An Apparatus for Automatically Regulating the Supply of Air to Furnaces under Forced Draught.
Year: 1886

page_text: Date of Application, 27th Nov., 1886
Complete Left, 26th Aug., 1887
Complete Accepted, 25th Nov., 1887
An Apparatus for Automatically Regulating the Supply of Air to
Furnaces under Forced Draught.
I, WILLIAM JOHN CLARK of Southwick Engine Works Sunderland Engineer do
hereby declare the nature of this invention to be as follows
My invention has for its object to regulate the supply of air to each furnace auto-
matically and independently however many furnaces there may be worked from one
air supply whether the air is supplied under pressure into an air-tight stoke hole
or closed ash pit or whether a current is induced by means of a fan or jet of air or
steam.
The regulation of the air supply is to allow less air to be supplied to the fire as the
fuel in any one furnace is consumed and the fire becomes thinner and conversely when
more fuel has been put on to allow a greater supply of air to pass to the fire.
This I effect in the following manner :-
The ashpit of each furnace is closed and air is admitted to it by an aperture
sufficiently large to admit the required quantity of air to obtain the desired rate of
combustion. Air is also admitted to the top of the fire. The passage of air to the
closed ash-pit and to the top of the fire is controlled by valves.
As the fuel in any one furnace is consumed and the fire becomes thinner the
resistance offered to the passage of air through it becomes less and the pressure in
the ash-pit is thereby reduced or conversely as fuel is added and the fire made thicker
the resistance to the passage of air is increased causing an increase of pressure in the
ash-pit.
This difference of pressure I cause to operate the valve or valves in such manner
that when the bars are sufficiently covered the valve or valves become fully open and
admit a full supply of air and as the fire burns down and requires less air the valve
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page_text: gradually closes thereby preventing an undue volume of air from passing through the
fire when it is not required with its consequent lowering of temperature and loss
of efficiency and also the depriving of the other furnaces of their due supply of air.
The valve may be a a flap valve opening outwards so that the external pressure tends
to close it but which is acted on by springs or otherwise which tend to open it as the
pressure upon the back and front become equal-Or it may be a disc valve closed by
the action of a spring or weight and opened by a diaphragm acted on by the pressure
in the ash-pit or furnace or other forms of valves might be used.
The valve for admitting air to the ash-pit I arrange in such manner that when it
nearly closes more and more impediment is offered to its closing and prevents it from
absolutely closing, but the valve for admitting air above the fire I arrange to close
absolutely when the fire gets thin.
Dated this 27th day of November 1886.

page_text: Furnaces under Forced Draught.
We, GEORGE CLARK and JAMES HENRY HAVELOCK CLARK both of Southwick
Engine Works, Sunderland Engineers, Executors of the late William John Clark of
the same place, 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 :—
This invention has for its object to regulate the supply of air to each furnace auto-
matically and independently however many furnaces there may be worked from one
air supply whether the air is supplied under pressure into an air tight stoke hole
or closed ash pit or whether a current is induced by means of a fan or jet of air or
steam.
The regulation of the air supply is to allow less air to be supplied to the fire as the
fuel in any one furnace is consumed and the fire becomes thinner and conversely when
more fuel has been put on to allow a greater supply of air to pass to the fire.
This is effected in the following manner.
The ashpit of cach furnace is closed and air is admitted to it by an aperture
sufficiently large to admit the required quantity of air to obtain the desired rate of
combustion. Air is also admitted to the top of the fire. The passage of air to the
closed ash pit and to the top of the fire is controlled by valves.
As the fuel in any one furnace is consumed and the fire becomes thinner the
resistance offered to the passage of air through it becomes less and the pressure in the
ash pit is thereby reduced or conversely as fuel is added and the fire made thicker
the resistance to the passage of air is increased causing an increase of pressure in the
ash pit.
