LIFTER BAR, METHOD FOR MAKING A LIFTER BAR, METHOD FOR ASSEMBLING A LIFTER BAR AND A GRINDING MILL

Abstract

This relates a lifter bar, method for making a lifter bar, a method for assembling a lifter bar and a grinding mill for ore grinding. The lifter bar comprises a lifter bar body having an outer surface conforming the outer surface of the lifter bar, and a fixing element for connecting the lifter bar to the shell of the grinding mill. The lifter bar body further comprises a first portion and a second portion forming a continuous lifter bar body. The fixing element is embedded to the first portion such that it forms part of the fixing surface of the lifter bar. The second portion is made of polyurethane and forming 35-85% of the volume of the lifter bar.

Claims

1. A lifter bar mountable to a shell of a grinding mill for ore grinding, said lifter bar having a volume, said lifter bar further having an outer surface comprising a fixing surface to be arranged against the shell and a wear surface facing toward interior of the grinding mill, the lifter bar comprises a lifter bar body having an outer surface conforming the outer surface of the lifter bar, and a fixing element for connecting the lifter bar to the shell of the grinding mill, the lifter bar body further comprising a first portion and a second portion forming a continuous lifter bar body, the fixing element is embedded to the first portion such that it forms part of the fixing surface of the lifter bar, said first portion of the lifter bar body is made of rubber, the second portion is made of polyurethane and forming 35-85% of the volume of the lifter bar.

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. A lifter bar according to claim 1, wherein the first portion of the lifter bar body is recycled.

7. A lifter bar according to claim 1, wherein the second portion comprises polyurethane 40-80% of the volume of the lifter bar.

8. A lifter bar according to claim 1, wherein the lifter bar further comprises a reinforced wearing plate attached to the lifter bar body in the second portion, the reinforced wearing plate comprises metal, said reinforced wearing plate further comprises a wearing surface for forming a part of the outer surface of the lifter bar in a distal end of the second portion or in the vicinity of the second portion; and an attachment structure provided to the reinforced wearing plate for attaching the reinforced wearing plate to the lifter bar body, said attachment structure protruding into the second portion of the lifter bar body for forming a connection with polyurethane.

9. A lifter bar according to claim 1, wherein the fixing element is a mechanical fixing element.

10. A lifter bar according to claim 1, wherein the fixing element is a lifter channel.

11. Method for making a lifter bar according to claim 1, the method comprising the steps of: providing a mould for moulding the lifter bar; adding polyurethane into the mould for forming the second portion of the lifter bar body, the polyurethane is in such a state that it is arranged to react in the mould an form a connection with a material of the first portion of the lifter bar body; and adding rubber into the mould for forming the first portion of the lifter bar body, the material of the first portion is in such a state that it is arranged to react in the mould such that the polyurethane in the second portion and the rubber in the first portion form a connection with each other for forming a continuous lifter bar body.

12. Method according to claim 11, wherein the method further comprises the steps of: providing a reinforced wearing plate comprising a wearing surface and an attachment structure for mechanically engaging with the second portion of the lifter bar body; and arranging the reinforced wearing plate in the mould such that the wearing surface forms at least part of the outer surface of the moulded lifter bar.

13. Method according to claim 11, wherein the step of providing a mould comprises providing a mould made of sheet metal having a thickness of less than 10 mm, preferably less than 5 mm and most preferably 0.2-2 mm.

14. Method for assembling a lifter bar according to claim 1 to a shell of a grinding mill, the method comprising the steps of: attaching the lifter bar to the shell of the grinding mill by arranging the fixing element against the shell; and fastening the lifter bar to the shell with fastening means through the fixing element.

15. A grinding mill comprising multiple lifter bars arranged to a shell of the grinding mill, said lifter bars are according to claim 1.

16. A grinding mill according to claim 15, wherein the grinding energy per ton of ore of the grinding mill is 1-30 kWh/t and preferably 3-20 kWh/t.

17. A grinding mill according to claim 15, wherein the grinding mill having a diameter of 1-15 m, preferably 1.5-10 m.

18. A grinding mill according to claim 15, wherein the grinding mill having a length of 1-15 m in horizontal direction, preferably 2-8 m.

