EP0837732A1

EP0837732A1 - Separating intermixed materials of different specific gravity

Info

Publication number: EP0837732A1
Application number: EP96922716A
Authority: EP
Inventors: Benjamin V. Knelson
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-07-13
Filing date: 1996-07-11
Publication date: 1998-04-29
Anticipated expiration: 2016-07-11
Also published as: AU700809B2; BR9609442A; ATE197915T1; EA199800122A1; EA000326B1; EP0837732B1; WO1997002894A1; AR002839A1; PE5498A1; MXPA98001208A; CA2226514A1; DE69611170D1; AU6351596A

Abstract

A centrifugal separator for separating heavy metals from lighter or includes a bowl (10) rotatable about its axis and defining annular collection areas (19, 20) on the peripheral surface of the bowl at axially spaced positions along the bowl. At the peripheral wall (11) in each area is provided a plurality of angularly spaced discharge openings (29) which are controlled by pinch valves (42) to periodically allow the radial escape of the collected material. The pinch valves of a first area (19) are controlled at different timing to the pinch valves of a second area (20) to vary the concentration of the materials collected in the different areas. The pinch valves are operated by a pressurized liquid system which is fed to the different areas through a swivel coupling mounted at a longitudinal shaft supporting the bowl.

Description

SEPARATING INTERMIXED MATERIALS OF DIFFERENT SPECIFIC GRAVITY

This invention relates to an apparatus and method for separating intermixed materials of different specific gravity and in particular an arrangement employing a rotating bowl having discharge ports in the bowl allowing heavier materials collecting in the bowl to discharge outwardly of the bowl under centrifugal action for collection.

One example of an arrangement of this type is shown in U.S. Patent 5,338,284 of the present inventor which discloses a centrifuge bowl having a peripheral wall with the bowl being rotated about a longitudinal axis so that the peripheral wall rotates about the axis and causes centrifugal force at the peripheral wall to effect separation of materials passing over the peripheral wall. The arrangement provides a plurality of axially arranged collection areas each of which has a plurality of angularly spaced discharge ports so that the materials collecting in the collection areas are discharged outwardly from the bowl for collection. Pinch valves control the discharge.

Another arrangement is shown in International application WO93/13864 by McAlister.

It is one object of the present invention to provide improvements in the above arrangement of the present inventor to enable an enhancement of the efficiency of separation.

According to a first aspect of the invention there is provided a method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis;

SUBSTITUTE SHEET feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining in the materials collected on the peripheral wall an inner surface of the materials over which the fed materials pass; defining on the peripheral wall at least one axially localized area for collecting heavier materials while lighter materials pass over the area for discharge; defining at the area around the peripheral surface recess means spaced outwardly of the inner surface; providing at the area a plurality of angularly spaced discharge ports at an outer surface of the recess means, each for allowing materials collecting in the area to discharge outwardly from the peripheral wall; collecting the outwardly discharge materials; allowing the material discharging from the discharge port to form a natural generally conical shape extending in both in angular and axial directions which is substantially free from confinement by walls of the recess means with an apex at the discharge port and a base of the conical shape at the inner surface, the shape and depth of the recess means being arranged relative to the angular spacing of the discharge ports such that bases at the inner surface of the conical shapes of the discharge ports at least substantially meet.

According to a second aspect of the invention there is provided a method of separating intermixed particulate materials of different specific gravity comprising:

SUBSTITUTE SHEET providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining in the materials collected on the peripheral wall an inner surface of the materials over which the fed materials pass; defining on the peripheral wall at least one axially localized area for collecting heavier materials while lighter materials pass over the area for discharge; defining at the area around the peripheral surface recess means spaced outwardly of the inner surface; providing at the area a plurality of angularly spaced discharge ports at an outer surface of the recess means, each for allowing materials collecting in the area to discharge outwardly from the peripheral wall; collecting the outwardly discharge materials; including providing for each discharge port a deflection guide body and supporting the body radially inwardly of the discharge port; including supporting the body so that materials pass on each angularly spaced side of the body and also on each axially spaced side of the body.

