IM- PROVED MACHINERY FOR SEPARATING SUBSTANCES OF DIFFERENT SPECIFIC GRAVITIES
Year: 1863

page_text: LETTERS PATENT to Henry Holcroft, of Rue de la Grandière, Tours,
in the Empire of France, Civil Engineer, for the Invention of "IM-
PROVED MACHINERY FOR SEPARATING SUBSTANCES OF DIFFERENT SPECIFIC
GRAVITIES."
Sealed the 30th June 1863, and dated the 21st January 1863.
PROVISIONAL SPECIFICATION left by the said Henry Holcroft at the
Office of the Commissioners of Patents, with his Petition, on the 21st
January 1863.
I, HENRY HOLCROFT, of Rue de la Grandière, Tours, in the Empire of
France, Civil Engineer, do hereby declare the nature of the said Invention
for "IMPROVED MACHINERY FOR SEPARATING SUBSTANCES OF DIFFERENT SPECIFIC
GRAVITIES," to be as follows:-
This Invention relates to a novel arrangement of automatic machinery
whereby crushed ores or mixtures of granular and other substances supplied
thereto may be assorted or separated according to their specific gravities.
The machine I propose to use in conjunction either with a head or stream
of water, or of compressed air, or other gaseous body, according to the
substances to be operated upon.
It consists of a circular vessel within the walls of which an annular chamber
is formed. Supposing it be desired to operate upon crushed ores I bring this

page_text: chamber into communication with a head of water or connect it with a force
pump. The inner surface of the walls of the vessel are composed of curved
plates, which overlap the one the other, and thereby form passages nearly
equal in length to the depth of the vessel for the escape of the water from the
annular chamber into the body of the vessel.
Affixed to this vessel and arranged concentrically therewith is a cylinder open
at both extremities and fitted at its lower edge with a broad flange that reaches
near to the walls of the vessel. The upper end of the cylinder rises any
convenient distance above the edge or lip of the vessel. Over the vessel is
placed a hollow cone open at top and bottom and of such dimensions that when
bearing upon the vessel its lower edge will project beyond the edge or lip
thereof. This cone is free to slide on vertical guides, but it has a tendency to
keep in contact with the vessel by its own weight or by the pressure of springs
upon the guiding lugs with which the cone is provided. Down the central
cylinder the ground ore or other material intended to be operated upon is
discharged by preference in a continuous stream, while water is admitted as
above intimated to the annular chamber. As the pressure of the water is
maintained it will escape from the chamber in thin streams into the vessel
through the openings before mentioned. The effect of the streams thus
escaping from under the overlapping edges of the curved plates will be
that the streams will take a whirling motion and meeting the descending
pulverized material, they will carry it upwards and discharge the lighter
particles over the top edge of the cone.
The heavier particles will however lodge against the inclined sides of
the cone, and as they accumulate and are still pressed by the whirling
stream against the cone, they will force the cone upwards and thereby
open a passage for their discharge between the cone and the lip of the
vessel. The decrease in pressure will permit the cone to move towards its
former position.
When adapting the machine to the cleaning of grain it will merely be
requisite to substitute compressed air or gases for the water and to partially
close the conical cover so as to prevent the too rapid escape of the air or
gas forced into the machine.
An obvious modification of the above described machine is to adapt to the
vessel a loose bottom which is kept in place by a counterweight or its
equivalent. As therefore the material to be separated from the light
particles that are carried away by the flow of water accumulates on the
bottom of the vessel the loose bottom will be depressed and allow of the

page_text: discharge of the deposit. When this is effected it will rise again to its
place and the operation of washing out the light particles will proceed as
before.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Holcroft in the Great Seal Patent Office on the 21st
July 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
HOLCROFT, of Rue de la Grandière, Tours, in the Empire of France, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of January, in the year of our Lord
One thousand eight hundred and sixty-three, in the twenty-sixth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Henry Holcroft, Her special license that I, the said Henry Holcroft,
my executors, administrators, and assigns, or such others as I, the said
Henry Holcroft, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVED MACHINERY FOR SEPARATING SUBSTANCES OF DIFFERENT SPECIFIC
GRAVITIES," upon the condition (amongst others) that I, the said Henry
Holcroft, by an instrument in writing under my hand and seal, should par-
ticularly describe and ascertain the nature of the said Invention, and in
what manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Henry Holcroft, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the Drawing hereunto annexed,
and to the letters and figures marked thereon (that is to say) :-
This Invention relates to a novel construction of automatic machinery
whereby crushed ores or mixtures of granular and other substances supplied
thereto may be assorted or separated according to their specific gravities.

