An assembly element for use in a vertical mill and a vertical

Abstract

According to an embodiment, assembly element (100) for use in a vertical grinding mill is disclosed configured to crush raw materials, the assembly comprising crushing elements (111-116) circumferentially distributed, characterized in that the assembly element (100) further comprises a set of leverage means (213) and (230-232) springs configured to push the crushing elements (111-116) in a radially outward direction.

Description

AN ASSEMBLY ELEMENT FOR USE IN A VERTICAL MILL AND A VERTICAL MILL HAVING SAID ASSEMBLYField of the invention

[0001] The present invention relates a vertical grinding mill configured to crush raw materials such as stones or minerals into a powdered product for further processing. The invention further relates to an assembly element further assembling such a vertical grinding mill.

[0002] Vertical grinding mills are also called vertically stirred grinding mills or vertical auger mills.Background art

[0003] A vertical grinding mill is a type of grinder used to grind or crush materials into extremely fine powder for use in mineral dressing processes, paints, pyrotechnics, cements and ceramics.

[0004] Different types of such a vertical grinding mill exist, like ball-ring mills in which balls roll between an upper ring and a bowl for performing the milling, or roller-bowl mills in which the milling process involves compression and grinding of material between a bowl and rolls.

[0005] In US4660776A a vertical grinding mill is disclosed used to pulverize emery, alumina, etc. into fine or ultrafine particles by grinding. The material is pulverized to fine particles by friction between the material and the grinding medium.

[0006] In US395134A an apparatus for crushing material containing particles that are hard to pulverize is disclosed. The apparatus comprises a grinding plate in which rollers move for crushing the material.

[0007] In EP1419010A1 another vertical griding mill is disclosed having grinding rollers and auxiliary rollers on a grinding bed, which is formed by a feed material on a grinding path of a rotating grinding bowl.

[0008] The vertical grinding mills known in the art have in common that they make use of static grinding rollers. A disadvantage thereof is that the material that needs to be crushed needs to be classified and separated based on its size prior to the crushing. Another disadvantage is that the grinding rollers may be damaged when the materialcontains particles having a hardness greater than the material of the rollers itself.

[0009] It is an object of the present invention to alleviate said identified and other disadvantages of vertical griding mills known in the art.Summary of the invention

[0010] This object is achieved, in a first aspect of the present invention, by an assembly element for use in a vertical grinding mill according to claim 1 . The assembly element assembly is configured to crush raw materials in combination with a mill house as discussed later. The assembly comprises crushing elements circumferentially distributed and is characterized in that the assembly further comprises a set of leverage means and one or more pushing means configured to push the crushing elements in a radially outward direction.

[0011] The crushing element are also known as grinding rollers or grinding balls. It should however further be understood that they preferably have the shape of a donut as will be further illustrated. By the crushing elements, material is pulverized to fine particles by friction between the surface of the elements against the mill house wherein the assembly is used.

[0012] The crushing elements are circumferentially distributed at the outer surface of the assembly, and preferably there are at least three elements present. In other embodiments, the assembly may comprise four, five, or more preferably six crushing elements. Independently of the number of crushing elements, they are circumferentially distributed in a symmetric manner around the centre point or midpoint of the assembly. An advantage of having six crushing elements circumferentially distributed around the centre point of the assembly is that the assembly is more balanced against dynamic shock loading of the system.

[0013] A crushing element comprises an outer surface comprising a material to crush raw materials, such as steel, ceramic or a rubber-ceramic composite (explained in more detail herein further). The crushing is performed by pushing the surface of the crushing element close to or against an inner wall or housing of a vertical mill wherein the element is integrated, and by simultaneously rotating the assembly such that the crushing elements also radially move against said inner wall. Raw material is then crushed between the crushing elements and the inner wall or housing of a vertical mill.

[0014] Therefore, the assembly is further configured in such a way that a rotationaround a central axis of the assembly results in a substantially circular movement of the crushing element within a same plane. A substantially circular movement means that the assembly with the crushing elements rotates around the central axis, but that some deviations are possible because of, for example, a mechanical unbalance. The assembly thus has a midpoint or centre point through which a central axis can be inserted. This central axis can then be driven be a gear set driven by a motor. By the combined rotating and pushing, the raw materials can then be crushed more efficiently.

