IMPROVEMENTS IN BRICK KILNS
Year: 1884

page_text: COMPLETE SPECIFICATION.
I, HERBERT JOHN ALLISON, of the firm of Allison Brothers, of 52 Chancery
Lane, London, in the county of Middlesex, Patent Agents, do hereby declare the
nature of my invention for "IMPROVEMENTS IN BRICK KILNS," and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
"
This invention applies to what is known as a permanent base" of a brick
kiln-that is a system of furnaces, flues and reservoirs permanently constructed to
support the pile of unburned bricks, in contradistinction to the ordinary arrange-
ment of such bricks for the purpose of burning them.
The objects to be gained in constructing a permanent kiln or kiln base
substantially, as hereinafter described, are to obtain a greater percentage of
perfectly burned bricks than results from the ordinary methods of burning; to
secure economies and durability in construction; and to save labor and fuel.
The invention consists in constructing a permanent brick kiln base of fire brick,
clay, or other suitable material, molded in situ by means of removable molds or
forms; and further in constructing bot air reservoirs extending through from one
side to the other of the kiln, and in constructing and locating certain of the hot
air Blues so as to better direct the heat toward the ends of the kiln.
Reference is to be had to the accompanying drawings, forming part of the
specification, in which similar letters of reference indicate corresponding parts in
all the figures.
Figure 1. is a front elevation of my improved kiln base, partly in section on
line y. y. Figure 2.
Figure 2. is a sectional and elevation of the same on line a. x. Figure 1.
Figure 3. is a plan of a portion of the kiln base.
.
A suitable foundation being laid, upon it are placed molds or forms constructed
of boards and open at top and bottom, then fire clay or other suitable material,
properly mixed and tempered, is filled into said molds or forms and pressed down
sufficiently to make a solid mass.
Left for a certain time the blocks of clay-the contents of the molds or forms,
become sufficiently dry and firm to permit the safe removal of the boards that form
L

page_text: The boards or molds being removed the blocks molded or formed by and in them
remain in place forming the piers, arches, keys and other solid permanent portions
of the kiln base in their proper relative positions.
Each pier and arch may be molded or formed in a single block and afterwards
be cut or separated in situ, vertically or horizontally, or both, into two or more
blocks as indicated in Figures 1, and 2, wherein A, A1, represent, respectively, the
individual piers separated from each other or molded separately as indicated by
the vertical lines a, a, and divided into blocks by molding or cutting along the
horizontal lines b, b.
Or said piers and arches may all be molded or formed together, in one mass by
the use of suitable molds or frames and be afterwards divided by cutting into
blocks of such sizes and shapes as may be desired in view of their subsequent
behaviour when expanding and contracting in drying and under the application
and withdrawal of heat.
Or the structure may be built up from the foundation in successive layers molded
in place, one layer or course being molded on the top of another when the prior
one has become sufficiently dry to support the weight.
All these methods have been tested and found practical but a combination of
them is preferred.
This kiln consists substantially of series of piers A, A', and arches B, constructed
in situ and forming series of vaulted passages C, that extend entirely from one
side to the other of the kiln and from the bottom to near the top thereof, and each
passage C, is in effect divided into a lower air spaco d, and an upper hot air
reservoir f, by series of flues D, whose ingress openings extend along one or both
sides of each passage C, on a line about half way between the grate bars and the
passage roof, and whose egress openings terminate in channels g, in the upper
surface of the kiln, for the purpose of conducting the heat from the reservoirs f to
the bricks to be burned.
In the lower part of each passago C, are placed grate bars E, that in narrow
kilns extend from one side to the other of the kiln, so that the passages C, may be
fired from either end, and beneath the grate bars are ash pits F-But in wide kilns
the grates may be discontinued, or broken in the middle by clay or brick slabs as
shown at O, Figure 2, the passages C, however being continuous.
The ends of the passagos C, are designed to be walled up as shown in Figure 1,
leaving no openings excepting for the furnace doors F, and ash pits F¹. Preferably
for the sake of durability the piers A, are set inclining inward from bottom to top
toward the central pier A¹, as indicated in the drawings, so that when cooling and
contracting after heating and expanding they shall tend to contract and lean
toward a contral point instead of contracting or warping so as to separate from
each other as is usually the caso with perpendicular piers. The ends of the kiln
may be supported by buttresses as indicated at G, Figure 1. In practice, however,
the piers may safely be set upright from side to side of the kiln and be made to
inclino only from end to end.
After the blocks H, that cap the piers and form the flanks or springings of the
arches and are molded in place, have become sufficiently set or dried, the key
stones I, are also molded in situ and of such dimensions that on their shrinkago
and the shrinkago of the contiguous parts they will become properly fitted and
adjusted in place.
The sides of this kiln are, preferably, covered with one or more courses of bricks,
as indicated at k, Figure 2.
The furnace doors F, are set at coach end of each passage C, and along the sides
of the kiln ledges l, are constructed to form convenient supports for the furnace
doors when the latter are temporarily removed from their normal positions.
As above referred to an important part of my invention relates to the hot air
Blues D, by which the heat is conveyed from the hot air reservoirs to the bricks
(not shown) that are piled on top of the kiln base to be burned. It was found
that if these flues were all constructed of the same dimensions and located along

page_text: the same horizontal line the temperature at the various parts of the kiln could not
be controlled so perfectly as desired.
For the best working or firing of a kiln it is desirable that the heat be first
directed or thrown more toward the ends than to the centre or middle of the
structure, for if the centre or middle be at first more highly heated than the ends
the tendency is for the temperature to disproportionally increase there at the
expense of that at the ends, and the result is that the central bricks are burned
long before the others.
To overcome these objections-to direct and maintain the heat at will at the ends
in order to burn the bricks there equally with those at the centre-I locate the
ingress openings of the extreme end flues D, at a higher elovation than any of the
others, and make them and their corresponding flues larger than the central flues
as indicated in Figure 2, and I also make the immediately contiguous flues and
their ingress openings larger than the more inner ones, as shown.
By reason of this construction the draft up through the end flues may, by
proper adjustment of the furnace doors, be made greater than through any of
the others, and the heat at and above these points bo first directed toward the ends
of the structuro.
And because these end flues are the first to reach a comparatively high
temperature and are more capacious than the more central flues it is easy to
maintain an almost even temperature throughout every part of the kiln.
The operation of this kiln is as follows:-The coal fires being properly started
on the grate bars the furnace doors are closed; the air then passes in through tho
ash pits and up through the ignited coal into the reservoirs f, and forces out the
colder air through the flues D.
When the reservoirs f, are of a bright red heat the furnace doors at one side
are opened, and immediately currents of the external air pass through the open
doors and directly over the surface of the ignited coal and nearly across the kiln.
Owing to the large supply of heat and hot air stored now in the reservoirs f, there
is sufficient heat radiated down to the coal below to cause it to burn on the surface,
The admitted air becoming then thoroughly heated rises with the products of the
combustion of the coal; some passing out directly from the air spaces d, through
a few of the flues D, near the opposite side of the kiln, while the remainder rising
to the tops of the reservoirs displaces the highly heated air and gases already
stored there and forces them down and out of the other flues D, thereby causing
the currents of hot air and gases in the reservoirs f, to move in opposite direction
to the currents passing over the surface of the coal below. Consequently the
flues D, immediately over the open furnace doors are only supplied by hot air and
gases stored in the reservoirs f, which, in turn, are filled by the currents of hot air
and gases coming from the opposite side of the kiln; hence the reservoirs f, will be
continuously supplied with sufficient heat to cause the ignition of the surface of the
coal below.
Should the beat decline in a reservoir below the required temperaturo a partial
or complete closing of the door will cause a rapid accumulation of heat, as the draft
will then pass up through the coal.
The air spaces d, and hot air reservoirs f, are of such capacity, have such
extensive radiating surfaces-that when they have become heated perfect com-
bustion of the fuel and gases and consequent economy of fuel are assured.
The temperature of the kiln and the burning of the bricks superimposed thereon
may be perfectly controlled by means of the kiln doors.
When the kiln has become heated the opening of a door at one end of a
passage C, will drive the heated air to the opposite end thereof where the door
is closed, and out through the flues D, located there into channels g, and thence
through the passages formed in the bricks piled on the kiln, thus burning tho
bricks close to the side of the kiln opposite the open door, then by closing this door
and opening the opposite one the heated air will move in a reverse direction, and
thus the bricks on both sides will be equally burned.

page_text: The doors are usually both closed for five or ten minutes between each change
from side to side, and are left open on either side about half an hour each time.
It is believed that, owing to the several ways of arranging the drafts, i.e. first,
lurning with both doors of a passage C, closed and the draft passing up through
the coal; secondly, by burning the coal on the top by leaving one door wholly or
partly open; and, thirdly, by reversing the doors opened-tho operator has moro
control over his fires than in any kiln before invented.
In constructing all the parts of this kiln base in situ of blocks of convenient
dimensions, or of larger blocks that are afterwards cut into two or more, special
care is always had to mold or cut the blocks in such shapes that they will best
withstand the distorting influences of frequent heating and cooling.
And in practice it is fully demonstrated that by giving the end bricks in the
superimposed pile to be burned a start or advantage in heating at the beginning.
of the firing, by constructing and locating the end flues, as described, with special
reference to this object, a very much larger proportion of the bricks will be properly
burned and there will be much less waste from imperfectly or excessively burned
bricks.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1st In a permanent brick kiln base molded in situ, series of passages or hot
air reservoirs extending through from one side to the other and having exit flues
only on the sides substantially as herein shown and described.
2d A brick kiln base constructed substantially as herein shown and described
of fire clay or other suitable material. molded in situ in or by means of removablo
forms or molds.
3d A brick kiln base provided with series of flues leading upward from hot air
reservoirs; the end flues being larger or of greater capacity than the more central
flues, substantially as and for the purposes described.
4th A brick kiln base constructed with its extreme end flues of greater capacity
than the central flues and with their ingress openings on a higher level than the
ingress openings of the central flues, substantially as herein described and for the
purposes set forth.
Dated this 7th day of October 1884.