AU780346B2 - A grinding machine - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant/s: M.I.M. Holdings Limited and Erich Netzsch GmbH Co Holding KG Actual Inventor/s: Peter Charles Woodall and Udo Enderle Address for Service: BALDWIN SHELSTON WATERS MARGARET

STREET

SYDNEY NSW 2000 Invention Title: 'A GRINDING MACHINE' Details of Associated Provisional Application No. PQ0849 dated 08 Jun 1999 The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 28289AUP00 FIELD OF INVENTION The invention relates to a grinding machine.

The invention has been developed primarily as an ultra-fine grinding machine for use in large scale mineral processing and leaching operations and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to that particular field of use.

BACKGROUND

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

A known ultra-fine grinding machine has a shell defining a grinding chamber, grinding discs in the chamber mounted on a shaft, and a product separator. The shaft is generally driven by a motor through a reduction system which in some embodiments includes a gearbox and in other embodiments includes a pulley system. Product or product particles are fed into one end of the chamber and, once ground, exit the opposite end of the chamber. The grinding process is achieved by rotation of the grinding discs which agitate a grinding medium which is in grinding contact with the product. The product separator retains the grinding medium within the chamber while allowing the ground product to exit the second end.

The grinding process causes frictional wear on the inner surface of the shell. To prolong the operational life of the shell and to prevent leakage of partially ground product from the chamber it has been known for the shell to include a sacrificial rubber lining.

Such a lining must be replaced periodically, which necessitates halting the grinding machine. In some prior art machines the lining includes a plurality of separate rubber or 25 other sacrificial blocks which are individually adhered or otherwise secured to the interior of the shell. Accordingly, replacement of the lining involves removing the -3wom or damaged blocks and replacing them with fresh blocks. This process is time consuming, expensive, labour intensive and requires the machine to be off-line for a considerable period.

In partial answer to these problems other prior art machines utilise an alternative method of replacement. More particularly, the shell is removably mounted to the machine so that when a replacement lining is required the shell is detached and transported to a lining factory at a site remote from the grinding site. To facilitate removal of the shell, it is known to have it mounted on wheels which run along tracks.

Thus, to remove the shell, the necessary bolts and other securement devices are removed for allowing the shell to move along the tracks and clear of the remainder of the machine.

While the removable shell decreases the amount of down-time for the grinding machine, it is time consuming, expensive and inconvenient to perform. Moreover, to minimise down-time a second shell is required to operate while the first is being relined.

This increases the associated capital cost of the machine.

It is an object of the present invention, at least in preferred embodiments, to overcome or ameliorate one or more of the disadvantages of the prior art or to provide an alternative.

In this specification, the term "tubular" is to be interpreted broadly to cover both structures of circular cross-section, such as right-cylindrical, and frusto-conical, structures, as well as structures of non-circular cross-section.

-4- SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a grinding machine for grinding particles, the machine including: a shell having an inner an inner surface for defining a tubular grinding chamber; grinding elements in the chamber for grinding the particles; and a sacrificial lining extending over substantially the entire inner surface, said lining being a single integral entity.

According to a second aspect of the invention there is provided a grinding machine for grinding particles, the machine including: a shell having an inner surface for defining a tubular grinding chamber; grinding elements in the chamber for grinding the particles; a sacrificial lining on the inner surface; and detecting means for determining when a region of said lining has worn outwardly to a predetermined remaining thickness of the lining.

15 According to a third aspect of the invention there is provided a shell for a oo grinding machine the shell including a plurality of shell parts separable from one another each shell part having a shell-part surface, the shell part surfaces together constituting an inner surface of the shell and the inner surface defining a tubular grinding chamber.

According to a fourth aspect of the invention there is provided a sacrificial lining for lining substantially an entire inner surface of a grinding machine shell, the lining being a single integral entity.

According to a fifth aspect of the invention there is provided a method of maintaining a grinding machine of a type for grinding particles and having a shell with an inner surface defining a tubular grinding chamber, grinding elements in the chamber 25 for grinding the particles and a first sacrificial inner shell lining constituted by a single integral entity wherein the shell is dismantlable into a plurality of shell parts, the method including the steps of: dismantling the shell into the shell parts; removing the lining; replacing the lining with a second lining; and reassembling the shell.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', and the like are to be construed in an inclusive sense opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited".