[0015] As already highlighted, the assembly comprises a set of leverage means and pushing means, for example one or more springs, configured to push the crushing elements in a radially outward direction. According to the invention, there is one leverage mean and at least one pushing means associated with each crushing means. Preferably, the pushing means are springs, and more preferably there are more than one springs per leverage element, and thus per crushing element. The springs are preferably parallel. The number of springs depends on the force that needs to be provided to push the respective crushing element in the radially outward direction, and it was found that the number is preferably three. When a large piece of feed, for example 25 up to 50mm, enters the mill it will force the crushing element inwards the assembly as it is flinging out only with a centrifugal force. Due to the pushing means a shock load because of the large piece of feed jamming the roller will be compensated thereby allows to continue the crushing of raw materials.

[0016] The springs are set at an initial tension when mounted. This way they exert a radial outward force on a continuous basis. In other words, the springs are mounted in such a way that they constantly push the crushing elements in the radially outward direction even if the assembly does not rotate around a central axis as will be further explained. The value of the initial tension depends on different parameters, such as the number of springs per crushing means, the hardness of the surface of the crushing element, the hardness of the materials to be crushed, and the hardness of the surface against which the crushing elements are pushed by the springs. In other words, the function of the springs should need be seen as shock absorbing means, on the contrary, they are designed and mounted such that they exert a radially force in an outward direction.

[0017] The leverage means, in some embodiments also called a dog bone because ofits particular shape, together with the one or more springs pushes the crushing element in said radially outward direction. The way the crushing element is pushed depends on the manner how the one or more springs leverage the crushing element by the leverage means are mutually connected and assembled on the assembly. The springs may push or pull on the leverage means (preferably near an end of the leverage means), such that the leverage means can rotate around a point of rotation thereby pushing the crushing means towards the radially outward direction.

[0018] The preferred way is by pulling with the springs on an end of the leverage means hereby pushing the crushing element to the outside of the assembly element. Furthermore, the point of rotation is preferably on the opposite end, in the form of a fixture with the crushing element on the middle of the leverage means.

[0019] An advantage is that a risk of damaging the surface of the crushing elements used to crush the raw materials is limited. In case the raw material comprises particles having a hardness greater than the hardness of said surface, the springs will allow an inward movement of the crushing element for preventing any damages.

[0020] Differently formulated and in line with said second advantage, the use of springs also results to the fact that the assembly, and therefore the vertical mill, can be adapted to the maximal hardness of the material that can be crushed. This hardness will be determined by the hardness of the surface of the crushing element, but also by the spring stiffness or spring constant of the one or more springs used to push the crushing element in the radially outward direction.

[0021] Through the pushing of the crushing elements in the radially outward direction, a third advantage is that the assembly can be used for a longer period. The wearing of the surface of the different crushing elements does not have to be uniform to guarantee a proper functioning of the vertical mill wherein it is integrated. Through the pushing, the surfaces will remain pushed against the inner wall of the vertical mill. This way, the crushing elements, and in particular the part comprising the surface to crush raw materials, need only to be replaced if they are completely worn out.

[0022] According to an embodiment, the leverage means and the springs are comprised on a central rotatable element. This central rotatable element forms the main body of the assembly. It comprises an aperture in the middle thereof for housing the central axis driven by a motor, as discussed above. The aperture further comprisesa protuberance or groove for transferring a momentum from the axis to the central rotatable element.

[0023] The central rotatable element further comprises means for holding the leverage means and springs in a secure and rigid manner. As already highlighted, per crushing element there are preferably three springs and one leverage means. The springs are on one of their ends fixed to the central rotatable element by stopping means, and on their other ends connected to an end of the leverage means. When assembled, the springs are pre-tensioned resulting in a forward force on the leverage means, in other words pushing it.

