IMPROVEMENTS IN PNEUMATIC MACHINERY OR APPARATUS FOR THE SEPARATION OF MINERALS AND OTHER MATERIALS OF DIFFERENT DENSITIES
Year: 1879

page_text: LETTERS PATENT to Benjamin Woolley Hart, of Garway Road, in the County
of Middlesex, for the Invention of "IMPROVEMENTS IN PNEUMATIC MACHINERY
OR APPARATUS FOR THE SEPARATION OF MINERALS AND OTHER MATERIALS
OF DIFFERENT DENSITIES."
Sealed the 12th September 1879, and dated the 1st April 1879.
PROVISIONAL SPECIFICATION left by the said Benjamin Woolley Hart
at the Office of the Commissioners of Patents on the 1st April 1879.
BENJAMIN WOOLLEY HART, of Garway Road, in the County of Middlesex.
"IMPROVEMENTS IN PNEUMATIC MACHINERY OR APPARATUS FOR THE SEPARATION
OF MINERALS AND OTHER MATERIALS OF DIFFERENT DENSITIES."
My Invention relates to improved machines or apparatus of that class in which
air is employed for the separation of associated minerals and other materials of
different densities, which machines are commonly known as air jigs or
separators.
оге
Various attempts have been heretofore made to produce an efficient machine for
the application or employment of air for the separation of associated minerals
differing in density from each other. The universal presence of air ensures a
constant and adequate supply of the same in all cases whereas the absence of a
sufficient supply of water in connection with valuable mines frequently causes
great inconvenience. Therefore the production of an efficient pneumatic jigging or
separating machine is obviously of very great importance.
But none of the machines as heretofore produced have proved satisfactory. They
have been found defective in construction, and are not economical in their working.
I have therefore devised my improved machine, in which I have avoided the
defects existing in those heretofore produced, and in which the system or method
of air or pneumatic jigging may be effected very advantageously.
My improved machine or apparatus is constructed as follows, that is to say :-It
has a box of metal, wood, or other suitable material, whose peculiar formation is an
important feature of my Invention; this box is made widest at its rear or hopper
end; its sides are continued from this rear end at right angles, and of the same
width for a short distance, and then converge or incline to meet the front, which is
very narrow.
The depth of the said box is greatest at its rear or back, and least at

page_text: its front, so that when the said box is placed on a level or horizontal surface its
back is higher than its front. The top of the said box is closed by an apron or
sieve-bed which forms an inclined plane from the back to the front of the said box.
This apron or sieve-bed is formed of wire gauze or perforated metal secured in a
suitable frame, which is fitted closely to a flange surrounding the said box. The
said box is provided at its back and sides with a vertical flange attached to the
said frame; the height of the said flange is greatest at the back, and diminishes
from near the back to the front of the said box, so that as the ore or other
material being treated in the said machine travels down the inclined plane or bed,
its lighter portions raised by the puffs of air will be discharged over the edge of
the said vertical flange while the heavier portions pass to the front of the box
which is provided with a gate so constructed and arranged that it may be raised to
discharge the heavy portions of the separated materials.
In the box below the said sieve-bed, and parallel to the same, I place a per-
forated metal plate, and below the same is a false bottom of wood or metal so
constructed that its greatest depth or thickness is at the back of the said box, and
whose upper surface inclines toward the front of the said box, parallel, or nearly so,
with the sieve-bed.
The admission of air to the said box is effected in the following manner :-
Attached to the lower central part of the back of the box is a valve chest or case
containing a valve for regulating the quantity of air admitted into the said box.
This valve is preferably formed in parts or sections arranged to slide over openings
through which the air passes to the sieve-bed. The said casing also contains
another valve which is operated to open and close intermittently to produce the
puffs of air required for jigging the material on the aforesaid sieve-bed. This puff
valve is operated by means of a lever or set of levers connected with a ratchet-
wheel which has rotary motion imparted to it by any suitable means.
Air compressed by a suitably arranged fan, air-pump, or blower passes into a
regulating receiver, and thence to the aforesaid valve-box. This regulating receiver
is provided with an escape or relief valve for discharging the compressed air when
the density thereof is in excess of that required for the treatment of the material
in the said sieve-bed. I prefer to construct this escape valve of wood or other
light material for the reason that when so constructed I can diminish the density
of the air passing to the sieve-bed more effectively and conveniently than when a
metal valve is used.
For regulating the weight on this valve, and consequently the density or pressure
in the said receiver, I employ a series of metal discs, and increase or diminish the
number of them on the said valve, according to the density required.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Benjamin Woolley Hart in the Great Seal Patent Office on the 1st
October 1879.
BENJAMIN WOOLLEY HART, of Garway Road, in the County of Middlesex.
"IMPROVEMENTS IN PNEUMATIC MACHINERY OR APPARATUS FOR THE SEPARATION
OF MINERALS AND OTHER MATERIALS OF DIFFERENT DENSITIES."
My Invention relates to improved machines or apparatus of that class in which
air is employed for the separation of associated minerals and other materials of
different densities.
Various attempts have been heretofore made to produce an efficient machine for
the application or employment of air for the separation of associated minerals
differing in density from each other. The universal presence of air ensures a
constant and adequate supply of the same in all cases, whereas when machines for
separating by water are used the absence of a sufficient supply of water in con-
nection with valuable mines frequently causes great inconvenience. Therefore the
production of an efficient pneumatic jigging or separating machine is obviously of
very great importance. But none of the machines as heretofore produced have
proved satisfactory. They have been found defective in construction, and are not
economical in their working. I have therefore devised my improved machine, in
which I have avoided the defects existing in those heretofore produced, and in
which the system or method of air or pneumatic jigging may be effected very
advantageously.
My improved machine or apparatus is illustrated in the accompanying Drawings,

