IM- PROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE.” PROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE
Year: 1875

page_text: LETTERS PATENT to John Clark, of Paisley, in the County of Renfrew,
North Britain, Thread Manufacturer, for the Invention of "IM-
PROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE.”
PROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE.”
PROVISIONAL SPECIFICATION left by the said John Clark at the
Office of the Commissioners of Patents, with his Petition, on the
9th July 1875.
I, JOHN CLARK, of Paisley, in the County of Renfrew, North Britain,
Thread Manufacturer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE," to be as
follows:-
=
This said Invention has reference to a new or improved mode and
means of admitting and conducting air to a chamber or recess at the
back bridge or wall of steam boiler and other furnaces, and also of
heating the said air while doing so, for the purpose of, and before

page_text: allowing it to intermingle with, and completely burn or inflame the
smoke and gases passing over the said bridge from the fuel and furnace,
all in a more simple and economical manner than heretofore.
The nature and novelty of this Invention consist in admitting and
conducting the air (for combining with and burning the said smoke
or smoky gases) from the outside walls of the furnace by and within
metallic pipes, led through the main flue or flues of the boiler or
furnace, preferably in the opposite direction to that in which the hot
gases are passing through these flues from the said bridge to the
chimney, so that the air is thus heated by the hot gases acting on the
outside of the pipes, which then admit it through a back wall in the
flue behind the ordinary flame wall into the space between these walls
which is formed into a hot-air chamber by arching or covering it over
by an angled fire-brick, or other equivalent roof highest behind, and
with numerous narrow openings between the bricks to still more
heat and direct the air in thin currents upwards to the smoky gases,
which are impinging on or passing close over this angled roof.
No claim is made for a mere hot-air space behind or within the flame
bridge, as this has been frequently used before, but only for the
arrangement or arranging of heating pipes for conducting and admitting
the air thereto, in the manner and for the purposes herein-before and
herein-after stated.
These new or improved air-heating pipes when applied to Cornish or
flue boilers, with the furnaces within tho flues, would be arranged to
conduct the air either direct through the back wall or brickwork in a
straight line to the said hot-air chamber, or in through the ash-pit in
front, through the walls of the hot-air chamber to the back end of the
main flue and back again by a bend along another return pipe, before
entering the hot-air chamber. And when applied to furnaces below or
without boilers, these new or improved air-heating pipes would be led
in through the middle of the main flues formed in the brickwork to the
said hot-air chamber, otherwise essentially as described for fluc boilers
with the furnaces within them. These air-heating pipes may be made
of cast or malleable iron, or of steel, copper, or brass, and would
preferably be made large enough (as, say from 4 to 8 inches) to admit
the air freely and allow of its expansion in heating (unless fanners or

page_text: '
blowers are used to insure the inward current); and these pipes are
fitted with inlet valves or dampers for regulating the admission of the
air.
.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Olark in the Great Seal Patent Office on
the 5th January 1876.
г
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
CLARK, of Paisley, in the County of Renfrew, North Britain, Thread
Manufacturer, send greeting.
!
'
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters. Patent, bearing date the Ninth day of July, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
ninth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Clark, Her special licence, that
I, the said John Clark, my executors, administrators, and assigns, or
such others as I, the said John Clark, 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 FURNACES
FOR THE PREVENTION OF SMOKE," upon the condition (amongst others) that
I, the said John Clark, niy 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 Clark, do hereby declare
the nature of my said Invention, and in what manner the same is
shad and cocontained
1
1

page_text: several Figures on the two accompanying Sheets of Drawings, and to
the reference letters marked thereon, that is to say :-
My said Invention has reference to a new or improved mode and
means of admitting and conducting air to a chamber or recess at the
back bridge or wall of steam boiler and other furnaces, and also of
heating the said air while doing so, for the purpose of and before
allowing it to intermingle with, and completely burn or inflame the
smoke and gases passing over the said bridge from the fuel and furnace,
all in a more simple and economical manner than heretofore.
The nature and novelty of my said Invention consist in admitting and
conducting the air (for combining with and burning the said smoke
or smoky gases) from the outside walls of the furnace by and within
metallic pipes, led through the main flue or flues of the boiler or furnace,
preferably in the opposite direction to that in which the hot gases are
passing through these flues from the said bridge to the chimney, so that 1
"the air is thus heated by the hot gases acting on the outside of the
pipes, which then admit it through a back wall in the flue behind the
ordinary flame wall into the space between these walls, which is formed
into a hot-air chamber by arching or covering it over by an angled
fire-brick or other equivalent roof, highest behind, and with numerous 2
narrow openings between the bricks, to still more heat and direct tho
air in their currents upwards to the smoky gases which are impinging
on or passing close over the said perforated bridge or roof.
No claim is made for a mere hot-air space behind or within the flame
bridge, as this has been frequently used before, but only for the 2
arranging or arrangement of heating pipes for conducting and admitting
the air thereto, in the manner and for the purposes herein-before and
herein-after stated.
These new or improved air-heating pipes when applied to Cornish or
'flue boilers, with the furnaces within the flues, would be arranged to 3
conduct the air either direct through the back wall or brickwork in a
straight line to the said hot-air chamber, or in through the ash-pit in
front through the walls of the hot-air chamber to the back end of the
main flue, and back again by a bend along another return pipe before
entering the hot-air chamber. And when applied to furnaces below or 3
without boilers, these new or improved air-heating pipes would be led
in through the middle of the main flues formed in the brickwork to the