[0024] The other end of the leverage means comprises an aperture such that via appropriate means such as a bolt the leverage means is connected to the central rotatable elements. The bolt may further comprise a bushing for supporting said bolt. Preferably, instead of a bushing a bearing, like a roller or ball bearing, is used. The bearing allows a rotation around said bolt. Furthermore, the bearing facilitates an additional pushing force in conjunction with the pushing means, like the springs. The crushing means are then connected to the leverage means in the middle thereof.

[0025] As will be shown in the appended examples, preferably the assembly comprises two of said central rotatable elements, one of the top and one on the bottom, and are rigidly connected to each other via appropriate means such as bolts.

[0026] Each of the two central rotatable elements preferably comprises the leverage means and springs discussed herein. This results in a configuration wherein each crushing element is pushed via a leverage means and one or more springs at the top side, and via a leverage means and one or more springs at the bottom side. Since the preferred set-up is having three springs per leverage means and per crushing element on one central rotatable element, this results in six springs pushing a respective crushing element in the radially outward direction.

[0027] An advantage of having two central rotatable elements on the top and bottom side is that the crushing elements are pushed in a more stable and solid manner.

[0028] The central rotatable element typically further comprises grooves to accommodate the crushing elements.

[0029] Now with reference to the leverage means, according to an embodiment the leverage means comprises a width around the fixture to the crushing elements whichis larger than the fixture to the central rotatable element at the end of the springs.

[0030] In a further aspect, the invention provides a vertical mill comprising the assembly element according to the first aspect of the invention.

[0031] Preferably, the vertical mill comprising more than one assembly stacked in a vertically manner, as already discussed above. An advantage of such a set-up is that the grinding area per square meter can be increased, thereby allowing the mill to get an increased grinding area.

[0032] According to a third aspect, the invention provides a mill house comprising the vertical mill according to the second aspect of the invention.

[0033] According to a fourth aspect, a method is discloses comprising the steps of providing a vertical grinding mill according to the second aspect, comprising an assembly element according to the first aspect and feeding raw materials into the mill and rotating the assembly element around a central axis thereby crushing the raw materials.Brief description of the figures

[0034] The present invention will now be described in more detail with reference to specific embodiments of the invention, given only by way of illustration, and with reference to the accompanying drawings.

[0035] Figure 1 is a top view of the assembly element according to an embodiment of the invention;

[0036] Figure 2 is a perspective view of the assembly element illustrated in figure 1 ;

[0037] Figure 3 is a side view of the assembly element illustrated in figure 1 and 2;

[0038] Figure 4 is detailed view of springs and a leverage means of the assembly element illustrated in the aforementioned figures;

[0039] Figure 5 is another detailed view of the crushing elements of the assembly element illustrated in the aforementioned figures; and

[0040] Figure 6 is an exploded view of a crushing element as present in the assembly element illustrated in the aforementioned figures.Description of embodiments

[0041] The expression “comprise” and variations thereof, such as, “comprises” and “comprising” as used herein should be construed in an open, inclusive sense, meaning that the embodiment described includes the recited features, but that it does notexclude the presence of other features, as long as they do not render the embodiment unworkable.

[0042] The expressions “one embodiment”, “a particular embodiment”, “an embodiment” etc. as used herein should be construed to mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such expressions in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. For example, certain features of the disclosure which are described herein in the context of separate embodiments are also explicitly envisaged in combination in a single embodiment.

[0043] The singular forms “a,” “an,” and “the” as used herein should be construed to include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its broadest sense, that is as meaning “and / or” unless the content clearly dictates otherwise.

[0044] Figure 1 illustrates a top view of the assembly element 100 according to an embodiment of the invention. Since the assembly element 100 is configured to be integrated in a vertical grinding mill, and since the set-up of the assembly element 100 is assembled in a symmetric manner, it should however be understood that the view as illustrated in Figure 1 can also be regarded as a bottom view.

[0045] In other words, the technical features of the assembly elements, such as the springs and the leverage elements are present twice, on a top side and on bottom side.

