IMPROVEMENTS IN THE GRINDING OF CEMENTS AND OTHER SUBSTANCES, AND IN THE CON- STRUCTION OF MILLSTONES FOR THE SAME
Year: 1856

page_text: LETTERS PATENT to William Porter, of No. 9, Lansdowne Villas,
Brompton, Middlesex, Civil Engineer, for the Invention of "IMPROVEMENTS
IN THE GRINDING OF CEMENTS AND OTHER SUBSTANCES, AND IN THE CON-
STRUCTION OF MILLSTONES FOR THE SAME."
PROVISIONAL SPECIFICATION left by the said William Porter at the
Office of the Commissioners of Patents, with his Petition, on the 8th
November 1856.
I, WILLIAM PORTER, of No. 9, Lansdowne Villas, Brompton, Middlesex,
Civil Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE GRINDING OF CEMENTS AND OTHER SUBSTANCES, AND IN
THE CONSTRUCTION OF MILLSTONES FOR THE SAME," to be as follows:-
This Invention consists in a frame of iron or other suitable material, in
which stones proper for grinding, after the manner of a corn mill, are put
together, framed and secured in the form of an ordinary millstone. This frame
I construct with a number of cells of suitable sizes, in which I place such
stones, or any other material proper for composing millstones. The partitions
of such cells are sufficiently high to form a level surface with the face of the
millstone. I further secure the stones in their beds with plaster or other
suitable material.
Also, my Invention consists in an improved joint between the materials com-

page_text: posing such millstones. These joints I make with any suitable metal, or any
alloy having copper, tin, lead, zine, or the like for its base, which metal I
pour
in a molten state between the joinings of such stones for the purpose of fixing
and solidifying the same. The stones or materials composing such millstones,
for the reason afterwards given, are either laid so as to touch one another
partially, or are set a short distance away from each other.
And my Invention also consists in the insertion of plates of metal of a kind
similar to that before described, or in the insertion of timber packings between
the joints of the stones, which stones I secure by iron hoops in the ordinary
manner, or by a frame, as already described. I find that millstones constructed
with these metals or materials between their joints, either in connection
or otherwise with tho luting commonly made use of, that the edges of the
stones are not so liable to chip off or to abrade from the friction of the material
they grind as when the surfaces of the sides of the stones are made to fit truly
to each other, because, in my improved method of constructing such millstones
the interposed lamination of such metal or other material serves as a protection
to the edges or corners of such joints, and prevents the substance which is
being ground getting between the joints of the stones. On taking up mill-
stones which have been for some time in use, the joints of which have been
made with an alloy of lead and antimony, I havo invariably found that the
openings caused by the chipping of the material composing. the stone bad
become filled with the metal forming the joint.
And further, my Invention consists in the use of an elastic cushion or
packing, in order to regulate the pressure of the millstone runner against the
bedstone, according to the description of material being ground. This cushion
or packing I place between the centre pin of the millstone spindle, on which the
millstone hangs, and its foot, or under the footstep thereof.
.
By these improvements I am enabled to construct or build millstones more
economically, and also to drive them at a much greater velocity, than those
constructed in the ordinary manner, however well such millstones may have
:been built, or however carefully the stones composing them may have been
made to fit each other. Millstones constructed according to my improved
'method I find are able to grind a much greater quantity of material with the
same power, be it cement, stone, or other hard substance, and to grind such
more equably than those which have hitherto been constructed. They are also
more easily repaired, and are required to be taken up much seldomer for that
purpose.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Porter in the Great Seal Patent Office on the
8th May 1857.
:
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
PORTER, of No. 9, Lansdowne Villas, Brompton, Middlesex, Civil Engineer,
send greeting.
T
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent; bearing date the Eighth day of November, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Porter, Her special licence that I, the said William Porter, my
executors, administrators, and assigns, or such others as I, the said William
Porter, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE GRINDING OF
CEMENTS AND OTHER SUBSTANCES, AND IN THE CONSTRUCTION OF MILLSTONES FOR
THE SAME," upon the condition (amongst others) that I, the said William
Porter, my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in. the Great Seal Patent
Office within six calendar months next and immediately after the date of the
said Letters Patent...
NOW KNOW YE, that I, the said William Porter, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in' and by the following
statement (that is to say):
'1
My Invention consists, first, in an improved. method' of constructing or
building millstones, intended more particularly to grind cements and other
hard substances, after the manner of a corn mill, by which such grinding
is more easily and more perfectly accomplished; and, secondly, in the use of a
spring, cushion in connection with the mill spindle, in such manner that
the whole weight or part thereof of the upper. millstone. may be thrown upon
the said cushion, in order to regulate the pressure of the runner or upper mill-
stone upon the lower millstone or bedstone, and to maintain the centre pin of
the mill spindle in close contact with the rind of the upper. millstone,