page_text: The machine which admits of many modifications in its constructive features
I use in conjunction either with a head or stream of water or other fluid, or of
compressed air or other gaseous body according to the nature of the substances'
to be operated upon.
The principle of action however of the machine, whatever may be the
modifications in the details of its construction will in all cases be the same,
the object of the Invention being to obtain by the action of a vortex (into
which the substances to be assorted are thrown) a separation according to
their specific gravities of the substances under treatment and their deposition
in different positions in the vortex vessel from whence they may be discharged
automatically into separate receptacles.
In the accompanying Drawing Fig. 1 represents in sectional elevation
a machine constructed according to this Invention for assorting automatically
on the vortex principle substances of different specific gravity..
It may be described as consisting of a circular vessel a, a, between the
inner and outer walls of which a chamber 6 is formed, which chamber,
supposing it to be desired to operate upon crushed ores, is brought into
communication with a head of water or connected with a force pump.
The inner walls of the vessel I have found by experiment it is best to
form of a segmental shape as shewn, and these walls I construct of curved
plates c, c, which overlap the one the other, and thereby form a series of
radial passages. These passages I fill with curved strips which are pierced
to permit of jets of water issuing from the chamber into the interior or
body of the vessel, and thereby creating a vortex in the vessel.
Affixed to this vessel and arranged concentrically therewith is a cylinder d
open at both extremities and fitted at its lower edge with a broad flange that
reaches near to the walls of the vessel. This cylinder is intended to act as á
shute for guiding the substances to be assorted down to the centre of the
vessel and retaiuing it for a time under the action of the vortex.
The upper end of the cylinder rises any convenient distance above the
edge or lip of the vessel a, b, c, and over the vessel I place a hollow cone e
open at top and bottom, and of such dimensions that when bearing upon
the vessel its lower edge will project beyond the edge or lip thereof. This
cone forms in fact a contracted continuation of the vessel a, b, c. It
is free to slide on vertical guides f, f, projecting from the base g of
the machine, which base in this instance is dish-shaped to receive one
portion of the discharged assorted material. The cone e has a tendency to
keep in contact with the vessel a, b, c, which supports it by its own weight

page_text: assisted by the pressure of springs upon the guiding lugs with which the cone
is provided.
The Drawing shews this cone e as constructed with a water jacket
after the manner of the vessel a, b, c, for the purpose of keeping up the
whirl of the water in the compound vessel, but this water jacket is not
essential. When used it is to be coupled with the water chamber 6 by means
of a flexible pipe or pipes which will allow of a vertical movement of the
apparatus. Down the central cylinder the ground ore or other material
to be operated upon is discharged by preference in a continuous streami
while water is admitted as above intimated to the water chambers. As the
supply of water is maintained the water will escape in streams or jets,
into the vessel through the openings before mentioned. The effect of the
streams thus escaping will be that a whirling motion will be imparted
to the water which meeting the descending pulverized material will drive
it towards the periphery of the vessel and cause it to accumulate in layers
according to the specific gravity of the particles. The lighter particles will
by the force of the current be carried upward and discharged over the top
edge of the cone while the heavier particles will lodge against the inclined
sides of the cone. As these accumulate, and are still pressed by the
whirling stream against the cone, they will force the cone and the vessel
apart, and a passage will thereby be opened for the discharge of the assorted
granules between the cone and the lip of the vessel. The decrease in
pressure consequent on the discharge of the granules will permit of the cone
again assuming its former position.
Fig. 2 shews in sectional elevation, and Fig. 3 in sectional plan view a
modification of this vortex machine, in which instead of the detached
conical continuation of the vessel a, b, c, the inner wall of the vessel
is continued upwards without a break or separation, openings being made
therein at the proper level for the discharge of the lighter portion of
the assorted granules into a trough h formed by the outer wall of the
vessel. There is also a central discharge pipe i for discharging these lighter
particles which are received into the dished base plate g. A series of
shutes are provided at the periphery of the vessel (one only being
shewn in the Drawing) for the discharge of the heaviest granules as
they aceumulate in the bottom of the vessel. These shutes are severally
closed by a valve 1, carried by a swivel crank arm m which has its fulerum
on the side of the vortex vessel. Surrounding the vessel is a circular
frame n carried by standards n' from the base plate g, its object being
to arrest the arms m, as the vessel sinks by reason of the increasing weight