This difference of pressure is caused to operate the valve or valves in such manner
that when the bars are sufficiently covered the valve or valves become fully open and
admit a full supply of air and as the fire burns down and requires less air the valve
gradually closes thereby preventing an undue volume of air from passing through the
fire when it is not required with its consequent lowering of temperature and loss of
efficiency and also the depriving of the other furnaces of their due supply of air.
The valve may be a flap valve opening outwards so that the external pressure tends
to close it but which is acted on by springs or otherwise which tend to open it as the
pressure upon the back and front become equal. Or it may be a disc valve actuated
by the relative pressure on two sides of a diaphragm assisted by springs or weights.
The valve opening as the pressure in the ashpit rises and closing as the pressure falls.
Or other forms of valves inight be used.
The valve for admitting air to the ashpit is arranged in such manner that in closing,
an increasing resistance is offered to its motion and the valve brought to rest without
finally closing. Provision being made for regulating the minimum amount of opening,
but the valve for admitting air above the fire is arranged to close absolutely when the
fire gets thin.

page_text: In order that the invention may be fully understood reference is made to the
drawings hereunto annexed shewing arrangements for supplying air as above described
to the furnaces of a marine boiler but the invention can also be applied to other
furnaces.
Figure 1 is a front view partly in section of one end of a steam boiler with three
furnace flues and with apparatus arranged according to this invention for controlling
the admission of air to each furnace. Figure 2 is a vertical section through the front
end of the central furnace flue. Figure 3 is a vertical cross section on the line A¹ B
and Figure 4 is an elevation of the automatic regulating apparatus on a larger scale.
Figure 5 is a vertical section of another form of valve which may be used in place of
that shewn at Figures 3 and 4. Figure 6 is a vertical section of a valve for admitting
air to the top of the fire.
Figure 7 is a front view of an arrangement suitable for being used when a forced
draught is applied either through a closed stoke hole or by a fan or jet of steam or
air. Figure 8 is a vertical longitudinal section of the front end of one of the furnace
flues. Figure 9 is a front elevation and Figure 1.0 a vertical section on a larger scale
of the valve apparatus fitted at the front end of the same.
In the automatic regulator shewn at Figures 3 and 4 A is the valve chest, B the
inlet branch, C the outlet branch which is connected to the ashpit, D a valve centred
on spindle E opening and closing the aperture of branch C, F. G. a lever keyed on
spindle E, the end F being connected to the spring H in tension. The other end of
this spring is attached to an eye formed on bolt I which passes through lug K cast on
side of branch C and fixed in position with nut L. Under the end G of lever is a
case M. containing spring N in compression. The spring presses upwards a disc fixed
to a spindle P which spindle passes through the upper closed end of the case and carries
an adjustable cap Q on its upper end. The lower end of the spring rests on a screw O
which screws into the lower end of the case M.
The action of the valve is as follows:-On starting the fire and applying the blast
the valve would be in its closed position as the pressure of the blast would tend to
close it but it is prevented from entirely closing and is kept open about one fourth
more or less as desired, by the end G of lever coming in contact with the adjustable
cap with its spring and adjusting screw 0, this gives any desired amount of opening
of valve, when the fires are in this condition. There is then little or no pressure in
ashpit; but as the fire becomes thicker by the addition of fresh fuel, the resistance to
the passage of air through the bars is increased, and the pressure in the ashpit rises,
this reacting on the face of valve, will with the assistance of spring H cause the valve
to open, thus admitting the full amount of air to the furnace; this amount can be
increased or reduced as required by adjusting nut L which regulates the amount of
tension on spring H. As the fire burns down, the resistance to the air passing through
the bars will be reduced consequently the valve will gradually close, thus preventing
an undue amount of air from passing through the furnace when not required. It will
be seen that the end G of lever only comes in contact with the cap Q, when the valve
has nearly arrived at its closed position; this besides regulating the quantity of air to
be admitted when the valve has reached that position, gives by the additional com-
pression of the spring N an initial force tending to reopen the valve when fresh fuel
has been again put on the fire.
