Note: Descriptions are shown in the official language in which they were submitted.
~Z4(~653
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CENTRIFUGAL SEPARATOP~
BACKGROUND OF THE INVENTION
This invention relates to a centrifugal sepa-
rator which can be used to extract heavy metals such
as gold from a slurry containing the metal mixed with
other materials.
There is disclosed in my Canadian Patent No:
1,111,809 a device of this general type which comprises
a bowl having a base and a peripheral wall which is
cylindrical and upstanding from the base. The peri-
pheral wall has a plurality of axially spaced inwardly
projecting rings arranged on its inner periphery and
between each ring and the next adjacent ring is pro-
vided a plurality of openings in the peripheral wall.
The bowl is encased in an outer wall which defines a
chamber between the outer surface of the peripheral
wall and the outer wall into which water can be inject-
ed under pressure so as to pass through the openings
into the interior of the bowl and particularly between
the rings.
The slurry or materials to be separated is
deposited into the bowl at the base by eed duct so
the material is then thrown outwardly by rotation of
124~S3
the bowl to pass up the peripheral wall to an open mouth
at the opposite end thereof to the base. During the
passage over the peripheral wall, the materials are
separated due to their different specific gravity with
the lighter material discharging with the fluid or
water out of the open mouth and the heavier materials
remaining trapped on the peripheral wall between the
rings.
This arrangement, while achieving substantial
success in view of its considerable improvements from
prior art arrangements, has a number of disadvantages.
Firstly, the separation which takes place on
the peripheral wall is not optimized due to the relati-
vely crude design of the bowl.
Secondly, the pressure required in the cham-
ber around the peripheral wall in order to force the
liquid or water through the openings into the bowl
against the effects of centrifugal force is high and
therefore the amount of water flow into the bowl is
generally unsatisfactory.
Thirdly, after a batch of the material has
been passed through the bowl, it is necessary to open
thé bowl and wash down the remaining materials from in-
side the bowl using a hose and separate water supply
~z40653
and this has been found to be somewhat onerous and dis-
advantageous.
Earlier devices of this type are also shown
in Australian patent applications 22055/35 and 17487/34
(both by MacNicol). However, these early devices are
extremely crude and certainly are less sufficient than
the arrangement shown in my Canadian patent stated above.
SUMMARY OF THE INVENTION
.
It is one object of the present invention,
therefore, to provide a centrifugal separator of this
type which has an improved separating action.
It is a further object of the present inven-
tion to provide a separator of this type where the de-
sign of the bowl and particularly the openings enables
the pressure within a chamber surrounding the peripheral
wall to be reduced while still obtaining the required
high level of fluid flow through the openings.
It is a yet further object of the invention
to provide a separator of this type which is self-wash-
ing after completion of a batch of the material.
According to a first aspect of the inventionthere is provided an apparatus for cenmtrifugally sepa-
rating intermixed materials of different specific gra-
vities comprising a centrifuge bowl having a base and
124~6~;~
-- 4
a peripheral wall surrounding an axis passing through
the base and generally upstanding from the base to an
open mouth, a plurality of axially spaced inwardly pro-
jecting rings mounted on an inner surface of the peri-
pheral wall and a plurality of openings extending
through the peripheral wall from an outer surface to
the inner surface thereof, the openings being arranged
between each ring and the next adjacent ring and in
spaced relation around the peripheral wall, means moun-
ting the bowl for rotation about the axis, means for
feeding the materials into the bowl such that during
rotation of the bowl they flow over the peripheral wall
for discharge from the open mouth and means for apply-
ing fluid to the outer surface of the bowl so as to
pass through the openings and fluidize the materials
between the rings, the openings passing through the
peripheral wall in a direction inclined to an axial
plane passing therethrough so as to tend to direct the
fluid around the peripheral wall.
This arrangement has a number of advantages.
