IMPROVEMENTS IN THE MANU- FACTURE OF PORTLAND CEMENT
Year: 1862

page_text: LETTERS PATENT to John Langston, of North Street, Strood, in the
County of Kent, for the Invention of "IMPROVEMENTS IN THE MANU-
FACTURE OF PORTLAND CEMENT."
Sealed the 3rd October 1862, and dated the 9th April 1862.
PROVISIONAL SPECIFICATION left by the said John Langston at the
Office o the Commissioners of Patents, with his Petition, on the 9th
April 1862.
I, JOHN LANGSTON, of North Street, Strood, in the County of Kent, do
hereby declare the nature of the Invention for "IMPROVEMENTS IN THE MANU-
FACTURE OF PORTLAND CEMENT," to be as follows:-
This Invention has for its object improvements in the manufacture of
Portland cement. In the manufacture of Portland cement it is usual to grind
the materials (the chalk and "mud") with a large quantity of water, and to
run the mixture into settling ponds; when it has settled the water is run off,
and the deposit is dug out, and placed on heated floors open to the air to dry,
after which it is burnt.
Now, according to my Invention, I employ in grinding the materials only so
much water as as to make a dough or paste suitable for being at once dried
without the separation of water by settling. The drying apparatus I employ
consists of ovens heated by furnaces or fire holes below, and the flues from
these furnaces pass over the top of the ovens in the vaulting of the roof.
Ovens so arranged will dry the materials more rapidly than the open floors,

page_text: and with smaller expenditure of fuel. The passing the materials from the
grinding apparatus to the drying ovens without the use of the settling ponds
renders it necessary that no lumps should be allowed to escape the grinding
apparatus; hence I employ, to effect or to complete the grinding, rollers set at
a short distance the one from the other, and between which the materials are
caused to pass; or a roller revolving at a short distance from a stationary
surface may be employed. Care is taken that the materials shall be thoroughly
mixed before being dried. Mechanical means may be employed for carrying
forward the paste through the drying ovens to or into the drying kiln. The
fire holes of the drying ovens or some of them may be so arranged as to
produce coke for burning the cement.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Langston in the Great Seal Patent Office on the
9th October 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
LANGSTON, of North Street, Strood, in the County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of April, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said John Langston, Her special licence that I, the said John Langs-
ton, my executors, administrators, and assigns, or such others as I, the
said John Langston, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times there-
äfter during the term therein expressed, should and lawfully might makė, 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 MANUFACTURE OF PORTLAND CEMENT," upon the condition (amongst others)
that I, the said John Langston, 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 John Langston, do hereby declare
the nature of the said Invention, and in what manner the same is to be

page_text: performed, to be particularly described and ascertained in and by the following.
statement thereof, that is to say:
This Invention' has for its object improvements in the manufacture of
Portland cement. In the manufacture of Portland cement it is usual to grind
the materials (the chalk and "mud ") with.à large quantity. of water, and to
run the mixture into settling ponds'; when it has settled the water is run off,
and the deposit is dug out and placed on heated floors open to the air to dry,
after which it is burnt. :.
.:
་་ ་ ་་་
Now, according to my Invention, I employ in grinding the materials only so:
much water as to make a dough or paste suitable for::being at once dried.
without the separation of water by settling. The drying apparatus I.employ
consists of ovens heated by furnaces or fire holes below, and the flues from
these furnaces pass over the top of the ovens in the vaulting of the roof.
Ovens so arranged will dry the materials more rapidly than the open floors,
and with smaller expenditure of fuel. The passing the materials from the
grinding apparatus to the drying ovens without the use of the settling ponds
renders it necessary that no lumps should be allowed to escape the grinding
apparatus; henco I employ, to effect or to complete the grinding, rollers set at
a short distance the one from the other, and between which the materials are.
caused to pass; or a roller revolving at a short distance from a stationary
surface may be employed. Care is taken that the materials, shall be thoroughly
mixed before being dried. The fire holes of the drying ovens or, some of them
may be so arranged as to produce coke for burning the cement. :
And in order that my said Invention may be most fully..understood, and,
readily carried into effect, I will proceed to describe the inanner in which
I prefer to conduct the manufacture.
:
The mud, if of very good quality, may be used without preparation, but.
when of ordinary quality, I prefer that it should be prepared in a similar
manner to that at present practiced by breaking it down in a suitable vessel
with water by revolving harrows or stirrers, and if it contains sand or other
heavy matter in any considerable quantity, I make it sufficiently liquid to
deposit the sand or other heavy matter in the vessel in which the mud is
broken down, or as it runs from this vessel to the place where it is stored, or
from which it is directly taken for use. I also cause the mud to pass through
a sieve of wire gauze as it passes out of the vessel above mentioned; this
sieve separates the larger and lighter impurities. The chalk after it has been
broken into small pieces, and the flints (if present) removed by hand picking,
is passed through a pair of rollers, such as is shown in plan at Figure 1, and
in end view at Figure 2 on the annexed Sheet of Drawings. These rollers,

