IMPROVEMENTS IN FURNACES
Year: 1875

page_text: LETTERS PATENT to Kenneth Henry Cornish, of No. 6, New Inn,
Strand, in the County of Middlesex, Consulting Surgeon, for the
Invention of "IMPROVEMENTS IN FURNACES."
PROVISIONAL SPECIFICATION left by the said Kenneth Henry Cornish
at the Office of the Commissioners of Patents, with his Petition,
on the 13th May 1875.
I, KENNETH HENRY CORNISH, of No. 6, New Inn, Strand, in the
County of Middlesex, Consulting Surgeon, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN FURNACES," to be as
follows:-
This Invention has several objects, which all tend to the saving of
fuel and its more perfect and profitable combustion. It is easily and
cheaply applicable to existing furnaces, as well as for the construction of
new ones, and will, if scientifically adapted and used, give nearly, and in
some cases quite as good results as may reasonably be looked for from
A

page_text: The principal objects are,-
First. To enable the flame space between the upper surface of the
fire-bars and the roof of the furnace to be increased or decreased in a
ratio with the state in which the fuel may be at various stages in the
process of combustion, increased to a maximum when fresh fuel is
placed on the grate, diminished to a medium when the charge is half
consumed, reduced to a minimum when burnt so low as to require
a fresh charge, these mutations being effected gradually and auto-
matically.
Second. To regulate the supply of air above as well as below the
grate after coaling and during combustion, such supply being invariably
heated before passing along the roof of the furnace, and in most cases
that also which is supplied from the ash-pit; this regulation of the 1
quantity being effected automatically and in accordance with the
varying air requirements caused by the continued combustion of the
fuel.
Third. The supply of a measured and graduated amount of very
hot air at the far end of the furnace, to be mixed at that point in 2
sufficient quantity with the various gases generated during the entire
process of combustion, which would then be consumed profitably,
though at present a large per centage of such products passes away in
a detrimental manner in the form of soot, carburetted hydrogen, car-
bonic oxide, and the like; the quantity of air thus supplied to be also 2
regulated automatically.
Fourth. To accomplish the objects enumerated, so far as the me-
chanical requirements are concerned, automatically and by a self-
regulating arrangement, and preferably by the mere act of recoaling the
furnace as the commencing stage in the series of mutations, and by the 3
changes produced by combustion in the weight of the fuel during the
second and all subsequent stages.
Fifth. To construct fire-bars capable of clinking the fuel automatically
by the gravitated force of the fire-grate and its appendages.
To obtain these ends I construct the fire-grate in such a manner that 3
it shall sink to the necessary extent when the charge of fuel is placed

page_text: on it, and rise gradually as the weight of the charge is reduced by the
act of combustion. There are various ways in which this may be
effected familiar to mechanics, but the one which for various reasons I
prefer to employ is to pivot the fire-grate on axles or standards, so
arranged that it shall slope downwards and backwards, the fulcrum of
the lever being placed about fifteen or eighteen inches from the door.
The portion of the lever (or fire-grate) which lies between the door and
the fulcrum (the point where it is pivotted or axles) is the short arm,
and in this case the light one.
To gain length and for other purposes I fix to the sides or other con-
venient part of the fire-grate, cither where it is pivotted, or behind to
some convenient point in the short arm of the lever, one or more arms
which shall project through the front of the furnace, and in conjunction
with the fire-grate form a bent lever. By weighting this I can make it
heavier instead of lighter than the long arm, the degree depending of
course upon the weight added, and the distance from the fulcrum at
which the weight or counterpoise is placed. By weighting the short arm
to the amount necessary I obtain that the weight of the fresh charge
shall bring down the long arm and increase the flame space, and that it
shall gradually rise again, diminishing the flame space, as combustion
progresses, and at the same time the counterpoise shall bring down the
short arm in an equivalent ratio. As the long arm rises the flame space
between the fire-bars and the roof of the furnace becomes diminished,
and as it falls this flame space is increased. The ends of the bent levers
which project beyond the front of the furnace I employ to actuate the
valves which supply air, and for other purposes.
In marine furnaces I counteract the effect which the roll of the ship
would have on the pivotted fire-grates when in balance by springs or
other counterchecks.
In order to supply the furnace with the proper amount of air required
by the fuel in its various stages of consumption, and at the different
points where it may be most advantageously employed, and preferably
with this air in a highly heated state, I fit heating boxes of iron to the
inner side of the door of the furnace, and to that part of the furnace
front which is immediately over the door. These boxes are fitted with
iron plates, with proper openings to allow the air to flow freely over
their heated surfaces, That on the furnace door has no top, that above

