IMPROVEMENTS IN FURNACES FOR THE PREVENTION OF SMOKE
Year: 1874

page_text: LETTERS PATENT to George Nimmo, of the City of Glasgow, in the
County of Lanark, North Britain, Steel Maker, for the Invention
man PonyENTION OF SMORE"
PROVISIONAL SPECIFICATION left by the said George Nimmo at the
Office of the Commissioners of Patents, with his Petition, on the
8th June 1874.
I, GEORGE NIMMO, of the City of Glasgow, in the County of Lanark,
North Britain, Steel Maker, 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 consists in certain improvements in the forming
or constructing of apertures and doors for regulating the admission of
air in front of the fire and fire-grates of steam boiler and other furnaces

page_text: burning small coal or other fuel which produce black smoke, all for
the prevention or burning of the same within the furnace before
escaping to the chimney, being substantially improvements upon the
Invention for which Letters Patent were granted to the petitioner,
dated 21st November 1873, No. 3792. And the nature of the im-
provements forming this said Invention consists in making the front
part of the hearth, or firing "dumb" or "dead" plate within the
charging doors, and close in front of and across the whole burning
fuel with an opening, or a set of openings, up through from the
under side or front part of the ash-pit, and fitting the same with a
hinged or sliding door or doors, either within these openings or above
or below them for regulating the admission of a proper amount of
air by hand setting or automatic lever, or other equivalent mechanism,
and preferably with a counterbalancing weight or spring acting in the
one direction to retain them where set, or shift them gradually close
after being set open by a water, pneumatic, or other equivalent regu-
lator, such as used for regulating the time of closing of many kinds
of valves.
The new or improved air opening may be cut out of the present
hearth plates in the form of a long part across nearly the wholo front
of the fire, and have the door hinged either to the back or front edge
so as either to open up or down and direct the air upon the burning
fire, and when level close the hole so as to make the hearth level
for the firing of the fuel, or drawing out of the clinkers as usual;
and when a sliding door was used it might cither fill this hole right
out to the front, or slide above or below, the air holes made in longi-
tudinal or transverse slits, or other equivalent interstices through the
hearth plate; or otherwise, the furnace bars might be brought quite
forward to near the charging closed doors, and have a part of them
left clear in front without fuel, with the hinged or sliding door set
close above or below this part of the hearth to regulate the admission
of air up through the spaces between the bars in front of the burning
fuel.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Nimmo in the Great Seal Patent Office on
the 5th December 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
NIMMO, of the City of Glasgow, in the County of Lanark, North Britain,
Steel Maker, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of June, in the year of
our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said George Nimmo, Her special licence, that
I, the said George Nimmo, my executors, administrators, and assigns,
or such others as I, the said George Nimmo, my exccutors, admini-
strators, 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 George Nimmo, my executors or administrators, by an in-
strument in writing under my, or tlieir, or one of their hands and seals,
should particularly describe and ascertain the nature of the said In-
vention, 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 George Nimmo, do hereby declare
the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement in writing, reference, being had to the illustrative
figures and reference letters on the accompanying Sheet 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 my said Inven-
tion into effect or practice, the same reference letters and numerals
indicating the same or like parts in all the Figures.
My said Invention consists in certain improvements in the forming
or constructing of apertures and doors for regulating the admission

