Patent Application
20240082849
The present disclosure relates to a roller crusher having two generally parallel rollers, wherein the roller crusher comprises a flange attached to at least one of the ends of one of the rollers. The present disclosure further relates to a method for operating a roller crusher.
When crushing or grinding rock, ore, cement clinker and other hard materials, roller crushers may be used having two generally parallel rolls which rotate in opposite directions, towards each other, and which are separated by a gap. The material to be crushed is then fed into the gap. One type of roller crusher is called high pressure grinding rollers or high pressure roller crushers. This type of comminution has been described in U.S. Pat. No. 4,357,287 where it was established that it is in fact not necessary to strive for single particle breakage when trying to achieve fine and/or very fine comminution of material. Quite opposite, it was found that by inducing compression forces so high that briquetting, or agglomeration of particles occurred during comminution, substantial energy savings and throughput increases may be achieved. This crushing technique is called interparticle crushing. Here, the material to be crushed or pulverized is crushed, not only by the crushing surfaces of the rolls, but also by particles in the material to be crushed, hence the name interparticle crushing. U.S. Pat. No. 4,357,287 specifies that such agglomeration may be achieved by using much higher compression forces then what was previously done. As an example, forces up to 200 kg/cm2 were previously used, whereas the solution in U.S. Pat. No. 4,357,287 suggests to use forces of at least 500 kg/cm2 and up to 1500 kg/cm2. In a roller crusher having a roller diameter of 1 meter, 1500 kg/cm2 would translate into a force of more than 200 000 kg per meter length of the rollers whereas previously known solutions could, and should, only achieve a fraction of these forces. Another property of the interparticle crushing is that a roller crusher should be choke fed with the material to be crushed, meaning that the gap between the two opposed rolls of the roller crusher should always be filled with material along the entire length thereof and there should also always be material filled to a certain height above the gap to keep it full at all times and to maintain a state of particle-on-particle compression. This will increase the output and the reduction to finer material. This stands in sharp contradiction to older solutions where it was always emphasized that single particle breaking was the only way fine and very fine particle comminution could be obtained.
Interparticle crushing, as opposed to some other types of crushing equipment, such as e.g. sizers, has the attribute that it does not create a series of shocks and very varying pressure during use. Instead, equipment using interparticle crushing is working with a very high, more or less constant pressure on the material present in the crushing zone created in and around the gap between the rolls.
In order to maintain crushing effect all along the length of the grinding rollers, flanges may be arranged to ends of the crushing rolls; one flange at each end of one roll, or one flange at one end of each roll, but on opposite ends of the roller crusher. With such an arrangement, it is possible to create a more efficient and uniform roll feed entry. The flanges will allow for material being fed such that a preferred material pressure is created over the entire length of the crusher rolls. It has been shown that it is possible to increase capacity of a given roller crusher with up to 20%, or sometimes even more, by using flanges. A general problem associated with grinding rollers without flanges is that the ratio between the roller diameter and the roller width is very important due to a significant edge effect, i.e. the crushing result is reduced at the edges of the rollers. This is because of the fact that material may escape over the edges of the rollers thereby reducing the crushing pressure on the material towards the gap at the edges of the rollers. Without flanges, it is thus necessary to recycle both material escaping the rolls and some of the material having passed the gap at the edges of the crusher rolls due to a lower pressure resulting in reduced breakage at the edges.
However, during operation of a grinding crusher with flanges, the flanges and also edges of opposite crusher roller is under a lot of stress and wear, and build-up material will gather in the transition between the crusher roller surface and the flange. Such excessive build-up material needs to be removed consistently during operation of the grinding crusher.
Prior art has suggested a scraper element for removing build-up material in the transition between the crusher roller surface and the flange, see for example AU2018264756 or U.S. Pat. No. 5,054,701.
Proceeding therefrom, it is an object of the present disclosure to provide a roller crusher having flanges, wherein the flanges and edges of opposing roller crusher ends are subjected to less stress and wear.
