IMPROVEMENTS IN AND RELATING TO THE COMBUSTION OF FUEL FOR THE PRODUCTION OF HEAT, AND IN FURNACES THERE- FOR
Year: 1879

page_text: LETTERS PATENT to John Thomson King, of Liverpool, in the County of Lancaster,
Patent Agent, for the Invention of "IMPROVEMENTS IN AND RELATING TO THE
COMBUSTION OF FUEL FOR THE PRODUCTION OF HEAT, AND IN FURNACES THERE-
FOR." A communication from abroad by Henry M. Pierce, of Grand Rapids, in
the County of Kent, and State of Michigan, one of the United States of
America.
Sealed the 24th February 1880, and dated the 1st September 1879.
"
PROVISIONAL SPECIFICATION left by the said John Thomson King, at the
Office of the Commissioners of Patents on the 1st September 1879.
THE
JOHN THOMSON KING, of Liverpool, in the County of Lancaster, Patent Agent.
IMPROVEMENTS IN AND RELATING TO THE COMBUSTION OF FUEL FOR
PRODUCTION OF HEAT, AND IN FURNACES THEREFOR." [A communication from
abroad by Henry M. Pierce, of Grand Rapids, in the County of Kent, and State of
Michigan, one of the United States of America.]
The object of this Invention is, first, to secure perfect combustion of the fuel, and
secondly, to apply the results of such combustion to heating purposes.
The essentials to ensure perfect combustion are, first, such a supply of air or
oxygen as shall give to each atom of carbon its combining equivalents; secondly,
such a thorough intermingling mechanical mixture or association of the air
or oxygen and carbon that the combination or chemical union termed com-
bustion becomes possible for each atom of carbon, and is facilitated, and thirdly,
a continued and sustained temperature never less than the combining point or
temperature of initial combustion.
If a lump of coal is laid upon a clear fire the first result is distillation or reduction
of the fuel from a solid to a vapour; the second, ignition and complete oxidation of
such vapour; the third, optical disappearance of all the elements of the lump of coal
except the incombustible matters remaining in the form of ash.
If the vapors or gases arising from the distillation of the fuel, or first step of the
process, are cooled below a given temperature (say about 800° F. or 1,000° F.) or
the heat is in any manner abstracted therefrom, chemical union, transformation, or
combustion is interrupted, there follows a deposit of carbon or soot, the formation
of "black smoke" and loss of fuel; secondly, if there is an insufficient supply of air
or oxygen to give to each atom of carbon its combining quantity, then, although the
temperature be not lowered, a portion only of the carbon will be completely

page_text: oxydised, and other portions will be deposited as soot or go off as
"black smoke,"
and there will be a loss of fuel; and thirdly, though the temperature be maintained
at a proper degree, and though a full supply of air or oxygen be present, yet if the
mechanical mixture or association of the carbon and oxygen is not such as to permit
a chemical union, the combustion will be imperfect, and the same results in the
formation of "black smoke," deposit of soot, and loss of fuel takes place.
The first part of my Invention therefore consists in preventing radiation as far as
possible, and preserving the temperature of the vapors and gases arising from the
initial combustion (or distillation) at or above the point at which a deposit of carbon
takes place, and at the same time causing the said vapors and gases in conjunction
with the requisite volume of air or oxygen to produce combustion to traverse
a confined space, and through such a distance before reaching the point where the
heating is to be effected as will ensure a thorough mingling and union of the
elements and induce perfect combustion.
The second part of the Invention consists in so constructing and arranging a
furnace that the volume of the gases from the fuel on the grate shall continue long
enough in their passage and be kept hot enough to burn until entire combustion is
effected, and in supplying air to said products of combustion at points in the path
thereof between the grate and point of utilization of the heat, and before any
portion of the flame and hot gases has fallen to a temperature below the point of
ignition.
The third part of the Invention consists in such an arrangement of the flues or
passages for the products or hot gases from the grate to the boiler that said passages
are returned or doubled upon themselves so as to secure an increased space or
distance (and consequently increased time) for combustion to take place before the
point of utilization of the heat is reached, and this without increasing the radiating
surface of the furnace, and with the advantage of causing the heat abstracted (if
any there be) from the gases at the points of more perfect combustion and con-
sequently higher temperatures, to be absorbed by the vapors and gases at the
points of initial combustion (or distillation), thus equalizing and preserving the
temperatures throughout the furnace.
The fourth part of the Invention consists in the provision of a combustion.
chamber under the boiler of a furnace, said chamber being divided by a longitudinal
horizontal diaphragm to form an upper and lower flame flue, having a return
chamber at the end of the fire flue to which air is admitted, and a combustion
chamber adjoining the boiler and over the fire place, being separated therefrom by
the said diaphragm.
.
On the accompanying sheet of Drawings, one form or modification of niy
Invention is shewn applied to a steam generator. Fig. 1 being a front elevation
after the fire front is removed; Fig. 2 a rear elevation of the same having the rear
wall removed; and Fig. 3 a side view of a boiler in position in my improved
furnace, the latter being shown in vertical longitudinal section.
. A designates the boiler in position in the furnace B; D indicates the fire box, and
G the grate. A passage P surrounded by brick walls leads to the combustion
chamber C, the latter being supplied with air by means of the register R to facilitate
and complete combustion. In the chamber C the course of the products of
combustion is changed, and the volume goes in the opposite direction through the
upper passage P¹ to the front of the boiler. The lengths and areas of the passages
P and P and chamber C are such as to afford ample space and time for complete
combustion, so that when the chamber C¹, communicating directly with the front of
the boiler, is reached only the products of perfect combustion remain.
E indicates a diaphragm or partition separating the passages P and P', and also
separating the chamber C from the fire place.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Thomson King in the Great Seal Patent Office on the 28th
February 1880.
"
JOHN THOMSON KING, of Liverpool, in the County of Lancaster, Patent Agent.
IMPROVEMENTS IN AND RELATING TO THE COMBUSTION OF FUEL FOR THE
PRODUCTION OF HEAT, AND IN FURNACES THEREFOR." A communication from abroad
by Henry M. Pierce, of Grand Rapids, in the County of Kent, and State of Michigan,
one of the United States of America.
The object of this Invention is, first, to secure perfect combustion of the fuel;
and, secondly, to apply the results of such combustion to heating purposes.
The essentials to secure perfect combustion are, first, such a supply of air or
oxygen as shall give to each atom of carbon its combining equivalents; secondly,
such a thorough intermingling mechanical mixture or association of the air or
oxygen and carbon that the combination or chemical union termed combustion
becomes possible for each atom of carbon, and is facilitated; and, thirdly, a continued
and sustained temperature never less than the combining point or temperature of
initial combustion.
If a lump of coal is laid upon a clear fire the first result is distillation or reduc-
tion of the fuel from a solid to a vapor; the second, ignition and complete oxidation
of such vapor; the third, optical disappearance of all the elements of the lump of
coal except the incombustible matters remaining in the form of ash.
If the vapors or gases arising from the distillation of the fuel, or first step of the
process, are cooled below a given temperature (say about 800° F. or 1,000° F.) or
the heat is in any manner abstracted therefrom, chemical union, transformation, or
combustion is interrupted, and there follows a deposit of carbon or soot, the formma-
tion of "black smoke," and loss of fuel; secondly, if there is an insufficient supply
of air or oxygen to give to each atom of carbon its combining quantity, then,
although the temperature be not lowered, a portion only of the carbon will be com-
pletely oxydized, and other portions will be deposited as soot, or go off as "black
smoke," and there will be a loss of fuel; and, thirdly, though the temperature be
maintained at a proper degree, and though a full supply of air or oxygen be present,
yet, if the mechanical mixture or association of the carbon and oxygen is not such as
to permit a chemical union, the combustion will be imperfect, and the same
results in the formation of "black smoke," deposit of soot, and loss of fuel takes
place.
The first part of my Invention, therefore, consists in preventing radiation as far
as possible, and preserving the temperature of the vapors and gases arising from
the initial combustion (or distillation) at or above the point at which a deposit of
carbon takes place, and at the same time causing the said vapors and gases, in
conjunction with the requisite volume of air or oxygen to produce combustion, to
traverse a confined space, and through such a distance before reaching the point
where the heating is to be effected as will ensure a thorough mingling and union of
the elements and induce perfect combustion.
The second part of the Invention consists in so constructing and arranging a
furnace that the volume of the gases from the fuel on the grate shall continue long
enough in their passage and be kept hot enough to burn until entire combustion
is effected, and in supplying air to said products of combustion at points in the
path thereof between the grate and point of utilization of the heat, and before any
portion of the flame and hot gases has fallen to a temperature below the point of
ignition.
The third part of my Invention consists of such an arrangement of the flues or
passages for the products or hot gases from the grate to the boiler that said pussages
are returned or doubled upon themselves so as to secure an increased space.or

page_text: distance (and consequently increased time) for combustion to take place before the
point of utilization of the heat is reached, and this without increasing the radiating
surface of the furnace, and with the advantage of causing the heat abstracted (if
any there be) from the gases at the points of more perfect combustion, and conse-
quently higher temperatures to be absorbed by the vapors and gases at the points 5
of initial combustion (or distillation), thus equalizing and preserving the tempera-
tures throughout the furnace.
The fourth part of the Invention consists in the provision of a combustion
chamber under the boiler of a furnace, said chamber being divided by a longitudinal
horizontal diaphragm to form an, upper and lower flame flue, having a return- 1
chamber at the end of the fire flue to which air is admitted, and a combustion
chamber adjoining the boiler and over the fire place or chamber being separated
therefrom by the said diaphragm. In the construction of furnaces adapted to carry
out the methods devised by me, and broadly set forth under the preceding divisions,
Numbers 1 and 2, various forms may be adopted, as, for instance, continuous and 1
recurrent or return flues interposed between the fire chamber or initial point of
combustion and the point of initial heating or utilization of the heat, said flues
provided with supplemental or secondary air inducts, see Figs. 1, 2, and 3; or by
means of an expansion chamber with reverbatory arch and supplemental or
secondary air inducts interposed between the fire chamber or point of initial com- 2
bustion and the point of initial heating or utilization of the heat, see Figs. 4, 5, 6,
and 7. Either of these general forms may be modified at will to adapt it to use
as a glass furnace, puddling furnace, for evaporating pans, stationary or marine
steam boilers, &c., as hereinbefore specified, or for any special use demanded.
A material advantage is always gained by ensuring that the construction is such
that time and space are allowed for complete combustion to take place before the
resultant gases, &c., are applied for their heating effect or utilization.
I will now proceed to describe in detail three forms of furnace embodying my
Invention.
Fig. 1 is a front elevation of a boiler with my improved recurrent or return flue
furnace applied, the fire front removed.
Fig. 2 is a rear elevation of the same having the rear wall removed.
Fig. 3 is a vertical longitudinal section of the same.
. The usual heat of fire is about 1,000°, the heat necessary for ignition being about
800° At a lower temperature combustion ceases. Steam at 60 pounds pressure
has a temperature of about 295°, at 100 pounds 332°. Hence the temperature of
the water surfaces of ordinary steam boilers is from 400° to 500°, at least, below
that necessary for ignition, consequently if the products of combustion, gases, and
vapors are allowed to come in contact with the water surfaces of the boiler before
complete oxidation of the carbon or complete combustion has taken place, smoke is
formed, and either deposited in the form of soot or carried out of the chimney.
The same result is produced in the case of evaporating pans, glass pots, and
generally where similar causes exist.
As to space. Authorities give the bulk of the results of combustion of one pound
of bituminous coal as 1,725 cubic feet. In case of a grate measuring five feet in
depth, the burning of coal being at the rate of twelve pounds to a foot of grate per
hour, which is an ordinary instance, the consumption of coal is six pounds per
minute, the volume of products 10,350 cubic feet per minute, and the fire box is
consequently filled 70 times per minute.
Although combustion under very favorable circumstances is rapid, I believe the
cubic contents of the fire box or combustion chamber in the above case is not more
than one tenth of that which is necessary for the perfect and economical combustion
of the fuel commonly burned therein.
To remedy the defects above referred to in the existing practice in the use of
'fuel I propose, first, to protect the vapor and gas rising from the fuel from all
cooling surfaces, so far as practicable, until after combustion is complete; secondly,
to secure ample space and time for that thorough admixture of elements necessary

page_text: for the chemical combustion of the bulky vapors inseparably connected with the
process of combustion; and, thirdly, to apply the vapors arising from combustion
only after combustion is complete.
In Figs. 1, 2, and 3, A indicates a boiler (which I have chosen simply for purposes
of illustration) in position in the furnace B; D indicates the fire box, and G the grate.
A passage P surrounded by fire brick walls leads to the combustion chamber C, the
latter being supplied with air by means of the register R to facilitate and complete
combustion. In the chamber C the course of the products of combustion is changed
and the volume goes in the opposito direction through the upper passage P¹ to the
front of the boiler or to the point of utilization of the heat.
The lengths and areas of the passages P and P¹ and chamber C are such as to
afford ample space and time for complete combustion, so that when the chamber C¹,
communicating directly with the front of the boiler or with the point of applica-
tion or utilization of the heat is reached, only the products of perfect combustion
remain.
