IMPROVEMENTS IN ATTRITION MILLS
Year: 1882

page_text: LETTERS PATENT to Thomas Leggett Sturtevant a Citizen of the United
States residing at Framingham in the County of Middlesex and State of
Massachusetts for an Invention of "IMPROVEMENTS IN ATTRITION MILLS,'
COMPLETE SPECIFICATION filed by the said Thomas Leggett Sturtevant
at the Office of the Commissioners of Patents on the 1st December 1882.
THOMAS LEGGETT STURTEVANT, a citizen of the United States residing at
Framingham in the County of Middlesex and State of Massachusetts, "IMPROVE-
MENTS IN ATTRITION MILLS,"
This invention relates to a class of attrition mills for grinding phosphates,
ores, grain and other materials, of a class in which the material to be ground
furnishes its own self renewing grinding surfaces, in other words, in which
the operation of grinding is effected simply by attrition between the particles
of the material. The objects of these improvements are first, to enable the
circular edge most exposed to wear of the rotary head to be renewed, as wear
ensues, which I accomplish by the employment of a movable or adjustable
inner or outer reinforce or lining to each head, confined in place by bolts, or
other means which enable it to be adjusted in position within or outside of the
head, as occasion requires. A second object of my improvements is to provide
means for effectually and rapidly removing the flour or powder, as fast as it forms
thereby facilitating the grinding operation by preventing clogging of the unground
portions of the material, this feature in my improvements being effected by the
employment in combination with the rotary head of a case or receiver for con-
taining in connection with suitable side housings the bulk of the material to be
ground, which case revolves upon its supports, and is formed with cells or
depressions into which the powdered material falls, and by which such flour is
raised to a point above the mass of unground material, and allowed to drop and
is then removed by a suction fan or other means, the rotary receiver or case

page_text: constituting a continuous elevator to receive and raise the powder from the
unground material to a point where it may be readily removed.
The drawings accompanying this specification represent in Fig. 1, a side
elevation, in Fig. 2 a vertical and longitudinal section and in Figure, 3, a cross-
section of an attrition mill containing my improvements. Figure, 4, is a modification
of the elevator to be explained.
In these drawings A represents a circular head or disc recessed or chambered in
front, and at rear secured to one end of a horizontal rotary shaft B mounted in
suitable standards C C¹ and provided with pulleys A', B¹, the latter being the
driven. One edge of the head A revolves in close proximity to the rear side of an
upright flat standard or housing a, erected upon the floor of the apartment near
standard C, this standard or housing a having a twin standard a¹ erected parallel
to it on the side away from standard C, the intermediate space being occupied
by the rotary receiver hereinbefore referred to. A circular opening b is created in
the standard a opposite the head A, this opening being of equal diameter with the
outer circumference of such head.
To provide means for compensating for wear about the edge of the head A,
which is within opening b or about the outer margin of the opening b, I employ an
adjustable lining c which is a tube closely filling the bore or chamber of such
head; this lining being secured in place within the head by bolts c', as shown in
the drawings, or by other means, which will enable such lining to be adjusted in
position and fed outward, as occasion requires. The outer end of the lining c
protrudes beyond the margin of the bore of the head, and extends into and closely
fills the aperture 6 in the housing a. In the operation of mills of this construction
about the only wear ensuing upon the parts is at the inner margin or mouth of
the chamber in the rotary head; or in the present instance, the margin of the
opening b, which is in contact, to a greater or less extent with some portions of the
unground material in the receiver. The lining enables the worn surface to be
renewed, as occasion requires, and in practice I prefer to construct such lining of
chilled cast-iron, or other very hard material to resist effects of abrasion, as long as
possible.
D in the accompanying drawings represents a circular ring, composed of a flat
band, such ring being situated uprightly between the housings a a¹ and maintained'
in position thereat by horizontal anti-friction rolls d d etc, pivoted between such
housings, and distributed about, and bearing upon the circumference of the ring
plate D and constituting bearings to permit the latter to rotate. The ring plate D
is put in rotary motion (preferably in a direction opposite to that of the head A)
by an annular toothed rack e, formed upon its circumference, which rack engages
with and is driven by a pinion f secured to the outer end of a horizontal shaft g,
mounted in bearings in the lower part of the standard C, this shaft g being put
in motion by a belt, gear or toothed wheel from the pulley A', or by gearing or
other mechanical means.
Within the inner periphery of the ring plate D, I create by any suitable means,
a series of cells, depressions, or enclosures ii etc, as shown in Figures 2 and 3, of the
drawings, and at the upper part of each housing a a', I provide openings ; or k as
shown in said Figures. The opening j is the filling mouth of the mill, through
which the unground material is supplied, while the opening k provides an outlet
for the powder raised by the ring plate D, this outlet k being connected with a
suction fan, or other means for removing such powder.
In the use of this mill, the material to be ground is supplied to the interior of
the ring plate D or more strictly speaking, to the receiver bounded by such plate
on one hand, and the housings a a¹ on the other, as fast as is requisite to supply
the demand.
A portion of the material to be ground fills the chamber of the head A and
rotates with it to provide the requisite moving grinding surface, while the
remainder in the receiver under the action of the rotary ring plate tumbles about