According to a first aspect of the disclosure, this and other objects are achieved, in full or at least in part, by a roller crusher having two generally parallel rollers arranged to rotate in opposite directions, and separated by a gap, each roller having two ends, the roller crusher comprising:
The roller crusher of the first aspect may be advantageous as it allows removing built-up material accumulated on the flange and/or on the envelope surface at an end portion of the roller adjacent the flange in a more efficient way. The rotatable cutter unit could be regarded as a plurality of movable impact surfaces, each of these impact surfaces being defined on a respective one of the plurality of cutter elements. The material is removed as a result from the impact forces created between the material build-up on the roller and these impact surfaces during operation. The impact forces will increase with an increase in relative speed between the material build-up (i.e. determined by the tangential speed of the envelope surface of the roller with a flange) and the speed of the impact surface (i.e. determined by the tangential speed of the cutter elements on the rotatable cutter unit). By the provision of a rotatable cutter unit, the material removal is not solely relying on the impact forces created by the movement of the roller with respect to the material removal device, as is the case when the material removal device is a stationary scraper and thus defines a stationary impact surface. Instead, by rotating the rotatable cutter unit, an impact surface of the rotatable cutter unit may obtain a considerable tangential speed on its own. If rotating the rotatable cutter unit in the same rotational direction as the roller with the flange, the impact forces may be considerably increased, allowing a more efficient and reliable material removal. A further advantage of the rotatable cutter unit is that it allows tailoring the impact forces for the specific situation. There may for example be situations where it is less desirable to have a high impact force. For such situations, the rotating speed of the rotatable cutter unit may be reduced to lower the impact forces during material removal without affecting the operation of the crusher itself (i.e. the rotating speed of the roller with the flange can be kept constant). It may even be situations where it is desirable to lower the impact forces beyond what can be achieved with a stationary scraper. For such situations, the rotatable cutter unit may be rotated in a rotational direction opposite to the rotational direction of the roller with the flange. A yet further advantage of the rotatable cutter unit is that the provision of a plurality of cutter elements increases the overall wear resistance of the material removal device as compared to a stationary scraper. The plurality of cutter elements will share the wear, whereby individual cutter elements will have a longer expected lifetime. This allows increasing the time period of operation before material removal device maintenance, hence reducing down-time of the roller crusher.
As readily appreciated by the person skilled in the art, the rotatable cutter unit may be rotated about a cutter unit rotational axis. The cutter unit rotational axis is preferable parallel with a rotational axis of the roller with a flange. However, it is conceivable that the cutter unit rotational axis is angled with respect to the rotational axis of the roller with a flange, as will be described in more detail in what follows.
The rotatable cutter unit may be arranged such the cutter unit rotational axis forms a tilt angle α with respect to the rotational axis of the roller in the radial plane of the roller which intersects the cutter unit rotational axis. This implies that the rotatable cutter unit will be unparallel with the flange of the roller, resulting in a varying distance between the rotatable cutter unit and the flange in the radial direction of the roller. The tilt angle may be in the range of 0 to 90 degrees, preferably within the range 0 to 45 degrees.
The rotatable cutter unit may alternatively, or additionally, be arranged such the cutter unit rotational axis forms a skew angle with respect to the rotational axis of the roller in the tangential plane of the roller which is orthogonal to said radial plane of the roller which intersects the cutter unit rotational axis. This implies that the rotatable cutter unit will be unparallel with the flange of the roller, resulting in a varying distance between the rotatable cutter unit and the flange along the tangential direction of the roller surface. The skew angle may be in the range of 0 to 20 degrees, preferably within the range 0 to 15 degrees. Preferably, the skew angle is defined such that the distance between the rotatable cutter unit and the flange is at its minimum on an upstream end of the material removal device. This may be advantageous as it may facilitate removal of the broken off build-up material at the down-stream end of the material removal device as a result of the distance between the rotatable cutter unit and the flange being wider there.
The rotatable cutter unit may be rotated in the same rotational direction as the rotational direction of the roller with a flange. Alternatively, the rotatable cutter unit may be rotated in a rotational direction being opposite to the rotational direction of the roller with a flange. The rotational speed of the rotatable cutter unit may be within the range of 1 rpm up to 200 rpm. As readily appreciated by the person skilled in the art, the important factor will be the relative difference in tangential velocity between the roller surface and the cutter elements of the rotatable cutter unit at the point of impact between the same. If the rotatable cutter unit rotates along the same rotational direction as the rotational direction of the roller with a flange, the highest relative difference in tangential velocity will typically be obtained. If the rotatable cutter unit rotates along the rotational direction being opposite to the rotational direction of the roller with a flange, the relative difference in tangential velocity will be lower. At a particular ratio between the rotational speed of the roller and the rotational speed of the rotatable cutter unit, the relative difference in tangential velocity will be zero which will result in loss of cutting action. Therefore, when operating the rotatable cutter unit along the rotational direction being opposite to the rotational direction of the roller, care must be taken to avoid this operating condition. For an efficient cutting operation, the relative tangential speed is preferably higher than 1.25 times the tangential speed of the roller surface.