[0046] The assembly element 100 comprises six crushing elements 111 -116, which is the preferred embodiment. It should however be noted that the assembly element may comprise less than six crushing elements, but also more than six crushing elements. Irrelevant of the number of elements, it is further preferred that they are positioned and located in a symmetric manner with the midpoint 120 being the point of symmetry.

[0047] This midpoint or centre point 120 comprises an aperture, and as can be seen from this top view 100, there is a protuberance at the left side of the opening 120. This protuberance allows the transfer a momentum originating from a motor, for examplean electric motor, by a central axis to the assembly element 100.

[0048] With reference to figure 2, which is a perspective view 200 of the assembly element 100 illustrated in figure 1 , the crushing elements 111-116 have a round shape. On the outer surface of a respective crushing element 221 , there is material in the shape of a donut. This material is suitable for crushing raw materials, such as stones and minerals, and is for example selected from steels (in particular steel alloys with chromium and / or nickel), ceramics, white cast irons alloyed with nickel and chromium, or ceramic-rubber composites. A preferred material for the outer surface of the crushing elements has a Brinell hardness value of at least 400 BHN, preferably at least 450 BHN, such as at least 480 BHN and / or a Rockwell hardness of at least 50 HRC, preferably at least 55 HRC. The Brinell hardness value can be determined in accordance with ASTM E10 (2015) and the Rockwell hardness value can be determined in accordance with ASTM E18 (2022). Examples of materials which are suitable are AR500 steel, Hardox®500 steel, Ni-Hard, hardened grade4140 steel.

[0049] The crushing elements 221 further have a central bearing 222 around which the hard material is provided. The central bearing 222 allows a rotation of a respective crushing element around its central axis. Hence, all the provided crushing elements 111 -116 can rotate around their respective axis, and the complete assembly element 100 can also rotate around its own central axis 120.

[0050] Thus, it should thus be noted that the crushing elements 111 -116 can rotate around the central axis 120, but simultaneously can also rotate around their own central axis.

[0051] Now further with again reference to figure 2, the assembly element 200 comprises a top central rotatable element 201 and a bottom central rotatable element 202.

[0052] In the illustrative embodiment of figure 2, the top central rotatable element 201 and bottom central rotatable element 202 are rigidly connected to each other via bolts. This means that they are detachable from each other by unscrewing the bolts or screws when needed.

[0053] It is also possible that the top central rotatable element 201 is welded to the bottom central rotatable element 202 such that they cannot be detached from eachother and form a rigid piece.

[0054] A third possibility is that the top central rotatable element 201 and the bottom central rotatable element 202 are cast as a single piece, thereby forming one rigid piece.

[0055] Now with reference to the top central rotatable element 201 , on one side thereof fixing means 233 are provided for holding springs 230-232.

[0056] The fixing means 233 can be welded onto the topside of the top central rotatable element 201 . The fixing means 233 further comprises a shoe 234 on which the springs 230-231 on one side are attached to.

[0057] The other side of the springs 230-232 are connected to a leverage means 213. On said side that are connected to the leverage means 213 is such a way that they push the leverage means 213 with the point 210 as the point of rotation. On the same leverage means 213 a crushing element is attached thereon via fixture 211 . As already highlighted, a same configuration is performed on the bottom central rotatable element 202.

[0058] Through this configuration, the springs 230-232 are pre-tensioned which results in a forward force on the leverage means 213, and thus resulting is a pushing of the crushing means 111 -116 in the outward radially direction.

[0059] Note that in this configuration, the springs 230-232 are positioned in a perpendicular direction with respect to the leverage means 220. This allows the transfer of the pushing force in an efficient manner.

[0060] Although not illustrated, the springs 230-232 could also be located on the other side of the leverage means 213, such that the pull the end of the leverage means 213 instead of pushing. Note however that this also change to whole configuration of the central rotatable elements 201-202, so this is not a preferred configuration.

[0061] Figure 3 is a side view 300 of the assembly element already illustrated in figure 1 and figure 2, wherein the top central rotatable elements 201 and bottom central rotatable element 202 are also illustrated.

