AU2014210606A1 - A vertical stirred media mill screw - Google Patents

Abstract

A VERTICAL STIRRED MEDIA MILL SCREW An agitating screw (10) of a vertical stirred media mill, the screw (10) would be received in an outer casing and rotated through repeated revolutions continuously in the direction (11) so as to cause slurry to circulate vertically through the mill, with the slurry adjacent the radially outer portions of the screw (10) being moved in the upward direction (12). The screw (10) includes a generally central upright shaft (13) via which the screw (10) is driven, with the shaft (13) having a flange (14) to which wear portions (18) are attached.

Description

1 A VERTICAL STIRRED MEDIA MILL SCREW FIELD [0001] The present invention relates to agitating screws employed in vertical stirred media mills. BACKGROUND [0002] Vertical stirred media mills, include a generally cylindrical casing surrounded by magnets. The inner surface of the cylindrical casing encompasses a chamber within which there is located a rotatably driven agitating screw. The chamber is prefilled with grinding media, usually steel balls. The material to be ground is delivered in a form of slurry to the interior of the chamber, with the screw rotated to agitate the contents. The product is then extracted taken from the upper levels of the chamber. Typically agitating screws include a generally upright central shaft provided with a spiral mounting flight. Attached to the flight are wear members. The wear members have an upper spiral surface that engages the material being ground and the grinding media, with the spiral surface including an inner spiral surface and an outer spiral surface. The inner spiral surface slopes downwardly towards the central shaft, while the outer spiral surface extends generally radially outwardly. When viewed in vertical side section the outer surface it is generally horizontal. In operation of the mill, magnets adjacent the casing urge the grinding media to the casing inner side surface to aid in grinding material. Rotation of an agitating screw causes circulation of the slurry and create a shear zone between the tip of the agitating screw and the magnets. [0003] A disadvantage of the above described vertical mill is that the magnetic force attracting the steel grinding media diminishes radially inwardly. [0004] A further disadvantage is that the grinding media located radially inward have a lower centricular force applied to them when the screw is rotated. [0005] The above disadvantages result in the radially inner steel grinding media being urged radially outwardly to a less extent than the balls are located closer to the casing. This distracts from the efficiency of the mill.

2 [0006] Slurry is only forced radially upward by centrifugal force generated by the agitating screw. Slurry located radially inward are lifted by the action of the agitating screw without being passed through the shear zone located between the tip of the agitating screw and the magnets. OBJECT [0007] It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages. SUMMARY [0008] There is disclosed herein a wear member for a vertical grinding mill, the mill having and agitating screw including a base, the base including a generally upright central shaft, via which the screw is rotatably driven through repeated revolutions, with a generally central upright longitudinal axis, and a spiral mounting flange fixed to the shaft and extending angularly about and longitudinally of said axis; the wear member including: an inner mounting through which fasteners pass to secure the wear member to the spiral flange; and a wear portion fixed to the mounting and extending outwardly therefrom so that when fixed to the shaft the wear portion extends outwardly relative to said axis, with the wear member having a radially inner surface and a radially outer surface, with the outer surface extending angularly and longitudinally relative to said axis and downward outwardly from said inner surface. [0009] Preferably, the surfaces are upper surfaces. [0010] In an alternative preferred form, the surfaces are lower surfaces. [0011] Preferably, the surfaces are upper surfaces and said wear portion has a lower radially inner surface and a lower radially outer surface, with the lower radially outer surface extending angularly and longitudinally relative to said axis and downward outwardly from said lower inner surface. [0012] In a first preferred form each outer surface is generally flat in side section.

3 [0013] In an alternative preferred form, each outer surface is arcuate in side section. [0014] Preferably, each inner surface is flat in side section. [0015] Preferably, each inner surface is radial in side section. [0016] There is further disclosed herein an agitating screw of a vertical grinding mill, the screw including: a base, the base including a generally upright central shaft, via which the screw is rotatably driven through repeated revolutions, with a generally central upright longitudinal axis; a spiral mounting flange fixed to the shaft and extending angularly and longitudinally of said axis; and the above wear member fixed to the mounting flange. [0017] There is also disclosed herein, a vertical grinding mill having the above agitating screw. BRIEF DESCRIPTION OF DRAWINGS [0018] A preferred form of the present invention will now be described by way of example with reference to the accompanying that schematically depicts in side elevation an agitating screw of a vertical grinding mill. DESCRIPTION OF EMBODIMENTS [0019] In the accompanying drawings there is schematically depicted an agitating screw 10 of a vertical stirred media mill. The screw 10 would be received in an outer casing and rotated through repeated revolutions continuously in the direction 11 so as to cause slurry to circulate vertically through the mill, with the slurry adjacent the radially outer portions of the screw 10 being moved in the upward direction 12. [0020] The screw 10 includes a generally central upright shaft 13 via which the screw 10 is driven. Fixed to the shaft 13 and preferably integrally formed of the shaft 13 is a spiral mounting flange 14. The flange 14 extends longitudinally of and angularly about the longitudinal axis 15 of the shaft 13.

