Mineral-separator device

Abstract

Mineral separator device 10 for separating minerals from a slurry, comprising a rotatable drum 12 having a front end 20 to receive material, an inside surface 24, and a rear end 22. A scraper blade su

Description

The present invention relates to a mineral-separator device or mineral separator, and in particular to a mineral separator drum device and / or a multi-gravity separator. The invention further relates to a method of front driving a mineral-separator device when separating minerals from a slurry. For certain types of mined material, valuable very fine high-density mineral material is needed to be separated from lower density gangue material. For example, tin, tungsten, or free gold may need to be separated from host rock. To achieve this, slurry is formed of the mixture and is fed into a mineral-separator device having a drum. The drum is rotated and axially oscillated. Scraper blades are supported on a scaffold or frame which extends radially from the axis of the drum. The blades rotate at a different speed relative to the drum surface and scrape the surface of the drum. The slurry is fed into the middle of the drum, via the front of the drum, which is typically elevated relative to the rear of the drum. The slurry is washed down the slope of the drum and rinsed by a feed of water. Higher density material is washed down the slope more slowly than the lower density material. The higher density material can therefore be scraped forwards by the scraper blades, to be collected separately from the lower density material. Such a device is commonly referred to as a separator drum or multi-gravity separator. To rotate the drum and the scraper blades, the drum and blades are driven from the rear end. However, the rear end of the drum is downstream of the slurry and so is “dirty” since it can be affected by slurry spills. This increases wear on the rotating components. The rear driven rotation mechanisms are also complex, weak, and extremely difficult to maintain. It would be desirable to rotate the drum from the front end, which is upstream of the slurry feed and is therefore “clean”, easing maintenance requirements. However, feed pipes need to feed slurry and / or water through the front of the drum, and therefore the front of the drum need to be kept open for these feed pipes. The present invention seeks to provide a solution to these problems. According to a first aspect of the present invention, there is provided a mineral-separator device for separating minerals from a slurry, the mineral-separator device comprising: a drum having a front end for receiving the slurry therethrough into the drum, an inside surface for receiving the slurry thereon, and a rear end, the drum being rotatable; a scraper blade support for supporting scraper blades for scraping at the inside surface of the drum for separating minerals from the slurry, the scraper blade support being rotatable and being between the front end and the rear end; a drum drive shaft extending through the front end and configured to rotate the drum; and a scraper-blade-support drive shaft extending through the front end and configured to rotate the scraper blade support; the drum drive shaft and the scraper-blade-support drive being separate to and concentric with one another. The drum drive shaft extends through the drum from the front of the drum and fixes to the drum at or adjacent to the rear end. The scraper blade support is between the ends of the drum, in a central region of the drum. Since the shafts are concentric, which is to say that one surrounds the other and have a common or substantially common axis, both of these shafts can be accommodated, whilst maintaining an open front end for feed tubes to extend through. The drum drive shaft and the scraper-blade-support drive being described as “separate” is to clarify that they are distinct components and are not one-and-the-same component. Preferably, the scraper-blade-support drive shaft may be tubular, the drum drive shaft being concentrically received within the scraper-blade-support drive shaft. Advantageously, the scraper-blade-support drive shaft may be configured to rotate at a different rate of rotation to the drum drive shaft. As such, the scraper blades move relative to the drum and can scrape the inner surface thereof. Beneficially, the drum drive shaft may be configured to rotate slower than the scraper-blade-support drive shaft. However, alternatively, the drum drive shaft may rotate faster than the scraper-blade-support drive shaft. Additionally, an inter-drive-shaft bearing is positioned between the drum drive shaft and the scraper-blade-support drive shaft. This permits the relative rotation between the drum drive shaft and the scraper-blade-support drive shaft, whilst allowing one to support the other. In a preferable embodiment, the device further comprises a ground support mount at, adjacent or over the drum drive shaft, scraper-blade-support drive shaft and / or inter drive-shaft bearing for connecting to ground support means for supporting the drum drive shaft, scraper-blade-support drive shaft, and / or inter-drive-shaft bearing from the ground, an outer bearing being positioned between the scraper-blade-support drive shaft and the ground support mount. The ground support mount allows for the