page_text: rather above the centre of its vertical section, an iron plate to or on
axles or pivots projecting backwards from the inner surface of the front
of the furnace. This plate carries studs projecting backwards so placed
as to come in contact at desired points with the pins on the ends of the
fire-bars, the pressure of any pin or any stud sufficing to turn the fire-
bar a quarter turn, so that the action of two pins on two correspondent
studs will give the fire-bar a half turn, making that which was the
uppermost portion of the bar the lowest.
It will be found convenient in practice to first turn every alternate
fire-bar, and then to turn the other alternate fire-bars. For this reason
the plate should carry four rows of studs suitably arranged in relation to
the points at which they are successively intended to come into contact
with the pins on the ends of the fire-bars. I prefer so arranging the
plate and studs that this contact may take place automatically, while the
near end of the fire-grate is falling, and that which lies in the far end
of the furnace rising, so that the fire-bars may be gradually rotated by
the force of gravity, but cases may occur where more power is required,
and I therefore arrange to have the power of turning the fire-bars by
raising the projecting bent arms before re-coaling. This can easily be
effected by adjustment screws against the upper or lower part of the
pivotted plate. Thus the whole or any of the desired movements, changes
in the flame space, admission of regulated quantities of hot air, above,
below, at the back of the fire, or elsewhere, the rotation of the fire-
bars, signalling, may be effected automatically by the act of coaling,
and the change is produced in the gravity of the fuel during combustion.
The advantages of my Invention are many. Smoke is prevented in all
stages; the heat of the furnace is maintained after coaling; the consump-
tion of the fuel is much slower, and the amount of heat generated greater
and more constant, giving a larger and steadier supply of steam in engine
boilers with far less fuel; the clinkers are prevented from forming, and the
necessity for frequently poking the fire removed, while the fire-bars will
last longer, as the surface in contact with the fuel is changed with every
charge, and has time to cool down before being subjected again to
intense heat. There is a cool furnace door or stoke hole, and as nothing
is left to the discretion of the fireman, the engineer can so arrange the
mechanism that he may get the maximum of effective work out of any
given kind of fuel, everything being effected by the cheap and certain

page_text: powers obtained by directing gravital force to a given attainable end.
It can moreover be applied easily and cheaply to existing furnaces, the
old doors being available.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Kenneth Henry Cornish in the Great Seal Patent
Office on the 12th November 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, KENNETH
HENRY CORNISH, of No. 6, New Inn, Strand, in the County of Mid-
dlesex, Consulting Surgeon, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of May, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Kenneth Henry Cornish, Her special licence
that I, the said Kenneth Henry Cornish, my executors, administrators,
and assigns, or such others as I, the said Kenneth Henry Cornish, 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," upon the condition (amongst others) that
I, the said Kenneth Henry Cornish, my 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 Kenneth Henry Cornish, 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
Drawing forming a part of this Specification:-
:

page_text: This Invention has several objects in view all of which tend to the
saving of fuel and to its more perfect and profitable combustion. It is
applicable to most existing furnaces as well as for the construction of
new ones, and will, if scientifically adapted and used, give nearly as good
results in old as can be reasonably looked for from such as may be
specially constructed with a view to the employment of this Invention.
I will in the first place enumerate the principal of these objects
seriatim.
First. To enable the flame space between the upper surface of the
fire-bars and the roof of the furnace to be increased or diminished
according to the state of combustion in which the fuel is, increased to
a maximum when fresh coal is placed in the furnace, and reduced to a
minimum when the whole charge of fuel has been heated to the point of
incandescence, this mutation being effected automatically.
Second. To regulate the supply of air above as well as below the grate
after coaling and during combustion, such supply being invariably
heated before passing along the roof of the furnace, and in most
instances that also which is supplied from the ash-pit, this regulation
of the quantity being effected automatically and in accordance with
the varying air requirements caused by the continuous combustion of
the fuel.
Third. The supply of an additional amount of heated air at the far
end of the furnace to be mixed with the various gases generated during
the entire process of combustion, which now to a great extent pass away
at the back of the furnace (in that part of the flame space which lies
between the ends of the uttermost fire-bars and the commencement of
the boiler tubes, and usually slopes upwards and backwards), in an at
best partially consumed state, but which if mixed at that point with a
sufficient quantity of atmospheric air, especially if such air reached it in
a highly heated state, would be consumed profitably, though at present
such products pass away for the most part in a detrimental manner in
the form of soot, carburetted hydrogen, carbonic oxide, and the like. The
quantity of air thus supplied to be also regulated automatically.
.
Fourth. To enable the fire-bars to clink the carbon automatically.
Fifth. To obtain a great additional heating surface at the back of the
furnace and extract the heat from the flame thoroughly.

