FIELD OF INVENTION

The present invention relates generally to crushing, grinding, comminuting or similar processing of materials such as mineral ores, rock and other materials, and more particularly to apparatus for use in such processing.

BACKGROUND OF THE INVENTION

Grinding mills are one form of apparatus used for processing materials as described above. Typical grinding mills generally comprise a drum-shaped shell mounted for rotation about its central axis. The axis of the shell is generally horizontally disposed or slightly inclined towards one end. The interior of the shell forms a treatment chamber into which the material to be processed is fed.

In one form of mill known as a SAG (semi autogenous grinding) mill, a grinding medium such as balls or rods is fed to the treatment chamber (i.e. the inside of the shell) with the material to be processed. During rotation of the shell the grinding medium acts on the material to cause the crushing or grinding action. The grinding medium and material to be processed are carried up the side of the shell as a result of the centrifugal force created by rotation of the shell, and then afterwards it falls towards the bottom of the shell under the influence of gravity.

To assist in lifting the material up the side of the shell, lifter bars are often provided, which are secured to the interior surface of the shell. The shell lifter bars extend generally longitudinally along the shell and are circumferentially spaced apart around the inner surface. The higher the material travels up the shell the better the grinding of the material. In addition, so called head lifter bars are also used. These head lifter bars are mounted in a radially-spaced manner on each of the opposite ends of the grinding mill, and serve a similar purpose to the shell lifter bars.

During operation of the grinding mill, the surface of the shell (and head) lifter bars is worn away by the action of the material being ground down. One particular problem is that high wear and material overthrow may occur at each end of the grinding mill, contributing to high wear in the shell lifter bars, and also potential for cracking or damage to the metal wear face in the shell lifter bars. It is among the objects of some embodiments of the present invention to mitigate the above or other disadvantages associated with prior art lifter bars, and particularly head lifter bars.

SUMMARY OF THE INVENTION

According to a first aspect there is provided a head lifter bar for mounting on an end of a grinding mill and defining a longitudinal axis extending between a periphery end and a hub end thereof and a vertical plane extending through the longitudinal axis; the bar comprising a rear wall, an upper surface, a front wall opposite the rear wall and defining an upper portion thereof, and a profiled surface extending between the upper surface and the upper portion of the front wall; the profiled surface defining a central portion oriented at a first acute angle to the vertical plane, a periphery end portion extending from the central portion to the periphery end, and a hub end portion extending from the central portion to the hub end, wherein the periphery end portion is recessed from the central portion such that the upper surface is narrower at the periphery end than at the central portion and the periphery end portion is oriented at a second acute angle to the vertical plane at the periphery end, where the second acute angle is greater than the first acute angle.

Optionally, the head lifter bar may comprise a plurality of sections coupled together to form the head lifter bar. The plurality of sections may coupled via an internal connection co-axial with the longitudinal axis.

Optionally, the periphery end portion expands as it extends towards the periphery end.

Optionally, or alternatively, the hub end portion is recessed from the central portion such that the upper surface is narrower at the hub end than at the central portion.

Optionally, the upper surface at the periphery end portion (and/or at the hub end portion) is recessed relative to the upper surface at the central portion such that the upper surface is lower (nearer a lower surface) at the periphery end (and/or at the hub end) than at the central portion.

Optionally, the upper surface at the periphery end (and/or the hub end) is oriented at an angle of between approximately 3 degrees and approximately 9 degrees (in some embodiments between approximately 4 degrees and approximately 6 degrees) to a horizontal plane extending through the longitudinal axis normal to the vertical plane.

Optionally, the upper surface tapers continuously from the central portion to the periphery end (and/or to the hub end). Alternatively, the upper surface may taper in a discontinuous manner (such as in a stepped manner or in a combination of curves and straight lines).

Optionally, the periphery end portion (and/or the hub end portion) tapers continuously from the central portion to the periphery end (and/or to the hub end). Alternatively, the periphery end portion (and/or the hub end portion) may taper in a discontinuous manner (such as in a stepped manner or in a combination of curves and straight lines). One or both end portions may comprise a plurality of stepped portions, each successive stepped portion having a planar surface recessed relative to the planar surface of the previous stepped portion (for example by an angle between 6 and 12 degrees) or a planar surface of the central portion for the first stepped portion. One advantage of having stepped surfaces is that metal reinforcement parts can be provided having planar surfaces, which are easier and cheaper to cast.

