IMPROVE- MENTS IN THE MANUFACTURE OF PORTLAND CEMENT
Year: 1876

page_text: LETTERS PATENT to Robert Owen White and John Bazley White, Junior,
both of Swanscombe, in the County of Kent, for the Invention of "IMPROVE-
MENTS IN THE MANUFACTURE OF PORTLAND CEMENT."
Sealed the 5th January 1877, and dated the 9th November 1876.
PROVISIONAL SPECIFICATION left by the said Robert Owen White and
John Bazley White at the Office of the Commissioners of Patents on the 9th
November 1876.
ROBERT OWEN WHITE and JOHN BAZLEY WHITE, Junior, both of Swanscombe,
in the County of Kent. "IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND
CEMENT."
The object of the Invention is to reduce considerably the cost of manufacture of
Portland cement. For this purpose we take chalk and clay in the natural state
in which they are found, and without the admixture of water we obtain an intimate
mixture of these materials by placing them together into a hopper, from which they
pass to a series of pairs of crushing rollers.
The materials as they leave the hopper have first to pass through a pair of fluted
crushing rollers; they next pass through another pair of plain rollers placed closer
together than the first pair and running at a greater surface speed. From these they
may pass between a third and a fourth pair of rollers placed still closer together and
running still faster. By this means the materials are reduced to a thin sheet, the
chalk within which is in a thoroughly disintegrated state. After the materials have
thus been crushed and mixed together by means of rollers they may be introduced
into a pug mill and moulded into bricks, or the crushed and mixed material may be
otherwise moulded into bricks. The moulded bricks or blocks are afterwards burnt
in a kiln to the degree to which it is now usual to carry the burning of Portland
cement.
The kilns are heated by the burning of fuel-in any ordinary manner, no fuel
being mixed up with the materials of which the cement is composed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Owen White and John Bazley White in the Great Seal
Patent Office on the 8th May 1877.
ROBERT OWEN WHITE and JOHN BAZLEY WHITE, Junior, both of Swanscombe,
in the County of Kent. "IMPROVEMENTS IN THE MANUFACTURE OF PORTLAND
CEMENT."
The object of the Invention is to reduce considerably the cost of manufacture of
Portland cement. For this purpose we take chalk and clay in the natural state in
which they are found, and without the admixture of water we obtain an intimate
mixture of these materials by placing them together into a hopper, from which they
pass to a series of pairs of crushing rollers.
The materials as they leave the hopper have first to pass through a pair or pairs
of fluted crushing rollers from which they pass to other pairs of plain rollers placed
closer and closer together and running at increased surface speeds. By this means
the materials are reduced to a thin sheet, the chalk within which is in a thoroughly
disintegrated state and mixed with the clay. After the materials have thus been
crushed and mixed together by means of rollers they may be moulded into bricks
to be burnt in any ordinary manner, no fuel being mixed up with the materials of
which the cement is composed.
In carrying out our Invention the numbers of pairs of rollers used in the roller
mixing machine may be varied, we prefer however to use five pair. The relative
dimensions and speeds of the pairs of rollers may also be varied.
A convenient arrangement of the machine is as follows:-At the top of the
machine is a hopper into which we feed the materials, chalk and clay, in proper pro-
portions, and in the raw state in which they are obtained. The materials descend
from the hopper to a pair of horizontal rollers fluted longitudinally. These rollers
are, say, about 12 inches in diameter at the points of the flutes, and are adjusted to
work at 13 inches apart from centre to centre and to make about 10/2 revolutions
a minute. From these rollers the materials descend by preference to a second pair
of fluted rollers of about the same diameter placed closer together, say, about
11 inches from centre to centre, and making about 24 revolutions a minute.
From these the materials drop to a pair of smooth rollers about 1 foot 3 inches in
diameter, 3/16 inches apart, and making, say, 39 revolutions a minute. From these
again to another pair of rollers placed still closer together, say about 3/32 in. apart,
1 foot 9 inches in diameter, and driven at about 58 revolutions per minute. All
the above rollers we have made 3 feet long. From the last-inentioned rollers
the materials drop to another pair placed still closer, say about 1/32 in. apart,
2 feet 3 inches in diameter, and driven at still greater surface speed, say
88 revolutions per minute; they are also set at right angles to the other rollers
and are made about 4 feet 6 inches long. The stream of materials descending
on to these rollers from the rollers above then becomes doubled or gathered
together, and is thereby intimately mixed together. A very perfect mixing of
the materials may however be obtained even if the last pair of rollers are
placed in a line with the other rollers and not at right angles to them. A
scraper is by means of a weight or spring, or any other suitable method, held
up to the under side of each of the several rollers to prevent the material
being carried round with them, and at the ends of the spaces between the
several pairs of rollers there are end plates which prevent the material from
escaping and compel it to pass downwards between the rollers. The several
rollers are geared. together by toothed wheels at their ends so that they shall
revolve together at the required speeds and be driven by a belt wheel on the
axis of one of the rollers. The lowest pair of rollers may be driven by a separate
belt and belt wheel or ordinary gearing. The materials having thus been mixed
together in the machine are afterwards moulded into bricks or blocks to be burnt.
We prefer to use for this purpose that class of machine in which the materials are

page_text: fed by rollers into a box across the bottom of which a series of moulds formed in a
revolving table are caused to pass in succession; the moulds are filled as they pass
below the filling box and are emptied after passing beyond the box, but other
machines for moulding bricks or blocks may be used for the purpose. All that is
required is that the machine should perform its work quickly, no perfect moulding
of the bricks being required so long as they are of about the same size and will hold
together to allow of their being stacked in a kiln.
It will be seen that by the herein-before described process of making cement the
ordinary addition of water to the materials is entirely dispensed with, and con-
sequently the tedious and costly processes of draining and driving off the water
which has been so added is done away with, a result which has before been aimed
at but not attained.
It is intended that the bricks or blocks as they come from the moulding
machinery shall without the intervention of any drying stove process be at once
placed in one of the chambers of a Hoffman's or such-like kiln, where they will be
exposed to the heated gases passing from one or other of the other chambers where
cement is being burnt, and be afterwards in their turn burnt, or the blocks may be
air dried before being burnt in a Hoffman or other kiln.
Having thus described the nature of our Invention and the manner of performing
the same, we would have it understood that we do not confine ourselves to
the precise details given of the roller mixing machine, as the number of pairs of
rollers used and their relative sizes and speeds may be considerably varied, but we
claim,
First. The manufacture of Portland cement substantially in the manner herein-
before described, the chalk and clay being both thrown together in their natural or
raw state into a hopper, from which they pass through successive pairs of rollers
running at increasing surface speeds and placed closer and closer together so as to
obtain an intimate mixture of these materials, and the mixed materials being after-
wards moulded or formed into blocks and burnt.
Second. The manufacture of Portland cement from chalk and clay without the
admixture of water or fuel, substantially in the manner herein described.
In witness whereof, I, the said John Bazley White, Junior, have hereunto set
my hand and seal, this Eighteenth day of April, One thousand eight hundred
and seventy-seven.
J. BAZLEY WHITE, J². (L.S.)