Patent Description:
Grinding processes have already been used for more than half a century in the ceramics, pigment, paint, paper and pharmaceutical industry. In such a process, coarse slurry particles are introduced into a specified device in which these coarse slurry particles are ground, usually in the presence of grinding media like ceramic grinding beads, in order to obtain a finer product particle size of the slurry. The grinding of the mineral slurry is carried out by mixing the introduced slurry and the grinding beads or media using grinding discs which are mounted on a mill shaft within a chamber. In particular, the mineral slurry is conveyed through the chamber and the coarse particles in the slurry are ground during conveyance within the chamber so as to obtain a refined mineral slurry at the outlet of the chamber. Such devices for grinding slurry are also called mills. An example of a grinding disc for a mill is disclosed in <CIT>. Classical mills however do not allow for using the total potential power of the rotor on which the discs are mounted, thus achieving only lower power input and lower feed rates. Furthermore, it is highly desirable to extend the lifetime of the rotor discs. In particular, the component lifetime depends on the application type and the imposed stress on the rotor discs.

The power input of a stirred media mill is directly influenced by stirrer revolutions per minute. An optimum setting of speed will assist in prolonging the lifetime of the rotor discs. There might be a particular need for rotor discs which are running at a lower speed effectively decreasing shear forces between discs and grinding media. Furthermore, there might be a need to save a considerable amount of material and labour for operating such mills or devices for grinding slurry. Not least, there might be a need to provide a cheaper disc with respect to the effort of maintenance and service requirements.

It is an object of the present invention to provide an improved grinding of mineral slurries.

This object is achieved by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

According to a first aspect of the present invention, a circular disc element is provided. The circular disc element comprises at least two beam elements each beam element extending beyond an outer circumference of the circular disc element in an extension direction which is parallel to a radial direction of the disc element. It is also possible that the extension direction is radially extending with respect to the disc element, i.e. the extension direction is congruent to the radial direction. The circular disc element further comprises at least two holes extending through the circular disc element in a longitudinal direction which is substantially perpendicular to each of the extension directions of the at least two beam elements. For example, the longitudinal direction is substantially perpendicular to the radial direction of the disc element. In particular, the at least two holes may extend through the circular disc element in a longitudinal, rotationally symmetric axial direction which is substantially perpendicular to each of the extension directions of the at least two beam elements. The at least two beam elements are equidistantly spaced apart from each other with respect to a circumferential direction of the circular disc element, which circumferential direction corresponds to the outer circumference of the circular disc element.

The circumferential direction may be measured along the circumference of the circular disc element. Along this circumferential direction, the at least two beam elements are spaced apart from each other in an equidistant manner. This means that in case of two beam elements, the angle between each beam element amounts to <NUM>°. In case of three beam elements, the angle between each beam element with respect to the circumferential direction amounts to <NUM>°. However, in a preferred embodiment, the circular disc element comprises exactly four beam elements such that the angle between each beam element with respect to the circumferential direction amounts to <NUM>°. According to other embodiments of the present invention, the circular disc element comprises five or more and up to twelve, i.e. five to twelve beam elements.

The circular disc element may also be called a hybrid disc since the beam elements which extend beyond the outer circumference of the circular disc element are connected in an adjustable manner to the circular disc element. Such a hybrid disc in a stirred media mill, e.g. in a device for grinding slurry, which will be described hereinafter, provides the possibility of having a higher power input and an enhanced slurry throughput. For example, wet mineral slurry, in particular calcium carbonate slurry, may be advantageously ground using inventive circular disc elements. Based on such a circular disc element, the bypass flow will be reduced and, additionally, the product quality will be improved since less retains, e.g. coarse particles, remain in the ground slurry. Furthermore, the inventive circular disc element provides for less recirculation, a higher power draw at lower rotational speeds of the circular disc element(s) within the mill and an increased efficiency of the operation of a stirred media mill, e.g. a device for grinding slurry containing grinding media, like ceramic grinding beads.

The circular disc element may for instance be attached to a rotational shaft within a chamber of said mill, which is also defined as a device for grinding slurry hereinafter. The hybrid disc, e.g. the circular disc element, is a combination of a centre disc section and agitating arms. The agitating arms are defined as the beam elements, which extend beyond the outer circumference of the circular disc element. The centre disc section is defined as the circular disc element itself. By means of the centre disc section, e.g. the circular disc element, the unintended bypass flow along the rotational shaft can be reduced. Due to a high power input, the hybrid disc can be operated at lower rotational speed. As a result, the inventive circular disc element allows for improving vertical mill operations and maximizing the throughput of slurry within the stirred media mill.

The centre disc section of the hybrid disc, e.g. the circular disc element, comprises at least two beam elements, which may be connected to the circular disc element, e.g. the centre disc, by means of a key connection or a key joint. The outer circumference of the circular disc element may have a circular shape limiting the circular disc element in the radial direction. The circular disc element may have a flat shape, wherein the thickness of the circular disc element is much smaller than the lateral extension of the circular disc element in the radial direction. In other words, the term "flat circular disc element" should be understood as a circular disc element with a diameter measured in the radial direction of the circular disc element that is much greater than the thickness of the circular disc element in the longitudinal direction. For example, the ratio between diameter and thickness is between <NUM> and <NUM> and preferably between <NUM> and <NUM>.