page_text: prefer that this vertical flange should be flat on its inner surface and inclined or
sloping on its outer surface, as shewn in Figure 7, to ensure the proper discharge of
the mineral over the same, as hereinafter described.
It is very disadvantageous to discharge the denser mineral over a large area for
the reason that its volume is very much less than that of the gangue, so that it
spreads out very thin, and it is difficult to collect in its separated condition. For
instance, if 20 per cent. by weight of galena is in association with 80 per cent. of
quartz, galena having a specific gravity 7.5, and quartz 26, the proportion by
volume of the galena to the quartz will be only as 8 to 92. But by having the
bed in my machine contracted at the front, as above described, the heavy mineral
as it reaches the same will be collected within a narrow area and may be con-
veniently conducted into a hopper f, whence its discharge is controlled by the
adjustment of a hinged valve e', the flow of the heavy mineral into the said hopper
being regulated by a gate or flap e*.
In some instances I provide the box a below the said sieve bed b with a false
bottom of wood or metal, so constructed that its upper surface inclines towards the
front of the said box, parallel or nearly so with the sieve-bed b.
The box a is provided with a suitable hopper, as shewn at g, for receiving the
minerals to be treated and conducting them to the said box. This hopper is
preferably furnished with a pivotted or hinged plate g¹, which is adjustable by the
screw g² or by other suitable means to regulate or stop the feed.
The admission of air to the box a is effected by apparatus provided therefor in
the following manner:-Attached to the lower central part of the back of the box a
is a valve chest or case h containing a valve i which is operated to open and close
by a lever or set of levers connected with a ratchet wheel which has rotary
motion imparted to it by any suitable means. I prefer that this ratchet wheel
should be provided with four teeth, and should have a speed of one hundred
revolutions a minute, thereby producing four hundred openings and four hundred
closings of the valve, but the number of teeth may be increased or diminished and
the number of revolutions may also be increased or diminished, according to the
desired number of the movements of the valve in a given time. The said ratchet
wheel is arranged to act upon a pawl 2 on the lever ³, which is connected by a
link with the lever on the valve spindle, as shewn in Figure 4. The spring
or a weight serves to effect the return of the valve after the action of each tooth of
the wheel i¹.
Air compressed by a suitably arranged fan, air pump, or compressor at ; passes
thence to the aforesaid valve-box or chest provided with an escape or relief valve k
for discharging the compressed air when the density thereof is in excess of that
required for the treatment of the material on the said sieve-bed. I prefer to
construct this escape valve of wood or other light material for the reason that when
so constructed I can diminish the density of the air passing to the sieve-bed more
effectively and conveniently than when a metal escape-valve is used. For regu-
lating the weight on this valve and consequently the density or pressure in the
said valve box or chest I employ a series of metal discs and increase or diminish
the number of them on the said valve according to the density required. is a
pipe extending from the air-chamber and provided with a gauge m for ascertaining
the pressure in the said chamber.
In using an apparatus constructed as above described, the mineral placed in the
hopper g descends and spreads forward on the ore bed, the quantity being regulated
by the adjustable gate or plate g³. The compressed air passes through a pipe of
suitable diameter from the compressor to the valve-box, in which the air pressure
is controlled by the aforesaid escape-valve, whence it passes, as above described, to
the air-chamber and to the mineral on the sieve bed, while, by means of the said
pressure-gauge the pressure of the air within the chamber can be ascertained so
that the air therein may be maintained as nearly as possible at the proper density
to constitute a medium in which the gangue or lighter portion will be suspended or
float, while the heavier portion of the mineral rises little or not at all. The lighter