page_text: said hot-air chamber, otherwise essentially as described for flue boilers
with the furnaces within them.
These air-heating pipes may be made of cast or malleable iron, or
of steel, copper, or brass, and would preferably be made large enough.
(as, say from 4 to 8 inches) to admit the air freely and allow of its
expansion in heating (unless fanners or blowers are used to insure the
inward current), and these pipes may be fitted with inlet valves or
dampers for regulating the admission of the air.
And in order that the nature and mode of performing my said Inven-
tion may be properly understood I shall now proceed to describe the
several Figures and modifications or arrangements thereof shown on the
two accompanying Sheets of Drawings, which I have hereunto appended
for the purpose of showing the best modes and means I am at present
aware of for putting the Invention into effect or practice, the same
letters being used to indicate the same or like parts in all the Figures
where shown.
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Figures 1 and 2 on Sheet 1 are a longitudinal and a transverse section
of a Cornish or two-flue boiler A, furnace and brickwork, taken respec
tively on the irregular lines or planes 1. 1 and 2 2, 2¹ 2',
each on the other Figure; and Figure 3. is a sectional plan of the said
boiler only, taken through the centre 3 3 above one furnace, and on
the line 3. 3' below the other in the nearest flue of Figure 1, all
corresponding to each other, and fitted with one modification or arrange-
ment of my said improvements or Invention. A is the outer cylindrical
shell of the boiler built in the brickwork B, and having the two fire-box
and fluc tubes C, C, running from end to end, with the furnace mouth D
and fire-grate D¹ fitted within each flue in front of the bridge or flame
wall E at the back of the ash-pit F, all formed and fitted so far in an
ordinary manner, but having air admitted in a new manner through the
smaller pipe a of two cast-iron pipes a, a¹, entering from each ash-pit F.
Each pipe a is led through the wall E to the back part C¹ of the heating
flues C, C, where they are united by the semicircular knee or bend a¹,
joining it with the back end of the larger pipe a', which is carried
forward through the wall E¹ into the close chamber G between the two
walls E, E', surmounted by the perforated iron or fire-clay block or
cover G perforated with a transverse row of narrow longitudinal
openings g, all so that the air enters from the hot ash-pit F of cach

page_text: furnace D, D¹, passing through the pipes a and a', the latter of which
being larger allows it to expand as it gets heated, and assists its course
or current into the close chamber G, from which it escapes up through
the interstices g, so as to meet the unconsumed gases or smoke from the
coal or other fuel passing over the bridge G', so as to ignite and burn it
over this bridge, or as the gas and air pass along the top of the flues C, C,
the course of the flames and smoke from the furnace D, D', is indicated
by red arrows, and that of the air by black arrows.
In addition to the said air pipes a, a¹, a", additional or supplementary
air pipes b, b, may be fitted at cach side of the grate bars D', and level
with them to form part of the grate hearth, and open at front through
the furnace front or hearth plate at 6*, so as to convey air direct into
the close air chamber G through these pipes b, b, which being very hot
with the fire on them would heat the air in its passage, and so pass out
through the openings g with the air entering by the pipes a, a¹, and
assist it in burning the smoke, as before stated.
Although not shown in the Drawings the entrance at a* to the air
pipes a, or that of the ash-pit leading thereto, or the entrances a*, b*, to
the pipes a, b, may be fitted with inlet doors or valves to regulate or
control the amount of air admitted to suit the kind of fuel or amount of
smoke or gases to be consumed.
Figures 4, 5, and 6, on Sheet 2, are a transverse, a longitudinal, and a
horizontal section respectively taken on the lines 1 1, 2 2, and
33, all of an ordinary horizontal egg-ended steam boiler A as set or
built in its brickwork B, and fitted with a modification of my said:
improved hot-air arrangements, and illustrative of the application of
this Invention to such boilers with the furnaces D, D¹, below for the
consumption of the smoke therefrom.
1
Figure 7 on the same Sheet shows a longitudinal section of the fire-
box D, D¹, of an ordinary locomotive or portable steam engine boiler, as a
fitted with and illustrative of the application thereto of a modification of
my said improvements or Invention.
Figures 8 and are a transverse and a longitudinal section of an
ordinary type of marine engine steam boiler A, respectively taken on
the lines 1. 1 and 2. - 2, the furnace D, D', of which is fitted with
another modification of my said improved hot-air arrangement and pipes
for the burning and prevention of smoke in marine boilers,

