AU776074B2

AU776074B2 - Lifter bar

Info

Publication number: AU776074B2
Application number: AU10025/02A
Authority: AU
Inventors: Ivan Svenson
Original assignee: EVANS DEAKIN ENGINEERING Pty L
Current assignee: Bradken Resources Pty Ltd
Priority date: 1995-01-05
Filing date: 2002-01-03
Publication date: 2004-08-26
Anticipated expiration: 2016-01-05
Also published as: AU1002502A

Description

P/00/01 1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION DIVISIONAL PATENT Invention: Lifter bar The following statement is a full description of this invention, including the best method of performing it known to us: Freehills Carter Smith Beadle, Sydney/00401 1524.1 1 Lifter Bar Field of the invention The present invention relates to a lifter bar for a grinding mill used for grinding ore.

Background of the invention Grinding mills are used for grinding mineral bearing ores into relatively small particles which can then be subsequently processed for mineral extraction. A grinding mill typically comprises a cylindrical shell which, on its inner surface is lined with a plurality of metallic or rubber liners.

The liners protect the inner surface of the shell from being worn away by the ore being ground.

The liners are held in place by lifter bars which are bolted to the shell and clamp opposite longitudinal edges of each liner to the inner surface of the drum. The lifter bars comprise S: elongate members which extend substantially for the length of the shell and are circumferentially spaced about the inner surface of the shell. In order to fix the bars to the shell, each lifter bar is provided with a plurality of counter-sunk holes, which extend wholly through S the bar in the radial direction of the shell. Bolts are then passed through the holes from the inside of the shell and extend through holes provided in the shell. Each bolt is provided with a S. head shaped so as to mate with the counter-sunk holes in the lifter bar. A nut is then screwed on to the opposite end of each bolt in order to fix the lifter bar and liners to the shell. When the grinding mill is in use the shell is rotated and the lifter bars lift the ore and any grinding balls to a point where they fall by action of gravity, thereby producing a tumbling action which has the effect of grinding the ore.

2 Summary of the invention According to the invention there is provided a lifter bar assembly adapted to be mounted to the inner surface of a rotatable shell of a grinding mill, the lifter bar assembly comprising: an elongate member having an upper portion which is in use exposed to material to be ground by said mill when said lifter bar is mounted to the inner surface of the shell, and a lower portion adapted to lie adjacent the inner surface of the shell; a plurality of elongate fastening studs releasably secured to said elongate member and spaced apart from each other, along the length of said elongate member, and projecting in a direction away from said upper portion, said studs being adapted to pass through mounting holes formed in the shell; the studs each having screw threads formed on or adjacent the distal end thereof .o adapted to receive a securing nut for releasably securing the respective studs and the elongate member to the shell; the studs being releasable from the elongate member by rotating the studs q.

2 ~relative to the elongate member from a position exterior of the shell.

ddd The approximate ends of the studs may have screw threads thereon, and the elongate member preferably has corresponding threaded bores associated therewith with which the studs are @99* engaged to releasably secure the studs to the elongate member. The threaded bores may be formed in nuts located in recesses in the elongate member. The recesses preferably are configured such that the nuts are constrained against rotation when in those recesses.

The elongate member may have a series of holes therein which correspond with the recesses, and the studs extend through the holes to engage with the nuts located in the recesses. The nuts may have sleeves mounted thereon which are co-axial with the threaded bores, the sleeves being located in those holes to thereby secure the nuts within the recesses.

The studs may have drive formations thereon for rotating the studs relative to the elongate member. The drive formations may be of lesser diameter than the outer diameter of the screw threads on the studs.

The elongate member preferably has a continuous upper surface which is exposed to material to be ground by the mill when the lifter bar assembly is fixed to the inner surface of the shell.

The invention extends to a method of attaching a lifter bar assembly to the rotatable shell of a grinding mill, and to a method of detaching a lifter bar assembly from said rotatable shell.

