Improvements in Bands or Aprons for Mineral Concentrating Machines
Year: 1897

page_text: .
PROVISIONAL SPECIFICATION.
"Improvements in Bands or Aprons for Mineral Concentrating
Machines."
I, CHARLES ARTHUR ALLISON, of 52 Chancery Lane, London, in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention (which
has been communicated to me from abroad by George Johnston, Mining Engineer,
Citizen of the United States, residing in the City and County of San Francisco,
State of California), to be as follows:-
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This invention relates to bands or aprons for mineral concentrating machines,
such band or aprons being made of caoutchouc or india rubber, and the invention
consists in a particular form of the flanges or ribs at the sides of such bands,
whereby they are made symmetrical on each side of a vertical axis, parallel as to
their vertical faces; rounded on the top, and the material in the flanges being
so disposed that when the band passes over the rollers on which it is mounted,
the flow or distortion of the flanges is equal or nearly equal cach way laterally,
and consequently of half the intensity as when such flow and distortion is to one
side of the flange.
Dated this 4th day of March. 1897.
ALLISON BROS.
Agents for the Applicant.
"
Improvements in Bands or Aprons for Mineral Concentrating
Machines."
I, CHARLES ARTHUR ALLISON, of 52 Chancery Lane, London, in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention, (which
has been communicated to me from abroad by George Johnston, Mining Engineer,
A Citizen of the United States, residing in the City and County of San Francisco,
State of California), and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement:.
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My invention relates to bands employed on what are called mineral concentrating.
machines, for separating metallic sand, or concentrates, from the silicious material,
or gangue, in extracting gold.

page_text: My invention consists in so constructing the guard flanges, or ledges, at the
sides of such bands, of a symmetrical section, parallel on each side of a vertical
axis, so that distortion by flexure causes an equal, or nearly equal, flow of the
elastic substance each way from the centre, thus diminishes its degree or intensity
in the same proportion.
The object of my invention is to add to the endurance of such concentrator bands
by avoiding to a great extent the distortion and consequent fracture of the flanges
by passing over drums or rollers, such fracture causing, in practice, a limit of
endurance for the bands.
Referring to the drawings:-
Fig. 1 is a diagram showing the method of mounting common concentrator
bands.
Fig. 2 is a section showing a concentrator band made according to my invention.
Fig. 3 shows diagrams to indicate the distortion of the flanges as it occurs when
the band passes over the drum on which it is mounted.
Fig. 4 shows diagrams of other forms for the flanges of concentrator bands,
wherein distortion is unequally diffused by flexure.
The process called concentration, or the selection of metallic particles from sand,
on flat moving bands agitated and supplied with water, is so well known that other
portions of the machinery will be understood without illustration. I have there-
fore confined my drawing to the band itself and the drums or rollers on which it
is mounted.
;.
:
+
These bands are commonly of india rubber, from four to six feet wide and long
enough to pass round drums as shown in Fig. 1, the depression at A being to wash
off the mineral particles that adhere to the surface.
The drums B around which the band C passes are all mounted on a vibratory
or oscillating frame, set with a slight slope towards the end D. Pulverised ore and
water are supplied at E, the band moves in the direction indicated by the arrow,
the sand and water flowing off at F, by gravity, and the concentrates or metallic
particles because of their greater weight and for other reasons, passing on over the
drum at G and lodging in the tank H as before explained.
At the sides of the bands C there are provided ledges or flanges J to prevent the
water and sand from escaping over the edges of the band and as these flanges are
by reason of their longer radius subjected to severe strain and distortion in passing
over the drums B they are liable to fracture after being some time in use and
from this fact their endurance becomes a measure of the time that a concentrator
band will last in practice.
Such distortion to be injurious need not be disposed over a large area, because
if occurring even in a narrow line, or section, it will cause the material to crack
and the fracture soon extends to the larger section.
As these flanges are commonly made, the distortion of shape is not uniform but
falls with especial intensity on particular points in the section. To avoid this I
construct the flanges J as shown in Fig. 2, parallel on the sides M, rounded on the
top and equally disposed on each side of the axis a-b, so that when strained by
passing over drums the material in the flanges flows laterally equally each way,
as indicated in Fig. 3 by the diagrams I, II, and III.
The diagram I shows the normal form of the flange, II the form when partially
strained or compressed, and III the form when in extreme compression, or when
passing the points N in Fig. 1.
In Fig. 4 is shown sections for flanges that have been made and tried for endur-
ance. In the diagrams V and VII to fold inward, the one VI to turn outward and
the one IV with a radial face on the inside and a curved face on the outside.
In all of these forms it is easy to trace out a point of extreme tension and com-
pression that promotes fracture under intermittent flexure that occurs in use. These
diagrams are introduced to assist in explaining the action of the flanges shown in
Figures 2 and 3.

page_text: 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:-
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Concentrator bands provided with ledges or flanges at their edges, flat and parallel
on their sides, rounded on top and disposed equally on each side of a vertical axis.
so that by flexure and compression the elastic material will flow equally each way
from the centre and distortion be uniformly diffused throughout the section.
Dated this 30th day of November 1897.
ALLISON BROS.
Agents for the Applicant.