WO2012012880A1

WO2012012880A1 - Wear-resistant liner assembly

Info

Publication number: WO2012012880A1
Application number: PCT/CA2011/000862
Authority: WO
Inventors: Pramod Kumar; David J. Page; Robert Mepham
Original assignee: Polycorp Ltd.
Priority date: 2010-07-26
Filing date: 2011-07-26
Publication date: 2012-02-02

Abstract

A liner assembly mountable to a shell of a grinding mill, the shell being rotatable around an axis thereof. The liner assembly includes a number of wear plates, a number of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars, and a number of fastening subassemblies. The liner assembly also includes a number of wear elements, each wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of a leading intermediate portion located substantially between a leading face of the lifter bar and a lifter channel therein. The liner portion includes one or more liner portion body materials in which each wear element is at least partially embedded. The wear elements are substantially more abrasion-resistant than the liner portion body material.

Description

WEAR-RESISTANT LINER ASSEMBLY

TECHNICAL FIELD

[0001] The present invention is related to a liner assembly including one or more wear elements, mountable to a shell of a grinding mill.

BACKGROUND OF THE INVENTION

[0002] In known autogenous and semi-autogenous grinding mills, ore-bearing rocks are at least partially broken by the impact of other ore due to a cataracting or tumbling motion resulting from the rotation of the shell. (In a semi-autogenous grinding mill, the ore is also comminuted by grinding media, as well as by the ore itself.) A charge, including ore (and in a semi-autogenous mill, also including grinding media) is positioned in the shell. As is well known in the art, lifter bars are positioned on the shell for lifting a portion of the charge as the shell is rotated, to provide a better cataracting effect, i.e., to lift the portion of the charge higher than the charge would be raised in the absence of the lifter bars.

[0003] A conventional grinding mill 18 and portions thereof are illustrated in Figs.

1 A- I D. (As will be described, the remainder of the drawings illustrate the present invention.) In the prior art grinding mill 18, a liner 20 including lifter bars 22 and wear plates 24 (positioned between the lifter bars 22) is attached to a shell 26, so that the lifter bars 22 and the wear plates 24 are subjected to wear, rather than the shell 26. As is well known in the art, the shell 26 is rotated about its central axis 27 (Fig. 1A) in the direction indicated by arrow "A" in Figs. I B- I D when the grinding mill 18 is operating, and the charge (not shown) moves in a cataracting or tumbling motion in the opposite direction, indicated by arrow "B". It will be understood that part of the liner 20 is omitted from Fig. 1 A for clarity of illustration.

[0004] With use, the liner 20 becomes progressively more worn over time. Typical wear profiles 28, 30 are shown in Fig. I B. The original outlines 32, 34 of the lifter bars 22 and the wear plates 24 are also shown in Figs. I B- I D. The first wear profile 28 shows the manner in which the lifter bars 22 and the wear plates 24 typically are worn after an initial period of use. The second wear profile 30 shows a typical wear profile of the prior art lifter bars 22 and the prior art wear plates 24 after further use. [0005] Further typical wear profiles are shown in Figs. 1C and I D, as will be described. It will be understood that the wear profiles shown in Figs. I B-I D represent a typical progression in which the prior art lifter bars 22 and wear plates are worn down. It will also be understood that, although the wear profiles shown in Figs. I B- ID are typical, actual wear profiles may differ significantly from each other, due to a number of factors.

[0006] As can be seen in Fig. I B, a fastener subassembly 36 partially positioned inside a lifter channel 38 attaches each lifter bar 22 to the shell 26. As is well known in the art, the lifter channel 38 preferably includes a slot 40 therein, in which a head 42 of a bolt 44 of the fastener subassembly 36 is receivable. Upon installation of the lifter bar 32 on the shell, the head 42 is positioned in the slot 40, where the head 42 engages engagement parts 46 of the lifter channel 38 when the bolt 44 is tightened. The bolt 44 is tightened in conventional manner, as follows. When the head 42 is located in the slot 40, the bolt 44 extends outwardly through an opening 48 in the shell 26, and a nut 50 is threadably engaged with an outer end 52 of the bolt 44, and tightened against a washer 54 positioned by a spacer 56 positioned between an exterior surface 58 of the shell 26 and the washer 54. As the nut 50 is tightened, engaging the washer 54, the head 42 is urged outwardly, i.e., against the engagement parts 46, to secure the lifter bar tightly to the shell. As is well known in the art, each lifter bar is secured to the shell along the lifter bar's length by a number of fastener subassemblies 36.

[0007] As can be seen in Figs. I B- I D, the fastening subassemblies 36 typically engage only the lifter bars 22. Conventionally, the lifter bars 22 overlap the wear plates 24 in part, so that the wear plates 24 are held against the shell by the lifter bars 22, i.e., in this conventional arrangement only the lifter bars 22 are directly engaged by the fastener subassemblies 36. However, because of the manner in which the lifter bars overlap part of the wear plates, the lifter bars and the wear plates are secured to the shell by the fastening subassemblies.

[0008] Because the lifter bars 22 protrude inwardly relative to the wear plates 24, a significant proportion of the impact energy resulting from the tumbling charge (i.e., as the shell rotates) is directed toward the lifter bars 22. It appears that the intensity of the impacts of the charge falling onto the lifter bars (i.e., the amount of kinetic energy released upon the impact of pieces of the charge on the lifter bars) tends to decrease as the lifter bars become progressively more worn. This is thought to be because, as the lifter bars become more worn, they are gradually able to lift less of the charge, so that less impact energy is released overall, upon impact of the charge. However, there tends to be relatively more abrasion, and relatively less impact energy released, as the liner becomes more worn. Where the liner is made of rubber (i.e., at least in part), the rate of wear tends to increase when the liner becomes more worn, because rubber resists impact better than abrasion.

[0009] The extent to which the lifter bars are worn also affects the extent to which protection is provided by the lifter bars 22. Accordingly, a newer (less worn) lifter bar provides more protection to the shell than an older (i.e., more worn) lifter bar, but the newer lifter bar is also worn down more quickly, because it protrudes inwardly (toward the central axis) more than the older lifter bar.

