A. NEW AND USEFUL PROCESS OF GRINDING AND SEPARATING, AND A NEW AND USEFUL ATTRITION MILL
Year: 1882

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "A. NEW AND USEFUL PROCESS OF GRINDING AND
SEPARATING, AND A NEW AND USEFUL ATTRITION MILL." A communication
from abroad by Henry A. Duc, junior, of the City of Charlestown, State of
South Carolina, United States of America.
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 19th January 1882.
SYDNEY PITT, of Sutton, in the County of Surrey. "A NEW AND USEFUL.
PROCESS OF GRINDING AND SEPARATING, AND A NEW AND USEFUL ATTRITION
MILL." A communication from abroad by Henry A. Duc, junior, of the City of
Charlestown, State of South Carolina, United States of America.
In all those processes of grinding and separating with which I am acquainted.
and in which a current of air has been withdrawn from the grinding apparatus,
such air after performing its function in withdrawing the ground or reduced.
material has been allowed to escape, either carrying with it a considerable amount
of the finely reduced material which was thus lost, or else necessitating the employ-
ment of settling or dust rooms.
By the improvement herein described the air is constantly used over again, being
returned to the mill from which it has been withdrawn, thereby the material
which is withdrawn from the mill is constantly presented to its settling chamber
or separator until it has been deposited from the flowing current and removed from
the mill; this prevents escaping dust and also secures a greater uniformity in the
selected material, which is removed when reduced from the apparatus.
In the improved mill the material is reduced by contact and friction against
itself, as distinguished from a method of abrading or reducing the material against
a grinding surface not formed of the material itself. The mill is also provided with
an arrangement for taking up any wear which may occur in it.
That which is considered new is claimed in the claims hereto annexed.
In the Drawings similar letters refer to similar parts.

page_text: Figure 1 represents a general view in perspective, part of the apparatus being
broken away, of the mill and separating chambers; Figure 2, a horizontal section
through the mill, shewing the feed passages and plough; Figure 3, a section through
Figure 2 on the line y, y; Figure 4, a section through Figure 2 on the line x, x ;
Figure 5, a view of the pipe protecting shoe.
The mill is constructed as follows:-
A represents a revolving shell, the shape of which is shown clearly in Figure 3;
this shell is revolved upon a shaft B, and the shell is preferably so attached to this
shaft that when in operation the mass of the material is situated in a plane which
intersects the end of the shaft. By this arrangement uniformity of motion and
reduction of strain is obtained.
The shell A has a circular opening on the side opposite the supporting shaft, as
is clearly shown; through this opening the feed, air supply, and air exhaust passages
pass, as also the plough or wearing surface. A frame or casting C, supporting the
various contrivances which operate in the mill, is provided, and may be supported
in any suitable way; this frame carries a dovetailed slide Y, shown clearly in
Figure 2, which can be slid up on the slide ways and removed from the mill; this
slide contains passages for the air supply, the supply of material to be ground, and
the air exhaust, and it also supports the plough, hereinafter to be fully described.
The air returning from the separators enters the mill through the passage D opening
into the mill through openings W.
The material is fed to the mill through the passage Z, which may be provided
with a suitable hopper and with a valve to close against the external air if desired.
The reduced material is withdrawn through the passage E.
The slideway likewise supports in a suitable channel F the self feeding plough
bar G. The openings W, F, Z, and E are all located together in the bottom of the
mill. Supported upon the, and at a point where the material in the mill first
meets it, is the removable shoe H, shown clearly in Figures 4 and 5.
This shoe or hood slopes downward toward the end of the plough bar, and its
office is to compact the material to form a grinding surface against which the
rotating material may be abraded.
Next in order the plough bar G presents itself to the rotating material, and next
again is the feed opening Z, and next the exhaust opening E.
The openings Z and E are partially protected by projections on the frame work.
The plough bar G is curved so as to feed downward at right angles to the plane of
rotation of the revolving material, that is, its centre corresponds with the centre of
rotation of the revolving material. The apparatus with which this mill may be
connected in practice in order to secure a continuous operation is shown clearly in
Figure 1.
The exhaust pipe E connects with the pipe E', provided with a telescopic joint
allowing of the withdrawing of the supporting frame; this pipe E' delivers into the
selecting chamber K, which is provided with a delivery tube M. and automatic
valve b. The funnel N, provided with a delivery tube, is located in the upper part
of this chamber, and delivers at the valve c, as shown. This chamber K commu-
nicates with blower P by the pipe R, and the blower P connects at its circumference
with pipe R, delivering into the second depositing chamber L, which is provided
with a delivering pipe M', which pipe is provided with an automatic valve a, as
shown. The upper end of this depositing chamber L is provided with a cloth
bag O, which may be kept extended by cord and weight d, as shown; this balloon
or bag O allows for the escape of a certain amount of air in case of a pressure in
the chamber L greater than the pressure of the atmosphere, but sieves out any
material suspended in the air. The chamber L is provided with a pipe S at its
upper portion, which pipe has a flexible tube, preferably made of fibrous material,
allowing the passage of the air, which pipe is marked T; this tube T communicates
with a pipe D', provided with valve V, which pipe D¹ communicates with the
delivery passage D, by which the air reenters the chamber.

