AU2007293940B2

AU2007293940B2 - Grinding unit having cooling device

Info

Publication number: AU2007293940B2
Application number: AU2007293940A
Authority: AU
Inventors: Ernst Michael Haas
Original assignee: FLSmidth AS
Current assignee: FLSmidth AS
Priority date: 2006-09-08
Filing date: 2007-09-03
Publication date: 2011-04-14
Anticipated expiration: 2027-09-03
Also published as: DE102006042825A1; AU2007293940A1; EP2061600B1; CN101557876A; CN101557876B; ES2364592T3; ATE513618T1; EP2061600A1; WO2008028883A1

Abstract

The invention relates to a grinding unit (2) for a vibration mill (1), particularly a disk vibration mill, wherein a milling chamber (3) is configured in the grinding unit (2), the chamber being delimited on the side by a grinding wall (4) and comprising a cooling device (38) surrounding the wall. In order to achieve a practical improvement, the cooling device (38) comprises two or more cooling channels (39) abutting the grinding wall (4) from the outside and disposed circumferentially along at least one common circumferential section of the grinding wall (4), wherein adjacent cooling channels (39) are spaced from each other at least circumferentially in section by a circumferentially extending support projection (41). The support projection (41) supports the grinding wall (4) against a housing (11) surrounding it from the outside. The invention further relates to a vibration mill (1), particularly a disk vibration mill, having said grinding unit incorporated.