drive shafts and associated components to be supported relative to the ground, for example via a machine frame or chassis. A bearing between the ground support mount and the outer drive shaft allows the outer drive shaft to rotate whilst still being supported by the stationary ground support mount. Preferably, the inter-drive shaft-bearing and / or the outer bearing is a split bearing. This allows for easier maintenance. In particular, the outer bearing being split allows for the bearing to be changed in the event that the scraper-blade-support drive shaft has an enlarged or wider diameter at either end, particularly at the front end, to support component connections. Additionally, the device may further comprise an epicyclic gearbox having a ring gear, planetary carrier shaft, and sun gear shaft, the epicyclic gearbox configured to determine the rate of rotation of the scraper-blade-support drive shaft and of the drum drive shaft. An epicyclic gearbox provides a compact arrangement. Advantageously, the ring gear may be configured to be driven so as to be the input of the epicyclic gearbox and may be fixed relative to the scraper-blade-support drive shaft, one of the planetary carrier shaft and the sun gear shaft may be fixed relative to the drum drive shaft, and the other of the planetary carrier shaft and the sun gear shaft may be held stationary. Beneficially, the device may further comprise a torque arm configured to hold the sun gear shaft or the planetary carrier shaft stationary. The torque arm carries the reaction torque. Preferably, the torque arm has a first end which is configured to hold the sun gear shaft or the planetary carrier shaft stationary, and a second end which is fixed to the ground support mount. The stationary shaft of the gearbox would face away from the ground support mount, and so the torque arm allows for the ground support mount to extend across or over the body of the gearbox and fix to the ground support mount. However, it will be appreciated that the second end of the torque arm could instead be bolted to an alternative ground support mount, and / or to the machine frame or chassis directly. Additionally, the device may further comprise a pulley for driving the epicyclic gearbox. The pulley is mounted to the body of the gearbox, and may drive the ring gear directly. The pulley is driven by a belt, which in turn is moved via an electric motor. The pulley is preferably a V-belt pulley. A V-belt provides high power transmission efficiency. However, it will be appreciated that other forms of belt drive could be considered. Additionally, non-belt-based drives could be considered, and so the pulley could be omitted. For example, drive could be provided from a reduction gear or via hydraulics, Advantageously, the drum drive shaft may be a single piece. In other words, the drum drive shaft is integrally formed as a one piece. This can provide improved strength. Conventionally, the drum drive shaft in a rear-driven multi-gravity separator is provided as two parts which are interposed by and connected to a gearbox. Input and output shafts from the gearbox are both supported by radial and axial bearings mounted in bearing housings. Any bearing wear can create bending moment loading on the splined shaft ends where they connect to the gearbox and this can result in premature shaft failure. Optionally, scraper blades supported by the scraper-blade support are provided. Additionally, the device further comprises at least one feed pipe for feeding slurry and / or water to the inside surface of the drum, the feed pipe extending through the front end of the drum. The drive shafts are driven from upstream of the outlet of the feed pipe. As such, the drive of the drive shafts is at a reduced risk of being contaminated by slurry. In a preferable embodiment, the device may comprise an axial oscillation means for axially oscillating the drum. The axial oscillation assists with the separation of the slurry into minerals and gangue. Preferably, the device further comprises ground support means for elevating the front end of the drum relative to the rear end. This provides a tilt to the drum for the gangue of the slurry to be washed down. According to a second aspect of the invention, there is provided a method of front driving a mineral-separator device according to a first aspect of the invention when separating minerals from a slurry, the method comprising: feeding a slurry including minerals and gangue through the front end to the inside surface of the drum of the mineral-separator device; and rotating the drum and scraper blade support from the front end so that the scraper blades scrape the slurry and separate minerals from gangue. The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an isometric view of an embodiment of a mineral-separator device according to a first aspect of the invention; Figure 2 shows a top view of the mineral-separator device of Figure 1; Figure 3 shows a cross-section of the mineral-separator device of Figure 1, along the line AA in Figure 2; and Figure 4 shows an enlargement of a portion of Figure 3. Referring to Figures 1 to 4, there is shown a mineral-separator device 10 having a drum 12, a scraper blade support 14, a drum drive shaft 16, and a scraper-blade-support drive shaft 18. The mineral-separator device 10 may