page_text: of air in front of the fire and fire-grates of steam boiler and other furnaces
burning small coal or other fuel which produces black smoke, all for
the prevention or burning of the same within the furnace before
escaping to the chimney, and which are substantially improvements
upon the Invention for which Royal Letters Patent were granted to me
dated 21st November 1873, No. 3792.
Figures 1 and 2 are a sectional side and end view of the front part
of a horizontal double-flued land steam boiler as fitted with fire-grate
in the flues, having one modification of my improvements applied
thereto, and in which the new air opening A and its closing door B
are formed right across the hearth plate 1, and having the latter hinged
in the front thereof.
Figures 3 and 4 are a corresponding side and front end section of a
marine boiler with three horizontal furnace flues fitted with a slightly
different modification (or arrangement of my said improvements from
that shown in Figures 1 and 2) in which the air is admitted through
short longitudinal or rectangular openings A in the hearth plate 1, and
having their closing door B hinged in the reverse direction close to the
ends of the furnace bars to allow the air free entrance, and at the same
time prevent the fire and fuel from getting through the air holes by the
pitching of the vessel, or other cause.
Figures 5 and 6 are a longitudinal section and front view of the front
end of an ordinary horizontal land boiler, with the fire-grate below the
boiler, and fitted with a modification of my new air openings A formed
(much similar to that shown in Figures 3 and 4) in longitudinal recesses
through the front hearth plate 1, but with a sliding door B below
instead of a swivelling door. Figure 6 A. shows a plan of the hearth plate
1 and closing door B, with the slits or openings A in them for the
admission of air to the front of the fire and fuel at 3
3.
· Figures 7 and 8 are a longitudinal section and a front clevation of
the furnace. part of a steam boiler, with short longitudinal air openings
A through the front plate 1, similar to that shown in Figures 5 and 6,
but with a close box A¹ below, with an angled sliding door B in front of
the long opening A² into this air box, to regulate the admission of the
air to the front part 3 of the burning fuel; and Figure 8 A is a horizontal
section of the furnace mouth 2 and plate 1, showing the openings A
through the latter for admitting the air to the front of the fire.

page_text: Figures 9 and 10 are a sectional elevation and a front view of a
furnace mouth suitable for steam boiler and other furnaces, and fitted
with a modification of the air openings A, left clear through the fire-
bars themselves in front, with an oscillating closing door B below these
openings for the admission and regulation of the air to the front of the
fire and fuel in accordance with my said Invention or improvements; or
it might be fitted with a sliding door B.
Referring to these Figures 1 to 8, the nature, novelty, and mode of
performing my said Invention or improvements consist all as follows,
namely, in making the front part of the hearth or firing "dumb" or
"dead" plate 1 (a little within the charging doors 2, and close in front
of and across the whole burning fuel at 3. 3) with one long opening A,
as shown in Figures 1 and 2; or it might be a set of rectangular openings
A, as shown in Figures 3 to 8, formed up through the plates 1 for the
admission of the air from the under side of the plate 1 and front part of
the ash-pit 4. The entrance or passage of the air through the openings
A is regulated by a long swivelling door B hinged either at the front.
edge of the recess A, as shown at Figures 1 and 2, to direct the air on to
the front of the burning fuel 3, or at the back edge, as shown in Figures
3 and 4, angled in the reverse direction to retain the fuel on the bars 5
and yet admit the air freely over the top edge and through the lateral
recesses in the door B, which is raised and lowered to open and close, or
set it to any intermediate position, cither by the crank spindle O and
hand lever and ratchet wheel, and pall D, D¹, as in Figures 1 and 2, or
by a simple lever C on the axle of the door B, actuated by the drawing
hand rod D, with ratchet teeth D¹, which in either casc holds the door
at any desired position by the weight of the door itself, all so as to
regulate the admission of a proper amount of air to maintain the com-
bustion of the fuel across the front at 3---3, which by this means
effectually heats and inflames or burns the gases and smoke above, and
rising off the whole surface of each fresh charge of fuel added to the fire.
Referring to Figures 5, 6, and 6 A, the new holes A are closed and
opened so as to regulate the admission of the air by the lateral sliding
door B reciprocated in slides or snugs 6 formed close below the hearth
plate 1 by the short hand crank spindle D and pinion C, on its inner end
working into a rack on the under side of the door B, as scen particularly
in Figure 6 A. In this arrangement the ash-pit is shown as divided
horizontally near the middle into two chambers 4 and 4 by the division