page_text: Sixth. To accomplish all the various objects above mentioned, so far
as the mechanical requirements are concerned automatically and by self
regulating arrangements and preferably by the mere process of
re-coaling the furnace as the commencing stage in the series of
mutations, and by the changes produced in the weight of the fuel during
combustion in the second and all subsequent stages.
I accomplish these objects in the following manner as described here
and in the Drawings hereunto annexed, though I claim the right of
varying the manner of automatically carrying into effect those principles,
the novel application of which to furnaces and their combination with
others now well known constitute the essence of my Invention.
Firstly. In dealing with the question how to increase or diminish the
flame space of a furnace according to the stage of consumption in which
its charge of fuel may be, it is necessary to state that it is, in my
opinion, a matter of great importance that there should be a larger flame
space after each coaling interval than during that period of combustion
in which the fuel has parted with the greater portion of its gaseous
constituents, in order that the gaseous and free carbonaceous bodies
rising in vast quantities from the newly ignited fuel, especially if of a
bituminous nature, should have plenty of space to mix freely with the
large quantities of heated atmospheric air which ought to be supplied
them in the upper and middle portions of the flame space so that they
may be burned in such a manner as to expend the whole of their
energies in giving heat instead of absorbing it (as they would if cold air
was supplied), and then quitting the flue in the form of smoke, flame 2
and noxious gases, as is too frequently the case; and that it is also in
my opinion a matter of almost equal moment that the grate or fire-bars
carrying the fire should be raised nearer to the roof of the furnace, as
the coal parts with its rich heat giving constituents and becomes
incandescent, giving off mainly carbonic oxide which requires a com-
paratively small flame space, and thus enables the fuel while at its
steadiest heat to be brought closer to its work of heating the boiler
and tubes. Now as coals vary enormously as to the quantity of
bituminous and volatile matters which they contain, and since the flame
space requisite for bituminous coal is far greater than is necessary for 3
the advantageous consumption of anthracite, especially in the earlier
stages, and as the quantity of air required also varies very greatly, being
much larger where bituminous fuels are employed, it is evident that

page_text: in order to burn all kinds of fuel in the same furnace, each to its greatest
advantage, the fireman must have the power of increasing or diminishing
the flame space with exactitude so as to meet the requirements of the
fuel supplied to him, and that he should equally have the power of
regulating the amount of air required for consumption in the various
stages
Leaving the regulation of the air supply for the present I proceed to
my immediate subject, the regulation of the flame space, and to be more
easily understood describe a marine furnace.
The interior of an ordinary marine furnace is divided by the grate and
fire-bars into two principal parts; that above the fire-bars, which slope
more or less downwards and backwards, and that below the fire-bars
which is commonly called the ash-pit. In the former the fuel is burnt
and heat generated from it; into the latter ashes fall, and air is supplied
generally through a valvular door in the front of the furnace. Beyond
the far end of the fire-bars the flame space runs vertically, or nearly so,
up to a point about six inches below the highest range of boiler tubes,
through which the flame passes into the flue, the entire furnace being
constructed in the interior of the boiler itself, and surrounded by water
everywhere, except at the front. Figure 1 gives a fair idea of a properly
proportioned boiler of this kind. As the grate and its fire-bars divide
the furnace into flame space above and ash-pit below, the lowering of
the grate, wholly or in part, will increase the flame space at the
expense of the ash-pit, and the raising it will diminish the flame space
and increase in an equal ratio that of the ash-pit. A large flame space
is required after coaling, especially with bituminous fuel, but when the
coal becomes incandescent it will act far more powerfully on that part
of the boiler which forms the crown or roof of the furnace if it be
brought a foot or more closer to it. It should be gradually raised
upwards as the mass of glowing fuel decreases in weight and quantity.
There are various methods of raising the grate and fire-bars familiar
to skilled mechanics. It may be done purely by mechanical means, or
by hydrostatic power, but I prefer to employ a fire-grate resting on axles
or standards, see Figures 2, 3, 4. By using an arm C attached to A at a
convenient point I obtain a bent lever, to the arm of which I fix a
counterpoise or a spring, which is also aided by so much of the weight
of the fire-grate and bars as is on the furnace door side of the pivots a¹.

