IMPROVEMENTS IN FURNACES FOR STEAM BOILERS AND OTHER PURPOSES
Year: 1862

page_text: LETTERS PATENT to Robert Dunn, of Newcastle-upon-Tyne, Engineer,
for the Invention of "IMPROVEMENTS IN FURNACES FOR STEAM BOILERS
AND OTHER PURPOSES."
Sealed the 23rd December 1862, and dated the 16th July 1862.
PROVISIONAL SPECIFICATION left by the said Robert Dunn at the Office
of the Commissioners of Patents, with his Petition, on the 16th July
1862.
I, ROBERT DUNN, of Newcastle-upon-Tyne, Engineer, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN FURNACES FOR STEAM
BOILERS AND OTHER PURPOSES," to be as follows:-
This Invention relates to certain improvements in furnaces for steam boilers
and other purposes, whereby the prevention of smoke and an economy of fuel
are effected.
According to one part of this Invention it is proposed to make the fire bars
tubular and to construct them in two or more lengths, the tube of any one
length being fitted so as to correspond with the tube of the contiguous length
or lengths with the view of forming a continuous passage for air from the
front of the furnace to the bridge. The length next the bridge fits into a
metal frame or chamber upon which the bridge is placed. At the back of
this frame or chamber are one or more orifices through which the air passing

page_text: through the tubular bars makes its egress and then mingles with the gases
evolved from the fuel, whereby the combustion of such gases is caused.
Another part of the Invention consists in forming openings on the under-
sides of the tubular fire-bars so as to admit air thereinto, which air will then
pass along the tube even when the front portion of the bars has become stopped
up.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Robert Dunn in the Great Seal Patent Office on the
16th January 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
DUNN, of Nowcastle-upon-Tyne, Engineer, send greeting.
.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixteenth day of July, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-sixth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Robert Dunn, Her special license that I, the said Robert Dunn,
my executors, administrators, and assigns, or such others as I, the said
Robert Dunn, my executors, administrators, or 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, an
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN FURNACES
FOR STEAM BOILERS, AND FOR OTHER PURPOSES," upon the condition (amongst
others) that I, the said Robert Dunn, my executors or administrators
by an instrument in writing under my hand and seal, or under the band
and seal of one of them, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be per-
formed, 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 Robert Dunn, 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,
reference being had to the accompanying Drawings, and to the letters and
figures marked thereon, that is to say :-
My said Invention relates to certain improvements in furnaces for steam

page_text: boilers and other purposes whereby the prevention of smoke and an economy of
fuel are effected.
According to one part of this Invention it is proposed to make the fire-bars
tubular, and to construct them in two or more lengths, the tube of any one
length being fitted so as to correspond with the tube of the contiguous length
or lengths, with the view of forming a continuous passage for air from the
front of the furnace to the bridge. The length next the bridge fits into a
metal frame or chamber upon which the bridge when used is placed. Through
and at the back of this frame or chamber are one or more orifices by which
the air passing through the tubular bars makes its egress and then mingles
with the gases evolved from the fuel whereby the combustion of such gasès is
caused.
Another part of the Invention consists in forming openings on the under-
sides of the tubular fire-bars so as to admit air thereinto, which air will then
pass along the tube even when the front portion of the bars has become
stopped up.
And in order that my said Invention may be fully understood, I shall now
proceed more particularly to describe the same, and for that purpose I shall
refer to the several Figures on the Sheets of Drawings hereunto annexed, the
same letters of reference indicating corresponding parts in all the Figures.
Figure 1 on Sheet One of my Drawings represents a longitudinal vertical
section of one form of my improved furnace as applied to a cylindrical flue
steam generator; Figure 2 is a corresponding transverse section of the same;
Figure 3 is a plan of the furnace with one half of the improved fire-bars
removed; and Figures 4 and 5 are full sized transverse sections showing two
forms of these bars.
A is the internal flue or portion of the boiler; and B, B, are the hollow
fire-bars made in two lengths and joined end to end at a. The contiguous
ends of the bars are formed with snugs or projections 6 on their under sides,
which drop into the central space or opening c formed in the double bearer C
and are thereby held in their places longitudinally. The upper end of the
upper length of fire-bar rests upon any suitable form of bearer at D, and tho
lower end or that farthest in the furnace fits into a cast-iron hollow frame E
upon which is built the fire-bridge F (when employed) as is clearly shown
in Figure 1. Beneath this frame and hinged thereto is a door G capable of
being opened and closed from the front of the furnace by a rod and handle
for the purpose of clearing out any deposit of ashes which may take place
behind the bridge and frame. A semicircular channel is formed vertically in
the abutting ends. of the two lengths of fire-bars and extends from the bottom