page_text: It will thus be observed that a continuous and substantially closed circuit is
provided for the air, which is withdrawn from the mill and which passes through
the selecting apparatuses here shown and again back into the mill.
The operation of the apparatus can now be readily understood. The chamber A
is caused to revolve at a high velocity in the direction shown by the arrow in
Figure 4 by means of the shaft B and suitable power. The material to be reduced
is fed to the mill through the feed opening Z, which may be provided with a
suitable hopper and a regulating apparatus for insuring a continuous feed if desired.
As soon as the material falls into the mill it immediately rotates with the same
velocity as the revolving shell, and it is firmly held against the periphery of this
revolving shell by centrifugal force, and it is additionally forced to rotate with it
by the radial ribs or projections J. In the rotation the material fed to the mill
passes underneath the confining and compressing shoe H and by it is compacted
against the plough bar G into a solid grinding body or surface. The material to
be abraded, which is compacted into a rotating annulus or ring within the shell, is
continually forced against the stationary material held beneath the shoe H and
circumferentially supported by the plow bar G. So much of said material as
passes beneath the plough bar G is brought under the influence of the exhaust
passing upward through the opening E, as shown by the arrows, and this exhaust
performs a selecting function upon the material passing beneath it, so as to remove
only such material as is sufficiently reduced. The size of the material to be
withdrawn can be determined by the velocity of the exhaust.
The depth to which the plough bar enters the material may be either regulated
by hand and a set screw or the bar may be allowed to automatically feed to the
required depth, its weight carrying it downward being arrested by the compacted
surface of the revolving material against which it would bring up. The feed
openings Z and exhaust openings E are likewise protected by removable shoes,
although but little wear will be experienced in those parts.
When the fan P has been put in operation the abraded material when sufficiently
reduced is drawn through the pipe E' and escapes into the selecting or depositing
chamber K. In this chamber the velocity of the air is greatly reduced owing to
the greater area of cross section of this chamber than the inlet passage, and the
largest particles which are withdrawn from the mill will fall to the bottom of this
chamber and be fed out through the delivery pipe M and valve b. In the upper
part of this chamber the funnel opening N is placed, and there being a greater area
for the passage of the air above the funnel N than through the annular opening
surrounding it a certain additional amount of reduced material will be there
deposited, which material will be of a somewhat finer grade than that passed
through the tube M. The blower P withdraws the air and its suspended reduced
material through the pipe R' and forces it downward through the pipe R, where
most of the remainder of the suspended material is deposited owing to another
reduction in the velocity of the movement of the air, and escapes through the
pipe M¹ and valve a, thence the air which has been substantially freed of the
reduced material supported in it is passed onward through the pipe S, flexible
pipe T, valve D, pipe D¹, and return opening D into the mill. By reason of the
previous material of the balloon O, aided as it may be by the previous pipe. T, no
greater pressure than the pressure of the atmosphere can exist in the pipe R and
chamber L, thereby the blower is relieved from any pressure greater than that of
the atmosphere acting against it, and a partial vacuum may be maintained in the
mill A and exhaust tubes E, E', so as to prevent the possible escape of any air and
dust into the chamber wherein the mill is contained. By means of the valve V
the amount of air to the mill and consequently the velocity of the exhaust can be
accurately determined. By means of the sliding frame Y, telescopic joint in
pipe E¹, and flexible tube T, the feed openings and plough may be readily
withdrawn from the mill. Of course other means might be devised for accom-
plishing this same result, but it has been found that those shown are simple and