Description

1 Grinding unit with cooling arrangement The present invention relates to a grinding unit for a vibration mill, in particular for a disk vibration mill, a grinding chamber which is laterally bordered by a grinding wall 5 being formed in the grinding unit, and a grinding wall being formed in the grinding unit, and having a cooling arrangement surrounding the grinding wall. A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known 10 or that the information it contains was part of the common general knowledge as at the priority date of any of the claims. Throughout the description of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other 15 additives or components or integers. Grinding units or vibration mills of this type serve for example for the grinding comminution of a sample of pourable, granular material to be ground in the course of the preparation of the sample for desired analyses, for example for x-ray-based 20 examinations of the elements contained, by suitable equipment (for example XRF). Material to be ground that is flushed into the grinding space by a liquid is also conceivable. The sample, which may for example be a sample of rock, ore, slag, etc., is mixed and ground up in the vibration mill with auxiliary substances and then pressed with additional pressing aids into a tablet, which is passed on to an analyser 25 to analyse the constituents. The sample must be comminuted in such a way that all the constituents produce a homogeneous mixture, for which a fine and uniform comminution of the material to be ground in the vibration mill is essential. It is often required that a certain proportion of the particles (for example 90%) must be below a certain size (for example 32 qm) after the grinding process. For a quantitative 30 determination of contents, it is essential that the analysis is based on an exactly determined amount of sample. For this purpose, a controlled automotive vibration mill may have a metering device for charging the grinding unit with material to be ground and auxiliary materials in an always exactly defined amount. After the elapse of an adjustable grinding period (known as the grinding phase), the ground sample material SPEC-849447.doc 2 is emptied into a sample collecting container during an adjustable discharge phase. In the case of some compositions of material to be ground, it may happen, in particular after the end of the grinding operation, that with automatic discharge some of the material remains adhered to the grinding unit, in particular in the discharge 5 regions of the grinding vessel, the discharge region and the outlet. As a result of this, not the entire amount of the sample is available for analysis, and consequently the result of the analysis may be falsified. Moreover, there is the risk of a subsequent sample being contaminated by the adhered material and rendered unusable for the analysis. It has been found that the tendency for material to remain adhered may 10 increase, in particular when the vibration mill is in operation for a prolonged period of time, as a result of the frictional heat produced and the rise in temperature of components and of the material to be ground that is thereby caused. To this extent, a rise in temperature may have disadvantageous effects in particular when certain desired, for example paraffin-based, grinding auxiliary materials are added, as a 15 result of more material remaining adhered. In addition, and in particular non-uniform temperature distribution in the grinding unit can also lead to undesired geometrical distortion, i.e. change in shape and position, of components. The adhesions of material and deviations in shape and position can have particularly disadvantageous effects on the grinding wall bordering the grinding chamber, in that this may cause the 20 grinding gap that is formed by a grinding ring or a grinding stone to lose its original parallel bordering delimitation, which is essential for achieving fine ground material particles and uniform particle size. To counteract heating, a grinding unit mentioned at the beginning for a vibration mill has a cooling arrangement surrounding the grinding wall. In the case of such a vibration mill, the grinding wall of the grinding 25 chamber is surrounded by an annular flow space, which is bordered by an outer casing and by bottom and top walls delimiting the upper and lower ends of the flow space. Even if such a cooling gap that borders the grinding wall over the entire height promises to provide direct and uniform cooling, the achievement of particularly fine and uniform ground material particles can still prove to be difficult, depending on the 30 material to be ground. On this basis, it would be preferable to develop a grinding unit or vibration mill of the type mentioned at the beginning advantageously, in such a way as to improve in SPEC-849447 doc 3 particular the suitability for producing small ground material particles with a particle size that is as uniform as possible. According to the present invention, there is provided grinding unit for a vibration mill, 5 including a grinding chamber which is laterally bordered by a grinding wall being formed in the grinding unit, and having a cooling arrangement surrounding the grinding wall, wherein the cooling arrangement has two or more cooling channels bordering the grinding wall from the outside and extending circumferentially along at least one common circumferential portion of the grinding wall, adjacent cooling 10 channels being spaced apart from one another, at least over a portion of the circumference, by means of a circumferentially extending supporting projection, by means of which the grinding wall is supported against a housing surrounding it on the outside and wherein a discharge channel, in particular running in an annular manner around the grinding base, is provided for the discharge of ground material from the 15 vibration mill and in that the cooling grooves are provided in a housing part, in particular in a housing ring, of the grinding unit that is adjacent to the discharge channel. It has surprisingly been found that such a supporting projection of