page_text: It is clear that if the fire-grate be so balanced that the long arm of the
bent lever A, C, is rather lighter than the bent arm C and its portion
of A behind the pivot a, it will be carried downwards, when a charge
of coal is thrown into the furnace, and rise gradually as the process of
combustion lightens the load placed on the fire-grate. Thus the act
of coaling causes the flame to be regulated automatically and with
practical precision. By shifting a counterpoise on the bent arm C the
stoker can alter the relative gravities of the two arms of the balanced
lever.
It is my intention to utilise the greater portion of the counterpoise
for the automatic regulation of the air supply, but to prevent confusion
I shall explain how and why hereafter. The bent arm C will indicate
the state of the fuel, and may easily be made to signal as soon as fresh
fuel is required, and a second time if the fuel is allowed to go dangerously
low. In marine boilers the effect of roll or pitch must be counteracted
by springs or other mechanical powers.
Secondly. In dealing with object No. 2, namely, to regulate the supply
of air above as well as below the grate after coaling and during com-
bustion, such supply being invariably heated before passing along the
roof of the furnace, and in most instances that also which is supplied
from the ash-pit, this regulation of the quantity being effected auto-
matically and in accordance with the varying air requirements caused
by the continuous combustion of the fuel.
For the sake of clearness I will treat of this in conjunction with the
third object, namely,-The supply of an additional amount of heated air
at the far end of the furnace to be mixed with the various gases gene-
rated during the entire process of combustion, which now to a great
extent pass away at the back of the furnace (in that part of the flame
space which lies between the ends of the uttermost fire-bars and
commencement of the boiler tubes and usually slopes upwards and
backwards) in an, at best, partially consumed state, but which if mixed
at that point with a sufficient quantity of atmospheric air, especially if
such air reached it in a highly heated state, would be consumed pro-
fitably, though at present products pass away for the most part in a
detrimental manner in the form of soot, carburetted hydrogen, carbonic
oxide, and the like, the quantity of air thus supplied to be also regulated
automatically.

page_text: Before entering into details as to the method of accomplishing these
objects I must premise by stating that though the air requirements of
bituminous differ greatly from those of anthracite fuel both kinds
require a much larger supply of air for a few minutes after coaling or
otherwise firing than at any subsequent stage, and that for the prevention
of smoke much of this air must be supplied above the fire-grate. If the
air be introduced cold the temperature of the furnace will be lowered
in an exact ratio with the amount of cold air introduced, and although
smoke will be prevented from forming it will be at the cost of a great
increase in the amount of fuel consumed; the greater the excess of air
introduced above the actual requirements the greater will be the loss of
heat. But if this air be introduced into the roof of the furnace in a
highly-heated state it will combine with the gases without abstracting
heat from them, and there will be a large saving in fuel properly con-
sumed, instead of a loss or an excess of fuel burnt to waste. If in
addition to this highly-heated air (which should for a few minutes after
coaling be introduced through or above the door of the furnace, at first
pretty freely, but gradually diminishing in quantity until entirely shut
off, which should be from about 5 to 10 minutes after the fire has been
replenished with fresh fuel) other currents of highly-heated air meet the
hydrocarbonaceous and other gaseous products of combustion as these
latter reach the point beyond the grate at which the flame space runs
upwards and backwards to supply the orifices of the boiler tubes
intensely hot flame and perfect consumption of the products distilled
from the charge of fuel resting on the fire-bars will be the result, and if
the air supplied to the ash-pit for the draught below the fire-bars be pre-
viously highly heated, as in my opinion it should be, not only will the
combustion be more perfect and the heat actually applied to the heating
surfaces of the boiler and its tubes far greater, but the fuel will be con-
sumed much more slowly, provided that the automatic arrangements I
am about to describe are so constructed as not to allow an excess of
more than one-fourth over the quantity actually necessary in theory,
for the proper combustion of the fuel to enter the furnace, and
though the reason why a slower fuel combustion at this stage may be
predicted under these conditions are obvious to the scientific mind.
I think it right to state the grounds upon which I advance this
opinion. In the first place it has been amply proved during the last
twenty years that if a proper supply of highly heated air be admitted
over the fire-grate through the door and gradually cut off there is an