The rotatable cutter unit may be mounted on, or attached to, a rotating shaft. The rotating shaft may be a through-going rotating shaft. This implies that the rotating shaft extends through the rotatable cutter unit. This may be advantageous as it allows supporting the rotating shaft at both ends of the rotatable cutter unit, hence providing improved structural integrity. It is however conceivable that the rotatable cutter unit is mounted on, or attached to, a rotating shaft which is not through-going. This may have the advantage that it is easier to replace the rotatable cutter unit.
The rotatable cutter unit has a plurality of cutter elements arranged tangentially about the rotatable cutter unit. This implies that the cutter elements are arranged along a periphery of the rotatable cutter unit. In other words, each cutter element will be arranged on a circular path. It further implies that the cutter elements are arranged radially distanced from the cutter unit rotational axis. Preferably, the cutter elements are arranged at the same radial distance from the cutter unit rotational axis. However, it is conceivable that the cutter elements are arranged at different radial distances from the cutter unit rotational axis. For example, every other cutter element may be arranged at a first radial distance from the cutter unit rotational axis and remaining cutter element arranged at a second radial distance from the cutter unit rotational axis, wherein the first and second radial distances are different. This may allow providing a material removal device which increases the material removal efficiency once it has reached a certain degree of wear. The cutter elements may be mutually equidistantly arranged tangentially about the rotatable cutter unit. This implies that the distance between one cutter element and its neighbour will be the same for all cutter elements. It is however also conceivable that the cutter elements are arranged at different distances from each other.
The rotatable cutter unit may be integrally formed by a single element. This implies that the plurality of cutter elements will constitute radially extended protrusions on such a single element. Alternatively, the rotatable cutter unit may be an assembly of two or more elements. This will be further described hereinbelow and example embodiments will be defined.
According to an embodiment, each cutter element of the plurality of cutter elements presents an impact surface arranged to face the material to be cut away. The term “impact surface” should be construed as any surface of the cutter element which makes contact with material accumulated on the flange and/or on the envelope surface at an end portion of the roller adjacent the flange. This implies that the impact surface faces the material to be removed. The impact surface may be wear resistant. This may be achieved in different ways. For example, the impact surface may be a wear-resistant layer deposited onto a further material which does not have to be wear resistant. One example thereof is a diamond coating deposited on a hard element such as a steel element. Alternatively, the impact surface may be a surface of a dedicated element made from a wear resistant material, as will be further described in what follows.
According to an embodiment, the impact surface is substantially planar and arranged transverse to a tangential direction of motion of the cutter element. This example embodiment resembles the geometry of a stationary scraper of the prior art and may be easier and cheaper to manufacture due to its inherit simplicity. It is conceivable that the substantially planar impact surface is slightly angled with respect to the transverse direction. For example, the the impact surface may be arranged within the range 60 to 120 degrees, or 75 to 105 degrees or 80 to 100 degrees or 18 to 95 degrees to the tangential direction of motion of the cutter element.
According to an embodiment, the impact surface has a front portion and a rear portion which interconnect each other, wherein the front portion is arranged upstream of the rear portion as seen in relation to a tangential direction of motion of the cutter element and wherein the front portion is arranged closer to the flange than the rear portion. This may be advantageous as it allows creating very strong impact forces on localized regions of the material build-up on the roller with the flange with the front portion, thereby increasing the likelihood of breaking away larger portions of material. The rear portion may then step in and aid in further removing material from the roller and/or conveying the already removed material away from the flange region.
According to an embodiment, the rear portion is shaped so as to convey cut away material in a direction away from the flange. This implies that the rear portion is shaped to achieve a propeller of turbine effect.
According to an embodiment, the rear portion is substantially planar and forms an oblique angle with respect to the tangential direction of motion of the cutter element. This may be advantageous as it is relatively easy and cheap to manufacture.
According to an embodiment, the rear portion is curved inwardly so as to form a bowl-shape, also called concave shape. The bowl-shape may further enhance the propeller effect and thereby further enhance the conveying of already removed/loosened material from the flange region.
According to an embodiment, each cutter element of the plurality of cutter elements comprises a cutter element holding structure and an active cutting element attached thereto, wherein the active cutting element presents said impact surface. This may be advantageous as it allows using dedicated cutting elements which may thus be tailored specifically for the cutting. One example of such active cutting elements could be elements having a wear-resistant surface deposited thereon. Such a wear-resistant surface may be a diamond coating deposited on a further material such as a hard element, e.g. a steel element. Alternatively, the active cutting element may be entirely made from a wear-resistant material. Another advantage is that the active cutting element may be replaced when worn out without having to replace the cutter element holding structure, which may thus be reused. This may reduce the overall waste and cost.
