IMPROVE- MENTS IN APPARATUS AND FURNACES FOR HEATING, WELDING, OR MELTING METALS, PARTS OF WHICH IMPROVEMENTS ARE APPLICABLE TO OTHER FURNACES
Year: 1858

page_text: PROVISIONAL SPECIFICATION left by Robert Armstrong and John
Galloway at the Office of the Commissioners of Patents, with their
Petition, on the 14th April 1858.
We, ROBERT ARMSTRONG, of North Woolwich, in the County of Essex,
Civil Engineer, and JOHN GALLOWAY, of Manchester, in the County of Lancaster,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN APPARATUS AND FURNACES FOR HEATING, WELDING, OR MELTING METALS,
PARTS OF WHICH IMPROVEMENTS ARE APPLICABLE TO OTHER FURNACES," to be as
follows:-
The principal objects of our Invention are to obtain more perfect.com-
bustion of the fuel, to increase the heat, and to prevent the issue of opaque
smoke, and to economize fuel.
We proceed in the following manner-In applying our Invention to an
ordinary reverberatory forge furnace, such as is commonly used for forging
blooms, slabs, or bars, from piles of scrap iron, and for other similar purposes,
heated by bituminous or smoky coal supplied by hand firing, stoked in the usual
way, and provided with a chimney shaft of the ordinary proportions of about 36
feet high by 18 or 20 inches square, and surmounted by the usual damper and
lever apparatus. We increase the height of the chimney to about 48 or 56
feet for the purpose of improving the draught and enabling us to work with
thicker fires. The gases produced by the thick fires are consumed by air
admitted above the surface of the fuel in the following manner :-We erect
upon the top or arched crown of the furnace one or more series of narrow
parallel channels formed of brickwork or other suitable material, forming a hot

page_text: air drain, through which a constant supply of atmospheric air is admitted in
numerous thin streams in order to its becoming more readily heated, and is
thence passed through one or more suitable apertures into the grate room or
fire-place for the purpose of supporting and effecting the combustion of the
carbonic oxide or other inflammable gases therein generated. When more than
one series of tubular channels are required to form this hot air drain, we prefer
that the cold air should first pass into those channels having the smallest
diameter, and afterwards through those of gradually larger sectional dimensions
and collective area towards the place where the air enters into the furnace,
which we prefer to be through one or more narrow transverse passages, slits,
or openings across the anterior portion of the roof of the grate room or
fire-place. And where the construction of the said roof will admit, we prefer
that the heated air should be conveyed through one or more or between
two descending bridges projecting downwards into the fire chamber in such
manner as to direct the combined currents of hot air in one or more sheet-
formed streams into or upon the inflamed gas, as the latter arises from the coal
on the front portion of the grate, and in the vicinity of that part upon which
the charges of coal are first deposited, or between that part and the fire-bridge.
We also admit a variable but limited amount of air through a register or
valve in the front wall or door of the fire-place through a passage or passages
which for distinction's sake may be called the cold air drain; this air may be
cold or it may be heated by passing through a perforated fire-brick shield or
otherwise.
This cold air drain is used when the air supplied by the hot air drain is
deficient in quantity, and also for preventing smoke, and occasionally in con-
junction with a damper apparatus at the chimney in the following manner :-
At the side of the chimney within four or five feet of the ground or close to
the neck of the flue leading into it, or in other convenient position near the
base of the chimney, we make an opening of eight or ten inches square, or
more or less, and apply thereto a damper plate or valve of any convenient
form, having a lever or rod and handle by which the same can be opened or
shut with facility, such rod being led by suitable guides to a convenient
position near the fire-door or usual place of charging the furnace with coal, so
as to be within reach of the stoker or furnace-man's hand when firing, and
also close to the handle of the register of the cold air drain in such manner
that both handles may be moved simultaneously or separately when required.
In charging the furnace before introducing any fresh coal into the fire, the
chimney valve is opened, and in about 15 or 30 seconds after the coal is intro-
duced and the fire-door or cooling mouth is closed up, the chimney valve is closed.

page_text: The smoke and the great influx of cold air at the fire-door during charging are
thus prevented or diminished, because the opening of the chimney valve
diminishes or spoils the draught of the chimney for the time. If from the intro-
duction of too large a charge of coal or any other cause a thin grey smoke should
still be produced in firing, it may be prevented by opening the cold air register
for a few seconds, after which it is closed, and the chimney valve is afterwards
closed. In many cases the erection of a lofty chimney may be dispensed with by
adapting a rotary fan blowing machine turned by any convenient prime mover,
and arranged in the following manner :-The delivery pipe of such rotary fan
must be provided with two branches, one conveying the air to a closed ash-pit,
and the other to the hot-air drain before described. In some cases where chimneys
of the ordinary size are already built we prefer that a small fan only be used for
forcing sufficient air through the hot-air drain. In other cases where it may
be expedient for obtaining a higher temperature to use two series of hot-air
channels of different areas, we prefer that the fan should be placed in con-
nection with both in such manner as to draw or exhaust the supply of air first
through the smaller channels, and then to deliver or propel the same through
the larger channels before passing into the furnace. In certain cases where
the construction of a large number of very small channels may be difficult as
well as troublesome to clean out when required, we prefer to use a smaller
number of larger channels, and insert therein a number of round balls of either
conducting or non-conducting substances; the said channels then to be placed
in a more inclined position, so that such balls could be put in or taken out
again with facility; the object of their introduction being, that by their means
a large area of heating surface would be exposed to the air passing through or
amongst them in addition to the surface of the channels themselves.
Our next improvement is the adaptation of two or more feeding mouths or
retorts, through which the coals are pushed forwards on to the grate by means
of pistons moved in two or more rectangular channels by screws, the lower
portion of each feeder being a cast-iron trough, and the roof forming an
arched retort of fire brick, the whole set sloping towards the fire gratè at an
angle of about 15 or 20 degrees from the horizontal, in order to leave room
for manipulating with the fire bars under the feeding mouths of the retorts.
By employing two or more of these feeding retorts, and working them
alternately, the fire may be kept very regular and uniform. The kind of fire
bars we recommend to be used in conjunction with this retort firing are to be
made of a tapered form, with their smaller ends towards the fire bridge and
their wider ends at the front end of the grate room, under the discharging end
of the retorts, where, on account of the smaller spaces between them, they