[0010] It will be understood that further wear results in the wear profile moving generally outwardly, toward the shell 26, i.e., generally in the direction indicated by arrow "X" in Fig. 1 B. As is well known in the art, when an inner surface 60 of the lifter channel 38 is at least partially exposed to wear (i.e., exposed for engagement with the charge), the lifter bars 22 and the wear plates 24 are replaced. This condition is illustrated in Fig. I D, in which an exposed portion 61 of the inner surface is shown. Typically, an operator (not shown) determines that a part of the inner surface 60 is exposed via visual inspection. Replacement of the lifter bars 22 and the wear plates 24 is usually effected at this point because continuing to use the worn lifter bars and wear plates would soon result in the lifter channel, the remaining portions of the lifter bars and the wear plates, and parts of the fastener subassemblies becoming disengaged from the shell 26, and mixed with the charge. This would quickly cause significant operational problems, and would also require significant repairs to the grinding mill. In these circumstances, therefore, replacement of the lifter bars and the wear plates upon exposure of a part of the inner surface 60 of the lifter channel 38 is conventionally considered to be the most economic and practical approach. Also, the replacement of all the lifter bars and wear plates in the mill at the same time is thought to be economically prudent, as the extent of wear overall is typically about the same throughout.

[001 1 ] From the foregoing, it can be seen that a region 62 of the lifter bar 22 (located upstream in part, and inwardly relative to the lifter channel) is critical. Because the region 62 tends to wear relatively quickly due to its location, and because it is proximal to the lifter channel, the wear of the critical region 62 tends to result in relatively quick replacement of the lifter bars and the wear plates. As shown in Fig. I B, for instance, a part 64 of the lifter channel 38 is within a relatively short distance of the wear profile 30, and is also relatively close to a leading face of the lifter bar 22.

[0012] However, as can be seen in Figs. I B-I D, when the lifter bars 22 and wear plates 24 have become worn, the balance of material remaining at other locations in the lifter bar 22 and the wear plates 24 is significantly more substantial than the material in the critical region 62. For example, as illustrated in Fig. I B, a significant amount of material remains in a region of the lifter bar 22 identified by reference numeral 66. It can therefore be seen in Figs. I B-I D that, because of the manner in which the lifter bar 22 and the wear plates 24 have been worn down, the upper surface 60 of the lifter channel 38 ultimately is partially exposed to only a limited extent before the liner is replaced. As can be seen in Fig. I D, replacement of the lifter bars 22 and wear plates 24 is required at that point, even though substantial amounts of material remain in other portions of the lifter bar 22 and the wear plates 24.

[0013] Fig. 1 C shows the prior art liner 20 of Fig. I B after further wear, resulting in a third wear profile 68. The third wear profile 68 is proximal to the lifter channel 38 at a point identified in Fig. 1C as "Y". Those skilled in the art will appreciate that, as illustrated in Fig. 1 C, in both of the worn prior art lifter bars 22, the inner surfaces 60 of the lifter channels 38 are about to be exposed, in part. Fig. I D shows the prior art liner 20 after still further wear, resulting in a fourth wear profile 69. It can be seen in Fig. I D that a large amount of material (identified as 66' in Fig. I D) remains in regions of the lifter bars 22 which are generally located in a downstream side of each lifter bar 22 respectively, and are generally centrally located in the wear plates 24. Also, as illustrated in Fig. I D, significant amounts of material in the wear plates 24 have not been worn away when the lifter bars are due to be replaced. Those skilled in the art will appreciate that the significant amounts of material in the lifter bars 22 and the wear plates 24 which remain when they are required to be replaced represent wasted expense.

[0014] Those skilled in the art will also appreciate that, when the lifter bars and wear plates in a grinding mill are required to be replaced, the downtime required to permit such replacement also involves significant costs, particularly due to lost production. To the extent that the mill lining's working life can be extended, therefore, incurring the significant costs associated with mill downtime can be delayed, or even can be incurred less frequently. SUMMARY OF THE INVENTION

[0015] For the reasons set out above, there is a need for a wear-resistant liner assembly that overcomes or mitigates one or more of the disadvantages of the prior art.

[0016] In its broad aspect, the invention provides a liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof. The liner assembly includes a number of wear plates, each wear plate having a wear plate body, and a number of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars. Each lifter bar includes a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction, a lifter bar body, and a lifter channel connected to the lifter bar body. The lifter bar body also includes a leading intermediate portion located substantially between the leading face and the lifter channel. Each pair of the lifter bars between which a selected one of the wear plates is positionable includes a leading lifter bar positioned upstream relative to the selected wear plate, and a trailing lifter bar positioned downstream relative to the selected wear plate. The liner assembly also includes a number of fastening subassemblies for securing the lifter bars to the shell. Each fastening subassembly has a first element at least partially receivable in the lifter channel and engageable therewith, and a second element for cooperating with the first element, to secure the lifter bar to the shell. In addition, the liner assembly includes a number of wear elements. Each wear element is positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates. The liner portion includes one or more liner portion body materials in which each wear element is at least partially embedded. Each wear element is substantially more abrasion-resistant (i.e., substantially more wear-resistant) than the liner portion body material.

[0017] In another aspect, the liner portion body material is rubber and the wear element is a high carbon steel.

[0018] In yet another aspect, the rubber has an approximate Shore "A" hardness of 65

+/- 5 and the steel has a hardness of at least approximately 200 Brinnell. [0019] In another aspect, the liner portion is the lifter bars, and each wear element is at least partially positioned in the leading intermediate portion of each lifter bar body.

[0020] In another of its aspects, the invention provides a grinding mill for comminuting ore in a charge. The grinding mill includes a shell rotatable in a predetermined direction around a central axis thereof and a liner assembly mounted to the shell. The liner assembly includes a number of the wear plates, a number of the lifter bars, secured to the shell with the wear plates positioned between respective pairs of the lifter bars, and a number of fastening subassemblies securing the lifter bars to the shell. The grinding mill also includes a number of wear elements, each wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates. The liner portion additionally includes one or more liner portion body materials, in which each wear element is at least partially embedded. Each wear element is substantially more abrasion-resistant (i.e., substantially more wear-resistant) than the liner portion body material.

