IMPROVEMENTS IN FURNACES AND BOILERS FOR HEATING PURPOSES, AND FOR THE GENERATION OF STEAM
Year: 1880

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS
IN FURNACES AND BOILERS FOR HEATING PURPOSES, AND FOR THE
GENERATION OF STEAM," A communication from abroad by Stephen
W. Underhill, of Croton Landing, in the County of Westchester, State of
New York, United States of America.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 9th December 1880.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. " IMPROVEMENTS IN FURNACES. AND BOILERS FOR HEATING
PURPOSES, AND FOR THE GENERATION OF STEAM." [A communication from
abroad by Stephen W. Underhill, of Croton Landing, in the County of Westchester,
State of New York, United States of America.]
These improvements relate to boilers and furnaces for use with hot water heating
apparatus, and for steam generators, and have for their object economy of fuel,
rapidity and uniformity of action, with the advantage of requiring but little
attention.
These objects are obtained, first, by comparatively perfect combustion; secondly,
by maintaining the temperature of the heating surfaces of the boiler at an efficient
point for a great distance from the fire; thirdly, by the absorption of heat to be
given off when the fire declines; fourthly, by exposing the pipes containing the
coolest water to the coolest drafts.
The nature of the said Invention consists in a fire box and long continuous flue,
through which the water tubes pass, and constitute the heating surface of the
boiler. This flue may be straight or turned back and forth in various ways to suit
the place or purpose of use. The following is a form of construction which I
prefer :-
.
I make use of a brick furnace divided longitudinally by a vertical wall, and by
bricks or tiles placed between the central and side walls forming a continuous spiral
Que from the fire box to the chimney. This flue may also be divided by vertical

page_text: pass.
When
partitions, and through the flue or flues thus formed the water tubes
used as a hot water heating apparatus the feed water enters the upper end of the
spiral flue, and passing down any desired distance, and then out and in again over
the fire and up the lower part of the flue to a point near where the tubes had
previously passed out of said flue. By this arrangement the water moves in the
upper and cooler part of the flue in a direction opposite to the draft, and in the
lower and hotter part in the same direction as the draft.
For use as a steam generator I combine with the furnace and boiler a water and
steam reservoir and mud drum, and the details of construction are varied to suit
the purposes of steam generation.
I will now describe the preferred construction of the furnace more in detail.
The bottom, top, side, front, and rear wall are of brick, and sufficiently thick to
prevent radiation of heat. The enclosed space is divided lengthwise by a middle
wall, which extends from top to bottom the entire distance, but not the entire
length from front to back, being short of the front and rear walls. Between the
side and middle walls are fitted horizontal partitions of brick or tiling inclined in
opposite directions at the opposite sides of the centre wall, and united at the ends
so as to form a continuous spiral or back and forth flue from the fire box to the
chimney. The bricks or tiles forming the partitions are supported by offsets
formed upon the side and middle walls, so that they can be removed without
disturbing the walls when repairs are needed, and the bricks or tiles connecting the
ends rest on metal bars set in the walls. The rear and front walls will preferably
be formed with openings between the ends of the partitions to give access for
cleaning the flues, which openings will be filled with loose brick sealed with clay,
so as to be readily opened as required. The spiral flue thus formed is sub-divided
between the side and middle walls by vertical partitions of brick, which may be
built up from the bottom of the furnace and the flue bottoms, or horizontal
partitions formed by bricks placed in the intervening spaces, or the walls or vertical
partitions of the whole or any portion of the furnace may rest upon the tiling.
The fire box and lower flues may be arched over with fire brick, and the vertical
partitions dividing the upper flues may rest upon the top of the arches. These
vertical partitions form small spiral passages, which will each contain a water tube,
as hereafter described. From the fire box the products of combustion are compelled
to pass back and forth in contact with the walls, so that the whole stack will
become heated, while the tubes which are arranged in flues, as next described, are
in direct contact with the heated gases.
The above is a description of the general construction.
The following description of the water tubes refers to a hot water heating
apparatus for heating green houses and for other purposes.