According to a third aspect of the invention there is provided a method of separating intermixed particulate materials of different specific gravity comprising:

SUBSTITUTE SHEET providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; providing a feed material and feeding the feed material to the bowl so as to pass over the peripheral wall and to cause a heavier portion of the materials to collect on the peripheral wall while a remaining lighter portion of the feed material escapes from the open mouth; defining on the peripheral wall for rotation therewith at least one first axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the first recess for discharge; defining on the peripheral wall for rotation therewith at least one second axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the second recess for discharge, the second recess being downstream of the first recess; providing at the first and second recesses discharge means at an outer surface of the recess, each for allowing materials collecting in the recess to discharge outwardly from the peripheral wall; collecting the outwardly discharged materials from the first recess; collecting the outwardly discharged materials from the second recess separately from the materials from the first recess and returning the materials from the second recess to the feed material.

SUBSTITUTE SHEET According to a fourth aspect of the invention there is provided a method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining on the peripheral wall for rotation therewith at least one first axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the first recess for discharge; defining on the peripheral wall for rotation therewith at least one second axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the second recess for discharge, the second recess being downstream of the first recess; providing at the first and second recesses first and second discharge means each at an outer surface of the respective recess, each for allowing materials collecting in the recess to discharge outwardly from the peripheral wall; each of the first and second discharge means having valve means for controlling discharge of the materials from the recess;

SUBSTITUTE SHEET collecting the outwardly discharged materials from the first and second recesses; and providing first and second control means for separately controlling the valve means of the first and second recesses respectively so as to provide for each of said first and second recesses different discharge characteristics to provide different concentrations of the materials collected.

Embodiments of the invention will now be described in conjunction with the accompanying drawings in which:

Figure 1 is a vertical cross-sectional view showing schematically a first embodiment of centrifugal separator according to the present invention.

Figure 2 is a cross-sectional view along the lines 2-2 of Figure 1.

Figure 3 is a vertical cross-sectional view similar to that of Figure 1 on an enlarged scale.

Figure 4 is a vertical cross-section similar to that of Figure 1 of a further embodiment of the invention showing some modifications and additions.

Figure 5 is an enlarged view of one part only of Figure 4.

Figure 6 is an enlarged view of another part only of Figure 4

The embodiment shown in Figures 1 , 2 and 3 is modified relative to the above mentioned U.S. Patent 5,338,284 of the present inventor which shows a centrifugal separator having a plurality of rings defining therebetween recesses with each recess having a plurality of angularly spaced discharge nozzles. Each discharge nozzle is controlled by a pinch valve. The material discharged from the pinch valves is collected.

Reference should be made to the above patent for further details of the elements shown schematically in the drawings herein.

In Figures 1 , 2 and 3, therefore, the apparatus comprises a centrifuge bowl generally indicated at 10 including an inner bowl wall 1 1 and

SUBSTITUTE SHEET an outer housing 12 defining therebetween a space 13 for fluidization water supplied through a hollow drive shaft 14 in a duct 15 within the shaft. The drive shaft is connected to the bowl for co-rotation of the inner bowl and the outer housing with the shaft. The shaft is mounted on bearings 16 and is driven by a drive system generally indicated at 17.

The inner bowl is shaped to define a frusto conical base portion 18, a first annular recess 19 and a second annular recess 20. This shape is therefore modified relative to the previous arrangement in that there are only two recesses and the base portion includes the frusto-conical wall extending from a flat base 21 onto which the feed materials are discharged by a feed duct

22. The materials thus are spread outwardly by engagement with the flat base 21 and engage onto the frusto-conical wall 18 so as to turn and move up the wall of the bowl. The base and frusto-conical wall are covered by a liner Iayer

23. The liner Iayer 23 also engages into the recesses 19 and 20. The recesses 19 and 20 are each of generally rectangular cross section as shown in Figure 1 but the liner material is shaped so that it becomes thicker toward a base of the recess thus shaping the recess into a generally V shape. In some embodiments the liner Iayer can be omitted or of constant thickness so that the recesses are rectangular as shown in the left-hand side of figure 1.