19. A grinding mill according to claim 15, wherein the shell of the grinding mill having a thickness of 0.5-10 cm.

20. A grinding mill according to claim 15, wherein said grinding mill is arranged to grind input material of which at least 80% has particle size between 0.1-300 mm, preferably 1-250 mm and most preferably 80-220 mm to grinded output material of which 80% has particle size between 0.02-3 mm, preferably 0.05-2.5 mm and most preferably 0.2-2 mm.

21. A grinding mill according to claim 15, wherein the grinding mill further comprises shell plates arranged between adjacent lifter bars.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the following the lifter bar will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

[0023] FIG. 1 shows a grinding mill;

[0024] FIG. 2 shows a cross section of the grinding mill in FIG. 1;

[0025] FIG. 3 shows a lifter bar; and

[0026] FIG. 4 shows an embodiment according to a lifter bar shown in FIG. 3.

DETAILED DESCRIPTION

[0027] FIG. 1 shows, as already described earlier, that the solid material is grinded in a drum shaped shell 2 mounted for rotation about its central axis in the grinding mill 3. The axis of the rotatable shell 2 is generally horizontally arranged or slightly inclined towards one end in the grinding mill 3. The interior of the shell 2 forms a treatment chamber and has a cylindrical wall. The inner surface of the chamber is plated with shell plates for protecting the shell 2 because the material to be processed is fed to the treatment chamber and grinding it causes wear in the chamber. The interior wall of the shell 2 is equipped with lifter bars 1 for lifting the material inside the shell 2 along the rotation so that as the shell 2 rotates the lifter bars 1 lift up the solid material along the inside wall of the shell 2 to a point where gravity causes the solid material to fall down inside the shell 2 and by falling down the solid material is crushed. A line of lifter 1 bars extend from one end of the drum to another and they are arranged in a short spacing adjacently along the cylindrical wall of the shell 2 such that there are shell plates arranged between adjacent lifter bars 1. As compared to the shell plates the lifter bars 1 protrude more from the shell 2 wall than the shell plates.

[0028] In other words FIG. 1 shows a longitudinal cross-section of a horizontal grinding mill 3 having an inner shell 2 comprising a cylindrical wall which the shell 2 comprises lifter bars 1 mounted to the cylindrical wall of the shell 2. The grinding mill 3 rotates about its central axis x in a predetermined direction. The axis of the shell 2 is horizontally disposed or slightly inclined toward the other end of the shell 2. The surface of the inner shell 2 is plated with a lining such as shell plates, wear plates or similar elements for protecting the drum against wear caused by grinding. The lining is attached between the lifter bars 1 such that the lifter bars 1 and the lining together protect the surface of the inner shell 2 of the grinding mill 3.

[0029] FIG. 2 shows a cross-section of the grinding mill 3 shown in FIG. 1 taken along line A-A. The grinding mill 3 rotates in a predetermined direction around its axis indicated by x. The lifter bars 1 are arranged such that they are mounted to the shell 2 of the grinding mill 3 extending in the longitudinal direction of the horizontally arranged grinding mill. The lifter bar 1 comprises a mechanical fixing element, such as channel, a profile or an insert element in the bottom of the lifter bar 1 for mechanically fixing the lifter bar 1 to the shell 2. The lifter bar 1 is secured to the shell 2 of the grinding mill 3 with fasteners such as bolts extending from the shell 2 of the grinding mill 3 to the channel, the profile or the insert element in the bottom of the lifter bar 1 securing the lifter bar 1 to the interior wall of the grinding mill 3.

[0030] FIG. 3 shows one example of a lifter bar 1 as a cross-sectional view. The lifter bar 1 has an outer surface 1a comprising a fixing surface 1b to be arranged against the shell 2 and a wear surface 1c facing toward interior of the grinding mill 3. Part of the wear surface 1c is faced against shell plates arranged next to the lifter bars 1. The lifter bar 1 comprises a lifter bar body 10 and a fixing element 11 for connecting the lifter bar 1 to the shell 2 of the grinding mill 3 (the shell and the grinding mill are not shown in the figure). The lifter bar body 10 further has an outer surface conforming to the outer surface 1a of the lifter bar 1. The lifter bar body 10 further comprises a first portion 10a and a second portion 10b such that the first portion 10a and the second portion 10b form a continuous lifter bar body 10. The first portion 10a comprises the fixing element 11 for connecting the lifter bar 10 to the shell 2. The fixing element 11 is embedded to the first portion 10a such that it forms part of the fixing surface 1b of the lifter bar 1.