Two feed water tubes or return pipes of the heating apparatus enter through the
rear wall at the base of the chimney, and each is forked within the flue and coupled
with tubes that pass through the spiral flues, and follow the same downward for
one and a half turns when the tubes pass out through the front wall, then down-
ward, re-enter the furnace at a point over the fire door, passing through the fire
box to the spiral flue leading therefrom, through which the pipes pass upward two
complete turns nearly and then go out through the front wall, at which is the point
of discharge for the hot water. The feed water enters the flues at the place of least
heat, and passes in a direction opposite to the current in the flue the distance
desired before passing through the front wall. By this arrangement the heated
products of combustion in the upper portion of the flues is in continual contact with
the tubes containing water, that decreases in temperature toward the chimney,
consequently the greatest possible amount of heat is extracted. The tubes pass
through the wall into the fire box and the lower highly heated flues, so that the
water which was warmed in the upper portion of the flue becomes rapidly and
highly heated before its final exit. By this construction the water may be rapidly
beated by a quick fire, and at the same time the stack becomes heated by the
surplus heat. Then the fire may be checked and arranged to burn slowly, and the

page_text: radiated heat in connection with that produced by the slow fire will maintain the
required temperature for a long time without attention being necessary. A few
bours of strong firing will cause the storing of a sufficient amount of heat to keep
up an equable temperature throughout the night, a matter of the utmost importance
in heating greenhouses. This construction utilises a large proportion of the heat
from the fuel, first, by reason of the long flue space, allowing ample time and giving
ample surface for absorption of heat; second, by the perfect combustion of the fuel
obtained by the comparatively small amount of water surface in the fire box and
adjacent flues, allowing these to become sufficiently heated to burn the gases from
the coal. When soft coal is used the supports of the water tubes will be cast iron
pipes perforated with small holes, the ends of said pipes passing through the side
walls to allow access of air to the fire box and flues for consuming the gases.
Thirdly, the absorption of heat by the brick flues maintains the temperature of the
draft at an efficient point for a long distance from the fire.
For special use as a steam generator the details of construction and arrangement
of tubes will be preferably as next described.
In the lower part of the stack, and separated from the fire box by the middle
wall, is placed the water reservoir and mud drum, which extends through the front
and rear walls for convenience of access. Above the stack is fitted a steam drum
provided with steam dome, safety valve, and all necessary fixtures, and is connected
to the water tubes as hereafter described. Tubes pass through the inclined flues
lengthwise of the furnace, and are connected at their ends with cross tubes at the
front and rear; the cross tubes consequently connect each with one set of longi-
tudinal tubes at the side of the middle wall. The cross tubes are within the end
walls, and those at the front extend through the side walls and connect at their
ends with vertical tubes at the opposite sides of the stack, the one vertical tube
being made larger, as it is for steam, and connects with the steam drum through
the upper cross pipe and a short vertical connection. The front cross tubes are
also formed solid or partitioned at their middle length, so that there is no connec
tion through them from one side to the other. The lower front cross tube is
necessarily but half the length of the furnace, as it connects with but one set of
longitudinal tubes and is also in connection with the water and mud drum. I prefer
to use two sets of longitudinal tubes through the fire space and adjacent flues, one
set terminating at the vertical steam pipe after one complete turn. At the back
of the furnace the water drum and steam drum are connected by a pipe. To facilitate
construction and to remove any sediment that may accumulate in the longitudinal
tubes, the cross tubes are cast with tubular bosses corresponding to and opposite
the openings of the longitudinal tubes, so that the tool used for expanding the
longitudinal tubes can be inserted through the bosses. These bosses extend through
the front and rear walls, so that their caps are outside and not subject to the
intense heat of the inside, and are convenient of access for cleaning the interior of
the longitudinal tubes.
The walls are made with openings for the bosses to pass, which openings will be
made large enough in the upper flues for the removal of the ashes and soot. To
allow for the contracting and expanding of the tubes, a ring of abestos, paper, or
other yielding packing is placed around the bosses and clamped by an outer plate
to a ring set in the brickwork.
The stack of the furnace and boiler is strengthened by columns of metal tied at
their upper ends by plates from which the steam drum is suspended, the drum in
turn sustaining the longitudinal and transverse tubes directly and by suspension
rods, so that they do not rest on the walls and are free to expand and contract.
By the arrangement of tubes described, the circulation of the water is from the
water drum through the lower cross pipe, which supplies the lower set of
longitudinal tubes which pass through the fire box and adjacent flue, and join in
the back part of the stack to the lower cross tube, which is joined to the lower
longitudinal tubes in the lower flue on the other side of the middle partition wall,
which passing through said lower flue are joined to the lower cross-pipe on front

page_text: side of stack, which in turn is joined to lower part of upright steam pipe, causing
the water (as the pipes are inclined upward in this direction) to pass through the
fire-box and lower flues, and with the accumulating steam to pass up the steam
pipe to the steam drum.