The bowl in the area of the recesses is formed by two annular discs 24 and 25 connected by a cylindrical base wall 26. The liner material 23 as shown in the right-hand side of figure 1 is of constant thickness so as to follow the side walls 25 and 24 part way through their depth and then increases in thickness to form the V shape. In figure 3, the liner material is of increasing thickness through the whole of the recess so as to form constantly diverging walls.

SUBSTITUTE SHEET The base walls 26 of the recesses are spaced from a cylindrical wall 28 of the outer housing so as to provide a space therebetween into which the fluidizing liquid or water can penetrate for injection through two or three rows of openings 30 in the base wall 26 into the interior of the recess.

The base 26 of each recess has a number of discharge ports 29 at angularly spaced positions around the recess as best shown in Figure 2. These discharge ports are of the general shape shown in the above patent except that the ports do not include injection openings for injection of water into the recess. The ports comprise simply discharge ports with a longitudinal duct which diverges in shape as previously described with a pinch valve at the outer end for controlling the amount of material discharged.

As shown in Figure 2, the injection openings 30 are arranged to be inclined relative to a radius of the bowl so as to tend to inject the liquid tangentially around the bowl to effect the fluidizing action on the materials in the recess.

The recesses are modified relative to the above prior patent in that the depth of the recess is significantly increased and in addition a flow guide body 32 is provided in association with each of the discharge ports 29. Each flow guide body 32 is positioned radially inwardly of the respective discharge port so as to set the location spaced inwardly from the port but lying within the recess. Various shapes of guide body can be used, but in the arrangement shown the guide body 32 is spherical. Each guide body 32 supported by a pair of support arms 33 and 34 extending vertically upwardly from the guide body. The support arms 33 and 34 are coupled to the liner 23 by engagement into a pair of slots 34A formed at the top and bottom side walls respectively of the recess so that the guide body 32 can be moved radially outwardly of the bowl into the slots and is held in position by the centrifugal forces on the guide body

SUBSTITUTE SHEET and by the frictional engagement of the arms in the slots. The radial position of the guide body can be adjusted by bending the arms.

The separation of the materials therefore occurs generally at the mouth of the recesses and between the walls 24, 25. The separation occurs at an inner surface of the material indicated at 35 in which the heavier materials collect into the recesses between the wall 24 and 25. The lighter materials pass over the collection area defined by the recesses and over the open mouth of the bowl to a collection system schematically indicated at 36. The heavier materials collect within each of the recesses for movement outwardly through the discharge ports 29 for collection of the heavier materials within a collection system schematically indicated at 37.

The position of the guide bodies immediately forward of the discharge ports acts to support the material radially inward of the guide body to prevent that material from pressing radially outwardly on the discharge port due to the high centrifugal force. It will be appreciated, in the absence of the guide bodies, all the centrifugal force on the material will press the material against the discharge port providing a very high force at that location. The guide body takes away some of that force and transfers the force to the bowl wall while the material can slip around the guide body both at top and bottom as shown in figure 3 and on the sides as shown in figure 2.

The discharge zone of each discharge port is therefore generally conical with an apex at the discharge port at an axis of the cone extending radially inwardly of the bowl. The cone thus diverges outwardly around the guide body with the angle of the cone being dependent upon the slippage of the material which is related to its repose angle. In addition the material is fluidized by injection of the water through the openings 30 tending to prevent

SUBSTITUTE SHEET the high centrifugal force on the material from drying the material and thus forming an immovable wedge of material in front of the discharge port.

The depth of the recess is however modified relative to the previous arrangement in that as shown in Figure 2 the cone of the discharge zone in front of each discharge port diverges so that the bases 35A, 35B of the cones intersect at the inner surface 35 of the material. In addition the cone is arranged as shown in Figure 1 so that the sides 35C cone of the discharge zone extends to a position adjacent the walls 24 and 25. The discharge zone therefore defines a pattern on the inner surface 35 which is substantially circular with those circular discharge patterns overlapping so as to draw material from substantially the whole of the inner surface at the recesses 19 and 20. The separation of the material at the inner surface therefore provides a Iayer of the heavier material on the inner surface which is then collected and discharged gradually outwardly as the material is discharged from the discharge ports 29.