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a section view of a grinding machine according to an embodiment of the invention; Figure 2 is a schematic perspective view of the grinding machine; Figure 3 is a schematic elevation view of the grinding machine; Figure 4 is a schematic end view of the grinding machine as shown in Figure 3; and Figure 5 is a schematic section through another embodiment of the grinding machine.

i o°° o o o o °o o .o* g* DETAILED DESCRIPTION Referring to the drawings, grinding machine 1, for grinding particles, includes a shell 2 having an inner surface defining a cylindrical grinding chamber 3.

Grinding elements in the form of rotatable grinding discs 4 in chamber 3 are for grinding the particles. Discs 4 are mounted on a shaft 5 which is connected via a reduction system to a motor, the reduction system and motor not being shown. In one embodiment the reduction system includes a gear box and in another embodiment it includes a pulley system. The machine further has a sacrificial rubber lining 6 on the inner surface of shell 2, the lining being a single integral entity. In one embodiment, the lining is of a rubber known commercially as The grinding machine includes a pair of detecting means each including a conductive wire 7 and 8 (see Figures 3 and embedded in lining 6. Each wire 7 and 8 is positioned in lining 6 to be effective for detecting when the lining has worn down to a point where a predetermined thickness of the lining remains. To this effect the wires are appropriately positioned for determining when the lining has worn, from the initial inner .i face 9 of the lining, to a predetermined depth of wear, this depth corresponding to the predetermined remaining thickness. The distance of each wire from initial inner face 9 corresponds to the respective predetermined depth relating to that wire. The machine is configured to determine that the lining has worn to each predetermined depth on breakage of the respective wire, as will be explained in more detail below.

Wires 7 and 8 each form part of an electrical circuit for conducting electric current through the respective wire. Each circuit includes breakage detecting means in the form of an ammeter 10 for determining when breakage of the respective wire occurs.

Each wire 7 and 8 extends along a helical path from a position adjacent one end 11 of shell 2 to a position adjacent the opposite end 12 of the shell.

In one embodiment, one of the wires, wire 7, is at a distance from inner face 9 equal to 50% of the thickness of lining 6 prior to wearing. Wire 7 is therefore effective for determining when the lining has worn to a depth of wear of 50% of this thickness.

The other wire, wire 8, is at a distance firom inner face 9 equal to 90% of the thickness of lining 6 prior to wearing. This wire is therefore effective for determining when the lining has worn to a depth of wear of 90% of the thickness.

Outer ribbing in the form of a number of steel belts 13 extends around lining 6 to render the lining more rigid.

.o Shell 2 is made up of two shell parts 14 and 15 which arejoined to each other along a horizontally extending joint 16. Each shell part 14 and 15 includes a semitubular portion of the inner surface of shell 2, which, because of the cylindrical shape of grinding chamber 3, is also semi-cylindrical. Consequently when the shell parts are placed together as shown in Figures 1 to 4 the portions together define the inner surface and hence chamber 3. Shell parts 14 and 15 have complementary locking means 17, indicated schematically in Figure 2, to lock them together. The locking means are sufficiently strong to withstand pressure exerted on them which results from the pressure built up in chamber 3 during the grinding process.

Shell 2 is dismantlable by moving shell part 14 upwards away from shell part It will be appreciated that the upward movement of shell part 14 away from shell part involves a component of movement transverse to the axial direction of chamber 3. It -8 will also be appreciated that each shell part 14 and 15 extends the full length of the shell, from end 11 to end 12. These features of the shell facilitate removal of lining 6 from the shell, which will be discussed further below.

In use, product particles to be ground are inserted into chamber 3 through a feed opening (not shown) at end 11. Also in the chamber during the grinding process are particles of a grinding medium (not shown) which are in grinding contact with the product particles. The product particles are ground by the high velocity spinning action of grinding discs 4 which agitates and causes a stirring effect on the grinding medium particles. The grinding medium particles, in turn, grind the product particles by way of attrition or abrasion. During this process the surfaces of the product particles are repeatedly chipped, producing very fine-sized progenies. The ground product particles are discharged from chamber 3 through a discharge opening (not shown). A product separator (not shown) permits discharge of the ground product while retaining the grinding medium in the chamber.

Wearing of lining 6 occurs during the grinding process. This necessitates replacement of the lining which, according to an aspect of the invention, takes place during maintenance of the grinding machine.

The method of maintaining the grinding machine includes the basic steps of dismantling shell 2 into shell parts 14 and 15, removing lining 6, replacing the lining with another lining, and reassembling the shell.

