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Патент USA US2129874

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Sept E3, Mw»
.1. Ross
Filed April 8, 1937
2 Sheets-Sheet l ‘
Filed April 8, 1957
.2 sheets-sneak
qïaän f H 055
Patented Sept. 13, 1938
John Ross, Custer, S. Dak.
Application April 8, 1937, Serial No. 135,775
3 Claims.
This invention relates to concentrators and
IB is a hopper or bin 24 having a discharge pipe
trating gold sands.
The general object of the invention is to pro
25 discharging into the hopper 23 and provided
with a shut-off gate 26. Surrounding the feed
tion including a concentrating tubular element
through which the gold containing the sand is
blown, the bottom of the concentrator being pro
vided with riffles so that the heavier materials
10 will fall to the bottom of the concentrating tube
while the lighter` materials, such as sand and
gravel will be blown out of the concentrator tube
at the end thereof.
Another object is to provide means whereby
15 the material being concentrated may be heated
before being discharged into the concentrating
tube, and another object is to provide means for
regulating the flow of materials to the concen
trating tube.
A further object is to» provide means whereby
the concentrate may be readily removed from
the concentrating tube when necessary.
Other objects will appear in the course of the
following description.
My invention is illustrated in the accompany
ing drawings wherein:
Figure l is a side elevation of a dry concen
trator constructed in accordance with my in
Figure 2 is an enlarged section on the line 2_2
of Figure 1.
Figure 3 is an enlarged vertical section through
the feeding mechanism and a portion of the
Disposed at any desired distance above the pipe
particularly to a dry concentrator for concen
5 vide a concentrator of a Very simple construc
(Cl. 209-477)
concentrating tube.
Referring to these drawings, I0 designates a
concentrating tubular member which may have
any desired diameter and which is supported
adjacent its forward and rear ends or at any
suitable points by supporting brackets II. The
40 tube is embraced by a band I2 extending from
one supporting bracket, the band being split and
held clamped upon the tube by the bolt I3.
Preferably the forward end of the tube IIJ is
screw-threaded for the attachment, if desired, of
a pipe coupling I4. The rear end of the tube
I0 is operatively connected to a fan or blower
casing l5 of any suitable or usual construction
having therein the fan I6 which is illustrated as
being driven by a belt or sprocket Il from a
50 motor I8, preferably an internal combustion
The tube I D is formed in two sections con
nected by a four-way pipe fitting I9. The down
wardly discharging branch of this pipe fitting
55 is closed by a removable plug 20.
Inserted in
the upwardly extending branch of this> pipe fit
ting I9 is a pipe reducing bushing 2l. Extend
ing downward through this bushing and verti
cally adjustable therein- is a feed tube 22, the
60 upper end of which terminates ín a hopper 23.
tube 22 is a sleeve 2'I which may be connected
by a pipe 28 to the exhaust from the motor I8
so that the heated products of combustion from
this motor may be discharged into this sleeve 2l
and surround that portion of the feed pipe 22 just
above the bushing 2|.
Disposed at intervals along the bottom of the
tube l0 are the forwardly and upwardly inclined
riffles 29, each riffle being approximately semi
circular in form, as illustrated. As illustrated.
the tube I il is formed with a plurality of diagonal
kerfs 30 into which the rifñes 29 are inserted.
These riilles are preferably one-third as high as
the inside diameter of the tube and slant toward
the discharge end of the tube.
While I do not wish to be limited to this, yet 20
preferably hard rubber riffles are used as these
will wear longer than steel riiiles. When, how
ever, the sand or gravel is moist, the steel riflies
work the best as the material slides over them
easier. These riiiies are spaced from 4” to 6”
apart, according to the size of the tube.
The rifñes are inserted in the kerfs 3B and
after the rifñe is put in place, the walls of the
kerf are slightly battered with a hammer so that
they overhang the riiiie slightly and this will 30
prevent the rili‘le from falling out while the shoul
ders or corners 3I prevent the riflies from slipping
The feed tube 22 is one-third as large in diam
eter as the concentrating tube I0. The blast of
air must be strong enough to keep sand and
gravel moving and this, of course, is regulated
either by proper valves or by controlling the
engine speed. The forward end of the tube I0
is supported slightly higher than the feed end of
the tube I0 and I find that l" to the foot gives
the proper angle. This permits the washing out
of the concentrating tube when the concentrat
ing operation is finished.
To clean out the concentrating tube, the
gate 26 is first closed and the blower is run until
the feed tube and feed hopper are entirely empty.
Then the bolt I3 of the clamp I2 is loosened.
This permits the forward section of the concen
trating tube to be rotated within the fitting I9
and given a one-half turn.
The riiiies are then
at the top of the concentrating tube and by
tapping the tube with a hammer, all the concen
trates will drop to the bottom of the tube or
onto the smooth side of the inverted tube. 'I’hen 55
a suitable receptacle is placed beneath the plug
20 and the plug removed. By pouring a pail or
two of water into the discharge end of the
tube Il), the water will ñow rearward and wash
all the concentrates back an-d they will come 60
out through the lower opening of the four-Way
pipe fitting and be discharged into the recepta
cle. The plug 20 should be left out until all the
water has drained out of the tube before start
ing up again.