page_text: of the accumulating assorted material contained therein, and thereby to
open the valves and permit of the discharge of the granules. In this
instance it will be seen that the whole of the vortex vessel is borne up
by the coiled springs o, and that it slides upon vertical guide rods o¹, projecting
from the base plate g.
The mode of constructing the inner wall of the vortex vessel will be readily
understood by reference to Fig. 4 which represents a developed cylindrical
section of the bottom of the vessel taken in the dotted circle of Fig. 3.
Water at a pressure is supplied to the chamber 6 through the opening b¹.
When using a central discharge pipe i it is advisable to employ the
conical shield p for preventing the granulated substance to be assorted
from falling directly through the discharge pipe as it is fed to the vessel.
As the mixture of granular substances of varying specific gravity are fed
to the machine it will slide down the cone and falling into the vortex
will be carried round and round in the stream. The granules, supposing
them all to be heavier than water will be whirled towards the largest
diameter of the vortex vessel. The heaviest body of the mixture will
fall to the bottom of the vessel and revolve in and settle into the space
indicated by the red color, or thereabouts, the exact position depending
on the pressure maintained in the chamber b, b. The lighter bodies will
take the position indicated by the yellow colour; but as soon as the layer
of the light bodies accumulates sufficiently to reach the edge of the central
discharge pipe i certain of those bodies will flow with the liquid out of
the apparatus. The curvature of the revolving mass will bring the water
and the bodies circulating in it up to the level of the apertures or perforations
in the periphery of the vortex vessel, and a portion of the light bodies
will then flow through these apertures and discharging with the liquid
into the gutter h will find egress out of the apparatus through the aperture h¹;
as the flow of bodies entering the apparatus is continuous the layer of
the heaviest body will go on increasing until its weight overcoming the
resistance of the coiled springs o, o, will cause the depression of the vortex
Ivessel and the movement of the valves from the mouth of the shutes.
Free egress will thus be given to the heavy layer until the diminution
of the load in the vessel is sufficient to enable it to rise under the reacting
power of the springs o, o, when it will again assume its former position.
The vortex may be produced by jets as shewn, or by jets placed anywhere
in the interior of the vortex vessel, or by longitudinal fissures covered over
with guide plates to direct the gushing liquid.
Figures 5 and 6, shew in sectional elevation and sectional plan a further