page_text: In order to explain more clearly the nature of these improvements, reference
is herein made to certain Drawings, of which the following is a description,
namely:-
Figure 1 is an elevation, partly sectional, of a pair of millstones and
accessaries, arranged after the manner of a corn mill. This Figuro serves to
shew the arrangement of the millstones, and of such parts as are affected
by my improvements.
Figure 2 is a plan of one of my improved millstones, and Figure 3 is a
section of the same, both of which are drawn to a larger scale than Figure 1.
Figure 4 is a plan of another improved millstone; Figure 5 is a section of
the same, both of which are drawn to scale same as Figures 2 and 3.
Figure 6 is a section of the foot box and step, represented in Figure 1, and
drawn to a much larger scale; Figure 7 is a plan of the same.
Millstones are made in general of silicious stones of great hardness, and as
a homogenous stone of this description is seldom found in one piece, it is
necessary to construct them of several stones, which are chosen of equal hard-
ness in order to obtain a homogenous surface. These stones (denominated
generally "burrs "), after having been worked to the shape necessary to form
a millstone and carefully surfaced, are made to adhere one to another by
means of a luting, such as plaster of Paris, and then bound together by iron
hoops in the usual and well-known manner. When cements or other hard
materials are ground by means of millstones constructed in this way, the
friction of such materials frequently breaks the edges or corners of the stones
or burrs at the joints which compose the same, and thus channels or grooves
are made in the face of such millstones, through which channels the cement
or other material which is being ground passes imperfectly pulverized; but
by the use of millstones constructed according to my improved method, the
escape of the cement imperfectly pulverized, or other substance, through such
channels or grooves does not occur.
One of my improved methods of constructing such millstones is as follows:-
I select French burr stones, or other substances proper for grinding the
required materials. I first work one of these burrs a, Figures 2 and 3,
composing the eye of the millstone, to the required shape, more or less
accurately, and place it upon a level iron plate or a stone slab, with that side
which has to form the face of the millstone downwards, and resting upon the
plate or slab; I then work another burr a' in a similar manner, and place it
also upon the plate or slab by the side of the first burr, and I repeat this
operation until the eye of the millstone is completely formed, the interstices
formed by such stones being partially in contact, or not touching each other