By screwing the feed tube 22 up or down
through the reducing bushing 2l, the feed may
The gravel that travels through the concentrator
must be screened through a %” mesh screen
so that the blower can properly handle it. Of
course, it is to be understood that the screened
gravel is discharged into the bin or hopper 24
and from there it passes through the feed spout
into the feed tube hopper and thence into the
be regulated. By screwing the feed tube up, the feed tube and into the concentrator. There the
feed will be increased and will be decreased by ì blower blows it through the concentrating tube
10 screwing the feed tube down.
Of course, where
the gravel is damp, the feed must be slowed up
somewhat and while the moisture does not inter
fere with proper separation, yet I have made
provision to apply a little heat around the feed
tube, as before described, without any additional
cost to the operator.
It is to be noted that the feed pipe 25 extends
straight downward from the bin or hopper 24 and
that the pipe 22 also extends straight downward.
20 This is necessary Where this concentrator is be
ing used for placer sands and gravel because
such sand or gravel is very likely to be damp.
This dampness does not occur where ore has to
be ground up for concentration, but it does occur
where this concentrator is used, as it is particu
larly designed to be used for placer mining. If
the feed tube or any other feeding member were
inclined even at a steep angle, there is liability
of the sands, because of their moisture, sticking
to the inclined surface and clogging. This is not
the case, however, where the feed tube is verti
cal. Furthermore, I have provided a heating
means, namely, the spaced sleeve 21, for driving
olf any latent moisture which may still remain
in the sand.
It is also an absolute necessity in an appa
ratus of this kind that the feed should be capa
ble of being regulated and this is secured by the
adjustment of the feed tube 22 nearer to or
further from the bottom of the concentrating
pipe. If the feeding means is not capable of
adjustment, then the machine will either be over
loaded or run empty. The tube 22 will feed the
sand down into the concentrating tube no faster
than the blower carries the sand away. Further
more, with this construction, should the blower
stop from some cause, the sand will stop feeding
into the tube, in other words, it will build up
beneath the lower end of the tube and as it can
not pass laterally from the tube, it will stop all
feed from the tube.
By placing the blower l5 at the rear end of
the concentrating tube lll and placing the feed in
front of the blower, I prevent the blower from
being scored or injured by the ñne particles of
and over the riñles.
Inasmuch as the gold is
much heavier than the sand and gravel, it will
settle to the bottom of the concentrating tube
while the sand and gravel will be blown out. As
before stated, the discharge end of the concen
trating tube IS is provided with a coupling I4 s0 15
that the concentrating tube may be extended, if
necessary, by connecting another piece of tubing
having, of course, the riflies 29 therein.
Where there is a good deal of fine or flour gold
in the sand and gravel together with coarse gold 20
or nuggets larger than %" or larger than the
reticulations of the screen, it is advisable to use
a larger screen and use two concentrators on one
machine side by side of the same size and design.
Then the undersized material which has passed 25
through the screen is again screened and this
ñne material is run through one concentrator
and the coarser material through the other.
rline blast of air that acts upon the ñne material
must be reduced in strength while the blast of 30
air that carries away the coarser material may
be increased. By doing this, all the ñne and
all the coarse gold can be saved. Obviously
where a gang of these machines are being used,
all the blowers may be operated from one shaft 35
driven by one motor.
What is claimed isi
1. A dry concentrator of the character de
scribed, including a four-way pipe fitting, a tubu
lar concentrator section rotatably engaged with
the forward end of the pipe fitting and having a
series of riffles on its bottom, a second pipe sec
tion connected to the rear end of the pipe fitting,
a blower communicating with the last named
pipe section, a cleanout plug vdisposed at the
lower end of the pipe section, a pipe reducing
bushing in the upper end of the four-way pipe
section, a feed tube extending through the bush
ing and vertically adjustable therein, and means
for regulatably discharging sand and gravel into 50
said hopper.
2. A dry concentrator of the character de
scribed, including a concentrating tube having
noted that the tube lll forward of the feed tube 22
a series of forwardly inclined bañles disposed at
spaced distances in the bottom of the tube, means 55
for rotatably supporting the tube whereby it may
be turned through a half-circle, a blower dis
charging into the rear end of the tube, a feed
pipe discharging into the rear end of the tube,
and a cleanout opening at the rear end of the
is unobstructed except by the relatively shallow
tube, the concentrating tube being upwardly in
riffles in the bottom of the tube.
clined towards its forward end whereby when
the concentrating tube is inverted and the clean
out opening is opened, the concentrate will fall to
the bottom of the concentrating tube and may be (lo
washed out of the cleanout opening.
3. In a dry concentrator of the character de
scribed, a concentrating tube, the bottom of the
tube having a series of kerfs cut therein and
slanting toward the forward end of the tube, and 70
baflies inserted and held in place in said kerfs.
sand which would be the case were a suction fan
used for drawing the sand and gravel through the
concentrating tube. Furthermore, a suction fan
has much less power than a blower. It will be
Thus there is
nothing which will impede the free movement of
'the sand and gravel and lighter material along
~ the tube, and there is nothing which will tend
to disturb the gold or heavier material which
has fallen into the spaces between the riiiles.
This concentrator can be built in different
sizes, from a hand-operated machine up to a size
that will handle a large amount of sand and
70 gravel. I have found that it will work in con
nection with any kind of gravel screening plant.
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