In one example, therefore, the axial height of each recess is of the order of 6 inches and the radial depth of the recesses is of the order of 6 inches and these dimensions are arranged so that they provide approximately the arrangement of the discharge zone as shown.

The shaping of the liner to substantially follow the shape of the discharge cone as shown on the right hand side of Figure 1 assists in avoiding stationary material being located within the recesses. However the fluidization of the material in the recess by the injection openings 30 provides a gradual migration of the material around the recess to enter the discharge zone of each discharge port. However the main effect of the discharge ports is to collect the material from the inner surface 35 and to gradually move that material outwardly to the discharge port. The guide body 32 assists in increasing the

SUBSTITUTE SHEET angle of the discharge cone so as to increase the dimension of the discharge pattern at the inner surface.

It will be noted from Figure 3 that the inner surface 35 of the material within the recess is defined by inner edges 24A and 25A of the side walls 24 and 25 and that the inner surface at the recess 19 is thus frusto¬ conical with a cone angle following or substantially equal to that of the inside surface of the portion 18 of the bowl. The length of the portion 18 is arranged so that it is sufficient that the Iayer of the materials from the feed tube 22 is smoothed by the centrifugal action to lie as a Iayer 22A which is of substantially constant thickness over the upper part of the wall portion 18 as the materials 22A approach the inner surface 35. At the position where the materials enter the area of the inner surface 35, the materials are thus moving directly parallel to the inner surface 35 to avoid gouging of the material within the recess. The separation therefore occurs as the materials flow smoothly over the inner surface 35 with an exchange of heavier materials for lighter materials in the conventional manner of a centrifuge. The heavier materials thus collect within the recess and the lighter pass in the Iayer 22A to the next recess for further separation and final discharge from the mouth.

In some cases it may be desirable to add a perforated Iayer of a rigid material as indicated at 35X lying in the plane of the inner surface 35. Thus the perforated material 35X can be formed from expanded metal or similar perforated rigid material forming a frusto-conical section which is attached to the inner edges 24A and 25A to hold the perforated section in place. This perforated section therefore assists in guiding the material flow 22A over the inner surface 35 and to yet further avoid gouging, that is the penetration of the material flow into the recess. Such gouging, if it occurred, would cause extraction of the heavier materials from the recess and return of those heavier

SUBSTITUTE SHEET materials into the material flow 22A so that such heavier materials would be lost.

Turning now to Figure 4, this is modified relative to the cross section shown in Figure 1 to show further detail of the construction of the housing and launders 36A and the shaft 14. Further, the cross section is modified to show further details of the ducts 29A supplying control air to the pinch valves 42. Thus each row of pinch valves includes a supply duct 42A which communicates actuating air to the respective row of pinch valves and that duct 42A is supplied through the supply ducts 29A from a manifold arrangement 29B provided at the shaft 14.

The arrangement in Figure 4 is yet further modified by the addition of a third recess 50 downstream of the recesses 19 and 20. The third recess 50 is substantially identical to the first two recesses and is of a slightly increased diameter matching the increase in diameter between the recesses 19 and 20 due to the conical shape of the bowl wall.

As previously described, the material discharged from the recesses 19 and 20 is collected in a launder 37A and the tailings materials discharged over the mouth of the bowl is collected in the launder 36A. In the embodiment shown in Figure 4 an additional launder 51 is provided which collects the material solely from the recess 50 and supplies this material to a pump 52. Downstream of the pump 52 is provided a manually operable valve 52A which can be operated to return the material to the feed 53 entering the feed duct 22 or to direct the material to the concentrate collection. In an alternative arrangement, the bowl may have only two recesses with the concentrate from the second recess being collected separately from the first and passed to the pump for selected direction to the feed or to the concentrate depending upon the grade of material being processed.

SUBSTITUTE SHEET In this way the third (or second) concentrating ring or recess 50 is provided as a scavenger ring. The content of this ring is continuously discharged through the pinch valves into the launder 51 and is from that launder pumped, on operation of the valve 52A back into the feed inlet of the machine. The concentrate grade of the scavenger ring is not adequate to discharge into the concentrate stream from the launder 37A but contains some values worth recovering. Thus recirculating the discharge from the recess 50 into the in feed of the machine will move the values from the scavenger ring into one of the two lower rings for later discharge as concentrate.