According to an embodiment, the active cutting element is made of a wear-resistant material. This may be advantageous as it allows reducing the wear of the active cutting element during use. Non-limiting examples of such wear-resistant materials are diamond embedded materials, Tungsten carbides, hard metals, and Vanadium carbide.
According to an embodiment, the rotatable cutter unit has an annular engagement portion and wherein each cutter element of the plurality of cutter elements is releasably arranged to the annular engagement portion. The term “annular engagement portion” should be construed as an annularly shaped part of a structure, which could consist of one element or an assembly of elements, which forms an outer periphery onto which the plurality of cutter elements can be releasably arranged. The annular engagement portion could e.g. be the peripheral annular portion of a rotatable disc. The provision of releasable cutting element may be advantageous as it allows selectively replacing individual cutting elements. Thus, if e.g. one cutting element is damaged, remaining cutting elements may be left untouched and replacement only undertaken for the damaged element.
According to an embodiment, the rotatable cutter unit further comprises a main support structure and at least two cutter element support structures, wherein the at least two cutter element support structures are releasably arranged with respect to the main support structure and shaped as circular ring sectors which together form a circular ring, and which circular ring presents the annular engagement portion. In principle, the rotatable cutter unit may comprise any number of cutter element support structures. Thus, it is also conceivable to provide a single cutter element support structure. However, the provision of at least two cutter element support structures has the advantage that it allows mounting on a main support structure which is rotationally arranged on a through-going shaft. The at least two cutter element support structures may have the same dimensions. Thus, for an embodiment having two cutter element support structures, each of the cutter element support structures may constitute a 180 degree circular ring sector. Alternatively, for an embodiment having three cutter element support structures, each of the cutter element support structures may constitute a 120 degree circular ring sector. Alternatively, for an embodiment having four cutter element support structures, each of the cutter element support structures may constitute a 90 degree circular ring sector. It is also conceivable that the two or more cutter element support structures have different dimensions. Every embodiment will however have one thing in common: The at least two cutter element support structures will together form a circular ring, and the circular ring will present the annular engagement portion. These example embodiments may be advantageous as they provide a modularity to the design, hence facilitating easier and faster maintenance. By the provision of the at least two cutter element support structures, a complete module including several cutter elements may be removed from the material removal device in a single operation. This may also improve the speed and reliability when replacing cutter elements on a material removal device, since every cutting element may be replaced by replacing only the at least two cutter element support structures.
According to an embodiment, each cutting element of the plurality of cutting elements is releasably arranged in the annular engagement portion by a geometrical locking engagement. This may be advantageous as it allows making the construction impact resistant. During operation, the cutter elements will repeatedly make impact with material build-up on the roller having a flange, which will result in a torsional load on in the connection region between the cutter element and the annular engagement portion. By the provision of a locking engagement, this load may be at least partly absorbed by the structures themselves, hence reducing load on fasteners, such as e.g. bolts, screws and nuts, which are typically used to provide said releasable arrangement of the cutter elements to the annular engagement portion. The geometrical locking engagement may be embodied in different ways as will be detailed hereinbelow.
According to an embodiment, the geometrical locking engagement is at least partly defined by a protruding structure of the cutting element being inserted into an associated recess of the annular engagement portion, wherein the protruding structure and the associated recess has complementary shapes.
This is regarded as a preferred way of providing the locking engagement. It is achieved by the provision of complementary shapes on the cutter elements and the annular engagement portion, respectively. Such complementary shapes may be a protrusion that locks, by its mere shape, to a recess when inserted therein. A simple example may be a rod protruding into a bore. One conceivable way of providing a locking engagement could be to provide a plurality of bores directed radially inwardly on the periphery of the annular engagement portion and allow the cutter elements protruding into these bores. They may then be secured to the annular engagement portion by bolting. As readily appreciated by the person skilled in the art, the bolts will not absorb a majority of the torsional loads, which will instead be absorbed by the bore-protrusion arrangement having the complementary shapes.
According to an embodiment, the associated recess of the annular engagement portion is defined on a side surface thereof. This may be advantageous as it allows easier replacement. The provision of the recesses on a side surface of the annular engagement portion may reduce the risk of jam between the annular engagement portion and the cutter elements as a result from dust and contamination entering into the recesses.
