Improvements in and relating to Grinding-mills.
Year: 1894

page_text: Date of Application, 20th Jan., 1894
Complete Specification Left, 8th Oct., 1894-Accepted, 10th Nov., 1894
PROVISIONAL SPECIFICATION.
Improvements in and relating to Grinding-mills.
I, ROMULUS NORWOOD, of 127 Pomeroy Street, New Cross Road, in the
County of Surrey, Manufacturer, do hereby declare the nature of this invention to
be as follows:-
My invention relates to grinding-mills and its chief object is to provide an
improved mill well adapted for the grinding and re-grinding of plaster, pigments
and the like.
In some grinding-mills as heretofore constructed, the operative surface of the
upper mill-stone has a dished or concave portion surrounded by a flat or plane
annular portion, and is arranged in combination with a lower mill-stone having its
entire operative surface flat or plane, the lower stone being rotated whilst the upper
stone remains stationary.
In making a grinding-mill according to my present invention, I construct and
arrange the upper and lower mill-stones as follows, viz. :-I make the upper mill-
stone with the usual central hole or eye, and to permit the material to be ground
to enter between the stones, I form in the upper stone a suitable number of furrows
which extend from the said hole or eye half way or about half way to the skirt of
the stone, preferably in a direction tangential to the eye, which furrows are
gradually tapered or diminished both in width and depth from the eye to the outer
ends of the said furrows; and I make the entire operative surface of the upper
stone from the said hole or eye to the skirt, flat or plane and perfectly smooth with
the exception, of the said furrows and also, if necessary, of a very slight face-
cracking to ensure the proper action of the stones upon the material. I combine
this upper mill-stone with a lower mill-stone the entire operative surface of which
is flat or plane and perfectly smooth with the exception, if necessary, of a very
slight face-cracking, the lower stone being rotated whilst the upper stone is kept
stationary.
I have found that a grinding-mill having the mill-stones thus constructed and
arranged, is very advantageous for grinding or reducing plaster, pigments and the
like to an impalpable powder.
For feeding the material to be ground into the eye of the upper stone, I employ
a suitable hopper and I combine, with the said hopper, automatic mechanism for
continuously and uniformly feeding the material from the said hopper into the eye
of the upper stone.
Dated the 20th dev of Lannon 1001
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in and relating to Grinding-mills.
I, ROMULUS NORWOOD, of 127 Pomeroy Street, New Cross Road, in the
County of Surrey, Manufacturer, 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 relates to grinding-mills and its chief object is to provide an
1 D 017

page_text: p
and the like.
wen adapted for the grinding and regrinding
Plaster, pigmenos
In some grinding-mills as heretofore constructed, the upper millstone has a
dished or concave part around the central hole or eye, which dished or concave
part is surrounded by a flat or plane annular grinding surface, and the said upper
stone is arranged in combination with a lower millstone having its entire operative
surface flat or plane, the lower stone being rotated whilst the upper stone remains
stationary.
Now I have found that, by making a grinding-mill in the manner hereinafter
described, I am enabled to dispense with a dished or concave part around the eye
of the upper stone.
In making a grinding-mill according to my present invention, I construct and
arrange the upper and lower millstones as follows, viz. :-I make the upper mill-
stone with the usual central hole or eye, and to permit the entrance between the
stones of the material to be ground, I form in the upper stone a suitable number of
furrows which extend from the said hole or eye half way or about half way to the
circumference or skirt of the stone, preferably in a direction approximately
tangential to the eye, which furrows are made of the peculiar shape hereinafter
described and I make the whole of the under surface of the upper stone from the
said hole or eye to the skirt, flat or plane and preferably smooth with the exception,
of the said furrows and also, if necessary, of a very slight face cracking to ensure
the proper action of the stones upon the material. I combine this upper millstone
with a lower millstone having the whole of its upper surface flat or plane and
perfectly smooth, with the exception, if necessary. of a very slight face-cracking,
the lower stone being arranged to be rotated whilst the upper stone is kept
stationary.
I have found that a grinding-mill having the millstones thus, constructed and
arranged is very advantageous for grinding or reducing to an impalpable powder,
plaster, pigments and the like.
For feeding the material to be ground into the eye of the upper stone, I employ
a suitable hopper and I combine with the said hopper automatic mechanism for
continuously and uniformly feeding the material from the said hopper into the
eye of the upper stone. Or I can employ other convenient devices for this
purpose.
In the accompanying drawing
Figure 1 is an underside view of one form of my improved upper millstone,
Figure 2 illustrates by means of sections on the lines a, r', x2, a³, Figure 1,
respectively, the peculiar formation of the furrows, and
Figures and 4 are similar views, illustrating another modification of my
invention.
203
The upper millstone S shown in Figure 1 is made with the usual central hole or
eye E, and with furrows f approximately tangential to the eye E. These furrows
extend from the eye E to a point rather more than half way from the said eye to
the circumference or skirt of the stone. The arrow shown in Figure 1 indicates
the direction in which the lower stone (which is not shown in the drawing) rotates
relatively to the upper stone S. The furrows fat the side or edge f¹ thereof are
of considerable depth, say about one inch deep, next the eye E, and gradually
diminish in depth to their outer ends, as clearly shown by the sections x, x¹, x²,
in Figure 2. They also diminish more abruptly in depth from the side or edge f¹
to the side or edge f2 of the furrow as clearly shown in Figure 2. As will be seen
on referring to Figure 1, they are also gradually tapered or reduced in width from
the end next the eye to the outer end of the furrow. This taper formation,
however, is not essential. If desired the said furrows may be of equal width
throughout as shown in Figures 3 and 4, their depth being gradually diminished
both longitudinally and transversely as above described with reference to Figures 1
and 2. The plane or operative surface of the stone S is preferably dressed with a
slight face-cracking as and for the purpose hereinbefore explained.
T

page_text: In constructing a grinding-mill I combine my improved upper millstone with a
rotary lower millstone having its entire upper surface flat or plane and smooth,
with the exception, if desired, of a slight face-cracking.
In the operation of this grinding-mill, the material to be ground, being fed
through the eye E of the upper stone S, easily enters the furrows and moves
outward along the same upon the surface of the lower stone, from their deeper to
their shallower ends. The lower stone, by reason of its rotary motion, gradually
conveys the material in the said furrows from their deeper edge f to their
shallower edge f, where the said material enters as required between the grinding
surfaces of the two stones. The material is thus fed very regularly or
uniformly between the said grinding surfaces without liability to choking of the
furrows.
If the lower stone is to be rotated in the reverse direction, the dress of the
upper stone must be reversed, the furrows extending tangentially to the eye, or
nearly so, in the reverse direction to that indicated in the drawing.
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 :-
First. The improved millstone constructed with the peculiarly shaped furrows,
substantially as herein before described.
Second. A grinding-mill in which the upper millstone is constructed as above
set forth and is arranged in combination with a rotary lower millstone, substantially
as and for the purpose specified.
Dated this 8th day of October 1894
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.