The lower cross pipe which joins the water drum also joins the lower part of the
upright pipe, which supplies water from the water drum to each of the upper front
cross pipes on the same side of stack as the firebox, and as the cross pipes are
closed or partitioned in the middle, and each set of longitudinal tubes incline
upward from in front of stack, and the same side as firebox to the back of the
stack which they join, and the rear cross tubes on opposite side of partition wall
are joined by set of longitudinal tubes inclined upwards to front of stack, and are
joined to front cross pipes, which in turn are joined to the upright pipe, thus a
supply of water is furnished from the water drum to each of the cross pipes in
the front of the stack and at same side as the firebox, which pass through the
longitudinal tubes and rear cross tubes and longitudinal tubes on opposite side
of partition wall, to the front cross tubes and upright pipe carrying the hot water
and accumulated steam to the steam and water drum when the steam is separated
from the water, and the water is again returned to the water drum through the
pipe connecting said drums.
The water drum being comparatively large and containing a large volume of
water, the circulation of water through it will be slow. This will give opportunity
for the impurities held in suspension to settle in the drum, from which such
collections can be blown out or removed from time to time. The drum may be
fitted with plates to break the current of water from the return pipe, and thereby
facilating the settlement of foreign matters.
As the mineral impurities in solution are precipitated by the evaporation of the
water, and their consequent concentration every time this occurs by the water
passing through the longitudinal tubes, there is an opportunity for it to settle in
the water drum.
As the circulation of the water and steam is very rapid through the longitudinal
tube, and very slow through the drum, all the sediment is carried from the tube
by the rapid current and deposited in the drum, thus entirely preventing the
accumulation of scale on the heating surfaces, and accumulating it at a point
entirely removed from the fire, when the deposit will remain in a soft condition.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
9th June 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. IMPROVEMENTS IN FURNACES AND BOILERS FOR HEATING
PURPOSES, AND FOR THE GENERATION OF STEAM." A communication from
abroad by Stephen W. Underhill, of Croton Landing, in the County of Westchester,
State of New York, United States of America.
These improvements relate to boilers and furnaces for use with hot water heating
apparatus, and for steam generators, and have for their object economy of fuel,
rapidity and uniformity of action, with the advantage of requiring but little
attention. These objects are obtained, first, by comparatively perfect combustion;
secondly, by maintaining the temperature of the heating surfaces of the boiler at
an efficient point for a great distance from the fire; thirdly, by the absorption of
the heat to be given off when the fire declines; fourthly, by exposing the pipes
containing the coolest water to the coolest drafts.
The nature of the said Invention consists in a fire box and long continuous flue,
through which the water tubes pass, and constitute the heating surface of the boiler.
This flue may be straight or turned back and forth in various ways to suit the
place or purpose of use.
The following is a form of construction which I prefer :-
I make use of a brick furnace divided longitudinally by a vertical wall and by
bricks or tiles placed between the central and side walls, forming a continuous
spiral flue from the fire-box to the chimney. This flue may also be divided by
vertical partitions, and through the flue or flues thus formed the water tubes
pass.
When used as a hot water heating apparatus, the feed water enters the upper
end of the spiral flue, and passing down any desirable distance, and then out and in
again, over the fire and up the lower part of the flue to a point near where the
tubes had previously passed out of said flue.
By this arrangement the water moves in the upper and cooler part of the flue in
a direction opposite to the draft, and in the lower and hotter part in the same
direction as the draft.
For use as a steam generator, I combine with the furnace and boiler a water and
steam reservoir and mud drum, and the details of construction are varied to suit
the purpose of steam generation.
In the accompanying Drawings, Figure 1 is a vertical longitudinal section, and
Figure 2 is a sectional plan view of the boiler and furnace, as adapted for heating
purposes; Figure 3 is a vertical longitudinal section of the boiler and furnace as
constructed for a steam generator; Figure 4 is a sectional plan view on line X, X, of
Figure 3; Figure 5 is a front view with the front wall removed; Figure 6 is a
partial front elevation; and Figure 7 of a detail section.
Similar letters of reference indicate the same parts in all the Figures.
