Improvements in or relating to Furnaces.
Year: 1898

page_text: TRUVIDIUNAL DIECIFICATION.
Improvements in or relating to Furnaces.
I, JAMES STUART LETHEM, of 76, Bignor Street, Cheetham, Manchester, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
to be as follows:-
The object of my invention is to give in an improved manner at a point or
points above the grate an automatic supply of air or of steam and air to furnaces;
to regulate this supply, and to shut it off in whole or in part also automatically:
except in cases where the automatic shutting-off may be dispensed with.
I explain my invention firstly as applied to a furnace working with natural
draught; and secondly as applied to a furnace working with forced draught.
In a furnace working with natural draught I find that a supply of air over
the grate can generally be given most conveniently and effectively through a
valve or valves in the furnace door, also that in such furnaces a supply of both
steam and air is seldom required for such purposes as checking smoke and pro-
moting a more thorough combustion of the fuel, but that a supply of air alone
usually suffices. And so far as natural draught furnaces are concerned, my in-
vention provides an improved device or devices for securing that the air-valve
or valves in the door, or certain of them, shall be open at the time when the
furnace door is closed after charging or stirring the fire, and that they shall
remain fully open for a predetermined time after closing the door, on the expiry
of which time the valves (or valve) shall be gradually closed by automatic
mechanism, also in a predetermined time, or approximately so; and the air-
valve or valves may be completely closed or to such an extent merely as is judged
permissable. Alternatively only that part of my invention which relates to
the automatic opening of the air-valves may be used.
For the purpose of my invention as applied to natural draught furnaces, I
pivot the door-handle to the door itself, or to a projection from the same, in a
suitable position and manner, so as to permit of the handle turning freely on
its axis for a certain limited distance. By means of stops on the door-handle or.
on the door, I limit the travel of the handle so that the angle between the face
of the door and one side of the handle (taking a line through the axis and centre
of the latter) shall ever be less than a right angle; while the angle enclosed
between the door face and the other side of the handle shall ever be greater than
a right angle. In a handle so pivoted and arranged it will be found that a pull
or push applied to it in the act of closing the door, will always rotate the handle
in a certain direction and to the extent permitted, while a pull or push upon the,
handle in the act of opening the door will rotate the handle in the opposite
direction. The air-valve or valves in the door are suitably connected with the
handle in such a manner that a pull or push upon the latter in closing the
furnace door will automatically open the valves.
To supplement the action of the handle in opening the air-valves, and for the
same purpose, I sometimes attach a suitable projection to the front plate. of the
furnace. In opening the furnace door this projection comes in contact with a
ונס ...D

page_text: moveable part of the air-valve and opens the latter. On the door being closed
the air-valve remains open. I may provide for the automatic opening of the
air-valve or valves in the door, by means of either of these devices, or may
employ them both, and in the latter case should one device get out of order the
remaining one would do the work.
In employing automatic mechanism to close the air-valve or valves in a furnace
door, through which valve air alone is passed into the furnace by suction or
natural draught, the practice has been as follows. At the time the door has
just been closed the air-valve is open, but no sooner has the door been closed
than the automatic closing mechanism comes into play, and gradually closes the
air-valve in a given time. To illustrate what has hitherto been the practice,
let it be supposed that one minute is the given time in which gradually to close
the air-valve; then in one second after closing the furnace door, the air-valve
would be closed one-sixtieth part, in fifteen seconds it would be one-quarter
closed, in thirty seconds it would be half-closed, and so on, or approximately
SO. But in the case of a furnace supposed to smoke more or less for one minute
after firing, it would be found that the densest smoke would be produced about
midway in the period for which smoke was visible, that is, in about thirty
'seconds after closing the furnace door, while it would be found that very little
smoke was observable immediately after closing the door. Yet according to the
usual practice the air-valve would be half shut and the air supply correspondingly
reduced, at the time smoke was at its worst and a full air supply most needed.
In arranging the self-closing mechanism in my invention I do not begin to
close the air-valves immediately on the door being shut, but for a predetermined
time after closing the door the valves are left fully open; and only after the
expiry of such predetermined time does the automatic device gradually close
them. I find that smoke is much diminished by this feature of my invention.