[0021] In another of its aspects, the invention provides a method of resisting wear in a grinding mill for comminuting ore in a charge, the grinding mill having a shell rotatable in a predetermined direction around a central axis thereof. The method includes the steps of providing a number of the wear plates, and providing a number of the lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars. Also, a number of wear elements is provided, each wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates. The liner portion additionally includes at least one or more liner portion body materials, in which each wear element is at least partially embedded, each wear element being substantially more abrasion-resistant than the liner portion body material. In addition, a number of fastening subassemblies is provided, to secure the lifter bars to the shell. With the fastening subassemblies, the lifter bars and the wear plates are secured to the shell.

[0022] In another of its aspects, the invention provides a liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof. The liner assembly includes a number of wear plates, and a number of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars. Each lifter bar includes a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at lest partially facing a direction opposite to the predetermined direction, a lifter bar body, and a lifter channel connected to the lifter bar body. The lifter bar body also includes a leading intermediate portion located substantially between the leading face and the lifter channel. Each lifter bar body is made of one or more lifter bar body materials. Each pair of the lifter bars, between which a selected one of the wear plates is positionable, includes a leading lifter bar positioned upstream relative to the selected wear plate and a trailing lifter bar positioned downstream relative to the selected wear plate. In addition, the liner assembly includes a number of fastening subassemblies for securing the lifter bars to the shall. The liner assembly also includes a number of wear elements, each wear element being substantially more abrasion-resistant than the lifter bar body material, each wear element being positioned at least partially in each lifter bar for resisting wear of the leading intermediate portion by the charge as the shell rotates.

[0023] In yet another of its aspects, the invention provides a liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof. The liner assembly includes a number of wear plates, each wear plate including a wear plate body, and a number of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars. Each lifter bar includes a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction, a lifter bar body, and a lifter channel connected to the lifter bar body. The lifter bar body additionally includes a leading intermediate portion located substantially between the leading face and the lifter channel. Each wear plate body includes one or more wear plate body materials. Each pair of the lifter bars between which a selected one of the wear plates is positionable includes a leading lifter bar positioned upstream relative to the selected wear plate and a trailing lifter bar positioned downstream relative to the selected wear plate. The liner assembly also includes a number of fastening subassemblies for securing the lifter bars to the shell. In addition, the liner assembly includes a number of wear elements, each wear element being substantially more abrasion-resistant than the wear plate body material, each wear element being positioned at least partially in each wear plate for resisting wear of the leading intermediate portion by the charge as the shell rotates. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be better understood with regard to the attached drawings, in which:

[0025] Fig. 1A (previously described) is a longitudinal cross-section of a typical grinding mill of the prior art;

[0026] Fig. I B (previously described) is a cross-section of a portion of the grinding mill of Fig. 1 A showing typical wear profiles of a mill liner including lifter bars and wear plates of the prior art, drawn at a larger scale;

[0027] Fig. 1 C (previously described) is a cross-section of the prior art mill liner of

Fig. 1 B showing a typical wear profile after further wear;

[0028] Fig. I D (previously described) is a cross-section of the prior art mill liner of

Fig. 1 C showing a typical wear profile after further wear;

[0029] Fig. 2A is a cross-section of an embodiment of a liner assembly of the invention, mounted to a shell;

[0030] Fig. 2B is a cross-section of the liner assembly of Fig. 2A after the liner assembly has been subjected to wear, with an estimated wear profile;

[0031 ] Fig. 2C is a cross-section of a lifter bar of the liner assembly of Fig. 2A mounted to the shell, drawn at a larger scale;

[0032] Fig. 2D is a longitudinal cross-section of an embodiment of a grinding mill of the invention including the liner assembly of the invention, drawn at a smaller scale;

[0033] Fig. 2E is a top view of the lifter bar of Figs. 2A and 2C, drawn at a larger scale;

[0034] Fig. 3 is a cross-section of an alternative embodiment of the liner assembly of the invention mounted to the shell, drawn at a larger scale; [0035] Fig. 4 is a cross-section of another alternative embodiment of the liner assembly of the invention, mounted to the shell;

[0036] Fig. 5 is a cross-section of another embodiment of the liner assembly of the invention, mounted to the shell;

[0037] Fig. 6 is a cross-section of an alternative embodiment of the liner assembly of the invention, mounted to the shell;

[0038] Fig. 7 is a cross-section of another alternative embodiment of the liner assembly of the invention, mounted to the shell;

[0039] Fig. 8 is a cross-section of another alternative embodiment of the liner assembly of the invention, mounted to the shell;

[0040] Fig. 9 is a top view of an alternative embodiment of a wear element of the invention, drawn at a larger scale; and

[0041 ] Fig. 10 is a flow chart schematically representing an embodiment of a method of the invention.

DETAILED DESCRIPTION

[0042] In the attached drawings, like reference numerals designate corresponding elements throughout. Reference is first made to Figs. 2A-2D to describe an embodiment of a wear-resistant liner assembly of the invention referred to generally by the numeral 120. As can be seen in Figs. 2A-2D, the liner assembly 120 preferably is mountable to a shell 126 of a grinding mill 1 18 (Fig. 2D) in which ore in a charge (not shown) is comminuted, the shell 126 being rotatable in a predetermined direction (indicated by arrow "A") around a central axis 127 thereof. In one embodiment, the liner assembly 120 preferably includes a number of wear plates 124, each wear plate 124 having a wear plate body 172. The liner assembly 120 preferably also includes a number of lifter bars 122 securable to the shell 126 with the wear plates 124 positioned between respective pairs 174 of the lifter bars 122, as will be described. Preferably, and as shown in Figs. 2A and 2C, each lifter bar 122 includes a leading face 176 on an upstream side 177 of the lifter bar 122 at least partially facing the predetermined direction, and a trailing face 178 on a downstream side 179 of the lifter bar 122 at least partially facing a direction opposite to the predetermined direction. It is also preferred that each lifter bar 122 includes a lifter bar body 180 and a lifter channel 138 connected to the lifter bar body 180. The lifter bar body 180 preferably also has a leading intermediate portion 183 located substantially between the leading face and the lifter channel 138 (Figs. 2A, 2B). Each pair 174 of the lifter bars 122 between which a selected one of the wear plates (identified as 124A in Fig. 2B) is positionable includes a leading lifter bar (identified as 122A in Fig. 2B) positioned upstream relative to the selected wear plate 124A, and a trailing lifter bar (identified as 122B in Fig. 2B) positioned downstream relative to the selected wear plate 124A. It is also preferred that the liner assembly 120 includes a number of fastening subassemblies 136 for securing the lifter bars 122 to the shell 126, each fastening subassembly 136 including a first element 144 at least partially receivable in the lifter channel 138 and engageable therewith, and a second element 150 to cooperate with the first element 144, to secure the lifter bar 122 to the shell 126 (Fig. 2C). The liner assembly 120 preferably also includes a number of wear elements 190, each wear element 190 preferably being positioned at least partially in the liner portion 170 selected from the group consisting of the lifter bars 122, the wear plates 124, and combinations thereof, for resisting wear of the leading intermediate portion 183 by the charge as the shell 126 rotates. It is preferred that the liner portion 170 includes one or more liner portion body material(s) in which the wear element 190 is at least partially embedded. Preferably, each wear element 190 is substantially more abrasion-resistant than the liner portion body material(s).