page_text: Figures 10 and 11 are a vertical and a horizontal section of the
furnace part D, D', of an ordinary form of air or reverberatory furnace
B, used for the smelting and heating of iron and other materials, shown
as fitted with a modification of my improved air heating, and smoke
consuming arrangements, illustrating the application of my said In-
vention to such furnaces.
Referring to the modification or arrangement shown in Figures 4, 5,
and 6, the air is all admitted from the front below the furnace mouth
and hearth plate D at 6* through two of the side tubular bars 6, as in
Figures 1 to 3, direct into the chamber G between the back walls E and
E', and through the rest of the tubes 61 (between the others 6 of which
in this case the whole body of the furnace bars or grate is formed) into
the close chamber f, from which the air is then led into the pipe a
(instead of direct from the ash-pit F as in the said Figures 1 to 3), and
on through the bend a¹¹ and return pipe a', as in the said Figures 1 to 3,
and as indicated by the black arrows, so as to mingle with and consume
the heavy hydrocarbon gases or smoke in a flame while passing over the
bridge and jets of air at G³, g, these gases and the heated products of
combustion being indicated by red arrows as in the other Figures. In
this arrangement Figures 4 to 6, the ash-pit F is closed in at F" and
fitted with a door or valve to regulate the amount of air to be admitted
below the grate D', and so that the rest of the air required to support
proper combustion will pass through the tubular grate bars b, b1,
although a door or valve may also be fitted at the front ends 6* of these
tubes to regulate the air passing in through them to consume the
gases. The back end of the new inlet and return air heating pipes a, a¹,
and their bend a" are (in this case, Figures 4 to 6) carried out beyond
the building B of the boiler, so as to be conveniently used for drying
and heating purposes, such as by a chamber or plate at B¹ for drying
workers' clothes, or for heating vessels of water or other material
required in the works where these boilers are erected, and although one
set of these new or improved cast-iron pipes a, a, are only shown in
each furnace in Figures 1 to 6, it is to be understood that two or 'morc
sets might be used, and that they might be made of malléable iron,
steel, copper, or other metal or mixture of metals which would stand the
heat, and be as good conductors thereof to the air inside of them, and
further, that although these pipes a, a¹, have been shown horizontal and
below the bridge G', they might be placed higher behind, as indicated in
'
་

page_text: red lines in Figure 5, so that the incandescent or heated gases and
products of combustion (passing through the flue at C¹ below the back
part of the boiler A), would impinge or surround them and heat the air
passing through them to a higher temperature than when the pipes are
placed below, as shown in black lines in these several Figures 1 to 6.
Referring to Figure 7, and the application or adaptation of my said
improvements as therein shown to locomotive fire-boxes, I fit a door F¹¹
in front of the ash-pit F to regulate the admission of air thereto to pass
up through the grate bars D', which I form wholly of long and short
air-heating tubes b', ', alternately, all resting on a bar D", surmounted
by a low fire-brick division bridge or wall c some little distance from
the front or tube plate of the fire-box D, so as to leave an air chamber G
with a contracted or thin opening g at the top, across the whole, and into
which the ends of the short tubes open, while the long tubes take in or
receive the air from the outside at their front ends 6* over the door F¹
of the ash-pit F, and both sets of tubes being jointed with their other
open ends into a close air chest f placed across the back end of the fire-
box, and having divisions in it between each pair of tubes, it follows
that the air is conveyed back and heated in each long tube bar 6¹ to a
compartment of the chest f, and further heated in returning forward
through cach corresponding short tube bar & into the air chamber G,
from which it passes up in a hot stream at f', as indicated by the black
arrows, to inflame or burn the gases before entering or while passing
through the tubes C of the boiler.
In applying my said improvements to the furnaces of marine boilers
and to air or reverberatory furnaces for the smelting and heating of
metals, and shown in Figures 8, 9, and 10, and 11, I make the furnace
bars all of air-heating metal tubes 6', carried on a cross bar D" below
the hearth plate D near their front end 6*, where the air enters them,
and having all their back ends carried in the front wall E of the flamo
bridge, with their back ends all opening direct into the hot air
chamber G between the said wall and the back wall E', so that the
air, after being heated in passing through the tubular bars 6', passes up
through the transverse row of longitudinal slits in the bridge G¹ over
the hot air chamber G, all as indicated by the black arrows, so as to
mix with and burn the black or unconsumed gases passing the bridge,
all otherwise substantially as described in reference to the former
Figures, and indicated by the red arrows, which show the course of the