the outer housing, 20 supporting the grinding wall from the outside between the cooling channels, has advantageous effects on the achievable fineness and uniformity of the ground particles. This is attributed to the fact that the cooling action remains good, almost unchanged, even dependent on the cross-sectional shape and size of the cooling channels, while in addition a residual, but nevertheless significant tendency for the 25 grinding wall to be SPEC-849447.doc WO 2008/028883 PCT/EP2007/059170 -4 distorted - remaining in spite of cooling - is counteracted. In addition, the rear support provided according to the invention for the grinding wall between adjacent cooling channels, which preferably 5 acts approximately halfway up the grinding wall, makes it possible to perform a comparatively short grinding operation even without cooling, during which, without support, an approximately barrel-like outward bulging of the grinding wall would otherwise quickly occur, due 10 to the heating. It is preferred for the cooling channels to be provided as cooling grooves in an inner wall surface of a housing part of the grinding unit that abuts against the grinding wall on the outside and for the supporting projection that abuts against the 15 grinding wall from the outside with its free end to be an integral part of the housing part. Such a configuration is appropriate if the grinding wall is intended to consist of an abrasion-resistant hard, and to this extent brittle, material, while the outer 20 housing part may consist of an easier to machine and less notch-sensitive material, for example of steel or light metal. A suitable configuration may be that the grinding wall is cylindrically formed and the cooling grooves are provided in a cylindrical wall surface of a 25 housing ring of the grinding unit that abuts against said grinding wall on the outside. It is also preferred for the housing ring to be thermally shrink fitted onto the grinding wall. Preferably, the outer housing part may be heated up before assembly and then 30 the grinding wall fitted into the opening in the housing part that is provided for it. During the subsequent cooling, the housing part contracts, producing a press fit between the spaced-apart portions of the wall surface in which the cooling grooves are 35 provided and the outer side of the grinding wall. Alternatively or in combination, there is the possibility of the grinding wall being adhesively bonded into the outer housing part. To achieve a WO 2008/028883 PCT/EP2007/059170 -5 cooling effect that is as uniform as possible over the circumference, it is preferred for the cooling grooves to extend along a substantial circumferential portion, preferably over a circumferential angle of 5 approximately 350'. For example, the cooling grooves may extend from a common inflow portion to a common outflow portion, which is separated from said inflow portion in terms of throughflow, preferably by means of a radial wall projection of the housing part 10 surrounding the grinding wall. If a cooled liquid, for example water, is fed through the inflow portion, it flows in a definite direction through the cooling channels to the outflow portion. The inflow portion and outflow portion may preferably be connected to a 15 cooling unit, which makes circulation of the coolant at a controlled coolant temperature possible. To achieve advantageous flow conditions, the supporting projection may be interrupted in the region of the inflow portion and/or the outflow portion. A suitable development is 20 made possible by a circumferential groove with a ring seal, for example with an 0-ring, being respectively provided in the wall surface of the housing part that abuts against the perpendicular grinding wall from the outside, above and at a spacing from the uppermost 25 cooling groove and below and at a spacing from the lowermost cooling groove. Uniform support of the grinding wall is achieved if the housing part in which the cooling grooves are provided has, above the uppermost cooling groove and below the lowermost 30 cooling groove, preferably on both sides of the ring seals, wall regions which abut against the grinding wall from the outside in a supporting manner. According to a further aspect, which may also be of independent significance within the scope of the 35 present invention, there is the possibility of a discharge channel, preferably running in an annular manner around the grinding base, being provided for the discharge of ground material from the vibration mill WO 2008/028883 PCT/EP2007/059170 -6 and of the cooling grooves being provided in a housing part, preferably in a housing ring, of the grinding unit that is adjacent to the discharge channel. In this way, adhesions of the ground material and 5 temperature-related deviations in shape and position in the discharge channel are counteracted. According to yet another aspect, which may likewise be independently of significance, there is the possibility of the grinding unit having a connection for a blowing medium, 10 preferably compressed air, for blowing out the discharge channel to clean it, which connection opens out for distributing purposes into an annular channel that is bordered by the housing part in which the cooling grooves are provided and by an adjacent housing 15 portion, so that a narrow annular gap remains as a passage to the discharge channel. The narrow annular gap may have, in a cross-sectional plane oriented transversely in relation to the circumferential direction, a width of preferably several or a few 20 fractions of a millimeter up to possibly a few millimeters. If compressed air is blown into the annular channel, it flows through the narrow annular gap, the defined gap width in the discharge channel having the effect of establishing a desired specific 25 air flow, which is advantageous for the blowing out of residues of ground material. If the small gap width were made smaller as a result of thermal distortion, the blowing out would be made more difficult or under some circumstances prevented, while on the other hand 30 the flow conditions advantageous for blowing out would not be achieved if there