IMPROVEMENTS IN MILLS FOR GRINDING AND PULVERIZING MINERAL OR OTHER SUBSTANCES
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by Allan Craig at the Office of
the Commissioners of Patents, with his Petition, on the 8th April
1870.
I, ALLAN CRAIG, of 12, May Terrace, Mount Florida, in the County
of Renfrew, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN MILLS FOR GRINDING AND PULVERIZING MINERAL OR OTHER
SUBSTANCES," to be as follows:-
One part of this Invention relates to improvements in the construction
and arrangement of mills for grinding and pulverizing mineral and other
substances, wherein a horizontal stone or metal grinder is arranged to
rotate with its under surface in close proximity to an under stationary
stone or grinding surface, the latter resting in a pan or being surrounded
by a raised rim to retain or confine the mineral or other substances to
be ground or pulverized within a limited space. Heretofore the pan or
supporting surface for the bottom stone or grinding surface has been
formed with a flat bottom, and it has been usual to steady the vertical
shaft or axis for driving the upper rotating stone or grinder by means
of a bush or centre fixed in the bottom stationary stone or grinder.

page_text: According to this part of my improvements I cast or form the bush
or collar for steadying the vertical driving shaft as part of the pan or
bed upon which the lower stone or grinder rests, the bush or collar
rising, by preference, two or three inches above the upper surface of
the lower stone or grinder, by which arrangement mineral or other
substances, when required, may be conveniently ground with water or
other fluids, and by this means be prevented from flowing into the journals,
bearings, or other working parts of the mill. This part of my improve-
ments is also applicable to the pans or beds of edge rollers for grinding
or pulverizing mineral or other substances.
According to another part of my improvements I cast metal grinding
surfaces for grinding minerals or other substances with grooves of
considerable depth, whereby such metal grinding surfaces are prevented
from getting smooth until they are worn out. I fill the grooves of the
bottom grinder with cement or other suitable substance to within a
quarter of an inch or thereabouts of the top. The grooves of the upper
grinder may also be partly filled up if desired.
According to another part of my improvements I support the upper
rotating grinding surface upon the driver by means of adjusting screws,
which pass through screw sockets in projections upon the inner cir-
cumference of the upper grinder, such projections also serving as guides
for the driver to enter between and thus actuate the upper grinding
surface when motion is communicated to the central axis. As the
grinding surfaces wear away the screws can be so adjusted as to bring
the grinding surfaces into proper contact again. By this improved
arrangement and construction of the metal grinders the grinding surface.
of the upper runner and that of the lower stationary grinder are of
equal area,
Another part of my improvements has for its object improved mcaus
of raising or lowering the upper rotating stone or grinder in order
to adjust its position accurately, when required, to that of the lower
grinding surface. For this purpose the step in which the foot of the
vertical driving shaft revolves is fixed upon a horizontal lever, one end
of which is capable of moving on a pin joint attached to the frame of
the mill. The other end of the lever is supported upon a transverse
lever, one end of which is connected to a rod which passes up through
the pan or bed plate outside of the stationary grinding surface. Upon

page_text: the end of the rod there is a screw nut, by which means the transverse
lever and with it the lever which supports the central driving axis can
be raised and lowered sufficiently to accurately adjust the grinding surface
of the upper runner to that of the lower stationary grinding surface.
The materials to be ground are fed into the mill in the ordinary
manner.