These and further features of the invention are made apparent from description of preferred embodiments thereof given below by way of example. In the description reference is made to the accompanying drawings, but the specific features shown in the drawings should not be construed as limiting on the invention.

Brief description of the drawings Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: .2 Figure 1 is a plan view of a first embodiment of the lifter bar; .o Figure 2 is a view of section B-B of the lifter bar shown in Figure 1; S Figure 3 is a view of section A-A through the lifter bar shown in Figure 2; :15 Figure 4 is a schematic view of a portion of a grinding mill having installed therein the lifting bar as shown in Figures 1-3; fl-- Figure 5 is a section view of a second embodiment of the lifter bar; Figure 6 is a schematic view of a portion of a grinding mill having installed therein a third embodiment of the 5 lifter bar; and .'70 Figure 7 is a section view of a lifter bar having a through slot.

Detailed description of the embodiments With reference to the accompanying drawings, it can be seen that a lifter bar 10 for a grinding mill 12 provided with a rotatable shell 14 used for grinding ore, comprises an elongated member 16, typically made of a metal or metal alloy, having an upper portion 18 provided with a continuous surface 20. When the lifter bar 10 is installed in the grinding mill 12, the surface is exposed to and contacted by the ore to be ground. Lower portion 22 of lifter bar 10 lies adjacent inner surface 24 of shell 14 when lifter bar 10 is installed in the grinding mill 12.

Fastening means 26 for releasably fastening the elongate member 16 to the shell 14 is coupled 4 at one end the lower portion 22 and, as shown most clearly in Figure 4, is adapted for coupling at an opposite end to the shell 14.

The lifter bar 10 is provided with three recesses in the form of slots 28 which extend transversely through lower portion 22. A separate hole 30 extends through the lower portion 22 to each slot 28.

Fastening means 26 comprises three components, a first part in the form of a nut 32, a sleeve 34 and an elongate element in the form of stud 36 which is threaded at first and second ends 38 and 40. End 40 terminates in a hexagonal protrusion 41 to which a spanner can be coupled for screwing stud 36 into nut 32.

The nut 32, as is illustrated in figure 1 and 2, is positioned in the slot 28 so that the nut 32 is prevented from rotating while it is located in the slots 28 Nut 32 is provided with a hole having an upper threaded portion 42 for engaging first end 38 of *2 0 the stud 36, and a concentric and increased diameter lower portion 44 provided with a thread for threadingly engaging the sleeve 34.

When assembling the lifter bar 10, the nut 32 is passed through slot 28 and the sleeve 34 passed through hole 30 and threadingly engaged with the lower portion 44 of the nut 32. Sleeve 34 is provided with an outer diameter smaller than the diameter of hole 30 so as to allow movement S of the sleeve 34 within the hole 30 and corresponding movement of the nut 32 within slot 28.

.ooooi S When connected to the nut 32, the sleeve 34 extends to the end of hole 30. In this way, the ,020 sleeve 34 effectively retains the nut 32 within the lifter bar 10. Stud 36 is then passed through sleeve 34 and the first end 38 loosely screwed into the upper threaded portion 42.

The elongate member 16 with attached fastening means 26 is then placed inside shell 14 and disposed between adjacent shell liners 46. The liners are typically made from metal or rubber S and are used to protect inner surface 24 from wearing away through contact with the ore being ground. Holes (not shown) are formed in the shell 14 through which the second end 40 of the stud 36 can pass. A washer 50 is placed over end 40 and nut 52 screwed onto the second end to effectively attach the lifter bar 10 to the interior of the shell 14. Lower portion 22 of each lifter bar 10 abuts the longitudinal edge of adjacent liners 46 so that, when fastened in place, lifter bars 10 also act to clamp the liners 46 to shell 14. The movement of the nut 32 within slot 28 allowed by the difference in diameter of the sleeve 34 and hole 30 allows easy alignment of studs 36 with the holes in the shell 14. The bottom surface of member 16 is provided with a recess 47 for fitting over a portion of adjacent liners 46. The recess 47 is also employed in the prior art lifter bars and does not form part of the invention.

