Improvements in Steam Boiler and other Furnaces."
Year: 1891

page_text: Date of Application, 31st Jan., 1891'
Complete Specification Left, 31st Oct., 1891-Accepted, 5th Dec., 1891”
PROVISIONAL SPECIFICATION.
Improvements in Steam Boiler and other Furnaces."
I THOMAS GEORGE LISHMAN, of No. 20 Berkley Road, Redland, Clifton,
Bristol, in the County of Gloucester Engineer, do hereby declare the nature of
this invention to be as follows:-
My invention, relates to the construction of furnaces generally but is more
especially applicable to steam boiler furnaces.
In carrying out my invention I provide a curved plate placed along the bottom
of and fitting: the. boiler flue. At each end of this plate is secured an air-chamber.
On the said plate I fix an angle-iron bar for carrying, the grate or fire-bars, which
I propose to make of cast metal and then chill them; or to make them of a mixture
of metal which will produce cast steel or very hard metal whereby clinker is
prevented from adhering to them in the furnace. The top of the inner air-chamber
is formed with grates having narrow spaces or with a perforated plate, from which'
heated air is distributed into the combustion chamber at that point. The front
of the furnace may be also provided with a second air-chamber forming the frame
of the firing door, from which hot air is distributed onto the fuel in the furnace.
In the space between. the. two air-chambers which are secured to the plate are
placed the grate-bars which are by preference placed transversely although they
may be longitudinally placed in the furnace. They are formed with a hole or holes
through them so that when placed together in position tubular communication is
formed between the air-chambers, the air for perfecting combustion is passed from
one air-chamber to the other through the tubular passage or passages and is
thereby highly heated by the time it is delivered into the fuel or combustión
chamber.
I also provide a pipe placed on the furnace plate underneath the grate-bars and
in communication at its outer end with a main air-conduit, the inner end being
connected when required with the inner air-chamber, it is also provided with holes
for the passage of air to the fuel. A connection is formed between this pipe and
the front and back air-chambers. The inlet of the air supplied by means of 'à fan'
or by other suitable means for obtaining air under pressure is regulated by valves
or by other suitable means..
When applying my improvements to existing, steam boilers in which the ordinary
draught is sufficient, I dispense with the means for obtaining a forced supply of
air. In such cases I may, however, apply a steam-jet to the tubular air-passage
for the purpose of causing a more rapid delivery of air into the air-chambers.
The inner air-chamber is placed in any suitable position in.the flue, and may be
protected at back and front by fire-brick walls. It can also be, arranged" to be
usedrin conjunction with ordinary, grates and furnaces.
By the hereinbefore described means I secure a more perfect combustion of the
gases, a great economy in fuel and a complete consumption of smoke.
Dated the 31st day of January 1891.
G. F. REDFERN & Co.,
4, South Street, Finsbury; London; Agents for the Applicant:

page_text: COMPLETE SPECIFICATION.
Improvements in Steam Boiler and other Furnaces.
1, THOMAS GEORGE LISHMAN, of No. 20, Berkley Road, Redland, Clifton,
Bristol, in the County of Gloucester, 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:-
My invention relates to the construction of furnaces generally but is more
especially applicable to steam boiler furnaces.
In carrying out my invention I provide a curved plate placed along the bottom
and following the shape of the boiler flue. At each end of this plate is an air-
chamber, the top of the inner air-chamber being formed with grates having narrow
spaces or with perforations, from which heated air is distributed into the combustion
chamber at that point.
On the said plate I fix angle-iron bars for carrying the grate or fire-bars, which
I propose to make of cast metal and then chill them; or I may make them of a
mixture of metal which will produce cast steel or very hard metal whereby
clinker is prevented from adhering to them in the furnace, the said bars being
arranged, by preference, transversely in the space between the two air-chambers
although they may, if desired, be arranged in sections placed longitudinally in the
furnace. They are formed with a hole or holes through them so that when placed
together in position tubular communication is formed between the air-chambers.
The air for perfecting combustion is passed from one air-chamber to the other
through the tubular passage or passages and is thereby highly heated by the time
it is delivered into the fuel or combustion chamber.
The inner air-chamber is placed in any suitable position in the flue, and may
be protected at the front or at the back and front by fire-brick walls or bridges.
The front of the furnace may be also provided with a second air-chamber forming
the frame of the firing door, from which hot air is distributed onto the fuel in the
furnace.
I also provide a pipe placed on the curved plate underneath the grate-bars and
in communication at its outer end with a main air-conduit, the inner end being
connected when required with the inner air-chamber; it is also provided with holes
for the passage of air to the fuel. A. connection is formed between this pipe and
the front and back air-chambers. The inlet of the air supplied by means of a fan
or by other suitable means for obtaining air under pressure is regulated by valves
or by other suitable means.
When applying my improvements to existing steam boilers in which the ordinary
draught is sufficient, I dispense with the means for obtaining a forced supply
of air. In such cases I may, however, apply a steam-jet to the tubular air-
passage for the purpose of causing a more rapid delivery of air into the air-
chambers.
The inner air-chamber can also be arranged to be used in conjunction with
ordinary grates and furnaces.
To enable my invention to be fully understood I will describe how it can be
carried into practice by reference to the accompanying drawings, in which :—
Figure 1 is a longitudinal section of a steam-boiler having a furnace constructed
according to my invention:
Figure 2 is a horizontal section; and,
Figure 3 is a front end elevation of the same:
Figures 4 and 5 are sections on the lines A B and C D respectively of
Figure 1:
Figure 6 is a similar view to Figure 1 but shewing my improvements applied
to a boiler-furnace having ordinary fire-doors when using a forced draught:
Figures 7 and 8 are sections on the lines E F and G H respectively of
Figure 6:

