IMPROVEMENTS IN MEANS AND APPARATUS FOR SUPPLYING AIR TO THE FURNACES OF MARINE AND OTHER STEAM BOILERS AND INCREASING THE RAPIDITY AND EFFICIENCY. OF COM- BUSTION THEREIN; FOR DIMINISHING WASTE OF HEAT; AND FOR PREVENTING THE OVERHEATING OF STOKEHOLDS
Year: 1882

page_text: LETTERS PATENT to James Howden, of Glasgow, in the County of Lanark,
North Britain, Engineer, for an Invention of IMPROVEMENTS IN MEANS AND
APPARATUS FOR SUPPLYING AIR TO THE FURNACES OF MARINE AND OTHER
STEAM BOILERS AND INCREASING THE RAPIDITY AND EFFICIENCY. OF COM-
BUSTION THEREIN; FOR DIMINISHING WASTE OF HEAT; AND FOR PREVENTING
THE OVERHEATING OF STOKEHOLDS.
PROVISIONAL SPECIFICATION left by the said James Howden at the
Office of the Commissioners of Patents on the 14th June 1882.
JAMES HOWDEN, of Glasgow, in the County of Lanark, North Britain, Engineer,
"IMPROVEMENTS IN MEANS AND APPARATUS FOR SUPPLYING AIR TO THE FURNACES
OF MARINE AND OTHER STEAM BOILERS AND INCREASING THE RAPIDITY AND
EFFICIENCY OF COMBUSTION THEREIN; FOR DIMINISHING WASTE OF HEAT; AND FOR
PREVENTING THE OVERHEATING OF STOKEHOLDS
"
This Invention has principally for its object the supplying of air required for
combustion in the furnaces of marine and other steam boilers in an improved
manner and so as to diminish the waste of heat ordinarily taking place in existing
arrangements, whilst the improvements as applied in connection with marine
boilers have the important advantage of securing ventilation and coolness in the
stokeholds.
In carrying out the Invention according to some modifications a forced draught
is employed, a more rapid and effective combustion of the coal or other fuel being
thereby obtained. The air for combustion is supplied at a pressure above that of
the atmosphere as is done in torpedo and other small steamers, but instead of
enclosing the entire stokehold and keeping it airtight and under pressure, which
is quite impracticable in large vessels or even in moderately sized vessels for
ordinary purposes, the air is confined in an airtight casing formed by a shell or
false front, enclosing a space or spaces in front of the furnaces and at other parts
of the boilers if thought desirable.

page_text: In one arrangement or modification the furnace and ashpit doors in the false
front or air casing are made sufficiently airtight, and the furnaces and ashpits the
entrances of which may be fitted with doors or valves or suitably proportioned
gratings receive the air under pressure from the common space in the air casing;
but provision is by preference made by means of partitions and suitable valves for
shutting off or isolating any furnace from the general air supply when it is
necessary to introduce fresh fuel or to withdraw ashes. Any suitable fan or
blowing apparatus may be used for supplying air into the casing, and the apparatus
may be arranged to draw the air or part of it from the stokehold, the air entering
the stokehold by ventilating funnels or otherwise. In this way a moderate and
cool temperature will be maintained in the stokehold, and the heat ordinarily
radiated into the stokehold in an injurious and very inconvenient manner will be
taken up by the air and utilised.
The air may be admitted into the furnaces above the fire bars only; or partly
through tubular fire bars leading it to the inner ends of the furnaces; or it or a
portion of it may be admitted beneath the fire bars or be led directly to the sides
or inner ends of the furnaces. Where provision is thus made for admitting air at
different parts the several inlets are fitted with valves by which the proportion
of air entering by each may be regulated so as to obtain the best results.
