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Патент USA US3023959

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March 6, 1962
Filed Sept. 3, 1958
2 Sheets-Sheet 1
/66 /78
March 6, 1962
Filed Sept. 3, 1958
2 Sheets-Sheet 2
FIG. 4-.
Patented Mar. Q, 1962
tion of a water surface of predetermined characteristics
permitting ore bearing froth to be skimmed from the
surface thereof readily and conveniently.
Lincoln E. Bankerd, 8550 Tia Maria ‘Way,
La Mesa, Calif.
Filed Sept. 3, 1958, Ser. No. 758,746
2 Claims. (Cl. 233-7)
It is a further object of this invention to provide a
novel means for separating heavier particles of metal
bearing sand from useless gangue.
Other objects and advantages will be apparent to those
skilled in the art, it is believed, from the following de
The present invention relates to the art of concentrat
tailed description of the method of concentrating metal
ing metallic ores and particularly to a novel apparatus
especially adapted to concentrate crushed metallic ores. 10 lic ores and apparatus therefor when taken in connection
with the accompanying drawings in which:
The majority of metallic ores are found in nature in
association with high percentages of useless material such
as quartz rock. To economically utilize the ore, it is
FIG. 1 is a horizontal side view of the ore concen
trator partially broken away and partially sectionalized.
FIG. 2 is a sectional view taken substantially along the
necessary to separate the useful material from the use
less before smelting by a process known as concen 15 line 2--2 of FIG. 1.
A process for concentrating known as forth ?otation
FIG. 3 is a partial sectional View taken substantially
along the line 3—3 of FIG. 1.
FIG. 4 is a graph illustrative of the shape of liquid
well known in the art, is used for separating the metallic
surfaces formed as a result of the forces of rotation
compound from ?nely ground rock particles. The ?ota
tion process takes advantage of the fact that certain 20 caused by the action of the ore concentrator.
FIG. 5 is an enlarged partial sectional View of the valve
liquids will “wet” certain substances but not others. These
means utilized in controlling discharge of the gangue and
liquids, or ?otation reagents, may be mixed with a slurry
of ?nely ground ore and water and upon agitation in the
Referring now to the drawings:
presence of air, a plurality of very ?ne bubbles coated
by the oily ?otation reagents, are formed. The ?ne 25 An ore concentrator in accordance with the present
invention is indicated generally at 10. The device, which
particles of the metallic compound having been “wetted”
is rotatably mounted in a frame 12, includes a vessel
by the ?otation reagent, are drawn into the oily ?lm sur
14, a ba?le assembly indicated generally at 16, and a
rounding the minute air bubbles and adhere thereto.
centrally positioned operation control member indicated
The buoyancy of the air bubbles causes the admixture of
?otation reagent, air and metallic compound to rise to 30 generally at 18.
The vessel 14 is provided with an axially extending
the surface of the ?uid to form a froth which is then
shaft 20 which is journalled in a bearing 22 carried by
separated with an excess of water to provide a mixture
the base of the frame 12. The vessel 14 is rotated by a
of the relatively pure metallic compound and the readily
constant speed motor (not shown) which drives the drive
volatile ?otation reagent and water. The gangue and
other .impurities, including the excess water, are dis 35 ing pinion 24. The driving pinion 24 meshes with a ring
gear 26 encircling a lower part of the vessel 14. By
charged separate from the froth.
this construction the vessel 14 is free to rotate about its
In the process of grinding the ore a number of particles
central major axis at a speed determined by the constant
too large to be ?oated by the minute bubbles are formed.
These larger particles remain in the main body of the
speed motor. The vessel 14 is generally parabolic in
mixture, and generally remain near the bottom of the 4:0 cross section and, as will be more fully shown later, the
precise form of the paraboloid is a function of the an
container utilized. They are thus discharged with the
gular speed of rotation to be imposed upon the vessel in
aqueous suspension of gangue.
operation. As used throughout this speci?cation the
Generally, the larger and heavier particles may be as
words “parabolic in cross section” as applied to the Vessel
sumed to contain the same percentage of metallic com
pound as the original ore. It is, therefore, desirable for 45 l4 and as is clearly shown in the drawings shall mean
that the axial or vertical cross section as determined by a
reasons of economy that these particles be returned to
plane intersecting the central vertical axis of the vessel
the grinder for regrinding to release the occluded metal
would de?ne a curve which would be generally parabolic.
lic compound to reduce the loss of useable compound to a
The axial or vertical cross section is to be distinguished
In the conventional froth ?otation process now in use 50 from the horizontal cross section, the latter of which
would be circular.
