ZA200703206B - Improved diamond recovery - Google Patents

Description

IMPROVED DIAMOND RECOVERY l I ll ) | No el

FIELD OF THE INVENTION

The application of this invention lies in many fields, it is generally applicable in any application that requires transport or conveying of material. One application is in the field of diamond recovery by the process of diamond gravel sorting. It has been found that the invention is favourably applicable, for example, in loading ships, conveying material in factories and industrial process plants. Apart from mineral beneficiation and industrial conveying the invention can be applied in the food industry, as an example of its versatility.

BACKGROUND

Conveyor belts that have the feed portion of the belt located inside a pipe are described in US patent 5,052,545, in the applicant's earlier South African patent 2002/00644 and in US patents 5,735,386, 6,405,855, 6,422,381 and 6,675,958.

The applicant's patent 2002/00644 dealt primarily with diamond recovery where the conveyor belt feed being located inside a pipe improved security by enclosing the diamond-bearing gravel, with its return portion located below.

The pipe has a hinge at an intermediate position of its length, capable of hinging the pipe into a reduced length, for transport to remote sites, with the belt still in the pipe. Idler rollers are provided at intervals to support the belt on its return stretch. The drive roller, return idler and idler roller supports are mounted on the pipe so that assembly of these items on site and set up is not required, so that maintenance is simplified. A key difficulty with this apparatus, however, is that a new belt cannot be installed in the pipe except by threading it through the pipe and then on site joining the ends to form a closed loop; a factory formed joint is not an available option. From practical experience of working in conditions where the material is damp or wet it adheres to the belt and causes spillage; this requires the belt to be scraped clean and belt ’ .

iso 2 0 0 7 scrapers do not function well with the type of belt joint that is possible on site, they become damaged or ineffectual and/or damage the belt at the joint.

THE INVENTION

The present invention provides an improved conveying apparatus, the apparatus including an endless conveyor belt with both its feed and return portions enclosed in a pipe, with at one end a drive roller for driving the belt and at the other end an idler or drive roller, with the feed portion above the return portion and the feed portion cupped by the pipe.

The term “cupped” refers to the edges of the feed portion of the belt being lifted up so that the belt assumes a trough shape, the better to hold the material; the belt is cupped by the pipe as the belt is wider than the pipe in the position where it is located above the return portion of the belt. Preferably the drive roller and the idler roller are located at elevated positions selected so that the feed portion of the belt at the top of the roller is located above the level of the diameter of the pipe. The elevated level is also selected so that the roller is less exposed to foreign material at ground level and is more accessible for adjustment, maintenance and replacement.

This arrangement allows a belt to be made up in the factory to a required length, with a high quality vulcanised joint or splice and inserted into the pipe, likewise it can be removed for replacement by simply pulling the belt loop out of the pipe. Spare factory-made belts may be kept on site to allow quick replacement in the case of belt failure thus maintaining optimum production.

In accordance with a preferred embodiment of the invention the pipe is made of a plastic material or other material of low coefficient of friction, the pipe supported by lying in a semi-pipe of steel.

The semi-pipe of steel may be a hemi-pipe, that is a pipe slit along its length on its diameter, however, the pipe may be a semi-pipe slit along its length at

® position resulting in less than the diameter or more than the diameter, the latter case to embrace the plastic pipe more fully.

Preferably the plastic pipe is given a precise fit in the steel half-round pipe or hemi-pipe, this can be done by suitable selection of the outer diameter of the plastic pipe and the inner diameter of the steel pipe and/or by partially splitting the half round steel pipe centrally along its length so that it can be bent to suit the diameter of the plastic pipe, held in this position by clamping, spot welded along the length of the partial split. The plastic pipe is then removed and the split is welded along its length to give a perfect plastic pipe to steel pipe fit.

The plastic may be a poly vinyl chloride (PVC), polyethylene (PE) material or - a high density poly ethylene (HDPE), just to name three possible materials, any other plastic selected to optimise performance may be used.

Using plastic pipes instead of steel pipes, benefits from the low coefficient of friction, for example pu = 0,4 rather than yu = 1,4; the lower friction provides a lower energy requirement which is important in remote sites and lower heat.