page_text: inineral carried forward from the hopper along the sieve-bed and distended by the
air passes into sections thereof, successively diminishing in area by the convergence
of the sides, and overflows the said sides which extend diagonally to its course of
travel, while the heavier mineral carried forward in like manner to the narrow
front of the bed passes therefrom at a lower level, its discharge being regulated by
the said adjustable hinged valve.
I will now explain the principle upon which the operation of my apparatus or
machine is based, and which differs from the principle on which preceding air
separating machines have been constructed.
It is an axiom in ore dressing that the most favorable condition under which
minerals differing in specific gravity are to be separated is that furnished by a
medium of such a density that the lighter mineral or gangue will float and the
heavier or valuable mineral will sink in the same.
Having brought the air to this required density the object next effected is the
maintaining of it continuously, or as nearly so as possible in that condition, that
is to say, to replenish continuously in the chamber the air escaping through the
mineral on the bed.
The escape of air which is checked as well by the volume as by the weight of
the mineral being practically taken as a constant quantity, and the replenishing
air also as a constant but uniformly varied quantity there will be slight or fractional
differences in the density of the air in the chamber and corresponding slight
fractional oscillations in the mineral on the sieve-bed, because when the valve is
opening the air-supply is reaching a maximum, and vice versa, when it is closing
the supply is reaching a minimum. In the first of these periods the gangue or
lighter portion is rising while the heavier material rises little or not at all, and in
the second the heavier portion is falling while the lighter portion falls little or not
at all. In this case when the said valve opens and closes four hundred times in a
minute, as aforesaid, there will be 800 oscillations, in each of which separation of
the minerals takes place, while when the minerals are raised in a mass by thrusts,
as in the hydraulic jigger, the separation is dependant solely on the subsequent fall
of the minerals in the ratio of their specific gravities.
The employment of the said flap-valve or other suitable valve and the con-
sequent oscillating action of the air is for the purpose of counteracting any
inaccuracy in the pressure of the air on the mineral on the sieve-bed; but in some
cases I may provide means for adjusting the said valve and its operating mechanism,
so that the said valve will remain open, in which case there will be a constantly
equal pressure without such oscillations; or for the said purpose I may construct
the machine without the said valve.
Having thus fully described my said Invention, and the manner of performing
the same, I wish it understood that I claim,-
First. The box containing the sieve-bed and constructed with its sides either
level or sloping downward from the back to the front and converging toward the
front, substantially as and for the purpose specified.
Second. The upward continuation of the said sides by the vertical flange, whose
height corresponds with the depth of the mineral on the sieve bed, and which has a
flat or nearly flat inner surface and an inclined outer surface, substantially as
described, and as shewn in Figure 7 of the Drawings, for the purpose specified.
Third. In an apparatus or machine in which air is used for the purpose specified,
the construction of the bed and its sides in such a manner that by the action of the
air the lighter portion of the mineral will be discharged over the sides of the box
while the heavier mineral is discharged at the front end of the same, substantially
as and for the purpose set forth.
Fourth. In an apparatus or machine in which air is used for the purpose
specified, the construction of the box containing the sieve-bed in such a manner
that the heavier mineral is discharged at or from a comparatively narrow
contracted opening at the front end of the same, substantially as and for the purpose
set forth.
or

page_text: Fifth. Providing the box of the said apparatus with a gauge for ascertaining the
pressure of the air in the air-chamber, substantially as set forth.
Sixth. The flap-valve or other suitable valve with a reciprocating or other motion
for admitting the air from the air-chest to the air-chamber below the sieve-bed, in
the manner and for the purpose specified.
Seventh. The relief valve so arranged and operating as to afford the means
whereby the pressure of the air in the said apparatus may be regulated, substantially
as and for the purposes specified.
Eighth. The combination of parts comprising the air-chest, the flap or other
suitable valve, the air-chamber and the sieve-bed, so constructed and arranged that
a continuous ascending current of air is supplied to the sieve-bed, uniformly varying
in pressure and producing corresponding oscillations of the mineral on the bed, for
the purpose specified.
Ninth. The combination of the sieve-bed and air-chamber with the means for
supplying without the agency of a valve a continuously ascending current of air to
the mineral on the sieve-bed, for the purpose specified.
Tenth. In combination with the sieve-bed the hopper provided with the
adjustable plate or other suitable means for the regulation of the feed and the
devices for the regulation of the discharge, substantially as specified.
Eleventh. A machine or apparatus consisting of the parts constructed and
combined as shewn in the accompanying Drawings, and operating as and for the
purposes specified.
In witness whereof, I, the said Benjamin Woolley Hart, have hereunto set
my hand and seal, this Twenty seventh day of September, in the year of
our Lord One thousand eight hundred and seventy nine.