CA1038357A

CA1038357A - Tube mill

Info

Publication number: CA1038357A
Application number: CA205,050A
Authority: CA
Inventors: Bruno Hillinger; Erwin Scheifinger; Alfred Krenn; Peter Karas
Original assignee: Waagner Biro AG
Current assignee: Waagner Biro AG
Priority date: 1973-07-19
Filing date: 1974-07-18
Publication date: 1978-09-12
Also published as: DE2432121A1; GB1431618A; AU7126574A; NL7409831A; FR2237680B1; FR2237680A1; BE817813A; JPS5048551A

Abstract

Abstract of the Disclosure A tube mill of improved and simplified construction and which pro-vides increased service life, comprises a cylindrical casing, a lining of grinding plates arranged to have a polygonal internal cross-section within the casing, and a plurality of plate mounting supports mounted in axially consecutive rings on the inside of the casing and to which at least some of the grinding plates are directly or indirectly attached, the plate mounting supports of each ring being angularly displaced about the casing axis with respect to the plate mounting supports of the next adjacent ring or rings so that plate mounting supports of the next adjacent rings are out of axial alignment. Grinding plates which are anchored to the casing may be mounted on anchor bolts which are permitted to tilt in at least one plane. A
resilient intermediate member may be provided between the grinding plate and the casing or the plate mounting support respectively to which the plate is mounted. The grinding plates may be mounted resiliently on an elastic band which has substantially the same width as the plates and is positioned between the plates and the plate mounting supports and/or the casing. Coupl-ing pins may interconnect adjacent grinding plates permitting the two plates to pivot during assembly.

Description

~IB357 The invention relates to a tube mill lined with grinding plates to define a polygonal, for example square, internal cross-section.
It has already been proposed to provide tube mills with a polygonal internal cross-section. Such mills contain a large number of grinding plates of different geometries and their production therefore involves the preparat-ion of a large number of patterns for casting the plates Moreover, the com-pact lining causes the specific weight of such a mill to be considerable and the power unit for driving the mill must be of conformable size.
The present invention avoids the above-mentioned drawbacks without impairment of the service life of the mill and of its lining of grinding plates.
According to the invention there is provided a tube mill comprising a cylindrical casing, a lining of grinding plates arranged to have a poly-gonal internal cross-section within the casing, and a plurality of plate mounting supports mounted in axially consecutive rings on the inside of the casing and to which at least some of the grinding plates are directly or indirectly attached, the plate mounting supports of each ring being angularly displaced about the casing axis with respect to the plate mounting supports of the next adjacent ring or rings so that plate mounting supports of next adjacent rings are out of axial alignment.
Preferably the plate mounting supports forming the several rings are interconnected by struts extending axially along the casing of the mill, and they thus constitute an internal reinforcement against buckling of the casing.
For anchoring the grinding plates to the casing, particularly at the corners, a preferred arrangement utilises anchoring bolts, and the cast-ings forming the grinding plates contain openings in which the anchoring bolts are held in a manner permitting swivel deflection in at least one plane, whereas the sides of the grinding plates facing the casing are each formed with a conical or truncated pyramidal projection which provides a bearing face abutting the casing. The bearing face of each grinding plate may be provided with a soft resilient intermediate layer consisting for instance of a 1 mm gauge piece of cardboard graphitised on both sides, a lead or aluminium washer, or of a coating of plastics sprayed directly on said bear-ing surface, the grinding plate being anchored to the casing of the mill by a bolt.
Further, there may be provided, affixed to the base between the plate mounting supports and/or the mill casing and the grinding plates, an elastic band of about the width of the grinding plates and extending in the direction of the circumference of the mill or casing of the mill. In said elastic band may be provided with inwardly conically diverging locally recessed sockets of preferably circular cross-section for the reception of corresponding projections on the grinding plates to form connections resembl-ing those formed by press studs.
Yet another preferred feature consists in providing the grinding plates with locally convexly cambered bearing surfaces and in interconnecting the plates by coupling pins interposed between the plate edges and formed with cylindrically curved abutment faces having relatively spaced centres of curvature.
The above and other features and advantages of the inYention will become further apparent from the following description, given by way of example, of preferred embodiments of the invention, reference being had to the accompanying generally schematic drawings of which:-Figure 1 is a transverse cross-section, taken on line I - I in Figure 2, of a tube mill showing the plate mounting supports welded into place;
Figure 2 is a longitudinal section of the tube mill taken on line II - II in Figure l;
Figure 3 illustrates an arrangement for securing the grinding plates to the plate mounting supports;
Figure 4 illustrates another arrangement for securing the grinding plates to the plate mounting supports;
Figure 5 is a detail longitudinal cross-section showing a grinding plate secured by means of a swivelling bolt;