Through the circular disc element, at least two holes, in particular through-holes, extend in the longitudinal direction. The at least two holes may be arranged on the circular disc element in such a manner that the holes are equidistantly spaced apart from each other with respect to the circumferential direction of the circular disc element. There may be a space or distance between the at least two holes and the centre point of the circular disc element. However, there may be a further hole within the circular disc element at its centre for receiving a rotational shaft of the device for grinding slurry described hereinafter. The at least two holes extending through the circular disc element may for instance be steam holes which are required to ensure a stable operation of the mill. In particular, steam bubbles which would disturb the grinding operation by inhomogeneity of the grinding media conditions in the grinding zone can be kept away from the main grinding zone.

The circular disc element, which may be imagined as a flat shaped circular disc may have cutting sections or cut-out sections which form recesses at the circumference of the circular disc element. In these cut-out sections, the beam elements may be attached to the circular disc element. This aspect will be described in more detail in the description of the figures.

The beam elements have an extension direction, which is parallel to a radial direction of the disc element, wherein the radial direction starts at the centre point of the circular disc element. In other words, there is an offset between the extension directions of the beam elements and the radial directions of the circular disc element. However, the term "parallel" does also include that the extension directions of the beam elements are congruent to respective radial directions of the disc element. In particular, the beam elements may also extend beyond the outer circumference of the circular disc element in a radial direction of the circular disc element. In this case, there is no offset between the extension direction of the beam element and the radial direction of the disc element.

Where the term "comprising" is used in the present description and claims, it does not exclude other non-specified elements of major or minor functional importance. For the purposes of the present invention, the term "consisting of" is considered to be a preferred embodiment of the term "comprising of". If hereinafter a group is defined to comprise at least a certain number of embodiments or elements, this is also to be understood to disclose a group, which preferably consists only of these embodiments or elements.

Terms like "obtainable" or "definable" and "obtained" or "defined" are used interchangeably. This e.g. means that, unless the context clearly dictates otherwise, the term "obtained" does not mean to indicate that e.g. an embodiment must be obtained by e.g. the sequence of steps following the term "obtained" even though such a limited understanding is always included by the terms "obtained" or "defined" as a preferred embodiment.

The beam elements and the holes should be arranged such that the disc is in balance (any imbalance should preferably be avoided). Therefore, it is preferred according to the present invention that the number of extending beam elements "n" is even and at least <NUM> (n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM> etc.), while the number of the holes "m" correlates with the number of the beam elements "n" in that m = k * <NUM>. 5n, k being <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> or the number of extending beam elements "n" is uneven (n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM> etc.), while the number of the holes "m" correlates with the number of the beam elements "n" in that m = k * n, k being <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> or that the number of beam elements "n" is <NUM>, while the number of holes "m" correlates with the number of the beam elements "n" in that m = k * n, k being <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. For example, the inventive disc may have <NUM> extending beam elements and <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and up to <NUM> holes or e.g. <NUM> beam elements and <NUM> or <NUM> (or more) holes or <NUM> beam elements with <NUM>, <NUM>, <NUM> or more holes. According to an embodiment of the invention, the number of extending beam elements is equal to the number of holes extending through the circular disc element.

In a preferred embodiment, four beam elements are attached to the circular disc element and extend beyond the outer circumference of the circular disc element. In this preferred embodiment, also four holes are located on the circular disc element such that these four holes extend through the circular disc element in the longitudinal direction. According to other embodiments of the present invention, the circular disc element may comprise five or more, preferably five to eight and up to twelve, i.e. five to twelve beam elements. The corresponding five to twelve, preferably five to eight beam elements correspondingly may have five to twelve, preferably five to eight holes being located on the circular disc element such that these holes extend through the circular disc element in the longitudinal direction. The axis of the holes may be parallel to an axis of the circular disc element, which axis of the circular disc element goes through the centre point of the circular disc element.

According to another embodiment of the invention, the at least two holes and the at least two beam elements are arranged in an alternate manner on the circular disc element with respect to the circumferential direction.

This means that in case of four beam elements and four holes at the circular disc element, the angle between each beam element amounts to <NUM>° and the angle between each hole also amounts to <NUM>° with respect to the circumferential direction. Between two extending beam elements, one hole is arranged on the circular disc element with respect to the circumferential direction. Analogously, one extending beam element is arranged between two holes on the circular disc element with respect to the circumferential direction.

According to another embodiment of the invention, each of the at least two holes is equidistantly arranged between the at least two beam elements with respect to the circumferential direction.

This means that in case of four holes and four extending beam elements, the angle between each hole amounts to <NUM>° with respect to the circumferential direction and the angle between each extending beam element amounts to <NUM>° with respect to the circumferential direction. Furthermore, in case of four holes and four extending beam elements, the angle between a beam element and a neighbouring hole amounts to <NUM>° in the circumferential direction. However, in the preferred embodiment, the holes and the extending beam elements are arranged in an alternate manner on the circular disc element with respect to the circumferential direction. This aspect will be described in more detail in the description of the figures.

