Improvements in and relating to Hot-air Furnaces.
Year: 1890

page_text: Date of Application, 6th May, 1890-Accepted, 25th Oct., 1890
COMPLETE SPECIFICATION.
Improvements in and relating to Hot-air Furnaces.
I, JOHN HUBERT NEVINS, residing at Number 625 15th Street, South Minneapolis,
in the County of Hennepin and State of Minnesota, one of the United States of
America, Manufacturer do hereby declare the nature of this invention and in what
mannor the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
This invention relates to certain improvements in hot air furnaces for heating
purposes; and it has for its objects to provide for the perfect combustion of the fuel,
by means of a downward draught of air into the combustion chambers of the furnace,
so that the inflammable gases, arising from the fuel therein, as well as the fuel,
may be perfectly consumed on a slow or rapid principle, as more fully hereinafter
explained.
My invention consists essentially in a furnace a single fire chamber, and a central
vertical eduction flue extending through it or having a series of fire chambers,
arranged at proper intervals, around a central flue, and communicating therewith by
means of a series of flues, leading from the upper parts of said fire chambers to the
said eduction flue, in connection with an air chamber surrounding all of the fire
chambers and the flues leading therefrom, the said fire chambers and the flues being
entirely surrounded with a cold air chamber, communicating with the hot air
chamber by means of apertures through its bottom, and the hot air chamber being
provided with eduction passages, through which the hot air may be carried off, through
suitable flues to various points to he used.
The above-mentioned objects are attained by the means illustrated in the accom-
panying drawings, in which-
Figure 1, represents a horizontal sectional view taken on the line XX, of Figure 2,
showing a furnace constructed according to my invention;
Figure 2, represents a side elevation of the furnace with a portion of the lower
part broken away, so as to show the flues by means of which the air is drawn from
the respective floors of a building into or through the furnace ;
Figure, represents a transverse vertical sectional view of the furnace, taken on
the line, y-y, of Figure 1 ;
Figure 4, represents a sectional view of one of the feed devices through which fuel
is introduced to the fire chamber, and air is admitted downwardly into the combustion
chamber thereof;
Figure 5, represents a horizontal sectional view, showing a modification of the fire
chamber;
Figure 6, represents a vortical sectional view of a modification;
Figure 7, indicates a sectional view of the central dome and grate ;
Figure 8, represents a horizontal sectional view of a modification of the furnace,
showing the same constructed with a single fire chamber; and-
Figure 9, is a transverse vertical sectional view of said modification.
Referring to the drawings, the letter, A, indicates the external shell or casing of
the furnace, which is cylindrical in shape, preferably, and constructed of any suitable
material.
Within the shell, A, and concentric therewith, an inner shell, B, of less diameter
than the external shell, is located, an intervening space, C, being left between the two
shells, which forms a cold air passage which connects with the external air by means
of air ducts, E, entering at suitable points near the top of the air space. The bottom
of the internal shell, is elevated above the bottom of the external shell, leaving an