The bottom b, top a, side wall c, and front and rear walls d, e, are of brick, and
sufficiently thick to prevent radiation of heat. The enclosed space is divided
lengthwise by a middle wall f, which extends from top to bottom the entire distance
but not the entire length from front to back, being short of the front and rear
walls. Between the side walls c and middle wall f are fitted horizontal partitions g,
Figure 1, of brick or tiling inclined in opposite directions at the opposite sides of
the centre wall, and united at the ends so as to form a continuous spiral or back

page_text: and forth flue from the fire-box h, to the chimney i. The bricks or tiles forming
the partitions g are supported by offsets formed upon the side and middle walls so
that the tiles or bricks can be removed without disturbing the walls when repairs
are needed, and the bricks or tiles connecting the ends rest on metal bars (not
represented) set in the walls. The rear and front walls will preferably be formed
with openings between the ends of the partitions to give access for cleaning the
flues, which openings will be filled with loose brick sealed with clay so as to be
readily opened as required. The spiral flue thus formed is subdivided between the
side and middle walls by vertical partitions f¹ of brick, which may be built up
from the bottom of the furnace, and the flue bottoms or partitions g formed by
bricks placed in the intervening spaces, or the walls f' of the whole or any portion
of the furnace may rest upon the tiling. The fire-box and lower flues may be
arched over with fire brick, and the vertical partitions f¹ dividing the upper flues
may rest upon the top of the arches. These vertical partitions f¹ form small
spiral passages which will each contain a water tube, as hereafter described. The
fire-box h is fitted with grate bars, as usual, and it will be seen that the products
of combustion are compelled to pass back and forth in contact with the walls so
that the whole stack will become heated, while the tubes which are arranged in
flues, as next described, are in direct contact with the heated gases.
The above description of the general construction refers to all the Figures of the
Drawing. The following description of the water tubes is with reference to Figures
1 and 2, which shows them as arranged for a hot water heating apparatus for
heating green houses and for other purposes:-
The tubes entering through the rear wall at the base of the chimney i are the
feed water tubes or the return pipes of the heating apparatus, and the pipes m are
the tubes for delivery of hot water. There are two tubes 7, cach of which is forked
within the flue, and coupled with tubes n that pass through the spiral flues and
follow the same downward for one and a half turns, when the tubes pass out
through the front wall, then downward, reenter the furnace at a point over the
fire door, passing through the fire-box to the spiral flue leading therefrom, through
which the pipes pass upward two complete turns nearly, and then go out through
the front wall at 'm, which is the point of discharge for the hot water. The tubes n
are supported upon cross bars o that are set in the walls of the furnace. As shown,
the feed water enters the flues at the place of least heat, and passes in a direction
opposite to the current in the flue, the distance desired before passing through the
front wall. By this arrangement the heated products of combustion in the upper
portion of the flues is in continual contact with the tubes containing water that
decreases in temperature toward the chimney, consequently the greatest possible
amount of heat is extracted. The tubes pass through the wall into the fire-box
and the lower highly heated flues, so that the water which was warmed in the
upper portion of the flue becomes rapidly and highly heated before its final
exit at m.
By this construction the water may be rapidly heated by a quick fire, and at the
same time the stack becomes heated by the surplus heat; then the fire may be
checked, and arranged to burn slowly, and the radiated heat in connection with
that produced by the slow fire will maintain the required temperature for a long
time without attention being necessary. A few hours of strong firing will cause
the storing of a sufficient amount of heat to keep up an equable temperature
tbroughout the night, a matter of the utmost importance in the heating of green
houses.
This construction utilizes a large proportion of the heat from the fuel, first, by
reason of the long flue space allowing ample time, and giving ample surface for
absorption of heat; secondly, by the perfect combustion of the fuel obtained by the
comparatively small amount of water surface in the fire box and adjacent flues,
allowing these to become sufficiently heated to burn the gases from the coal. When
soft coal is used the supports o of the tubes will be cast iron pipes perforated with
small holes, the ends of said pipes passing through the side walls to allow access of

page_text: air to the fire-box and flues for consuming the gases. Thirdly, the absorption of
heat by the brick flues maintains the temperature of the draught at an efficient
point for a long distance from the fire.
In ordinary boilers both for steam and hot water, and in steam boilers especially,
this rapid reduction of temperature is the principal source of waste. The large
amount of boiler surface near the fire rapidly reduces the intensity of the beat of
the escaping gases to a temperature not much above that of the steam and water
within the boiler, when any amount of additional surface beyond this point will
not increase the efficiency of the boiler, and all the remaining heat in the escaping
gases is allowed to pass up the chimney. This waste necessitates a stronger fire
and draught, which in turn increases the amount of heat passing up the chimney.
In the boiler of this Invention this is to a great extent avoided, as I will now
show.