The plastic pipe also has a lower weight than a steel pipe, due to the lower density of plastic than steel; this results in a weight saving of up to 40%.

The plastic pipe has the further advantage of being rust free which is important at sea or coastal conditions while the half round steel pipe can easily be galvanised or powder coated which is difficult in the case of a complete pipe of any appreciable length. However, use in the sun shows that unsupported plastic pipes sagged, leading to difficulties as the plastic pipe had not enough rigidity to support itself over any appreciable length. It will be appreciated that the plastic pipe weight, the belt weight and the load weight must all be supported.

In accordance with a preferred embodiment of the invention, the belt surface is ground to an accurate thickness dimension on the apparatus; this is done by means of a grinding roller being mounted adjacent the driving roller or the idler roller, adjusted to a required position and rotated so as to grind off high

® spots of the belt as the belt is driven. Once the belt is accurate the grinding roller may be removed. Even factory produced high quality beits have increased thickness at the joint, this causes difficulty with belt scrapers, grinding the belt in situ creates a highly accurate belt surface for scraping and trouble-free belt scraping becomes possible.

Preferably the apparatus has a belt scraper added to it. The grinding of the belt may be adopted even for a belt that has been spliced in the field, if necessary.

A right cylindrical (straight profile) of the drive roller is preferred with two peripheral flanges to prevent material spillage where the belt flattens out on going over the pulley. The drive roller is the one which places the feed portion of the belt in tension in the pipe, the drive roller is preferably given a rubberised surface to increase the grip between the belt and the pulley and reduce or prevent slippage. The two peripheral flanges can be bolted each in two halves onto the pulley.

Preferably two guide roll sets are provided at each of the two ends of the pipe, where the belt exits and enters the pipe, positioned so as to guide the edges of the belt so that they do not abrade the ends of the pipe. The rollers are adjusted in the known way by shifting the left and right plummer blocks longitudinally for correct tracking of the belt on the rollers. The two flanges, together with the guide rolls and the pipe itself help to retain the belt in a central position which once set up needs very little or no further adjustment.

The two split flanges of steel or any other suitable plastic material are bolted to the sides of the drive pulley so as to prevent spillage of conveyed material as the belt assumes a horizontal flat form as it exits from the pipe from a half round form that it has inside the pipe.

The driving roller and/or the idler roller can be made with a convex profile or camber to ensure self-centring of the tracking of the belt on the roller. The drive roller may be given a rubberized surface and a larger diameter (which

® increases contact area) to provide better transfer of the drive force from the roller to the belt and less slip for a given belt tension.

Thus the present invention provides a procedure for effective belt scraping on any conveyor belt of first grinding the belt to an accurate thickness over it full length by applying a roller grinder to the belt at a drive roller or idler roller, adjusted to grind a consistent thickness while driving the belt, then applying a belt scraper to the belt.

The belt scraper may be of less complex type than is often required, because of the enhancement of the belt by the process described, of grinding the belt to an accurate thickness in situ. The belt may be of the type having multiple contiguous scraping elements, each spring loaded and adjustable.

With both the feed and return portions of the belt being located inside the pipe transport and handling is less likely to cause damage, the belt can be pulled out of the pipe beforehand. :

In accordance with a preferred embodiment of the invention there is provided a dolly consisting of a frame and road wheels (or cross-country wheels) with clamps for clamping to one or more pipes of the apparatus according to the invention, together with a tow hitch also adapted for connexion to the pipes, for towing them behind a tow vehicle. This makes the overland transport highly practical and economic in suitable circumstances.

Particularly long pipes can be manufactured so that they can be reduced in length for transport, e.g. by folding as described in the applicant's patent referred to above or by being split by disconnecting a joint intermediate of the operational length of the pipe; e.g. a bolted flanged joint. This allows a reduction of the pipe length to one suitable for more convenient and cost effective transport, while at the same time allowing quick set up of the plant at a site, for use. The quick set up is enabled because when the pipe is hinged out to its full operative length, the belt is already in the pipe and on the idlers, drive and return idler. So the usually demanding task of aligning the drive roller and return idler and other idlers is obviated. The pipe confers security against theft from the material being conveyed.