page_text: all, that is to say, the spaces 6 between such stones I fill with any of the
following metals, or an alloy composed of such, namely, tin, lead, zinc, bismuth,
copper, and the like, (using antimoney in some cases to give hardness to
lead.) These metals, or one of them, or any suitable mixture of the same,
I pour between the joinings 6 of such stones, having previously secured
the joints at the outside by means of clay or earth, in order to prevent
the escape of the molten metal, by which metal the stones are fixed and
solidified. I now fit the outside or skirt burrs a² in a similar manner to the
eye burrs a,
a', just described, and then I fill the joinings b' between such skirt
burrs as well as those joinings 6 between the skirt and eye burrs also
with metal, in a similar manner to that just described; I then cover the
outside of the millstone with plaster, and secure the stones composing the same
with iron hoops c on the periphery thereof in the usual way.
I further make good the back of the millstone with plaster in the ordinary
way, after which I lift the millstone from the iron plato or slab and cut off
any projecting picces of the metal I had poured between the "burrs." I
prefer such joints of millstones constructed in such manner as described not
to be more than one-eighth of an inch in thickness. Sometimes I cut chases 6*
in the stones across the joinings, which I fill with metal or wood to prevent
the escape of unground matter. The metals or their alloys which melt at a
comparatively low temperature answer best in the construction of my improved
millstones, because if the melted metal is poured into the joints at too great a
heat the same is liable to damage the burrs. I find that on this account
with some description of stones, such as French burrs, it is not convenient to
pour in the metal or alloy at a temperature beyond 650 degrees Fahrenheit, or
thereabouts, without previously heating the stones to prevent them cracking
from the heat of the metal. When zinc is used alone its temperature of
fluidity is too bigh to admit of all the stones being preserved intact when the
joints of such are made with this metal in a molten state. Copper attains its
fluidity at a much higher temperature, and would likewise endanger the
solidity of the several component stones or burrs; yet if suitable stones can be
procured, and the joints of which are made without damaging such stones,
either copper, zinc, or other metal, when used for that purpose, is effective;
but I prefer the joints being made with a mixture of lead and antimony, in
the proportion of fifteen parts of the former to one part of the latter. But
copper, zinc, tin, iron, lead, or any suitable mixture of the same, may be
inserted between stones or burrs by the same being first cast or rolled into
suitable plates about one-eighth of an inch in thickness, and then fitted accu-
rately to the stones, or the stones to them; but this method is costly as respects

page_text: labor, and, moreover, does not answer the purpose so well as the fused joints
before described, which latter require less labour and that of a less skilled
character. Sometimes I form the joints between the stones with wooden planks
about one quarter of an inch in thickness, placed endways of the grain to the
grinding surface. In all cases I furrow the working faces of the millstones in
the ordinary manner, according to the nature of the materials to be ground.
Sometimes I construct the eye of the millstone with plaster joints in the usual
way, but I form the outside or skirt joints b' after one of my improved methods.
When metal is used in a molten state to make the joints it is not necessary to
,expend so much labor in surfacing the burrs or stones as it is usual to do in
the case of millstones built in the ordinary way, where the proper working of
such millstones depends; altogether upon the component parts being joined
accurately one to another, and this is a source of economy in their construc-
tion as-respects-labor. Even in cases where the utmost care has been taken
to make the stones or burrs fit one to another with great accuracy, the friction
of any hard matter upon which such millstones may act breaks the corners or
edges of the burrs at the joints, and consequently forms the channels or
grooves before referred to in the face of the millstone; but when millstones
are used which have been constructed with the materials above indicated
between their joints, the edges or corners of the burrs or stones of which they
are composed are not liable to break, however hard the cement or other matter
ground may be, because the interposed lamination of metal or wood serves
more or less as a protection to the corners of such burrs, and prevents the
substance which is being ground getting between the joints, and thus escaping
in an imperfectly pulverized state: These millstones are able to grind a greater
quantity of cement or other hard substances, and to grind the same more
equably than any others which have hitherto been constructed. They may bo
driven at a higher velocity; they will work a longer time without requiring
to be dressed, and this operation of dressing can be performed in a shorter
time, because the joints of millstones constructed after my method retain tho
level of the general surface, whereas the stones or burrs of which ordinary
millstones are formed break at the joints; this makes it necessary at each
dressing to cut off a portion of the face of the millstone in order to reduce the
whole surface to the level of such broken parts. On taking up millstones which
had been for some short time in use; and the joints of which I had experi-
mentally made with an alloy of lead and antimony, I have found the metal
forming the outside or skirt joints & to be level with the general surface of the
millstones, and any opening caused by the chipping of the edges of such burrs
to be filled with the metal of which the joint had been composed.. The eye