As fire grates of the usual width in internal furnaces of marine boilers would
with the increased air pressure consume a greater quantity of coal in a given time
than would be desirable in boilers of ordinary proportions, the grate spaces are by
this Invention in some cases narrowed by means of portable hollow pieces of cast-
iron or firebrick by preference extending the whole length of each grate. Air is
admitted to these hollow side pieces and becomes part of the supply for combustion
being admitted to the fuel through small holes at the parts of the side pieces
nearest the fuel. With this arrangement the height of the furnace remains
unaltered and a sufficient depth of fuel is maintained for securing effective and
economical combustion with the forced draught. In some modifications the air
spaces between fire bars as in ordinary grates are dispensed with, and the air is
admitted from the front, sides, and back only, or partly from tubular fire bars
placed closely together. This arrangement is specially suitable when using anthra-
cite as fuel or when using small coal.
In some cases the air may be led to the casing or chamber in front of the
furnaces through suitable passages or casings from the back or end of the boiler
furthest from the furnaces; or the air may be drawn from around the funnel or
uptakes so that a part of the heat which would otherwise pass off may be utilised
and the neighborhood of the boiler be kept cooler. It is however also provided
that the heat carried off by the escaping fire gases shall be much less than with
ordinary modes of working. It is, indeed necessary to restrict the outlet space or
spaces for the fire gases in order to maintain the desired pressure of the air supply
without wastefully passing more air than is required through the furnaces. For
this purpose the boiler tubes may be made comparatively numerous and small in
diameter; it is however preferred to use tubes of the usual sizes, and to partially
close the exit ends of the tubes, either by partial plugs or by bars of iron arranged
against the ends of rows of the tubes. It is preferred to thus close the upper parts
of the exit ends of the tubes, and to leave the lower parts open for the escaping
gases and the accompanying dust and cinder; and the closing bars are made
movable to give access for cleaning the tubes. Or the egress of the fire gases may
be restricted by employing a comparatively reduced size of uptake or funnel or
by applying valves or dampers therein. In consequence of the restricted egress
the fire gases are kept longer in contact with the heating surfaces of the boiler and
their heating action rendered more efficient than in ordinary boilers.
The herein before described improvements may be carried out in combination
with any suitable mechanical stoking apparatus, or with hoppers constructed to
receive considerable quantities of fuel and from which the fuel passes gradually
and chiefly by gravitation into the furnaces, or with mechanical aid, and without

page_text: the frequent opening of the furnace doors required with ordinary arrangements.
A door or cover at the outer end of each hopper may be sufficient; and the air may
be admitted into each hopper so as to pass through the fuel into the furnace
When employing hoppers as described the fire bars may be considerably inclined
or mechanism may be arranged to insure the progressive movement of the fuel to
the inner end of the furnace.
The arrangements of air casings with internal partitions and valves or doors
herein before described may be employed with some advantage with the ordinary
draught instead of the forced air supply, and in some cases the air or part of it may
enter the casing directly through ventilating funnels.
When the air for combustion is supplied under pressure and the described
arrangements are adopted, the boilers for a given work or duty can be made
smaller than heretofore; and higher steam pressures can be used with safety and
without the great waste of heat unavoidable with existing arrangements, so that
a given power can be obtained without the boilers occupying so much space in a
steamship.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said James Howden in the Great Seal Patent Office on the
13th December 1882.
JAMES HOWDEN, of Glasgow, in the County of Lanark, North Britain, Engineer,
"IMPROVEMENTS IN MEANS AND APPARATUS FOR SUPPLYING AIR TO THE FURNACES
OF MARINE AND OTHER STEAM BOILERS AND INCREASING THE RAPIDITY AND
EFFICIENCY OF COMBUSTION THEREIN FOR DIMINISHING WASTE OF HEAT, AND FOR
PREVENTING THE OVERHEATING OF STOKEHOLDS
"
My said Invention has principally for its object the supplying of air required
for combustion in the furnaces of marine and other steam boilers in a novel and
improved manner by which a more rapid and effective combustion may be obtained
and the great waste of heat may be diminished which ordinarily takes place in
existing arrangements; whilst my improvements as applied in connection with
marine boilers have the important advantage of securing ventilation and coolness
in the stokeholds.