[0043] It will be understood that the embodiments of the liner assembly are illustrated in Figs. 2A and 2C as initially installed, i.e., prior to being subjected to wear. It will also be understood that the second element 150 preferably is a nut threadably engageable with the first element 144 and tightenable thereon in conventional fashion, to urge the lifter bar 122 generally outwardly (i.e., in the direction indicated by arrow "C" in Fig. 2A) as and when the nut 150 is tightened on the bolt 144.

[0044] As noted above, in operation, the shell is rotated in the predetermined direction, i.e., the direction indicated by arrow "A". It will be understood that the charge (not shown) moves generally in the direction indicated by arrow "B", in a cataracting or tumbling motion, as the shell rotates in the predetermined direction. For the purposes hereof, "upstream" means in the predetermined direction of rotation, and when used with reference to a particular element, means in the predetermined direction relative to the particular element. Also, for the purposes hereof, "downstream" means in the direction opposite to the predetermined direction of rotation, and when used with reference to the particular element, means in the direction opposite to the predetermined direction relative to the particular element.

[0045] Those skilled in the art will appreciate that the liner portion body material may be any suitable material, or materials. Also, the wear element may be any suitable abrasion- resistant material, or materials. For example, the lifter bar body and the wear plate body may be made of steel, and if so, then the wear element 190 is made of a substantially more abrasion-resistant material. For instance, the wear element may be any suitable ceramic material(s). However, as is known in the art, the lifter bar body and the wear plate body preferably are made of rubber, and the wear element 190 preferably is made of a high carbon steel.

[0046] Accordingly, in one embodiment, the liner portion body material preferably includes rubber, and the wear element 190 is made of a high carbon steel.

[0047] The wear element 190 preferably is substantially more abrasion-resistant than the liner portion body material, for reasons that will be described. For instance, in one embodiment, the rubber of the liner portion body material has an approximate Shore "A" hardness of 65 +/- 5 and the steel has a hardness of at least 200 Brinnell.

[0048] As can be seen in Fig. 2A, in one embodiment, the liner portions 170 preferably are the lifter bars 122 with wear elements 190, and each wear element 190 is at least partially positioned in the leading intermediate portion 183 of each lifter bar body 180. In this embodiment, the leading face 176 of each lifter bar 122 at least partially includes an exposed part 194 of each wear element 190, and each wear element 190 additionally includes an unexposed part 196 at least partially located in the leading intermediate portion 183 (Figs. 2A, 2B).

[0049] As can be seen in Figs. 2A-2C, the wear element 190 preferably is positioned for resisting wear of the leading intermediate portion 183. As shown in Fig. 2B, due to its position in the lifter bar 122, the wear element 190 is significantly more exposed to wear (i.e., exposed to engagement with the charge) once the lifter bars 122 and the wear plates 124 have been subjected to sufficient wear that the wear profile intersects the wear element 190. This is illustrated by a wear profile 192 in Fig. 2B. It will be understood that the wear profile 192 is an approximation of a wear profile that results after a period of wear.

[0050] Those skilled in the art will appreciate that the wear element may be formed in any suitable shape. As can be seen in Fig. 2C, in one embodiment, the wear element 190 preferably is substantially rectangular in cross-section, having opposing inward and outward surfaces "I" and "O" respectively, and upstream and downstream surfaces "U" and "D" respectively. It will be understood that the wear element preferably has substantially the same length as the body of the liner portion (i.e., lifter bar or wear plate) in which it is located. As can be seen in Fig. 2E, for instance, the wear element 190 preferably is about the same length as the lifter bar body 180. As shown in Fig. 2D, the liner assembly 120 preferably is mounted in the shell 126 in conventional fashion, in the grinding mill 1 18. (It will be understood that part of the liner assembly 120 is omitted from Fig. 2D for clarity of illustration.)

[0051 ] Referring to Fig. 2B, it can be seen that, after the liner assembly is initially subjected to sufficient wear, a portion 193 of the inner surface "1" of the wear element 190 is exposed for engagement with the charge. Also, due to the position of the wear profile 192 in the wear plate 124 immediately preceding the lifter bar 122, more of the initially exposed part 194 of the wear element 190 is engageable with the charge at this point than previously (e.g., before the liner assembly is subjected to wear, as shown in the situation illustrated in Fig. 2A).

[0052] As is known, the impact energy on the more prominent parts of the liner assembly generally decreases as the liner assembly becomes more worn. This appears to be due to the lifter bars being gradually able to lift smaller portions of the charge, so that less impact energy is released overall as the lifter bars become more worn. As the liner assembly becomes more worn, however, the extent to which the liner is subjected to abrasion increases, i.e., as the liner becomes more rounded.

[0053] It can therefore be seen that the invention takes advantage of this tendency, by positioning the wear element so that it is not directly engaged by the charge until a significant portion of the liner assembly has been worn away. The wear element is exposed when the liner assembly has been worn down to an extent, as illustrated in Fig. 2B. Thus, the wear element, which is more resistant to abrasion than the lifter body material in which it is embedded, is exposed for engagement with the charge at a point when the liner is subjected to relatively more abrasion, and relatively less impact. In this way, the benefit of including the abrasion-resistant wear element is maximized, i.e., as compared to a wear element that would be positioned in the liner for earlier engagement with the charge, when the liner is subjected to relatively more impact energy. The invention is intended also to utilize a relatively small amount of wear-resistant material in the wear element, to provide a substantial benefit for a relatively small cost. The invention thus achieves a surprisingly effective result in a cost-effective manner.