However, it should be noted that wearing of the lining does not occur evenly. It has been found that wearing occurs faster at the feed end of the chamber (end 11) than at the discharge end (end 12). To address this, the method includes a further step after the -9step of removing lining 6. The further step includes reversing the same unevenly worn lining by rotating it through 180 degrees about an axis extending perpendicularly to the lining's longitudinal axis, replacing it, permitting it to wear further, and then removing it again and replacing it with a new unworn lining.

The decision as to when to reverse existing lining 6, and when to remove it completely and replace it with the unworn lining, is based on certain predetermined depths of wear having been reached.

When lining 6 wears to a depth corresponding to the distance of wire 8 from inner face 9, the wearing action breaks the wire. The ammeter 10 connected to wire 8 then registers a termination of the current flowing through the wire. From the termination of current it is determined that the wire has broken and therefore that wear has occurred to this depth. Because wire 8 is embedded in lining 6 at a distance from inner face 9 corresponding to 50% of the thickness of the lining prior to wear occurring, this is the percentage depth of wear at which the wire is broken. Reversing of the lining is carried out at this stage.

"o *.To reverse lining 6, locking means 17, which hold shell parts 14 and 15 together, are undone and shell 2 is dismantled as described above. Lining 6 is then lifted off shell part 15, reversed as described above, and replaced on the shell part. Then, shell part 14 is returned to its former position to cover the lining and is once again secured to shell part 15 by the locking means.

The grinding process is then continued until wire 7 is broken. Because of the distance of wire 7 from inner face 9 as discussed above, breakage of the wire occurs at a depth of wear of 90% of the thickness of the lining prior to wear occurring. At this stage shell 2 is again dismantled, whereafter lining 6 is removed, and this time replaced by a new, unworn lining.

Removal of the worn lining and replacement by a new lining is carried out in much the way that worn lining 6 was reversed, except that no reversal takes place.

Referring to Figure 5, there is shown another embodiment 18 of the grinding machine according to the invention. In this embodiment, the lining 19 has a pair of laterally projecting ribs 20, one on either side of the lining. Each rib 20 extends substantially the length of the lining and is sandwiched between a respective pair, 21 or 22, of the flanges 23 of the shell parts 24 of the grinding machine.

Outer ribbing in the form of a number of steel belts 25, similar to steel belts 13 mentioned above, extends around lining 19 to render it more rigid. However, belts differ from belts 13 in that they each consist of a pair of belt portions 26. Each belt portion 26 extends circumferentially with respect to, and substantially halfway around, the lining. Each belt portion 26 has a pair of transversely projecting tabs 27 at its opposite ends. Tabs 27 of each belt portion 26 are sandwiched between the respective two flanges of each pair 21 or 22. Belt portions 26 are held together in this way. As the shell parts 24 are tightened to each other on assembly of the grinding machine, tabs 27 are forced by the flanges of each pair 21 and 22 to embed in the respective adjacent rib The flanges locate lining 19 and locate belt portions 26 with respect to the lining.

Consequently, the lining is prevented from twisting during operation of the grinding machine. This assists in preventing damage to the wear detecting wires (not shown in Figure 5) embedded in lining 19.

11 In all respects other than those specifically mentioned, grinding machine 18 is substantially identical to grinding machine 1.

Whereas the linings defined and described above have wires for determining wear to each of two predetermined depths, it will be appreciated that wires can be embedded in the lining to determine wear to three or more predetermined depths. This will provide a useful arrangement in cases where the wear rate is unknown or extremely uneven.

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that it may be embodied in many other **forms.

S.

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Claims (41)

1. A grinding machine for grinding particles, the machine including: a shell having an inner surface for defining a tubular grinding chamber; grinding elements in the chamber for grinding the particles; and a sacrificial lining extending over substantially the entire inner surface, said lining being a single integral entity.

2. A grinding machine according to claim 1 further including detecting means for determining when a region of said lining has worn outwardly to a predetermined remaining thickness of the lining.

3. A grinding machine according to claim 2 wherein said detecting means is configured for determining when a region of said lining has worn outwardly to a predetermined depth of wear from an initial inner face of the lining said depth corresponding to said remaining thickness.

4. A grinding machine according to claim 3 wherein the detecting means includes o 15 a conductive wire embedded in the lining at a distance from the inner face, the distance Scorresponding to said depth, the machine being configured for said determining to occur on breakage of the wire.