According to an embodiment, each cutter element of the plurality of cutter elements comprises a cutter element holding structure and an active cutting element attached thereto, wherein the active cutting element presents said impact surface, and wherein the protruding structure forms a part of the cutter element holding structure. This may be advantageous as it allows an even more modular system. The dedicated cutting elements, termed herein as “active cutting elements” allow for individual replacement without having to replace the rest of the cutting element (i.e. the cutter element holding structure). However, during replacement, it is conceivably easier to replace the whole cutting element to a new one, including thus both the active cutting element and the cutter element holding structure. Once a cutting element has been removed, it may however be taken to a workshop or other dedicated facility, at which the worn-out active cutting element can be replaced by a new one on the cutter element holding structure. Thus, the same cutter element holding structure may be used many times.
According to an embodiment, the cutter element holding structure comprises a support portion protruding out from the same in a direction counter to a tangential direction of motion of the cutting element, said support portion being arranged such that it is supported by the annular engagement portion. This may be advantageous as it further aids in absorbing the torsional loads exerted in the cutter elements during operation. When a cutter element makes impact with material on the roller having a flange, the cutter element will be forced backwards. Since the cutter element is arranged in the annular engagement portion which is located radially inwardly from the point of impact (i.e. at the impact surface of the cutter element), the cutter element will exert a torsional load at the position where the cutter element is arranged in the annular engagement portion. This will, in turn, result in that the cutter element will strive to bend backwards around this point. By the provision of the backward-facing protrusion on the cutter element, this bending will be counteracted by the protrusion being supported by the annular engagement portion. In a way, this may be regarded as yet another means of geometrical locking. In some embodiments, the protrusion is supported by the annular engagement portion by being in direct contact therewith. In other words, the protrusion may be in abutment with the annular engagement portion. In other embodiments, the protrusion is supported by the annular engagement portion by being in direct contact with one or more further elements which in turn are in a direct contact with the annular engagement portion. Thus, the support may not require abutment.
According to an embodiment, the roller crusher further comprises wear shields structured and arranged to protect at least parts of the rotatable cutter unit. The wear shields may be advantageous as they allow protecting the rotatable cutter unit from the harsh environment in which it is intended to operate. During crusher operation in general, and in particular during removal of build-up material from the roller with a flange, there will be a high density of high-velocity stone, sand and dust constantly impinging on surfaces of the rotatable cutter unit, hence increasing the risk of wear on the parts, as well as damage due to penetration into cavities and gaps, which may also increase the complexity of maintenance and replacement.
According to an embodiment, the roller crusher comprises a first set of wear shields structured and arranged to protect a first side of the rotatable cutter unit, and a second set of wear shields structured and arranged to protect a second side of the rotatable cutter unit, and wherein at least wear shields of one of the first and second sets of wear shields have edge walls for interconnecting the first and second set of wear shields at the annular engagement portion between the plurality of cutter elements when mounted on the rotatable cutter unit. The first set of wear shields may comprise two or more wear shields. The second set of wear shields may comprise two or more wear shields. The wear shields may be mounted onto the rotatable cutter unit as a last step. This implies that, for embodiments having cutter elements which are releasably arranged to the annular engagement portion, the cutter elements are first arranged to the annular engagement portion, whereby the first and second sets of wear shields are mounted onto the rotatable cutter unit. This has the advantage of allowing protection to the fastening system used to releasably arrange the cutter elements to the annular engagement portion.
The wear shields may be made of hardened steel, hardened iron, hardened metals, carbides, braced with tungsten carbides, or high wear-materials such as weld overlay.
It is conceivable to control the rotational speed of the rotatable cutting unit based on input from one or more sensors. Such sensors could be e.g. level sensors or gauge sensors configured to measure properties of the roller with the flange. However, the rotational speed of the rotatable cutting unit may alternatively or additionally be controlled based on sensor data from the material removal device itself. For example, the rotational speed of the rotatable cutting unit may be controlled based on sensor data pertaining to the rotational velocity of the rotatable cutting unit and/or the torsional strain in the material removal device.
According to an embodiment, the rotation device comprises a drive unit. The drive unit may be a motor, such as e.g. an electrical motor. Alternatively, the drive unit may be pneumatically or hydraulically driven.
According to an embodiment, the rotation device further comprises a transmission system which includes a gear box. The gear box may be a high-reduction ratio gear box. For example, the gear box may have a reduction ratio of 4, 6, 8, 10 or 12 times. It is however conceivable to use higher reduction ratios such as e.g. 60, 80 or 100 times. This may be advantageous as it allows using a less powerful drive unit.
The rotatable cutter unit may be arranged on different positions in relation to the roller with a flange. Typically, the rotatable cutter unit may be arranged with respect to the roller with a flange at 5 to 1 o'clock as defined when the rotational direction of the roller is clockwise.