Firstly, the openings which can be tangential or as
close to the tangential direction as is practically
possible, generate a flow of fluid within the bowl
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between the rings which swirls around the bowl so as
to improve the fluidization of the material collecting
between the rings. Thus, in prior devices it has been
found that the material can compact between the openings
and thus not properly fluidize and of course any com-
paction will reduce the efficiency of the separation.
The present arrangement therefore allows the bed of mate-
rial between the rings to be fully fluidized so that sepa-
ration can take place throughout the whole of the bed
and throughout all the height of the peripheral wall.
Furthermore, the tangential openings can be
provided by projections stamped from the peripheral
wall extending outwardly from the peripheral wall with
an opening in the projection facing forwardly toward
the direction of rotation. In this way, the opening
tends to pump water from the enclosure surrounding the
peripheral wall inwardly into the bowl and thus reduce
the pressure necessary in the enclosure or surrounding
jacket.
Furthermore, at the end of processing of a
batch of the material when the bowl is stopped, the
substantially tangential openings jet the fluid around
the bowl and therefore act to wash the bowl without
the necessity for further externally supplied water.
-
~Z4~6S3
-- 6
According to a second aspect of the inven-
tion, therefore, there is provided an apparatus for
centrifugally separating intermixed materials of dif-
ferent specific gravities comprising a centrifuge bowl
having a base and a peripheral wall surrounding an
axis passing through the base and generally upstanding
from the base to an open mouth, a plurality of axially
spaced inwardly proiecting rings mounted on an
inner surface of the peripheral wall and a plurality of
openings extending through the peripheral wall from an
outer surface to the inner surface thereof, theopenings
being arranged between each ring and the next adjacent
ring and in spaced relation around the peripheral wall,
means mounting the bowl for rotation about the axis,
means for feeding the materials into the bowl such that
during rotation of the bowl they flow over the periphe-
ral wall for discharge from the open mouth and means
for applying fluid to the outer surface of the bowl so
as to pass through the openings and fluidize the mate-
rials between the rings, wherein a first diameter ofthe peripheral wall adjacent said mouth is greater than
a second diameter of the peripheral adjacent the base
and wherein the ratio of total opening area to unit
area at said first diameter is greater than at said
~2~06S3
-- 7
second diameter.
It has surprisingly been found that in order
to maximize the area of the peripheral wall which is
used in the concentration or separation of the material,
it is necessary to vary the proportion ofopening area to
unit area, depending upon the diameter of the bowl.
It is previously known to provide a bowl which is of
increasing diameter from the base to the open mouth
since this improves the flow of the material from the
inlet over the open mouth. However, it has recently
been found that in such an arrangement, the varying cen-
trifugal force obtained causes the balance between the
in-flowing fluid through the openings and the centrifugal
force of the material to be only satisfactory in a re-
latively small area of the height of the wall.
This problem has been overcome by varying the
ratio of the opening area particularly by varying or in-
creasing the number of holes of the same diameter per
unit area so that there are more holes per unit area
at the larger diameters of the bowl than at the smaller
diameters.
Furthermore, the increase is not directly re-
lated to the diameter, but to a fraction of the diame-
ter with the fraction in turn depending upon the lar-
lZ~a~653
- 8 -
gest diameter of the bowl.
According to a third aspect of the invention
there is provided an apparatus for centrifugally sepa-
rating intermixed materials of different specific gra-
vities comprising a centrifuge bowl having a base and
a peripheral wall surrounding an axis passing through
the base and generally upstanding from the base to an
open mouth, a plurality of axially spaced in-
wardly projecting rings mounted on an inner surface of
the peripheral wall and a plurality of openings extend-
ing through the peripheral wall from an outer surface
to the inner surface thereof,the openings being arranged
between each ring and the next adjacent ring and in spa-
ced relation around the peripheral wall, means mount-
ing the bowl for rotation about the axis, means for
feeding the materials into the bowl such that during
rotation of the bowl they flow over the peripheral wall
for discharge from the open mouth and means for apply-
ing fluid to the outer surface of the bowl so as to
pass through the openings and fluidize the materials bet-
ween the rings, the peripheral wall being formed from
a plurality of wall portions each having a cylindrical
form and each extending axially from one ring to the
next adjacent ring, the diameters of the wall portions
~Z4V6~3
g
increasing from a wall portion adjacent the base to a
wall portion adjacent the open mouth.