page_text: to a greater or less extent, the result being that between the two forces the materials
are continually being reduced to powder.
A certain proportion of the lightest portion of the powder will be drawn directly
upward through the receiver, and discharged by way of the outlet without
assistance from the rotary ring plate D, but certain portions of this powder will
tend to settle to the lower part and bottom of the receiver, and clog the unground
particles of the material...
The pockets or cells, arranged as before stated, in or on the inner face of ring
plate D, receive this portion of the powder, and constantly operate to elevate and
discharge such powder through outlet k, whence it is conveyed from the mill; the
bulk of unground material generally throughout the receiver being disturbed
or stirred by the rotations of the elevator, and the separation of the flour thereby
facilitated.
In lieu of elevating the powdered material by means of the pockets in the rotary
ring plate, as explained, alternative means of effecting the same result would be to
dispense with these cells, as forming part of or secured to such ring plate, and
employ an endless band E supported upon suitable rollers and travelling about the
lower part of said ring plate, see Figure, 4; this endless band carrying a series of
buckets F, F, etc, equidistant from each other, and adapted to enter in succession
peripheral openings G etc, in the ring plate, and receive and elevate the powder
deposited in them, as they travel in and out of these openings.
In this case it would be well to employ a screen, situated above the elevator in
such position, as to receive the powder deposited upon it by the travelling buckets,
the screen being so constructed and situated with respect to the filling orifice f of
the receiver, as to return to such receiver the coarse particles in the powder,
while the fine portions of such powder pass through the screen, into a suitable
receptacle.
In addition to or in lieu of the rotary ring plate D for agitating or tumbling the
unground material in the receiver, a rotary agitator, composed of a shaft contained
centrally within the receiver, and provided with radial arms may be employed, the
shaft being rotated by a pulley and belt, or otherwise. An agitator or stirrer of
any suitable construction may be employed to effect more general disturbance of
the unground material than would be the case with the rotary ring plate.
CLAIMS:
•
1st In attrition mills the combination with the rotary head, carrying the
moving portion of the unground material, and the receiver containing the com-
paratively stationary unground portion thereof, of a movable part to such receiver
for removing the ground portions of the material substantially as set forth.
2nd The combination with the rotary head and housings, of the rotary receiver
provided upon its inner periphery with cells, ledges, or their equivalents to receive
the ground portions of the material, substantially as described.
3rd The combination with the receiver rotary head, and the adjacent housing
or wall of the receiver, of the adjustable tubular lining or outer reinforce closely
fitting the bore or periphery of the rotary head and the opening in the housing
opposite such head, substantially as explained.
4th The rotary recessed head, supported and driven by a suitable shaft in com-
bination with said shaft and the receiver, composed of the housings and the rotary
ring plate, substantially as explained.
5th The combination, with the rotary recessed head, the housings, and ring plate,
of the anti-friction rolls constituting the support of the said elevator substantially
as stated.
6th The combination of the rotary head, the receiver, and a device for stirring
or agitating the bulk of unground material in such receiver, substantially as
explained.

page_text: 7th The combination of the receiver D, with head A having removable bushing c,
whereby the edge of the head nearest said receiver may be removed and replaced
às fast as worn.
In witness whereof I the said Thomas Leggett Sturtevant have hereunto
set my hand and seal this 17th day of October 1882.
THOMAS LEGGETT STURTEVANT (L.S.)