According to another embodiment of the invention, the extension of the at least two beam elements in the longitudinal direction is greater than the extension of the circular disc element in the longitudinal direction. In other words, the at least two beam elements have a thickness measured along the longitudinal direction which is greater than the thickness of the circular disc element which is also measured along the longitudinal direction. This means that the at least two beam elements protrude from abutting surfaces of the circular disc element in a region in which the extending beam elements overlap with the circular disc element, e.g. in a region in which the extending beam elements do not extend beyond the outer circumference of the circular disc element. In particular, there may be two sections of the extending beam elements, wherein in a first section of the extending beam elements, the extending beam elements do not extend beyond the outer circumference of the circular disc element and therefore overlap with the circular disc element whereas in a second section of the extending beam elements, the extending beam elements extend beyond the outer circumference of the circular disc element and therefore protrude beyond the outer circumference of the circular disc element in the extension direction or in the radial direction of the circular disc element.

According to another embodiment of the invention, the extension of the at least two beam elements in the longitudinal direction is adjustable.

In particular, the at least two beam elements are height-adjustable in the longitudinal direction. It is possible that the adjustment of the extension of the at least two beam elements in the longitudinal direction is carried out by a manual change of the at least two beam elements. However, it is also possible that the adjustment of the extension of the at least two beam elements in the longitudinal direction is carried out by a variation of the shape of the at least two beam elements which are attached to the circular disc element. This is especially the case if the beam element forms a part of the disc, for example if the circular disc element and the beam elements are manufactured by iron casting. In other words, the term "adjustable" means not necessarily immediate adjustments but also such adjustments, which result from the production of circular disc elements with different beam shapes.

The beam elements and the circular disc element are separately manufactured wherein it is possible that the beam elements are releasably connected to the circular disc element.

According to another embodiment of the invention, the circular disc element further comprises an inner circumference which is defined by a curved fitting surface, wherein the circular disc element is attachable to a rotational shaft by means of a force-fit connection or a form-fit connection.

Such a force-fit connection or a form-fit connection may provide a reliable fit of the circular disc element on the rotational shaft. For example, the circular disc element may be attached to the rotational shaft by means of a fitting key. However, it is also possible that the circular disc element may be attached to the rotational shaft by means of a welded or soldered connection. However, it is preferred that the circular disc element is attached to the rotational shaft by means of a releasable connection.

The circular disc element may further comprise a sleeve element or a sleeve in the region of the inner circumference, wherein the sleeve element protrudes from the abutting surfaces of the circular disc element in the longitudinal direction. In particular, the sleeve element which is located at the inner circumference of the circular disc element is thicker than the remaining region of the circular disc element such that a better force-fit connection or form-fit connection to the rotational shaft can be achieved. In particular, a better stability of this connection to the rotational shaft can be achieved.

According to another embodiment of the invention, the length with which the at least two beam elements extend beyond the outer circumference of the circular disc element is adjustable.

In particular, the second section of the beam elements, e.g. the section of the beam element which extends beyond the outer circumference of the circular disc element is adjustable. The adjustment may be carried out by a manual change of the length of the beam elements, for example by shifting the beam elements into another position. However, it is also possible that the adjustment may be carried out by manufacturing beam elements with different beam lengths.

According to another embodiment of the invention, the diameter of the at least two holes extending through the circular disc element is adjustable. The adjustment of the diameter of the at least two holes may be carried out by the attachment of specified plates to the circular disc element, wherein the specified plates each have a hole with a different diameter. In this manner, a manual adjustment of the diameter of the at least two holes in the circular disc element can be achieved. This aspect will also be described in more detail in the description of the figures.

According to another embodiment of the invention, the at least two beam elements are attached to the circular disc element by means of a connection selected from the group consisting of a force-fit connection, a form-fit connection, a key connection, an adhesive connection, a welded connection and a soldered connection.

In a preferred embodiment, the at least two beam elements are attached to the circular disc element by means of a key connection or a key joint. In particular, the preferred embodiment comprises four beam elements which are attached to the circular disc element by means of a key connection. The connection, in particular the key connection, may be located at a cut-out section of the circular disc element. The cut-out sections at which the beam elements are mounted to the circular disc element may form recesses on the outer circumference of the circular disc element.

According to another embodiment of the invention, the circular disc element comprises three, four, five, six, seven or eight beam elements. According to another embodiment of the invention, the circular disc element comprises three, four, five, six, seven or eight holes. However, in a preferred embodiment of the invention, the circular disc element comprises exactly four beam elements and exactly four holes, which are arranged in an alternate manner as described above.

According to another aspect of the present invention, a use of the circular disc element described above as grinding means in a grinding process is provided. "Grinding means" according to the present invention are means which support the grinding process, i.e. which support the grinding of e.g. a mineral slurry in the presence of grinding beads.

In particular, the circular disc element described above is used in a device for grinding slurry, in particular wet mineral slurry. It is possible that a combination of the inventive circular disc element and other grinding discs, which have a different shape is used as grinding means in a grinding process. In particular, different types of grinding discs including the inventive circular disc element can be used as a grinding means in a grinding process. The grinding process may be described as a process in which wet mineral slurry is fed into a grinding device as described herein yielding a particulate slurry with lower or reduced particle size. The mineral slurry may for instance be a calcium carbonate slurry.

According to another aspect of the present invention, a device for grinding slurry is provided. The device comprises an elongated chamber having a rotational shaft extending between a first end and a second end of the elongated chamber. The at least one circular disc element described above is attached to the rotational shaft between the first end and the second end of the chamber such that slurry is ground within the chamber when the slurry is conveyed from the first end to the second end of the chamber.