[0062] Figure 4 is a detailed view 400 of a crushing element with the fixing means 233for connecting the springs 230-232 to the leverage means 213.

[0063] Figure 5 is another detailed view 500, but now in a perspective.

[0064] It should be further noted that the top central rotatable element 201 and bottom central rotatable element 202 comprise grooves to house the crushing elements, such that they can jut out of the assembly element when pushed by the springs 230-232.

[0065] Figure 6 is an exploded view of a crushing element 221 as illustrated by the assembly element 100 in the aforementioned figures. As already highlighted, the crushing element 221 is attached onto leverage means 213 via fixture 211. The crushing element 211 further comprises a set of ball bearings 602 gripping the fixture 211 when assembled. For protecting the bearings 602 against external threats like dust and moisture protective measures are provided, like cover 602. Between said covers 602, there are rubber lids as well as barriers to further cover the two bearings 602. When the bearings 602 are covered by said protective covering means, the covered bearings are housed in housing means 603 for further protection against said external treats. Further, when housed in the housing means 603, a covering surface 604 is provided as the surface of the crushing element 221. Finally, holding means comprising an upper ring 601 and a bottom ring 605 for clutching the covered bearings 602 in the housing means 603 are provided.

Claims

Claims1.- An assembly element (100) for use in a vertical grinding mill configured to crush raw materials, the assembly comprising crushing elements (111 -116) circumferentially distributed, characterized in that the assembly element (100) further comprises a set of leverage means (213) and one or more pushing means configured to push the crushing elements (111-116) in a radially outward direction.2.- The assembly element (100) of claim 1 , wherein the assembly element (100) is further configured such that a rotation around a central axis (120) results in a substantially circular movement of the crushing elements (111 -116) within a same plane.3.- The assembly element (100) according to any one of the preceding claims, wherein the assembly element (100) comprises at least three, preferably four, more preferably five and most preferably six crushing elements (111 -116).4.- The assembly element (100) according to any one of the preceding claims, wherein the pushing means comprises one or more springs (230-232), and wherein each crushing element (111-116) is pushed by a respective spring (230-231 ) and a respective leverage mean (213).5.- The assembly element (100) according to claim 4, wherein the leverage means (213) and springs (230-232) are configured to push the crushing elements (111 -116) in the radially outward direction by pushing or pulling.6.- The assembly element (100) according to any one of the claims 4 to 5, wherein the springs (230-232) are multiple parallel springs (230-232).7.- The assembly element (100) according to any one of the claims 4 to 6, wherein the leverage means (213) and springs (230-232) are comprised on a central rotatable element (201-202).8.- The assembly element (100) according to claim 7, wherein the leverage means (213) comprises at least one fixture (210) on the central rotatable element (201-202) and at least one fixture (211 ) on the crushing element (111-116).9.- The assembly element (100) according to claim 8, wherein the fixture (211 ) comprises a bolt comprising a bearing (602) clamped thereon thereby allowing a rotation of the crushing element (111 -116) around said fixture (211 ).10.- The assembly element (100) according to claim 9, wherein the leverage means (213) comprises a width around the fixture (211 ) at the crushing element (111 -116) which is larger than the fixture (210) at the central rotatable element (201 -202).11 .- The assembly element (100) according to any one of claims 7 to 10, wherein the central rotatable element (201 -202) comprises grooves to accommodate the crushing elements (111-116).12.- The assembly element (100) according to any one of the claims 7 to 11 , comprising two central rotatable elements (201 -202) each comprising springs (230- 233) and leverage means (213).13.- A vertical grinding mill comprising one or more assembly elements (100) of any one of the preceding claims.14.- The vertical grinding mill of claim 13, wherein the one or more assembly elements (100) are superimposed.15- A mill house comprising the vertical grinding mill of any of the claims 13 to 14.16.- A method of grinding raw materials comprising the steps of: providing a vertical grinding mill as claimed in claims 13 to 15, comprising an assembly element (100), as claimed in any of the foregoing claims 1 to 11 and feeding raw materials into the mill and rotating the assembly element (100) around a central axis (120) thereby crushing the raw materials.

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