A yet further modification shown in Figure 4 relates to the mounting of the support ring 34 which, instead of being mounted by axially extending support elements 38 is instead supported by radially extending support elements 38A which extend from the ring radially outwardly therefrom as shown at 38A in Figure 2 so as to hold the ring at the required position midway up the recess and centered around the central axis of the bowl. The number of support arms 38A can be selected in accordance with structural requirements but in general there will be four such support arms positioned intermediate the discharge ports and therefore intermediate the guide body 32.

Turning now to Figures 4, 5 and 6, the details of the control system to the valves 42 are shown. Thus the valves 42 of the channel 50 are controlled commonly by a fluid supply duct 60 which is separate from the fluid supply duct 61 of the channels 19 and 20. This allows the valves 42 of the channel 50 to be operated in a pulsed manner with a rate of the pulses greater than that of the valves of the channels 19 and 20 so as to pull off an increased amount of material. Thus the total period that the valves are open for the channel 50 is greater than the total period that the valves open for the channels 19 and 20 to provide an increase in the amount of material discharged. In

SUBSTITUTE SHEET some circumstances this can be obtained not by increasing the rate of the pulses but by increasing the period of the pulses.

The pulsing of the valves of course acts to discharge the material in sequential portions. All of the valves of a respective one of the channels are open simultaneously by the provision of fluid pulses in the respective supply duct 60, 61.

In Figure 5, the connection of the supply ducts 60 and 61 to a hub 62 of the shaft is shown. The shaft is thus formed by three concentric tubes 63, 64 and 65. Between the tubes 63 and 64 is provided a first annular duct 66. Between the tubes 65 and 64 is provided a second annular duct 67 and inside the innermost tube 65 is provided a third duct 68. The duct 61 is connected to the duct 68 by one or more radially extending pipes 69 which extend radially through the hub 62. Similarly the duct 67 is connected to the duct 60 by a plurality of radially extending pipes 70 which are axially offset from the pipes 69. Thus the pipes 69 connect with the duct 68 at the very end of the duct. The duct 68 terminates at a position spaced axially from the end of the tube 65 since the tube 64 ends at a position spaced axially from the end of the tube 65. The hub 62 includes a block 71 which has a threaded bore 72 receiving an end of the tube 64. The block 71 further includes a counter bore 73 into which the tube 65 extends with the counterbore providing an end part of the duct 68 which connects with the ducts 69. The block 71 is received in an end of the tube 63 and acts to close the end of the tube 63. At the lower end of the block 71 is provided a plurality of ducts 74 which extend radially outwardly from connection with the annular duct 66 within the tube 63.

The hub 62 further includes a sleeve 75 and an outer sleeve 76. The sleeve 75 is directly connected around the outside of the tube 63. The sleeve 76 is spaced outwardly and defines an annular channel connected with

SUBSTITUTE S EET the ducts 74 and extending therefrom to an opening in a base wall 77 of the outer bowl or jacket. Water supplied through the duct 66 of the shaft thus passes outwardly through the radial duct 74 and through the annular channel between the sleeve 75 and 76 to and through the base 77 for fluidizing the bowl as previously described.

The tube 63 defines the outer most surface of the shaft which is carried in the bearings 16 as previously described. The tube 63 projects through the lowermost bearing 16 and into engagement with the pulley 17 and terminates at the pulley 17. The tube 63 has threaded into it at its lower end a rotary union 79 for injecting water through the rotary union into the rotating shaft defined by the tube 63. The rotary union is a commercially available item conventionally used on rotary elements of this type for injecting a fluid into the rotating shaft. In this case the tubes 64 and 65 extend through the rotary union 79 for connection to a second rotary union 80 for supply of fluid to the ducts 67 and 68. The rotary union 79 includes a male thread 82 at its lower end onto which is attached a cap 83 which closes the lower end of the rotary union for sealing the lower end and preventing the escape of water from the lower end of the rotary union. The cap 83 includes a spring biased seal 84 biased downwardly by the spring 85 to provide engagement of sealing member 86 against a sealing washer 87 at a lower end of the cap 83. The washer 87 is held in place by a bolted end plate 88 screw fastened to the body of the cap 83.