In particular, the device for grinding slurry, e.g. the stirred media mill, is fed with grinding media, in particular ceramic beads, in a size range from <NUM> to <NUM>, depending on the desired product fineness. The beam elements of the circular disc element agitate and accelerate the media or beads within the chamber. The grinding takes place mainly between the beads and an inner wall or an inner surface of the chamber and between the beads themselves. The beam elements however provide for a more efficient acceleration of the media or beads as compared to only a flat disc without beam elements. This in turn provides for an improved throughput of mineral slurry through the chamber. Furthermore, the circular disc element reduces the bypass flow along the shaft in the longitudinal direction, e.g. in the axial direction of the shaft. In this manner, a reduction of the amount of coarse particles in the product can be achieved. This in turn provides for an improved product quality.

The slurry to be ground is introduced into the preferably vertically arranged, elongated chamber at a bottom part of the elongated chamber. Afterwards, the introduced slurry is conveyed through the elongated chamber in an upward direction such that the ground slurry can be discharged from the elongated chamber at a top part of the elongated chamber. During the conveyance of the slurry through the elongated chamber, coarse particles of the slurry are refined such that the product, e.g. the refined slurry, can be discharged at the top part of the elongated chamber. Within the elongated chamber, a rotational shaft rotates such that the circular disc element or the circular disc elements, which is/are attached to the rotational shaft also rotate(s). The rotating circular disc elements with the extending beam elements accelerate the beads and reduce the bypass flow along the shaft while rotating. The required product particle size may be obtained by adjusting the feed rate, the slurry concentration, the amount of grinding media or beads and/or the speed of the milling shaft.

It is possible that a combination of the inventive circular disc element and other rotating discs on the rotational shaft are used to grind the slurry within the elongated chamber.

According to an embodiment of the invention, a plurality of circular disc elements is attached to the rotational shaft between the first end and the second end of the chamber such that slurry is ground within the chamber when the slurry is conveyed from the first end to the second end of the chamber.

In particular, the inventive circular disc elements are arranged in juxtaposition or in a consecutive manner within the elongated chamber. Therefore, the introduced slurry to be ground passes several, in particular all of the plurality of circular disc elements arranged within the elongated chamber. It is possible that the plurality of circular disc elements is combined with a plurality of other disc elements which have a different shape within the elongated chamber.

It should be understood that the first end of the elongated chamber comprises the inlet of the chamber in which the slurry to be ground is fed into the elongated chamber and the second end comprises the outlet of the chamber in which the ground slurry or refined slurry is discharged from the elongated chamber.

According to another embodiment of the invention, a plurality of protruding elements is attached to an inner surface of the chamber wherein each of the plurality of protruding elements protrudes into the elongated chamber such that a part of each of the plurality of protruding elements is arranged between two respective circular disc elements.

In particular, an alternate arrangement of protruding elements and circular disc elements is realized within the elongated chamber. The protruding elements may also have the shape of a disc with a central through-hole through which the rotational shaft of the device for grinding slurry extends. However, the protruding elements and the rotational shaft are not connected. There is rather a distance between them, which allows a conveyance of the slurry through the chamber. A protruding element is, therefore, attached to an inner wall or in a surface of the elongated chamber via its outer circumference. Therefore, the rotating circular disc element is attached to the rotational shaft wherein the protruding elements are attached to the elongated chamber. The protruding elements protrude into the elongated chamber perpendicular to the longitudinal direction of the rotational shaft or the longitudinal direction of the circular disc element. There may be a region of the circular disc element, in particular the beam elements of the circular disc element, in which the beam elements overlap with the protruding elements when looking into the longitudinal direction. In other words, a part of each of the plurality of protruding elements is arranged between two respective circular disc elements, e.g. between two respective beam elements extending beyond the outer circumference of the circular disc element. However, there is no direct connection between the beam elements and the protruding elements.

According to another aspect of the present invention, a method for grinding a mineral slurry is provided. In a step of the method, a slurry is fed into an elongated chamber having a rotational shaft extending between a first end and a second end of the elongated chamber. In a second step, at least one circular disc element as described above is rotated within the elongated chamber, wherein the at least one circular disc element is attached to the rotational shaft extending between the first end and the second end of the chamber. In another step of the method, the slurry is ground within the chamber when the slurry is conveyed from the first end to the second end of the chamber.

The circular disc element, in particular the extending beam elements of the circular disc element, accelerate the slurry within the chamber such that beads of the slurry interact with an inner surface or inner wall of the chamber resulting in a refinement of the mineral slurry. Furthermore, an interaction between the beads and the slurry themselves also leads to a refinement of the slurry during conveyance of the slurry through the chamber. After grinding the slurry within the chamber, it is discharged from the second end of the chamber, in particular at the outlet of the chamber which is arranged at a top part of the chamber such that the discharged ground slurry can be used for further processing.

<FIG> shows a circular disc element <NUM> with extending beam elements <NUM>, wherein the extending beam elements <NUM> extend beyond an outer circumference <NUM> of the circular disc element <NUM>. The circular disc element <NUM> further comprises holes <NUM>, in particular through-holes, which extend through the circular disc element <NUM>. The circular disc element <NUM> further comprises a further hole or a central hole <NUM> for receiving a rotational shaft not shown in <FIG>. In other words, the circular disc element <NUM> comprises an inner circumference <NUM>, which limits the central hole <NUM>. Therefore, the circular disc element <NUM> comprises a curved fitting surface <NUM> with a circular shape at the inner circumference <NUM> of the circular disc element <NUM>.