otherwise be referred to as a multi-gravity separator or a drum separator. The drum 12 has a front end 20 and a rear end 22, separated from each other by an axial extent of the drum 12. The drum 12 is generally cylindrical, although, as can be seen in Figure 2, the drum 12 has a slight taper towards the front end 20 such that the drum 12 is generally frustoconical. The front end 20 of the drum 12 is preferably open and in use receives a slurry including minerals and rock-based gangue therethrough. As such, there is preferably at least one feed pipe [not shown] which extends through the front end 20 of the drum 12. In other words, the feed pipe extends through the open front face of the drum 12. There may be a plurality of feed pipes, for example one or more feed pipes for slurry and one or more separate water feed pipes. An inside surface 24 of the drum 12, which is also generally cylindrical, is for receiving the slurry thereon. The inside surface 24 is preferably continuous, which is to say that there are no holes in the drum 12 surface. The inside surface 24 is preferably polyurethane lined. The rear end 22 of the drum 12 is preferably closed by a back plate 26. The drum 12 is fastened to the back plate 26 via bolts 28, for example. The drum 12 is rotatable by the drum drive shaft 16. The drum drive shaft 16 extends axially from outside of the drum 12, adjacent to the front end 20, through the front end 20, and preferably to the rear end 22. The drum drive shaft 16 extends along an axial centre of the drum 12. The drum 12 may be connected to the drum drive shaft 16 via the drum drive shaft 16 being fixed to the back plate 26, for example via fasteners such as bolts 28. There may be collars or flanges on the drum drive shaft 16 to facilitate such fastening. The drum drive shaft 16 is preferably otherwise a single integral piece. The scraper blade support 14 has a plurality of arms 30 which extend radially relative to an axis of the drum 12, and has a generally framework, scaffold, or spider form. Each arm 30 has a plurality of scraper blades 32 supported therefrom. Preferably, the plurality of scraper blades 32 supported from each arm 30 are arranged along a front to rear direction of the drum 12 on a sub-arm 34 which extends forwards and backwards from its respective arm 30. The scraper blades 32 are configured to scrape the inside surface 24 of the drum 12, and so are in close contact therewith. The scraper blades 32 may be disconnectable from the scraper blade support 14 to allow for replacement. For example, each sub-arm 34 of scraper blades 32 may be replaced as a single cartridge. The scraper blade support 14 is positioned between the front end 20 and the rear end 22. In particular, the arms 30 of the scraper blade support 14 extend radially from a central region of the drum 12 defined along the axis thereof. The scraper blade support 14 is rotatable by the scraper-blade-support drive shaft 18. As such the scraper blade support 14 is fixed to the scraper-blade-support drive shaft 18. The scraper-blade-support drive shaft 18 extends axially from outside of the drum 12, adjacent to the front end 20, through the front end 20, and to the arms 30 of the scraper blade support 14, which are between the front end 20 and the rear end 22. As such, the scraper-blade-support drive shaft 18 terminates inside the drum 12, between the front end 20 and the rear end 22. The scraper-blade-support drive shaft 18 is tubular or hollow, defining a central void. Part of the drum drive shaft 16 is received concentrically within the scraper-blade-support drive shaft 18, and as such is in the central void. However, since the scraper-blade-support drive shaft 18 terminates in a central region of the drum 12, and the drum drive shaft 16 extends to the rear of the drum 12, the drum drive shaft 16 extends beyond the end of the scraper-blade-support drive shaft 18. The drum drive shaft 16 and drum 12 are configured to rotate at a different, and preferably a slower, rotational speed than the scraper-blade-support drive shaft 18 and the scraper blade support 14. However, it will be appreciated that the drum drive shaft 16 and drum 12 may rotate faster than the scraper-blade-support drive shaft 18 and the scraper blade support 14. The difference in rotational speed means that the scraper blades 32 move relative to the inside surface 24 of the drum 12 so as to scrape it. The difference in rotational speed is very small. For example, for every 60 rotations of the drum 12, the scraper blade support 14 may be rotated 61 times. However, it will be appreciated that the difference in rotational speed may vary depending on the composition of the slurry to be processed. Since there is a difference in rotational speed, there is preferably a bearing between the scraper-blade-support drive shaft 18 and the drum drive shaft 16, here termed an inter-drive-shaft bearing 36. The inter-drive-shaft bearing 36 is preferably a split bearing to allow for easy replacement. The drum 12, scraper blade support 14, drum drive shaft 16, and / or scraper-blade-support drive shaft 18 are supported relative to the ground by ground support means. There is preferably a front mount 38, exterior to the drum 12 and at or adjacent to the front end 20 of the drum 12 for attaching to ground support means, and a rear mount 40 exterior