bodies to the sieve 4 is hindered even when the mixing shaft 3 is in a stationary state.

The sieve 4 is assembled from several sieve frames (see, in particular, the enlarged image in Fig. 2a), on each of which one or two sieve elements 12 are mounted. In this case, the sieve frames 15 are arranged parallel to each other and, by means of central bushings 17, are installed one after the other on the exhaust pipe 20.

To fix the sieve frames 15 from axial displacement, one of the sieve frames 15 in the mounted state of the sieve is adjacent to the grinding container 2. Further, between the individual sieve frames 15, distance (spacer) bushings 26 are provided. In addition, the sieve frame 15, installed on the free end of the exhaust pipe 20, is fixed by an axial retainer 29.

In a preferred embodiment, the first and last sieve frames 15 have only one sieve element 12 mounted on their respective free end faces. Each of the sieve frames 15 located between the first and last sieve frames 15 is provided with sieve elements 12 on both of its end faces.

The sieve elements 12 have sieve openings 13, as shown, in particular, in Fig. 2b. The sieve openings 13 have such transverse dimensions (dimensions in the cross-section) as to pass through themselves only the carrier substance coming from the grinding chamber 7 together with the ground material being ground. The grinding bodies do not pass through the sieve openings 13.

After the carrier substance, having passed together with the crushed material through the sieve element 12, ends up in the internal space of the sieve frame 15, it can go into the exhaust pipe 20 through the corresponding outlet openings 19 in the central bushings 17 of the sieve frames 15 and the outlet openings 27 in the exhaust pipe 20. From there, the carrier substance with the crushed material is finally removed from the grinding container 2.

Due to the fact that the sieve 4 is located in the sieve chamber 21, the grinding bodies are in principle held at a distance from the sieve 4. However, it is entirely possible for the grinding bodies to enter the sieve chamber 21 through the channel between the mixing shaft 3 forming the sieve chamber 21 and the wall of the grinding container 2. At the same time, due to the rotational movement of the section of the mixing shaft 3 forming the sieve chamber 21, the grinding bodies located in the sieve chamber 21 are also set in rotational movement around the longitudinal axis of the mixing shaft 3. In order to ensure the movement of the grinding bodies from the sieve chamber 21 under the action of the centrifugal forces arising in this case, slots 22 are provided in the section of the mixing shaft 3 forming the sieve chamber 21. Thus, the sieve elements 12 practically do not come into contact with the moving grinding bodies. This makes it possible to largely eliminate wear of the sieve elements 12 due to contact with the grinding bodies. On the outer rings 16 of the sieve frames 15, there may be increased contact with the grinding bodies if there are a sufficient number of grinding bodies in the sieve chamber 21, accumulated in the region of the gaps 22, before they can exit the sieve chamber 21 through the gaps 22 under the action of centrifugal forces. For this reason, the outer rings 16 are preferably made of a wear-resistant, often ceramic, material.

Since the individual components of the material being ground have a significantly lower weight than the grinding bodies, the centrifugal forces acting on the material being ground are insufficient to overcome the suction force acting on the sieve elements 12.

Fig. 3 shows a separate sieve frame 15 together with a sieve element 12 before its installation on the exhaust pipe 20. The sieve element 12 is shown with a partial cut-out in order to show the internal space of the sieve frame 15.

As can be seen in the drawing, the screen element is preferably designed as essentially or completely flat. The screen element is preferably designed as a disk, the working surfaces (large surfaces) of which extend completely or at least essentially in the radial direction.

The outer ring 16 of the sieve frame 15 is connected to the central sleeve 17 by means of spokes 18. Due to this, there is a lot of space in the inner space of the sieve frame 15 for the carrier substance and the crushed material passing into it through the sieve element 12. Then, through the discharge openings 19 in the central sleeve 17, which in the assembled state of the sieve frame are combined with the discharge openings 27 in the exhaust pipe 20, the carrier substance together with the crushed material can be discharged into the exhaust pipe 20.

In Fig. 4, 4a and 5 another embodiment of the invention is shown. In it, one or - most often - several equalizing channels 23 are additionally provided. The equalizing channels 23 are formed by pipes which, in the mounted state of the sieve, extend between the exhaust pipe 20 and the central bushings 17 of the sieve frames 15. The equalizing channels 23 can ensure the above-mentioned pressure equalization. For this purpose, the equalizing channels 23 have openings 30. These openings, in the mounted state of the sieve, coincide with openings 28 in the spacer bushings 26, located between the sieve frames 15.

