Improvements in Mills or Machines for Grinding and Amalgamating Gold, Silver, and other Ores or Hard Substances.
Year: 1891

page_text: Date of Application, 4th Feb., 1891
Complete Specification Left, 29th May, 1891-Accepted, 18th July, 1891
PROVISIONAL SPECIFICATION.
Improvements in Mills or Machines for Grinding and Amalgamating
Gold, Silver, and other Ores or Hard Substances.
I, GEORGE FRASER of Auckland in the Colony of New Zealand, Engineer, do
hereby declare the nature of this invention to be as follows:-
My invention refers to improvements in mills or machines for grinding and
amalgamating gold, silver, and other ores or hard substances wherein there is a
continuous feed and corresponding discharge all as hereafter described.
The machine or mill is composed of a body or frame, centrally in which
revolves a shaft to which a muller or muller carrier is keyed, the shaft is
driven through bevel gearing and rigger or pulleys at base from any prime mover.
The muller carrier comes down over and conforms to the body or frame and so
forming a sort of sleeve thereon. To the lower end of the muller frame the muller
is bolted which latter corresponds approximately in shape with the bottom of the
mill. The upper outer edge of the muller carries a ring or shoe which is removable
and on this ring there are rollers each mounted and carried by separate spindles
and these rollers revolve against a removable wearing ring round the lower sides of
the mill bottom which latter is preferably set at a corresponding angle to that of
the axes on which the rollers revolve. The mill bottom is surrounded all round
with top sides. The position of the muller with regard to the base of the basin is
adjusted by means of handles at top on a screw spindle working on the vertical
muller shaft and whereby the muller can be raised or lowered as required. There
is a central overflow round the muller carrier formed by a conical outer frame and
vertical inner frame having a cone shaped pan above and surrounding the vertical
inner frame at top for regulating the overflow, the upper portion of the central
overflow leading to a basin from which there is an outlet pipe for carrying away the
overflow to settlers or concentrators, if such are required, and in the basin there is
an inclined plane for guiding the required fall to the outlet pipe.
The level of the overflow is or may be adjusted by screws above same for
regulating the height or position of the cone or tray. There is a pipe at base of
mill communicating with a cup for admitting or drawing off the quicksilver used at
any required time during the working of the mill and for squeezing amalgam from
it or for retorting the silver and returning it to the mill.
The mode of operation is as follows:-
Quicksilver is put into bottom of mill through the cup and pipe. The muller is
raised about two inches off the bottom of the mill by means of the screw at top.
The mill is then half filled with water and set in motion (for a mill five feet in
diameter the muller revolves at from sixty to eighty revolutions per minute).
The ore is then fed by regular feeding being first roughly crushed either by
ordinary stamps or stamper battery or by a stone breaker or by any other suitable
machine so as to pass through a half inch mesh, and may be fed from any of the
above named machines or otherwise. The ore and water are introduced near the
outer edge of mill over the rollers.
The centrifugal force from the revolving of the muller keeps the rollers hard up
against the ring, the friction of which causes the whole of the rollers to revolve,
each on its own bottom, revolving and grinding on top of ring on muller, besides
grinding on the outer ring and each roller grinding the one against the other.
For a mill of the dimensions above stated the ore is fed in at the rate of from
five to eight hundredweight per hour and a quantity of water in proportion to the
nature of the ore under treatment. Through the revolving of the muller and the
separate revolving of each of the rollers, there is a complete circulation of

page_text: the particles amongst the grinding surfaces, until the gold and silver are entirely
freed. By the centrifugal force of the muller, the heavy portions of contents
of mill are thrown out to its periphery and the lighter portion of contents are
consequently in centre of mill where the silent overflow is applied. Then again the
height of overflow is placed at considerable distance from the grinding surfaces
which gives a further separation by gravitation. By feeding of ore and water at
periphery of mill displacement takes place at centre by discharge through the
silent overflow." By the above means a complete separation of the particles
is made, or again in further explanation, the conical outer cylinder which cuts
off all commotion from the contents of outer portion of mill while the vertical
cylinder cuts off all commotion caused by the friction of the central upright part
of muller; the contents of the annular space between the two cylinders remaining
in a state of quiet, so that as the mill is fed with ore and water, the overflow
carries away only particles of light specific gravity while gold and silver of
heavy specific gravity go to the bottom of mill and are there amalgamated with the
quicksilver.