page_text: increased steam supply, no smoke, a saving in fuel ranging from 10 to
20 per cent., and a cool furnace door with a decrease of beat in the stoke
hole varying from 20 to 30 degrees of Fahrenheit, while the experience
of the last fifty years has also proved that though the admission of a
continuous current of cold air at the same points over the grate prevents
smoke, the production of steam is diminished from 25 to 30 per cent.,
and that it is only when there is ample boiler power to allow of heavier
firing and by a consumption of 25 to 30 per cent. more coal that the
previous supply of steam can be obtained. This waste of fuel and loss
of heat is caused chiefly by the entry into the furnace above the grate of
excessive amounts of cold air, which, mingling with the products of
combustion, abstract a considerable proportion of their heat and cause
the flames which are produced by their admixture with the oxygen
contained in the air to rush forward too rapidly and pass through the
boiler tubes into the flue with too great a velocity, and before they have
parted with the 80 to 90 per cent. of their heat which ought to be
absorbed by the heating surfaces of the boiler and its tubes, and thus
profitably employed. This onrush of flames also draws in an excessive
amount of cold air, not only from the orifices in and about the door of
the furnace but also through the ash-pit, the draught or suction of the
flue being greatly increased by the enhanced heat and excessive velocity
of the vapours which pass away from it into the stack.
It is well known that air in its normal cool condition is far more
attracted by heat than it is if artificially heated, and that in becoming
heated it cools the body from which it abstracts heat in an equivalent
ratio, and it is on the basis of these well known physical laws that I
assert that all the air supplied to a furnace in all stages of combustion
ought to be previously heated to as high a degree as possible, and that
this should be done by utilising so much of the furnace heat as would
otherwise be wasted, or nearly so, in order that whether the air be
supplied freely or sparely from above or below, from in front or behind,
it should be made as nearly red hot as it can be. As hot air would flow
into the body of the furnace far more gently than cold the distillation
of the gases from the fuel would proceed more slowly and regularly, and
the wear and tear of the fire-bars would be considerably lessened, for
since the flame space ought, where the supply of air is regulated with
due precision, always to be filled with bright flame moving sufficiently
slowly to communicate the greater part of its heat to the boiler and

page_text: tubes before reaching the flue and stack; and as the the grate would also
be fed with a gently moving current there would be no fierce draught
through the fire-bars unduly consuming them and the fuel resting on
them. The rate at which the hydrocarbonaceous gases would be
distilled from the fuel would be much slower, whether with wood,
bituminous coal, or anthracite, but they would be perfectly consumed
as fast as they were generated, and the length of the first period during
which ten volumes of air are required to one of the hydrocarbonaceous
gases would probably be doubled while the heat generated would be
steadier and stronger, for in point of fact the further portion of the
flame space would be converted into a huge Bunsen's burner. The coal
will now have lost about 20 to 25 per cent. in weight, and the principal
portion of the grate will have risen proportionally.
In the remaining stages we have to deal with an incandescent mass of
fuel giving out a great and steady heat, from which carbonic oxide is
the principal gas thrown off. The supply of air from below should be
much smaller than in the preceeding stage, as also that supplied from
above and behind (while none must pass in through the door), as carbonic
oxide only requires two and a half volumes of air to make flame; there-
fore, not more than three to three and a quarter volumes should be
admitted, and my system will enable the engineer to regulate this supply
with a precision hitherto unattainable, nothing being left to the discretion
of the firemen and stokers as regards air supply. As the fuel loses
weight the grate will gradually rise towards the roof, bringing the
glowing mass closer and closer to that portion of the heating surface,
and the supply of air will be gradually diminished in an equivalent
ratio, both of great advantage, provided that a sufficient volume of very
hot air be poured into the back of the furnace where the rest of the
flame space runs upwards. It is obvious that under these conditions
the carbon would be consumed much more slowly than if cold air was
freely admitted, and the heat generated applied to better advantage. In
order to obtain these results however the engineer must, as I have before
stated, have the power of arranging with precision the extent to which
air is supplied to given parts during given periods, and of varying the
proportions to suit the requirements of different kinds of fuel. The
chemical analysis of the fuel in use, and the greater or less rapidity with
which it loses weight while being burnt, will afford him much assistance
in determining these points, but he will have the power of so arranging