page_text: form a species of "dead plate," and serve to moderate the active combustion
of the coals in that position where distillation only of the coals ought to be
going on, and where the rich hydro-carbon gases are liberated, which after-
wards enter into the most intense or complete combustion when mixing with
the largest supply of oxygen at the bridge of the furnace. We also apply the
tapered fire bars with or without the coal feeding retorts to any kind of
furnaces, some of which we now proceed to describe. When taper fire bars
are to be used to an iron puddling or similar furnace, with or without the coal
feeding retorts, they are to be made with their thicker ends parallel for a
considerable length outside of the grate room, in order to their being easily
drawn out or partially drawn out of their places for cleaning, turning, and
adjusting. With the same view the smaller ends of the bars for about a
foot of their length must be made of a round section and rest in notches cast
for the purpose in a special "bearing bar "placed within a slight recess in the
brickwork under the fire bridge; the remainder or middle portion of the fire
bar which has to support the fuel in active combustion being square in section,
which we prefer, or it may be of triangular or pentagonal or other suitable
form.
In respect of the position of the above described taper fire bars, we prefer
to place them in a longitudinal direction with the body of the furnace where
hand firing is used, in the same manner as the parallel bars in ordinary use;
but where the coal feeding retorts are used, taper bars may sometimes be
placed transversely across the grate room, and arranged head and tail fashion,
with their thick and thin ends alternately on each side of the grate, both sides
of the furnace being readily accessible for the purpose of withdrawing, cleaning,
and turning the bars, or adjusting the width of the air spaces between them,
the said air or draught spaces being enlarged by a partial withdrawal of the
thick end of the bars outwards at one or both sides of the furnace, and
diminished by a contrary movement. This mode of adjustment is important
in obtaining the most complete distillation and combustion of bituminous coal
in the same furnace at the same time, in so far as by this means slow combus-
tion is readily attained by diminishing the air spaces near to where the coal is
first deposited, and vice versa. Quick combustion can at the same time be
obtained by widening the air spaces at the contrary or bridge end of the grate,
where the most energetic combinations of the furnace gases with the atmo-
spheric oxygen take place, and where, consequently, flame of the highest
possible temperature and without smoke is produced. The efficacy of the
above mode of working a furnace with detached moveable transverse taper
bars in obtaining and regulating the the greatest possible degree of heat at the

page_text: right place for the rapid melting and refining of metals, calcining ores, and
many other purposes, will be evident, and it has this advantage, that it requires
little or no supplementary air being admitted above the fuel to burn smoke.
Smoke, in fact, under sufficient temperature of flame can scarcely be said to
exist, at least in a visible state, and therefore in such a case the use of the cold
air drain may be generally dispensed with, and even the hot air drain need to
be used for that purpose only to a partial extent, that is, a smaller quantity of
air at a higher temperature will be found sufficient. In some modifications of
air furnaces for welding and forging purposes, where a more moderate heat is
required, but particularly in the furnace of a steam boiler where such intense
heats are found to be highly injurious, the entire prevention or combustion
of smoke cannot be practically accomplished by periodically charging or "hand
firing" without the admission of a large supplementary supply of air, hot or
cold, above the fuel, hot being greatly to be preferred for economy, and cold
air for suddenness or completeness of apparent effect. In those cases, instead
of having the supplementary air drains either in the front wall or in the roof
of the furnace, we propose to place one such air drain with or without a
register valve or regulating apparatus, or other means of opening and closing,
at each side of the grate room. These lateral air drains when so situated
may be used either with a constant aperture for air, or opened and closed
alternately in conjunction with the alternate using of two coal feeding retorts
fixed in the front of the furnace, as before described, when more convenient
for the work the furnace is employed about, this arrangement may be reversed,
allowing either or both the air drains to retain the same position as first
recommended, and the coal feeding retorts placed one on each side. The
latter then occupying corresponding places to those usually occupied by the
ordinary hopper feeding mouth in the common hand firing of air furnaces;
which hand firing, in fact, when carefully managed alternately on each side, the
most nearly approaches to retort firing, only making use of the rake instead of
the piston to push the coal in with.
Whichsoever of the above arrangements may best suit the local circum-
stances and position of the furnace, the method of arranging the bars
transversely across the grate room and mode of adjustment are equally
applicable, provided both sides of the furnace are readily accessible to the
fireman, in which case there is an additional advantage in using these taper
moveable fire bars to those already stated, and that is, the capability of causing
them to revolve either separately by hand, or together occasionally, by a series
of short cranks on their projecting ends taking into a longitudinal guide bar
or frame on one or both sides of the grate, to which a suitable to-a-fro

page_text: motion may be imparted. The effect of thus causing the fire bars to revolve
is to assist in advancing the coals forward, especially when the grate is slightly
inclined from the feeding mouth towards the bridge. In this mode of using
these bars it is necessary to have a portion of the thick as well as of the small
end of each bar with a circular neck or gudgeon of suitable length to rest in
corresponding notches in two longitudinal bearing bars, one on each side of
the grate.