This arrangement provides a novel structure
of bowl which instead of being formed integrally with
curved or inclined peripheral wall, can be formed from
a number of cylindrical wall portions, each rolled from
a flat s~rip subsequent to the provision of the open-
ings as previously defined.
Thus, the bowl can be simply and inexpensively
manufactured and provides the preferred outwardly in-
clined wall.
According to a fourth aspect of the invention
there is provided an apparatus for centrifugally sepa-
rating intermixed materials of different specific gra-
vities comprising a centrifuge bowl having a base and a
peripheral wall surrounding an axis passing through the
base and generally upstanding from the base to an open
mouth, a plurality of axially spaced inwardly
projecting rings mounted on an inner surface of the
peripheral wall and a plurality of openings extending
through the per~pheral wall from an outer surface to the
inner surface thereof,the openings being arranged between
each ring and the next adjacent ring and in spaced rela-
tion around the peripheral wall, means mounting the bowl
:~24~653
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for rotation about the axis, means for feeding the mate-
rials into the bowl such that during rotation of the
bowl they flow over the peripheral wall for discharge
from the open mouth and a discharge opening through the
base for discharging collected material from the bowl,
the discharge opening lying wholly radially outwardly
of an axial projection onto the base of the inner peri-
phery of the ring next adjacent the base and having a
radial dimension greater than the distance between said
projection and the radially outer edge of the base so
that the discharge opening extends into a recess in the
peripheral wall.
It is one advantage of this aspect of the in-
vention therefore that a discharge opening can be pro-
vided of a sufficiently large size to allow the proper
and complete discharge of the material at the end of
processing of a batch, particularly bearing in mind the
self-washing aspect of the tangential openings as pre-
viously defined. At the same time the discharge open-
ing is positioned at a location where it does not in-
terfere with the normal operation of the processing
where the material is fed into the bowl through a duct
which discharges adjacent the base. Thus, the discharge
opening is positioned beneath the first one of the rings.
i240653
11 --
With the foregoing in view, and other advan-
tages as will become apparent to those skilled in the
art to which this invention relates as this specifica-
tion proceeds, the invention is herein described by re-
ference to the accompanying drawings forming a part
hereof, which includes a description of the best mode
known to the applicant and of the preferred typical em-
bodiment of the principles of the present invention, in
which:
DESCRIPTION OF THE DRAWINGS
.
Figure 1 is a cross sectional view through a
centrifugal separator according to the invention, the
cross section being shown at 1-1 in Figure 2.
Figure 2 is a cross sectional view along the
lines 2-2 of Figure 1.
Figure 3 is a fragmentary cross sectional
view taken on the same cross section of Figure 1 show-
ing the wall of the bowl in enlarged view.
Figure 4 is an isometric fragmentary view of
a portion of the wall of the bowl.
Figure 5 is a cross sectional view along the
lines 5-5 of Figure 4 showing one opening in a first
step of the manufacture thereof.
Figure 6 is a view similar to Figure 5 showing
124~)6~3
- 12
a second step in the course of manufacture of the open-
ings of Figure 4.
Figure 7 is a cross sectional view through a
jig used for the manufacture of the bowl showing the bowl
partly assembled on the jig.
Figure 8 is a cross sectional view on an en-
larged scale along the lines 8-8 of Figure 2.
Figure 9 is a cross sectional view along the
lines 9-9 of Figure 3.
In the drawings like characters of reference
indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Turning firstly to Figure 1, a centrifugal
separator is shown in cross section and comprises gene-
rally, an outer casing 10 which supports a centrifuge
bowl generally indicated at 11 for rotation on a shaft
12 about a central axis of the shaft and of the cylin-
drical container 10.