Fig. 6-8 show various embodiments of sieve openings 13 in sieve elements 12.

As shown in Fig. 6 and 6a, at least some of the sieve openings 13 have a larger transverse dimension on the side of the sieve element 12 through which the carrier substance together with the material to be ground passes into the sieve frame 15 than on the side of the sieve element 12 facing the interior of the sieve frame 15. In this case, the transition from the larger transverse dimension to the smaller transverse dimension is preferably funnel-shaped or conical. With such an embodiment of the sieve openings 13, in addition to the material to be ground, grinding bodies can initially at least partially enter into the sieve opening 13. Accordingly, the largest transverse dimension A of the sieve opening 13 is larger than the transverse dimension of the grinding bodies. This gives the advantage that the grinding bodies cannot strike with force against the edge of the sieve opening 13, which is important for the operation of the sieve, since before that they penetrate into the corresponding sieve opening 13. The grinding bodies contact not so much the edges as the surface of the sieve opening 13, which additionally reduces wear.

In this case, the smallest transverse dimension B of the sieve opening 13, or its smallest clear cross-section, can be smaller than that of the grinding bodies, which prevents the grinding bodies from passing through the corresponding sieve opening 13. Alternatively, in the embodiment shown in Fig. 6, 6a, the aforementioned smallest transverse dimension can also be larger than that of the grinding bodies - depending on whether it is a question of the dynamic or static embodiments mentioned above.

The considered design of the sieve contributes to the fact that the grinding bodies cannot pass through the sieve openings, in particular, they cannot pass through them even when the sieve is stationary, since then, even after penetrating the sieve opening, they will slide down its inclined surface under the action of their own weight and fall out, i.e. back into the sieve chamber.

In Fig. 6 and 6a, the wear-resistant layer VSS surrounding or encircling the circumferential side surface of the sieve frame 15 is clearly visible.

In the embodiment of the sieve shown in Fig. 6, the transverse dimension of at least some or all of the sieve openings 13 also first decreases in a funnel-shaped or conical manner, starting from the side of the sieve element 12 from which the carrier substance enters the sieve frame 15, and then decreases in a stepwise manner (see Fig. 6b). From the point where the transverse dimension of the sieve opening decreases in a stepwise manner, it ultimately forms a channel 14, which has, as a rule, a constant transverse dimension. In this case, only this channel 14 has a transverse dimension smaller than the average transverse dimension, or diameter, of the grinding bodies. Accordingly, the grinding bodies can penetrate into the sieve opening 13 up to this channel 14. However, the channel 14 is located so far in the interior of the sieve opening 13 that, in order to reach this channel, the grinding body that has penetrated into the sieve opening must leave its normal path of movement. Accordingly, the grinding body reaches channel 14 only after its kinetic energy has decreased and therefore does not cause significant damage in the area of channel 14.

The example of the sieve frame design shown in Fig. 7 fully corresponds to the example shown in Fig. 6. There is only one difference between the embodiments of the invention shown in these drawings. Between the immediately adjacent sieve frames, jumpers or blades PF are provided. They are designed to create a pumping effect that ensures the movement of the grinding bodies outward, i.e. to the periphery, or facilitates such movement.

In the embodiment of the invention shown in Fig. 8 (left side), the sieve openings 13 also have a cross-section which, in particular, tapers in a funnel shape, i.e. conically, or trapezoidally. In this case, their smallest transverse dimension C or clear cross-section may be larger than the transverse dimension of the grinding bodies. In addition, on the side of the sieve element 12 facing the interior of the sieve frame 15, a partition 24 is installed, arranged in such a way as to cover the sieve openings 13. However, between the partition 24 and the sieve element 12, a spacer element 26 is located. Accordingly, between the partition 24 and the sieve element 12 there is a small "clearance", namely a gap. This gap has such a width that grinding bodies that have entered the sieve opening 13 cannot pass through it. However, the carrier substance together with the material being ground can pass through the gap into the internal space of the sieve frame 15. In this embodiment of the invention, it is also possible to eliminate the abrasive effect of the grinding body that has entered the sieve opening 13 and reached the partition 24 on the elements of the sieve structure.