there are no means provided to accurately divide the
The operation control member 18 includes a slurry feed
gangue and the froth. Conventionally, a certain amount
pipe 28, an air feed pipe 3%, a mixing cylinder 32, and a
of froth and ?otation reagent is carried along with the
hollow mixing shaft 34. The mixing cylinder 32 is posi
gangue and lost. Since the ?otation reagent is expen
sive, it would be desirable, if possible, to retain as large 55 tioned vertically with respect to the vessel 14- and has a
central axis which coincides with the central axis of the
a percentage of it as possible so that it may be recycled.
vessel 14. One end 36 of the mixing cylinder is rotatably
In addition, because of the turbulence in the ?otation
mounted in a hearing 38 carried by the top portion of the
cell or container, at certain amount of gangue is sep—
frame 12;. The other end 46) is provided with a bearing
arated with the froth. The presence of the gangue in
creases the cost of subsequent smelting and accordingly, 60 42 within which is rotatably mounted the mixing shaft 34.
In addition, the end 40 is provided with a plurality of
is undesirable.
bypass channels 44 which communicate between the
It is an object of the present invention to provide an
chamber 46 formed between the inner walls of the mixing
ore concentrator which will substantially separate the
cylinder 32 and the exterior surface of the mixing shaft 34
froth, the metal bearing sand and the gangue from one
another in a rapid and economically feasible manner.
65 and the lower portion of the vessel 14. The end 4t]! is also
provided with a receiving chamber 48 which communi
It is a further object of this invention to provide an
cates directly with the bottom of the vessel 14.
ore concentrator by means of which the maximum num
The bottom of the vessel 14 is provided with a generally
ber of metallic particles are “Wetted” by the ?otation
conical protrusion 59 which is axially aligned with the
reagent, permitting maximum possible metallic com
cylinder 32. By this construction ?uid ?owing
pound recovery.
from the mixing cylinder 32 into the vessel 14 is urged
It is a further object of this invention to provide an
to follow the ?ow path represented by the arrows 51.
ore concentrator especially adapted to permit the forma
The slurry feed pipe 28 is provided with a gland 52
encircling the top of the mixing cylinder 32 permitting
thereby relative motion between the feed pipe 28 and the
mixing cylinder 32. The mixing shaft 34 protrudes above
the feed pipe 28 and is journalled in a bearing 54 housed
therein. The top of the mixing shaft 34‘ is connected to
the water line is controlled by the valve 114 thus assuring
an accurate control of the discharge of the froth col
In addition to accurately separating out the froth, means
are provided to individually separate sand and gangue
into separate components. In order to achieve such sep
aration, certain theoretical considerations must be taken
the air feed pipe 36, relative motion between the mixing
shaft and the air feed pipe being permitted by a gland 56.
into account. It can be shown that when a vessel such as
The mixing shaft 34 is hollow throughout its length pro
a cylinder is partially ?lled with water and rotated about
viding, in cooperation with the air feed pipe 30, an air 10 its vertical axis at a predetermined angular velocity, the
channel 58. Between the feed pipe ‘28 and the feed pipe
surface of the water will assume the shape of a paraboloid.
30 is a mixing shaft drive pulley 60 which is powered by
It may be shown that the equation for the paraboloid thus
a suitable source (not shown) and by means of which the
formed is as follows:
mixing shaft 34 may be rotated with respect to the mixing
cylinder 32. The air feed pipe 39 is provided with an air 15
control valve 62 which permits accurate, control of the
where H is the height of a particular point of the curve
volume of air introduced into the air channel 58. The
above the vertex of the paraboloid, r is the displacement
mixing shaft 34 is provided with a plurality of openings
of the point from the axis of the vertex, W is the angular
64 and a plurality of mixing blades 66. By this construc
tion, when slurry is fed through the feed pipe 28 and air 20 velocity, and g is the acceleration due to gravity.
It will be apparent from this equation that the cross
through the feed pipe 30, the air and slurry are mixed
sectional shape of the water surface in a rotating con
within the mixing chamber 32 and thoroughly agitated by
tainer will be a function of the angular speed of rotation.
the mixing blades 66.