After starting the fire the tubes within the fire-box very soon become sufficiently
heated to make steam, but the temperature of the gases is soon reduced as they
pass up the flue to a point too low to be effective in making steam; but instead of
the heat then escaping up the chimney, as in ordinary boilers, it is absorbed by the
brick work further on. The bricks surrounding the fire-box, and for a considerable
distance up the flue, will then become hotter than the contents of the boiler, when
they will not only continue to absorb heat from the still hotter draught, but their
radiant heat will be absorbed by the water within the tubes, and their action will
then resemble a local fire for heating the tubes. Before the flue becomes much
heated near the chimney there will be sufficient heat absorbed by the boiler from
the fire, the heated gases in the lower flues, and by the radiation of heat from the
brick in the same to furnish all the steam or hot water required. The chimney
damper may then be turned off so as to allow but little more combustion of fuel
than is necessary to produce the amount of heat required by the boiler, while the
heat absorbed by the boiler is replaced by the fire. The small amount of draught
passing up the chimney carries off but little heat. Owing to the perfect combustion
the accumulation of acid and soot is avoided, thereby preserving the tubes, and
rendering the apparatus very durable.
The main features of the boiler as explained may be obtained by bending the
flues in various forms besides the one illustrated. Consequently, the construction
of the boiler may be made to suit the place and purposes of use.
For special use as a steam generator the details of construction and arrangement
of tubes will be preferably as next described and illustrated in the Figures 3 to 7.
In the lower part of the stack, and separated from the fire-box by the middle
wall f, is placed the water reservoir and mud drum A which extends through the
front and rear walls for convenience of access, and is provided at its ends with man
holes and caps. Above the stack is fitted a steam drum B which is provided with
steam dome, safety valve, and all necessary appurtenances, and is connected to the
water tubes, as hereafter described. The tubes n pass through the inclined flues
lengthwise of the furnace, and are connected at their ends with cross tubes n¹ at
the front, and cross tubes n² at the rear; the tubes n¹, n², consequently connect
each with one set of tubes n at the side of the middle wall. The tubes n', n², are
within the end walls, and those at the front extend through the side walls and
connect at their ends with vertical tubes p, p'. At the opposite sides of the stack
the tube p being made larger, as it is for steam, and connects with steam drum B
through the upper cross pipe n' and short vertical connection q. The tubes n' are
also formed solid or partitioned at their middle length, so that there is no connection
through them from the tubes n' at one side to tubes n¹ at the other side. The
lower tube n¹ is necessarily but half the length of the furnace, as it connects with
but one set of longitudinal tubes n, and is also in connection with the mud drum A,
as seen most clearly in Figure 5. I prefer to use as shown two sets of tubes n
through the fire space and adjacent flues, one set terminating at the steam pipe pl
after one complete turn. At the back of the furnace the drum A and drum B are

page_text: connected by a pipe r. To facilitate construction and to remove any sediment that
may accumulate in the tubes n, the cross tubes n¹, n², are cast with tubular bosses 8
corresponding to and opposite the openings of tubes n, so that the tool used for
expanding tubes n can be inserted through the bosses s. The bosses 8 extend
through the front and rear walls, so that their caps s¹ are outside, and not subject
to the intense heat of the inside, and are convenient of access for cleaning the
interior of the tubes n. The walls are made with openings for the bosses to pass,
which openings will be made large enough in the upper flues for the removal of the
ashes and soot.
To allow for the contracting and expanding of the tubes, as shown in Figures 6
and 7, a ring of asbestos, paper, or other yielding packing is placed around the
bosses, and clamped by an outer plate r² to a ring 82 set in the brick work. The
stack of the furnace and boiler is strengthened by columns t of metal tied at their
upper ends by plates t¹ from which the drum B is suspended, the drum in turn
sustaining the longitudinal and transverse tubes directly, and by suspension rods,
so that they do not rest on the walls, and are free to expand and contract. By the
arrangement of tubes described the circulation of the water is from drum A,
Figure 5, through lower pipes n¹ which supplies the lower set of tubes n which
pass through the fire box and adjacent flue, and join in the back part of the stack
to lower tube n², Figure 3, which is joined to the lower tubes n in the lower flue
on the other side of the middle partition wall f, which passing through said lower
flue are joined to lower pipe n' on front side of stack, which in turn is joined to
lower part of upright pipe p', causing the water (as the pipes are inclined upward
in this direction) to pass through the fire-box and lower flues, and with the
accumulating steam to pass up pipe p¹ to steam drum B.