Preferably the drive is bolted to the pipe in a way that allows its removal, so that if required it can be removed, e.g. for transport, should his make handling and loading easier.

Preferably similarly, the return idler is bolted to the pipe in a way that allows its removal. oo

A feeder trough can be added to the plant, adapted for conveying (e.g. diamondiferous gravel) to the feed end of the conveyor, i.e. at the return idler end.

A delivery chute can be provided as well, and other components as may be required or desired for various applications.

Two split flanges of steel or over suitable plastic material may be bolted to the sides of the drive pulley so as to prevent the spillage of conveyed material as the belt assumes a horizontal mode from a half round mode on exit from the pipe on moving over the drive pulley.

Two adjustable counter rotational split guide rollers may be located on each side of the pipe where the belt enters and exits the pipe to keep the belt away from the pipe at its two ends to prevent belt and pipe wear where the belt enters and exits the pipe.

The two adjustable clamping flanges may be adjusted at the two ends of the drive pulley to a distance the same as the width of the belt so that the belt in conjunction with setting on the drive and idler pulley bearing pillar or plumber blocks tracks in the centre of drive pulley. The two flanges may be split and be easily adjusted laterally and securely clamped to the drive pulley by means of the two clamping screws.

In an embodiment, four factors, the adjustable flanges on the two ends of the drive pulley, the two sets of guide rollers on the belt entry and exit ends of the pipe the adjustment on the drive pulley and the adjustment on the idler pulley ensures that the belt tracks in the central position and remains in this position so that once the conveyor belt system is set up very little if any further adjustment is required.

The conveyor may be supplied with a soft start or a variable speed drive to allow for a slow incremental start up. This will go a long way towards longer than normal belt life and intervals between routine maintenance.

THE DRAWINGS

The invention will be more fully described by way of example, with reference to the accompanying drawings, in which : -

Figure 1 is a photograph of the delivery end of a conveying apparatus,

Figure 2 is a photograph of the in-feed end of the conveying apparatus,

Figure 3 is a photograph of the in-feed end of the conveying apparatus with a beit grinder mounted,

Figure 4 is a photograph end-on of the in-feed end of a conveying apparatus with a belt grinder mounted,

Figure 5 is a photograph of the delivery end of a conveying apparatus, showing the belt scraper,

Figure 6 is an end view of the scraper, partially sectioned,

Figure 7 is a side sectional view of the scraper,

Figure 8 is an enlarged view of a part of the scraper,

Figures 9 and 10 are an elevation and plan view respectively of a means of transport of the apparatus,

Figure 11 is a perspective view of a partial length of the conveying apparatus,

Figure 12 is a side view of the conveying apparatus,

Figure 13 is a flowsheet showing the operation of an embodiment of the invention.

THE PREFERRED EMBODIMENT

The improved conveying apparatus for a plant for recovery of diamond, other precious and semi-precious stones and minerals, has an endless conveyor with both its feed and return portions enclosed in a pipe. Figure 1 shows at one end 1 a drive roller 2 for driving the belt 3 and figure 4 shows at the other end 5 an idler roller 6, with the feed portion 7 of the belt above the return portion 8 and the feed portion cupped by the pipe 9. Figures 1 and 4 show the edges 10 of the delivery and feed portions of the belt respectively being lifted up so that the belt assumes a trough shape, i.e. cupped; the belt is cupped by the pipe all along the length of the pipe. The drive roller and the idler roller are located at elevated positions by being mounted on top of the beams 11 and 12 respectively; the feed portion of the belt at the top 13 of the idler roller is located above the level 14 of the diameter of the pipe. It is found that surprisingly the drag on the belt is negligible, for example a mere 4 amps drain on a 1,2 Kw. Varying lengths can be used, e.g. from 6 m to 12 m long, according to application.

Figure 4 shows how the belt surface is ground to an accurate thickness dimension in situ on the apparatus; a grinding roller 4 is mounted adjacent the idler roller, which is adjusted to a required position by screw adjustments 15 and 16 and rotated by the motor 17 in the opposite direction to the rotation of

® the idler roller, so as to grind off high spots of the belt as the belt is driven.

