Improvements in Grinding Mills.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Grinding Mills.
I, ALFRED GEORGE WELLS, of No. 22, Billiter Street, in the City of London,
Gentleman, do hereby declare the nature of this invention to be as follows:-
This invention has reference to improvements in grinding mills and relates
more particularly to that class used for grinding ores and similar bodies and is
designed to render the action continuous, more rapid and effective, and to reduce
the loss of mercury which has hitherto taken place in the settling pans used in
separating the metal particles.
Heretofore the ore after reduction has been discharged over the sides of the pan
by the centrifugal action imparted to the ore by the rotation of the pan, or by
charging the mill with a stated amount of ore which after reduction has been
cleared and then separated in the settling pans, the loss of mercury in the latter
being considerable.
Now according to this invention the pan is provided with a central discharge
orifice and the central portion of its base is raised so that the whole of its inner
bottom surface will be inclined. Through the central portion a vertical shaft
connected with the driving mechanism passes and revolves freely. The central
portion where it surrounds the vertical shaft is made of sufficient thickness that
one or more cores or openings extending throughout its depth can be formed in
it, through which the pulverised ore finds its way to a discharge pipe. Above
the raised central portion of the pan and keyed onto the central driving shaft
is a circular yoke, which conforms somewhat to the shape of the bottom of the pan,
and is enabled to revolve freely therein. To the outer and upper surface of the
lower portion of this yoke is attached a metal ring, the lower portion of the inner
wall of the pan having attached to it a corresponding ring, the faces of these two rings
being of such shape that they form a groove or channel in which roll metal or other
balls, by which the ore is ground or crushed. Below the grinding balls is a con-
tinuous opening formed by the space between the ring on the inner wall and the
ring on the revolving yoke and beneath this opening is a channel in the lowest
portion of the bottom of the pan, in which is placed mercury to receive the
liberated metal particles. A cylinder open at each end surrounds, and is fixed to,
the raised central portion of the pan and extends for some distance below the level
of the water in the pan, almost to the inner crown of the revolving yoke. This
cylinder acts as a shield by preventing undue agitation of the pulverised ore and
water within it, and assists in controlling the discharge and allows the heavier
particles to fall by gravity to the lower part of the pan. A brush or other suitable
contrivance is attached to the inner portion of the revolving yoke, in such a manner

page_text: that it will extend down the cylinder or shield, sufficiently to enable it to pass
immediately over the tops of the cores or openings, thus preventing accumulation
at the orifice or orifices leading to the discharge pipe.
The action is as follows:-The ore is fed into a hopper attached to the side of
the pan, whence it falls on to the rings on the revolving yoke and on the lower
portion of the inner wall of the pan, where it is ground or crushed by the balls of
steel iron or other suitable material running therein. The pulp passing through
openings in the revolving yoke and through the opening between the two rings is
forced by the fresh ore fed into the pan up the inclined surface of the bottom of
the pan until it reaches the top of the raised central portion, whence it falls
through the cores or openings to the discharge pipe, the 'comparatively still water
within the shield allowing the heavier particles to fall back by gravitation to the
lower part of the pan. The mercury containing the liberated metal particles,
is drawn off as required, by means of an iron tap or other suitable contrivance.
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COMPLETE SPECIFICATION.
Improvements in Grinding Mills.
I, ALFRED GEORGE WELLS, of 22, Billiter Street, also of 29, Cornhill, London,
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:-
This invention relates to certain improvements in or applicable to mills for
grinding auriferous and argentiferous ores and the like and extracting the metal
particles by mercury, and is designed to render the action of such mills continuous,
and more rapid and effective than hitherto, and to avoid the loss of mercury which
occurs in existing mills of the kind, in which the ore pulp is discharged over the
side of the pan by the centrifugal action imparted to the ore by the rotation of
the pan.
To this end, the invention is characterized by so constructing and arranging the
parts of the mill as to cause the ore pulp to be discharged centrally of the pan, in
lieu of peripherally thereof as hitherto, whereby loss of mercury will be pre-
vented and a more complete extraction of the metal particles will be effected.
On the accompanying drawings; Fig. 1, represents a vertical section. of the
improved mill; and Fig. 2 represents a sectional plan thereof through A-B, Fig. 1.
a, is a stationary pan, which, at its outer periphery, is adapted to support a water
tight casing, a¹, bolted thereto, as at a², and a grinding ring, a³, seated therein,
as at a³, and, at its lower portion, is formed with an annular trough, 45, serving to
contain mercury, and is fitted with a tap, a, for discharging the contents of the
trough, and, within the circumference of the trough, is formed with an upwardly
inclined bottom, a', which, at its central part, a8, rises to above the level of the
liquid contents of the pan, and below such level, is formed with central pulp.
outlets, a, which communicate with a discharge pipe, a¹0.
The upraised central part, as, of the pan, a, is also adapted, as at all, to serve
as a bearing to the upper part of a vertical shaft, b, which is mounted in a foot-

