Background to the Invention Operation of a grinding mill typically involves feeding material and water into one end of the mill and discharging the ground product at the other end of the mill. The product is typically discharged through. a discharge cone which forms part of a discharge end wall of the grinding mill. The discharge cone typically comprises a number of discharge cone elements arranged around the central axis of the mill.

Each discharge cone element typically comprises a body portion and a nose cone. The body portion typically comprises top and bottom plates separated by one or more upright members. The nose cone projects from the body portion towards the centre of the discharge end wall and includes a central vane and a flange, extending from either side of the vane, and formed integrally with the top plate.

The discharge cone elements may be constructed entirely of steel. A problem with all-steel discharge cone elements is that they are extremely heavy, which may reduce the amount of material which can be loaded into the grinding mill and thus reduce the throughput of the mill.

Furthermore, because the steel discharge cone elements are heavy, they can be difficult to maneuver during installation and/or removal from the mill.

In response to the above problem, discharge cone elements have been constructed from a composite of materials. Upright member (s) have been constructed from steel or rubber coated mild steel plate and the remaining components, in particular the top and bottom plates and the nose cone, have been constructed substantially of

rubber.

Although such composite material discharge cone elements are lighter than all-steel discharge cone elements, they suffer from another problem. Portions of the rubber components have been found to wear out reasonably quickly thus necessitating the entire discharge cone element to be replaced on a more frequent basis.

Replacement of the discharge cone elements is extremely costly in terms of both the cost of replacement element and downtime of the grinding mill.

Summary of the Invention According to a first aspect of the present invention there is provided a discharge cone for a grinding mill, the discharge cone comprising a plurality of discharge members, each discharge member being formed from a composite of-materials and comprising a body portion and a nose cone, the body portion comprising a top plate and a bottom plate separated by at least one upright member disposed between the top and bottom plates, the nose cone being cast from metal and projecting from the body portion towards the centre of the discharge cone.

Preferably, the body portion is formed from a composite of rubber and metal.

Preferably, the top and bottom plates are both formed from a composite of rubber and metal.

Preferably, the nose cone comprises a central vane and a downwardly curving flange extending from either side of the vane.

Preferably, the flange is arranged to form a substantially continuous surface with a bottom surface of the top plate.

Preferably, the central vane is integrally formed with one of the at least one uprights.

Preferably, one or more of the at least one uprights includes a metal rib extending along the side of the upright (s) corresponding to the direction in which the

grinding mill, in use rotates, the metal rib arranged, in use to form a continuous surface with the bottom surface of the top plate.

Preferably, the top and bottom plates each comprise a metal reinforcing sheet disposed between layers of rubber.

Preferably, each of the discharge members further comprises a lifting boss, located on the axis perpendicular to the top and bottom plates, the axis passing through the centre of mass of the discharge member, the lifting boss adapted for use in manoeuvring the discharge member for installation and/or removal from the grinding mill.

Preferably, the lifting boss is integrally formed with one of the at least one uprights and projects through the top plate.

Alternatively, each of the discharge members further comprises a pair of lifting lugs, located on the top surface of the top plate and positioned either side of the axis which passes through the centre of mass of the discharge member.

Preferably, the nose cone further comprises a clamping tongue at the end of the nose cone which projects towards the centre of the discharge cone, the clamping tongue adapted, in use, to allow the discharge member to be fixed in position in the grinding mill.

Preferably, the clamping tongue is adapted, in use, to connect each discharge member to a clamping ring.

Preferably, the at least one upright is constructed of white iron steel. The at least one upright may have a non-constant radial cross-section.

Preferably, the nose cone is constructed of white iron steel.

According to a second aspect of the present invention there is provided a discharge member for a grinding mill as defined in the first aspect of the present invention.

Brief Description of the Drawings Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a plan view of the discharge end wall of a grinding mill from inside the mill ; Fig. 2 is a perspective rear view of two discharge cone members connected to a clamping ring ; Fig. 3 is a perspective view from below of the discharge cone members of Fig. 2; Fig. 4 is a top view of the discharge cone members of Fig. 2 ; Fig. 5 is a perspective view from the side and below of the discharge cone members of Fig. 2, with one of the discharge cone members partially cut away; and Fig. 6 is a perspective front view of the discharge cone members of Fig. 2.

Detailed Description of the Drawings Referring firstly to Fig. 1, a grinding mill has a discharge end wall 10, including inner and outer sections. The inner section is a discharge cone which is made up of a number of discharge cone members 11 each attached to a clamping ring 12 located towards the centre of the discharge end wall 10. The discharge end wall 10 of the grinding mill illustrated in Fig. 1 has ten discharge cone members 11. However, this number may vary according to the type of grinding mill. The outer section of the discharge end wall 10 comprises a plurality of cavity channels 13, which surround the discharge cone members 11. In use, material in the grinding mill passes through a screening wall (not shown) before entering the cavity channels 13 at the rim of the discharge end wall 10. As the grinding mill rotates, the material under gravitational and centrifugal force, passes through the cavity channels 13 into the discharge cone members 11 and exits the grinding mill through the centre of the

discharge end wall 10.

Referring now to Figs. 2 to 6, each discharge cone member 11 has a body portion 19 and a nose cone 24 projecting away from the body portion 19 towards the clamping ring 12, which in use is located at the centre of the discharge end wall 10. In the embodiment shown in Figs. 2 to 6, the nose cone 24 is integrally formed with part of the body portion 19. The entirety of nose cone 24 is cast from metal, for example steel, and the body portion 19 is constructed of a composite of materials, namely metal and rubber.