For a given quantity of water in, for example, a cylindri
As will be more fully explained hereinafter, the mix
ture of air and slurry introduced into the vessel 14 may be 25 cal container, an increase in angular velocity increases
the height attained by the water in the container.
considered as a separable mixture of metal bearing froth,
This is illustrated in FIG. 4 wherein 3 parabolas are
water, gangue and un?oated metallic particles, or sand.
plotted utilizing the above formula for angular velocities
Means are provided to individually separate the froth,
of 60, 90, and 120 revolutions per minute, respectively.
sand and gangue into separate components.
For a submerged body rotating in the liquid mass ‘be
As will be shown later, the froth migrates to the surface 30
tween the curves 2—0—7 and 3—0-—6 certain buoyant
of the slurry. Removal of the froth is accomplished by
forces are at work. Assume in FIG. 4 that 116 represents
a plurality of skimmer assemblies as at 68. Each skim
a bubble. There are two forces acting on this bubble,
mer assembly includes a skimmer 70 mounted on a skim
one vertically and one horizontally. The force acting
mer bearing 72 which is slidably mounted on the mixing
cylinder 32. The skimmer 70 is provided with a skimmer 35 vertically is equal to W(H6—H5)dA. The horizontal
force acting on the bubble which tends to move the bubble
blade 74 which is formed so as to parallel the surface of
the water in the vessel 14. The skimmer blade 74 is pro
to the left, as shown in FIG. 4, is equal to W(H4—-H3)dA.
In the above equations W represents the angular velocity,
vided with a froth de?ecting chute 76 formed integrally
dA the cross sectional area of an incremental prism of
therewith, said chute communicating with a froth dis
charge conduit 78. The conduit 78 terminates in a froth 40 the bubble parallel to the force referred to, and H-3,
launder 80 encircling the vessel 14 into which the froth
H-4, H-5, and H-6 represent the relative heights shown
in FIG. 4.
carried by the conduit ‘78 is discharged. Suitable means
are provided to remove the froth from the launder 80.
It will be apparent from an examination of FIG. 4
In order to accurately adjust the skimmer blades 74
that the second buoyant force tending to move the bubble
with respect to the water surface indicated at 82, the skim 45 to the left, as shown in FIG. 4, is considerably greater
than the vertical buoyant force.
mer assemblies are each provided with elevator control
means 84. Encircling the upper part of the mixing cylin
The horizontal force depends on the slope of the para
der 32 are a plurality of elevator gears 86. An elevator
bola for the difference in pressure head, while the vertical
bracket 88 threadedly engages the elevator gears 86 and I
force depends on a difference in head equal to the diam~
the ‘bracket 88 is restrained from turning relative to the 50 eter of the bubble. The horizontal buoyant force may
mixing cylinder 32 by elevator bracket retaining slide 90
be thus increased by increasing the angular velocity of the
which engages a pin 92 ?xed to the cylinder 32. Depend
ing from each of the elevator brackets 88 are three skim
mer elevator rods 94, each elevator rod being connected
to an individual skimmer bearing. Each of the elevator 55
vessel which increases the slope of the parabolic curve
describing the cross section of the surface of the water
while at the same time this increase in velocity increases
the difference in the pressure heads acting on the left and
right sides of the bubble.
gears 86 is provided with an elevator motor 96 having a
worm gear 98 engaging the gear 86. Each of the motors
From these considerations it will be apparent that for
96 may be individually controlled by suitable electric
a bubble of air lighter than the surrounding media, the
switches indicated at 100. The elevator‘ gears 86 which
forces will tend to move the bubble horizontally to the
are free to turn on the cylinder 32 raise or lower the in 60 surface of the ?uid. This tendency permits a rapid ac
dividual elevator brackets 88 which in turn raise or lower
cumulation of froth at the surface where the Skimmers
the individual skimmer assemblies 68.
immediately remove it. However, for bodies which are
The skimmer 70 is free to rotate in the: bearings 72 and
heavier than the media surrounding it, that is the gangue
in operation are rotated in a direction opposite the direc
and sand, different considerations must be applied.
tion of rotation of the Vessel 14. This rotation is accom 65 Referring again to FIG. 4, assume that the vessel 14 is in
plished by a turning skimmer motor 102 which drives a
cross section generally identical to the curve 2-0—7 rep
turning shaft 104. The turning shaft 104. is provided
resented by the number 118 and that this vessel is being
with a plurality of gears 106 which engage a geared por
tion 108 of the skimmers 70. By this construction each
rotated at 90 revolutions per minute and has su?icient
water so that the surface thereof describes in cross sec
of the skimmers may be rotated with respect to the water
tion the curve 3—-0-6 represented by 120. Consider
surface 82 and may be positioned vertically therewith.