[0054] In one embodiment, and as an example, the wear element preferably is about one inch (2.54 cm.) wide, and about two inches (5.08 cm.) tall. (That is, the inner and outer surfaces ("I" and "O") are about one inch (2.54 cm.) wide, and the upstream and downstream surfaces ("U" and "D") are about two inches (5.08 cm.) wide.) In this example, the lifter bar has an overall width ("W", in Fig. 2C) of about 10 inches (25.4 cm.), and the leading face 176 of the lifter bar is about 10 inches (25.4 cm.). It will be understood that the foregoing dimensions are only exemplary. As described above, the optimum dimensions and shapes of the lifter bars, wear plates, and the wear elements depend on a number of factors in each case. In general, the width of the wear element can vary, for instance, between about 4 inches (10.16 cm.) and about 10 inches (25.4 cm.).

[0055] As noted above, in one embodiment, the liner portion body material preferably is rubber, and the liner portion is formed in a mold (not shown), as is known. It is also preferred that the wear element is positioned in the mold for the liner portion when the liner portion (i.e., the lifter bar or the wear plate or both, as the case may be) is formed, so that the wear element is integral to the liner portion in which it is included.

[0056] Before the wear element 190 is located in the mold, the wear element 190 preferably is primed, and a coat of a suitable adhesive is applied thereto. Those skilled in the art would be aware of suitable primers and adhesive materials. After the wear element 190 is located in the mold, each liner portion is compression molded and vulcanized, as is known, so that the wear element is chemically bonded to the liner portion body material. Because the process of compression molding a primarily rubber element having a steel or other metal insert therein is well known, further description of the process of forming the liner portions is unnecessary. [0057] Those skilled in the art will also appreciate that the manner in which wear progresses in each grinding mill differs somewhat, due to a number of factors. The wear element, and the liner portion in which the wear element is positioned, may have a variety of forms. Also, and as described, the wear elements may be positioned in lifter bars, wear plates, or any combination thereof. Those skilled in the art would appreciate that the optimum embodiment for resisting wear in each case depends on a wide variety of factors.

[0058] Preferably, and as can be seen in Fig. 2C, the shell 126 includes a shell body

129 and a shell lining 131 which is somewhat resilient. The wear plate body 172 includes a cooperating portion 133. As shown in Fig. 2C, in one embodiment, the cooperating portions 133 of the bodies 172 of adjacent wear plates 124 are positioned between the lifter bar body 180 and the shell lining 13 1 . This provides an interlocking effect so that, when the lifter bar body 180 is pulled outwardly (i.e., in the direction indicated by arrow "C" in Fig. 2A) as the second element 150 (i.e., the nut) is tightened on the first element 144 (i.e., the bolt), the lifter bar body 180 squeezes the cooperating portions 133 against the shell lining 131. In this way, the lifter bar 122 is secured directly to the shell 126, and also the wear plates 124 adjacent thereto are secured (i.e., indirectly) to the shell 126.

[0059] Many other ways of securing the lifter bars and the wear plates to the shell would occur to those skilled in the art. For example, the fastening subassembly could engage with the wear plate body, and the lifter bar body could have portions that fit between the wear plate body and the shell. Or the lifter bars and the wear plates might each be directly attached to the shell 126. However, a liner assembly with such other arrangements for fastening would be within the scope of the invention described herein.

[0060] Additional embodiments of the liner assembly of the invention are illustrated in Figs. 3-8. It will be understood that the embodiments of the liner assembly shown in Figs. 3-8 are illustrated as initially installed in a grinding mill in each case, i.e., prior to being subjected to wear.

[0061 ] In Fig. 3 another embodiment of the liner assembly 220 is illustrated. The liner assembly 220 preferably includes lifter bars 222 which include wear elements 290. As can be seen in Fig. 3, the wear element 290 is positioned at least partially in the leading intermediate portion 283. Preferably, the lifter bar 222 includes a lifter bar body 280 with a covering segment 297 thereof at least partially located between a leading face 276 of the lifter bar 222 and the wear element 290, i.e., upstream relative to the upstream surface "U" of the wear element 290. The covering segment 297 preferably is positioned for subjection thereof to wear prior to subjection of the wear element 290 to wear. That is, at least part of the covering segment is subjected to wear prior to subjection of the wear element to wear.

[0062] Depending on the manner in which the liner assembly is worn, the liner assembly 220 may be advantageous, as compared to the position of the wear element 190 in the lifter bar 122 of the liner assembly 120. As described above, in general, the liner assembly is worn down progressively, so that the impact energy released by the cataracting charge generally decreases as the liner assembly becomes more worn (due to the more worn lifter bars lifting less of the charge), and the liner assembly is subjected to relatively more abrasion. Because the wear element 290 is fully embedded in the lifter body material, as compared to the liner assembly 120, the exposure of the wear element 290 is delayed until relatively later, in the process of wearing down the liner assembly 220. The wear element 290 thus is exposed after the liner has already been subjected to wear, i.e., the wear element 290 is subjected to wear when the liner is generally subjected to more abrasion, and relatively less impact. This means that the wear element 290 is exposed to engagement with the charge when its abrasion-resistant characteristic can have the most effect, namely, when the liner is subjected to more abrasion, and somewhat less impact. As noted above, and as those skilled in the art will appreciate, it may be that, due to various factors, the embodiment of the liner assembly illustrated in Fig. 3 (i.e., in which the wear element is fully embedded) may not be the optimum design in some situations.

[0063] Another embodiment of the liner assembly 320 is illustrated in Fig. 4.

Preferably, the liner assembly 320 includes lifter bars 322, which include wear elements 390. The wear element 390 has a substantially planar upstream surface "U" located to substantially face the predetermined direction, the upstream surface "U" being positioned relative to a leading face 376 of the lifter bar 322 to substantially define a predetermined angle Θ therebetween. Preferably, the predetermined angle 0 is about 15°. The lifter bar 322 preferably also includes a covering segment 397 located upstream from the upstream surface "U" of the wear element 390.