page_text: Figure 9 is a longitudinal section; and,
Figure 10 is a horizontal section of part of a boiler flue embodying my
improvements and shewing the fire-bars cast in sections placed longitudinally.in
the furnace:
Figure 11 is a section on the line E F of Figure 9:
Figure 12 is a longitudinal section of as much of a steam-boiler having ordinary.
fire-doors as is necessary to illustrate the application of my improvements when
using a natural draught:
Figure 13 is a front end elevation of the boiler:
Figure 14 is a longitudinal section of a steam-boiler having ordinary fire doors.
and provided with a steam jet applied to my tubular air-passage.
Similar letters in all the figures indicate similar or corresponding parts.
Referring to Figures 1 to 5, which shew my improvements in furnaces applied
to a Cornish boiler, is the shell of the boiler, and is the flue thereof.
c is the plate which I provide along the bottom of the boiler flue b, such plate
being curved to follow the shape of the said flue, as clearly seen in Figures 4 and 5,
and a space d being advantageously left between the plate and the flue.
e is the air-chamber secured to the front end of the curved plate c and divided
by partitions into three parts a¹, a' and is the air-chamber at the rear end
of the said plate, such chamber consisting of a box, perforated on its top
side and secured to a plate g fixed to the curved plate c. g is a door for
allowing the chamber f to be cleared of ashes.
h, are the fire-bars placed transversely in the boiler flue 6 and supported at
each of their ends on an angle-iron bar fixed to the curved plate c. j, j and
kare the holes formed in bosses in the fire-bars h, which holes, when the bars
are placed in position in the furnace, form tubular passages, the passage
constituted by the holes in the middle of the, bars forming, with a hole c¹ in
a plate c², a communication between the middle part of the outer air-chamber e
and the inner air-chamber, while the two passages formed by the holes j, j
near the ends of the bars and by holes d', also in the plate c² effect
communication between the inner air-chamber and the two parts a', a'
respectively of the outer air-chamber e. The plate c is supported on the angle-
irons i, i.
I is the second air-chamber which I advantageously provide at the front of
the furnace and which forms the frame of the firing door m. The said chamber /
communicates, by means of the holes n, n, with the parts a', a¹ of the air-
chamber e, and is perforated on the side which faces the fuel chamber.
o is the pipe which I place on the curved plate e underneath the fire-bars h; and p
is the main air-conduit with which it communicates at its outer end, the said air-
conduit deriving the air supply from a blast fan or other suitable apparatus not
shewn in the drawing; q is a valve operated by a handle, for regulating the
quantity of air forced into the pipe o; s, s are the holes in the pipe o for the passage
of air, up between the bars h, h, to the fuel.
02 is a hinged flap for allowing any ashes which may pass through the holes s
into the tube o to be pushed out by means of a rake introduced through an opening o
closed by a cover o*.
The air-chamber e is connected by a pipe t (having a sliding-valve t¹) with the
main air-conduit . The air-chamber is protected from the fire by a bridge u at
the front supported on the plate c².
vis a perforated bridge depending from the top of the flue b at the rear of the
chamber the said bridge serving to direct the gases from the fuel into more
intimate contact with the hot air issuing from the chamber f, thereby ensuring
thorough combustion.
It will be seen that the whole of the front of the furnace is closed in, the firing
door m, however, being made hollow. Its inner side is perforated and its outer
side is fitted with a hit-and-miss grating to allow outside air, when required, to be

page_text: admitted direct to the fuel chamber. Doors w are also fitted to the front of the
furnace at the lower part for allowing access to the ash pit.
With this construction, if the valves and be open, a portion only of the air
"forced by the fan or the like through the main air-conduit p passes'in the direction
indicated by the arrows in Figures 1 and 2 through the pipe t into the central
part of the chamber e and thence, through the central tubular passage in the
fire-bars and the pipe, to the air-chamber f
A portion of the air which has become highly heated during its passage through
the fire-bars passes out through the, perforations in the chamber and mingles
with the gases from the fuel. The remainder of the air passes through the side
tubular passages j, j in the fire-bars to the parts a', a of the chamber e and
thereby becomes more highly heated. The air then passes through the holes
into the chamber whence it issues onto the burning fuel. 'A. portion of the air
coming from the main air-conduit passes into the pipe o and is distributed
through the holes, underneath the fire-bars h. "By entirely closing the valve
of course the whole of the air-blast can be directed through the furnace-bars.
n, n
When the furnace is intended for burning anthracite coal I find it advantageous
to connect the inner end of the pipe o with the air-chamber and to disconnect
the outer end of such. pipe from the air-chamber e. By this means a 'greater
quantity of air is caused to pass directly through the fuel from beneath the.
grate-bars. In this case the middle air passage in the fire-bars would not be
required.
The pipe o can, if-required, be dispensed with, the air to the under side of
the bars then being supplied by natural draught.
It will be obvious that the front air-chamber e can, if required, be so connected
with the main air conduit that the air shall be forced therefrom through all
the passages in the fire-bars to the back air-chamber ƒ so' that "the whole of
the air will be delivered at the back end of the furnace. The air-chamber
in 'this case could of course be'dispensed with.
The arrangement illustrated in Figures 6, 7 and 8 is' the same as that herein-
before described with reference to Figures 1 to 5 except that the usual front
frame and doors, of the furnace are retained, (these, however, are not 'shewn 'in
the drawings). "There is therefore no second air-chamber in this arrangement
and. the side passages in the fire-bars and corresponding compartments in the
front air-chambere are consequently not required. The heated air is in this
case only delivered at the back of the furnace.
If required the pipe o may communicate'directly with the inner air-chamber fas
well as with the outer air-chamber e, a regulating valve being in this case provided
to control the passage of air to the said chamber.
In Figures 9 to 11 several fire-bars h, are shewn cast together so as to form a
grate made up of sections ', ' placed longitudinally in the fluc. 'The front sections
are supported upon the front air-chamber and a transverse bridge or bar and the
rear sections are supported by the said bridge or bar and by the plate e². 'j, j'and' k
are the tubular passages in the fire-bars.
When applying my furnace to steam-boilers having ordinary fire-doors and worked
with natural draught, as shewn in Figures 12 and 13, 1 employ the' two' air-
chambers e, and and the fire-bars having tubular, passages connecting the said
chambers arranged in the same manner as shewn in Figures 6, 7 and 8, but' the
conduit for the fan-blast with its pipe connecting the front air-chamber thereto and
the pipe beneath the fire-bars are of course not required. The air is advantageously
admitted to the air-chamber é through a regulating or hit-and-miss grating. This
arrangement I have found to be very satisfactory as far as regards the prevention
of smoke but the economical results are not so good as in the arrangement herein-
before described and illustrated in Figures 1 to 5.
In the modification shewn in Figure 14 in which a steam-jet supplied by a pipe y
is applied, when required, to the boiler' furnace worked by natural draught for the

page_text: purpose of causing a more rapid delivery of air into the air-passage in the fire-bars,
dispense with the front air-chamber and employ instead thereof a casting fitted
to the front plate of the furnace. Instead of employing a perforated box to form
the inner air-chamber f as herein before described, the said chamber may be formed
of two plates e and the latter supporting a rear fire-bridge &. The top of the
chamber consists of a grating g' (or a perforated plate) through which the heated
air issues in the direction of the arrows to mingle with the gases as they pass over
the fire-bridges and v.
is a flap valve or door for regulating the admission of air to, and clearing out
the ashes from the chamber f
In all cases suitable provision is made such as openings covered by doors to allow
access to the air-chambers.
By my invention I ensure a perfect combustion of the gases and effect
considerable economy in fuel and complete prevention of smoke.
I have shewn my improvements by way of example applied to the furnaces of
steam-boilers but it will be understood without description or illustration that they
are equally applicable to other furnaces.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is :-
1. The manufacture and use of the improved grate or fire-bars for steam-boiler
or other furnaces herein described, such bars being formed with holes therein in
such a manner that, when placed together, tubular passages are formed substantially
as, and for the purpose, hereinbefore described and illustrated in the several figures
of the accompanying drawings.
2. A steam-boiler or other furnace having a fire-grate constructed of bars
having a tubular passage or passages formed therein substantially as, and for the
purpose, hereinbefore described and illustrated in the several figures of the
accompanying drawings.
3. In a steam-boiler or other furnace the combination of air-chambers such as e, f
and with the fire bars and curved plate for heating air and distributing it in
the furnace, substantially as hereinbefore described and illustrated in the
accompanying drawings.
4. The manufacture and use of steam-boiler and other furnaces substantially
as hereinbefore described and illustrated in Figures 1 to 5, Figures 6 to 8, Figures 9
to 11, Figures 12 and 13 and Figure 14 respectively of the accompanying
drawings.
11
01
.
1001
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.