A feed duct 13 is mounted centrally of the
container 10 for feeding material into the bowl with ex-
cess material escaping over the rim of the bowl into an
annular channel 14 from which it runs to an outlet 15
at one side of the container 10.
The bowl 11 comprises an inner bowl assembly
~Z4~653
_ 13
14 and an outer bowl assembly 15 thus defining a cham-
ber between the two parts of the bowl which surrounds
the peripheral wall of the inner bowl assembly 14. A
central duct is provided through the shaft 12 and indi-
cated at 16 for supplying water under pressure to the
enclosure indicated at 17 between the two bowl portions.
Openings 18 provided in the peripheral wall
of the inner bowl portion 14 allow water to enter through
the peripheral wall to join with the material flowing
from the inlet 13 to the annular chamber 19. The shaft
12 is driven by a pulley 21 from an electric motor 22
so as to be rotated in a clockwise direction at a speed
of the order of 400 rpm.
In use, material in slurry form containing
fractions of high specific gravity, particularly gold,
mixed with other material is fed into the duct 13 from
a supply pipe and enters the bowl 11. The material is
then washed over the peripheral wall of the bowl and
escapes from the mouth into the annular duct 19. On
the peripheral wall the separation takes place as will
be explained in more detail hereinafter and the lighter
fractions or tailings escape from the bowl through the
outlet 20 to be discarded.
Turning now to Figures 3 and 4, the structure
~Z4(~653
- 14
of the inner bowl 14 is shown in detail. Specifically,
the inner bowl 14 comprises a plurality of peripheral
wall portions 23, each of which is cylindrical with the
next outer portion being of larger diameter than the
portion closer the base.
The wall portions 23 are spaced by rings 24
which again are stepped in increasing diameter from
the base toward the open mouth terminating in an end
ring 25. One of the wall portions is shown in Figure
4 and it will be noted that this comprises a cylindrical
portion which has been rolled from a flat plate and in-
cludes a welded seam line 26. In one example, the wall
portion is formed from 14 gauge stainless steel and has
a width of two inches and a diameter varying from twenty
inches up to twenty-seven inches.
The wall portion is initially cut from a flat
plate of stainless steel into the required dimension
for forming the diameter concerned. At this stage,
openings generally indicated at 27 are formed in the
flat strip by the technique shown in Figures 5 and 6.
As shown in Figure 5, the openings are formed
by a first step in which a projection is punched into
the flat strip by a forming tool 28. The projection is
indicated at 29 and is punched so that it has a substan-
~Z4~ 3
tially flat front face 30 which extends substantiallyat right angles to the flat plate indicated at 231.
The projection 29 from the front face 30 tapers both
in width and height to a position spaced from the front
face 30 and indicated at 31 at which it smoothly rejoins
with the plate 231.
The front face 30 is arranged slightly in-
clined from the right angled direction in order that
there is sufficient material of the wall left at this
point so that it does not quite break away from the
edge indicated at 32 of the plate 231. Thus, the front
face 30 is in fact a fine web of material at the front
of the tapered projection 29.
The depth of operation of the punch tool 28
is such that the distance of the inner surface of the
projection 29 from the outer surface of the edge 32 is
of the order of 1/16 inch. In addition, it will be
noted from Figure 4 that the front face 30 of the pro-
jection 29 is substantially circular having a diame-
ter substantially equal to or slightly greater thantwice the wall thickness plus 1/16 inch.
As a second step in the manufacturing pro-
cess, a drill bit 32 is applied to the front face 30.
The diameter of the drill bit is, in one example, 1/16
~24G6;~3
- 16
inch so that it just passes between the inner walls of
the projection and the outer edge of the edge 32 at an
angle to pass along the inner wall to the point 31.
In this way, the opening in the front face 30 is formed
by a perfectly circular hole 33 which faces substanti-
ally directly along the outer surface of the plate 231.