The tubes 63, 64 and 65 forming the shaft all rotate commonly with the hub 62 in driving rotation of the bowl. The rotary union 79 is stationary so that the tube 63 rotates within the stationary rotary union.

The second rotary union 80 includes a cap portion 89 which is attached to the lower ends of the tubes 64 and 65 for rotation therewith. Thus

SUBSTITUTE SHEET the cap portion 89 includes a female screw thread 90 receiving a male thread of the tube 64 therein. Seals 91 and 92 prevent the escape of fluid to the outside of the tubes 64 and 65 respectively. The cap 89 includes a central duct 93 communicating with the duct 68. The cap further includes a plurality of ducts 94 arranged at radially spaced positions around the central duct 93 and communicating with a counter bore section 95 within the end cap 89 communicating with the duct 67. The end cap 89 is bolted by bolts 96 to the lower part of the rotary union indicated at 97. The lower part of the rotary union 80 is a commercially available item having an upper cap portion 98 which rotates with the cap 89 and a lower portion which remains stationary and is connected to suitable supply ducts (not shown) for communicating the fluid into the ducts 93 and 94.

The single shaft as shown, therefore, provides the communication of the fluidizing water around the outer most one of the annular channels together with communication of control fluid through the central circular channel and through the inner annular channel. If required, a yet further tube can be provided in the construction of the shaft so as to provide four ducts coaxially arranged each inside the next. Such four ducts are then used to provide the fluidizing liquid and to provide three sets of control fluid each for controlling a respective one of the valves sets of the channels 19, 20 and 50. This arrangement allows each of the channels to be individually tailored in regard to its discharge characteristics to the amount of concentrate collecting in that particular channel.

SUBSTITUTE SHEET

Claims

CLAIMS:

1. A method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining in the materials collected on the peripheral wall an inner surface of the materials over which the fed materials pass; defining on the peripheral wall at least one axially localized area for collecting heavier materials while lighter materials pass over the area for discharge; defining at the area around the peripheral surface recess means spaced outwardly of the inner surface; providing at the area a plurality of angularly spaced discharge ports at an outer surface of the recess means, each for allowing materials collecting in the area to discharge outwardly from the peripheral wall; collecting the outwardly discharge materials; allowing the material discharging from the discharge port to form a natural generally conical shape extending in both in angular and axial directions which is substantially free from confinement by walls of the recess means with an apex at the discharge port and a base of the conical shape at the inner surface, the shape and depth of the recess means being arranged

SUBSTITUTE SHEET relative to the angular spacing of the discharge ports such that bases at the inner surface of the conical shapes of the discharge ports at least substantially meet.

2. The method according to Claim 1 wherein the bases overlap.

3. The method according to Claim 1 including providing in each conical shape a deflection guide body and supporting the body radially inwardly of the discharge port.

4. A method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining in the materials collected on the peripheral wall an inner surface of the materials over which the fed materials pass; defining on the peripheral wall at least one axially localized area for collecting heavier materials while lighter materials pass over the area for discharge; defining at the area around the peripheral surface recess means spaced outwardly of the inner surface; providing at the area a plurality of angularly spaced discharge ports at an outer surface of the recess means, each for allowing materials collecting in the area to discharge outwardly from the peripheral wall;

SUBSTITUTE SHEET collecting the outwardly discharge materials; including providing for each discharge port a deflection guide body and supporting the body radially inwardly of the discharge port; including supporting the body so that materials pass on each angularly spaced side of the body and also on each axially spaced side of the body.

5. The method according to Claim 3 or 4 wherein the body is substantially spherical.

6. A method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; providing a feed material and feeding the feed material to the bowl so as to pass over the peripheral wall and to cause a heavier portion of the materials to collect on the peripheral wall while a remaining lighter portion of the feed material escapes from the open mouth; defining on the peripheral wall for rotation therewith at least one first axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the first recess for discharge; defining on the peripheral wall for rotation therewith at least one second axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the second recess for discharge, the second recess being downstream of the first recess;

SUBSTITUTE SHEET providing at the first and second recesses discharge means at an outer surface of the recess, each for allowing materials collecting in the recess to discharge outwardly from the peripheral wall; collecting the outwardly discharged materials from the first recess; collecting the outwardly discharged materials from the second recess separately from the materials from the first recess and returning the materials from the second recess to the feed material.

7. A method of separating intermixed particulate materials of different specific gravity comprising: providing a centrifuge bowl having a peripheral wall and an open mouth; rotating the bowl about a longitudinal axis so as to rotate the peripheral wall around the axis; feeding the materials to the bowl so as to pass over the peripheral wall and causing a heavier portion of the materials to collect on the peripheral wall while a lighter portion of the materials escapes over the open mouth; defining on the peripheral wall for rotation therewith at least one first axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the first recess for discharge; defining on the peripheral wall for rotation therewith at least one second axially localized annular recess extending radially outwardly from the peripheral wall for collecting heavier materials while said lighter materials pass over the second recess for discharge, the second recess being downstream of the first recess;

SUBSTITUTE SHEET providing at the first and second recesses first and second discharge means each at an outer surface of the respective recess, each for allowing materials collecting in the recess to discharge outwardly from the peripheral wall; each of the first and second discharge means having valve means for controlling discharge of the materials from the recess; collecting the outwardly discharged materials from the first and second recesses; and providing first and second control means for separately controlling the valve means of the first and second recesses respectively so as to provide for each of said first and second recesses different discharge characteristics to provide different concentrations of the materials collected.

8. The method according to Claim 6 or 7 including providing the discharge means as a plurality of angularly spaced discharge ports and for each discharge port providing a deflection guide body engaging and guiding materials moving toward the discharge port and supporting the body radially inwardly of the discharge port.

9. The method according to Claim 8 including supporting the body so that materials pass on each angularly spaced side of the body and also on each axially spaced side of the body.

10. The method according to Claim 8 or 9 wherein the body is substantially spherical.

1 1. The method according to Claim 7 including providing the discharge means as a plurality of angularly spaced discharge ports and for each discharge port providing a separate valve of said valve means.

SUBSTITUTE SHEET

12. The method according to claim 1 1 wherein each valve is pulsed so as to open and close the valve repeatedly to discharge the material in sequential portions.

13. The method according to Claim 12 wherein the control means of each area controls all of the valves of that area simultaneously.

14. The method according to Claim 12 wherein the control means of each area controls the valves to control a total period that the valves are open and wherein the total period for the second area is greater than that of the first so as to discharge a greater volume of material.

15. The method according to Claim 12 wherein the control means are arranged to provide an increased rate of pulsing for the second area.

16. The method according to claim 7 wherein the bowl has a support shaft and each of the valves is controlled by a fluid supply circuit includes a portion thereof extending along the shaft.

17. The method according to claim 16 wherein the fluid supply circuits include coaxially arranged duct portions extending along the shaft, each duct portion being supplied with fluid from a separate stationary swivel coupling mounted on the shaft.

18. The method according to claim 17 wherein the swivel couplings are arranged at axially spaced positions.

19. The method according to claim 17 wherein a first of the duct portions comprises a central tube of the shaft and a second of the duct portions coaxially surrounds the central tube.

20. The method according to claim 19 including supplying fluidizing liquid to the bowl through the peripheral wall, wherein the fluidizing liquid is supplied through a duct portion of the shaft surrounding said first and second duct portions of the fluid circuits.

SUBSTITUTE SHEET

21. The method according to any preceding claim wherein the heavier material is collected in at least one annular recess having upper and lower sides of the recess including innermost edges with the innermost edge of the lower side being closer to a central axis of the bowl than the innermost edge of the upper side, such that the material defines an inner surface in the recess located by the innermost edges and which is frusto-conical in shape and wherein the peripheral wall of the bowl includes a lower frusto-conical portion over which the materials flow before reaching the recess, the lower frusto¬ conical portion being shaped to guide the materials in a flow direction to flow across the inner surface of the material in the recess.

22. The method according to claim 21 including providing a perforated protection surface across the inner surface of the material in the recess to prevent gouging of the material in the recess by the material flowing over the lower portion.

SUBSTITUTE SHEET