were a widening of the gap. The grinding unit may be equipped with temperature sensors, which may preferably be arranged in the region of the grinding wall. The sensors may send measuring 35 signals to a control system of a connected cooling unit, in order to keep the temperature of the grinding wall as constant as possible in the course of control by adapting the inflow temperature according to WO 2008/028883 PCT/EP2007/059170 -7 requirements. The invention also comprises a vibration mill, in particular a disk vibration mill, having a grinding unit that can be made to vibrate by means of a vibratory drive, the grinding unit realizing a lesser 5 or greater number of the previously explained features according to the invention. The invention is described in more detail below with reference to the accompanying figures, which show a 10 preferred exemplary embodiment and in which: Figure 1 shows a sectional view through the grinding unit according to the invention of a disk vibration mill in a preferred embodiment, in 15 a first operating position for the grinding process; Figure 2 shows the grinding unit represented in Figure 1, in a second operating position for the 20 discharge process; Figure 3 shows a side view of the vibration mill with the grinding unit shown in Figures 1 and 2; 25 Figure 4 shows as a single part in perspective a housing ring which in the fitted state encloses the grinding wall and in which cooling channels with a supporting projection are provided, and 30 Figure 5 shows an enlargement of the detail V taken from Figure 1. Figure 1 shows in a cross-section the upper region of a 35 vibration mill 1 according to the invention or a grinding unit 2 according to the invention, as provided by a preferred embodiment. Figure 3 shows an overall, partly schematic, view of the vibration mill. This is WO 2008/028883 PCT/EP2007/059170 -8 what is known as a disk vibration mill. Its grinding unit 2, shown in Figure 1, represents a subassembly which can be made to vibrate by a separate vibratory drive, connected to the grinding unit, and which 5 includes a grinding chamber 3 that is bordered on the outside by a cylindrical grinding wall 4. This is adjoined on the underside during the grinding operation by a substantially circular grinding base 5. Lying on the latter in the exemplary embodiment shown is a 10 grinding ring 6 and a grinding stone 7, which is a round solid body, not shown in section in the representation. The outside diameter of the grinding ring 6 is less than the inside diameter of the grinding wall 4, and the outside diameter of the grinding stone 15 7 is less than the inside diameter of the grinding ring 6. The grinding gap 8 thus formed between the grinding wall 4 and the grinding ring 6 and the grinding gap 9 formed between the grinding ring 6 and the grinding stone 7 make a lateral relative movement of the 20 grinding ring 6 and the grinding stone 7 possible, both with respect to each other and with respect to the grinding wall 4. The latter is adjoined on the upper side, in a sealed manner, by a grinding cover 10. In Figure 1, in which the grinding base 5 is in its upper 25 possible position, during what is known as the grinding phase, the vertical distance between the grinding base 5 and the grinding cover 10 is only slightly greater than the height of the grinding ring 6 and the grinding stone 7, so that exactly the desired play for the 30 lateral movement is produced. The grinding wall 4 is adjoined radially on the outside by a housing ring 11, which is screw-connected on the underside to a housing base 12 and thereby connected to a drive flange 13. On the upper side, the housing ring 11 is screw-connected 35 to a housing cover 14. The underside of the latter has a recess 15, in which a seal 16, in the chosen example an 0-ring, is fitted at the periphery and fitted therein is a grinding cover 17. The underside of the WO 2008/028883 PCT/EP2007/059170 -9 housing cover 14, of the seal 16 and of the grinding cover 17 are pressed against the upper end face of the grinding wall 4 by the clamping force of cover screws 18 distributed along the circumference. The housing 5 cover 14 and the grinding cover 17 have off-center through-passage openings to form a charge opening 19. Through this opening, the material to be comminuted (not represented) can be filled from above into the grinding chamber 3, where it spreads out in the 10 grinding gaps 8, 9. If, as still to be described below, lateral vibrating movements of the grinding elements 6, 7 in relation to one another and in relation to the grinding wall 4 occur, the grinding gaps 8, 9 continually change locally in their width, 15 whereby the material to be ground is ground between the grinding elements 6, 7 and the grinding wall 4. The grinding wall 4, the grinding ring 6 and the grinding stone 7 may be produced from a material that is particularly suitable for this purpose, in particular 20 from an abrasion-resistant, hard material, while a conventional structural material, for example steel or light metal, can be used for the housing ring 11 and the other housing parts. Screw-connected onto the underside of the housing base 12 is a holder 20, which 25 with its free end carries a cylinder 21, which is represented in a simplified form and the piston 22 of which, protruding on the upper side, is fixed on the underside to the grinding base 5 by means of a screw connection. The cylinder 21 has two connections 23, 24 30 for supplying a pressurized fluid, such as air, or a hydraulic fluid. In the operating position shown in Figure 1, a pressure medium is fed through the lower connection 24, acts from below upon a pressure surface (not represented) of the piston 22 inside the cylinder 35 21 and presses said piston upward with the grinding base 5, until a step 25 of the grinding base 5 comes into limiting positive engagement with the grinding wall 4. The act of the step 25 coming up against a WO 2008/028883 PCT/EP2007/059170 - 10 lower bevel 26 of the grinding wall 4 and a region of the grinding base 5 that upwardly adjoins the step 25 fitting into the cross-section enclosed by the grinding wall 4 that takes place