4 [0021] Fixed to the flange 14 via threaded fasteners (not illustrated) is a plurality of wear members 16. Each wear member 16 forms a segment of a spiral, with each wear member 16 including a mounting portion 17 and a radially outer wear portion 18. [0022] Each mounting portion 17 extends in a spiral manner about the axis 15 and tapers in thickness towards the shaft 13. Each mounting portion 17 is also provided with a plurality of apertures 20 that are aligned with corresponding apertures ( not illustrated) in the flange 14 so that threaded fasteners such as bolts, can pass therethrough for engagement with nuts so that upon tensioning of the threaded fasteners the wear members 16 are secured to the flange 14. [0023] The mounting portion 17 has an upper surface 24. Although the surface 24 can have an inclination relative to the axis 15 (when viewed in a sectioned side elevation), preferably the surface 24 extends generally radially and therefore generally horizontally outward from the shaft 13. Accordingly the wear portion 18 may have or may not have a further wear layer overlaying the surface 21. [0024] The mounting 17 also has a lower surface 23. Although the surface 23 can have an inclination relative to the axis 15 (when viewed in a sectioned side elevation) preferably the surface 23 extends downwardly from the shaft 13. [0025] The wear portion 18 also has a lower spiral surface 22 that extends outwardly downward from the surface 23. In this embodiment, the surface 22 is generally flat (in a section side elevation), however when viewed in a side elevation it could also be arcuate so as to be slightly convex or even slightly concave. The surface 22 may be parallel to the surface 21 so that the wear portion 18 between the surfaces 21 and 22 is of a generally constant thickness. [0026] The wear portion 18 has an upper spiral surface 21 that extends outward downwardly from the surface 24. In this embodiment the surface 21 is generally flat (in sectioned side elevation), however when viewed in side elevation it could also be arcuate so as to be slightly convex or even slightly concave. The surface 21 may also be covered by another wear surface (not illustrated). [0027] The above described preferred embodiment has the advantage that the above described steel grinding media are urged radially outwardly under the influence of gravity since the surface 21 slopes downwardly toward the inner surface of the casing. This enhances the grinding effect of the balls and therefore the grinding efficiency of the mill.

Claims (10)

1. A wear member for a vertical grinding mill, the mill having and agitating screw including a base, the base including a generally upright central shaft, via which the screw is rotatably driven through repeated revolutions, with a generally central upright longitudinal axis, and a spiral mounting flange fixed to the shaft and extending angularly about and longitudinally of said axis; the wear member including: an inner mounting through which fasteners pass to secure the wear member to the spiral flange; and a wear portion fixed to the mounting and extending outwardly therefrom so that when fixed to the shaft the wear portion extends outwardly relative to said axis, with the wear member having a radially inner surface and a radially outer surface, with the outer surface extending angularly and longitudinally relative to said axis and downward outwardly from said inner surface.

2. The wear member of claim 1, wherein the surfaces are upper surfaces.

3. The wear member of claim 1, wherein the surfaces are lower surfaces.

4. The wear member of claim 3, wherein the surfaces are upper surfaces and said wear portion has a lower radially inner surface and a lower radially outer surface, with the lower radially outer surface extending angularly and longitudinally relative to said axis and downward outwardly from said lower inner surface.

5. The wear member of any one of claims I to 4, wherein each outer surface is generally flat in side section.

6. The wear member of any one of claims 1 to 4, wherein each outer surface is arcuate in side section.

7. The wear member of any one of claims 1 to 6, wherein each inner surface is flat in side section. 6

8. The wear member of any one of claims I to 7, wherein each inner surface is radial in side section.

9. An agitating screw of a vertical grinding mill, the screw including: a base, the base including a generally upright central shaft, via which the screw is rotatably driven through repeated revolutions, with a generally central upright longitudinal axis; a spiral mounting flange fixed to the shaft and extending angularly and longitudinally of said axis; and the wear member of any one of claims 1 to 8 fixed to the mounting flange.

10. A vertical grinding mill having the agitating screw of claim 9. CITIC HIC Australia Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON