IMPROVEMENTS IN THE CON- STRUCTION OF FURNACES BY APPARATUS FOR THE MORE PERFECT COMBUSTION AND ECONOMY OF FUEL AND PREVENTION OF SMOKE."
Year: 1869

page_text: LETTERS PATENT to Charles Fairbairn, of Marion Villa, Sciennes,
Edinburgh, in the County of Mid Lothian, North Britain, Con-
sulting Engineer, for the Invention of "IMPROVEMENTS IN THE CON-
STRUCTION OF FURNACES BY APPARATUS FOR THE MORE PERFECT COMBUSTION
AND ECONOMY OF FUEL AND PREVENTION OF SMOKE."
PROVISIONAL SPECIFICATION left by the said Charles Fairbairn at
the Office of the Commissioners of Patents, with his Petition,
on the 8th March 1869.
I, CHARLES FAIRBAIRN, of Marion Villa, Sciennes, Edinburgh, in
the County of Mid Lothian, North Britain, Consulting Engineer, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE CONSTRUCTION OF FURNACES BY APPARATUS FOR THE MORE PERFECT COM-
AND ECONOMY OF FUEL AND PREVENTION OF SHOкE," to be as
follows:-
This Invention relates to improvements in furnaces, which consist of.
an arrangement in the angle of the furnace bars, perforated fire-bricks,
and hot-air passages as liereafter described introduced to a hollow:

page_text: hanging bridge in the furnace, whereby the combustion of the uncon-
sumed gases is rendered more complete and the formation of smoke
prevented.
I construct land and marine boiler furnaces and other kinds of close
furnaces as follows:-The furnace bars are placed at a greater angle
than is usual, being lowest at the back of the furnace. A banging
bridge is built close up to the boiler and over the ends of the furnace
bars; this bridge is hollow, and with perforations opening downwards
and backwards from the furnace. Another bridge on which the ends of
the furnace bars usually rest behind the first is built hollow in some
cases, containing an air passage leading to the hanging bridge, and an
air valve or door opening below the furnace bars. In other cases, where
possible, I conduct the air through pipes or flues directly to the hanging
bridge, these pipes or flues passing through the flues which conduct the
products of combustion to the chimney. The bottom of the hanging bridge
is a little below the level of the top of the other or second bridge and the
passage between them rises in a slanting direction backwards. The
products of combustion in passing away, are arrested, and made to
descend round the bottom of the hanging bridge, and coming in contact
with the incandescent fuel at the hottest part of the furnace at the
same time receiving the necessary supply of oxygen are consumed.
The amount of air introduced is managed at will by a valve or door
worked by an apparatus to be hereafter described.
As regards locomotive boiler furnaces I apply the same principle
modified to suit the particular case, for instance, at a certain distance
from the tube plate in the fire-box are two fire clay hanging bridges,
hollow and perforated, one placed above and resting on the other,.a
rectangular space being left between them; the top of the upper one
is close against the crown of the fire-box; the bottom of it is
perforated and delivers its air into the rectangular passage, through
which part of the products of combustion pass. The bottom of the
lower one is a little below the bottom row of tubes and perforated
below; the products of combustion pass below it and are consumed
as described above. The hanging bridges are easily removed, being
held in their places by angle iron; two tubular stays at each side of the
fire-box supply air to the bridges.
The apparatus for opening and closing the air valve or door is con-
structed as follows:-A small cylinder 'containing two pistons and rods

page_text: and enclosed in a box at any suitable place convenient to the furnace
door and air valve. One end of the cylinder is closed, the other
partially open. A small thumb screw with a tapered groove running
its whole length is screwed into the closed end of the cylinder; the
groove serves to. let in the air at any required velocity; the differential
motion of the two pistons when returning serves to let it escape between
them. The furnace door carries a lever attached by a rod or chain to
the air valve and also to the pistons in the cylinder. On opening the
furnace door to charge the fire the air valve is opened, a weight placed
on the end of a lever pushes in the pistons. On shutting the furnace
door the valve and pistons are left in that position, and begin to
close at any required velocity, being regulated by the quantity of air.
admitted through the groove in the thumbscrew at the end of the
cylinder.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Fairbairn in the Great Seal Patent Office
on the 8th September 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
FAIRBAIRN, of Marr Villa, Sciennes, Edinburgh, in the County of Mid
Lothian, North Britain, Consulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of March, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me; the said Charles Fairbairn; Her special
licence that I, the said Charles Fairbairn, my executors, administra-
tors, and assigns, or such others, as I, the said Charles Fairbairn, 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 CONSTRUCTION OF FURNACES BY APPARATUS FOR THE MORE PERFECT COM-
BUSTION AND ECONOMY OF FUEL AND PREVENTION OF SMOKE," upon the
condition (amongst others) that I, the said Charles Fairbairn, my.
executors or administrators, by an instrument in writing, under my,