-2-Figure 6 is a cross-section on line VI - VI in Figure 5;
Figures 7 and 8 illustrate respectively possible alternative designs of bolt head;
Figure 9 is an elevational section of a grinding plate directly attached to the mill casing in the corner of the lining of the mill;
Figure 10 is a cross-sectional plan view taken on line X - X in Figure 9;
Figure 11 is a transverse cross-section of a tube mill in which the grinding plates are attached to the casing with an interposed elastic backing band;
Figure 12 is an enlarged detail view illustrating the method of securing the grinding plates in detail, taken on line XII - XII in Figure 13;
Figure 13 is a cross-section on line XIII - XIII in Figure 12;
Figure 14 shows a joint between a grinding plate and the elastic backing band;
Figure 15 shows an alternative joint arrangement, and Figures 16 to 19 respectively show different designs of coupling pin for interconnecting the grinding plates.
Referring to Figures 1 and 2, the tube mill shown includes a casing 2. Welded to the inside of the mill casing 2 are a plurality of plate mount-ing supports 1 disposed in a manner forming axially consecutive rings 3 to 6 on the inside of the casing 2. The plate mounting supports of each ring are displaced angularly about the cylinder axis (preferably by equal angles) with respect to the plate mounting supports of the next adjacent ring or rings so that the plate mounting supports of the next adjacent rings are out of axial alignment by preferably equal angles. The several plate mounting supports are interconnected by struts 7 extending parallel to the cylinder axis which thus, in conjunction with the plate mounting supports, provide a multiple helix reinforcing structure strengthening the casing 2. Moreover, the con-volutions of the helix may be connected by stiffening braces to form a lattice structure.
The several plate mounting supports 1 are each composed of two angle 1~ 1038357 section components 9 and 10 interconnected by stiffening members 11 positioned in axial alignment with the struts 7.
The incoIporation nfthe plate mounting supports in the reinforcing structure of the mill results in the overall dead weight of the mill being reduced. Furthermore, the number of drilled holes required for securing the grinding plates to the mill casing is reduced by the attachment of the grind-ing plates directly to the plate mounting supports. This design also pro-vides a wider freedom of choice for the grinding plates themselves, so that a standardisation of types can be achieved without the necessity of having to consider the pitch of the bolts.
Figure 3 is a section of a plate mounting support 1 and the method of affixation of a grinding plate 13 is shown at the same time. The under-surface 24 of the grinding plate 13 contains two grooves 15 engaged by the angle section components 9 and 10 of the plate mounting support 1 which is welded to the inside of the casing 2. In order to minimise wear of the plate mounting supports their sides are faced with replaceable armour plates 16.
Figure 4 is a structural variant of Figure 3 in which the grinding plates 13 are formed with a convex bearing portion 21 which rests on the plate mounting support 1, preferably with the interposition of a resilient insert 32. The grinding plates 13 are secured to the mill casing 2 or the chair 1 by means of a bolt 14 carrying nuts 17 having crowned bearing faces which allow the nuts to tilt. The bolt is held in a precast opening 20 in the grinding plate. It is a*tached to the casing 2 by the stiffening member 11 which contains a suitable hole.
The m0thod of attachment of the grinding plates illustrated in Figure 4 is particularly suitable for securing the last member of the lining of grinding plates and for the design of a point bearing. The arrangement permits the number of bolt connections to be reduced.
By welding the plate mounting supports to the casing and providing struts 7 between the several plate mountlng supports 1 the casing of the mill is s*rengthened and external ribbing to provide buckling strength can be dis-, -4-~ 10;~83S7 pensed with. Moreover, the thickness of the casing of the mill can be reduced without loss of rigidity. When the mill is being assembled, the rings being supplied for the purpose in segments, the creation of the butt jointing is simplified and assembly time can be saved.