E indicates a diaphragm or partition separating the passages P and P', and also
separating the chamber C¹ from the fire place or fire chamber.
Certain advantages, as economy of space and diminution of radiating surfaces
render the arrangement shewn desirable, and this particular form constitutes one
part of my Invention.
I will next proceed to describe the furnace shewn in the Drawing, Figs. 4, 5, 6,
and 7, wherein the time and space for thorough admixture of the elements necessary
for complete combustion is obtained by retardation and reverberation within an
expansion chamber.
Fig. 4 is a longitudinal sectional elevation through the furnace.
Fig. 5 is a transverse sectional elevation of the furnace and a boiler at the line
3, 3, Fig. 4.
Fig. 6 is a transverse sectional elevation through the main-air chamber of the
furnace at the line A, A, of Fig. 4.
Fig. 7 is a transverse sectional elevation through the expansion chamber of the
furnace at the line X, X, of Fig. 4.
In the Drawing c, Figures 4 and 5, is the fire box of the furnace into which the
fuel to be burned is supplied; & are the grate bars, and e the ash pit below the
grate, the fire box and ashpit being furnished with doors as usual; f is the bridge
wall of the fire box which forms one side of the air chamber g situated immediately
back of the fire-box and ashpit, having an air passage h opening to the outside in
the side wall of the furnace, and a series of fine openings or air vents i, i, &c.,
communicating from the air chamber to the expansion chamber k.
chamber is closed on all sides excepting for the air passages just named.
The air
The air passage h is furnished with a covering pivoted to the wall at top so
as to serve as a valve to admit more or less air as it is more or less widely opened.
Back of the fire box and air chamber is an enclosed space k, which may be of
the same width as the fire chamber and air box and some two or three times as
long as its width, formed by backward extension of the side walls a, a, of the
furnace. The end wall of this chamber (which I term the "expansion chamber ")
has an opening m for the admission of air into the expansion chamber in which is
set a grating o pierced with a series of fine apertures so that the air in entering
may be divided into fine jets. This air-opening is covered by a pivotted door p
which serves as a valve to regulate the amount of air admitted in that direction
into the expansion chamber k. The furnace or fire box. .C, the passages over the
air chamber g, and the expansion chamber are covered over by a single arch of
fire brick extending from the front wall of the fire box to the rear wall of-the
expansion chamber, forming a reverberatory covering.
The boilers b, b, (or equivalents) are placed. preferably horizontally along side of
the furnace, at such an elevation as to permit of the extension of the expansion
chamber k under the frear end of the boilers, as shewn in Figs. 4 and 7.. This
extension of the expansion chamber is marked s.

page_text: In other constructions and for other purposes the extension may be a simple
flue or throat leading from the expansion chamber to the point of application
or utilization of the heat.
Beneath the boilers b, b, is a space extending from the extensions of the expansion
chamber to the front wall of the furnace, which space is floored with fire brick,
and forms the flue q or passage-way for the flame and heat. The boilers are set
so as to form the upper side of this flue, and also to extend into the extension s
of the expansion-chamber, so that the flame and heat of the furnaces first come in
contact with the boilers in the extension chamber 8. The boilers do not extend
to the front walls of the furnace, thus leaving a space t at the end of the flue (see
Fig. 4) from which the flame and heat enter the flues of the boiler and pass through
them into the chimney or stack u.
The advantages of this construction and arrangement is that the smoke and
gases from. the burning fuel in the fire box, after passing over the bridge wall
formed by the air chamber g, have sufficient room to expand in the expansion chamber
k, where they have time to become thoroughly intermingled with the air which
enters through the air vents i from the air chambers, and through the air openings
o at the rear end, and are oxidized thereby. The air which enters through the
air-chamber g becomes heated from its proximity to the fire-box and ash-pit, and
thus prevents the chilling of the carbonaceous products of the fuel. Just at the
point where the highly heated products of combustion of the fuel are about to come
into contact with the boiler they are met with a fresh supply of atmospheric air
in, fine jets through the openings o in the grating n, the quantity of air introduced
at that point being so adjusted by the valve door p as to secure the complete
oxidation of the gaseous and carbonaceous products of the fuel. The result is that
a very intense heat is generated which is greatest at the rear end of the expansion
chamber and in its extensions under the boilers.
If it is desired to have two sets of boilers in connection with one furnace the
second set may be similarly placed on the other side of the furnace, in which case
the air may be admitted into the air-chamber g through the ash pit e or through
a passage under the ashpit.
Finally I will describe the furnace shewn in Figs. 8, 9, 10, and 11, which is a
modification of the two preceding, embracing the advantageous features of each and
in many respects deemed by me the most desirable form.
Fig. 8 is a side elevation of the furnace.
Fig. 9 is a front elevation of the same.
Fig. 10 is a longitudinal central section on the line x, x, Fig. 9.
Fig. 11 is a transverse vertical section in the line y, y, Fig. 10.
A indicates the outer wall or brick work of the furnace, the form of which will
be adapted to the special object in view. In the present instance the walls are
extended up and arched to enclose a boiler B and form a flue 6 over the same which
terminates in the uptake U. The side walls are built hollow, as at a, to form air
heating chambers and are perforated as at a¹ to admit air, said perforations being
guarded by suitable doors or graduated slides. The inner walls of these air
chambers are also perforated at a² to admit air to the fuel upon the grate and at as
to deliver air to the smoke, gas, &c. back of the bridge wall. It will be noticed
that the heated air entering back of the bridge wall through perforations or slots a³
will be delivered in jets across the path of the products of combustion.
The rear wall of the furnace is also built hollow, as at C, and communicates with
a hollow floor or hot air space C¹ (for purposes hereinafter specified), said hot air
chamber C receiving air from without through ports c, c, guarded by registers or
graduated slides c'. D indicates the fire box provided with a suitable grate d, ash
pit d', and bridge wall d². The bridge wall is hollow and perforated at its rear, as
at d³, to deliver heated air into the gases, vapors, and products of combustion as
they escape over the bridge wall. In the side walls of the furnace in line with the
bridge wall d are ports d' for admission of air to the bridge wall, said ports
guarded by graduated slides, as in fact are all the external air ports of the hollow

page_text: walls. In advance of the ports d' so as to open into the expansion chamber at the
rear of the bridge-wall d³ is a port E (or ports) closed by a slide door so that the
condition of the flame and gas back of the bridge-wall can be examined at
pleasure.
Within the furnace and arranged between the fire box. D and the boiler B (or
other object to which the heat is to be applied), so as to form the return flue G, is
an arch or diaphragm F which from a point over or in rear of the bridge-wall
extends down and back so as to form a deflector (f) which deflects the products of
combustion or causes them to dip down after passing the bridge-wall, and thus
brings them into and across the path of the air jets from the bridge and side walls.
This deflecting arch or diaphragm has another function which will herein after
appear.
C is a hollow floor laid in the furnace back of the bridge, and which is built
with a transverse ridge or elevation, as at C², so as to form with the deflecting arch
Fa throat or throttle T which serves to retard the escape of the gases from the
fire box and expansion chamber before complete combustion has taken place. This
hollow hearth or floor C¹ communicates with the hollow rear wall C from which it
receives heated air and delivers the same through perforations or slots c³ to the
gases and vapors or gaseous fuel as the same escapes past the throttle T. This
ridge or elevation c³ is in some respects a supplemental bridge wall.
The space H below the arch or diaphragm F and between the bridge wall d² and
ridge c² (or supplemental bridge wall) serves as an expansion chamber for the gases
and vapors from the fire box, while the deflecting arch F causes the reverberation of
the same, and ensures that intimate intermingling and admixture of air with the
smoke and gases from the burning fuel which is so necessary to complete
combustion.
In the furnace wall a at various points along the course of the flues are ports
8, 8, or sight holes for examining the interior and testing the temperature with a
pyrometer if desired, while opposite the head of the boiler are doors 8, 8, by which
access may be had to the flues of the boiler.
•
I, K, indicate the doors of the fire-box and ash-pit.
The operation of this furnace will be substantially as follows:-The burning fuel
in the fire box will receive a limited and regulated supply of heated air from the
air chambers a in the side walls through ports or slots a², and the smoke, gases, and
vapors passing over the bridge wall d² will meet a cross current of heated air
entering back of the bridge-wall through ports or orifices a³. In addition thereto
air can be admitted into the expansion chamber H through the perforations d³ in
the rear of the bridge wall, and. the amount thus admitted can be regulated at will
by the slides covering the ports d'. The smoke, gases, &c., after passing the bridge-
wall are deflected by the arch F and reverberated in expansion chamber H, where a
thorough expansion of the same is permitted and oxidation effected.
The escape of the products of combustion from the expansion chamber is some-
what retarded by the throttle T, and at the time they are passing the throttle an
additional amount of air to ensure complete combustion is supplied through ports c³,
so that by the time the flame, &c., enter flue G the combustion is so perfect that
little or no carbonaceous matter or soot will be deposited. The course of the
products of combustion from the fire-box to the uptake is indicated by arrows,
Fig. 10.