Optionally, one or both of the periphery end portion and the hub end portion is between approximately 15% and 35% of the total length of the bar. In some embodiments, one or both of the periphery end portion and the hub end portion is between approximately 20% and 30% of the total length of the bar.

Optionally, the central portion is between approximately 30% and 70% of the total length of the bar.

Optionally, the total length of the bar is between approximately 1 metre and approximately 3 metres.

Optionally, the central portion is oriented at an angle of between approximately zero degrees and 50 degrees, advantageously between 20 degrees and approximately 40 degrees (in some embodiments between approximately 25 degrees and approximately 35 degrees) to the vertical plane.

Optionally, the upper surface at the periphery end (and/or the hub end) is oriented at an angle of between approximately 35 degrees and approximately 60 degrees (in some embodiments between approximately 40 degrees and approximately 55 degrees) to the vertical plane. Optionally, the width of the upper surface in the horizontal plane at the central portion is between approximately 40% and 70% of the width of the bar in the horizontal plane.

Optionally, the width of the upper surface in the horizontal plane at the periphery end (and/or the hub end) is between approximately 25% and 40% of the width of the bar in the horizontal plane (in some embodiments between approximately 30% and approximately 38% of the width of the bar in the horizontal plane).

Optionally, the ratio of the height of the bar to the width of the bar is between approximately 1 .5 to 1 and 1 to 1 .

Optionally, the central portion is oriented at an acute angle to the both the vertical plane and the horizontal plane.

Optionally, the front wall is generally parallel to the rear wall, and/or the longitudinal axis, for substantially the entire length of the bar.

Optionally, the front wall comprises a substantially planar surface parallel to the vertical plane for substantially the entire length of the bar.

Optionally, the rear wall comprises a substantially planar surface parallel to the vertical plane for substantially the entire length of the bar.

Optionally, the rear wall extends for substantially the full height of the bar for substantially the entire length of the bar.

Optionally, the upper surface at the hub end portion is recessed relative to the upper surface at the central portion such that the upper surface is lower (nearer a lower surface) at the hub end portion than at the central portion.

Optionally, the upper surface tapers continuously from the central portion to the hub end portion. Alternatively, the upper surface may taper in a discontinuous manner (such as in a stepped manner or in a combination of curves and straight lines).

Optionally, the elongate bar further comprises a lower surface extending between the rear wall and the front wall.

Optionally, the lower surface defines a mounting channel. The mounting channel may define threaded apertures into which fixing bolts may be screwed.

Optionally, one or more of the rear wall, the upper surface, and the front wall extend between the opposite ends. Optionally, each or both of the periphery and hub ends may be oriented transverse (in some embodiments normal) to the longitudinal axis.

The bar may comprise a longitudinal support and a plurality of structural supports. These supports may be surrounded (or partially surrounded) by elastomer to prevent the structural plates from being directly impacted by a grinding medium when used in a grinding mill. The structural supports may be made from, for example, a metal or alloy.

Optionally, adjacent head lifter bars may be separated by liners or other components.

A top protective plate portion may be mounted over a top surface of the elastomer enclosure over the structural plates.

The ore and charge located at the lower part of a mill as the mill rotates protects the underlying shell liners from direct impact of ore or charge. Overthrow of ore and balls (or other charge) beyond this level of ore and charge results in such ore or balls striking unprotected shell liners and causing significant wear thereof.

It should now be appreciated that this aspect assists in reducing overthrow of ore and balls by having a variable angle of the head lifter profiled surface at the periphery end, in contrast to the current fixed angle design for head lifters.

By retaining a relatively large cross section at the central portion of the head lifter bar, superior wear resistance, and therefore increased operational life of the head lifter bar, is provided.

According to a second aspect there is provided a grinding mill comprising (i) a rotatable shell, (ii) end walls coupled to opposing sides of the rotatable shell, and (iii) a plurality of head lifter bars according to the first aspect mounted on an inner surface of at least one of the end walls in radially spaced relation.

Optionally, a discharge end wall of the grinding mill may include a plurality of grates mounted thereon (optionally, with lifter bars between adjacent grates), and the plurality of head lifter bars may be mounted on an inner surface of an inlet end wall.