Once the belt is accurate the grinding roller is removed.

The driving roller is made with a convex profile or camber as is seen in the views if figures 5 and 6, to ensure self-centering of the tracking of the belt on the roller, after the idler roller has been set up orthogonal to the belt direction.

The drive roller is driven by a chain 18 from a motor 19, running on sprockets 20 and 21. The motor and driving roller are mounted on the pipe by means of transverse cradles extending between the two beams 11 and secured by straps or hoop clamps 22, with a pedestal 23 for the motor, incorporating a chain tensioning platform 24 . Beams 12 are mounted in similar way with v cradles and straps 25-to the other end of the pipe and carry the idler roller in i rt plummer blocks 26 with screw adjustment 17; the grinding roller is also mounted on the beams, on plummer blocks 27. :

The views of figures 5 to 8 show that the apparatus has a belt scraper 28 added to it. The belt scraper has multiple contiguous scraping elements 29, each spring loaded by a spring 30 and adjustable by screw 31 and lock nut 32. Each scraper element is made of “Vesconite” (trade mark) which wears well to the shape of the belt, each being initially adjusted to the convex shape of the rubberised driving roller. The scraper elements are held between the plates 33 and 34, which are bolted to the beams.

Figures 9 and 10 show a dolly 35 consisting of a frame 36 and road wheels 37 with clamps 38 for clamping to one or more pipes of the apparatus, together with a tow hitch 39 also clamped to the pipes, for towing them behind a tow vehicle 40. For example, apparatus comprising pipes up to 9 or 12 metres can be transported in this way, in suitable circumstances.

A feeder trough can be added to the plant, adapted for conveying (e.g. diamondiferous gravel) to the feed end of the conveyor, i.e. at the return idler end.

. ®

A delivery chute can be provided as well, and other components as may be required or desired for various applications.

Referring to figures 11 and 12 of the drawings, the improved conveying apparatus 41 for a plant for recovery of diamond, other precious and semi- precious stones and minerals, or transport of any material, like loading sawdust onto a ship, for example, has an endless conveyor with both its feed portion 42 and return portion 43 enclosed in a plastic pipe 44. The plastic pipe is supported by a hemi-pipe 45 which cradles the plastic pipe. Figure 12 shows at one end 46 a drive roller 47 for driving the belt 42-43 and at the other end 48 an idler roller 49, with the feed portion 42 of the belt above the return portion 43 and the feed portion cupped by the pipe 44. The drive roller is a motorised roller with an electric drive motor located inside the roller pipe.

The drive roller and the idler roller are mounted on top of the beams 50 and 51 respectively. Feed of material is provided by the funnel 52.

The beams 50 and 51 are mounted on the pipe by means of transverse cradles 53, 54, 55 and 56 extending between the beams and secured by straps or hoop clamps 57, 58, 59 and 60.

OPERATIONAL DETAILS

Referring to Figure 13, heavy Alluvial or kimberlite concentrate from a dense medium separation plant rotary pans or jugs are fed into container one at the feeder bin. The material is fed over a vibratory screen where it is washed clean of fine material -2mm over the first half of the screen and subjected to a blowing fan to get rid of excess water over the 2" half of the vibratory screen.

The material then passes over the second screen where it is blow dried using a series of blower fan units. The -2mm fines fall through the screens into the shoot and are automatically or manually washed down through the center of the container into a pipe conveyor or into a gravel pump or jet pump which conveys this material to a waste dump. The back end of the conveyor is fitted with a sponge rubber plug which prevents 4-2mm sand. From exiting the bottom end of the conveyor but allows water and fine sludge to exit into a

LY

® suitable sump from which water can be recovered for recreation or gravity fed or pumped away.