The quicksilver containing the amalgam is taken from the mill through cups and
pipes.
The advantages are:-
A complete crusher and amalgamator in itself, crushing from half inch mesh to
the finest pulp.
The silent discharge or overflow carries away only matter of light specific
gravity, while gold and silver (of greater specific gravity) is retained in the mill
and amalgamates with the quicksilver. Does away with the necessity of gratings
or screens, copper plate, tables, rifles, blankets and berdans.
Reduces loss of silver to a minimum.
Reduces low grade ore at a profit.
This machine is of simplest application in setting down, being self contained
can be set to do work on less outlay and time of any machine pertaining to do
its work.
Can increase present stamper battery work, by adopting rough crushing then
pass direct through these mills for finish and amalgamation with the result of being
more perfect and profitable than by battery alone.
Dated this 4th day of February 1891.
GEORGE FRASER.
By Brewer & Son,
Agents.
COMPLETE SPECIFICATION.
Improvements in Mills or Machines for Grinding and Amalgamating
Gold, Silver, and other Ores or Hard Substances.
I, GEORGE FRASER of Auckland in the Colony of New Zealand, Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:—
My invention refers to improvements in mills or machines for grinding and
amalgamating gold, silver and other ores or hard substances wherein there is a
continuous feed and corresponding discharge all as hereafter described.
The invention will be best understood by describing same with reference to the
accompanying drawings.
Fig. 1 is a sectional elevation and Fig. 2 a plan of my improved grinding and
amalgamating mill or machine constructed according to my invention.
The machine or mill is composed of a .body or frame A centrally .in which
revolves a shaft G to, which a muller carrier B is keyed,.the shaft G.is driven
through bevel gearing H and rigger or pulley at base from any prime mover.

page_text: The muller carrier B comes down over and conforms to the body or frame of the
machine and so forming a sort of sleeve thereon. To the lower end of the muller
frame the muller B₁ is bolted, which latter corresponds approximately in shape
with the bottom A. of the mill. The upper outer edge of the muller carries a ring
or shoe E which is removable, and on this ring there are rollers C each mounted
and carried by separate spindles and these rollers C revolve against a removable
wearing ring D round the lower sides of the mill bottom which latter is preferably
set at a corresponding angle, as shown, to that of the axes on which the rollers
revolve. The mill bottom A is surmounted all round with top sides F. The
position of the muller with regard to the base of the basin is adjusted by means of
handles I at top on a screw spindle I¹ working on the vertical muller shaft G and
whereby the muller can be raised or lowered as required. There is a central
overflow round the muller carrier B formed by a conical outer frame P and
vertical inner frame Q having a cone-shaped pan W above and surrounding the
vertical inner frame Q at top for regulating the overflow, the upper portion of the
central overflow leading to a basin R from which there is an outlet pipe S for carrying
away the overflow to settlers or concentrators if such are required, and in the
basin R. there is an inclined plane T for giving the required fall to the outlet pipe.
The level of the overflow is or may be adjusted by screws J J above same for
regulating the height or position of the tray R and by screws X X for the cone W.
There is a pipe at the base of the mill communicating with a cup Y for admitting
or drawing off the quicksilver used, at any required time during the working of the
mill and for squeezing amalgam from it or for retorting the silver and returning it
to the mill. V V are distance pieces for holding in position the central overflow
formed by the rings PQ and it is by this central overflow that the particles of
light specific gravity find their way to the tray or basin R as hereafter described,
so to say, silently and quietly, and hence it may be called a "silent overflow."