It will be understood in speaking of the air-valve that I mean valve or valves
according to circumstances, and in the case of a door having more air-valves than
one that I may connect all said valves, or only certain of them, or it may be none
of them, with the automatic closing mechanism..
In applying my invention to a furnace which is fitted with a device for pro-
ducing a forced draught beneath the grate, and in certain other cases such as
when the natural draught is very sluggish or when there is a tendency to down-
draught in the chimney, I find it necessary to employ a steam-jet or steam-jets
to force a supply of steam and air into the furnace at a point or points above the
grate. This device I shall refer to as a steam-air device. When I I employ the
steam-air device I prefer to give the steam-air supply, not through a valve or
valves in the furnace door, but at the extreme front of the furnace and over the
furnace door, or nearly so. With regard to the prevention of smoke, it is not
perhaps of much consequence at what point or place the steam-air supply is
passed into the furnace over the grate, for a given quantity of steam and air
will, so far as my experience extends, be equally effective in checking smoke,
whether it be given at the front through the upper part of the furnace opening,
or conveyed through a chamber, pipe, or other device, to some place or point
further within the furnace where it is discharged. But I find that the point or
place of discharge is most important for other reasons, seeing that on the place
of discharge depends the durability of the steam-air device itself, and to some
extent the efficiency of the furnace, the safety and comfort of the fireman and
the preservation of the furnace front. It has been customary in previous steam-
air devices of this kind to conduct the steam-air supply by means of chambers,
pipes, nozzles, or other devices to points inside the furnace, and hitherto these
devices have all extended more or less within the furnace front. But it has been
found that no such device, within a furnace, can be depended upon to withstand
the heat to which it is exposed, and that either it gets out of order, or is burnt
away altogether in a relatively short period of time.
Then it has also been found in a forced draught furnace, with air under pres-

page_text: sure in the ashpit, that there is a troublesome tendency when the door is open,
for fumes, flames and sparks to be forced outward into the stokehold, and to pre-
vent this, it has generally been necessary while the door is open, to reduce the
pressure under the grate, at a loss however of efficiency, for the time being, as
the combustion of fuel is retarded while the under-grate pressure is reduced.
Further, it has been found in practice, that the fronts of furnaces, working
under forced draught suffer severely from the heat to which they are exposed;
and that the heat in the stoke-holds of such furnaces is very great. To reduce this
high temperature in the stokehold by keeping the fronts cool, it has sometimes
been thought necessary to cause a stream of water under pressure to circulate
through chambers in the fronts, & through a chamber in the furnace door itself;
and a steam-air device has been employed to discharge steam and air into the
furnace through a chamber within the mouth of the same during such time as
the furnace door is open. But the device for circulating water through the
fronts is difficult to keep in good order, and I prefer to dispense with it, and to
effect the same purpose by giving a limited quantity of steam and air by means
of my steam-air device, during such time as forced draught is being used under
the grate.
In addition to checking the formation of smoke and effecting a more thorough
combustion of the fuel, my invention makes it unnecessary to reduce the pres-
sure under the grate when the door is open; it checks the escape of fumes,
flames and sparks into the stokehold; when the door is open it interposes a
screen of cool air between the furnace and the fireman; and can be utilized to
protect the furnace fronts; also my device is certainly durable, because I keep
it outside the furnace altogether.
For the purpose of my invention so far as the steam-air device is concerned,
I attach externally to the front plate of the furnace, a door-frame upon which
I hang or hinge the furnace door. This frame surrounds the opening, generally
on all sides, & may be cast upon the furnace front, or otherwise attached to it.
Upon the upper part of this door frame I cast, or suitably attach, a passage
or horizontal chamber, circular or nearly so in cross section, and in length
approximately equal to the width of the door-frame. In the lower part of this
passage or chamber, I make a long opening (or instead of one opening, I may
make several smaller openings) which communicates with the upper part of the
furnace opening, and so with the furnace.
The ends of the said passage or chamber are closed, excepting that one (or
both) of them carries a pipe, the inner end of which extends a certain distance
into the said passage, and having its outer end communicating with atmospheric
air; and into the outer end of this pipe I introduce a steam-jet which is con-
nected with any convenient source of steam supply. I connect the valve con-
trolling the steam supply with the furnace door, by means of suitable connections,
in such a manner that on the opening of the door, the steam valve is opened,
and a steam-air supply passes through the said passage into the furnace at the-
upper part of the furnace opening; it enters the furnace in an inward and
downward direction; and while the door is open serves the aforesaid purposes
of counteracting the tendency on the part of fumes, flames and sparks to surge
outward into the stokehold, and of protecting the fireman from excessive heat.
On the door being closed the steam-air supply is continued for a pre-determined
time in order to check the formation of smoke; after this predetermined time
has passed the steam valve is gradually closed by automatic mechanism also in.a
predetermined time, or approximately so. Or instead of the steam-air supply
being entirely shut-off, it may only be shut off in part; in which case it will
tend to keep the fronts cool and make them last longer.
I may provide an automatic or other device for closing the outer end of the tube
in the aforesaid passage during such time as the steam air supply is shut off.
Dated this 23rd day of Septcamber 1898.

page_text: Improvements in or relating to Furnaces.
I, JAMES STUART LETHEM, of 76, Bignor Street, Cheetham, Manchester, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
-
The object of my invention is to give in an improved manner at a point, or
points, above the grate an automatic supply of air, or of steam and air, to fur-
naces; to regulate this supply, and to shut it off in whole, or in part, also auto-
matically; except in cases where the automatic shutting off may be dispensed
with.
I explain my invention firstly as applied to a furnace working with natural
draught; and secondly as applied to a furnace working with forced draught.
In a furnace working with natural draught, I find that an over-grate air
supply is generally given most conveniently and effectively through a valve or
valves in the furnace door, also that in such a furnace a supply of air alone
usually suffices to check smoke and promote combustion, and that a supply of
both steam and air is seldom required. And in so far as natural draught furnaces
are concerned my invention provides an improved device, or devices, for securing
that the air-valve, or valves, in the door, or certain of them, shall be open at the
time when the furnace door is closed after charging or stirring the fire, and that
they shall remain fully open for a predetermined time after closing the door, on
the expiry of which time the valve, or valves, shall be gradually closed by auto-
matic mechanism also in a predetermined time or approximately so; and the
air valve, or valves, may be completely shut or to such an extent merely as is
judged permissable. Alternatively only so much of my invention as relates to
the automatic opening of the air valves may be used.
I explain my invention, firstly, as applied to a furnace working with natural
draught; and its nature and the manner in which it is carried into practical
effect will be understood on reference to the annexed drawings and the following
explanation thereof.
Fig. 1 on the drawings is a front elevation of a furnace door, with an air
admission chamber projecting externally; a type of door chosen because upon
it' the application of my invention can be conveniently shown. The air-valve,
consisting of a grid and slide arrangement is fully open.
Fig. 2 is a front elevation of an automatic device suitable for the purpose of
closing the said air-valve in the manner required by my invention. It shews the
position of the automatic mechanism at the time of shutting the furnace door
and while the air-valve remains fully open.
Fig. 3 is a front elevation of the upper part of the automatic device and shews
the position of the said device some brief time after shutting the furnace door,
but while the valve is still fully open.
Fig. 4 is a front elevation of the door with the valve closed.
Fig. 5 is a front elevation of the upper part of the automatic device at rest
and in its normal position after it has closed the valve in the door.
Fig. 6. is a horizontal section of the door, through the line A-B in Fig. 1;
the door being shut, but the valve open.
Fig. 7 is also a horizontal section of door, through A-B in Fig. 1, the door
open to the full extent permissable and the valve open also.
Fig. 8 is a horizontal section of door, through line C-D in Fig. 4, shewing
door open, but valve closed.
Fig. 9 is a vertical section of door through the line E--F in Fig. 1, showing

page_text: handle arrangement; also a vertical section of the external air chamber through
centre.