[0064] In this embodiment, the upstream surface "U" is positioned so that it is substantially orthogonal to the wear profile (not shown) that is anticipated to develop in the absence of the wear element 390. It will be understood that the liner assembly 320 is preferred in circumstances different from those in which other liner assemblies of the invention are preferred. It is believed that locating the wear element 390 so that the upstream surface "U" is substantially orthogonal to the typical wear profile (i.e., as it would otherwise develop, in the absence of the wear element) may, in some circumstances, improve the wear resistance offered by the wear element 390 (e.g. as compared to the wear element 290 in the liner assembly 220, and the wear element 190 in the liner assembly 120), so that a leading intermediate portion 383 is subjected to wear later.

[0065] As described above, the wear elements may be positioned in the wear plates.

In another embodiment of the liner assembly 420, illustrated in Fig. 5, the liner portions 470 preferably are wear plates 424, and each wear element 440 is positioned in each wear plate body 472 for resisting wear of the leading intermediate portion 483 of the trailing lifter bar 422 located downstream relative to the wear plate 424 and adjacent thereto.

[0066] As can be seen in Fig. 5, each wear plate 424 preferably is mounted to the shell between a leading lifter bar 422A and a trailing lifter bar 422B. Preferably, each wear plate 424 has an upstream side 402 positioned proximal to the upstream lifter bar 422A, and a downstream side 404 positioned proximal to the downstream lifter bar 422B. It is preferred that each wear element 490 is located in the downstream side 404 of the wear plate body 472. It is believed that the location of the wear element 490 in the wear plate body 472 is advantageous in some circumstances. Preferably, the wear element 490 is positioned upstream from the leading face 476 of the downstream lifter bar 422B by a short distance 405 to position the wear element so as to generally resist wear in a region immediately upstream from the leading intermediate portion 483. It is believed that, because the wear element 490 is located a relatively short distance upstream from the leading intermediate portion 483 in the trailing lifter bar 422B, the wear resistance provided by the wear element 490 tends to decrease the extent to which such leading intermediate portion 483 is subjected to wear.

[0067] As can be seen in Fig. 5, the downstream side 404 of the wear plate 424 preferably includes an exposed surface 406 positioned for engagement with the charge, i.e., when the wear plate 424 is secured to the shell 126. The wear element 490 preferably includes an exposed part 408 that is substantially coplanar with the exposed surface 406, and an unexposed part 410 embedded in the wear plate body 472. Where the wear element 490 is substantially rectangular in cross-section and is partially defined by its inward, outward, upstream, and downstream surfaces (I, O, U, and D respectively), the inward surface I preferably is substantially coplanar with the exposed surface 406 of the downstream side 404. Also, the balance of the wear element 490 preferably is the unexposed part 410.

[0068] This orientation of the wear element 490 that is rectangular in cross-section is thought to be advantageous because, as the wearing down of the liner assembly 420 progresses, the upstream side U of the wear element is positioned for direct wear thereon. The wear element 490 is elongate in cross-section, i.e., upstream and downstream surfaces ("U" and "D") are longer than the inner and outer surfaces ("I", "O"). It is thought that positioning the wear element 490 so that its upstream surface "U" is substantially orthogonal to the exposed surface 406 is likely to result in the wear element 490 offering maximum resistance to wear. This is because the wear profile would, in the absence of the wear element 490, probably be formed generally parallel to the exposed surface 406, as shown in Fig. I B.

[0069] Another embodiment of the liner assembly 520 is illustrated in Fig. 6. In this embodiment, the downstream side 504 of a wear plate 524 includes an exposed surface 506 positioned for engagement with the charge, when the wear plate 524 is secured to the shell. Each wear element 590 preferably includes an exposed segment 512 which protrudes generally inwardly (i.e., generally toward the central axis) relative to the exposed surface 506 when the wear plate 524 is secured to the shell, and an unexposed segment 514 embedded in a wear plate body 572. Preferably, the wear element 590 is located a short distance 505 from a leading face 576 of a trailing lifter bar 522 to position the wear element 590 so as to generally resist wear in a region immediately upstream from the leading intermediate portion 583. Also, the wear element 590 preferably is positioned so that its upstream face "U" is substantially orthogonal to the exposed surface 506.

[0070] Another embodiment of the liner assembly 620 is illustrated in Fig. 7. As can be seen in Fig. 7, in this embodiment, a wear element 690 is completely embedded in the wear plate body 672 of a wear plate 624. The downstream side 604 of the wear plate 624 has an exposed surface 606 that is substantially planar. Preferably, the wear element 690 has a substantially planar upstream surface "U" substantially facing the predetermined direction. The upstream surface U preferably is positioned relative to the surface 606 to substantially define a preselected angle oc therebetween. As can be seen in Fig. 7, in one embodiment, it is preferred that the preselected angle cc is approximately 1 10°. Those skilled in the art will appreciate that the preselected angle oc will vary in each grinding mill, depending on the conditions therein, which are affected by a wide variety of factors.

[0071 ] In the liner assembly 620, the upstream surface "U" of the wear element 690 is positioned so that it is substantially orthogonal to the wear profile (not shown) that is anticipated to develop in the absence of the wear element 690. It will be understood that the liner assembly 620 is preferred in circumstances different from those in which other liner assemblies of the invention are preferred.

[0072] As can be seen in Fig. 8, in another embodiment of the liner assembly 720, wear elements 790A and 790B are included in lifter bars 722A, 722B and a wear plate 724 positioned therebetween, so that a leading intermediate portion 783 is subjected to wear later than would be the case in the absence of the wear elements 790A, 790B. It is believed that the liner assembly 720 may provide cost-effective wear resistance in certain situations, for example, where the liner assembly would otherwise be worn down relatively quickly, and thus the additional cost in wear elements would be justified. It will be understood that various combinations of positions of the wear elements in both the lifter bars and the wear plates may be advantageous, depending on the conditions in the grinding mill. For instance, the wear elements may be positioned in the wear plates as illustrated in Figs. 6 and 7, and the wear elements may also be positioned in the lifter bars as illustrated in Figs. 3 and 4.

[0073] As can be seen in Fig. 2D, the invention includes the grinding mill 1 18 for comminuting ore in a charge (not shown in Fig. 2D). The grinding mill 1 18 includes the shell 126 rotatable in the predetermined direction around a central axis 127 thereof, as described above. For clarity of illustration, the grinding mill 1 18 is shown in Fig. 2D as including the liner assembly 120 mounted to the shell, also as described above. However, those skilled in the art will appreciate that any of the embodiments of the liner assembly described above are mountable in the shell. As noted above, it will be understood that only part of the liner assembly 120 is shown in Fig. 2D for clarity of illustration.