page_text: step, and can be driven by gearing; 63; from any convenient source of motive
power, and, above the bearing, all, is keyed, as at 63, to an overhanging yoke, 64,
which descends around the upraised central part, as, of the pan, approximately
conforming at its bottom part, 65, to the shape of the inclined bottom, a',,of the pan,
and, at its lower part, is adapted to support a grinding ring, 66, bolted thereto, as
at b7.
The grinding faces of the rings, a³, 66, are so shaped as to form a channel adapted
to support a series of crushing balls, c, made of steel, iron or other suitable material
and which can freely rotate in such channel; and the edges, of such rings are spaced
apart to form a continuous annular opening, d, below the crushing balls and
serving to deliver the crushed material directly to the sub-posed mercury
trough, as. The distance between the bottoms, a7, 65, of the pan, a, and yoke, 64,
may be regulated and adjusted by means of a yoke top, 68, bolted, as at 6º, to the
yoke, 64, and an adjusting screw, 610, taking its bearing on the end of the shaft, b,
and a set nut, 611.
1
Between the upraised central part, as, of the pan, and the surrounding yoke, 64,
is fitted a cylindrical shield, e, which is adjustably secured to the part, a³, by
brackets, e¹, and bolts, e2, and extends from below the water level in the pan almost
to the crown of the yoke and serves to prevent undue agitation of the ore pulp in
the vicinity of the outlets, a³, which latter are further fitted with an adjustable
shutter, a, by which the level of the overflow can be adjusted as required, so that
the discharge of the ore pulp can be efficiently controlled.
In the operation of the mill; the yoke, 64, with its grinding ring, 66, is caused, by
the means described, to rotate within the pan, a, and its grinding ring, a³, and
causes the balls, c, to roll around in the channel formed by the grinding
rings, a³, 66, with a crushing action which is peculiarly effective in pulverizing
the ore, which, fed into a hopper, a¹³, attached to the casing, a¹, falls into such
channel and under the balls, c. The pulp passes by the opening, d, and by other
openings, 62, in the yoke, 64, to the bottom of the pan, in the trough, a', of which
the metal particles are extracted by the mercury, while the lighter particles of
pulp float up the inclined surface of the pan bottom, until they pass away through
the outlets a, the heavier particles circulating and undergoing further crushing
treatment until sufficiently reduced. The mercury and extracted metal particles
are drawn off from the trough, a', by the tap, a6.
If required, brushes or like means may be attached to the inner side of the
yoke, 64, in position to prevent any accumulation of floating matter around the
outlets, a⁹.
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:
In mills for grinding auriferous and argentiferous ores and the like and extract-
ing the metal particles by mercury; in combination; a stationary pan adapted
at its periphery to support a water casing a feed hopper and a grinding ring, and
at its lower part formed with an annular mercury trough, and having
an upwardly inclined bottom which at its central part is cylindrical
and is formed with pulp outlets and is fitted with an adjustable shutter
serving to regulate the level of the overflow and with an adjustable shield serving
to steady and prevent undue agitation of the pulp in the vicinity of the outlets
and is also adapted to act as a bearing to a central shaft; an overhanging yoke
keyed to the shaft and descending around the upraised central part of the pan and
approximately conforming at its bottom to the shape of the inclined bottom of the
pan and adapted at its lower part to support a grinding ring, the grinding rings
of the pan and yoke being so shaped and disposed as to form a channel adapted to
support a series of crushing balls and a continuous annular opening leading to
the mercury trough of the pan; a series of crushing balls adapted to roll around
within the channel formed by such grinding rings and to be actuated by the

page_text: rotation of one of such rings; means of regulating and adjusting the distance
between the bottoms of the pan and the yoke; and means for rotating the central
shaft; as set forth.
Dated this 29th day of April. 1898.
DAY, DAVIES & HUNT,
Chartered Patent Agents,
321, High Holborn, London, W.C., Agents for the Applicant.