The opening then communicates with the open topped
channel formed on the inside of the plate 231 by the
press tool 28, the bottom surface of which is indica-
ted at 291 and lies at a shallow angle to the plate231.
The stamping process shown in Figure 5 and the
drilling process shown in Figure 6 are carried out as
separate stages of the working of the plate 23 result-
ing in a plurality of holes or openings 27 as shown in
Figure 4 which are staggered, that is formed in three
rows with the central row offset from the two outer
rows to a middle point between the two outer rows.
After the flat plate has been stamped and
drilled, it is then rolled by a conventional rolling
process to the required diameter and the seam 26 weld-
ed to complete the cylindrical wall portion.
The rings 24 are separately manufactured from
a suitable gauge metal by cutting from a flat sheet and
.. . .
~Z~ S3
it will be noted from Figure 3 that the rings are of
gradually increasing diameter but have the same radial
extent which, in one example, is of the order of two
inches. The end plate 25 has an inner periphery step-
ped to the same extent as the previous rings 24, but
has a greater radial extent to provide sufficient mate-
rial for an opening 251 which is one of a plurality of
such openings around the periphery. In addition, the
plate 25 is of thicker material than the rings 24.
After the manufacture of all the rings and
wall portions is complete, the bowl is assembled as
shown in cross section in Figure 7 on a jig 33. The
jig 33 provides a series of stacked cylindrical form-
ers on which the bowl is assembled. Thus, firstly
the plate 25 is positioned around a first cylindrical
portion indicated at 252 of the jig following which the
outermost wall portion indicated at 232 is loosely
positioned on the plate 25 and an annular spacer 34 is
positioned within the wall portion 232. At this stage
the first ring indicated at 241 is placed on the next
former section 253 with its spacing from the plate 25
defined by the spacer 34 and its radial position defined
by the former portion 253. The outer periphery of the
ring 241 thus defines the position of the wall portion
~;240~53
- 18 -
232 and therefore the wall portion 232 can be tacked
to both the ring 25 and the ring 241 to temporarily
locate these in position.
In the next step a further wall portion 233
is loosely placed on the plate 241, a further spacer
35 is located in position and a further ring 242 is
positioned on the next former section 254. The thus
assembled pieces are again tacked in position and the
process is repeated until a complete unit is tacked
together and checked for proper positioning and is then
welded by complete weld lines extending around between
each wall portion and the adjacent rings.
Reverting to Figure 3, it will be noted that
the lowermost wall portion 23 is welded to a base 35
around the majority of the periphery thereof. However,
at one position of the periphery of the base 35, an out-
let 361 is positioned; The outlet 361 is circular in
cross section with one tangent lying directly beneath a
projection of the lowermost ring 24. The diameter of
the opening 36 is however greater than the radial ex-
tent of the ring 24 so that it extends into a recess
371 provided in the lowermost peripheral wall portion
23. This is shown more clearly in Figure 9.
Turning again to Figure 1, the plate 25 of the
1240653
_ 19 -
inner drum 14 is bolted to a flange 36 of the outer
bowl 15 so that the two bowls form an integral unit
which co-rotates with the shaft 12. The flange 36
also includes a down-turned outer rim 37 which lies out-
side and substantially parallel to the outer wall of
the outer bowl 15. The channel 19 is defined by a base
wall 38 and an upstanding wall 39, the top edge of the
upstanding wall extending into the space between the
depending rim and the surface of the outer bowl 15 so
as to provide effectively a seal to prevent material
escaping from the bowl from splashing over the upstand-
ing wall 39 into the interior of the housing.
It will be noted that the channel 19 has a
highest point opposite the outlet 20 where the base 38
is attached to the side wall of the housing 10 at a
point well above the outlet and then curves smoothly
downwardly to the outlet 20 at the diametrically oppo-
site position. The upstanding wall 39 is therefore of
varying height depending upon the angular position re-
lative to the base 38.