INDUSTRIAL APPLICABILITY

[0074] An embodiment of a method 863 of resisting wear in a grinding mill for comminuting ore in a charge includes the step of, first, providing a number of wear plates, each of the wear plates having the wear plate body (step 865, Fig. 10), and providing a number of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars (step 867). Also, a number of wear elements is provided, each of the wear elements being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates. The liner portion additionally includes one or more liner portion body materials, in which each wear element is at least partially embedded, and each of the wear elements is substantially more abrasion- resistant (i.e., substantially more resistant to wear) than the liner portion body material (step 871 ). In addition, a plurality of fastening subassemblies is provided (step 873). Finally, with the fastening subassemblies, the lifter bars and the wear plates are secured to the shell (step 875). It will be appreciated by those skilled in the art that, although steps 865 to 873 are shown in a particular order in Fig. 10, the order in which those steps are performed is not significant (e.g., the wear element is provided in the liner portion when it is formed, as described above), and such order may vary.

[0075] An alternative embodiment of the wear element 990 is shown in Fig. 9. The wear element 990 is partially defined by an upstream surface "U" which, when the liner portion in which the wear element 990 is positioned in secured to the shell, faces substantially in the predetermined direction (i.e., the direction in which the shell rotates). The wear element 990 also includes a downstream surface "D" facing substantially in the direction opposite to the predetermined direction. Preferably, the wear element 990 additionally includes a mechanical mounting element 998 positioned at the downstream surface D, for connecting the wear element 990 to the liner portion body material (not shown in Fig. 9).

[0076] As described above, in one embodiment, the wear element is chemically bonded with the lifter body material, for example, where the lifter body material is rubber, when the liner portion is formed. However, the mechanical mounting means 998 is intended to provide a mechanical means for connecting the wear element 990 with the lifter body material, i.e., in addition to the chemical bonding resulting from the manner in which the lifter bar is formed. Those skilled in the art will appreciate that an improved connection between the liner portion body material and the wear element would result in the wear element being subjected to more wear before the liner portion is required to be replaced. [0077] As illustrated, the mechanical mounting means 998 is an elongate element formed into a repeating curve pattern along its length, and the mechanical mounting means 998 is attached to the downstream side "D" of the wear element 990. However, many alternative ways of providing for a mechanical, physical connection between the downstream side "D" and the liner portion body material would occur to those skilled in the art.

[0078] It will also be appreciated by those skilled in the art that the invention can take many forms, and that such forms are within the scope of the invention as described above. For instance, wear inserts may be included in both the lifter elements and the wear plates in a liner assembly of the invention. The foregoing descriptions are exemplary and their scope should not be limited to the preferred versions contained herein.

Claims

A liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof, the liner assembly comprising: a plurality of wear plates, each said wear plate comprising a wear plate body; a plurality of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars; each said lifter bar comprising: a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction; a lifter bar body; a lifter channel connected to the lifter bar body; the lifter bar body additionally comprising a leading intermediate portion located substantially between the leading face and the lifter channel; each said pair of the lifter bars between which a selected one of said wear plates is positionable comprising: a leading lifter bar positioned upstream relative to the selected wear plate; a trailing lifter bar positioned downstream relative to the selected wear plate; a plurality of fastening subassemblies for securing the lifter bars to the shell, each said fastening subassembly comprising: a first element at least partially receivable in the lifter channel and engageable therewith; a second element for cooperating with the first element, to secure the lifter bar to the shell; a plurality of wear elements, each said wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates; the liner portion comprising at least one liner portion body material in which each said wear element is at least partially embedded; and each said wear element being substantially more abrasion-resistant than said at least one liner portion body material.

2. A liner assembly according to claim 1 in which said at least one liner portion body material comprises rubber and the wear element comprises a high carbon steel.

3. A liner assembly according to claim 2 in which the rubber has an approximate Shore "A" hardness of 65 +/- 5 and the steel has a hardness of at least approximately 200 Brinnell.

4. A liner assembly according to claim 1 in which the liner portion is the lifter bars and each said wear element is at least partially positioned in the leading intermediate portion of each said lifter bar body.

5. A liner assembly according to claim 1 in which: the liner portion is the lifter bars; and the leading face of each said lifter bar at least partially comprises an exposed part of each said wear element, and each said wear element additionally comprises an unexposed part at least partially located in the leading intermediate portion.

6. A liner assembly according to claim 5 in which each said lifter bar body comprises a covering segment thereof at least partially located between the leading face and the wear element, the covering segment being positioned for subjection thereof to wear prior to subjection of the wear element to wear.

7. A liner assembly according to claim 6 in which the wear element comprises a substantially planar upstream surface located to substantially face the predetermined direction, the upstream surface being positioned relative to the leading face to substantially define a predetermined angle therebetween.

8. A liner assembly according to claim 5 in which each said lifter bar body additionally comprises a covering segment thereof at least partially located between the leading face and the wear element such that at least part of the covering segment is subjected to wear prior to subjection of the wear element to wear.

9. A liner assembly according to claim 1 in which: the liner portion is the wear plates; and each said wear element is positioned in each said wear plate body for resisting wear of the leading intermediate portion of the trailing lifter bar located downstream relative to said wear plate and adjacent thereto.

10. A liner assembly according to claim 9 in which each said wear element is located in a downstream side of the wear plate body, the downstream side being located proximal to the trailing lifter bar relative thereto.

1 1. A liner assembly according to claim 10 in which: the downstream side of the wear plate comprises an exposed surface positioned for engagement with the charge when the wear plate is secured to the shell; each said wear element comprises: an exposed part substantially coplanar with the exposed surface; and an unexposed part embedded in the wear plate body.

12. A liner assembly according to claim 10 in which: the downstream side of the wear plate comprises an exposed surface positioned for engagement with the charge when the wear plate is secured to the shell; and each said wear element comprises: an exposed segment which protrudes toward the central axis relative to the exposed surface when the wear plate is secured to the shell; and an unexposed segment embedded in the wear plate body.

13. A liner assembly according to claim 10 in which the downstream side of the wear plate comprises an exposed surface that is substantially planar and each said wear element comprises a substantially planar front face substantially facing the predetermined direction, the front face being positioned relative to the surface to substantially define a preselected angle therebetween.