page_text: modification of the vortex vessel, the object being to explain the adaptation
of the Invention to the separation of beavy metallic bodies, such as
gold, from their gangues or metalliferous sand, in which operation it is
desirable to use mercury as well as water to form the vortex. Below
the vessel a, b, c, is a chamber q, q, for containing mercury, and that
chamber is connected by means of vertical tubes r, r, with the interior of the
vessel. These tubes r allow of mercury being injected at a certain stage
of the operation from the chamber 9 to the interior of the vessel in the form
of jets or streams, and to prevent the tubes from acting as obstructions to the
vortex they are each provided with a wedge-shaped hood to deflect the water
from the pipes. The auriferous crushed ore or sand glides down the cone p
in measured charges and at regular intervals of time and falls on to a layer
of mercury occupying the bottom of the vortex vessel a, b, c, the level
of which layer is shown by the dotted line 1, 1, the space occupied by a
measured charge of the auriferous ore is contained between the dotted lines 1, 1,
and 2, 2. A vortex of water disposed exactly as before described and acting
precisely in the same way gives a rotatory motion to the layer of mercury,
that liquid carrying easily round with it the measured charge of auriferous
ore or sand which for the most part will float on the surface of the mercury.
During this first operation the only bodies issuing out of the apparatus with
the water are the earthy matters in suspension and such light substances as
are easily borne away with the current.
After a certain lapse of time (sufficient to allow all the component parts
of the revolving mass to take their natural position in the vortex) a cock s
in connection with the chamber q is opened, and water under pressure (or
it may be an elastic fluid such as hot air) is admitted into the chamber 9.
The water pressing upon the mercury forces out a charge equal in volume
to the measured charge of bodies revolving in the vortex vessel. The
mercury passing up the elbow tubes r, r, issues in jets into the vortex vessel,
thereby increasing the rapidity of the vortex. At the same time the level
of the revolving mass gradually rises and causes the bodies floating on
its surface to flow slowly out of the apparatus through the discharge pipe i.
When the whole charge of mercury is driven out of the chamber 9, into
the vortex vessel, that vessel will still contain a portion of the measured
charge of auriferous ore operated upon and that portion occupying the
space included between the lines 2, 2, and 3, 3, will of necessity retain the
heaviest body of the mixture. After the expulsion of the mercury from
the chamber the cocks is shut. to cut off the water under pressure

page_text: from the chamber, and the cock t (see Fig. 6) is opened. The water
filling the chamber 9 will now escape and allow the mercury to return
by its own gravity into the chamber, another measured charge of auriferous
ore may then be supplied to the vortex vessel as before. This operation
is to be repeated until the mercury becomes saturated with gold, at which time
the mercury is to be drawn off by means of a cock r¹. The mercury may
then be treated in the usual way for obtaining the gold in the metallic
state.
An obvious modification in the construction of the vortex vessel by
which the automatic discharge of the assorted granules will be ensured is
to adapt to the vessel a loose bottom which is kept in place by a counter-
weight or its equivalent. This is shewn in sectional elevation at Fig. 7
in which u is a hollow piston forming the loose bottom of the vessel and
capable of sliding vertically in a cylindrical continuation of the vessel.
The upper part of this cylindrical portion is pierced with a ring of holes
v which as the piston descends by reason of the increasing weight of the
accumulating assorted substances will permit the discharge of the lowest
layer of assorted granules from the vortex vessel. A water jacket b surrounds
this vessel the inner wall of which is formed after the manner shewn at
Fig. 4, and the upper face of the hollow piston or moving bottom u is formed
in a similar manner. The water jacket 6 and the chamber in the piston
are connected by a flexible pipe w so that water under pressure may be
supplied alike to both chambers to produce the vortex. This piston is made
sufficiently watertight by elastic packing, as a gutta percha hose x, x,
inflated by a liquid under pressure.
In this as in the first described arrange-
ment the lighter portion of the granular substances fed into the vessel
down the cylinder d is carried over the upper edge of the vessel while
the heavy body accumulates on the piston u, u. The piston thus loaded is
counterbalanced in every position by the weighted lever y and the chain *,
part of which chain rests on the ground and is gradnally raised up from it
as the piston moves down by the accumulation of the heavy substance.
When the piston descends below the level of the apertures v, v, a portion of
the heavy layer issues out of the vessel and after the egress of that portion the
piston will rise again above the level of the apertures.
Having now set forth the nature of my Invention of "Improved Machinery
for Separating Sulistances of Different Specific Gravities," and explained
the manner of adapting the same to varied circumstances, I wish it to be
understood that under the above in part recited Letters Patent, I claim the

page_text: means above described for effecting (through the medium of a vortex) the
separation of substances of different specific gravities.
In witness whereof, I, the said Henry Holcroft, have hereunto set
my hand and seal, the Twenty-first day of July, in the year of our
Lord One thousand eight hundred and sixty-three.
Witness,
J. W. MOFFATT,
66, Chancery Lane.
H. HOLCROFT. (Ls.)