Fig. 10 is a plan of door handle.
i
A
For the purposes of my invention I cast, or otherwise attach to the front of
the furnace door a the two lugs b to which I pivot handle c at some suitable
point c (see Figs. 4, 6, 9, 10); and I cast, or otherwise attach to the 'slide the
two lugs d hinging the handle to them also at some suitable point (Figs. 4
and 10). The manner in which the handle is hinged and pivoted may vary. but
it is essential that it revolve freely on its axis for a certain limited distance und
in doing so operate the air-valve. By means of stops on the handle or on the
door itself, the travel of the handle is limited so that the angle between the face
of the door and one side of the handle (taking a line G-H, in Fig. 10, through
its axis and centre) shall ever be less than a right angle, while the angle con-
tained by the face of the door and the other side of the handle shall ever be
greater than a right angle; (see angles I, G, Hand J, G, H in Fig. 10). "In
a handle so pivoted and arranged it will be found that a push or pull applied to
it in the act of shutting the door will always rotate the handle in a certain
direction and to the extent permitted, while a push or pull applied to it, as if,
in the act of opening the door will always rotate the handle in the opposite
direction. The air-valve (which as shewn in the drawing may be a grid and
slide valve or of any other suitable construction) must be connected to the handle
in such a manner that a push or pull upon the latter in the act of shutting the
door will automatically open the said valve; while a push or pull in the opposite
direction will close it. In the drawings, (see Figs. 6 and 8) the front of the door
and the side of the external chamber are utilized to limit the travel of the handle,
but it is obvious that in cases where there is no external chamber, some other
suitable stop can be provided.
To supplement, the action of the handle in opening the air-valve in the door,
and for the same purpose I sometimes attach to the furnace front.a cam e, with
faces e and e. I also cast or otherwise attach to the slide d a projection or pro-
jections which may correspond with lugs ', or be of any suitable shape.
(See Figs. 1, 4, 6 and 7). This arrangement works as follows; on opening the
furnace door the projections & attached to the moveable part of the air-valve
come into contact with came and in passing across its face e¹ are pushed into a
position which opens the air valve in door. Subsequently on the door being
shut the valve remains open. (See Figs. 6, 7 and 8).
11.
I may provide for the automatic opening of the valve by either or both of these
devices. In the latter case should one device get out of order the other will do
the work. Also I may use any suitable air-valve, and may apply my invention
to any suitable type of furnace door.
In employing automatic mechanism to close the air-valve in a furnace door,
in cases in which air alone is passed into the furnace by suction or natural
draught the practice has been as follows; at the instant of shutting the door the
valve in same is open, but immediately that the door has been shut the auto-
matic closing mechanism comes into action and the air-valve begins to close
forthwith. I have found that this practice restricts the air supply too soon
and that the combustion of the carbonaceous gas is more thorough if the air-
valve is held fully open for some predetermined time after the door itself is shut,
and then after the expiry of such predetermined time gradually closed. This
is the main feature of novelty in my invention as far as the automatic, closing
device is concerned, and I may employ any suitable mechanism to close the air-
valve at the time and in the manner described. When a door, has more air-
valves than one, I may operate all of them automatically, or only certain of
them; and I may close them entirely or only to the extent judged permissable.
In certain cases I may discard the automatic closing device altogether, leaving
the air-valve to be closed by hand.
In Figs. 2, 3 and 5, on accompanying drawings a suitable automatic device

page_text: is shewn. It consists of a cataract, or regulator, j, charged as usual with a
certain quantity of some suitable liquid; of a bell-crank connected at ¹ by
chain to piston-rod of cataract j, and also connected at by chain to
fast pulley cast or attached to, and con-centric with, one of the lugs i of door a;
of a lever m pivoted at m³, and connected by chain h to the lugs of moveable.
slide ; also of a slotted link connecting bell-crank to lever m..
These may
be suitably attached to a fixed back-plåte ˜n, with guide pulleys and ². The
end of chain g is made fast to pulley f.
was
On the furnace door being opened preparatory to firing, as shown in Fig. 7,
the chain g is wound for a part of its length upon pulley f, and the bell-crank k
(previously at rest in the position shewn in Fig. 5) is pulled into the position
shewn in Fig. 2; while, by means of the connection y, the poise and piston-
rod have also been raised. At the same time the link 7, actuated by bell-
crank, has pushed the pivoted lever m into a position which permits the air-
valve to be opened as previously described; (see Fig. 2). Obviously by raising
the piston-rod the piston itself, located within the cylinder of cataract
also raised, causing the liquid which lay above the piston to pass through a
suitable valve to the lower part of the cylinder beneath the piston. These
changes all take place in the act of opening the furnace door; the extent to
which the door is opened being regulated by stop e² of cam e; (see Fig. 7).