now a small particle of rock 122 resting on the side of
In order to assure continual ?ow of froth through the
discharge conduit 78 the mixing cylinder 32 carries a
water line 11% which has a discharge line 112 adjacent the
the vessel 14 and being held there by the centrifugal force
resulting from the rotation of the vessel. Vector 124
represents the centrifugal force applied to the particle 122
froth de?ector chute 76. The volume of water through 75 in magnitude and direction. Vector 126 represents the
component of the vector 124, normal to the tangent of
sand launder 1661 and the gangue launder 162. By this
construction the mixture is discharged from the vessel 14
the vessel wall at its point of contact. Vector 128 repre
sents the resultant of vectors 124 and 126. Vector 128
is thus parallel to the tangent and indicates that the forces
working on the particle 122 cause it to travel upward
along the side of the vessel.
It will be obvious that there are other forces which
in three separate portions, that portion proceeding up the
channel 154) through the over?ow launder assembly 166
and that portion proceeding up the channel 152 through
the sand launder 160 and the gangue launder 162.
Means are provided by which the size of the particles
might be considered, such as friction, but that these forces
being discharged through the sand launder 160- and the
will be insigni?cant in comparison to the forces discussed.
gangue launder 162 may be externally controlled. Each
Now referring again to FIG. 1, if the vessel 14 is ro 10 of the assemblies 160 and 162 include an encircling plate
tated at such a speed so as to establish the water surface
168 as par-t of the peripheral extremity of the vessel 14.
82, from the above considerations it will be apparent that
This plate 168 contains a plurality of ori?ces 170 through
the froth will move to the surface and be collected by
which ?uid may pass. Encircling the plate 168 is a
the Skimmers. Since slurry is being continuously intro
movable port ring 172. The port ring is provided with a
duced into the vessel from the bottom, it must discharge 15 plurality of openings 174 capable of axially coinciding
at a substantially constant rate from the top. While the
with the ori?ces 170-. The upper edge of the ring 172 is
slurry is moving upward, the particles heavier than water
geared to mesh with a driving gear 176. The driving
move outward toward the shell of the vessel, as explained
gear 176 is driven by a shaft 178 passing through the
above. Of course the larger the particle the more rapid
ba?le plate 140, the outer baf?e plate 154 and journalled
the rate of outward migration, since it will be apparent 20 within a bearing 188 carried by the vessel cover 132.
that the centrifugal forces are a function of the mass of
the particles. The rate of ?ow of the slurry decreases
gradually toward the top of the vessel 14 because, as is
The shaft 178 is connected to a bell crank 182 which is
in turn pinned to the piston rod 184 of a hydraulic cylin
der 186. The hydraulic cylinder 186 is powered by suit
able hydraulical lines which are connected to suitable
apparent vfrom an examination of FIG. 4, the cross sec
tional area of the water body is increased. At the same 25 hydraulic gland lines 190 carried by the mixing cylinder
time the centrifugal force being applied to particles with
32. The hydraulic lines are provided with conventional
valvirrg suitable for controlling such a hydraulic system.
Since the assemblies 160 and 162 may be independently
controlled, the volume of water passing through the sepa
136 increasing substantially the effective radius. Secured 30 rate ori?ces may be accurately controlled. Thus, if it is
to the walls of the mixing cylinder 32 is a vessel cover
known that the material passing up the vessel 14 contains
in the water body increases since the radius of the vessel
is increased.
Near its top the vessel wall is ?ared outwardly as at
132 which is curved outwardly and upwardly to form a
space between the peripheral edge 134 of the vessel 14
a large percentage of gangue and only a small percentage
of ore bearing sand, the sand launder 160 may be com
and the peripheral edge 136 of the cover 132. Between
pletely closed and the gangue discharged through the
the cover 132 and the walls of the vessel 14 is suspended 35 gangue launder assembly 162. Encircling the individual
the ba?ie assembly 16. The ba?ie assembly 16 includes
launders 160, 162, and 166, are ?uid receiving chutes
a ba?ie plate 140, one side of which is secured to the
192 which carry the material discharged from the respec
vessel 14 by an open web 142, the other side of which
tive launders.
is secured to the cover 132 by the web 144. The lower
In the operation of the device thus described the vessel
edge 146 of the plate 140 is contoured generally to con 10 14 is rotated at a preselected angular velocity. For the
form to the opposing wall of the vessel 14 while the op
vessel shown in FIG. 1 the angular velocity is 90 revolu
posite wall 148 is contoured to parallel the peripheral
tions per minute and the shape of the vessel in cross sec
edge 136 of the cover 132.