The various aspects detailed hereinafter are independent of each other, except where stated otherwise. Any claim corresponding to one aspect should not be construed as incorporating any element or feature of the other aspects unless explicitly stated in that claim. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects will be apparent from the following specific description, given by way of example only, with reference to the accompanying drawings, in which:

Figs. 1 A to 1 E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a first embodiment of the present invention;

Figs. 2A to 2E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a second embodiment of the present invention;

Figs. 3A to 3E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a third embodiment of the present invention;

Figs. 4A to 4E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a fourth embodiment of the present invention;

Figs. 5A to 5E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a fifth embodiment of the present invention;

Figs. 6A to 6E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a sixth embodiment of the present invention;

Figs. 7A to 7E are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar according to a seventh embodiment of the present invention;

Fig. 8 is a simplified, partially cut away schematic perspective view of a grinding mill including a plurality of radially spaced head lifter bars of the type shown in Figs. 1 A to 1 E, mounted on an inner side thereof, according to another embodiment of the present invention;

Fig. 9 is an enlarged view of a portion of the grinding mill of Fig. 8;

Fig. 10 is a front elevation view of the inner side shown in Fig. 8;

Fig. 11 is an enlarged, simplified, perspective view of a portion of the inner side of Fig. 10; and Fig. 12 is an enlarged, simplified, perspective view of a portion of an alternative inner side of a grinding mill similar to that shown in Fig. 10.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is first made to Figs. 1A to 1 E, which illustrate a head lifter bar 10a according to a first embodiment of the present invention. The head lifter bar 10a is for mounting on an end wall of a grinding mill (described in more detail below).

In this embodiment, the head lifter bar 10a is approximately 1.2 metres long, 18cm wide, and 24cm high; although the dimensions of the head lifter bar 10a (including the ratios of length to width to height) may be selected to suit any particular grinding mill or other application.

The head lifter bar 10a defines a longitudinal axis 12 extending between a periphery end 14a and a hub end 16a thereof. A vertical plane 18 extends through the longitudinal axis 12, and a horizontal plane 20, perpendicular (or normal) to the vertical plane 18, also extends through the longitudinal axis 12 (best seen in Fig. 1 E).

The bar 10a comprises a rear wall 24a, an upper surface 26a, a front wall 28 opposite the rear wall 24a, and a profiled surface 30a extending laterally between the upper surface 26a and an upper portion 32 of the front wall 28, and longitudinally between the periphery end 14a and the hub end 16a. The upper surface 26a extends laterally between the rear wall 24a and the profiled surface 30a, and longitudinally between the periphery end 14a and the hub end 16a. In this embodiment, the upper surface 26a is planar and parallel to the longitudinal axis 12.

The profiled surface 30a defines a central portion 36 oriented at an acute angle to the vertical plane 18. In this embodiment, the acute angle is approximately 30 degrees, although in other embodiments, the acute angle may be selected within the range from approximately 20 degrees to 40 degrees to the vertical plane 18. The central portion 36 is located at a middle portion 38 (best seen in Figs. 3A and 5A) of the bar 10a.

The profiled surface 30a also defines a periphery end portion 40a extending from the central portion 36 to the periphery end 14a, and a hub end portion 42a extending from the central portion 36 to the hub end 16a. In Figs. 1A and 1 B the hub end portion 42a is a continuation of, and has the same shape as, the central portion 36, but in other embodiments, such as the third to seventh embodiments described below, the hub end portion 42 has a different shape to the central portion 36. In other embodiments, the hub end portion 42 may have a different shape to both the central portion 36 and the periphery end portion 40.

The periphery end portion 40a is recessed from the central portion 36 in that the upper surface 26a is narrower at the periphery end 14a than at the central portion 36. However, the profiled surface 30a expands as it extends towards the periphery end 14a (best seen in Fig. 1A) because the distance from the upper portion 32 of the front wall 28 to the upper surface 26a increases. This means that the periphery end portion 40 enlarges in the horizontal plane 20 as it approaches the periphery end 14a.

In this embodiment, the central portion 36 defines an angle (a) 44 of approximately thirty degrees to the vertical plane 18; whereas the periphery end 14a defines an angle (b) 46 of approximately fifty degrees. The periphery end portion 40a has a generally planar shape and slopes continuously from the periphery end 14a to the central portion 30a.