The mode of operation is as follows:
Quicksilver is put into the bottom of mill through the cup and pipe. The
muller is raised about two inches off. the bottom of the mill by means of the screw
at top 1', operated by hand wheel I. The mill is then half filled with water and
set in motion (for a mill five feet in diameter the muller revolves at from sixty to
eighty revolutions per minute). The ore is then fed by regular feeding, being first
roughly crushed either by ordinary stamps or stamper battery or by a stone
breaker or by any other suitable machine, so as to pass through a half inch mesh,
and may be fed from any of the above named machines or otherwise. The ore and
water are introduced near the outer edge of mill over the rollers.
The centrifugal force from the revolving of the muller B', keeps the rollers hard
up against the ring D the friction of which causes all the rollers to revolve, each
on its own bottom or axis revolving and grinding on top of ring E on the muller B³,
besides grinding on the outer ring D and each roller grinding the one against the
other.
For a mill of the dimensions above stated the ore is fed in at the rate of from
five to eight cwt. per hour and a quantity of water in proportion to the nature of
the ore under treatment. Through the revolving of the muller B' and the separate
revolving of each of the rollers C, there is a complete circulation of the particles
amongst the grinding surfaces until the gold and silver or other metal is entirely
freed. By the centrifugal force of, the muller B₁, the heavy portions of contents
of mill are thrown out to its periphery and the lighter portions of contents are
consequently in centre of mill where the silent overflow is applied; then again the
height of overflow being at considerable distance from the grinding surfaces gives
a further separation by gravitation. By feeding of ore and water at periphery of
mill displacement takes place at centre by discharge through the "silent overflow"
as previously described and shown in the drawing Figure 1.
By the above means a complete separation of the particles is made, or again in
further explanation, the conical outer cylinder P which cuts off all commotion
from the contents of outer portion of mill while the vertical cylinder Q cuts off*

page_text: all commotion caused by the friction of the centre upright part of muller or muller
carrier B the contents of the annular space between the two cylinders remaining
in a state of quiet, so that as the mill is fed with ore and water the overflow
carries away only particles of light specific gravity while gold and silver of
heavy specific gravity go to the bottom of mill and are there then amalgamated
with the quicksilver.
The quicksilver containing the amalgam is taken from the mill through cup and
pipe Y Y Y Fig. 1.
The advantages are:
A complete crusher and amalgamator in itself crushing from half inch mesh to
the finest pulp.
The silent discharge or overflow carries away only matter of light specific
gravity, while gold and silver (of greater specific gravity) are retained in the mill
and amalgamate with the quicksilver. This machine does away with the
necessity of the employment of gratings or screens, copper plate tables, "rifles,"
blankets" and "berdans."
Reduces loss of silver to a minimum.
Reduces low grade ore at a profit.
This machine is of simplest application in setting down, being self contained, can
be set to do work on less outlay and time of any machine pertaining to do its
work.
Can increase present stamper battery work by adopting rough crushing the
material then being passed direct through these mills for finish and amalgamation,
with the results being more perfect and profitable than by battery alone.
I do not confine myself absolutely to the details of construction shown and
described although I have found the arrangement shown to answer well in practice:
some modifications might however be made without departing from the essential
features of the invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. A continuous grinder having a continuous feeding of ore or tailings, or concen-
trates or other hard substances with a continuous discharge the latter composed of
the cylinders or cone P and Q surrounded by the basin K at top with outlet pipe S
and the cone W together forming a silent overflow, as before described and shown.
in drawings Figs. 1 and 2.
2. The application of a silent overflow substantially as set forth.
3. The application to such machines of a cup and pipes for introducing and.
drawing off the quicksilver as applied to this machine and substantially as shown
and described with reference to Figure 1 of the accompanying drawings.
4. The improvements in mills or machines for grinding and amalgamating gold,
silver and other ores or hard substances constructed arranged and acting substan-
tially as hereinbefore described and illustrated with reference to the accompanying
drawings.
Dad 20th do 1001
GEORGE FRASER..
By Brewer & Son,
Agents.