In the embodiment of the invention shown in Fig. 8 (on the right side), the sieve openings 13 have a conical longitudinal cross-section. However, they can also have a constant longitudinal cross-section. In any case, a partition 24 is provided on the side of the sieve element 12 facing the interior of the sieve frame 15. It is directly adjacent to the sieve element 12 and covers the sieve openings 13. However, in this embodiment, the partition 24 has at least one opening 25, which is arranged with an offset relative to the sieve openings 13, and is otherwise preferably made completely impermeable. In the region of said offset between the sieve opening 13 and the opening 25 in the partition 24, the width of the sieve element 12 is reduced with the formation of a gap between the partition 24 and the sieve element 12. Through this gap, the carrier substance can pass into the interior of the sieve frame 15 together with the material to be ground. The grinding bodies cannot pass through this gap. In this case, it is also possible to eliminate the abrasive effect of the grinding bodies that have entered the sieve opening 13 and reached the partition 24 on the elements of the sieve structure.

Other

At the present time, protection may also be sought, if necessary, in relation to the following set of features, in the form given below or supplemented by additional technical features disclosed in the description and/or in the drawings, and/or supplemented by individual or all features of one or more dependent claims in the current version of the claims, despite their reference to claim 1 of the claims in its current version:

A mill with agitation of the grinding medium, in particular a bead mill, comprising a grinding container in which a stirring shaft is mounted so as to rotate, preferably carrying stirring elements, with the formation between the stirring shaft and the wall of the grinding container of a grinding chamber, into which the material to be ground is introduced, transported by a flowing carrier substance, as a rule in the form of a suspension, wherein the grinding chamber is partially filled with grinding bodies, and the material to be ground transported by the flowing carrier substance together with the carrier substance itself is discharged through a sieve 4, which retains the grinding bodies entering the region of the sieve 4, wherein the sieve 4 either consists of only one sieve element, ideally extending substantially radially or, in particular, obliquely, which makes it possible to dispense with the use of a sieve element forming a side surface extending along the circumference; or consists essentially of several, preferably at least ten, sieve elements arranged one after the other along the longitudinal axis L of the bead mill 1 with the possibility of parallel passage of the material discharged from the mill through them.

List of reference designations:

1 stirring mill/bead mill

2 grinding container

3 mixing shaft

4 separation system / sieve

5 entrance

6 exit

7 grinding chamber

8 mixing elements

9 electric motor

10 belt drive

11th building

12 sieve element

13 sieve holes

14 channel sieve hole

15 sieve frame

16 outer ring of the sieve frame

17 central bushing

18 spokes

19 drain holes in the center bushing

20 exhaust pipe

21 sieve chamber

22 rotor hole/slot

23 equalizing channel

24 partition

25 hole in the partition

26 spacer element / spacer sleeve

27 outlet holes in the exhaust pipe

28 feed hole in spacer sleeve

29 axis lock

30 holes in the alignment channel

VSS wear layer

A largest clear cross-section / cross-sectional dimension of the sieve opening 13

B smallest clear cross-section / cross-sectional dimension of sieve opening 13

C clear cross-section / cross-sectional dimension of sieve opening 13

PF blade

L is the longitudinal axis of the mill, the axis of rotation.

Claims (20)