The lower cross pipe n³, Figure 5, which joins water drum A, also joins the lower
part of upright pipe p which supplies water from drum A to each of the upper
cross pipes n' on the same side of the stack as the fire-box, and as the cross pipes n¹
are closed or partitioned in the middle, and each set of tubes n incline upward
from n¹ in front of the stack, and the same side as the fire-box to n² at the back of
the stack which they join, and tubes n² on opposite side of partition wall fare
joined by set of tubes n inclined upwards to front of stack, and are joined to cross
pipes n which in tnrn are joined to upright pipe p²; thus a supply of water is
furnished from water drum A to each of the cross pipes n¹ in the front of the stack,
and same side as the fire-box which pass through the tubes n and tubes n², and
tubes n on opposite side of partition wall to cross tubes n¹ and upright pipe p,
Figure 5, carrying the hot water and accumulated steam, to steam and water
drum B, where the steam is separated from the water, and the water is again
returned to drum A through piper, Figure 3.
The drum A being comparatively large and containing a large volume of water,
the circulation of the water through it will be slow. This will give opportunity
for the impurities held in suspension to settle in the drum, from which such
collections can be blown out or removed from time to time. The drum may be
fitted with plates, as shown at u, to break the current of water from pipe r, and
thereby facilitate the settlement of foreign matters.
As the mineral impurities in solution are precipitated by the evaporation of the
water and their consequent concentration every time this occurs by the water
passing through the tubes n, there is an opportunity for it to settle in the water
drum A. As the circulation of the water and steam is very rapid through the tube n,
and very slow through the drum A, all the sediment is carried from the tube n by
the rapid current and deposited in the drum A, thus entirely preventing the
accumulation of scale on the heating surfaces, and accumulating it at a point
entirely removed from the fire, where the deposit will remain in a soft condition, a
very important consideration in a steam boiler, and believed to be more perfectly
obtained in this boiler than has before been considered possible.
Having thus described the nature of the said Invention, and the manner of

page_text: performing the same, I declare that what I claim as the Invention to be protected
by the hereinbefore in part recited Letters Patent is,―
1st. In a water heater or steam generator a long continuous flue, connecting the
fire-box with the chimney, fitted with water pipes constituting the heating surface
of the boiler in the manner and for the purposes shown, said flue being straight, or
bent in such manner as will best suit the place or purposes for which it is intended.
2nd. In water heaters a furnace divided vertically by a middle wall, and hori-
zontally by partitions between the middle and outer walls, whereby a continuous
flue is formed around the middle wall, and extending from the fire box to the
chimney, and fitted with the water pipes within the flue, substantially as described
and shown.
3rdly. In water heaters the combination with furnace stack of the middle
wall f, with or without the intermediate partitions f¹ and inclined partitions g,
forming a continuous flue, and the tubes l, m, and n, substantially as shown and
described.
4thly. In a water heater provided with a continuous flue connecting the fire-box
and chimney, fitted with water pipes within the flue in such a manner as to allow
the cool return water to flow down the pipes, which enter the flue near the
chimney in a direction opposite to the draught within the flue a desirable distance,
thence out through the wall of the flue to enter the fire-box or flue near it, and
pass up in the direction of the draught to a point near where it previously left said
flue, thence passing out through the wall.
5thly. In water heaters and steam generators provided with a continuous flue
connecting the fire-box with the chimney, fitted with water pipes in the manner
described, the water drum A, and steam and water drum B, connected with the
pipes, substantially as and for the purposes set forth.
6thly. In water heaters and steam generators provided with a continuous flue
connecting the fire-box to the chimney, fitted with water pipes in the manner
described, the tubes n', n², connecting the longitudinal tubes n, and provided with
the bosses & extending through the end walls of the stack, substantially as and for
the purposes set forth.
7thly. The partitioned tubes n', tubes n, rising pipes p, p, drum A, and drum B,
combined with the water tubes n in a water heater and generator, having its
water tubes contained in a continuous flue, substantially as shown and described.
8thly. In water heaters and steam generators having their heating surfaces
formed of tubes, the end tubes n¹, n², formed with bosses 8 extending through
the walls and fitted with caps, substantially as and for the purposes shown.
9thly. In a water heater or steam generator a long continuous flue connecting
the fire-box with the chimney, provided with tubes which constitute the heating
surface of the boiler, and divided with longitudinal brick partitions, substantially as
set forth.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Eighth day of June, in the year of our Lord One
A. M. CLARK. (L.S.)