to the drum 12 and at or adjacent to the rear end 22 of the drum 12 for connecting or attaching to ground support means. The front mount 38 supports the drum drive shaft 16 and / or scraper-blade-support drive shaft 18 and preferably comprises a collar or sheath which extends around the scraper-blade-support drive shaft 18 to support the scraper-blade-support drive shaft 18 and drum drive shaft 16 held therein. A bearing is housed within this collar which interfaces between collar and the scraper-blade-support drive shaft 18. The bearing is preferably a split bearing to allow for easy replacement, due to the scraper-blade-support drive shaft 18 having a large flange 41, and may be referred to as an outer bearing 42 so as to distinguish it from the inter-drive-shaft bearing 36. The inter-drive-shaft bearing 36 is also circumscribed by the collar. One or more bushings may also be provided to ensure the radial location of the two shafts 16, 18. The rear mount 40 supports the drum drive shaft 16 and preferably comprises a push-pull bracket bearing assembly. This can provide radial support as well as axial thrust for the axially oscillating motion of the machine. Alternative axial oscillating means or axial oscillators for oscillating the drum 12 along its axis may also be considered. The ground support means is configured so that the drum 12 is angled or tilted relative to the horizontal, with the front end 20 of the drum 12 elevated relative to the rear end 22 of the drum 12. The drum drive shaft 16 and the scraper-blade-support drive shaft 18 are preferably each rotated by a common driving means or drive, the relative rotation between the drum drive shaft 16 and the scraper-blade-support drive shaft 18 being provided by gearing. Preferably, the device further comprises an epicyclic gearbox 44 having a ring gear, planetary gears, a planetary carrier shaft 46 connected to the planetary gears, a sun gear and sun gear shaft 48 fixed to the sun gear shaft 48. Further description of the working of the epicyclic gearbox 44 is omitted for brevity. The ring gear is the input of the epicyclic gearbox 44, and so is driven. The ring gear is fixed to a housing or body 50 of the gearbox 44 and there is a pulley 52 on the exterior of the housing for being rotated by a belt. Preferably, the pulley 52 is a V-belt pulley 52, having a plurality of V-shaped grooves, and a V-belt [not shown] is provided for rotating the V-belt pulley 52. The ring gear is fixed relative to the scraper-blade-support drive shaft 18 via bolts 28 interconnecting the gearbox body 50 and the flange 41 of the scraper-blade-support drive shaft 18. As such, the scraper-blade-support drive shaft 18 rotates at the same rotational speed as is provided by the V-belt. The planetary carrier shaft 46 is preferably the output of the gearbox 44 and is fixed to the drum drive shaft 16. Preferably, the planetary carrier shaft 46 and / or the drum drive shaft 16 are splined to allow mating therebetween. The gearbox 44 is configured so that the planetary carrier shaft 46, and hence the drum drive shaft 16, rotates more slowly than the ring gear, and hence the scraper-blade-support drive shaft 18. The sun gear shaft 48 is held stationary or fixed. This is achieved by a torque arm 54 which carries reaction torque from the sun gear shaft 48. A first end of the torque arm 54 is fixed to the sun gear shaft 48. A second end of the torque arm 54 is fixed to the front mount 38. Since the sun gear shaft 48 of the gearbox 44 faces away from the front mount 38, the torque arm 54 has a generally elongate body between the first and second ends which extends over, under or across the body 50 of the gearbox 44 so as to meet the front mount 38. The elongate body of the torque arm may be generally arcuate to assist with extending over the gearbox 44 and better carrying the reaction torque. It will be appreciated that alternative gearbox configurations may be considered, such as the planetary carrier shaft 46 being held stationary and the sun gear shaft 48 being fixed to the drum drive shaft 16, or non-epicyclic gearing arrangements. In use, the V-belt rotates the gearbox body 50 and ring gear which rotates the scraper-blade-support drive shaft 18 and scraper blade support 14. By virtue of the gearing, the drum drive shaft 16 rotates slightly more slowly. The feed pipes feed slurry and water into the drum 12 via the front end 20 of the drum 12, and the drum 12 is axially oscillated. The denser minerals are washed down the slope of the drum 12 more slowly than the less dense gangue, and so the minerals are scraped forwards into a mineral output at or adjacent to the front end 20 of the drum 12. The gangue is washed down to a gangue output at or adjacent to the rear end 22 of the drum 12. It is therefore possible to provide a front driven mineral-separator device. When maintenance of, or alteration to, the bearings, gearbox, or belt drive is required, this can be achieved quickly and easily by virtue of the drive being at the front “clean” end of the drum. The front driven arrangement is achieved by virtue of concentric shafts for the drum and scraper blade support. The words ‘comprises / comprising’ and the words ‘having / including’ when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.

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