Improvements in Millstones and in the Method of Making them.
Year: 1892

page_text: Date of Application, 27th Sept., 1892-Accepted, 29th Oct., 1892
COMPLETE SPECIFICATION.
Improvements in Millstones and in the Method of Making them.
We, THOMAS LEGGETT STURTEVANT, Gentleman, a citizen of the United
States, residing on Winthrop Street, in the Town of Framingham, County of.
Middlesex, and State of Massachusetts, U.S.A., and WILLIAM HENRY ELLIS,
Treasurer, a citizen of the United States, residing at No. 5 Lombard Street, in the
City of Boston, County of Suffolk, and State of Massachusetts, U.S.A., 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:-
Our invention relates to composite millstones made up of small, irregular lumps
of emery united by binding material.
By the use of lumps of emery, as distinguished from grains or very large blocks,
and by isolating the lumps from each other in a mass of binding material, and
distributing them throughout it, the millstone is made to have a self-renewing face,
presenting "lands" and also furrows continuous from eye to skirt for the escape of
the reduced material.
We employ as the binding material for uniting the lumps of emery a metal
melting at a comparatively low temperature.
We have attained the best results with zinc, but we do not wish to be limited to
the use of zinc, but consider as within the scope of our invention, the use of any
molten metal melting at a comparatively low temperature, as we find that, by the
use of such a metal, the heat is not so great as to injure or impair the lumps of
emery employed.
We construct the skirt of the millstone of lumps of emery and molten metal, such
as zinc, and may form the eye and the furrows in any suitable way. By the use of
metal such as zinc or lead, we can utilize their malleability as the metal, after the
stone is made, can be pounded down about the lumps or pieces of emery, should
they loosen. Metal of this character can also be changed or dressed when
necessary.
Should a block or lump of emery become separated from the stone, a new block
may be inserted in its place by first heating the metal, inserting the stone and
pouring in fresh metal, which, if it does not immediately attach itself to the body
or the stone, can be caused to join it by a soldering iron or by a gas jet, which will
melt the two surfaces and cause them to run together.
The accompanying drawings show one form of millstone in which our invention
is embodied, and also illustrate the process of forming the stone.
.
Fig. 1 is a detail view in section of a mold in which the skirt-sections are
separately formed;
Fig. 2 is a perspective view of a skirt-section and a furrow-strip;
Fig. 3 is a plan view of a millstone with one of the skirt-sections and two of the
furrow-strips separated from the others;
Fig. 4 is a plan view of the composite stone; and
Fig. 5 is a section on the line 5-5 of Fig. 4.
We will describe one specific way of carrying out our invention, but we do not
wish to limit ourselves to it, the scope and extent of our invention being designated
in the claims at the end of this Specification.
Before proceeding to a detailed description of the drawings we would say that
lumps of emery possess great advantages over all other grinding agents known.
The problem has been how to secure the lumps together by a suitable binding
material. We have tried slag, lead, antimony, lead hardened with antimony, and

page_text: cast iron, and have finally tried zinc. In the choice of metals, several things are
to be considered, such as cost, the softness or hardness, the weight of the metals
and their melting point. We give below the relative weights and melting points
of several metals.
As before remarked, the use of a metal such as cast iron, melting at a high
point, is undesirable, for the reason that it has such a harmful effect upon the
emery as to often rot it and make it crumble. Lead is too heavy and too soft.
Tin is too expensive. Zinc, so far as we have yet discovered, is the best metal to
use, for the above as well as for other reasons which might be mentioned.
We shall therefore describe zinc as the metal employed in forming our improved
millstone, but intend to claim as our invention, the use not only of zinc, but other
metals, melting at a low temperature and possessing the requisite malleability.
In carrying out our invention, we fill a mold A, of suitable shape, such as shown
in Fig. 1, with small, irregular lumps or blocks of emery, usually varying in size
from one to two inches in diameter. After the mold is thus filled with the lumps of
emery, we pour in through a suitable opening a, the molten metal, such as zinc,
until the interstices between the lumps are filled, and a segmental block, such as
shown at B, in Fig. 2, is formed.
The eye, C, of the stone, Figs. 3 and 4, may be formed of buhr stone, esopus
stone, metal or other suitable material. Between the skirt-segments B, are
interposed furrow-strips D, preferably of zinc or such metal, or they may be of
iron, stone or other suitable material. The eye, skirt-segments and furrow-strips,
when assembled, may be firmly bound together by a band or hoop E. The skirt
composed of lumps of emery and zinc may be made in any suitable way. It need
not necessarily be made in sections. The furrow-strips may be differently arranged.
Separate furrow-strips may be omitted, and suitable furrows formed in the skirt.
In a millstone constructed in accordance with our invention, the grinding
material is generally firmly embedded and grasped. When not firmly grasped, the
yielding and malleable character of the soft metal used permits of its being pounded
down about the emery, which it then securely holds. The wearing of the eye
coincidently with that of the skirt is insured, and the proper dressing of the stone
is facilitated.
The stone eye is made of a material softer than the emery of the skirt, because,
as the skirt traverses a greater distance than the eye in a given time, it does more
work and would wear more quickly unless it were made harder to resist this wear.
By our invention, these conditions are compensated and provided for, so that a
uniform wear of all parts of the stone is insured.
Should it be necessary, the stones can be cut down to compensate for any
differences of wear.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is-
1. The herein described improvement in the art of making millstones, which
consists in forming the skirt of the stone by binding together small, irregular lumps
or blocks of emery with molten metal melting at a comparatively low temperature,
and then securing the skirt to a suitable eye.
2. The herein described improvement in the art of making millstones, which
consists in forming a number of segments for the skirt of small, irregular lumps of
emery, and molten metal, such as zinc, melting at a comparatively low temperature,
arranging the segments around an eye, and securing them thereto, substantially as
set forth.
3. The herein described improvement in the art of making millstones, which
consists in forming a number of segments by binding together small, irregular
lumps of emery with zinc, arranging the segments with furrow-strips around an eye,
and securing them thereto.
4. The millstone herein described, comprising a skirt having a working surface
composed of small, irregular lumps or blocks of emery embedded in, firmly grasped
and held apart by molten metal which melts at a comparatively low temperature,
as set forth.
5. The herein described millstone comprising a skirt having a working face
composed of small, irregular lumps of emery embedded in a molten metal which
melts at a comparatively low temperature, as described, an eye of a different
material, and furrow-strips interposed between the skirt-segments.
6. A millstone having a skirt with its working face composed of small, irregular
lumps or blocks of emery, having the spaces or interstices between them filled with
a comparatively soft metal melting at a comparatively low temperature,. sub-
stantially as described.
7. A millstone comprising a skirt with its working face composed of small,
irregular lumps of emery having the interstices between them filled with a malleable
metal which can be consolidated when cold about the blocks or lumps, and melting
at a comparatively low temperature.
8. The herein described improvement in the art of repairing millstones, com-
prising small, irregular lumps of emery embedded in a metal melting at a
comparatively low temperature, which consists in inserting a new block of emery
into the cavity, from which a block has been removed, melting the metal about the
block, and adding new metal to firmly secure the new lump to the stone, sub-
stantially as described.
Dated thin 10th day of Awoust 1899
EDWARD H. MASON,
To T. L. S.
Witness to signature,
E. B. POWERS.
THOMAS LEGGETT STURTEVANT.
WILLIAM HENRY ELLIS.