The advantages of the form of furnace shewn in Figs. 8, 9, 10, and 11 of the
Drawings, are, that owing to the manner of throttling the products of combustion
before their escape from the expansion-chamber, and also owing to the manner of
delivering the heated air to the products of combustion, both in the expansion-
chamber and at the throttle, thorough oxidation or complete combustion is more
readily and rapidly effected.
Though for purposes of illustration I have chosen to shew my Invention in
connection with steam boilers, yet I do not design to limit its application thereto;

page_text: as by obvious modifications it may be readily applied to the various purposes for
which furnace heat is required, a few of which I have hereinbefore specified; nor
do I propose to limit its use to the burning of solid fuel, for it will be apparent that
the several constructions will be equally efficient if the fire box be changed to adapt
it to 'the use of liquid fuel or gaseous fuel, many devices for such purposes being
now well known and requiring no description herein.
Neither do I confine myself to the precise forms of construction herein shewn to
produce the desired results, my Invention consisting mainly in surrounding the
grate and the volatilized fuel with non-conducting surfaces in connection with
means of supplying air and retaining the air and gases in contact for such time and
in such space as shall admit of a thorough admixture and union of the elements
necessary to complete combustion, and this before application or utilization of the
résultant heat.
Having thus described my Invention, what I claim and desire to secure by
Letters Patent is,―
1st. The combination in a furnace of a fire-box, a tortuous flue (or an expansion-
chainber) arranged between the fire box or point of initial combustion and the
(boiler or other) initial heating point, or point of utilization of the heat, and a series
of air inlets adapted to deliver air to the products of combustion in the tortuous
flue (or expansion-chamber), the whole arranged and adapted to induce complete
combustion before utilization of the heat, substantially as specified.
2nd. As an improvement in furnaces the combustion chamber divided by a
longitudinal horizontal diaphragm forming an upper and a lower flame-flue, a return
chamber at the end of the fire flue to which air is admitted, and a combustion
chamber immediately over the fire chamber and above said diaphragm, whereby
the combustion of all the gases is made complete and utilized, substantially as herein
described with relation to Figs. 1, 2, and 3.
3rd. In a furnace, the grate G, passage P, chamber C, with means for supplying
air, the passage P₁ and the chamber C communicating with the boiler or other
object to be heated, substantially as described and shewn in Figs. 1, 2, and 3.
4th. As an improvement in furnaces, the combination with a fire box and an air-
chamber arranged within the bridge wall, of an expansion chamber interposed
between the fire box or initial-combustion chamber, and the initial heating point,
substantially as described, Figs. 4, 5, 6, and 7.
5th. The combination in a furnace of a fire box, an air-chamber arranged in the
bridge wall, an expansion chamber interposed between the fire-box or initial
combustion-chamber and the initial heating point, and an extension flue leading
from the expansion chamber to the point of utilization of the heat, substantially as
and for the purpose specified, Figs. 4, 5, 6, and 7.
6th. The combination in a furnace of a fire-box, an air-chamber in rear thereof
and delivering air into an expansion chamber, and an expansion chamber interposed
between the fire box or initial point of combustion and the (boiler or) initial heating
point, the expansion chamber provided with a secondary air supply inlet at its rear
or near the initial heating point, substantially as and for the purpose set forth,
Figs. 4, 5, 6, and 7.
7th. The combination in a furnace of a fire box, an expansion chamber back of
the fire box, perforated walls which deliver air into the expansion chamber, and a
deflecting arch or diaphragm, substantially as and for the purpose specified, Figs.
8, 9, 10, and 11.
Sth. The combination in a furnace of a fire box, an expansion chamber back of
the fire box, perforated side walls, which deliver air into both the fire box and the
expansion chamber, and a deflecting arch or diaphragm interposed between the fire
box and expansion chamber and the object to which the heat is to be applied,
substantially as specified, Figs. 8, 9, 10, and 11.
The combination in a furnace of a fire box, a deflecting arch or diaphragm inter-
posed between the fire box and the object to which the heat is to be applied, and a

page_text: perforated elevated floor or supplemental bridge-wall forming a throttle between
the floor and deflecting arch, substantially as and for the purpose specified, Figs.
8, 9, 10, and 11.
In witness whereof, I, the said John Thomson King, havo hereunto set my
hand and seal, this Twenty seventh day of February, in the year of our
Lord One thousand eight hundred and eighty.