The opening 361 of the inner bowl 14 passes
through an opening 40 in the bottom of the outer bowl
so as to provide a mouth 41 and closure cap 42 on the
underside of the outer bowl 15. The opening 361 is
12~653
_ 20
therefore normally closed during operation of the de-
vice.
Turning now to the upper structure of the
device as shown best in Figures 1, 2 and 8, the outer
cylindrical wall of the housing 10 is shown at 43 in
Figure 8 and includes an inwardly extending flange 44
at a position adjacent the top edge of the wall 43. At
the top edge is provided an in-turned rim 45 parallel
to the flange 44. The flange 44 supports and is bolted
to a rectangular framework generally indicated at 46
which carries the central feed duct 13. The rectan-
gular framework comprises a pair of end plates 47 bolt-
ed by bolts 48 to the flange 44, a pair of upstanding
transverse beams 49 which extend across from one end
plate 47 to the other and which support the duct 13 to-
gether with support beams S0 at right angles to the
beams 49.
The beams 49 each carry a pair of spaced L-
shaped brackets 51 arranged adjacent the ends thereof
and these in turn support a ring 52 which has an outer
diameter slightly less than the inner diameter of the
flange 44 so that it can pass inside the inner peri-
phery of the flange 44 to take up the position shown
in Figure 8. The ring 52 is bolted to the bracket 51
:LZ4~653
- 21
by a bolt 53 which also, by way of a flat head 54, sup-
ports a ring-shaped wear insert 55. The wear insert
55 is also supported relative to the ring 52 by further
bolts 56 which extend around the ring 52 adjacent the
inner periphery thereof.
A plurality of bolts 57 is arranged with the
bolts attached around the periphery of the flange 44 ad-
jacent the wall 43. One of the bolts is shown in Figure
8 including a nut 58 with the bolt bent inwardly at
right angles to provide a hanger portion 59. A cur-
tain 60 of the same material as the wear resistant in-
sert 55 is formed into a ring with a plurality of holes
adjacent the upper edge so the curtain can be hung over
the inwardly projecting hanger portions 59 and pushed
outwardly to engage the shank of the bolt 57.
The ring 55 of the wear resistant material is
then flexed into position as shown in Figure 8 where
its edge projects outwardly from the ring 52 to a posi-
tion underlying the hanger 59 and engaging the inner
surface of the ring 60. Thus, the portions 55 and 60
lie at right angles as shown in Figure 8 with the outer
periphery of the portion 55 protecting the hangers 59.
Reverting to Figure 1, it will be noted that
the bottom edge of the ring 60 lies beneath the upper
, .
i2~i~653
- 22
edge of the bowls so the material escaping from the bowls
when flung outwardly therefrom, engages either the cur-
tain 60 or the outer edges of the ring 55. These wear
resistant inserts are formed from a plastic material
which has some flexibility and therefore is resistant
to wear from the high speed water and grit which can be
thrown out from the bowl . The unique design of the
hangers and of the ring 55 which protects those hangers
ensures that the material is prevented from engaging
any metal parts or supports of the device and therefore
wear is restricted to the wear inserts which are resis-
tant and can be replaced after a time.
Turning again to Figure 3, the wall portions
23 are manufactured with the openings 27 such that there
are more openings per square inch or per unit area in
the wall portion 23 of largest diameter than the wall
portion 23 of smallest diameter. In fact, the number
of holes per unit area in cases where the holes are
all of the same diameter as preferred, or in other
words the ratio of hole area to unit area is arranged
to increase with the increase in diameter.
The number of holes in each of the wall por-
tions can be calculated from the following formula:
No. of holes = k~d (1 ~(d/d
( ~ K )
lZ4(1653
- 23
where d = diameter of wall portion
dl= diameter of smallest wall
portion
k = constant
K = a constant
In one example using a 30 inch outside diame-
ter of the bowl, k can be 1.45 and K can be 4. However,
K can lie in the range two to four.