14. A liner assembly according to claim 1 in which: each said wear element is partially defined by an upstream surface facing substantially in the predetermined direction when the liner portions are secured to the shell, and a downstream surface facing substantially in the direction opposite to the predetermined direction; and each said wear element additionally comprises a mechanical mounting element positioned at the downstream surface, for connecting the wear element to the liner portion body material.

15. A grinding mill for comminuting ore in a charge, the grinding mill comprising: a shell rotatable in a predetermined direction around a central axis thereof; a liner assembly mounted to the shell, the liner assembly comprising: a plurality of wear plates, each said wear plate comprising a wear plate body; a plurality of lifter bars secured to the shell with the wear plates positioned between respective pairs of the lifter bars; each said lifter bar comprising:

a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction; a lifter bar body; a lifter channel connected to the lifter bar body; the lifter bar body additionally comprising a leading intermediate portion located substantially between the leading face and the lifter channel; each said pair of the lifter bars between which a selected one of said wear plates is positioned comprising: a leading lifter bar positioned upstream relative to the selected wear plate; a trailing lifter bar positioned downstream relative to the selected wear plate; a plurality of fastening subassemblies securing the lifter bars to the shell, each said fastening subassembly comprising: a first element at least partially receivable in the lifter channel and engaged therewith; a second element for cooperating with the first element, for securing the lifter bar to the shell; a plurality of wear elements, each said wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates; the liner portion additionally comprising at least one liner portion body material, in which each said wear element is at least partially embedded; and each said wear element being substantially more abrasion-resistant than said at least one liner portion body material.

16. A grinding mill according to claim 15 in which said at least one liner portion body material comprises rubber and the wear element comprises a high carbon steel.

17. A grinding mill according to claim 16 in which the rubber has an approximate Shore "A" hardness of 65 +/- 5 and the steel has a hardness of at least approximately 200 Brinnell.

18. A method of resisting wear in a grinding mill for comminuting ore in a charge, the grinding mill having a shell rotatable in a predetermined direction around a central axis thereof, the method comprising the steps of:

(a) providing a plurality of wear plates;

(b) providing a plurality of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars, each said lifter bar comprising: a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction; a lifter bar body; a lifter channel connected to the lifter bar body; the lifter bar body additionally comprising a leading intermediate portion located substantially between the leading face and the lifter channel; each said pair of the lifter bars between which a selected one of said wear plates is positionable comprising: a leading lifter bar positioned upstream relative to the selected wear plate; a trailing lifter bar positioned downstream relative to the selected wear plate; providing a plurality of wear elements, each said wear element being positioned at least partially in a liner portion selected from the group consisting of the lifter bars, the wear plates, and combinations thereof, for resisting wear of the leading intermediate portion by the charge as the shell rotates, the liner portion additionally comprising at least one liner portion body material, in which each said wear element is at least partially embedded, each said wear element being substantially more abrasion-resistant than said at least one liner portion body material; providing a plurality of fastening subassemblies, each said fastening subassembly comprising: a first element at least partially receivable in the lifter channel and engageable therewith; a second element for cooperating with the first element, to secure the lifter bar to the shell; and (e) with the fastening subassemblies, securing the lifter bars and the wear plates to the shell.

19. A liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof, the liner assembly comprising: a plurality of wear plates; a plurality of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars; each said lifter bar comprising: a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction; a lifter bar body; a lifter channel connected to the lifter bar body; the lifter bar body additionally comprising a leading intermediate portion located substantially between the leading face and the lifter channel; each said lifter bar body comprising at least one lifter bar body material; each said pair of the lifter bars between which a selected one of said wear plates is positionable comprising: a leading lifter bar positioned upstream relative to the selected wear plate; a trailing lifter bar positioned downstream relative to the selected wear plate; a plurality of fastening subassemblies for securing the lifter bars to the shell, each said fastening subassembly comprising: a first element at least partially receivable in the lifter channel and engageable therewith; a second element for cooperating with the first element, to secure the lifter bar to the shell; and a plurality of wear elements, each said wear element being substantially more abrasion-resistant than said at least one lifter bar body material, each said wear element being positioned at least partially in each said lifter bar for resisting wear of the leading intermediate portion by the charge as the shell rotates.

20. A liner assembly according to claim 19 in which said at least one lifter bar body material comprises rubber and the wear element comprises a high carbon steel.

21. A liner assembly according to claim 20 in which the rubber has an approximate Shore "A" hardness of 65 +/- 5 and the steel has a hardness of at least approximately 200 Brinnell.

22. A liner assembly mountable to a shell of a grinding mill in which ore in a charge is comminuted, the shell being rotatable in a predetermined direction around a central axis thereof, the liner assembly comprising: a plurality of wear plates, each said wear plate comprising a wear plate body; a plurality of lifter bars securable to the shell with the wear plates positioned between respective pairs of the lifter bars; each said lifter bar comprising: a leading face on an upstream side of the lifter bar at least partially facing the predetermined direction, and a trailing face on a downstream side of the lifter bar at least partially facing a direction opposite to the predetermined direction; a lifter bar body; a lifter channel connected to the lifter bar body; the lifter bar body additionally comprising a leading intermediate portion located substantially between the leading face and the lifter channel; each said wear plate body comprising at least one wear plate body material; each said pair of the lifter bars between which a selected one of said wear plates is positionable comprising: a leading lifter bar positioned upstream relative to the selected wear plate; a trailing lifter bar positioned downstream relative to the selected wear plate; a plurality of fastening subassemblies for securing the lifter bars to the shell, each said fastening subassembly comprising: a first element at least partially receivable in the lifter channel and engageable therewith; a second element for cooperating with the first element, to secure the lifter bar to the shell; and a plurality of wear elements, each said wear element being substantially more abrasion-resistant than said at least one wear plate body material, each said wear element being positioned at least partially in each said wear plate for resisting wear of the leading intermediate portion by the charge as the shell rotates.

A liner assembly according to claim 22 in which said at least one wear plate body material comprises rubber and the wear element comprises a high carbon steel. A liner assembly according to claim 23 in which the rubber has an approximate Shore "A" hardness of 65 +/- 5 and the steel has a hardness of at least approximately 200 Brinnell.