tion conforms generally to the curve 118 in FIG. 4. The
At the juncture of the lower edge 146 and the opposite
mixture of ?otation reagent, water, ?nely ground particles
wall 148 the baffle plate 140 divides the rising water body 45 of ore, sand and gangue are introduced into the slurry
into two portions, one of which ?ows into the channel
‘feed pipe 28. The hollow mixing shaft 34 is rotated so
150 formed between the opposite wall 148 and the periph
as to agitate the incoming slurry by suitable operation of
eral edge 136, the second of which ?ows into the channel
the drive pulley 60. The skimmer assemblies 68 are
152 formed between the peripheral edge 134 of the ves
positioned to conform to the water surface 82 by suit
sel 14 and the lower edge 146 of the baf?e plate 140.
50 able activation of the elevator motors 96 through the
The material moving into the channel 150 comprises
motor switches 193. The skimmer motor 162 is started
principally water, unemulsi?ed ?otation reagent, small
by throwing the skimmer switch 194 which causes the
quantities of very ?ne rock and some froth which has
skimmer assemblies to rotate in a direction opposite of
not been removed by the skimmers 70. That portion of
the direction of the rotation of the vessel 14. As the
the mixture which passes into the channel 152‘ consists 55 ?uid falls through the mixing cylinder 32, ‘air is intro
essentially of Water, the heavier sand and gangue and
duced into the system through the air feed pipe 30. The
some moderate to ?ne particles. This mixture is forced
slurry, as it falls down the mixing cylinder 32, is thor
to ?ow to the outer extremity of the upper portion of the
oughly agitated by the mixing blade 66 and aerated by
vessel 14 where, because of the sudden increase in the
air passing through the openings 64. The slurry enters
effective radius of the vessel 14 the centrifugal forces
the vessel by Way of the receiving chamber 48 and
are increased markedly.
proceeds to ?ll the vessel, the water surface conforming
At the outer extremity of the channel 152 a further
generally to the simulated water surface 82. The skim
division is made. Secured to the peripheral edge 134 of
mers 76 remove the froth which migrates to the surface
the vessel 14, and as the part of the baffle assembly 16,
82, the froth being discharged through the conduits '78
is a generally U-shaped outer ba?le plate 154. The baf?e 65 and into the launder 86. If the froth is heavy, water is
plate 140 is provided with a projecting tongue 156 which
passed through the discharge lines 112 to facilitate re
forms in cooperation with the outer baf?e plate 154 a gen
moval of the froth. Since the operation is continuous, the
erally S-shaped ?ow path for the mixture. As material
removal of froth is continuous.
proceeds up the channel 152 it enters into a precipitation
As the individual segments of ?uid pass up the vessel
chamber 158 and the heaviest particles are forced by the 70
are intercepted by the ba?ie assembly 16. The sand
rotating forces toward the sand launder assembly 160,
and gangue follow the channel 152 while the ?ne parti
while the water and ?ner particles flow around the tongue
cles, water, and un?occulated ?otation reagent pass up
156 and up to the gangue launder assembly .162. The
the channel 156. The material passing up the channel
outer bai?e plate 154 is secured to the body of the ba?ie
plate 140 by a web 164 and is further positioned by the 75 150 is discharged through the over?ow launder 166.
Depending on the size of the particles and the percent
age of gangue ‘as compared to sand, the sand launder
assembly 160 and gangue launder assembly 162 are
adjusted to provide ?ow paths leading to the ?uid receiv
ing chutes 192 by suitable activation of‘ the bell crank
182. The material discharged through the sand launder
160, which accumulates in the precipitation chamber 158,
may then be separated and reground for recycling, while
the material discharged through the gangue launder 162
said skimmer blades with respect to said surface; means
carried by said vessel for rotating said skimmer assem
blies in a direction opposed to that of the vessel; a vessel
cover carried by said member, said cover cooperating
with said ?ared wall to form a space therebetween; a
ba?ie assembly positioned between said ?ared Wall and
said cover to divide said space into a plurality of chan
nels; a sand launder assembly and a gangue launder as
sembly communicating with one of said channels, said
may be discarded.