Figures 5 and 6 are respectively a schematic longitudinal section and cross-section of a lining composed of grinding plates in which the design of the plate mounting supports 1 has been greatly simplified. The grinding plates 1 are provided in their centres with a trough-shaped countersink 22 which in cross-section converges towards the underside 24 of the plate, but which is of constant width in the lengthwise direction. In the centre of the bottom of this countersink there is a slot 23 which extends to the under-side 24 of the plate 13. The slot 23 diverges in the downward direction and the end of an anchoring bolt 14 will therefore be held in the grinding plate in such manner that it has all round freedom of angular movement. This bolt can be drawn into the countersink 22 in the surface 27 of the grinding plate 13 until the head 25 of the bolt rests on the bottom of the countersink. For this purpose the bolts 14 used in Figures 5 and 6 have a specially designed T-shaped head 25, whereas in Pigure 8, as an alternative they have a pear-shaped head 25. In the further alternative of Figure 7 a separate ball-shaped, split intermediate bearing member 26 is provided to avoid the need for a special head. The shaft of the bolt 14 in the four forms of construct-ion can be deflected in such a way that the nut 17 at the shell end of the stud bears flush on the casing 2, the bolt axis being normal to the casing surface. The bolt axis can be tilted for the purposes of assembly as far as the geometry of the slot 15 will allow. Hence in a particular form of con-struction all the grinding plates 13 will have a central countersink or recess of like shape, the same locating means for a bolt and a common geometry, thereby facilitating standardisation and reducing the number of casting patterns needed for production. This advantage is due to the fact that the grinding plates merely form the inside lining faces, whereas separate plates 16 are provided to protect the plate mounting supports 1 from wear.
In the embodiments illustrated in Figures 7 and 8 the roughness of the countersink 20 in the casting for the reception of the head 25 of the anchoring bolt 14 is so considerable that the arrangement does not call for the provision of special means to prevent the head 25 of the bolt from rotat-ing. Consequently the head may be a body of revolution. However, if for reasons of production economy i* is desired to use a standard bolt, then this can be done by providing an intermediate fitting 26 of the kind illus-trated in Figure 7. In these forms of construction minor imprecision and irregularities in the longitudinal pitch of the bores in the casing of the mill can be compensated for the same type of plate.
In order to improve the seating of the grinding plates 13 their under sides may be provided, as indicated in Figures 9 and 10, with conical or frustrum-shaped elevations 21, so that each plate is supported only by a central face. Also, a resilient intermediate layer, such as a washer, may be provided under the bearing face 28 of the grinding plate 13.
Figures 9 and 10 are a cross-section and longitudinal section respectively of an arrangement in which a grinding plate is anchored directly to the casing 2 of the mill, as required for instance for lining the corners in a tube mill of polygonal internal cross-section. A cylindrical casing 2 having an axis of curvature 8 contains a grinding plate 13 which has a grind-ing surface 27 having an axis of curvature 31. The cylindrical casing 2 of the mill with its plate mounting supports welded in is lined over the entire inner surface of the mill with grinding plates of this kind having grinding geometries in conformity with the shape of the lining. The several grinding plates 13 centrally abut the casing 2 or the plate mounting support 1 at a point, their edges 39 being extending outwardly to a point just short of actual mutual contact. The sides 24 of the grinding plates 13 remote from their grinding surfaces and facing the shell 2 of the mill form a truncated pyramidal elevation 21 of which the minor truncated face serves as the bearing surface 28. Interposed between this bearing surface 28 and the shell 2 respectively the plate mounting support 1 is a relatively soft layer 29. This layer 29 may consist either of a 1 mm gauge piece of cardboard graphicised on both sides, or of a lead or aluminium washer, or a plastics coating may be sprayed on the bearing face 28, the latter arrangement having the advantage that it cannot be lost. The intermediate layer could, of course, be secured by means of an adhesive.