page_text: the mechanism that the mere act of coaling and the diminution of the
weight of the charge while burning shall be so utilised mechanically as
to open and close the various passages through which the external air
would pass to be heated automatically and in due order, and I effect
this where extreme accuracy is required by making balanced levers of
the valves or shutters, and actuating the lightor arm of each lever directly
or indirectly, as may be convenient, by one or other on both the bent
arms C of the balanced bent lever which forms the fire-grate, as shewn
in the Drawing; but if this fire-grate, which has the immense and
unique advantage of enabling the varying weight of the consuming fuel
to regulate the air supply to a nicety automatically, be not employed,
then they must be regulated by some mechanism capable of being set to
time. Probably a power obtained by the descent of a weight regulated
by an instrument constructed on the principle of the musical metromone
would act but roughly and inaccurately as compared with the plan
described by me, while the cost would be greater.
In adopting my system to an ordinary boiler I should first ascertain
whether there was sufficient flame space for the charge of fuel employed,
because if there was not I should reduce the width of the grate. By
this the flame space is increased, and I should further increase it by
using my balanced grate. The charge, though smaller, would give more
heat, even if no change was made in the air supply. I should then
proceed to fit the door and bridge with air-heating and air-regulating
arrangements, as described, such regulation be effected automatically
in the case of that admitted through the door by the fall of the bent
arms C, C, as the fuel consumes, and in the case of that entering through
the bridge by valves set by the engineer, and so arrange the pivoted
levers as to cause the lowering or rising of the bent arms C, C, to actuate
them in such a manner that they may produce the exact effect desired
in the case of each separate valve or shutter, and as the fall of the bent
levers has been shewn to accord with the diminution of the weight of
the fuel burnt on that part of the fire-grate which forms the long arm of
the bent levers, of which C, C, form practically the short arm. The
regulation of the air supply will be effected automatically and with great
precision by the act of coaling, and the difference in the weight of the a
fuel caused by the action of the fire in the furnace.
As regards the automatic self-clinking fire-bars, which form an

page_text: labour, as well as doing gently and gradually what is now done suddenly
and with violence, besides being cheaper, lighter, and less liable to
damage from the constant application of continuous excessive heat on
the surface in contact with the fuel. The Drawings, and the description
referring to each Drawing, will give such explanation as is necessary as
to their form and the manner in which they act. Like the rest of my
Invention they are actuated automatically by the rise and fall of the
balanced fire-grate and its appendages.
In many furnaces the theoretical accuracy with which I have shewn
that the air supply can be regulated is not necessary, and as good, nay,
perhaps better practical results will be obtained by the simpler arrange-
ment which I shall shew in my Drawings.
In place of the various heaters and tubes I have just described, I
employ only a heater fastened to the inner side of the door, through
which the 7 additional volumes of air required for the combustion of
the hydrogen are supplied for the required period, such supply being
regulated automatically by the rise and fall of the pivoted grate, and I
supply the quantity of hot air necessary for the proper combustion of
the carbonic oxide during the whole period of combustion by some such
arrangement as that shewn in the Drawings, Figures 11, 12, and 13.
The quantity of air entering the bridge (from about three to five
volumes) is regulable by valves set by the engineer. This arrangement is
much cheaper than that first described, and is difficult to put out of order.
The improvement however is rather one of detail than of principle.
With regard to the utilization of the flame and heat generated in the
furnace, I have to describe an addition which I consider to be of great
practical value, and especially so far as tubular boilers are concerned.
1
It is well known that in tubular boilers the lower boiler tubes are
those most liable to damage from the heat of the flame as it passes from
the flame space; and it is equally well known that the points at which
they are most affected are the mouths where the flames enter them. At
the other end where the heat finds an exit in the form of a gas at a high
temperature the tubes are rarely if ever injuriously affected. It is
absolutely necessary that any metal subjected to the intense heat
generated in the flame space shall enclose water or some other cognate
fluid or it will inevitably be melted. This is due to the action of
flame.