The holes <NUM> may have the function of steam holes, which are arranged at a specified distance to the centre of the circular disc element <NUM>. In <FIG>, each of the holes <NUM> are spaced apart from the centre of the circular disc element <NUM> with the same distance.

The beam elements <NUM> are attached to the circular disc element <NUM> in such a manner that the extending beam elements <NUM> extend beyond the outer circumference <NUM> of the circular disc element <NUM>. In particular, the extending beam elements <NUM> can be divided into two sections, wherein a first section of the beam elements <NUM> overlaps with the circular disc element <NUM> and another section, e.g. a second section with a length <NUM> of the extending beam elements <NUM>, extends beyond the outer circumference <NUM> of the circular disc element <NUM> and therefore does not overlap with the circular disc element <NUM>.

The extending beam elements <NUM> are spaced apart from each other in an equidistant manner with respect to a circumferential direction <NUM> of the circular disc element <NUM>. The embodiment of <FIG> shows the arrangement of six extending beam elements <NUM>, which are attached to the circular disc element <NUM>. In this case, the angle between each of the extending beam elements <NUM> with respect to the circumferential direction <NUM> amounts to <NUM>°.

Between each of the extending beam elements <NUM>, one hole <NUM> is arranged. In other words, the holes <NUM> and the beam elements <NUM> are arranged on the circular disc element <NUM> in an alternate manner. It is possible that the angle in the circumferential direction <NUM> between each hole <NUM> and each beam element <NUM> is the same. Therefore, the holes <NUM> and the extending beam elements <NUM> are equidistantly arranged on the circular disc element <NUM> in an alternate manner with respect to the circumferential direction <NUM>.

The extending beam elements <NUM> extend in a radial direction, wherein the radial direction is congruent to the extension direction <NUM> of the beam elements <NUM>. <FIG> therefore shows the simplest embodiment of the inventive circular disc element <NUM> in which the beam elements <NUM> extend along the radial directions of the circular disc element <NUM>.

<FIG> shows the arrangement of two circular disc elements <NUM> on a rotational shaft <NUM>, wherein the circular disc elements <NUM> are attached to the rotational shaft <NUM> by means of a force-fit connection or a form-fit connection. Preferably, the attachment of the circular disc elements <NUM> to the rotational shaft <NUM> is provided by a fitting key connection.

<FIG> also shows a part of a chamber <NUM> of a device for grinding slurry, wherein protruding elements <NUM> protrude into the elongated chamber <NUM>. The elongated chamber <NUM> of which only a part is shown in <FIG> extends along the longitudinal direction <NUM>. Furthermore, the rotational shaft <NUM> also extends along the longitudinal direction <NUM> such that the circular disc elements <NUM> are attached to the rotational shaft <NUM> in juxtaposition.

The protruding elements <NUM> may be imagined as circular disc elements, which are attached to the chamber <NUM> via their outer circumference. In other words, the protruding elements <NUM> are attached to the static chamber <NUM> and the circular disc elements <NUM> are attached to the rotational shaft <NUM>. Thus, the circular disc elements <NUM> are rotating within the static chamber <NUM> in order to accelerate beads of the slurry to be conveyed through the chamber <NUM>. A moving path <NUM> of the slurry, e.g. the beads of the slurry, is also shown in <FIG>. The beam elements <NUM> of the circular disc element <NUM>, which are also called agitating arms, accelerate the beads within the chamber <NUM> such that a refinement of the beads can be achieved by the interaction between the beads themselves and between the beads and an inner wall or an inner surface of the chamber <NUM>. A grinding zone <NUM> is also shown in <FIG>. This grinding zone <NUM> shows the region in which the beads are ground or refined with the help of the extending beam elements <NUM>, the inner wall of the chamber <NUM> and the protruding elements <NUM>.

<FIG> shows a top view of a circular disc element <NUM> without beam elements <NUM>. This figure clarifies that the circular disc element <NUM> comprises cut-out sections <NUM>, e.g. cutting sections, at its outer circumference, wherein the cut-out sections <NUM> provide a region for receiving the extending beam elements <NUM> not shown in <FIG>. In a preferred embodiment, the circular disc element <NUM> comprises exactly four cut-out sections <NUM> for receiving exactly four extending beam elements <NUM>.

The circular disc element <NUM> comprises an outer circumference <NUM> which limits the outer diameter of the circular disc element itself. The diameter of the circular disc element <NUM> may be between <NUM> and <NUM>. Preferably, the diameter of the circular disc element <NUM> is about <NUM>. The circular disc element <NUM> comprises a central hole <NUM>, wherein the central hole <NUM> is defined by the inner circumference <NUM>. The inner circumference <NUM> however is defined by a curved fitting surface <NUM> which is adapted for receiving the rotational shaft <NUM> not shown in <FIG>. The circular disc element <NUM> comprises a sleeve element <NUM> which is arranged at the inner circumference <NUM> of the circular disc element <NUM> and which forms a region that is thicker than the remaining part of the circular disc element <NUM> with respect to the longitudinal direction. This aspect can be seen in <FIG>, which shows that the sleeve element <NUM> has a greater extension in the longitudinal direction <NUM> of the circular disc element <NUM> than the remaining part of the circular disc element <NUM>.