The coarse +2mm material exits the end of the drying screen and is fed away from underneath the container by means of a pipe conveyor into container 2 through a port in the side of the container so as to feed onto a double deck sizing screen which is turn feeds onto a single deck sizing screen. The screens allow for the screening of the material into the size fractions required for feeding the x-ray machines namely 2-4, 4-6, 8-16, and 16-32mm or 2-4, 4- 6, 6-12, 12-24mm material. These material fractions drip into underlying material storage bins, where the individual gravel size factions are fed by means of two parallel situated pipe conveyors to exit through the floor of container 2 into the underlying ve x-ray machine situated in container 3. The two coarser feactions feeding to the ve 113 x-ray machine and the two finer fractions feeding to the ve 116 machine. As the bottom halves of the material storage bins in container 2 are split horizontally near to where the tapered sections begin the bins can be turned so that any combination of material sized fractions can be fed into any pipe and therefore fed into any of the ve machines. This versatility allows for accommodating material treated which is predominantly coarse of fine. For treatment of finer material only the ve 113 machine can be replaced by a second ve 116 material to increase through put.

In container 3 the material concentrate generate by the x-ray machine exits through the concentrate shoots either directly into the glove boxes where the diamonds are remove and dropped in a underlying holding safe or the concentrate passes directly into the underlying pipe conveyors to be returned to the security concentrate storage bin for reintroducing into the system to be refed (second pass). Through the x-ray machines. This process drastically reduces the amount of concentrate to be sorted in the glove boxes. It also allows for secure bulk storage of first pass concentrate for treatment at irregular prescribed intervals by selected persons when second stage x-ray concentration takes place.

a ®

The barren of waste material is fed from the x-ray machines into two underlying pipe conveyors to a storage dump. The barren or waste material generated after diamond sorting in the glove boxes is reintroduced into the system for recantation to prevent diamonds from being purposely discarded 5 . with the barren material.

Where build up of extraneous high luminous material apart from diamonds takes place the waste material can be specifically sorted or directed into the underlying safe for late sorting or discarding by delegated persons.

Pipe painted mat black for solar heat absorption. The pipe conveyor carrying material converted from container 1 to container 2 acts as a second stage dryer and dust extractor. The pipe conveyor is fitted with two fans, a blower fan situated near the material receiving end of the conveyor and an extractor fan near the exit end of the conveyor in between the two fans are situated a senses of deflector paddles to agitate the gravel on its passage along the conveyor this facilitates the drying process in addition a series of infra red lamps are situated at regular intervals, inside the pipe conveyor the facilitate heating of the air passing through the conveyor and thus facilitating the drying of the gravel. Any dust generated during the conveying and agitating of the gravel is extracted by the extractor fan and removed from the system before entering container 2.

Ideally gravel should be fed to the ve x-ray machines in a dry or damp condition (moisture conflict of — 4%) this can be achieved by regulating the of air from over the drying screen in container 1 and through the pipe drying conveyor between containers 1 and 2 by regulating the speed of the fans which are controlled by variable speed controls where the system is operated during wet conditions or at night the infrared lamps can also be employed to facilitate drying of the material

REFERENCE NUMERALS

PY

1 DRIVE END OF CONVEYOR > DRIVE ROLLER 3 CONVEYOR BELT 4 GRINDING ROLLER 5 IDLER END OF CONVEYOR 6 IDLER ROLLER 7 FEED PORTION OF BELT 8 RETURN PORTION OF BELT 9 PIPE 10 EDGES 11 BEAM 12 BEAM 13 TOP OF IDLER ROLLER 14 LEVEL OF PIPE DIAMETER

IS 15 SCREW ADJUSTMENT 16 SCREW ADJUSTMENT 17 MOTOR 18 CHAIN 19 MOTOR 20 SPROCKET 21 SPROCKET 22 HOOP CLAMP 23 PEDESTAL 24 CHAIN TENSIONING PLATFORM 25 HOOP CLAMP 26 PLUMMER BLOCKS 27 PLUMMER BLOCKS 28 BELT SCRAPER 29 SCRAPING ELEMENT 30 SPRING 31 ADJUSTABLE SCREW 32 LOCK NUT 33 PLATE 34 PLATE

® 35 DOLLY 36 FRAME 37 ROAD WHEEL 38 CLAMP 39 TOW HITCH 40 TOW VEHICLE 41 CONVEYOR 42 FEED PORTION OF BELT 43 RETURN PORTION OF BELT 44 PLASTIC PIPE 45 STEEL HALF PIPE 46 DRIVE END OF CONVEYOR 47 MOTORISED DRIVE PULLEY 48 IDLER END OF CONVEYOR