page_text: It has been repeatedly demonstrated that the gas which issues from
the boiler tubes into the flue, though of a very high temperature has no
other effect on sheet iron of moderate thickness (say of millboard)
than to bring it to a red heat. The fact that the lower boiler tubes
wear out first proves that they receive an undue amount of the flame
generated, and consequently that the upper tubes, which be it
remembered ought to be the hottest, do not get sufficient. The flames
pass through the boiler tubes in an unequally distributed ratio, and
when they issue into the flue they contain a very large amount of
available heat which passes away as waste through the chimney.
My object is to ensure a more even distribution of the flames through
such boiler tubes as it is theoretically necessary to subject to the intense
heat of flame; to greatly increase the heating surface in the flame space
itself, so that the flame may play upon surfaces less liable to injury
than the mouths of of boiler tubes, and to extract much of that heat from
the gases which now passes away through the chimney.
I enclose a space containing about three-fifths of the boiler tubes in
that portion of the boiler from which the mouths of the said boiler tubes
open into the flame space, and preferably in the form shewn in Figure 9,
and on each side stretch two boiler plates across to the back of the flame
space connecting them with the roof of the flame space above, and also
with the sides, as shown in the back elevation and plan filed herewith.
These plates which I prefer should be of copper must enclose water
admitted into them freely from all parts to which they are connected,
and thus become an integral part of the boiler. In a boiler thus con-
structed or in one converted to this system the flame will slide along the
great heating surfaces which enclose the three-fifths of the boiler tubes,
and pour into the tubes in an even torrent after beating against the
roof of the flame space with an increased energy. If it were allowed to
escape on reaching the flue, there would be little if any gain in the
amount of heat imparted to the water, although I should obtain two
of the ends sought, even distribution of the flames into the tubes, and a
large additional heating surface. It is therefore necessary to abstract as
much heat as possible before the gases finally leave the flue. At the
front of the boiler tubes I mark out a space containing four-fifths of the
tube ends where they open into the flue in some such manner as that
shown in front elevation, Figure 10, and enclose this space in a sheet-
iron box with sliding or ordinary doors in front in order to give access

page_text: for cleaning. These doors should, when closed, be within a few inches of
the mouths of the tubes, although the sheets which form the sides and
roof of this box may with advantage be continued forward across the
flue till they reach the front boiler plates. Since the flame must now
pass through the space enclosed at the back of the furnace, and issue in
the form of a very hot gas into the iron box on which it has no other
effect than to make it red hot. This gas having no exit into the flue is
forced to pass back through those boilers tubes enclosed in the box into
the spaces on each side of the added heating surfaces, each of which
spaces contains one-fifth of the boiler tubes. On coming here it is
compelled to play on the outer surface of the lateral heating surfaces,
and then bend forwards again and travel into the flue through the
outermost tubes; a blower may with advantage be used above the iron
box described.
It is probable that the employment of the means described will enable
so much to be extracted from the flame and gases, that they will leave
the flue at a temperature of only 300° Fahrenheit.
In constructing the bridge so as to heat the air at the back of the
furnace provision must be made to prevent the air pipes leading into the
furnace from becoming choked. I give a simple and efficacious con-
struction in my Drawing. The boiler tubes can be cleaned as at present,
but it will seldom be necessary to clean those at the sides.
DESCRIPTION OF THE DRAWING.
Figure 1 is a longitudinal vortical section of a furnace shewing how
the positions of the fire-grate alter the flame space, the position of the
hot air channels in the bridge, and an external view of one of the
heating surfaces added in the back of the flame space.
Figures 2 and 4, plans of fire-grate shewing levers at side and at
front.
Figure 3, side view of grate with slot to balance on standard.
Figure 5 is a section through the head of a fire-bar shewing the
position of four pins, and a section through one of the two pins by
which each fire-bar is rotated, each pin moving at a quarter turn.
Figure 6 is a vertical section through the front of the furnace, and
5 a plate pivoted at both ends which carries the pins, by contact with
B