The bar 10a also has a lower surface 50 extending between the rear wall 24a and the front wall 28 from the periphery end 14a to the hub end 16a. The lower surface 50 defines a C-shaped mounting channel 52 (best seen in Figs. 1 C to 1 E) in registration with an elongate steel reinforcement (not shown) enclosed within the bar 10a and extending almost the entire length of the head lifter bar 10a. The steel reinforcement provides structural support for the head lifter bar 10a and defines threaded apertures (not shown) to facilitate mounting of the bar 10a onto an end wall of a grinding mill in a conventional manner.

Although not illustrated in Figs. 1 A to 1 E, as is conventional for a head lifter bar, the head lifter bar 10a includes steel (or other metal or alloy) plates enclosed by elastomeric material (for example, vulcanized rubber). The steel plates (structural supports) may be oriented longitudinally, transversely (to the longitude), and/or parallel to the upper surface 26a and/or the profiled surface 30a.

The elastomeric enclosure provides flexible support for the structural plates, and resistance to wear when the head lifter bar 10a is located within a grinding mill by preventing direct contact between charge (for example, steel balls) and ore within the grinding mill and the surface of the steel plates. The vertical plane 18 is parallel to the rear wall 24a and the front wall 28; whereas, the horizontal plane 20 is parallel to the upper surface 26a and the lower surface 50.

Reference will now be made to Figs. 2A to 2E, which are simplified, schematic views (plan, front elevation, left end elevation, right end elevation, and perspective, respectively) of a head lifter bar 10b according to a second embodiment of the present invention. It will be appreciated that the views shown in Figs 2A to 2E (and also the corresponding views of Figs 3 to 7) correspond to those of Figs. 1A to 1 E. Furthermore, the parts in Figs. 2A to 2E corresponding to parts in the first embodiment (Figs. 1 A to 1 E) have the same numeral but include a “b” subscript instead of an “a” subscript. A similar approach is taken for Figs 3 to 7.

The primary difference between head lifter bar 10b and head lifter bar 10a is that the upper surface 26b slopes from the central portion to the periphery end 14b, such that the periphery end portion 40b slopes backwards (towards the rear wall 24b) and downwards (towards the lower surface 50). In this embodiment, the upper surface 26b slopes at an angle of approximately five degrees to the horizontal plane 20, but other angles are possible in other embodiments.

Reference will now be made to Figs. 3A to 3E, which are corresponding views (to Figs. 1A to 1 E) of a head lifter bar 10c according to a third embodiment of the present invention.

The primary difference between head lifter bar 10c and head lifter bar 10a is that in head lifter bar 10c the hub end portion 42c is recessed in the same manner as the periphery end portion 40c (which is the same as periphery end portion 40a), thus both ends 14c, 16c of the head lifter bar 10c are recessed, but both ends 14c, 16c are in the same plane as the upper surface 26c.

Reference will now be made to Figs. 4A to 4E, which are corresponding views (to Figs. 1A to 1 E) of a head lifter bar 10d according to a fourth embodiment of the present invention.

The head lifter bar 10d has a periphery end portion 40d similar to periphery end portion 40b (i.e. that of the second embodiment), and hub end portion 42d similar to hub end portion 40c (i.e. that of the third embodiment). Thus both ends 14d, 16d of the head lifter bar 10d are recessed, but only the periphery end 14d is lower than the upper surface 26d. Reference will now be made to Figs. 5A to 5E, which are corresponding views (to Figs. 1A to 1 E) of a head lifter bar 10e according to a fifth embodiment of the present invention.

The primary difference between head lifter bar 10e and head lifter bar 10c is that in head lifter bar 10e the upper surface 26e slopes downwards from the central portion to the periphery end 14e, and downwards from the central portion to the hub end 16e. This means that the periphery end portion 40e and the hub end portion 42e both slope backwards (towards the rear wall 24e) and downwards (towards the lower surface 50). In this embodiment, the upper surface 26e slopes at an angle of approximately five degrees to the horizontal plane 20, but other angles are possible in other embodiments, and the upper surface 26e may slope at a different angle towards the periphery end 14e than towards the hub end 16e. Thus, both ends 14e, 16e of the head lifter bar 10e are recessed, and both ends 14e, 16e are lower than the plane of the upper surface 26e at the central portion.