The circular disc element <NUM> comprises a radial direction <NUM>, which has its origin in the centre point of the circular disc element <NUM>. In particular, the circular disc element <NUM> has several radial directions <NUM>, which have their origin in the centre point of the circular disc element <NUM>. The circumferential direction <NUM> is measured along the outer circumference <NUM> of the circular disc element <NUM>.

Through-holes <NUM> are located on the circular disc element <NUM>. The holes <NUM> may have a diameter <NUM>, which is adjustable. Holes <NUM> are arranged in an equidistant manner with respect to the circumferential direction <NUM> on the circular disc element <NUM>. Analogously, the cut-out sections <NUM> located at the outer circumference <NUM> of the circular disc element <NUM> are also arranged in an equidistant manner at the circular disc element <NUM> with respect to the circumferential direction <NUM>.

<FIG> shows an isometric view of a circular disc element <NUM> having four extending beam elements <NUM> in the region of the cut-out sections <NUM> of the circular disc element <NUM>. The extending beam elements <NUM> extend beyond the outer circumference <NUM> of the circular disc element <NUM>. Furthermore, four holes <NUM> are arranged on the circular disc element <NUM>. The beam elements <NUM> are equidistantly spaced apart from each other along the circumferential direction <NUM> and the holes <NUM> are also equidistantly spaced apart from each other on the circular disc element <NUM>. The isometric view in <FIG> also shows that the sleeve element <NUM> at the inner circumference <NUM> of the circular disc element <NUM> has a greater thickness than the remaining part of the circular disc element <NUM>. The sleeve element <NUM> provides at its inner circumference <NUM> a curved fitting surface <NUM>, which is adapted for receiving the rotational shaft <NUM> not shown in <FIG>. Therefore, the circular disc element <NUM> provides in the region of the sleeve element <NUM> a central hole <NUM> through the circular disc element <NUM> in the longitudinal direction <NUM>. The holes <NUM> which are spaced apart from the centre point of the circular disc element <NUM> also extend in the longitudinal direction <NUM> or parallel to the central axis of the circular disc element <NUM>.

<FIG> shows a top view of the circular disc element <NUM> as shown in <FIG>. From <FIG>, the equidistant arrangement of the holes <NUM> with respect to the circumferential direction <NUM> can be recognized. Analogously, the equidistant arrangement of the extending beam elements <NUM> with respect to the circumferential direction <NUM> can also be recognized in <FIG>.

In contrast to the embodiment shown in <FIG>, the extension directions <NUM> of the beam elements <NUM> are spaced apart from the radial directions <NUM> of the circular disc element <NUM>. However, the extension directions <NUM> of the beam elements <NUM> are arranged in a parallel manner to the radial directions <NUM> of the circular disc element <NUM>. In this aspect, the circular disc element <NUM> shown in <FIG> is different from the embodiment as shown in <FIG>. However, the embodiment of the circular disc element <NUM> shown in <FIG> also comprises an alternate arrangement of the holes <NUM> and the beam elements <NUM> with respect to the circumferential direction <NUM> of the circular disc element <NUM>.

<FIG> also shows that the extending beam elements <NUM> overlap with the circular disc element <NUM> in a first section and extend beyond the outer circumference <NUM> of the circular disc element <NUM> in a second section. The extending beam elements <NUM> are connected with a key connection <NUM> to the circular disc element <NUM> in the region of the first section of the beam elements <NUM>, i.e. in the overlapping region of the beam elements <NUM> and the circular disc element <NUM>.

<FIG> also shows attachment means <NUM>, for example in the form of attachment holes nearby the holes <NUM>. These attachment means <NUM> may be configured for attaching plates to the circular disc element <NUM>, wherein the plates are not shown in <FIG>. The plates which are described in <FIG> may be configured to adapt the diameter of the holes <NUM> on the circular disc element <NUM>.

<FIG> shows a side view of a beam element <NUM>, which is adapted to be connected to the circular disc element <NUM> not shown in <FIG>. The beam element <NUM> comprises a recess <NUM>, which is configured to receive a connecting part of the circular disc element <NUM>, in particular for connecting the beam element <NUM> to the circular disc element <NUM> by means of a key connection <NUM> or a key joint. The beam element <NUM> further comprises a slot <NUM> in the form of an elongated hole with a radius <NUM>. The radius <NUM> for instance amounts to about <NUM>. The slot <NUM> extends in the extension direction <NUM> of the extending beam elements <NUM>. The slot <NUM> is configured for receiving fastening elements, for example screws as will be described in more detail in <FIG>.

<FIG> shows the cross-sectional view A-A through the circular disc element shown in <FIG>. The cross-sectional view of <FIG> shows that the sleeve element <NUM> has a greater thickness as the remaining part of the circular disc element <NUM>. The sleeve element <NUM> is adapted to receive the rotational shaft <NUM> not shown in <FIG> with its curved circular fitting surface <NUM>. In particular, the rotational shaft <NUM> not shown in <FIG> is received by the central hole <NUM> of the circular disc element <NUM>. The enhanced thickness of the sleeve element <NUM> along the longitudinal direction <NUM> provides for a proper connection between the rotational shaft <NUM> and the circular disc element <NUM>. <FIG> also shows the outer circumference <NUM> of the circular disc element.