page_text: joints band the joints & between the skirt and eye burrs in some cases I have
found to be a little lower than the general! surface of the millstone, but this
does not in any way effect the proper working of the same.
Another of my improved methods of constructing millstones is a franie d of
iron (Figures 4 and 5), or other suitable material, containing a number of
cells or openings; having their sides or partitions e sufficiently high to form a
level surface e' with the face of the millstone, in which stones a', proper for
grinding after the manner of a.corn mill, are put together, framed, and secured
in the form of an ordinary millstone. I retain the stones in their beds with
plaster or other suitable cement. Sometimes I dispense with the outside ring
of the frame, and I employ hoops of iron in the ordinary manner, as shown in
Figures 2 and 3. I have not thought it necessary to shew, a separate view of
the bedstone, the joints of which I construct in a manner similar to those of
the runners above described.
L
I will now proceed to describe the second part of my Invention. Figures 6
and 7 represent an enlarged view of the footstep f and the footbox f, showi
on Figure 1, in which the millstone spindle g.rests. h is an elastic cushion of
caoutchouc, or other elastic material, placed between two discs of wood i, or
other material non-conductive of heat. This cushion I use in order to regulate
the pressure of the runner against the bedstone ³, according to the kind of
material to be ground, and to maintain the centre pin o of the mill spindle in
close contact with the rind 7 of the upper millstone. Sometimes I place the
cushion h in the rind 7, or between the centre pin o of the mill spindle g, on
which the millstone bangs, and its foot m, or at any convenient place under
the footstep thereof. In addition, I make use of the ordinary means n of
raising and lowering the upper millstone, and to maintain it at the requisite.
distance from the bedstone. With an elastic cushion placed as above
described I am enabled to use a heavier runner than those in ordinary use,
because the action of such cushion allows me to place any portion of the
weight of such runner upon the face of the bedstone, the remainder of the
weight resting upon the footstep. It also causes the runner to press upon
the matter being ground with greater force when such increased pressure is
requisite, on account of the quantity of matter. between the stones, and when
the couch of the said matter is, comparatively thin, the runner bears with less
weight on the bedstone, whereby the friction is reduced, and less power, in
consequence of such reduction of the friction, is required to work the mill
stones. But in the ordinary way, without an elastic cushion, let the couch of
cement or other matter being ground between the stones be however thin, thoro
is the same pressure of the runner on the bedstone, whether such pressure is

page_text: requisite or not, for the pulverisation of the said couch. The friction of the
two stones, and consequently the power required to drive them, is uniform,
whether the couch be thick or thin, the quantity of cement or other matter
ground greater or less; whereas according to my method the friction of
the upper and lower stones is proportionate within certain limits of the thick-
ness of the said interposed couch, that is to say, the power required to work
the stones bears a notable proportion to the said couch, let the quantity ground
be more or less, the velocities of the stones being the same in both cases. The
cushion, when the same is made of caoutchouc or vulcanized india-rubber, for
a runner weighing one and a half tons, should be about three-fourths of an inch
in thickness, and have an area of about ten square inches. In order that its
elasticity and compressibility may have free action, the same should not be
confined at its sides or edges h', but the cushion should have liberty to expand.
Instead of an india-rubber cushion a steel spring may be used; or the bridge
tree p, as shewn in Figure 1, may be of steel, or other material possessing
elasticity, in order to effect the same object.
I do not confine myself to any particular method of building my improved
millstones with metallic joints, or with plates of metal or of wood, but I have
described what I believe to be the most convenient way of doing the same, and
the most efficient in operation.
Having fully explained the nature of my Invention, I shall now state
particularly such parts whereof I claim as being new :-
First, I claim the forming and securing the joints or joinings of the com-
ponent parts of compound millstones by running melted metal into such
joints, or introducing plates, layers, or pieces of metal or wood into such
joints or between such component parts, as aforesaid, in manner herein-before
described.
Secondly, supporting the runner or upper stone of a mill upon an elastic
cushion or spring placed under the footstep, or in any other convenient position,
for the purposes herein-before described.
In witness whereof, I, the said William Porter, have hereunto set my
hand and seal, this Eighth day of May, in the year of our Lord One
thousand eight hundred and fifty-seven.
WILLIAM PORTER. (L.B.)