According to an embodiment, the rotatable cutter unit is arranged with respect to the roller with a flange at 9 to 12 o'clock as defined when the rotational direction of the roller is clockwise. This may be advantageous for some roller crushers where access and/or fastening of the rotatable cutter unit is typically limited at the lower end.
According to an embodiment, the rotatable cutter unit is arranged with respect to the roller with a flange at 6 to 9 o'clock as defined when the rotational direction of the roller is clockwise. This may be advantageous for some roller crushers where access and/or fastening of the rotatable cutter unit is typically limited at the upper end but may also be advantageous as the removed build-up material in this position easily is directed towards and removed from the roller crusher through an outlet chute together with the crushed material below the roller crusher.
According to a second aspect of the disclosure, there is provided a method for operating a roller crusher according to the first aspect, wherein the method comprises at least the step of at least partially cutting away material accumulated on the flange and/or on the envelope surface at an end portion of the roller adjacent the flange by means of the material removal device.
Similarly, and correspondingly to the first aspect of the disclosure above, this second aspect of the disclosure will provide substantial advantages over prior art solutions.
Other objectives, features and advantages of the present disclosure will appear from the following detailed disclosure, from the attached claims, as well as from the drawings. It is noted that the disclosure relates to all possible combinations of features.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the [element, device, component, means, step, etc.]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
As used herein, the term “comprising” and variations of that term are not intended to exclude other additives, components, integers or steps.
The disclosure will be described in more detail with reference to the appended schematic drawings, which show an example of a presently preferred embodiment of the disclosure.
The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the disclosure to the skilled addressee. Like reference characters refer to like elements throughout.
As discussed in the background part of this disclosure, the arrangement of flanges to the ends of the crushing rollers (as shown in
With reference to
With reference to
The material removal device 100 having the rotatable cutter unit 110 may be advantageous as it allows removing built-up material 41 accumulated on the flange 36, 36′ and/or on the envelope surface 37, 37′ at an end portion of the roller adjacent the flange 36, 36′ in a more efficient way. The rotatable cutter unit 110 could be regarded as a plurality of movable impact surfaces 131a, 131b, each of these impact surfaces 131a, 131b being defined on a respective one of the plurality of cutter elements 120. The material 41 is removed as a result from the impact forces created between the material build-up 41 on the roller 3, 4, 3′, 4′ and these impact surfaces 131a, 131b during operation. The impact forces will increase with an increase in relative speed between the material build-up 41 (i.e. determined by the tangential speed of the envelope surface 37, 37′ of the roller 3, 4, 3′, 4′ with a flange) and the speed of the impact surface 131a, 131b (i.e. determined by the tangential speed of the cutter elements 120 on the rotatable cutter unit 110). By the provision of a rotatable cutter unit 110, the material removal is not solely relying on the impact forces created by the movement of the roller 3, 4, 3′, 4′ with respect to the material removal device 100, as is the case when the material removal device is a stationary scraper and thus defines a stationary impact surface. Instead, by rotating the rotatable cutter unit 110, an impact surface 131a, 131b of the rotatable cutter unit 110 may obtain a considerable tangential speed on its own. If rotating the rotatable cutter unit 110 in the same rotational direction as the roller 3, 4, 3′, 4′ with the flange 36, 36′, the impact forces may be considerably increased, allowing a more efficient and reliable material removal. A further advantage of the rotatable cutter unit 110 is that it allows tailoring the impact forces for the specific situation. There may for example be situations where it is less desirable to have a high impact force. For such situations, the rotating speed of the rotatable cutter unit 110 may be reduced to lower the impact forces during material removal without affecting the operation of the crusher itself (i.e. the rotating speed of the roller 3, 3′ with the flange 36, 36′ can be kept constant). It may even be situations where it is desirable to lower the impact forces beyond what can be achieved with a stationary scraper. For such situations, the rotatable cutter unit 110 may be rotated in a rotational direction opposite to the rotational direction of the roller 3, 3′ with the flange 36, 36′. A yet further advantage of the rotatable cutter unit 110 is that the provision of a plurality of cutter elements 120 increases the overall wear resistance of the material removal device 100 as compared to a stationary scraper. The plurality of cutter elements 120 will share the wear, whereby individual cutter elements 120 will have a longer expected lifetime. This allows increasing the time period of operation before material removal device maintenance, hence reducing down-time of the roller crusher 1.
Such roller crushers work according to a technique called interparticle crushing. The crushing rollers 3, 4 rotates counter to each other as illustrated schematically in
Another prior art roller crusher is disclosed in e.g. WO2013/156968, in which each of the grinding rollers with bearings is arranged in interconnected arch-shaped frame sections, wherein each interconnected arch shaped frame sections are pivotably connected to a base frame. The disclosed subject matter within this disclosure is equally applicable in such a prior art roller crusher arrangement.