1. A mill (1) with mixing of the grinding medium, comprising a grinding container (2) in which a mixing shaft (3) is mounted with the possibility of rotation to form a grinding chamber (7) between the mixing shaft (3) and the wall of the grinding container (2), into which the material to be ground, transported by a fluid carrier substance, is introduced, and which is partially filled with grinding bodies driven by a rotating mixing shaft (3) to ensure grinding of the material to be ground, carried by the fluid carrier substance through the grinding chamber (7), wherein the material to be ground, transported by the fluid carrier substance, together with the carrier substance itself, is discharged through a sieve (4) that retains the grinding bodies entering the area of the sieve (4), wherein the sieve (4) comprises several sieve elements (12) arranged one behind the other along the longitudinal axis of the mill (1) with the possibility of parallel passage of the material discharged from the mill through them, wherein the working surfaces of the sieve elements (12), facing the flow of the discharged material to the grinding chamber (7), extend obliquely or radially with respect to the axis of rotation of the mixing shaft (3), characterized in that the sieve elements are mounted on several sieve frames (15), located one after the other at a distance from each other along the axis of rotation of the mixing shaft, and the sieve frames (15) forming the sieve (4) are located in the sieve chamber (21), located in the mixing shaft (3). 2. The mill (1) according to claim 1, characterized in that each sieve element (12) forms the end surface of a sieve frame (15) closed in the circumferential direction, and each sieve element (12) preferably consists of steel, in particular stainless steel. 3. The mill (1) according to item 2, characterized in that it contains sieve frames (15), both end surfaces of which are formed by sieve elements (12). 4. A mill (1) according to one of the previous paragraphs, characterized in that it contains sieve frames (15) with an outer ring (16) having a closed side surface running along the circumference. 5. The mill (1) according to item 4, characterized in that the outer ring (16) consists of ceramics, or its circumferential side surface has a wear-reducing coating, in particular a ceramic coating. 6. A mill (1) according to item 4 or 5, characterized in that the outer ring (16) of the sieve frame (15) is connected by spokes (18) to the central sleeve (17) of the sieve frame (15). 7. The mill (1) according to claim 6, characterized in that at least one discharge opening (19), preferably several discharge openings (19), is made in the central sleeve (17) of the sieve frame (15) for discharging the flowing carrier substance and the crushed material carried by it. 8. A mill (1) according to one of the previous paragraphs, characterized in that the sieve frames (15) are installed on an exhaust pipe (20) designed with the possibility of removing the flowing carrier substance and the crushed material transported by it from the sieve frame (15). 9. A mill (1) according to one of the preceding claims, characterized in that at least six sieve frames (15), preferably at least ten, and even more preferably at least fifteen, sieve frames (15) are arranged one after the other along the longitudinal axis. 10. A mill (1) according to one of the previous paragraphs, characterized in that the grinding chamber (7) is connected to the sieve chamber (21) through rotor openings (22), preferably made in the form of slits (22), the axes of the main extensions of which run parallel to the longitudinal axis. 11. A mill (1) according to one of the previous points, characterized in that during its operation the sieve frames (15) rotate, in particular due to the fact that they are mounted on a rotating exhaust pipe (20). 12. The mill (1) according to claim 11, characterized in that the exhaust pipe (20) is provided with at least one equalizing channel (23), preferably several equalizing channels (23), through which or which the fluid carrier substance with the material to be ground is supplied to at least one gap and discharged into it, wherein each equalizing channel (23) is preferably formed by a pipe located between the exhaust pipe (20) and the central bushings (17) and, in particular, fixed by them. 13. A mill (1) according to one of the preceding paragraphs, characterized in that the individual sieve openings (13) in the sieve element (12), preferably rotating with the mixing shaft (3), have, on the input side facing the flow of the discharged material to the grinding chamber (7), a larger transverse dimension than the grinding bodies. 14. The mill (1) according to item 13, characterized in that the above-mentioned sieve openings (13) are funnel-shaped and narrow inward. 15. The mill (1) according to claim 14, characterized in that the funnel-shaped narrowing section of the sieve opening (13) in its narrowest place passes, preferably abruptly, into a channel (14), the transverse dimension of which is smaller than the transverse dimension of the grinding bodies. 16. The mill (1) according to one of claims 13-15, characterized in that on the outlet side of the sieve openings (13) on the corresponding inner working surface of the sieve element (12) a partition (24) is installed located at a distance from it, preferably made in the form of a shield with the formation between the inner working surface of the sieve element (12) and the partition (24) of a gap, through which, after passing the narrowest point of the sieve opening (13), the fluid carrier substance with the material being ground transported by it must pass, wherein the gap preferably has a width that is at least 30% smaller than the transverse dimension of the smallest grinding body. 17. The mill (1) according to claim 16, characterized in that in the partition (24) itself there are holes (25), the longitudinal axes of which run parallel to the longitudinal axis of the mill (1), wherein the holes (25) in the partition (24) and the corresponding holes (13) in the sieve element (12) are located with an offset from each other in the radial and/or circumferential direction, as a result of which, in order to exit the sieve hole (13) through the hole (25) in the partition (24), the fluid carrier substance with the material being ground transported by it must pass through the gap between the inner working surface of the sieve element (12) and the partition (24), wherein the gap preferably has a width at least 30% smaller than the transverse dimension of the smallest grinding body. 18. A mill (1) according to one of paragraphs 1-17, characterized in that it is made in the form of a bead mill. 19. A mill (1) according to one of paragraphs 1-18, characterized in that the mixing shaft (3) is designed to carry mixing elements (8). 20. A mill (1) according to one of paragraphs 1-19, characterized in that the material to be ground, transported by a fluid carrier substance, is introduced into the grinding chamber (7) in the form of a suspension.

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