When the door is again shut the air-valve in same has been opened by the auto-
matic opening device. Figs. 1 and 2 shew the position of door handle C, slide d,
and of the automatic closing apparatus generally, immediately after the door
has been shut.
The shutting of the door has liberated so much of chain glas had previously
been wound round pulley f when door was opened; and the weighted piston
falls under the force of gravity, operating the various parts of the closing
mechanism in falling. When the fall of the piston has restored these to their
normal positions, shewn in Fig. 5, lever m has closed the air-valve in door by
dragging its moveable part slide d into the position shewn in Figs. 4 and 8.
The speed of the piston's fall is as usual determined by the rate at which the
liquid is permitted to pass from beneath the piston to above it. It will be
observed however on reference to Fig. 3, that the piston has to sink some dis-
tance in the cylinder (as is shewn by the altered positions of bell-crank k,
poise and piston rod ¹) before lever m is disturbed. Consequently the air-
valve, operated by lever m, has also remained undisturbed and open to its full
extent; this is due to the slotted arrangement of link 1 (Figs. 2, 3, and 5), which
does not operate lever m until it, link 7, has moved a certain distance, or in
other words does not begin to close the air-valve until the piston has been tra-
velling downwards for some predetermined time and distance. Air valve may
be understood to mean air-valves in cases where more than one are employed.
I explain my invention, secondly, as applied to a furnace working with forced
draught. In a forced draught furnace, and in some other cases, find, that, for
the over-grate air supply it is desirable to give air under pressure. Sometimes
a supply of air under pressure is readily obtainable; otherwise and more fre-
quently I employ a steam-jet, or jets, to force a supply of air into the furnace
over the grate in which case the air supplied is mixed with a little steam; but
for brevity I shall refer to it as the air supply. In automatically giving such
supply of air under pressure, by means of my device, I give it while the furnace
door is open and for some predetermined time after said door has been shut, or
approximately so.
It has been customary in pressure devices of this kind (one of the main objects
of which is the prevention of smoke) to conduct the air-supply by chambers,
nozzles, pipes or other means, to some point or points within the furnace. Conse-
quently parts of all such devices have been exposed to great heat and have
rapidly got out of order. I greatly prolong the life of my device by keeping
every part of it outside the furnace.
L

page_text: "In a forced draught furnace with air under pressure in a closed ashpit, it is
often found that flames are forced outward into the stoke-hold' on the opening.
of the furnace door; and to correct this it is usual for the under-grate pressure
to be shut off, or reduced in some way, while the furnace door is open; and this
implies that the combustion of fuel is also retarded at such times. The air
automatically given, by my device, on the furnace door being opened; checks
the outrush of flames, sparks and fumes without it being necessary to reduce the
under-grate pressure in the least, and consequently without retarding combus-
tion. To mitigate, or prevent the formation of smoke I continue the air-supply
for sometime after the furnace door is shut, after the expiry of which the air is
shut off wholly or in part. I describe automatic mechanism suitable for giving
and shutting off the air supply; but any suitable automatic device may be
employed; or the air supply may be turned on and off by hand.
The nature of my invention as applied to a forced draught furnace and its
practical working will be ascertained on reference to the accompanying drawings,
and the following explanation of the same.
Fig. 11 on the drawings is a front elevation of a device for giving a supply
of air under pressure, or of steam and air, to a furnace..
Fig. 12 is a vertical section of part of same, through line A-B in Fig. 11.
For the purpose of my invention I cast, or otherwise attach, to the furnace
fronto a door frame p, with fixed lug p', to which is hinged furnace door q.
may also cast, or attach to the front o, a stop or cam which determines the
extent to which the door may be opened, and a handle catch p³, (see Fig. 11):
To one of the lugs g of the door, I cast or attach the fast pulley to which is
fastened one end of a chain 3, the other end of which is connected to bell-crank u
of the automatic mechanism.