page_text: or arch E, with an opening up through it behind at E', the upper
division 4 being closed in front by the door or plate F below the grate
5, so that the air in this case passes in by the lower chamber 4 of the
ash-pit below the arch E, and returns between it and the fire-bars 5, so
as to get heated before passing up through these and the air spaces A,.
formed in the "dumb" plate 1 and sliding door B, all as indicated by
the blue arrows in Figure 5.
Referring to Figures 7, 8, and 8A, the front of the air box A' is
preferably made slanting outwards towards the open mouth A2 at the
lower edge, and the door B is guided in slides b at the ends where racks
are formed on it, through which it is raised and lowered by the
pinions C on the cross spindle C¹ gearing into them, worked by the hand
lever D, and is held in any position by the pall D¹; but the door B
might be hinged at the upper or lower edge of the opening A3, and
opened and closed by a simple hand lever instead of sliding; in either case
regulating the admission of air to the box A¹ where it is heated before
passing through the opening A, for the better combustion of the fuel 3
in front and gases above, as in the former modifications.
Referring to the modification of my said improvements, shown in
Figures 9 and 10, the air is admitted through the openings at A between
the furnace bars 5, left quite clear of fuel at A above them for the
air to pass up, as indicated by the arrows under and round the inner
edge of the door B, actuated and set more or less open by the hand
lever C, which fixes or holds it at any desired position by the notched or
pin quadrant C₁ according to the amount of air desired to be admitted
for the burning of the fuel at the front 3 and smoke above, all otherwise
as described in reference to the former Figures; and this or any of the
other arrangements, Figures 1 to 4, might be fitted with the dividing
plate. E and door F in the ash-pit 4 for heating the air before entering
the furnace or openings A.
In some cases the new or improved openings A may simply be cut out
of the present hearth plates 1 in the form of a recess A across nearly the
whole front of the fires 3 below the furnace doors 2, and having the air
door B fitted into it and drawn out quite in front by. a rocking spindle
below, connected by levers and links or by racks and pinions, or..
otherwise; these doors B might slide longitudinally or laterally on the
top of the hearth plate 1 and holds A in it instead of under them, as

page_text: shown in Figures 5, 6, and 6A, and the oscillating doors B in
Figures 1 to 4, might oscillate down below the plate 1 instead of above
it, as there shown, and although lateral and longitudinal rectangular air
openings A only have been shown and described, other forms of openings
might be made through the front hearth or plate 1. In all cases when
the openings A and doors B are closed, the front plate 1 is left as clear
and level as possible for the firing or charging of the fuel, and Drawing
out of the clinkers, all in a usual manner.
Instead of the hand moving lever and fixing mechanism C, D, herein.
shown and described, for setting and regulating the position of the
doors B, and consequently the admission of air after every new charge
of fresh or "green" fuel, and closing these doors by hand when the
smoke is consumed; this may also be effected by levers or other
equivalent mechanism-connected to the doors B, so that when once set
open to the desired extent after each charge of fresh fuel, a spring,
weight, or other equivalent would automatically and gradually close them
when the smoke was consumed, regulated in the manner of pneumatic
or water "cataracts," such as used for regulating the opening and
closing of the valves for steam engines and for other purposes.
Having thus described the nature of my said Invention, and the
manner in which the same is or may be performed, I have to state that
I do not restrict myself to the precise details herein described and
delineated, but what I believe to be novel and orignal, and there-
fore claim as the Invention secured to be by the herein-before in part
recited Letters Patent is,-
First. The general arrangements of openings A formed up through
the front hearth 1 of steam boiler and other furnaces, and their
regulating doors B and other parts or fittings, all substantially as and
for the purposes herein described and distinguished under the several
modifications, and shown in the accompanying. Drawings or any mere
modification thereof.
Second. The forming of openings A up through the hearth plate 1 of
steam boiler and other furnaces, and in fitting the same with regulating
doors for the admission of air to keep the front, fucl regularly burning,
and so as to ignite and burn the gases as they rise off the fresh fuel over

page_text: the whole fire behind, all substantially as herein described and shown
in the accompanying Drawings.
In witness whereof, I, the said George Nimmo, have hereunto
set my hand and seal, this Fourth day of December, in the
year of our Lord One thousand eight hundred and seventy-
four.
Witness,
W. R. M. THOMSON,
+
Patent Agent,
Glasgow.
GEORGE NIMMO. (L.S.)