page_text: to near the top of each bar; the two channels when the bars are in position
forming an air passage communicating with the interior of the hollow bars.
This passage is shewn at d in the detail plan of the under side of the two
abutting ends of the bars at Figure 6. .As the bearer C is made double or
with a central space between its two sides a free thoroughfare is afforded for
the passage of air from the ash-pit through the passages d into the lower
length of the fire-bars in case the admission of air through the upper and front
end of the fire-bars should become impeded by the presence of foreign matter
inside the upper length of bar. The arrows indicate the course of the air
currents. through the fire-bars and frame and behind the bridge where they
mingle with the unconsumed gases passing off with the other products of
combustion. In some cases I propose to cast my fire-bars with a supplemen-
tary division H (Figure 5) extending along the whole length of the bar and
situate a short distance below the real top or surface I of the bar, so that in
the event of the top of the fire-bar burning away the deposit of slag upon the
second top or division H will serve to protect it from the heat and will thus
enable the bar to be used as an air bar long after its surface is burnt away.
In order to prevent the ends of the bars from rising a transverse snug or
projection e is cast on the end of one bar and fits into a corresponding notch or
recess in the corresponding bar as shewn in Figure 1.
Figures 7 and 8 represent respectively a longitudinal vertical section and a
half transverse section of my improved construction and arrangement of fire-
bars as applied to an external flue boiler. In this case a passage K is left
behind the bridge between it and the setting L, for the free passage of the air
after traversing the fire-bars and passing under the bridge. In this modifi-
cation the lower ends of the bars rest upon a special bearer M which is separate
and distinct from the casting or frame E supporting the fire-bridge F. The
door G closes horizontally against the bearer M, and forms when closed tho
bottom of the air passage under the bridge and frame. N is a bell crank,
and O a handle for opening and closing the door G from the front of the
furnace. Figure 1 and 2, on Sheet 2 of my Drawings, represent in longi-
tudinal and transverse section the application of my fire-bars and mode of
setting to an ordinary tubular marine boiler. As their construction and
arrangement is precisely similar to that herein-before described inreference to
Figures 1, 2, and 3, on Sheet 1, further description is unnecessary. Figures 1
and 2, on Sheet 3 of my Drawings, represent respectively in longitudinal and
horizontal section, my improved fire-bars and setting as applied to a locomotive
furnace or fire-box. In this case the hollow fire-bars B, B; are supported
upon a metal frame U. (which, however, forms no part of my present Invention)

page_text: this frame contains the three bearer's C, D, and M, and is supported near its
centre at each side upon pivots or centres P, P, turning in brackets Q, Q,
secured to the bottom of the fire-box. The frame with the fire-bars upon it
inclines downwards towards the front end of the fire-box, or that end furthest
from the fire-door, so that when the engine is running forward a powerful
current of cold air will constantly pass up the interior of the bars and tend to
keep them cool, the forward ends of the bars being made to project below the
bottom of the fire-box for the purpose of catching the air. E is a hollow
metal frame situate at the back or fire-door end of the fire-box or furnace,
and extending across the fire-box from side to side. The front edge of this
frame next the fire-bar ends is bevilled or inclined downwards on the upper
side and a corresponding bevel or incline is formed on the under sides of the
ends of the fire-bars, so that the latter will fit down upon the bevelled edge of
the frame, when in position. f.f, are a series of stays or supports cast in the
front portion of the hollow metal frame for the purpose of strengthening the
same; the lower part or bottom of this frame consists of a hinged door G
which is opened occasionally to clear out any deposit inside the frame. This
door is opened by means of the lever R and rod S, which latter is jointed to
a vertical lever T fast on one of the pivots or centres of the supporting frame U.
This lever is held in a vertical position so as to keep the fire-bars in their
proper places down upon the edge of the frame or box E by a pin in a curved
guide bar V, secured to the side of the boiler, but on the withdrawal of this
pin the moveable frame U is so hung as to drop into the position indicated by
the dotted lines, and instantly to discharge the whole of the fire when requisite.
Lugs or projections g, g, are formed upon the sides of the moveable frame U
for the purpose of supporting the fire-bars laterally and preventing them from
falling over sideways. The air which enters the frame E escapes by the
pipes W, W, fitted into the top of the frame E and is by them directed
towards the centre of the fire-box a little above the level of the fuel where it
mingles with the gases and assists the process of combustion.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe in conclusion, that what I consider to be novel
and original, and therefore claim as the Invention secured to me by the berein-
before in part recited Letters Patent, is,―
First, the general constructions and arrangements of furnaces for steam
boilers and other purposes as herein-before described.
Second, the application and use to and in steam boiler and other furnaces
of two or more lengths of hollow fire-bars in combination with a metal frame

page_text: or chamber at the back of the furnace, substantially in the manner and for the
purpose herein-before described.
Third, the forming of openings on the under side of the hollow fire-bars
above referred to for the purpose of admitting air therein in case the passage of
air through the upper length of bar should become obstructed as herein-before
described.
In witness whereof, I, the said Robert Dunn, have hereunto set my
band and seal, this Sixteenth day of January, One thousand eight
hundred and sixty-three.
ROBERT DUNN. (L.S.)