The bottom surface of the bowl or base 35 is
slightly conical, that is it is formed by a very shal-
low cone and carries on the upper surface thereof a
wear resistant layer 61 again of the flexible plastic
material previously mentioned in relation to shields
55 and 60.
In operation, material is fed through the in-
let duct 13 from a suitable piped supply. The material
contains the high specific gravity fraction to be se-
parated in combination with generally very much larger
quantity of other materials such as sand, gravel and
other impurities such as lower specific gravity me-
tals. It is preferred that the material is filtered
down to % inch. The material is then fed in a slurry
form which can contain ten gallons of water per minute
for each cubic yard of material per hour.
lZ406~3
_ 24
The material entering vertically downwardly
through the duct 13 contacts the base of the bowl and
is thrown outwardly by the rotation of the bowl and
the material already present in the bowl. The level
of liquid and material which is obtained in a typical
example is shown at 62 in Figure 1.
The centrifugal action on the material acts
to separate higher speciic gravities toward the outer
or peripheral surface of the inner bowl 14. This mate-
rial tends to collect between the rings 24 while light-
er material and water flows to the outer rim of the
bowl to be thrown outwardly for collection at thé out-
let 20.
Without the presence of the openings 27 in
the peripheral wall, the material would merely tend to
pack between the rings and against the peripheral wall
thus preventing any further separation of the packed
material or of further material added to the bowl. It
is necessary therefore to keep the material between the
rings against the peripheral wall fluidized so that con-
tinual separation can take place. Thus, in each bed
~z4u6cj3
- 25
formed between an adjacent pair of rings, the material
at the upper surface of the bed, that is closest to
the centre of the bowl, must constantly exchange with
material entering the bowl, dependent upon the speci-
fic gravity. In addition, material actually in the bed
must also constantly exchange so that the higher speci-
fic gravity material moves outwardly eventually contact-
ing the peripheral wall itself.
This fluidization of the beds is achieved by
injecting the water from the outer container 17 through
the peripheral wall into the bed. Not only is the water
injected into the bed but also it is injected with a
component tangential to the bed and opposite to the
direction of movement of the bowl so that the whole of
the ring of material in between a pair of adjacent
rings is constantly on the move relative to the bowl
and is therefore constantly fluidized. The proportion
of liquid entering the bowl through the openings is
preferably of the order of 25% to 33%.
Using the proportion of holes as previously
explained, the fluidization of the beds is such that
substantially all of the beds act to properly separate
the materials and therefore each can collect the high-
est specific gravity material. Without such variation
~240~;53
_ 26
in the holes, the balancing forces between the centri-
fugal force and the water injection providing fluidi-
zation of the bed are not retained at the required
values to obtain the proper separation,
After the passage through the bowl of a suit-
able quantity of material, which in the example shown
may be of the order of six cubic yards, the feed of
material and water through the duct 13 is halted follow-
ing which the bowl itself is halted. At this time the
cap or plug 42 is removed from the opening 36 and a
suitable container positioned beneath the opening to
collect the material remaining within the bowl. The
water injected into the inner bowl through the openings
27 tends to wash around the peripheral wall in view
of the tangential direction in which it is injected
thus again fluidizing the bed of material and washing
it away fro~ the lower ring adjacent that portion of
the peripheral wall onto the base and from the base to
the opening 36.
The diameter of the opening 36 is designed
to accommodate the amount of water injected into the
bowl so that the bowl empties rapidly and conveniently
by-the flow of water into the container for further
separation in accordance with conventional techniques.
124V653
- 27
The device is then ready for a further batch
of material with the plug 42 replaced and the bowl
fully emptied of the materials separated from the pre-
vious batch.
Since various modifications can be made in
my invention as hereinabove described, and many appa-
rently widely different embodiments of same made within
the spirit and scope of the claims without departing
from such spirit and scope, it is intended that all
matter contained in the accompanying specification
shall be interpreted as illustrative only and not in a
limiting sense.