<FIG> shows an isometric view of the circular disc element <NUM> according to another embodiment of the invention. Therein, the extending beam elements <NUM> of the circular disc element <NUM> each comprise an extension element <NUM> which is fastened to the beam elements <NUM> by means of fastening elements <NUM>, in particular by means of a screw connection. <FIG> shows that the extension element <NUM> is fixed to a respective beam element <NUM> by means of two screws. The fastening elements <NUM>, e.g. the screws, extend through the elongated hole <NUM> of the beam element <NUM> in order to fasten the extension element <NUM>. The extension element may have the shape of a cuboid. The extension element <NUM> may be chamfered at least two edges which are directed towards the beam element <NUM> when the extension element <NUM> is fastened to the beam element <NUM>.

<FIG> further shows plates <NUM> ,which are attached to an abutting surface of the circular disc element <NUM>. The plates <NUM> have a hole <NUM> and in particular provide a means for adapting the diameter of the hole <NUM>. In particular, plates <NUM> having holes <NUM> with different sizes or diameters may be provided and fastened to the abutting surface of the circular disc element <NUM> in order to adapt the diameter of the holes <NUM>. The plates <NUM> may be fastened to the circular disc element <NUM> by means of fastening elements <NUM> which correspond to the fastening holes <NUM> shown in <FIG>.

<FIG> shows a top view of the circular disc element <NUM> shown in <FIG>. This figure clearly shows that the extending beam elements <NUM> each have an extension direction <NUM> which is parallel to the radial direction <NUM> of the circular disc element <NUM>. <FIG> also shows that the extending beam elements <NUM> are attached to the circular disc element <NUM> in an equidistant manner with respect to the circumferential direction <NUM>. The diameter <NUM> of the circular disc element <NUM> may be between <NUM> and <NUM>. Preferably, the diameter <NUM> of the circular disc element <NUM> amounts to about <NUM>. The diameter of the central hole <NUM> of the circular disc element <NUM> may be between <NUM> and <NUM>. Preferably, the diameter <NUM> of the central hole <NUM> amounts to about <NUM>.

Extension elements <NUM> are attached to each of the beam elements <NUM> by means of fastening elements <NUM>. The fastening elements <NUM> may be screws which extend through the elongated hole <NUM> of the beam elements <NUM> not shown in <FIG>. The fastening elements <NUM>, e.g. the screws, extend through the beam elements <NUM> perpendicular to the longitudinal direction <NUM> in order to fasten the extension elements <NUM> to the beam elements <NUM>. <FIG> shows a configuration in which exactly two screws attach the extension elements <NUM> to each of the beam elements <NUM>.

<FIG> further shows the arrangement of the plates <NUM> on the abutting surface of the circular disc element <NUM> in order to adapt the diameter of the holes <NUM> in the circular disc element <NUM>. Fastening elements <NUM> are also used to fasten the plates <NUM> to the circular disc element <NUM>. <FIG> shows that the plates <NUM> are equidistantly spaced apart from each other with respect to the circumferential direction <NUM> on the circular disc element <NUM>.

<FIG> shows a configuration in which exactly four beam elements, each having an extension element <NUM>, are arranged in a region of the cut-out sections <NUM> of the circular disc element <NUM>. <FIG> further shows the configuration in which exactly four holes <NUM> are arranged on the circular disc element <NUM>, the diameter of each hole being adjustable by the hole within a plate <NUM> which is mountable to the abutting surface of the circular disc element <NUM>. In the configuration shown in <FIG>, the holes <NUM> are equidistantly spaced apart from each other with respect to the circumferential direction <NUM> of the circular disc element <NUM>, wherein the angle between each of the holes <NUM> amounts to <NUM>°. The configuration also shows an alternate arrangement of the holes <NUM> and the beam elements <NUM> on the circular disc element <NUM>.

<FIG> shows a side view of the circular disc element <NUM> shown in <FIG> clearly shows that the fastening elements <NUM>, e.g. the screws, extend through the elongated hole <NUM> of the beam element <NUM>. The elongated hole <NUM> provides for an adjustable connection between the extension element <NUM> and the extending beam element <NUM>. In other words, the length with which the extension element <NUM> extends beyond the outer circumference <NUM> of the circular disc element can be adjusted by shifting the extension elements <NUM> within the elongated hole <NUM>. It should be understood that the extension elements <NUM> may be a part of the beam elements <NUM>. However, it is also possible that the extension elements <NUM> may be considered as separate parts with respect to the beam elements <NUM>.

<FIG> shows an isometric view of a rotational shaft <NUM> on which a plurality of circular disc elements <NUM> having extending beam elements <NUM> are mounted. <FIG> also shows that the extension elements <NUM> are mounted to the respective extending beam elements <NUM> of each circular disc element <NUM> of the plurality of circular disc elements <NUM>.

<FIG> shows a combination of the inventive circular disc elements <NUM> having the extending beam elements <NUM> and the extension elements <NUM> mounted thereon with conventional rotating discs <NUM> for grinding slurry. Different embodiments of the arrangement of different types of grinding discs are possible.

<FIG> shows a device for grinding slurry comprising an elongated chamber <NUM> with a rotational shaft <NUM> mounted within the elongated chamber <NUM>. The rotational shaft <NUM> extends between the first end 2a and the second end 2b within the elongated chamber <NUM>. The plurality of the inventive circular disc elements <NUM> is mounted to the rotational shaft <NUM> in the region of the bottom part, e.g. at the first end 2a of the chamber <NUM>. These inventive circular disc elements <NUM> are combined with other rotating discs <NUM> which are mounted to the rotational shaft <NUM> at the top part, e.g. at the second end 2b of the chamber <NUM>.