IO launder assemblies each having a plurality of openings
therein communicating with the exterior of said vessel and
It will be apparent that other ‘means may be provided
means for independently controlling the size of said open
to control the size of the openings through which the
sand and gangue are discharged. For example, FIG. 5
2. A hydrodynamic ore concentrator for separating ore
shows a modi?cation of the system previously described,
bearing froth, sand and gangue in an aqueous mixture
As shown in FIG. 5, the ori?ces 170 may be provided
comprising: a frame; a vessel adapted to receive said mix
with a valve assembly 196. The valve assembly 196 in
ture mounted on said frame; said vessel being generally
cludes a valve bonnet 198 ?xed to a valve stem 200. A
parabolic ‘in axial cross section and having an outwardly
second valve bonnet 202 is slidably mounted on the valve
?ared wall at the top thereof; power means for rotating
stem 200. The valve stem slides in a valve guide 204‘.
Encircling the valve stem 200 is‘ a compression spring 206 20 said vessel at a predetermined constant speed to form a
mixture surface within said vessel, said surface being gen
which is seated on one side against the valve bonnet 198,
erally parabolic in axial cross section; an operation con
and on the other against a pin and washer 208.
trol member carried by said frame and suspended Within
A rocker arm 210 bisects the spring 206 and is slidabl-y
said vessel; a plurality ‘of skimmer assemblies carried by
mounted on the valve stem 200. The rocker arm 210 is
connected to a rod 212 which in turn is connected to cam
wheel 214.
The cam Wheel 214 may be rotated by a motor (not
shown) which drives the spur gear 216. The cam wheel
is further provided with two oppositely disposed cams
said member, said assemblies each including a skimmer
having a skimmer blade, and a froth de?ecting chute;
means carried by said member for vertically positioning
said skimmer blades with respect to said surface; means
carried by said vessel ‘for rotating said skimmer assem
220 which engage cam followers 222. The cam wheel 30 blies in a direction opposed to that of the vessel; a vessel
cover carried bywsaid member, said cover cooperating with
214- is driven at a constant speed and the valve bonnets
oscillate in accordance with the cams and cam followers.
said ?ared wall to form a space therebetween, a ba?ie
assembly positioned between said ?ared wall and said
The valve bonnet 198 is normally seated against the out
cover to divide said space into a plurality of channels;
within the chamber 224 and through the action of the rod 35 an over?ow launder communicating with one of said
channels; a sand launder assembly and a gangue launder
212 which is controlled by the cam, the bonnet 198 closes
assembly communicating with the second of said channels,
oif the interior of the ori?ce while the bonnet 202, mov
each of said launder assemblies including an encircling
ing from the seat, permits the accumulated sand to be
side of the ori?ce .170.
Sand or gangue accumulates
plate having a plurality of ori?ces therethrough and a
As soon as the cam followers pass the cams, the bonnet 40 relatively movable port ring having a plurality of open
ings spaced to- be axially aligned with said ori?ces, said
198 once again seals the exterior of the ori?ce and per
openings and ori?ces cooperating to form a'comrnunicat
ing path between the interior and exterior of- said vessel;
and means for moving said port ring relative to said plate
to vary the size of said communicating path.
sand or gangue to accumulate in the chamber 224.
The speed with which this discharge can be made will be
controlled by the speed at which the cam wheel is rotated.
Having fully described my invention, it is to be under
stood that I do not wish to be limited to the details set
forth, but my invention is of the full scope of the ap
pended claims.
References Cited in the ?le of this patent
I claim:
1. A hydrodynamic ore concentrator for separating ore 50
bearing froth, sand and gangue in an aqueous mixture
comprising: a frame; a vessel'adapted to receive said mix
ture mounted on said frame; said vessel being generally
parabolic in axial cross section and having an outwardly
?ared wall at the top thereof; power means for rotating 55
said vessel at a predetermined constant speed to form
a mixture surface ‘within said vessel, said surface being
generally parabolic in axial cross section; an operation
control member carried by said frame and suspended with
in said vessel; a plurality of skimmer assemblies carried 60
by said member, said assemblies each including a skim
Seymour _____________ __ Aug. 22,
Raasloif ______________ __ May 1,
Raaslo?f ______________ __ Nov. 5,
St. Pierre _______ __,_____ Dec. 26,
King ____; ___________ __ Oct. 25,
Jones _____ ___ _________ .._ Apr. 5,
Gale ____ ____________ .. Aug. 18,
Dunham _.____ _________ __ Mar. 25,
Wells ________________ __ Feb. 1,
, Jones ____________ __,___ Mar. 15,
rner having a skimmer blade, and a froth de?ecting chute;
of 1932
means carried by said member for vertically positioning
Australia _____________ __ Aug. 8, 1933
Australia ____________ _.. June 24, 1938
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