in this operating position 5 shown in Figure 1, has the effect that the grinding chamber 3 is sealed along the outer circumference of its grinding base during the grinding operation. Figure 2 shows by comparison, a second operating 10 position, in which pressurized fluid is applied to the upper connection 23. Inside the cylinder 21, a pressure-receiving surface of the piston 22 is thereby acted upon from above in a manner not represented any more specifically, so that the piston 22 draws the 15 grinding base 5 downward until it comes to a defined positively engaging stop against a collar 27 of the housing base 12. In the lowered operating position shown, a circumferentially extending gap 28 is produced between the grinding base 5 and the grinding wall 4, 20 through which gap the material comminuted during grinding passes into an annular discharge channel 29 as a result of the centrifugal forces occurring when further vibration is induced, and therein up to an outlet opening 30 to an outlet 31, as a result of 25 vibration being induced. In cross-section, the discharge channel 29 is delimited radially inward by the grinding base 5, on the underside by a seal 32 supported resiliently on the housing base and by the housing base 12, and radially outward by the housing 30 base 12, while the housing ring 11 and the grinding wall 4 adjoin in the upward direction. The cross section formed in this way of the discharge channel 29 lies with respect to the grinding chamber such that it is offset obliquely downward/radially outward. 35 Figure 3 schematically illustrates that the grinding unit 2 shown in Figures 1 and 2 is supported at the drive flange 13 on the underside by means of spring- WO 2008/028883 PCT/EP2007/059170 - 11 damper elements 33 on a fixed base. Flange-mounted by means of screw connections onto the underside of the flange 13, which on the upper side merges into a sleeve 13', is a vibratory drive 34. In the example chosen, 5 this drive has a drive motor 35, here an electric motor, the shaft 36 of which rotates an off-center unbalanced or eccentric mass, which is known per se and therefore not included in the drawing, in a housing 37 located above said shaft. The rotary vibration 10 produced in this way in the drive device is transmitted by way of the drive flange 13 to the entire connected grinding unit 2, including all the walls involved in the grinding process and in the discharge of the ground material. 15 Again with reference to Figures 1 and 2, it is shown that the vibration mill 1 or its grinding unit 2 is equipped with a cooling arrangement 38, for the rear or outer cooling of the grinding wall 4. This cooling 20 arrangement has in the example shown two cooling channels 39, directly bordering the grinding wall 4 from outside and spaced apart parallel to each other. As Figure 4 also illustrates in perspective, these are two cooling grooves 39, which are provided in the wall 25 surface 40 of the housing ring 11 of the grinding unit 2 that abuts against the grinding wall 4 on the outside. The cooling grooves 39, which in the example chosen, but not necessarily, extend parallel to each other over a circumferential angle of approximately 350 30 degrees, are spaced apart from each other by means of a likewise circumferentially extending supporting projection 41, which is formed in the manner of a rib. As Figures 1, 2 show, in the assembled state, this supporting projection 41, which is similar to a segment 35 of a ring, engages in a supporting manner against the outer side of the outer wall 4. In this case, the supporting projection 41 is an integral, i.e. one piece, component part of the housing ring 11. Figure 4 WO 2008/028883 PCT/EP2007/059170 - 12 also shows that the cooling grooves 39 extend from a common inflow portion 42 to a likewise common outflow portion 44, which is separated from said inflow portion in terms of throughflow by means of a radial wall 5 projection 43 of the housing ring 11. As a result, the inflow and outflow are separated in terms of throughflow, so that a deliberate circulation of coolant, which is provided for example by a cooling unit equipped with a control or regulating system, can 10 be enforced. Figure 1 shows in this respect that a radial through-passage bore is provided in the inflow portion 42 (and in the outflow portion concealed in Figure 1), in the thread of which bore a connection for a fluid line or a closure element 45 (as represented) 15 can be screwed. Figure 4 also shows that the supporting projection 41 is interrupted in the region of the inflow and outflow portions 42, 44, or ends before these portions. In Figures 1 and 2 it can be seen that a circumferential groove 46 with a ring seal 20 47 is respectively provided in the wall surface 40 of the housing ring 11 that abuts against the perpendicular grinding wall 4 from the outside, above the upper cooling groove 39 and below the lower cooling groove 39. The housing ring 11 in which the cooling 25 grooves 39 are provided also has above the upper cooling groove 39, on each of both sides of the ring seals 47, wall regions which adjoin the grinding wall 4 in a supporting manner from the outside. Figures 1 and 2 also show that the housing ring 11 in which the 30 cooling grooves 39 are provided, is directly adjacent to the discharge channel 29 running around the grinding base 5. It becomes clear in connection with Figure 5 that the vibration mill 1 has a connection 48 for a blowing medium, in the example chosen compressed air, 35 which opens out into an annular channel 49, which is bordered by the housing ring 11 in which the cooling grooves 39 are provided and by the adjacent housing WO 2008/028883 PCT/EP2007/059170 - 13 base 12, so that a narrow annular gap 50 is produced as a passage to the discharge channel 29. All features disclosed are (in themselves) pertinent to 5 the invention. The disclosure content of the associated/accompanying priority documents (copy of the prior patent application) is also hereby incorporated in full in the disclosure of the application, including for the purpose of incorporating features of these 10 documents in claims of the present application.