page_text: intermedinte space, D, which connects with the space C, before mentioned, and the
said bottom of the internal shell, is provided with apertures through which the cold
air passes up into the heating chamber as indicated by the arrows.
Within the furnace and grouped around the central eduction flue, (as shown in
Figures 1 and 3,) are arranged a series of fire pots and combustion chambers, E',
three of such being shown in the present instance, although it is evident that more or
less may be employed without departing from the spirit of my invention.
The said fire pots are provided with the usual grates, E³; at the bottom and below
the grates are located the ash pits, G, provided with door openings, H, through the
external shell of the furnace. The upper ends of the fire hoxes are enclosed by
means of plates, I, which have openings from which extend upwardly the feed tubes, K,
which pass through the crown of the furnace, and terminate in the plane thereof,
the said tubes being provided with perforated covers, L, through which air passes to
ensure complete combustion in the combustion chambers; the said covers being
removable for the purpose of charging fuel into the fire pots. Within the feed tubes
are located internal tubes, M, which are made flaring at their upper and lower ends,
the upper ends being larger than the lower ends, and fitting in the upper part of the
feed tubes to which they are fastened in any suitable manner. The lower ends of
the said internal tubes extend below the lower ends of the feed tubes, into the upper
parts of the combustion chambers, the object being to permit the gases as they flash
upwards when the cover is removed, to pass up between the internal and external
tubes, and prevent the flame from flushing up through the feed tube.
The letter, N, indicates an annular flue or climber, located within the inner shell,
around the upper portions of the fire chambers, and with said annular chamber
the upper parts of the fire clambers are connected, by means of radial flues, P.
so that the products of combustion may pass from the fire chambers into said annular
chamber.
The letter, R, indicates a flue extending centrally, from near the bottom through
the crown of the furnace and connecting with a suitable chimney or stack. From
the annular flue before mentioned, extend downwardly, the flues, S, which are bent
inwardly, at about right angles and connect with the central flue, it, near its lower
end, the connecting ends of the flues being gradually contracted as shown in
Figure 3, of the drawings.
T. indicates a vertical flue, concentric with and surrounding the flue, R. The
said flue, T, extends from a point below the bottom of the furnace up into the furnace,
terminating in a dome, U, at the centre of the crown of the furnace. The said
flue, T, is provided with a chamber, V, at its lower end, into which enter a series of
flues of tubes, W, extending from the various floors or apartments of the building in
which the furnace is located, for the purpose of ventilating the same. As shown in
Figure 3, the air drawn through the flue, T, and the tubes, W, enters the heating
chamber of the furnace, and is heated for further use.
In the modification shown in Figures 6 and 7 of the drawings, the grate of the
furnace is provided with a hollow cone, V, which rises from the centre of said grate
vertically, into the fire clumber, being perforated at its apex, so as to admit nir from
below, Love the bel of fuel in the fire box, to ensure perfect combustion in the
combustion chamber.
In the modification shown in Figures 8 and 9, a single fire chamber, concentric
with and surrounding the central eduction Blue, is shown. In each of the latter
instances, however, the general arrangement of the heating flues, connecting with the
central eduction flue is the same, as shown in Figures 2 and 3, the products of com-
bustion being carried up centrally through the Turnace, and the combustion in the
combustion chamber being maintained by a down draught or a draught of air
entering above the bad of fuel, in the fire pot.
The hot air chamber, at suitable points, is provided with oduction flues, X, through
which the hot air may be passed off to suitable places for use.
The operation of my invention will be clearly understood from the above

page_text: description in connection with the drawings, in which the course of the air for
supporting combustion, the products of combustion and the cold and heated air, is
shown by arrows.
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 I
claim is-
First. In a furnace, the combination with the fire pot and combustion chamber
thereof, having a downward draught, opening into the combustion chamber, of a central
eduction flue passing vertically up through the furnace, and flues connecting tho
upper part of the combustion chamber with the bottom of said central flue, substantially
as and for the purpose specified.
Second. In a furnace, the combination of a central eduction flue, a series of fire
chambers grouped around said central flue, and a series of flues connecting the
upper parts of the fire chamber with the lower part of the connecting fluos, whereby
the products of combustion are carried off from the furnace, substantially as specified.
Third. In a furnace, the combination of a fire chamber located therein, a series of
flues and a central eduction flue, said series of flues connecting the upper part of the
combustion chamber with the lower part of the eduction flue, a cold air chamber
surrounding the fire chamber and flucs, and cold air induction flues leading to said
chamber, substantially as and for the purpose specified.
Fourth. In a furnace, the combination of a fire chamber, a feed tube, and a
flaring tube located in said feed tube and extending below the same, into the
combustion chamber of said fire chamber, whereby the flame is prevented from
flashing out of the feed tube when the cover is removed for charging, substantially as
specified.
Fifth. In a furnace, the combination of a fire chamber, a central eduction flue
connected with the combustion chamber thereof, a heating chambor, a concentric
air flue surrounding the central eduction flue, having air inductions at its lower
end and connecting with the heating chamber at its upper end, whereby the air
from a building may be withdrawn and heated for subsequent use, substantially as
specified.
Sixth. In a furnace, the combination of the external shell, a concentric internal
shell, forming an intervening cold air space, a series of fire chambers, an annular
Aue connecting therewith, a series of downwardly extending flues, and a central
eduction flue, with which the said flues are connected at its bottom, whereby the
products of combustion are carried off through the centre of the furnace, substantially
as specified.
Seventh. The combination in a furnace, having a central eduction flue, of a fire
chamber located therein, and a grate, having a central conical dome extending
vertically into the fire pot of the chamber, and a downward draught opening at the top,
substantially as and for the purpose specified.
Dated this 6th day of May 1890.