As also illustrated in
As initially described, a problem with this type of grinding assemblies is that material tend to build up at the corner 40 (see
After having described the function of the material removal device in the context of the roller crusher and in particular the roller 3 with a flange 26 as illustrated in
The material removal device 100 consists of three main parts: A rotatable cutter unit 110 which is attached to a rotating shaft 150 which is supported by brackets 151a, 151b, a transmission system 180 connected to the rotating shaft 150, and a drive unit 190 connected to the transmission system 180.
The material removal device 100 is mounted on the roller crusher 1 such that the rotatable cutter unit 110 is located at a preferred region of material removal at the roller 3 with a flange 36. This is schematically illustrated in
The rotatable cutter unit 110 will now be described in detail with reference to the above referenced figures. The rotatable cutter unit 110 has a plurality of cutter elements 120 arranged tangentially about the rotatable cutter unit 110. Each cutter element 120 presents an impact surface 131a, 131b arranged to face the material to be cut away. The rotatable cutter unit 110 is arranged to rotate along a rotational direction R about the cutter unit rotational axis A. When rotating in this manner, the impact surface 131a, 131b will make contact with material build-up 42 at the roller 3 with the flange 26, and cut away at least a part thereof, as detailed earlier with reference to
The cutter elements 120 may be releasably arranged on the rotatable cutter unit 110. As best illustrated in
Also illustrated clearly in
Turning now to
The active cutter elements 130, 230, 330 may be attached to the cutter element holding structures 122, 222, 322 by gluing or brazing. For providing further strength, a locking engagement may be used.
As previously mentioned, the rotatable cutter unit 110 is an assembly consisting of a plurality of interconnected elements. Focus have so far been on the cutter elements 120, 220, 320. Now, the inner parts of the rotatable cutter unit 110 will be described in detail with reference to
For all example embodiments discussed herein, the cutter elements 120 are attached to the main support structure 112 via a series of dedicated support structures, termed herein as “cutter element support structures” 140. These structures are thus mounted onto the main support structure 112 at an inner end thereof and presents the annular engagement portion 142 at an outer end thereof, at which annular engagement portion 142 the cutter elements 120 are to be releasably arranged.
The cutter element support structure 140 comprises an inner portion 145 which has a plurality of first through holes 146 and a plurality of second through holes 147. The purpose of the first through holes 146 is to provide a means for securing the cutter element support structure 140 to the main support structure 112 by means of fastening bolts 148. This is best illustrated in
Turning now to
As to protect the rotatable cutter unit 110, previously mentioned wear shields 160, 165 are provided. The wear shields 160a-c, 165a-c are most clearly seen in
The material removal device 200 consists of three main parts: A rotatable cutter unit 110 which is attached to a rotating shaft 250 which is supported by bracket 251, a transmission system 180 connected to the rotating shaft 250, and a drive unit 190 connected to the transmission system 180. The rotatable cutter unit 110 is thus mounted on, or attached to, a rotating shaft 250 which is not through-going as was the case for rotatable shaft 150 of the first example embodiment. This arrangement may have the advantage that it is easier to replace the rotatable cutter unit. It may also facilitate using higher tilt angles as will be further described in what follows.
The cutter unit rotational axis A is preferable parallel with a rotational axis F of the roller 3. However, it is conceivable that the cutter unit rotational axis A is angled with respect to the rotational axis F of the roller 3. This is illustrated in
The rotatable cutter unit 110 may be rotated in the same rotational direction as the rotational direction of the roller 3 with a flange 36. Alternatively, the rotatable cutter unit 110 may be rotated in a rotational direction being opposite to the rotational direction of the roller 3 with a flange 36. The rotational speed of the rotatable cutter unit 110 may be within the range of 1 rpm up to 200 rpm. As readily appreciated by the person skilled in the art, the important factor will be the relative difference in tangential velocity between the roller surface and the cutter elements of the rotatable cutter unit at the point of impact between the same. This is illustrated in
If the rotatable cutter unit 110 rotates along the same rotational direction as the rotational direction of the roller 3 with a flange 36 (
For the counter-rotating cases illustrated in
The person skilled in the art realizes that the present disclosure by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the example embodiments of the rotatable cutter unit presented herein constitute relatively complex assemblies of a plurality of elements. Important to keep in mind is however, that the rotatable cutter unit of the disclosure should not be construed as limited to such assemblies. It is also conceivable to provide a rotatable cutter unit from a single material in which the claimed features are integrally formed. As an example, a rotatable cutter unit may be formed from a single steel element and cut to create the cutting elements as radially outwardly directed protrusions of the same. Each cutting element may be cut to provide an impact surface of suitable shape. Wear resistance may be increased on the impact surfaces e.g. by depositing a wear-resistant material thereon, such as e.g. a diamond coating. Such an embodiment, though not explicitly illustrated in the drawings, is considered to be straight-forward for the person skilled in the art to design based on the present disclosure and common general knowledge in the field. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed, from a study of the drawings, the disclosure, and the appended claims.