page_text: which the pins at the heads of the fire-bars are actuated as the grate
rises and falls. The adjustment screws enable this plate to be made
rigid either when the grate rises, or when it falls, as may be desired.
In the Drawing the end of the grate next the front is actuating the
fire-bar by its descent. There should be two rows of pins on this plate
for each alternate sets of fire-bars if my improved fire-bars are used,
first one set of alternate fire-bars should be rotated a half turn, so that
the fuel may rest on that part of the bar which was previously the
lowest, and then the other set of alternate fire-bars should be similarly
rotated by the continued descent or rise of this end of the fire-grate.
If the rotation is effected by the descent of the fire-grato it is done
gradually and automatically; but if by the rise of this end of the
grate, it must be pulled up by the hand, the bent levers C, C, being
lifted.
Figure 7 is a side view of one of my improved fire-bars.
Figure 8, plan of boiler with top removed, shewing tubes and
position of heating surfaces in flame space containing water; also of
the iron box enclosing four-fifths of tubes in the flue.
Figure 9, back elevation of boiler tubes showing position in vertical
section of heating surfaces in flame space containing water. The dotted
lines show relative position of the box in flue intended to force the
return of heated gases to the back of the furnace.
Figure 10, front elevation of boiler tubes showing iron side and top
plates of the box in flue. Dotted lines show position of heating surfaces
containing water at back. Below the roof line on each side front surfaces a
of these plates are shewn.
Figure 11, vertical longitudinal section through the centre of the
bridge shewing how air passes from it to the fire; also fire-clay plate
in front of the bridge to keep the air pipes leading from bridge from
being choked by ashes or dirt.
Figure 12, elevation of fire-clay plate in front of bridge.
Figure 13, elevation of side of boiler shewing valve for admission
of air through the bridge during the whole period of combustion.
Figure 14, front of furnace shewing door with valve for the admission
of 7 to 8 volumes of air at first stage of combustion, gradually cut-off 3

page_text: to nothing as the combustion proceeds; this is effected automatically
by the rise and fall of the grate. In position given the grate is loaded,
the bent arms are up lifting the slide, which lifts the pivoted lever valve
leaving the air holes leading into the heating box on the inner side of
the door all open; these close gradually as the valve falls as com-
bustion proceeds. The dotted lines shew the position of the bent arms,
slide, and pivoted lever valve when air holes are closed. If the surface
of the slide which lifts the pin on the pivoted lever valve be constructed
as a hinged set rod the engineer can vary the distance which the arms
descend to close the valve, or the same result may be produced by
shifting the position of the pin.
Figure 15 is a vertical longitudinal section of a heating apparatus
attached to the inner side of the furnace door; it is an iron box, the
side next the fire being the door plate in which are air holes, as shown
in Figure 14; the two ends, roof, and bottom are solid, the back surface
which faces the interior of the furnace having sloping flanges like
those of venetian blinds, running horizontally, as shewn in Figure 16,
and the box itself being filled with flat plates having similar apertures
and sloping flanges. The box and plates may be of cast iron or fire-
clay, or both combined.
Figure 16 is a view of heating box on door, as seen on inside of
furnace.
Like letters indicate the same parts throughout the Drawings.
A, pivoted fire-grate; a, pivot; B, standard on which it pivots; C, C,
arms forming bent lever; D, counterpoise or spring; E, combustion
chamber; F, body of furnace; G, air chambers or bridge; H, fire-bar;
I, neck of fire-bar; i, i, pins to rotate fire-bar; K, plate carrying pins;
k, k, pins; L, L, adjustment screws; M, furnace door; N, sliding plate
on door; O, pivoted valve on door; o, o, o, air holes; P, P, ash-pit
doors; Q, box on door filled with heating plates R, R; S, S, heating
surfaces in combustion chamber; T, iron box in flue; U, bridge;
V, fire-clay plate; v, v, v, air channels or pipes; W, valve admitting
air to bridge.
Having thus fully described my said Invention, and the manner of
performing the same, I wish it understood that I claim, —
-
First. In a furnace a balanced fire-grate, as and for the purposes

page_text: Second. The supply of hot air throughout the whole period of com-
bustion, regulated in quantity automatically, as described.
Third. The arrangements for increasing the heating surfaces in the
combustion chamber, as described.
Fourth. The employment of an iron box in the flue enclosing the
mouths of boiler tubes, as and for the purpose described.
Fifth. The Invention, substantially as described.
In witness whereof, I, the said Kenneth Henry Cornish, have
hereunto set my hand and seal, this Twelfth day of November,
in the year of our Lord One thousand eight hundred and seventy-
five.
KENNETH HENRY CORNISH. (L.S.)
Witness,
HY. J. NOONE,
8, Southampton Buildings,
London.