Claims

1. Grinding unit for a vibration mill, including a grinding chamber which is laterally bordered by a grinding wall being formed in the grinding unit, and having a cooling 5 arrangement surrounding the grinding wall, wherein the cooling arrangement has two or more cooling channels bordering the grinding wall from the outside and extending circumferentially along at least one common circumferential portion of the grinding wall, adjacent cooling channels being spaced apart from one another, at least over a portion of the circumference, by means of a circumferentially extending supporting 10 projection, by means of which the grinding wall is supported against a housing surrounding it on the outside and wherein a discharge channel, in particular running in an annular manner around the grinding base, is provided for the discharge of ground material from the vibration mill and in that the cooling grooves are provided in a housing part, in particular in a housing ring, of the grinding unit that is adjacent to the 15 discharge channel.

2. Grinding unit according to Claim 1 wherein the cooling channels are provided as cooling grooves in a wall surface of a housing part of the grinding unit that abuts against the grinding wall on the outside and in that the supporting projection that 20 abuts against the grinding wall from the outside with its free end is an integral part of the housing part.

3. Grinding unit according to any one of the preceding claims wherein the grinding wall is cylindrically formed and the cooling grooves are provided in a 25 cylindrical wall surface of a housing ring of the grinding unit that abuts against said grinding wall on the outside.

4. Grinding unit according to any one of the preceding claims wherein the housing ring is thermally shrink-fitted onto the grinding wall. 30

5. Grinding unit according to any one of the preceding claims wherein the grinding wall is adhesively bonded into the housing ring. SPEC-849447.doc 15

6. Grinding unit according to any one of the preceding claims wherein the cooling grooves extend along a substantial circumferential portion, in particular over a circumferential angle of approximately 350 degrees. 5

7. Grinding unit according to any one of the preceding claims wherein the cooling grooves extend from a common inflow portion to a common outflow portion, which is separated from said inflow portion in terms of throughflow, in particular by means of a radial wall projection of the housing part surrounding the grinding wall. 10

8. Grinding unit according to any one of the preceding claims wherein the supporting projection is interrupted in the region of the inflow portion and/or the outflow portion.

9. Grinding unit according to any one of the preceding claims wherein a 15 circumferential groove with a ring seal is respectively provided in the wall surface of the housing part that abuts against the grinding wall from the outside, above the uppermost cooling groove and below the lowermost cooling groove.

10. Grinding unit according to any one of the preceding claims wherein the housing 20 part in which the cooling grooves are provided, has above the uppermost cooling groove and below the lowermost cooling groove, wall regions which abut against the grinding wall from the outside.

11. Grinding unit according to any one of the preceding claims wherein the 25 grinding unit has a connection for a blowing medium, in particular compressed air, for blowing out the discharge channel, which connection opens out into an annular channel, which is bordered by the housing part in which the cooling grooves are provided and by an adjacent housing portion, so that a narrow annular gap remains as a passage to the discharge channel. 30

12. Vibration mill, having a grinding unit according to any one of the preceding claims that can be made to vibrate by means of a vibratory drive.

13. Vibration mill according to claim 13 comprising a disk vibration mill. SPEC-84947.doc 16

14. Grinding unit according to any preceding claim wherein the grinding unit is for a disk vibration mill. 5

15. Grinding unit substantially as herein described with reference to the accompanying drawings. SPEC-849447.doc