Above the door frame I provide a horizontal chamber r (Figs. 11 and 12) which
is circular or approximately so in internal cross section, with an opening along.
part, or the whole of, its length, leading to passage r¹. (See Fig. 12). Chamber r
may be about as long from end to end, as the opening to the furnace is wide, or.
it may be somewhat shorter. Passage is made of any suitable size and is
wedge-shaped in vertical section; its narrow outlet being directed towards the
furnace. Un reference to Fig. 12 it will be noticed that the air supply is given
at the top of the opening of the furnace and above door q; and it will be seen
that every part of the device itself is outside the furnace front o. An end of
chamber is pierced, the opposite end being generally left solid; and to the
pierced, or open, end is connected a suitable length, or lengths, of pipes, which
may be shaped as shewn (but any suitable shape will do) into which is introduced
the steam jets. The blower, or pressure device, shewn in, Fig. 11 is furnished
with a shutter s². When steam is not relied on to obtain air under pressure,
the steam jet is omitted, and pipe s is modified accordingly. By introducing
a vertical partition in chamber both ends of r may be pierced and two steam-
air devices, or blowers, connected with said chamber, or a vertical blower similar
tos may be connected centrally to chamber r in which case both ends of said
chamber can be closed. In Fig. 11 of accompanying drawings an automatic
device for turning on or off the air supply is shewn; consisting of a cataract t,
charged with some suitable liquid, a'bell-crank w, and a rod ; the latter being
connected to piston-rod t of cataract in any suitable manner, and also to a
slotted arm of bell-crank at . To rod are also attached the slotted projec-
tion operating shutters, and projecting cams and operating steam
The cataract t and bell-crank u may be conveniently attached to a fixed
back plater, to which may also be attached suitable guides,, to keep rod v.
vertical as it rises and falls. Steam valve to is connected to some suitable source
of steam supply, and through steam pipe controls the supply of steam to jet s¹.
(See Fig. 11).
valve .
The manner in which my invention works is as follows. On opening the fur-
nace door, chain is wound for a certain distance upon pulley q², and by

page_text: When v
means of connection 3 an arm of bell-crank u is drawn over towards the said
pulley, raising the other arm of the said bell-crank and with it rod v.
is raised it is obvious that the piston is raised in cataract t. Steam valve wc and
shutter are both opened at the same time, as indicated by dotted lines in
Fig. 11. It follows therefore that simultaneously with the opening of the furnace
door a sheet of air is forcibly driven into the furnace from the front.
On the furnace door being closed, chain 73 is unwound, and piston-rod t falls
under gravity, lowering with it rod and its attachments. The rate of the
piston's fall is regulated by the rate at which the liquid is permitted to pass
from beneath the piston to above it. On the lowering of rod v, the projection v
operates shutter 3 at once, but practically does not restrict the air supply until
the said shutter is almost closed; while cam does not begin to turn off the
steam supply until it comes in contact with handle w¹, which is not until rod v
has fallen some distance. Therefore after the furnace door is shut there is,
approximately, a predetermined time during which an unrestricted air-supply
is given to the furnace, and only on the expiry of such time is it gradually shut
off, either entirely or to the extent judged desirable. (See Fig. 11).
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The improvements in or relating to apparatus for the more efficient intro-
duction and regulation of an over-grate supply of air, or of steam and air, to the
furnace; and of, improvements in apparatus for automatically shutting off the
said over-grate supply of air, or of steam and air; constructed and applied sub-
stantially as herein before described and illustrated by the drawings annexed.
2. In a furnace door an improved handle pivoted in the manner substantially
as herein before described and for the purposes stated.
3. The combination in, or in connection with, a furnace door of a pivoted
handle and of a cam attached to the furnace front, both substantially as described
herein before, and for the purposes stated.
4. In a furnace working with natural draught an improved automatic device
for gradually closing the air-valve, or valves, in the furnace door, the action of
which device is delayed, so that it does not begin to close the said valve, or
valves, as soon as the furnace door is shut, but permits the air-valve or valves
in said door to remain fully open for some predetermined time after the furnace
door itself is shut, or approximately 80; and only on the expiry of such predeter-
mined time begins to close the said valve or valves, closing them in a further
predetermined time, or approximately so; substantially as herein before described
and for the purposes stated.
5. In a furnace, the front and door of which are not water-jacketed, an im-
proved device for introducing at the times stated an overgrate supply of steam
and air, or of air under pressure, to the furnace, every part of which device is
kept outside of, or external to, the front of the furnace; substantially as herein-
before described and for the purposes stated.
001 1. of T. 1900.