Embodiment 1. A roller crusher having two generally parallel rollers arranged to rotate in opposite directions, and separated by a gap, each roller having two ends, the roller crusher comprising:
Embodiment 2. A roller crusher according to Embodiment 1, wherein each cutter element of the plurality of cutter elements presents an impact surface arranged to face the material to be cut away.
Embodiment 3. A roller crusher according to Embodiment 2, wherein said impact surface is substantially planar and arranged transverse to a tangential direction of motion of the cutter element.
Embodiment 4. A roller crusher according to Embodiment 2, wherein said impact surface has a front portion and a rear portion which interconnect each other, wherein the front portion is arranged upstream of the rear portion as seen in relation to a tangential direction of motion of the cutter element and wherein the front portion is arranged closer to the flange than the rear portion.
Embodiment 5. A roller crusher according to Embodiment 4, wherein the rear portion is shaped so as to convey cut away material in a direction away from the flange.
Embodiment 6. A roller crusher according to Embodiment 5, wherein the rear portion is substantially planar and forms an oblique angle with respect to the tangential direction of motion of the cutter element.
Embodiment 7. A roller crusher according to Embodiment 5, wherein the rear portion is curved inwardly so as to form a bowl-shape.
Embodiment 8. A roller crusher according to any one of Embodiments 2 to 7, wherein each cutter element of the plurality of cutter elements comprises a cutter element holding structure and an active cutting element attached thereto, wherein the active cutting element presents said impact surface.
Embodiment 9. A roller crusher according to Embodiment 8, wherein the active cutting element is made of a wear-resistant material.
Embodiment 10. A roller crusher according to any one of the Embodiments 1 to 9, wherein the rotatable cutter unit has an annular engagement portion and wherein each cutter element of the plurality of cutter elements is releasably arranged to the annular engagement portion.
Embodiment 11. A roller crusher according to Embodiment 10, wherein the rotatable cutter unit further comprises a main support structure and at least two cutter element support structures, wherein the at least two cutter element support structures are releasably arranged with respect to the main support structure and shaped as circular ring sectors which together form a circular ring, and which circular ring presents the annular engagement portion.
Embodiment 12. A roller crusher according to Embodiments 10 or 11, wherein each cutting element of the plurality of cutting elements is releasably arranged in the annular engagement portion by a geometrical locking engagement.
Embodiment 13. A roller crusher according to Embodiment 12, wherein the geometrical locking engagement is at least partly defined by a protruding structure of the cutting element being inserted into an associated recess of the annular engagement portion, wherein the protruding structure and the associated recess has complementary shapes.
Embodiment 14. A roller crusher according to Embodiment 13, wherein the associated recess of the annular engagement portion is defined on a side surface thereof.
Embodiment 15. A roller crusher according to Embodiments 13 or 14 when dependent on claim 8, wherein the protruding structure forms a part of the cutter element holding structure.
Embodiment 16. A roller crusher according to Embodiment 15, wherein the cutter element holding structure comprises a support portion protruding out from the same in a direction counter to a tangential direction of motion of the cutting element, said support portion being arranged such that it is supported by the annular engagement portion.
Embodiment 17. A roller crusher according to any one of Embodiments 1 to 16, further comprising wear shields structured and arranged to protect at least parts of the rotatable cutter unit.
Embodiment 18. A roller crusher according to any one of Embodiments 1 to 17, wherein the rotatable cutter unit is arranged with respect to the roller with a flange at 9 to 12 o'clock as defined when the rotational direction of the roller is clockwise.
Embodiment 19. A roller crusher according to any one of Embodiments 1 to 17, wherein the rotatable cutter unit is arranged with respect to the roller with a flange at 6 to 9 o'clock as defined when the rotational direction of the roller is clockwise.
Embodiment 20. A method for operating a roller crusher according to any one of Embodiments 1 to 19, wherein the method comprises at least the step of at least partially cutting away material accumulated on the flange and/or on the envelope surface at an end portion of the roller adjacent the flange by means of the material removal device.