The body portion 19 has a top plate 20 and a bottom plate 21, spaced apart by a first upright 22 and a second upright 23. The discharge cone member 11 may have only one upright, or alternatively, may have two or more uprights. The top and bottom plates 20 and 21 are shaped as annular segments and are of approximately the same dimensions.

Each of top and bottom plates 20 and 21 are constructed of two layers of rubber separated by a metal reinforcing sheet 27 and 28 respectively. The metal reinforcing sheets 27 and 28 provide added strength and rigidity to the top and bottom plates 20 and 21 as well as facilitating connection of the top and bottom plates 20 and 21 to the first and second uprights 22 and 23 by a plurality of bolts. The metal reinforcing sheets 27 and 28 are constructed of, for example, mild steel plate.

The bottom plate 21 has a ridge 29 connected to the bottom surface at the inner end of the bottom plate 21. The ridge, in use, is adapted to sit on a frame at the discharge end of the grinding mill so as to support the discharge member 11 in use.

The first and second uprights 22 and 23 in one embodiment are substantially rectangular prismatic in shape and are cast from metal, for example, white iron steel. The first and second uprights 22 and 23 are arranged, in use, so that their longest side is orientated

radially with respect to the clamping ring 12. The second upright 23 extends along the radial length of the body portion 19. The first upright 22 extends from the outer end of the body portion 19 only partially along the radial length of the body portion 19.

In an alternative embodiment, the first and second uprights 22 and 23 have a non-constant radial cross-section, whereby the first and second uprights 22 and 23 have portions which are thinner and thicker depending on which regions of the first and second uprights 22 and 23, in use, are subjected to the most wear. By thinning out the regions of the uprights 22 and 23 which are not subjected to much wear, the weight of the discharge cone member 11 can be reduced. Furthermore, by thickening the regions of the uprights 22 and 23 which experience the most wear, the operational life of the discharge cone members 11 can be extended. The exact shaping of the first and second uprights 22 and 23 is dependent on the grinding mill in which the discharge cone member 11 is to be used.

The second upright 23 has a steel rib 34 extending along the side of the second upright 23 corresponding to the direction in which the grinding mill, in use, rotates. The steel rib 34 is located towards the top of the second upright 23 and has a substantially rectangular cross-section, so that the lower surface of the steel rib 34 forms a continuous surface with the bottom surface of the top plate 20. The purpose of the steel rib 34 will become apparent further on in the specification.

The nose cone 24 has a central vane 30 and a downwardly curving flange 31 extending from either side of the central vane. In use, the nose cone 24 is arranged so that the lower surface of-downwardly curving flange 31 forms a substantially continuous surface with the bottom surface of the top plate 20. The central vane 30 is integrally formed with the second upright 23, such that

the second upright 23 and the nose cone 24 are cast as a single piece.

Each discharge cone member 11 also has a clamping tongue 25 integrally formed at the inner end of the nose cone 24, i. e. remote from the body portion 19. The clamping tongue 25 is adapted, in use, to connect each discharge cone member 11 to the clamping ring 12. The clamping ring 12 is an annular disc with a raised outer edge 40, the outer edge 40 being shaped to have a close fit with the top surface of the nose cone 24. This helps prevent the loss of fines from the discharge end of the grinding mill, by deflecting the fines into a trunion (not shown). The clamping ring 12 is provided with apertures, evenly spaced around the disc. The clamping tongue 25 also has an aperture whereby, attachment of the discharge cone member 11 is achieved by aligning the aperture in the clamping tongue 25 with one of the apertures in the clamping ring 12 and passing a bolt therethrough. The clamping ring 12 is cast from a metal, for example steel.

In use, the material enters the body portion 19 of the discharge cone member 11 through a passageway 32 created between the top and bottom plates 20 and 21 and the first and second uprights 22 and 23. Material will also enter through a similar passageway created between the top and bottom plates 20 and 21 of two neighbouring discharge cone members lla and llb and the first upright 22 of one discharge cone member lla and the second upright 23 of a neighbouring discharge cone member llb.

The material then passes between the top and bottom plates 20 and 21 under gravitational and centrifugal force. The majority of the material moves along the side of the second upright 23 corresponding to the direction in which the grinding mill, in use, rotates.

Because this results in a higher localised region of wear, the steel rib 34 is provided to reduce the wear to the rubber top plate 20.

Material exiting the grinding mill exits the

discharge cone member 11 through exit 33, which is formed by the central vanes 30, the bottom plates 21 and opposing sides of the flanges 31 of the two neighbouring discharge cone members lla and llb. A majority of the impact and wear caused by the material exiting the discharge cone members lla and llb occurs along the bottom surface of the flange 31 and the side walls of the central vane 30.

Each discharge cone member 11 also has a lifting boss 26, located on the axis perpendicular to the top and bottom plates 20,21, the axis passing through the centre of mass of the discharge member 11. The axis also passes through the second upright 23, such that the lifting boss is integrally formed with the second upright 23 and projects through the top plate 20. The lifting boss 26 is therefore also cast from metal for example white iron steel. The lifting boss 26, is adapted, in use, to facilitate lifting and maneuvering of the discharge cone member 11 for installation into and/or removal from the grinding mill. Alternatively, each discharge cone member 11 may be provided with a pair of lifting lugs, positioned either side of the axis which passes through the centre of mass of the discharge member 11 such that the lifting lugs facilitate stable lifting and maneuvering of the discharge member 11.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word"comprise"or variations such as "comprises"or"comprising"is used in an inclusive sense, ie. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.