page_text: •
efficient. When desired the mill feed openings and bar may be made of other
material than iron, as, for instance, some vitreous material, so as to prevent the
discoloration due to the small amount of iron which may be worn off. By making
the inner ribs J of sufficient width, so as to compress the air in the mill at its
periphery, the fan P may be dispensed with when the material is to be reduced to
a very fine degree, because then the mill would itself act as a fan, forcing the air
outward through the air delivery E'.
It is plain likewise that different forms of selecting chambers might be employed
without departing from the spirit of the Invention. I have shown two selecting
chambers and three delivery apertures for the material, but it is obvious that one
chamber and one aperture might be employed if preferred.
What I claim and desire to secure by Letters Patent is,-
The combination of a rapidly revolving vessel supported and revolved by shaft
and the stationary plough entering through the central opening and supporting a
plough adapted to engage with and abrade the revolving surface of compacted
material, said plough being supported on an exhaust tube for withdrawing the
abraded material, substantially as described.
In an attrition mill, the combination of a rapidly revolving chamber, in which a
body of the material to be abraded is formed by centrifugal force, and a stationary
plough supported near the periphery of said chamber and adapted to enter and
abrade the compacted material, and an exhaust tube through which the air is
drawn by suitable mechanism having its orifice located in immediate vicinity to
he abrading plow, so as to withdraw the abraded material as soon as it is reduced
to a sufficiently comminuted condition without retaining the same unnecessarily
within the apparatus, substantially as described.
The combination with an attrition mill of an air tube for withdrawing the air
and reduced material from the mill, a series of separating chambers, an independent
blower or exhauster connected with said tube, and a return pipe from said blower
into the mill, substantially as and for the purpose set forth.
The combination with an attrition mill of an air tube for withdrawing the air
and reduced material from the mill, a series of separating chambers, a blower or
exhauster connected with said pipe, a return pipe from said blower into the mill,
and a pervious bag for permitting the escape of air to prevent excess of pressure
in the return pipe while retaining the particles carried by the air, substantially as
set forth.
The combination in an attrition mill of a transverse plough or bar extending to
the outside of the mill, and appliances supporting the same to permit it to be
moved to or from the interior of the mill to compensate for wear at the end of the
plough bar, for the purpose specified.
The combination in a rotating shell open at one side and a curved plough bar
secured in guides in which it may be moved to carry its end to and from the inner
face of the shell, substantially as set forth.
The combination in an attrition mill of a rotating shell, a slide supporting a
plough bar, and a feed tube for delivering the material within the mill, said slide
being supported upon a frame arranged to permit the slide to be readily withdrawn
from the mill and replaced therein, substantially as set forth.
An attrition mill provided with three independent passages delivering into the
mill from the outside of the chamber, one for the exhaust of the air from the mill,
one for the return of the air so exhausted to the mill, and the other for feeding
the material to be reduced to the mill, substantially as set forth.
The combination in an attrition mill of a shoe constructed to direct the body of
material beneath it, and adapted to compress the said material against the
periphery of the mill, and a plough bar arranged across the shell at the rear of and
close to the shoe, and adapted to act against said material, substantially as set
forth.
The combination with an attrition mill of a casing containing a separating or

page_text: selecting chamber provided with an inlet and with outlets communicating with
receptacles for different grades of material, and arranged at different heights,
substantially as and for the purpose set forth.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Twelfth day of January, in the year of our Lord One
thousand eight hundred and eighty two.
AYDNEY SYMM
SYDNEY TIT.
(mo.)