The grinding plate 13 is anchored to the casing 2 by a bolt 14 which is schematically indicated in Figure 10. The bolt is located in a countersink in the cast grinding plate so that the bolt head is exposed to little abrasive wear during use of the mill. In order to secure the bolt 14 on the inside of the mill the bolt hole may be formed with a groove to prevent the bolt from turning. Important in this form of construction is the point bearing area, irregularities and imprecision of the casing 2 and the grinding plate 13 at the butt joint being absorbed by the intermediate layer 29. The grinding plate itself is a casting which is easy to produce and in which internal stresses can thus be largely avoided. The grinding surface 27 of the grinding plate is cylindrically arched but its curvature does not agree with that of the shell 2 of the mill.
Figures 11 to 19 illustrate two embodiments of a lining composed of grinding plates for tube mills in which bolts are entirely eliminated.
Linings lacking bolts have already been proposed for circular cross-sections but when there is a departure from the circular section difficulties arise whenever there are minor dimensional faults, and linings of grinding plates lacking bolts for tube mills of polygonal cross-section present particular difficulties, especially near the corners.
Figure 11 exemplifies a lining lacking bolts for a tube mill of polygonal internal cross-section in which an elastic backing in the form of elastic bands 32 is interposed between the grinding plates 13, the casing 2 and the welded cylinder chairs 1. The elastic band 32 may be a rubber band having a Shore hardness between 60 and 85. The number of elastic bands for a complete cross-section corresponds to the number of corners of the poly-gonal mill cross-section, and each separate band begins roughly at the middle of one side of the cross-section and extends across the corner to the middle of the next side.
Figures 12 and 13 are respecti~ely longitudinal and cross-sections illustrating the method of affixation in greater detail. Figure 12 shows a grinding plate 13 about to be mounted directly adjacent a curve in the elastic band 32. Projections 34 formed on the underside 24 of the plate can be seen. These projections 34 engage sockets 33 recessed into the elastic band 32, the projections and the sockets together forming a-kind of press stud connection. In order to secure this connection the elastic band 32 contains bores 35 under its surface near the sockets 33, and pins 36 are inserted into these bores when the grinding plate 13 has been pressed into engagement. Consequently the hardness of the elastic backing is increased at the joints. The elastic band 32 is connected by a countersink bolt 38 and a washer 37 to a base which in this case is a plate mounting support adapted to be dismantled. Figure 13 shows the construction of the plate mounting support 1 which is composed of two radial fins 9 and 10 connected by a head plate forming a capping. In order to prevent the fins 9 and 10 from being abrasively worn they are protected by wear plates 16 which are bolted to the sides of the plate mounting support.
In Figure 14 the construction of the press stud type of connection o the grinding plate 13 to the flexibly elastic backing 32 is shown in detail. The right hand half of the drawing shows the part detached and the left hand half shows the plate attached to the backing. The underside of the grinding plate 13 is formed with a downwardly enlarged or undercut pro-jection 34. The elastic band 32 contains a corresponding socket 33 which the projection 34 enters by elastically deforming the socket 33 in the band 32.
; At the same time a loose ring 18 is pressed into the surface of the band 19, deforming the same and thereby stiffening the elastic band 32 at the press join~ sufficiently to prevent the connection from becoming easily undone.
Figure 15 illustrates another arrangement for securing a press stud type of connection. A metal ribbon 19 is here interposed between the elastic band 32 and the grinding plates 13, the ribbon containing semi-circular openings 12 positioned each at the location of a respective project-ion on the grinding plate and corresponding socket in the elastic band. The elastic band 32 is secured to the base by screws, the ribbon 19 simultaneously I