When the shell 14 is loaded with ore and rotated, the lifter bars assist in producing a tumbling action of the ore and metal grinding balls or other grinding media which may be loaded in the grinding mill 12 to facilitate grinding of the ore. Slots 28 are located below the level of upper (exposed) surface 48 of the liners 46 when the lifter bar 10 is fastened in the grinding mill 12.

A second embodiment 10' of the lifter bar is illustrated in Figure 5. In this embodiment, the same reference numbers are used to indicate identical features of the first embodiment and a prime symbol is used to indicate features which have been modified in this embodiment in comparison to the first embodiment.

The main differences between the lifter bar 10 of the first embodiment and the lifter bar 10' of S. the second embodiment is that the slot 28' extends only partially rather than wholly through the lower portion 22' of the lifter bar. Further, the sleeve 34 of the first embodiment has been S dispensed with so that the fastening means 26' comprises only the nut 32 and the threaded stud 36. End 40 of the threaded stud 36 is fastened to the outside of the shell 14 by way of a non-slip nut 52'. Disposed between the nut 52, and the outside surface of shell 14 is a recessed washer 50' and a sealant washer 51' partially received within the recessed washer 50'. A pair of eyelets '4d..

62 are also formed on opposite sides of the surface 20 of lifter bar 10'. The eyelets 62 are provided to assist in the lifting and transporting of the lifter bars In essentially all respects, the lifter bar 10' functions in an identical manner to lifter bar 9. However, the lifter bar 10' is simpler to install and manufacture as it does not require the sleeve 34 of the first embodiment and the slots 28 did not pass wholly through the lower portion 22' of t the lifter bar 04.: A further embodiment 10" of the lifter bar is shown in Figure 6. The lifter bar 10" in essence comprises the combination of the lifter bar 10' of Figure 5 together with a liner 46" formed integrally with lower portion 22' of the lifter bar. The fastening means 26' of the lifter bar 10" is identical to that of the lifter 10'. The liner portion 46,' can take any suitable shape or configuration.

In a variation of the lifter bar 10" shown in Figure 6, the slot 28' for receiving the fastening means 26' can in fact alternately be placed in the liner portion 46". However, this is not 6 preferred as greater stresses will then be placed on the threaded stud 36 due to the weight distribution of the lifter bar From the above description it will be apparent that the present embodiment has numerous advantages over the prior art. Significantly, the present embodiment does not require bolt holes which extend wholly through the elongate member 16 in the radial direction in order to allow fastening to the shell 14. Therefore the inherent weaknesses of the prior art lifter bars are avoided by the present embodiment. Further, as the upper surface 20 is continuous and free of bolt holes has much improved wear characteristics. In addition, the slots 28 which the fastening means 26 engage may be located below the level of upper surface 48 of liners 46 and therefore are not acted upon by the ore being ground or grinding media.

It will be apparent to those skilled in the mechanical arts that numerous modifications and variations may be made to the above-described embodiment without departing from the basic inventive concepts. For example, the upper portion 18 is shown as being substantially rectangular (or more precisely ingot shaped) in cross-section. However, other configurations are 15 possible such as triangular. Further, although the slots 28 area shown as not extending wholly through the lower part 22, (that is they are in the form of blind holes), they could be as is illustrated in figure 7, that is the slots 28 pass all the way through the lifter bar 10. (The illustration in figure 7 includes like numbering of features to that of figure In addition when fastening the lifter bar 10 to the interior of shell 14, rather than loosely screwingstud 36 onto nut 32 prior to placing the lifter bar 14 into the shell 14, the stud 36 can be screwed onto nut 32 from the outside of shell 14. All such modifications and variations are deemed to be within the ~scope of the present invention, the nature of which is to be determined from the foregoing description.

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