A slurry with particulate material to be milled <NUM> is introduced into the chamber <NUM> at the first end 2a and are conveyed through the chamber <NUM> to the top part, e.g. to the second end 2b of the chamber <NUM> where the ground slurry is discharged from the chamber <NUM>. On its way from the first end 2a to the second end 2b of the chamber <NUM>, the slurry gets ground and therefore refined by means of the circular disc elements <NUM>, grinding media, like ceramic grinding beads within the chamber <NUM> and the inner wall or inner surface <NUM> of the elongated chamber <NUM>. Furthermore, protruding elements <NUM> are mounted to the inner wall or inner surface <NUM> of the chamber <NUM>, wherein the protruding elements <NUM> protrude into the chamber <NUM> perpendicularly to the longitudinal direction <NUM>. The flow path <NUM> of the slurry <NUM> is also shown in <FIG>. The grinding of the particulate material in the slurry is carried out by the interaction of the circular disc elements <NUM> which accelerate the grinding media (beads) and the inner wall or inner surface <NUM> of the chamber <NUM> as well as the protruding elements <NUM> reaching into the chamber <NUM>. The protruding elements <NUM> may have the shape of discs which are attached to the inner wall <NUM> of the chamber <NUM> via their outer circumferences. In particular, the protruding elements <NUM> provide contra-discs to the circular disc elements <NUM> whereas one protruding element may be arranged between at least a part of the circular disc element <NUM>, in particular between at least a part of the beam elements <NUM> of the circular disc element <NUM>.

It is possible that only <NUM>% of the circular disc elements, e.g. the hybrid discs, are combined with these contra-discs, e.g. with the protruding elements <NUM>. For example, it is possible that <NUM>% of the circular disc elements <NUM> at the top part 2b and <NUM>% of the circular disc elements <NUM> at the bottom part 2a are not intercalating with the contra-discs. In other words, only <NUM>% of the circular disc elements <NUM> arranged within the device <NUM> for grinding slurry have arranged a protruding element <NUM> between them whereas the other <NUM>% of the circular disc elements <NUM> do not have a protruding element <NUM> arranged between them.

<FIG> shows a cross-sectional view through a circular disc element <NUM> according to an embodiment of the invention. In particular, <FIG> shows the cross-section B-B from <FIG> except the chamber <NUM>. The cross-section B-B of <FIG> shows a cross-section through the circular disc element <NUM> having four beam elements <NUM> with extension elements <NUM> mounted thereon. Extension elements <NUM> are fastened to the beam elements <NUM> by means of fastening elements <NUM>, in particular by means of screws. <FIG> further shows the arrangement of the holes <NUM> which extend through the circular disc element <NUM> in the longitudinal direction. Furthermore, fastening holes <NUM> for receiving the fastening elements <NUM> of <FIG> are shown.

<FIG> further shows that the circular disc element <NUM> is connected to the rotational shaft <NUM> by means of a fitting key <NUM>.

<FIG> shows a method for grinding mineral slurry. In a first step S1 of the method, slurry <NUM> is fed into an elongated chamber <NUM> having a rotational shaft <NUM> extending between a first end 2a and a second end 2b of the elongated chamber <NUM>. In a second step S2, at least one circular disc element <NUM> as described above is rotated, wherein the at least one circular disc element <NUM> is attached to the rotational shaft <NUM> extending between the first end 2a and the second end 2b of the chamber <NUM>. In another step S3, the slurry <NUM> is ground within the chamber <NUM> when the slurry <NUM> is conveyed from the first end 2a to the second end 2b of the chamber <NUM>. In particular, the slurry <NUM> is ground by an interaction with grinding media (grinding beads) within the chamber, the particulate material itself and by an interaction of the slurry <NUM> with the inner wall <NUM> of the chamber <NUM> and the protruding elements <NUM> reaching into the chamber <NUM>. The agitating arms, e.g. the beam elements <NUM> of the circular disc element <NUM>, may be configured for accelerating the grinding media/beads and the slurry <NUM> within the chamber <NUM>.

Claim 1:
A circular disc element (<NUM>) for a device (<NUM>) for grinding slurry, comprising:
at least two beam elements (<NUM>), each beam element extending beyond an outer circumference (<NUM>) of the circular disc element (<NUM>) in an extension direction (<NUM>) which is parallel to a radial direction (<NUM>) of the disc element (<NUM>);
at least two holes (<NUM>) extending through the circular disc element (<NUM>) in a longitudinal direction (<NUM>) which is substantially perpendicular to each of the extension directions (<NUM>) of the at least two beam elements (<NUM>);
wherein the at least two beam elements (<NUM>) are equidistantly spaced apart from each other with respect to a circumferential direction (<NUM>) of the circular disc element (<NUM>), which circumferential direction (<NUM>) corresponds to the outer circumference (<NUM>) of the circular disc element (<NUM>);
wherein each beam element (<NUM>) comprises a recess (<NUM>), wherein the recess (<NUM>) receives a connecting part of the circular disc element (<NUM>),
wherein each beam element (<NUM>) comprises a slot (<NUM>) in the form of an elongated hole with a radius (<NUM>), wherein the slot (<NUM>) extends in the extension direction (<NUM>) of the extending beam element (<NUM>), and wherein the slot (<NUM>) is configured for receiving fastening elements.