page_text: 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 the said Charles Fairbairn, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed; to be particularly described and ascertained in and
by the following statement thereof, that is to say :-
} This Invention relates to improvements which consist of an arrange-
ment in the angle of the furnace bars, perforated fire-bricks, and hot-
air passages as hereafter described introduced to a hollow hanging
bridge in the furnace whereby combustion of the unconsumed gases
is rendered more complete and the formation of smoke prevented.
The mode of construction as applied to steam boiler furnaces is as
follows: The furnace bars are placed at a greater angle than usual,
being lowest at their back; a hanging bridge is built close up to the
boiler and over the ends of the furnace bars. This bridge is hollow, and
with perforations opening downwards; another bridge on which the
ends of the furnace bars usually rest is built hollow containing an air
passage leading to the hanging bridge and an air valve or door opening
below the furnace bars. In other cases where possible I conduct the
air through pipes or flues directly to the hanging bridge, these pipes
or flues passing through the flue which conduct the products of com-
bustion to the chimney.
Figure 1 of the accompanying Drawings is a longitudinal section of a
steam boiler furnace constructed according to my Invention; Figure 2
is a plan of the same with the boiler removed; Figures 3 and 4 are
transverse sections taken at thé bridge, and shewing the two methods of
conducting air to the furnace through the hollow bridge.
A is a bridge immediately beyond the furnace bars built hollow and
with an opening C below the furnace bars for admitting air; upright
pipes D are built into the brickwork on each side of the furnace
forming a communication between the opening C. and the hanging
hollow bridge. This passage leads the air into the hanging bridge,
from whence it is delivered through the perforations E into the flame
and escaping products of combustion. In Figure 4 the air enters to the
hanging bridge by the pipes M on each side of the boiler, which are led

page_text: along the flues, and so conducts the air into the furnace.' The con-
struction of other close furnaces for various purposes is carried out on
the same plan modified to suit the particular case.
The apparatus for opening and closing the air valve or door is con-
structed as shewn in Figure 5 and its application in Figure 6. A
small cylinder P with a hollow piston rod and piston R, through which
passes another piston S is placed on front of the boiler as shewn in
Figure 6; one end of this cylinder is open, the other is closed with a
lid having a valve T opening inwards to admit the air: The internal
piston is connected to the crank V and allows the small piston to move
sufficient to let the air out. The crank V is fixed on the upper end of
the upright rod, shown on Figure 6, which is supported on journals
fastened on front of the boiler; on the lower end of the upright rod is
a crank connected to the air valve or door; on the middle of the rod is
fastened a crank shewn in Figure 6; on opening the furnace door the
middle crank is carried back which turns the upright rod round, pressing
the piston R to the end of the cylinder, and opening the air door in
the hollow bridge; on shutting the furnace door the weight of the air
valve or door closes the passage between the two pistons S and R, the
air begins to enter the cylinder behind the pistons through the small
valve T by which means the air entering slowly the air door is gradually
closed.
And having now described the nature of my Invention, and in what
manner the same is to be performed, I claim as my improvements as
follows:-
First. The arrangement of perforated hollow arch, and methods of
leading air into it, and delivering the air into furnaces as herein-before
described and illustrated in the accompanying Drawings.
Second. The apparatus for regulating the admission of air, constructed
as described herein and illustrated in the Drawings.
In witness whereof, I, the said Charles Fairbairn, have hereunto
set my hand and seal, this Eighth day of September, in the
vear of our Lord One thousand eight hundred and sixty-nine..
(L.S) CHARLES FAIRBAIRN.