page_text: and flues.
Although in these Figures, 4 to 11 inclusive, the furnace grates are
shown as wholly formed of air-heating metal tubes or pipes, this need
not always be so, as when it was found that the air required to burn the
smoke, and passing through the tubes was not sufficient to keep them
cool enough to prevent them burning, then ordinary furnace bars may
be used in the centre part of the furnace, and only sufficient tube hars
fitted on each side of these to allow the air to pass in sufficient quantity
and at a velocity which would prevent them burning; and it will be
understood that in all these improved arrangements it is preferred to
close in the ash-pit or chamber F, and only admit the air below the
grate by a regulating door or valve at F¹ to maintain the proper state of
combustion of the fuel over the grate, while the air to burn the hydro-
carbon gases or smoke is to be as much as possible passed through the
new or improved arrangement of pipes or tubes a, a', a", b, and 6¹,
described in reference to and shown in the Drawings. These pipes when
long (and convenient, or when made in separate lengths), as at a and a¹,
in Figures 1, 2, and 3, ought to increase in diameter inwards as the air
gets heated in them, to allow of its expansion and accelerate its speed
or draught towards the air chamber G or furnace, where the air ignites
with the gases and smoke to be burnt.
Although all the improved air conducting and heating pipes a, a¹,
described in reference to and shown in the Drawings receive their air
through end openings at the front of the ash-pit or front of the furnaco
(this being found preferable in practice) it is to bo understood that theso
pipes may be made without their connecting bends a", and each receive
the air at their back ends B*, Figures 1, 5, and 6, behind the back of
the brickwork B, and have all their front-ends opening and conducting
the air heated by them into the chamber G to enter the furnace and
burn the smoke either without or in combination with the pipes 6 or b',
leading air in from the front of the furnaces, all otherwise as before
described, over and behind the interstices and bridge 7 G¹, and theso
pipes in this case might be made small and more numerous, and have
their back ends at B* jointed into a close air entering box with a great
number of apertures in its front face, and have a light hinged or hanging
sheet metal flap or door in the inside which would admit air freely, but
when a blast of the hot-air or gases was forced back through the pipes

page_text: a, a', it would close the said door over the holes and prevent the escape
of the hot air or fire.
Figure 12 is a plan to a small scale of one modification of my said
improvements as applied to an ordinary horizontal two flue steam boiler
and its furnace A, B, C, D, substantially similar to that shown in the
detailed sectional Figures 1, 2, and 3, on Sheet 1, but showing the
further application of my said improvements to the heating purposes by
carrying the new or improved air heating pipes' a from the ash-pit F (or
hot chamber, Figures 4 to 6) away behind the boiler into or round, or
so as to undulate within a. drying or other house, chamber, or oven O, as
at o, so as to heat it before being joined to the return heating pipe a¹ to
be re-heated and passed into and through the chamber G, and slits or
apertures g, g, to combine with and burn the smoke or hydrocarbon
gases passing over the bridge G₁ of each furnace D, D¹, and which will
be another or further use of this my new or improved mode and means
of supplying heated air to furnaces for the prevention of smoke.
"
In practice it has been found that these improvements, besides
burning and preventing the escape of all black smoke from the chimneys
of boiler and other furnaces to which they have been applied, effect at
the same time a great saving in coal or fuel.
'
Having thus described the nature and mode of performing my said
Invention, I may' observe that in the several modifications or arrange-
ments of my improvements I have indicated by italics or small letters
the parts which I believe to be new or improved and those which I
consider have been used heretofore I have indicated-by-capitals-or-large-
letters; and I may observe further that I do not desire to confine myself
exclusively to the precise construction or the particular arrangement of
the parts which I have herein described and shown, as many variations
may be made therefrom without departing from the main or essential
features of my said Invention, but what I consider novel and original,
and therefore claim as the Invention secured to me by the herein-before
in part recited Letters Patent is,—
First. The general arrangement of the parts of furnaces, with their.
respective modifications of air induction and heating metal tubes for the
prevention of smoke therein, all substantially as herein described and

page_text: Second. The arrangement of metal pipes a, a¹, a", and b, b¹, for the
induction and heating of air to and for furnaces for consuming or
preventing the formation or escape of black smoke therefrom, all
substantially as described in reference to the respective modifications
shown in the accompanying Drawings or any mere modification
thereof.
Third. The making of air heating and induction pipes for furnaces
larger in diameter or area as they proceed inwards, to allow of free
expansion, and induce a better draught of the air within them, to
consume or prevent the production or escape of smoke from furnaces,
all substantially as herein described in reference to and shown in the
accompanying Drawings, or any mere modification thereof.
In witness whereof, I, the said John Clark, have hereunto set
my hand and seal, this Thirtieth day of December, in the
year of our Lord One thousand eight hundred and seventy-
five.
Witness,
A. MORTON STRATHERN,
Engineer,
Paisley.
JOHN CLARK. (L.S.)