In carrying out my Invention in most cases an important feature is the use of
a forced draught to give a more rapid and effective combustion of the coal or other
fuel used in the furnaces. The air for combustion is supplied at a pressure above
that of the atmosphere, as is done in torpedo boats, but instead of enclosing the
entire stokehold and keeping it airtight under pressure which is quite impracticable
in large vessels or even in vessels of moderate size used for ordinary purposes, the
air is confined in an airtight casing formed by a false front of thin plates enclosing
a space or spaces in front of the furnaces, and at other parts of the boilers where
considered necessary or desirable in carrying out my Invention with the object of
saving heat.
In some cases the air in the casing may have access to the furnaces or ashpits
just like the air from the stokehold in existing arrangements, but in arrangements
which 1 prefer there is in each case a common air chest or compartment of the
casing which is separated by partitions from the furnaces and other parts, whilst
the furnaces are separated from each other and the supply of air to each is regu-
lated by means of suitable valves. One compartment may be used for adınitting
air above the fuel of each furnace also through tubular fire bars and into the ashpit
thereof one valve being used to regulate the admission and for shutting off the
supply when fuel has to be introduced or ashes withdrawn, the quantities of air
admitted to these several parts being regulated by gratings or valves on the interior
doors. I however prefer to admit the air separately either above or below the fuel
or through the fire bars separate partitions and valves being provided for this
purpose. In this way the amount of air to each compartment may be regu-
lated at pleasure and interior doors on the ashpit and firebar inlets can be
dispensed with.
When several boilers are arranged alongside of each other the common air casing
may extend over the whole series, the air from the fan or blowing apparatus being
led into the casing at one or more places. Arrangements can in this case be simply
made to shut off any boiler from the series, as well as any single furnace in any of
the boilers.
The residuary heat of the fire gases after passing through or over the heating
surface of the boiler or boilers may be prevented from passing away too rapidly by
partially closing the ends of the tubes of tubular boilers, or analogous parts of other
boilers, or the velocity of the escaping gases may be regulated at some part of the
passages leading to the chimney or funnel, and the gases may be made to give up

page_text: a considerable portion of their remaining heat to the air supplied to the common
casing by being passed through tubular or other suitable passages in a part of the
air casing or in a casing communicating therewith, the cold air entering from the
fan or other blowing apparatus being made to pass in contact with the outsides of
such tubular or other passages. By this means the great heat which would
otherwise be lost as in torpedo boats, or in ordinary steam boilers is utilised in
licating the air for combustion thus effecting great economy of fuel and obtaining
an equal evaporation of water, or supply of steam from a much smaller boiler or
fire grate to that from the usual marine boiler worked with natural draught, whilst
at the same time the boiler room or stokehold is kept cool and the temperature of
the uptakes and funnel is comparatively low.
As I prefer to work the fan or blowing apparatus in the stokehold the air
therein is always kept cool and fresh by the supply which continually enters to
replenish what is taken by the fan. And as the false front of the air casing which
covers the greater part of the boiler ends is always comparatively cool no heat
from the furnaces or ashpits is radiated into the stokehold as in ordinarily fired
boilers, or as in torpedo boats, so that with the shell of the boilers properly protected
by a non-conducting material no part of the boiler room can be heated to any great
extent from the working of the boilers.
When boilers are used which have the exit of the fire gases at the end of the
boiler opposite to that at which the furnaces are, then the air for combustion is
according to this Invention led from the fan or blowing apparatus through a casing
fitted with tubes or passages through which the escaping fire gases pass, and the
air heated by this means is led along the side or sides of the boiler to the air casing
at the front or furnace end being distributed from this casing to the furnaces as
hereinbefore described.
The advantages of economy, coolness, and ventilation in the working of steam
boilers are also secured under my Invention by using the air casing and other
novel arrangeinents hereinbefore described and by using a natural draught for the
air supply and without employing a fan or blowing apparatus. In arrangements
operating with natural draught in this way the air may enter the casing from the
stokehold or through ventilators above deck, and it may be partly heated by the
escaping fire gases before entering the casing on the front of the boiler or boilers.
When the forced air supply is not used the evaporation will be about equal to that
of ordinary boilers having the same grate surface.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append eight sheets of explanatory
drawings to be hereinafter referred to and representing by way of example a few
of the numerous modifications and applications of which my improved arrangements
are susceptible, premising that in these drawings the same reference numerals are
used to mark the same or like parts wherever they are repeated.
Figures 1 and 2, on sheet 1 of the drawings are en end elevation and a sectional
end elevation of a small tubular boiler having a single internal furnace; and figure 3,
is a longitudinal vertical section of the same boiler, whilst figure 4, is a vertical
section through the smoke box which in this example is at the end of the boiler
opposite to the furnace end. In this modification the air from the fan or blowing
apparatus enters by a pipe, 31, into a casing, 32, formed at the smoke-box end of the
boiler just above the tubes, and fitted with a number of vertical tubes, 33, through
which the fire gases pass to the uptake, 34, there being formed below the casing, 32,
and tubes, 33, a chamber or sinuke box, 35, through which the fire gases pass from
the horizontal boiler tubes, 36, to the vertical or air-heating tubes, 33. A space, 37,
38, 39, is enclosed at the sides of and beneath the smoke box, 35, coininunicating
with the upper part or casing, 32, at the side further from the air inlet, 31, and the
air after passing in contact with the vertical tubes has access by the space, 37, 39, to
two pipes, 40, extending one along each side of the boiler to the furnace end.
the furnace end the air enters from the pipes, 40, into a casing, 41, constructed of
thin plates so as to enclose and cover rather more than the front of the furnace, 42,
At

page_text: and ashpit, 43. The casing is partly formed by a cylindrical casting, 44, fitted with
an outer fire door, 45, and ashpit door, 46, and made with a horizontal plate, 47,
which forms an extension of the ordinary dead plate. The outer dre door, 45, has
attached to it by studs a smaller inner door or plate, 48, which closes an inner
opening into the furnace, 42, but which is formed with a number of holes for
admitting a suitable proportion of air above the fire bars, the jets of air so admitted
being, by preference directed downwards by deflectors on the inner side of the
door, 45. Openings are formed in the cylindrical part of the casting, 44, to admit
the air from the casing, 41, into the space between the outer and inner doors, 45, 48,
and into the ashpit 43. With these arrangements the air required for combustion
is supplied under pressure, (by means of a fan or any suitable blowing apparatus,
which however is not shown) and entering by the pipe, 31, takes up what would
otherwise be waste heat from the escaping fire gases passing through the vertical
tubes, 33, whilst the casing, 41, at the furnace end of the boiler causes the heat which
would otherwise be radiated wastefully and injuriously into the stokehold to be
taken up by the air which is compelled to enter the furnace through the casing.
As the method of using a forced and heated draught in the manner described
renders the combustion of the fuel very rapid and effective, the width of the space
for fuel may with advantage be made less than that of furnaces of ordinary
proportions for a given size of boiler. It is however in most cases desirable to
retain the ordinary height of the furnace space and with this view the grate space
may be most conveniently and advantageously narrowed by placing along the sides
of it hollow fireclay (or iron) pieces or tubes, 49, with inlet openings at their front
ends for the admission of air from the casing, 41, and with perforations along them
for the issue of the air into the furnace.
The boiler shown on sheet, 1, of the drawings being of a known type as regards
its general and internal construction such construction does not require to bo
particularly described herein; and this same remark also applies to the boilers shown
on the other sheets of drawings.
Figures 5, and 6, on sheet 2 of the drawings are a sectional end elevation and a
longitudinal vertical section of a marine steam boiler having two internal
furnaces, 42, communicating directly with a combustion chamber, 50, from which
the fire gases return through tubes, 36, to the front or furnace end. Figure, 7, on
sheet, 3, is an end elevation showing three such boilers combined. In this
modification the casings, 32, 37, 38, 39, 41, to which the air under pressure has access
from the inlet pipe, 31, instead of being partly at the back and partly at the front
end of the boiler are combined at the front end. This modification also differs
from that shown upon sheet, 1, in having provision for what may be termed a
controllable or adjustable differential distribution of the air, and in having tubular
fire bars, 51. These fire bars, 51, which may be of any suitable section communicate
with a hollow bridge, 52, having orifices at its front through which the air passing
through the fire bars issues into the furnace, 42. For the distribution of the air
from the casing, 41, there are provided adjustable valves 53, 54, 55, one 53, admitting
the air into the space between the outer and inner fire doors, 45, 4S, a second, 54, for
admitting it into a space formed under the dead plate extension, 47, and com-
municating with the front ends of the tubular fire bars, 51, and a third, 55, for
admitting it into the ashpit, 43.
A damper or valve, 56, is shown as fitted in the uptake, 34, for the purpose of
preventing the too rapid escape of the fire gases to which they might be liable in
consequence of the air for combustion being supplied under pressure. Such dampers
may be applied in any or all of the modifications and will afford convenient means
for adjusting the greater or less freedom of exit as may be required under different
circumstances. I however prefer to restrict the rapidity of escape of the fire gases
to some extent by arrangements in addition to or independent of adjustable
dampers or valves; and in the examples so far described and shown on sheets, 1
and 2, of the drawings, the desired restriction is obtained by making the aggregate
area of the air-heating, tubes, 33, suflicily small relatively to the aggregate area

page_text: of the boiler tubes, 36. For the same purpose the boiler tubes, 36, may be made
comparatively numerous and small in diameter, or their exit ends may be partially
closed, either by partial plugs or by bars of iron arranged against the ends of rows
of the tubes. I prefer to thus close the upper parts of the exit ends of the tubes,
and to leave the lower parts open for the escaping gases and the accompanying
dust and cinder; and the closing bars are made movable to give access for cleaning
the tubes. In a similar way the passage of the fire gases through the air-heating
tubes, 33, may be restricted by means of firebrick pieces or plugs placed at their
upper ends, and doors may be provided in the uptake, 34, to give access for moving
or adjusting such pieces when required. In consequence of the restricted egress
the fire gases are kept longer in contact with the heating surfaces of the boiler,
and their pressure is maintained, whereby their heating action is rendered more
efficient than in ordinary boilers.
When a number of boilers are combined as shown in figure, 7, the air under
pressure may be supplied by two or more inlet pipes, 31, and each of the air casings
may be fitted with valves so that the supply to cach boiler may be regulated
independently of the others or be entirely cut off from any one or more when
required. I may also here mention that when there are two or more furnaces in
any one boiler I prefer to have the internal passages between each furnace and the
uptake kept distinct, so that the action of each furnace and the supply of air to it
may be regulated quite independently of the other furnace or furnaces.
Figures, 8, and 9, on sheet 3, of the drawings are a front and side elevation of a
boiler which is to a considerable extent like that shown in figures, 5 and 6, berein-
before described, but which is represented as having an additional feature. This
consists in obtaining the supply of air for combustion through ventilating funnels, 57,
above deck, and through a casing 58, surrounding the funnel, 59. From this casing
the air is drawn by a fan, 60, and forced into the casing, 32, wherein the heat it
takes up in the upper casing 58, is supplemented by what it receives from the air-
heating tubes indicated by dotted lines in figure, 8. The fan (60) or any suitable
blowing apparatus may be arranged to act on the air at any convenient part of
the course thereof towards the furnaces, but I prefer to have the air operated on
by the blowing apparatus before being heated at all or before much heat has been
imparted to it.
My improvements may be carried out in combination with any suitable
mechanical stoking apparatus or with hoppers constructed to receive considerable
quantities of fuel, and from which the fuel passes gradually and chiefly by
gravitation into the furnaces, or with mechanical aid, and without the frequent
opening of the furnace doors required with ordinary arrangements.
A door or
cover at the outer end of each hopper may be sufficient; and the air may be
admitted into each hopper so as to pass through the fuel into the furnace.
employing hoppers as described the fire bars may be considerably inclined, or
mechanism may be arranged to insure the progressive movement of the fuel
towards the inner end of the furnace.
When
Figures, 10 and 11 on sheet 4, of the drawings are a sectional front elevation
and a longitudinal vertical section of a two-furnace marine steam boiler, each
furnace of which has constructed in front of it a hopper, 61, for holding a con-
siderable supply of fuel, the bottom of the hopper being inclined and the fire bars
also having a downward inclination so that the fuel may gradually move with
little or no assistance towards the inner end of the furnace. An inlet space, 62,
with an adjustable valve is provided for admitting air from the casing, 41, into the
hopper; and a door, 63, is fitted to the inclined front of the hopper to give access for
stoking instruments. The arrangements for supplying air under pressure and for
making it utilise waste beat shown in figures, 10, and 11, are substantially the
same as those herein before described.
In figure, 12, on sheet, 5, of the drawings one half is a front elevation and the
other half is a vertical section, the two halves showing slightly modified arrange-
ments adapted for carrying out my improvements partially; and figure, 13, is a

page_text: longitudinal vertical section corresponding to the left hand half of figure, 12, and
showing part of a boiler. As hereinbefore stated some of the advantages of my
Invention may be secured when only a natural draught is used instead of a forced
draught. Thus for example as shown in the left hand half of figure, 12, an air
casing, 63, may be fixed in front of each furnace, 42, and ash pit, 43, this casing
covering a space somewhat greater than the furnace and ashpit openings and
preventing or diminishing radiation of heat therefrom into the stokehold. An
adjustable valve, 64, is provided for admitting a regulated supply of air by natural
draught into the casing, 63. The arrangements shown in the right hand half of
figure, 12, are substantially the same as those herein before described with reference
to sheets, 1 and 2, of the drawings excepting that a valve, 64, is provided for
admitting air by natural draught into the casing, 32, containing the air-heating
tubes, 33. The air may be admitted by a door or valve at any other part of the
casing, 63, or 32, if considered more convenient than the valve, 64.
Figures, 14, and 15, on sheet 6, of the drawings are a plan and a sectional
elevation of a marine steam boiler of the kind known as hay stack boilers, and
having four furnaces. The air from the fan or blowing apparatus enters by a
pipe, 31, into a casing, 32, forming the base of the funnel, 59, and provided with air-
heating tubes, 33, (indicated by dotted lines in figure, 15) From the casing, 32, the
air passes by a pipe, 65, to a distribution pipe, 66, extending round the boiler, and
from this last pipe, 66, short branches each of which is by preference provided with
an adjustable valve, lead the air into casings, 41, covering and enclosing each of the
furnace and ashpit openings.
Figures 16, 17, and 18, on sheet 7, of the drawings show the application of a
portion of my improvements to an ordinary upright land boiler, figure, 16, being
a sectional side elevation, figure, 17, a plan, and figure, 18, a front elevation. In
this example the pipe, 31, supplying the air under pressure leads it directly into the
casing, 41, which covers and encloses the furnace and ashpit openings.
Figures 19 and, 20, on sheet S, of the drawings are a sectional end elevation and
a longitudinal vertical section of a horizontal cylindrical land boiler having two
internal furnaces, and which is provided with a modification of my improved air
supplying and heat-utilising arrangements. In this modification the air from the
fan or blowing apparatus enters by a pipe, 31, into a casing, 67, connected by air
heating tubes, 33, through which the air passes to another casing, 68, which com-
municates by a pipe or duct, 69, with the casing, 41, covering and enclosing the
furnace and ashpit openings. The air-heating tubes, 33, are in a part of the flue
through which the fire gases are led after having acted on the boiler.
Figures, 21, 22, and 23, on sheet, 8, of the drawings represent the application of
a modification of my improved arrangements to a steam boiler of the locomotive
class. In this application the air may enter the apparatus through the action of
natural draught or through the action of the blast pipe operating as in ordinary
locomotives; I however prefer to have the exhaust from the engines freer and
with less back pressure than is usual in ordinary locomotives and to introduce the
air by means of a fan or blowing apparatus worked by a small donkey engine, this
arrangement being I believe more economical in power. The air from the fan or
blowing apparatus is led by a pipe, 31, to a space, 70, formed between the outer
shell of the locomotive at the smoke box end and an inner smoke box shell, 35, and
from this space the air passes through a casing, 32, formed above the inner sinoke
box shell, 35, and fitted with air-heating tubes, 33. From the casing, 32, the air
passes by two flat pipes, 71, to the air casing, 41, formed upon the fire box end of
the boiler and from this latter casing, 41, the air has access through a valve, 53, to
the space between the fire doors, 45, 48, and through another valve, 55, to the
ashpit, 43. A valve, 72, is also fitted to the ashpit, 43, to allow of air being admitted
when the fan or blowing apparatus is not working or at other times when thought
desirable.
In carrying out my Invention in some cases the air spaces between fire bars as
in ordinary grates are dispensed with, and the air is admitted from the front, sides,

page_text: and back only or partly from tubular firebars placed closely together. This
arrangement is specially suitable when using anthracito as fuel or when using
small coal.
Having thus particularly described my said Invention and the manner of
performing the same I have to state that I do not restrict myself to the precise
details herein described or delineated but that what I believe to be novel and
original and claim as the Invention secured to me by and in terms of the
hereinbefore in part recited Letters Patent is :-
1. The combination of apparatus or arrangements for supplying air to the furnaces
of marine and other steam boilers wherein the air supplied under pressure by a fan
or blowing apparatus first passes into a casing and in contact with tubes or passages
through which the fire gases escape or through equivalent heat-exchanging apparatus
so as to take up residuary heat from the fire gases, and next passes through pipes
or passages to, or enters a casing covering more or less of the furnace end of the
boiler, such casing having within it suitably proportioned openings or adjustable
valves through which the air under pressure and heated enters each furnace and
ashpit, the parts being arranged and operating substantially as and for the purposes
herein before described.
2. The combination of apparatus or arrangements for supplying air to the furnaces
of marine and other steam boilers wherein the air is supplied under pressure to a
casing covering more or less of the furnace end of the boiler, such casing having
within it suitably proportioned openings or adjustable valves through which the air
under pressure enters each furnace and ashpit, the parts being arranged and operating
substantially as and for the purposes herein before described.
3. The application to a marine or other steam boiler of an air casing covering
more or less of the furnace end of the boiler and having within it suitably
proportioned openings or adjustable valves through which the air supplied by
natural draught and with or without passing through heat-exchanging apparatus
so as to take up heat from the escaping fire gases, enters each furnace and ashpit
the parts being arranged and operating substantially as and for the purposes
herein before described.
4. The combination of tubular fire bars leading air to a hollow fire bridge or of
hollow perforated side pieces leading air so as to issue into the furnace at the sides
or of both tubular bars and side pieces, with any of the combinations of air supplying
apparatus forming the subject matter of the preceding claims, all the parts being
in each case arranged and operating substantially as and for the purposes herein-
before described.
5. The arranging of the air-supplying apparatus for two or more furnaces in one
boiler or two or more combined boilers, so that the supply of air to cach furnace
or boiler can be independently regulated substantially as hereinbefore described.
6. The combination of a hopper or mechanical stoking apparatus with the
improved air supplying apparatus or arrangements substantially as and for the
purposes herein before described.
In Witness whereof, I, the said, James Howden have hereunto set my hand
and seal this twelfth day of December in the year of our Lord One thousand
right h
Witness
EDMUND HUNT
Patent Agent
Glasgow.
JAMES HOWDEN (L.S.)