Is 49 IDLER PULLEY 50 BEAM 51 BEAM 52 FEED CHUTE : 53 CRADLE 20 54 CRADLE 55 CRADLE 56 CRADLE 57 STRAP 58 STRAP 25 59 STRAP 60 STRAP

Claims (19)

1 i [> — [EE — oh — CLAIMS

1. An improved conveying apparatus, the apparatus including an endless conveyor belt with both its feed and return portions enclosed in a pipe, with at one end a drive roller for driving the belt and at the other end an idler or drive roller, with the feed portion above the return portion and the feed portion cupped by the pipe.

2. A conveying apparatus as claimed in claim 1, in which the drive roller and the idler roller are located at elevated positions selected so that the feed portion of the belt at the top of the roller is located above the level of the diameter of the pipe thus to cup the belt at least at the feed portion.

3. A conveying apparatus as claimed in either one of claims 1 or 2, in which the belt is made up in a factory to a required length, with a high quality vulcanised joint or splice and inserted into the pipe, able to be removed for replacement by simply pulling the belt loop out of the pipe.

4, A conveying apparatus as claimed in claim 3, in which spare factory-made belts are supplied along with the conveying apparatus so that they can be kept on site to allow quick replacement in the case of belt failure.

5. A conveying apparatus as claimed in any one of claims 1 to 4, in which the pipe is made of a plastic material or other material of low coefficient of friction, the pipe supported by lying in a semi-pipe of steel.

6. A conveying apparatus as claimed in claim 5, in which the semi- pipe of steel is a hemi-pipe, that is a pipe slit along its length on its diameter.

7. A conveying apparatus as claimed in either one of claims 5 or 6, in which the plastic pipe is given a precise fit in the steel half-round hemi pipe or the semi-pipe, by suitable selection of the outer diameter of the plastic pipe and the inner diameter of the steel pipe .

8. A conveying apparatus as claimed in claim 7, in which the steel half pipe is partially split along its length, bent to an almost perfect fit with the plastic pipe and welded along the partial split.

9. A conveying apparatus as claimed in any one of claims 1 to 8, provided with a grinding means on the apparatus adapted for the belt surface to be ground to an accurate thickness dimension by the grinding means while the belt is on the apparatus.

10. A conveying apparatus as claimed in claim 8, in which the grinding means comprises a grinding roller mounted adjacent the driving roller or the idler roller, adjusted to a required position and rotated so as to grind oft high spots of the belt as the belt is driven.

11. A conveying apparatus as claimed in either one of claims 8 or 9, which is provided with a simple belt scraper having only spring loaded adjusting screws.

12. A conveying apparatus as claimed in any one of claims 1 to 11, in which the drive roller of the apparatus has a flange on either end of the roller.

13. A conveying apparatus as claimed in claim 12, in which the flanges are each a split flange and bolted together so as to be clamped onto the drive roller.

positioned to guide the edges of the belt so that it does not wear the ® ends of the pipe.

15. A conveying apparatus as claimed in any one of claims 1 to 14, provided with a dolly consisting of a frame and wheels with clamps for clamping to one or more pipes of the apparatus, together with a tow hitch also adapted for connexion to the pipes, for towing them behind a tow vehicle.

16. A conveying apparatus as claimed in any one of claims 1 to 15, in which the pipe is hinged at an intermediate position in its length to allow for hinging it to a shorter overall length for transport.

17. A process of providing a conveying apparatus which includes the steps of passing a conveyor belt loop through a pipe and bolting a drive roller and an idler roller at opposite ends of the pipe with the belt looped over the rollers.

18. A process as claimed in claim 17, in which a belt grinding roller is mounted at one end of the pipe, the belt is driven and the grinding roller is driven to grind the belt smooth.

19. A process as claimed in either one of claims 17 or 18, in which the pipe is a plastic pipe and is fitted in a semi pipe pf steel so as to be supported by the semi-pipe under it. Signed this 10" of April 2007. A_=7 KXgent for Applicant Hahn & Hahn -=-====---000------------