~ -8-serving as a washer for the screws 38.
The particular form of the lining also admits of polygonal cross-sections other than square, e.g. pentagonal, hexagonal or octagonal. As will be understood by reference to Figure 11 the elastic bands 32 are so disposed that they each extend from the centre of a chair around one corner to the centre of the neighbouring plate mounting support. The elastic bands 32 thus each bridge a corner and permit grinding plates to be secured in each corner without bolts.
Figures 16 to 19 illustrate other embodiments of a lining for a tube mill which requires no bolts. Figure 16 shows two grinding plates 13 which are connected by a rectangular section coupling pin 40. This connect-ing pin has a hook 41 facing the casing 2 of the mill, and this serves for attaching the pin 40 to the casing. The shorter sides of the rectangular coupling pin 40 have a cylindrical camber and this is received into corre-sponding grooves 43 in the lateral edges of the grinding plates 13 which are therefore able to pivot during assembly. In order to prevent the two grind-ing plates from mutually interfering when they move, the centres of curvature 45 and 46 of the two cylindrically cambered abutment faces 43 and 44 are relatively spaced.
Figure 17 illustrates a similar construction of the connection between two neighbouring grinding plates 13, which, unlike the plates in Figure 16, are here set at a relative angle. Consequently the coupling pin 40 which may also be regarded as being a key, has a lenticular configuration.
Naturally hooks 41 may here also be provided, as described with reference to Figure 16.
Figure 18 is another construction of a coupling pin 40 which is divided for the interposition of a wedge 42 to adjust the thrust applied by the halves of the coupling pin 40 to the grinding plates 13 and thus to the casing 2 of the mill. This arrangement is particularly suitable for the last members of a lining ring. In this embodiment both parts of the coupling pin 40 are provided with a hook 41.
In Figure 19 the illustrated arrangement is similar to that in _g_ -l~B3S7 ' Figure 18, but the key 42 is replaced by a component 47 resembling a key which is attached to the casing 2 of the mill by a bolt 14. Owing to the geometry of the coupling pin 40 the two illustrated grinding plates 13 are forced apart so that their ends not shown in the drawing will be thrust against abutments or other grinding plates. The grinding plates 13 illus-trated in Figures 16 to 19 are formed with convex enlargements forming bear-ing surfaces 48 at each end which directly rest on the plate mounting supports 1 or directly on the casing 2. This form of construction permits the support-ing surface to diverge considerably from the geometrical form of a plane or of a circular cylindrical shell and the manufacturing tolerances of such large parts may be fairly coarse.
The described embodiments have the advantage that the number of bolted connections between the casing and the grinding plates can be consid-erably reduced so that, besides saving or minimising the time needed for drilling the casing during assembly, supervision of the plant during operation is also much simpler as fewer bolt heads need be inspected for wear. Indeed the invention indicates how bolted connections can be eliminated entirely.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A tube mill comprising a cylindrical casing, a lining of grinding plates arranged to have a polygonal internal cross-section within the casing, and a plurality of plate mounting supports mounted in axially consecutive rings on the inside of the casing and to which at least some of the grinding plates are directly or indirectly attached, the plate mounting supports of each ring being angularly displaced about the casing axis with respect to the plate mounting supports of the next adjacent ring or rings so that plate mounting supports of the next adjacent rings are out of axial alignment.