The above embodiments all have periphery end portions 40 and hub end portions 42 that have a continuous slope with respect to the vertical plane 18; and the periphery end portions 42 have a continuous slope at an acute angle to the vertical plane 18 (recessed with respect to the vertical plane 18). However, other embodiments are possible where the recess with respect to the vertical plane 18 is discontinuous. Two examples of these are illustrated in the sixth and seventh embodiments, although variations of these are possible.

Reference will now be made to Figs. 6A to 6E, which are corresponding views (to Figs. 1A to 1 E) of a head lifter bar 10f according to a sixth embodiment of the present invention.

In the sixth embodiment, the end portions 40, 42 are stepped. The periphery end portions 40f 1 and 40f2 are mirror images of the hub end portions 42f1 and 42f2.

The end portions 40f 1 , 40f2, 42f 1 , 42f2 and the central portion 36 are all aligned at the upper portion 32 of front wall 28. However, the central portion is inclined backwards at an angle of approximately thirty degrees (angle b 46); the first periphery and hub end portions 40f 1 , 42f 1 are both inclined backwards at an angle c 44x of approximately forty degrees; and the second periphery and hub end portions 40f2, 42f2 are both inclined backwards at an angle d 44y of approximately fifty degrees. This ensures that both the first and second end portions 40f 1 , 42f 1 , 40f2, 42f2 are both recessed relative to the central portion 36. However, but both ends 14f, 16f are in the same plane as the upper surface 26f.

One advantage of using stepped end portions is that the metal or alloy supports that are aligned with, but located behind, the stepped end portions can be in sheet form, which is easy to fabricate or cast.

In other embodiments, more than two periphery end portions and more than two hub end portions may be provided. The periphery end portions may not be mirror images of the hub end portions.

Reference will now be made to Figs. 7A to 7E, which are corresponding views (to Figs. 1A to 1 E) of a head lifter bar 10g according to a seventh embodiment of the present invention.

The primary difference between head lifter bar 10g and head lifter bar 10f is that in head lifter bar 10g the upper surface 26g slopes downwards from the central portion to the periphery end 14g, and downwards from the central portion to the hub end 16g. This means that the periphery end portions 40g1 , 40g2 and the hub end portions 42g1 , 42g2 both slope backwards (towards the rear wall 24g) and downwards (towards the lower surface 50). In this embodiment, the upper surface 26g slopes at an angle of approximately five degrees to the horizontal plane 20, but other angles are possible in other embodiments, and the upper surface 26g may slope at a different angle towards the periphery end 14g than towards the hub end 16g.

Reference is now made to Fig. 8 and 9, which are a simplified, partially cut away schematic perspective view, and an enlarged detail view, of a grinding mill 100 according to another embodiment of the present invention. The grinding mill 100 includes a plurality of radially spaced head lifter bars 10a of the type shown in Figs. 1A to 1 E. The grinding mill 100 rotates in the direction shown by arrow “R” in Figures 8 to 11 .

The grinding mill 100 comprises a front (inlet) side 102 spaced from a rear (discharge) side 104 by a cylindrical shell 106. An inner surface 108 of the inlet side 102 is populated with radially spaced head lifter bars 10a, each being separated from its adjacent head lifter bar 10a by a liner 110 of any convenient design, but typically trapezoidal when viewed from the front. The grinding mill 100 comprises an inlet aperture 120 into which ore to be comminuted is fed, and an outlet or discharge aperture 122 through which the comminuted ore is discharged.

As best seen in the enlarged detail (box labelled 126), the head lifter bars 10a are oriented such that the periphery end 14a is mounted at a periphery 134 of the inlet side 102 and the hub end 16a is mounted at a hub 136 of the inlet side 102. A plurality of grates 138 (only partly visible in Fig. 9) are mounted in a radially spaced manner on an inner surface of the discharge side 104. Fig. 10 is a front elevation view of the inner surface 108 showing the distribution of head lifter bars 10a on the inner surface 108. Fig. 11 is an enlarged, simplified, perspective view of a sector (labelled 140) of the inner surface 108 with the liners 110 removed for clarity.

Shell lifter bars 142 are provided on an inner surface of the cylindrical shell 106. The shell lifter bars 142 extend generally longitudinally along the shell 106 and are circumferentially spaced apart around the inner surface thereof.