page_text: as shewn in the Drawing are equal in diameter the one to the other, and they
are conveniently about 40 inches in length. The bearings of one of the
rollers are fixed, and those of the other are made so that they can slide between
horizontal guides on the frame, and there are strong springs which press this
latter roller up towards the first, but the rollers are so set they shall not
come in contact the one with the other, but that there shall be an aperture of
about a quarter of an inch between the two, so that the rollers may take the
chalk freely. The rollers are driven conveniently by a steam engine, and they
are geared together by spur wheels with long teeth, so that they will not come
out of gear in consequence of the play of the rollers; and in order that the
rollers may act by rubbing as well as by crushing, I prefer that the spur
wheels gearing the rollers together should have an unequal number of teeth,
but the inequality of surface speed of the rollers should not be great or the
chalk will not pass freely through the rollers; a difference of surface speed of
about one-tenth is suitable. The chalk is fed between the rollers by hand labor,
and after passing through them is made to fall on a screen, to which a constant
vibratory motion is communicated; this sieve separates pieces of flint or other,
material which have escaped the hand picking, and passed the rollers by
causing them to spring apart; with some qualities of chalk this screen is not
required. The chalk having been thus roughly crushed, is reduced to the
requisite degree of fineness by another similar pair of rollers, which, however,
are set closer together, the distance between them being only sufficient to
allow them to take the material through. I would here remark that in place
of making the two crushing rollers forming a pair equal to each other in
circumference, and driving them at a different number of revolutions per
minute, the difference which I consider it desirable there should be in their
surface speeds may be equally well obtained by making them unequal in
diameter, and gearing them together with wheels having the same number of
teeth, so that they may make the same number of revolutions per minute.
From the second pair of rollers the chalk is passed into a pug mill, into which
the mud is run, and where the materials are thoroughly and intimately mixed,
and the mixture is then removed to the drying apparatus or oven without, as
heretofore, separating water by settling after mixing the materials, the materials
being mixed to such a consistency that this is not necessary, and the process
having been so conducted that no lumps remain to be separated.
Figures 3, 4, & 5 show apparatus or ovens for drying cement constructed
according to my Invention, in which it will be remarked that the drying floors
are enclosed or vaulted over, and that the apparatus or ovens are adapted to
produce coke as well as to dry the cement. Figure 3 is a front view, partly

page_text: in section, of a pair of ovens for drying cement, the fire hole or furnace of one
of the pair being made suitable for producing coke for burning the cement;
Figure 4 is a vertical, and Figure 5 is a horizontal section, shewing one of
the drying floors.
The section Figure 4 is taken through the ordinary fire hole or furnace.
a, a, is the basement mass of the oven, which may be of concrete or other
suitable material, and is cased with fire-bricks; bare the fire-bars; and c, the
fire-door; d is the drying floor; it is made of fire-tiles, and supported on
arches of fire-brick e, e; under this the fire circulates and passes up at the
back over the retaining ridge d' at the edge of the drying floor into the drying
chamber f; the draft then enters the flue g at the front of the chamber f, and
passes to the back, as is shewn, into the stack, and there are dampers to
regulate the draft in the flues; g' is an opening for the introduction of the
cement compound which is to be dried; and h a door for withdrawing the
cement when dried; i is the fire hole, which is suitable for making coke; it
is a vaulted chamber under the drying floor, furnished with a counterpoised
door j at the front, which can be raised or lowered, and which when raised
leaves exposed the whole front of the chamber i, so that the coke may be
readily removed from the chamber. There is a passage from the chamber i
to the flue, which is capable of being regulated by a damper.
The process of manufacturing coke is conducted in the usual manner, the
heat resulting from the operation being made available for drying cement.
The cement when dry is burnt as is usual, it may be with the coke made
during the process of drying. I find it convenient to arrange the fire holes for
producing coke and those of the ordinary construction alternately in the line
or series of drying ovens, but this may be varied.
In witness whereof, I, the said John Langston, have hereunto set my
hand and seal, this Ninth day of October, in the year of our Lord One
thousand eight hundred and sixty-two.
JOHN LANGSTON. (L.S.)