5. A grinding machine according to claim 4 wherein the wire is operatively associated with breakage detection means for detecting said breakage. S 20 6. A grinding machine according to claim 5 wherein the wire forms part of an 9999 S. electrical circuit for conducting electrical current through the wire and the breakage detecting means includes a meter for detecting termination of the current through the wire.

7. A grinding machine according to claim 6 wherein the wire extends along a helical path from a position adjacent one end of the shell to a position adjacent the opposite end of the shell.

8. A grinding machine according to any one of claims 3 to 7 wherein the grinding machine includes a plurality of the detecting means for determining when a region of the lining has worn to any of a plurality of predetermined depths, each said depth -13- corresponding to the distance of a respective one of the detecting means from the inner face.

9. A grinding machine according to claim 8 wherein one of the detecting means is configured for determining when the lining has worn to a depth of wear of 50% of the thickness of the lining prior to the wearing and another of the detecting means configured for determining when the lining has worn to a depth of wear of 90% of the thickness of the lining prior to the wearing. A grinding machine according to any one of claims 3 to 9 wherein the lining is surrounded by ribbing which includes an outer rigidifying belt.

11. A grinding machine according to claim 10 wherein the belt is of metal.

12. A grinding machine according to claim 11 wherein the metal includes steel.

13. A grinding machine according to any one of claims 10 to 12 wherein the ribbing includes a plurality of like said belts.

14. A grinding machine according to any one of claims 1 to 13 wherein the lining is of an elastomeric material. A grinding machine according to claim 14 wherein the lining is of rubber.

16. A grinding machine according to any one of claims 1 to 15 wherein the grinding chamber is cylindrical.

17. A grinding machine according to any one of claims 1 to 15 wherein the 20 grinding chamber is frusto-conical.

18. A grinding machine according to any one of claims 1 to 17 wherein the shell is dismantlable into a plurality of shell parts.

19. A grinding machine according to claim 18 wherein the chamber has a longitudinal axis and the shell parts are separable by moving one of the shell parts in a direction having a component transverse to the direction of the axis. -14- A grinding machine according to claim 19 wherein each shell part extends from one end of the shell to an opposite end of the shell.

21. A grinding machine according to claim 20 wherein the plurality of shell parts consists of two shell parts each including a semi-tubular portion of the inner surface.

22. A grinding machine according to claim 21 wherein the two shell parts are joined along a horizontally extending joint.

23. A grinding machine according to claim 22 wherein each shell part has a pair of transversely projecting flanges at the joint, each flange of one of the shell parts lying adjacent a respective flange of the other shell part, whereby the shell parts are securable to each other by securing together the respective adjacent flanges.

24. A grinding machine according to claim 23 wherein the lining has a pair of transversely projecting ribs each of which is sandwiched between a respective two of the flanges of the shell parts. A grinding machine according to claim 24 wherein each rigidifying belt includes two belt portions each extending circumferentially substantially halfway around the lining, each belt portion having a pair of transversely projecting tabs at its opposite ends, each tab 1• being sandwiched between a respective two of the flanges of the shell parts.

26. A shell for a grinding machine according any one of claims 1 to 25, the shell including a plurality of shell parts separable from one another, each shell part having a shell-part surface, the shell-part surfaces together constituting an inner surface of the shell and the inner surface of defining a tubular grinding chamber. S•27. A shell according to claim 26 wherein the chamber has a longitudinal axis and the shell parts are separable by moving one of the shell parts in a direction having a S•component transverse to the direction of the axis.

28. A shell according to claim 27 wherein each shell part extends from one end of the shell to an opposite end of the shell.

29. A shell according to claim 28 wherein the plurality of shell parts consists of two shell parts each including a semi-tubular portion of the inner surface. A shell according to claim 29 wherein the two shell parts are joined along a horizontally extending joint.

31. A shell according to claim 30 wherein each shell part has a pair of transversely projecting flanges at the joint, each flange of one of the shell parts lying adjacent a respective flange of the other shell part, whereby the shell parts are securable to each other by securing together the respective adjacent flanges.

32. A sacrificial lining for lining substantially the entire inner surface of a grinding machine shell, the lining being a single integral entity.

33. A sacrificial lining according to claim 32, operatively associated with detecting means for determining when a region of the lining has worn outwardly to a predetermined remaining thickness of the lining.