2. A tube mill according to Claim 1, wherein the several rings of plate mounting supports are interconnected by struts extending axially of the casing.

3. A tube mill according to Claim 1, wherein the plate mounting supports are comprised by a pair of angle members disposed crosswise of the casing axis and welded to the casing.

4. A tube mill according to Claim 2, wherein the struts in co-operat-ion with the plate mounting supports form an internal stiffening to prevent buckling of the casing and constitute a multiple helix internal reinforcing structure.

5. A tube mill according to Claim 4, wherein the convolutions of the helix are connected by stiffening braces to form a kind of lattice structure.

6. A tube mill according to Claims 2 and 3, wherein stiffening members are provided between the angle members forming the plate mounting supports in alignment with the stiffening struts, said stiffening members being provided with means for anchoring the grinding plates to the plate mounting supports using bolts.

7. A tube mill according to Claim 1, including grinding plates anchored to the casing, such grinding plates containing a cast-in opening 11 , which receives the head of an anchoring bolt in a manner permitting the bolt to tilt in at least one plane, and the undersides of the grinding plates which face the casing are formed with a conical or truncated pyramidal elevation providing a bearing face which abuts the casing.

8. A tube mill according to Claim 7, characterized in that the opening in the grinding plate comprises a trough-shaped countersink with a central slot at the bottom extending to the underside of the grinding plate and re-ceiving the bolt so that the bolt is pivotably deflectable therein.

9. A tube mill according to Claim 7 or 8, wherein the anchoring bolt has a T-shaped head about which the bolt may pivot.

10. A tube mill according to Claim 7 or 8, wherein the head of the anchroing bolt is embraced by a cylindrical bearing member which is received within the opening.

11. A tube mill according to Claim 7 or 8, wherein the head of the anchoring bolt is embraced by a cylindrical split bearing member which is received within the opening.

12. A tube mill according to Claim 7, wherein the opening is con-stricted between the inner face and the underside of the plate and thereafter conically flares or diverges towards the underside.

13. A tube mill according to Claim 12, wherein the bolt head has a spherical bearing surface which engages the plate at the constriction.

14. A tube mill according to Claim 1 or 7, wherein a soft resilient intermediate member is provided between the grinding plate and the part, i.e. the casing or plate mounting support, on to which it is mounted.

15. A tube mill according to Claim 1 or 7, wherein a soft resilient intermediate member is provided between the grinding plate, and the part i.e. the casing or plate mounting support, on to which it is mounted, and the intermediate member comprises a 1 mm gauge piece of cardboard graphitised on both sides, a lead or aluminium washer, or a coating of plastics sprayed on the bearing face of the grinding plate.

16. A tube mill according to Claim 1 or 7, wherein the grinding face and the bearing face are cylindrically arched but the axes of curvature and the radii of curvature of said two surfaces differ.

17. A tube mill according to Claim 1, wherein there is affixed to a base between the plate mounting supports and/or the casing and the grinding plates, an elastic band of substantially the width of the grinding plates and extending in the direction of the circumference of the mill casing, in-wardly conically diverging locally recessed sockets are provided in said elastic band to receive corresponding projections on the grinding plates to form snap connections.

18. A tube mill according to Claim 17, further including bores extend-ing parallel to and closely under the surface of the elastic bands near said sockets into which pins are inserted to secure the projections of the grind-ing plate in the elastic band.

19. A tube mill according to Claim 17, wherein the number of elastic bands for a complete cross-section corresponds to the number of corners of the polygonal mill cross-section, and each separate band begins roughly at the middle of one side of the cross-section and extends across the corner to the middle of the next side.

20. A tube mill according to Claim 17, further including a loose ring which is pressed into the material of the elastic band around each point of connection between the grinding plates and the elastic bands and serving locally to stiffen the joints and prevent them from working loose of their own accord.

21. A tube mill according to Claim 17, wherein the elastic bands are fixed by metal ribbons of substantially the same length as the bands and which contain semi-circular or circular openings at each point of connection the surface of the elastic bands being thus additionally rigidified in this region. 13

22. A tube mill according to Claim 1, wherein the grinding plates have locally convexly cambered bearing surfaces and are interconnected by coupling pins provided between the lateral edges of the plates and formed with cylindrically curved abutment faces having relatively spaced centres of curvature.

23. A tube mill according to Claim 22, wherein the coupling pins have a lenticular cross-section.

24. A tube mill according to Claim 22, wherein the coupling pins have a substantially rectangular cross-section, the shorter sides thereof being semi-circularly curved.

25. A tube mill according to Claim 22, wherein the coupling pins are provided with hook-shaped anchoring elements for attaching them to the casing.

26. A tube mill according to Claim 22 or 25, wherein the coupling pins are of split construction and a wedge or key-like member is insertable between the two parts.