[0031] The fixing element 11 may be a lifter channel connected and embedded to the lifter bar body 10 in the first portion 10a such that the lifter channel forms part of the fixing surface 1b of the lifter bar 1. Through the lifter channel 11 the lifter bar 1 can be mounted to the inner surface of the shell 2 of the grinding mill 3 together with fastening means.

[0032] The lifter bar 1 has length of 0.2-3 m and advantageously 0.5-1.5 m, width of 1 is 50-350 mm and advantageously 100-200 mm and height of 100-500 mm, advantageously 120-300 mm. The volume of the lifter bar 1 is 30-200 litres, preferably 50-100 litres, most preferably 60-90 litres. The second portion of lifter bar which is PU, covers 35-85% from the total volume of the lifter bar. Dimensions in the lifter bar 1 are such that the length defines the reach of the lifter bar 1 when installed to the grinding mill and extending in the longitudinal direction of the horizontally arranged grinding mill, the width defines the reach of the installed lifter bar 1 along the periphery of the shell of the grinding mill and the height defines the reach of the lifter bar 1 from the mounting surface of the lifter bar 1 to the opposing end of the lifter bar 1.

[0033] In an embodiment of the lifter bar shown in FIG. 4 the lifter bar further comprises a reinforced wearing plate 12 attached to the lifter bar body 10 in the area of the second portion 10b such that the wearing plate 12 forms part of the outer surface 1a of the lifter bar 1. The reinforced wearing plate 12 comprises a wearing surface 13 for forming part of the outer surface 1a of the lifter bar 1 and an attachment structure 14 provided to the reinforced wearing plate 12 for attaching the reinforced wearing plate 12 to the second portion 10b of the lifter bar body 10. The wearing surface 13 is formed as a flat plate-like structure and the attachment structure is a protrusion from the plate-like wearing surface 13. The wearing surface 13 has an outer surface 13a and an inner surface 13b. The outer surface 13a of the wearing surface 13 forms part of the outer surface of the lifter bar 1 together with the outer surface of the lifter bar body 10. The attachment structure 14 is attached to the inner surface 13b of the wearing surface 13 and protrudes from the inner surface 13b of the wearing surface 13 into the lifter bar body 10. The length of the attachment structure 14 is at least ⅓ of the width of the lifter bar 1 and said attachment structure is arranged to protrude into the lifter bar body 10 forming a tight connection with the lifter bar body.

[0034] In one embodiment the lifter bar 1 comprises a reinforced wearing plate 12 attached to the lifter bar body 10 in the second portion 10b. The reinforced wearing plate 12 comprises metal, said reinforced wearing plate 12 further comprises a wearing surface 13 for forming a part of the outer surface of the lifter bar 1 in a distal end of the second portion 10b or in the vicinity of the second portion 10b. An attachment structure 14 is provided to the reinforced wearing plate 12 for attaching the reinforced wearing plate 12 to the lifter bar body 10, said attachment structure 14 protruding into the second portion 10b of the lifter bar body 10 for forming a connection with polyurethane.

[0035] The attachment structure 14 engages mechanically with the lifter bar body 10 and therefore a preferable shape of the attachment structure 14 is annular or round arch like a clamp or a fixing ring comprising a hole 15 arranged to extend through the attachment structure 14. The through hole 15 in the attachment structure 14 is arranged in a direction same as the longitudinal direction of the lifter bar 1 when the reinforced wearing plate is connected to the lifter bar body 10 for achieving more durable connection with the lifter bar body 10. The attachment structure 14 has a width in the direction of the through hole 0.3-5 cm. In other words the attachment structure is made of a material having thickness of 0.3-5 cm. A plurality of attachment structures 14 are associated with the wearing surface 13 such that the attachment structures 14 are distributed along the length of the wearing surface 13. Both the wearing surface 13 and the attachment structure 14 are made of metal but they may be made of different metal. The wearing surface 13 is preferably made of weldable wear-resistant metal.

[0036] In one embodiment the attachment structure 14 is arranged to protrude inside the lifter bar body 10 such that the attachment structure 14 is throughout embedded in the lifter bar body 10.

[0037] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.