34. A sacrificial lining according to claim 33, wherein said detecting means is configured for determining when a region of said lining has worn outwardly to a predetermined depth of wear from an initial inner face of the lining, said depth 15 corresponding to said remaining thickness. :o 35. A sacrificial lining according to claim 34 wherein the detecting means includes a conductive wire embedded in the lining at a distance from the inner face, the distance corresponding to said depth, the detecting means being suitable for said determining to :.occur on a breakage of the wire. 20 36. A sacrificial lining according to claim 35, wherein the wire is operatively ioo• associable with breakage detecting means for detecting said breakage.

37. A sacrificial lining according to claim 36 wherein the wire is capable of forming part of an electrical circuit for conducting electrical current through the wire and the breakage detecting means includes a meter for detecting termination of the current through the wire.

38. A sacrificial lining according to claim 37 wherein the wire extends along a helical path from a position adjacent one end of the lining to a position adjacent an opposite end of the lining. -16-

39. A sacrificial lining according to any one of claims 34 to 38 wherein the lining is operatively associable with a plurality of said detecting means for determining when the lining has worn to any of a plurality of predetermined depths, each said depth corresponding to the distance of a respective one of the detecting means from the inner face. A sacrificial lining according to claim 39 wherein one of the detecting means is configured for determining when the lining has worn to a depth of wear of 50% of the thickness of the lining prior to the wearing and another of the detecting means is adapted for determining when the lining has worn to a depth of wear of 90% of the thickness of the lining prior to the wearing.

41. A sacrificial lining according to any one of claims 32 to 40 wherein the lining is surrounded by ribbing which includes an outer rigidifying belt.

42. A sacrificial lining according to claim 41 wherein the belt is of metal.

43. A sacrificial lining according to claim 42 wherein the metal includes steel.

44. A sacrificial lining according to any one of claims 41 to 43 wherein the ribbing includes a plurality of like said belts. o A sacrificial lining according to any one of claims 32 to 44 wherein the lining is of an elastomeric material.

46. A sacrificial lining according to claim 45 wherein the lining is of rubber.

47. A sacrificial lining according to any one of claims 32 to 46, the lining taking the .form ofa substantially tubular body. oooo o 48. A sacrificial lining according to claim 47, including an outwardly projecting rib extending axially along each diametrically opposite side of said tubular body.

49. A method of maintaining a grinding machine of a type for grinding particles and having a shell with an inner surface defining a tubular grinding chamber, grinding elements in the chamber for grinding the particles and a first sacrificial inner shell lining constituted by a single integral entity lining substantially the entire inner surface of the -17- shell, wherein the shell is dismantlable into a plurality of shell parts, the method including the steps of: dismantling the shell into the shell parts; removing the lining; replacing the lining with a second lining; and reassembling the shell. A method according to claim 49 wherein the step of replacing the first lining includes the step of placing the second lining on one of the shell parts.

51. A method according to claim 49 or claim 50 wherein the first lining has an inner face and detecting means for determining where a region of the first lining has worn outwardly to a predetermined depth, the step of removing the first lining taking place once the determining has occurred.

52. A method according to claim 51 wherein the method includes the step, after the step of removing the first lining and before the step of replacing the first lining with a second lining, of rotating the first lining through 180 degrees about an axis extending perpendicularly to the longitudinal axis of the fist lining, replacing the first lining and repeating the step of removing the first lining after it has worn further. S53. A method according to claim 52 wherein the machine has two said detecting means, the first occurrence of the step of removing the first lining taking place when a i 20 first of the detection means determines that the region of the first lining has worn to the first predetermined depth, and the second occurrence of the step of removing the lining taking place when the second of the detection means determines that the lining at said oooo region has worn to the second predetermined depth.

54. A grinding machine for grinding particles, the machine being substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. A sacrificial lining for lining an inner surface of a grinding machine shell, the lining being substantially as herein described with reference to any one of the embodiment of the invention illustrated in the accompanying drawings and/or examples. 18-

56. A method of maintaining a grinding machine, the method being substantially as herein described with reference to any on of the embodiments of the invention illustrated in the accompanying drawings and/or examples. DATED this 12 th day of March, 2004 BALDWIN SHELSTON WATERS Attorneys for: M.I.M. Holdings Limited and Erich Netzsch GmbH Co Holding KG •0 0 0 S 0 0* 0 *o *o