In the form of valve shewn at Figure 5 A is the valve chest, B the inlet branch,
C the outlet branch, D the valve fixed to spindle E which is guided at bottom end by
a bridge piece F in branch B and at top end by an arched bracket G fixed to face of
valve chest A, Ha flexible diaphragm of india rubber or other suitable material,
I a guard for saving diaphragm H and fixing it in position, K a spring in compression
placed between a collar L at lower end and an adjustable nut O at upper end, the
nut O being screwed into bracket G, M M nut and check nut to adjust amount of
opening desired when valve is in its closed position.
Its action is similar to that of Figures 3 and 4. The amount of opening having
been fixed by nuts M M the pressure in ash pit will rise through the addition of fresh
fuel, the increased pressure acting on the surface of the diaphragmn which has a greater

page_text: area than the valve, will overcome the pressure of the atmosphere acting on the exterior
of the diaphragm, and compress the spring K, thereby opening the valve and admitting
a full supply of air to ash pit, as the fire burns thin this pressure in the ash pit will be
reduced, the pressure of the atmosphere on the exterior of the diaphragm combined
with the compression of the spring, will then overcome the pressure in the inside of
the diaphragm, and the valve will gradually close, admitting less air to ash pit until
fresh fuel is again added, when the same action will be repeated.
In the valve shewn at Figure 6 A is the valve chest, B the inlet branch which is
connected to ash pit, C the outlet branch which is connected to the furnace above the
fire. The description of valve Figure 5 will apply to the further description of this
valve, the lettering and mode of action being the same, except that the valve entirely
closes when the fire has burned thin. It will therefore be seen that the supply of air
to the top of the fire is also automatically regulated and entirely shut off when the
fires are thin. The way in which the air is conducted from the outlet branch C of
the valve chest to the top of the fire is clearly shewn by the parts in section in
Figure 1.
In the air admission valve shewn at Figures 7, 8, 9 and 10 the ashpit door A itself
forms the valve, it is centred on a shaft B at the outer end of which is a lever C. At
the extreme end of this lever is attached a spring D in tension which is carried at its
upper end by a bolt E passing through a bracket F bolted to furnace front. The
tension of this spring can be regulated by nut G. Further in on lever C is attached
a second spring H which is also supported at its upper end by a bolt I passing through
bracket F, this bolt being allowed a certain amount of play before the nuts K K come
to a bearing on the bracket.
The action of this valve is similar to those shown by Figures 3, 4 and 5. As in
those cases the valve when in its closed position is kept open about one fourth more
or less as desired. When fresh fuel is added, (the valve A being then in its closed
position) the pressure in the ash pit rises, and acts on the face of valve, which aided
by the action of the springs then opens, thus admitting a full supply of air, as the fire
burns thinner, the pressure in the ash pit falls, and the valve gradually closes, when
more fuel being added, the same operation is repeated.
A little before the valve closes the spring H comes into play, and by its adjustment
with the nuts K K will give any desired amount of opening of the valve when in its
closed position and at the same time give an additional force tending to open the valve
when fresh fuel has been added.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed we declare that what we claim is :-
1. An arrangement or apparatus for automatically regulating the supply of air
(under forced draught) to furnaces both below and above the fire bars or below or
above only as may be desired. Such apparatus being actuated by the difference of
pressure on the opposite sides of a valve or diaphragm assisted by weights or springs
when desired.
2. Apparatus constructed substantially as herein before described and illustrated
at Figures 1 to 6 for automatically regulating the supply of air to furnaces working
under forced draught.
3. Apparatus constructed substantially as herein before described and illustrated at
Figures 7, 8, 9 and 10 for automatically regulating the supply of air to furnaces
working under forced draught. A similar arrangement being applied for admission
of air above the fire bars if desired.
acl
1007
CARPMAEL & Co.,
A gents.