As the cylindrical shell 106 is rotated, the head lifter bars 10a lift the ore and charge (e.g. steel balls) within the grinding mill 100. Using head lifter bars 10a having a slope at the periphery end portion 40a that is recessed from the central portion 36 reduces overthrow of ore and steel balls which occurs in the absence of these features. This is because where conventional head lifter bars (having nonrecessed periphery portions) are used, a nearly vertical face of the head lifter bar is provided near the periphery of the inlet side 102. This nearly vertical face of the head lifter bar throws the ore and the charge (located between adjacent head lifter bars 10a), beyond the region where the contents of the mill 100 forms a bed of ore and charge (referred to as the charge level). This charge level protects the shell liners beneath it from direct impact of ore or charge, so any ore or charge that is thrown beyond this charge level will strike unprotected shell liners.

Without these features, especially on the periphery 134 of the mill 100, the movement of the head lifter bars result in the material being thrown higher and further beyond the charge on the opposite side of the mill 100 and striking the mill shell 106 higher than the charge level of the mill 100. This reduces grinding efficiency as this material is not thrown at the charge and therefore is not being used to comminute the material in the charge, and also results in charge/ore-on-shell impact without the interstitial charge bed protecting the shell liners and shell lifters 142 . This causes premature wear and failure of the outer shell liners. When the height and face angle of the head lifter bar is adjusted towards the radius of the head lifter, the media throw is not as high. This is especially important at the outer radius, as this provides the highest starting trajectory leading to this detrimental over-throwing of the ore and charge.

Instead of using the head lifter bars 10a, any of the other lifter bar designs as illustrated in Figs. 2 to 7 may be used. A grinding mill may be provided that has a combination of different head lifter bar designs all mounted on the same inner surface 108.

A grinding mill may be provided that has head lifter bars as described above on both the front (inlet) side 102 and the rear (discharge) side 104.

In other embodiments, the grinding mill may be a ball mill, or other type of tumbling mill, rather than a SAG mill.

Various modifications may be made to the above described embodiments within the scope of the present invention. For example, different profiles of ends may be provided than those described. The dimensions of the lifter bar, the angles specified, the ratio of end portions to central portion, and the like may be differ from those described above or illustrated in the drawings.

The terms “comprising”, “including”, “incorporating”, and “having” are used herein to recite an open-ended list of one or more elements or steps, not a closed list. When such terms are used, those elements or steps recited in the list are not exclusive of other elements or steps that may be added to the list.

Unless otherwise indicated by the context, the terms “a” and “an” are used herein to denote at least one of the elements, integers, steps, features, operations, or components mentioned thereafter, but do not exclude additional elements, integers, steps, features, operations, or components.

The presence of broadening words and phrases such as "one or more," "at least," "but not limited to" or other similar phrases in some instances does not mean, and should not be construed as meaning, that the narrower case is intended or required in instances where such broadening phrases are not used.

List of Reference Numerals head lifter bar 10a to 10g longitudinal axis 12 periphery end 14a to 14g hub end 16a to 16g vertical plane 18 horizontal plane 20 rear wall 24a to 24g upper surface 26a to 26g front wall 28 profiled surface 30a to 30g upper portion (of front wall) 32 central portion (of profiled surface) 36 middle portion (of head lifter bar) 38 periphery end portion (of profiled surface) 40a to 40g first part periphery end portion (of profiled surface) 40f 1 second part periphery end portion (of profiled surface) 40f2 first part periphery end portion (of profiled surface) 40g1 second part periphery end portion (of profiled surface) 40g2 hub end portion (of profiled surface) 42a to 42g first part periphery end portion (of profiled surface) 42f 1 second part periphery end portion (of profiled surface) 42f2 first part periphery end portion (of profiled surface) 42g1 second part periphery end portion (of profiled surface) 42g2

Angle a (of periphery end portion) 44

Angle c (of first periphery and hub end portions) 44x

Angle d ((of second periphery and hub end portions)) 44y.

Angle b (of central portion) 46 lower surface 50

C-shaped mounting channel 52 grinding mill 100 front (inlet) side (of grinding mill) 102 rear (discharge) side (of grinding mill) 104 cylindrical shell (of grinding mill) 106 inner surface (of the discharge side) 108 liner 110 inlet aperture (of grinding mill) 120 outlet or discharge aperture (of grinding mill) 122 detail box 126 periphery (of inlet side) 134 hub (of inlet side) 136 grates 138 sector detail 140 shell lifter bars 142